The northern Walker Lane refraction experiment: Pn arrivals and the northern Sierra Nevada root     

John N. Louie  Weston Thelen  Shane B. Smith  James B. Scott  Matthew Clark  Satish Pullammanappallil   《Tectonophysics》2004,388(1-4):253

In May 2002, we collected a new crustal refraction profile from Battle Mountain, Nevada across western Nevada, the Reno area, Lake Tahoe, and the northern Sierra Nevada Mountains to Auburn, CA. Mine blasts and earthquakes were recorded by 199 Texan instruments extending across this more than 450-km-long transect. The use of large mine blasts and the ultra-portable Texan recorders kept the field costs of this profile to less than US$10,000. The seismic sources at the eastern end were mining blasts at Barrick's GoldStrike mine. The GoldStrike mine produced several ripple-fired blasts using 8000–44,000 kg of ANFO each, a daily occurrence. First arrivals from the larger GoldStrike blasts are obvious to distances of 300 km in the raw records. First arrivals from a quarry blast west of the survey near Watsonville, CA, located by the Northern California Seismic Network with a magnitude of 2.2, can be picked across the recording array to distances of 600 km. The Watsonville blast provides a western source, nearly reversing the GoldStrike blasts. A small earthquake near Bridgeport, CA. also produced pickable P-wave arrivals across the transect, providing fan-shot data. Arrivals from M5 events in the Mariana and Kuril Islands also appear in the records. This refraction survey observes an unexpectedly deep crustal root under the northern Sierra Nevada range, over 50 km in thickness and possibly centered west of the topographic crest. Pn delays of 4–6 s support this interpretation. At Battle Mountain, Nevada, we observe anomalously thin crust over a limited region perhaps only 150 km wide, with a Moho depth of 19–23 km. Pn crossover distances of less than 80 km support this anomaly, which is surrounded by observations of more normal, 30-km-thick crust. A 10-km-thick and high-velocity lower-crustal “pillow” is an alternative hypothesis, but unlikely due to the lack of volcanics west of Battle Mountain. Large mine and quarry blasts prove very effective crustal refraction sources when recorded with a dense receiver array, even over distances exceeding 600 km. New elastic synthetic seismogram modeling suggests that Pn can be strong as a first arrival, easing the modeling and interpretation of crustal refraction data. Fast eikonal computations of first-arrival time can match pickable Pn arrival times.  相似文献   

Semi‐active control of sliding isolated bridges using MR dampers: an experimental and numerical study     

Sanjay S. Sahasrabudhe  Satish Nagarajaiah 《地震工程与结构动力学》2005,34(8):965-983

Sliding base‐isolation systems used in bridges reduce pier drifts, but at the expense of increased bearing displacements under near‐source pulse‐type earthquakes. It is common practice to incorporate supplemental passive non‐linear dampers into the isolation system to counter increased bearing displacements. Non‐linear passive dampers can certainly reduce bearing displacements, but only with increased isolation level forces and pier drifts. The semi‐active controllable non‐linear dampers, which can vary damping in real time, can reduce bearing displacements without further increase in forces and pier drifts; and hence deserve investigation. In this study performance of such a ‘smart’ sliding isolation system, used in a 1:20 scaled bridge model, employing semi‐active controllable magneto‐rheological (MR) dampers is investigated, analytically and experimentally, under several near‐fault earthquakes. A non‐linear analytical model, which incorporates the non‐linearities of sliding bearings and the MR damper, is developed. A Lyapunov control algorithm for control of the MR damper is developed and implemented in shake table tests. Analytical and shake table test results are compared. It is shown that the smart MR damper reduces bearing displacements further than the passive low‐ and high‐damping cases, while maintaining isolation level forces less than the passive high‐damping case. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Spatio-temporal analysis of land use in urban mumbai -using multi-sensor satellite data and gis techniques     

J. Kamini  Satish C. Jayanthi  V. Raghavswamy 《Journal of the Indian Society of Remote Sensing》2006,34(4):385-396

The process of urbanization has induced rapid changes in the land use leading to many infrastructural and environmental problems, one of them being the frequent flooding during rains in major cities across the world. Present paper analyses the spatio-temporal variations in the urban land use of the Mithi river catchment in Mumbai and its effect on the river, its drainage and flooding events in catchment area, specifically in conjunction with the July 26, 2005 flood event in Mumbai City. Multi sensor satellite data and GIS techniques have been used to generate land use/land cover at three different points of time and study variations in the Mithi river course, thus correlating the land use/cover changes vis-a-vis the hydrographic and meteorologic information for the Mithi river catchment. Results point to the adverse human-induced influences on the Mithi river and its catchment. Almost 50% reduction in river width and 70% decrease in mudlfats and open spaces have been observed. There is also a clear rise in builtup from 29% to 70% between 1966 and 2005, thus increasing the impervious surface which in turn increases run-off during major rainfall, eventually flooding the city.  相似文献   

Geospatial Modelling and Mapping of Snow Avalanche Susceptibility     

Satish Kumar  Pankaj Kumar Srivastava  Snehmani 《Journal of the Indian Society of Remote Sensing》2018,46(1):109-119

The main objective of this study was to mapping the potential avalanche susceptible zones in Siachen region of the Western Indian Himalaya. A geospatial analytical hierarchy process (AHP) model based on expert judgements has been applied in this study. Five most important terrain based avalanche occurrence parameters including slope, aspect, curvature, elevation and ground cover are employed in the present model. The ASTER GDEM and Landsat 8 OLI imagery are used to generate the avalanche occurrence parameters. A pairwise comparison matrix is computed to estimate the weight values for input terrain parameters. These weight values are then assigned to each respective avalanche occurrence parameter and employed in a geospatial AHP model to generate an avalanche susceptibility map. Finally, an avalanche inventory has been utilized to validate the results. The avalanche susceptibility map has been compared with the avalanche inventory map by calculating the area under the receiver operating characteristics curve (ROC-AUC) technique.  相似文献   

Tidal Propagation in the Mandovi–Zuari Estuarine Network, West Coast of India: Impact of Freshwater Influx     

A.S. Unnikrishnan  S.R. Shetye  A.D. Gouveia 《Estuarine, Coastal and Shelf Science》1997,45(6):737-744

The Mandovi–Zuari estuarine network on the west coast of India consists of shallow strongly converging channels, that receive large seasonal influx of fresh water due to the monsoons. The main channels, the Mandovi and Zuari estuaries, connect the network to the Arabian Sea. Observations show that tidal amplitude in the channels remains unchanged over large distances (|mS40 km) from the mouths of the main channels and then decays rapidly over approximately 10 km near the head. To understand the dynamics behind this behaviour, a numerical model for tidal propagation has been used that simulates the observed tidal elevations well. Momentum balance in the model is predominantly between pressure gradient and friction. In the region of undamped propagation, the model behaviour is consistent with the theory that geometric amplification balances frictional decay leaving the tide unchanged. This balance breaks down near the upstream end, where channels are narrowest, and mean velocity associated with freshwater influx is sufficiently large to prevent upstream propagation of tide. This leads to rapid decay in tidal amplitude. The model also shows that the mean water-level rises in the upstream direction, in the region of the decay.  相似文献   

A Comparative Evaluation of the Geotechnical Index Properties of Clayey Sediments along the West Coast of India     

Thomas Mathai  M. Suresh Chandran  S. B. Nair  M. R. Asoka Kumar  Satish Kumar  P. Praveen Kumar  K. N. Rajarama  T. Stephen George 《Marine Georesources & Geotechnology》2007,25(3):151-165

Sediment core samples collected during geotechnical surveys along the West Coast of India in the near shore areas of Arabian Sea have generated data on the geotechnical index properties of clayey sediments up to nearly 5 m depth below seafloor. A comparative study of three sectors within themselves is attempted before carrying out a final evaluation between the sectors. Cohesive clayey sediments of Gujarat sector are comparable though widely variant in a few aspects; in the Maharashtra-Goa-Karnataka sector though, plasticity levels and clay type vary, and activity and consistency levels are quite similar. Though broadly comparable, the clayey sediments of Kerala-Tamilnadu sector have quite diverse characteristics that fail to conform to any particular pattern as each area has an exclusive set of geotechnical properties.  相似文献   

A block Karhunen–Loève Transform based efficient lossy compression algorithm for optical remote sensing imagery     

Satish Kumar 《国际地球制图》2017,32(10):1159-1170

In present study, a block Karhunen–Loève Transform (KLT) based efficient lossy compression algorithm for optical remote sensing imagery is proposed. A Discrete Wavelet Transform (DWT) is performed on each band of the imagery to remove the spatial correlation. Each band of the imagery is decomposed into non-overlapping blocks of similar size and the transform coefficients of each block in the wavelet domain are treated as a single object. A rate-distortion optimization is introduced to perform rate allocation of multiple bands. Each band is partitioned into code-blocks. The embedded block coding with optimized truncation algorithm is executed on the code-blocks to produce final bit-stream. The complexity of the proposed algorithm is compared with global KLT-DWT. The result reports the complexity of JPEG 2000 (Part 1) is lowest with encoding time 114 ms as compared to global KLT-DWT (N = 1024), global DWT-KLT (N = 1024), block-based DWT-KLT (N = 512), block-based DWT-KLT (N = 256), block-based DWT-KLT (N = 128), block-based DWT-KLT (N = 64) and block-based DWT-KLT (N = 32).  相似文献   

GIS-based MCDA–AHP modelling for avalanche susceptibility mapping of Nubra valley region,Indian Himalaya     

Satish Kumar  Pankaj Kumar Srivastava  Snehmani 《国际地球制图》2017,32(11):1254-1267

Avalanches are behind the majority of fatalities and heavy damage to property in snow-covered mountainous terrain like Himalaya. Recognizing avalanche susceptible areas and publication of avalanche susceptibility maps assist decision-makers and planners to execute suitable measures to reduce the avalanche risk. The present study is an attempt to prepare an avalanche susceptibility map of the Nubra valley region using multi-criteria decision analysis–analytical hierarchy process model in GIS environment. The most prominent avalanche occurrence factors used in this model are slope, aspect, curvature, elevation, terrain roughness and ground cover. ASTER GDEM V2 and Landsat 8 satellite imagery were used to generate considered factors. For validation of the results, prediction rate/accuracy is calculated using the avalanche inventory map of documented avalanche locations. To calculate the prediction accuracy, area under the ROC curve (ROC-AUC) method has been used. The prediction accuracy of the validation results using ROC-AUC shows 91%.  相似文献   

Application of ERT and GPR for demarcating the saline water intrusion in coastal aquifers of Southern India     

V. Satish Kumar  Ratnakar Dhakate  B. Amarender  S. Sankaran 《Environmental Earth Sciences》2016,75(5):393

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Joint traveltime inversion of wide-angle seismic data and a deep reflection profile from the central North Sea     

Michael McCaughey  Penny Barton  & Satish Singh 《Geophysical Journal International》2000,141(1):100-114

We report results from the Seismic Wide-Angle and Broadband Survey carried out over the Mid North Sea High. This paper focuses on integrating the information from a conventional deep multichannel reflection profile and a coincident wide-angle profile obtained by recording the same shots on a set of ocean bottom hydrophones (OBH). To achieve this integration, a new traveltime inversion scheme was developed (reported elsewhere) that was used to invert traveltime information from both the wide-angle OBH records and the reflection profile simultaneously. Results from the inversion were evaluated by producing synthetic seismograms from the final inversion model and comparing them with the observed wide-angle data, and an excellent match was obtained. It was possible to fine-tune velocities in less well-resolved parts of the model by considering the critical distance for the Moho reflection. The seismic velocity model was checked for compatibility with the gravity field, and used to migrate and depth-convert the reflection profile. The unreflective upper crust is characterized by a high velocity gradient, whilst the highly reflective lower crust is associated with a low velocity gradient. At the base of the crust there are several subhorizontal reflectors, a few kilometres apart in depth, and correlatable laterally for several tens of kilometres. These reflectors are interpreted as representing a strike section through northward-dipping reflectors at the base of the crust, identified on orthogonal profiles by Freeman et al. (1988) as being slivers of subducted and imbricated oceanic crust, relics of the mid-Palaeozoic Iapetus Ocean.  相似文献