• S Mukhopadhyay

      Articles written in Journal of Earth System Science

    • Simultaneous inversion of the aftershock data of the 1993 Killari earthquake in Peninsular India and its seismotectonic implications

      S Mukhopadhyay J R Kayal K N Khattri B K Pradhan

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      The aftershock sequence of the September 30th, 1993 Killari earthquake in the Latur district of Maharashtra state, India, recorded by 41 temporary seismograph stations are used for estimating 3-D velocity structure in the epicentral area. The local earthquake tomography (LET) method of Thurber (1983) is used. About 1500P and 1200S wave travel-times are inverted. TheP andS wave velocities as well asVP/VSratio vary more rapidly in the vertical as well as in the horizontal directions in the source region compared to the adjacent areas. The main shock hypocentre is located at the junction of a high velocity and a low velocity zone, representing a fault zone at 6–7 km depth. The estimated average errors ofP velocity andVP/VSratio are ±0.07 km/s and ±0.016, respectively. The best resolution ofP and S-wave velocities is obtained in the aftershock zone. The 3-D velocity structure and precise locations of the aftershocks suggest a ‘stationary concept’ of the Killari earthquake sequence.

    • Saddle-shaped reticulate Nummulites from Early Oligocene rocks of Khari area, SW Kutch, India

      S Sengupta Sampa Sarkar S Mukhopadhyay

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      Saddle-shaped reticulate Nummulites from the Early Oligocene rocks of Khari area, SW Kutch, India is reported here for the first time. Unusual shape of this Nummulites is due to the curved nature of the coiling plane, indicating space constrained postembryonic test growth. With regular development of chambers, septa and septal filaments, the saddle-shaped Nummulites constitutes the third morphotype of N. cf. fichteli Michelotti form A. Other morphotypes of the species reported earlier include inflated lenticular and conical tests. Multiple morphotypes of N. cf. fichteli form A indicates varied test growth in response to substrate conditions. Morphological variability exhibited by N. cf. fichteli form A from Kutch and some Early Oligocene reticulate Nummulites from the Far East are comparable. This faunal suite is morphologically distinct from the contemporary reticulate Nummulites of the European localities.

    • Long-term ozone decline and its effect on night airglow intensity of Li 6708 ˚A at Varanasi (25°N, 83°E) and Halley Bay (76°S, 27°W)

      P K Jana I Saha S Mukhopadhyay

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      A critical analysis has been made on the long-term yearly and seasonal variations of ozone concentration at Varanasi (25°N, 83°E), India and Halley Bay (76°S, 27°W), a British Antarctic Service Station. The effect of O3 depletion on night airglow emission of Li 6708 ˚A line at Varanasi and Halley Bay has been studied. Calculations based on chemical kinetics show that the airglow intensity of Li 6708 ˚A line has also been affected due to the depletion of O3 concentration. The yearly variations and seasonal variations of intensities of Li 6708 ˚A line for the above two stations are shown and compared. It has been shown that the rate of decrease of intensity of Li 6708 ˚A line was comparatively more at Halley Bay due to dramatic decrease of Antarctic O3 concentration.

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