Paleoseismological Analysis Along the Astara Fault System (Talesh Mountain, North Iran)

The Astara Fault System(AFS) is located in the northwest Alborz, east of Talesh Mountain(TM) and west of the South Caspian Basin(SCB). The AFS is one of the basement rock faults in Iran that is heavily involved in seismotectonic activity of the Talesh region, and to which subsidence of the SCB is attributed. There is little information available concerning previous AFS seismic activities and its properties. In order to elucidate the seismic behavior and activities of the AFS, we conducted a research study on paleoseismology of the fault. Based on paleoseismic evidence, two scenarios could be taken into consideration, one of which has three and another has four seismic events with magnitudes Mw in the range of 6.7 to 7.2. Evidence of these seismic events is within sedimentary succession as they have occurred during the past 3 ka(this age is determined based on the deposition rate of the region). Six carbon samples were taken for C~(14) age determination tests, the results of which clearly demonstrated that the EvIV(scenario A) and EvⅢ(scenario B) had occurred before 27,444 cal BP, while other events occurred in the time period between 27,444 cal BP and 3 ka ago. If we consider the occurrence of three or four seismic events(based on the two scenarios) to be between 27,444 cal BP and 3 ka ago, the average recurrence interval is 7,119 ± 1,017, but evidence for these events has been removed. If we assume EvI to be the youngest event(in both scenarios), the minimum elapsed time is therefore 3 ka.     

Analyses of Inclined Cracks Neighboring Two Iso-Path Cracks in Rock-Like Specimens Under Compression

Crack propagation process in pre-cracked rock like specimens has been studied experimentally and numerically considering three cracks in the middle part of each specimen. The rock-like specimens are specially prepared from Portland pozzolana cement, fine sands and water. These pre-cracked cylindrical specimens (each containing a single inclined crack in the neighborhood of two iso-path cracks) are experimentally tested under compressive loading. The same problems are numerically simulated by a modified displacement discontinuity method using higher order displacement discontinuity elements and higher order special crack tip elements for crack tip treatment to increase the accuracy of the Mode I and Mode II stress intensity factors obtained based on linear elastic fracture mechanics theory. The crack propagation and coalescence paths of the inclined crack are estimated by implementing a suitable iteration algorithm of incremental crack length extension in a direction predicted by using the maximum tangential stress criterion. The numerical and analytical crack extension analyses are compared which are in good agreement and show the validity, applicability and accuracy of the present work.     

Permeability upscaling of fault zones in the Aztec Sandstone,Valley of Fire State Park,Nevada, with a focus on slip surfaces and slip bands

The effect of open and filled slip surfaces on the upscaled permeability of two fault zones with 6 and 14 m strike-slip in an eolian Aztec Sandstone, Nevada, USA is evaluated. Each fault zone is composed of several fault components: a fault core, bounded by filled through-going slip surfaces referred to as slip bands, and a surrounding damage zone that contains joints and deformation bands. Slip band geometry, composition, and petrophysical properties are characterized. Measurements and modeling show that slip band permeabilities can vary over 12 orders of magnitude depending on the degree of fill within the slip bands. The slip bands along with other fault zone components are represented in finite volume numerical calculations and the impact of various slip-band representations on upscaled fault zone permeability is tested. The results show 2 orders of magnitude variation in upscaled fault zone permeability in the fault-normal direction and a factor of 2 variation in the fault-parallel direction. The numerical results presented here are compared to the earlier numerical results in which structured Cartesian grids were used for the numerical simulations, and are in qualitative agreement with earlier calculations but use about a factor of 250–400 fewer numerical cells.     

The Response of Macrobenthic Communities to Environmental Variability in Tropical Coastal Waters

The relative contributions of spatial and temporal fluctuations are different in shaping natural communities in a tropical coastal/estuarine system. Understanding how coastal communities respond to these fluctuations is still equivocal, and thus, available data are rare. Here, multiple analytical approaches were used to identify key spatial and temporal factors, and to quantify their relative roles in shaping a macrobenthic community through space (contamination degree, physical parameters, and sediment characteristics) and time (climatic factors, season, and year). A dataset of eight sampling times was analyzed over a period of 2 years, in which macrobenthic species abundances were sampled. A total of 33 species were identified, including 18 bivalves, 5 gastropods, and 4 crustaceans. The other taxa were less diverse. The results show that there were no significant temporal changes of macrobenthic community structure, but spatial changes were significant and synchronized with environmental factors (i.e., sediment characteristics, water depth, and the distance from anthropogenic sources). This study demonstrates that spatial factors played a primary role in structuring of macrobenthic assemblages, whereas the influence of temporal factors appeared less across geographically distinct sites. Thus, temporal variation of a coastal macrobenthic community appears to be controlled by partly different processes at different scales.     

珠江口盆地西部文昌A凹陷断裂特征与成因探讨

在前人勘探解释的基础上,通过三维高分辨率地震资料,应用相干属性分析等技术对区域断裂进行精细化解释。研究表明盆地内发育着典型的犁式、花状构造、旋转正断层等伸展构造样式,在珠三南断裂影响下,南部边界断裂以阶梯状排列形成断阶构造。始新世—中中新世,断裂走向在持续右旋张扭应力场下以NE→EW→NWW顺时针方向旋转,张裂强度逐渐减弱。晚始新世—早渐新世,盆地在太平洋板块俯冲后退、印亚板块碰撞、古南海向南俯冲下发育EW向断裂,晚渐新世在南海扩张事件影响下前期右旋应力场得到加强,形成大量近EW向断裂,中新世后演化为NWW向断裂。文昌A凹陷断裂构造的演化、成因机制与南海北部陆缘应力场变化一致。该研究有利于进一步了解南海北部陆缘含油气盆地的构造特征和演化规律,提高油气勘探开发的效率。     

Evaluating the efficacy of SVMs,BNs, ANNs and ANFIS in wave height prediction

Wave Height (WH) is one of the most important factors in design and operation of maritime projects. Different methods such as semi-empirical, numerical and soft computing-based approaches have been developed for WH forecasting. The soft computing-based methods have the ability to approximate nonlinear wind–wave and wave–wave interactions without a prior knowledge about them. In the present study, several soft computing-based models, namely Support Vector Machines (SVMs), Bayesian Networks (BNs), Artificial Neural Networks (ANNs) and Adaptive Neuro-Fuzzy Inference System (ANFIS) are used for mapping wind data to wave height. The data set used for training and testing the simulation models comprises the WH and wind data gathered by National Data Buoy Center (NDBC) in Lake Superior, USA. Several statistical indices are used to evaluate the efficacy of the aforementioned methods. The results show that the ANN, ANFIS and SVM can provide acceptable predictions for wave heights, while the BNs results are unreliable.     

A desert in the delta: Participatory assessment of changing livelihoods induced by commercial shrimp farming in Southwest Bangladesh

In recent years, shrimp aquaculture, which is undertaken largely in the tropical countries, has experienced spectacular growth in response to expanding global demand and higher economic return. Shrimp exports bring substantial foreign exchange to the producing countries and also generate employment for various stakeholders related to this industry. Despite a number positive aspects (e.g., foreign exchange, employment and food) of shrimp farming, the industry has serious negative environmental impacts. Because of the degradation of natural resources, commercial shrimp farming imposes socio-economic costs on rural resource-reliant communities as their traditional means of food production and livelihoods are displaced. Bangladesh produces 2.5 percent of the global production of shrimp. The country earned about 400 million dollars (U.S.) from shrimp exports during 2004-2005, up from only US$3.17 million in 1971-72. Bangladesh is suffering because of unplanned expansion of this aquaculture and increasingly called as “a desert in the delta”. The purpose of this paper is to identify the impact of commercial saltwater shrimp farming on rural livelihood patterns in southwest Bangladesh using different Participatory Research methods. The authors suggest that vulnerabilities in livelihoods of the rural communities increased due to narrowing down agricultural production, income sources and natural supply of food. Other socio-economic impacts (e.g., landuse patterns, homestead and family structure, daily movement pattern and activities, drinking water, and law and order) also followed as a reaction to the changing ecological conditions. It is also found that economic benefits from shrimp cultivation to the communities was minimal or even negative due to the polarization and outflow of profits, which is augmenting the threat of poverty.     

Seasonal Shift in Community Structure of Periphytic Ciliates in Estuarine Waters in the Northern Bay of Bengal,Bangladesh

To investigate the seasonal heterogeneity of the periphytic ciliate communities, a 1-year baseline survey was conducted in the Karnaphuli River estuary, northern Bay of Bengal, Bangladesh. A total of 54 ciliate species were recorded, including seven common and 14 dominant species. Maximum species number was in autumn whereas maximum abundance was in winter; the minimum for both occurred in summer. Multivariate analyses, i.e., canonical analysis of principal coordinates (CAP) and principal co-ordinates analysis (PCoA), revealed a clear seasonal heterogeneity of community structure and environmental variables. Multivariate correlation analysis (RELATE) demonstrated that the community structure of the periphytic ciliate communities was significantly correlated with environmental variables, and best matching analysis (BIOENV) indicated that heterogeneity of community patterns was mainly driven by water temperature, pH, dissolved oxygen, total dissolved solids and nutrients. Species richness and diversity peaked in autumn whereas species evenness peaked in summer. These results suggest that environmental conditions shape periphytic ciliate community structure, which is a potentially useful bio-indicator of estuarine water quality.     

Mercury in soil from the area of Dayton,Ohio

Mercury concentrations in “A-zone” soil from seventeen urban, suburban, and rural town locations in the area of Dayton, Ohio range from 0.24 to 1.50 ppm. A positive correlation is indicated between the mercury concentrations and the amount of fallout of settleable particulate matter from the air at these sites. Airborne pollution may be an important source of the element in Dayton area soils.