Focal mechanisms and earthquake generating stress system in the Indonesian region

Thirty nine focal mechanisms for shallow, intermediate and deep earthquakes that occurred during the period 1964–1967 in the Indonesian Region have been studied from the first initial motion of the P or PKP waves.The position of the two nodal planes, maximum-pressure axis and maximumtension axis are presented in this paper. The correlation between the state of the pressure distributions and earthquake generating stress systems that produce shallow, intermediate and deep earthquakes are also presented. There is some systematic agreement between the results of the same study already given by others and which is presented in this paper.The dominant modes of deformation are reverse or thrust fault and normal fault rather than strike-slip faulting.