1902 Turkestan earthquake

The geological forces at play around Kyrgyzstan and Xinjiang are directly related to the ongoing collision of the Indian Plate into the Eurasian Plate.[4] The topography of this region is influenced by broad crustal deformation as a result of convergence along the Main Himalayan Thrust. Before the Indian subcontinent collided with Eurasia, there were island arcs and microcontinents that were also converging. These terranes were later accreted to Eurasia as India closed the gap with Eurasia, and are now in present-day Central Asia. Ancient suture zones mark the boundary between these accreted terranes. This deformation and accretion led to the formation of the Tien Shan mountains, which are moving 7±2 mm/yr towards the south along faults running along its base.[4] The region is dominated by large, north and south-dipping thrust faults along the southern base of the Tien Shan mountains, and the northern boundary of the Tarim basin, one of them being the Aheqi Fault Zone.[4]

While scientific knowledge of the event is rather sparse, due to the period in which it happened, research has given new insights into the earthquake of August 22, 1902. In a 2017 research, the earthquake was determined to have occurred at a depth of 18 km with the epicenter coordinates at 39.87° N 76.42° E, instead of most global event catalogs which place the epicenter coordinates at 40.0° N 77.00° E. The earthquake magnitude was also recalculated to be 7.7, while older figures presented magnitude 8.3 (written as 8.25) or 8.6.[5]

Thrust faulting was the culprit of this event, involving a rupture on the Ttiotegongbaizi-Aerpaleike Fault located at the southern flanks of the Tien Shan range.[6][7] This fault is 200 km long, and expresses itself like a gentle wave-shape. It dips north at varying angles of 25° to 60°. It was this fault that was responsible for an M_wc 6.3 earthquake that killed some 26 people in March 1996.[8][9]

Apparently, no surface ruptures were produced thus suggesting that the event may have been a blind thrust earthquake. It had a maximum intensity of X to XI (Extreme) on the Mercalli intensity scale, and X on the Rossi-Forel scale.[6]

The earthquake struck at 8:00 am on August 22, lasting for one and a half minutes, and reported to be extremely violent. Severe aftershocks were felt every day up till August 30. The mainshock was said to have been recorded on seismographs in Europe.[10]

In the villages of Shizijie, Bajiahu, Niujuanzi, Zhuanglangmiao, Xidatang, Shichang, in Boluotonggu, and the mountain areas around Dazimiao and Reshuiquanzi, many wood and mud houses collapsed while those that remained intact were tilted. More than 2,000 homes were destroyed, resulting in more than 280 people dying. Many temples were also completely destroyed. Surface fissures tore through the ground, ranging from 0.2 meters to one meter wide, and up to several kilometers long. The earthquake also triggered landslides and opened wide cracks near the mountains.[11]

In Kashgar, the mainshock collapsed sun-dried brick walls and collapsing homes, resulting in 16 deaths. Masonry buildings however did not sustain serious damage.[10]

The Artush district north of Kashgar suffered more devastating consequences. The earthquake collapsed almost every house in the area. Some 667 people were killed, and thousands more injured.[10]

The village of Astyn saw 400 fatalities, and in Jangi, 20 fatalities.[12]

In Yarkand, there was less serious damage to the city, but two children lost their lives due to collapsing walls. There was also damage being reported in Narin and Atbashi with no deaths recorded.[10]

In total, some 2,500 people were killed, however, the death toll may have been high as 20,000.[13][14][15]

• List of earthquakes in 1902
• List of earthquakes in China