Exploratory models of long-term crustal flow and resulting seismicity across the Alpine-Aegean orogen

Abstract

[1] Long-term crustal flow is computed with a kinematic finite element model based on iterated weighted least squares fits to data and prior constraints. Data include 773 fault traces, 106 fault offset rates, 510 geodetic velocities, 2566 principal stress azimuths, and velocity boundary conditions representing the rigid parts of the Eurasia, Africa, and Anatolia plates. Model predictions include long-term velocities, fault slip rates, and distributed permanent strain rates between faults. One model assumes that geodetic velocities measured adjacent to the Aegean Trench reflect a temporarily locked subduction zone; in this case, long-term subduction velocity averages 45 mm/yr and rapid crustal extension is predicted in the southern Aegean Sea. Another model assumes steady creeping subduction; in this case, subduction velocity averages only 29 mm/yr, and the eastern Aegean Seafloor is predicted to be more nearly rigid. Long-term seismicity maps are computed for each model on the basis of the SHIFT hypotheses and previous global calibrations of plate boundary earthquake production. Retrospective comparisons to seismic catalogs are encouraging: map patterns, spatial distribution functions, and total earthquake counts are all comparable. While neither model accurately predicts earthquake rates at all magnitudes, the creeping subduction model is more accurate for strong m6+ events, which dominate the seismic hazard.