P. K. Champati Ray

Influence of neotectonic activity on groundwater salinity and playa development in the Mendha river catchment, western India

The groundwater salinity of Mendha river, one of the important streams that feed Sambhar playa in Rajasthan in western India, was studied to understand the effect of neotectonic activity on groundwater quality and salinity. We attempted to decouple the tectonic control of salinity and its contribution in the development of playa deposits in Rajasthan. Multiresolution, multidate satellite data products such as IRS‐1C, IRS‐1D LISS‐III, PAN and Landsat MSS were digitally enhanced and analysed to model the morphotectonic evolution and hydrological regime of the region. Electrical conductance data from spatially distributed points in the Mendha river basin were correlated with the aquifer geometry deciphered from borehole lithologs and lineaments and major geomorphic features interpreted from satellite images. The results of the study reveal that the aquifer geometry is controlled by subsurface structures that have been influenced by neotectonic activity in the past 8–9 ka, significantly influencing the hydrological regime and salinity of Sambhar playa.

Spectral mapping of morphological features on the moon with MGM and SAM

Abstract Three types of morphological features observed in different lunar crustal terrains were studied and mapped using hyperspectral Moon mineralogy mapper (M 3 ) data onboard Chandrayaan 1 mission in order to assess the utility of cascaded MGM-SAM spectral mixture modeling approach to characterize the surface materials, which may occur as mineral mixtures, at different topography of the lunar surface. Selected morphological features include: the impact melts in Orientale basin, sinuous rilles in Procellarum KREEP Terrane (PKT) and a rayed crater in Feldspathic Highland Terrane (FHT). Methodology involves extraction of spectrally pure pixels (endmembers) of the area using Pixel Purity Index (PPI), identification of mineralogy of the selected endmember spectrum using the Modified Gaussian Method (MGM) and mapping of mineralogically identified endmembers using the Spectral Angle Mapper (SAM) method. Mapping results demonstrate both the capabilities and the limitations of the MGM method of spectral deconvolution and the SAM method of spectral matching as effective tools for compositional characterizations of morphological features on the lunar surface. As a method of spectral deconvolution, MGM was able to identify and characterize both high- and low – Ca pyroxenes along with plagioclase feldspar. The Spectral Angle Mapper (SAM) was able to map identified mineral mixtures from MGM.

Ionospheric Total Electron Content for Earthquake Precursor Detection

Understanding earthquake precursory phenomena based on ionosphere perturbation is a fairly new field in geoscience today and has achieved promising success. Scientists across the globe are now trying to learn insight about the physical and chemical processes involved in the upper atmosphere and beyond during the earthquake preparatory period. One of such studies is based on global navigation satellite system (GNSS) observations. Global Positioning System (GPS) is currently one of the most popular global navigation satellite positioning systems widely available for such society application. GPS has led to technical revolutions in the field of applications like navigation as well as in upper atmospheric/ionospheric studies. GPS signals from the satellites encountered the ionosphere before it is captured by the receiver on the ground. In this process, the free electrons in the ionosphere affect the propagation of the signals by changing their velocity and direction of travel. A number of recent investigations have suggested that satellites and ground-based facilities like that of GNSS may detect earthquake precursors a few hours or days prior to the main event due to ionospheric perturbations induced by initiation of earthquake process. The typical phenomenological features of ionospheric precursors of strong earthquakes are summarised by Pulinets et al. (2003). The parameter of ionosphere that produces most of the effects on radio signals is the total electron content (TEC). The TEC is defined by the integral of electron density in a 1 metre square column along the signal transmission path. The ionosphere causes GPS signal delays to be proportional to the TEC along the path from the GNSS satellite to a receiver. The TEC measurements obtained from dual frequency GNSS receivers are one of the most important parameters to characterise Earth’s ionosphere. The changes in the Earth’s ionosphere can be used to derive the information about an impending earthquake. Therefore, it is very important to monitor the TEC variation due to tectonic deformation prior to an earthquake and its validation in real-world situation.

Simulation Outputs of Major Debris Flows in Garhwal Himalaya: A Geotechnical Modeling Approach for Hazard Mitigation

Landslides, one of the major geological hazards, contribute to natural disasters in mountainous region around the globe owing to a wide variety of causative as well as triggering factors like heavy rainstorms, cloudbursts, glacial lake outburst (GLOF), earthquakes, geo-engineering setting, unplanned human activities, etc. In different parts of the Himalaya, landslide has evolved as a frequent problem which severely affects life, property, and livelihood of this mountainous area thriving mainly on pilgrimage, tourism, and agriculture (Anbalagan et al. 2015; Anbalagan 1992; Champati Ray and Chattoraj 2014; Gupta et al. 1993; Kumar et al. 2012; Onagh et al. 2012; Sarkar et al. 1995, 2006; Sundriyal et al. 2007). With the background of higher elevation, rough hilly landscape, scanty cultivated land, strong monsoonal effect, and less industrial growth restricting economic progress, repeated landslide events keep human life and property at stake (Champati Ray et al. 2013a, b, 2015; Ketholia et al. 2015; Paul and Bisht 1993). Landslides in the Himalayan region are on an average smaller in dimension and have shallow depth, but these are more recurring in nature and thereby do not get noticed by authorities but cause higher cumulative losses over a period of time. Landslides, in the Himalaya, are observed particularly in highly fractured and sheared rock mass close to faults and also in weathered hard rocks. The climatic factors play an important role in weathering and disintegration of rock mass that are finally brought down by gravity (Kumar et al. 2007, 2012). Most of these landslides wreak havocked not only on life and property but manifest changes in landform due to large-scale mass wasting, landslide-dammed lake formation, and breaching leading to large-scale landform modification (Champati Ray 2013; Champati Ray et al. 2015).

Mass change of Gangotri glacier based on TanDEM-X measurements

We analyzed the surface elevation change and geodetic mass change of Gangotri glacier, over the period 2011 and 2013, utilizing high horizontal and vertical resolution topographic data, acquired by bistatic radar interferometry of the TanDEM-X/TerraSAR-X satellite formation. Short term investigation of surface elevation change of glaciers at reasonably good accuracy is possible by using multi temporal TanDEM-X data. The surface elevation change further can be converted into glacier volume change and mass change. The mass change of glaciers is direct response of climate change and hence can be taken as a proxy to study climate change. The study area includes the Gangotri group of glaciers, located in the Central Himalaya, India.