Seismic zones defined by Geological Survey of Bangladesh in 1977. Description Seismic Zone is the expression of proneness of a region to earthquake occurrence in the historical past including the expectations in future. A region experiencing more frequent and large earthquakes has a higher seismicity compared to one with less frequent and small earthquakes. Both the temporal and spatial distributions of all earthquakes, small and big, have to be systematically accounted for by determining their past behaviour to determine the future trend. In addition to seismicity, the main input for seismic zoning maps is the ground motion attenuation characteristics. It is for this reason that seismic zoning should be revised after the occurrence of violent earthquake ground motions in areas where past intensity data are not available. In the preparation of seismic zoning map the common data which are considered include: soil type and foundation conditions, ground structure and its dynamic characteristics, intensity distribution during past earthquakes, ground motion attenuation characteristics, envisaged development and location of major cities, economic status and simplification shape. On the basis of distribution of earthquake epicentres and morphotectonic behaviour of different tectonic blocks Bangladesh has been divided into three generalised seismic zones. In 1977, the Government of Bangladesh constituted a Committee of Experts to examine the seismic problem and make appropriate recommendations. The Committee proposed a zoning map of Bangladesh in the same year. In the zoning map, Bangladesh has been divided into three generalized seismic zones. The northeastern folded regions of Bangladesh are the most active zones and belong to the zone-I. The Bask seismic coefficient of this zone is 0.08. The zone II consists of the regions of recent uplifted Pleistocene blocks of the Barind and Madhupur and the western extension of the folded belt and the Bask coefficient for this zone is 0.05. The southwest Bangladesh is seismically quiet zone and represented by zone III with Bask coefficient 0.04. Ground condition (firm or soft) has not been taken into consideration during the seismic zonation of Bangladesh. Characteristic features of seismic zonation of Bangladesh are presented in the table below: Zone I : Basic Seismic Coefficient 0.08 g Area: North and eastern regions of Bangladesh (Seismically most active) with the proximity to the active east-west running fault and the Main Boundary Fault to the north in India. The Chittagong-Tripura Folded Belt experiences frequent earthquakes. Seismic Risk: High Seismic Coefficient: 0.08 Mercalli Scale: IX: Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. Liquefaction. Zone II : Basic Seismic Coefficient 0.05 g Area: Lalmai, Barind, Madhupur Tracts, Dhaka, Comilla, Noakhali and western part of Chittagong Folded belt. comprising the central part of Bangladesh represents the regions of recent uplifted Pleistocene blocks of the Barind and Madhupur Tracts. Seismic Risk: Medium Seismic Coefficient: 0.05 Mercalli Scale: VIII: Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. Zone III : Basic Seismic Coefficient 0.04 g Area: Khulna division - South-western part of Bangladesh (Seismically relatively quiet) Seismic Risk: Low Seismic Coefficient: 0.04 Mercalli Scale: VII: Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Source The seismic boundaries has been reproduced on geographic area coverage of Bangladesh from a published graphic file by Geological Survey of Bangladesh. The seismic boundaries was determined in 1977. The description of the layer has been obtained from Banglapedia. Limitation of Use This GIS data and any other information presented on this web site is strictly limited to non commercial use. Disclaimer Geospatial Bangladesh makes no representation or warranty as to the accuracy, completeness, reliability or suitability of the GIS data and any other information provided in this website for any specific purpose and disclaims any responsibility or liability for any expenses, losses, damages and costs which may be suffered or incurred as a result of or in connection with using or relying on the data or the information provided in this website. Content Type Printable Map Attributes Field Name: zone Field Type: String Field Width: 100 Data Type: Text Field Description: The values in the field defines seismic zones of Bangladesh defined by Geological Survey of Bangladesh in 1977. Description of Values: The field values has been described in the Description section. EPSG:4326