In Situ Soil-Specific Nonlinear Properties Back-Calculated from Vertical Array Records during 1995 Kobe Earthquake
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 131, Issue 12
Abstract
In situ nonlinear soil properties are investigated based on vertical array records obtained during the 1995 Hyogoken Nambu earthquake (Kobe earthquake) at soft soil sites near the earthquake fault zone. Spectrum ratios between ground surface and deeper levels are calculated for the main shock and associated small shocks and S-wave velocities and damping ratios in surface soil layers to best reproduce them are back-calculated by means of an inversion analysis (extended Bayesian method) assuming one-dimensional vertical horizontal shear (SH)-wave propagation. Obvious differences in S-wave velocities and damping ratios are found between the main shock and the small shocks. Clear strain-dependent modulus degradations which can be differentiated for different soil types are recognized. The degradations are essentially consistent with some of laboratory test results to date for each soil type at least for or larger, though for gravelly soils back-calculated values tend to show milder degradations than laboratory test results presumably due to large inclusion of fines in actual ground. Back-calculated damping ratios show essentially the same trend as in laboratory tests, although the absolute values are in most case a few percent higher in the strain range smaller than .
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Acknowledgments
Dr. I. Suetomi of the National Research Institute for Earthquake Science and Disaster Prevention (formerly Researcher in Central Research Institute of Sato Kogyo Com. Ltd.) who kindly provided the computer program of EBM and helped this analytical research is gratefully acknowledged. The Kansai Electric Power Company and the Kobe Municipal Office who successfully gained the vertical array records and the Committee of Earthquake Observation and Research in Kansai Area (CEORKA) which generously disseminated them are greatly appreciated.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 131 • Issue 12 • December 2005
Pages: 1509 - 1521
Copyright
© 2005 ASCE.
History
Received: Aug 4, 2003
Accepted: Jan 21, 2005
Published online: Dec 1, 2005
Published in print: Dec 2005
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