DEPTH-DEPENDENT SEISMIC ATTENUATION IN THE GRANADA ZONE (SOUTHERN SPAIN)

Coda-Q estimates for the Granada Basin (Southern Spain) are obtained by analyzing earthquakes occurring within or close to the borders of this area. The data set is composed of 54 earthquakes with local magnitudes ranging between 2.2 and 4.0 and with epicentral distances to the nearest station smaller than 10 km. A single-scattering process is assumed. Coda-Q values obtained show a clear dependence on frequency according to the relationship Q = Qof", where n ranges from 0.81 to 0.89. After removing the main site effects and discussing the possible multiple-scattering influence, the lapse-time dependence is interpreted as due to attenuation variations with depth. This result agrees with the variation of coda Q obtained by using different sets of events with increasing hypocentral depth ranges.