Zoning Surface Rupture Hazard along Normal Faults: Insight from the 2009 Mw 6.3 L'Aquila, Central Italy, Earthquake and Other Global Earthquakes

Abstract

Following the observation of surface faulting in populated areas affected by the 2009 M w 6.3 L’Aquila earthquake (central Apennines of Italy), we propose general criteria for delineating zones of surface fault‐rupture hazard (SFRH) along active normal faults. Similar to other countries with surface faulting hazard, Italy does not have explicit and comprehensive codes and/or regulations concerning this important issue. Our proposal, which is explicitly inspired by the California Alquist–Priolo Earthquake Fault Zoning Act (A–P), compares the 2009 coseismic surface faults to surface rupture data collected globally for several normal‐faulting earthquakes. We propose earthquake fault zones and fault setbacks, which are asymmetrically shaped around the fault trace. The zones are wider on the hanging wall, consistent with the observation of wider coseismic rupture zones in the hanging wall block compared to the footwall block. For faults mapped in detail, we suggest a 150‐m‐wide earthquake fault zone (EFZ) on the hanging wall and a 30‐m‐wide EFZ on the footwall. The suggested widths of the fault setback (S) on the hanging wall and footwall are 40 m and 15 m, respectively. Considering the data collected for the L’Aquila fault system and abroad, we are confident that our proposal is conservative enough for Apennine‐like normal faults.