Josodhir Das

MODIS land surface temperature data detects thermal anomaly preceding 8 October 2005 Kashmir earthquake

During the morning (03:50:40 UTC) of 8 October 2005 a major (M w 7.6) shallow focus (26 km) earthquake struck Kashmir (Himalayan region). Its epicentre was located 10 km NNE of Muzaffarabad (USGS 2005, Magnitude 7.6—Pakistan, available online at http://earthquake.usgs.gov/eqcenter/eqinthenews/2005/usdyae/). The present manuscript is an attempt to study the development of thermal anomaly in land surface temperature (LST) preceding this earthquake. Using data from Moderate Resolution Imaging Spectroradiometer (MODIS) onboard National Aeronautics and Space Administration (NASA) Terra satellite, the daily daytime LST images have been analysed for the correlation between LST variations and Kashmir earthquakes. An evident correlation of thermal anomaly in LST that is apparently related to pre‐seismic activity has been identified. An attempt has also been made to quantify the change in LST (in °C) with reference to previous day temperature values and background data (MODIS LST data from 2000–2004). A 4–8°C rise in LST to the south of the earthquake epicentre has been observed seven days before the major event. Air temperature data from two meteorological stations (Islamabad and Srinagar) also supports the observations made through MODIS LST data. The role of terrain parameters like rock types, vegetation and topography upon the spatial and temporal variations of anomalous temperature area have been studied.

Remote sensing and GIS application in change detection of the Barak River channel, N.E. India

Rivers flowing through the alluvium invariably have very low gradient forcing the river to flow slowly in a meandering and zigzag path. Nature and intensity of meandering is governed by the geological and tectonic conditions of the river basin. Barak River in tectonically active south Assam (Northeast India) exhibits intense meandering and shifting of the river course. Topographic data of two different years and satellite images of 4 different years covering a section of the Barak River have been investigated to verify the nature of changes undergone by the river through times. This study reveals active northward shift of the river and a prominent neck-cut off in the initial part of the study area. Northward shift of the river also occurred in the area west of Silchar. But, in the western part the river has shifted both towards north and south. Oscillatory shifting in the river channel has also been noticed. The river has shown a overall northward shift which is probably due to uplift of the southern part of the Barak River valley.

False topography perception phenomena and its correction

Abstract The remote sensing data of a rugged terrain always suffer from topographic effects and, in such cases people frequently perceive valleys as ridges, and vice versa in the optical imagery of Sun-synchronous satellite. The appearance of inverse topography can be termed as false topography perception ( FTP) FTP has been observed in various satellites images such as Landsat, IRS, and SPOT The problem of FTP becomes more severe in high altitude areas of hilly terrain, such as Himalayan terrain. FTP is usually caused by the combination of various interrelated factors; among them are topographic relief, Sun elevation, the azimuth angle, viewing angle, and hatching or engraving features present on the slopes. Once satellite data of rugged terrain are acquired, then all FTP-influencing factors are fixed, except for the viewing angle of the observer. Hence, the correction of FTP becomes straightforward. There are two ways to correct satellite dala for FTP effects: ( a) rotate the image by between 135° -180°...

Satellite data in a rapid analysis of Kashmir earthquake (October 2005) triggered landslide pattern and river water turbidity in and around the epicentral region

The Kashmir earthquake of 8 October 2005 that epicentred 10 km northeast of Muzaffarabad town caused widespread slope failures (landslides) extending from Balakot in the northwest to Khudpura in the southeast through Muzaffarabad and Kuroli, with the slides concentrated mostly along the river valley. The southeasterly (sun‐facing) hill slopes were affected predominantly. These landscape changes and the sudden increase in turbidity in the Neelam River have been delineated on earth‐observing satellite data. The occurrence of the landslides is observed linearly along a NW–SE line extending for about 40 km in and around the epicentral zone. From the damage pattern it is deduced that this linear zone might be the maximum displaced block during the earthquake, generated by reverse thrusting.

Strong motion records

INTRODUCTION The Department of Earthquake Engineering, Indian Institute of Technology Roorkee, Roorkee, India operates a network of 17 structural response recorders (SRR) in the Kachchh region with the help of financial support from the Department of Science and Technology (DST), New Delhi, India. The main event was recorded at 13 stations (Figure 5-1). A 10-story residential building within the complex of the Regional Passport Office at Ahmedabad was instrumented under a separate DST-sponsored program on instrumentation of multistory buildings. The motion recorded at the ground floor of this building is the only ground motion acceleration record available for this event.

Active tectonics of the Eastern Himalayan foothills region and adjoining Brahmaputra Basin based on satellite images

Deformation pattern of sedimentary rocks of the Eastern Himalayan foothills and other features developed in the adjoining Brahmaputra Basin are displayed prominently on satellite images. Siwaliks of the Arunachal Himalayas show severe effect of tectonic movements suffered by the region, whereas those of the Bhutan Himalayas appear to have been less affected. A prominent tectonic block, the Dafla Hills block, could be identified in the Arunachal Himalayas, revealing the nature of tectonic forces prevailing in the region and this region also could act as a source for generating future earthquakes. East of this block, the Siwalik rocks display spectacular deformation pattern. Northward movement of basement rocks below the Siwaliks is recorded in the region of Hatisar Gap wherein the Siwalik rocks are missing and probably dragged in along with the basement. Alluvium faults observed at some places are the testimony of recent operative tectonic activity in the region. It also appears that the Brahmaputra Basin is creeping below the foothills region under prevailing compressional tectonic regime.

False topographic perception phenomena observed with the satellite images of Moon's surface

False Topographic Perception Phenomena (FTPP) are commonly observed in images of rugged terrain on the surface of the Earth acquired by polar-orbiting satellites. It is interesting to note that due to the absence of atmosphere, vegetation and presence of numerous craters on its surface, the Moon illustrates very vividly and uniquely FTPP, which is less obvious with images of the Earth. In this article images of the Moon taken during the six missions of the NASA Apollo programme and from the Chandrayan-1 Indian satellite are used to demonstrate FTPP on the surface of the Moon. Numerous craters present on the surface of the Moon are perceived as hillock/plateau and vice versa. Combinations of various interrelated factors, for example topographic relief, observer position, Sun azimuth and elevation angles, are responsible for FTPP. Craters in the northern hemisphere of the Moon exhibit FTPP as the Moons surface was imaged from southern side under equatorial illumination.

Probabilistic seismic hazard assessment of NW and central Himalayas and the adjoining region

The Himalayan region has undergone significant development and to ensure safe and secure progress in such a seismically vulnerable region there is a need for hazard assessment. For seismic hazard assessment, it is important to assess the quality, consistency, and homogeneity of the seismicity data collected from different sources. In the present study, an improved magnitude conversion technique has been used to convert different magnitude scales to moment magnitude scale. The study area and its adjoining region have been divided into 22 seismogenic zones based upon the geology, tectonics, and seismicity including source mechanism relevant to the region. Region specific attenuation equations have been used for seismic hazard assessment. Standard procedure for PSHA has been adopted for this study and peak ground motion is estimated for 10% and 2% probability of exceedance in 50 years at the bed rock level. For the 10% and 2% probability of exceedance in 50 years, the PGA values vary from 0.06 to 0.36 g and 0.11 to 0.65 g, respectively considering varying b-value. Higher PGA values are observed in the southeast part region situated around Kaurik Fault System (KFS) and western parts of Nepal.

SAR interferometry in post-seismic ground deformation detection related to the 2001 Bhuj earthquake, India

The 2001 Bhuj earthquake, which occurred due to rupturing of a hidden reverse fault, caused large-scale ground deformation. The ground deformations in the Bhuj earthquake-affected region have been analysed using two interferometric synthetic aperture radar (InSAR) data sets. The data sets belong to the years 2003–2004 and 2004–2005, covering an area east of Bhuj falling on near-flat terrain north of Kutch Mainland Fault (KMF). Two interferograms have been generated successfully displaying the interference fringes in the study area, enabling us to draw interesting observational inferences. The 2003–2004 interferogram image exhibits upliftment of about 8 cm (surface motion towards the satellite) around Kunjisar village and also upliftment of 25 and 5 cm in the other two areas north of Kunjisar, whereas the interferogram image belonging to the year 2004–2005 reveals subsidence of about 17 cm (surface motion away from the satellite) in Kunjisar area along with subsidence of about 28 and 5 cm in the two areas north and northwest of Kunjisar, respectively. Hence, between the years 2003 and 2005, two different episodes of upliftment and subsidence have been observed in the study area. The ground upliftment during 2003–2004 probably indicates that the last phase of ground deformation in the earthquake-affected region has been followed by the onset of subsidence during 2004–2005 as the rock volume involved in stress–strain processes began to experience a relaxation phase.

A remote sensing technique for identifying geometry and geomorphological features of the Indo-Burman frontal fold belt

Satellite images are capable of displaying prominently the geometry and morphology of folds, especially when these have large spatial extent. The frontal part of the Indo-Burman fold belt, falling in parts of Bangladesh and north-east India, has developed into exemplary linear N–S oriented doubly plunging folds in late Tertiary sedimentary rock sequences and are arranged in a set of alternating ridge-forming anticlines and valley-forming synclines. Formation of these folds is attributed to E–W oriented compressional tectonics resulting out of eastward subduction of the Indian plate below the Burmese plate. Fold types present in the area appear to be simple but the present fold geometrical arrangement reveal some interesting features. The 90-m SRTM-DEM (Shuttle Radar Topographic Mission–Digital Elevation Model), remote sensing techniques, principal component analysis and resolution merging were used to understand the geometry and morphology of the folds covering a large area, through comparative assessment and enhancement of the structural features. This study includes identification of: multi-folds within a visibly single entity; the overlapping nature of folds and the interrelation between anticlines; the geometry of fold noses; fault-affected fold limbs causing bulging; and anticline bifurcation and formation of elliptical and cuspate synclines; as well as recognition of exposed eroded-out folded layers of the anticline and the effect of deformation and faulting. The doubly plunging nature of the folds and higher topography at the middle latitudes of the study area could have formed due to up-arching tectonic activity.