Coastal Morphology and Long-term Shoreline Changes along the Southwest Coast of India

The part of southwest coast of India extending from Poovar in the south to Kasaragod in the north is considered as one of the highly dynamic coastal areas of Indian peninsula. Over the years due to rapid urbanization as well as other natural and anthropogenic activities, the coast is under severe pressure which in turn has reduced the percentage status of healthy / stable coast. Unscientific shoreline protection methods adopted without conducting appropriate studies to assess the suitability of the said method to a particular coastal stretch has often led to negative impacts. As a result, many areas that were once stable have turned eroding and in certain cases, the observed extent of erosion is severe warranting immediate protection measures. In this context, a study was carried out to assess the long-term shoreline changes along the southwest coast and to decipher the causative factors responsible for these changes. Accordingly, a 46 year period from 1968 to 2014 was studied using multi-dated shoreline images and Survey of India (SOI) topographic charts. The DSAS software (USGS) is used to compute the rate of shoreline changes along different sectors of the coast and accordingly the entire coastal stretch is classified into 7 classes depicting the present status (stable / dynamically stable / unstable) of the coast. The analysis revealed that almost 60 % of the coastline is eroding with about 29 % showing an accreting trend.     

A Bay–River Coupled Model for Storm Surge Prediction Along the Andhra Coast of India

The paper describes a two-dimensional bay–river coupled numerical model for storm surges along the Andhra coast of India. The effect of the Krishna and Godavari rivers on the surge development is analysed. A comparative study of the surge generated by a tropical cyclone with and without the inclusion of rivers is done in detail. Three cyclones that struck the Andhra coast in November 1977, May 1990 and November 1996 were used for the simulation studies. It is found that the idealized model without a river overestimates the sea-level elevation as compared to a more realistic bay–river coupled model. The temporal variation of surge values at the mouth of the rivers is also studied for all three cyclone cases. It is found that the effect of the presence of rivers depends on the strength of the cyclone, its point of landfall and the location of the rivers with respect to the landfall point.     

Beach erosion and acceretion—An example from Kerala,Southwest Coast of India

The thickly populated coastal zone of Kerala, India is facing severe problems due to attack of high waves during the southwest monsoon. Systematic beach profiling at 5-km intervals was carried out along the 560-km stretch of the Kerala coast during the pre-and postmonsoon seasons in 1984. Beach volume changes were calculated at each profile station, and the erosional and accretional trends for the entire coastal tract were demarcated in a map. Total erosion along 55 stations is 1276 m³/m. The general erosional and acceretional trends were also found to coincide with diverging and converging littoral currents deduced from the wave refraction diagrams. Such study at periodic intervals will be highly useful for proper management of the coastal zone.     

Probabilistic Seismic Hazard Assessment Along the Southeastern Coast of Vietnam

On the basis of the analysis of geological, tectonic characteristics and earthquake manifestation features, a causative relation between geodynamic regime and seismicity has been established for the southeastern coastal zone and continental shelf of Vietnam. The probabilistic methods have been used to evaluate ground shaking effects at Nha Trang city aswell as for the entire study area. Short, intermediate and long term predictions of ground shaking (in the form of peak ground accelerationmaps) show high risks in the coastal zone of central Vietnam and in the southeastern continental shelf of the country.     

近2 ka闽浙沿岸泥质沉积物物源分析

对近2 ka以来闽浙沿岸泥质沉积物进行了粘土矿物和元素测试,粘土矿物对比分析表明,所研究的泥质沉积物来源为长江沉积物.金属元素聚类分析以及使用判别函数,均得到了与上述一致的结果.沉积物物源的定量计算表明,近2 ka以来闽浙沿岸泥质沉积物中长江的贡献基本稳定在83%～85%,可以排除有黄河沉积物输入的可能,且历史上黄河的改道与北徙并没有对本区的沉积环境和沉积物来源产生明显的影响.     

Run-up and Inundation Pattern Developed During the Indian Ocean Tsunami of December 26, 2004 Along the Coast of Tamilnadu (India)

The tsunami run-up, inundation and damage pattern observed along the coast of Tamilnadu (India) during the deadliest Indian Ocean tsunami of December 26, 2004 is documented in this paper. The tsunami caused severe damage and claimed many victims in the coastal areas of eleven countries, bordering the Indian Ocean. Along the coast of Indian mainland, the damage was caused by the tsunami only. Largest tsunami run-up and inundation was observed along the coast of Nagapattinam district and was about 10–12 m and 3.0 km, respectively. The measured inundation data were strongly scattered in direct relationship to the morphology of the seashore and the tsunami run-up. Lowest tsunami run-up and inundation was measured along the coast of Thanjavur, Puddukkotai and Ramnathpuram districts of Tamilnadu in the Palk Strait. The presence of shadow of Sri Lanka, the interferences of direct/receded waves with the reflected waves from Sri Lanka and Maldive Islands and variation in the width of continental shelf were the main cause of large variation in tsunami run-up along the coast of Tamilnadu.     

Mapping Shoreline Variability of Two Barrier Island Segments Along the Florida Coast

Recent projections of global climate change necessitate improved methodologies that quantify shoreline variability. Updated analyses of shoreline movement provide important information that can aid and inform likely intervention policies. This paper uses the Analyzing Moving Boundaries Using R (AMBUR) technique to evaluate shoreline change trends over the time period 1856 to 2015. Special emphasis was placed on recent rates of change, during the 1994 to 2015 period of active storm conditions. Small segments, on the order of tens of kilometers, along two sandy barrier island regions on Florida’s Gulf and Atlantic coasts were chosen for this study. The overall average rate of change over the 159-year period along Little St. George Island was ??0.62?±?0.12 m/year, with approximately 65% of shoreline segments eroding and 35% advancing. During periods of storm clustering (1994–2015), retreat rates along portions of this Gulf coast barrier accelerated to ??5.49?±?1.4 m/year. Along the northern portion of Merritt Island on Florida’s Atlantic coast, the overall mean rate of change was 0.22?±?0.08 m/year, indicative of a shoreline in a state of relative dynamic equilibrium. In direct contrast with the Gulf coast shoreline segment, the majority of transects (65%) evaluated along the oceanfront of Merritt Island over the long term displayed a seaward advance. Results indicate that episodes of clustered storm activity with fairly quick return intervals generally produce dramatic morphological alteration of the coast and can delay natural beach recovery. Additionally, the data show that tidal inlet dynamics, shoreline orientation, along with engineering projects, act over a variety of spatial and temporal scales to influence shoreline evolution. Further, the trends of shoreline movement observed in this study indicate that nearshore bathymetry—the presence of shoals—wields some influence on the behavior of local segments of the shoreline.     

The Mechanism and Enrichment Mode of Tight Sand Oil Formation in the Southwest Ordos Basin

<正>The high quality source rock widely developed in the area which provides a large amount of hydrocarbon for the large area tight sand oil formation,the delta tight sand widely developed next to the source rock vertically which provides a large amount of reservoir space for the large area tight sand oil formation,and hydrocarbon generation synchronizes with reservoir rock densification process,     

新疆乌伦古湖冰滑痕特征及其形成机理

新疆乌伦古湖滨湖地区发育一种特殊的冰滑痕。冰滑痕长度可达数十米,宽度可达1~5 m。冰滑痕的形态类似于推土机推过的痕迹,其基本形态由头部、侧翼和滑动面三部分构成。头部发育丘形沙堆,侧翼发育线状沙脊,滑动面总体平整,局部发育冰融沙锥、冰融水滴坑、工具痕、冰融痕、次级滑痕等伴生沉积构造。冰滑痕是湖冰破碎后向岸漂移并在岸上滑移形成的。冰滑痕的形态和规模受湖面风力、湖冰的厚度、湖冰的动能、冰块的大小、冰块底部的光滑程度、湖岸的地形和坡度、湖滩沉积物的粒度和成分构成等多种因素的综合影响。冰滑痕的形成经历了:①湖冰破裂阶段;②浮冰向浅水区运动开始接触湖底阶段;③水下冰滑痕形成阶段;④陆上冰滑痕形成阶段;⑤冰融阶段等5个阶段。冰滑痕主要出现在乌伦古湖的水下滨湖带、冰坝堆积带、湖冰活动带和湖冰影响带等四个微相带。冰滑痕形成后接受湖泊波浪和陆地风的改造并逐渐被埋藏保存到地层记录中。乌伦古湖的冰滑痕是在特殊的气候背景和天气条件下形成的,因而既具有重要的古气候指示意义,又具有重要的古湖泊沉积环境指示意义。     

江陵凹陷八岭山—花园多层系盐和盐泥构造及其形成机制

近年来在八岭山-花园背斜构造翼部有新的油气发现,有必要对其构造性质进行再认识。通过地震解剖,认为渔洋组-新沟嘴组(K2y-Ex)有盐和盐泥两类构造叠置,可进一步划分为盐丘-盐柱多层叠置构造、盐泥丘-盐泥株(柱)构造和盐泥丘构造;盐泥构造的形成是塑化的盐泥岩顺层蠕动使每一单层变厚、多层累加增厚的叠加效应结果,盐泥沿早期断层侵入或底辟导致逆断层的产生,使断层具有下正上逆的特点;差异负荷和火山热对流为其主导动力学机制;渔洋组-沙市组下段(K2y-Es下)盐丘-盐柱产生期为中始新世,主要形成期为晚渐新世,沙市组上段-新沟嘴组(Es上-Ex)盐泥构造产生期为晚渐新世,两者均于更新世基本定型;盐泥构造翼部地层-盐泥封挡和上倾尖灭岩性-盐泥封挡圈闭为潜在的油气藏勘探类型。     

我国沿岸晚第四纪砂坝-泻湖体系的沉积模式

我国沿岸晚第四纪砂坝-泻湖体系可以分为海侵型、海退型、稳定型和局部海侵型,其理想分布模式为:海侵型分布于大陆架至冰后期最大海侵线之间的沉积层下部;海退型形成于最大海侵线至现代海岸线之间全新世沉积层上部;稳定型则出现在最大海侵线附近的狭窄地带。我国海岸线通过构造沉降带和隆起带,沉降带接受大量河流输沙,为多种砂坝-泻湖沉积体系准备了条件.隆起带沿岸沉积物来源贫乏,主要发育稳定型和局部海侵型砂坝-泻湖体系.     

Biogeographical Patterns of Marine Benthic Macroinvertebrates Along the Atlantic Coast of the Northeastern USA

The biogeography of marine benthic macroinvertebrates of US Atlantic estuaries and inshore coastal areas from Delaware Bay north to Passamaquoddy Bay was studied to compare recent data with historical biogeographic studies, define physical–chemical factors affecting species’ distributions, and provide information for calibrating benthic indices of environmental condition. Five years (2000–2004) of data from 614 non-polluted, soft-bottom stations from the National Coastal Assessment were analyzed. Multi-dimensional scaling done on Bray-Curtis similarity matrices of species’ relative abundance (547 species) suggested seven subregions: two based on salinity (oligohaline, mesohaline) and five based on latitude. Species’ distribution patterns for stations with salinities ≥18 (n = 558) were strongly influenced by latitude; Cape Cod was a clear faunal transition zone (R = 0.92, p < 0.001). Conversely, for stations with salinities <18 (n = 56), salinity was the more important factor. An ordination of abiotic variables (temperature, salinity, sediment percent silt-clay, depth) correlated well with the ordination of species’ relative abundance data (R = 0.77, p < 0.001). The first split of a multivariate regression tree was by a summer bottom temperature of 20°C at Cape Cod. Salinity and percent silt-clay led to further splits. These results support the existence of Virginian and Transhatteran biogeographic provinces. They constitute a baseline for addressing broad-scale and long-term issues such as global climate change, species invasions, and conservation planning.     

西南某泥石流发育特征及危险性分析

四川省境内某泥石流沟为大渡河左岸的一级支流,活动明显,沟口公路和村庄都曾遭受其危害.采用单沟泥石流危险性评价方法,结合遥感图像解译及现场调查,对泥石流的形成条件、类型、危险性进行了分析.根据该沟泥石流发生的特点,对泥石流的工程效应进行了分析,发现该沟是低频的中等易发泥石流,对大渡河和上下水库的影响均不大.     

Geochemistry of the Cauvery Estuary,East Coast of India

Major ion chemistry of water and elemental geochemistry of suspended and surficial sediments collected from the Cauvery Estuary were studied to understand the geochemical processes in this tropical estuarine system. Specific conductance (EC), total dissolved solids (TDS), and total suspended matter (TSM) increased conservatively with increasing chlorinity. In general, SO₄ ^2?, Na, K, Ca, and Mg showed an increasing trend while H₄SiO₄ and PO₄ ^3? showed a decreasing trend toward the sea. Additional removal mechanisms operating for these ions in the Cauvery Estuary have been identified based on observed concentrations. Factor analysis pointed out the sources contributing to the observed trends in estuarine water chemistry. POC and PON decreased toward the high chlorinity zone. TSM in the Cauvery Estuary were mostly of inorganic nature. Stable carbon isotope values showed that the carbon was equally of marine and terrestrial origin and helped to delineate the contribution of river water and seawater. The ? mean size (a logarithmic grain size scale commonly used by sedimentologists) indicated that the surficial sediments were primarily comprised of coarse and silt, whereas suspended sediments were principally silt and clay. Suspended sediments were enriched in clays compared to surficial sediments. Quartz and feldspar were abundant among detritals while chlorite, kaolinite, and montmorillonite were dominant among clays. Silicon was the most abundant element in the sediments followed by Al, Ca, Na, K, Fe, Mn, and P. Heavy metals were enriched in the suspended sediments compared to the surficial bottom sediments as follows: Fe = 3.5, Mn = 7.4, Pb = 1.1, Zn = 15.2, Cu = 7.4, and Cr = 4.0. The levels of Cd, Cr, Zn, and Fe increased up the middle reaches and then decreased toward the sea due to urban effluent and fertilizer input. Size fractionation studies indicated that the metal concentration in the finer fraction was 50% higher by mass than the coarse silt and fine silt fractions. Chemical fractionation studies showed that the abundance of metals were in the order of residual > organic/sulfide > carbonate > Fe/Mn oxide > exchangeable fractions.     

白龙江流域坪定-化马断裂带滑坡特征及其形成演化

沿坪定-化马断裂带发育数个大型或巨型滑坡。这些断裂带滑坡特点明显,成因类似,各滑坡一般发育多个次级滑坡体,滑坡岩土体由次生黄土、断裂带强风化带、断裂破碎带组成,具双层或三层结构。滑坡总体顺断裂走向下滑,历史上曾多次活动。近年来变形监测资料表明,断裂带滑坡目前处于匀速蠕变阶段,表现为蠕滑→拉裂（塑流拉裂）→次级滑坡体启动下滑的特征。它是在断裂活动、地震、降雨、人类工程活动等内外动力耦合作用下形成的,坪定-化马断裂的长期活动为滑坡形成提供了前提条件,断裂带的岩土体性质是滑坡长期活动的物质基础,而降雨、地震、坡脚开挖等是滑坡体失稳下滑的主要诱发因素。因而,有必要进一步研究断裂带滑坡在内外动力耦合作用下的成灾机理,为滑坡灾害防治预警提供科学依据。     

A model of the subsidence history of the West Coast of India

The occurrence of earthquakes all along the West Coast of India and in the Arabian Sea is explained systematically in terms of the interaction between the underthrusting Indian ocean floor and the Indian subcontinent. This north ward compression due to the repeated underthrusting of the oceanic floor has caused the formation of trenches, grabens and normal faults on the continental margin.     

东沙岛西南泥火山区的地震烃类检测

近年来通过多道地震、浅剖及海底采样调查在东沙岛西南海域发现了大量喷溢甲烷的泥火山,通过研究泥火山可能会发现含气层,具有重大的油气资源指示意义.一条多道地震剖面显示,在该海域一泥火山MV3附近存在一个具有极性反转的埋藏背斜构造,其振幅绝对值随偏移距增大而增大.为探究该背斜是否含有烃类气体,开展了速度分析、AVO反演和频率...     

航片判译茅台赤水河沿岸的滑坡

作者采用1:1.5万黑白航片判译茅台赤水沿岸滑坡共41个；其中体积大于1．5万m^3的滑坡16个，判译准确率达88％，漏、错判2个；体积大于10万m^3的滑坡12个，判译准确率达94％，漏判1个；体积大于30万m^3的滑坡6个，判译准确率达100％；判译验证不稳定蠕动体2个，体积的大于或等于5万m^3。对区内滑坡的发育规律及破坏模式作了分析研究。     

Simulation of Storm Surges Along Myanmar Coast Using a Location Specific Numerical Model

Coastal flooding induced by storm surges associated with tropical cyclones is one of the greatest natural hazards sometimes even surpassing earthquakes. Although the frequency of tropical cyclones in the Indian seas is not high, the coastal region of India, Bangladesh and Myanmar suffer most in terms of life and property caused by the surges. Therefore, a location-specific storm surge prediction model for the coastal regions of Myanmar has been developed to carry out simulations of the 1975 Pathein, 1982 Gwa, 1992 Sandoway and 1994 Sittwe cyclones. The analysis area of the model covers from 8° N to 23° N and 90° E to 100° E. A uniform grid distance of about 9 km is taken along latitudinal and longitudinal directions. The coastal boundaries in the model are represented by orthogonal straight line segments. Using this model, numerical experiments are performed to simulate the storm surge heights associated with past severe cyclonic storms which struck the coastal regions of Myanmar. The model results are in agreement with the limited available surge estimates and observations.