| Abstract: | The Litang fault zone (LFZ) is an active fault zone within the northwestern Sichuan sub-block. Field investigation reveals new evidence for its late Quaternary offset, neoteric earthquake ruptures and surface-rupturing segmentation, from which long-term slip-rates, characteristic earthquake magnitudes and recurrence intervals on the fault zone are estimated. This study shows that the LFZ consists of three subordinate faults, and they are the northern Maoyaba fault, Litang fault and Kangga-Dewu fault, respectively. All of them are dominated by leftlateral strike-slip with reverse dipslip component on different segments. Based on offset landforms and ages of relevant deposits collected from seven sites, it is estimated that the average leftlateral slip-rate on the LFZ reaches 4.0±1.0 mm/a in the past 14 ka BP, and vertical (reverse) dipslip rate in the range of 0.1-1.8 mm/a. Three subordinate faults are independent earthquake rupturing segments, on which the maximum moment magnitude of the characteristic earthquakes is estimated to be 7.0–7.3, and their average recurrence interval to be 500–1000 a. The latest earthquake ruptures occurred 119±2 years ago on the northern Maoyaba fault, about 1890 AD on the Litang fault, and in 1948 AD on the Kangga-Dewu fault, and this may indicate a unidirectional migration for surface rupturing earthquakes along the Litang fault zone, related to stress triggering between the segments. |
