Abstract
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.