Scaling of Maximum Observed Magnitudes with Geometrical and Stress Properties of Strike-Slip Faults

Abstract:

Providing constraints for maximum magnitude earthquake on major continental strike-slip faults is important for seismic hazard estimates of populated areas near these faults. We test potential scaling of observed maximum earthquake magnitudes along thirty strike-slip fault sections worldwide with various properties including cumulative displacement, mapped fault length, seismogenic thickness and angle between fault strike and maximum horizontal shear stress. For 70-80% of the total dataset associated generally with interplate events, the maximum magnitude scales logarithmically with the seismogenic thickness times either cumulative displacement or mapped fault length. Most faults in this population have slip rate > 5mm/yr, cumulative displacement >10 km and relatively high angles to the maximum compressive stress direction. The remaining 20-30% dataset involves events at some distance from a plate boundary proper on faults with slip rate < 5mm/yr, cumulative displacements <10 km and 40-45° to the maximum horizontal stress. These earthquakes have larger magnitudes than expected from the scaling relations of the previous population, likely because of larger stress drops and rupture of multiple fault segments.