Based on field investigations, interpretations of high‐resolution UAV images, and analyses of available InSAR data, we mapped the fault geometry and surface ruptures of the 2021 M_w 7.4 Maduo earthquake that occurred on a low‐activity strike‐slip fault within the Tibetan Plateau. The results indicate that (a) the earthquake activated a fault that is ∼161 km long and has complicated structural geometry; (b) the surface rupture occurs over a distance of 148 km, but is separated into three distinct segments by two large gaps (38 and 20 km, respectively); (c) within the surface‐rupture segments, the horizontal and vertical displacements are typically 0.2–2.6 m (much lower than the InSAR‐based slip maximum of 2–6 m at depth) and ≤0.4 m, respectively. The two large gaps of the Maduo surface rupture represent the two largest surface‐rupture discontinuities of strike‐slip earthquakes ever documented, and coincide with structurally complicated fault portions and near‐surface soft sediments.

The rupture patterns of large earthquakes in transpressional systems can provide important information for understanding oblique motion and strain partitioning between tectonic blocks. The 1927M8.0 Gulang earthquake occurred on the transpressional boundary between the Tibetan and Gobi‐Alashan blocks. Our results, combined with those of previous studies show that the Lenglongling fault (LLLF) and Southern Wuwei Basin fault (SWBF) have both ruptured during the Gulang earthquake, but they exhibited different motions. An ~120‐km‐long surface rupture zone formed along the LLLF, with a left‐lateral strike‐slip motion and a coseismic horizontal offset of ~2.4–7.5 m. Bending, bifurcation, and change of the slip sense occurs at both ends of the fault. An ~42‐km‐long rupture zone formed along the SWBF, with a coseismic vertical offset of ~0.6–2.8 m. Thus, the Gulang earthquake is a complex rupture event where strike‐slip and thrust faults ruptured simultaneously. Analysis of deep and shallow structures and three‐dimensional finite‐element modeling reveal that the north dipping LLLF and the SWBF may converge downward to a low‐angle décollement, accommodating the strike‐slip and thrust motions during the earthquake, respectively. This pattern of deformation partitioning is similar to some other earthquakes where oblique block convergence is generally partitioned into strike‐slip motion on steeply dipping faults and vertical motion on gently dipping faults. Our study also suggests that the strain partitioning pattern in the NE Tibetan Plateau may be controlled by changes of the regional principal compressive stress directions and fault geometry at depth.

The Lenglongling fault (LLLF) is located along the northeastern margin of the Tibetan Plateau and forms a part of the Tianzhu seismic gap along the Qilian‐Haiyuan fault zone. Little is known about the recurrence of large earthquakes along the LLLF nor the associated seismic hazards of the gap. Here the six most recent surface rupturing paleoearthquakes of the LLLF are revealed by measurement of offset landforms, trench excavations, and radiocarbon dating. They are labeled E1–E6 from youngest to oldest, and their timings are constrained to the following time ranges: 636–498 to present, 2951–1155, 4016–3609, 5325–4476, 7284–6690, and 8483–7989 years BP, respectively. The LLLF displays evidence of fresh, recent surface rupture, and the trench sections reveal that the fault ruptured to the ground surface during the most recent event. Based on this fresh surface rupture and historical earthquake records, the latest event E1 was most likely the 1927 M8.0 Gulang earthquake. In conjunction with previous studies, Gulang earthquake might be a complicated event characterized by the combined rupture of both strike‐slip and thrust faults. The average recurrence interval of the six paleoearthquakes is 1643 ± 568 years, and the coefficient of variation is 0.34, indicating that the LLLF follows a quasiperiodic recurrence model. Based on this new understanding of the last event, the LLLF may not be a part of the Tianzhu seismic gap. However, an earthquake of up to M_W7.6 could still rupture the gap sections composed of the Jinqianghe, Maomaoshan, and Laohushan faults.

The Xiaojiang fault zone (XJFZ) is an important part of the Xianshuihe-Xiaojiang fault system, acting as the eastern boundary of the Chuan-Dian block on the southeastern margin of the Tibetan Plateau and accommodating the lateral extrusion of the block. The faulting activity and paleoseismic history on the southern segment of the XJFZ remain poorly understood. Here, trench excavations and radiocarbon dating revealed that four recent surface-rupturing paleoearthquakes have occurred on the Jianshui fault (JSF) in the southern segment of the XJFZ since ~15370 yr BP. The ages of these events, labeled E4-E1 from oldest to youngest, are limited to the following time ranges: 15360-12755, 10845-6900, 1455-670, and 635-145 yr BP, respectively. The most recent event E1 was most likely the 1606 Jianshui earthquake. These events appear to occur unregularly in time. The time interval between the last two events is $726±235$ yr, and the average recurrence interval for all four events is $4589±3132$ yr. The deformed strata show that the JSF is characterized kinematically by transtension, which likely respond to the apparent change in the direction of clockwise rotation of the Chuan-Dian block around the eastern Himalayan syntaxis. Combined with the analysis of the neighboring NW-striking faults, our study suggests that the south-southeastward motion of the Chuan-Dian block is likely to be firstly accommodated in part by the right-lateral shear and dip-slip motions of the Qujiang and Shiping faults and continues across the Red River fault zone, then is transmitted southward along the Dien Bien Phu fault. Therefore, the southern segment of the XJFZ plays a dominant role in the tectonic deformation of the southeastern Chuan-Dian block, with a high seismic hazard.

On 8 January 2022, the $Mw$ 6.7 Menyuan earthquake occurred near the stepover of the Lenglongling (LLLF) and Tuolaishan (TLSF) faults of the Qilian–Haiyuan fault zone in the middle of the northeastern Tibetan plateau. Field investigations and unmanned aerial vehicle‐based photogrammetry revealed that the earthquake generated five surface rupture zones with different strikes and kinematic properties. Two large rupture zones, R1 (∼22.8 km long) and R2 (∼3.9 km long), occurred along the northern branch of the western LLLF and the eastern segment of TLSF, respectively, and featured left‐lateral strike slips. Among the three small rupture zones, the left‐lateral strike‐slip‐type R3 (0.6 km long) was located in the extension direction of R2, whereas the thrust‐type R4 (∼3.3 km long) and R5 (∼1.1 km long) zones were located north of the central section of R1. These complex multifault ruptures were caused mainly by the rupture of strike‐slip faults on both sides of the stepover structure. A small amount of compressive shortening strain was released during the earthquake due to regional oblique compression. The total length of the rupture zone was ∼31.7 km; the maximum left‐lateral and vertical offsets were 3.5 ± 0.3 and 0.47 ± 0.04 m, respectively. Compared with the relationship observed between coseismic slips and magnitudes in historical and modern earthquakes in western China, the 2022 Menyuan earthquake produced a large coseismic slip in relation to its magnitude. The distribution characteristics of the aftershock belts and their relationship with rupture zones showed that the seismogenic fault of the earthquake was nearly east–west‐striking TLSF, which may have triggered the rupture of the northern branch of the western LLLF. In addition, only a small segment of TLSF was ruptured, indicating that the accumulated strain could not be released completely during the earthquake and that this remains the most likely area for the occurrence of large earthquakes in the future.