Integrated vision of the shallow subsurface inactive deformation zone (Lorca, SE IberianPeninsula)

A multidisciplinary study unsing a number of different geophysical methodologies forcharacterizing the nature and structure of the shallow subsurface was carried out in an area of activedeformation located in (SE Iberian Peninsula). An approximately 400 km long network of prominentactive faults oriented NE-SW near parallel to the coast line constitute a singular tectonic feature thatcharacterize the southeastern part of the Iberian Peninsula. This transpressive tectonic corridor, knownas the Eastern Betics Shear Zone (EBSZ) is considered one of the longest and most active fault systemin the Iberia Peninsula. The EBSZ system is a strike slip plate boundary, which is accommodating theconvergence within Iberia of the interaction between the Nubian and Eurasian plates. The fault networkfeatures a reverse and left-lateral strike-slip kinematics with a characteristic sigmoidal trend delineatedby a number of major individual faults as well as other less relevant faults. Within and along thislocalized deformation corridor many destructive earthquakes with relative high intensities have affectedthis region since historical times The interdisciplinary geophysical datasets acquired place strongconstraints on the high-resolution structure of the well defi ned fracture system. The datasets reveal thethickness and properties of the critical zone (CZ) layer. The study includs: Electrical ResistivityTomography (ERT), fi rst arrival time seismic tomography, and multichannel analysis of surface waves(MASW). The combination of these three methods yields complementary benchmarks for mappingshallow subsurface fault zones and the physical properties of the CZ layer. The resulting model andinterpretation reveal new information on the relationship between the topographical slope and thethickness of the CZ layer related to the transport process and the accumulation of regolith alteration.The distribution of the CZ layer is characterized by layers with low P-wave & S-wave velocity anomalies(