• Naresh Kumar

Articles written in Journal of Earth System Science

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

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

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.

• Role of site effect for the evaluation of attenuation characteristics of P, S and coda waves in Kinnaur region, NW Himalaya

The site effect and attenuation studies are carried out for Kinnaur region of northwest Himalaya, India. A total of 109 local events happened in Kinnaur region of magnitude range 1.6–4.5, are utilized for present work. The earthquake records are influenced by the site effect depending on soft sediment thickness beneath the recording sites. Therefore, in the present study, records are corrected for site effects to estimate P ($Q_{p}$), S ($Q_{s}$) and coda ($Q_{c}$) wave quality factor. The regional frequency dependent attenuation relations, i.e., $Q_{p}$(f)$=$(29$\pm$1)$f^{(1.01±0.05)}$, $Q_{s}$ (f)$=$(38$\pm$5)$f^{(1.1±0.06)}$ and $Q_{c}$(f)$=$(74$\pm$11)$f^{(1.17±0.01)}$ are established for the Kinnaur region. The Kinnaur Himalaya mainly belongs to Higher Himalaya Crystalline (HHC) and Tethys Himalaya, where these two geological units are differentiated by the South Tibetan Detachment System (STDS). The resonance frequencies and attenuation characteristics are estimated for both regions, i.e., HHC and Tethys Himalaya. A comparison is made between HHC and Tethys Himalaya in the form of resonance frequencies and attenuation properties. The low value resonance frequency and high rate of attenuation towards the northern side of STDS, i.e., Tethys Himalaya support the presence of low-grade metasedimentary rocks. It suggests that Tethys Himalaya has high seismic hazard potential zone compared to HHC.

$\bf{Highlights}$

$\bullet$Site effects have been incorporated to estimate attenuation characteristics of P, S and coda waves in Kinnaur region, NW Himalaya.

$\bullet$The regional frequency dependent attenuation relations i.e., $Q_{p}$(f)=(29$\pm$1)$f^{(1.01±0.05)}$, $Q_{s}$ (f)=(38$\pm$5)$f^{(1.1±0.06)}$ and $Q_{c}$(f)=(74$\pm$11)$f^{(1.17±0.01)}$ are established for the Kinnaur region. The close resemblance of resonance frequencies with the geology of the study region has been observed.

$\bullet$The Tethys Himalaya lies in present study region has high seismic hazard potential zone as compare to Higher Himalaya Crystalline.

• Geochemical characteristics of fluorine- and chlorine-bearing biotite from Tusham Ring Complex, NW India: Constraints on halogen distribution and geodynamic evolution

The present study is carried out to understand the factors controlling halogens present in biotites, role of halogens in metallogeny in context to the magmatic evolution of Tusham Ring Complex (TRC), NW Indian Shield. The investigated rocks are identified with hypersolvus, high-K calc-alkaline, peraluminous, ferroan-enriched and typical A-type granitoids affinity. They are enriched in SiO$_{2}$, Na$_{2}$O + K$_{2}$O, REEs (except Eu), LILE + HFSE, elevated in Fe/Mg, Ga/Al, Th/U, A/CNK ratio and depleted in CaO, MgO, Sr, Cr, Ni, P, Ti, V and Eu abundances. The sequential accumulation of incompatible trace elements (LILE, HFSE, REEs and others) in studied rocks overlaps almost entirely the range of rare metal granitoids and high heat-producing granitoids. The elemental geochemistry in conjunction with high abundances of F (0.80–7.11 wt%) and Cl (0.44–1.56 wt%) in biotite mineral collectively attribute to hydrothermal fluid activity and the subsequent mineralization around TRC region. Our new results suggest that the acidic magmatism that occurred in the TRC is considered as a part of the plume-related Neoproterozoic Malani Igneous Suite (MIS) anorogenic magmatism.

$\bf{Highlights}$

$\bullet$ The bulk geochemistry data and the high concentration of fluorine (0.80–7.11 wt%) and chlorine (0.44–1.56 wt %) in biotite mineral indicate halogen enriched magmatic source.

$\bullet$ The halogen enriched magma is an important key to understand the magmatic evolution and metallogeny of Tusham Ring Complex.

$\bullet$ The high concentration of rare metal, rare earth metals and radioactive elements suggests that the investigated granitoids are rare metal granitoids with high heat producing capacity.

$\bullet$ The acid volcano-plutonic rocks of Tusham Ring Complex are important barcodes to reconstruct the Neoproterozoic Rodinia supercontinent and related tecto-magmatic activities occurred in NW Indian shield.

• Evaluation of heavy rainfall warnings of India National Weather Forecasting Service for monsoon season (2002–2018)

The major objective of any national weather forecasting services is to provide weather forecast and warnings and other meteorological related information to the public and government for the safety of life and property and economic activities. The heavy rainfall causes huge loss to the public in form of flood and landslide in varying severity mainly during monsoon season (June–September). Hence its accurate prediction is essential and the accuracy of prediction needs to be verified quantitatively to evaluate its strength and weakness. The National Weather Forecasting Centre (NWFC) of India Meteorological Department (IMD) issues heavy rainfall (HR) warnings for the safety of life and property of the public. In this study, verification of operational heavy rainfall (HR) warning issued by NWFC of IMD for 36 sub-divisions of India is carried out. The verification scores presented in the study are for 24 hrs (D1), 48 hrs (D2) and 72 hrs (D3) lead period average warning skills during 2014–2018 and year-wise trend of the HR warnings for the period 2002–2018. In general, it is observed that there are significant improvements in skill scores in recent years. The improvement in D3 is at higher rate as compared to D1 scores. The improvement in the recent years is mainly due to improvement in model resolution and data assimilation in the Numerical Prediction (NWP) Models runs by Ministry of Earth Sciences (MoES), Government of India and their interpretation and utilization by the forecasters for objective consensus forecast using an objective decision support system and synoptic value addition.

$\bf{Highlights}$

$\bullet$ There is significant improvement in heavy rainfall warning skill of India Meteorological Department during monsoon season in recent two years (2017 and 2018) as compared to 2002–2016.

$\bullet$ The skill scores namely, Probability of Detection (PoD), Critical Success Index (CSI) and Heidke Skill Score (HSI) has improved by 48%, 46% and 33%, respectively, as compared to mean of scores between 2002–2016 for Day 1 (D1) warning.

$\bullet$ In Day 3 (D3) warning, there is an improvement by 69%, 54% and 54% in PoD, CSI and HSS respectively during 2017–2018 as compared to mean of 2013–2015. The improvement in D3 warning is at higher rate as compared to D1 warning.

$\bullet$ In general, the skill scores are higher over the regions with higher frequency of heavy rainfall and lower over less prone regions of heavy rainfall.

$\bullet$ These improvements in the forecast warning skill may be attributed to availability and use of latest forecasting models with high resolution and better data assimilation. Apart from the above, the structured monitoring of the monsoon circulations parameters, interpretation of NWP models guidance through Forecast Demonstration Project (FDP), objective consensus through decision support system and subjective consensus amongst the forecasters through video conference contributed significantly improved HR warning in recent years.

• Influence of the water–sediment interaction on the major ions chemistry and fluoride pollution in groundwater of the Older Alluvial Plains of Delhi, India

Fluoride (F$^{-}$ ) pollution in groundwater of the Older Alluvial Plain (OAP) of Delhi has been reported as a major problem. About 34% of the groundwater samples collected for this study had F$^{-}$ level beyond the permissible limit; with F$^{-}$ concentration in the range of 0.14–3.15 mg/L (average 1.20 mg/L). In this context, this article for the first time attempts on the genesis of major ions chemistry and F$^{-}$ pollution in groundwater of OAP Delhi by going beyond the statistical analysis to sediment geochemistry, chemical weathering processes and understanding of the processes using stable environmental isotopes ($^{2}$H and $^{18}$O). The XRD of the OAP sediments revealed the dominance of fluor-biotite, albite, calcite, quartz, and chlorite. Whereas, the separated clay revealed the dominance of chlorite, kaolinite, and illite minerals. The saturation index (SI) values indicated that the groundwater chemistry is in the process of further F$^{-}$ enrichment by way of sediment groundwater interaction. With the given mineralogy of the sediments, the dominance of major ions like Na$^{+}$), K$^{+}$, Mg$^{2+}$, Ca$^{2+}$, Cl$^{-}$ and F$^{-}$ has been attributed to chemical weathering of biotites, phlogopites, albite, and calcite during sediment–water interaction. While the dominance of SO$_{4}$ $^{2-}$ has been attributed to anthropogenic sources and confirmed by its association with heavier stable isotopes of hydrogen ($\delta^{2}$H: −50.44 to −40.02 per thousand) and oxygen ($\delta^{18}$O: −7.19 to −5.62 per thousand) indicating evaporative enrichment during isotopic fractionation.

• Spatial and temporal variation in daily precipitation indices over Western Himalayas

In the recent past, there were extensive floods in the Western Himalayan region (WHR) due to continuous long spells of heavy rainfall for 3–4 days that caused a huge loss in life and property over the region. WHR is a data sparse region, with limited meteorological stations having a continuous long spell of daily precipitation data. In the present study, spatial and temporal variability of seasonal as well as annual precipitation, precipitation days and maximum accumulated daily, 2 days, 3 days, 4 days and 5 days precipitation over WHR is considered by using daily precipitation data of 18 meteorological stations of the region. Out of 18 meteorological stations, five stations have continuous data from 1901 to 1980 and remaining 13 stations data is considered for their common period from 1981 to 2014. Accordingly, the analysis is carried out in two parts, first for 1901–1980 (for 5 stations) and second for 1981–2014 (for all the 18 stations). The analysis suggests high variability in the spatial and temporal distribution of seasonal as well as maximum accumulated daily to 5 days precipitation over WHR. In general, increasing trends in maximum accumulated precipitation in lower altitude stations and decreasing trends in higher altitude stations are observed in monsoon season and vice-versa in the winter season during the period 1981–2014. The increase in maximum accumulated daily to 5 days precipitation is up to 9.7 mm per decade during 1901–1980 and is up to 45.5 mm per decade during 1981–2014 in monsoon season in lower altitude stations. Thus, the increase in maximum accumulated precipitation during monsoon season becomes manifold during 1981–2014 as compared to the period 1901–1980.

• # Journal of Earth System Science

Volume 130, 2021
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019