From t.j.m.vanderlinden at uu.nl Wed Dec 11 19:28:53 2019 From: t.j.m.vanderlinden at uu.nl (Linden, T.J.M. van der (Thomas)) Date: Wed, 11 Dec 2019 08:28:53 +0000 Subject: [GPlates-discuss] Strange behavior reconstruction to 0 Ma Message-ID: Hello, I have been working with pygplates to reconstruct raster data. To do that I make a grid at 0.5 degree latitude-longitude and put those as points in a shape (or a gpml). These points are then reconstructed to different ages. As a habit my reconstructions start at 0 Ma and go with time steps of 10 Myr. While looking at the "reconstruction" at 0 Ma, I noticed that the coordinates changed. The "original" and "reconstructed" points are still the same, but they moved off the grid. At other time steps the coordinates of the "original" points seem to be on the grid. I could not find an explanation for this behavior and it seems unwanted to me. Cheers, Thomas -------------- next part -------------- An HTML attachment was scrubbed... URL: From john.cannon at sydney.edu.au Wed Dec 11 20:03:43 2019 From: john.cannon at sydney.edu.au (John Cannon) Date: Wed, 11 Dec 2019 09:03:43 +0000 Subject: [GPlates-discuss] Strange behavior reconstruction to 0 Ma In-Reply-To: References: Message-ID: Hi Thomas, It sounds like you're reconstructing present day raster data to past times. And that you uniformly grid your points once at present-day (rather than at each time step), then assign plate IDs once at present day (eg, using static polygons dataset), and then reconstruct them to past times. This sounds slightly different than the raster reconstruction previously discussed on this list (where the points are uniformly gridded and assigned plate IDs at each past time, rather than present day): https://mailman.sydney.edu.au/pipermail/gplates-discuss/2019-July/000746.html Does that sound right? If so, then I'm not sure how "The "original" and "reconstructed" points are still the same, but they moved off the grid". All I can think of is a non-zero rotation at present day, or a non-zero anchor plate, when reconstructing. But that sounds unlikely. Regards, John From: GPlates-discuss On Behalf Of Linden, T.J.M. van der (Thomas) Sent: Wednesday, 11 December 2019 7:29 PM To: gplates-discuss at mailman.sydney.edu.au Subject: [GPlates-discuss] Strange behavior reconstruction to 0 Ma Hello, I have been working with pygplates to reconstruct raster data. To do that I make a grid at 0.5 degree latitude-longitude and put those as points in a shape (or a gpml). These points are then reconstructed to different ages. As a habit my reconstructions start at 0 Ma and go with time steps of 10 Myr. While looking at the "reconstruction" at 0 Ma, I noticed that the coordinates changed. The "original" and "reconstructed" points are still the same, but they moved off the grid. At other time steps the coordinates of the "original" points seem to be on the grid. I could not find an explanation for this behavior and it seems unwanted to me. Cheers, Thomas -------------- next part -------------- An HTML attachment was scrubbed... URL: From sabin.zahirovic at sydney.edu.au Tue Dec 24 13:46:35 2019 From: sabin.zahirovic at sydney.edu.au (Sabin Zahirovic) Date: Tue, 24 Dec 2019 02:46:35 +0000 Subject: [GPlates-discuss] GPlates: Update to relative and absolute plate motions in Muller et al. (2019) model Message-ID: <05181BF8-E0FD-4877-90FB-AD2D4EEF5B54@sydney.edu.au> Dear GPlates users, friends and colleagues, As many of you wind down for a well-deserved break, the GPlates team at Sydney has been working hard in Santa?s workshop to send out an update on our global plate reconstructions. There are updates to the relative and absolute plate motions in the Muller et al. (2019) reconstructions, and v2.0 of the model (including GPlates files, age-grids, global and regional animations, stretching factor grids, etc.) are available to download from here: https://protect-au.mimecast.com/s/ZOhFC3Q8Z2Fyw7jmsgiE00?domain=earthbyte.org The Muller et al. (2019) v2.0 release notes are below. Relative and absolute plate motions * Full synchronisation of east Asia reconstructions of Young et al. (2018) from 250 to 130 Ma, including the closure of the Mongol-Okhotsk Ocean * Improved kinematics of the back-arc basin history along western North America (250 to 180 Ma) so that the seafloor spreading isochrons are consistent with the implied plate motions * Pacific absolute plate motion fixes following Torsvik et al. (2019) * Absolute optimised frame, with simplified hierarchy at 5 Myr intervals with optimisation weighting parameters of * 0-80 Ma: TR=1, NR=1, HS=1; * 80-170 Ma: TR=1, NR=0.5; * 170-250 Ma: TR=1, NR=0.2 * Where TR=trench migration optimisation, NR=net rotation optimisation and HS=hotspot track fitting, in an optimisation framework as described in Tetley et al. (2019), with numbers referring to relative weights of the optimisation parameters. These parameters were iteratively determined to provide the most optimal absolute plate motion model, given the relative plate motion revisions listed above. Interpolation of deformation grids * Using nearneighbor rather than spherical interpolation (removing areas that have had no deformation) * Applying rigid blocks within deformed regions (e.g. Tarim craton, Khorat platform, etc.), as well as oceanic age-grid, as masks to remove anomalous areas of extrapolation * Previous versions had a tiny amount of negative values in stretching factors, but these grids are now clipped to values above zero References M?ller, R. D., Zahirovic, S., Williams, S. E., Cannon, J., Seton, M., Bower, D. J., Tetley, M. G., Heine, C., Le Breton, E., Liu, S., Russell, S. H. J., Yang, T., Leonard, J., and Gurnis, M., 2019, A global plate model including lithospheric deformation along major rifts and orogens since the Triassic: Tectonics, v. 38, no. Fifty Years of Plate Tectonics: Then, Now, and Beyond. Tetley, M.G., Williams, S.E., Gurnis, M., Flament, N. and M?ller, R.D., 2019. Constraining absolute plate motions since the Triassic. Journal of Geophysical Research: Solid Earth, 124, 7231-7258. Torsvik, T. H., Steinberger, B., Shephard, G. E., Doubrovine, P. V., Gaina, C., Domeier, M., Conrad, C. P., and Sager, W. W., 2019, Pacific?Panthalassic reconstructions: Overview, errata and the way forward: Geochemistry, Geophysics, Geosystems, v. 20, no. 7, p. 3659-3689. Young, A., Flament, N., Maloney, K., Williams, S., Matthews, K., Zahirovic, S., and M?ller, R. D., 2018, Global kinematics of tectonic plates and subduction zones since the late Paleozoic Era: Geoscience Frontiers. Let me know if you get stuck with any of the files. Hope you all have a wonderful break, and a fantastic start to 2020! 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