Interseismic coupling along the Mexican subduction zone seen by InSAR and GNSS

In the Mexican subduction zone, the heterogeneous spatial density of the GNSS network is limiting the capability to measure and study the variability of the surface deformation field all along the subduction zone. To improve the spatial coverage of interseismic deformation estimates, we combine InSAR and GNSS data. We use four Sentinel-1 descending tracks covering a large part of the Mexican Pacific coast from Jalisco to Oaxaca, over the period from 2016 to 2019.5. The InSAR and GNSS time series, over the same 3.5-year period, are corrected for the coseismic deformations of two M-w > 7 earthquakes but not for slow slip events (SSE) and postseismic surface displacements. We present estimates of mean surface velocities over the study period, which combine the linear inter-SSE trend and transient aseismic slip. By inverting these velocities, we estimate the short term coupling at the plate interface, which shows large lateral variations. InSAR data significantly improves the resolution of the inversion, compared to a model based only on GNSS data. Although not representative of long-term coupling in areas with large transient events, the short-term coupling estimates highlight the role of transient signals, such as slow slip events, on the coupling variability measured by geodesy. In agreement with GNSS times series over longer time period, the data also suggest that the Jalisco area (longitude from -106 degrees E to -104 degrees E), where no large transient events are observed, is highly coupled with a coupling ratio higher than 0.8. (C) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this study, a method for spatial estimation of surface deformation in the Mexican subduction zone is proposed by combining InSAR and GNSS data. The results show large lateral variations in interseismic deformation. InSAR data significantly improves the resolution of the estimates compared to a model based only on GNSS data. The study also finds a high coupling ratio in the Jalisco area in the absence of large transient events.