1889 Chilik earthquake
The 1889 Chilik earthquake occurred on July 11 on the Gregorian calendar, or June 30 on the Julian calendar at 15:14 local time in the Tien Shan mountains. The earthquake measured an estimated Mw 7.9 to Mw 8.3 on the moment magnitude scale and was assigned a X (Extreme) on the Mercalli intensity and Rossi-Forel scales.[2]
   | |
| UTC time | 1889-07-11 22:14:00 |
|---|---|
| Local date | 11 July 1889 |
| Local time | 15:14 |
| Magnitude | Mw 7.9–8.3 Ms 8.3 |
| Depth | 40 km (25 mi) |
| Epicenter | 43.2°N 78.7°E[1] |
| Areas affected | Kazakhstan, Kyrgyzstan |
| Max. intensity | X (Extreme)[1] |
| Casualties | 23+ dead |
Tectonic setting
The geological forces at play in the Turkestan region are directly related to the ongoing collision of the Indian Plate with the Eurasian Plate.[3] 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 between the two landmasses that were also converging. These terranes were later accreted to Eurasia as northward-moving India closed collided 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 their base.[3] The region is dominated by large, north and south-dipping thrust faults along the southern edge of the Tien Shan mountains, and the northern boundary of the Tarim basin, one of them being the Aheqi Fault Zone.[3]
Earthquake
In the days before the mainshock, many survivors reported peculiar behaviors of animals, including dogs howling and cats being restless.[4]
A post-earthquake survey of the region using reports of the earthquake's damage and effects led to the conclusion that the epicenter was located in the Chilik River Valley. No surface ruptures were identified during the survey as data was obtained via questionnaire given to eyewitnesses. The epicenter zone is elongated in the north northeast-south southwest direction approximately 100 km southwest of Almaty.[5]
Given the earthquake only had a maximum intensity assigned X on the Rossi-Forel scale, and its borad coverage over a wide area, the hypocenter depth is estimated to be at least 40 km beneath the surface. The length of surface ruptures associated with the earthquake is estimated at 200 to 300 km, with an average slip of 6.7 to 9.1 meters for an event consisting of thrust and strike-slip mechanisms. Modern field investigations however, was only able to find 175 km of surface ruptures and fault scarps on multiple fault strands. A 30-km-long scarp on the Saty Fault, an oblique-reverse structure is assumed to have formed during the 1889 earthquake. Dextral surface ruptures were also identified on the Beshkaragai Fault for a length of 40 km, where a maximum slip of 4.5 meters was observed. Another 100 km surface rupture was identified near the summits of the Kurmentey Range, a subrange in the Tien Shan. The surface ruptures consisted of dextral strike-slip motion of at least 8 meters.[5]
Impact
At Verny (now Almaty), the locals described the ground motion as a slow oscillation, rocking, wave-like motion. The earthquake was the most intense ever felt in the town since 1887. Shaking was so strong that many people and farm animals reportedly fell off their feet and were thrown off the ground by yards. Eyewitnesses reported seeing people thrown up into the air as much as one arshin (71.12 cm). The earthquake itself did not cause severe and widespread damage because new buildings were recently constructed following the 1887 earthquake. Official reports stated that 491 residents reported damage to their homes after the quake.[4]
Casualties
The shock, despite its intensity, did not result in extreme numbers of fatalities. In the village of Uytala, there were seven recorded deaths, including an elderly man and six children. Four people suffered serious injuries. In Shelek (Chilik), Malovodnoye, and Mikhailovsk, the earthquake collapsed walls and brought down roofs, killing 17 people.[4]
References
- NGDC. "Significant Earthquake Information". Retrieved 23 August 2021.
- Frank Krüger; Galina Kulikova; Angela Landgraf (14 September 2018). "Magnitudes for the historical 1885 (Belovodskoe), the 1887 (Verny) and the 1889 (Chilik) earthquakes in Central Asia determined from magnetogram recordings". Geophysical Journal International. 215 (3): 1824–1840. doi:10.1093/gji/ggy377. Retrieved 17 April 2021.
- Bihong Fu, Yoshiki Ninomiya, Jianming Guo (2010). "Slip partitioning in the northeast Pamir–Tian Shan convergence zone" (PDF). Tectonophysics. 483 (3–4): 344–364. Bibcode:2010Tectp.483..344F. doi:10.1016/j.tecto.2009.11.003.CS1 maint: multiple names: authors list (link)
- Alkuat Nurmagambetov (1999). Seismic history of Almaty (in Russian). LEM. p. 68.
- K. E. Abdrakhmatov, R. T. Walker, G. E. Campbell, A. S. Carr, A. Elliott, C. Hillemann, J. Hollingsworth, A. Landgraf, D. Mackenzie, A. Mukambayev, M. Rizza, R. A. Sloan (2016). "Multisegment rupture in the 11 July 1889 Chilik earthquake (Mw 8.0–8.3), Kazakh Tien Shan, interpreted from remote sensing, field survey, and paleoseismic trenching". Journal of Geophysical Research: Solid Earth. 121 (6): 4615–4640. doi:10.1002/2015JB012763. hdl:2381/38249.CS1 maint: multiple names: authors list (link)