Characterizing site response in the Attock Basin,Pakistan, using microtremor measurement analysis     

S. M. Talha Qadri  Md. Aminul Islam  M. R. Shalaby  Khaista Rehman Khattak  S. H. Sajjad 《Arabian Journal of Geosciences》2017,10(12):267

The Attock Basin is situated close to the northwest of Pakistan. Recent seismic event of October 2015 (7.5M_w) near the Pakistan Afghanistan border has proved that the area of interest is seismically active and triggered a series of aftershocks of magnitude even greater than 6.5M_w. This seismic activity has posed danger to the future of the people and infrastructure especially to the northwestern part of the country. Therefore, site response analysis is essential for estimating local site conditions in response to seismic events. Ambient noise recordings were made at 50 sites within urban and semi-urban settlements in the Attock Basin to analyze the site response of the small but densely populated basin. At each of these sites, the fundamental frequency of the soft sediments (f ₀), the amplitude (A ₀) of corresponding H/V spectral ratios, the thickness of soft sediment (H) lying over competent lithology, and the soil vulnerability index (K _g) were studied. Results were correlated with sparsely available borehole data to enhance the credibility of the study conducted for microzonation and predicting the site response to earthquake seismicity in the Attock Basin. The soil vulnerability index was found to range from moderate to high. Results clearly showed that the study area exhibits low to moderate fundamental frequency with greater soft sediment thicknesses distributed throughout the study area. Moreover, higher impedance contrasts were found at most of the sites within the central part of the Attock Basin, thus reflecting a moderate to high susceptibility of damage in those regions in response to seismic events.  相似文献   

A multi-isotope approach (O,H, C,S, B and Sr) to understand the source of water and solutes in some the thermal springs from West Coast geothermal area,India     

Sitangshu Chatterjee  Md. Arzoo Ansari  Archana S. Deodhar  Uday Kumar Sinha  Ashutosh Dash 《Arabian Journal of Geosciences》2017,10(11):242

The West Coast belt, consisting of nearly 60 thermal springs, is one of the most diversified geothermal fields in India. The present work describes the multi-isotopic (O, H, C, S, B and Sr) characterization of thermal waters carried out in the Tural-Rajwadi geothermal field, situated in southern sector of the west coast geothermal area. The aim of this study is to delineate the origin of thermal water as well as to ascertain the sources of carbon, sulphur, boron and strontium dissolved in those thermal springs. The stable isotopes (δ²H and δ¹⁸O) and tritium data indicate that these thermal springs are not recently recharged rain water rather, it contains very old component of water. Oxygen-18 shift is observed due to rock-water interaction over a long period of time. Carbon isotopic composition of DIC points out to the silicate weathering with soil CO₂ coming from C₃ type of plants whereas δ³⁴S of dissolved sulphate confirms the marine origin of sulphate. This marine signature is basically derived from paleo-seawater possibly entrapped within the flows. Boron isotopic data reveals that both the seawater and rock dissolution are the sources of boron in the thermal waters whereas high ⁸⁷Sr/⁸⁶Sr ratios (0.7220–0.7512) of the thermal waters conclusively establishes that archean granitic basement is the predominant rock source of strontium, not the Deccan flood basalts. In addition, like strontium, concentrations of lithium, rubidium and caesium are also governed by the rock-water interaction. Thus, the combined use of this multi-isotope technique coupled with trace element concentrations proves to be an effective tool to establish the sources of solutes in the thermal water.  相似文献   

Temporal change of glaciers area and geomorphometric parameters in Parbati valley,Himachal Pradesh,India     

Sarfaraz Ahmad  Khatib Khan  Nepal Singh  Zabiullah Ansari  Md. Mulhim 《Environmental Earth Sciences》2017,76(11):407

Temporal change in the glacier coverage is analyzed for the period between 1962 and 2003 in Parbati valley, Himachal Pradesh. It is observed that the total glacier cover has been decreased by 17% ranging between 8 and 100% for individual glacier. The pattern of de-glaciation shows a high degree of shrinkage in outer zone of Parbati valley, while least shrinkage is observed in the inner valley. The present study is conducted to establish relationship between glacio-geomorphic parameters and glaciers shrinkage pattern to predict the future glacier cover in warming scenario. A systematic change is observed for glacio-geomorphic parameters associated with temporal change in glacier cover. It is observed that mean and minimum elevation, slope, relief and duration of insolation have changed substantially. Maximum elevation, plan/profile curvatures and aspect have shown less change from 1962 to 2003. A correlation matrix between glacio-geomorphic parameters for glaciers between 1962 and 2003 shows that the recent glaciers are much more controlled by terrain characteristics than that in the recent past.  相似文献   

Occurrences of damaging earthquakes between the Himachal and Darjeeling Himalayas: Tectonic implications     

Md. Afroz Ansari  Prosanta K. Khan 《Acta Geophysica》2014,62(4):699-736

Detailed analysis of intensity for ten damaging historical earthquakes in the central arcuate belt between the Himachal and Darjeeling Himalayas was carried out in the backdrop of isoseismal eccentricity, source depth and Indian plate obliquity. Results indicate that the elongated axes of the isoseismals and strike of ruptures for shallow earthquakes are almost parallel with strike of the Himalayan arc, and clearly conformable with the obliquity. An empirical power law relationship between eccentricity and focal depth established under the present study illustrates that the deeper events are more influenced by the bending of the penetrating Indian lithosphere, whereas the shallower events are principally controlled by the obliquity. A positive correlation between eccentricities and obliquity obviously supports this inference. The present study further reveals that the constant decrease in Indian plate obliquity from Himachal to Nepal-Bihar Himalaya is well compatible with the graben structures and horizontal shearing along this arcuate segment.  相似文献   

Optimization of slope angle and its seismic stability: A case study for the proposed open pit coalmine in Phulbari, NW Bangladesh     

Md. Rafiqul Islam  Mohammed Omar Faruque 《山地科学学报》2013,10(6):976-986

The present study reflects upon the results of substantial program of two-dimensional Finite Element Method （FEM） numerical analyses of the open pit that links to slope angle optimization associated with the safety factor of the pit slope of a coal mine in Bangladesh. In the present analyses, two types of models have been presented. The first model estimates safety factor without seismic effect on the overall pit slope of the model; the second model incorporates safety factor with seismic stability of the model. The calculated optimum slope angle of the first model is 31% with a rational safety factor of 1.51, prior to the seismic effect. However, the value is reduced to 0.93, 0.82, and 0.72, after we applies the seismic effect in the second model with M6, M6.5, and M7, respectively. Finally, our modeling results emphasize that for the case of the proposed Phulbari coalmine, there is extremely high prospect for causing massive slope failure along the optimum pit slope angle with 31% if the mine area felt seismic shaking, like the Sikkim （in northern India） earthquake with M6.9 on September 18, 2011.  相似文献   

Upregulation of hypoxia-inducible factor (HIF)-1α and HIF-2α mRNA levels in dragonet Callionymus valenciennei exposed to environmental hypoxia in Tokyo Bay     

Kodama K  Rahman MS  Horiguchi T  Thomas P 《Marine pollution bulletin》2012,64(7):1339-1347

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Effects of bottom bracings on torsional dynamic characteristics of horizontally curved twin I-girder bridges with different curvatures   总被引：1，自引：0，他引：1  

Robiul Awall  Toshiro Hayashikawa  Takashi Matsumoto 《地震工程与工程振动(英文版)》2012,11(2):149-162

Curved twin I-girder bridges (CTIGBs) have low torsional stiffness that makes them vulnerable to dynamic loads.This study investigates the effects of bottom bracings on the torsional dynamic characteri...  相似文献   

Litterfall of three subtropical mangrove species in the family Rhizophoraceae     

Md. Kamruzzaman  Sahadev Sharma  A. T. M. Rafiqul Hoque  Akio Hagihara 《Journal of Oceanography》2012,68(6):841-850

This study was conducted to evaluate and compare the litterfall dynamics of three mangrove species in the family Rhizophoraceae: Rhizophora stylosa, Kandelia obovata, and Bruguiera gymnorrhiza, in Manko Wetland, Okinawa Island, Japan. Over 3?years, these species showed highest litterfall of leaves and stipules in summer and the lowest litterfall in winter. Litterfall of flowers and fruits peaked in July for R. stylosa, and in August and again in October?CNovember for K. obovata. Litterfall of flower buds, flowers, and propagules occurred throughout the year for B. gymnorrhiza, but was highest in summer. Litterfall of propagules was highest in September and May for R. stylosa and K. obovata, respectively. Kendall??s coefficient of concordance revealed that the monthly changes for leaf, stipule, flower, and fruit litterfalls of all the species were strongly and significantly concordant among the years. The conversion rate of flowers to propagules was 2.3?% in R. stylosa, 5.9?% in K. obovata, and 10.3?% in B. gymnorrhiza. Total annual litterfall in R. stylosa was significantly different from K. obovata and B. gymnorrhiza; however, the latter two species showed no significant differences. Leaves contributed the most to the total litterfall of all three species, and represented 58.4, 54.0, and 50.4?% of the total litterfall for R. stylosa, K. obovata, and B. gymnorrhiza, respectively. Except for branches and flower bud primordia, all other components of litterfall had clear annual cycles for all three species. Rhizophora stylosa and K. obovata showed a negative correlation between leaf production and reproductive organ production, but B. gymnorrhiza tended to increase leaf production with increasing reproductive organ production.  相似文献   

Agrobiodiversity of Muda Rice Agroecosystem:A case Study in Largest Granary Area of Malaysia     

Amir Shah Ruddin Md Shah　Mashhor Mansor　Shahrul Anuar Mohd Shah　Che Salmah Mohd Rawi　Abu Hassan Ahmad　Ibrahim Jaafar 《湿地科学》2008,6(1):34-44

A survey was carried out at the largest rice cultivation area in Peninsular Malaysia,the Muda rice agroecosystem.The main objective of this study was to document the overall biodiversity associated with this unique agroecosystem by using a combination of sampling techniques in order to record different groups of fauna and flora.The total number of biota recorded and identified from the rice field ecosystem during the study period consisted of 46 species of zooplankton,81 species of aquatic insects,5 species of rodents,7 species of bats,87 species of birds,11 species of fishes and 58 species of weeds.A long-term study should be carried out as more species are expected to be recorded when more of the Muda rice agroecosystem area has been sampled to obtain sufficient information on the Muda rice agrobiodiversity.  相似文献   

The influence of solar‐induced thermal stresses on the mechanical weathering of rocks in humid mid‐latitudes          下载免费PDF全文

Jennifer Aldred  Martha Cary Eppes  Kimberly Aquino  Rebecca Deal  Jacob Garbini  Suraj Swami  Alea Tuttle  George Xanthos 《地球表面变化过程与地形》2016,41(5):603-614

The role of solar‐induced thermal stresses in the mechanical breakdown of rock in humid‐temperate climates has remained relatively unexplored. In contrast, numerous studies have demonstrated that cracks in rocks found in more arid mid‐latitude locations exhibit preferred northeast orientations that are interpreted to be a consequence of insolation‐related cracking. Here we hypothesize that similar insolation‐related mechanisms may be efficacious in humid temperate climates, possibly in conjunction with other mechanical weathering processes. To test this hypothesis, we collected rock and crack data from a total of 310 rocks at a forested field site in North Carolina (99 rocks, 266 cracks) and at forested and unforested field sites in Pennsylvania (211 rocks, 664 cracks) in the eastern United States. We find that overall, measured cracks exhibit statistically preferred strike orientations (47° ± 16), as well as dip angles (52° ± 24°), that are similar in most respects to comparable datasets from mid‐latitude deserts. There is less variance in strike orientations for larger cracks suggesting that cracks with certain orientations are preferentially propagated through time. We propose that diurnally repeating geometries of solar‐related stresses result in propagation of those cracks whose orientations are favorably oriented with respect to those stresses. We hypothesize that the result is an oriented rock heterogeneity that acts as a zone of weakness much like bedding or foliation that can, in turn, be exploited by other weathering processes. Observed crack orientations vary somewhat by location, consistent with this hypothesis given the different latitude and solar exposure of the field sites. Crack densities vary between field sites and are generally higher on north‐facing boulder‐faces and in forested sites, suggesting that moisture‐availability also plays a role in dictating cracking rates. These data provide evidence that solar‐induced thermal stresses facilitate mechanical weathering in environments where other processes are also likely at play. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献