Engineering Reconnaissance Following the Magnitude 5.7 Tripura Earthquake on January 3, 2017

Abstract

On January 3, 2017, adjoining states of Tripura and Bangladesh witnessed a moderate earthquake of a magnitude of 5.7 (Mwb) originating in the Dhalai district of Tripura with an intensity of IV to VI in Modified Mercalli intensity (MMI) scale. The earthquake caused damages in reinforced concrete (RC) building structures, old masonry buildings, nonengineered rammed earth/adobe houses, landslides, liquefaction, and ground cracks at different locations near the epicenter of Tripura. Two districts, Dhalai and Unakoti, situated in the northern part of Tripura were mostly affected due to this earthquake. However, it is noteworthy that low-cost houses, such as bamboo houses, bamboo reinforced rammed earth houses and brick masonry houses with frames made of precast reinforced cement concrete (RCC) pillars performed relatively better as compared to unreinforced/unstabilized rammed earth and brick masonry houses. Analysis of damages identify cases of initiation of lateral spreading near the riverbank, landslide due to inadequate slope and presence of unstabilized soil, shear cracks and joint failure at earthen walls, structural cracks in rammed earth and masonry buildings situated at hill slopes, and minor structural cracks in RCC buildings as predominant damage features. Suggestions on enhancement of seismic safety of different types of structures are also discussed keeping a view on the current construction practices at Tripura. This study will help to develop preparedness for the possible vulnerability issues learned from this earthquake and assist to identify the future direction of research for overcoming seismic hazard for this state.