Abstract

The JMA intensity was calculated for all the important events that the Earthquake Engineering Laboratory (LIS) has recorded since 1990. First, a pre-selection was made taking into account only events that had been recorded in more than 5 sites. Every record was plotted and revised by visual inspection in order to rule out those with high noise level or poor waveform quality. A frequency domain filter was applied to each component, then in the time domain the vectorial summation was computed and data was sorted out in descending order. The amplitude at which the cummulative amplitude reached a value of 0.3s was taken to compute the JMA intensity. The results are shown in the form of graphs that relate the value of JMA to the maximum acceleration and in the form of maps showing the spatial distribution of intensities.

Abstract

Synthetic strong motion records for the 1991, Mw 7.6, Limón, Cosa Rica earthquake were computed for several hundred different source models. The rotd50 (response spectra) was used to compare synthetic and observed data at seven stations that recorded the event. The source model that minimized the misfit was selected to calculate new synthetic records at present-day stations. The result indicated that the fault length reached some 100 km long by 40 km deep. The largest peak ground acceleration would have been recorded in the stations located along the Caribbean coast, close to the epicenter. A post-earthquake bridge inspection calculation using our scenario earthquake predicted a high level of damage to several bridges that collapsed in 1991.