The 2021 Mw 7.4 Madoi Earthquake: An Archetype Bilateral Slip‐Pulse Rupture Arrested at a Splay Fault. Issue 2 (19th January 2022)

• Record Type: Journal Article
• Authors: Chen, Kejie; Avouac, Jean‐Philippe; Geng, Jianghui; Liang, Cunren; Zhang, Zhenguo; Li, Zhicai; Zhang, Shengpeng
• Is Part Of: Geophysical research letters. Volume 49:Issue 2(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-19
• Subjects: Madoi Earthquake -- splay fault -- bilateral rupture -- high‐rate Global Navigation Satellite System (HR‐GNSS); Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2021GL095243
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We combine measurements of ground deformation from Synthetic Aperture Radar images, high‐rate Global Navigation Satellite System and tele‐seismic waveforms to study the rupture kinematics of the Madoi Earthquake, which occurred in eastern Tibet on 21 May 2021 and reached a moment magnitude M w 7.4. The data show nearly pure left‐lateral motion along a 170 km long rupture and a total duration of 36 s. The earthquake initiated near the middle of the main segment and evolved in a bilateral slip pulse rupture which propagated at a sub‐Rayleigh speed of 2.6–2.8 km/s. In our model, slip is concentrated at depth of less than ∼15 km and reaches a maximum of 4.2 m. The rupture arrested ∼10 s after branching on the extensional splay faults at both extremities. The branching onto the splay faults and the eventual arrest of the rupture is used to provide constraints on the fault frictional properties. Plain Language Summary: The M7.4 Madoi Earthquake, which occurred in eastern Tibet on 21 May 2021 is the largest event since the 2008, M8.0 Wenchuan earthquake. It therefore generated widespread interests among the Chinese public and scientific community. Here, we model the temporal evolution of fault slip during the earthquake using geodetic and seismic observations. Our study reveals a slip‐pulse that ruptured a 170 km long fault system, extending from the surface to about 15 km at depth, with horizontal shear slip of up to 4.2 m. The rupture initiated near the middle of the ruptured fault, propagated bi‐laterally along the fault trace, and ended after branching on splay‐faults. Forking seems to have arrested the rupture. The Madoi Earthquake relates to the eastward extrusion of Tibet which is driven by the northward indentation of India into Eurasia. Key Points: The 2021 M w 7.4 Madoi Earthquake ruptured bilaterally for about 170 km with most of slip being concentrated at less than 15 km depth The rupture was arrested after propagating on splay faults Propagation along the most misoriented splay fault suggests a dynamic friction possibly as low as 0.05