|Budget Amount *help
¥9,000,000 (Direct Cost : ¥9,000,000)
Fiscal Year 1998 : ¥4,600,000 (Direct Cost : ¥4,600,000)
Fiscal Year 1997 : ¥4,400,000 (Direct Cost : ¥4,400,000)
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.