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

• Published in: Journal of geophysical research. Solid earth Vol. 121; no. 6; pp. 4615 - 4640
• Main Authors: Abdrakhmatov, K. E., Walker, R. T., Campbell, G. E., Carr, A. S., Elliott, A., Hillemann, C., Hollingsworth, J., Landgraf, A., Mackenzie, D., Mukambayev, A., Rizza, M., Sloan, R. A.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-06-2016; American Geophysical Union
• Subjects: central Asia; Detection; Earth Sciences; Earthquakes; Escarpments; Fault lines; Faults; Forming; Geological faults; Geomorphology; Geophysics; historical earthquakes; Holocene; Imagery; intraplate earthquakes; Landscape; Length; Oil fields; Plate tectonics; recurrence interval; Remote sensing; Rupture; Rupturing; Satellite imagery; Satellites; Sciences of the Universe; Segments; Seismic activity; seismic hazard; Seismology; Sequencing; Slip; Spaceborne remote sensing; Surveying; Tectonics; Time; Trenching
• ISSN: 2169-9313; 2169-9356
• DOI: 10.1002/2015JB012763

The 11 July 1889 Chilik earthquake (Mw 8.0–8.3) forms part of a remarkable sequence of large earthquakes in the late nineteenth and early twentieth centuries in the northern Tien Shan. Despite its importance, the source of the 1889 earthquake remains unknown, though the macroseismic epicenter is sited in the Chilik valley, ~100 km southeast of Almaty, Kazakhstan (~2 million population). Several short fault segments that have been inferred to have ruptured in 1889 are too short on their own to account for the estimated magnitude. In this paper we perform detailed surveying and trenching of the ~30 km long Saty fault, one of the previously inferred sources, and find that it was formed in a single earthquake within the last 700 years, involving surface slip of up to 10 m. The scarp‐forming event, likely to be the 1889 earthquake, was the only surface‐rupturing event for at least 5000 years and potentially for much longer. From satellite imagery we extend the mapped length of fresh scarps within the 1889 epicentral zone to a total of ~175 km, which we also suggest as candidate ruptures from the 1889 earthquake. The 175 km of rupture involves conjugate oblique left‐lateral and right‐lateral slip on three separate faults, with step overs of several kilometers between them. All three faults were essentially invisible in the Holocene geomorphology prior to the last slip. The recurrence interval between large earthquakes on any of these faults, and presumably on other faults of the Tien Shan, may be longer than the timescale over which the landscape is reset, providing a challenge for delineating sources of future hazard.
Key Points
The 1889 Mw 8.0‐8.3 Chilik earthquake may have involved at least 175 km of rupture with measured slip of 10 m
The earthquake may have ruptured three segments, involving both oblique left‐ and right‐lateral slip
The 1889 earthquake was the only surface rupture for at least 5 ka and probably for much longer