Late-Quaternary Slip Rate and Seismic Activity of the Xianshuihe Fault Zone in Southwest China

The Xianshuihe fault zone is a seismo-genetic fault zone of left-lateral slip in Southwest China. Since 1725, a total of 59 Ms ≥ 5.0 earthquakes have occurred along this fault zone, including 18 Ms 6.0–6.9 and eight Ms ≥ 7.0 earthquakes. The seismic risk of the Xianshuihe fault zone is a large and realistic threat to the western Sichuan economic corridor. Based on previous studies, we carried out field geological survey and remote sensing interpretation in the fault zone. In addition, geophysical surveys, trenching and age-dating were conducted in the key parts to better understand the geometry, spatial distribution and activity of the fault zone. We infer to divide the fault zone into two parts： the northwest part and the southeast part, with total eight segments. Their Late Quaternary slip rates vary in a range of 11.5 mm/a –（3±1） mm/a. The seismic activities of the Xianshuihe fault zone are frequent and strong, periodical, and reoccurred. Combining the spatial and temporal distribution of the historical earthquakes, the seismic hazard of the Xianshuihe fault zone has been predicted by using the relationship between magnitude and frequency of earthquakes caused by different fault segments. The prediction results show that the segment between Daofu and Qianning has a possibility of Ms ≥ 7.0 earthquakes, while the segment between Shimian and Luding is likely to have earthquakes of about Ms 7.0. It is suggested to establish a GPS or In SAR-based real-time monitoring network of surface displacement to cover the Xianshuihe fault zone, and an early warning system of earthquakes and post seismic geohazards to cover the major residential areas.

Slip Rate of Yema River–Daxue Mountain Fault since the Late Pleistocene and Its Implications on the Deformation of the Northeastern Margin of the Tibetan Plateau

The slip rate of Yema River-Daxue Mountain fault in the western segment of Qilian Mountains was determined by the dated offset of river risers or gullies. Results indicate that the left-lateral fault slip rate is 2.82± 0.20 mm/a at Dazangdele site, 2.00 ± 0.24 mm/a at Shibandun site, and 0.50± 0.36 and 2.80±0.33 mm/a at two sites in Zhazihu. The ideal average slip rate of the whole fault is 2.81 ± 0.32 mm/a. The lower slip rate confirms part of the displacement of Altyn Tagh fault was transformed into an uplifting of the strap mountains in the western segment of Qilian Mountains, whereas another part transformed into sinistral displacement of Haiyuan fault. This study illustrates that the slip of large strike-slip faults in the northeastern margin of the plateau transforms into crust thickening at the tip of the fault without large-scale propagation to the outer parts of the plateau.

Uniform Strike-Slip Rate along the Xianshuihe-Xiaojiang Fault System and Its Implications for Active Tectonics in Southeastern Tibet

Recent studies on the Xianshuihe-Xiaojiang fault system suggest that the Late Quaternary strike-slip rate is approximately uniform along the entire length of the fault zone, about 15±2 mm/a. This approximately uniform strike slip rate strongly supports the clockwise rotation model of the southeastern Tibetan crust. By approximating the geometry of the arc-shaped Xianshuihe-Xiaojiang fault system as a portion of a small circle on a spherical Earth, the 15±2 mm/a strike slip rate corresponds to clockwise rotation of the Southeastern Tibetan Block at the （5.2±0.7）×10^-7 deg/a angular velocity around the pole （21°N, 88°E） relative to the Northeast Tibetan Block. The approximately uniform strike slip rate along the Xianshuihe-Xiaojiang fault system also implies that the Longmeushan thrust zone is not active, or at least its activity has been very weak since the Late Quaternary. Moreover, the total offset along the Xiaushuihe-Xiaojiang fault system suggests that the lateral extrusion of the Southeastern Tibetan Block relative to Northeastern Tibetan Block is about 160 km and 200-240 km relative to the Tarim-North China block. This amount of lateral extrusion of the Tibetan crust should have accommodated about 13-24% convergence between India and Eurasia based on mass balance calculations. Assuming that the slip rate of 15±2 mm/a is constant throughout the entire history of the Xianshuihe-Xiaojiang fault system, 11±1.5 Ma is needed for the Xianshuihe-Xiaojiang fault system to attain the 160 km of total offset. This implies that left-slip faulting on the Xianshuihe-Xiaojiang fault system might start at 11±1.5 Ma.

Large slip rate detected at the seismogenic zone of the 2008 M_W7.9 Wenchuan earthquake

Repeating microearthquakes were identified along the edge of the rupture area of the 2008 MW7.9 Wenchuan earthquake. Slip rates at depths derived from seismic moments and recurrence intervals are found to be systematically larger than those observed at surface. This large deep slip rate may explain the odds about the occurrence of this unanticipated event. Our observations here suggested that seismic hazard could be underestimated if surface measurements alone are employed.

The advance in obtaining fault slip rate of strike slip fault-A review

Slip rate along the major active fault is an important parameter in the quantitative study of active tectonics.It is the average rate of fault slip during a certain period of time,reflecting the rate of strain energy accumulation on the fault zone.It cannot only be directly applied to evaluate the activity of the fault,the probabilistic seismic hazard analysis,but also important basic data for the study of geodynamics.However,due to the nonstandardized process of obtaining fault slip rates for a given strike-slip fault,the results could be diverse based on various methods by different researchers.In this review,we analyzed the main advances in the approaches to obtain fault slip rate.We found that there are four main sources affecting the final results of slip rate:the displacement along the fault,the dating of the corresponding displacement,the fitting of the displacement and corresponding dating results,and paleoslip analysis.The main advances in obtaining fault slip rates are based on improving the reli-ability of the above four main factors.To obtain a more reasonable and reliable slip rate for a given fault,it is necessary to select a suitable method according to the specific situation.

Geodetic slip rate and locking depth of east Semangko Fault derived from GPS measurement

65 km Semangko Fault is part of southern segments of Sumatran Fault Zone(SFZ)which is complex corresponds to the transition from the strike-slip regime of the SFZ to the normal faulting tectonics of the Sunda Strait.The recent publication showed branches of Semangko Fault:West Semangko Fault(WSF)and East Semangko Fault(ESF).This study estimated geodetic slip rate and locking depth of ESF using Global Positioning System(GPS)time series data from 2007 to 2019 from all available GPS sites.GPS velocities refer to Sundaland Plate were used to estimate the fault parameters of the WSF and ESF simultaneously.Non-uniformity of velocity direction shows the complexities of Semangko Fault possibly caused by the contribution of all faults around ESF.An ESF geodetic slip rate,which is 12.5±2 mm/yr was lower than WSF,which is 16.5±2 mm/yr.It is consistent with the rigid block nature of the SFZ system as northern segment slip rates have similar value.Small slip rates are possibly leading to lower generated seismic moment than the major segment of SFZ.

The slip rate and strong earthquake recurrence interval on the Qianning-Kangding segment of the Xianshuihe fault zone

The geometry of the Qianning-Kangding segment of the Xianshuihe fault zone is quite complex, and it is composed of four secondary-faults, i.e., the Yalahe fault, Selaha-Kangding fault, Zeduotang fault and Moxi fault. On this segment, three strong earthquakes with M(7.0 occurred in 1725, 1786 and 1955, respectively. Based on a study of fault landform and geochronology (14C and Thermoluminesense), this paper documents the average horizontal slip rates during the late-Quaternary on all the secondary-faults of the Qianning-Kangding segment as follows: Yalahe fault: (2.0(0.2) mm/a; Selaha-Kangding fault: (5.5(0.6) mm/a; Zeduotang fault: (3.6(0.3) mm/a; Moxi fault: (9.9(0.6) mm/a. The results from the investigation of surface ruptures of historical earthquakes, coseismic-slip and paleo-earthquakes show that the strong-earthquake recurrence intervals are thousands of years on the Yalahe fault, and 230 to 350 years on the Selaha-Kangding and Zeduotang faults. In the next one hundred years, the recurrence of a strong-earthquake on these faults appears impossible. However, the strong-earthquake recurrence interval on the Moxi fault is about 300 years. Up to now, it has been 214 years since the last earthquake (magnitude 7) occurred in 1786, therefore, this fault is now approaching the condition favorable for the next strong earthquake recurrence.

SLIP RATE AND RECURRENCE INTERVAL OF STRONG EARTHQUAKE OF QIANNING—KANGDING SEGMENT ON XIANSHUIHE FAULT

Located on the western of Sichuan, the east border of Tibet plateau, Xianshuihe fault is a significant strong earthquake zone. From Huiyuansi pull\|apart basin in Qianning, Xianshuihe fault can be divided two segments\|NW section and SE section: the construction of the former is single and a main fault; the construction of the latter is complex and composed by three parallel faults, its main fault is named as Selaha—Kangding fault, which distributes along Jinlongsi, Sehala, Mugecuo and Kangding. Yalahe fault, located at the NE direction of the main fault, and Zeduotang fault, located at the SW direction of the main fault, are all secondary faults, which are 9～13km away from the main fault. At the south of Kangding, the segment of Xianshuihe fault is a single main section, called as Moxi fault. On the basis of recent researching results, this paper mainly discusses the slip rate and recurrence interval of strong earthquake of the SE segment (Qianning—Kangding) on Xianshuihe.

Activity Features and Slip Rate of the Lingwu Fault in Late Quaternary

The I ingwu fault is in the eastern boundary of the southern section of Yinchuan graben. It hasa close relation to seismicity in the Lingwu-Wuzhong region.Few researches have been done.In this Paper,on the basis of tee data obtained from field investigation,the activity features inLate Quaternary have been discussed.The vertical displacement and its slip rate have been alsoestimated.The fault is 48km in length,being divided into 3 segments according to geologicaland topographical characteristics.The last rupture along its northern and middle segments wasoccurred in late of Late Pleistocene or early Holocene while that along the southern segmentwas occurred in midle Holocene.The vertical slip rate is estimated as 0.23～025mm/a sinceabout 66ka B.P.based on the vertical displacements of terracesⅠ,Ⅱ and Ⅲ and their ages.

Deformation Pattern and Holocene Slip Rate Along the Fukang Fault in Eastern Tianshan, China

The deformation pattern and Holocene slip rate along the Fukang fault in Eastern Tianshan, China are analyzed and studied using the data obtained in field investigation. The result indicates that the Fukang fault consists of 4 low-angle south-dipping thrust faults with stepover, displaying recent tectonic activity. The movement along the termination parts of the fault is weaker, with an average vertical slip rate of 0 13～0 33 mm/a in Holocene, and along the middle part of the fault is stronger, with an average vertical slip rate larger than 1.42 mm/a in Holocene. The Holocene deformation pattern along the fault displays generally steady slip, multi-phase intermittent movement along its western segment, and persistent movement along its middle and eastern segments, which have caused rapid dislocation up to the surface in an earlier phase.

Study of the Late Quaternary Slip Rate Along the Northern Segment on the South Branch of the Longling-Ruili Fault

The Longling-Ruili fault is an important active fault in Southwestern China,striking generally northeast.The fault controls the development of the sedimentary series and magmatic action on its two sides,as well as the development of the Longling basin,Mangshi basin and the Zhefang basin along it.Due to limited Quaternary sediments and harsh natural conditions,the study of late Quaternary fault activity on the northern segment of the Longling-Ruili fault is lacking and the time of the newest faulting and the Quaternary slip rate are not clear at present.Based on the interpretation of remote images,quantitative geomorphologic deformation measurements and dating of young terrace deposits and alluvial fans,this paper obtains some new results as follows.The northern segment of the Longling-Ruili fault is a Holocene dextral strike-slip fault with some component of a normal slip.The terrace T 1 composing mainly of alluvial deposits formed during 4ka B.P.was offset by the northern segment of the Longling-Ruili fault and its left-lateral and its vertical displacements are 8m ～ 12m and 2m,respectively.The late Pleistocene alluvial fan was displaced with a left-lateral and vertical displacement of 70m and 18m,respectively.The strike-slip rate of the Longling-Ruili fault is 2.2mm/a ～ 2.5mm/a and the vertical slip rate is 0.6mm/a since the late Pleistocene epoch.The strike-slip rate of the Longling-Ruili fault is 1.8mm/a ～ 3.0mm/a and vertical slip rate is 0.5mm/a during the Holocene epoch.The proportion of horizontal to vertical displacement is about 4:1,which means that the vertical slip rate on the northern segment of the Longling-Ruili fault is about 25% of the horizontal slip rate.The left-lateral slip rate in the late Holocene is consistent with the GPS measurement.The strike slip rate is of great consistency in different time scales since the late Pleistocene epoch,indicating that the activity of the Longling-Ruili fault is of great stability.

Slip Rates of the Major Faults on the Mid-southern Section of the North-South Seismic Belt Calculated from the Block Theory

In this paper,using the 1999 ~ 2007 GPS velocity field data,and by choosing the optimal block model,we obtained the deformation models applicable to the boundary zones of major blocks and the slip rates of block boundary faults on the mid-southern segment of the North-South Seismic Belt. The results show that: on the Longmenshan fault zone,the tensional and compressive slip rate is small on the Baoxing-Wenchuan segment,about 0. 5 ~ 1. 8mm·a- 1, and the rate is relatively significant on the segment of the Wenchuan-Maoxian,as 1. 8 ~ 3. 8mm·a- 1; on the Xianshuihe fault belt,there is a certain difference in spatial distribution between the tensional slip rate and strike-slip rate: the tensional slip rate( 8. 1mm·a- 1) is bigger than the sinistral strike-slip rate( 4. 8mm·a- 1) at the north of the Luhuo region; the tension and compression slip rate is basically the same as the strike-slip rate at Luhuo-Dawu; the Dawu-Kangding section presents a trend of decreased strike-slip rate and increased tensional slip rate; the Kangding-Shimian segment shows a strike-slip nature; the strike-slip rate is significantly greater than the tension /compression rate on the Xiaojiang fault zone; the slip rate on the Red River fault zone shows obvious spatial segmentation,the slip rate is smaller in its northwest part,but with a certain amount of tensional /compression component,4. 7mm·a- 1on the Jingdong segment. The segment east of Jingdong( western Gejiu) is mainly of strike-slip,with a slip rate of 4. 5mm·a- 1.

Slip Rate on the Altyn Tagh Fault on the West of the Cherchen River (Between 85°～ 85°45′E) Since Late Quaternary

Because of the significance to the formation and evolution of the Tibetan plateau, the displacement and slip rate of the Altyn Tagh fault have been topics full of disputation. Scientists who hold different opinions on the evolution of Tibet insist on different slip rates and displacements of the fault zone. In the article, study is focused on the late Quaternary slip rate of the Altyn Tagh fault west of the Cherchen River (between 85°E and 85°45’E). On the basis of high resolution SPOT images of the region, three sites, namely Koramlik, Aqqan pasture and Dalakuansay, were chosen for field investigation. To calculate the slip rate of the fault, displacement of terraces was measured on SPOT satellite images or in situ during fieldwork and thermo-luminescence (TL) dating method was used. To get the ages of terraces, samples of sand were collected from the uppermost sand beds that lie just under loess. The method for calculating slip rate of fault is to divide the displacement of terrace risers by the age of its neighboring lower terrace. The displacement of rivers is not considered in this article because of its uncertainties. At Koramlik, the slip rate of the Altyn Tagh fault is 11.6±2.6mm/a since 6.02±0.47ka B.P and 9.6±2.6mm/a since 15.76±1.19ka B.P. At Aqqan pasture, about 30km west of Koramlik, the slip rate is 12.1±1.9mm/a since 2.06±0.16 ka B.P. At Dalakuansayi, the slip rate of the fault is 12.2±3.0mm/a since 4.91±0.39ka B.P. Hence, we get the average slip rate of 11.4±2.5mm/a for the western part of the Altyn Tagh Fault since Holocene. This result is close to the latest results from GPS research.

Slip Rate and Strong Earthquake Dislocation along the Moxi-Mianning Segment of the Xianshuihe-Anninghe Fault Zone

The results from interpretation of the aerophotos and in-situ seismogeological researches show that there are some obvious late-Quaternary activities along the Moxi-Mianning segment of the Xianshuihe-Anninghe fault zone, with the characteristics of sinistral-slip movement accompanied by some significant vertical slip components. Since late-Quaternary, the average horizontal slip rate of the segment at the south of Moxi along the Xianshuihe fault is 6.0～9.9mm/a and 4.7～5.3mm/a along the segment at the north of Mianning of the Anninghe fault. The results from the investigation of coseismic dislocation and ground rupture show that the ground rupture caused by 1876 Kangding-Luding earthquake with M 7 3/ 4 can extend to the south of Tianwan. The segment at the north of Mianning of the Anninghe fault has a background for producing M7.5 earthquake and the geological record of the last strong earthquake must be the proofs of the 1327 earthquake with M>6.0 with poor historical records.

Discussion on the Abnormally Low Active Fault Slip Rate of the M_S 8. 0 Wenchuan Earthquake

Based on the collection of active fault slip rate data of large intra-continental shallow thrust earthquakes occurring in the triangular seismic region of the East Asia continent,a preliminary analysis has been performed with results showing that the Wenchuan,Sichuan, China earthquake ( MS = 8.0) of May 12,2008 occurred on the Longmenshan Mountain active fault with an abnormally low slip rate.

Evaluation of Slip Rate on Astara Fault System, North Iran

Due to its strategic location, the Astara fault system （AFS）, which is located in Iran, has given rise to a number of earthquakes. In spite of its frequent seismic events, limited information is available for AFS. Slip rate is one of the important variables for future scrutiny of seismic risk of this fault system. The main objective of this research is to study slip rates at intermediate and short terms for this fault system using geological, geodetic observations and empirical method. Using the geological data, the intermediate-term horizontal and vertical slip rates for AFS have been determined to be 2.8±0.2 and 0.27±0.03 mm/year, respectively. In addition, the short-term slip rates of the fault, based on the geodetic method （using displacement values of two GPS stations： HASH and DAMO） and assuming attenuation of 60% （to fold the sediment of South Caspian Basin and shortening of Talesh Mountain range）, determined to be 1.23±0.03 and 2.05±0.05 mm/year for the horizontal and vertical slips, respectively. Finally, evaluation of the slip rate using empirical relationship yields 10 mm/year for the entire fault system, which seems rather implausible.

Slip rate of the seismogenic fault of the 2021 Maduo earthquake in western China inferred from GPS observations

Seismic and field observations indicate that the Mw7.4 Maduo earthquake ruptured the Jiangcuo fault,which is a secondary fault~85 km south of the northern boundary of the Bayan Hor block in western China.The kinematic characteristics of the Jiangcuo fault can shed lights on the seismogenic mechanism of this earthquake.Slip rate is one of the key parameters to describe the kinematic features of a fault,which can also provide quantitative evidences for regional seismic hazard assessments.However,due to lack of effective observations,the slip rate of the Jiangcuo fault has not been studied quantitatively.In this study,we consider the interaction between the Jiangcuo fault and the eastern Kunlun fault,and estimate the slip rates of the two faults using the interseismic GPS observations across the seismogenic region.The inferred results show that the slip rates of the Jiangcuo fault and the Tuosuo Lake segment of the Kunlun fault are 1.2±0.8 and 5.4±0.3 mm a^(-1),respectively.Combining the slip rate with the average slip inferred from the coseismic slip model,the earthquake recurrence interval of the Jiangcuo fault is estimated to be 1800700+3700 years(1100–5500 years).Based on the results derived from previous studies,as well as calculations in this study,we infer that the slip rate of the Kunlun fault may decrease gradually from the Tuosuo Lake segment to the eastern tip.The Jiangcuo fault and its adjacent parallel secondary faults may have absorbed the relative motion of blocks together with the Kunlun fault.

Late Quaternary Tectonic Activity and Slip Rates of Active Faults in the Western Hexi Corridor,NW China

The Yinwashan and Xinminpu faults are located in the Jiuxi Basin in the western end of the Hexi Corridor. The determination of their activity and slip rates is of great significance for understanding the eastward extension of the Altyn Tagh fault. Based on geological and geomorphologic field survey, trench excavation, optically stimulated luminescence dating, we define the fault geometry and kinematic properties of the two faults. Based on fault scarps measurement using differential GPS and 10 Be surface exposure dating, we determined vertical slip rate of 0.09±0.01 mm/yr for the Yinwashan fault and 0.1±0.02 mm/yr for the Xinminpu fault. Using the dips observed in trenches and natural sections, we estimated horizontal shortening rates of 0.05±0.03 and 0.23±0.06 mm/yr, respectively. No significant strike slip motion is observed on these two faults, and we infer that this region was dominated by horizontal shortening in the Late Quaternary. Although the shortening rate is quite low on each individual fault, together with other faults in this area, these two faults have an essential role in transferring slip from the eastern end of the Altyn Tagh fault and in accommodating the northeastward growth of Tibetan Plateau.

Paleoseismological Study of the Late Quaternary Slip-rate along the South Barkol Basin Fault and Its Tectonic Implications,Eastern Tian Shan,Xinjiang

The easternmost Tian Shan lies in eastern Xinjiang, Central Asia. The South Barkol basin fault（SBF） in the northern part of the easternmost Tian Shan is a major tectonic structure in this orogenic region. The late Quaternary activity, paleoseismology, and deformation characteristics of the fault provide important clues for understanding the tectonic process of the eastern Tian Shan orogen and implementing seismic mitigation. Through interpretation of high-resolution satellite images, unmanned aerial vehicle measurements, and detailed geological and geomorphic investigations, we suggest that the fault exhibits clear left-lateral slip along its western segment. Paleoseismic trenches dug near Xiongkuer reveal evidence of six large paleoearthquakes. The four latest paleoearthquakes were dated： the oldest event occurred at 4663 BC–3839 BC. Data on the horizontal offsets along the probable 1842 Barkol earthquake coseismic rupture suggest clear multiple relationships between cumulative offsets and possible ~4 m of coseismic left-lateral slip per event. From the cumulative offsets and 14 C sample ages, we suggest an average Holocene left-lateral slip rate of 2.4–2.8 mm/a on the SBF, accounting for ~80% of lateral deformation within the entire eastern Tian Shan fault system. This result is comparable with the shortening rate of 2–4 mm/a in the whole eastern Tian Shan, indicating an equal role of strike-slip tectonics and compressional tectonics in this orogen, and that the SBF may accommodate substantial lateral tectonic deformation.

GPS-constrained inversion of present-day slip rates along major faults of the Sichuan-Yunnan region, China

A linked-fault-element model is employed to invert for contemporary slip rates along major active faults in the Sichuan-Yunnan region (96°-108°E, 21°-35°N) using the least squares method. The model is based on known fault geometry, and constrained by a GPS-derived horizontal velocity field. Our results support a model attributing the eastward extrusion of the Tibetan Plateau driven mainly by the north-northeastward indentation of the Indian plate into Tibet and the gravitational collapse of the plateau. Resisted by a relatively stable south China block, materials of the Sichuan-Yunnan region rotate clockwise around the eastern Himalayan tectonic syntaxis. During the process the Garzê-Yushu, Xianshuihe, Anninghe, Zemuhe, Daliangshan, and Xiaojiang faults, the southwest extension of the Xiaojiang fault, and the Daluo-Jinghong and Mae Chan faults constitute the northeast and east boundaries of the eastward extrusion, with their left slip rates being 0.3-14.7, 8.9-17.1, 5.1 ± 2.5, 2.8 ± 2.3, 7.1 ± 2.1, 9.4 ± 1.2, 10.1 ± 2.0, 7.3 ± 2.6, and 4.9 ± 3.0 mm/a respectively. The southwestern boundary consists of a widely distributed dextral transpressional zone other than a single fault. Right slip rates of 4.2 ± 1.3, 4.3 ± 1.1, and 8.5 ± 1.7 mm/a are detected across the Nanhua-Chuxiong-Jianshui, Wuliangshan, and Longling-Lancang faults. Crustal deformation across the Longmenshan fault is weak, with short-ening rates of 1.4 ± 1.0 and 1.6 ± 1.3 mm/a across the Baoxing-Beichuan and Beichuan-Qingchuan segments. Northwest of the Longmenshan fault lies an active deformation zone (the Longriba fault) with 5.1±1.2 mm/a right slip across. Relatively large slip rates are detected across a few faults within the Sichuan-Yunnan block: 4.4±1.3 mm/a left slip and 2.7±1.1 mm/a shortening across the Litang fault, and 2.7±2.3 mm/a right-lateral shearing and 6.7±2.3 mm/a shortening across the Yunongxi fault and its surrounding regions. In conclusion, we find that the Sichuan-Yunnan region is divided into more than a dozen active micro-blocks by a large number of faults with relatively slow slip rates. The eastward extrusion of the Tibetan Plateau is absorbed and adjusted in the region mainly by these faults, other than a small number of large strike-slip faults with fast slip rates.