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3D Displacement Maps of the 2019–2020 Puerto Rico Earthquake Sequence from DInSAR and MAI and Comparison with Mapped on Land Faults

Puerto Rico has been recently affected by an earthquake sequence that began on December 28, 2019 and to this writing has not ended. So far, more than 2,000 earthquakes have affected the island, of which 32 earthquakes have had magnitudes of 4.5 or greater. The main shock of 6.4 Mw occurred on January 7 and has been the most destructive earthquake to hit Puerto Rico in 100 years. One person has died, a hundreds of buildings have been damaged. Although earthquake damage is evident, we are unaware of any reported on land surface ruptures. Four epicenters of magnitudes 4.9, 5.0, 5.6 and 5.9 were located on land or close to the coast. We use Multi Aperture Interferometry (MAI) and DInSAR to obtain 3D estimation maps of the ground displacement. We used Synthetic Aperture Radar data of the Copernicus Sentinel-1 satellite operated by the European Space Agency and processed it with Environment for Visualizing Images software. We then produced line-of-sight and along-track displacement maps, which yielded 3D coseismic displacement maps. In addition, we spatially compared the location of ground displacement with previously mapped faults on geological maps and on a digital elevation model produced from Lidar at 10 m resolution. The study area is covered by Oligocene to Miocene clastic and carbonate rocks that contain NE-SW to E-W striking normal faults. Underneath these rocks lie a Cretaceous volcanic and sedimentary sequence with NW-SE striking sub-vertical faults with normal and left-lateral senses of movement. The focal mechanisms calculated by the U.S. Geological Survey for the four on land >4.8 M earthquakes indicate NE-SW striking normal faulting and NW-SE left-lateral faulting, which suggests a similar strain regime compared to the mapped faults in the study area. Results show the greatest ground displacement occurred west of the city of Ponce up to 12 cm between 12/28/2019 and 01/09/2020 and up to 19 cm between 01/02/2020 and 01/14/2020 in the line sight of the radar.

Presenting Author: Zelalem Demissie

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