Interaction Between Slow Slip Event and Earthquakes: The Case of the 2017-2018 Guerrero SSE (Mexican Subduction) Seen by Remote Sensing

Session: From Aseismic Deformation to Seismic Transient Detection, Location and Characterization
Type: Oral
Date: 4/29/2020
Time: 05:30 PM
Room: 230 + 235
Description: 

Mexican subduction is characterized by the occurrence of large slow slip events (SSE). In Guerrero, SSEs are among the largest observed in the world. In this study, we focus on the 2017-2018 SSE that lasted for several months on the Mexican subduction interface, in the Guerrero state area. In the same period, three major earthquakes occurred along the Mexican subduction (Sept. 7 Mw 8.2 Tehuantepec; Sept. 19 Mw 7.1 Puebla and Feb. 16 Mw 7.5 Pinotepa). This period of time makes it an ideal time to study the interactions between SSEs and earthquakes. In Guerrero region, the permanent GPS network has a low spatial density with uneven station distribution. To enhance the spatial resolution, and better understand the interactions between seismic and aseismic event, we complete the geodetic observations with an InSAR study covering about 350x500 km.

We use time series of Sentinel-1 radar images for the period 2016-2018. The main challenge was to extract the ground deformation signal related to the SSE from InSAR data dominated by atmospheric signal (equivalent amplitude up to 20cm). We extract transient SSE signal with two different approaches: a parametric method (which consists of a regularized least-square inversion), and an Independent Component Analysis (ICA) of the InSAR time series to decompose the signal without imposing a priori information on the SSE signal. Both methods provide consistent results and allow the atmospheric signal to be separated from the tectonic signal without prior correction from atmospheric models.

We obtain accurate SSE surface displacements maps along the radar line-of-sight, matching observations on available GPS time series. The temporal evolution of the SSE shows a velocity change correlated to the Sept. 2017 earthquakes which suggests an interaction between seismic and aseismic events. We also invert InSAR surface displacements for slip on the subduction interface using an elastic half-space medium. Our slip distribution model gives an equivalent magnitude Mw 7.2) This model shows a similar location of the slip that previous event.

Presenting Author: Louise Maubant

Authors