Dynamics of the Wulong landslide revealed by broadband seismic records

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• 作者：Zhengyuan Li ; Xinghui Huang ; Qiang Xu ; Dan Yu ; Junyi Fan…
• 关键词：Wulong landslide ; Broadband seismic signals ; Source time functions ; Dynamic landslide process
• 刊名：Earth, Planets and Space
• 出版年：2017
• 出版时间：December 2017
• 年：2017
• 卷：69
• 期：1
• 全文大小：2739KB
• 刊物类别：Earth Sciences, general; Geology; Geophysics/Geodesy;
• 刊物主题：Earth Sciences, general; Geology; Geophysics/Geodesy;
• 出版者：Springer Berlin Heidelberg
• ISSN：1880-5981
• 卷排序：69

文摘

The catastrophic Wulong landslide occurred at 14:51 (Beijing time, UTC+8) on 5 June 2009, in Wulong Prefecture, Southwest China. This rockslide occurred in a complex topographic environment. Seismic signals generated by this event were recorded by the seismic network deployed in the surrounding area, and long-period signals were extracted from 8 broadband seismic stations within 250 km to obtain source time functions by inversion. The location of this event was simultaneously acquired using a stepwise refined grid search approach, with an error of ~2.2 km. The estimated source time functions reveal that, according to the movement parameters, this landslide could be divided into three stages with different movement directions, velocities, and increasing inertial forces. The sliding mass moved northward, northeastward and northward in the three stages, with average velocities of 6.5, 20.3, and 13.8 m/s, respectively. The maximum movement velocity of the mass reached 35 m/s before the end of the second stage. The basal friction coefficients were relatively small in the first stage and gradually increasing; large in the second stage, accompanied by the largest variability; and oscillating and gradually decreasing to a stable value, in the third stage. Analysis shows that the movement characteristics of these three stages are consistent with the topography of the sliding zone, corresponding to the northward initiation, eastward sliding after being stopped by the west wall, and northward debris flowing after collision with the east slope of the Tiejianggou valley. The maximum movement velocity of the sliding mass results from the largest height difference of the west slope of the Tiejianggou valley. The basal friction coefficients of the three stages represent the thin weak layer in the source zone, the dramatically varying topography of the west slope of the Tiejianggou valley, and characteristics of the debris flow along the Tiejianggou valley. Based on the above results, it is recognized that the inverted source time functions are consistent with the topography of the sliding zone. Special geological and topographic conditions can have a focusing effect on landslides and are key factors in inducing the major disasters, which may follow from them. This landslide was of an unusual nature, and it will be worthwhile to pursue research into its dynamic characteristics more deeply.Graphical abstractIn order to trace the dynamic process of the Wulong landslide, we estimate its source time functions (lower panel of the following image) using long-period seismic signals extracted from 8 broadband seismic stations within 250 km of the landslide. The topography in landslide area varies dramatically, enhancing the complexity in its movement characteristics. The moving direction of the sliding mass changed twice during the event (upper panel of the following image), leaving a Scouring Zone, a Main Depositional Zone and a Debris Depositional Zone. Our inversion results can perfectly characterize its movement features, including three stages of the landslide divided by two major collisions. Additionally, kinematic parameters of the sliding mass, such as velocities, are provided, with the maximum velocity of 35 m/s resulting from the height difference between the cliff and the Tiejianggou valley. Basal friction coefficients are also estimated and are consistent with the topography in the landslide area.