Source Characteristics of the 2020 Mw 7.4 Oaxaca, Mexico, Earthquake Estimated from GPS, InSAR, and Teleseismic Waveforms

On 23 June 2020, an Mw 7.4 earthquake struck offshore Oaxaca, Mexico, providing a unique opportunity to understand the seismogenic tectonics of the Mexican subduction zone. In this study, near-field coseismic deformation caused by the event was retrieved from Global Positioning System (GPS) observations and Interferometric Synthetic Aperture Radar (InSAR) measurements. Given static geodetic measurements, high-rate GPS waveforms, and teleseismic waveforms, the fault geometry and rupture process for the 2020 Oaxaca earthquake were robustly determined by nonlinear joint inversions. The main slip was located at a depth of 20–30 km with a peak slip of 3.4 m near the epicenter. The total released moment was 1.70×1020 N·m, corresponding to Mw 7.4. The whole rupture process lasted 14 s, with the dominant rupture slip occurring 5–8 s after initial rupture. The mainshock rupture mostly occurred along the fault strike, covering a size of ∼55 km(along strike)×∼35 km(along dip) and totally overlapping with the 1965 Mw 7.5 rupture zone. We speculate that this 2020 earthquake is a repeat event following that in 1965. Fluid percolation under the slab may be one of the key factors affecting the seismogenic depth in the Oaxaca region.