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Investigating paleoseismicity using fault scarp morphology of the Dushanzi Reverse Fault in the northern Tian Shan, China

Wei, Zhanyu, He, Honglin, Su, Peng, Zhuang, Qitian, Sun, Wen
Geomorphology 2019 v.327 pp. 542-553
data collection, lidar, statistical analysis, terraces, topography, trenching, China
This study uses the morphology of fault scarps to study the paleoseismic history of the Dushanzi Reverse Fault (DRF) in the northern Tian Shan region, China. Using high-resolution LiDAR DEMs to create a large number of scarp profiles, we detected slope breaks in the fault scarp morphology to quantify the number of paleoearthquakes that occurred on the scarps and obtained the along-strike scarp height distribution to determine the cumulative and single-event vertical displacements. Our results revealed four surface-rupturing events with similar co-seismic vertical displacements of ~1.4 m via the statistical analysis of displacement datasets and slope breaks, which were in agreement with the findings from paleoseismic trenching. We then assessed the paleomagnitudes using the empirical scaling relationships between moment magnitude and rupture parameters and the recurrence interval for surface-rupturing events using the formation ages of the displaced terrace surfaces. The results indicate that the possible magnitudes range from Mw 6.5 to 6.7, even reaching Mw ~7.2 in the case of a multi-fault rupture of the entire anticline-fault belt, with an average recurrence interval of ~2.4–3.0 ka. This study also demonstrates the importance of using high-resolution topographic data in paleoseismic investigations, which enables the determination of fine-scale tectono-geomorphic interpretations and detailed offset measurements over large regions along the fault.