利用BP神经网络技术建立自贡地区地震动地形效应模型及其在汶川地震中的效验  

A seismic topographic effect model in Zigong area established by a BP technique and its verification with the Wenchuan earthquake

作　　者：周红[1] 常莹 ZHOU Hong;CHANG Ying(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Institute of Mining Engineering,BGRIMM Technology Group,Beijing 100160,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]矿冶科技集团有限公司矿山工程研究设计所,北京100160

出　　处：《地球物理学报》2022年第6期2022-2034,共13页Chinese Journal of Geophysics

基　　金：国家自然科学基金面上项目(42174070)资助。

摘　　要：地形效应是地震学、地震工程学和工程地震学中非常重要的研究课题.地震震后调查发现:地形起伏变化引起了更严重的地震灾害,地震仪器也记录到复杂的三维地形对地震动具有放大效应.关于地形激发的地震动效应问题,目前仍处于定性研究阶段,得到了一些定性的结论:如地形效应表现为与地形坡度相关、与山脊和山谷相关、与山形坡面形态相关、与山体高宽比相关、与地形变化的尺度相关等等.这些定性结论没能给出影响地形效应的主要因素,如何预测地形效应仍是难题.本文通过谱元数值模拟方法,计算了自贡地区的地震动地形效应的放大系数,同时引入BP神经网络技术,揭示了地形放大系数可以用不同尺度地形上的变化来表述,即可以用地形高程、地形变化梯度及其高阶变化梯度来表示.据此为参量,文中建立了地形效应BP神经网络的预测模型,并将该预测模型的结果与自贡地形台阵在汶川地震中的主震记录获得的地形放大系数结果进行了对比,给出了预测结果与实际结果的差异范围,讨论了造成差异的成因,该论文提出的研究方法为更全面的研究地形效应提供了重要的研究思路.The seismic topographic effect is an important research topic in earthquake engineering.Post-earthquake investigations have revealed that topographic effects can cause catastrophic disasters and seismic instruments have recorded magnified ground motions due to complex topography.At present,most studies on the topographic effect focus on qualitative interpretations and confirm that the topographic effect is qualitatively correlated to the topographic slope,the geometric scale,and so on.However,the main factors controlling topographic effects are still unknown.In this paper,the theoretical topographic magnification factor in simulated ground motions at Zigong area is calculated by the spectral element method.The control parameters for establishing the topographic effect model are studied by the back-propagation(BP)neural network technology.These parameters include the topographic elevation,the first-order topographic gradient and higher-order topographic gradients in two orthogonal directions,which are related to topographic features,such as the topographic slope,the topographic geometry scale,and the topographic shape.To validate the model,the topographic effect predicted from the BP neural network model is compared with the observed Zigong magnification factors of the Wenchuan earthquake.These results shed light on the mechanism of the topographic effect.

关 键 词：BP神经网络技术 地震动地形效应 汶川地震 

分 类 号：P315[天文地球—地震学]