The Haiyuan Fault is a major

active Active may refer to: Music * ''Active'' (album), a 1992 album by Casiopea * Active Records, a record label Ships * ''Active'' (ship), several commercial ships by that name * HMS ''Active'', the name of various ships of the British Royal ...

intracontinental

strike-slip 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 ...

(sinistral) fault in Central Asia. TibetanPlateauTectonics

Tectonic setting

The Haiyuan Fault forms part of the northeastern boundary of the

Tibetan Plateau The Tibetan Plateau (, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the Ti ...

, which is an area of

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called ''sial'' be ...

that has been thickened by the ongoing

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

between the

Indian Plate The Indian Plate (or India Plate) is 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 , began mov ...

and the

Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

. The Haiyuan Fault extends for approximately from the central

Qilian Shan The Qilian Mountains (, also romanized as Tsilien; Mongghul: Chileb), together with the Altyn-Tagh (Altun Shan) also known as Nan Shan (, literally "Southern Mountains"), as it is to the south of Hexi Corridor, is a northern outlier of the Kun ...

in the west, to the Liupan Shan, in the east. It is one of the group of structures that accommodates the overall eastward spreading of the plateau, that also includes the

Altyn Tagh Fault The Altyn Tagh Fault (ATF) is a 2,000 km long, active, sinistral (left lateral) strike-slip fault that forms the northwestern boundary of the Tibetan Plateau with the Tarim Basin. It is one of the major sinistral strike-slip structures that t ...

, Kunlun Fault and the

Xianshuihe fault system The Xianshuihe fault system is a major active sinistral (left-lateral) strike-slip fault zone in southwestern China, at the eastern edge of the Tibetan Plateau. It has been responsible for many major earthquakes, and is one of the most seismicall ...

Geology

It is characterized by left-lateral strike-slip motion along its length, the motion transits to thrust at the eastern end, accommodated by the Liupanshan Fault. The average slip rate along the Haiyuan Fault is 3.2–9 mm/yr.

Tianzhu seismic gap

The Tianzhu seismic gap is a long, unruptured segment on the western end of the fault. It has not seen any major earthquakes for the past 1,000 years and was identified as a

seismic gap A seismic gap is a segment of an active fault known to produce significant earthquakes that has not slipped in an unusually long time, compared with other segments along the same structure. There is a hypothesis or theory that states that over long ...

. It poses a high risk for the capacity of large earthquakes. An earthquake recurrence period of roughly 1,000 years has been suggested, with the last earthquakes on that section dated at 1092 AD and 174 or 374 AD. Locking depth of the fault range from .

Creeping Section

At the western end of the 1920 earthquake surface rupture, and between the Tianzhu seismic gap (from 37.11° N, 103.68° E to 37.00° N, 104.15° E) lies a section of the fault that displays a phenomenon known as an

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 in ...

at shallow depths.

Seismicity

The fault was the source of two very large and destructive earthquakes in 1920 and 1927. Two events in 143 A.D. or 374 A.D. and in 1092 may have been large earthquakes with estimated magnitudes of 8.0 or higher.

1920

On the evening of December 16, 1920, a M7.8–8.5 earthquake struck

Haiyuan County Haiyuan County (, Xiao'erjing: خَيْ‌يُوًا ثِيًا) is a county under the administration of the prefecture-level city of Zhongwei in the southwest of the Ningxia Hui Autonomous Region of the People's Republic of China. It is bordered b ...

, killing over 270,000 people. Shaking intensity reached a maximum of XII (''Extreme''), the uppermost limit on the

Modified Mercalli intensity scale The Modified Mercalli intensity scale (MM, MMI, or MCS), developed from Giuseppe Mercalli's Mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. It measures the eff ...

. The fault ruptured for a length of nearly in this event.

Surface rupture In seismology, surface rupture (or ground rupture, or ground displacement) is the visible offset of the ground surface when an earthquake rupture along a fault affects the Earth's surface. Surface rupture is opposed by buried rupture, where the ...

s from the earthquake have been well documented and a maximum surface displacement of was recorded.

1927

A magnitude 7.7 quake struck Gansu Province on the morning of May 22, 1927, the earthquake occurred on a different segment from the one involved in the 1920 quake. This earthquake caused the deaths of more than 40,000 people, and 200,000 livestock. It is thought to have been produced along a south-dipping

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If ...

located north of the Haiyuan Fault strand. This fault has been interpreted to be a branch of the Haiyuan Fault at depth.

1990

On October 20, 1990, a 5.8 earthquake ruptured a small section of the fault with a maximum China seismic intensity of VIII. Serious damage was reported along a section of the fault. The earthquake produced surface fissures and cracks. The ancient walls of Songshan collapsed. No formal geological investigation was conducted although it is believed to have produced a surface rupture for several kilometers. One fatality was reported.

1995

The 1995 Yongden earthquake on July 21, a 5.6 earthquake struck near Yongden County, northeast of Lanzhou. It left 14 people killed, 533 injured and 8,860 homeless. At least 11,704 homes were destroyed and a further 5,083 were extensively damaged. Serious damage occurred to road and agricultural infrastructures. Livestock and farmland were destroyed by landslides. A maximum intensity of VII was evaluated. The earthquake was the result of movement along a previously unmapped south–southwest dipping

2022

An 6.6 or 6.9 earthquake struck Menyuan County in January 2022, causing little damage and few minor injuries. The earthquake was felt with a maximum intensity of IX on the

China seismic intensity scale The China seismic intensity scale (CSIS) is a national standard in the People's Republic of China used to measure seismic intensity. Similar to EMS-92 on which CSIS drew reference, seismic impacts are classified into 12 degrees of intensity, or ' ...

(IX on the

) over a 157 km³ area. It generated a

surface rupture In seismology, surface rupture (or ground rupture, or ground displacement) is the visible offset of the ground surface when an earthquake rupture along a fault affects the Earth's surface. Surface rupture is opposed by buried rupture, where the ...

along the Lenglongling segment of the Haiyuan Fault. On-site investigations found up to of left-lateral strike-slip offsets. The surface rupture also crossed the tunnel of a high-speed railway linking

Lanzhou Lanzhou (, ; ) is the capital and largest city of Gansu Province in Northwest China. Located on the banks of the Yellow River, it is a key regional transportation hub, connecting areas further west by rail to the eastern half of the country. H ...

Ürümqi Ürümqi ( ; also spelled Ürümchi or without umlauts), formerly known as Dihua (also spelled Tihwa), is the capital of the Xinjiang Uyghur Autonomous Region in the far northwest of the People's Republic of China. Ürümqi developed its ...

, causing severe damage to a bridge and the tracks. Modelling of the earthquake suggest it had a maximum coseisic slip of around at a depth of along the

rupture Rupture may refer to: General * Rupture (engineering), a failure of tough ductile materials loaded in tension Anatomy and medicine * Abdominal hernia, formerly referred to as "a rupture" * Achilles tendon rupture * Rupture of membranes, a "wate ...

References

{{East Asia plates Seismic faults of Asia Strike-slip faults Geology of Tibet Geology of China