Magnetotelluric investigation in a seismogenic source area: Evidences from the 1930 Irpinia earthquake area

Abstract

On 23 July 1930, the Irpinia region in southern Italy experienced a destructive (M 6.7) earthquake that struck the eastern sector of the southern Apennines moutain belt. Previous studies suggest that this earthquake was caused by a seismogenic source having oblique right-lateral kinematics and striking at an angle between the general trend of NE-verging large dip-slip faults in the southern Apennines (~ NW-SE) and the E-W near-vertical, strike-slip right lateral faults that have been recently discovered in the foreland, east of the main extensional axis. Also, the ~14 km hypocentral depth of the 1930 earthquake that has been calculated in previous studies is likely located within the basement below the Apula carbonate platform succession. This puts the source of the 1930 earthquake not only in an intermediate region between pure normal (NW-SE) and strike-slip right-lateral (E-W) large seismogenic faults in the southern Apennines, but also at an hypocentral depth between the 12-13 km depth of the earthquakes caused by normal faulting (like the Irpinia 23 Nov. 1980, M 6.9 one) and the 15-20 km depth of the earthquakes caused by strike-slip faulting in the foreland (like the 31 Oct.-1 Nov. 2002, M 5.8 Molise ones). In this framework, we performed a magnetotelluric (MT) study to investigate the evidence of preferential direction in resistivity anisotropy and to compare it with the strike of the 1930 seismogenic fault.