Abstract

An Mw 5.9 thrust earthquake occurred on 21 January 2016 in the northeastern Tibetan plateau, where another similar earthquake had ruptured in 1986. Because of the complexity and close proximity of multiple faults in this area, the exact causative fault sources for these two events have not previously been determined. We determined the seismogenic fault structural geometry of the 2016 event by analyzing the coseismic deformation from Sentinel‐1A images, aftershock relocations, and geological data. Furthermore, field investigations and the relocated aftershocks for the 1986 event were used to investigate its seismogenic fault and relation with the 2016 Menyuan earthquake. The results indicate that the reverse slip of both events was distributed on the southwest‐dipping Minyue‐Damaying fault, where the 2016 event ruptured the deep segment and the 1986 event ruptured the shallow segment. We envision that the depth segmentation played an important role in the occurrence of two moderate earthquakes rupturing the same active fault but separated by almost 30 yr, which is thought much shorter than the average earthquake recurrence cycle. Our study indicates that seismic risks could be underestimated if depth segmentation is not considered.

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