HR: 08:15h
AN: MR31B-02    [Abstracts]
TI: Laboratory Studies on the Role of the Crustal Fluids in Micromechanics of Earthquake Generation Processes
AU: * Masuda, K
EM: koji.masuda@aist.go.jp
AF: Geological Survey of Japan, Institute of Geology and Geoinformation, National Institute of Advanced Industrial Science and Technology, Central 7, 1-1-1 Higashi, Tsukuba, 305-8567 Japan
AB: Laboratory micromechanics studies are useful methods to understand the earthquake generation processes. We can analyze the small scale mechanics in the laboratory but micromechanisms of microcrack generation may be same as the elementary processes of earthquake generation in nature. In particular, crustal fluids play the critical roles in triggering the seismic activity and fault growth. A series of laboratory studies on the role of water in microcrack triggering and microrack growth were carried out. Effects of chemical reactions between the geological materials and fluids on mechanical behavior are also important under the conditions of fault process zones. The Geological Survey of Japan has developed the multi-channel acoustic emission monitoring system (ex. Lei et al., JGR, 2000) by which we can monitor space-time distributions of hypocenters of microcracks during the experiments. We also measure the velocities of elastic-waves in rock samples to construct the velocity structure like the seismic tomography. We also developed the gas-medium high-pressure and high-temperature deformation apparatus in order to carry out deformation and friction experiments under the seismogenic environments. (1) Microcrack activities are triggered and induced by water infiltrated to the stressed rock specimen. Especially, they are observed at the front of the infiltrated water where gradient of water pressure is large or maximum. (2) Changes of crack shape are estimated based on the crack model and measured Vp Vs changes during the water infiltration to the stresses rock. As water infiltrated into the specimen, the aspect ratio of cracks becomes larger. This finally caused the coalescence of microcracks and macroscopic failure of the sample. (3) Effects of chemical reaction on the mechanical behavior are observed in the deformation and friction experiments under high-pressure and high-temperature conditions in the presence of water.
DE: 5102 Acoustic properties
DE: 5104 Fracture and flow
DE: 5112 Microstructure
DE: 7209 Earthquake dynamics (1242)
DE: 8045 Role of fluids
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005