Abstract: The Kalpintag Fault locates at the most forefront of Kalpintag nappe tectonics, and can be separated into eastern and western segments by Piqiang Fault. Six large trenches are excavated along the western segment and four paleoearthquakes can be distinguished in the three trenches of them. The first paleoevent occurred about 12ka BP, the second event occurred about 8.6ka BP, the third event occurred about 5ka BP,and the last event occurred after (1.73±0.15) ka BP, which probably is the Xike'er M6.8 earthquake in 1961 AD. The four paleoevents are characterized by 3～4ka quasi-periodic recurrence interval. The Kalpintag nappe structure are composed of 5～6 rows of fold-reverse fault zones. The faults with the latest activity are located at the forefront of the fold-reverse fault zones with 10km spacing between each fault. The north-dipping and listric style fault surfaces merged into the detachment surface in the deep along the bottom of Cambrian at 6～10km depth. The field investigation discovered that earthquake ruptures and paleoearthquake traces can be found not only along Kalpintag Fault but also along other faults, but the rupture length and seismic slip are smaller than that formed by an M≥7 earthquake. Although five paleoearthquakes since 14ka BP are obtained along western segment of Kalpintag Fault, some events are probably missed because of less trenches and dating samples. Many problems such as magnitude of these events, seismogenic fault and their rupture zones formed by one or several events await study in the future.

Key words: paleoearthquake, Kalpintag Fault, southwest Tianshan

摘要： 柯坪塔格断裂位于西南天山柯坪塔格推覆构造的最前缘,以皮羌断裂为界分成东西两段。在柯坪塔格断裂西段开挖了6个规模较大的探槽,6个探槽都揭露出断层,但其中3个探槽的古地震事件不清晰,另外3个探槽有古地震遗迹。通过分析研究,共确定了全新世以来的4次古地震事件:第1次古地震事件发生于距今约12ka,第2次事件发生于距今约8.6ka,第3次事件大致发生于距今约5ka,第4次事件发生于距今(1.73±0.15)ka以来,很可能是1961年西克尔6.8级地震。这4次古地震事件具有约3～5ka的准周期重复特征。天山南麓有5～6排推覆体,每排推覆体的前缘都发育活动逆断裂,它们向下收敛于寒武系底部的滑脱面,因此,天山南麓的地震破裂非常复杂,这4次古地震事件的震级、发震构造等问题都有待于今后的深入研究。

关键词: 古地震, 柯坪塔格断裂, 西南天山