Seismic Hazard Assessment for Mymensingh City

Mymensingh, a major city located 115 km north of the capital city, is around 140 km away from the epicenter of the 1897 magnitude 8.1 Great Indian earthquake. The recently updated Bangladesh National Building Code (BNBC-2020) places this city in Seismic Zone IV with the highest seismic zone coefficient (Z = 0.36). Closest major fault capable of generating large magnitude (M ≥ 7) earthquakes is the east–west trending Dauki fault along the northern Bangladesh–India border. Recent paleo-seismic trench investigations at Haluaghat, a border town 40 km north of Mymensingh city reveals repeated earthquake effects in the past few hundred years. Results from published probabilistic and deterministic seismic hazard assessment studies are compiled and critically reviewed for a better understanding of the seismic hazard for Mymensingh city. The authors have also used the neo-deterministic seismic hazard assessment (NDSHA) method to study the effect of a large-magnitude earthquake on the Dauki fault. It is concluded that the zone coefficient of 0.36 in BNBC-2020 is a reasonable estimate of maximum PGA for Mymensingh city. Finally, the effect of local surface soil is studied using 1D seismic soil response computations for selected soil profiles of Mymensingh city with DEEPSOIL software. Comparison is made with response spectra code provisions of BNBC-2020.