Expected peak ground acceleration in Uttarakhand Himalaya,India region from a deterministic hazard model

A method of seismic zonation based on the deterministic modeling of rupture planes is presented. Finite rupture planes along identified lineaments are modeled in the Uttarakhand Himalaya based on the semi empirical technique of Midorikawa (Tectonophysics 218:287–295, 1993). The expected peak ground acceleration thus estimated from this technique is divided into different zones similar to zones proposed by the Bureau of Indian standard, BIS (Indian standards code of practice for earthquake-resistant design of structures, 2002). The proposed technique has been applied to Kumaon Himalaya area and the surrounding region for earthquakes of magnitude M > 6.0. Approximately 56000 km² study area is classified into the highest hazard zone V with peak accelerations of more than 400 cm/s². This zone V includes the cities of the Dharchula, Almora, Nainital, Haridwar, Okhimath, Uttarkashi, Pithorahargh, Lohaghat, Munsiari, Rudraprayag, and Karnprayag. The Sobla and Gopeshwar regions belong to zone IV, where peak ground accelerations of the order from 250 to 400 cm/s² can be expected. The prepared map shows that epicenters of many past earthquakes in this region lie in zone V, and hence indicating the utility of developed map in defining various seismic zones.     

The first peak ground motion attenuation relationships for North of Vietnam

The first attenuation relationships of peak ground acceleration (PGA) and peak ground velocity (PGV) for northern Vietnam are obtained in this study. Ground motion data are collected by a portable broadband seismic network in northern Vietnam as a part of cooperation between the Institute of Geophysics, Vietnamese Academy of Science and Technology, Vietnam and Institute of Earth Sciences, Academia Sinica, Taiwan. The database comprises a total of 330 amplitude records by 14 broadband stations from 53 shallow earthquakes, which were occurred in and around northern Vietnam in the period between 01/2006 and 12/2009. These earthquakes are of local magnitudes between 1.6 and 4.6, focal depths less than 30 km, and epicentral distances less than 500 km. The new attenuation relationships for PGA and PGV are:

log₁₀(PGA)=-0.987+0.7521M_L-log₁₀(R)-0.00475R,     

Robust attenuation relations for peak time-domain parameters of strong ground motions

This study presents new attenuation models for the estimation of peak ground acceleration (PGA), peak ground velocity (PGV), and peak ground displacement (PGD) using a hybrid method coupling genetic programming and simulated annealing, called GP/SA. The PGA, PGV, and PGD were formulated in terms of earthquake magnitude, earthquake source to site distance, average shear-wave velocity, and faulting mechanisms. A worldwide database of strong ground motions released by Pacific Earthquake Engineering Research Center (PEER) was employed to establish the models. A traditional genetic programming analysis was performed to benchmark the proposed models. For more validity verification, the GP/SA models were employed to predict the ground-motion parameters of the Iranian plateau earthquakes. Sensitivity and parametric analyses were carried out and discussed. The results show that the GP/SA attenuation models can offer precise and efficient solutions for the prediction of estimates of the peak time-domain characteristics of strong ground motions. The performance of the proposed models is better than or comparable with the attenuation relationships found in the literature.     

An empirical attenuation model of the peak ground acceleration (PGA) in the near field of a strong earthquake

Natural Hazards - Empirical methods are commonly employed to predict the PGA distribution of an earthquake and are widely used. However, current empirical methods assume the seismic source to be a...     

K-Ar age of Ukra glauconites from the Kutch Basin, India

The present paper reports the K-Ar ages determined on glauconitic samples collected from the Ukra Member of the Mesozoic Bhuj Formation in two different sections, one located on the Ghuneri-Ghaduli road near Katesar Mahadeo temple and the other at the base of the Ukra hill in the northwestern part of the Kutch Mainland area. Three glauconite samples viz., Ukra_KT-1, Ukra_KT-4 and Ukra_UH-3 have yielded K-Ar ages of 107.9 ± 3.4 Ma, 105.5 ± 3.3 Ma and 103.5 ± 3.4 Ma, respectively. The sample Ukra_KT-l treated with 0.5N HC1 and analysed in duplicate has yielded a mean age of 104 ± 2.3 Ma while the sample Ukra_KT-4 treated with 0.1N HCl has given an age of 106.5 ± 3.3 Ma. The ages of the treated and untreated glauconites are indistinguishable within 2σ uncertainty with a mean of 105.2 ± 1.3 Ma, which has been interpreted as the depositional age of the Ukra Member of the Mesozoic Bhuj Formation. The study has further indicated that mild acid treatment (up to 0.5N HCl) does not lead to any loss of radiogenic argon in the glauconites and can be helpful in purification of the samples.     

A reconnaissance of the Recent sediments of the Ranns of Kutch, India

The Ranns of Kutch are flat salt-covered desert areas (sabkhas) which are just above the normal tidal range and may be regarded as supratidal flats. They are flooded annually by the storm tides of the Southwest Monsoon. As the waters recede and evaporate they leave behind a crust of halite, and gypsum crystals grow within the clays and sands. The increase in salinity of the interstitial waters as they are traced inland is reflected in the higher boron content of the clays. The Mg²⁺/Ca²⁺ ratio of these waters increases from 3 on the coast, to 240 in the evaporite environment of the shoreline of Pachham Island. Much of the sediment of the Ranns was probably once derived from the Indus and Nara rivers which used to flow into the western end of the Great Rann. Clay is now probably carried in by the monsoon storm tides after being transported along shore from the Indus, and also from the rivers of Kutch and Kathiawar. Coarser siliciclastic sediment is carried into the eastern inland portion of the area by the Luni and other intermittently flowing rivers and streams. Some sand and silt is blown into the Ranns from the surrounding hilly areas. Foraminifera are found concentrated in the sandier fractions of the sediments, having been transported there primarily by tidal currents and also by the wind. One species of Ammonia is almost the only fauna found in the sediments of the very saline environment around Pachham Island.     

Geomodelling of certain bauxite profiles from Kutch, Gujarat state, India

Bauxite deposits of Kutch occur in two different environments, viz. continental and marine, and hence it is of considerable interest from the points of view of genetic aspects, exploration and exploitation. Based on detailed exploration data some new softwares are developed to synthesise the geological and geochemical data. After studying the geostatistics, trend surface analysis has been carried out. With the aid of computer analysis and graphics, a geomodelling study has been attempted for the bauxite deposits that are derived from basalt (continental environment) and another one is presented which is associated with the marine environment. The significance of geomodelling study is substantially brought out.     

Attenuation relations of peak ground acceleration and velocity in the Southern Dead Sea Transform region

Using the recorded earthquake strong ground motion, the attenuation of peak ground acceleration (PGA) and peak ground velocity (PGV) are derived in the southern Dead Sea Transform region. The expected values of strong motion parameters from future earthquakes are estimated from attenuation equations, which are determined by regression analysis on real accelerograms. In this study, the method of Joyner and Boor [Bull Seismol Soc Am 71(6):2011–2038, 1981] was selected to produce the attenuation model for the southern Dead Sea Transform region. The dataset for PGA consists of 57 recordings from 30 earthquakes and for PGV 26 recordings from 19 earthquakes. The attenuation relations developed in this study are proposed as replacement for former probabilistic relations that have been used for a variety of earthquake engineering applications. The comparison between the derived PGA relations from this study with the former relations clearly shows significant lower values than the other relations.     

Alkaline magmatism from Kutch, NW India: implications for plume–lithosphere interaction

Geochemical data are presented for primitive alkaline rocks from the Kutch region, north–northwest of Deccan Volcanic Province (DVP) of west central India, which is generally regarded as related to the Reunion Plume. The trace element systematics of these rocks are similar to those of ocean-island basalts, but there is considerable compositional variation, which is related to a strong overprint from the lithosphere on plume-derived magmas. This subcontinental lithospheric mantle (SCLM) component has geochemical characteristics that overlap those observed in spinel lherzolite xenoliths entrained in these rocks. Phlogopite and apatite in the SCLM are of metasomatic origin attributed to the infiltrating fluids and/or melts derived from rising mantle plume material. The composition of the alkaline rocks is consistent with a regional upwelling of deep mantle related to marginal rifting and with OIB-type geochemical characteristics. Thermal inhomogeneities within such plume swath resulted in small diapirs, which may have undergone melt segregation at the base of the lithosphere (100 km) and incorporated varying amounts of SCLM during ascent.     

Paleogene stratigraphy of Kutch,India: an update about progress in foraminiferal biostratigraphy

The Paleogene sections of Kutch are the reference for the regional chronostratigraphic units of India. The ages of these dominantly shallow marine carbonates are mainly based on larger benthic foraminifera (LBF). The taxonomic revisions of the LBF and the progressively refined shallow benthic zonations (SBZ) have necessitated the present study on updating the stratigraphy of the area. The sedimentation in Kutch commenced with the deposition of volcaniclastics in terrestrial environments in the Paleocene. The marine transgression in SBZ 5/6 deposited finer clastics and carbonates, designated as Naredi Formation, in early Eocene. There is no evidence of marine Paleocene in Kutch. A major hiatus spanning SBZ 12 to SBZ 16 was followed by the development of a carbonate platform and deposition of Harudi Formation – Fulra Limestone during the Bartonian, SBZ 17. The hiatus corresponds to a widespread stratigraphic break in Pakistan and India to Australia, referred as the ‘Lutetian Gap.’ The Maniyara Fort Formation is assigned to SBZ 22 B and SBZ 23, and its age is revised to Chattian. Climate played a major role in building up of the Paleogene stratigraphic succession of Kutch, the carbonates formed during the warming intervals and the stratigraphic gaps were in the intervening cooling periods.     

Groundwater-recharge estimation using a surface electrical resistivity method in the Himalayan foothill region, India

A new method for the estimation of groundwater recharge is presented using a surface resistivity method and isotope technique. A linear relationship was obtained between the resistivity of the unsaturated top layer and the recharge estimated using a tritium tagging technique for the piedmont zone in the Himalayan foothill region, India. The relation can be used for the estimation of recharge using surface electrical resistivity measurements for the same geological formation. The data used for the study are 32 vertical electrical resistivity sounding measurements at a station interval of 2 km, tritium tagging studies at six selected sites and pre- and post-monsoon water-level monitoring in the piedmont zone of the Himalayan foothill region (India). The results of this study were mapped using GIS techniques. In the study area, a well-defined empirical relationship between unsaturated zone resistivity and recharge per cent was obtained. The method suggests a new application of surface electrical resistivity data in determining recharge per cent due to infiltration. The technique of estimating groundwater recharge using surface electrical resistivity measurement is efficient, economic, less time consuming and easy to use compared with other methods used for this purpose.

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Resumen Se presenta un método nuevo para estimar recarga de agua subterránea utilizando un método superficial de resistividad y una técnica de isótopos. Se ha obtenido una relación linear entre la resistividad de la capa superior no saturada y la recarga estimada utilizando la técnica de tritio marcado etiquetado para la zona de piedemontes en la región de colinas al pie del Himalaya, India. La relación puede utilizarse para estimar recarga usando mediciones superficiales de resistividad eléctrica para la misma formación geológica. Los datos utilizados en el estudio consisten de treinta y dos mediciones de sondeos eléctricos verticales de resistividad en un intervalo de estaciones de dos km, estudios de tritio marcado en seis sitios seleccionados y monitoreo de niveles de agua, pre-monzón y post-monzón, en la zona piedemontes de la región de colinas al pie del Himalaya (India). Se mapearon los resultados de este estudio utilizando técnicas SIG. Se obtuvo para el área una relación empírica bien definida entre la resistividad de la zona no saturada y el porcentaje de recarga. El método sugiere una aplicación nueva de los datos superficiales de resistividad eléctrica en la determinación del porcentaje de recarga ocasionado por infiltración. La técnica de estimar recarga de agua subterránea utilizando mediciones superficiales de resistividad eléctrica es eficiente, económica, demanda poco tiempo, y fácil de utilizar en comparación con otros métodos que se utilizan para este propósito.

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Resumé Une nouvelle méthode permettant destimer la recharge des eaux souterraines a été présentée, utilisant une méthode de résistivité de surface et des méthodes isotopiques. Une relation linéaire a été obtenue entre la résistivité de la zone non saturée et la recharge estimée grâce au Tritium dans la zone du Piedmont au pied de lHimalaya, Inde. La relation peut être utilisée pour lestimation de la recharge en utilisant la méthode de résistivité de surface dans la même formation géologique. Les données utilisées pour létude sont vingt-deux sondages électriques réalisés tous les deux kilomètres, létude de la signature du tritium en six endroits sélectionnés, et la comparaison des niveaux piézométriques pré et post moussons. Les résultats de cette étude ont été cartographiés en utilisant les techniques SIG. Dans la zone détude une relation très bien définie entre la recharge (%) et la résistivité de la zone non saturée a été obtenue. La méthode suggère une nouvelle application de la résistivité de surface, pour déterminer le pourcentage de la recharge due à linfiltration. Cette technique est efficace, économique, rapide et facile à mettre en oeuvre, en comparaison dautres techniques utilisées pour atteindre le même objectif.

     

The effects of attenuation and site on the spectra of microearthquakes in the Jubilee Hills region of Hyderabad,India

Microearthquake spectra from Jubilee Hills, Hyderabad are analyzed to observe the effect of attenuation and site on these spectra. The ratios of spectral amplitudes at lower and higher frequency are measured for three different stations at varying epicentral distances to estimate Q value for both P-and S-wave in near and sub-surface layer. Average estimates of Qp and Qs are 235 and 278 respectively. Value of Qs/Qp larger than 1.0 suggests dry crust for most of the Jubilee Hills region. The near-surface low Qp and Qs for 0 km to 0.9 km depth coincide with the soil layer, top and semi-weathered and highly fractured zone. In contrast, at a shallower depth beneath the Jubilee Hills area, Hyderabad, we obtain high Qp and Qs zone, which corresponds to the dense and high velocity rocks of the region. The varying corner frequencies for these spectra are inferred to be characteristics of site. Comparisons of disparity in spectral content with reference to hard rock site conclude that lithology of the northwest part of Jubilee Hills area amplify about twice the incoming seismic signal, as compared to the southern part best outlined at 8 to 10 Hz only.     

Damage due to the Mw 7.7 Kutch, India earthquake of 2001

This paper presents a study of the damage due to the M_w 7.6–7.7 intraplate Kutch earthquake of 26 January 2001. It was a powerful earthquake with a high stress drop of about 20 MPa. Aftershocks (up to M 4) have continued for 2.5 years. The distribution of early aftershocks indicates a rupture plane of 20–25 km radius at depths of 10–45 km along an E–W-trending and south-dipping hidden fault situated approximately 25 km north of the Kutch Mainland Fault. The moment tensor solution determined from regional broadband data indicates reverse motion along a south-dipping (by 47°) fault. The earthquake is the largest event in India in the last 50 years and the most destructive in the recorded history in terms of socioeconomic losses with 13,819 deaths (including 14 in Pakistan), collapse/severe damage of over a million houses and US$10 billion economic loss. Surface faulting was not observed. However, intense land deformations have been observed in a 40×20-km meizoseismal area. These include lateral spreading, ground uplifts (about a meter), ground slumping and deep cracks. Liquefaction with ejection of sand and copious water was widespread in the Banni grassland, Rann areas (salt plains), along rivers and also in the coastal areas up to 200 km distance from the epicenter in areas of intensity VII to X+. Stray incidences of liquefaction have occurred up to distances of at least 300 km. For the first time in India, multistory buildings have been destroyed/damaged by an earthquake. The maximum acceleration is inferred to be 700 cm/s² and intensities are 1–3 units higher in soil-covered areas than expected from the decay rate of acceleration for hard rock.     

Strong ground motion attenuation in Aswan area, Egypt

Recent and paleo seismicity indicate that moderate seismic activity is relatively large for Aswan area. This is a warning on the possibility of occurrence of earthquakes in the future too. No strong motion records are available in Aswan area for engineers to rely upon. Consequently, the seismological modeling is an alternative approach till sufficient instrumental records around Aswan become available. In the present study, we have developed new ground motion attenuation relationship for events spanning 4.0?≤? M _w?≤?7.0 and distance to the surface projection of the fault up to 100 km for Aswan based on a statistically simulated seismological model. We generated suites of ground motion time histories using stochastic technique. The ground motion attenuation relation describes the dependence of the strength of the ground motions on the earthquake magnitude and distance from the earthquake. The proposed equation for peak ground acceleration (PGA) for the bed rock is in the form of: $ {\mathbf{log}}{\text{ }}\left( {{\mathbf{PGA}}/{\mathbf{gal}}} \right){\text{ }} = {\mathbf{1}}.{\mathbf{24}} + {\mathbf{0}}.{\mathbf{358}}{M_{\mathbf{w}}} - {\text{ }}{\mathbf{log}}\left( {\mathbf{R}} \right){\text{ }}-{\text{ }}{\mathbf{0}}.{\mathbf{008}}{\text{ }}{\mathbf{R}}{\text{ }} + {\text{ }}{\mathbf{0}}.{\mathbf{22}}{\text{ }}{\mathbf{P}} $ . Where PGA is the peak ground acceleration in gal (cm/s²); M_w, its moment magnitude; R is the closest distance between the rupture projection and the site of interest; and the factor P is a dummy variable. It is observed that attenuation of strong motion in Aswan is correlated with those used before in Egypt.     

Evidence for right-lateral strike-slip environment in the Kutch basin of northwestern India from moment tensor inversion studies

The Kutch region located in northwestern part of India is an ancient rift basin that was active until Cretaceous period. The region falls close to the India–Arabia and the India–Eurasia plate boundaries and has experienced devastating earthquakes in the past, namely the 1819 Allah Bund earthquake, the 1956 Anjar earthquake and the 2001 Bhuj earthquake. To understand the tectonics of this region with respect to the adjacent plate boundaries, we invert seismic waveform data of 11 earthquakes in this region recorded by a network of the Institute of Seismological Research (ISR) during 2007–2009. The study yields focal mechanism solutions of reverse fault and strike-slip type mechanism. The inferred fault planes correlate well with the local trends of the known tectonic faults while the principal stress directions derived from stress inversion based on a linearized least squares approach, trend agreeably with the ambient stress field directions. A consistently right-lateral sense of shear is found on all the local faults as derived from each of the matching planes of the focal mechanism solutions computed in the present study. It is inferred that in the Kutch region a right-lateral strike-slip environment prevails along predominantly EW to NW-SE oriented deep-seated pre-existing faults in an otherwise compressive stress regime. This, in conjunction with the left-lateral movements along the Girnar mountain in southern Saurashtra, inferred from previous studies, indicates a westward escape of the Kutch–Saurashtra block as a consequence of the northward collision of the Indian plate with respect to the Eurasian landmass.     

Application of trace metal anomalies for recognition of petroleum prospects in surface sediments of Kutch and Saurashtra Basins, India

Seepage of hydrocarbons, either as macroseepage or microseepage, can set up near-surface oxidation-reduction zones that favour the development of a diverse array of chemical and mineralogic changes. In this study trace metal alterations were mapped that appear to be associated with hydrocarbon microseepages in the oil/gas fields. A total of 210 soil samples were collected from near surface sediments of Kutch and Saurashtra Basins, India. The soil samples were collected from a depth of 2–2.5 m. The paper reports the chemical alterations associated with trace metals in soils that are related to hydrocarbon microseepages above the Kutch and Saurashtra Basins, India. The soil samples for trace metals; Scandium (Sc), Vanadium (V), Chromium (Cr), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Barium (Ba) and Strontium (Sr) were analyzed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The concentrations of the trace elements ranged between for Sc (12.69 to 21.91 ppm), V (109.20 to 436.05 ppm), Cr (87.15 to 481.57 ppm), Co (18.25 to 64.31 ppm), Ni (57.55 to 263.15 ppm), Cu (44.88 to 143.96 ppm), Zn (137.60 to 502.31 ppm), Ba (149.27 to 921.46 ppm) and Sr (143.93 to 425.63 ppm) were obtained. It was observed that trace elements concentrations were tremendously increased when compared with normal concentration in the soils. The adsorbed soil gas analysis showed the presence of high concentrations of ΣC₂₊ (C₂H₆, C₃H₈ and n-C₄H₁₀) ranged between 1 to 121 ppb respectively. Integrated studies of trace elements over adsorbed light gaseous hydrocarbon (ΣC₂₊) anomalies showed good correlation. The carbon isotopic composition of δ¹³C₁ of the samples ranges between — 36.6 ‰ to ?22.7‰ (Pee Dee Belemnite) suggest thermogenic source for hydrocarbon gases. The increase in trace metal concentrations near oil/gas producing areas, suggests that soil chemical change to a reducing environment, presumably due to the influence of hydrocarbon microseepage, which could be applied with other geo-scientific data to identify areas of future hydrocarbon exploration in the frontier areas.     

Coda wave attenuation characteristics for Kumaon and Garhwal Himalaya,India

Natural Hazards - Uttarakhand Himalayas are among one of the most seismically active continental regions of the world. The Himalayan belt in this region is divided into Kumaon and Garhwal Himalaya....