Central America is one of the most tectonically active areas in the world, and its high seismicity rate demands the establishment of seismic instrumentation to monitor earthquake occurrence. The first seismological equipment installed in the region dates from 1882. In El Salvador, seismological observations began in the late nineteenth century when 15 Wiechert seismographs arrived in the country. A network of 12 short-period telemetric seismic stations became fully operational in El Salvador in late 1984; this network currently consists of 18 seismographs. Earthquake monitoring in the other countries of the region by permanent networks has operated since the 1970s. In the 1990s, all the countries in the region acquired SEISLOG data acquisition systems and new equipment, including broadband stations, which were donated to improve their seismic networks. In 1998, the Central America Seismological Center (CASC) was established in Costa Rica, marking a new stage in seismological observation in the region. The goal of this center is to locate regional earthquakes and compile seismic databases to be used in the estimation of seismic hazard. This paper summarizes the progress on seismic monitoring in El Salvador and reviews the scientific achievements of the CASC after three years of operation.

A review of historical data for locally and regionally generated tsunamis indicates that 11 events have struck the coast of El Salvador between 1859 and 2002. Two of these tsunamis caused significant death and destruction. Five of the tsunamis were triggered locally, three regionally (from other countries of Central America), and three were triggered by distant earthquakes in the Aleutian, Chilean, and Colombian subduction zones. Nearly 200 fatalities have been caused by local tsunamis. Reported damages range from coastal flooding to the destruction of villages. Earthquakes of magnitude 7 or higher having epicenters offshore or onshore (close to the coastline) could trigger tsunamis that would impact the coastal areas of El Salvador. A preliminary estimation of tsunami hazard indicates that the entire Pacific coast of Central America is at risk from impact by tsunamis. In this paper, we illustrate the potential damage in El Salvador that could be caused by a distant tsunami with a numerical simulation of the 31 January 1906 Colombia tsunami.