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GEOLOGICAL DISASTERS AND SURFACE RUPTURES OF JANUARY 23, 2024 MS7.1 WUSHI EARTHQUAKE, XINJIANG, CHINA
ZHANG Bo-xuan, QIAN Li, LI Tao, CHEN Jie, XU Jian-hong, YAO Yuan, FANG Li-hua, XIE Chao, CHEN Jian-bo, LIU Guan-shen, HU Zong-kai, YANG Wen-xin, ZHANG Jun-long, PANG Wei
SEISMOLOGY AND GEOLOGY    2024, 46 (1): 220-234.   DOI: 10.3969/j.issn.0253-4967.2024.01.013
Abstract1290)   HTML76)    PDF(pc) (14676KB)(810)       Save

The MS7.1 earthquake in Wushi, Xinjiang on January 23, 2024, represents the largest earthquake in the Tianshan seismic belt since the 1992 Suusamyr MS7.3 earthquake in Kyrgyzstan. Preliminary precise aftershock localization and initial field investigations indicate an NE-trending aftershock zone with a length of 62km that is concentrated at the mountain-basin transition area. This event produced geological hazards, including slope instability, rockfalls, rolling stones, and ground fissures, primarily within a 30-kilometer radius around the epicenter. The epicenter, located approximately 7 kilometers north of the precise positioning in this study, witnessed a rapid decrease in geological hazards such as collapses, with no discernible fresh activity observed on the steep fault scarp along the mountainfront. Consequently, it is inferred that the causative fault for this main shock may be an NW-dipping reverse fault, with potential rupture not reaching the surface.

Moreover, a surface rupture zone with a general trend of N60°E, extending approximately 2 kilometers, and displaying a maximum vertical offset of 1m, was identified on the western side of the micro-epicenter at the Qialemati River. This rupture zone predominantly follows the pre-existing fault scarp on higher geomorphic surfaces, indicating that it is not new. Its characteristics are mainly controlled by a southeast-dipping reverse fault, opposite in dip to the causative fault of the main shock. The scale of this 2-kilometer-long surface rupture zone is notably smaller than the aftershock zone of the Wushi MS7.1 earthquake. Further investigation is warranted to elucidate whether or not the MS5.7 aftershock and the relationship between the SE-dipping reverse fault responsible for the surface rupture and the NW-dipping causative fault of the main shock produced it.

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GEOLOGICAL HAZARD CHARACTERISTICS AND MACROSCOPIC EPICENTER OF NOVEMBER 25, 2016, ARKETAO, XINJIANG, MW6.6 EARTHQUAKE
YAO Yuan, CHEN Jie, LI Tao, FU Bo, WANG Hao-ran, LI Yue-hua, CHEN Jian-bo
SEISMOLOGY AND GEOLOGY    2018, 40 (2): 426-439.   DOI: 10.3969/j.issn.0253-4967.2018.02.010
Abstract722)      PDF(pc) (9829KB)(247)       Save
The MW6.6 Arketao earthquake occurred on November 25, 2016 in Muji Basin of the Kongur extensional system in the eastern Pamir. The region is the Pamir tectonic knot, one of the two structural knots where the India plate collides with the Eurasian plate. This region is one of the most active areas in mainland China. The seismogenic structure of the earthquake is preliminarily determined as the Muji dextral-slip fault which locates in the north of Kongur extensional system. Based on field surveys of seismic geological hazard, and combined with the characteristics of high altitude area and the focal mechanism solution, this paper summarizes the associated distribution and development characteristics of sandy soil liquefaction, ground fissures, collapse, and landslide. There are 2 macroscopic epicenters of the earthquake, that is, Weirima village and Bulake village. There are a lot of geological hazards distributed in the macroscopic epicenters. Sand liquefaction is mainly distributed in the south of Kalaarte River, and area of sand liquefaction is 1 000m2. The liquefaction material gushed along the mouth of springs and ground fissures, because of the frozen soil below the surface. More than 60% of soil liquefactions are formed in the mouth of springs. According to the trenching, these liquefactions occurred in 1.8 meters underground in the gray green silty clay and silty sand layers. The ground fissures are mainly caused by brittle failure, and the deformation of upper frozen soil layer is caused by the deformation of lower soil layer. The ground fissures at Weirima village are distributed in a chessboard-like pattern in the flood plain of Kalaarte River. In the Bulake village, the main movement features of the ground fissure are tension and sinistral slip, and the directions of ground fissures are 90°~135°. The collapse and landslide are one of the important geological disasters in the disaster area. The rolling stones falling in landslide blocked the roads and smashed the wire rods, and the biggest rolling stone is 4 meters in length. We only found a small landslide in the earthquake area, but there are a large number of unstable slopes and potential landslides in the surroundings. The ground fissures associated with sand liquefaction are an important cause of serious damage to the buildings.
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LATE QUATERNARY CRUSTAL SHORTENING RATE OF THE BEILUNTAI FAULT IN SOUTHERN TIAN SHAN, XINJIANG
YAO Yuan, SONG He-ping, CHEN Jian-bo, LI Shuai, JIA Hai-liang
SEISMOLOGY AND GEOLOGY    2018, 40 (1): 71-86.   DOI: 10.3969/j.issn.0253-4967.2018.01.006
Abstract1055)   HTML    PDF(pc) (7565KB)(248)       Save
The Beiluntai Fault is a Holocene active fault. It is the boundary between southern Tian Shan and Tarim Basin. Since the late Quaternary, steady activities of the Beiluntai fault have resulted in offsets, folds, and uplift of pluvial terraces. We used the high-resolution RTK topographic surveys to reveal that the fault scarp morphology on the Akeaiken(Ak) segment and Zhuanchang(Zc) segment of the Beiluntai fault. We found that the crustal shortening of Ak and Zc segments are dominated by thrusting and folding-uplift, respectively. We employed th optically stimulated luminescence(OSL) dating method to develop a new chronology for the different pluvial terraces, indicating that they formed at 49.14~58.51, 27±3, 13.72~14.64, 7.13±0.88, (3.32±0.43) ka, respectively. These data permitted to estimate the crustal shortening rate(about 2.4mm/a) remains largely constant on the Ak segment, while the crustal shortening rate of Zc segment was 1.43~1.81mm/a since the Fan4 pluvial terraces was abandoned. Compared with the Ak segment, the crustal shortening rate of the Zc segment declined obviously. This shows that the NS-trending crustal shortening rate of the Beituntai fault decreased gradually from west to east. A comprehensive comparison of the reverse fault-fold belt system in the front of southern Tian Shan also indicates that the crustal shortening rate drops from west to east.
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SURFACE RUPTURE FEATURES OF THE 2008 YUTIAN MS 7.3 EARTHQUAKE AND ITS TECTONIC NATURE
XU Xi-wei, TAN Xi-bin, WU Guo-dong, CHEN Jian-bo, SHEN Jun, FANG Wei, SONG He-ping
SEISMOLOGY AND GEOLOGY    2011, 33 (2): 462-471.   DOI: 10.3969/j.issn.0253-4967.2011.02.019
Abstract1908)      PDF(pc) (1019KB)(2581)       Save

High-resolution satellite image interpretation and field investigation indicate that the surface rupture zone produced by the Yutian MS7.3 earthquake is~25km long along a NS-trending fault at the western piedmont of a snow-covered range at the upper reach of the Yurungongkash River,about 20km south of the Ashikule Volcanoes.The surface rupture zone consists of different striking ruptures with both normal and left-lateral faulting components.The maximum left-lateral and vertical co-seismic slips measured in the field are~1.8m and~2.0m,respectively.Its seismogenic NS-trending fault belongs to the secondary structure at the NE-trending tensile area of the southwestern end of the Altyn Tagh Fault,which conforms to the eastward escape of the Kunlun-Qaidamu-Qilian block,relative to the Western Kunlun block.

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PRELIMINARY STUDY OF LATE QUATERNARY CRUSTAL SHORTENING RATE ALONG KUQA DEPRESSION IN SOUTH TIANSHAN, XINJIANG
WU Chuan-yong, SHEN Jun, CHEN Jian-bo, LI Jun, XIANG Zhi-yong, XIE Tian, SONG Zheng-na, WANG Cui
SEISMOLOGY AND GEOLOGY    2006, 28 (2): 279-288.  
Abstract2241)      PDF(pc) (10180KB)(648)       Save
The Kuqa depression is located in the middle segment of the southern Tianshan Mountains. There are four E-W extending rows of reverse fault and anticline zones in the depression. From the south Tianshan Mountains towards the Tarim basin, they are the mountain piedmont, the Kasangtuokai, the Qiulitag and the Yaken reverse fault and fold zones. After a month field working, we find the crustal shortening of the Kuqa depression in late Quaternary is almost caused by the Kasangtuokai, the Qiulitag and the Yaken reverse fault and fold zones. The reverse fault and anticline zones in the Kuqa depression are very different in tectonic feature. We accurately surveyed these tectonics with total station and differential GPS in order to get a new cognition of the deformation characteristic and the slip rate. Based on the deformation characteristics of conceptual fault-propagation fold and field investigation, we think the deformation of the fault-propagation fold in the Kuqa depression is caused by faulting rather than folding. The crustal shortening rate caused by the fault is approximately near to the actual rate. So we only surveyed the deformation near the fault. The Kasangtuokai anticline is a fault-propagation fold. From late Quaternary, the deformation of Kasangtuokai anticline is mainly caused by total-uplift of the hanging wall. The deformation rate is about 1.0~2.0mm/a. The deformation feature of the Dongqiulitag anticline is similar to that of the Kasangtuokai, while the crustal shortening rate is little more than that of Kasangtuokai, about 2.5mm/a. The Qiulitag anticline is a very complicated tectonic. It is a fault-bend fold. There are two reverse faults on the core and the north limb of the Qiulitag anticline. Its tectonic deformation includes two parts: the fold rise and the uplift of the hanging wall of the fault. By surveying and dating, we get the crustal shortening rate of the Qiulitag anticline limb of about 1.06~2.0mm/a. Considering the shortening of the core fault and southern limb, the total rate is possibly more than 3.0mm/a. The Yaken anticline is a blind thrust fault-anticline fold. Its shortening rate is 1.5~2.0mm/a. So the total crustal shortening rate of the Kuqa depression is more than 5.0~7.0mm/a from late Quaternary.
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THE BASIC FEATURES OF THE ACTIVE TECTONICS IN THE KUQA DEPRESSION OF THE SOUTHERN TIANSHAN
SHEN Jun, WU Chuan-yong, LI Jun, XIANG Zhi-yong, CHEN Jian-bo, XIE Tian, SONG Zheng-na, WANG Cui
SEISMOLOGY AND GEOLOGY    2006, 28 (2): 269-278.  
Abstract1574)      PDF(pc) (4400KB)(1422)       Save
The distribution, tectonic style and new displacement and other features of the main active tectonics in Kuqa depression in the front of southern Tianshan were introduced in this paper. This depression is an “eye-shaped” tectonics in plane. It is composed of two fold zones in the south and north respectively. The northern one close to the main southern Tianshan Range is a southward thrusting fault-folding system. The most recent active fold in this system is the Kasangtuokai fold belt. The southern one close to the Tarim Basin is a northward thrust fault-fold system. The recent active folds in this system are the Qiulitage fault-fold belt and other young folds in its south, such as the Yaken fold. These two folding systems embrace the Baicheng Basin which likes an eyeball in the eyelids. The Kasangtuokai Fault with a length of 60km in the north and the Qiulitag Fault with the length over 200km in the south are the most important active faults in Kuqa depression. The younger and smaller folds in the south of Qiulitag anticline belt indicate the southward propagation of the thrust fault in Kuqa depression. The petroleum seismic profiles show that the folding and faulting processes are controlled by the detachment fault between the sediment cover and the basement of the basin. The depth of the detachment fault is around 10km and possibly defines the main seismogenic zone in the depression area.
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THE SEISMOGENIC TECTONICS OF THE MS 6.8 BACHU-JIASHI,XINJIANG EARTHQUAKE IN FEB.24, 2003
SHEN Jun, CHEN Jian-bo, WANG Cui, WU Chuan-yong, SONG Zheng-na
SEISMOLOGY AND GEOLOGY    2006, 28 (2): 205-212.  
Abstract1867)      PDF(pc) (7873KB)(1308)       Save
The MS 6.8 Bachu-Jiashi earthquake of Feb.24, 2003 occurred in the western Tarim Basin and is possibly the continuation of the Jiashi strong earthquake swarms in 1997-1998. However, its focal mechanism and rupture process are different from that of the Jiashi strong earthquake swarms, according to our preliminary study on its seismic tectonics with geomorphologic information from satellite images, the deep structures from the petroleum seismic exploration, the macro damage and isoseismic features from field investigation, the relocation of the epicenters of the aftershocks, and the regional seismic tectonics from both deep and surface tectonics. The occurrence of the MS 6.8 Bachu-Jiashi earthquake is closely related with the revealed reverse fault on the Maigaiti slope belt between the Bachu uplift and Kashi depression in western Tarim Basin. The sites of the ground fissures found in the field fit with the revealed reverse fault. Isoseismal features are also corresponding to the rupture direction of the fault. These evidences indicate that the MS 6.8 Bachu-Jiashi earthquake is the result of the southward rupturing from deep to shallow along a north-dipping reverse fault in Tarim Basin. This reverse fault is possibly the result of the propagation of the thrust fault-fold system named Kalpintag thrust belt in the front of Tianshan.
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