Multiple Mw≥6.5 Strong-Major Paleoearthquakes Occurred Before the 2017 Mw 6.3 Jinghe Earthquake: Evidence from Trenching the Jinghenan Fault

Abstract

AbstractPartial fault segment rupture may increase local earthquake hazards. To verify whether a strong earthquake will occur after the lower ramp rupture 2017 v6.3 Jinghe earthquake, we excavated a trench at the east segment of the fault near the Xiatianji reservoir. Integrating the trench wall interpretation and stratigraphic optically stimulated luminescence (OSL) ages, we constrain four paleoearthquakes. They are named E1–E4 from the oldest to the youngest and occurred at 29.8 ± 3.0, 22.4 ± 1.9, 14.7 ± 1.9, and after 11.6 ± 0.9 ka B.P., respectively. The average recurrence interval between E1, E2, and E3 is 7.3 ± 0.7 ka B.P. This recurrence interval may have exceeded the elapsed time since the most recent surface rupturing earthquake. The overlap between the last event and the average recurrence interval may indicate that the time since the most recent event reaches the recurrence interval, and a major earthquake (7 < M < 8) may yet occur after the 2017 Jinghe event. Most historical and instrumental major great earthquakes occurred on higher slip rate faults at the northern and southern piedmont of Tian Shan. The low slip rate thrusts within the Tian Shan also have the potential to generate major earthquakes.