Seismic strong motion estimation with risk evaluation in Mexico City

我们调查了1985年墨西哥城湖床地区发生的一次大幅度、长周期、持续时间长的强震，它造成了大量的建筑物破坏。我们合理地估计了强震，并在湖床地带进行了建筑反应分析。对墨西哥城的地震危险性进行了评估，并总结了预防地震灾害的对策。为此，我们进行了以下三个方面的研究：1.强动作。(1)分析了墨西哥城湖床带三维小台阵记录到的强震。我们用浅、深两种结构估算了理论波场。同时，从理论上分离了体波和面波。此外，我们还考虑了土体的非线性和沉降性，对体波传播进行了数值模拟。(2)对墨西哥城多个钻孔台站记录的强震进行了分析，并对不同岩土区的波场进行了调查。我们利用深部结构估计了一些理论波场，并指出面波是由墨西哥火山带激发的。(1)建立了考虑强震特征的三维非线性土-建筑物相互作用分析模型。在假设的格雷罗地震期间，我们对墨西哥城湖床地带的低到高层建筑进行了相互作用分析，这与1985年的地震相似。在1985年的地震中，我们解释了中层建筑的许多损坏。(2)对墨西哥城不同岩土区进行了相同的分析，解释了当地破坏程度的差异。3.城市防灾。我们开始改进墨西哥城现有的地震风险评估系统，考虑强震特征和建筑反应。此外，我们正在估计墨西哥城因一些地震造成的经济损失。

We investigate large-amplitude long-period strong motions with long duration, which caused much building damage in the lakebed zone of Mexico City during the 1985 earthquake. We estimate strong motions reasonably, and perform a building response analysis in the lakebed zone. We evaluate seismic risk in Mexico City, and summarize countermeasures for earthquake disaster prevention. For these purposes, we performed the following 3 research themes.1.Strong motions. (1) We analyzed strong motions recorded at a 3-dimensional, small array station in the lakebed zone of Mexico City. We estimated a theoreticalwavefield, using a shallow and deep structures. Also, we separated body andsurface waves theoretically. Furthermore, we performed a numerical simulation for body-wave propagation, considering nonlinearity and subsidence of soils. (2) We analyzed strong motions recorded at several borehole stations in Mexico City, and investigated wavefields in different geotechnical zones. We estimated some theoretical wavefields using deep structures, and indicated that surface waves were excited by the Mexican Volcanic Belt.2.Buildings. (1) We developed a 3-dimensional nonlinear soil-building interaction analysis, which considered characteristics of strong motions. We performed the interaction analysis for low- to high-rise buildings in the lakebed zone of Mexico-City during the hypothetical Guerrero earthquake, which is similar to the 1985 earthquake. We interpreted much damage to mid-rise buildings during the 1985 earthquake. (2) We conducted the same analysis in different geotechnical zones of Mexico City, and interpreted local differences in damage level.3.Urban disaster prevention. We started to improve an existing seismic risk evaluation system for Mexico City, by considering strong-motion characteristics and building responses. Also, we are estimating economical damage in Mexico City due to some earthquakes.