SEISMOLOGY AND GEOLOGY ›› 2015, Vol. 37 ›› Issue (4): 1147-1161.DOI: 10.3969/j.issn.0253-4967.2015.04.017

• Research Paper • Previous Articles     Next Articles

analyses on the triggering facrors of large quantities of landslides in the upper reaches of the minjiang river, sichuan province

LI Yan-hao, JIANG Han-chao, XU Hong-yan, LIANG Lian-ji   

  1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
  • Received:2015-10-18 Online:2015-12-20 Published:2016-01-28

四川岷江上游滑坡触发因素分析

李艳豪, 蒋汉朝, 徐红艳, 梁莲姬   

  1. 中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029
  • 通讯作者: 蒋汉朝
  • 作者简介:李艳豪, 女, 1988年生, 2015年于中国地震局地质研究所获第四纪地质学专业硕士学位, 主要研究方向为新生代环境重建与古地震, 电话: 13793929206, E-mail: liyanhao0069@163.com。
  • 基金资助:

    中国地震局地质研究所基本科研业务专项(IGCEA1118)和地震动力学国家重点实验室自主研究课题(LED2013A03)共同资助。

Abstract:

Over the past geological and historical period, tens of thousands of landslides occurred in the upper reaches of the Minjiang River, an area which is characterized by alpine valleys and has been densely populated over the past several hundreds of years. Discussing the triggering factor of these landslides is of great significance to geological hazard mitigation and prevention in this region. In this paper, we focus on four aspects of regional rainfall, shape features of landslide slopes, the corresponding relationship between landslide area and earthquake magnitude, and the recurring features of the reconstructed palaeoearthquake record at Diexi. Compared with those in Nepal, both mean seasonal rainfall accumulation and mean daily rainfall for the past 30 years are too low to reach the threshold values triggering landslides in the upper reaches of the Minjiang River. Secondly, landslides in the study area are usually absent of inner gorges(canyon topography)on the hillslope toes, which are confirmed in previous studies as typical features of landslides triggered by storms. Thirdly, wide distribution of the landslides in the study area supports our notion of earthquake-triggering because the landslides triggered by storms commonly distribute locally. Fourthly, periodicity analysis of the reconstructed palaeoearthquake record at Diexi provides a few cycles of twenty to thirty years, possibly corresponding to the earthquakes of magnitudes>5.0 or 5.5 which are believed to have caused soft-sediment deformation in the study area. In contrast, like the 2008 MS8.0 Wenchuan earthquake, the average recurrence interval of the large earthquakes in the study area is 2.6ka. They caused tens of thousands of landslides and provided more coarse silt particles for the nearby lake sediments at least in 330 years for each time. This is consistent with exponential increase of earthquake magnitude from large to medium and of the landslide area with the increased earthquake magnitude. To sum up, we suggest that tens of thousands of landslides in the upper reaches of the Minjiang River were most likely triggered by earthquakes instead of storms. This preliminary viewpoint needs further examination in the future.

Key words: upper reaches of the Minjiang River, landslide mechanism, earthquake, storm, shape features of landslide slopes, recurrence interval

摘要:

以高山峡谷为地貌特征的岷江上游地区人口密集, 在晚更新世以来发生了数以万计的滑坡, 探讨该地区滑坡发生的主要触发因素对该地区的地质灾害防治意义重大。文中从区域降雨特点、滑坡坡形特点、地震震级大小与滑坡面积的对应关系以及叠溪已恢复地震记录的周期性分析等方面入手展开探索性研究。在降雨方面, 与滑坡灾害严重的尼泊尔相比, 岷江上游无论是累积降雨量还是日降雨量均未达到触发滑坡的关键阈值。在坡形方面, 岷江上游的滑坡不具有暴雨触发滑坡形成的坡底峡谷地形特征, 而具有地震触发滑坡形成的自上而下较为平坦的坡面特征。在震级大小与滑坡面积的对应关系中, 岷江上游的大面积滑坡分布支持地震触发, 与暴雨触发的局部小面积滑坡形成鲜明对比。在叠溪已恢复地震记录的周期分析中, 我们获得能够导致该地区软沉积物变形的>5.0或5.5级地震的复发周期集中于二三十年, 而引发大面积滑坡的可能类似汶川特大地震的平均复发间隔为2.6ka。这与中等—特大地震以及滑坡面积随地震震级一般呈现指数增长关系相吻合。据此, 我们初步认为, 岷江上游地区晚更新世以来发育的大量滑坡由降雨触发的可能性很小, 绝大部分可能为地震触发。这一初步认识有待今后的细致研究进一步验证。

关键词: 四川岷江上游, 滑坡成因, 地震, 暴雨, 滑坡坡形, 复发间隔

CLC Number: