January, 2026 || Volume 30 No.01
Volume 30(1) January 2026 (1-6)
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1
Flash floods in Uttarakhand Himalaya: Reasons and remediation
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ABSTRACT
The Himalayan region has been suffering from different kinds of climate-induced geological hazards, out of which the flash floods have been often due to one of the causes of erratic rainfall or cloudbursts, ice/snow avalanches, glacial lakes outburst, landslide lakes outburst, fluvial extremes, abrupt river incisions, reservoir-dam failure, or a combination of two or more of these. The floods have instigated loss of lives and livestock, and/or damage to properties and structures leading to disasters of variable magnitudes. The aspects that have been responsible are, climate change or global warming and stresses persuaded by unplanned anthropogenic activities. It is to be stated that ‘çloudburst’ is defined as more than 100 mm rainfall per hour, suddenly occurring over a small area. The ‘flash flood’ is the fast and impulsive inundation, while the normal ‘flood’ is slower and more prolong that affect generally larger areas with steadily increasing water level. The constricted drainage system and narrow river valley have been attributed to the rainfall-triggered flash floods at many places. There has been cascading effect also due to earthquakes, (caused by plate convergence), to landslides to landslide-lake formation followed by its sudden rupturing to flash floods. It is the landscape and geomorphological features of the Himalaya that control the damage pattern during a catastrophe.
2
Crust-mantle seismic structure along Jakhau-Mandvi DSS Profile: A geodynamic perspective
K. Chandrakala* and Prakash Kumar
CSIR- National Geophysical Research Institute, Uppal Road, Hyderabad- 500 007, India
ABSTRACT
Kutch rift basin situated in the northwestern part of the Deccan volcanic province, is characterised by sustained intermediate to deep crustal earthquake activity since historical times, unheard in other global stable terrains. This region underwent through several geotectonic, thermal and magmatic episodes in the past, whose signatures are manifested in various forms including the complex and heterogeneous crust-mantle velocity structure. In order to delineate hydrocarbon-rich Mesozoic sediments and underlying basement configuration, seismic refraction and wide-angle reflection data was acquired along the four Deep Seismic Sounding profiles. In the present study, we reprocessed the seismic data along one of these profiles, shot across the southwestern part of the Kutch region, that runs from Jakhau to Mandvi on the west coast. Our study delineated occurrence of a six-layered sequence above the granitic–gneissic basement (Vp: 5.90–6.00 km/s), with their thicknesses varying from 5.5 to 8 km. It includes, Tertiary sediments (Vp: 2.0 km/s), Deccan basalts (Vp: 4.70 km/s), upper low velocity Mesozoic sediments (Vp: 3.3 km/s), Mesozoic limestone (Vp : 5.1 km/s) followed by Mesozoic volcanics (Vp: 5.50 km/s) and another low velocity Mesozoic sediments (Vp: 5.30 km/s). It is underlain by mid-crustal layer (Vp: 6.30-6.40 km/s) located at depths of around 8 to 12.5 km, which is further underlain by a relatively thinner lower crustal layer (Vp: 6.80-6.90 km/s). Below this layer, we also delineated two distinct underplated magmatic layers (Vp: 7.20 -7.50 km/s) above the Moho, characterize by velocity 7.7-8.0 km/s. Moho is delineated at an extremely shallow depths from 25 to 35 km. Conspicuously, we also depicted a frozen mantle magma chamber (Vp: 8.0 km/s), in the uppermost mantle, which coincides with the location of Katrol Hill Fault. It appears that this region has undergone persistent magmatism, massive subcrustal erosion and asthenospheric upwarping.
3
Insights into crustal structure of Aravalli-Delhi Fold Belt and adjoining Bundelkhand craton-Marwar block from gravity models: Significance for Precambrian tectonics in NW India
Om Prakash, Niraj Kumar, A. K. Pandey, K. N. D. Prasad and A. P. Singh*
CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad-500007 (India)
ABSTRACT
The 2.5D crustal density structure is modelled using complete Bouguer anomaly along two W-E profiles across the Marwar block, Aravalli-Delhi Fold Belt (ADFB), and the Bundelkhand craton, constituting the north-western edge of the Indian Shield. The rock density closely mimics the litho-tectonic units that preserve the Archean-Proterozoic evolutionary history. The Bouguer anomaly along the profiles, corresponds to significant variation in crustal structure, with Moho depth varying from 34 to 40 km under the Marwar block, ~45 km under high-relief ADFB and <42 km under the Bundelkhand craton. A highdensity (2.78 g/cm3) 6-8 km thick sill in the upper crust and a 10-12 km thick high-density (3.05 g/cm3) body as the mantle underplating at the Moho, represent the source conduit of the Neoproterozoic Malani Igneous Suite in the Marwar block. The significant lithological variation within the 8-10 km thick upper crust with a 12-13 km thick elongated high-density (3.05 g/cm3) basaltic body with a diffused Moho signature, possibly representing the mantle underplating due to orogenic root delamination under the ADFB. The lateral variation in the crustal structure across the craton suggests the orogenic reworking during the early-mid Proterozoic and mantle upwelling in an extensional regime during the Neoproterozoic in the ADFB and Marwar lock.
4
Seismic site characterization in the region near Korba coalfield, Chhattisgarh (India)
Tushar Singhania1,2, Niptika Jana1* and Sanjit Kumar Pal1
Department of Applied Geophysics, Indian Institute of Technology (Indian School of Mines)
Dhanbad, Dhanbad-826004, Jharkhand, India
ABSTRACT
This study employs seismic techniques for the site characterization of the Korba region in Chhattisgarh, India. Seismic activity has been reported in this region lately, classifying this region in seismic zone III, according to the Building Materials and Technology Promotion Council (BMTPC) assessment (2006). We gather data from 30 different locations in the Korba region, using the Tromino instrument. We estimate the fundamental frequency, construct shear wave velocity for subsurface classification of the Korba region, and develop Horizontal-to-Vertical Spectral Ratio (HVSR) curves for ambient noise data in accordance with the National Earthquake Hazards Reduction Programme (NEHRP) criteria. We calculated the liquefaction vulnerability index (Kg), amplification value, and peak resonant frequencies from the HVSR curve. Amplification factors range from 1.18 to 10.02, while the peak resonant frequencies span from 1.146 to 15.062 Hz. Vs30 for the region varies between 140.06 and 646.90 m/s. These findings indicate presence of soft soil in the western portion of the region, which is situated along the Hasdeo River's bank. In majority of the places, we discovered that the Kg value was less than 10, indicating low liquefaction vulnerability in the examined area.
5
Seismic hazard mapping in Gorakhpur, India: A multi parametric approach using predominant frequency, amplification and engineering bed rock depth
Shashank Shekhar1, Anurag Tiwari1*, G P Singh1 and J L Gautam2
Department of Geophysics, Banaras Hindu University, Varanasi-221005, India
ABSTRACT
Gorakhpur city, situated in the Indo-Gangetic Plain of northern India and classified under Seismic Zone IV, is increasingly getting vulnerable to earthquake induced ground motion due to its proximity to active Himalayan belt, growing urban footprint and soft alluvial subsurface conditions. This study presents a comprehensive seismic hazard assessment based on key site parameters, including average shear wave velocity up to 30 m (??30), predominant frequency (??), fundamental time period (??), peak amplification (??), engineering bed rock depth (???) and the Seismic vulnerability index (??). Ambient noise data is used to estimate ?? and ??, while shear wave velocity profiles were obtained through study of Multichannel Analysis of Surface Waves (MASW). Spatial interpolation and GIS-based mapping of these parameters, reveal significant heterogeneity in the subsurface response characteristics. Zones with low ??30, low ??, longer ??, high ???, high ?? and high ?? values, primarily in the southern parts of the city, demonstrating a high potential for ground motion amplification and structural resonance. The ?? index, effectively highlights the most seismically vulnerable zones within the city, while ??? is estimated using predominant frequency and shear wave velocity. The results underline the critical need for microzonation-based land use planning, earthquake-resilient construction, and site-specific design codes. This study provides essential input for seismic risk reduction and sustainable urban development in Gorakhpur, and establishes a framework for similar assessments in other seismically active regions of the Indo-Gangetic basin.
6
Fault plane solutions of the earthquakes (1.8? ML ? 3.5) in the Himachal Himalaya, India
Ankush Kumar Ruhela*, J. Das and S.C. Gupta
Department of Earthquake Engineering, Indian Institute of Technology Roorkee,
Roorkee- 247667, India
ABSTRACT
It is widely acknowledged that even when earthquakes occur inside a specific confined area, there can be significant variations in the focal mechanism solutions. Several earthquakes have been detected by broadband seismometers coupled with a digital recorder (Centaur) at six stations in the Himachal Himalaya during 2018-2019. Therefore, we addressed an approach for identifying the orientation of fault planes in the studied area. In this paper, we retrieved the fault plane solutions of 25 earthquakes using a double couple fault plane method, based on P-wave polarity readings and amplitude ratio with the help of the Seisan program. Earthquakes exhibit diverse fault plane solutions. From a total of 25 earthquakes, 3 show normal faulting, 19 show reverse faulting, and 3 show strike-slip mechanism. This is because rupture lengths for local events (M < 3.5) are typically in the range of a few hundred meters to a kilometer, and events may occur on faults with varying orientations. The maximum concentration of thrust faults is consistent with the trend of the Himalayan collisional zone and the location of major faults. Except for some showing a dip greater than 60°, earthquakes with precisely measured depths characterise a zone from 0.1 25 km with an average dip of about 44.6°. All focal mechanisms of events that are available within this zone, indicate a steeper dip. An earthquake that occurred near the Sundarnagar fault, shows a strike-slip mechanism. Based on this interpretation, there may be a genetic relationship between the Himalayan block above the MBT and a transverse structural feature in the underthrusting Indian plate (Sundarnagar fault). Earthquakes reveal a trend of directions concerning the T-axis and P-axis with all types of fault plane solutions.
7
Deep learning-based model for groundwater quality prediction in Kanyakumari District, Tamil Nadu, India.
Centre for Geotechnology, Manonmaniam Sundaranar University,
Tirunelveli – 627 012, Tamil Nadu (India)
ABSTRACT
In this study, a Deep learning-based model, Stochastic Neural Network (SNN), which excels in handling uncertain and complex data, is customized to predict groundwater quality in the Kanyakumari District of Tamil Nadu (India), where groundwater is considered a critical source for drinking and agricultural purposes. The SNN model captures the stochastic nature of the data and provides reliable predictions by simulating multiple possible outcomes, making the model ideal for groundwater quality prediction. A range of groundwater quality indicators, such as pH, EC, TDS, etc. were used to train the model. Rainfall patterns were found to have a considerable impact on water quality over a ten-year period, emphasizing the importance to include seasonal data into prediction models. Hence, rainfall data was also included in order to evaluate its impact on groundwater quality. The deep learning model demonstrated its effectiveness with 95% prediction accuracy. The model's capacity to distinguish between classes was evaluated by the Classification Report, Receiver Operating Characteristic (ROC) curves, Area Under the Curve (AUC) values and the confusion matrix. In addition to this, Cross-validation (CV) was employed to confirm the model's performance and also to test the reliability of the results. This study provides an efficient method that can assist in sustainable use of groundwater resources.
8
Centre for Geothermal Energy Research (CGER) at CSIR–NGRI, Hyderabad: Advancing sustainable geothermal energy in India
CSIR-National Geophysical Research Institute, Hyderabad 500007, India
ABSTRACT
The CSIR–National Geophysical Research Institute (CSIR NGRI), Hyderabad (India), is country’s unique geoscientific research institution, dedicated to research investigations spanning from near-surface processes to deep Earth exploration with a strategic focus on natural resource exploration (groundwater, mineral, geothermal energy, and hydrocarbon) and hazard assessment for sustainable development. Among various renewable energy resources, geothermal energy stands out as a reliable, clean, and sustainable resource, capable of providing continuous baseload power, independent of climatic or seasonal variability (Gupta and Roy, 2007).