Baldev Arora - Academia.edu (original) (raw)

Papers by Baldev Arora

Research paper thumbnail of Crustal structure of Northeast India as evidenced by receiver function imaging: tectonic and geodynamic implications

International journal of earth sciences, Mar 16, 2024

Research paper thumbnail of 2-D geoelectrical model for the Parnaı́ba Basin conductivity anomaly of northeast Brazil and tectonic implications

A magnetometer array study in the north-northeast of Brazil has revealed a roughly NE-SW-trending... more A magnetometer array study in the north-northeast of Brazil has revealed a roughly NE-SW-trending conductive structure in the southeastern part of the intracratonic Parnaíba Basin. The magnetovariational response functions of this structure are numerically modelled to constrain its geometry to facilitate its geological and tectonic interpretation. The 2-D numerical model that incorporates the ocean effect and can account for the spatial and period dependence of the observed response locates the source regions of enhanced conductivity in a graben structure in the basement as well as in a block confined to the central part of the basin with an embedded resistive body. The anomalous electrical character of the sediments in the central part of the basin is consistent with the magnetotelluric data, the graben structure in the basement is corroborated by the aeromagnetic data. The formation of the graben structure is considered to be a manifestation of the extensional tectonics associated either with the Brasiliano orogeny or with the Jurassic-Cretaceous magmatic events. The diabase dikes intruded in the basin in association with the Jurassic-Cretaceous magmatic activity are shown to be accountable for the mapped resistive body entrapped in the conducting Paleozoic sediments. The thermal effects associated with magmatic activities are invoked to produce enhanced conductivity by the generation of carbon through the pyrolysis of hydrocarbon-saturated sediments.

Research paper thumbnail of Gravity and Geodetic Studies in India : Historical Observations and Advances During the Past Decade

Proceedings of the Indian National Science Academy, 2018

Gravimetry and Geodesy deal with the mass distribution and transport in the dynamic Earth system ... more Gravimetry and Geodesy deal with the mass distribution and transport in the dynamic Earth system and determination of Earth's shape and size. Since the 18th century, Indian scientists have been extensively contributing to the progress of Gravity and Geodetic studies. This article discusses the historical geodetic developments and summarizes the efforts that involve measurements and modelling of gravity and geodetic data in India over the past decade, using conventional land surveys to satellite observations. Historical obsevations, such as the Great Trigonometrical Survey during 1790-1850 for defining geodetic reference frame and gravity and geodetic observations in the Himalayan region (1830-1843) for hypothesising the concept of Isostasy, are phenomenal contributions made from studies in India. Recent studies are largely focused on understanding of subsurface mass distributions and mass variability due to different geophysical phenomenon, refining of geodectic datum, continental deformation and resource exploration.

Research paper thumbnail of The Enhancement of a Crustal Conductive Anomaly in the Southeastern Paraná Basin by Vertical and Impedance Transfer Functions

5th International Congress of the Brazilian Geophysical Society, 1997

Research paper thumbnail of Wadia Institute of Himalayan Geology

Journal of the Geological Society of India, 2018

Research paper thumbnail of Geomagnetic Measurements in Remote Regions Preface

Annals of Geophysics, 2009

Research paper thumbnail of Application of polarization ellipse technique for analysis of ULF magnetic fields from two distant stations in Koyna-Warna seismoactive region, West India

Natural Hazards and Earth System Science, 2010

Research paper thumbnail of 2-D geoelectrical model for the Parnaı́ba Basin conductivity anomaly of northeast Brazil and tectonic implications

Research paper thumbnail of Preface

Research paper thumbnail of Assesment of the response of the meteorological/hydrological parameters on the soil gas radon emission at Hsinchu, northern Taiwan: A prerequisite to identify earthquake precursors

Journal of Asian Earth Sciences

The present study is an attempt to assess and quantify the influence of the meteorological (atmos... more The present study is an attempt to assess and quantify the influence of the meteorological (atmospheric temperature and pressure) and hydrological (rainfall and ground water head-GWH) parameters on the soil gas radon emission at Hsinchu, northern Taiwan. The quasi-periodic variations corresponding to diurnal and semi diurnal periods were estimated and eliminated by decomposing the time series for the period of September 16, 2009 to March 5, 2010 to singular spectrum analysis. The reconstructed non-periodic variations, which reproduce the salient feature of recorded time series, were searched for meteorological/hydrological influences in radon emission. The combined response of barometric pressure and atmosphere temperature are found to be small when compared to the total variability in radon. The influence of rainfall on radon is found to be strongest. At the onset of rainfall, radon shows a step-jump that attains peak with a time lag of 12-15 h. This enhancement is attributed to entrapment of soil gas in the top soil cover as increased soil moisture prevents escape of radon into the atmosphere (capping effect). The decay of radon after the recession of rainfall is approximated by double exponential decay terms, one corresponding to the natural decay of radon with half life of 3.84 days and second representing slow weakening of capping effect. The third effect related to internal loading due to rise and fall of groundwater modulates the propagation of radon in overlying strata, accounting for the long term variations in radon. The rainfall inflicted changes in radon look strikingly similar to earthquake related precursory or coseismic perturbations, inferred by long term synotopic observations. It is surmised that unless radon variations are corrected for meteorological/hydrological contamination, some precursory signals are masked on one hand while on the other hand some anomalies are falsely viewed as earthquake precursors.

Research paper thumbnail of Time of occurrence of maximum in low latitude horizontal intensity and its dependence on magnetic activity

Research paper thumbnail of Daily variation of the geomagnetic field near the focus of Sq-current system in Indian longitude

Journal of Earth System Science, 1983

The paper presents the first results on the behaviour of solar quiet-day variations of the geomag... more The paper presents the first results on the behaviour of solar quiet-day variations of the geomagnetic field components at Gulmarg. Combining the data from Russian stations in the same longitude belt, the annual average daily variations are calculated which show, in the horizontal component (H), a reversal of phase between Gulmarg and Tashkent. Studying the Sq-variations at Gulmarg separately for the three seasons, the daily variation of H duringd-months is predominantly diurnal in character with the maximum before noon. Duringe-months, and more so inj-months, daily variation of the H field is predominantly semidiurnal in character with minimum around 08–09 hr LT and maximum around 14 hr LT consistently during 1978, 1979 and 1980. These features of the Sq at Gulmarg are suggested to be due to the deformations of the current loops caused by the changing latitude of focus during the course of the day.

Research paper thumbnail of Precursory signatures in the radon and geohydrological borehole data for M4.9 Kharsali earthquake of Garhwal Himalaya

Science of The Total Environment, 2009

Research paper thumbnail of Lunar modulation on the occurrence frequency of the afternoon counter-electrojet events at Trivandrum

Planetary and Space Science, 1981

Research paper thumbnail of External Sq currents in the India-Siberia region

Journal of Geophysical Research, 1993

Research paper thumbnail of Geomagnetic induction and conductive structures in north-west India

Geophysical Journal International, 1982

Research paper thumbnail of Contributions from oceanic and ionospheric dynamos to the lunar daily variation at Alibag

Geophysical Journal International, 1979

Research paper thumbnail of Multi-Parameter Geophysical Observatory: gateway to integrated earthquake precursory research

Research paper thumbnail of Time of occurrence of maximum in low latitude horizontal intensity and its dependence on magnetic activity

Research paper thumbnail of Daily variation of the geomagnetic field near the focus of Sq-current system in Indian longitude

Journal of Earth System Science, 1983

The paper presents the first results on the behaviour of solar quiet-day variations of the geomag... more The paper presents the first results on the behaviour of solar quiet-day variations of the geomagnetic field components at Gulmarg. Combining the data from Russian stations in the same longitude belt, the annual average daily variations are calculated which show, in the horizontal component (H), a reversal of phase between Gulmarg and Tashkent. Studying the Sq-variations at Gulmarg separately for the three seasons, the daily variation of H duringd-months is predominantly diurnal in character with the maximum before noon. Duringe-months, and more so inj-months, daily variation of the H field is predominantly semidiurnal in character with minimum around 08–09 hr LT and maximum around 14 hr LT consistently during 1978, 1979 and 1980. These features of the Sq at Gulmarg are suggested to be due to the deformations of the current loops caused by the changing latitude of focus during the course of the day.

Research paper thumbnail of Crustal structure of Northeast India as evidenced by receiver function imaging: tectonic and geodynamic implications

International journal of earth sciences, Mar 16, 2024

Research paper thumbnail of 2-D geoelectrical model for the Parnaı́ba Basin conductivity anomaly of northeast Brazil and tectonic implications

A magnetometer array study in the north-northeast of Brazil has revealed a roughly NE-SW-trending... more A magnetometer array study in the north-northeast of Brazil has revealed a roughly NE-SW-trending conductive structure in the southeastern part of the intracratonic Parnaíba Basin. The magnetovariational response functions of this structure are numerically modelled to constrain its geometry to facilitate its geological and tectonic interpretation. The 2-D numerical model that incorporates the ocean effect and can account for the spatial and period dependence of the observed response locates the source regions of enhanced conductivity in a graben structure in the basement as well as in a block confined to the central part of the basin with an embedded resistive body. The anomalous electrical character of the sediments in the central part of the basin is consistent with the magnetotelluric data, the graben structure in the basement is corroborated by the aeromagnetic data. The formation of the graben structure is considered to be a manifestation of the extensional tectonics associated either with the Brasiliano orogeny or with the Jurassic-Cretaceous magmatic events. The diabase dikes intruded in the basin in association with the Jurassic-Cretaceous magmatic activity are shown to be accountable for the mapped resistive body entrapped in the conducting Paleozoic sediments. The thermal effects associated with magmatic activities are invoked to produce enhanced conductivity by the generation of carbon through the pyrolysis of hydrocarbon-saturated sediments.

Research paper thumbnail of Gravity and Geodetic Studies in India : Historical Observations and Advances During the Past Decade

Proceedings of the Indian National Science Academy, 2018

Gravimetry and Geodesy deal with the mass distribution and transport in the dynamic Earth system ... more Gravimetry and Geodesy deal with the mass distribution and transport in the dynamic Earth system and determination of Earth's shape and size. Since the 18th century, Indian scientists have been extensively contributing to the progress of Gravity and Geodetic studies. This article discusses the historical geodetic developments and summarizes the efforts that involve measurements and modelling of gravity and geodetic data in India over the past decade, using conventional land surveys to satellite observations. Historical obsevations, such as the Great Trigonometrical Survey during 1790-1850 for defining geodetic reference frame and gravity and geodetic observations in the Himalayan region (1830-1843) for hypothesising the concept of Isostasy, are phenomenal contributions made from studies in India. Recent studies are largely focused on understanding of subsurface mass distributions and mass variability due to different geophysical phenomenon, refining of geodectic datum, continental deformation and resource exploration.

Research paper thumbnail of The Enhancement of a Crustal Conductive Anomaly in the Southeastern Paraná Basin by Vertical and Impedance Transfer Functions

5th International Congress of the Brazilian Geophysical Society, 1997

Research paper thumbnail of Wadia Institute of Himalayan Geology

Journal of the Geological Society of India, 2018

Research paper thumbnail of Geomagnetic Measurements in Remote Regions Preface

Annals of Geophysics, 2009

Research paper thumbnail of Application of polarization ellipse technique for analysis of ULF magnetic fields from two distant stations in Koyna-Warna seismoactive region, West India

Natural Hazards and Earth System Science, 2010

Research paper thumbnail of 2-D geoelectrical model for the Parnaı́ba Basin conductivity anomaly of northeast Brazil and tectonic implications

Research paper thumbnail of Preface

Research paper thumbnail of Assesment of the response of the meteorological/hydrological parameters on the soil gas radon emission at Hsinchu, northern Taiwan: A prerequisite to identify earthquake precursors

Journal of Asian Earth Sciences

The present study is an attempt to assess and quantify the influence of the meteorological (atmos... more The present study is an attempt to assess and quantify the influence of the meteorological (atmospheric temperature and pressure) and hydrological (rainfall and ground water head-GWH) parameters on the soil gas radon emission at Hsinchu, northern Taiwan. The quasi-periodic variations corresponding to diurnal and semi diurnal periods were estimated and eliminated by decomposing the time series for the period of September 16, 2009 to March 5, 2010 to singular spectrum analysis. The reconstructed non-periodic variations, which reproduce the salient feature of recorded time series, were searched for meteorological/hydrological influences in radon emission. The combined response of barometric pressure and atmosphere temperature are found to be small when compared to the total variability in radon. The influence of rainfall on radon is found to be strongest. At the onset of rainfall, radon shows a step-jump that attains peak with a time lag of 12-15 h. This enhancement is attributed to entrapment of soil gas in the top soil cover as increased soil moisture prevents escape of radon into the atmosphere (capping effect). The decay of radon after the recession of rainfall is approximated by double exponential decay terms, one corresponding to the natural decay of radon with half life of 3.84 days and second representing slow weakening of capping effect. The third effect related to internal loading due to rise and fall of groundwater modulates the propagation of radon in overlying strata, accounting for the long term variations in radon. The rainfall inflicted changes in radon look strikingly similar to earthquake related precursory or coseismic perturbations, inferred by long term synotopic observations. It is surmised that unless radon variations are corrected for meteorological/hydrological contamination, some precursory signals are masked on one hand while on the other hand some anomalies are falsely viewed as earthquake precursors.

Research paper thumbnail of Time of occurrence of maximum in low latitude horizontal intensity and its dependence on magnetic activity

Research paper thumbnail of Daily variation of the geomagnetic field near the focus of Sq-current system in Indian longitude

Journal of Earth System Science, 1983

The paper presents the first results on the behaviour of solar quiet-day variations of the geomag... more The paper presents the first results on the behaviour of solar quiet-day variations of the geomagnetic field components at Gulmarg. Combining the data from Russian stations in the same longitude belt, the annual average daily variations are calculated which show, in the horizontal component (H), a reversal of phase between Gulmarg and Tashkent. Studying the Sq-variations at Gulmarg separately for the three seasons, the daily variation of H duringd-months is predominantly diurnal in character with the maximum before noon. Duringe-months, and more so inj-months, daily variation of the H field is predominantly semidiurnal in character with minimum around 08–09 hr LT and maximum around 14 hr LT consistently during 1978, 1979 and 1980. These features of the Sq at Gulmarg are suggested to be due to the deformations of the current loops caused by the changing latitude of focus during the course of the day.

Research paper thumbnail of Precursory signatures in the radon and geohydrological borehole data for M4.9 Kharsali earthquake of Garhwal Himalaya

Science of The Total Environment, 2009

Research paper thumbnail of Lunar modulation on the occurrence frequency of the afternoon counter-electrojet events at Trivandrum

Planetary and Space Science, 1981

Research paper thumbnail of External Sq currents in the India-Siberia region

Journal of Geophysical Research, 1993

Research paper thumbnail of Geomagnetic induction and conductive structures in north-west India

Geophysical Journal International, 1982

Research paper thumbnail of Contributions from oceanic and ionospheric dynamos to the lunar daily variation at Alibag

Geophysical Journal International, 1979

Research paper thumbnail of Multi-Parameter Geophysical Observatory: gateway to integrated earthquake precursory research

Research paper thumbnail of Time of occurrence of maximum in low latitude horizontal intensity and its dependence on magnetic activity

Research paper thumbnail of Daily variation of the geomagnetic field near the focus of Sq-current system in Indian longitude

Journal of Earth System Science, 1983

The paper presents the first results on the behaviour of solar quiet-day variations of the geomag... more The paper presents the first results on the behaviour of solar quiet-day variations of the geomagnetic field components at Gulmarg. Combining the data from Russian stations in the same longitude belt, the annual average daily variations are calculated which show, in the horizontal component (H), a reversal of phase between Gulmarg and Tashkent. Studying the Sq-variations at Gulmarg separately for the three seasons, the daily variation of H duringd-months is predominantly diurnal in character with the maximum before noon. Duringe-months, and more so inj-months, daily variation of the H field is predominantly semidiurnal in character with minimum around 08–09 hr LT and maximum around 14 hr LT consistently during 1978, 1979 and 1980. These features of the Sq at Gulmarg are suggested to be due to the deformations of the current loops caused by the changing latitude of focus during the course of the day.