Estimation of seismic hazard in Gujarat region, India   总被引：1，自引：1，他引：0  

Sumer Chopra  Dinesh Kumar  B. K. Rastogi  Pallabee Choudhury  R. B. S. Yadav 《Natural Hazards》2013,65(2):1157-1178

The seismic hazard in the Gujarat region has been evaluated. The scenario hazard maps showing the spatial distribution of various parameters like peak ground acceleration, characteristics site frequency and spectral acceleration for different periods have been presented. These parameters have been extracted from the simulated earthquake strong ground motions. The expected damage to buildings from future large earthquakes in Gujarat region has been estimated. It has been observed that the seismic hazard of Kachchh region is more in comparison with Saurashtra and mainland. All the cities of Kachchh can expect peak acceleration in excess of 500?cm/s² at surface in case of future large earthquakes from major faults in Kachchh region. The cities of Saurashtra can expect accelerations of less than 200?cm/s² at surface. The mainland Gujarat is having the lowest seismic hazard as compared with other two regions of Gujarat. The expected accelerations are less than 50?cm/s² at most of the places. The single- and double-story buildings in Kachchh region are at highest risk as they can expect large accelerations corresponding to natural periods of such small structures. Such structures are relatively safe in mainland region. The buildings of 3?C4 stories and tall structures that exist mostly in cities of Saurashtra and mainland can expect accelerations in excess of 100?cm/s² during a large earthquake in Kachchh region. It has been found that a total of 0.11 million buildings in Rajkot taluka of Saurashtra are vulnerable to total damage. In Kachchh region, 0.37 million buildings are vulnerable. Most vulnerable talukas are Bhuj, Anjar, Rapar, Bhachau, and Mandvi in Kachchh district and Rajkot, Junagadh, Jamnagar, Surendernagar and Porbandar in Saurashtra. In mainland region, buildings in Bharuch taluka are more vulnerable due to proximity to active Narmada-Son geo-fracture. The scenario hazard maps presented in this study for moderate as well as large earthquakes in the region may be used to augment the information available in the probabilistic seismic hazard maps of the region.  相似文献   

Estimation of site amplification functions in Gujarat region, India     

Sumer Chopra  Dinesh Kumar  B. K. Rastogi  Pallabee Choudhury  R. B. S. Yadav 《Natural Hazards》2013,65(2):1135-1155

Site response in the Gujarat region is studied using local earthquake data recorded at 32 sites spread all over Gujarat region, India. Out of these 32 sites, 15 sites are located in Kachchh region, 8 in Saurashtra and 9 in mainland Gujarat region. These sites are underlain by different types of rocks/sediments of different ages. Out of 32 stations, 7 stations are on Quaternary deposits, 6 on Tertiary, 11 on Deccan, 3 on Jurassic, 3 on Cretaceous and 2 on Proterozoic rocks. The predominant frequencies at these sites depend strongly on the local geology. The average predominant frequencies of the sites on Quaternary sediments are 2.4?Hz, 5.3?Hz on Tertiary, 7.5?Hz on Jurassic, 7.2?Hz on Deccan, 4.6?Hz on Cretaceous and 7.5?Hz on Proterozoic formations. The average site amplification values at predominant frequencies are 3.7 for the sites of Quaternary deposits, 3.3 for Tertiary, 3.3 for Cretaceous rock, 4.2 for Deccan trap, 4.1 for Jurassic sites and 4.6 for Proterozoic. The damage to the houses during 2001 Bhuj earthquake is compared with the amplification at predominant frequencies at those sites. The spatial variation of predominant frequencies and the site amplifications at different frequencies corresponding to the natural frequencies of different storey buildings are studied, which will be useful in the evaluation of seismic hazard in the region.  相似文献   

Triggered/migrated seismicity due to the 2001 M w7.7 Bhuj earthquake, Western India     

B. K. Rastogi  Sandeep Kumar Aggrawal  Nagabhushan Rao  Pallabee Choudhury 《Natural Hazards》2013,65(2):1085-1107

Paper describes triggered seismicity to 200?km distance and for a decade due to the 2001 M _w7.7 Bhuj earthquake. The Kachchh region is seismically one of the most active intraplate regions of the World due to the occurrence of two large earthquakes 1819 (M _w7.8) and 2001 (M _w7.7). Though, it has high hazard but was known to have low seismicity in view of the occurrence of fewer smaller shocks. However, the status seems to have changed after 2001. Besides the strong aftershock activity for over a decade, seismicity has spread to nearby faults in Kachchh peninsula and at several places southward for 200?km distance in Saurashtra peninsula. Beyond the rupture zone of the 2001 Bhuj earthquake, more than 40 mainshocks of M _w?~?3?C5 have occurred at 20 different locations, which is unusual. The increased seismicity is inferred to be caused by stress perturbation due to the 2001 Bhuj earthquake by viscoelastic process. In Saurashtra, over and above the viscoelastic stress increase, the transient stress increase by water table rise in monsoons seems to be affecting the timing of mainshocks and associated sequences of earthquakes.  相似文献   

Seismic hazard and site-specific ground motion for typical ports of Gujarat   总被引：3，自引：3，他引：0  

Jaykumar Shukla  Deepankar Choudhury 《Natural Hazards》2012,60(2):541-565

Economic importance of major ports is well known, and if ports are located in seismically active regions, then site-specific seismic hazard studies are essential to mitigate the seismic risk of the ports. Seismic design of port sites and related structures can be accomplished in three steps that include assessment of regional seismicity, geotechnical hazards, and soil structure interaction analysis. In the present study, site-specific probabilistic seismic hazard analysis is performed to identify the seismic hazard associated with four typical port sites of Gujarat state (bounded by 20°–25.5°N and 68°–75°E) of India viz. Kandla, Mundra, Hazira, and Dahej ports. The primary aim of the study is to develop consistent seismic ground motion for the structures within the four port sites for different three levels of ground shaking, i.e., operating level earthquake (72 years return period), contingency level earthquake (CLE) (475 year return period), and maximum considered earthquake (2,475 year return period). The geotechnical characterization for each port site is carried out using available geotechnical data. Shear wave velocities of the soil profile are estimated from SPT blow counts using various empirical formulae. Seismicity of the Gujarat region is modeled through delineating the 40 fault sources based on the seismotectonic setting. The Gujarat state is divided into three regions, i.e., Kachchh, Saurashtra, and Mainland Gujarat, and regional recurrence relations are assigned in the form of Gutenberg-Richter parameters in order to calculate seismic hazard associated with each port site. The horizontal component of ground acceleration for three levels of ground shaking is estimated by using different ground motion attenuation relations (GMAR) including one country-specific GMAR for Peninsular India. Uncertainty in seismic hazard computations is handled by using logic tree approach to develop uniform hazard spectra for 5% damping which are consistent with the specified three levels of ground shaking. Using recorded acceleration time history of Bhuj 2001 earthquake as the input time motion, synthetic time histories are generated to match the developed designed response spectra to study site-specific responses of port sites during different levels of ground shaking. It is observed that the Mundra and Kandla port sites are most vulnerable sites for seismic hazard as estimated CLE ground motion is in order of 0.79 and 0.48 g for Mundra and Kandla port sites, respectively. Hazira and Dahej port sites have comparatively less hazard with estimated CLE ground motion of 0.17 and 0.11 g, respectively. The ground amplification factor is observed at all sites which ranges from 1.3 to 2.0 for the frequency range of 1.0–2.7 Hz. The obtained spectral accelerations for the three levels of ground motions and obtained transfer functions for each port sites are compared with provisions made in Indian seismic code IS:1893-Part 1 (2002). The outcome of present study is recommended for further performance-based design to evaluate the seismic response of the port structures with respect to various performance levels.  相似文献   

Agricultural Area Diversification and Crop Water Demand Analysis: A Remote Sensing and GIS Approach     

B. U. Choudhury  Anil Sood  S. S. Ray  P. K. Sharma  S. Panigrahy 《Journal of the Indian Society of Remote Sensing》2013,41(1):71-82

Large scale adoption of input intensive rice–wheat cropping system in the centrally located Jalandhar district of Indian Punjab has led to over-exploitation of ground water resources, intensive use of chemical fertilizers and deterioration of soil health. To overcome these shortfalls, in the present study, agricultural area diversification plan has been generated from agricultural area and crop rotation maps derived from remote sensing data (IRS P6-AWiFS and RADARSAT ScanSAR) along with few agro-physical parameters in GIS environment. Cropping system indices (area diversity, multiple cropping and cultivated land utilization) were also worked out from remote sensing data .Analysis of remote sensing data (2004–05) revealed that rice and wheat individually remained the dominant crops, occupy 57.8% and 64.9% of total agricultural area (TAA), respectively. Therefore, in the diversified plan, it is suggested that at least 39% of the current 40% TAA under rice–wheat rotation should be replaced by other low water requiring, high value and soil enriching crops, particularly in coarse textured alluvial plain having good quality ground water zones with low annual rainfall(<700 mm). This will reduce water requirement to the tune of 15,660 cm depth while stabilizing the production and profitability by crop area diversification without further degradation of natural resources.  相似文献   

Geochemistry and petrogenesis of anorogenic(?) granitoids of west Garo Hills,Meghalaya     

D. K. Choudhury  A. K. Pradhan  S. Zakaulla  K. Umamaheswar 《Journal of the Geological Society of India》2012,80(2):276-286

The granite in Samingiri — Dilsekgiri area occurs as discordant, isolated pluton within the migmatitic terrain of West Garo Hills district, Meghalaya. The pluton is exposed over 140 sq km (18 km × 8 km). It exhibits structures of solid state and piecemeal stoping effect proximal to the contact and enveloped by a contact metamorphic aureole of albite-epidote-hornfels facies. Modally, it is biotite-monzogranite and biotite-syenogranite with minor biotite, chlorite, epidote and sericite and accessories like zircon, apatite, allanite, pyrite, magnetite and sphene. Geochemically, it is marked by restricted composition (69–76 wt% SiO₂), high alkalies, low Ca, metaluminous to strongly peraluminous (Molar Al₂O₃/CaO+Na₂O+K₂O = 0.95 ? 1.54), high FeO/MgO, high Ga/Al, high contents of Rb, Sr, Ba, Y, Zr and Ce and depleted in Ti and P. The field observation, mineralogical and geochemical aspects indicate the post-tectonic nature of West Garo pluton more like as A-type granite formed by partial melting of lower crustal blocks followed by low to moderate degree of fractional differentiation. Low Ca, alkaline nature and peraluminous character point to A-type nature of West Garo granite significantly different from other granites of Meghalaya Plateau. Rb-Sr age (616±86 Ma) of granite, however, corresponds to widespread Middle to Upper Pan African activity, a thermal event prevailed during Late Proterozoic — Early Palaeozoic (500–800 Ma) period, manifested in the form of several granitic intrusions in the basement gneissic complex and the overlying Proterozoic metasediments of the Shillong Group in Meghalaya Plateau.  相似文献   

Numerical investigation of the stability of landslide-affected slopes in Kerala,India, under extreme rainfall event     

Das  Tanmoy  Rao  Vansittee Dilli  Choudhury  Deepankar 《Natural Hazards》2022,114(1):751-785

Natural Hazards - This study examines the stability and failure mechanisms of two landslide-affected slopes in Kerala, India, after an extreme rainfall event. The landslide was triggered by an...  相似文献   

Implications for planning of hydroelectric projects in Northeast India: an analysis of the impacts of the Tipaimukh project     

Choudhury  Nazrana Begam  Dey Choudhury  Soma Roy 《GeoJournal》2021,86(4):1999-2019

In recent years, while developed countries are decommissioning hydroelectric projects (HEPs)/dams at a higher rate than constructing new ones, developing economies are doing the opposite. Although HEPs are regarded green, renewable and cheap, recent studies reveal that they do more harm than good. The impacts of HEPs are multiple, including socio-economic, environmental and geopolitical. India’s Northeastern (NE) region is a part of the Ganges–Brahmaputra–Meghna river basin, and has immense hydropower potential. A large number of HEPs are planned or under construction in the region, mainly in the hilly states of Arunachal Pradesh, Manipur, Meghalaya, Sikkim and Mizoram. One such mega project is the Tipaimukh multipurpose HEP, to be constructed on the Barak river in the state of Manipur. The project is highly controversial, and is being protested against by the locals, academicians, researchers, social activists, NGOs, as well as Bangladesh. Further, a serious cost–benefit analysis, judicious environmental impact assessment and democratic public hearings have been questioned. The area submergence of the project is disproportionately high compared to other such projects of NE India, and the project site and the adjoining areas form a part of Indo-Burma global biodiversity hotspot. The present study details the impacts of the project from multidisciplinary perspectives, categorized into bio-physical, socio-economic and geopolitical impacts, including impacts on the downstream riparian nation—Bangladesh. Based on the study, we have provided recommendations, if ever the construction of project is actualized. Since there is lack of any such analysis, the present study is of immense significance on the decision making of the project, and paves a guideline for impact analysis of the upcoming large number of projects of the region.

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X-ray spectroscopy of Cygnus X-3     

M. Choudhury  A. R. Rao 《Journal of Astrophysics and Astronomy》2002,23(1-2):39-43

We have analysed the X-ray spectra of the highly variable X-ray source Cygnus X-3 over a wide energy range from 5 keV to 150 keV using data selected from the RXTE archives. Separate analysis of the low and hard states show the presence of a hard powerlaw tail in both the states. Here we present the result of the wide band spectral study of the source.  相似文献   

The multifrequency angular power spectrum of the epoch of reionization 21-cm signal     

Kanan K. Datta  T. Roy Choudhury  Somnath Bharadwaj 《Monthly notices of the Royal Astronomical Society》2007,378(1):119-128

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