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31.
A hydrological–lithostratigraphical model was developed for assessment of transmission losses and groundwater recharge from runoff events in arid water courses where hydrological and meteorological records are incomplete. Water balance equations were established for reaches between hydrometric stations. Because rainfall and tributary flow data are scarce, lateral inflow, which is an essential component of the water balance equation, could not be estimated directly. The solution was obtained by developing a method which includes a hydrological–lithostratigraphical analogy. This is based on the following assumptions: (a) runoff resulting from a given rainfall event is related to the watershed surface lithology; (b) for a given event, the spatial distribution of runoff reflects the distribution of rainfall: and (c) transmission losses are uniquely related to the total inflow to the reach. The latter relationship, called the loss function, and the water balance equation comprise a model which simultaneously assesses lateral inflow and transmission losses for runoff events recorded at the terminal stations. The model was applied to three reaches of the arid Nahal Tsin in Israel. In this case study, the transmission losses were of the same order of magnitude as the flow at the major hydrometric stations. The losses were subdivided into channel moistening, which subsequently evaporates, and deep percolation, which recharges groundwater. For large runoff events, evaporation was substantially smaller than the losses. The mean annual recharge of groundwater from runoff events in the Tsin watershed was 4·1×106 m3, while the mean annual flow volume at the major stations ranged from 0·6 to 1·5×106 m3. Once in 100 years, the annual recharge may be seven times higher than the mean annual value, but the recharge during most years is very small. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   
32.
The Dead Sea is an extensional basin developing along a transform fault plate boundary. It is also a terminal salt basin. Without knowledge of precise stratigraphy, it is difficult to differentiate between the role of plate and salt tectonics on sedimentary accumulation and deformation patterns. While the environmental conditions responsible for sediment supply are reasonably constrained by previous studies on the lake margins, the current study focuses on deciphering the detailed stratigraphy across the entire northern Dead Sea basin as well as syn and post-depositional processes. The sedimentary architecture of the late Quaternary lacustrine succession was examined by integrating 851 km of seismic reflection data from three surveys with gamma ray and velocity logs and the stratigraphic division from an ICDP borehole cored in 2010. This allowed seismic interpretation to be anchored in time across the entire basin. Key surfaces were mapped based on borehole lithology and a newly constructed synthetic seismogram. Average interval velocities were used to calculate isopach maps and spatial and temporal sedimentation rates. Results show that the Amora Formation was deposited in a pre-existing graben bounded by two N-S trending longitudinal faults. Both faults remained active during deposition of the late Pleistocene Samra and Lisan Formations—the eastern fault continued to bound the basin while the western fault remained blind. On-going plate motion introduced a third longitudinal fault, increasing accommodation space westwards from the onset of deposition of the Samra Formation. During accumulation of these two formations, sedimentation rates were uniform over the lake and similar. High lake levels caused an increase in hydrostatic pressure. This led to salt withdrawal, which flowed to the south and southwest causing increased uplift of the Lisan and En Gedi diapirs and the formation of localized salt rim synclines. This induced local seismicity and slumping, resulting in an increased thickness of the Lisan succession within the lake relative to its margins. Sedimentation rates of the Holocene Ze'elim Fm were 4–5 times higher than before. The analysis presented here resolves central questions of spatial extent and timing of lithology, deposition rates and their variability across the basin, timing of faulting at and below the lake floor, and timing and extent of salt and plate tectonic phases and their effect on syn and post-depositional processes. Plate tectonics dictated the structure of the basin, while salt tectonics and sediment accumulation were primarily responsible for its fill architecture during the timeframe examined here.  相似文献   
33.
Wind tunnel and field calibration of five aeolian sand traps   总被引:4,自引:0,他引:4  
The efficiency of five aeolian sand samplers was tested via wind tunnel experiments and field measurements. The samplers were: the Big Spring Number Eight (BSNE) sampler, the Modified Wilson and Cooke (MWAC) sampler, the Suspended Sediment Trap (SUSTRA), the Pollet catcher (POLCA), and the saltiphone. In the wind tunnel, the samplers were calibrated against an isokinetic sampler (a modified Sartorius SM 16711 sampler with adjustable flow rate), and this for three sand types (median diameter: 132, 194 and 287 μm) and five wind speeds (ranging from 6.6 to 14.4 m s−1). In the field, seven calibration tests of two weeks each were conducted. The absolute efficiencies of the BSNE, MWAC and POLCA are more or less comparable and vary between 70% and 120%, depending on sediment size and wind speed. For the SUSTRA, the efficiency is somewhat lower for fine sands and for wind speeds above 11 m s−1. Finally, the saltiphone can accurately detect the periods of saltation transport, but in its current version, the instrument is not accurate when measuring the absolute saltation flux. The most recommendable sampler in the test is the MWAC, not only because of its high efficiency, but also because its efficiency is independent of wind speed.  相似文献   
34.
TOPO-EUROPE: The geoscience of coupled deep Earth-surface processes   总被引:2,自引:0,他引:2  
TOPO-EUROPE addresses the 4-D topographic evolution of the orogens and intra-plate regions of Europe through a multidisciplinary approach linking geology, geophysics, geodesy and geotechnology. TOPO-EUROPE integrates monitoring, imaging, reconstruction and modelling of the interplay between processes controlling continental topography and related natural hazards. Until now, research on neotectonics and related topography development of orogens and intra-plate regions has received little attention. TOPO-EUROPE initiates a number of novel studies on the quantification of rates of vertical motions, related tectonically controlled river evolution and land subsidence in carefully selected natural laboratories in Europe. From orogen through platform to continental margin, these natural laboratories include the Alps/Carpathians–Pannonian Basin System, the West and Central European Platform, the Apennines–Aegean–Anatolian region, the Iberian Peninsula, the Scandinavian Continental Margin, the East-European Platform, and the Caucasus–Levant area. TOPO-EUROPE integrates European research facilities and know-how essential to advance the understanding of the role of topography in Environmental Earth System Dynamics. The principal objective of the network is twofold. Namely, to integrate national research programs into a common European network and, furthermore, to integrate activities among TOPO-EUROPE institutes and participants. Key objectives are to provide an interdisciplinary forum to share knowledge and information in the field of the neotectonic and topographic evolution of Europe, to promote and encourage multidisciplinary research on a truly European scale, to increase mobility of scientists and to train young scientists. This paper provides an overview of the state-of-the-art of continental topography research, and of the challenges to TOPO-EUROPE researchers in the targeted natural laboratories.  相似文献   
35.
New multichannel seismic and bathymetric data are presented, which clarify the Plio-Quaternary evolution of the northern Gulf of Aqaba (Elat) and the Dead Sea Transform (DST). The seismic data reveal two main seismic sequences, a lower (pretectonic) and an upper (syntectonic) unit, separated by a prominent unconformity. These units are each linked to a distinct tectonic phase in the history of the DST. Parallel horizons and an undisturbed internal structure point to a tectonic quite time or pure strike-slip without extension or compression during the first (pretectonic) phase. The second (syntectonic) phase, which begins in the early Pliocene, is characterized by a major change in the activity of the DST. The pretectonic sedimentary unit subsided and, consequently, dips southward with a supplementary inclination to the east. The coeval sedimentation of the syntectonic unit is recorded by the divergent reflection pattern and onlap terminations on the unconformity. The apparent fault system seems to be rearranged in the second phase. The stepover of the main strand of the DST from the eastern side of the Elat Deep to the western side of the northern Gulf of Aqaba was mapped in detail for the first time. The very smooth shape of the stepover and the apparent lack of extensional tectonics do not fit with the classical pull-apart basin model for the Elat Deep and point to a decoupling of the crystalline basement from the sedimentary overburden. Comparisons of the new geophysical findings with analog models support this assertion.  相似文献   
36.
南中国海成因:右行拉分作用与左行转换挤压作用交替   总被引:6,自引:0,他引:6  
总结分析了南中国海各次级盆地及其周缘有关盆地的裂谷作用序列 ,认为它们的裂谷作用序列是相似的 ,虽然存在局部差异。古近纪 (—早中新世 )和新近纪分别为一级裂谷阶段和后裂谷阶段 ,并可进一步划分次一级裂谷和后裂谷阶段。南中国海总体几何学特征及其次级盆地和周缘盆地的几何学特征表明 ,它们的裂谷作用是以近南北向主断裂为主剪切的右行拉分作用。在右行拉分过程中 ,东越南断裂的南延 (翼他陆架部分 )可能没有发生巨大脆性平移而表现为巨大的右行韧性牵引 ;印支—苏门答腊地块是被东越南断裂、东安达曼海断裂、红河断裂和苏门答腊断裂等四条断裂围限的呈菱形的右行走滑双重构造。深海盆的洋壳在许多方面与概念化大洋洋壳不同 ,相互矛盾的各种磁异常条带年龄并不可信。它的洋壳是右行拉分作用形成的洋壳。它们的后裂谷作用是以近南北向主断裂为主剪切的左行转换挤压反转变形为特征。联系到裂谷作用序列 ,南中国海成因具有右行拉分作用、裂谷作用和左行转换挤压作用交替出现的特征 ,表现了具有转换性质的“开”与“合”的更迭  相似文献   
37.
Several seamounts in the Ionian Sea, the largest unit in the eastern Mediterranean, have magnetic anomalies. The magnetization vectors of six of these seamounts have been calculated. These paleomagnetic data suggest that the Ionian Sea is composed of several crustal units which came to their present location from different directions. This implies that there has been relative motion in the past between various land masses around the Ionian Sea. The possibility that the Ionian Sea is composed of several crustal units is supported by observations of the magnetic field over the area which is of different character in the north and south. The major limitation in applying the paleomagnetic data into an evolutionary scheme is that all the seamounts in the Ionian Sea as well as its crust are undated.  相似文献   
38.
Mapping the floor of the Sea of Galilee (Lake Kinneret) with a shallow seismic system of 3.5 kHz resulted in interesting data that were not obtained previously with standard single-channel seismic systems. Over most of the lake acoustic penetration is not possible, probably because of the high gas content in the top sedimentary sequence. However, in a few areas, excellent penetration of about 20 m was achieved. One area is a terrace in the southern part of the lake, south of a small bathymetric escarpment at depths of 13–21 m along Israel latitudinal Grid 238. It is unclear whether the existence of gas in the sediment or other parameters are responsible for the marked difference in acoustic penetration on both sides of the scarp.Another area with acoustic penetration is in the vicinity of hot and salty submarine springs. Although there is no difference in the composition of the upper sedimentary layers between these areas and neighbouring areas, there is a marked difference in the acoustic penetration. The contact between areas with acoustic penetration to areas without acoustic penetration is very sharp. The craters of the submarine springs are usually located on the borders of the areas with acoustic penetration or even at some distance away from them. It is possible that the activity of the hot and salty submarine springs controls the acoustic penetration. However, determination of the exact mechanism for the existence of the zones of acoustic penetration must await further studies of the sediments, especially for measurements of various parameters that control the seismic response of the rock.Another discovery made with the shallow seismic profiles is the existence of some bathymetric irregularities on the floor of the Sea of Galilee. In view of the high sedimentation rate in the lake, which tends to smooth the floor, a bathymetric irregularity such as a linear bathymetric step could be a surface expression of an active fault.  相似文献   
39.
We study the azimuthally dependent hyperbolic moveout approximation for small angles (or offsets) for quasi‐compressional, quasi‐shear, and converted waves in one‐dimensional multi‐layer orthorhombic media. The vertical orthorhombic axis is the same for all layers, but the azimuthal orientation of the horizontal orthorhombic axes at each layer may be different. By starting with the known equation for normal moveout velocity with respect to the surface‐offset azimuth and applying our derived relationship between the surface‐offset azimuth and phase‐velocity azimuth, we obtain the normal moveout velocity versus the phase‐velocity azimuth. As the surface offset/azimuth moveout dependence is required for analysing azimuthally dependent moveout parameters directly from time‐domain rich azimuth gathers, our phase angle/azimuth formulas are required for analysing azimuthally dependent residual moveout along the migrated local‐angle‐domain common image gathers. The angle and azimuth parameters of the local‐angle‐domain gathers represent the opening angle between the incidence and reflection slowness vectors and the azimuth of the phase velocity ψphs at the image points in the specular direction. Our derivation of the effective velocity parameters for a multi‐layer structure is based on the fact that, for a one‐dimensional model assumption, the horizontal slowness and the azimuth of the phase velocity ψphs remain constant along the entire ray (wave) path. We introduce a special set of auxiliary parameters that allow us to establish equivalent effective model parameters in a simple summation manner. We then transform this set of parameters into three widely used effective parameters: fast and slow normal moveout velocities and azimuth of the slow one. For completeness, we show that these three effective normal moveout velocity parameters can be equivalently obtained in both surface‐offset azimuth and phase‐velocity azimuth domains.  相似文献   
40.
雪藻高密度连续培养中生物量和花生四烯酸的高产率   总被引:7,自引:1,他引:7  
以 1 .4cm和 2 .8cm光径的平板光生物反应器 ,恒定高光强 [2 4 0 0 μE/(m2 ·s) ],通气、无菌高密度连续培养雪地绿藻 (简称雪藻 )。连续采收并补充等量新鲜培养液 ,当藻体生物量(以去灰分干重表示 ,AFDW)达恒态时 ,研究雪藻比生长速率 (SGR)、藻体的生物产量、总脂肪酸 (TFA)和花生四烯酸 (AA)产率。结果表明 ,尽管随着比生长速率增加 ,雪藻高密度连续培养体系的AA/TFA、TFA/AFDW和AA/AFDW三个指标有不同程度的降低 ,但生物产量、总脂肪酸及其花生四烯酸产出都相当高。 2 .8cm光径的平板光生物反应器中 ,雪藻SGR为0 .2d- 1 时 ,每平方米光照面积日获 35 .3gAFDW的高产量 ;SGR 0 .1 35d- 1 时 ,TFA产率最大 ,为7.0g/(m2 ·d) ,此时AA产率也最高 ,达 2 .6g/(m2 ·d)。尽管 1 .4cm光径的反应器的培养体积比前者下降了 5 0 % ,但细胞浓度明显提高 ,单位光照面积的AFDW和TFA最大日产率只下降了37.3%和 1 0 % ,分别为 2 2 .1和 6.3g/(m2 ·d) ,而AA的最大日产率也是 2 .6g/(m2 ·d)。结果还表明 ,氮或磷营养亏缺能明显提高雪藻AA含量的各项指标 ,同时高光强也有利于雪藻累积AA。  相似文献   
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