scholarly journals Determination of path attenuation and site characteristics of the North-west Himalayan region and adjoining regions within the Indian Territory using Generalized inversion method

2020 ◽  
Vol 63 (6) ◽  
Author(s):  
Nelliparanbil Harinarayan ◽  
Abhishek Kumar
Keyword(s):  
Seismic Hazard ◽  
Predominant Frequency ◽  
Site Class ◽  
North West ◽  
The North ◽  
Generalized Inversion ◽  
Site Characteristics ◽  
Generalized Inversion Technique ◽  
Recording Station

North-west Himalayas and its adjoining regions have been experiencing deadly earthqaukes from time to time and are home for a large portion of population of Indian subcontinent. Knowledge of regional path attenuation and site parameters are prerequisite while attempting seismic hazard studies towards minimizing damages during future earthqaukes for a region. Present work focuses on the determination of path attenuation and site characteristics of earthqaukes recording stations, located in the north-west Himalayas and its adjoining regions, within India. It is done using two- step generalized inversion technique. In the first step of inversion, non-parametric attenuation curves are developed by constraining attenuation to be a smooth decaying function with hypocentral distance. Qs = (105 ± 11)f (0.94 ± 0.08) as S wave quality factor is obtained indicating that the region is seismically active having high degree of heterogeneities in the crustal medium. In the second step of generalized inversion, site amplification curve, at each recording station, is computed as the ratio of site spectral amplitude of horizontal and vertical components. In addition, based on Horizontal to vertical spectral ratio (HVSR) method, predominant frequency of each recording station is calculated. Values of predominant frequencies based on HVSR and generalized inversion are found matching for each of the recording station. Based on obtained predominant frequency, site class of 101 recording stations, which at present are absent, are determined in this work. Determined path attenuation as well as site parameters can be collectively used for developing regional ground motion models and subsequently for seismic hazard studies for the selected region.

scholarly journals Estimation of path attenuation and site characteristics in the north-west Himalaya and its adjoining area using generalized inversion method

2018 ◽  
Author(s):  
Harinarayan Nelliparambil Hareeshkumar ◽  
Abhishek Kumar
Keyword(s):  
Site Amplification ◽  
Inversion Method ◽  
Predominant Frequency ◽  
S Wave ◽  
North West ◽  
Hypocentral Distance ◽  
The North ◽  
Generalized Inversion ◽  
Site Characteristics ◽  
West Himalaya

Abstract. Present work focuses on the determination of path attenuation as well as site characteristics of PESMOS managed recording stations, located in the north-west Himalaya and its adjoining region, using two-step generalized inversion technique. In the first step of inversion, non-parametric attenuation curves are developed. Presence of a kink is observed at around 105 km hypocentral distance while correlating the path attenuation with the hypocentral distance indicating the presence of Moho discontinuity in the region. Further, Qs = 105 f0.94 as S wave quality factor within 105 km, is obtained indicating that the region is possibly heterogeneous as well as seismically active. In the second step of inversion, site amplification curves are developed separately from the attenuation corrected data for horizontal and vertical components of the accelerogram. Further, site amplification spectra is computed as the ratio of the obtained horizontal and vertical components to determine the amplification function and predominant frequency for each of the PESMOS managed recording stations, exist within the study area. The predominant frequency based on generalized inversion method and based on horizontal to vertical spectral ratio of S wave portion of the accelerogram matches well. Maps showing spatial distribution of predominant frequencies and amplification functions across the study region are also developed based on the present work.

IX. Contributions to terrestrial magnetism.—No. IV

1843 ◽  
Vol 133 ◽  
pp. 113-143 ◽  
Keyword(s):  
Pacific Ocean ◽  
West Coast ◽  
China Seas ◽  
North West ◽  
The North ◽  
The Pacific ◽  
The Pacific Ocean ◽  
The Times ◽  
The China Seas

In the present number of these Contributions, I resume the consideration of Captain Sir Edward Belcher’s magnetic observations, of which the first portion, viz. that of the stations on the north-west coast of America and adjacent islands, was discussed in No. II. The return to England of Her Majesty’s ship Sulphur by the route of the Pacific Ocean, and her detention for some months in the China Seas, have enabled Sir Edward Belcher to add magnetic determinations at thirty-two stations to those at the twenty-nine stations previously recorded. In the notice of the earlier observations, a provisional coefficient was employed in the formula for the temperature corrections of the results with the intensity needles, as no experiments had then been made for the determination of their individual co­efficients. As soon therefore as Sir Edward Belcher had completed the observation of the times of vibration of those needles at Woolwich, as the concluding station of the series made with them, Lieut. Riddell, R. A. undertook the determination of their several coefficients, which was performed in the manner and with the results described in the subjoined memorandum.

Loran-C Chains: Determination of Extent of Cover

1988 ◽  
Vol 41 (02) ◽  
pp. 149-173 ◽  
Author(s):  
K. F. Woodman ◽  
J. Juleff ◽  
R. A. Allen
Keyword(s):  
Field Strength ◽  
North Sea ◽  
Western Europe ◽  
Accurate Determination ◽  
Propagation Path ◽  
North West ◽  
The North ◽  
The North Sea ◽  
Geometric Effects

A mainly theoretical study has been undertaken to demonstrate how the extent of cover from a hyperbolic navigation system chain can be evaluated. The impetus for the study was the need to assess how Loran-C could be extended over Western Europe, particularly in the South western Approaches, North Sea, English Channel and Bay of Biscay sea areas.The technique described in this article leads to an accurate determination of the electric field strength at a distance from each transmitting site and takes into account the complexities of the ground-wave propagation path. This field-strength contour is combined with the geometric effects of station siting (expansion factors) to yield a constant S/N contour (–10 dB) which defines the ¼n.m. error and hence the limit of cover for the hyperbolic chain under study.In order to exercise the analytical methods a hypothetical Loran-C chain was studied comprising a master station at Lessay (France), with secondary stations at Soustons (also in France), at Sylt (dual rated; off the North Sea coast of Germany, near the Danish border) and at a fourth station located in north-west Britain on the Hebridean island of Barra. The study indicated that such a hypothetical chain would significantly improve Loran-C cover over much of western Europe.

scholarly journals Considérations physiques sur le passage Nord-ouest; by the same. Communicated by the Right Hon. the Earl of Minto, G. C. B. F. R. S

1837 ◽  
Vol 3 ◽  
pp. 484-484
Keyword(s):  
Sea Water ◽  
Freezing Point ◽  
Atmospheric Temperature ◽  
North West ◽  
The North ◽  
The Mean ◽  
Coppermine River ◽  
The Right ◽  
North Latitude

The author of this memoir, considering that the practicability of a North-west Arctic passage must depend on the mean summer atmospheric temperature of the most northern point of the continent of America being above that at which the congelation of sea water takes place, applies himself to the determination of these temperatures. The results of his calculations are given in a table, exhibiting the extreme and the mean temperatures of the atmosphere for each of the summer months, from May to September, at all degrees of latitude, from 60° to 80° inclusive. According to this table, the temperature of zero, which is about the freezing point of sea water, prevails, at 60° of latitude, on the 10th of May; at 61° lat. on the 20th of May; at 63°, on the 1 st of June; at 65°, on the 10th of June; at 67°, on the 20th of June; and at 71°, during the whole of the months of July and August. The author concludes that navigators can reach, without danger of being obstructed by ice, the latitude of 71° during these latter months: and that since the American continent does not probably extend beyond 70° north latitude a passage to the North-west is then open. He recommends, however, that instead of attempting it by the dangerous navigation of the polar sea, a coasting voyage between the continent and the numerous islands which exist in that ocean should be undertaken; or, what he thinks still more promising of success, an expedition by land for exploring the country intervening between the Coppermine River and Hudson’s Bay.

A nonlinear model of flow in meandering submarine and subaerial channels

1999 ◽  
Vol 400 ◽  
pp. 295-331 ◽  
Author(s):  
JASIM IMRAN ◽  
GARY PARKER ◽  
CARLOS PIRMEZ
Keyword(s):  
Sediment Concentration ◽  
Turbidity Current ◽  
Specific Data ◽  
North West ◽  
Coriolis Effects ◽  
The North ◽  
Density Flow ◽  
Meander Bends ◽  
Water Entrainment

A generalized model of flow in meandering subaqueous and subaerial channels is developed. The conservation equations of mass and momentum are depth/layer integrated, normalized, and represented as deviations from a straight base state. This allows the determination of integrable forms which can be solved at both linear and nonlinear levels. The effects of various flow and geometric parameters on the flow dynamics are studied. Although the model is not limited to any specific planform, this study focuses on sine-generated curves. In analysing the flow patterns, the turbidity current of the subaqueous case is simplified to a conservative density flow with water entrainment from above neglected. The subaqueous model thus formally corresponds to a subcritical or only mildly supercritical mud-rich turbidity current. By extension, however the analysis can be applied to a depositional or erosional current carrying sand that is changing only slowly in the streamwise direction. By bringing the subaqueous and subaerial cases into a common form, flow behaviour in the two environments can be compared under similar geometric and boundary conditions. A major difference between the two cases is the degree of superelevation of channel flow around bends, which is modest in the subaerial case but substantial in the subaqueous case. Another difference concerns Coriolis effects: some of the largest subaqueous meandering systems are so large that Coriolis effects can become important. The model is applied to meander bends on the youngest channel in the mid-fan region of the Amazon Fan and a mildly sinuous bend of the North-West Atlantic Mid-Ocean Channel. In the absence of specific data on the turbid flows that created the channel, the model can be used to make inferences about the flow, and in particular the range of values of flow velocity and sediment concentration that would allow the growth and downfan migration of meander bends.

Determination of the Shear Strength of Unsaturated Loess Based on the Fractal Model Theory of Unsaturated Soils

2012 ◽  
Vol 170-173 ◽  
pp. 25-28
Author(s):  
Jing Yu Chen ◽  
Ying Hai
Keyword(s):  
Shear Strength ◽  
Model Theory ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Fractal Model ◽  
North West ◽  
The North ◽  
Unsaturated Loess ◽  
The Relationship

The shear strength value of unsaturated loess is required in the design in geotechnical engineering in the North and the North West of China. In 2004, a new method, that is the fractal model theory, was proposed for determining the shear strength of unsaturated soil. Based upon the fractal model theory, the surface fractal dimension DS and the air entry value of two unsaturated loess samples are obtained from their soil-water characteristic curve (SWCC), the shear strength contribution due to matric suction of the two loess samples is determined, a new approach for determination of the shear strength of unsaturated loess with its SWCC is presented. By comparing results of this paper with those of the laboratory tests, the relationship between the SWCC and the shear strength of unsaturated loess is discussed and the validity of the fractal model theory for unsaturated loess is explained.

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