Complicated tectonics. The Indo-Australian plate (upon which the Indian Subcontinent and Australia rest) meets with Asia along the Himalayas (the tectonic collision which led to its rise) and through the islands of South-East Asia.
The dynamics between the meeting-points were responsible for the famous tsunami.
There’s some evidence there’s a tsunami threat along the boundary to the north running all the way to the Burma/Bangladesh coast, paper on that in the last year.
Ignorant leadership.