2008年古田4.1、4.6级地震强震动观测记录

Strong Motion Observation Records of Gutian ML4.1 and ML4.6 Earthquakes in 2008

水口水电站重力坝强震反应台阵在古田ML4.1、ML4.6地震中获得了强震资料,通过对观测资料初步分析,得到以下认识:如果仅用基岩自由场顺河向振动的峰值加速度进行估算,该大坝遭受的地震强度达到Ⅵ度,这与通过现场灾害评估得出大坝位于Ⅴ度区外的结论相悖;坝底和基岩自由场竖直向和顺河向振动情况一致,但幅度存在差异;对于坝体的峰值加速度,相比较于坝底,坝中部三方向均有不同程度的放大,坝顶三方向均有不同程度的缩小;从坝底至坝顶,峰值加速度出现滞后现象,但并不明显,说明坝体刚性较大。此次地震中坝体主要呈整体振动特性。

Strong motion data of strong motion response array for the gravity dam of Shuikou Hydropower Station were obtained during Gutian ML4.1 and ML4.6 earthquakes. The following findings can be gained through initial analyses of the observation data： 1） some channels of the array failed to obtain records due to instrumental faults; 2） if only based on peak accelerations of free field bedrock along the river, the earthquake intensity of the dam will be up to VI, which is opposite to the conclusion drawn by the field catastrophic evaluation that the dam lies outside the area of intensity V; 3） the free field vibrations in vertical and along-river directions are same for the bottom dam and bedrock, while there is variance on the magnitudes; 4） compared to the bottom dam, the three directions peak accelerations of the middle part of dam body are amplified to some extent, while the values are reduced to some degree at the top dam; 5） from the bottom to the top of the dam, there is indistinct lagging for the peak accelerations. This means that the dam has relatively large rigidity and the dam body appears to vibrate as a whole structure in the earthquakes.