岷县漳县6.6级地震典型滑坡特征及其诱发机制

Study of the Characteristics and Inducing Mechanism of Typical Earthquake Landslidesof the Minxian-Zhangxian M_S6.6 Earthquake

地震和降雨是滑坡产生的两大诱因。一般认为二者的耦合作用概率小,在现实中也较少发现有此种实例。岷县漳县6.6级地震中黄土地震滑坡广泛发生,本文通过现场调查,在相关降雨量数据、航空影像空间分析的基础上研究了两个地点(永光村滑坡和堡子村滑坡)的典型地震黄土滑坡的空间展布特征和发生、发展过程,分析了诱发机制。结果发现:(1)地震滑坡呈带状分布与地震发震构造走向一致;(2)位于极震区范围的永光村黄土滑坡具有泥流特征,土体含水量可达塑限以上,是由于过量降水和强地震动耦合作用下发生;(3)堡子村黄土地震滑坡则主要为强地震动所诱发,滑距较短,并具滞后发生特性。本结果对未来地震中滑坡的预防与防治具有借鉴意义。

Earthquakes and rainfall are two main factors to induce landslides. Generally, these two events rarely occur at the same time. However, their coupling occurred in a widespread region during a loess earthquake landslide caused by the Minxian--Zhangxian Ms6.6 earthquake on July 22, 2013, which resulted in significant losses of life and property. The characteristics of develop- ment and influencing factors of two typical earthquake landslides including the Yongguang and Puzi landslides are investigated on the basis of site survey, rainfall data, and aerial images. The results indicate that many earthquake landslides are distributed in a band in accordance with the trends of seismo-tectonics. In addition, moisture content was above the plastic limits of loess in the Yongguang landslide, which showed characteristics of mudflow. The reasons for its occur- rence differ from previous earthquake landslides and include the coupled effects of excessive rain- fall and strong ground motion. Moreover, strong ground motion was also the main factor in the Puzi earthquake landslide, in which the slide distance was very short and continued 40 rain fol- lowing the earthquake. Such investigation results of the two typical loess earthquake landslidesare very helpful for the prevention and control of earthquake landslides in the future.