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.

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.

Petroleum systems and hydrocarbon potential of the North-West Himalaya of India and Pakistan

2018 ◽  
Vol 187 ◽  
pp. 109-185 ◽  
Author(s):  
J. Craig ◽  
N. Hakhoo ◽  
G.M. Bhat ◽  
M. Hafiz ◽  
M.R. Khan ◽  
...  
Keyword(s):  
Hydrocarbon Potential ◽  
North West ◽  
Petroleum Systems ◽  
The North ◽  
West Himalaya

Seismotectonics of the Ionian-Akarnania Block (IAB) and Western Greece deduced from a local seismic deployment.

2020 ◽  
Author(s):  
Antoine Haddad ◽  
Athanassios Ganas ◽  
Ioannis Kassaras ◽  
Matteo Lupi
Keyword(s):  
Fault Zone ◽  
Velocity Model ◽  
Focal Mechanisms ◽  
Seismogenic Zone ◽  
The South ◽  
S Wave ◽  
North West ◽  
The North ◽  
Short Period ◽  
Western Greece

<p>From July 2016 to May 2017, we deployed a local seismic network composed of 15 short-period seismic stations to investigate the ongoing seismotectonic deformation of Western Greece with emphasis on the region between Ambrakikos Gulf (to the north) and Kyparissia (to the south). The network was deployed to investigate the behavior of key crustal blocks in western Greece, such as the Ionian-Akarnania Block (IAB).</p><p>After applying automatic P- and S- wave phase picking we located 1200 local earthquakes using HypoInverse and constrained five 1D velocity model by applying the error minimization technique. Events were relocated using HypoDD and 76  focal mechanisms were computed for events with magnitudes down to M<sub>L</sub> 2.3 using first motion polarities.</p><p>We combined the calculated focal mechanisms and the relocated seismicity to shed light on the IAB block boundaries. Three boundaries highlighted by previous studies were also evidenced :</p><p>-The north-west margin of the block, the Cephalonia Transform Fault, Europe‘s most active fault. NW-striking dextral strike-slip motion was recognized for this fault near the Gulf of Myrtos and the town of Fiskardo.</p><p>- The south-east margin is the Movri-Amaliada right-lateral Fault Zone, activated during the Movri Mt. M<sub>w</sub> 6.4 earthquake sequence.</p><p>- The Ambrakikos Gulf (a young E-W rift) and the NW-striking left-lateral Katouna-Stamna Fault zone depict the north and north-eastern margins of the IAB block.</p><p>Seismicity lineaments and focal mechanisms define theKyllini-Cephalonia left-lateral fault, which is also highlighted by bathymetry data. We interpret this fault as the south-western margin of IAB separating an aseismic area observed between Cephalonia and Akarnania from a seismogenic zone north of Zakynthos Island and bridging NW Peloponnese with Cephalonia.</p>

Intermontane-basin development in the past 4 Myr in the north-west Himalaya

Nature ◽  
1982 ◽  
Vol 298 (5873) ◽  
pp. 432-436 ◽  
Author(s):  
Douglas W. Burbank ◽  
Gary D. Johnson
Keyword(s):  
North West ◽  
Intermontane Basin ◽  
The Past ◽  
The North ◽  
Basin Development ◽  
West Himalaya

Accuracy of wavelets, seismic inversion, and thin-bed resolution

2017 ◽  
Vol 5 (4) ◽  
pp. T523-T530
Author(s):  
Ehsan Zabihi Naeini ◽  
Mark Sams
Keyword(s):  
Seismic Data ◽  
Reservoir Characterization ◽  
Low Frequency ◽  
Seismic Inversion ◽  
Inversion Method ◽  
Frequency Content ◽  
Frequency Model ◽  
North West ◽  
The North ◽  
Well Data

Broadband reprocessed seismic data from the North West Shelf of Australia were inverted using wavelets estimated with a conventional approach. The inversion method applied was a facies-based inversion, in which the low-frequency model is a product of the inversion process itself, constrained by facies-dependent input trends, the resultant facies distribution, and the match to the seismic. The results identified the presence of a gas reservoir that had recently been confirmed through drilling. The reservoir is thin, with up to 15 ms of maximum thickness. The bandwidth of the seismic data is approximately 5–70 Hz, and the well data used to extract the wavelet used in the inversion are only 400 ms long. As such, there was little control on the lowest frequencies of the wavelet. Different wavelets were subsequently estimated using a variety of new techniques that attempt to address the limitations of short well-log segments and low-frequency seismic. The revised inversion showed greater gas-sand continuity and an extension of the reservoir at one flank. Noise-free synthetic examples indicate that thin-bed delineation can depend on the accuracy of the low-frequency content of the wavelets used for inversion. Underestimation of the low-frequency contents can result in missing thin beds, whereas underestimation of high frequencies can introduce false thin beds. Therefore, it is very important to correctly capture the full frequency content of the seismic data in terms of the amplitude and phase spectra of the estimated wavelets, which subsequently leads to a more accurate thin-bed reservoir characterization through inversion.

scholarly journals Rupture process of the 2014 Orkney earthquake, South Africa

2017 ◽  
Vol 17 (4B) ◽  
pp. 75-81
Author(s):  
Okubo Makoto ◽  
Artur Cichowicz ◽  
Hiroshi Ogasawara ◽  
Osamu Murakami ◽  
Shigeki Horiuchi
Keyword(s):  
South Africa ◽  
Strong Motion ◽  
Rupture Process ◽  
Gold Mine ◽  
Distribution Analysis ◽  
S Wave ◽  
Aftershock Distribution ◽  
North West ◽  
The North ◽  
Initial Rupture

An earthquake has occurred at 10:22:33 UT on 5 August 2014 in the Klerksdorp district, the North West province of South Africa. Its hypocenter is located beneath an Orkney town, where more than 10 gold mines exist. The Council for Geoscience (CGS) in South Africa reported that the magnitude and depth was ML5.5 and 4.7 km, respectively. CGS has been operating 17 surface seismic acceleration stations with 10 km interval in average, and obtained continuous acceleration seismograms through the time of the earthquake and following aftershocks. Using these seismograms, we analyzed the mainshock rupture process of this earthquake. Analyzing these seismograms, we found the ‘initial rupture’ with a Richter scale approximately 4 has occurred 0.3 sec before mainshock. Furthermore, by applying detailed aftershock distribution analysis, we found most of aftershocks occurred surrounding upper and southern part of mainshock rupture area, including initial rupture hypocenter. In order to understand detailed rupture process of this event, we surveyed for strong motion generating area (SMGA) of mainshock by applying Isochrones backprojection method (IBM) to the mainshock S wave waveforms. SMGA distribution seems to fill the vacant space of the aftershock distribution and initial rupture’s hypocenter. And we also found that a horizontal layered seismic vacancy exists between aftershocks with gold mine blastings. This fact implies mainshock rupture did not extent up to gold mine.

Colliding Continents

2013 ◽  
Author(s):  
Mike Searle
Keyword(s):  
Indian Plate ◽  
Mountain Range ◽  
Polar Regions ◽  
Geological Evidence ◽  
North West ◽  
Ice Cap ◽  
The North ◽  
West Himalaya ◽  
Tectonically Active ◽  
The Himalaya

The Himalaya is the greatest mountain range on Earth: the highest, longest, youngest, the most tectonically active, and the most spectacular of all. Unimaginable geological forces created these spectacular peaks. Indeed, the crash of the Indian plate into Asia is the biggest known collision in geological history, giving birth to the Himalaya and Karakoram, one of the most remote and savage places on Earth. In this beautifully illustrated book, featuring spectacular color photographs throughout, one of the most experienced field geologists of our time presents a rich account of the geological forces that were involved in creating these monumental ranges. Over three decades, Mike Searle has transformed our understanding of this vast region. To gather his vital geological evidence, he has had to deploy his superb skills as a mountaineer, spending weeks at time in remote and dangerous locations. Searle weaves his own first-hand tales of discovery with an engaging explanation of the processes that formed these impressive peaks. His narrative roughly follows his career, from his early studies in the north west Himalaya of Ladakh, Zanskar and Kashmir, through several expeditions to the Karakoram ranges (including climbs on K2, Masherbrum, and the Trango Towers, and the crossing of Snow Lake, the world's largest ice cap outside polar regions), to his later explorations around Everest, Makalu, Sikkim and in Tibet and South East Asia. The book offers a fascinating first-hand account of a major geologist at work-the arduous labor, the eureka moments, and the days of sheer beauty, such as his trek to Kathmandu, over seven days through magnificent rhododendron forests ablaze in pinks, reds and white and through patches of bamboo jungle with hanging mosses. Filled with satellite images, aerial views, and the author's own photographs of expeditions, Colliding Continents offers a vivid account of the origins and present state of the greatest mountain range on Earth.

Observed spatio-temporal changes of winter snow albedo over the north-west Himalaya

2016 ◽  
Vol 37 (5) ◽  
pp. 2304-2317 ◽  
Author(s):  
H. S. Negi ◽  
P. Datt ◽  
N. K. Thakur ◽  
A. Ganju ◽  
V. K. Bhatia ◽  
...  
Keyword(s):  
Temporal Changes ◽  
Snow Albedo ◽  
North West ◽  
The North ◽  
Winter Snow ◽  
West Himalaya ◽  
Spatio Temporal
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