ANALYSIS OF SEISMIC ACTIVITY IN COSTA RICA DURING 2010 AND SUMMARY OF MAJOR SEISMIC EVENTS IN COSTA RICA FROM 1983 TO 2012

Abstract

The goal of this work is to analyze the seismic activity recorded by the OVSICORI-UNA seismic network in 2010; we also gathered information of the main events felt since 1984. The earthquake location is made using P- and S- arrivals, and source parameters are characterized using polarities and waveforms. The subduction process of the Cocos tectonic plate beneath the Caribbean one caused two important earthquakes of magnitudes 6.2 and 6.1 Ml in the southwest of Puerto Quepos, and another one of magnitude 5.3 Ml at the entrance of the Nicoya Gulf. None of earthquakes caused  any  damage  but  were  felt  strongly  by  the  population.  In  addition,  two  seismic  swarms occurred in 2010. The first one struck the vicinity of the Irazu Volcano in the month of July, with a maximum magnitude of 3.2 Ml. The second one hit Ujarras and Durika of Buenos Aires in the province of Puntarenas with magnitudes between 2.9 to 4.0 Ml. The triple junction zone among the Nazca, Cocos plate and the Panama block was also a scene of important seismic activity during 2010. In general, the Costa Rican population felt approximately 107 earthquakes while 4000 earthquakes were recorded by the OVSICORI-UNA’s seismic network during 2010. The historical records show that the strongest earthquake in Costa Rica reached a magnitude of Mw 7.6 and intensity of IX in the Mercalli Modified Scale.