Name : YOSHIDA,  Shingo
            Position : Associate Professor
            Division/Center : Earthquake Prediction Research Center
            Research Area : Experimental Seismology, Physics of Earthquake Generation Prosesses
 
 
 
 
 
 

Research :

Our main objective of research is to establish a physical earthquake generation model through experimental studies, taking into
       account the interaction between the mechanical failure itself and other phenomena such as fluid movement, electro-magnetic
       phenomena, and chemical effects. Precursory phenomena may be produced by these interactions during rupture nucleation process.
       Recently many researchers have attempted to use seismo-electric signals for earthquake prediction, but the physical origin is not fully
       understood. We performed fracture experiments using dry granite and found that electric potential changed not only at the time of main
       failure but also during the rupture nucleation process. We proposed a quantitative model which can explain the generation of electric
       signals in terms of the piezoelectric effect of quarts and electrical relaxation in the matrix. We also conducted experiments with
       saturated rocks and found that electric potential changed markedly just prior to dynamic rupture. This signal is probably caused by
       accelerating evolution of dilatancy as cracks grow in the rock before rupture, resulting in water flow into the dilatant region with an
       electric current produced concurrently. We have developed a new apparatus specially designed to quantitatively clarify electric signal
       generation due to water flow, in collaboration with the Institute of Physical and Chemical Research(RIKEN). Using this apparatus, we
       continue laboratory experiments and also examine chemical effects on electric current generation.
 

Publications :

Yoshida, S., Convection current generated prior to rupture in saturated rocks, J. Geophys. Res., 106, B2, 2103-2120, 2001.

Yoshida, S., and A. Kato, Single and double asperity failures in a > large-scale biaxial experiment, Geophys. Res. Lett., 28, 3, 451-454, 2001.

Yoshida, S., O. C. Clint and P. R. Sammonds, Electric potential changes  prior to shear fracture in dry and saturated rocks, Geophys. Res. Lett., 25,  10, 1577-1580, 1998.

Yoshida, S., M. Uyeshima and M. Nakatani, Electric potential changes > associated with slip failure of granite: Preseismic and coseismic signals, > J. Geophys. Res., 102, 14,883-14,897, 1997.