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汶川5月12日8.0级地震在构造上起因于印度板块与欧亚板块以每年约5cm的速度聚敛,并因此而引起青藏高原的地壳物质向四川盆地及中国东南大陆运移。主震震源及余震活动集中于以龙门山为中轴的一条长约350km、宽约100km的地震活动带。震源深度一般分布于地壳脆性-韧性转换边界以上约10~20km区间的地壳震源层之中,属浅源构造地震。主要震源机制与龙门山构造运动方式密切相关,以其地壳厚度向西急剧加厚、重力梯度带、高波速比(Vp/Vs~2.2)等深部异常及逆冲断层兼具走滑性质的地质构造为特征。在震源辐射、路径传播和场地效应研究的基础上,分别计算并比较了岩石和土壤条件下的地震响应谱,特别强调了土壤条件下的场地放大效应;同时对与地震安全性有关的一些问题如地质灾害、地震频谱设计、地震早期预警系统及中、长期至短期地震预报等进行了探讨;特别提供了一个由加权平均计算、以岩石条件下震波衰减模式为基础的地震频谱设计参考实例。地震构造与动力学研究可融入工程地质与环境工程等学科发展。经历汶川地震考验的一些新近设计和建设的工程项目可为今后改进工程建筑规范与标准提供重要而有益的参考。地震预报是当今一大难题,但需探索研究,不可懈怠。地震减灾与预防是目前比较切合实际的安全举措。
The Wenchuan earthquake on May 12 was structurally caused by the convergence of the Indian Plate and the Eurasian plate at an annual rate of about 5 cm. As a result, the crustal material in the Qinghai-Xizang Plateau migrated to the Sichuan Basin and the southeastern China. The main shocks and aftershocks are concentrated on a seismic belt about 350 km long and about 100 km wide centered on the Longmen Mountain. Depth of focal depths are generally distributed in the crustal seismic layers of about 10 ~ 20km above the crustal brittle-ductile transitional boundary, and belong to shallow-source tectonic earthquakes. The main focal mechanism is closely related to the tectonic movement of Longmen Shan. It is characterized by sharp thickening of the crust to the west, deep anomalies such as gravitational gradient zone and high velocity ratio (Vp / Vs ~ 2.2), and geology with thrust-strike faults Constructed as a feature. Based on the study of source radiation, path propagation and site effects, the seismic response spectra under rock and soil conditions are calculated and compared respectively, with special emphasis on the site amplification effect under soil conditions. Meanwhile, some issues related to seismic safety Such as geological disasters, seismic spectrum design, early warning system of earthquake and medium- to long-term and short-term earthquake prediction. In particular, a reference example of seismic spectrum design based on seismic wave attenuation mode under rock condition is provided by weighted average calculation. Earthquake tectonics and dynamics research can be integrated into disciplines such as engineering geology and environmental engineering. Some newly designed and constructed projects that have experienced the test of the Wenchuan earthquake can provide important and useful references for future improvement of construction codes and standards. Earthquake prediction is a big challenge nowadays. However, it is necessary to explore and study and not slacken. Earthquake Disaster Mitigation and Prevention are more realistic security measures.