JpGU-AGU Joint Meeting 2017

Presentation information

[JJ] Poster

S (Solid Earth Sciences) » S-SS Seismology

[S-SS17] [JJ] Fault Rheology and Earthquake Physics

Sun. May 21, 2017 1:45 PM - 3:15 PM Poster Hall (International Exhibition Hall HALL7)

convener:Takanori Matsuzawa(National Research Institute for Earth Science and Disaster Resilience), Takeshi Iinuma(National Research and Development Agency Japan Agency for Marine-Earth Science and Technology), Wataru Tanikawa(Japan Agency for Marine-Earth Science and Technology, Kochi Instutute for Core Sample Research), Hideki Mukoyoshi(Department of Geoscience Interdisciplinary Graduate School of Science and Engineering, Shimane University)

[SSS17-P22] Structural, mineralogical, and geochemical characteristics of an ancient megasplay fault in the Hidakagawa Formation, Kii Peninsula

*Takeaki Ogawa1, Tsuyoshi Ishikawa2, Shunya Kaneki1, Tetsuro Hirono1 (1.Department of Earth and Space Science, Graduate School of Science, Osaka University, 2.Kochi Institute for Core Sample Research, Japan Agency for Marine-Earth Science and Technology)

Keywords:accretionary prism, trace-element, fluid-rock interaction, megasplay fault, Shimanto belt

To understand the slip behavior of large earthquakes along subduction zone, a great deal of effort has been made on the accretionary complex such as the Shimanto Belt. Although extensive investigation along the trench is important, no studies have ever tried to analyze fault rocks in accretionary complex of west coast of Kii Peninsula. Here we focus on mélange unit in the Hidakagawa Formation, outcropped in the Mio region, Wakayama Prefecture. We revealed geological setting and mineralogical and geochemical characteristic by performing the structural description, Raman spectroscopic analysis, mineral composition analysis, and geochemical analyses of major- and trace-element concentrations of the fault rocks and its surrounding rocks.
The burial depth in this region was estimated 3-4 km, also indicating large cumulative displacement along the fault. Granuation of mineral grains and shear foliation were well developed in the slip zone, and high temperature (>350 °C) by fluid-rock interaction was estimated along the slip zone. These features were well coincided to those in the megasplay fault. Furthermore, we discuss the slip behavior and the slip parameters.