Focal mechanisms of some recent Himalayan earthquakes and regional plate tectonics

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Abstract
Focal mechanism solutions of 12 recent earthquakes along the northern boundary of the Indian-Eurasian plates, from Hindukush to Burma, have been determined assuming the double-couple hypothesis. It has been found that the majority of earthquakes are of thrust type with the pressure directions acting at right angles to the faults/mountains, but, for a few of the earthquakes the orientations of the pressure directions are almost along the strike of the faults. Such observations could be partly explained in terms of the concept of “flake tectonics” as proposed for continent-continent collisions. A number of earthquakes in the eastern Himalayas and Burma show normal dip-slip or predominantly strike-slip movements. These anomalies call for further refinements of the plate theory in this zone of complicated deformation.