This study evaluates soil-emitted radon (222Rn) as a short-term earthquake precursor using neural network and regression on decade-long data from the Garhwal Himalaya. The neural network model yielded higher predictive accuracy (R ≈ 0.91–0.92) than the multi-layer regression model (R ≈ 0.85), reflecting its strength in capturing the nonlinear behaviour. Statistically defined radon anomalies—exceeding ± 2σ from the modelled baseline—often preceded moderate earthquakes (Mw ≥ 3.0) by several days. These findings suggest that radon monitoring, integrated with data-driven models, can provide valuable short-term precursory information. The work highlights potential for reliable, data-driven earthquake forecasting in seismically active regions.

Crust and uppermost mantle shear-wave velocity in northeast India is elaborated based on the non-linear inversion of the Love wave group velocity data. This is the first time Love wave and SH wave tomography have been carried out in this region. We investigated the vertical and lateral variation of the SH wave velocity and the crustal thickness. We used the data from 26 broadband seismic stations that recorded the earthquakes from 2001 to 2015. Group velocity dispersion curves of 228 moderate and higher magnitude earthquakes are inverted to obtain tomography images of group velocities at periods 6–60 s. Low velocity is confined to the Bengal Basin (BB) and the Indo-Burma Ranges (IBR) at short periods. In contrast, high velocity is present in the Shillong Plateau (SP), Mikir Hills (MH), and Assam syntaxis. Higher velocity indicates an upward buckled crustal structure. The Tibetan plateau has a low velocity, indicating a thick crust and partial melt in the middle to lower crust. The inverted SH wave velocity models also show similar patterns. Based on such analysis, variation in the Moho depth below the study area could be estimated. Moho depth below SP and MH varies from 35 to 45 km. Moho depth below BB varies between 28 to 32 km. The uppermost crust in BB indicates a thick sediment deposit of 15- 20 km. The Moho depth of NE India gradually increases towards the Eastern Himalayas, Lhasa block, and IBR. Steeply dipping Moho below IBR indicates the subduction of the Indian plate below the Burma plate. The Tibet and Lhasa blocks show a crustal thickness of 85 km, which is the maximum compared to other parts of the study area. Highly variable shear wave crustal structures, added with low/high-velocity anomalies at different depths, give new insights into the heterogeneous and complex geotectonics.

In the past decade, the seismicity in the Garhwal Himalayas has been recorded by eight three-component broadband seismographs (BBS) deployed all along the Garhwal Himalayan Seismic Belt (GHSB). In this study, we estimated the source parameters of 52 local earthquakes of Mw1.5-3.3 using a 3-month seismicity catalog and the recordings of the broadband seismographs in a shear wave spectral inversion. This iterative technique is based on Brune's (1970) w-square circular source spectral model. The modeled source parameters, including corner frequency (fc), source- radius (r), stress drop (Delta 6), seismic moment (Mo), and moment magnitude (Mw), varied in the ranges of 1.3-11.58 Hz, 117.6-1054.4 m, 0.004-36 bar, 2.83E+11-1.33E+14 N-m, and 1.5-3.3 respectively. The highest computed stress drop (Delta 6max) is 36 bar, while the lowest computed stress drop (Delta 6 min) is 0.004 bar for events of Mw 2.84 and Mw 1.81, respectively. The scaling relation between fc and Mo is obtained as Mo = Afc 2.6 N-m/s3 where, (A = 4 x 1013) N-m/s3, while between Mo and Delta 6 the relation is found to be as log (Delta 6) = 0.605 log (Mo)-17.35 and Mo vs. radius, Mo = Br 1.24. where (B = 3 x 109). The relation between Mw and Mo is obtained as Mo = C Mw 7.51 , where (C = 1 x 1010) and other relations are obtained as follows: (Delta 6) = D Mw 4.7894 where (D = 0.0268), fc = E r 0.948 where (E = 1102.7), Depth (d) = F ( Delta 6) 0.111 . (F = 9.699). The estimation of earthquakes source parameters through waveform spectrum is an important component for the study of seismogenesis and obtaining scaling relations is crucial for understanding the seismic hazard assessment. The scaling relations are used to develop ground motion prediction equations (GMPEs) that relate earthquake source parameters to ground shaking characteristics (e.g., peak ground acceleration, spectral acceleration). The significant result is that our modelling indicates a scaling relationship between Mo and fc suggesting Mo fc 2.6 proportional to Constant for Garhwal Himalaya based on local earthquakes of Mw 1.5 to 3.3. These scaling relationships derived from our current study could enhance earthquake hazard modelling for the Garhwal Himalayan region. This, in turn, could allow earthquake engineers to construct more resilient buildings in the area.

In this study, we analyze the seismic attenuation characteristics of the Northwest Himalaya and adjacent regions using a dataset of 2,716 earthquakes (2.5 ≤ Mw ≤ 5.0) recorded from 2008 to 2015 by a network of 30 broadband seismographs. The single backscattering model was applied to estimate the quality factor of coda waves (Qc) across three lapse time windows (LTWs) at varying frequencies. Our results reveal that Qc increases with both frequency and LTW, suggesting a depth-dependent nature of seismic attenuation in the region. The average attenuation relationships for Qc, Qα and Qβ across the Northwest Himalaya are determined as follows for LTWs of 20, 30, and 40 s, respectively: Qc = (74 ± 14)f (1.27±0.06), Qc = (103 ± 26)f (1.16±0.08), and Qc = (140 ± 41)f (1.10±0.09). Our findings reveal significant variability in Qc, Qα and Qβ across the Tethys (TH), High (HH), Lesser (LH), and Shiwalik (SH) Himalaya regions, as well as the adjacent Indo-Gangetic Plains (IGP), with this variability strongly linked to structural heterogeneity and seismogenic processes in each region. We further establish attenuation relations for distinct tectonic units, observing the following hierarchy: [Qα,β,c−1(HH) < Qα,β,c−1(SH) < Qα,β,c−1(IGP) < Qα,β,c−1(LH) < Qα,β,c−1(TH)]. The Tethys Himalaya exhibits the high attenuation, likely due to its sedimentary structure, while the Higher Himalaya shows the low attenuation. These insights into attenuation characteristics across geotectonic segments in the Northwest Himalaya contribute to a more comprehensive seismic hazard assessment for the region.

Glaciers worldwide, including those in the Himalaya, are retreating under climate change, often leading to the formation and expansion of glacial lakes and an increased risk of Glacial Lake Outburst Floods (GLOFs). This study examines the evolution of the proglacial Bhilangana Lake (similar to 0.37 km(2); similar to 4750 m asl) and the associated glacier changes, including thinning and retreat, between 1968 and 2025 using satellite imagery, field measurements and hydrodynamic modelling. Results show lake expansion from similar to 0.12 km(2) in 2001 to similar to 0.37 km(2) in 2025, with an estimated volume of similar to 10.7 x 10(6) m(3), indicating exponential growth over time. A potential GLOF could release peak discharge of 3645 m(3)/s, with average flow velocity similar to 12 m/s, inundating similar to 6.8 km(2) and threatening hydropower projects, settlements and infrastructure downstream. Rising mean, maximum and minimum air temperatures at rates of 0.028, 0.052 and 0.05 degrees C/year, respectively, are identified as the primary drivers of lake expansion and accelerated melt, particularly in July-August. The zero-degree isotherm is shifting to higher elevations, and bias-corrected ERA5 data show good agreement at such altitudes, making it reliable for climate change analysis. Several over-deepening sites were also mapped as potential future lakes, with CMIP6 projections (similar to 0.8 degrees C/decade) indicating substantial glacial and hydrological changes, further elevating GLOF risk by the century's end.

We utilize the H-k stacking technique on P-wave receiver functions from 38 seismic stations to estimate the crustal thickness and Vp/Vs ratio in the NW Himalaya and the adjoining Indo-Gangetic Plain (IGP). We observe varying crustal thickness from similar to 29 km in the IGP to similar to 50-60 km in the Higher Himalayan Crystalline Zone. An abrupt crustal thickening of similar to 47-54 km observed near Jwalamukhi Thrust is due to significant crustal shortening along the fault. Inferred higher Vp/Vs values of 1.78-1.84 in the IGP may result from the underplating of mafic materials in the Precambrian. The presence of thick sediments towards the Himalayan Frontal Thrust, further, contributes to the extremely high Vp/Vs of 1.89-2.02. The intermediate Vp/Vs of similar to 1.74 in the Sub Himalayan Zone indicates the reworking of the mafic crust by delamination of the lower crust or the greater influence of the overlying Himalayan wedge, comprised of felsic to intermediate rock composition. Higher Vp/Vs values in the Kishtwar (1.81-1.93) and Kashmir Valley (1.80-1.93) are possibly due to the presence of volcanic rocks and the effect of the mid-crustal low-velocity layer. Integration of our results with previous studies reveals a heterogenous crustal structure characterized by both arc-normal and arc-parallel variations which may have resulted from varying convergence rates and the influence of subsurface extension of active transverse ridges beneath the Himalaya. The varying Vp/Vs values may result from diverse crustal rock compositions and partial melt/fluid zones. These partial melts alter the mechanical properties of rocks leading to brittle failure and thus promoting seismicity.

The seismic risk potential is also profoundly influenced by the frequency-dependent attenuation characteristics of seismic waves. The Northwest Himalaya, situated in the India–Eurasia collision zone, faces significant seismic risk, heavily influenced by the dissipation of seismic waves at various frequencies. This region has experienced many destructive earthquakes of varying magnitudes, highlighting its seismic activity. Prominent events are the recent highly destructive Mw 7.6 Kashmir earthquake of 2005 and the last century Mw 7.8 great Kangra earthquake of 1905. Our research focused on the P-wave (Qα), S-wave (Qβ), and coda wave (Qc) attenuation properties by analyzing data from 831 micro-to-moderate earthquakes (magnitude range 2.5–5.0) recorded by 20 seismic stations. The data recorded from 2008 to 2015 are used to obtain attenuation at 5 central frequencies between 1.5 and 12 Hz. Our findings reveal critical structural heterogeneities impacting seismogenesis, which are vital for assessing subsurface attenuation properties. This understanding is essential for evaluating seismic risks and the potential consequences on the densely populated regions of the world. We developed a model demonstrating the relationship between structural variations and the seismic attenuation characteristics of different geotectonic blocks, highlighting the uneven distribution of fault systems across the NW Himalayas. Seismic risk varies across geotectonic blocks, with changes in seismic attenuation from south to north. Factors such as fault types, material compositions, and levels of strain energy are associated with these structural disparities. The Higher Himalaya, characterized by crystalline rocks, has the lowest seismic attenuation for the present data, making it more susceptible to stronger earthquakes. Conversely, the Lesser Himalaya exhibits comparatively a slightly low earthquake risk due to higher attenuation levels. Similarly, attenuation indicates a slightly low risk for the Sub-Himalaya compared to the Indo-Gangetic Plain (IGP), owing to its comparatively high seismic attenuation. This understanding is crucial for developing effective earthquake resilience strategies in this section of the Himalayas and IGP.

Natural elements like uranium and its by-products can cause health problems if they are present in groundwater at excessive concentrations. Some industrial activities are known to elevate uranium concentrations, such as uranium mining, phosphate fertilizer production, nuclear power plants, metal processing, and coal combustion. This study gives information about the uranium concentration in groundwater samples collected from distinct water sources like hand pumps and tube wells from a variety of depths and numerous locations in Yamuna Nagar, Near Shivalik Hills, and the Origin of Saraswati River, India. Uranium concentration was measured using the LED fluorimetry technique. The average value of uranium (13.09 µg L −1 ) and annual effective dose (2.18 µSv y −1 ) is found to be within the as reported by WHO (Guidelines for drinking-water quality, World Health Organization, Geneva, 2011) and as reported by AERB (Drinking water specifications in India, Department of Atomic Energy, Mumbai, 2004) recommended safe limits of 30 µg L −1 and 60 µg L −1 respectively. For the evaluation of health risks associated with groundwater, the chemical toxicity risk and radiological risk of uranium in water are also assessed in this study. The activity of natural radionuclides in some locations is found to be high, which might be due to the local geology, hydrology, and type of industries in that region. The current study will benefit both residents and government agencies regarding uranium exposure to drinking water.

A moderate size earthquake (ML 5.9) occurred near Mechuka in Siang Valley on 23rd April 2019 at 20:15:50.00 UTC in the rupture zone of the great Assam earthquake of 15th August 1950. This shallow-focused earthquake occurred close to NE trending Main Central Thrust has a thrust fault mechanism striking parallel to this major tectonics of the Himalaya. Including this event, a dataset of 46 local, micro and low magnitude earthquakes (1.5 ≤ ML ≤ 5.9) of the Siang Valley of Arunachal Pradesh, NE India, are evaluated for the characteristics of the earthquake source, seismicity, stress drop and tectonic structures. The earthquake events were recorded by a close digital network of eight broadband seismic stations installed in December 2018 in the Siang Valley. The stress drop (Δσ) obtained for the Mechuka earthquake in the Siang Valley is 114.71 bars, the seismic moment (Mo) of 6.86E + 16 Nm and the source radius (r) of 1392.41 m. The seismic moments obtained from the microearthquakes vary between 2.44E + 11 and 6.86E + 16 Nm, and the source radius varies from 172.90 to 1392.41 m based on Brune’s circular source model 1970. The corner frequencies (fc) of the events range from 1.03 to 8.04 Hz. Seismically intense clustering of microearthquakes has a low-stress drop below 10 bar except for the Mechuka earthquake, which varies from 0.05 to 114.72. This high-stress drop of moderate earthquake compared to its low values of lower magnitude earthquakes indicates that the earthquake of 23rd April 2019 is associated with high-strength material accumulating high strain during the earthquake-building process. Moment magnitude of whole data set ranges from 1.52 to 5.16. The scaling relationship between Mo and fc is obtained as 9.089E + 16fc–9.52, and for Mo and Δσ are modelled to be related as Mo = 8.96E + 10Δσ2.86. Evaluated low-stress drop for the smaller size of earthquakes shows brittleness of the upper crustal region.

The study shows how geology and tectonic activity affect the soil gas 222 Rn concentration. The tectonically active zone, namely the Ghuttu region, which is located within the Himalayan seismic belt, was studied to decipher its impact on soil gas 222 Rn concentrations. A soil gas 222 Rn study was performed in the soil at a depth of 30 cm, and it varied from 426 f 156 Bq m-3 to 24,057 f 1110 Bq m- 3 with an average of 5356.5 f 1634.6 Bq m-3, and at 60 cm below the soil surface, the concentration varied from 1130 f 416 Bq m- 3 to 30,236 f 1350 Bq m- 3 with an average of 8928.5 f 2039.5 Bq m- 3 . These concentrations vary in soil from-3.4 % to 437.3 % as the depth moves from 30 cm to 60 cm. The variation in uranium content also shows anomalies, and higher values of uranium content in the soil affect the radon concentration in the study area. The average soil gas 222 Rn concentration in the Ghuttu window was found to be higher than that in its surrounding region. This is likely due to transportation from daughter products of uranium. 222 Rn mass exhalation rate measurements were also carried out, and a weak correlation with the soil gas 222 Rn concentration was observed. A significant variation in the mass exhalation rate was noticed in tectonically active areas. This study is vital to understanding the behavior of radon and uranium in tectonic regions.

This study compares the concentration of naturally occurring radionuclides in rocks and soil samples taken along the Manali-Leh highway from the Higher and Tethyn Himalayas. The activity of 226Ra, 232Th, and 40K in soil and rock samples was measured using an HPGe detector. The activity of these primordial radionuclides in soil and rocks differs considerably due to variations in geological and tectonic formations in the region. After a particular location, a significant decrease in radioactivity concentration in rocks and soil was also observed.

The observation of precursory signals of the 2021 Chamoli rock-ice avalanche provides an opportunity to investigate the multidisciplinary analysis approach of rock failure. On 7 February 2021, a huge rock-ice mass detached from the Raunthi peak at Chamoli district in Uttarakhand, India. The tragic catastrophe resulted in more than 200 deaths and significant economic losses. Here, we analyse radon concentration and seismic signals to characterise the potential precursory anomalies prior to the detachment. Continuous peaks of radon anomalies were observed from the afternoon of 5 to 7 February and decreased suddenly after the event, while a cumulative number of seismic tremors and amplitude variations are more intensified similar to 2.30 h before the main event, indicating a static to dynamic phase change within the weak zone. This study not only characterises abnormal signals but also models the rock failure mechanisms. The analysis unveils three time-dependent nucleation phases, physical mechanisms of signal generation and a complete scenario of physical factors that affected the degree of criticality of slope failure. The results of this study suggest gradual progression of rock cracks/joints, subsequent material creep and slip advancement acceleration preceded the final failure. Furthermore, the study highlights the importance of an early warning system to mitigate the impact of events like the 2021 Chamoli rock-ice avalanche.

The presence of underlying uranium deposits may contaminate the upper soil of a region. We have carried out a detailed investigation of radionuclides (Ra, Th, and K) present in the soil around the reported uranium deposit site in the Sikar district of Rajasthan, India. Measurements are carried out using the state-of-the-art gamma-ray spectroscopy (HPGe detector) technique. The specific activity of 226Ra, 232Th, and 40K are found in the range of 9.5 ± 0.5–50.6 ± 1.0 Bq kg−1, 11.0 ± 0.4–83.2 ± 1.5 Bq kg−1, and 177 ± 13–753 ± 47 Bq kg−1 with the mean values of 17.8 ± 7.5 Bq kg−1, 22.6 ± 13.4 Bq kg−1, and 393 ± 76 Bq kg−1 respectively. The average value of Ra Eq. activity is 80.4 Bq kg−1, below the recommended limit of 370 Bq kg−1. For radiological implications in the study area, the indoor and outdoor absorbed dose rates and age-dependent annual effective dose are estimated, which are also found below their prescribed safe limit values. The mean value of other hazard indices (Hin and Hex) and level indices (Iα and Iγ) are less than unity. Our study shows that the underlying uranium deposits do not contaminate the soil of the studied area and the soil is safe to use for various purposes.

The stress regime patterns of high-seismically active regions within the western part of the India-Eurasia collision, spanning from 67 degrees E to 83 degrees E and 27 degrees N to 39 degrees N, are elucidated through analysis of 684 Focal Mechanism Solutions from 1962 to 2021. Eighteen seismically active zones used for the stress tensor inversion, are defined based on the spatial extent of the seismicity, the depth distribution of seismic events, focal mechanism studies, and seismotectonics of the region. The defined regimes are: (1) Sulaiman Ranges and Lobe Region, (2) Hindukush, (3) Pamir, (4) Nanga Parbat Syntaxis, (5) Hazara Syntaxis, (6) Kashmir-Zanskar region, (7) Kangra-Chamba, (8) Kinnaur and Kaurik-Chango fault zone (KCFZ), (9) Garhwal, (10) Kumaon, (11) Karakoram fault zone, and (12) Gozha-Ashikule fault zone. Seismicity is reported only in the crust or up to mid-crust in most of the regions, except for the Pamir and Hindukush, where the seismicity can be observed down to 160 and 280 km, respectively. We report a clockwise rotation of the maximum horizontal stress (SHmax) of about 42 degrees and 21 degrees in the Hindukush and Pamir regions, respectively. with increasing focal depths from north west to north. The region where major and strong earthquakes occur indicates pure compressive regimes. Most of the zones support transpressive and transtensional tectonics with a few zones by normal and strike-slip fault regimes. Regions like Nanga Parbat syntaxis, Kinnaur, KCFZ, and Zanskar are exceptions, where extensional and transformational tectonic features dominate. Plate convergence force has less effect on defining the stress regime in the Karakoram fault zone and Gozha-Ashikule regions, which display transtensional and pure extensional regimes, respectively. Underthrusting of the Indian plate through complex tectonics is indicated by dominant compression stresses with evidences of normal, strike-slip, and oblique fault mechanisms.

Humans are exposed to radiation by the emission of radon gas from the soil surrounding them, necessitating the assessment of the radon exhalation levels in soil. The current study measures the radium concentration and radon mass exhalation rate in 34 soil samples obtained from diverse places near the purported uranium reserves in the Sikar districts of Rajasthan state, India. The concentration of radium is measured using the NaI scintillator detector, while the mass exhalation rate of radon is estimated using a smart RnDuo detector. The measured radium content in the soil is between 10.6–47.5 Bq kg−1 with an average value of 21.7 Bq kg−1. With an average value of 20.6 mBq kg−1 h−1, the radon mass exhalation rate ranges from 5.7–74.5 mBq kg−1 h−1. A positive correlation is observed between 226Ra concentration and 222Rn mass exhalation rate. This study shows that the soil of this area is safe in terms of radium content and radon mass exhalation rates.

The concentration of natural radionuclides ( 226 Ra, 232 Th, 40 K) in the fifty soil samples around the Khetri copper belt is measured using an HPGe detector. The values of 226 Ra, 232 Th, and 40 K are found to be lying in the range of 5.2 ± 0.3 to 27.5 ± 0.6 Bq kg −1 , 12.9 ± 0.4 to 38.8 ± 1.3 Bq kg −1 , and 113.3 ± 27.8 to 308.5 ± 31.2 Bq kg −1 respectively. The radium equivalent activity ranged from 38.63 to 93.35 Bq kg −1 with a mean value of 56.21 Bq kg −1 . The values of absorbed dose rate, annual effective dose, and annual gonadal dose rate are also estimated, which comes out to be less than their corresponding world average values. Hazard indices (internal and external) and level indices (alpha and gamma) are also observed to be less than unity. The soil of the study area can be considered safe for people living there because of its low radiological risk.

The main goal of the study is to evaluate the activity level of gamma radiation from uranium (238U), thorium (232Th) and potassium (40K) using gamma spectrometry with NaI(Tl) detector and concentration of heavy metals (HM), i.e. lead (Pb), cadmium (Cd), nickel (Ni), cobalt (Co), iron (Fe) and chromium (Cr) using atomic absorption spectroscopy (AAS) in soil samples taken from different places of Saraswati River, Yamuna Nagar, Haryana in India. The mean value of 238U, 232Th, 40K, radium equivalent activity and air-absorbed dose rate lies within the safe limit. The mean value of Radium equivalent activity and air-absorbed dose rate is within safe limits. The mean value of the corresponding HM is Fe > Pb > Ni > Co > Cd > Cr. The findings indicate that the level of HM in the soil sample of the study area is considerably below the acceptable limit.

We investigated sedimentary thickness and shear wave velocity structure in the western part of the Indo-Gangetic Plain (Punjab and Haryana Plain) and adjoining Siwalik Himalaya with the help of receiver function inversion at 20 broad-band seismological stations. This region is one of the most seismically vulnerable zones of the world due to the presence of thick surface sediments in the foreland basin that can amplify seismic waves and cause huge damage due to the earthquakes of the Himalaya. The study reveals a progressive thickening of sediments from southwest to northeast. The basement depth varies from similar to 1.5 to 1.7 km in the Central Alluvium Plain, similar to 1.8 to 2.8 km in the Zone of Terminal Fans, and attains a maximum of similar to 3.8 km near the Himalayan Frontal Thrust. The inverted models show the presence of soft alluvial with extremely low Vs (< 0.5 km s(-1)) and high Vp/Vs (similar to 2.5-3.0) at the top similar to 400-700 m of the surface at most of the stations. A comparatively higher velocity of surface sediments observed at northern stations suggests the presence of compact sediments at the surface. The layered sedimentary structure revealed by the S-wave velocity models supports the previous geophysical investigations using borehole data. The velocity-depth structure obtained in this study is important for evaluating the seismic hazard of the densely populated urban areas spread over this region.

The noble radioactive gas radon and its isotope thoron dominate terrestrial radiation in the indoor environment. These gases eventually disintegrate generating radioactive ions that readily adhere to aerosol particles. This study was conducted in a tectonically active location with significant radon concentrations. The obtained average values of radon mass exhalation and thoron surface exhalation rate from this study are higher than the global average values of 56 mBq kg(-1) h(-1) and 1000 mBq m(-2) s(-1), respectively. As the exhalation rates are higher, naturally the average radon and thoron concentrations are also greater than the worldwide average values of 40 and 10 Bq m(-3), respectively. No significant correlation was observed between Rn-222 and Rn-220 exhalation rate and indoor Rn-222/Rn-220 concentration. The exposure dose due to Rn-222, Rn-220 and their progenies shows no significant health risk.