Plateau 'pop-up' in the great 1897 Assam earthquake.

摘要: The great Assam earthquake of 12 June 1897 reduced to rubble all masonry buildings within a region northeastern India roughly the size England, and was felt over an area exceeding that 1755 Lisbon earthquake1. Hitherto it believed rupture occurred on north-dipping Himalayan thrust fault propagating south Bhutan2,3,4,5. But here we show northern edge Shillong plateau rose violently by at least 11 m during earthquake, this due buried reverse approximately 110 km in length dipping steeply away from Himalaya. stress drop implied geometry prodigious slip 18 ± 7 m explains epicentral accelerations observed exceed 1g vertically surface velocities 3 m s-1 (ref. 1). This quantitative observation active deformation ‘pop-up’ structure confirms faults bounding such structures can penetrate whole crust. Plateau uplift past 2–5 million years has caused Indian plate contract locally 4 2 mm yr-1, reducing seismic risk Bhutan but increasing Bangladesh.