Bhuj Earthquake: Mapping surface features using remote sensing data

The study area covers eastern part of Kutch peninsula, which is one of the few places outside the Himalayas that falls under the seismic  zone V, the zones defined by Geological Survey of India (GSI) and Indian Meterological Department (IMD) to be at the highest risks for earthquakes. An integrated approach using multi-source remote sensing data in conjunction with available geological and geophysical data are used. Spectral and spatial enhancement techniques were employed to the digital satellite data to construct a geological map of the area, and to identify the drainage pattern of the basin. Major structural elements like folds, faults were delineated. Regional scale lineaments and microlineaments of the area were  identified from satellite data. Ultimately these data along with the earthquake data were brought on a common GIS platform for analysis. The faults in most cases are associated with high lineament density and sharp increase in lineament density contours occurred along the trend of the faults. The Kutch Mainland Fault is found to be associated in most places with preferred orientation of lineaments in a particular direction. The Kutch Mainland Fault can be extended further  east on the basis of spatial distribution of earhquake data, than what  was inferred from the image. The epicenter of January 26, 2001 earthquake is also inferred to fall on this fault. 75% of the earthquakes with magnitude greater than  5 are associated with moderate, high and very high lineament density. Based on Mohr's theory of failure criteria and statistical analyses of remotely sensed lineament data, horizontal compressive stress values have been estimated at various sites of the study area. The directions of maximum compressive stress of different sites are found to coincide with directions of movement predicted by USGS in the area. The change detection study for images before and after the earthquake of January 26, 2001 indicate that the water that came up in the area due to the earthquake was purely a temporary phenomenon, viz. soil liquifaction.

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