DOCUMENTING AND COMMUNICATING GROUND FAILURE TRIGGERED BY THE 2020 SOUTHWEST PUERTO RICO SEISMIC SEQUENCE

The 2020 Southwest Puerto Rico seismic sequence was punctuated by a M6.4 mainshock on January 7, 2020. This event triggered landslides and liquefaction primarily in the municipalities of Guánica, Yauco, Guayanilla, Peñuelas, and Ponce. Following the mainshock event, geotechnical engineers and geoscientists from the University of Puerto Rico at Mayagüez (UPRM), the U.S. Geological Survey (USGS), and the Geotechnical Extreme Events Reconnaissance (GEER) Association conducted field investigations to document the ground failure caused by the earthquake sequence. Faculty and students from the Geology and Civil Engineering Departments at UPRM used social media platforms to share field observations and receive information from the public on potential new ground failure sites, and also compiled common misinformation and misconceptions about the earthquake sequence. The latter information was used by the USGS and other event managers for situational awareness to help improve communication.

A preliminary USGS online web map of our key field observations detailing the location and nature of ground failure (i.e. rockfalls, slumps, subsidence, liquefaction, lateral spreading, and ground cracks) was published quickly, and later replaced by a more refined data release and online dashboard including all observations. The GEER team published a report summarizing the seismic sequence activity and their ground failure field observations. In this study, we summarize these efforts towards both documenting and communicating information regarding earthquake-triggered ground failure. We also discuss how these observations are continuing to improve our ability to understand earthquakes and ground failure hazards in Puerto Rico.