July, 2024 || Volume 28 No.05
Volume 28(5) (2024)5-6
Click Here to open this PDF
1
Mapping of the active fault signatures in MBT-MBF zone in Dehradun - Multichannel Analysis of Surface Waves (MASW) approach
P. Sivasankar1,2, K. Satish Kumar1*, K. Swapna Sri1, P. Pavan Kishore1 and Anand K. Pandey1
1CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad-500007, India
2Centre of Exploration Geophysics, Osmania University, Hyderabad-500007, India
ABSTRACT
In the western part of Dehradun, the young active fault is deforming the Main Boundary Thrust (MBT) - Main Boundary Fault (MBF) zone and also displacing the younger terraces in strike slip manner along the Tons river section. We conducted Multichannel Analysis of Surface Waves (MASW) survey across the identified geologic and geomorphic expression, to map the litho-tectonic disposition across the active fault in the shallow subsurface, using shear wave velocity of the litho-units. It is inferred from the MASW profile sections that a high angle fault displaces the younger and older terraces with the Lower Tertiary rocks, with high shear wave velocities, abut against the Siwalik sandstone and thicker terrace deposits with lower shear wave velocities on the the other side. The presence of steeply dipping fault displacing younger terrace, is a unique observation in the MBF zone and the MASW technique has been successful in mapping the concealed fault.
2
Application of seismic inversion based maximum likelihood methods to monitor CO2 plume in Sleipner Gas Field, Norway
1Department of Geophysics, Institute of Science, Banaras Hindu University, Varanasi-221005, India
2Department of Earth Sciences, Indian Institute of Technology, Bombay, Mumbai-400076, India
ABSTRACT
Seismic inversion is a computational technique used in geophysics to infer the properties of subsurface geological formations by analyzing seismic data. In order to lower the concentration of CO2 in the atmosphere, as a part of carbon capture and sequestration operation, these inversion techniques are essential for detecting CO2 leaks injected underground. While there are other ways to carry out this inversion, such as band-limited inversion or model-based seismic inversion, the current study used maximum likelihood (ML) inversion techniques. In this technique, a probabilistic framework is used to quantify uncertainties in both the seismic data and the model parameters. The inversion process involves iteratively adjusting the model parameters to minimize the misfit between the observed seismic data and the data predicted by the model. The misfit is typically quantified using a measure such as the difference between observed and predicted seismic waveforms or attributes. The ML method is faster and provide higher resolution subsurface information in comparison with other traditional methods. In this study, to increase accuracy and comprehension of the dynamic behavior of the injected CO2 plume, time-lapse inversion and analysis of 4D seismic data are being used. The analyses of 4D seismic data includes predictability, temporal shift, cross correlation, and other crucial elements to learn more about the reservoir's response to CO2 injection. For the analysis of Sleipner Gas Field, Norway’s seismic data recorded in 1994 (pre-injection) and 2001 (post-injection) are used. The comparison of inverted impedance section from pre-injection and post-injection clearly shows the movement of CO2 plume in the subsurface. Also the use of ML inversion methods over traditional model based seismic inversion provides more accurate and less computation time and computation cost which is very important for any developing country to adopt CCS project.
3
The Atmospheric Global Electric Circuit: A Review
Swapnil S. Potdar and Devendraa Siingh*
Indian Institute of Tropical Meteorology, Ministry of Earth Sciences, Pune-411 008, India
ABSTRACT
In recent years, the studies in Global Electric Circuit (GEC) have received additional interest because of its potential to monitor climate and its use in representing the planets electrical subsystem in Earth system models. The new tools and climate models developed recently have improved our insight not only into various atmospheric processes involved in GEC, but also in their mutual interactions on the local and global scales. The processes occurring within the atmosphere and outside it in space have been observed to influence the Earth’s electrical environment and act as internal and external drivers of the GEC. In this article, we summarize the work done in these directions in order to focus our attention on the gaps in our understanding of GEC.
4
Investigations of multi-parametric anomalies associated with the 2017 Rudraprayag earthquake (M 5.1) in Uttarakhand (India) using wavelet analysis
wati1,3, Devbrat Pundhir1*, Birbal Singh2 and Saral Kumar Gupta3
1Seismo-electromagnetics & Space Research Laboratory (SESRL), Department of Physics, Raja Balwant Singh Engineering Campus, Agra,India-283105
2Department of Electronics & Communication Engineering, Raja Balwant Singh Engineering Technical Campus, Bichpuri, Agra, India-283105
3Department of Physical Sciences, Banasthali Vidyapith, Tonk, Jaipur, India-304022
ABSTRACT
In this paper, an attempt has been made to examine the existence of electromagnetic precursors of an earthquake of magnitude M 5.1 that occurred at Rudraprayag in India on 6th December 2017. For this purpose, ultra-low frequency (ULF) data, obtained at the Agra station by using a magnetometer are analyzed for the period from 10th November 2017 to 25th December 2017. The analysis has been carried out in two segments of 5 min and 1 min using wavelet transforms and decomposition methods. The results show the occurrence of several minor and major ULF bursts (transient amplitude enhancements) in the data, whose association with the earthquake is determined by examining the presence of electromagnetic pulse in them. It is seen that the bursts on 19th November, 1st December, and 4th December, show electromagnetic characters with pulse frequency lying between 0.04 and 0.05 Hz, pertaining to the ULF frequency range of 0.01 – 30 Hz, may possibly be associated with the Rudraprayag earthquake. This result is also supported by GPS-TEC ionospheric data at the Agra station that show anomalies during December 1-3. To further ascertain the connection between the unusual fluctuations in ULF and TEC data and the Rudraprayag earthquake, we also analyzed meteorological parameters including surface temperature, soil moisture, and soil temperature at the epicenter and Agra station both during the observation period. These analyses reveal anomalous variations starting from five days prior to the earthquake that continuing through the day of the event. The precursory perturbations observed in ULF, TEC, and meteorological parameters are interpreted within the framework of atmospheric gravity waves (AGW) that facilitate coupling between the lithosphere, atmosphere, and ionosphere (LAI), a theory previously reported by other researchers in the field
5
Investigation of groundwater flow regime using electrical resistivity tomography in a watershed of the Lesser Himalaya
1Department of Earth Sciences, Indian Institute of Technology Roorkee-247667, U.K., India
2Defence Geoinformàtics Research Establishment, DRDO, Chandigarh -160030, India
3Department of Geography, Banaras Hindu University, Varanasi-221005, UP, India
ABSTRACT
The hydrogeological pattern in the Himalayan region is highly variable due to diverse lithology, complex hydrogeological formations, and dynamic tectonic activities. This variability underscores the critical need to delineate groundwater flow along steep hillslopes under climate change scenarios to assess the sustainability of water resources in the hilly region. However, reliable flow evaluation demands robust subsurface evidence to better explain groundwater flow towards the stream or springs. The Electrical Resistivity Tomography (ERT) technique is a scanner that provides subsurface information based on subsurface distribution of geo-electrical properties to delineate the hill-slope scale hydrological processes. The study aimed to assess the feasibility of employing resistivity imaging to gain insight into the geological composition and hydrological behavior in the complex hilly Aglar watershed the of Uttarakhand region in Himalayan mountain belt of India. The geoelectrical survey employed the 2D electrical resistivity imaging technique with the Wenner-Schlumberger configuration with 48 electrodes. Apparent resistivity was collected in the field and inverted to true resistivity along the hill slopes. The imaging lines delineated variations in subsurface composition and preferential flow through unsaturated sap rock (fractured bedrock with weathering) in hillslope. The findings of this study offer valuable insights into the subsurface characteristics of the most permeable pathways that control groundwater resource availability and flow along the slopes of the watershed. The hard rock is exposed on the northern slope, and the southern slopes are less steep with fractured and weathered formations, facilitating strategic management and sustainable development in the Himalayan region.