GSA Connects 2021 in Portland, Oregon

Paper No. 59-4
Presentation Time: 2:30 PM-6:30 PM


VILLAFANE-PAGAN, Jobel and HUGHES, Kenneth, Department of Geology, University of Puerto Rico - Mayaguez, PO Box 9000, Mayaguez, PR 00681-9000

The Puerto Rico Seismic Network (2020) registered the largest earthquake in the sequence on 7-Jan-2020, at 04:24 AM (Local Time). The epicenter was 11 km south-southwest of Guayanilla, and the hypocenter was 6 km deep. The mainshock earthquake caused expected and notable temporary changes in Puerto Rico's groundwater elevation, river discharge near the epicenter and at the Baños de Coamo (hot spring site). The main purpose of the research was to summarize the variability of the water table elevation (magnitude and increase or decrease) that was registered during the Southwestern 2020 Puerto Rico seismic sequence. The groundwater elevation changes recorded by the United States Geological Survey (USGS) at active monitoring wells were evident and notable across Puerto Rico during the M6.4 mainshock event on 7-Jan-2020. The most significant groundwater elevation changes were registered in Guayanilla (+130 cm, UP), Manatí (-26 cm, Down), and Mayagüez (+12 cm, UP) with much smaller or no changes in water table depth in other wells across Puerto Rico and the U.S. Virgin Islands. The magnitude of groundwater elevation change is attributed to the relative distance of each well from the epicenter and the normal fault movement that caused the 6.4M earthquake. The documentation of groundwater elevation changes due to seismic activity is important scientifically because it can provide a better perspective of Puerto Rico's groundwater aquifers and their behavior during seismic events. The freshwater supply in Puerto Rico is important and sensitive to changes (drought, pollution, and saltwater intrusion). Therefore, further studies are needed to understand the groundwater elevation changes variability considering ground acceleration, ground displacement, and hydrogeological characteristics (aquifer resistivity, permeability, and porosity) of every monitoring station setting.