Fault scaling relationships, deformation rates and seismic hazards: an example from the Lazio Abruzzo Apennines, central Italy
Spatial variations in the number of seismic shaking events in a given time period (frequency) implied by measured throw-rates associated with active normal faults in central Italy are investigated through comparison with models of fault growth and the historical record of earthquake shaking for the region. Measured offsets of 18 ka glacial features provide a throw-rate database averaged over a time period much longer than the reliable portion of the historical earthquake record for the region (<ca. 1 ka). Throw-rates are greatest in the centre of the studied fault array and show a six-fold decrease from central to distal faults, implying spatial variations in the frequency of seismic shaking events. We attempt to validate these observations by comparing them with throw-rates predicted by a calculation that takes into account the growth patterns of normal fault systems that exhibit well-known scaling relationships between fault length and throw. We also convert the measured throw-rates into a map of implied frequency of seismic shaking events and attempt to validate the map by comparing it with the probably complete records of seismic shaking since 1349 A.D. that exist for 14 towns in the region. Our results confirm that the throw-rate database is compatible with both the record of historical seismic shaking and what we know about the growth of normal faults. The results imply that knowledge of fault scaling parameters and geological determined deformation rates are valuable tools in seismic hazard assessment.