5:15 PM - 6:30 PM
[SGL37-P21] Paleostress analysis in the most southern part of the Boso Peninsula, central Japan.
Keywords:minor fault analysis, paleostress history
The authors collected fault slip data from the Nishizaki, Shiramazu, Mera and Hata Formations to use for the multiple inversion method. As the results, reverse faulting regimes with a NE-SE trending σ1-axis are obtained from the Nisizaki Formation, strike-slip faulting regimes with a NE-SW trending σ1-axis and reverse faulting regimes with a NW-SE trending σ1-axis are from the Shiramazu Formation. On the other hand, strike-slip faulting regimes with a NNW-SSE trending σ1-axis and with the N-S trending σ1-axis are obtained from the Mera Formation, normal faulting regimes with a SW trending σ3-axis are from the Hata Formation. The authors observed that reverse faults strike-slip cut faults in the coast outcrops of the Shiramazu Formation.
Observations mentioned above suggest that the paleostress has developed through the time in this area as follows; a NE-SW horizontal compression as the first stage, a NNW-SSE horizontal compression as the second stage, then a NE-SW horizontal extension as the last stage. The authors suppose that the transition of paleostress observed between the first and the second stages probably be related to the directional change of the Philippine Sea plate motion.