The Corinthian Gulf (Greece) strong-motion databank

Abstract

Since 1991 when a strong motion monitoring network comprising eight SSAl-type digital accelerographs was installed across the western Corinthian Gulf, a rich dataset of records has been achieved. Up-to-now this dataset consists of 580 3-component accelerograms obtained from 140 events which occurred within the Corinthian Gulf with epicentral distances ranging from 1 to 100 km and with maximum horizontal peak acceleration values from 2 to 225 milli-g and magnitudes from 2.0 to 6.0 R. After preliminary inspection and scrutinization of the raw data, (i.e. uncorrected traces from the stations for each event along with the corresponding parameters, such as station and event location, instrument characteristics and settings, magnitude, etc.), the corrected waveforms with their spectral values, were then inserted into the Databank. This has been continuously upgraded as new records from events of the area become available. In the present work, the content of the databank is described and the capabilities offered are illustrated through specific applications. Thus, the variation of attenuation in different frequencies was studied using the 35 best recorded and located events in the area. The significant variations between north and south station attenuation laws calculated, show the importance of taking into account the local conditions. In studying the effect of local geological formations on the amplification of strong ground motion, it was found that the influence of the different soil conditions is apparent. The spectral amplitudes of Lakka station (alluvium) are on the average in the order of a magnitude higher than those of the north stations (rock) especially in the low and high frequency bands. Finally, the waveforms of small magnitude events are used as empirical Green’s functions in simulating future strong motions in the area. The successful simulation of the largest recorded events, points out once more the usefulness of such a databank in local and regional seismic hazard studies.