• Naresh Kumar

      Articles written in Journal of Earth System Science

    • Estimates of source parameters of 𝑀 4.9 Kharsali earthquake using waveform modelling

      Ajay Paul Naresh Kumar

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      This paper presents the computation of time series of the 22 July 2007 𝑀 4.9 Kharsali earthquake. It occurred close to the Main Central Thrust (MCT)where seismic gap exists.The main shock and 17 aftershocks were located by closely spaced eleven seismograph stations in a network that involved VSAT based real-time seismic monitoring.The largest aftershock of 𝑀 3.5 and other aftershocks occurred within a small volume of 4 × 4 km horizontal extent and between depths of 10 and 14 km. The values of seismic moment $(M_o)$ determined using P-wave spectra and Brune’s model based on $f^2$ spectral shape ranges from $10^{18}$ to $10^{23}$ dyne-cm.The initial aftershocks occurred at greater depth compared to the later aftershocks.The time series of ground motion have been computed for recording sites using geometric ray theory and Green ’s function approach.The method for computing time series consists in integrating the far-field contributions of Green ’s function for a number of distributed point source.The generated waveforms have been compared with the observed ones.It has been inferred that the Kharsali earthquake occurred due to a northerly dipping low angle thrust fault at a depth of 14 km taking strike N279°E, dip 14° and rake 117°. There are two regions on the fault surface which have larger slip amplitudes (asperities)and the rupture which has been considered as circular in nature initiated from the asperity at a greater depth shifting gradually upwards.The two asperities cover only 10%of the total area of the causative fault plane.However,detailed seismic imaging of these two asperities can be corroborated with structural heterogeneities associated with causative fault to understand how seismogenesis is influenced by strong or weak structural barriers in the region.

    • Meteorological features associated with unprecedented precipitation over India during 1st week of March 2015

      Naresh Kumar M Mohapatra A K Jaswal

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      Unprecedented precipitation along with heavy falls occurred over many parts of India from 28th February to 2nd March 2015. Many of the stations of northwest and central India received an all time high 24 hr cumulative precipitation of March during this period. Even the national capital, New Delhi, broke all the previous historical 24 hr rainfall records of the last 100 years to the rainfall record in March 2015. Due to this event, huge loss to agricultural and horticultural crops occurred in several parts of India. In the present study, an attempt is made to understand the various meteorological features associated with this unprecedented precipitation event over India. It occurred due to the presence of an intense western disturbance (WD) over Afghanistan and neighbouring areas in the form of north–south oriented deep trough in westerlies in middle and upper tropospheric levels with its southern end deep in the Arabian Sea, which pumped huge moisture feed over Indian region. Also, there was a jet stream with core wind speed up to 160 knots that generated high positive divergence at upper tropospheric level over Indian region; along with this there was high magnitude of negative vertical velocity and velocity convergence were there at middle tropospheric level. It caused intense upward motion and forced lower levels air to rise and strengthen the lower levels cyclonic circulations (CCs)/Lows. Moreover, the induced CCs/Lows at lower tropospheric levels associated with WD were more towards south of its normal position. Additionally, there was wind confluence over central parts of India due to westerlies in association with WD and easterlies from anticyclone over north Bay of Bengal. Thus, intense WD along with wind confluence between westerlies and easterlies caused unprecedented precipitation over India during the 1st week of March 2015.

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