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.

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The Tien Shan accommodates a significant portion of the India‐Eurasia N‐S convergence. In its northern part a zigzag pattern of mountain ranges bounds the western Ili Basin. The role of this basin in the overall shortening and the regional kinematics is not well understood. Geodetic data and instrumental seismicity are not sufficient to infer the role of individual faults and fault systems. We analyze GPS data and earthquake slip vectors and present the results of fault mapping based on remote sensing and field campaigns in the western Ili Basin. These observations indicate that E‐W thrust faults are active at the basin margins, and oblique and strike‐slip faults, both in the basin and in the Paleozoic rocks within the mountain ranges, have been active in the Late Quaternary. We propose a regional tectonic model in which the left‐lateral strike‐slip faults at the NW margin of the basin accommodate ~3‐mm/year NE‐SW shear. Smaller right‐lateral oblique faults transfer the motion in between the left‐lateral faults, and also take up shortening by rotations about vertical axes. We see the onset of internal deformation within the Ili Basin, although it has a strong basement. Our kinematic model is consistent with geodetic data, earthquake seismology, historical, and prehistorical surface faulting, and describes the first‐order features of active deformation that can be observed in the northern Tien Shan. Our study illustrates the importance of combining these different data sets to understand the regional tectonics.