T005-02
Systematic characterization of slow slip events along the Mexican subduction zone over 20 years

Monday, 7 December 2020: 07:05
Virtual
Mathilde Radiguet1, Ekaterina Kazachkina2, Louise Maubant3, Nathalie Cotte3, Vladimir Kostoglodov4, Adriano Gualandi5 and Kristel Chanard6, (1)Université Grenoble Alpes, Grenoble, France, (2)National Autonomous University of Mexico, Ciudad DE Armería, Mexico, (3)ISTerre Institute of Earth Sciences, Saint Martin d'Hères, France, (4)UNAM, Instituto de Geofisica, Mexico City, Mexico, (5)Organization Not Listed, Washington, DC, United States, (6)IGN Institut National de l'Information Géographique et Forestière, Paris, France
Recorded Presentation
Abstract:
Slow slip events (SSEs) represent a significant mechanism of strain release along subduction zones, and understanding their occurrence and relations with major earthquake is essential for a comprehensive understanding of the seismic cycle. Here, we focus on the Mexican subduction zone, characterized by the occurrence of recurrent large slow slip events, both in the Guerrero region, where the SSEs are among the largest observed worldwide, and in the Oaxaca region, where smaller, more frequent SSEs occur. Up to now, most slow slip studies in the Mexican subduction zone focused either on the detailed analysis of a single event, or were limited in short period of time. In this study, our aim is to build an updated and consistent catalog of major slow slip events in the Guerrero-Oaxaca region.

We analyze the GPS time series from 2000 to 2020 using Independent Component Analysis (ICA), in order to separate temporally varying sources of different origins (seasonal signals, SSEs and afterslip of major earthquakes). We are able to isolate a component corresponding to seasonal loading, which matches the temporal evolution of surface displacements estimated from the GRACE data. The sources (independent components) identified as sources of tectonic origin are inverted for slip on the subduction interface. We thus obtain a model of the spatio-temporal evolution of aseismic slip on the subduction interface over nearly 20 years, from which we can isolate around 30 individual SSE of equivalent magnitude Mw > 6.2.

The obtained catalog is coherent with previous studies (in terms of number of events detected, magnitude and duration) which validates the methodology, but extends over a longer period of time. It can be used to evaluate some general properties of SSEs in that region. The observed moment-duration scaling is close to M0~T3 , as expected for regular earthquakes, confirming the observation made by Michel et al. [Nature, 2020] for Cascadia SSEs, but extending the range of magnitude considered. Finally, we also investigate the spatio-temporal relations between the SSEs occurring in the adjacent regions of Guerrero and Oaxaca, and their interaction with local and distant earthquakes.

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