The 2001 Kunlun earthquake also known as the 2001 Kokoxili earthquake, occurred on 14 November 2001 at 09:26 UTC (17:26 local time), with an epicenter

Epicenter

The epicenter or epicentre is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates...

 near Kokoxili, close to the border between Qinghai

Qinghai

Qinghai ; Oirat Mongolian: ; ; Salar:) is a province of the People's Republic of China, named after Qinghai Lake...

 and Xinjiang

Xinjiang

Xinjiang is an autonomous region of the People's Republic of China. It is the largest Chinese administrative division and spans over 1.6 million km2...

 in a remote mountainous region. With a magnitude of 7.8 M_w

Moment magnitude scale

The moment magnitude scale is used by seismologists to measure the size of earthquakes in terms of the energy released. The magnitude is based on the seismic moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of...

 it was the most powerful earthquake in China

China

Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

 for 5 decades . No casualties were reported, presumably due to the very low population density and the lack of high-rise buildings. This earthquake was associated with the longest surface rupture ever recorded on land, ~450 km.

Earthquake damage

Due to the remoteness of the region, most reports of damage came from areas hundreds of kilometers from the epicenter. The nearest population centre, the city of Golmud

Golmud

Golmud , sometimes transliterated as Ge'ermu or Geermu, is a county-level city in Qinghai Province, Western China. Administrated by Haixi Mongol and Tibetan Autonomous Prefecture, it is the second largest city in Qinghai and the third largest in the Tibetan Plateau . The population is now about...

, reported severe shaking but no buildings collapsed. Some damage was reported at the construction site for the Qingzang railway

Qingzang railway

The Qinghai–Xizang railway, Qingzang railway, or Qinghai–Tibet railway , is a high-elevation railway that connects Xining, Qinghai Province, to Lhasa, Tibet Autonomous Region, in People's Republic of China....

(Qinghai-Tibet railway) and along the Qinghai-Tibet highway.

Tectonic setting

The Kunlun fault

Kunlun fault

The Kunlun fault is a strike slip fault to the north side of Tibet. Slippage along the long fault has occurred at a constant rate for the last 40,000 years. This has resulted in a cumulative offset of more than . The fault is seismically active, most recently causing the magnitude 7.8 2001 Kunlun...

 is one of the major sinistral strike-slip structures that accommodate the eastward motion of the Tibetan plateau

Tibetan Plateau

The Tibetan Plateau , also known as the Qinghai–Tibetan Plateau is a vast, elevated plateau in Central Asia covering most of the Tibet Autonomous Region and Qinghai, in addition to smaller portions of western Sichuan, southwestern Gansu, and northern Yunnan in Western China and Ladakh in...

 relative to the Eurasian plate

Eurasian Plate

The Eurasian Plate is a tectonic plate which includes most of the continent of Eurasia , with the notable exceptions of the Indian subcontinent, the Arabian subcontinent, and the area east of the Chersky Range in East Siberia...

. This motion is caused by the lateral spreading of the zone of thickened crust

Crust

Crust may refer to:* Crust * The Crust, television seriesPhysical sciences:* Crust , at least continent-wide structure* Soil crust, local biology-sensitive structureFood:* Crust, dense surface layer of bread...

 associated with the collision between the Indian and Eurasian plates.

Earthquake characteristics

The earthquake rupture began on a relatively small strike-slip fault segment at the western end of the Kunlun fault in the region of the mountain Buka Daban Feng. The rupture propagated to the east via an extensional stepover before following the main strand of the Kunlun fault. The region of co-seismic deformation (i.e. that occurred during the earthquake) is unusually large, with significant faulting being observed up to 60 km from the main rupture trace . This deformation occurs in two swathes, ca. 20 and 60 km from the main fault trace. Pre-existing lineaments and geomorphological features suggest that this earthquake-triggered displacement occurred on existing faults.

An analysis of the propagation speed indicates that the rupture propagated at a normal velocity along the original segment, but increased in velocity to above the S-wave

S-wave

A type of seismic wave, the S-wave, secondary wave, or shear wave is one of the two main types of elastic body waves, so named because they move through the body of an object, unlike surface waves....

 velocity after the jump across the extensional stepover and continued at that speed until propagation stopped. This makes the Kunlun earthquake the best documented example of a supershear earthquake

Supershear earthquake

A supershear earthquake is an earthquake in which the propagation of the rupture along the fault surface occurs at speeds in excess of the seismic shear wave velocity. This causes a form of sonic boom to occur.-Rupture propagation velocity:...

. It has been suggested that the unusually wide zone of co-seismic deformation is a direct result of the supershear rupture propagation.