Application of numerical method forS-wave focal mechanism determinations to earthquakes of Kamchatka-Kurile Islands Region

Abstract

The least squares method for the determination of focal mechanism using S-wave data developed by Udias (1964) has been applied to 34 earthquakes of the Kamchatka-Kurile Islands Regions. For most of the earthquakes studied the source mechanism was found to conform best to a double couple model. The accuracy and stability of the solutions are examined. The direction of the principal axes of stress for most of the solutions show a steeply dipping axis of tension and an almost horizontal axis of pressure. The orientation of the pressure axes is normal to the regional trend. The direction of the stresses suggest a thrust faulting with predominantly dip slip motions such that the continental block moves over the oceanic.