Physics-Based Earthquake Simulations in Slow-Moving Faults: A Case Study From the Eastern Betic Shear Zone (SE Iberian Peninsula)

Abstract

In regions with slow-moving faults, the incompleteness of earthquake and fault data complicates the study of seismic hazard. The instrumental and historical seismic catalogs cover a short period compared with the long-time interval between major events. Paleoseismic evidence allows us to increase the time frame of actual observations, but data is still scarce and imprecise. Physics-based earthquake simulations overcome the limitations of actual earthquake catalogs and generate long-term synthetic seismicity. The RSQSim earthquake simulator used in our study reproduces the earthquake physical processes based on a 3D fault model that contains the kinematics, the long-term slip rates and the rate-and-state friction properties of the main seismogenic sources of a region. The application of earthquake simulations to the Eastern Betic Shear Zone, a slow fault system at southeastern Spain, allows the compilation of 100 kyr-synthetic catalogs of MW > 4.0 events. Multisection earthquakes and complete ruptures of some faults in this region, preferentially on strike-slip dominant ruptures, are possible according to our simulations. The largest MW > 6.5 events are likely as a result of jumping ruptures between the Carboneras and the Palomares faults, with recurrence times of < 20,000 years; and less frequently between the Alhama de Murcia and the Los Tollos faults. A great variability of interevent times is observed between successive synthetic seismic cycles, in addition to the occurrence of complex co-ruptures between faults. Consequently, the occurrence of larger earthquakes, even MW ≥ 7.0, cannot be ruled out, contrasting with the low to moderate magnitudes recorded in the instrumental and historical earthquake catalog.