EL TERREMOTO DEL 4 DE MARZO DE 1924 (Ms 7,0): ¿UN GRAN TEMBLOR INTERPLACA RELACIONADO AL LÍMITE INCIPIENTE ENTRE LA PLACA CARIBE Y LA MICROPLACA DE PANAMÁ?

Abstract

The seismogenic source, the intensity distribution and the coseismic effects are investigated for theMarch 4, 1924 (Ms = 7.0) earthquake, which occurred in the central-pacific forearc of Costa Rica. A neotectonicstudy allows to define the characteristics of the cortical faulting related to this destructive earthquake. From acareful study of macroseismic data obtained from different bibliographic sources, the intensity distribution of thisearthquake is defined. Maximum intensities between VIII and IX in the Mercalli Modified scale were defined inthe mesoseismal area, which includes the towns of Orotina, San Mateo, San Ramón and Esparza. The earthquakeproduce the collapse and damage of a great number of houses and buildings, strong damage to the railroad, greatnumber of landslides, rock falls, earth cracks and liquefaction. The earthquake aftershock sequence includesvarious events with magnitudes Ms between 5.0 and 6.4. The main shock triggered seismic activity in differentfaults along the interior region of the country, and eruptions at the Irazú and Rincón de la Vieja volcanoes.With criteria such as an epicentral location using regional seismographic stations, the trend of the S wave andthe S-P from aftershocks, the mesoseismal area, and a possible earthquake rupture, it is suggested that theseismogenic source of the earthquake was the Tárcoles fault, although it is believed that the Bijagual faultsystem also contribute to the rupture process. These are transcurrent faults trending NE to N, that belong to adeformation zone located between the Caribbean plate and the Panamá microplate. For this reason, the March4, 1924 earthquake is considered an interplate event related to the incipient limit between those tectonic plates.