| Research Abstract |
During the last ten years, attention has been focused seismic generative zones in which earthquakes are centered 10-15 km below the surface of the crust. There is no doub that the mechanisms which cause earthquakes strongly depend on the physical and chemical properties of rocks in the crustal environment. There has been little practical research related to rock fracture, frictional sliding, and deformation which was conducted under these environmental conditions.
We have performed a experiment of rock fracture and flow under high pressure and temperature (0.8GPa and 400 C) using a novel triaxial testing apparatus to study the mechanism of earthquake ocurrence in the lower crust. In this year, in order to investigate the physic-chemical effect due to the existence of water in the lower crust we made the experiment for both of dry and water-satulated samples for more than a few days by a servo-controled system, and measured AE (Acoustic Emission) emitted in a sample by a PZT sensor. In the case of dry sample AE rarely ocurred until the 98% of peak stress at the temperature of 370 C and pressure of 100 MPa, and then many of AE were generated before ultimate fracture. In the case of saturated sample, AE rarely occured until peak stress at the temperature of more than 300 C and pressure of 100 MPa. However, brittle fractured took place ultimately in producing many AE.This result suggests that semi-brittle region may exist in the lower crust.
|
