D SRINAGESH
Articles written in Journal of Earth System Science
Volume 98 Issue 1 April 1989 pp 31-60
High velocity anomaly beneath the Deccan volcanic province: Evidence from seismic tomography
H M Iyer V K Gaur S S Rai D S Ramesh CVR Rao D Srinagesh K Suryaprakasam
Analysis of teleseismic
Volume 101 Issue 3 September 1992 pp 283-298
Anomalous granulite crust of South India — signatures from converted teleseismic waves
D S Ramesh D Srinagesh S S RAI K S PRAKASAM
Analysis of teleseismic waves using
Volume 129 All articles Published: 22 April 2020 Article ID 0112 Research Article
Magnitude estimation of regional earthquakes in India and its adjoining region
B NARESH PRANTIK MANDAL SOLOMON RAJU R VIJAYA RAGHAVAN G SURESH D SRINAGESH
To provide reliable and quick estimation of magnitude for moderate to large earthquakes at regional distances, two magnitude relations specific to the peninsular shield have been proposed based on long-period magnitude ($M_{A}$) and energy magnitude ($M_{E}$), using broadband velocity data of 23 regional events recorded at 18-station seismic network in the state of Telangana and Andhra Pradesh, India. $M_{A}$ is estimated using amplitude of filtered (0.03–0.08 Hz) broadband velocity seismograms, while $M_{E}$ is estimated based on radiated energy using broadband velocity spectra. It is observed that $M_{A}$ for larger events with $M_{w}$ >7.2 saturates, whilst $M_{E}$ does not suffer from saturation even for larger events. Thus, it is apparent that these two magnitude relations can provide magnitude estimates without saturation for all moderate to large regional earthquakes, which, in turn, can provide a homogeneous catalogue for moderate to large regional Indian earthquakes. The data transmission from remote stations to the central server at CSIR-National Geophysical Research Institute (NGRI) is quasi-real-time since it is connected by GPRS and VSAT. Using the proposed region specific magnitude relationships it becomes possible to estimate reliable magnitudes for moderate to large regional Indian earthquakes ($M_{w} \leq 7.2$) within 30 min of the occurrence of an event.
Volume 130 All articles Published: 17 February 2021 Article ID 0040 Research article
Appraisal of Veldurti–Kalva–Gani (VKG) fault, Cuddapah Basin, India: Gravity and magnetic approach
K SATISH KUMAR P SIVASANKAR S PARVEEN BEGUM B LAXMAN PHALKE MAHESH DEVIDAS V MAHA LAXMI NAIDU P SOLOMON RAJU D SRINAGESH
A ${\sim}$60 km long Veldurti–Kalva–Gani (VKG) fault is one of the identified strike-slip faults extending from Eastern Dharwar Craton (EDC) to Cuddapah basin in South Indian Shield. The recorded recent seismic activity during year 2012–2016 show occurrences of three microseismic events (<$M_{w}$ 2.0) in the vicinity of this fault. Historically, no major seismic events are recorded near this fault except magnitude of 5.0–5.9 (1843) earthquake at about ${\sim}$80 km west of this fault near Bellary. In the present study, analysis of available gravity, aeromagnetic and newly acquired ground gravity and magnetic data in the vicinity of the fault has been carried out to understand subsurface characteristics of this VKG fault and nearby structural features related to recent seismic activity. Analysis of aeromagnetic and gravity data shows shallow origin of the fault and earthquakes are associated with the zone of intersection like cross faults/lineaments which are parallel and perpendicular to the VKG fault. The calculated log normalized radially averaged power spectrum of the available gravity and aeromagnetic data shows four average depths $h_{0}$ (12.7 km), $h_{1}$ (6 km), $h_{2}$ (2.0 km) and $h_{3}$ (0.5 km). These estimated depths are possibly, bottom of the upper crust, thickness of the Cuddapah basin sediments, horizon of the basic sills, flows and the ferruginous quartzites and cumulative stratigraphic thickness of the Tadpatri shales and the Kurnools in the areas, respectively. The jointly inverted 2-D model from the ground gravity and aeromagnetic data along 2.7 km profile across VKG fault shows, faulting between Banganapalli Quartzite and Tadpatri Shales. The estimated average focal depth from the observed microseismic events is around 13 km. It is concluded from the present study that the observed microseismic events in the vicinity of VKG fault are associated with the intersection zones of cross faults/lineaments near the VKG fault and originated at an average depth of 13 km might be bottom of the upper crust. The estimated depths from the present analysis are well corroborated with previous geophysical studies.
$\bf{Highlights}$
$\bullet$ Mapping of Veldurti–Kalva–Gani fault through gravity, magnetic and aeromagnetic data which is associated with recent seismic activity.
$\bullet$ Understanding of origin of the seismic activity through spectral analysis.
$\bullet$ Estimation of depth to the basement, upper crust and thickness of Cuddapah basin sediments in the study region.
$\bullet$ Estimation of focal depth from seismological data and corroboration with spectral analysis of gravity and aeromagnetic data.
Volume 131 All articles Published: 8 April 2022 Article ID 0093 Research article
Urbanization effect on Hyderabad seismic station
S SHAHEENA PARVIN D SRINAGESH R VIJAYRAGHAVAN V K GAHALAUT
Seismographs record earthquakes and also record various types of noise, including anthropogenic noise. In the present study, we analyse the influence of the lockdown due to COVID-19 on the ground motion at CSIR-NGRI HYB Seismological Observatory, Hyderabad. We analyse the noise recorded a week before and after the implementation of lockdown by estimating the probability density function of seismic power spectral density and by constructing the daily spectrograms. We find that at low frequency (${\le}$1 Hz), where the noise is typically dominated by naturally occurring microseismic noise, a reduction of ${\sim}$2 dB for secondary microseisms (7–3 s) and at higher frequency (1–10 Hz) a reduction of ${\sim}$6 dB was observed during the lockdown period. The reduction in higher frequencies corresponding to anthropogenic noise sources led to improving the SNR (signal-to-noise ratio) by a factor of 2 which is the frequency bandwidth of the microearthquakes leading to the identification of microearthquakes with Ml around 3 from epicentral distances of 180 km.
Volume 132, 2023
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