• Josodhir Das

      Articles written in Journal of Earth System Science

    • Probabilistic seismic hazard assessment of Himachal Pradesh and adjoining regions

      Nilesh Shaligram Patil Josodhir Das Ashwani Kumar Madan Mohan Rout Ranjit Das

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      Seismically active Himachal Pradesh and adjoining regions comprising Himalayan orogenic belt with the experience of the great Kangra earthquake of 1905, has high potential for river valley projects. There are already operating hydropower projects, some under construction and a few more coming up. In view of this it is important to know the ground motion nature for various locales. The present study is about estimation of Peak Ground Acceleration (PGA) for the state of Himachal Pradesh and adjoining regions using probabilistic seismic hazard analysis (PSHA) approach. Standard procedure for PSHA has been adopted for this study and peak ground motion has been estimated for 10% and 2% probability of exceedance in 50 years at the bed rock level considering two cases: (i) varying 𝑏-value for each source zone, (ii) constant 𝑏-value for each source zone. For 10% probability of exceedance in 50 years, the PGA values vary from 0.096 to 0.15 g and 0.09 to 0.26 g considering varying 𝑏-value, and constant 𝑏-value, respectively. In case of 2% probability of exceedance in 50 years, the PGA varies between 0.07 to 0.24 g considering varying 𝑏-values and 0.14 to 0.37 g considering constant 𝑏-values. Higher PGA values are observed in the southeast part considering varying 𝑏-values whereas the region situated around Kaurik Fault System (KFS) has shown higher PGA values in case of constant 𝑏-value.

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

      Madan Mohan Rout Josodhir Das Kamal Ranjit Das

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      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.

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