Bangladesh

Bangladesh occupies a uniquely hazardous tectonic position at the junction of three tectonic entities: the Indian Plate, the Eurasian Plate, and the Burma Microplate. The country sits at the head of the Bay of Bengal, where the enormous sedimentary wedge of the Bengal Fan — built from erosion of the Himalayas — overlies a complex active [[fault]] and [[subduction-zone]] system. The Dauki Fault along Bangladesh's northern border with India is a major east-west thrust capable of generating earthquakes exceeding magnitude 8.0. The Indo-Burman Ranges along the eastern border mark an active subduction zone where the Indian Plate is descending beneath Myanmar. The Sylhet Trough and associated folds in northeastern Bangladesh record ongoing crustal shortening.

Historical accounts describe catastrophic earthquakes affecting the Bengal region. The 1897 Great Assam Earthquake (magnitude 8.1) caused massive destruction across northeastern India and Bangladesh, with reports of ground fissuring, landslides, and total destruction of buildings across a vast area. The 1885 Bengal earthquake (magnitude 7.0) killed over 100 people and caused widespread damage in the Sylhet region. The 1918 Srimangal earthquake (magnitude 7.6) caused severe damage and triggered landslides across the tea-growing hills. Analysis of paleoseismic trenches has revealed evidence of prehistoric great earthquakes on the Dauki Fault, with the most recent event estimated at magnitude 8.2–8.8. A future great earthquake on this fault would affect one of the world's most densely populated areas.

The tectonic setting of Bangladesh is further complicated by the extraordinary thickness of Ganges-Brahmaputra sediment — up to 20 kilometres in the Bengal Basin — which dramatically amplifies [[seismic-wave]] energy at the surface. [[liquefaction]] potential is extremely high across the deltaic lowlands, where water-saturated unconsolidated sediments could behave as a liquid during strong shaking, causing structures to sink or tilt. The capital Dhaka, a megacity of over 20 million people, sits on the Madhupur Terrace underlain by moderately firm sediments, but much of the city has expanded onto the surrounding floodplain. The combination of the subduction zone to the east, the Dauki Fault to the north, and the deep soft sediment basin throughout creates a multi-layered seismic hazard that seismologists consider one of the most underappreciated in Asia.