Paleoenvironmental history of submerged ruins on the Northern Euboean gulf coastal plain,central Greece     

Tina M. Niemi 《Geoarchaeology》1990,5(4):323-347

Hewn blocks from submerged ruins associated with the name Thronion are exposed during low, low tide along the northeastern shoreline of the fan delta which separates the Gulf of Euboea from the Maliakos Gulf, central Greece. Although the date of these ruins is not known, their submergence indicates that they predate the most recent marine transgression. Late Holocene sediments of the coastal plain adjacent to the ruins were studied using 34 auger cores drilled along two 1.3 and 1.1 km shore-normal sections. Cores were described in the field and sampled for sedimentologic and microfossil analyses. These analyses show that late Holocene transgressive marine and strandline units interfinger inland with deposits of a brackish water embayment. Subsequent progradation of the shoreline is marked by overlying slightly brackish to freshwater marsh sediments. A soil horizon developed on these marsh sediments defines a period of aerial exposure and land stability. Late Roman to Byzantine sherds (ca. 4th-13th Century A.D.) within the buried soil and a high phosphate content suggest that this soil developed in association with human habitation. the buried soil may be the surface on which the now-submerged ruins were built. the deposits below the buried soil indicate that prior to the period of soil formation, most of this area was under water and the paleoshoreline was landward of its present position. the ruins were later covered by lake or marsh deposits radiocarbon dated as 1400 A.D. the depth of the dated wood samples, 2.5–3.0 meters below the surface, indicates rapid sediment accumulation (ca. 40–55 cm/100 yrs) over the past 550 years. A small exposure of the ca. 1400 A.D. marsh silt and overlying post-1950 land fill near the ruins is the result of post-1400 A.D. erosion and recession of the shoreline. the lower pre-occupational and post-1400 A.D. transgressions were caused by a combination of eustatic sea level rise, tectonic subsidence, and fluctuations of sediment supply to this portion of the Kenourion fan delta.  相似文献   

Multifocus moveout revisited: derivations and alternative expressions     

Martin Tygel  Lúcio T. Santos  Jrg Schleicher 《Journal of Applied Geophysics》1999,42(3-4)

The multifocus moveout of Gelchinsky et al. [Gelchinsky, B., Berkovitch, A., Keydar, S., 1997. Multifocusing homeomorphic imaging: Parts I and II: Course Notes, Special Course on Homeomorphic Imaging. Seeheim, Germany] is a powerful tool for stacking multicoverage data in arbitrary configurations. Based on general ray theoretical assumptions and on attractively simple geometrical considerations, the multifocus moveout is designed to express the traveltimes of neighbouring rays arbitrarily located around a fixed central, primary reflected or even diffracted, ray. In this work, the basic derivations and results concerning the multifocus approach are reviewed. A higher-order multifocus moveout expression that generalizes the corresponding one of Gelchinsky is obtained from slight modifications of the original derivation. An alternative form of the obtained multifocus expression that is best suited for numerical implementation is also provided. By means of a simple numerical experiment, we also comment on the accuracy of the multifocus traveltime approximations.  相似文献   

Monitoring the temporal development of natural hazard risks as a basis indicator for climate change adaptation     

A. Zischg  S. Schober  N. Sereinig  M. Rauter  C. Seymann  F. Goldschmidt  R. Bäk  E. Schleicher 《Natural Hazards》2013,67(3):1045-1058

The potential effects of climatic changes on natural risks are widely discussed. But the formulation of strategies for adapting risk management practice to climate changes requires knowledge of the related risks for people and economic values. The main goals of this work were (1) the development of a method for analysing and comparing risks induced by different natural hazard types, (2) highlighting the most relevant natural hazard processes and related damages, (3) the development of an information system for the monitoring of the temporal development of natural hazard risk and (4) the visualisation of the resulting information for the wider public. A comparative exposure analysis provides the basis for pointing out the hot spots of natural hazard risks in the province of Carinthia, Austria. An analysis of flood risks in all municipalities provides the basis for setting the priorities in the planning of flood protection measures. The methods form the basis for a monitoring system that periodically observes the temporal development of natural hazard risks. This makes it possible firstly to identify situations in which natural hazard risks are rising and secondly to differentiate between the most relevant factors responsible for the increasing risks. The factors that most influence the natural risks could be made evident and eventual climate signals could be pointed out. Only with this information can the discussion about potential increases in natural risks due to climate change be separated from other influencing factors and be made at an objective level.  相似文献   

On the existence of small comets and their interactions with planets     

J. C. Brandt  M. F. A'Hearn  C. E. Randall  D. G. Schleicher  E. M. Shoemaker  A. I. F. Stewart 《Earth, Moon, and Planets》1996,72(1-3):243-249

Arguments are presented for a substantial, unexplored population of comets with radii less than 1 km. Known examples confirm this population and extrapolation of any plausible size-distribution function indicates large numbers. However, their accurate numbers, orbital characteristics, and physical properties are unknown. Thus, even though the small comets may be the most frequent cometary bodies impacting the planets, a quantitative evaluation is not currently possible. We advocate an optimized, dedicated search program to characterize this population.  相似文献   

Ground water sustenance of Nebraska's unique Sand Hills peatland fen ecosystems   总被引：1，自引：0，他引：1  

Harvey FE  Swinehart JB  Kurtz TM 《Ground water》2007,45(2):218-234

Many ecosystems have evolved under conditions where ground water is critical to the survival of the unique species contained therein. One example is Nebraska's Sand Hills fens. The Sand Hills region comprises lush interdunal valleys amid grass-stabilized dunes. One valley type, fens, are ground water-fed wetlands that have several meters of saturated, organic soils comprising peat formed under anaerobic conditions where plant growth exceeds decomposition. These fens support unique flora and fauna such as rush aster and northern redbelly dace that are typically found in more boreal regions of North America. This study characterized the hydrogeology of a representative fen in the Jumbo Valley to explore how these relict species survive in a hot, arid climate and to understand present and historical relations between ground water and these unique ecosystems. Results indicate that ground water's present role in sustaining the fens is twofold: (1) wetland plant transpiration of shallow ground water across the valley creates a cooler, humid microclimate that sustains the fens in the region's hot, arid climate and (2) the large volume of ground water pumped through the fens by plant transpiration transports necessary nutrients to the root zone. Results suggest that, in the past, in addition to its sustaining role, ground water also played a vital role in fen development and in fen preservation through nearly 15,000 years of existence. Thus, as with like ecosystems, the role of ground water must be considered in future Sand Hills fen protection, restoration, and management.  相似文献   

Understanding different perspectives on the preservation of community and heritage buildings in the Wellington Region,New Zealand     

Tatiana Goded  Andrew Beaupre  Michael DeMarco  Tina Dutra  Andro Gogichaishvili  Daniel Haley  Alex Hyman  Nicholas Kepka Calvetti  John Potter  Maureen Coomer  Kim Wright  Andrew King 《Natural Hazards》2017,87(1):185-212

The Canterbury (New Zealand) earthquake sequence of 2010–2012 caused unexpectedly extreme levels of damage and disruption, being an unparalleled event in New Zealand in terms of the damage extent. Christchurch’s heritage buildings were seriously damaged during these events, with churches especially affected in 22 February 2011 M _w 6.2 earthquake. During this earthquake, a total of 84% of the heritage unreinforced stone and 81% of the clay brick masonry churches in the Canterbury region were either considered unsafe (receiving red placards) or with restricted access (yellow placards). Following the earthquakes, authorities across New Zealand are reassessing the capacity of older buildings to resist earthquakes. Current legislation requires that a building judged as earthquake prone either be strengthened by retrofitting or be demolished within a legislated number of years. Many building owners are facing the problems of owning earthquake-prone buildings and lacking the funding to upgrade. This affects both community and heritage buildings, resulting in the likely abandonment or demolition of some buildings. To address the problem of the balance between life safety and preservation in the Wellington Region, this project gathered and compared the perspectives of the general public, church communities, heritage specialists, professional engineers, and local authorities to assist in balancing the interests of these stakeholders. As a result of the findings, several recommendations have been provided that include standardizing structural assessment processes and training, feasibility of additional public funding to upgrade buildings, new signage to increase public awareness of earthquake-prone buildings, and regular communication among stakeholders to understand and resolve differences.  相似文献   

北京市区大气气溶胶PM_(2.5)污染特征及颗粒物溯源与追踪分析   总被引：2，自引：0，他引：2  

陈媛  岑况  S.Norra  N.Schleicher  于扬 《现代地质》2010,24(2)

重点研究北京市区大气气溶胶中细粒子的污染特征,分析其质量浓度变化与各种自然影响因素的相关性,利用美国空气资源实验室的HYSPLIT模型对颗粒物进行溯源和追踪分析,为正确认识北京市区大气PM2.5污染状况提供重要基础数据,为以后的对比研究和制定相应的污染控制措施提供参考依据。结果表明:(1)PM2.5质量浓度的最高值出现在4月的沙尘天气期间中,由于受沙尘天气影响春季的PM2.5质量浓度居四季之首;(2)温度、相对湿度、风速、降水和气压等是影响PM2.5污染程度的重要因素,不同季节里、不同温度范围内,PM2.5的质量浓度与温度表现出不同的但都强烈的相关性;沙尘天气里风速低于某一阈值(10 km/h)时,PM2.5的质量浓度与风速呈负相关,反之则呈正相关;(3)沙尘主要来自西北、西北偏北或偏西方向,境外源有俄罗斯、蒙古和哈萨克斯坦等国的戈壁或沙漠地区,境内主要来自西部戈壁沙漠地带以及内蒙古的大范围干旱和半干旱地区,到达北京后继续向东或东南、东北方向运移,进入朝鲜、韩国、日本和俄罗斯等邻国。  相似文献   

Reliability analysis of the bearing failure problem considering uncertain stochastic parameters     

Thomas Most  Tina Knabe 《Computers and Geotechnics》2010

The consideration of uncertainties plays an increasing role in the design of geotechnical structures. An important procedure in the uncertainty analysis is the reliability assessment whereby the required statistical quantities and distributions are assumed to be known exactly. Due to small sample observations and missing information this is not the case in practical applications and uncertainties in the stochastic parameters themselves have to be considered. In our study we estimate the parameter variation of soil properties by statistical procedures and perform an extended reliability analysis of a shallow foundation considering these uncertainties. We propose a novel approach based on a Taylor series expansion which enables the estimation of the failure probability variation very efficiently.  相似文献   

Evidence for ground-rupturing earthquakes on the Northern Wadi Araba fault at the archaeological site of Qasr Tilah, Dead Sea Transform fault system, Jordan     

Jeremy M. Haynes  Tina M. Niemi  Mohammad Atallah 《Journal of Seismology》2006,10(4):415-430

The archaeological site of Qasr Tilah, in the Wadi Araba, Jordan is located on the northern Wadi Araba fault segment of the Dead Sea Transform. The site contains a Roman-period fort, a late Byzantine–Early Umayyad birkeh (water reservoir) and aqueduct, and agricultural fields. The birkeh and aqueduct are left-laterally offset by coseismic slip across the northern Wadi Araba fault. Using paleoseismic and archaeological evidence collected from a trench excavated across the fault zone, we identified evidence for four ground-rupturing earthquakes. Radiocarbon dating from key stratigraphic horizons and relative dating using potsherds constrains the dates of the four earthquakes from the sixth to the nineteenth centuries. Individual earthquakes were dated to the seventh, ninth and eleventh centuries. The fault strand that slipped during the most recent event (MRE) extends to just below the modern ground surface and juxtaposes alluvial-fan sediments that lack in datable material with the modern ground surface, thus preventing us from dating the MRE except to constrain the event to post-eleventh century. These data suggest that the historical earthquakes of 634 or 659/660, 873, 1068, and 1546 probably ruptured this fault segment.  相似文献   

Episodic mineralization of hydrothermal illite in the Soultz-sous-Forêts granite (Upper Rhine Graben, France)     

Anja M. Schleicher  Laurence N. Warr  Bernd Kober  Emmanuel Laverret  Norbert Clauer 《Contributions to Mineralogy and Petrology》2006,152(3):349-364

Episodic and localized illite mineralization is documented in the hydrothermally altered Soultz-sous-Forêts granite (Upper Rhine Graben, France). Separated grain-size fractions of altered granite and argillite vein samples contain mixtures of 2M₁ and 1M trans-vacant illite varieties. The platy pseudohexagonal 2M₁ illite phases dominate the vein fillings, whereas the 1M illite occurs largely as a fibrous pore-filling variety, which is particularly abundant in the granite matrix. Multiple phases of fluid injections into the granite body have resulted in different illite assemblages, each sample containing a mixture of polytype generations formed during different crystal growth events. On the basis of mineralogical and K–Ar isotopic constraints, the ages of these vein-mineralizing events are determined by plotting the K–Ar values of the various grain-size fractions against polytype abundance and the fitted volume-weighted crystallite thickness distributions. The results suggest a Permian age for the formation of the studied argillite veins, characterized by successive injections of hydrothermal fluids. Secondary episodes of illite crystallization occurred during Jurassic and Cretaceous (or even younger times) in both the veins and the granite matrix. There are indications that the polytype structure and composition of illite were strongly influenced by variations in fluid chemistry and the degree of fluid–rock interaction as the granite was progressively sealed during post-Variscan, episodic hydrothermal activity.  相似文献