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RUMShake: A pilot amplification study in western Puerto Rico
  • Preiser Brunat
Preiser Brunat
University of Puerto Rico - Mayaguez

Corresponding Author:[email protected]

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Each year the PRSN detects ~4,000 earthquakes within and around Puerto Rico, the Virgin Islands and the Eastern Dominican Republic. Given the seismic hazard presented by this earthquake activity it is critical to perform systematic and continuous studies aimed at understanding and mitigating the impacts of earthquakes. The major effects to a site are due to seismic wave amplification at specific frequencies caused by local unconsolidated sediments during strong ground motions. Therefore, it is important to recognize and mitigate these. The Puerto Rico Seismic Network (PRSN) at the University of Puerto Rico, Mayagüez (Recinto Universitario de Mayagüez [RUM]) and the Puerto Rico Strong Motion Program (PRSMP), in collaboration with the United States Geological Survey (USGS) are conducting a passive-source seismic experiment to investigate the potential for seismic amplification by soils in Mayagüez, Puerto Rico. The goal of this experiment is to quantify the potential soil amplification in Mayagüez, which is located in the western portion of the island. This region experienced significant damage from shaking in the 1918, 7.3 Mw earthquake offshore of western Puerto Rico, making it a prime target for a pilot study to examine soil amplification. Local soil and bedrock conditions in Mayagüez are similar to other areas of the Caribbean, so results will have implications throughout the region. For this study, eleven L-22 sensors with Reftek RT130 recorders were installed in April 2019 to collect data for a period of six months. Since this time, there have been sixty-one M3 or greater earthquakes in the region per month and six M6.5 or greater teleseisms that should provide data suitable for analysis. Data are currently being analyzed using simple spectral ratios of soil sites to bedrock sites. We will present information about the deployment, experiment goals, and preliminary results. The results of this experiment will provide data to refine future hazard mapping and ground motion models of the island.