Study on the geochemical correlation of crude oils of Palaeocene and Jurassic ages from the Potowar Indus Basin in northern Pakistan     

Muhammad Irfan Jalees  Fazeelat Tahira  Hina Saleem 《中国地球化学学报》2010,29(1):82-93

This study deals with a detailed geochemical characterization of three crude oils from the Upper Indus Basin, Punjab, Pakistan. The samples were obtained from three productive oil fields of the Datta Formation (Jurassic), Lochhart (Palaeocene) and the Dhak Pass zone (Palaeocene). The GC parameters for and the bulk properties of Datta Formation oils are essentially coincident with those of the oils from the Dhak Pass Formation in the Upper Indus Basin, Pakistan and the oils likely originate from a marine source rock. In contrast, the Lockhart Formation oils show different behaviors and seem to be originated from dirty carbonate rocks although all three crude oils are mature, being of non-biodegraded and somewhat mixed organic matter origin. Low Pr/Ph values and high C₃₅ homohopane index for the Lockhart Formation oils suggest a source of anoxic environment with low Eh while oils from the Datta Formation and Dhak Pass Formation showed different trends, i.e., lower values of C₃₅ homohopane index indicating different depositional environment than oil from the Lockhart Formation. All three crude oils from the Upper Indus Basin are mature for the hopane ratios, i.e., Ts/Ts+Tm, C₃₂22S/(S+R) and C₃₀ αβ/(αβ+βα) and sterane ratios, i.e., C₂₉22S/(S+R) and C₂₉ββ/(ββ+αα) but oils from the Lockhart Formation seem to be less mature than those from the Palaeocene and Datta Formation according to plots like API° vs. homohopane Index, Pr/Ph vs. sterane. The relative composition of 5α(H), 14β(H), 17β(H)-24-ethylecholestanes and the C₂₉20S/20S+20R index, indicate that all three crude oils are equally mature, which makes it unlikely with respect to the above said plots. This difference is may be due to the migratory chromatography which alters the concentrations of sterane and hoapnes and hence gives different results. These oils do not exhibit UCM and have complete n-alkane profiles indicating non-biodegradation.  相似文献   

GIS-based high-resolution spatial interpolation of precipitation in mountain–plain areas of Upper Pakistan for regional climate change impact studies     

Muhammad Waseem Ashiq  Chuanyan Zhao  Jian Ni  Muhammad Akhtar 《Theoretical and Applied Climatology》2010,99(3-4):239-253

In this study, the baseline period (1960–1990) precipitation simulation of regional climate model PRECIS is evaluated and downscaled on a monthly basis for northwestern Himalayan mountains and upper Indus plains of Pakistan. Different interpolation models in GIS environment are used to generate fine scale (250?×?250 m²) precipitation surfaces from PRECIS precipitation data. Results show that the multivariate extension model of ordinary kriging that uses elevation as secondary data is the best model especially for monsoon months. Model results are further compared with observations from 25 meteorological stations in the study area. Modeled data show overall good correlation with observations confirming the ability of PRECIS to capture major precipitation features in the region. Results for low and erratic precipitation months, September and October, are however showing poor correlation with observations. During monsoon months (June, July, August) precipitation pattern is different from the rest of the months. It increases from south to north, but during monsoon maximum precipitation is in the southern regions of the Himalayas, and extreme northern areas receive very less precipitation. Modeled precipitation toward the end of the twenty-first century under A2 and B2 scenarios show overall decrease during winter and increase in spring and monsoon in the study area. Spatially, both scenarios show similar pattern but with varying magnitude. In monsoon, the Himalayan southern regions will have more precipitation, whereas northern areas and southern plains will face decrease in precipitation. Western and south western areas will suffer from less precipitation throughout the year except peak monsoon months. T test results also show that changes in monthly precipitation over the study area are significant except for July, August, and December. Result of this study provide reliable basis for further climate change impact studies on various resources.  相似文献   

Effects of land use and climate variability on the main stream of the Songhua River Basin,Northeast China     

Muhammad Abrar Faiz  Faisal Baig  Ahmad Niaz  Tianxiao Li 《水文科学杂志》2020,65(10):1752-1765

ABSTRACT

In this study, three representative concentration pathways (RCPs) and 15 general circulation models of the Coupled Model Intercomparison Project Phase 5 were used to assess the behaviour of precipitation (P) and surface air temperature (SAT) over part of the Songhua River Basin. The Water Evaluation and Planning (WEAP) model linked with SAT and P was used for monthly simulation of streamflow to assess the influence of land use/land cover and climate change on the streamflow. The results suggest that, under RCP2.6, RCP4.5 and RCP8.5, the SAT over the study area may increase in the 21st century by 1.12, 2.44 and 5.82°C, respectively. Moreover, by the middle of the 21st century, streamflow in the basin may have decreased by 19%. The decrease in streamflow may be due to changed land use conditions and water withdrawal, having critical implications for management and future planning of water resources in the basin.  相似文献   

Architecture of the evaporite accumulation and salt structures dynamics in Tiddlybanken Basin,southeastern Norwegian Barents Sea     

Muhammad Hassaan  Jan I. Faleide  Roy H. Gabrielsen  Filippos Tsikalas 《Basin Research》2021,33(1):91-117

An extensive, reprocessed two‐dimensional (2D) seismic data set was utilized together with available well data to study the Tiddlybanken Basin in the southeastern Norwegian Barents Sea, which is revealed to be an excellent example of base salt rift structures, evaporite accumulations and evolution of salt structures. Late Devonian–early Carboniferous NE‐SW regional extensional stress affected the study area and gave rise to three half‐grabens that are separated by a NW‐SE to NNW‐SSE trending horst and an affiliated interference transfer zone. The arcuate nature of the horst is believed to be the effect of pre‐existing Timanian basement grain, whereas the interference zone formed due to the combined effect of a Timanian (basement) lineament and the geometrical arrangement of the opposing master faults. The interference transfer zone acted as a physical barrier, controlling the facies distribution and sedimentary thickness of three‐layered evaporitic sequences (LES). During the late Triassic, the northwestern part of a salt wall was developed due to passive diapirism and its evolution was influenced by halite lithology between the three‐LES. The central and southeastern parts of the salt wall did not progress beyond the pedestal stage due to lack of halite in the deepest evaporitic sequence. During the Triassic–Jurassic transition, far‐field stresses from the Novaya Zemlya fold‐and‐thrust belt reactivated the pre‐salt Carboniferous rift structures. The reactivation led to the development of the Signalhorn Dome, rejuvenated the northwestern part of the salt wall and affected the sedimentation rates in the southeastern broad basin. The salt wall together with the Signalhorn Dome and the Carboniferous pre‐salt structures were again reactivated during post‐Early Cretaceous, in response to regional compressional stresses. During this main tectonic inversion phase, the northwestern and southeastern parts of the salt wall were rejuvenated; however, salt reactivation was minimized towards the interference transfer zone beneath the centre of the salt wall.  相似文献   

An unconditionally stable time-stepping procedure with algorithmic damping: a weighted integral approach using two general weight functions     

Bruce W. Golley  Muhammad Amer 《地震工程与结构动力学》1999,28(11):1345-1360

An accurate algorithm for the integration of the equations of motion arising in structural dynamics is presented. The algorithm is an unconditionally stable single-step implicit algorithm incorporating algorithmic damping. The displacement for a Single-Degree-of-Freedom system is approximated within a time step by a function which is cubic in time. The four coefficients of the cubic are chosen to satisfy the two initial conditions and two weighted integral equations. By considering general weight functions, eight additional coefficients arise. These coefficients are selected to (i) minimize the difference between exact and approximate solutions for small time steps, (ii) incorporate specified algorithmic damping for large time steps, (iii) ensure unconditional stability and (iv) minimize numerical operations in forming the amplification matrix. The accuracy of the procedure is discussed, and the solution time is compared with a widely used algorithm. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Calibration of local magnitude scale for Hindukush continental subduction zone          下载免费PDF全文

Muhammad N.Mushtaq  Muhammd Tahir  Muhammd T.Iqbal  Muhammd A.Shah  Saleem Iqbal  Talat Iqbal 《地震科学（英文版）》2021,34(2):114-122

Hindukush is an active subduction zone where at least one earthquake occurs on daily basis. For seismic hazard studies, it is important to develop a local magnitude scale using the data of local seismic network. We have computed local magnitude scale for Hindukush earthquakes using data from local network belonging to Center for Earthquake Studies (CES) for a period of three years, i.e. 2015–2017. A total of 26,365 seismic records pertaining to 2,683 earthquakes with magnitude 2.0 and greater, was used with hypocentral distance less than 600 km. Magnitude scale developed by using this data comes to be M_L = logA + 0.929logr + 0.00298r – 1.84. The magnitude determined through formulated relation was compared with that of standard relation for Southern California and relation developed by the same authors for local network for Northern Punjab. It was observed that Hindukush region has high attenuation as compared to that of Southern California and Northern Punjab which implies that Hindukush is tectonically more disturbed as compared to the said regions, hence, seismically more active as well. We have calculated station correction factors for our network. Station correction factors do not show any pattern which probably owes to the geological and tectonic complexity of this structure. Standard deviation and variance of magnitude residuals for CES network determined using Hutton and Boore scale and scale developed in this study were compared, it showed that a variance reduction of 44.1% was achieved. Average of magnitude residuals for different distance ranges was almost zero which showed that our magnitude scale was stable for all distances up to 600 km. Newly developed magnitude scale will help in homogenization of earthquake catalog. It has been observed that b-value of CES catalog decreases when magnitude is calculated by using newly developed magnitude scale.  相似文献   

孟加拉国农业利用强度增加、土地利用/覆盖变化和土地退化     

Abu Muhammad Shajaat Ali 《地球科学进展》2006,21(2):183-191

在实地采访、地块土地利用/覆盖调查和1 260个土样的收集和实验室分析等野外工作的基础上,对比分析了1984—1985年和2003—2004年265个家户的人口、农业系统、土地利用和土壤质量数据,研究了孟加拉国6个村庄农业诱导强度增强对土地和土壤质量的影响。1984—2004年家户和土质数据的百分比变化用来构建诱导强度增强模型和土地退化模型中的统计变量和土地退化指标。结果表明：研究区种植强度和土地生产力的增加主要是由于低压泵灌溉的普及,化肥和杀虫剂的使用以及水稻、蔬菜和虾生产的多元化高产。诱导强度增强模型可以解释研究区81%的种植强度增量和73%的土地生产力增量。人口压力和市场驱动也诱发了农业利用强度的增加;环境约束起到了一定制约作用;低压泵灌溉等应对干旱的技术也对农业增产有一定贡献。然而动力耕作机、低压泵灌溉和化学物质的持续利用再加上除草性水稻、蔬菜和虾的频繁耕作和养殖已经导致土壤结构、质地和化学属性的退化,生产力也有所降低。利用强度越大的土地退化现象越严重,生产力下降得也更多。土地的不断退化将有可能会引发孟加拉国的马尔萨斯危机。  相似文献   

The role of visual saliency in the automation of seismic interpretation          下载免费PDF全文

Muhammad Amir Shafiq  Tariq Alshawi  Zhiling Long  Ghassan AlRegib 《Geophysical Prospecting》2018,66(Z1):132-143

In this paper, we propose a workflow based on SalSi for the detection and delineation of geological structures such as salt domes. SalSi is a seismic attribute designed based on the modelling of human visual system that detects the salient features and captures the spatial correlation within seismic volumes for delineating seismic structures. Using this attribute we cannot only highlight the neighbouring regions of salt domes to assist a seismic interpreter but also delineate such structures using a region growing method and post‐processing. The proposed delineation workflow detects the salt‐dome boundary with very good precision and accuracy. Experimental results show the effectiveness of the proposed workflow on a real seismic dataset acquired from the North Sea, F3 block. For the subjective evaluation of the results of different salt‐dome delineation algorithms, we have used a reference salt‐dome boundary interpreted by a geophysicist. For the objective evaluation of results, we have used five different metrics based on pixels, shape, and curvedness to establish the effectiveness of the proposed workflow. The proposed workflow is not only fast but also yields better results as compared with other salt‐dome delineation algorithms and shows a promising potential in seismic interpretation.  相似文献   

Vibration analysis of damaged and undamaged steel structure systems: cantilever column and frame     

Khan  Muhammad Abuzar  Akhtar  Kareem  Ahmad  Naveed  Shah  Feroz  Khattak  Naeem 《地震工程与工程振动(英文版)》2020,19(3):725-737

This paper presents the experimental and numerical studies conducted on a steel column and a steel frame structure using free vibration analysis. The effects of damages on structures were investigated, which were simulated by introducing multiple cracks at different locations in the experimental and numerical models. The acceleration responses of the test models, were recorded through an accelerometer, and were used to calibrate the numerical models developed in finite element based software. Modal frequencies of damaged and undamaged structures were compared and analyzed, to derive relationships for damaged and undamaged structures' frequencies in terms of crack depth. It was found that, due to the presence of cracks, the mechanical properties of a structure changes, whereby, the modal frequencies decrease. An approximately linear trend was observed for the frequency decrease with the increase in crack depth, which was also confirmed by the numerical models. The derived relationships were extended to further develop a mechanics-based damage scale for steel structures, to help facilitate structural health monitoring and screening of vulnerable structures.  相似文献   

Thermal structure of hot events and their possible role in maintaining the warm isothermal layer in the Western Pacific warm pool     

Wirasatriya  Anindya  Kawamura  Hiroshi  Helmi  Muhammad  Sugianto  Denny Nugroho  Shimada  Teruhisa  Hosoda  Kohtaro  Handoyo  Gentur  Putra  Yoppik Disma Girindra  Koch  Magaly 《Ocean Dynamics》2020,70(6):771-786

Ocean Dynamics - The short-lived events of high SST are called hot events (HEs) and can only be generated under the conditions of large daily heat gain due to strong solar radiation and weak wind....  相似文献