Application of SPAC and MASW Techniques to Earthquake-shaking Scenarios. The Case of the 1993-1994 Adra Earthquakes

Abstract

In Adra town during 1993 and 1994 small earthquakes took place with a magnitude of 5.0 (Mw). Despite these earthquakes were moderate, several buildings suffered damage. The local soil conditions influenced the characteristics of the earthquake-shaking scenarios. In fact, these scenarios played a key role about the type of buildings damages reported and their distribution. This study deals with the combination of Spatial Autocorrelation (SPAC) and Multichannel Analysis of Surface Waves (MASW) techniques to obtain the detailed surface shear-wave velocity (Vs) structure of the town. These seismic results have been applied to simulated earthquake ground motion scenarios, which are given in terms of peak ground acceleration (PGA), peak ground velocity (PGV), Arias intensity (AI), and peak ground acceleration (PGA) amplification factor maps. It was found that most of the damaged buildings fall into a transition area comprised between a region classified as EC8 Site Class B2 and another region classified as EC8 Site Class C where higher PGA, PGV, AI, and amplification factor values were found. Besides, the southeastern part of the town, which is the part of the town where is planned to grow, was classified as Site Class C which is prone to generate seismic amplifications.