[GPlates-discuss] Estimating uncertainty in plate positions and motion paths

[Ben Mather]

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
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Dr. Ben Mather | Computational Geophysicist
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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
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