@ ŒfÚŽGŽi˜ajF “ú–{’nkHŠwƒVƒ“ƒ|ƒWƒEƒ€˜_•¶W VolF 9-3Šª ”NF 1994”N •ÅF E.121-E.126•Å ’˜ŽÒi˜ajF - ƒ^ƒCƒgƒ‹i˜ajF - ´˜^i˜ajF
- ƒL[ƒ[ƒhi˜ajF - ŒfÚŽGŽi‰pjF PROCEEDINGS OF THE JAPAN EARTHQUAKE ENGINEERING SYMPOSIUM ’˜ŽÒi‰pjF Masahiro IIDA, Mario ORDAZ, Hitoshi TANIGUCHI, Carlos GUTIERREZ, Miguel SANTOYO ƒ^ƒCƒgƒ‹i‰pjF INTERPRETATION OF WAVE FIELD INSIDE THE MEXICO VALLEY ON THE BASIS OF BOREHOLE DATA ´˜^i‰pjF
During the 1985 Michoacan earthquake (Ms=8.1), seismic waves were amazingly amplified in the lakebed zone of Mexico City, which is approximately 400 km from the epicenter, and the long duration of the lakebed seismograms was a real surprise. In the present study, we hypothesize that the long coda is not only surface waves, but also long-period body waves, which are produced by the multipathing due to the long-distance path and the very soft surficial layers. We perform the nonstationary spectrum analysis, the 1-D elastic propagation analysis and the cross correlation analysis for borehole data at lakebed stations. These analyses indicate that the soft surficial layers afford to cause dominant-period waves, and that the long-duration records are composed of both surface waves and long-period body waves. ƒL[ƒ[ƒhi‰pjF - ‹LŽ–‹æ•ªF - ‹æ•ª @@@ˆÏˆõ‰ï˜_•¶W