Evaluating the coulomb static stress change and fault interaction in an extensional intra-volcanic arc: 1000 years of earthquake history in the Acambay Graben, Trans-Mexican Volcanic Belt

Abstract

One of the main challenges in slow slip-rate intra-continental fault systems is evaluating which fault could generate the next large earthquake. Therefore, it is crucial to characterize the spatiotemporal distribution of the seismicity and to understand the influence of moderate to large earthquakes on successive events. The Acambay Graben, in the central part of the Trans-Mexican Volcanic Belt, is an intra-continental normal fault system and the source of the 1912 Acambay earthquake (mb = 6.9) that ruptured mainly the Acambay-Tixmadejé fault as well as other fault segments of the graben. Paleoseismological studies have identified earlier events significant events produced by other graben faults, such as the Venta de Bravo Fault event occurred between 1026 and 1700 CE. In this study, we model the static Coulomb stress transfer related to the 1026–1700 and the 1912 CE events showing that the older event may have set the conditions to induce or accelerate the historical 1912 Acambay earthquake. In the same way, this last event could have triggered the Maravatío earthquake (February 22, 1979, Mw = 5.3). Furthermore, the cumulative variation of the Coulomb stress (Ev1 = 0.5–10 bar, Ev2 = 5–30 bar, Ev3 = 0.5–1 bar) corresponding to the three events reveals a spatial correlation between the areas that have experienced an increase in static stress with the regional distribution of the instrumental seismicity. The obtained results suggest that some active faults of the graben, which have accumulated static stress during the last 1000 years, are potential sources for the next fault rupture, i.e., faults that would need to be better studied and characterized. This information is of great importance to improve the seismic hazard assessment and risk estimations in the heavily populated Central Mexico region with more than 24 million people and better understand the fault interaction in slow slip-rate intra-continental fault systems.