2D-3D GPR as an efficient tool for paleoseismology: A successful case history across the Castrovillari fault (southern Apennines, Italy)

The localization and characterization of active faults is an essential key to improve the definition of the potential seismological hazard of a region. Paleoseismological surveys usually bases on trenches to detect shallow faulting events generated by strong Quaternary earthquakes. It is well-known that the realization of paleoseismological trenches can be expensive and often logistically complicated, moreover can reach only limitated depths, preventing the possibility to achieve global information. Therefore it is really strategic to understand if the site chosen for the excavation is suitable to efficiently intercept the fault strands, and if these are representative at regional scale. In this work, we realized a 2D/3D GPR and Global Navigation Satellite System (GNSS) surveys on the NNW-SSE Castrovillari fault (Calabrian region, Southern Italy) in order to detect and image shallow faults in a not invasive way. This geophysical study, supported by orthophoto interpretation and geological surveys, has been realized in collaboration with a paleo-seismological group. The main purpose of the study was to efficiently “guide” further trenching by localize the fault zone and defining accurate qualitative/quantitative faults characteristics, otherwise not achievable with other methods. By using advanced interpretation techniques like horizon/fault tracking and attribute analysis, we have located and defined the characteristics of a fault in three dimensions and detected a possible unknown fault strand within 2D dataset. Extending in depth the geological surface information, we provided useful geo-referenced data for an effective ground truth, revealing a good matching between the field geological structures and the geophysical interpretation.