Site Response at a Location Affected by Soil Softening and Liquefaction during the 2011 Tohoku Earthquake

M. Daví ； L. Kingdom ； M. Redaelli

《Geotechnical Hazard Mitigations: Experiment, Theory and Practice—Proceedings of the 5th International Conference on Geotechnical Engineering for Disaster Mitigation and Rehabilitation》 2017年 (2017/10) Pp. 227-241

https://doi.org/10.6140/9789864371419.201710.0019

摘要

Although the influence of liquefaction on seismic shaking at ground surface has been identified more than a decade ago, the number of quantitative studies on the induced changes in spectral acceleration is still limited. Japan's KiK-net offers abundant data that can be used to study this influence, as its stations are equipped not only with seismometers at ground surface but also with instruments installed down a borehole drilled in the bedrock. This paper focuses on one of the KiK-net stations which experienced liquefaction during the 2011 Tohoku earthquake. Spectral accelerations were calculated by propagating the shaking at bedrock level through the softer shallow layers with a linear-equivalent analysis that neglects the influence of liquefaction. By comparing this prediction with the spectral acceleration actually recorded at ground surface the effect of liquefaction on ground shaking at the surface is quantified. In summary, liquefaction reduces the spectral accelerations for periods shorter than 0.5s. For periods longer than 0.5s the spectral accelerations are amplified, particularly up to 1.3s.

關鍵字

Seismic site response ； Liquefaction ； Cyclic softening ； Spectral acceleration ； Tohoku earthquake