• PRAKASH CHAUHAN

      Articles written in Journal of Earth System Science

    • Vertical diffuse attenuation coefficient (Kd) based optical classification of IRS-P3 MOS-B satellite ocean colour data

      R K Sarangi Prakash Chauhan S R Nayak

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      The optical classification of the different water types provides vital input for studies related to primary productivity, water clarity and determination of euphotic depth. Image data of the IRSP3 MOS-B, for Path 90 of 27th February, 1998 was used for deriving vertical diffuse attenuation coefficient (Kd) and an optical classification based onKd values was performed. An atmospheric correction scheme was used for retrieving water leaving radiances in blue and green channels of 412, 443, 490 and 550 nm. The upwelling radiances from 443 nm and 550 nm spectral channels were used for computation of vertical diffuse attenuation coefficientKd at 490 nm. The waters off the Gujarat coast were classified into different water types based on Jerlov classification scheme. The oceanic water type IA (Kd range 0.035-0.040m-1), type IB (0.042-0.065 m-1), type II (0.07-0.1m-1) and type III (0.115-0.14m-1) were identified. For the coastal waters along Gujarat coast and Gulf of Kachchh, Kd(490) values ranged between 0.15 m-1 and 0.35 m-1. The depth of 1% of surface light for water type IA, IB, II and III corresponds to 88, 68, 58 and 34 meters respectively. Classification of oceanic and coastal waters based onKd is useful in understanding the light transmission characteristics for sub-marine navigation and under-water imaging.

    • Barren Island volcanism and seismicity: An intriguing finding

      GOUTHAM KRISHNA TEJA GUNDA PRASHANT KUMAR CHAMPATI RAY MAMTA CHAUHAN PRAKASH CHAUHAN S BALAJI

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      Barren Island volcano (BIV), India has started erupting vigorously from 2018 after a gap of 13 years (last active period 2004–2005) just after the 2004 tsunami. Although there is evidence of coupling between seismicity and earthquake in this region, it is not thoroughly researched. Here, we present satellite-based approach to monitor and understand the volcano dynamics w.r.t. associated seismicity at BIV using multispectral datasets, ${\sim}$ 20 yrs Volcanic Radiative Power (VRP) and ${\sim}$ 70 yrs historical earthquake data (1950–2020 July). The rate of frequency of earthquake has increased to 3.54 times during 1990–2020 as compared with 1950–1989 which signifies seismicity-induced pressure release that may have caused decompression in the region, leading to eruptions or at least modulation of the eruption. The VRP results clearly depicted the changes from low to high thermal regimes that indicate switching from open-vent to effusive activity of Barren Island volcano. The historical data of recent times show correlation of seismic and volcanic activities. The spatial-temporal distributions of earthquake swarm are not associated with volcano, but are clustered near the tectonic regimes. The volcanic activity is preceded by seismic activity along the regional tectonic structures. In addition, the 2018 eruptive phase has been analyzed for better understanding of the proposed event. The present research has provided significant supportive evidences to give adequate credence to this emerging hypothesis and also revealed the location of primary, secondary vents, flow tracts and all evolving volcanic landforms of the region and recorded the changes in flow directions. Further, for a comprehensive risk assessment of the region, volcanism, seismicity, and coastal dynamics along with crustal deformation need to be considered.

      $\bf{Highlights}$

      $\bullet$ The study has analyzed the eruption of Barren Island volcano and associated regional seismic activity from a Multi-Hazard perspective using satellite as well as field-based observations.

      $\bullet$ These results provided stronger supportive evidences for coupling seismicity and volcanic eruptions at Barren Island volcano for the first time in this region and open up new vistas for research in this direction.

      $\bullet$ The understanding of these two natural phenomena is very much needed for better preparedness with respect to disaster risk mitigation and management.

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