Japan Geoscience Union Meeting 2015

Presentation information

Oral

Symbol S (Solid Earth Sciences) » S-SS Seismology

[S-SS25] Strong Ground Motion and Earthquake Disaster

Mon. May 25, 2015 4:15 PM - 6:00 PM A04 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Kentaro Motoki(Kobori Research Complex), Chair:Seiji Tsuno(Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology), Kentaro Motoki(Kobori Research Complex)

4:30 PM - 4:45 PM

[SSS25-21] Simulation of irregular wave generation due to fault formation by an elasto-plastic finite deformation analysis

*Shotaro YAMADA1, Toshihiro NODA1, Akira ASAOKA2 (1.Nagoya University, 2.Association for the Development of Earthquake Prediction)

Keywords:natural fault, reverse fault, seismic wave, strain localization, inertial force, elasto-plastic body

The authors, in the past study1), simulated shear bands formation in ground due to strike-slip fault by using a soil-water coupled finite deformation code taking into inertia force, GEOASIA2). In the present study, the analysis code was employed to simulate formation of normal and reverse faults and wave generation due to the formation assuming a ground composed of a highly brittle soil. The analysis code mounts the SYS Cam-clay model3) as an elasto-plastic constitutive model which can describe a wide variety of soils within the same theoretical framework. Also, since the rate-type equation of motion is precisely time-integrated, progressive failure will be analyzed as a nonlinear dynamic problem, and then generation and/or propagation of waves induced by shear bands formation will also naturally be developed in the analysis4), 5). Making use of this characteristic, wave generation induced by fault formation was focused on. When the ground was compressed from lateral faces by displacement control under plane strain condition, a reverse fault-like failure was generated as a progressive failure with strain localization (Figure 1). At that time, elastic energy accumulated on the non-destructive area at the compression stage was released at once. In the case of a horizontally stratified ground, as failure progresses rapidly, acceleration motion was reached to the max. at first motion and decayed exponentially with time in a similar way that artificial earthquake shows (Figure 2). On the other hand, in the case of a ground with initial random imperfections, as some small failure events exist in a large failure event, an irregular wave like a natural seismic wave was generated (Figure 3). On the other hand, when the ground with the initial random imperfections was extended from lateral side by strain control, a normal fault was generated and another irregular wave was generated.

1) Noda, T., Yamada, S., Asaoka, A. and Kawai, Y. (2014): Numerical simulation of shear bands formation in ground due to strike-slip fault, Japan Geoscience Union Meeting 2014, SSS31-08.
2) Noda, T., Asaoka, A. and Nakano, M. (2008): Soil-water coupled finite deformation analysis based on a rate-type equation of motion incorporating the SYS Cam-clay model, Soils and Foundations, 48(6), 771-790.
3) Asaoka, A., Noda, T., Yamada, E., Kaneda, K. and Nakano, M. (2002): An elasto-plastic description of two distinct volume change mechanisms of soils, Soils and Foundations, 42(5), 47-57.
4) Noda, T., Xu, B. and Asaoka, A. (2013): Acceleration generation due to strain localization of saturated clay specimen based on dynamic soil-water coupled finite deformation analysis, Soils and Foundations, 53(5), 653-670.
5) Asaoka, A., Yamada, S. and Noda, T. (2013): Numerical analysis of failure of soil ground due to surface loading and generation of vibration induced by the failure, Japan Geoscience Union Meeting 2013, SSS28-18.