The Xianshuihe fault system or the Yushu-Ganzi-Xianshuihe fault system is a major active sinistral (left-lateral)

strike-slip fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

zone in southwestern China, at the eastern edge of the

Tibetan Plateau The Tibetan Plateau, also known as the Qinghai–Tibet Plateau or Qingzang Plateau, is a vast elevated plateau located at the intersection of Central Asia, Central, South Asia, South, and East Asia. Geographically, it is located to the north of H ...

. It has been responsible for many major

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

s, and is one of the most seismically

active fault An active fault is a fault that is likely to become the source of another earthquake sometime in the future. Geologists commonly consider faults to be active if there has been movement observed or evidence of seismic activity during the last 10,0 ...

zones in China.

Tectonic setting

The Xianshuihe fault system lies within the complex zone of

continental collision In geology, continental collision is a phenomenon of plate tectonics that occurs at Convergent boundary, convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroy ...

between the

Indian Plate The Indian plate (or India plate) is or was a minor tectonic plate straddling the equator in the Eastern Hemisphere. Originally a part of the ancient continent of Gondwana, the Indian plate broke away from the other fragments of Gondwana an ...

and the Eurasian Plate. It forms one of a set of sinistral fault zones that help accommodate the eastward spreading of the Tibetan Plateau. The fault zone defines the northern and eastern edges of the Qiangtang block (also known in part as the Sichuan-Yunnan block), and the southeastern boundary of the Bayan Har block. To the southeast it also forms the western margin of the South China Block.

Geometry

The Xianshuihe fault system comprises several distinct segments, with an overall length of 1,400 km. The main segments are the Dangjiang, Yushu, Ganzi, (or Ganzi-Yushu), the Xianshuihe, the Anninghe-Zemuhe, and the Xiaojiang faults. Each of these faults are themselves divided into smaller segments. The fault system has also been divided into a western part and an eastern part, with the division between the Ganzi and Xianshuihe segments.

Dangjiang segment

This segment is about 170 km in length. At its western end it connects to the Fenghuoshan Fault, which continues on into a poorly studied region. At its eastern end it overlaps with the Yushu segment to which it links through a right-stepping compressional

stepover The step over (also known as the ''pedalada'', the ''denílson'', or the ''scissors'', or the ''roeder shuffle'') is a dribbling move, or feint, in association football, used to fool a defensive player into thinking the offensive player, in poss ...

of 25 km, which is associated with a 20 km wide zone of uplift. The easterly 100 km of the segment are thought to have ruptured during the M7.6 1738 Dangjiang earthquake.

Yushu segment

The total length of this segment is about 170 km. At its eastern end the Yushu segment connects through to the Ganzi segment through the Batang Basin. The segment has two main sections that are linked via a left-stepping extensional stepover through the Longbao Lake Basin, a pull-apart structure 30 km x 6 km in size. In 2010 about 50–80 km of this segment ruptured during the M7.1

2010 Yushu earthquake The 2010 Yushu earthquake struck on April 14 and registered a magnitude of 6.9 Mw (USGS, EMSC) or 7.1 Ms

Ganzi segment

This approximately 300 km long segment is subdivided into three sections. The 70 km long Denke section that ruptured during an M7.0–7.5 earthquake in 1896, the 170 km long Manigange section that ruptured in a M7.7–8.0 earthquake in 1854 and the 65 km long Ganzi section, which ruptured in a M7.1–7.3 earthquake in 1866. The eastern end of the segment overlaps with the Xianshuihe segment via a 45 km left-stepping extensional stepover.

Xianshuihe segment

This approximately 350 km long northwest–southeast trending segment is divided into five main sub-sections, from northwest to southeast, the Luhuo, Daofu, Qianning, Kangding and Moxi. There is evidence of aseismic creep along much of this segment. An overall slip rate of 12 mm per year has been estimated for this segment from the analysis of InSAR data. In detail there is evidence of an increase from the northwestern end of the segment, consistent with ongoing shortening within the Bayan Har block. A series of historical earthquakes have been associated with the Xianshuihe segment, the most recent events on each section were 1786 ( M7.7 Moxi), 1893 (M7.0 Qianning), 1923 ( M7.3 Daofu), 1973 ( M7.6 Luhuo) and 2014 ( M6.3 Kangding).

Anninghe–Zemuhe segment

This ~250 km long segment is formed of two main sections; the Anninghe, which runs north–south in the north and the Zemuhe that runs NNW–SSE, linking together at a sharp bend. There is an additional fault that lies further east, the Dalingshan Fault. The Anninghe section has an estimated slip rate of 3.6–4.0 mm per year while that for the Zemuhe section is 3–5 mm per year. Paleoseimological investigations suggest that some of the large earthquake, such as those in 814 and

1850 Events January–March * January 29 – Henry Clay introduces the Compromise of 1850 to the United States Congress. * January 31 – The University of Rochester is founded in Rochester, New York. * January – Sacramento, Ca ...

ruptured across the bend between the two sections, while some, such as that in 1536 only ruptured the Anninge section.

Xiaojiang segment

The southernmost segment of the fault system runs for about 400 km from the end of the Zemuhe section to its junction with the right-lateral Red River Fault. The Xiaojiang Fault is subdivided into northern, central and southern sections. The northern section consists of a single fault strand, the central section of two main parallel fault strands and the southern sections of multiple fault strands. The

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

slip rate for the central and northern segments is estimated as 10–16 mm per year and currently 7–10 mm per year. Historical earthquake along this segment include a M8.0 event in 1833 and a M7.8 event in 1733.

Seismicity

Movements on this fault system have been responsible for many large historical earthquakes, with more than 20 events of magnitude greater than 6.5 since 1700. Some of these earthquakes have formed linked sequences, with each event being triggered by the previous one due to stress changes.

Creep

Like the

San Andreas Fault The San Andreas Fault is a continental Fault (geology)#Strike-slip faults, right-lateral strike-slip transform fault that extends roughly through the U.S. state of California. It forms part of the tectonics, tectonic boundary between the Paci ...

in California, the eastern part of the Xianshuihe fault system exhibits a behavior called

aseismic creep In geology, aseismic creep or fault creep is measurable surface displacement along a fault in the absence of notable earthquakes. Aseismic creep may also occur as "after-slip" days to years after an earthquake. Notable examples of aseismic slip i ...

. The Xianshuihe fault creeps at a rate of a few mm/yr between earthquakes.

Notable earthquakes

1786 Kangding-Luding earthquake An earthquake occurred on 1 June 1786 in and around Kangding, in what is now China's Sichuan province. It had an estimated magnitude of about 7.75 and a maximum perceived intensity of X (''Extreme'') on the Mercalli intensity scale. The initial qu ...

1850 Xichang earthquake The 1850 Xichang earthquake rocked Sichuan Province of Qing China on September 12. The earthquake which caused major damage in Xichang county had an estimated moment magnitude of 7.3–7.9 and a surface wave magnitude of 7.5–7.7 . An estimated ...

1923 Renda earthquake The 1923 Renda earthquake occurred on March 24 at 20:40 Time in China, local time between the counties of Dawu County, Sichuan, Daofu and Luhuo County, Luhuo in Sichuan, China. The estimated 7.3 earthquake was assigned a maximum modified Mercall ...

* 1955 Zheduotang earthquake *

1973 Luhuo earthquake The 1973 Luhuo earthquake struck near the town of Zhaggo in Garzê Tibetan Autonomous Prefecture of Sichuan Province, China on February 6, 1973, with a magnitude of 7.6 . The earthquake had a maximum intensity of X (''Extreme'') on the Modified M ...

1981 Dawu earthquake The 1981 Dawu earthquake occurred on , in Sichuan, China. Registering a surface-wave magnitude of 6.8, the earthquake killed about 150 people and injured roughly 300 more. It caused comprehensive damage within close range of its epicenter. Backg ...

2010 Yushu earthquake The 2010 Yushu earthquake struck on April 14 and registered a magnitude of 6.9 Mw (USGS, EMSC) or 7.1 Ms2022 Luding earthquake A 6.7 ( 6.8) earthquake struck Luding County in Sichuan provinces of China, province, China on 5 September 2022 at 12:52:19 Time in China, local time. The epicenter was located from Chengdu, or southeast of Kangding. Ninety-three people died, ...

References

{{Reflist Seismic faults of Asia Geology of China Strike-slip faults