High-Resolution Seismic Profiling in the Hanging Wall of the Southern Fault Section Ruptured During the 2016 M_w 6.5 Central Italy Earthquake

摘要

The Vettore-Bove normal fault system in central Italy ruptured during the 2016 M-W 6.5 Norcia earthquake causing extensive surface faulting. At the Pian Grande di Castelluccio hanging wall basin, along the southern section of the fault ruptured during the M-W 6.5 mainshock, we performed a high-resolution seismic reflection/refraction experiment aimed at (a) imaging the shallow pattern of the fault system, and (b) reconstructing the architecture of the continental infill. We collected three profiles for a total length of similar to 8 km. We used a reflection processing flow and non-linear refraction tomography to obtain migrated stack sections and P-wave velocity images resolved down to the depth of the pre-Quaternary substratum. The main profile in the northern part of the basin crosses the westernmost splays of the ruptured fault zone striking N150 degrees-170 degrees. Seismic imaging unravels a similar to 1 km-wide fault zone comprising three W-throwing splays and subsidiary faults, which affect the continental infill and produce a minimum aggregate Quaternary throw of similar to 400 +/- 100 m. Recent deformation is localized in this part of the surveyed fault section, attesting active displacement accumulation of the Vettore-Bove fault system. The other profiles in the central-southern part of the basin show additional faults, likely striking N20 degrees-40 degrees and which concurred to generate a similar to 500 m-deep depocenter. These faults were mostly active during an early extensional phase; however, one of them likely displaces shallow layers with a throw close to the resolution limit of seismic data (10 m), suggesting activity in the Late Pleistocene.