TIME SERIES DISPLACEMENT MAPS FOR THE 2019-2020 PUERTO RICO EARTHQUAKE SEQUENCE

Since December 28, 2019 more than 5,000 earthquakes have affected the Southwestern Puerto Rico, of which 96 earthquakes had magnitudes of 4.5 Mw or higher. The main shock of 6.4 Mw occurred on January 7 and was the most destructive earthquake to hit Puerto Rico in 100 years. The damage to the infrastructure left at least 6,000 people as homeless refugees. The earthquakes created landslides and liquefaction along the coast. We used Synthetic Aperture Radar (SAR) interferometry for mapping risk to facilitate prevention and mitigation. We used twenty-four Sentinel-1 Synthetic Aperture Radar data that were acquired from July 2019 to June 2020. The conventional Differential Interferometric SAR (DInSAR) and Multi Aperture Interferometry (MAI) are applied to examine the surface displacement due the co-seismic activities. The former produces the line-of-sight, and the MAI produces along-track displacement maps, then a combination of the two yielded 3D co-seismic displacement maps. We also investigated the aftershock activities from January 2020 to June 2020 using Small Baseline Subset (SBAS) and Permanent Scatterers (PS) multi-temporal interferometric approaches. These time-series algorithms gave us insights about the co-seismic and post-seismic displacement since both can differentiate the effects of surface displacement through time. Our result shows that the surface was displaced slightly to the west. The result revealed that the greatest surface displacement of up to 12 centimeters occurred west of the city of Ponce between 12/28/2019 and 01/09/2020. In both SBA and PS stacking, well-established interferometric fringes are identified by exploiting the phase difference between 01/02/2020 and 01/14/2020, 12/21/2019 and 01/14/2020 as well as 01/02/2020 and 01/26/2020. The focal mechanisms calculated by the Global Centroid-Moment-Tensor (CMT) for the four terrestrial 4.8+ Mw earthquakes also indicate NE-SW striking normal faulting and NW-SE left-lateral faulting, which suggests a similar strain regime compared to the onshore mapped faults in the study area.