中文摘要：

2015年12月25日山东平邑县发生石膏矿塌陷事件。采用各向同性塌缩点源模型计算了该塌陷事件在周围地表产生的位移场、水平应力场及在其附近的蒙山山前断裂上的库伦破裂应力变化。结果表明：1）塌陷中心的水平位移达18mm,在距离塌陷位置约5km范围内的水平位移〉1mm,方向指向塌陷中心;塌陷中心的垂直沉降达4mm,在塌陷中心约3km以内沉降〉1mm,水平位移和垂直位移在远处快速衰减到可以忽略不计,这是由于该塌陷源较浅,位移变化局限在地表局部所致。2）由于自由表面的影响,该塌陷造成地下2km深度的约5km范围内呈现面收缩应力状态,面收缩应力达1 000Pa;而在远处均处于面膨胀应力状态,膨胀应力最大约达1 000Pa,面膨胀应力在距塌陷中心约10km处迅速衰减到100Pa以下。在2km深度的平面上造成的最大主张应力和主压应力达10 000Pa,在主压应力大于主张应力的塌陷中心约5km范围内,主压应力呈现以塌陷为中心的径向分布,在距塌陷中心约5km以外,主张应力呈现以塌陷为中心的径向分布,随着距离的增大,主压应力和主张应力快速衰减到100Pa量级。3）该塌陷造成了其西北部的蒙山山前断裂（被认为不活动的断层段）上的库伦破裂应力降低,最大值达2 500Pa,造成了东南部的蒙山山前断裂（被认为第四纪左旋正断活动的断层段）上的库伦破裂应力增加,最大值达2 400Pa,在分析该断裂的危险性时要予以注意。

英文摘要：

A collapse happened in Pingyi County, Shandong Province, on December 25, 2015. The displacement field, stress field and Coulomb failure stress change on the Mengshan frontal fault generated by the collapse are calculated by using point collapse model in isotropic medium. The result shows that： （1） The maximum horizontal displacement is located at the center of the collapse with value of-18mm. The horizontal displacements are greater than lmm within-5km of the collapse with its direction pointing to the collapse center. The maximum subsidence is located at the center of the collapse with the value of 4mm. The subsidence is greater than lmm within -3kin of the collapse. The displacement field decays so rapidly that can be ignored at far away from the collapse for the shallow source, which caused local displacement field. （2） Influenced by the free surface, the contraction area stress within -5km of the collapse with the order of 1000Pa and expansion area stress in farther away areas at depth of 2kin are estimated, the expansion area stress of 1000Pa is estimated at the 5kin from the collapse center. Then the expansion area stress decays to 100Pa at the distance of 10km from the collapse. The maximum compressive and extensional principal stresses are estimated as 10000Pa at the depth of 2km. The compressive stress axes present radical direction pointing to the collapse within -5km of the center. In farther away from the collapse, The extensional principal stress axes present radical direction pointing to the center of the collapse. With farther distance to the collapse, the compressive and extensional stress decay rapidly to the order of 100Pa. （3）The Coulomb failure stress on the northwestern part of the Mengshan frontal fault, which is known as active segment of the Mengshan frontal fault, is decreased by the collapse with maximum value of 2500Pa. Whereas, the Coulomb failure stress on the southeastern part of the Mengshan frontal fault, which is known as left-lateral normal slip fault segment in Qua