Abstract
Statistical studies on the focal mechanisms in the Himalaya, Burma and Andaman Sea regions are conducted here by using more than 40 mechanism solutions obtained from the analysis of the distribution of initial motion of P waves. Generally, the pressure directions of the stresses which produced earthquakes in the regions are perpendicular to the trend of the Himalayan mountain belt and the earthquake zones except in northern Burma. Though the pressures in northern Burma are strange in appearance, they harmonize well with the distribution of geological faults in the region. Most of the tension directions are nearly normal to the directions of pressures.
Both pressure and tension axes are generally shallow dipping irrespective of focal depths, and this suggests the predominance of strike-slip faulting. In view of the distribution of geological faults in Burma, the faultings of shallow and intermediate earthquakes occurring in northern Burma and its vicinity are characterized by the predominance of the dextral strike-slip faulting.
The number of data used in the present study is too small to emphasize the result obtained here, but the hypothesis of the convergence of India and Eurasian continents seems to be not always consistent with the focal mechanisms.
