Resolving co- and early post-seismic slip variations of the 2021 MW 7.4 Maduo earthquake in east Bayan Har block with a block-wide distributed deformation mode from satellite synthetic aperture radar data

Abstract

On 21 May 2021 (UTC), an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau. The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake and in proximity to the seismic gaps on the east Kunlun fault. Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake. Rang offset displacements depict clear surface ruptures with a total length of ~170 km involving two possible activated fault segments in the earthquake. Coseismic modeling results indicate that the earthquake is dominated by left-lateral strike-slip motions of up to 7 m within top 12 km of the crust. The well-resolved slip variations are characterized by five major slip patches along strike and 64% of shallow slip deficit, suggesting a young seismogenic structure. Spatial-temporal changes of postseismic deformation are mapped from the early 6day and 24-day InSAR observations, and are well explained by time-dependent afterslip models. Analysis of GPS velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block, but showing significant lateral heterogeneities as evidenced by magnetotelluric observations. The block-wide distributed deformation of the east Bayan Har block along with the significant co-and post-seismic stress loading from the Maduo earthquake imply high seismic risks on regional faults, especially the Tuosuo Lake and Maqin-Maqu segments of the Kunlun fault that known as seismic gaps.

Stress Evolution Before and After the 2021 Mw 7.3 Maduo Earthquake in Northeastern Tibet and Its Influence on Seismic Hazards

“…Thus, the ΔCFS increase of 9 kPa in the Maqin-Maqu seismic gap was equivalent to tectonic loading for approximately 18-45 years. By calculating the stress change induced by the 2021 Maduo earthquake, we propose that future seismic hazards in the Maqin-Maqu seismic gap increased after 2021, which is consistent with the proposals of previous studies (He, Feng, et al, 2021;He, Wen, et al, 2021;Huang et al, 2021;Wang, Song, et al, 2021;Zhu et al, 2021). This finding helps explain the Mw 4.7 earthquake on 22 May 2021 (the day of the 2021 Maduo earthquake), which occurred in the center of the Maqin-Maqu seismic gap (Figure 6).…”

“…Additionally, as no major earthquakes (M > 6.5) have occurred on these two faults during the past 300 years according to historical earthquake data (https://data.earthquake.cn), attention should be paid to the increased hazards of these two faults. Aftershocks following the 2021 Maduo earthquake located in this stress increase zone B (Figure 6) (Wang, Fang, et al, 2021), indicating an overlap between these aftershocks and the bifurcation rupture segment connected to the main fault rupture of the 2021 Maduo earthquake, according to previous fault rupture modeling results (Chen et al, 2021;He, Feng, et al, 2021;He, Wen, et al, 2021;Jin & Fialko, 2021;Pan et al, 2021;Wang, Song, et al, 2021;.…”

“…The NWW‐trending KPJF extends around 370 km from east to west, where it connects to the Eastern Kunlun fault (EKLF) by the Kunlun Pass fault unzipped by the 2001 Mw 7.8 Kokoxili earthquake (Deng et al., 2007). Previous field investigations, aftershock relocation, and fault rupture modeling suggest that the 2021 Maduo earthquake ruptured approximately 170 km east of the KPJF (Chen et al., 2021; He, Feng, et al., 2021; He, Wen, et al., 2021; Pan et al., 2021; Jin & Fialko, 2021; USGS‐2; Wang, Song, et al., 2021; Wang, Wang, et al., 2021; Zhao, Chen, et al., 2021). Thus, a seismic gap of more than 200 km was left to the west of the KPJF, and the seismic hazards of the seismic gap are worth investigating (Wang, Wang, et al., 2021).…”

“…; USGS-2; Wang, Song, et al, 2021;. Thus, a seismic gap of more than 200 km was left to the west of the KPJF, and the seismic hazards of the seismic gap are worth investigating .…”

Simultaneous Rupture Propagation Through Fault Bifurcation of the 2021 Mw7.4 Maduo Earthquake

“…The earthquake was well-recorded in space geodetic images (He et al, 2022;J Liu et al, 2022) and nearby static (M. and high-rate Global Positional System (GPS) offsets (Gao et al, 2021). Earlier reports of the earthquake show that this was a bilateral rupture, which propagated ∼80 km to both sides of the epicenter (He et al, 2022;Ren et al, 2022;S. Wang, Song, et al, 2022).…”