震源深度对二维盆地放大的影响研究

Influence of the Focal Depth on Two-dimensional Basin Amplification

基于谱元法,采用4种不同倾角的盆地模型,研究了不同震源深度走滑地震非平面波入射时二维盆地放大规律,分析了盆地边缘放大的峰值及其位置与无量纲频率和盆地倾角的关系。结果表明:①随着震源深度的增大,水平方向上速度峰值比的最大值逐渐增大,在震源深度为10 km时达到最大,随后减小,且水平向和竖直向速度峰值比的最大值位置逐渐偏向盆地边缘。②震源深度较浅时,4种倾角的盆地在水平方向上的速度峰值比的最大值相差不大,差值始终小于1;震源深度较深且频率较高时(η≥1),4种倾角盆地的速度峰值比的最大值相差很大,差值达到3。

Based on the spectral element method,four basin models with different dip angles are used to study the amplification law of the two-dimensional basin when non-plane waves caused by the strike-slip earthquake at different focal depths travel in the basin.The relationship between the maximum amplification,its position at the edge of the basin and the dimensionless frequency,dip angle of the basin is analyzed.The results show that:①With the increase of focal depth,the peak velocity ratio increases gradually in the horizontal direction,and reaches the maximum when focal depth is 10 km,and then decreases.And the position of the maximum peak velocity ratio in horizontal and vertical directions gradually becomes close to the edge of the basin.②When the focal depth is relatively shallow,there is little difference between the maximum ratios of the peak velocity in horizontal direction among four basin models with different dip angles,and the difference is always less than 1.When the focal depth is deep and the frequency is high(η≥1),the maximum ratios of the peak velocity vary greatly,and the maximum difference reaches 3.