西秦岭北缘断裂宝鸡—武山段活动触发滑坡分布规律与成因机制

西秦岭北缘断裂沿"一带一路"交通廊道展布,是南北活动构造带强震丛集发育的节点之一,地震地质灾害风险极高。基于地质调查、测绘与数值分析,查明了断裂在天水地区触发的地震滑坡分布特征,探讨了断裂触发滑坡的形成机制。研究表明:(1)西秦岭北缘活动触发的巨、大型滑坡为断裂地貌过程的一部分,易在断裂的阶区聚集发育,其枢纽部位也有零星的分布;(2)巨大型滑坡集中于历史极震区内,断裂破裂过程中的近场惯性滑移、远场地震动是主要触发因素,二者耦合作用导致巨大型滑坡在断裂带两侧具有对称分布特征,活动强度由近及远而逐渐变弱;(3)断裂水平滑移、破裂引起的斜坡滑动变形以结构面贯通为主要表现形式,具有强烈的方向效应、近直立断层的区域地震动效应及地震波的山体地形放大效应,这些力学效应在滑坡破坏过程产生断裂结构面、次级羽裂结构面与滑动面,它们协同控制了滑坡的运动;(4)极端降雨触发的泥流是巨大型滑坡堆积体复活运动的主要形式,是现今防灾减灾重点。

DISTRIBUTION CHARACTERISTICS AND FORMATION MECHANISM OF LANDSLIDES TRIGGERED BY ACTIVITIES OF BAOJI-WUSHAN SEGMENT AT THE NORTHERN MARGIN OF WESTERN QINLING FAULT ZONE

The fault at the northern margin of western Qinling distributes along the transportation corridor of "the Belt and Road", which is one of the focuses with crowded development of strong earthquakes along the south-north active fault zone, having extremely high seismic risk of geological disasters. Based on geological survey, mapping and value analysis, the distribution characteristics of landslide disasters triggered in Tianshui area are summarized, and the mechanism for fault to trigger disasters is investigated. The study yields the following understanding:(1) As a part of geomorphic process of fault, the giant and large-scale landslides triggered by activities along the step of western Qinling fault zone easily developed in the fault zone with a scattered distribution in the hub positions of faults. (2) The giant and large-scale landslides concentrate on the meizoseismal area. When the faults start to fracture, the inertia fracture plane activities cause landslides along the fault zone and trigger seismic oscillation symmetrically distributed by the two sides of the fault zone, with the activity intensity of landslides gradually weakening from the near to the distant. (3) The slope sliding and deformation caused by horizontally fracture activities are mainly reflected by the appearance of structural plane, which features strong fracture direction effect, regional seismic oscillation effect of nearly vertical fault and mountain terrain amplification effect of seismic wave. Such mechanical effects cause fracture structure plane, secondary structure plane and sliding plane during the destruction process of landslides, and they coordinate with each other to control the slippage destruction of landslides.(4)The mud flow triggered by extreme rainfall is the main movement form of giant landslide reactivation. Now more attention of disaster prevention and mitigation should be paid on large mud flows.