Browsing by Author "Sandeep"

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3D attenuation tomography of the Uttarakhand, NW Himalaya: Linkage to fluid or partial melt zones - Seismic hazard
(Elsevier Ltd, 2024) Monika; Parveen Kumar; Sandeep; A. Joshi; S.K. Pal
This work proposes the shear-wave attenuation tomography of the Garhwal and Kumaun regions, Uttarakhand Himalaya, to investigate the crustal state. Based on attenuation characteristics, the high attenuated layer identified starts at ∼10 km in the Garhwal region and ∼5 km in the Kumaun region. The obtained model revealed that quality factor (Q) values vary from 16 to 664 and 49 to 866 at 1 Hz frequency for the Kumaun and Garhwal regions, respectively. The high attenuation rate (1/Q) in the Kumaun region compared to the Garhwal region may be due to the high attenuated layer at a shallower depth in the Kumaun region. The comparatively low attenuation rate of the Garhwal characterizes it as a region with high seismic hazard potential. Pioneeringly, layered frequency-dependent attenuation models are proposed up to a depth of 30 km for six different layers with 5 km thickness each, which will provide new insight into seismic hazard evaluation. © 2024 Elsevier Ltd
A review on geophysical parameters comparison in Garhwal and Kumaun Himalaya region, India
(Elsevier, 2020) Parveen Kumar; Sandeep
The present review is an effort to compare various geophysical parameters in the Garhwal and Kumaun region of North-West Himalaya. This exercise provide empirical evidence of distinct nature of these two regions. Three different parameters viz. the seismicity, plate velocity, and attenuation are compared in these two regions. For this purpose, compilation of the earthquake data, Global Positioning System (GPS) data and Quality factor data is made for Garhwal and Kumaun regions. The spatial distribution of 772 earthquake in these regions indicates that Kumaun region is seismically more active than Garhwal region specifically from Main Central Thrust (MCT) to South Tibetan Detachment System (STDS). The variation in velocity field as indicated by the GPS data also suggests the higher convergence rate for Kumaun region than Garhwal. Moreover, the attenuation studies by various researchers in these regions support the higher heterogeneous and tectonically active nature of Kumaun than Garhwal region. The possible reason for the variation of these parameters may be due to the presence of structural discontinuity on the fault between the Kumaun and Garhwal regions along the Pindar River i.e. Northward extension of Muradabad fault. © 2021 Elsevier Inc. All rights reserved.
Assessment of Site Amplification Using Borehole and Surface Data: Variability of Site Effect Estimation from Different Phases of the Accelerogram
(Springer Science and Business Media Deutschland GmbH, 2022) Parveen Kumar; Sandeep; Monika
Site amplification is evaluated using the borehole and surface data for the central Honshu region, Japan. This study investigates the role of different phases of the records towards the site amplification. In present work, different phases of the earthquake record, i.e. P-phase, S-phase and full waveform are analysed to check the variation of site effect obtained using these phases. Site amplification is estimated by using the horizontal to vertical spectral ratio (H/V) method proposed by (Lermo and Chavez-Garcia in Bull. seism. Soc. Am. 83:1574–1594, 1993). A total of 174 surface and borehole acceleration records of 26 local earthquakes occurred in Central Honshu region during the years 2008 to 2017 is utilized in this work. The large amplitudes of H/V curves observed at the surface as compare to borehole, indicates the presence of site amplification at surface in contrast of borehole. It also reflects the existence of soft and unconsolidated deposits at the surface as compare to borehole. The comparison of site amplification obtained using P-phase, S-phase and full waveform of acceleration record revealed that amplitude of H/V curve obtained using S-phase and full waveform is almost similar, whereas h/v curve of P-phase has low amplitude than h/v curve of S-phase and full waveform. This comparison is made separately for both surface as well as borehole data, and the same observation is observed in both cases. Hence, it is concluded that S-phase has major contribution towards the site amplification of acceleration record as compare to P-phase. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Characteristics of earthquake ground motions governing the damage potential for Delhi and the surrounding region of India
(Elsevier Ltd, 2023) Himanshu Mittal; Babita Sharma; Sandeep; Ambikapathy Ammani
The proximity of Delhi and the surrounding region to the active faults along with its geographical settings is a subject of discussion to comprehend the seismic resilience of the capital region of India. The region may be affected by the far-field earthquakes from the Himalayas as well as the near-field earthquakes associated with the local seismic activity. Considering the ordinary settings of this region, the present study is an insight to differentiate the damage potential of ground motion associated with near and far-field conditions to further see their consequences to understand the comprehensive seismic hazard of the region. The acceleration and velocity response analysis of recorded strong ground motions from far-field and near-field earthquakes exhibit a clear distinct behavior in the form of amplification and corresponding predominant period. The comparison of estimated normalized spectral accelerations with that of the seismic design code of the Bureau of Indian Standards (BIS), shows that the current Indian building design code is within the structural limits proposed for the seismic forces of long periods, however, exceeded amplitude of the normalized Spectral Acceleration for far-field earthquakes may be attributed towards the damage potential for the high rise buildings in the capital region of India. On the other hand, near-field earthquakes do not meet the criteria with the design code of BIS at lower periods from 0.02s to 0.09s along with the amplified Spectral acceleration. It also suggests that the structural heterogeneities within the subsurface of Delhi and the surrounding region have a strong bearing in contributing to the impact of seismic waves from near-field earthquakes producing short-period waves that may be disastrous for low-rise buildings. Based on the results, the study region affected by the distinct seismicity patterns is important to understand the shaking behavior of the different kinds of infrastructures/buildings in case of near-field and far-field earthquakes to appropriately utilize the information for constructing new buildings and strengthening the existing infrastructures in Delhi and the surrounding region of India. © 2023 The Authors
Characterization of shear wave attenuation and site effects in the Garhwal Himalaya, India from inversion of strong motion records
(Springer, 2021) Parveen Kumar; Monika; Sandeep; Sushil Kumar; Richa Kumari; Dinesh Kumar; Narendra Kumar
Research highlights: The frequency-dependent shear-wave quality factor and site amplification are computed simultaneously for the Garhwal region, NW Himalaya.A regional quality factor relationship of form, Qβ(f) = (102 ± 3.9)f(1.0±0.1) is established for the Garhwal Himalaya.The acceleration records corrected from the obtained site effect are used to develop attenuation relations at each recording station.The close resemblance of obtained Qβ(f) relations and the geology has been observed for the study region. Abstract: The frequency-dependent shear-wave quality factor (Qβ(f)) and site amplification are computed for the seismically and tectonically active Garhwal Himalaya. The inversion technique of strong motion data is applied to obtain Qβ(f) and site effect at each recording station. The strong motion data of 82 earthquakes recorded in the Garhwal region is used for the present inversion algorithm. The comparison of site effects obtained by the present inversion scheme and well developed H/V technique (H/V is the ratio of Fourier spectra horizontal to vertical components) shows that site effects computed through the inversion technique have close resemblance with these estimates from the H/V technique. Both horizontal components are used to establish the frequency-dependent Qβ(f) relations at each station. The values of ‘Qo’ and ‘n’ at different stations vary from 92 to 112 and 0.9 to 1.1, respectively. The close resemblance of obtained Qβ(f) relations at different stations suggest, the presence of almost similar type of lithology, i.e., hard rock at these stations. A regional quality factor relationship of form, Qβ(f) = (102 ± 3.9)f(1.0±0.1) is established for the Garhwal Himalaya based on modelled Qβ values of each station. This relationship reveals low Qo value (<200) and high n value (>0.8) for the Garhwal Himalaya, which correspond to tectonically and seismically active region. © 2021, Indian Academy of Sciences.
Determination of Arias intensity and modified Mercalli intensity scale for future scenario earthquake in the Uttarakhand Himalaya, India
(Springer, 2025) Parveen Kumar; Sandeep; Sandeep Kumar; Monika; Narendra Thrideep Kumar
The present work proposes the assessment of seismic hazards in the Uttarakhand Himalaya using Arias intensity (Ia) and modified Mercalli intensity (MMI). The Ia is computed using acceleration waveform data and the available empirical relation. A close similarity of Ia values computed from waveform data and empirical relation validates the applicability of this relation for the Uttarakhand Himalaya. After validation, the empirical relation is applied to generate the Arias intensity map for earthquakes of magnitude ≥ 4.5, and it is correlated with the available MMI scale. Subsequently, an empirical relationship is established between the obtained Ia values and the MMI scale. This relation is further utilized to prepare the Ia and isoseismal map in terms of the MMI scale for future potential earthquakes of magnitude 7.5 and 8.5 (Mw). The proposed isoseismal map for future anticipated earthquakes (M 8.5) reveals that a large population along with famous sanctuaries like Badrinath, Kedarnath, and Haimkunth Sahib falls within MMI scale ≥ IX, which causes considerable damage. The simulated results provide maximum peak ground acceleration (PGA) values of 840 gals and 513 gals for the 8.5 and 7.5 magnitude scenario earthquake at the Uttarkashi station. The present study identifies the vulnerable zone for seismic hazards, which provides insight into assessing and mitigating the risks associated with the study region. © Indian Academy of Sciences 2025.
Determination of site effect and anelastic attenuation at Kathmandu, Nepal Himalaya region and its use in estimation of source parameters of 25 April 2015 Nepal earthquake M w = 7.8 and its aftershocks including the 12 May 2015 M w = 7.3 event
(Springer Netherlands, 2018) Parveen Kumar; A. Joshi; Sushil Kumar; Sandeep; Sohan Lal
The destructive Mw = 7.8 Nepal earthquake happened in Nepal Himalaya, 80 km NW of Kathmandu city on 25 April 2015. A number of aftershocks in which one of them is Mw = 7.3 which occurred on 12 May 2015 are observed around the Kathmandu city of Nepal. In this paper, strong motion data of Nepal earthquake and its eight aftershocks having magnitude range 5.3–7.3, recorded at Kathmandu station is used to determine site effects and attenuation factor. Kathmandu city, capital of Nepal, is situated in a valley which consists of sediments of more than 300 m depth. Hence strong motion data recorded at Kathmandu station is strongly affected by site effect and anelastic attenuation. In this work, S-phase spectra recorded at Kathmandu station are corrected for site effect and anelastic attenuation to compute the source parameters of the events. The site effects and anelastic attenuation are estimated from inversion of strong motion data by using the inversion technique suggested by Joshi (Bull Seismol Soc Am 96:2165–2180, 2006a). The shear wave quality factor (Qβ(f)) is computed at Kathmandu station by using the inversion scheme as Qβ(f) = 68f0.58. The site effects and attenuation factor obtained by inversion technique are used to correct the spectrum for site effect and anelastic attenuation. The corrected source spectrum is compared with theoretical (Brune in J Geophys Res 78:4997–5009, 1970) spectrum to estimate various source parameters. Both horizontal component (North–South and East–West) are utilized to estimate the source parameters of 25 April 2015 Mw = 7.8 Nepal earthquake and its aftershocks. The best-fit theoretical spectrum provides final values of source parameters, i.e., stress drop, seismic moment, and source radius as 48.7 bars, 5.96 × 1027 dyne cm and 37.75 km, respectively, for the 25 April 2015 Mw = 7.8 earthquake and 1.40 × 1027 dyne cm, 44.7 bars, and 23.90 km, respectively, for the 12 May 2015 Mw = 7.3 earthquake. © 2018, Springer Science+Business Media B.V., part of Springer Nature.
Development of region specific earthquake early warning scaling relations for the Garhwal region using observed and simulated datasets: a step forward to disaster mitigation
(Springer Science and Business Media B.V., 2024) Suraj Kumar Pal; Sandeep; Shubham Gangajali; Parveen Kumar; Himanshu Mittal
The Garhwal region, situated in the central segment of the Himalayas, stands as one of the most seismically active areas in the Uttarakhand Himalaya. The newly established earthquake early warning (EEW) system in the Garhwal region emphasizes the critical need for magnitude scaling relations to enable real-time estimation of earthquake size. This study employs P-wave onset data from both observed and simulated records to develop magnitude scaling relations specific to the Garhwal region. Initially, we modified the semi-empirical technique (SET) for P-wave simulation and validated this modification using the 1991 Uttarkashi (Mw6.8) and 1999 Chamoli (Mw6.4) earthquakes in the Garhwal region. The modified semi-empirical technique (MSET) demonstrates its reliability, as evidenced by the comparatively low root mean square error (RMSE) between observed and simulated records for both earthquakes. Subsequently, we apply MSET to simulate seven additional future earthquakes (Mw7.0–8.5) at the hypocentral locations of the 1991 Uttarkashi and 1999 Chamoli earthquakes. Moreover, conventional EEW parameters, such as average period (τc) and peak amplitude displacement (Pd), are extracted from 107 observed and 63 simulated P-wave onsets, utilizing a 3 s time window. Using this combined dataset of observed and simulated data, we introduce magnitude scaling relations based on the τc and Pd parameters. Subsequently, the developed scaling relations are tested to predict earthquake magnitude using the average values of estimated EEW parameters. The relatively small errors, measuring at 4.47–0.75%, and 2.45–0.60% for τc–Mw and 5.71–1.60% and 4.90–1.57% for Pd–Mw scaling relations, respectively for the Uttarkashi and Chamoli earthquakes suggest the applicability of these proposed relations. However, the scaling relations developed tend to underestimate the magnitude of earthquakes larger than 7.5, potentially attributed to the saturation observed in these relations for big earthquakes. Additionally, the calculated lead time for future earthquakes will range from 4 to 60 s for the sites situated within epicentral distances of 56–200 km. This lead time has the potential to play a substantial role in disaster mitigation in the Garhwal region, especially in the Indo-Gangetic plains and Himalayan foothills. Hence, the development of scaling relations specific to the region is imperative for effective disaster mitigation and risk reduction in the Garhwal region. © The Author(s), under exclusive licence to Springer Nature B.V. 2024.
Earthquake Genesis and Earthquake Early Warning Systems: Challenges and a Way Forward
(Springer Science and Business Media B.V., 2022) Roshan Kumar; Himanshu Mittal; Sandeep; Babita Sharma
Abstract: Several natural hazards, including earthquakes, may trigger disasters and the presence of disaster drivers further lead to the massive loss of life and property, every year around the world. The earthquakes are unavoidable, as exact earthquake prediction in terms of date, and time is difficult. However, with the advancement in technology, earthquake early warning (EEW) has emerged as a life-saving guard in many earthquake-prone countries. Unlike other warning systems (where hours of warning are possible), only a few seconds of warning is possible in the EEW system, but this warning may be very helpful in saving human lives by taking the proper action. The concept of EEW relies on using the initial few seconds of information from nearby instruments, performing basic calculations, and issuing the warning to the farther areas. A dense network or enough network coverage is the backbone of an EEW system. Because of insufficient station coverage, the estimated earthquake location is error-prone, which in turn may cause problems for EEW in terms of estimating strong shaking for the affected areas. Seismic instrumentation for EEW has improved significantly in the last few years considering the station coverage, data quality, and related applications. Many countries including the USA, Mexico, Japan, Taiwan, and South Korea have developed EEW systems and are issuing a warning to the public and authorities. Several other countries, namely China, Turkey, Italy, and India are in process of developing and testing the EEW system. This article discusses the challenges and future EEW systems developed around the world along with different parameters used for EEW. Article Highlights: This article aims to provide a comprehensive review related to the developmentThe explicit emphasis is on the scientific development of EEW parametersThe challenges and future scopes for the effective implementation of EEWS are discussed in terms of the correct location, the magnitude estimation, the region-specific use of ground motion prediction equations, communication technologies, and general public awareness © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
Emergence of the semi-empirical technique of strong ground motion simulation: A review
(Geological Society of India, 2017) Sandeep; A. Joshi; P. Kumari; S. Lal; Vandana; Parveen Kumar; Kamal
High frequency ground motion simulation techniques are powerful tools for designing earthquake resistant structures in seismically active regimes. Simulation techniques also provide the synthetic strong ground motion in the regions where actual records are not available (Kumar et al. 2015).These techniques require several parameters of earthquake and other seismic information proceeding to the simulation. Practically estimation of parameters is a tough task, particularly in a region with limited information. This demands a simulation technique based on the easily estimated parameters for a new site. The purposes of this paper are to briefly review existing simulation techniques and to discuss in detail the new, simple and effective semi-empirical technique (Midorikawa 1993) of strong motion simulation. © 2017, Geological Society of India.
Emerging techniques to simulate strong ground motion
(Elsevier, 2020) Sandeep; Parveen Kumar; A. Joshi
Earthquakes are one of the most destructive natural events worldwide. It represents a globally societal challenge necessitating practical and operational solution for reducing loss and mitigating risk. This can be realized through earthquake hazard and risk assessment. In this context, simulation of strong ground motion emerged as one of the indispensable prerequisites for earthquake resistant structure design. Hence, this chapter describes the recent progress and also pioneering efforts for the most prevalent simulation techniques including Stochastic simulation technique (SST), Empirical Green’s function technique (EGFT), Composite source modeling technique (CSMT) and Semi empirical technique (SET). Moreover, the detail analysis of each and every technique in terms of input parameters, output, advantages and limitations has been illustrated. To this end, we hope that this overview would help the seismologists and earthquake engineers to look at this area of study from different angles to reveal some hidden opportunities. © 2021 Elsevier Inc. All rights reserved.
Estimation and Validation of Arias Intensity Relation Using the 1991 Uttarkashi and 1999 Chamoli Earthquakes Data
(Springer International Publishing, 2024) Parveen Kumar; Sandeep; Monika
Arias intensity is one of the most crucial ground motion parameters to estimate the amplitude, frequency and ground shaking duration content. In the present work, we have estimated Arias intensity for the Garhwal Himalaya, India using: (1) strong motion data of the 1991 Uttarkashi earthquake and the 1999 Chamoli earthquake and (2) available empirical relations. Further, these results are compared at several stations, and a close resemblance of estimated Arias intensity from the recorded data and empirical relations is observed, which validates the empirical relation for the present study region. Furthermore, the study region (30.0°N – 31.0°N; 78.6°E – 79.6°E) is divided into 100 small grids, and the Arias intensity values are computed at each grid. These values calculated at each corner of the grid are further utilized to prepare the contour maps of Arias intensity for the Garhwal Himalaya, India for the 1991 Uttarkashi (Mw 6.8) and the 1999 Chamoli (Mw 6.6) earthquakes. The Arias intensity maps are also prepared for the future scenario of earthquakes of magnitude Mw 8.5, keeping the rupture location at the epicentre of the Uttarkashi and Chamoli earthquakes. The Arias intensity maps reveal that 51% and 45% of the area consist of ˃ 0.11 m/s Arias intensity susceptible to landslide corresponding to the Uttarkashi and Chamoli earthquakes, respectively. Hence, the obtained Arias intensity is revealed to be a trustworthy parameter to define earthquake shaking essential to generate landslides. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
Estimation of the source parameters of the Nepal earthquake from strong motion data
(Springer Netherlands, 2016) A. Joshi; Monu Tomer; Sohan Lal; Sumer Chopra; Sandeep Singh; Sanjay Prajapati; M.L. Sharma; Sandeep
Kathmandu and its surrounding region were rocked recently by a devastating earthquake on April 25, 2015. This is the largest earthquake that has occurred in this region since the past eight decades. This earthquake was recorded on strong motion stations located about 470–522 km away from its epicenter. Records of accelerographs from these stations have been used to determine the location of this earthquake using hypo71 algorithm given by Lee and Lehr (HYPO71, a computer program for determining hypocenter, magnitude and first motion pattern of local earthquakes. US Geological Survey Open file report, 100, 1975). The recorded accelerograms have been corrected for site effects using site amplification curve obtained from ambient seismic noise recorded at each station. Site effect has been computed using H/V ratio method given by Nakamura (Q Rep RTRI 30(1):25–33, 1989) using ambient noise data. The corrected record is further used to obtain source displacement spectra. The source spectrum obtained from strong motion data is compared with theoretical source spectrum obtained from Brune’s (J Geophys Res 75:4997–5009, 1970) model for the horizontal components. The long-term flat level and corner frequency from source displacement spectra are used to calculate stress drop, source radius and seismic moment of this earthquake. The present study indicates that the Nepal earthquake originated 12.0 km below the epicenter located at 27.93°N, 84.70°E. The source radius, stress drop and seismic moment of this earthquake estimated from source displacement spectra are 44.13 ± 3.85 km, 18.68 ± 5.93 bars and 3.53 ± 0.28 × 1027 dyne cm, respectively. © 2016, Springer Science+Business Media Dordrecht.
Exploring the Concept of Self-Similarity and High-Frequency Decay Kappa-Model and fmax-Model Using Strong-Motion Surface and Borehole Data of Japan: A Statistical Approach
(Springer International Publishing, 2024) Rohtash Kumar; Raghav Singh; Amritansh Rai; Sandeep; S.P. Singh; S.P. Maurya; Prashant Kumar Singh
We statistically analyzed the fmax-model, κ-model and stress drop (Δσ) using surface and borehole data of the KIK-NET Japan seismological network. The statistical tests show no contribution of source in the fmax-model and κ-model. The ‘fmax’ values obtained in the present study are 4.2–11.0 Hz and 5–11.0 Hz for surface and borehole data, respectively. The impact of local heterogeneities and wave propagation path is clearly visible on both surface and borehole fmax-models. The same is confirmed by the p-value ‘t-test’. The multivariate linear regression (MVLR) has been applied for the analysis of dependent variables ‘κ(s)’ and ‘κ(w)’ w.r.t. independent variables epicentral distance and magnitude. The p-value calculated by t-test indicates the strong dependence of κ(s) and κ(w) on near-surface geology and the physical state of the wave travelling media but almost no contribution of magnitude. The contribution of near-surface geology in kappa values is also confirmed by the ‘κ0’ (kappa at epicentral distance = 0). The relationships between the fmax-model and the κ-model have been developed for the study region. The stress drop (Δσ(s)) assessed from surface data is 44.16-65.86 bars with an average value of 53.19 bars and borehole derived stress drop (Δσ(w)) is 46.38-68.13 bars with an average value of 54.16 bars. This study discards the effect of depth; type of earthquake, i.e. normal, reverse and strike-slip; and signal to noise ratio (SNR) on stress drop as there is no huge variation in both Δσ(s) and Δσ(w) with the seismic moment and source radius. Therefore, the study supports the concept of self-similarity. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.
Frequency-dependent Layered Q Model and Attenuation Tomography of the Himachal North-West Himalaya, India: Insight to Explore Crustal Variation
(Birkhauser, 2024) Parveen Kumar; V.J. Sahakian; Monika; Sandeep
The three-dimensional attenuation structure and frequency-dependent attenuation layered model are proposed for constraining seismic hazards and exploring the presence of an intra-crustal high conductive (ICHC) layer in the Himachal Himalaya, India. Using acceleration data recorded in the Himachal Himalaya, this work quantifies the attenuation characteristics in the form of shear-wave quality factor (Qβ). The low Qβ values (ranging 10–60) depict an aqueous fluid zone starting from a depth of ~ 11 km. This aqueous fluid identified in the study region closely resembles the ICHC layer identified by other researchers in its adjacent area. The geometry of the Main Himalayan Thrust (MHT) is explored in terms of the obtained attenuation model, which suggests the absence of a ramp structure of MHT below the Main Central Thrust (MCT) in the study region. The presence of an aqueous fluid zone identified at 11–20 km depth may be one of the possible reasons for high seismicity in the Himalayan seismic belt. This work also suggests a frequency-dependent shear wave attenuation (Qβ(f)) model of the form Qof n for six different layers of 5 km thickness each. The obtained layered model suggests low Q values, i.e., (49 ± 16) f (0.60±0.12) for layer 3 (10–15 km) and (27 ± 11) f (0.99±0.18) for layer 4 (15–20 km), corresponding to the aqueous fluid in the study region. The obtained Qβ(f) model appraises the region’s seismic hazard by describing the heterogeneity and tectonic activity level in the present study region. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.
Implications of Site Effects and Attenuation Properties for Estimation of Earthquake Source Characteristics in Kinnaur Himalaya, India
(Birkhauser, 2021) Richa Kumari; Parveen Kumar; Naresh Kumar; Sandeep
Site and path effects are always required to isolate the source term from a recorded seismograph for the estimation of source characteristics. In this paper, the site and path effects are assessed in terms of site amplification and anelastic attenuation (quality factor), respectively, to obtain an isolated source term for the estimation of earthquake source parameters in the Kinnaur Himalaya. These terms are then applied to calculate the source parameters of 75 local earthquakes in the range 1.5 ≤ moment magnitude (Mw) ≤ 3.6 recorded in the Kinnaur region. The scaling relations of earthquake source parameters are also established for this region. The site amplification curves and S-wave quality factor Qs(f) are determined and further utilized to correct the Fourier spectrum of earthquake records. The obtained source spectrum corrected for these two terms is compared with the theoretical source spectrum based on the Brune (J Geophys Res 75:4997–5009, 1970) source model. The root-mean-square error (RMSE) between the observed and theoretical spectrum is formulated by implementing iterative forward modeling. The obtained range of source parameters of 75 events reveals ranges of 2.73 × 1011–3.44 × 1014 N-m for seismic moment, 0.03–13 bar for stress drop, 0.3–0.9 km for source radius, and 5.64 × 1002–1.19 × 1008 J for radiated energy. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.
Investigation of the high frequency attenuation parameter kappa (κ) beneath the volcanic region of Kyushu using surface and borehole dataset
(Elsevier Ltd, 2025) Sandeep; Sonia Devi; Pragya Singh; Udai Pratap Singh; Shiv Kumar Pal; Parveen Kumar; Monika; Ashok M.Praveen Kumar; Himanshu Mittal
This study focuses on a detailed analysis of the high-frequency attenuation parameter, kappa (κ), to better understand seismic wave propagation in the volcanic region of Kyushu. In this analysis, κ values are examined beneath the volcanic area of the Kyushu region using strong motion data from the 2016 Kumamoto earthquake. The Surface and borehole data are utilized to evaluate the effects of site conditions and regional attenuation characteristics, respectively. The site attenuation parameter (κ0) ranges from 0.022s to 0.068s, as estimated from 21 surface stations. The κ0 values correlate with average shear-wave velocity in the top 30 m (VS30), showing a decrease as VS30 increases. Additionally, using borehole data, the region-specific S-wave quality factor (Qs) and κ0 are estimated in this region, resulting in values of 846 ± 75 and 0.050 ± 0.002s, respectively. The relatively lower Qs values and higher κ0 values observed in this study may be due to the extensive volcanic activities in the Kyushu region. The findings closely match previous studies, highlighting significant attenuation in the volcanic region. The average κ values for borehole data are 0.043s–0.053s for horizontal components (κH) and 0.038s–0.051s for vertical components (κv). Surface data shows κH values from 0.061s to 0.070s and κV from 0.039s to 0.046s. A relative comparison shows κH and κv are roughly equal in borehole conditions, while surface conditions reveal κH exceeds κv due to site effects on horizontal components. The estimated κ values are crucial for future site-specific seismic hazard analysis in Kyushu's volcanic regions. © 2025 Elsevier Ltd
Modeling of 2011 IndoNepal Earthquake and Scenario Earthquakes in the Kumaon Region and Comparative Attenuation Study Using PGA Distribution with the Garhwal Region
(Birkhauser Verlag AG, 2019) Sandeep; A. Joshi; S.K. Sah; Parveen Kumar; Sohan Lal; Sonia Devi; Monika
Kumaon and Garhwal regions are the chief terrains of Uttarakhand Himalaya. The present article simulates the strong ground motion of the 2011 IndoNepal earthquake in the Kumaon region using modified semi empirical technique (MSET). Acceleration records at ten stations in the near field region have been simulated which validates well with actual records and therefore confirms the reliability of MSET. In addition, MSET has been used to simulate strong motion records of future scenario earthquakes (Mw 7.0 and Mw 8.0) in Kumaon region by assuming the earthquake location same as that of 2011 IndoNepal earthquake. Isoacceleration maps are also provided, which reveals more than 400 gal value of PGA at epicentral distances less than 25 kms for an earthquake of magnitude 8.0. The comparison of isoacceleration map of future scenario earthquake (Mw 7.0) in Kumaon region has been done with isoacceleration map of 1991 Uttarkashi earthquake (Mw 6.8) in Garhwal region which suggests distinct attenuation characteristics of these two regions. © 2019, Springer Nature Switzerland AG.
Modeling of rupture using strong motion generation area: a case study of Hualien earthquake (M w 6.1) occurred on April 18, 2019
(Springer Science and Business Media Deutschland GmbH, 2023) Saurabh Sharma; Anand Joshi; Sandeep; Che-Min Lin; Chun-Hsiang Kuo; Kuo-Liang Wen; Sandeep Singh; Mukat Lal Sharma; Mohit Pandey; Jyoti Singh
The strong Hualien earthquake (Mw 6.1) occurred along the suture zone of the Eurasian Plate and the Philippine Sea Plate, which struck the Hualien city in eastern Taiwan on April 18, 2019. The focal mechanism of this earthquake shows that it is caused by a rupture within a thrust. In the present study, the rupture plane responsible for this earthquake has been modeled using the modified semi-empirical technique (MSET). The whole rupture plane is assumed to be composed of strong motion generation areas (SMGAs) along which the slip occurs with large velocities. The spatiotemporal distribution of aftershocks of this earthquake within identified rupture plane suggests that there are two SMGAs within the rupture plane. The source displacement spectra (SDS) obtained from the observed records have been used to compute the source parameters of these two SMGAs. The MSET efficiently simulates strong ground motion (SGM) at the rock site. The shallow subsurface shear wave velocity profile at various stations has been used as an input to SHAKE91 algorithm for converting records at the surface to that at the rock site. The simulated records are compared with the observed records based on root-mean-square error (RMSE) in peak ground acceleration (PGA) of horizontal components. Various parameters of the rupture plane have been selected using an iterative forward modeling scheme. The accelerograms have been simulated for all the stations that lie within an epicentral distance ranging from 5 to 100 km using the final rupture plane parameters. The comparison of observed and synthetic records validates the effectiveness of the simulation technique and suggests that the Hualien earthquake consists of two SMGAs responsible for high-frequency SGM. © 2022, The Author(s) under exclusive licence to Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences.
Modeling of the strong ground motion of 25th April 2015 Nepal earthquake using modified semi-empirical technique
(Springer International Publishing, 2018) Sohan Lal; A. Joshi; Sandeep; Monu Tomer; Parveen Kumar; Chun-Hsiang Kuo; Che-Min Lin; Kuo-Liang Wen; M.L. Sharma
On 25th April, 2015 a hazardous earthquake of moment magnitude 7.9 occurred in Nepal. Accelerographs were used to record the Nepal earthquake which is installed in the Kumaon region in the Himalayan state of Uttrakhand. The distance of the recorded stations in the Kumaon region from the epicenter of the earthquake is about 420–515 km. Modified semi-empirical technique of modeling finite faults has been used in this paper to simulate strong earthquake at these stations. Source parameters of the Nepal aftershock have been also calculated using the Brune model in the present study which are used in the modeling of the Nepal main shock. The obtained value of the seismic moment and stress drop is 8.26 × 1025 dyn cm and 10.48 bar, respectively, for the aftershock from the Brune model.The simulated earthquake time series were compared with the observed records of the earthquake. The comparison of full waveform and its response spectra has been made to finalize the rupture parameters and its location. The rupture of the earthquake was propagated in the NE–SW direction from the hypocenter with the rupture velocity 3.0 km/s from a distance of 80 km from Kathmandu in NW direction at a depth of 12 km as per compared results. © 2018, Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences.