Estudi dels esdeveniments sísmics no identificats corresponents a una àrea propera al Baix Camp (Tarragona)

Abstract

The aim of this study is to locate and interpret several undetermined events that have been undetected by seismological agencies and have only been recorded at the seismic station VAN2. Since these events were only recorded at one station, their localization can only be determined by the “location method with only a single station”. Moreover, this study seeks to test the validity of this unusual method with respect to the traditional location method. These undetermined events occurred in the Baix Camp area that is characterized by a moderate seismic activity and Quaternary active faults. After selecting the events, they are processed and analyzed with numerical algorithms in “Matlab” language. These programs allow us to study the frequency content of the events and to determine the first arrivals of the P and S waves. Subsequently, the “location method with only a single station” was applied to locate the undetermined events using an appropriate wave speed crustal model for the study area. To ratify this method, some determined seismic events from the “seismic series of Ametlla de Mar” were used. These events were localized with the “location method with only a single station” and the results were compared with the previous localizations from seismological agencies. Eight seismic events were located and the localization of five further events from the “seismic series of Ametlla de Mar” was confirmed. These thirteen seismic events are associated with the faults of the study area. Moreover, two additional events were identified as man-made events. Given the similarity of the locations of the events obtained by the two methods we can conclude that the “location method with only a single station” is a reliable method.