From mdarin at uoregon.edu Sat Oct 5 05:25:19 2019 From: mdarin at uoregon.edu (Mike Darin) Date: Fri, 4 Oct 2019 19:25:19 +0000 Subject: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Message-ID: <1570217126014.48712@uoregon.edu> Hello, I'm using GPlates to reconstruct the Arabia-Eurasia collision zone and to make a plot showing Total Arabia-Eurasia Relative Motion vs. Time. To do this, I fixed the Eurasia plate and then created a set of motion paths for points on Arabia. This worked great, as I was then able to export a text file containing the coordinates of each reference point at different time steps, which allowed me to calculate the distance that Arabia had traveled between each time step. However, there must be some uncertainty in the rotation model that is not currently reflected in the generated motion paths. I am wondering if and how I could generate error ellipses in map view for the motion paths, which would allow me to add error bars to each point on the plots that reflect the uncertainties in the locations of each reference point through time? This doesn't seem straightforward to me, so I am reaching out to the discussion list for suggestions. ? Thank you, Mike Michael H. Darin, Ph.D. Postdoctoral Research Associate Department of Earth Sciences University of Oregon -------------- next part -------------- An HTML attachment was scrubbed... URL: From ben.mather at sydney.edu.au Sat Oct 5 20:39:49 2019 From: ben.mather at sydney.edu.au (Ben Mather) Date: Sat, 5 Oct 2019 10:39:49 +0000 Subject: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths In-Reply-To: <1570217126014.48712@uoregon.edu> References: <1570217126014.48712@uoregon.edu> Message-ID: Hi Mike, Thanks for reaching out. In principle, if you had enough reconstructions (rotation files) you could build up an ensemble of plate models that would enable you to interrogate uncertainty information from (standard deviation, confidence intervals, etc.), but one of the key problems is it's unclear how to weight each reconstruction. For instance, one could always argue that the latest reconstruction is the "best" because it's the result of painstaking tweaks and adjustments of all those that came before it as a product of additional geological constraints. Nonetheless, if you see beyond this caveat, a qualitative comparison between the different models is still useful and some quantitative metrics can also be employed. Comparing the plate velocities and cumulative plate distance is relatively simple to do with motion paths, but it can give the false impression that the plate reconstructions do not agree at all. A test we are working on is to place a bunch of points equally spaced across the globe and measure the distance between these points through time for different rotation files. Essentially this is just comparing multiple motion paths across the globe. From there you would calculate (pseudo-)uncertainty maps of where the reconstructions agree and where they do not. This workflow is particularly suitable for pyGPlates because swapping rotation files a breeze, and it's easy to import other python modules that deal with statistical analysis. Once we have something in place (that works!) I'll send you the python scripts so you can customise it to your problem. Is that OK? Let me know if you have any other suggestions and if you would like to be involved with testing. Best regards, Ben -- Dr. Ben Mather | Computational Geophysicist Room 418, Madsen Building F09 School of Geoscience, Faculty of Science The University of Sydney, NSW 2006 m +61 422 470 117 w benmather.info t https://protect-au.mimecast.com/s/kHziCOMxNytYVKNMIvyvo8?domain=twitter.com On 2019-10-05 05:25:49+10:00 GPlates-discuss wrote: Hello, I'm using GPlates to reconstruct the Arabia-Eurasia collision zone and to make a plot showing Total Arabia-Eurasia Relative Motion vs. Time. To do this, I fixed the Eurasia plate and then created a set of motion paths for points on Arabia. This worked great, as I was then able to export a text file containing the coordinates of each reference point at different time steps, which allowed me to calculate the distance that Arabia had traveled between each time step. However, there must be some uncertainty in the rotation model that is not currently reflected in the generated motion paths. I am wondering if and how I could generate error ellipses in map view for the motion paths, which would allow me to add error bars to each point on the plots that reflect the uncertainties in the locations of each reference point through time? This doesn't seem straightforward to me, so I am reaching out to the discussion list for suggestions. ? Thank you, Mike Michael H. Darin, Ph.D. Postdoctoral Research Associate Department of Earth Sciences University of Oregon -------------- next part -------------- An HTML attachment was scrubbed... URL: From bruce.eglington at usask.ca Mon Oct 7 08:20:51 2019 From: bruce.eglington at usask.ca (Eglington, Bruce) Date: Sun, 6 Oct 2019 21:20:51 +0000 Subject: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths In-Reply-To: References: <1570217126014.48712@uoregon.edu>, Message-ID: Hi The issue is actually much more difficult to conceptualise because different parts of different models are variably uncertain and there is no reason to assume that the average of available models is any closer to reality. I doubt that motion paths are going to resolve better models from worse, other than to identify plate motions that are too fast, etc. In order to better constrain models, we will needs to have far more comprehensive data sets that can be ?draped? over the kinematic blocks to assess matches and mismatches. One can already start some of this with data like palaeomagnetics, geochronology, etc and, to a limited extent geochemistry and geology. In most cases, though, we need data sets with much better temporal and spatial resolution than are currently available. There are lots of ways in which machine learning and AI could help, if only we had better organised, structured and relevant data. The best that can be said at present seems to be that each model can be tested for validity with localised data sets where sufficient detail is available, from which we can start to improve models. None of this is to say that we should not attempt to develop ways to test model comparisons in anticipation of improved data compilations. By doing so, we will have a better idea of how to assess and compare models. It would also be useful to somehow be able to illustrate which parts of individual models are thought to be better constrained than other parts (time, polygons, motion, etc). Something like this would certainly help address the very real need to quantify model uncertainties to help potential end users. Bruce Eglington Get Outlook for iOS ________________________________ From: GPlates-discuss on behalf of Ben Mather Sent: Saturday, October 5, 2019 4:39:49 AM To: gplates-discuss at mailman.sydney.edu.au ; mdarin at uoregon.edu Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi Mike, Thanks for reaching out. In principle, if you had enough reconstructions (rotation files) you could build up an ensemble of plate models that would enable you to interrogate uncertainty information from (standard deviation, confidence intervals, etc.), but one of the key problems is it's unclear how to weight each reconstruction. For instance, one could always argue that the latest reconstruction is the "best" because it's the result of painstaking tweaks and adjustments of all those that came before it as a product of additional geological constraints. Nonetheless, if you see beyond this caveat, a qualitative comparison between the different models is still useful and some quantitative metrics can also be employed. Comparing the plate velocities and cumulative plate distance is relatively simple to do with motion paths, but it can give the false impression that the plate reconstructions do not agree at all. A test we are working on is to place a bunch of points equally spaced across the globe and measure the distance between these points through time for different rotation files. Essentially this is just comparing multiple motion paths across the globe. From there you would calculate (pseudo-)uncertainty maps of where the reconstructions agree and where they do not. This workflow is particularly suitable for pyGPlates because swapping rotation files a breeze, and it's easy to import other python modules that deal with statistical analysis. Once we have something in place (that works!) I'll send you the python scripts so you can customise it to your problem. Is that OK? Let me know if you have any other suggestions and if you would like to be involved with testing. Best regards, Ben -- Dr. Ben Mather | Computational Geophysicist Room 418, Madsen Building F09 School of Geoscience, Faculty of Science The University of Sydney, NSW 2006 m +61 422 470 117 w benmather.info t https://protect-au.mimecast.com/s/h2m6CVAGXPtBWl2zsyg4f1?domain=twitter.com On 2019-10-05 05:25:49+10:00 GPlates-discuss wrote: Hello, I'm using GPlates to reconstruct the Arabia-Eurasia collision zone and to make a plot showing Total Arabia-Eurasia Relative Motion vs. Time. To do this, I fixed the Eurasia plate and then created a set of motion paths for points on Arabia. This worked great, as I was then able to export a text file containing the coordinates of each reference point at different time steps, which allowed me to calculate the distance that Arabia had traveled between each time step. However, there must be some uncertainty in the rotation model that is not currently reflected in the generated motion paths. I am wondering if and how I could generate error ellipses in map view for the motion paths, which would allow me to add error bars to each point on the plots that reflect the uncertainties in the locations of each reference point through time? This doesn't seem straightforward to me, so I am reaching out to the discussion list for suggestions. ? Thank you, Mike Michael H. Darin, Ph.D. Postdoctoral Research Associate Department of Earth Sciences University of Oregon -------------- next part -------------- An HTML attachment was scrubbed... URL: From sabin.zahirovic at sydney.edu.au Mon Oct 7 21:42:49 2019 From: sabin.zahirovic at sydney.edu.au (Sabin Zahirovic) Date: Mon, 7 Oct 2019 10:42:49 +0000 Subject: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Message-ID: Hi Mike and team, I agree with Bruce, using alternative models is not likely going to capture the uncertainty present in the Arabia-Eurasia convergence. If one is just looking at the Arabia-Eurasia convergence rate during a time where Atlantic seafloor spreading is occurring, then one probably wouldn?t need to take into account the absolute reference frame, but just evaluate the uncertainties across the relative plate motion hierarchy (Arabia ? Africa ? North America ? Eurasia). However, as Bruce pointed out, other constraints might be useful, especially if intraplate deformation is significant. The reality at the moment is that this is not easy to do, and would generally need to be done on a case-by-case basis, by trawling back through the rotation file and checking whether uncertainty ellipses are published for the poles used, and so on. Would be cool to have this in GPlates one day! In terms of Ben?s suggestion, it might be interesting to see what different models propose/predict for the Arabia-Eurasia convergence. There?s a bunch of models to download from here: https://protect-au.mimecast.com/s/N2jgC0YZWVFvAkBrhwTTc3?domain=earthbyte.org (EarthByte models, Chris Scotese model, etc.), and I think Douwe van Hinsbergen and team have some GPlates-related files here: https://protect-au.mimecast.com/s/Z0mECgZowLH6zqyYtoIqRs?domain=geologist.nl Cheers, Sabin -- DR SABIN ZAHIROVIC | Postdoctoral Research Associate School of Geosciences | Faculty of Science THE UNIVERSITY OF SYDNEY Rm, 404, Madsen Building F09 | The University of Sydney | NSW | 2006 M +61 416 775 589 P +61 2 9351 2467 E sabin.zahirovic at sydney.edu.au | W https://protect-au.mimecast.com/s/24IBCjZrzqHExYmyH5HNOi?domain=earthbyte.org | R http://www.researchgate.net/profile/Sabin_Zahirovic F https://protect-au.mimecast.com/s/abfCClxwB5CGY1EzU18DDB?domain=facebook.com | T https://protect-au.mimecast.com/s/vl_PCmOxDQtXQplRiD2P6O?domain=twitter.com CRICOS 00026A This email plus any attachments to it are confidential. Any unauthorised use is strictly prohibited. If you receive this email in error, please delete it and any attachments. From: GPlates-discuss on behalf of "Eglington, Bruce" Reply-To: GPlates general discussion mailing list Date: Monday, 7 October 2019 at 8:21 am To: GPlates general discussion mailing list , "mdarin at uoregon.edu" Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi The issue is actually much more difficult to conceptualise because different parts of different models are variably uncertain and there is no reason to assume that the average of available models is any closer to reality. I doubt that motion paths are going to resolve better models from worse, other than to identify plate motions that are too fast, etc. In order to better constrain models, we will needs to have far more comprehensive data sets that can be ?draped? over the kinematic blocks to assess matches and mismatches. One can already start some of this with data like palaeomagnetics, geochronology, etc and, to a limited extent geochemistry and geology. In most cases, though, we need data sets with much better temporal and spatial resolution than are currently available. There are lots of ways in which machine learning and AI could help, if only we had better organised, structured and relevant data. The best that can be said at present seems to be that each model can be tested for validity with localised data sets where sufficient detail is available, from which we can start to improve models. None of this is to say that we should not attempt to develop ways to test model comparisons in anticipation of improved data compilations. By doing so, we will have a better idea of how to assess and compare models. It would also be useful to somehow be able to illustrate which parts of individual models are thought to be better constrained than other parts (time, polygons, motion, etc). Something like this would certainly help address the very real need to quantify model uncertainties to help potential end users. Bruce Eglington Get Outlook for iOS ________________________________ From: GPlates-discuss on behalf of Ben Mather Sent: Saturday, October 5, 2019 4:39:49 AM To: gplates-discuss at mailman.sydney.edu.au ; mdarin at uoregon.edu Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi Mike, Thanks for reaching out. In principle, if you had enough reconstructions (rotation files) you could build up an ensemble of plate models that would enable you to interrogate uncertainty information from (standard deviation, confidence intervals, etc.), but one of the key problems is it's unclear how to weight each reconstruction. For instance, one could always argue that the latest reconstruction is the "best" because it's the result of painstaking tweaks and adjustments of all those that came before it as a product of additional geological constraints. Nonetheless, if you see beyond this caveat, a qualitative comparison between the different models is still useful and some quantitative metrics can also be employed. Comparing the plate velocities and cumulative plate distance is relatively simple to do with motion paths, but it can give the false impression that the plate reconstructions do not agree at all. A test we are working on is to place a bunch of points equally spaced across the globe and measure the distance between these points through time for different rotation files. Essentially this is just comparing multiple motion paths across the globe. From there you would calculate (pseudo-)uncertainty maps of where the reconstructions agree and where they do not. This workflow is particularly suitable for pyGPlates because swapping rotation files a breeze, and it's easy to import other python modules that deal with statistical analysis. Once we have something in place (that works!) I'll send you the python scripts so you can customise it to your problem. Is that OK? Let me know if you have any other suggestions and if you would like to be involved with testing. Best regards, Ben -- Dr. Ben Mather | Computational Geophysicist Room 418, Madsen Building F09 School of Geoscience, Faculty of Science The University of Sydney, NSW 2006 m +61 422 470 117 w benmather.info t https://protect-au.mimecast.com/s/eDZmCp8AJQtkR9oxUx1MnP?domain=twitter.com On 2019-10-05 05:25:49+10:00 GPlates-discuss wrote: Hello, I'm using GPlates to reconstruct the Arabia-Eurasia collision zone and to make a plot showing Total Arabia-Eurasia Relative Motion vs. Time. To do this, I fixed the Eurasia plate and then created a set of motion paths for points on Arabia. This worked great, as I was then able to export a text file containing the coordinates of each reference point at different time steps, which allowed me to calculate the distance that Arabia had traveled between each time step. However, there must be some uncertainty in the rotation model that is not currently reflected in the generated motion paths. I am wondering if and how I could generate error ellipses in map view for the motion paths, which would allow me to add error bars to each point on the plots that reflect the uncertainties in the locations of each reference point through time? This doesn't seem straightforward to me, so I am reaching out to the discussion list for suggestions. ? Thank you, Mike Michael H. Darin, Ph.D. Postdoctoral Research Associate Department of Earth Sciences University of Oregon -------------- next part -------------- An HTML attachment was scrubbed... URL: From D.J.J.vanHinsbergen at uu.nl Mon Oct 7 21:53:58 2019 From: D.J.J.vanHinsbergen at uu.nl (Hinsbergen, D.J.J. van (Douwe)) Date: Mon, 7 Oct 2019 10:53:58 +0000 Subject: [GPlates-discuss] GPlates-discuss Digest, Vol 59, Issue 3 In-Reply-To: References: Message-ID: <8C7DC6CC-602F-456F-A174-21CA50155DC0@uu.nl> Hi Mike et al., Uncertainties in the plate convergence computations come mostly from uncertainties in anomaly picks, and are expressed in covariance matrices that are (at least for the last 83 Ma) available for the Atlantic part of the Eurasia (NAM-AFR)- Arabia plate circuit. Pavel Doubrovine and John Tarduno have worked out ways to propagate those errors through a plate circuit in 2008, and Pavel has applied this to the India-Asia plate circuit in van Hinsbergen et al JGR 2011. Uncertainties of intra-plate deformation are difficult to quantify (but there isn?t much of that in the last 83 Ma within Africa as far as I know). Since GPlates does not have an option that I know of to include such uncertainties, it won?t be able to show the error bars, you?ll have to code that yourself based on the original data. Cheers, Douwe -- Prof. Dr. Douwe J.J. van Hinsbergen | Chair in Global Tectonics and Paleogeography | Department of Earth Sciences | Utrecht University | Vening Meinesz Building A | Princetonlaan 8A | 3584 CB | Utrecht | Room 2.52 | tel. (030) 253 6712 | D.J.J.vanHinsbergen at uu.nl | https://protect-au.mimecast.com/s/cYwSCq7BKYtBMLn9SZq2uQ?domain=geologist.nl | On 7 Oct 2019, at 12:43 PM, gplates-discuss-request at mailman.sydney.edu.au wrote: Send GPlates-discuss mailing list submissions to gplates-discuss at mailman.sydney.edu.au To subscribe or unsubscribe via the World Wide Web, visit https://mailman.sydney.edu.au/mailman/listinfo/gplates-discuss or, via email, send a message with subject or body 'help' to gplates-discuss-request at mailman.sydney.edu.au You can reach the person managing the list at gplates-discuss-owner at mailman.sydney.edu.au When replying, please edit your Subject line so it is more specific than "Re: Contents of GPlates-discuss digest..." Today's Topics: 1. Re: Estimating uncertainty in plate positions and motion paths (Sabin Zahirovic) ---------------------------------------------------------------------- Message: 1 Date: Mon, 7 Oct 2019 10:42:49 +0000 From: Sabin Zahirovic To: GPlates general discussion mailing list , "mdarin at uoregon.edu" Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Message-ID: Content-Type: text/plain; charset="utf-8" Hi Mike and team, I agree with Bruce, using alternative models is not likely going to capture the uncertainty present in the Arabia-Eurasia convergence. If one is just looking at the Arabia-Eurasia convergence rate during a time where Atlantic seafloor spreading is occurring, then one probably wouldn?t need to take into account the absolute reference frame, but just evaluate the uncertainties across the relative plate motion hierarchy (Arabia ? Africa ? North America ? Eurasia). However, as Bruce pointed out, other constraints might be useful, especially if intraplate deformation is significant. The reality at the moment is that this is not easy to do, and would generally need to be done on a case-by-case basis, by trawling back through the rotation file and checking whether uncertainty ellipses are published for the poles used, and so on. Would be cool to have this in GPlates one day! In terms of Ben?s suggestion, it might be interesting to see what different models propose/predict for the Ar abia-Eurasia convergence. There?s a bunch of models to download from here: https://protect-au.mimecast.com/s/IJPhCr8DLRtMBw7xhzZqoh?domain=earthbyte.org (EarthByte models, Chris Scotese model, etc.), and I think Douwe van Hinsbergen and team have some GPlates-related files here: https://protect-au.mimecast.com/s/TU2ACvl0PoC1kOqvszRja3?domain=geologist.nl Cheers, Sabin -- DR SABIN ZAHIROVIC | Postdoctoral Research Associate School of Geosciences | Faculty of Science THE UNIVERSITY OF SYDNEY Rm, 404, Madsen Building F09 | The University of Sydney | NSW | 2006 M +61 416 775 589 P +61 2 9351 2467 E sabin.zahirovic at sydney.edu.au | W https://protect-au.mimecast.com/s/YCZ-CwVLQmi6w0kouK6ilt?domain=earthbyte.org | R http://www.researchgate.net/profile/Sabin_Zahirovic F https://protect-au.mimecast.com/s/MTvsCyoNVrcDB6KYtAdOKj?domain=facebook.com | T https://protect-au.mimecast.com/s/D-TMCzvOWKiDj8EKtBnvO0?domain=twitter.com CRICOS 00026A This email plus any attachments to it are confidential. Any unauthorised use is strictly prohibited. If you receive this email in error, please delete it and any attachments. From: GPlates-discuss on behalf of "Eglington, Bruce" Reply-To: GPlates general discussion mailing list Date: Monday, 7 October 2019 at 8:21 am To: GPlates general discussion mailing list , "mdarin at uoregon.edu" Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi The issue is actually much more difficult to conceptualise because different parts of different models are variably uncertain and there is no reason to assume that the average of available models is any closer to reality. I doubt that motion paths are going to resolve better models from worse, other than to identify plate motions that are too fast, etc. In order to better constrain models, we will needs to have far more comprehensive data sets that can be ?draped? over the kinematic blocks to assess matches and mismatches. One can already start some of this with data like palaeomagnetics, geochronology, etc and, to a limited extent geochemistry and geology. In most cases, though, we need data sets with much better temporal and spatial resolution than are currently available. There are lots of ways in which machine learning and AI could help, if only we had better organised, structured and relevant data. The best that can be said at present seems to be that each model can be tested for validity with localised data sets where sufficient detail is available, from which we can start to improve models. None of this is to say that we should not attempt to develop ways to test model comparisons in anticipation of improved data compilations. By doing so, we will have a better idea of how to assess and compare models. It would also be useful to somehow be able to illustrate which parts of individual models are thought to be better constrained than other parts (time, polygons, motion, etc). Something like this would certainly help address the very real need to quantify model uncertainties to help potential end users. Bruce Eglington Get Outlook for iOS ________________________________ From: GPlates-discuss on behalf of Ben Mather Sent: Saturday, October 5, 2019 4:39:49 AM To: gplates-discuss at mailman.sydney.edu.au ; mdarin at uoregon.edu Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi Mike, Thanks for reaching out. In principle, if you had enough reconstructions (rotation files) you could build up an ensemble of plate models that would enable you to interrogate uncertainty information from (standard deviation, confidence intervals, etc.), but one of the key problems is it's unclear how to weight each reconstruction. For instance, one could always argue that the latest reconstruction is the "best" because it's the result of painstaking tweaks and adjustments of all those that came before it as a product of additional geological constraints. Nonetheless, if you see beyond this caveat, a qualitative comparison between the different models is still useful and some quantitative metrics can also be employed. Comparing the plate velocities and cumulative plate distance is relatively simple to do with motion paths, but it can give the false impression that the plate reconstructions do not agree at all. A test we are working on is to place a bunch of points equally spaced across the globe and measure the distance between these points through time for different rotation files. Essentially this is just comparing multiple motion paths across the globe. From there you would calculate (pseudo-)uncertainty maps of where the reconstructions agree and where they do not. This workflow is particularly suitable for pyGPlates because swapping rotation files a breeze, and it's easy to import other python modules that deal with statistical analysis. Once we have something in place (that works!) I'll send you the python scripts so you can customise it to your problem. Is that OK? Let me know if you have any other suggestions and if you would like to be involved with testing. Best regards, Ben -- Dr. Ben Mather | Computational Geophysicist Room 418, Madsen Building F09 School of Geoscience, Faculty of Science The University of Sydney, NSW 2006 m +61 422 470 117 w benmather.info t https://protect-au.mimecast.com/s/ApukCD1jy9tp8jwXcn67eh?domain=twitter.com On 2019-10-05 05:25:49+10:00 GPlates-discuss wrote: Hello, I'm using GPlates to reconstruct the Arabia-Eurasia collision zone and to make a plot showing Total Arabia-Eurasia Relative Motion vs. Time. To do this, I fixed the Eurasia plate and then created a set of motion paths for points on Arabia. This worked great, as I was then able to export a text file containing the coordinates of each reference point at different time steps, which allowed me to calculate the distance that Arabia had traveled between each time step. However, there must be some uncertainty in the rotation model that is not currently reflected in the generated motion paths. I am wondering if and how I could generate error ellipses in map view for the motion paths, which would allow me to add error bars to each point on the plots that reflect the uncertainties in the locations of each reference point through time? This doesn't seem straightforward to me, so I am reaching out to the discussion list for suggestions. ? Thank you, Mike Michael H. Darin, Ph.D. Postdoctoral Research Associate Department of Earth Sciences University of Oregon -------------- next part -------------- An HTML attachment was scrubbed... URL: ------------------------------ Subject: Digest Footer _______________________________________________ GPlates-discuss mailing list GPlates-discuss at mailman.sydney.edu.au https://mailman.sydney.edu.au/mailman/listinfo/gplates-discuss ------------------------------ End of GPlates-discuss Digest, Vol 59, Issue 3 ********************************************** -------------- next part -------------- An HTML attachment was scrubbed... URL: From ben.mather at sydney.edu.au Tue Oct 8 09:15:19 2019 From: ben.mather at sydney.edu.au (Ben Mather) Date: Mon, 7 Oct 2019 22:15:19 +0000 Subject: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths In-Reply-To: References: Message-ID: Hi all, Great discussion! But just to clear up any confusion: the parameter uncertainty problem is less complicated than the inference problem some are alluding to. If you want the total uncertainty of the model given the data, then a likelihood function would need to be constructed that links a reconstruction to a set of observations (palaeomagnetic stripes, fossil records, etc.) and compares the misfit. From there you would sample the posterior probability, using a MCMC algorithm, and build up an ensemble of realisations until you can extract the posterior uncertainty. A frequentist approach may be preferable in some linear cases e.g. anomaly picks - thanks for the reading material, Douwe. Alas, as Sabin pointed out, all of this is outside the scope of what can be achieved short term. Rather than finding the posterior uncertainty, you can compare a suite of reconstructions using all the different rotation files available and quantify their collective uncertainty through time. The uncertainty on Arabia-Eurasia convergence will not reflect the total uncertainty of the model given the data, but it will reflect the uncertainty between rotation files. Admittedly, this is far from perfect, given the small set of reconstructions we have available and the weighting bias I mentioned earlier, but it's a start... I hope that gives a bit more insight into what I had in mind. Hopefully this will provide a better framework to assess and compare models - and, as Bruce suggests - illustrate where and when certain models are thought to be better constrained than other parts. Cheers, Ben -- Dr. Ben Mather | Computational Geophysicist Room 418, Madsen Building F09 School of Geoscience, Faculty of Science The University of Sydney, NSW 2006 m +61 422 470 117 w benmather.info t https://protect-au.mimecast.com/s/u7qqCYWL1vi4JJOPSGR6-l?domain=twitter.com On 2019-10-07 21:43:42+11:00 GPlates-discuss wrote: Hi Mike and team, I agree with Bruce, using alternative models is not likely going to capture the uncertainty present in the Arabia-Eurasia convergence. If one is just looking at the Arabia-Eurasia convergence rate during a time where Atlantic seafloor spreading is occurring, then one probably wouldn?t need to take into account the absolute reference frame, but just evaluate the uncertainties across the relative plate motion hierarchy (Arabia ? Africa ? North America ? Eurasia). However, as Bruce pointed out, other constraints might be useful, especially if intraplate deformation is significant. The reality at the moment is that this is not easy to do, and would generally need to be done on a case-by-case basis, by trawling back through the rotation file and checking whether uncertainty ellipses are published for the poles used, and so on. Would be cool to have this in GPlates one day! In terms of Ben?s suggestion, it might be interesting to see what different models propose/predict for the Arabia-Eurasia convergence. There?s a bunch of models to download from here: https://protect-au.mimecast.com/s/opgIC1WZXri9DD5KUXIsvX?domain=earthbyte.org (EarthByte models, Chris Scotese model, etc.), and I think Douwe van Hinsbergen and team have some GPlates-related files here: https://protect-au.mimecast.com/s/702HC2xZYvC9JJOAU9HENG?domain=geologist.nl Cheers, Sabin -- DR SABIN ZAHIROVIC | Postdoctoral Research Associate School of Geosciences | Faculty of Science THE UNIVERSITY OF SYDNEY Rm, 404, Madsen Building F09 | The University of Sydney | NSW | 2006 M +61 416 775 589 P +61 2 9351 2467 E sabin.zahirovic at sydney.edu.au | W https://protect-au.mimecast.com/s/b-WUC3Q8Z2FEJJ0VSvKOQC?domain=earthbyte.org | R http://www.researchgate.net/profile/Sabin_Zahirovic F https://protect-au.mimecast.com/s/jV2cC5QZ29FDQQ4OhlSf-N?domain=facebook.com | T https://protect-au.mimecast.com/s/CEP4C6X13RtBAA8xI9PPf8?domain=twitter.com CRICOS 00026A This email plus any attachments to it are confidential. Any unauthorised use is strictly prohibited. If you receive this email in error, please delete it and any attachments. From: GPlates-discuss on behalf of "Eglington, Bruce" Reply-To: GPlates general discussion mailing list Date: Monday, 7 October 2019 at 8:21 am To: GPlates general discussion mailing list , "mdarin at uoregon.edu" Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi The issue is actually much more difficult to conceptualise because different parts of different models are variably uncertain and there is no reason to assume that the average of available models is any closer to reality. I doubt that motion paths are going to resolve better models from worse, other than to identify plate motions that are too fast, etc. In order to better constrain models, we will needs to have far more comprehensive data sets that can be ?draped? over the kinematic blocks to assess matches and mismatches. One can already start some of this with data like palaeomagnetics, geochronology, etc and, to a limited extent geochemistry and geology. In most cases, though, we need data sets with much better temporal and spatial resolution than are currently available. There are lots of ways in which machine learning and AI could help, if only we had better organised, structured and relevant data. The best that can be said at present seems to be that each model can be tested for validity with localised data sets where sufficient detail is available, from which we can start to improve models. None of this is to say that we should not attempt to develop ways to test model comparisons in anticipation of improved data compilations. By doing so, we will have a better idea of how to assess and compare models. It would also be useful to somehow be able to illustrate which parts of individual models are thought to be better constrained than other parts (time, polygons, motion, etc). Something like this would certainly help address the very real need to quantify model uncertainties to help potential end users. Bruce Eglington Get Outlook for iOS ________________________________ From: GPlates-discuss on behalf of Ben Mather Sent: Saturday, October 5, 2019 4:39:49 AM To: gplates-discuss at mailman.sydney.edu.au ; mdarin at uoregon.edu Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi Mike, Thanks for reaching out. In principle, if you had enough reconstructions (rotation files) you could build up an ensemble of plate models that would enable you to interrogate uncertainty information from (standard deviation, confidence intervals, etc.), but one of the key problems is it's unclear how to weight each reconstruction. For instance, one could always argue that the latest reconstruction is the "best" because it's the result of painstaking tweaks and adjustments of all those that came before it as a product of additional geological constraints. Nonetheless, if you see beyond this caveat, a qualitative comparison between the different models is still useful and some quantitative metrics can also be employed. Comparing the plate velocities and cumulative plate distance is relatively simple to do with motion paths, but it can give the false impression that the plate reconstructions do not agree at all. A test we are working on is to place a bunch of points equally spaced across the globe and measure the distance between these points through time for different rotation files. Essentially this is just comparing multiple motion paths across the globe. From there you would calculate (pseudo-)uncertainty maps of where the reconstructions agree and where they do not. This workflow is particularly suitable for pyGPlates because swapping rotation files a breeze, and it's easy to import other python modules that deal with statistical analysis. Once we have something in place (that works!) I'll send you the python scripts so you can customise it to your problem. Is that OK? Let me know if you have any other suggestions and if you would like to be involved with testing. Best regards, Ben -- Dr. Ben Mather | Computational Geophysicist Room 418, Madsen Building F09 School of Geoscience, Faculty of Science The University of Sydney, NSW 2006 m +61 422 470 117 w benmather.info t https://protect-au.mimecast.com/s/u7qqCYWL1vi4JJOPSGR6-l?domain=twitter.com On 2019-10-05 05:25:49+10:00 GPlates-discuss wrote: Hello, I'm using GPlates to reconstruct the Arabia-Eurasia collision zone and to make a plot showing Total Arabia-Eurasia Relative Motion vs. Time. To do this, I fixed the Eurasia plate and then created a set of motion paths for points on Arabia. This worked great, as I was then able to export a text file containing the coordinates of each reference point at different time steps, which allowed me to calculate the distance that Arabia had traveled between each time step. However, there must be some uncertainty in the rotation model that is not currently reflected in the generated motion paths. I am wondering if and how I could generate error ellipses in map view for the motion paths, which would allow me to add error bars to each point on the plots that reflect the uncertainties in the locations of each reference point through time? This doesn't seem straightforward to me, so I am reaching out to the discussion list for suggestions. ? Thank you, Mike Michael H. Darin, Ph.D. Postdoctoral Research Associate Department of Earth Sciences University of Oregon -------------- next part -------------- An HTML attachment was scrubbed... URL: From bruce.eglington at usask.ca Tue Oct 8 10:22:12 2019 From: bruce.eglington at usask.ca (Eglington, Bruce) Date: Mon, 7 Oct 2019 23:22:12 +0000 Subject: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths In-Reply-To: References: Message-ID: Hi Ben Agreed that one can calculate something. The issue is what it means. Yes, to illustrate variability between models but, if none of them are correct, there is no way to assess this. However, just doing the calculations forces us all to think of what we want or mean to portray so the exercise is valuable. A simple illustration from an area I am more at home with is: the average age of the Earth is about 2000 Ma, based on available geochronology but this does not tell us anything useful. Working through the data does, however, show where we might have bias, uneven data distribution and a host of other information. Chris Scotese showed a comparison of various global models at the RFG conference a year or so ago, using spots for various major cities on different continents. It was very interesting because it showed similarities between some models and vast differences for others, all of which highlighted areas and time intervals requiring research and I think that much of what you are doing will be of similar use. Go for it and show us how to develop methodology for when better data are available. Bruce Bruce Eglington (Ph.D.) Murray Pyke Chair Geological Sciences 114 Science Place Saskatoon Saskatchewan S7N 5E2 Canada bruce.eglington at usask.ca Ph: +1-306-966-5732 [cid:image002.jpg at 01D57D33.C0C815C0] From: GPlates-discuss On Behalf Of Ben Mather Sent: Monday, October 7, 2019 16:15 To: Sabin Zahirovic ; gplates-discuss at mailman.sydney.edu.au; mdarin at uoregon.edu Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi all, Great discussion! But just to clear up any confusion: the parameter uncertainty problem is less complicated than the inference problem some are alluding to. If you want the total uncertainty of the model given the data, then a likelihood function would need to be constructed that links a reconstruction to a set of observations (palaeomagnetic stripes, fossil records, etc.) and compares the misfit. From there you would sample the posterior probability, using a MCMC algorithm, and build up an ensemble of realisations until you can extract the posterior uncertainty. A frequentist approach may be preferable in some linear cases e.g. anomaly picks - thanks for the reading material, Douwe. Alas, as Sabin pointed out, all of this is outside the scope of what can be achieved short term. Rather than finding the posterior uncertainty, you can compare a suite of reconstructions using all the different rotation files available and quantify their collective uncertainty through time. The uncertainty on Arabia-Eurasia convergence will not reflect the total uncertainty of the model given the data, but it will reflect the uncertainty between rotation files. Admittedly, this is far from perfect, given the small set of reconstructions we have available and the weighting bias I mentioned earlier, but it's a start... I hope that gives a bit more insight into what I had in mind. Hopefully this will provide a better framework to assess and compare models - and, as Bruce suggests - illustrate where and when certain models are thought to be better constrained than other parts. Cheers, Ben -- Dr. Ben Mather | Computational Geophysicist Room 418, Madsen Building F09 School of Geoscience, Faculty of Science The University of Sydney, NSW 2006 m +61 422 470 117 w benmather.info t https://protect-au.mimecast.com/s/G5QSClxwB5Cv5k2pT9L19C?domain=twitter.com On 2019-10-07 21:43:42+11:00 GPlates-discuss wrote: Hi Mike and team, I agree with Bruce, using alternative models is not likely going to capture the uncertainty present in the Arabia-Eurasia convergence. If one is just looking at the Arabia-Eurasia convergence rate during a time where Atlantic seafloor spreading is occurring, then one probably wouldn?t need to take into account the absolute reference frame, but just evaluate the uncertainties across the relative plate motion hierarchy (Arabia ? Africa ? North America ? Eurasia). However, as Bruce pointed out, other constraints might be useful, especially if intraplate deformation is significant. The reality at the moment is that this is not easy to do, and would generally need to be done on a case-by-case basis, by trawling back through the rotation file and checking whether uncertainty ellipses are published for the poles used, and so on. Would be cool to have this in GPlates one day! In terms of Ben?s suggestion, it might be interesting to see what different models propose/predict for the Arabia-Eurasia convergence. There?s a bunch of models to download from here: https://protect-au.mimecast.com/s/_d9UCnxyErCYqx7jCZ9zFv?domain=earthbyte.org (EarthByte models, Chris Scotese model, etc.), and I think Douwe van Hinsbergen and team have some GPlates-related files here: https://protect-au.mimecast.com/s/XfLFCoVzGQi0L8rZTOy7Aj?domain=geologist.nl Cheers, Sabin -- DR SABIN ZAHIROVIC | Postdoctoral Research Associate School of Geosciences | Faculty of Science THE UNIVERSITY OF SYDNEY Rm, 404, Madsen Building F09 | The University of Sydney | NSW | 2006 M +61 416 775 589 P +61 2 9351 2467 E sabin.zahirovic at sydney.edu.au | W https://protect-au.mimecast.com/s/vYovCp8AJQtBNynKH2cuTl?domain=earthbyte.org | R http://www.researchgate.net/profile/Sabin_Zahirovic F https://protect-au.mimecast.com/s/vXoaCr8DLRtG068oiQNjBv?domain=facebook.com | T https://protect-au.mimecast.com/s/PHtQCvl0PoC3j47KSwROKv?domain=twitter.com CRICOS 00026A This email plus any attachments to it are confidential. Any unauthorised use is strictly prohibited. If you receive this email in error, please delete it and any attachments. From: GPlates-discuss > on behalf of "Eglington, Bruce" > Reply-To: GPlates general discussion mailing list > Date: Monday, 7 October 2019 at 8:21 am To: GPlates general discussion mailing list >, "mdarin at uoregon.edu" > Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi The issue is actually much more difficult to conceptualise because different parts of different models are variably uncertain and there is no reason to assume that the average of available models is any closer to reality. I doubt that motion paths are going to resolve better models from worse, other than to identify plate motions that are too fast, etc. In order to better constrain models, we will needs to have far more comprehensive data sets that can be ?draped? over the kinematic blocks to assess matches and mismatches. One can already start some of this with data like palaeomagnetics, geochronology, etc and, to a limited extent geochemistry and geology. In most cases, though, we need data sets with much better temporal and spatial resolution than are currently available. There are lots of ways in which machine learning and AI could help, if only we had better organised, structured and relevant data. The best that can be said at present seems to be that each model can be tested for validity with localised data sets where sufficient detail is available, from which we can start to improve models. None of this is to say that we should not attempt to develop ways to test model comparisons in anticipation of improved data compilations. By doing so, we will have a better idea of how to assess and compare models. It would also be useful to somehow be able to illustrate which parts of individual models are thought to be better constrained than other parts (time, polygons, motion, etc). Something like this would certainly help address the very real need to quantify model uncertainties to help potential end users. Bruce Eglington Get Outlook for iOS ________________________________ From: GPlates-discuss > on behalf of Ben Mather > Sent: Saturday, October 5, 2019 4:39:49 AM To: gplates-discuss at mailman.sydney.edu.au >; mdarin at uoregon.edu > Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi Mike, Thanks for reaching out. In principle, if you had enough reconstructions (rotation files) you could build up an ensemble of plate models that would enable you to interrogate uncertainty information from (standard deviation, confidence intervals, etc.), but one of the key problems is it's unclear how to weight each reconstruction. For instance, one could always argue that the latest reconstruction is the "best" because it's the result of painstaking tweaks and adjustments of all those that came before it as a product of additional geological constraints. Nonetheless, if you see beyond this caveat, a qualitative comparison between the different models is still useful and some quantitative metrics can also be employed. Comparing the plate velocities and cumulative plate distance is relatively simple to do with motion paths, but it can give the false impression that the plate reconstructions do not agree at all. A test we are working on is to place a bunch of points equally spaced across the globe and measure the distance between these points through time for different rotation files. Essentially this is just comparing multiple motion paths across the globe. From there you would calculate (pseudo-)uncertainty maps of where the reconstructions agree and where they do not. This workflow is particularly suitable for pyGPlates because swapping rotation files a breeze, and it's easy to import other python modules that deal with statistical analysis. Once we have something in place (that works!) I'll send you the python scripts so you can customise it to your problem. Is that OK? Let me know if you have any other suggestions and if you would like to be involved with testing. Best regards, Ben -- Dr. Ben Mather | Computational Geophysicist Room 418, Madsen Building F09 School of Geoscience, Faculty of Science The University of Sydney, NSW 2006 m +61 422 470 117 w benmather.info t https://protect-au.mimecast.com/s/G5QSClxwB5Cv5k2pT9L19C?domain=twitter.com On 2019-10-05 05:25:49+10:00 GPlates-discuss wrote: Hello, I'm using GPlates to reconstruct the Arabia-Eurasia collision zone and to make a plot showing Total Arabia-Eurasia Relative Motion vs. Time. To do this, I fixed the Eurasia plate and then created a set of motion paths for points on Arabia. This worked great, as I was then able to export a text file containing the coordinates of each reference point at different time steps, which allowed me to calculate the distance that Arabia had traveled between each time step. However, there must be some uncertainty in the rotation model that is not currently reflected in the generated motion paths. I am wondering if and how I could generate error ellipses in map view for the motion paths, which would allow me to add error bars to each point on the plots that reflect the uncertainties in the locations of each reference point through time? This doesn't seem straightforward to me, so I am reaching out to the discussion list for suggestions. ? Thank you, Mike Michael H. Darin, Ph.D. Postdoctoral Research Associate Department of Earth Sciences University of Oregon -------------- next part -------------- An HTML attachment was scrubbed... URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: image002.jpg Type: image/jpeg Size: 2723 bytes Desc: image002.jpg URL: From mark.brandon at yale.edu Tue Oct 8 13:43:26 2019 From: mark.brandon at yale.edu (Brandon, Mark) Date: Tue, 8 Oct 2019 02:43:26 +0000 Subject: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths In-Reply-To: References: Message-ID: <712821C7-2AC0-4FD0-A6FF-B00B7DDC06A3@yale.edu> There are several approaches for estimating uncertainties for plate reconstructions. The covariance approach discussed previously goes back to the beginning of plate reconstructions. Keep in mind that this approach is a linearized approximation based on a truncated Taylor series. A comprehensive analysis is provided by Chang, Stock and Molnar?. ?ON THE STATISTICAL PROPERTIES OF ESTIMATED ROTATIONS? 1987, and ?The Rotation Group in Plate-Tectonics and the Representation of Uncertainties of Plate Reconstructions? 1990. This approach assumes that you have estimated covariance matrices for the time series of interest, but you may not have that information. An alternative approach is to use bootstrap resampling, which allows one to see how the best estimate for a reconstruction, either a single point in time or at multiple points on a path, are perturbed by the residuals (aka misfit) relative to the best-fit solution. The advantage of the bootstrap approach is that it avoids the truncated Taylor series approximation used for the estimated covariance approach of Chang and others. Note that these methods only consider stochastic errors and are only as good as the data that is available. The ?errors? discussed previously include a wider set of issues including biases and departures from assumptions (non-rigid plates), which may or may not be important. Keep in mind that scientists commonly tend to overestimate uncertainties. In fact, humans have little skill with probability. One example, of many, is the popularity of lotto tickets?. Best to rely on statistics rather than intuition for estimating uncertainties. One more point: There are many fields, with climate analysis being the most visible example, where an ensemble of model results are used to provide a mean solution and an associated variation around the mean. Many people are skeptical of this approach, but there are some good arguments in support. For both of the issues discussed above, search for ?bootstrap resampling?, and ?ensemble average?. Remember that, in the 21st century, it all about finding the right search terms?. Best, Mark From: GPlates-discuss on behalf of Ben Mather Reply-To: GPlates general discussion mailing list Date: Monday, October 7, 2019 at 6:15 PM To: Sabin Zahirovic , "gplates-discuss at mailman.sydney.edu.au" , "mdarin at uoregon.edu" Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi all, Great discussion! But just to clear up any confusion: the parameter uncertainty problem is less complicated than the inference problem some are alluding to. If you want the total uncertainty of the model given the data, then a likelihood function would need to be constructed that links a reconstruction to a set of observations (palaeomagnetic stripes, fossil records, etc.) and compares the misfit. From there you would sample the posterior probability, using a MCMC algorithm, and build up an ensemble of realisations until you can extract the posterior uncertainty. A frequentist approach may be preferable in some linear cases e.g. anomaly picks - thanks for the reading material, Douwe. Alas, as Sabin pointed out, all of this is outside the scope of what can be achieved short term. Rather than finding the posterior uncertainty, you can compare a suite of reconstructions using all the different rotation files available and quantify their collective uncertainty through time. The uncertainty on Arabia-Eurasia convergence will not reflect the total uncertainty of the model given the data, but it will reflect the uncertainty between rotation files. Admittedly, this is far from perfect, given the small set of reconstructions we have available and the weighting bias I mentioned earlier, but it's a start... I hope that gives a bit more insight into what I had in mind. Hopefully this will provide a better framework to assess and compare models - and, as Bruce suggests - illustrate where and when certain models are thought to be better constrained than other parts. Cheers, Ben -- Dr. Ben Mather | Computational Geophysicist Room 418, Madsen Building F09 School of Geoscience, Faculty of Science The University of Sydney, NSW 2006 m +61 422 470 117 w benmather.info t https://protect-au.mimecast.com/s/je-uCvl0PoC3j57kHX9e4v?domain=twitter.com On 2019-10-07 21:43:42+11:00 GPlates-discuss wrote: Hi Mike and team, I agree with Bruce, using alternative models is not likely going to capture the uncertainty present in the Arabia-Eurasia convergence. If one is just looking at the Arabia-Eurasia convergence rate during a time where Atlantic seafloor spreading is occurring, then one probably wouldn?t need to take into account the absolute reference frame, but just evaluate the uncertainties across the relative plate motion hierarchy (Arabia ? Africa ? North America ? Eurasia). However, as Bruce pointed out, other constraints might be useful, especially if intraplate deformation is significant. The reality at the moment is that this is not easy to do, and would generally need to be done on a case-by-case basis, by trawling back through the rotation file and checking whether uncertainty ellipses are published for the poles used, and so on. Would be cool to have this in GPlates one day! In terms of Ben?s suggestion, it might be interesting to see what different models propose/predict for the Arabia-Eurasia convergence. There?s a bunch of models to download from here: https://protect-au.mimecast.com/s/ytcwCxnMRvt34V1WHwlbpS?domain=earthbyte.org (EarthByte models, Chris Scotese model, etc.), and I think Douwe van Hinsbergen and team have some GPlates-related files here: https://protect-au.mimecast.com/s/ZsXCCzvOWKiApZMjfwp2ch?domain=geologist.nl Cheers, Sabin -- DR SABIN ZAHIROVIC | Postdoctoral Research Associate School of Geosciences | Faculty of Science THE UNIVERSITY OF SYDNEY Rm, 404, Madsen Building F09 | The University of Sydney | NSW | 2006 M +61 416 775 589 P +61 2 9351 2467 E sabin.zahirovic at sydney.edu.au | W https://protect-au.mimecast.com/s/n18GCBNZwLiO9r7LUr4UPv?domain=earthbyte.org | R http://www.researchgate.net/profile/Sabin_Zahirovic F https://protect-au.mimecast.com/s/62XgCGvmB5iQpR1zCXebRe?domain=facebook.com | T https://protect-au.mimecast.com/s/8AcYCK1qJZtGvN2RCykC9-?domain=twitter.com CRICOS 00026A This email plus any attachments to it are confidential. Any unauthorised use is strictly prohibited. If you receive this email in error, please delete it and any attachments. From: GPlates-discuss on behalf of "Eglington, Bruce" Reply-To: GPlates general discussion mailing list Date: Monday, 7 October 2019 at 8:21 am To: GPlates general discussion mailing list , "mdarin at uoregon.edu" Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi The issue is actually much more difficult to conceptualise because different parts of different models are variably uncertain and there is no reason to assume that the average of available models is any closer to reality. I doubt that motion paths are going to resolve better models from worse, other than to identify plate motions that are too fast, etc. In order to better constrain models, we will needs to have far more comprehensive data sets that can be ?draped? over the kinematic blocks to assess matches and mismatches. One can already start some of this with data like palaeomagnetics, geochronology, etc and, to a limited extent geochemistry and geology. In most cases, though, we need data sets with much better temporal and spatial resolution than are currently available. There are lots of ways in which machine learning and AI could help, if only we had better organised, structured and relevant data. The best that can be said at present seems to be that each model can be tested for validity with localised data sets where sufficient detail is available, from which we can start to improve models. None of this is to say that we should not attempt to develop ways to test model comparisons in anticipation of improved data compilations. By doing so, we will have a better idea of how to assess and compare models. It would also be useful to somehow be able to illustrate which parts of individual models are thought to be better constrained than other parts (time, polygons, motion, etc). Something like this would certainly help address the very real need to quantify model uncertainties to help potential end users. Bruce Eglington Get Outlook for iOS ________________________________ From: GPlates-discuss on behalf of Ben Mather Sent: Saturday, October 5, 2019 4:39:49 AM To: gplates-discuss at mailman.sydney.edu.au ; mdarin at uoregon.edu Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions and motion paths Hi Mike, Thanks for reaching out. In principle, if you had enough reconstructions (rotation files) you could build up an ensemble of plate models that would enable you to interrogate uncertainty information from (standard deviation, confidence intervals, etc.), but one of the key problems is it's unclear how to weight each reconstruction. For instance, one could always argue that the latest reconstruction is the "best" because it's the result of painstaking tweaks and adjustments of all those that came before it as a product of additional geological constraints. Nonetheless, if you see beyond this caveat, a qualitative comparison between the different models is still useful and some quantitative metrics can also be employed. Comparing the plate velocities and cumulative plate distance is relatively simple to do with motion paths, but it can give the false impression that the plate reconstructions do not agree at all. A test we are working on is to place a bunch of points equally spaced across the globe and measure the distance between these points through time for different rotation files. Essentially this is just comparing multiple motion paths across the globe. From there you would calculate (pseudo-)uncertainty maps of where the reconstructions agree and where they do not. This workflow is particularly suitable for pyGPlates because swapping rotation files a breeze, and it's easy to import other python modules that deal with statistical analysis. Once we have something in place (that works!) I'll send you the python scripts so you can customise it to your problem. Is that OK? Let me know if you have any other suggestions and if you would like to be involved with testing. Best regards, Ben -- Dr. Ben Mather | Computational Geophysicist Room 418, Madsen Building F09 School of Geoscience, Faculty of Science The University of Sydney, NSW 2006 m +61 422 470 117 w benmather.info t https://protect-au.mimecast.com/s/je-uCvl0PoC3j57kHX9e4v?domain=twitter.com On 2019-10-05 05:25:49+10:00 GPlates-discuss wrote: Hello, I'm using GPlates to reconstruct the Arabia-Eurasia collision zone and to make a plot showing Total Arabia-Eurasia Relative Motion vs. Time. To do this, I fixed the Eurasia plate and then created a set of motion paths for points on Arabia. This worked great, as I was then able to export a text file containing the coordinates of each reference point at different time steps, which allowed me to calculate the distance that Arabia had traveled between each time step. However, there must be some uncertainty in the rotation model that is not currently reflected in the generated motion paths. I am wondering if and how I could generate error ellipses in map view for the motion paths, which would allow me to add error bars to each point on the plots that reflect the uncertainties in the locations of each reference point through time? This doesn't seem straightforward to me, so I am reaching out to the discussion list for suggestions. ? Thank you, Mike Michael H. Darin, Ph.D. Postdoctoral Research Associate Department of Earth Sciences University of Oregon -------------- next part -------------- An HTML attachment was scrubbed... URL: From cscotese at gmail.com Tue Oct 8 16:06:04 2019 From: cscotese at gmail.com (Christopher Scotese) Date: Tue, 8 Oct 2019 00:06:04 -0500 Subject: [GPlates-discuss] GPlates-discuss Digest, Vol 59, Issue 6 In-Reply-To: References: Message-ID: To all, Attached is a copy of the powerpoint (as a pdf) I gave in Vancouver a couple years ago (that Bruce mentioned). I was trying to have a look at the uncertainties in plate models by comparing the geographic variance between various plate models. Have a look. Chris Scotese Prof. Christopher R. Scotese, Director, PALEOMAP Project 134 Dodge, Evanston Illinois 60202, 817 914 7090 (cell) *I know this is a long signature, but I think you'll enjoy the treasures hidden within.* My latest animation (uploaded June 1, 2019) https://protect-au.mimecast.com/s/GoXxCROAQotzvQvKu9StNM?domain=youtu.be Wow! Check out the interactive paleoglobes at: https://protect-au.mimecast.com/s/MEs9CVAGXPtRxXx4iz5MFf?domain=dinosaurpictures.org. You can see where your home was located at the time of the Permo-Triassic extinction or any other time in Earth History. Digital elevation models of all of the paleogeographic maps are now available at: https://protect-au.mimecast.com/s/4aOeCWLJY7iW5x5piKmEPj?domain=earthbyte.org GPlates compatible maps and software that can plot your data on the maps, can be freely downloaded at: https://protect-au.mimecast.com/s/PfELCXLKZoizXGX6ukSe84?domain=earthbyte.org View >50 Scotese animations at: https://protect-au.mimecast.com/s/XknOCYWL1vi4LgL0TMqpqk?domain=youtube.com This ESRI website features my maps & animations and has some nice interactives: https://protect-au.mimecast.com/s/J88fCZYM2VFp5x5mSPT8Ci?domain=apl.maps.arcgis.com Paleogeographic Atlases can be downloaded at: https://protect-au.mimecast.com/s/tZMcC1WZXri9MOMjUyNrtG?domain=uta.academia.edu Map Folios for different time periods can be downloaded at: https://protect-au.mimecast.com/s/dZthC2xZYvC9p6pxU0npk_?domain=uta.academia.edu An archive of Scotese publications can be found at: https://protect-au.mimecast.com/s/qUNsC3Q8Z2FEpxp8SOPEiV?domain=researchgate.net Download Google Earth (kml) versions of maps at: https://protect-au.mimecast.com/s/-E5BC4QZ1RFvB6BjsXwsHX?domain=globalgeology.com Download Scotese CV with links to publications: https://protect-au.mimecast.com/s/Ajl-C5QZ29FDZRZnHjuemO?domain=uta.academia.edu Lecture given at the Geological Society of London on October, 2017 https://protect-au.mimecast.com/s/BUpfC6X13RtBrMr3HldRBH?domain=youtube.com Hear Chris play the "Paleogeographer's Song" https://protect-au.mimecast.com/s/mFy1C71ZgLtJAyAPfE_shn?domain=youtube.com "Sailing away on uncharted seas, who knows what we might find. You needn't go far to take this trip because the journey's through your mind." On Mon, Oct 7, 2019 at 6:22 PM < gplates-discuss-request at mailman.sydney.edu.au> wrote: > Send GPlates-discuss mailing list submissions to > gplates-discuss at mailman.sydney.edu.au > > To subscribe or unsubscribe via the World Wide Web, visit > https://mailman.sydney.edu.au/mailman/listinfo/gplates-discuss > or, via email, send a message with subject or body 'help' to > gplates-discuss-request at mailman.sydney.edu.au > > You can reach the person managing the list at > gplates-discuss-owner at mailman.sydney.edu.au > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of GPlates-discuss digest..." > > > Today's Topics: > > 1. Re: Estimating uncertainty in plate positions and motion > paths (Eglington, Bruce) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Mon, 7 Oct 2019 23:22:12 +0000 > From: "Eglington, Bruce" > To: GPlates general discussion mailing list > , Sabin Zahirovic > , "mdarin at uoregon.edu" > > Subject: Re: [GPlates-discuss] Estimating uncertainty in plate > positions and motion paths > Message-ID: > < > QB1PR01MB261078B6599DBB72C3C1A80C9F9B0 at QB1PR01MB2610.CANPRD01.PROD.OUTLOOK.COM > > > > Content-Type: text/plain; charset="utf-8" > > Hi Ben > Agreed that one can calculate something. The issue is what it means. > Yes, to illustrate variability between models but, if none of them are > correct, there is no way to assess this. However, just doing the > calculations forces us all to think of what we want or mean to portray so > the exercise is valuable. A simple illustration from an area I am more at > home with is: the average age of the Earth is about 2000 Ma, based on > available geochronology but this does not tell us anything useful. Working > through the data does, however, show where we might have bias, uneven data > distribution and a host of other information. > > Chris Scotese showed a comparison of various global models at the RFG > conference a year or so ago, using spots for various major cities on > different continents. It was very interesting because it showed > similarities between some models and vast differences for others, all of > which highlighted areas and time intervals requiring research and I think > that much of what you are doing will be of similar use. Go for it and show > us how to develop methodology for when better data are available. > > Bruce > > > Bruce Eglington (Ph.D.) > Murray Pyke Chair > > Geological Sciences > 114 Science Place > Saskatoon > Saskatchewan > S7N 5E2 > Canada > > bruce.eglington at usask.ca > Ph: +1-306-966-5732 > > [cid:image002.jpg at 01D57D33.C0C815C0] > > From: GPlates-discuss On > Behalf Of Ben Mather > Sent: Monday, October 7, 2019 16:15 > To: Sabin Zahirovic ; > gplates-discuss at mailman.sydney.edu.au; mdarin at uoregon.edu > Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions > and motion paths > > Hi all, > > Great discussion! But just to clear up any confusion: the parameter > uncertainty problem is less complicated than the inference problem some are > alluding to. If you want the total uncertainty of the model given the data, > then a likelihood function would need to be constructed that links a > reconstruction to a set of observations (palaeomagnetic stripes, fossil > records, etc.) and compares the misfit. From there you would sample the > posterior probability, using a MCMC algorithm, and build up an ensemble of > realisations until you can extract the posterior uncertainty. A frequentist > approach may be preferable in some linear cases e.g. anomaly picks - thanks > for the reading material, Douwe. Alas, as Sabin pointed out, all of this is > outside the scope of what can be achieved short term. > > Rather than finding the posterior uncertainty, you can compare a suite of > reconstructions using all the different rotation files available and > quantify their collective uncertainty through time. The uncertainty on > Arabia-Eurasia convergence will not reflect the total uncertainty of the > model given the data, but it will reflect the uncertainty between rotation > files. Admittedly, this is far from perfect, given the small set of > reconstructions we have available and the weighting bias I mentioned > earlier, but it's a start... > > I hope that gives a bit more insight into what I had in mind. Hopefully > this will provide a better framework to assess and compare models - and, as > Bruce suggests - illustrate where and when certain models are thought to be > better constrained than other parts. > > Cheers, > Ben > > -- > Dr. Ben Mather | Computational Geophysicist > Room 418, Madsen Building F09 > School of Geoscience, Faculty of Science > The University of Sydney, NSW 2006 > m +61 422 470 117 > w benmather.info > t https://protect-au.mimecast.com/s/Wr50C91ZkQtpkxkZSKWiyI?domain=twitter.com > > > On 2019-10-07 21:43:42+11:00 GPlates-discuss wrote: > Hi Mike and team, > > I agree with Bruce, using alternative models is not likely going to > capture the uncertainty present in the Arabia-Eurasia convergence. If one > is just looking at the Arabia-Eurasia convergence rate during a time where > Atlantic seafloor spreading is occurring, then one probably wouldn?t need > to take into account the absolute reference frame, but just evaluate the > uncertainties across the relative plate motion hierarchy (Arabia ? Africa ? > North America ? Eurasia). However, as Bruce pointed out, other constraints > might be useful, especially if intraplate deformation is significant. The > reality at the moment is that this is not easy to do, and would generally > need to be done on a case-by-case basis, by trawling back through the > rotation file and checking whether uncertainty ellipses are published for > the poles used, and so on. Would be cool to have this in GPlates one day! > In terms of Ben?s suggestion, it might be interesting to see what different > models propose/predict for the Ar > abia-Eurasia convergence. There?s a bunch of models to download from > here: > https://protect-au.mimecast.com/s/e9zgCgZowLH7ANAgSYHxwU?domain=earthbyte.org > (EarthByte models, Chris Scotese model, etc.), and I think Douwe van > Hinsbergen and team have some GPlates-related files here: > https://protect-au.mimecast.com/s/WvrdCjZrzqHvnAn6s4wKsA?domain=geologist.nl > > Cheers, > Sabin > > -- > DR SABIN ZAHIROVIC | Postdoctoral Research Associate > School of Geosciences | Faculty of Science > > THE UNIVERSITY OF SYDNEY > > Rm, 404, Madsen Building F09 | The University of Sydney | NSW | 2006 > M +61 416 775 589 P +61 2 9351 2467 > E sabin.zahirovic at sydney.edu.au | W > https://protect-au.mimecast.com/s/gS1vCk8vAZtpO4OLSx5Tfi?domain=earthbyte.org | R > http://www.researchgate.net/profile/Sabin_Zahirovic > F https://protect-au.mimecast.com/s/6IX3CmOxDQtrj6j0tP5ssl?domain=facebook.com | T > https://protect-au.mimecast.com/s/hOa9CnxyErCY7x7yf5JF0f?domain=twitter.com > > CRICOS 00026A > This email plus any attachments to it are confidential. Any unauthorised > use is strictly prohibited. If you receive this email in error, please > delete it and any attachments. > > > From: GPlates-discuss > on behalf of > "Eglington, Bruce" bruce.eglington at usask.ca>> > Reply-To: GPlates general discussion mailing list < > gplates-discuss at mailman.sydney.edu.au gplates-discuss at mailman.sydney.edu.au>> > Date: Monday, 7 October 2019 at 8:21 am > To: GPlates general discussion mailing list < > gplates-discuss at mailman.sydney.edu.au gplates-discuss at mailman.sydney.edu.au>>, "mdarin at uoregon.edu mdarin at uoregon.edu>" > > Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions > and motion paths > > Hi > The issue is actually much more difficult to conceptualise because > different parts of different models are variably uncertain and there is no > reason to assume that the average of available models is any closer to > reality. I doubt that motion paths are going to resolve better models from > worse, other than to identify plate motions that are too fast, etc. In > order to better constrain models, we will needs to have far more > comprehensive data sets that can be ?draped? over the kinematic blocks to > assess matches and mismatches. One can already start some of this with data > like palaeomagnetics, geochronology, etc and, to a limited extent > geochemistry and geology. In most cases, though, we need data sets with > much better temporal and spatial resolution than are currently available. > There are lots of ways in which machine learning and AI could help, if only > we had better organised, structured and relevant data. > > The best that can be said at present seems to be that each model can be > tested for validity with localised data sets where sufficient detail is > available, from which we can start to improve models. > > None of this is to say that we should not attempt to develop ways to test > model comparisons in anticipation of improved data compilations. By doing > so, we will have a better idea of how to assess and compare models. It > would also be useful to somehow be able to illustrate which parts of > individual models are thought to be better constrained than other parts > (time, polygons, motion, etc). Something like this would certainly help > address the very real need to quantify model uncertainties to help > potential end users. > > Bruce Eglington > > Get Outlook for iOS > ________________________________ > From: GPlates-discuss > on behalf of Ben > Mather > > Sent: Saturday, October 5, 2019 4:39:49 AM > To: gplates-discuss at mailman.sydney.edu.au gplates-discuss at mailman.sydney.edu.au> < > gplates-discuss at mailman.sydney.edu.au gplates-discuss at mailman.sydney.edu.au>>; mdarin at uoregon.edu mdarin at uoregon.edu> > > Subject: Re: [GPlates-discuss] Estimating uncertainty in plate positions > and motion paths > > Hi Mike, > > Thanks for reaching out. > > In principle, if you had enough reconstructions (rotation files) you could > build up an ensemble of plate models that would enable you to interrogate > uncertainty information from (standard deviation, confidence intervals, > etc.), but one of the key problems is it's unclear how to weight each > reconstruction. For instance, one could always argue that the latest > reconstruction is the "best" because it's the result of painstaking tweaks > and adjustments of all those that came before it as a product of additional > geological constraints. > Nonetheless, if you see beyond this caveat, a qualitative comparison > between the different models is still useful and some quantitative metrics > can also be employed. Comparing the plate velocities and cumulative plate > distance is relatively simple to do with motion paths, but it can give the > false impression that the plate reconstructions do not agree at all. A test > we are working on is to place a bunch of points equally spaced across the > globe and measure the distance between these points through time for > different rotation files. Essentially this is just comparing multiple > motion paths across the globe. From there you would calculate > (pseudo-)uncertainty maps of where the reconstructions agree and where they > do not. > > This workflow is particularly suitable for pyGPlates because swapping > rotation files a breeze, and it's easy to import other python modules that > deal with statistical analysis. Once we have something in place (that > works!) I'll send you the python scripts so you can customise it to your > problem. Is that OK? Let me know if you have any other suggestions and if > you would like to be involved with testing. > > Best regards, > Ben > -- > Dr. Ben Mather | Computational Geophysicist > Room 418, Madsen Building F09 > School of Geoscience, Faculty of Science > The University of Sydney, NSW 2006 > m +61 422 470 117 > w benmather.info > t https://protect-au.mimecast.com/s/Wr50C91ZkQtpkxkZSKWiyI?domain=twitter.com > > > On 2019-10-05 05:25:49+10:00 GPlates-discuss wrote: > Hello, > I'm using GPlates to reconstruct the Arabia-Eurasia collision zone and to > make a plot showing Total Arabia-Eurasia Relative Motion vs. Time. To do > this, I fixed the Eurasia plate and then created a set of motion paths for > points on Arabia. This worked great, as I was then able to export a text > file containing the coordinates of each reference point at different time > steps, which allowed me to calculate the distance that Arabia had traveled > between each time step. > However, there must be some uncertainty in the rotation model that is not > currently reflected in the generated motion paths. I am wondering if and > how I could generate error ellipses in map view for the motion paths, which > would allow me to add error bars to each point on the plots that reflect > the uncertainties in the locations of each reference point through time? > This doesn't seem straightforward to me, so I am reaching out to the > discussion list for suggestions. ? > Thank you, > Mike > Michael H. Darin, Ph.D. > Postdoctoral Research Associate > Department of Earth Sciences > University of Oregon > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://mailman.sydney.edu.au/pipermail/gplates-discuss/attachments/20191007/bff40c65/attachment.html > > > -------------- next part -------------- > A non-text attachment was scrubbed... > Name: image002.jpg > Type: image/jpeg > Size: 2723 bytes > Desc: image002.jpg > URL: < > http://mailman.sydney.edu.au/pipermail/gplates-discuss/attachments/20191007/bff40c65/attachment.jpg > > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > GPlates-discuss mailing list > GPlates-discuss at mailman.sydney.edu.au > https://mailman.sydney.edu.au/mailman/listinfo/gplates-discuss > > > ------------------------------ > > End of GPlates-discuss Digest, Vol 59, Issue 6 > ********************************************** > > -------------- next part -------------- An HTML attachment was scrubbed... URL: -------------- next part -------------- A non-text attachment was scrubbed... Name: Scotese_GlobalPlateModels_v3r.pdf Type: application/pdf Size: 620280 bytes Desc: not available URL: From t.j.m.vanderlinden at uu.nl Wed Oct 9 18:20:45 2019 From: t.j.m.vanderlinden at uu.nl (Linden, T.J.M. van der (Thomas)) Date: Wed, 9 Oct 2019 07:20:45 +0000 Subject: [GPlates-discuss] Crustal stretching factor values Message-ID: Hi all, From the data provided with the M?ller Tectonics June 2019 article I exported the CrustalStretchingFactors to further process. The data contains values that go beyond my expectations. For instance at 10Ma the minimum is -99 and the maximum 235. From the article I understand for ? values greater than 1 represent extensional regions and values between 0 and 1 represent compressional regions. There are 12 values below 0 and 16 above 10, which I realise is only a very small fraction of the 64001 points. But two questions that remain: 1. Would it be safe to say the (very) high values are artefacts? For instance of the drawing of the topologies 2. How can values below 0 be explained? These seem fundamentally impossible. Best from Berlin, Thomas -------------- next part -------------- An HTML attachment was scrubbed... URL: From john.cannon at sydney.edu.au Thu Oct 10 02:11:21 2019 From: john.cannon at sydney.edu.au (John Cannon) Date: Wed, 9 Oct 2019 15:11:21 +0000 Subject: [GPlates-discuss] Crustal stretching factor values In-Reply-To: References: Message-ID: Hi Thomas, Regarding point (1), it is possible for strain to accumulate quickly in certain locations within the deforming regions. For example, some triangles in a network triangulation can have excessively high strain rates (depending on the specific deforming network). This can be mitigated somewhat by enabling strain rate clamping. It looks like the dataset referenced by the paper has clamping enabled for the project without crustal thinning grids (?Muller_etal_2019.gproj?) but disabled for crustal thinning grids (?Muller_etal_2019_7_Point_Density_Project_File.gproj?). If I enable clamping in the latter project, in all the brown (topological network) layers, then the maximum stretching factor reduces from about 300 to 160. And as it turns out, this also helps a lot with the negative stretching factors in point (2). https://protect-au.mimecast.com/s/Xa4HCD1jy9tkOKGGFWxAfd?domain=earthbyte.org Regarding point (2)? Yes theoretically it should not be possible to get negative stretching factors. However it seems in practice that numerical solutions using finite time steps can cause this. The differential equation for crustal thickness is ?DH/Dt = -H * SR? where H is thickness and SR is strain (dilatation) rate. So when the dilatation rate is positive (ie, extension) the thickness decreases exponentially ? which means it should decay towards zero but never cross zero (to become negative). However with a finite time interval the simplest integration is ?(H1 - H0) / delta_T = ? H0 * SR? or ?H1 = H0 * (1 - SR * delta_T)?. So H1 can be negative if ?SR * delta_T? is greater than 1.0. GPlates integrates using Runge-Kutta order 2 (with a time interval of 1My), but updating that to order 4 didn?t make it that much better (just tried that now). I think the time interval (1My) is a little too large for the strain rates we can encounter ? need to reduce ?SR * delta_T? ? I?ll look into that (maybe an adaptive time interval). Alternatively there?s strain rate clamping - another way to reduce ?SR * delta_T? which is why it seemed to work so well as mentioned above. As you noted it doesn?t happen much at all (which is probably why we didn?t notice it). Just looking into it now I noticed it happens when a deforming network ends and is replaced by an ?inactive? version (in the ?Inactive_Deforming_Meshes? layer). The term ?inactive? I think just means that although there?s still an ?active? topological network there is no deformation taking place within it (because it?s been built to remain rigid). Although it seems deformation is taking place in some cases (eg, ?LHR_Topo? becomes ?inactive? at 58Ma but has high deformation for some times during 58-41Ma) and high enough to trigger this problem (?SR * delta_T? is greater than 1.0). Disabling that layer (as opposed to just making the layer invisible) does help noticeably. But it happens in other layers too. However what really helps a lot is enabling strain rate clamping (mentioned above). But I?ll look further into the integration. Regards, John From: GPlates-discuss On Behalf Of Linden, T.J.M. van der (Thomas) Sent: Wednesday, 9 October 2019 6:21 PM To: gplates-discuss at mailman.sydney.edu.au Subject: [GPlates-discuss] Crustal stretching factor values Hi all, From the data provided with the M?ller Tectonics June 2019 article I exported the CrustalStretchingFactors to further process. The data contains values that go beyond my expectations. For instance at 10Ma the minimum is -99 and the maximum 235. From the article I understand for ? values greater than 1 represent extensional regions and values between 0 and 1 represent compressional regions. There are 12 values below 0 and 16 above 10, which I realise is only a very small fraction of the 64001 points. But two questions that remain: 1. Would it be safe to say the (very) high values are artefacts? For instance of the drawing of the topologies 2. How can values below 0 be explained? These seem fundamentally impossible. Best from Berlin, Thomas -------------- next part -------------- An HTML attachment was scrubbed... URL: From sebastianctroncoso at gmail.com Fri Oct 11 23:50:14 2019 From: sebastianctroncoso at gmail.com (=?UTF-8?Q?Sebasti=C3=A1n_Cabrera_Troncoso?=) Date: Fri, 11 Oct 2019 09:50:14 -0300 Subject: [GPlates-discuss] Question about gplates Message-ID: Hi, I'm writing to you because I have two questions about "Kinematics Tool": - When select the Plate ID, what happen if in the selected position (lat/lon) the plate changes across time? I should to change the Plate ID when it happen? - The position lat/lon is the present or past position? Thanks for your reply Best regards, Sebasti?n Cabrera -------------- next part -------------- An HTML attachment was scrubbed... URL: From john.cannon at sydney.edu.au Mon Oct 14 13:16:36 2019 From: john.cannon at sydney.edu.au (John Cannon) Date: Mon, 14 Oct 2019 02:16:36 +0000 Subject: [GPlates-discuss] Question about gplates In-Reply-To: References: Message-ID: Hi Sebasti?n, The lat/lon position displayed in the Kinematics Tool is the present day position - it?s also the last row of the displayed table (time 0Ma). For other times (rows) it?s the present-day position reconstructed to the past time of that row (using the Plate ID). So if you click on a feature (on the globe) and then click ?Use focused feature? then it will fill in the present-day lat/lon position (of the first vertex I believe) and Plate ID for that feature, and populate the table and graph with a history of velocities. Or you can type in your own Plate ID and present-day lat/lon. Regards, John From: GPlates-discuss On Behalf Of Sebasti?n Cabrera Troncoso Sent: Friday, 11 October 2019 11:50 PM To: gplates-discuss at mailman.sydney.edu.au Subject: [GPlates-discuss] Question about gplates Hi, I'm writing to you because I have two questions about "Kinematics Tool": - When select the Plate ID, what happen if in the selected position (lat/lon) the plate changes across time? I should to change the Plate ID when it happen? - The position lat/lon is the present or past position? Thanks for your reply Best regards, Sebasti?n Cabrera -------------- next part -------------- An HTML attachment was scrubbed... URL: