2020 Oaxaca Earthquake, Southeastern Mexico
Preliminary Results of Satellite SAR Differential Interferometric (InSAR) Analysis

We processed data acquired on June 19, 2020, and June 25, 2019, which cover the eastern part of the displacement area, as well as data from June 12 and June 24, 2020, which cover the western part. The two results were combined and displayed together. The upper figure shows the phase of the differential interferogram, with the epicenter marked by a red circle. Contour lines of MMI (Modified Mercalli Intensity), an index of seismic intensity obtained from the USGS, are also overlaid. Sentinel-1 SAR data are C-band (wavelength = 5.6 cm), and one cycle of phase change corresponds to surface displacement of half a wavelength (2.8 cm) in the satellite’s line-of-sight direction. An increase in phase indicates an increase in distance corresponds to movement away from the satellite. The lower figure shows vertical displacement converted from the amount of phase change, assuming no horizontal displacement. The phase pattern indicates uplift, with the maximum displacement estimated at about 90 cm. The uplift distribution caused by this earthquake extends in a WNW?ESE elliptical shape, covering an area of approximately 400 km × 250 km. In contrast, the earthquake hypocenter is estimated to be located at a depth of 20?30 km, near the edge of the uplifted region at the surface (*1). Considering the location of the hypocenter along with the position and shape of the uplift distribution, the results suggest that a reverse fault with a WNW?ESE strike was activated during this earthquake. Please note that these results are preliminary, and no corrections have been applied for atmospheric delay or other effects. 

*1: Published values by USGS, NTWC, PTWC, etc.