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Published April 16, 2023 | Published + Supplemental Material
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A Secondary Zone of Uplift Measured After Megathrust Earthquakes: Caused by Early Downdip Afterslip?


A secondary zone of surface uplift (SZU), located from 200 to 400 km landward of the trench, has been measured after several megathrust earthquakes. The SZU reached a few centimeters hours to days after the 2011 M_w 9.1 Tohoku (Japan) and 2010 M_w 8.8 Maule (Chile) earthquakes. Published coseismic finite-fault models for these events do not reproduce the measured SZU. One interpretation is that this SZU is universal, driven by volume deformation around the slab interface (van Dinther et al., 2019, https://doi.org/10.1007/s00024-019-02250-z). In contrast, we demonstrate the SZU may instead result from slip on the slab interface, and suggest it might be caused by rapid afterslip. We can reproduce the SZU with fault slip if elastic heterogeneities associated with the subducting slab are accounted for, as opposed to assuming homogeneous or layered elastic lithospheric structures.

Additional Information

© 2023. The Authors. Geophysical Research Letters published by Wiley Periodicals LLC on behalf of American Geophysical Union. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. We thank Emilie Klein, Ylona van Dinther, an anonymous reviewer, and the associate editor for their excellent suggestions that help improved the original manuscript. We thank Rishav Mallick for fruitful discussions. MS was partially supported by the National Aeronautics and Space Administration Earth Sciences Division under Grant 80NSSC19K1499. Data Availability Statement. Materials (without data sets) presented in this paper are archived and available on Zenodo (Ragon, 2022). Static GNSS offsets for the 2010 Maule earthquake have been published in Vigny et al. (2011) and Lin et al. (2013). GNSS time series have been process by Klein et al. (2022), with data provided by Centro Sismológico Nacional (CSN) of the Universidad de Chile (Báez et al., 2018), that can be retrieved from the GNSS database (http://GNSS.csn.uchile.cl). GNSS time series for the 2011 Tohoku earthquake have been processed by Periollat et al. (2022). Static GNSS time series are attributed to GNSS Products, CNRS, OSUG, ISTERRE (2022). The Bayesian simulations were performed with the AlTar2 package (https://github.com/lijun99/altar2-documentation). The Classic Slip Inversion (CSI) Python library (Jolivet et al., 2014) developed by Romain Jolivet was used to build inputs for the Bayesian algorithm. The mesh for the FEM simulations was built using Coreform Cubit (v2022.4, retrieved from http://coreform.com). We used the finite element code Pylith (Aagaard et al., 2013) to perform the simulations. Slab geometry, topography, and crustal elastic properties from Slab2, LITHO1.0, and ETOPO1 models are available in Hayes et al. (2018), Pasyanos et al. (2014), and Amante and Eakins (2009). 3D data were visualized using the open-source parallel visualization software ParaView/VTK (Ahrens et al., 2005). Figures were generated with the Matplotlib (Hunter, 2007) and Seaborn (Waskom, 2021) Python3 libraries.

Attached Files

Supplemental Material - 2022gl101510-sup-0001-supporting_information_si-s01.pdf

Published - Geophysical_Research_Letters_-_2023_-_Ragon_-_A_Secondary_Zone_of_Uplift_Measured_After_Megathrust_Earthquakes__Caused_by.pdf



Additional details

August 22, 2023
August 22, 2023