Surface manifestations after the Gujarat earthquake

摘要

Once again the myth about the Indian shield as a stable shield shattered the Indian geoscientific community after the Gujarat earthquake of January 2001. This earthquake occurred far from the edge of the Indian Plate and quite close to the M_s = 7.5 earthquake that occurred in 1819. The Gujarat earthquake caused severe damage and killed tens of thousands and left many more homeless. The Gujarat earthquake of 26 January 2001 generated intense shaking which was felt at about 70 percent of the region of India. The intense shaking brought out changes in the ocean and land surface. Singh et al. have found significant changes in ocean parameters (chlorophyll and suspended sediment concentrations) after the earthquake. The present communication discusses the changes on land surface revealed from IRS-ID LISS-III remote sensing data. IRS-ID, LISS-III digital data of numerous scenes prior and after the earthquake have been acquired from National Remote Sensing Agency, Hyderabad. Digital analyses of remote sensing data along various paths and rows have been carried out. The maximum surface manifestations have been found in the scene covered by row 90 and path 55, which was taken from detailed surface features extraction. The digital remote sensing data prior (4 January 2001) and after (29 January 2001) the earthquake were geo-referenced using topo-sheets and with the help of ground control points observed in the field using handy Global Positioning System (GPS). The FCC image of bands 4,2,1 prior and after the earthquake is shown in Figures 1 a and b, respectively. The comparison of two images shows significant surface manifestations. The band ratio of the two data sets (prior and after earth-quakes) has been carried out. The band ratio image is shown in Figure 1 c. The band ratio image of band 4 (Figure 1 c) clearly brought out changes in surface features after the earthquake of 26 January 2001. Prominent surface manifestations, paleo-channel and water bodies are clearly seen in and around Rann of Kutch. The area where these manifestations are seen is covered by saline soil, which looks brighter in both the images (Figures I a and b).