The seismically active Italian Apennine Mountains have experienced many devastating earthquakes, such as the 2009 L’Aquila earthquake. Many years of field observations, GPS and satellite remote sensing have produced a detailed map of slip of earthquake faults and of crustal strain.
In order to understand possible discrepancies between short-term and long-term rates of strain accumulation and how these relate to seismic hazard, it is important to understand (1) how strain accumulates with distance away from the active faults and within different rock types and, (2) how strain accumulation rates change between earthquakes.
In fracture mechanics terms, earthquake rupture occurs when the imposed stress intensity exceeds the local resistance to shear rupture propagation in the crust. The amount of coseismic slip that occurs will be dependent on the strain deficit that has accumulated on the fault and the 3D geometry of the fault. Strain is a key fracture mechanics scaling parameter.