Rupture Kinematics and Coseismic Slip Model of the 2021 Mw 7.3 Maduo (China) Earthquake: Implications for the Seismic Hazard of the Kunlun Fault

Abstract

The 21 May 2021 Maduo earthquake was the largest event to occur on a secondary fault in the interior of the active Bayanhar block on the north-central Tibetan plateau in the last twenty years. A detailed kinematic study of the Maduo earthquake helps us to better understand the seismogenic environments of the secondary faults within the block, and its relationship with the block-bounding faults. In this study, firstly, SAR images are used to obtain the coseismic deformation fields. Secondly, we use a strain model-based method and steepest descent method (SDM) to resolve the three-dimensional displacement components and to invert the coseismic slip distribution constrained by coseismic displacement fields, respectively. The three-dimensional displacement fields reveal a dominant left-lateral strike-slip motion, local horizontal displacement variations and widely distributed near-fault subsidence/uplift deformation. We prefer a five-segment fault slip model, with well constrained fault geometry featuring different dip angles and striking, constrained by InSAR observations. The peak coseismic slip is estimated to be ~5 m near longitude 98.9°E at a depth of ~4–7 km. Overall, the distribution of the coseismic slip on the fault is highly correlated to the measured surface displacement offsets along the entire rupture. We observe the moderate shallow slip deficit and limited afterslip deformation following the Maduo earthquake, it may indicate the effects of off-fault deformation during the earthquake and stable interseismic creep on the fault. The occurrence of the Maduo earthquake on a subsidiary fault updates the importance and the traditional estimate of the seismic hazards for the Kunlun fault.

Coseismic Slip Model of the 2021 Maduo Earthquake, China from Sentinel-1 InSAR Observation

“…It is not clear which model is correct. Secondly, the details of the coseismic slip distribution differ between previous studies [15,16] though the general features of the coseismic slip models are similar. Reference [15] found the peak coseismic slip is 6 m and [16] found the peak slip to be 5 m. Thirdly, previous work has not compared the coseismic slip models with surface offset data from geological investigations.…”

“…Interferometric synthetic aperture radar (InSAR) on board satellites can image the surface deformation from earthquakes [14]. The Maduo earthquake has been well imaged by multiple satellites, e.g., Sentinel-1 and ALOS-2 [15][16][17]. Although the Maduo earthquake has been well studied by several research groups [15][16][17], there are still some questions that remain to be addressed.…”

“…The Maduo earthquake has been well imaged by multiple satellites, e.g., Sentinel-1 and ALOS-2 [15][16][17]. Although the Maduo earthquake has been well studied by several research groups [15][16][17], there are still some questions that remain to be addressed. Firstly, there is a discrepancy in the fault geometry from previous work.…”

“…Firstly, there is a discrepancy in the fault geometry from previous work. Reference [15] prefers a vertically-dipping fault while [16] favors a model with northward dipping fault. It is not clear which model is correct.…”

Earthquake Magnitude Estimation from High-Rate GNSS Data: A Case Study of the 2021 Mw 7.3 Maduo Earthquake

“…The epicenter was located at (98.34 • E, 34.59 • N) and had a focal depth of 17 km (Figure 1). Field investigations immediately after the event [1,2], and Interferometric Synthetic Aperture Radar (InSAR) observation obtained within a few days after the main shock [3][4][5] confirmed that the seismogenic fault of the Maduo earthquake was the Kunlunshankou-Jiangcuo Fault, a secondary fault ~70-80 km to the south of the East Kunlun Fault within the Bayan Har block. This unexpected earthquake was the largest earthquake to have occurred in China since the 2008 Mw 7.9 Wenchuan earthquake [6][7][8], challenging the conventional perspective that the Bayan Har block acts as a quasi-stable block.…”