Study on the Reasonable Liquefaction Prediction for a Large Interplate Earthquake Based on the Representative Soil Profile Models


Abstract eng:
The 2011 Great East Japan Earthquake, with a magnitude of MW = 9.0, occurred in the Pacific Ocean about 130 km off the northeast coast of Japan’s main island on March 11, 2011. The epicentral distance was very long, about 380 to 400 km, and liquefaction occurred over a wide area of reclaimed land along Tokyo Bay. The most seriously damaged area was Urayasu City, where about 85% of the area was liquefied. Seismic intensities in the liquefied zones were not high, although the liquefied grounds were covered with boiled sand. Most likely, the very long duration of the main shock along with the large aftershock that hit 29 min later induced the severe liquefaction. When discussing the prediction and the countermeasure to liquefaction at future, it is necessary to consider the influence of the very long duration earthquake motion of a huge interplate earthquake. In Japan, the liquefaction prediction procedure is categorized as a technique for civil engineering structures and buildings. In the method for civil engineering structures, weighting factors for earthquake motion characteristics are provided for interplate and inland earthquakes. The objective of this study was to perform reasonable prediction of a huge interplate earthquake, including the seismic effects of long duration and the regionality of liquefaction strength using Representative Soil profile models created from existing ground survey results. The study area is Urayasu which suffered the most serious liquefaction damage. This area is divided into the reclaimed land which liquefied, and the natural deposition ground which is not liquefied. A ground model is the Representative Soil Profile Models which equalized the existing ground survey results in 250 m meshes. In order to carry out reasonable liquefaction prediction in case of a huge interplate earthquake, it was confirmed that it is necessary to take into consideration the regionality of a liquefaction strength ratio and the influence of a long-time continuation earthquake motion. The Confirm of the matching property with the real damage of a prediction result uses the fieldwork results after the earthquake due to Chiba Prefecture. In this fieldwork, the distribution of the amount of relative displacements of the structures on the pile foundation and a ground surface is obtained in detail. A liquefaction potential of the degree index of liquefaction is obtained from a liquefaction prediction result by integrating with a distribution of the depth direction of a safety factor against liquefaction. A liquefaction potential and the amount of ground-surface relative displacements tend to increase similarly, and were able to confirm the prediction result and the matching property of the real damage.

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Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
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 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 1161.:
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