Ultrafine particles preserved in the fault gouge of the Arima-Takatsuki Tectonic Line, Japan

Abstract:

 Coseismic friction causes comminution, grain-size reduction, and amorphization of minerals. These ultrafine particles are preserved in the fault: for example, particles (size of some tens of nanometers) have been reported only in the latest slip zone within the Taiwan Chelungpu fault that slipped during the 1999 Chi-Chi earthquake. On the other hand, these ultrafine particles might dissolve in the pore water and then disappear, because amorphous fine minerals have generally high water solubility. This indicates that the preserved ultrafine particles have potential as a proxy for identifying the slip zone of the most recent earthquake along a fault. However, the occurrence in the active faults has not been fully reported. Thus, we investigated the slip zone within the Arima-Takatsuki Tectonic Line considered to have slipped at the 1596 Keicho-Fushimi earthquake, and reported mineral particles within the slip zone together with the development of advanced method to quantify amorphous component.