1920年海原8.5级地震高烈度区滑坡编录与分布规律

INVENTORY AND SPATIAL DISTRIBUTION OF LANDSLIDES IN Ⅸ-Ⅺ HIGH INTENSITY AREAS OF 1920 HAIYUAN(CHINA) M8.5 EARTHQUAKE

发生在黄土高原的1920年12月16日的海原MS8.5级大地震触发了大量的滑坡,这些滑坡直接造成了大量的人员伤亡。近年来,出现了一些关于本次地震触发滑坡的专题研究,然而,这些研究多是基于局部震区或者个别单体滑坡进行,极少有关于该地震触发滑坡详细全面的成果出现。这种情况已经成为了深入理解海原地震触发滑坡的规模与程度、发育规律等的障碍。本研究拟基于谷歌地球平台,采用人工目视解译方法,以海原地震高烈度区(Ⅸ~Ⅺ)为研究区,开展地震滑坡解译工作,并分析这些滑坡的分布规律与影响因子之间的关系。结果表明本次地震在Ⅸ~Ⅺ度区内触发了至少5384处滑坡,滑坡总面积为218.78 km2。滑坡密度最高的区域为Ⅸ烈度圈的北西部分。通过分析这些滑坡与地形、地震、地质等因子的关系发现,高程1700~2000 m为滑坡的高发与高易发区间;大多数滑坡集中发育在坡度15°~25°范围内,滑坡密度随着坡度的增加而显著增加;坡位越低,也就是距离河流越近,滑坡密度越大;新生代地层、尤其是第四系黄土覆盖地区是海原地震滑坡发生的主要区域,也是高易发区域。本文为探索黄土地区地震滑坡发育规律、减轻黄土地震滑坡灾害等提供了科学参考。

The Haiyuan M S8.5 earthquake on December 16,1920,occurred at the loess plateau.It triggered a large number of landslides.The landslides directly caused a large number of casualties.In recent years,there have been some special studies on landslides triggered by the Haiyuan earthquake.However,most of these studies have limitations on their local study areas or individual landslides.There are few detailed and comprehensive results about landslides triggered by the earthquake.This situation has become an obstacle to understand the overall incidence and severity,spatial distribution law of the Haiyuan earthquake-triggered landslides.In this study,we carry out the visual interpretation of landslides in the high seismic intensity(Ⅸ-Ⅺ)areas of Haiyuan earthquake based on Google Earth platform,as well as analyze the relationship between landslides and several influence factors.Results show that the earthquake triggered at least 5384 landslides,which have a total landslide area of 218.78￣￣km 2.The highest density of landslides is located at the NW part of seismic intensityⅨcircle.Through analyzing the relationship between these landslides and topography,earthquake and geological factors,it is found that elevation 1700~2000￣￣m registers the largest landslide number and density.Most landslides are concentrated in the slope angle range of 15°~25°whereas the number density of landslides increases with the increase of slope angle.The lower the slope position is,i.e.,the closer to rivers,the greater the density of the landslides.The areas with Cenozoic strata underlying,especially the Quaternary loess covered areas,register most of the landslides and the high density of landslides.This study provides a scientific reference for exploring the law of the occurrence of seismic landslides and reduction and mitigation of earthquake-triggered landslides in loess area.