Uniform postglacial slip-rate along the central 600 km of the Kunlun Fault (Tibet), from 26Al, 10Be, and 14C dating of riser offsets, and climatic origin of the regional morphology

Abstract

Late Pleistocene-Holocene sinistral slip-rates on several segments of the Kunlun Fault in northeastern Tibet have been determined. These determinations are based on the measured displacement of alluvial surfaces whose surface ages were determined by cosmogenic 26 Al and 10 Be dating of quartz pebbles, and by 14 C dating of charcoal. In the west, at three sites along the Xidatan-Dongdatan segment of the fault, near 94uE, terrace riser offsets ranging from 24 to 110 m, with cosmogenic ages ranging from y1800 to y8200 yr, yield a mean left-lateral slip-rate of 11.7t1.5 mm yr x1 . Field observations indicate minimum offsets of 9-12 m; this offset, when combined with the long-term slip-rate, indicates that great earthquakes (My8) rupture this segment of the fault with a recurrence interval of 800-1000 yr. At two sites along the Dongxi-Anyemaqin segment of the fault, near 99uE, terrace riser offsets ranging from 57 to 400 m with 14 C ages ranging from 5400 to 37 000 yr BP yield a minimum slip-rate of y10 mm yr x1 . At one site, the 1937 January 7, M=7.5 and the penultimate earthquakes produced 4 m of left-slip and 0.4 m of reverse-slip. The maximum recurrence interval of earthquakes with such characteristic slip is thus y400 yr. Farther east, near 100.5uE, along the Maqen segment of the fault, the 180 m offset of a lateral moraine, emplaced between the last glacial maximum (20 ka) and 11 100 yr BP, yields a mean slip-rate of 12.5t2.5 mm yr x1 .