Stress State and Fault Strength Variation along Xiaojiang Fault Zone Revealed by Seismicity

2020 ◽  
Author(s):  
Yijian Zhou ◽  
Shiyong Zhou ◽  
Hao Zhang ◽  
Yu Hou ◽  
Weilai Pei ◽  
...  
Keyword(s):  
Fault Zone ◽  
Large Scale ◽  
Velocity Structure ◽  
Broad Band ◽  
High Stress ◽  
Head Wave ◽  
The Tibetan Plateau ◽  
Fault Geometry ◽  
Seismicity Pattern ◽  
Xiaojiang Fault

<p>Xiaojiang Fault (XJF) lies at the southeastern edge of the rhombic Sichuan-Yunnan block, and has an extent for over 400km from Qiaojia to Shanhua district. The Sichuan-Yunnan block experiences clockwise rotation and southwestward escaping from the Tibetan Plateau, producing complex fault geometry and seismicity pattern. The strong variation along fault segments provides a special opportunity to study the relationship between fault zone properties and seismicity pattern. However, the fine structure of XJF remains unknown due to the sparse observational stations.</p><p>Seismic data has its unique advantage of resolving fault zone properties at depth. We deployed 48 broad-band seismometers along XJF in order to capture detailed seismicity patterns. Our seismic network covers the northern and middle part of XJF, with an average aperture of 20km; the continuous observation from 2015 to 2019 guarantees enough data volume. We detected about 12,000 earthquakes by STA/LTA phase picking and association, and augmented the detection to over 50,000 events with template matching. The relocated catalog has lateral and vertical resolution of 500m and 1km, respectively; the magnitude of completeness (Mc) reaches ML0.3</p><p>This high-resolution catalog depicts detailed 3D fault geometry. The seismicity shows clustered lateral distribution, with the clusters’ depth extension ranging from 20km at northern to 35km at southern segments. Unmapped orthogonal faults on northern XJF are illuminated by seismicity, which matches orthogonal topography characteristics. Repeating events are detected from 8 seismicity clusters, under a threshold of 5 repeating families, indicating a creeping slip mode, while the separated low-seismicity segments exhibit a high locking rate. Taking advantage of the high detectability, we got reliable b-value estimation for different segments of XJF. The low-b regions correlate well with the margins of locking patches, which points to a high stress concentration. Velocity structure extracted from ambient noise and fault zone head wave present similar spatial variation, which further proved the seismicity pattern. The high heterogeneous characteristics of XJF may produce stress barriers, preventing future earthquake rupture from propagating to a large scale. </p>

Huge Landslides along the Jinsha River in Southeastern Tibetan Plateau and Their Association with the Recent Activity of Jinsha River Fault Zone

2020 ◽  
Author(s):  
Zufeng Chang ◽  
Hao Chang ◽  
Zebin Mao ◽  
Ruojin Guo
Keyword(s):  
Tibetan Plateau ◽  
Fault Zone ◽  
Large Scale ◽  
Late Quaternary ◽  
Average Rate ◽  
Economic Losses ◽  
The Tibetan Plateau ◽  
Jinsha River ◽  
Water Storage Capacity ◽  
Barrier Lake

<p>     The Jinsha river fault zone in the eastern margin of the Tibetan Plateau is an old suture structure after the shutting of the proto-Tethys and a large scale ultra-lithosphere fault zone consisted of  5 to 6 fault branches with a width of 50km, have a long  geological evolution history. Since late Quatery, this fault zone is mainly dominated by dextral strike slip with partial thrusting component, absorbing  partial energy of the extrusion movement of  Tibetan Plateau. Along the fault zone, lower terraces of Jinsha river at Muronglou, Buzhong, Langzhong, Guxue, etc. were displaced, indicating the fault zone is active in late Quaternary, with an average rate of 3.5～4.3mm/ /yr. horizontally and 0.9-1.1mm/yr. vertically respectively in Holocene. Influenced by the intense fault activity of Jinsha river fault zone, this region is characterized by fractured rocks, strongly weathered surfaces.</p><p>      The Jinsha river, the upstream of the Yangtze river, parallel to Jinshajiang fault zone, flows from north to south, forming deep river valley and huge terrain elevation difference. Numerous huge landslides have developed along the river, for example, there are 23 giant avalanches in the 38 km long reach from Narong to Rongxue, with general volumes of 10~70 million m<sup>3</sup> and even up to several hundreds million m<sup>3</sup>. Moreover, the landslides produce many loose clastic fragments which detonate many debris flows and river blocking. The latest disaster event is the Baige barrier lake in 2018 caused by landslide, with a water storage capacity of 524 million m<sup>3</sup>, causing tens of billions of yuan of economic losses. These landslides are distributed along the fault and its two sides, suggesting that these huge avalanches are closely related to the intense activity of the fault zone and special topography.</p><p>Keywords: Huge landslide, Jinsha River, Jinsha River Fault Zone, late Quatery activity</p>

Three-Dimensional P-Wave Velocity Structure Around the Xiaojiang Fault Zone and Its Tectonic Implications

2013 ◽  
Vol 56 (4) ◽  
pp. 400-410
Author(s):  
WU Jian-Ping ◽  
YANG Ting ◽  
WANG Wei-Lai ◽  
MING Yue-Hong ◽  
ZHANG Tian-Zhong
Keyword(s):  
Fault Zone ◽  
Wave Velocity ◽  
Velocity Structure ◽  
Three Dimensional ◽  
P Wave ◽  
Tectonic Implications ◽  
P Wave Velocity ◽  
Xiaojiang Fault ◽  
P Wave Velocity Structure

scholarly journals Hydrogeochemical Characteristics of Hot Springs and Their Short-Term Seismic Precursor Anomalies along the Xiaojiang Fault Zone, Southeast Tibet Plateau

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2638
Author(s):  
Chenhua Li ◽  
Xiaocheng Zhou ◽  
Yucong Yan ◽  
Shupei Ouyang ◽  
Fengli Liu
Keyword(s):  
Fault Zone ◽  
Meteoric Water ◽  
Hot Springs ◽  
Hot Spring ◽  
Epicentral Distance ◽  
Tibet Plateau ◽  
The Tibetan Plateau ◽  
Short Term ◽  
Seismic Precursor ◽  
Xiaojiang Fault

Significant hydrogeochemical changes may occur prior- and post-earthquakes. The Xiaojiang fault zone (XJF), situated in a highly deformed area of the southeastern margin of the Tibetan Plateau, is one of the active seismic areas. In this study, major and trace elements, and hydrogen and oxygen isotopes of 28 sites in hot springs along the XJF were investigated from June 2015 to April 2019. The meteoric water acts as the primary water source of the hot spring in the XJF and recharged elevations ranged from 1.8 to 4.5 km. Most of the hot spring water in the study area was immature water and the water–rock reaction degree was weak. The temperature range was inferred from an equation based on the SiO2 concentration and chemical geothermal modeling: 24.3~96.0 °C. The circulation depth for the springs was estimated from 0.45 to 4.04 km. We speculated the meteoric water firstly infiltrated underground and became heated by heat sources, and later circulated to the earth’s surface along the fault and fracture and finally constituted hot spring recharge. Additionally, a continuous monitoring was conducted every three days in the Xundian hot spring since April 2019, and in Panxi and Qujiang hot springs since June 2019. There were short-term (4–35 d) seismic precursor anomalies of the hydrochemical compositions prior to the Xundian ML4.2, Dongchuan ML4.2, and Shuangbai ML5.1 earthquakes. The epicentral distance of anomalous sites ranged from 19.1 to 192.8 km. The anomalous amplitudes were all over 2 times the anomaly threshold. The concentrations of Na+, Cl−, and SO42− are sensitive to the increase of stress in the XJF. Modeling on hydrology cycles of hot springs can provide a plausible physicochemical basis to explain geochemical anomalies in water and the hydrogeochemical anomaly may be useful in future earthquake prediction research of the study area.

scholarly journals Latest Quaternary Active Faulting and Paleoearthquakes on the Southern Segment of the Xiaojiang Fault Zone, SE Tibetan Plateau

Lithosphere ◽  
2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Peng Guo ◽  
Zhujun Han ◽  
Shaopeng Dong ◽  
Zebin Mao ◽  
Nan Hu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Fault Zone ◽  
Dominant Role ◽  
Fault System ◽  
Tectonic Deformation ◽  
Time Interval ◽  
The Tibetan Plateau ◽  
Lateral Extrusion ◽  
The Right ◽  
Xiaojiang Fault

Abstract 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.

scholarly journals Seismic velocity structure at the southern termination of the 2016 Kumamoto Earthquake rupture, Japan

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Yasuhira Aoyagi ◽  
Haruo Kimura ◽  
Kazuo Mizoguchi
Keyword(s):  
Fault Zone ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Earthquake Rupture ◽  
2016 Kumamoto Earthquake ◽  
Seismic Velocity Structure ◽  
Kumamoto Earthquake ◽  
Seismogenic Layer ◽  
The 2016 Kumamoto Earthquake ◽  
Tectonic Line

Abstract The earthquake rupture termination mechanism and size of the ruptured area are crucial parameters for earthquake magnitude estimations and seismic hazard assessments. The 2016 Mw 7.0 Kumamoto Earthquake, central Kyushu, Japan, ruptured a 34-km-long area along previously recognized active faults, eastern part of the Futagawa fault zone and northernmost part of the Hinagu fault zone. Many researchers have suggested that a magma chamber under Aso Volcano terminated the eastward rupture. However, the termination mechanism of the southward rupture has remained unclear. Here, we conduct a local seismic tomographic inversion using a dense temporary seismic network to detail the seismic velocity structure around the southern termination of the rupture. The compressional-wave velocity (Vp) results and compressional- to shear-wave velocity (Vp/Vs) structure indicate several E–W- and ENE–WSW-trending zonal anomalies in the upper to middle crust. These zonal anomalies may reflect regional geological structures that follow the same trends as the Oita–Kumamoto Tectonic Line and Usuki–Yatsushiro Tectonic Line. While the 2016 Kumamoto Earthquake rupture mainly propagated through a low-Vp/Vs area (1.62–1.74) along the Hinagu fault zone, the southern termination of the earthquake at the focal depth of the mainshock is adjacent to a 3-km-diameter high-Vp/Vs body. There is a rapid 5-km step in the depth of the seismogenic layer across the E–W-trending velocity boundary between the low- and high-Vp/Vs areas that corresponds well with the Rokkoku Tectonic Line; this geological boundary is the likely cause of the dislocation of the seismogenic layer because it is intruded by serpentinite veins. A possible factor in the southern rupture termination of the 2016 Kumamoto Earthquake is the existence of a high-Vp/Vs body in the direction of southern rupture propagation. The provided details of this inhomogeneous barrier, which are inferred from the seismic velocity structures, may improve future seismic hazard assessments for a complex fault system composed of multiple segments.

scholarly journals Seismic Structure of Local Crustal Earthquakes beneath the Zipingpu Reservoir of Longmenshan Fault Zone

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Haiou Li ◽  
Xiwei Xu ◽  
Wentao Ma ◽  
Ronghua Xie ◽  
Jingli Yuan ◽  
...  
Keyword(s):  
Fault Zone ◽  
Three Dimensional ◽  
P Wave ◽  
The Tibetan Plateau ◽  
Seismic Structure ◽  
Infiltration Depth ◽  
Low Velocity ◽  
Longmenshan Fault Zone ◽  
Velocity Models ◽  
Longmenshan Fault

Three-dimensional P wave velocity models under the Zipingpu reservoir in Longmenshan fault zone are obtained with a resolution of 2 km in the horizontal direction and 1 km in depth. We used a total of 8589 P wave arrival times from 1014 local earthquakes recorded by both the Zipingpu reservoir network and temporary stations deployed in the area. The 3-D velocity images at shallow depth show the low-velocity regions have strong correlation with the surface trace of the Zipingpu reservoir. According to the extension of those low-velocity regions, the infiltration depth directly from the Zipingpu reservoir itself is limited to 3.5 km depth, while the infiltration depth downwards along the Beichuan-Yingxiu fault in the study area is about 5.5 km depth. Results show the low-velocity region in the east part of the study area is related to the Proterozoic sedimentary rocks. The Guanxian-Anxian fault is well delineated by obvious velocity contrast and may mark the border between the Tibetan Plateau in the west and the Sichuan basin in the east.

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