Cascading rupture process of the 2021 Maduo, China earthquake revealed by the joint inversion of seismic and geodetic data

The 2021 Mw 7.4 Maduo earthquake occurred in the north-central Bayan Har block, which has been the most seismically active block of the Tibetan Plateau during recent decades. The Maduo earthquake provides an opportunity to study the rupture kinematics and seismogenic environment associated with subsidiary faults inside the block. We investigate the source rupture process of the Maduo earthquake by combining the seismological analyses and the joint inversion of geodetic and seismic data. We find that the source rupture propagates bilaterally on a splay fault geometry consisting of two steeply dipping segments. The slip distribution is dominated by sinistral slips and contains several asperities. The maximum slip is approximately 4.2 m, and the rupture duration is about 40 s. The spatiotemporal evolution of Coulomb failure stress (CFS) changes on the fault demonstrates the interactions of stress triggering between multiple asperities, indicating the cascading rupture process of the Maduo earthquake. Moreover, this event produces significant CFS increases on the subsidiary faults of the Bayan Har block, among which the Maduo-Gande and Tibet Dagou-Changmahe faults receive the largest stress loading. The occurrences of the 1947 Dari and 2021 Maduo earthquakes suggest that the seismic hazard of the subsidiary faults should not be neglected. Because the CFS on the Tuosuo Lake and Maqin-Maqu segments of the East Kunlun fault is also increased, the enhanced seismic hazard deserves further attention. In addition, the slip distribution illustrates that the source rupture is mainly concentrated in the brittle upper crust. We propose that the Maduo earthquake arises from the continuous loading on the internal fault of the Bayan Har block caused by the collision between the Eurasian and Indian plates, and the eastward extrusion of the middle-to-lower crustal flow facilitates the occurrence of this event. These factors constitute the seismogenic environment of the Maduo earthquake.