Earthquake Location Accuracy in the Puerto Rico-Virgin Islands Region

Abstract

The Puerto Rico Seismic Network (PRSN) has historically provided hypocentral information for earthquakes in the Puerto Rico-Virgin Islands (PRVI) region. The network has been operating since 1974, when the U.S. Geological Survey installed several short-period stations for the Electric Energy Authority that were used to evaluate local seismicity on the island of Puerto Rico for the construction of nuclear power plants in Guayama and Costa Norte. The network was later transferred in 1982 to the University of Puerto Rico at Mayaguez, where it has been operating under the jurisdiction of the Department of Geology since 1987. McCann (2002) provided additional details of the history of the network. The PRSN currently consists of 25 seismograph stations located in Puerto Rico and nearby islands (Table 1). Seismic data from these sites are recorded continuously and sampled at 100 sps. The network consists of both short-period and broadband instruments and includes two short-period stations that belong to the U.S. Army Corps of Engineers. Nineteen of the 25 stations are currently used to locate earthquakes in the PRSN Area of Responsibility defined by latitudes 17°-20°N and longitudes 63.5°-69°W (Figure 1). Stations not currently used in the earthquake location process are marked with a + symbol in Table 1. View this table: TABLE 1 Seismograph Stations Currently Operated by the Puerto Rico Seismic Network The upgrade in instrumentation and station coverage that the PRSN has undergone since its inception has important benefits for the effective monitoring of seismic activity in the PRVI region. These benefits include improved earthquake-detection capability and increased location accuracy that can help delineate seismogenic structures and define earthquake source zones for seismic-hazard analysis. In this study, we examine the degree of accuracy that can be expected for earthquakes located by the PRSN within the PRVI geographic region. This evaluation is based on the present configuration …