Full length articlePreliminary observations from the 3 January 2017, MW 5.6 Manu, Tripura (India) earthquake

- The Manu earthquake (Tripura, India) of January 3, 2017 (MW 5.6) was an intraslab event in the underlying Indian plate.
- The earthquake, despite its relatively deeper depth and low magnitude, caused soil liquefaction.
- Soil liquefaction during future large earthquakes is a major threat in the Tripura fold belt and Bengal basin regions.

On 3 January 2017, a MW 5.6 earthquake occurred in Dhalai district in Tripura (India), at 14:39:03 IST (09:09:03 UTC) with an epicentre at 24.018°N ± 4.9 km and 91.964°E ± 4.4 km, and a focal depth of 31 ± 6.0 km. The focal mechanism solution determined after evaluating data from seismological observatories in India indicated a predominantly strike-slip motion on a steeply dipping plane. The estimated focal depth and focal mechanism solution places this earthquake in the Indian plate that lies beneath the overlying Indo-Burmese wedge. As in the 2016 Manipur earthquake, a strong motion record from Shillong, India, appears to suggest site amplification possibly due to topographic effects. In the epicentral region in Tripura, damage assessed from a field survey and from media reports indicated that the macroseismic intensity approached 6-7 EMS with damage also reported in adjacent parts of Bangladesh. A striking feature of this earthquake were the numerous reports of liquefaction that were forthcoming from fluvial locales in the epicentral region in Tripura, and at anomalous distances farther north in Bangladesh. The occurrence of the 2017 Manu earthquake emphasises the hazard posed by intraplate earthquakes in Tripura and in the neighbouring Bengal basin region where records of past earthquakes are scanty or vague, and where the presence of unconsolidated deltaic sediments and poor implementation of building codes pose a significant societal and economic threat during larger earthquakes in the future.

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