Chuanyou Li’s research while affiliated with Institute of Geology, China Earthquake Administration and other places

On February 6, 2023, southeastern Türkiye experienced a devastating earthquake doublet along the East Anatolian Fault (EAF), with moment magnitude (MW) values of 7.8 and 7.5. These strong earthquakes resulted in at least 50,000 deaths and severe economic losses. Systematic research on coseismic surface ruptures induced by these events is vital for assessing the cascade rupture behaviors of plate boundary faults and future seismic hazards in the region. Interpretation of high-resolution post-earthquake satellite images and field investigations yielded the following results: (1) the two strong earthquakes had separate rupture zones. The first earthquake generated an approximately 280 km coseismic surface rupture along the southwestern segment of the main EAF, with 241 left-lateral displacements reaching up to 6.8±0.68 m, particularly 40 km northeast of the epicenter. The second earthquake produced a roughly 110 km surface rupture on an east-west branch of the EAF, with maximum displacements of 7.2±0.72 m. (2) The MW7.8 earthquake resulted in a cascading rupture across multiple segments of the southwestern section of the main EAF, with significantly variable displacements. The northeastern and southwestern parts of the main EAF and Malatya Fault remain at risk of strong earthquakes in the future. (3) The EAF rupture zone is densely populated, and due to the site amplification effect of loose sediments on foreland alluvial fans, foundation failures of buildings in the populated areas are common. Therefore, it is crucial to enhance the future seismic fortification capabilities in urban and rural areas along the EAF.

2023年2月6日土耳其东南部的东安纳托利亚断裂先后发生MW 7.8和MW 7.5双强震, 造成了至少5万人死亡及严重的经济损失, 开展双强震地表破裂的系统研究对了解板块边界断裂的级联破裂及区域未来强震危险性有重要意义. 基于震后高分辨率卫星影像系统的解译和应急科学考察, 本文得到如下结果: (1) 两次强震具有各自独立的破裂带, 第一次强震沿东安纳托利亚断裂西南段产生约280km主地表破裂带, 沿主破裂带获得241个地表位错, 其中震中东北40km处出现最大地表位错值(6.8±0.68)m; 第二次主震沿东安纳托利亚断裂北西侧的近东西向的分支断裂产生约110km主地表破裂带, 最大地表位错值(7.2±0.72)m. (2) 第一次主震导致东安纳托利亚断裂西南段多个断裂段的级联破裂, 各破裂段的平均地表位错量/最大地表位错量差异较大, 未来东安纳托利亚断裂东北部和西南部的部分断层段以及马拉蒂亚断裂仍存在强震发生的风险. (3) 此次东安纳托利亚断裂破裂带沿线分布着密集的居民点, 由于松散沉积的山前洪积扇的场地放大效应, 居民点建筑物的地基失效现象普遍存在, 未来需要重视提升东安纳托利亚断裂沿线城市及乡村的抗震设防能力.

Obvious macroscopic anomalies of geothermal fluids were observed before and after the Mw 7.8 earthquake in Turkey. In order to find out the relationship between geothermal fluid anomalies and earthquakes, we performed a systematic hydrogeochemistry and isotopic analysis of the geothermal fluids in the East Anatolian Fault Zone (EAFZ). The results show that these geothermal fluids were reconstructed (including: energy and materials) by earthquakes. Based on chlorine – enthalpy model, the temperature of the deep geothermal fluid has been increasing to 382 °C on the strength of the energy released by the seismic activity. However, the information of the deep geothermal fluid was eventually covered due to the infiltration of a large amount of shallow cold water after the earthquake. The abnormal concentrations of Ca2+ (54.04~501.58 mg/L), Mg2+ (6.58~116.20 mg/L), SO42– (6.37~287.74 mg/L), Sr (34.78~3244.8 μg/L), and Ba (1.89~196.48 μg/L) in geothermal water shown that the geothermal water has undergone complex water-rock interaction processes such as gypsum, calcite, dolomite, anorthite and serpentinization. Specially, significant gypsum dissolution was observed at HS05, HS09 and HS14 before and after the earthquake, suggesting that the earthquake broke the balance of water-rock reaction and promoted the dissolution of gypsum. Combined with geological background and previous studies, we propose that shallow sedimentary minerals, such as gypsum, have the potential to be used as earthquake warning indicators. However, shallow minerals are controlled by many external factors (e.g., temperature, pressure, climatic conditions, seasonal changes etc.), which greatly weakens their practical value in earthquake early warning.

The Nihewan Basin, renowned for the numerous world-class Paleolithic sites and diverse mammalian fauna preserved in its sedimentary sequence, is a key area for studying early human evolution in East Asia. Despite extensive studies on the fluvial-lacustrine basin sediments, the evolution and formation process and mechanism of the Nihewan Basin and Nihewan Paleolake remain unclear. Here we assess the spatial pattern and recent history of rock uplift of the Liuleng Shan, one of the main bedrock mountain ranges encompassing the Nihewan Basin, using river profile and topographic analysis. The transient topography of the Liuleng Shan is characterized by two generations of elevated non-lithological slope-break knickpoints that delimit the uplifted Dianziliang and Tangxian relict landscape surfaces, suggesting two episodes of accelerated rock uplift during the Cenozoic. We link the first phase of rapid rock uplift to the initiation of the central and northeastern portions of the North Liuleng Shan Fault (NLSF) during the opening of the Shanxi Graben System in the Late Miocene, implying the initiation of the Nihewan Basin at this time. We propose that the dextral transtensional southwestern portion of the NLSF formed and propagated northeastward at around 4.2 Ma, and was responsible for the second phase of surface uplift. This phase of deformation also terminated the Tangxian planation process and led to the further subsidence of the Nihewan Basin. Accordingly, drainage rearrangement and fault activity hydrologically closed the Nihewan Basin, resulting in the development of the Nihewan Paleolake. Our findings outline a timeline for the geomorphic evolution of the Nihewan Basin and Nihewan Paleolake, highlighting the dominant role of tectonics in their formation.

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.