Chuanyou Li

On 28 March 2025, a Mw 7.7 earthquake occurred on the Sagaing Fault in Myanmar. Security constraints prevented timely field investigations on its surface rupture, hindering analysis of seismotectonics and rupture dynamics. Using high‐resolution satellite imagery, we mapped a ∼420 km surface rupture and measured 540 dextral offsets, revealing an average slip of 2.7 m and a maximum of 5.6 m. The rupture consists of two sections separated by a low‐slip‐zone that aligns with the refined epicenter and a previously unmapped stepover, suggesting the earthquake most likely nucleated at this structure and then propagate bilaterally. The rupture extends beyond the known seismic gap and overlaps with some recent historical rupture, highlighting contrasting earthquake recurrence cycles along different fault sections. Our mapping provides essential documentation of an ultra‐long, multi‐segment rupture on a major continental strike‐slip fault under restricted field access, offering critical insights into the rupture behavior of similar faults worldwide.

Quantifying the slip rate along geometrically complex strike-slip faults is essential for understanding kinematics and strain partitioning in orogenic systems. The Karlik Tagh forms the easternmost terminus of Tian Shan and represents a critical restraining bend along the sinistral strike-slip Gobi-Tian Shan Fault System. The North Karlik Tagh Fault (NKTF) is an important fault demarcating the north boundary of the Karlik Tagh. While structurally significant, it is poorly understood in terms of its late Quaternary tectonic activity. In this study, we analyze the offset geomorphology based on interpretations of satellite imagery, field survey, and digital elevation models derived from structure-from-motion (SfM), and we provide the first quantitative constraints on the late-Quaternary slip rate using the abandonment age of deformed fan surfaces and river terraces constrained by the ¹⁰Be cosmogenic dating method. Our results reveal that the NKTF can be divided into the Yanchi and Xiamaya segments based on along-strike variations. The NW-striking Yanchi segment exhibits thrust faulting with a 0.07–0.09 mm/yr vertical slip, while the NE-NEE-striking Xiamaya segment displays left-lateral slip at 1.1–1.4 mm/yr since 180 ka. In easternmost Tian Shan, the interaction between thrust and sinistral strike-slip faults forms a transpressional regime. These left-lateral faults, together with those in the Gobi Altai, collectively facilitate eastward crustal escape in response to ongoing Indian indentation.

The present tectonic regime of the Qilian Shan is dominated by large northeast and northwest striking strike‐slip faults and northwest striking thrust faults. Deformation distribution between the subparallel Haiyuan Strike‐slip Fault and the Minle‐Damaying Thrust Fault (MDF) is crucial for understanding the orogenic mechanism of the northeastern Tibetan Plateau. However, the uncertain kinematics of the MDF and the stress variation along the strike‐varying Haiyuan Fault inhibit further discussion of their relationship. Five key sites along the MDF were selected for analysis of terrace abandonment ages and vertical offsets to determine the slip rates. Two finite element models were constructed to calculate the stress‐strain relationship between the Haiyuan Fault and MDF. We find that the activity of the MDF can be divided into two segments by a stepover with less activity and lower terrain at the Xida River site. Shortening rates of the MDF vary between 0.2 and 2.4 mm/a since the late Pleistocene with trapezoidal trends on both fault segments. The two finite element models and GPS data reveal that the strain rates are lower at the Xida River site but higher at the Menyuan Bend on the Haiyuan Fault. We infer that long‐term strain accumulation at the Menyuan Bend may have mitigated the tectonic activity northeast to the bend under the northeastward stress field, including the activity of the MDF at the Xida River site, and resulted in the segmentation of the MDF.

The Ganzi–Xianshuihe Fault Zone is a large-scale sinistral strike-slip fault zone on the eastern Tibet. As the boundary fault zone of the Bayankala Block and the Chuandian Block, it controls the clockwise rotation of the southeastern Tibet. However, there is still controversy regarding the activity changes between fault zones. Therefore, accurately determining the slip rates of faults in the area is crucial for characterizing regional plate motions and assessing associated seismic hazards. We focused on studying four fault segments near the Ganzi–Xianshuihe Fault Zone, including the Manigango, Ganzi, Luhuo, and Daofu segments. In each segment, we selected typical sinistral piercing points and carried out Unmanned Aerial Vehicle (UAV) photogrammetry to obtain high-resolution terrain data. We utilized LaDiCaoz_V2.2 and GlobalMapper software (LaDiCaoz_V2.2 and Global Mapper v17.0) to measure the offsets, together with optically stimulated luminescence (OSL) dating, to constrain the timing of fault activity. The estimated slip rates for the Manigango, Ganzi, Luhuo, and Daofu segments are as follows: 9.2 ± 0.75 mm/yr, 9.59 ± 1.7 mm/yr, 4.23 ± 0.66 mm/yr, and 7.69 ± 0.76 mm/yr, respectively. Integrating previous results with slip rates estimated in this study, our analysis suggests the slip rate of the Ganzi–Xianshuihe Fault Zone is around 8–10 mm/year, exhibiting a consistent slip rate from northwest to southeast. This reflects the overall coordination of the movement on the eastern Tibet, with the strike-slip fault zone only controlling the direction of movement.

The Tieluzi Fault is the largest structure in the East Qinling Mountains, and is considered to be the easternmost continuation of the Altyn Tagh‐Haiyuan‐Qinling Fault System (AHQFS) that allows the eastward extrusion of the Tibetan Plateau and South China Block. We studied the fault geometry and kinematics of the Tieluzi Fault using field investigations, detailed interpretations of high‐resolution satellite imagery and digital elevation models, and late Quaternary dating methods. Paleoseismic investigations indicate that the most recent earthquake along the Tieluzi Fault occurred before 1,500–1,300 cal. BP. Geological and geomorphological observations show that segments west of Lushi County are more active than those to the east. The spatial variations in tectonic activity along the Tieluzi Fault are interpreted to be related to four possible mechanisms: strike change, discontinuity, intersection, and branch. The late Quaternary left‐lateral slip rate is determined to be 0.9 ± 0.1 mm/yr on the Tieluzi Fault. The prominent left‐lateral faulting along the Tieluzi Fault suggests that most of the left‐lateral displacement along the eastern AHQFS has been accommodated by the Tieluzi Fault, which forms the most frontier of the eastward expansion of the Tibetan Plateau. Furthermore, we suggest that the left‐lateral faulting in the East Qinling Mountains is a response to relative eastward motion of the South China block pushed by the Tibetan Plateau with respect to the North China Plain Block. Also, our results indicate that the Tibetan Plateau has undergone a stepwise eastward expansion.

We investigate the present‐day strike‐slip faulting and intracontinental deformation of North China using horizontal GPS velocities and a block modeling strategy. The data demonstrate that the fault slip rates and block rotations in North China can be better constrained using GPS velocities where the influence of groundwater extraction has been reduced by applying median spatial filtering of the velocity field. The modeled senses of motion and slip rates on active faults are generally in good agreement with the geological estimates. The left‐lateral slip rate along the boundary fault of Weihe Graben is apparently lower than the differential motion between the South China Block and Ordos Block. The missing left‐lateral slip is accommodated by the counterclockwise rotation of the Ordos Block. The sinistral slip rate along the eastern segment of the Altyn Tagh‐Haiyuan‐Qinling fault system decreases eastward from ∼1.0 to ∼0 mm/yr, much slower than that expected in the fast eastward extrusion hypothesis. We interpret the systematic counterclockwise rotation of blocks and left/right‐lateral faulting in North China to be driven both by the left‐lateral shear between the South China Block to the south and Yinshan‐Yanshan Block to the north and a push from the Tibetan Plateau on the southwestern margin of the Ordos Block.

Studying the causative structure, extent, and magnitude of historical earthquakes is essential for regional seismic hazard assessment. There has been some debate in the literature regarding the epicenter, magnitude, and seismogenic source of the 1673 Tianzhen earthquake, one of the few documented strong earthquakes that occurred in northern Shanxi Graben, China. The Yanggao‐Tianzhen Fault (YTF) has long been recognized as a seismogenic fault; however, previous studies have suggested that the fault has not ruptured at the surface for several thousand years. In this work, we investigate fresh surface ruptures along the YTF based on field investigations, unmanned aerial vehicle photogrammetry, and ground‐penetrating radar surveys. Scarp formation at Yanjiabu is bracketed to the last 1.4 ± 0.6 kyr using optically stimulated luminescence dating. More importantly, we found that the Great Wall at Li'erkou (dated from 1546 CE) was likely faulted, which led us to conclude that the YTF is the causative fault of the 1673 event. Based on our measured fault parameters, the magnitude of the 1673 event was re‐estimated to Mw 6.8–7.2, suggesting that previous magnitudes were underestimated. Four trenches were excavated to investigate paleoearthquakes on the fault. Together with previous paleoseismic data, we suggest a bimodal rupture model in which the fault can produce multi‐segment rupturing events with large magnitudes, such as the 1673 event, and smaller partial or single‐segment rupturing events. Our results shed light on the reassessment of seismic hazards in the densely populated Yangao‐Tianzhen Basin and its nearby regions.

Editorial: Active faults and earthquake due to continental deformation

The Shanxi Graben System (SGS) is one of the first‐order Cenozoic tectonic features in North China. Understanding the kinematics of this tectonic system is crucial for deciphering the mechanism of continental rifting and the deformation pattern across North China. Although the SGS has long been thought to be a right‐lateral, transtensional shear zone, the geologic and geomorphologic evidence for dextral strike‐slip along its internal faults was slim and even controversial. Field investigations, interpretations of satellite imagery, and construction of decimeter‐scale digital elevation models from unmanned aerial vehicle surveys were used in this work to investigate the tectonic geomorphology of the eastern segment of the North Liulengshan Fault (NLSF) in the northern SGS. Although this fault segment was previously thought to be a pure normal fault, the presence of geomorphic features such as right‐laterally offset terrace risers and gullies, along with an analysis of fault‐slip data, suggests a component of right‐lateral strike‐slip displacement. Combined with optically stimulated luminescence dating of offset fluvial terraces, the late Quaternary right‐lateral strike‐slip and vertical slip rates of this fault segment are both estimated to be ∼0.2–0.3 mm/yr. The discovery of dextral strike‐slip along the NLSF provides compelling direct evidence for determining the dextral transtensional kinematics of the SGS. This puts new constraints on our knowledge that the evolution of the SGS is primarily driven by the outward expansion and growth of the Tibetan Plateau and supports the “bookshelf” rotation kinematic model for North China.