Tectonic implications of the September 2011 Sikkim earthquake and its aftershocks

This study presents results of the spatial patterns of 292 aftershocks of the Mw 6.9 Sikkim earthquake of September 2011, accurately located through analysis of three component waveforms registered by a five station broadband network operated immediately after its occurrence. Refined hypocentral parameters achieved through application of the hypoDD relocation scheme reveal tight clustering of events along a NW–SE trend with focal depths reaching ∼60 km. These trends viewed in conjunction with the strike–slip mechanisms of past earthquakes in Sikkim, including the main shock, affirm the predominance of transverse tectonics in this segment of the Himalaya where the Indian plate convergence seems to be accommodated by dextral motion along steeply dipping fault systems.