See more from this Division: Topical Sessions
See more from this Session: Reconciling Geologic and Geodetic Rates of Deformation
Monday, 6 October 2008: 4:10 PM
George R. Brown Convention Center, 332CF
Abstract:
In order to study the existence of possible deficits or surpluses of geodetic and earthquake strain in the Lazio-Abruzzo region of the central Apennines compared to 15±3kyrs multi seismic cycle strain-rates, horizontal strain-rates are calculated in 5km×5km and 20km×20km grid squares using slip-vectors from striated faults and offsets of Late Pleistocene-Holocene landforms and sediments. Strain-rates calculated over 15±3kyrs within 5km×5km grid squares vary from zero up to 2.34±0.54×10-7yr-1 and resolve variations in strain orientations and magnitudes along the strike of individual faults. Strain-rates over a time period of 15±3kyrs from 5km×5km grid squares integrated over an area of 80km×160km show the horizontal strain-rate of the central Apennines is 1.22×10-8yr-1(error +0.1×10-8yr-1 -0.05×10-8yr-1) and -2.94×10-10yr-1(error +3.90×10-10yr-1 -4.55×10-10yr-1) parallel and perpendicular to the regional principal strain direction (42o±1o), associated with extension rates of ≤ 3.2mmyr-1(error +0.8mmyr-1 -0.4mmyr-1) if calculated in 5km×80km boxes crossing the strike of the central Apennines. These strain-rates are comparable in direction to strain-rates calculated using GPS (over 126yrs, 11yrs and 5yrs) and seismic moment summation (over 700yrs), however the magnitude is about 2.4× less over a comparable area. 102yr strain rates are higher than 104yr strain-rates in some smaller areas (≈ 2000km2, corresponding to polygons defined by GPS campaigns and seismic moment summations) with the opposite situation in other areas where seismic moment release rates in large (> Ms 6.0) magnitude historical earthquakes are as low as zero. This demonstrates the importance of comparing the exact same areas and that strain-rates vary spatially on the length scale of individual faults AND on a timescale between 102yr and 104yr in the central Apennines. We use these results to produce a fault specific earthquake recurrence interval map and discuss the regional deformation related to plate boundary and sub-crustal forces, temporal earthquake clustering and the natural variability of the seismic cycle.
See more from this Division: Topical Sessions
See more from this Session: Reconciling Geologic and Geodetic Rates of Deformation