Seismic hazards assessment of Kumaun Himalaya and adjacent region     

P. N. S. Roy  S. K. Mondal  Mallickarjun Joshi 《Natural Hazards》2012,64(1):283-297

The ongoing continent?Ccontinent collision between Indian and Eurasian plates houses a seismic gap in the geologically complex and tectonically active central Himalaya. The seismic gap is characterized by unevenly distributed seismicity. The highly complex geology with equally intricate structural elements of Himalaya offers an almost insurmountable challenge to estimating seismogenic hazard using conventional methods of Physics. Here, we apply integrated unconventional hazard mapping approach of the fractal analysis for the past earthquakes and the box counting fractal dimension of structural elements in order to understand the seismogenesis of the region properly. The study area extends from latitude 28°N?C33°N and longitude 76°E?C81°E has been divided into twenty-five blocks, and the capacity fractal dimension (D ₀) of each block has been calculated using the fractal box counting technique. The study of entire blocks reveal that four blocks are having very low value of D ₀ (0.536, 0.550, 0.619 and 0.678). Among these four blocks two are characterized by intense clustering of earthquakes indicated by low value of correlation fractal dimension (D _c ) (0.245, 0.836 and 0.946). Further, these two blocks are categorized as highly stressed zones and the remaining two are characterized by intense clustering of structural elements in the study area. Based on the above observations, integrated analysis of the D _c of earthquakes and D ₀ of structural elements has led to the identification of diagnostic seismic hazard pattern for the four blocks.  相似文献   

14th International Conference on Ground Penetrating Radar, 2012     

Parul Joshi 《Journal of the Geological Society of India》2012,80(5):741-741

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Analysis of buried pipelines subjected to reverse fault motion     

Shantanu Joshi  Amit Prashant  Arghya Deb  Sudhir K. Jain 《Soil Dynamics and Earthquake Engineering》2011

Presently available simplified analytical methods and semi-empirical methods for the analysis of buried pipelines subjected to fault motion are suitable only for the strike-slip and the normal-slip type fault motions, and cannot be used for the reverse fault crossing case. A simple finite element model, which uses beam elements for the pipeline and discrete nonlinear springs for the soil, has been proposed to analyse buried pipeline subjected to reverse fault motion. The material nonlinearities associated with pipe-material and soil, and geometric nonlinearity associated with large deformations were incorporated in the analysis. Complex reverse fault motion was simulated using suitable constraints between pipe-nodes and ground ends of the soil spring. Results of the parametric study suggest that the pipeline's capacity to accommodate reverse fault offset can be increased significantly by choosing a near-parallel orientation in plan with respect to the fault line. Further improvement in the response of the pipeline is possible by adopting loose backfill, smooth and hard surface coating, and shallow burial depth in the fault crossing region. For normal or near normal orientations, pipeline is expected to fail due to beam buckling at very small fault offsets.  相似文献   

Impact of satellite soundings on the simulation of heavy rainfall associated with tropical depressions   总被引：1，自引：1，他引：0  

V. Rakesh  R. Singh  P. K. Pal  P. C. Joshi 《Natural Hazards》2011,58(3):945-980

The present study is carried out to examine the impact of temperature and humidity profiles from moderate resolution imaging spectroradiometer (MODIS) or/and atmospheric infrared sounder (AIRS) on the numerical simulation of heavy rainfall events over the India. The Pennsylvania State University–National Centre for Atmospheric Research fifth-generation mesoscale model (MM5) and its three-dimensional variational (3D-Var) assimilation technique is used for the numerical simulations. The heavy rainfall events occurred during October 26–29, 2005, and October 27–30, 2006, were chosen for the numerical simulations. The results showed that there were large differences observed in the initial meteorological fields from control experiment (CNT; without satellite data) and assimilation experiments (MODIS (assimilating MODIS data), AIRS; (assimilating AIRS data); BOTH (assimilating MODIS and AIRS data together)). The assimilation of satellite data (MODIS, AIRS, and BOTH) improved the predicted thermal and moisture structure of the atmosphere when compared to CNT. Among the experiments, the predicted track of tropical depressions from MODIS was closer to the observed track. Assimilation of MODIS data also showed positive impact on the spatial distribution and intensity of predicted rainfall associated with the depressions. The statistical skill scores obtained for different experiments showed that assimilation of satellite data (MODIS, AIRS, and BOTH) improved the rainfall prediction skill when compared to CNT. Root mean square error in quantitative rainfall prediction is less in the experiment which assimilated MODIS data when compared to other experiments.  相似文献   

Uranium mineralisation associated with felsic volcanism at Mohar,Shivpuri district,Madhya Pradesh     

D. Bhattacharya  G. B. Joshi  Rakesh Sharma 《Journal of the Geological Society of India》2011,78(1):57-62

Several small lensoidal bodies of felsic volcanics are exposed in a curvilinear pattern within the brecciated granitoids of Bundelkhand Gneissic Complex (BGC) at Mohar. Sub-surface data reveals extensive presence of these felsic volcanics below the sediment of Vindhyan Supergroup. It occurs like a sheet with thickness varying from 12 m to 134 m. Its lateral extent has been traced upto 4.8 km. Multiple flows of felsic magma are identified based on colour, granularity, cross cutting relations and cyclic distribution of multiple vesicular bands along the entire thickness of felsic magma. The felsic rock contains upto 13.21% K₂O. Chemical composition of these felsic volcanics varies across the column. Petrographically and chemically all these felsic volcanics are identified as rhyolite or rhyolite tuff.  相似文献   

Impact of satellite observed microwave SST on the simulation of tropical cyclones     

Vishal Bongirwar  V. Rakesh  C. M. Kishtawal  P. C. Joshi 《Natural Hazards》2011,58(3):929-944

The impact of realistic representation of sea surface temperature (SST) on the numerical simulation of track and intensity of tropical cyclones formed over the north Indian Ocean is studied using the Weather Research and Forecast (WRF) model. We have selected two intense tropical cyclones formed over the Bay of Bengal for studying the SST impact. Two different sets of SSTs were used in this study: one from TRMM Microwave Imager (TMI) satellite and other is the weekly averaged Reynold’s SST analysis from National Center for Environmental Prediction (NCEP). WRF simulations were conducted using the Reynold’s and TMI SST as model boundary condition for the two cyclone cases selected. The TMI SST which has a better temporal and spatial resolution showed sharper gradient when compared to the Reynold’s SST. The use of TMI SST improved the WRF cyclone intensity prediction when compared to that using Reynold’s SST for both the cases studied. The improvements in intensity were mainly due to the improved prediction of surface latent and sensible heat fluxes. The use of TMI SST in place of Reynold’s SST improved cyclone track prediction for Orissa super cyclone but slightly degraded track prediction for cyclone Mala. The present modeling study supports the well established notion that the horizontal SST gradient is one of the major driving forces for the intensification and movement of tropical cyclones over the Indian Ocean.  相似文献   

Hybrid attenuation model for estimation of peak ground accelerations in the Kutch region, India     

A. Joshi  Ashvini Kumar  K. Mohan  B. K. Rastogi 《Natural Hazards》2013,68(2):249-269

The Kutch region of Gujarat in India is the locale of one of the most devastating earthquake of magnitude (M _w) 7.7, which occurred on January 26, 2001. Though, the region is considered as seismically active region, very few strong motion records are available in this region. First part of this paper uses available data of strong motion earthquakes recorded in this region between 2006 and 2008 years to prepare attenuation relation. The developed attenuation relation is further used to prepare synthetic strong motion records of large magnitude earthquakes using semiempirical simulation technique. Semiempirical simulation technique uses attenuation relation to simulate strong ground motion records of any target earthquake. The database of peak ground acceleration obtained from simulated records is used together with database of peak ground acceleration obtained from observed record to develop following hybrid attenuation model of wide applicability in the Kutch region: $$ \begin{aligned} \ln \left( {\text{PGA}} \right) & = - 2.56 + 1.17 \, M_{\text{w}} - \, 0.015R - 0.0001\ln \left( {E + 15} \right) \\ &\quad 3.0 \le M_{\text{w}} \le 8.2;\quad 12 \le R \le 120;\quad {\text{std}} . {\text{ dev}}.(\sigma ): \pm 0.5 \\ \end{aligned} $$ ln ( PGA ) = ? 2.56 + 1.17 M w ? 0.015 R ? 0.0001 ln ( E + 15 ) 3.0 ≤ M w ≤ 8.2 ; 12 ≤ R ≤ 120 ; std . dev . ( σ ) : ± 0.5 In the above equation, PGA is maximum horizontal ground acceleration in gal, M _w is moment magnitude of earthquake, R is hypocentral distance, and E is epicentral distance in km. The standard deviation of residual of error in this relation is 0.5. This relation is compared with other available relations in this region, and it is seen that developed relation gives minimum root mean square error in comparison with observed and calculated peak ground acceleration from same data set. The applicability of developed relation is further checked by testing it with the observed peak ground acceleration from earthquakes of magnitude (M _w), 3.6, 4.0, 4.4, and 7.7, respectively, which are not included in the database used for regression analysis. The comparison demonstrates the efficacy of developed hybrid attenuation model for calculating peak ground acceleration values in the Kutch region.  相似文献