Possible influence of subducting ridges on the Himalayan arc and on the ruptures of great and major Himalayan earthquakes

Subduction of bathymetric features, such as ridges, seamounts, fractures etc., on the subducting plate influences the arc morphology and earthquake ruptures. We analyse their effect on the development of the arcuate shape of the Himalayan arc and on the ruptures of great and major Himalayan earthquakes. Besides the two most prominent ridges in the Indian Ocean, namely the Chagos-Laccadive-Deccan ridge and the 90°E ridge, which are assumed to extend up to the Himalayan arc, at least three major subsurface ridges have been mapped on the underthrusting Indian plate under the Indo-Gangetic plains. It appears that the subduction of the two most prominent ridges contributed to the development of the arcuate shape of the Himalayan arc. The interaction and subduction of the other subsurface ridges probably influenced the Himalayan arc morphology by causing a localised cusp in the frontal topography. Also, these ridges probably acted as barriers to the ruptures of the major and great Himalayan earthquakes.