Analysis Of Liquefaction During 2011 East Japan Earthquake - Part 1: Seismic Ground Behavior In Tokyo Port At The 2011 Off Pacific Coast Of Tohoku Earthquake - An Effective Stress Dynamic Analysis Focusing On The Impact Of The Aftershock

Seismic ground motions and behavior of excess pore water pressures on a reclaimed land during the 2011 off Pacific coast of Tohoku earthquake are studied numerically by using a computer program, "FLIP ROSE" (Iai et al, Soils Found 32 (2): 1-15, 1992; Int J Numer Anal Meth Geomech 35: 360-392, 2011). Long duration time of 30 min which includes both the mainshock and the aftershock is taken into account in the dynamic analysis considering build-up and dissipation of excess pore pressures as well. The site studied is located in Tokyo port, Japan, where seismic ground motions are obtained with vertically arrayed seismographs by Tokyo metropolitan government. It is shown that observed peak ground accelerations at each depth of ground are reasonably simulated. The ratio of excess pore water pressure is calculated as maximum of about 0.4 during aftershock, agreeing with the fact of no significant liquefaction at the site. It is noted that significant rise of excess pore water pressure is calculated in the aftershock, suggesting significant effect on liquefaction.