wave and flow response to an artificial surf reef laboratory measurements waves and currents are essential elements in the design of an artificial surfing reef asr asrs are primarily designed to optimize the surfing conditions i e increase the surfability of the incoming waves possibly in combination with the shoreline protection from erosion the currents generated by waves breaking on the asr play an important role in the surfability through the wave current interaction wci depending on the design the wci may negatively affect the surfability by causing the waves to break prematurely due to the current induced wave steepening in addition wave breaking tends to become more irregular due to the temporal variability of the underlying currents to mitigate the negative effects of wave breaking induced currents on the surfability three asr layouts are examined through detailed laboratory experiments the layouts differ in the alongshore separation distance between two symmetrical reef sides the ensuing flow circulations are examined in detail with both in situ current meters and video observations of surface drifters this is done for regular incident waves bichromatic incident waves and irregular incident waves all with equal energy a data analysis shows that for a given layout the mean flow patterns for regular bichromatic and irregular waves are qualitatively similar with oblique rip currents exiting at either side of the reef and strong flow circulations onshore of the gap in between the two reef sides increasing the separation distance leads to a significant reduction of the obliquely exiting rip currents at the outer sides of the reef but an increase in the flow circulation onshore of the gap this has a positive effect on the surfability by reducing the negative effects associated with the wci on the wave breaking thus providing longer rides

shoreline response to submerged structures a review abstract submerged coastal structures are widely perceived to be capable of providing beach protection without the adverse impacts including loss of beach amenity and aesthetic considerations often associated with more conventional structures such as revetments and groynes in addition there is growing interest in the concept that the layout and cross section of submerged coastal protection structures can be optimised to also enhance local surfing conditions however as submerged structures have only rarely been adopted for beach protection the shoreline response to these structures is not well understood at present therefore this review of the available published literature was undertaken with the aim of investigating the environmental and structural parameters governing shoreline response to submerged structures gleaned from the results of field laboratory and numerical studies undertaken to date the review reveals that contrary to expectations a majority of the submerged structures constructed to date have resulted in shoreline erosion in their lee furthermore the key environmental and structural parameters governing the mode i e erosion or accretion and the magnitude i e size of salient of shoreline response to submerged structures are yet to be identified although submerged coastal structures offer the potential for low aesthetic impact incorporating multi function design until the response of the adjacent shoreline to submerged structures is better resolved their use is likely to remain relatively limited

on the applicability of empirical formulas for natural salients to sardinia italy beaches abstract the paper presents an empirical analysis of the shoreline response to natural obstacles either submerged reefs and islands distributed along the sardinian italy coastlines exposed to different wave and wind climates the study focuses on salient morphological features whose geometrical properties have been acquired through an extensive field and image derived survey the current analysis has been used to propose geometric predictive formulas for stable salients that overcome some limitations affecting previous works a semi probabilistic method based on well known rate of change statistics is also presented to verify the equilibrium condition of salients analysis results suggest that site specific wave transmission in the lee of submerged reefs requires a range of salient limiting b s ratio values broader than those presented in the literature b being the length of the obstacle and s the distance between undisturbed beach and obstacle the b s ratio has been proved to be the main dimensionless variable for predicting salient amplitude and basal width in particular the proposed predictive equation suggests an erosion condition for some combinations of b sand the 8 times rule appears not to be applicable to natural salients

changes in streamflow components following logging and regeneration in the southern forest of western australia two small experimental catchments were established in the south west of western australia to study the effects of logging and subsequent regeneration on the mechanism of streamflow generation following a six year pre treatment calibration period 1976 1981 one catchment march road was logged and reforested in 1982 and the other april road south remained as a control logging resulted in an increase in groundwater levels and subsequently groundwater discharge area the deep permanent groundwater levels in the valley and upslope areas rose until 1986 and then began to decline the maximum rise was 5 m in the upslope areas the duration of shallow intermittent groundwater system perched on underlying clay was extended from 2 3 months in winter before logging to 5 6 months after logging the shallow groundwater level rose in the valley and began to discharge at the ground surface in 1986 logging resulted in an increase in streamflow the maximum increase 18 of annual rainfall was in 1983 one year after logging the increase in streamflow was due to a substantial decrease in interception and evapotranspiration increased recharge to the shallow groundwater system decreased soil moisture deficit and consequently an increase in throughflow the increase in base flow was about twice that of quick flow the changes in streamflow and its components in the subsequent years were closely related to the groundwater discharge area most of the quick flow was generated as saturation excess overland flow from the groundwater discharge area in the valley the expansion of the groundwater discharge area increased soil moisture content higher groundwater level and the presence of the shallow groundwater system for the extended periods were responsible for the process of streamflow generation

palynological evidence for the quaternary rates of accumulation along the dead sea rift and structural implications abstract continuous pollen diagrams obtained for five deep boreholes penetrating the thick quaternary sector of the dead sea rift fill have been correlated with the oceanic oxygen isotope records one of these was radiometrically dated by interfingering volcanics the quaternary sequence was subdivided into ten palynozones and the rates of accumulation are calculated for each in the three sub basins of the dead sea rift rates of accumulation in increments of 100 ky are calculated for two boreholes notera 3 in the north and amazyahu 1 in the south based on more detailed data obtained for these sequences the rates of accumulation indicate considerable subsidence of the southern dead sea at 2 3 1 8 m y during the last 250 ky the northern dead sea in the last 20 ky the central jordan valley at 2 2 2 0 m y and the hula at 1 5 1 25 m y and during the last 70 ky the regions separating these sub basins show very little accumulation and subsidence through the quaternary it is evident that the structural development of the dead sea rift sub basins is not synchronous

microearthquake activity in the dead sea region summary small earthquakes in the dead sea depression part of the jordan valley dead sea rift were recorded and analysed with 117 identified events of 0 5 ml 4 2 the microseismicity recorded by a local portable network during a period of about 20 months shows a normal rate of seismicity for the region with b values around 0 8 the recorded seismicity is mainly confined to the basin and its boundaries in the southern part of the dead sea basin we found a tendency to clustering which is clearly demonstrated in very similar seismograms of several events recorded at the same station two clusters on the eastern fault are separated by an area with no seismicity for at least 5 yr relative location of events in one of the clusters exhibits a clear north south lineament two active north south left lateral strike slip faults along the east and west boundaries of the southern section of the dead sea basin are distinguished and confirmed by using composite focal mechanism solutions in four out of more than 60 events we found normal faulting where one has a ml 4 1 for 34 events with 1 6 ml 4 2 we found seismic moment estimates m0 of 1 2 1019 m0 2 3 times 1022 dyne cm and brune stress drop estimates s between 0 6 and 92 bars for earthquakes of m0 smaller than about 5 times 1021 dyne cm we found only small variations in corner frequency f0 resulting in decreasing s with decreasing m0 this breakdown of the scaling relation for small earthquakes suggests an fmax slightly lower than 10 hz for the dead sea region the fmax is confirmed by available accelerometer data

regulation of nearshore circulation by submerged breakwater for shore protection a submerged breakwater induces a circulation with onshore currents over the structure and offshore currents through gaps resulting in sediment loss to the offshore region a new submerged breakwater with inclined multiple blades is tested by laboratory experiments and numerical simulations this breakwater can generate offshore currents over the structure and onshore currents through gaps suggesting onshore sediment supply

beach response to breakwater layouts of drainage pipe outlets during beach nourishment abstract managing drainage pipes to optimize beach nourishment is a complex problem in this study the salient landform is explored as a feasible plan that considers beach nourishment and breakwater geometry of the drainage pipe outlets the xbeach model was used to establish an idealized model for analyzing the beach response to three typical breakwater layouts straight landward convex and seaward convex the seaward convex breakwater layout was found to be the most effective option because it can accumulate the largest volume of sediment behind the structure the seaward convex layout was also used to analyze the beach response to incident wave angles ranging from 0 normal to the shore to 60 as the incident wave angle increases the volume of sand salient accumulated in the leeward of the breakwater and the flow speed in the cross show direction gradually decrease while the wave height and the flow speed in the along shore direction gradually increase however there is a critical angle of approximately 50 at which opposite trends of changes in bed level wave height and eulerian flow occur

some theoretical predictions on the relationships among spreading rate mantle temperature and crustal thickness a series of numerical experiments on mantle flow and melting predict a positive relation between mantle temperature and crustal thickness the models also demonstrate that crust formed at slow spreading rates is more sensitive to variations in mantle temperature than crust formed at fast rates so that the range of calculated thicknesses is much greater for crust formed at slower rates an instantaneous mantle temperature increase results in a transient pulse of melt production that is also more pronounced at slower spreading rates the predicted behavior is caused by the interplay between mantle flow driven by plate separation and that driven by thermal compositional and melt related buoyancy a temperature increase results in a decrease in mantle viscosity and an increase in the depth at which melting begins a lower viscosity leads to stronger buoyancy driven flow that carries more mantle to shallow depths below the ridge thermal buoyancy effects which may result in cooling and mixing of depleted and undepleted material under the ridge appear to be of greater importance at slower spreading rates the steady state results are broadly consistent with global compilations of oceanic crustal thickness that show larger variations in crustal thickness at slower spreading rates than at faster rates thicknesses estimated from seismic refraction data from crust formed within a single segment of the mid atlantic ridge but at different spreading rates 1 0 to 1 9 cm yr are consistent with but do not prove the model results the transient pulse of melt production associated with a rapid increase in mantle temperature might occur when a ridge becomes proximal to a hot spot

hydrogeochemical processes in an arid region of europe almeria se spain abstract in the lower andarax river basin 3 aquifer units have been defined namely the carbonate aquifer the deep aquifer and the detrital aquifer which between them contain a wide variety of water types identification of hydrogeochemical processes has been performed by studying a series of ionic ratios comprising the principal constituents together with b and li cl vs so4 cl vs mg cl vs li b vs li among the processes detected the circulation of groundwaters with high concentrations of so4 was found to have significant effects moreover in the coastal region naturally occurring processes related to the flushing of saline waters from sediments of marine origin occur in conjunction with others clearly of human origin that are related to saltwater intrusion a further factor is the entry from overlying deposits of waters with a high saline content this salinity is related to the flushing of sediments of marine origin the use of b and li together enables waters in which salinity is related to seawater to be distinguished from others in which salinity is related to evaporitic layers or to thermal areas the concentration of li is directly related to water temperature while that of b is greater in the most saline sectors of gypsiferous and or seawater origin

post miocene rifting and diapirism in the northern red sea abstract rifts and diapirs are the dominant structures in the bathyal zone of the northern red sea where commonly the diapirs ascend along normal faults associated with the rifts in this manner the diapirs form elongated features sometimes exceeding lengths of 30 km and widths of 4 km they also penetrate a sedimentary sequence about 1000 m thickness or less thicknesses generally considered to be barely adequate for the gravity conversion required to initiate diapiric motion we suggest that development of diapirs under these minimal overburden conditions was made possible by the high thermal gradients in the area resulting from the underlying attenuated continental crust and ascending mantle that prevail in the rift system of the northern red sea diapiric evolution was also dependent on the extensional tectonic regime with its numerous normal faults forming weaknesses along which the diapirs could move upwards

wide angle seismic constraints on the evolution of the deep san andreas plate boundary by mendocino triple junction migration recent wide angle seismic observations that constrain the existence and structure of a mafic layer in the lower crust place strong constraints on the evolution of the san andreas plate boundary system in northern and central california northward migration of the mendocino triple junction and the subducted juan de fuca lithospheric slab creates a gap under the continent in the new strike slip system this gap must be filled by either asthenospheric upwelling or a northward migrating slab attached to the pacific plate both processes emplace a mafic layer either magmatic underplating or oceanic crust beneath the california coast ranges a slab of oceanic lithosphere attached to the pacific plate is inconsistent with the seismic observation that the strike slip faults cut through the mafic layer to the mantle detaching the layer from the pacific plate the layer could only be attached to the pacific plate if large vertical offsets and other complex structures observed beneath several strike slip faults are original oceanic structures that are not caused by the faults otherwise if oceanic slabs exist beneath california they do not migrate north to fill the growing slab gap the extreme heat pulse created by asthenospheric upwelling is inconsistent with several constraints from the seismic data including a shallower depth to the slab gap than is predicted by heat flow models seismic velocity and structure that are inconsistent with melting or metamorphism of the overlying silicic crust and a high seismic velocity in the upper mantle yet either the pacific slab model or the asthenospheric upwelling model must be correct while the mafic material in the lower crust could have been emplaced prior to triple junction migration the deeper slab gap must still be filled a preexisting mafic layer does not reduce the inconsistencies of the pacific slab model such material could however compensate for the decrease in mafic magma that would be produced if asthenospheric upwelling occurred at a lower temperature these low temperatures however may be inconsistent with asthenospheric rheology

evolution of the stress field near the arava basin located along the dead sea fault system as revealed by joint sets abstract to reveal the development of the stress field near the arava basin located along the dead sea fault system we characterized joint sets that were exposed mainly in the santonian and eocene chalk rock outcropping in the study area in total 2600 strike orientations of single layer joints slj and multilayer joints mlj mirrored four main stress fields 1 hnw j1 326 2 hnnw j2 343 3 hnne j3 033 and 4 hn j4 360 the results showed that the relatively lower values of the fracture spacing ratio fsr and their standard deviations in j1 implied that j1 was formed during the burial stage of the eocene chalk formations the inconsistency between the statistical parameters of the log normal distributions of joint spacing and fsr raised doubt about the applicability of the saturation joint density model in our studied area the joint sets characteristics suggest that the regional hnw operated during the eocene during the miocene the regional stress field changed clockwise to hnnw probably in association with the early stage of transform motion along the dead sea fault in the pliocene pleistocene the hnne and hn local stress fields both operated and were accompanied by a tensional stress field that can be identified in the intensive normal faulting evolved along the western arava basin margins

design and application of a constant head well permeameter for shallow high saturated hydraulic conductivity soils a new constant head well permeameter has been designed to measure saturated hydraulic conductivities ks ranging from 10 6 to 10 3 ms 1 application to shallow soils of western australia in this ks range highlighted problems with different aspects of the borehole discharge response firstly steady state borehole discharge was only reached in 13 out of 50 tests conducted this was a consequence of the constraint placed on the volume of water storage 40 l of the permeameter for some non steady state cases techniques of estimating steady state discharge from the available data are examined secondly borehole discharge was observed to increase with time in 34 per cent of cases a satisfactory physical explanation of this phenomenon is not presently available other limitations in the application of the constant head well permeameter are noted examination of a number of recent theoretical developments in the determination of ks led to a preference of saturated unsaturated flow solutions by philip 1985 and reynolds et al 1985 these solutions involve the sorptive number to which the solutions were sensitive but not critically sensitive the theory was used to establish design criteria for the permeameter and to identify an optimum application strategy in terms of well dimensions and heads error estimation indicated that the designed permeameter was a practically useful field instrument

evolution of the late cenozoic inselberg landscape of southwestern jordan abstract in southwestern jordan a spectacular inselberg landscape has resulted from dissection of paleozoic sandstones following stripping of cretaceous tertiary carbonates erosion of the sandstones was tied to development of the adjacent dead sea rift in two ways subsidence along the rift axis provided a low base level that facilitated erosion and faulting associated with the dead sea and red sea rifts led to differential erosion and isolation of inselbergs most of the erosion took place in and after miocene time the major drainage outlet wadi yutm probably existed throughout development of the landscape but was temporarily blocked during a normal faulting episode following graben faulting and stream erosion aggradation of sand and playa sediment created a relatively flat plain above which rise erosional outliers of the sandstones

structure of the alula fartak fracture zone gulf of aden the alula fartak transform fault is associated with a broad steep sided valley running nne ssw across the mouth of the gulf of aden a discussion of the tectonics of the fracture zone is based principally on gloria side scan sonar and gravity data the transform valley is 180 km long and 25 km across has 3 5 km of relief and is bounded by transverse ridges the northern two thirds is highly asymmetrical in cross section the eastern wall dips 38 and appears to be a single scarp exposing a section of oceanic crust 3100 m thick the western wall is much less steep and accommodates several normal faults oriented at about 15 to its general trend a very fine long sonar target running along part of the valley delineates the main active strike slip fault the sonar data also reveal many fine faultlike targets between the main walls running approximately at right angles to the trend of the valley which may be anti riedel shears a 50 km long 7 5 km wide and 1 5 km high median ridge runs along the southern third of the transform valley gravity data show that the valley is underlain by a significant mass deficiency thought to be a large serpentinite intrusion the median ridge is suggested to be the surface manifestation of a large serpentinite diapir the ridges flanking the transform valley are above a level compatible with isostatic equilibrium and are interpreted as flexural features raised in response to the upward loads imposed on the lithosphere by the fracture zone valley and its underlying mass deficiency very shallow crust is located close to the ridge transform intersections this is considered to result from static flexure induced by the negative load of the transform valley superimposed on dynamic compensation of the spreading center valley evidence of a c 3 5 m y b p change in spreading direction suggests the transform has experienced a recent component of opening accounting for several aspects of its structure

the dead sea rift from continental rift to incipient ocean abstract the dead sea rift is a 600 km long approximately 20 km wide geomorphological depression showing a topographic relief of 1 000 to 3 000 m from the axial depression to the mountainous margins in many places the rift is the northern extension of the red sea young oceanic spreading centre and it is built of a series of internal basins the rift is the product of vertical displacements that downfaulted its floor and uplifted its margins but some sinistral strike slip offset affected the rift as well the tectonic evolution of the rift started probably in the pliocene subsequent to the termination of the intensive tectonic activity in the suez rift the transition of the tectonic activity from suez rift to the dead sea rift is due to a probable clockwise jump of the northern extension of the red sea spreading centre the dead sea rift with its internal basins and faulted precipitous escarpments presents an exceptional example for the earliest stages of the evolution of continental break up and of nascent passive continental margins tectonic interpretations of the voluminous geological and geophysical data from the rift and its margins are complicated because the information is equivocal part of the data suggests that the rift is an extensional structure whereas another part indicates that the rift is a product of regional sinistral strike slip faulting however it is suggested that the equivocal data are not necessarily conflicting because the evolution of the rift is probably associated with oblique resultant displacement of combined normal and strike slip faulting the quantitative ratio between the extensional and the lateral offset processes in the dead sea rift is controversial there is ground to presume that large downfaulting of the rift floor and intensive erosion of its uplifted margins removed and obscured critical data that could have provided reliable correlation between the eastern and western flanks nevertheless reconstruction of mesozoic depositional fades zones across the rift apparently indicates that the lateral displacements are approximately 10 km and seismic reflection profiles suggest vertical offsets reaching 7 km the series of secondary internal basins in the rift that seem equivalent to the linear system of axial basins in the northern red sea support the concept that the dead sea is under a tectonic regime that is comparable to the one that affected the red sea in the miocene these findings and the 25 to 50 reduction of crustal thicknesses underneath the rift indicate an incipient oblique oceanic spreading centre

shoreline response to multi functional artificial surfing reefs a numerical and physical modelling study the results of a series of 2dh numerical and 3d scaled physical modelling tests indicate that processes governing shoreline response to submerged structures such as artificial surfing reefs are different from those associated with emergent offshore breakwaters unlike the case of emergent offshore breakwaters where shoreline accretion salient development is expected under all structural environmental conditions the principal mode of shoreline response to submerged structures can vary between erosive and accretive depending on the offshore distance to the structure the predominant wave incidence angle and structure crest level also have important implications on the magnitude of shoreline response but not on the mode of shoreline response i e erosion vs accretion based on the results obtained here a predictive empirical relationship is proposed as a preliminary engineering tool to assess shoreline response to submerged structures

internal structure of the dead sea leaky transform rift in relation to plate kinematics abstract the structures along the dead sea transform rift are related to the motions of the sinai and arabia plates which border it and to the irregularities of their boundaries the total slip was 105 km left lateral but the present structures were formed mainly during the last 40 km of slip which probably occurred in the plio pleistocene along the southern half of the transform the strike slip motion takes place on en echelon faults this produces rhomb shaped grabens or pull aparts which are sometimes composite and in which there is local crustal separation thus much of the transform is leaky these structures occur in a morpho tectonic rift valley delimited by normal faults which express a small component of transverse extension along a few segments the shape of the transform is such that lateral motion produces local transverse compression the geometric relations of the structures along the transform define an eulerian pole of relative plate motions at 32 8 n 22 6 e 0 5 the older motion was somewhat different and is described by a pole located about 5 west of the above then the component of transverse extension and crustal separation was much smaller than now while local transverse compression was more important the northern half of the dead sea transform has an irregular shape and the bordering plates did not remain rigid as lateral motion continued here transverse compression is often important

new observations of the shallow seismic structure of young oceanic crust the results are presented of three new experiments carried out on the mid atlantic ridge mar near latitude 23 n using a unique method of studying the seismic structure of the uppermost few hundred meters of the oceanic crust the data were collected using a fixed ocean floor hydrophone receiver and a controllable explosive source that was towed within a few tens of meters of the rugged bottom topography these 1 to 2 km long refraction lines produced for the first time direct observations of the compressional wave velocity structure of the uppermost 200 300 m of the young igneous crust one experiment was carried out over the site of hole 648b of the ocean drilling program on a small volcano within the median valley of the mar the seafloor velocity was observed to be 2 1 km s 1 underlain by an approximately linear velocity gradient of 4 s 1 given that we know the crust at this location consists of fresh basalt lavas with laboratory measured velocities in excess of 5 8 km s 1 porosities at the seafloor of as high as 30 50 are inferred the two other experiments were located over 7 m y old crust near deep sea drilling project site 395 west of the mar separated by only 14 km laterally but by over 1400 m in water depth the experiment positioned in the 100 m thick sediment pond and that located 14 km to the south atop a prominent topographic high produced results that within the data resolution were indistinguishable the velocity of the uppermost basaltic basement was 4 1 km s 1 and the velocity gradient was less than 0 5 s 1 this 2 km s 1 difference in velocity between the two sites is assumed to be a consequence of age related modifications to the physical properties of the crust if the primary change is in only the total porosity then a 15 20 reduction is required to explain these observations this seems unlikely because any such pervasive process would have been previously observed in geophysical and sampling data e g off axis volcanism secondary mineral deposition tectonic compression a combination of many processes acting in unison would be necessary to produce such a decrease in porosity if the geometry of the cracks and voids were modified in just the right way then no change in total porosity is required to explain the velocity difference these on bottom refraction profiles are proven to be practical experiments that can provide precise information on a scale appropriate to many of the ocean floor s geologic features they produce results that may be correlated in a meaningful way with results of ocean drilling and downhole measurements

relative sea levels and coastal sedimentation in southeast australia in the holocene abstract in recent years australian studies of relative sea level change have shown reasonable consistency on the termination date of the postglacial marine transgression at c 6 500 14c years bp the following stillstand period has been characterized in some regions by a slight falling trend from a high stand or in other areas by a level not easily distinguished from the present the latter situation occurs on the embayed coast of new south wales here studies of depositional environments and sequences within bed rock embayments have linked the holocene sea level history to patterns of sedimentation on the inner shelf in bay barriers and in estuaries deposition of quartz rich sand in shoreface flood tidal delta and backbarrier environments occurred during the marine transgre sion and the subsequent stillstand shell fragments from these deposits have been radiocarbon dated shoreline displacement continues to the present day partly in response to changes in availability of sand in the shoreface zone and partly in response to variations in regional storminess patterns a nd the great shroud of the sea rolled on as it rolled five thousand years ago herman melville moby dick

structural trends in the northern red sea the northern red sea is underlain by a series of plio pleistocene sedimentary sequences that unconformably overlie evaporitic series of late miocene age a series of bathyal rifts and cogenetic diapirs trending approximately n s were recently discovered in that region between latitude 26 30 n and 28 n the rifts are up to 60 km long and 7 km wide and the diapirs commonly ascended along the rifts boundary faults the diapirs stem from the late miocene evaporites thus the discerned structural trends were developed during the plio pleistocene the encountered structural patterns deviate considerably from the nw se structural trends that prevail in the central red sea as well as in the faults that border the northern red sea and the gulf of suez the tectonic activity that formed the suez rift in the middle to late miocene was not rejuvenated there during the plio pleistocene and the new data indicate that the axis of the tectonic extension at the northern red sea jumped to show a northward orientation it is suggested that incipient spreading center extends from the red sea northward to the gulf of elat and the dead sea rift

incipient spreading center in the gulf of elat northern red sea abstract the gulf of elat located at the northern red sea is a rift that forms the southern section of the dead sea rift system a recent high resolution seismic reflection survey showed that lenticular grabens and axial anticlines are the predominant structures at the rift floor structural relationships suggest that after the lenticular graben was formed at the rift floor it was filled with sediments axial uplift along the rift caused the widening of the graben and the development of axial anticlines and at a later stage a new graben started to develop between the flank of the anticline and the boundary fault of the rift the data indicate that the tectonic regime affecting the southern dead sea rift is one of uplift and extension acting simultaneously it is presumed that upwelling of magma in the upper mantle extending northwards from the red sea is the cause for these uplift and extensional phenomena and that the gulf of elat is an incipient spreading center

the initiation of the dead sea rift an earlier theory proposed that the dead sea rift started as a shear transform between the arabian and african plates as a result of continental collision newer geological evidence implies a different mechanism for rift initiation mechanical theories and experimental results suggest that fracture initiation propagation and bifurcation along the rift cannot be explained by shear these features can best be explained and simulated by extensile processes recent discoveries of transitional properties of the crust mantle boundary along the rift and considerable thinning of the crust between the dead sea and the sea of galilee on the west side of the rift are interpreted as indications of an active mantle diapir that initiated fracture in this area by propagating horizontally bilaterally towards north and south this fracture reached conditions of bifurcation in several locations along the rift areas of major bifurcation also show characteristic local uplifts and local small grabens oblique to the rif

effect of submerged breakwater on profile development the project dynamics of beaches is carried out by a network of six european universities within the framework of the human capital and mobility program of the european union the aim of the project is to improve the existing knowledge on physical processes governing the nearshore zone due to effects of submerged breakwaters within the project hydrodynamic and morphological experiments have been carried out this paper discusses the results of the experiments that took place in a wave flume and the large wave basin at delft university of technology the experiments were carried out with movable beds and varying wave conditions

morphological response of a sandy shoreline to a natural obstacle at sa mesa longa beach italy abstract a case study is presented of a comprehensive analysis of the shoreline stability of a salient primary response in the lee of an emergent natural reef at sa mesa longa beach sardinia italy the analysis combines sources of information at different levels of detail and accuracy field surveys conducted with a gps unit remotely sensed imagery geometrical and shape predictive formulas and simulations with a 2d wave current sediment transport numerical model the morphological simulation results for the primary response agree qualitatively with field observations and predictions from empirical formulas the accuracy of a simplified wave energy model in defining the littoral sediment cell compared to the more detailed results of the morphological model is also investigated although the analysis has some limitations as highlighted in the paper the results appear to be promising in terms of applying the analysis to fragile morphologies in the lee of natural reefs in the mediterranean sea

shoreline response to a single shore parallel submerged breakwater submerged breakwaters sbws are becoming a popular option for coastal protection mainly due to their low aesthetic impact on the natural environment however sbws have rarely been employed for coastal protection in the past and therefore their efficacy remains largely unknown the main objective of the present study was to investigate the structural and environmental conditions that govern the mode of shoreline response i e shoreline erosion vs shoreline accretion to sbws the relative importance of the key structural and environmental parameters governing the response mode to a single shore parallel sbw is investigated through a combination of theoretical analysis and numerical modelling using physical considerations a theoretical response function model is derived under several simplifying assumptions including parallel depth contours linear wave theory shore normal waves and no wave current interaction numerical modelling is undertaken with the mike21 model suite to simulate the depth averaged velocity fields without morphological updating due to waves acting on a single shore parallel sbw located on a schematised beach with parallel depth contours in total 92 coupled wave current simulations were undertaken the results indicate that the mode of shoreline response to the sbw can be expressed in terms of the two non dimensional parameters h b h 0 and s b h b 3 2 l b h b 2 a 3 h b 1 2 variables defined in the text c 2010 elsevier b v all rights reserved less

geochemical evolution of groundwater on saturna island british columbia a detailed geochemical study of surface waters spring waters and groundwaters was undertaken to examine the geochemical evolution of groundwater on saturna island british columbia the purpose of the study was to characterize the nature and occurrence of saline waters and to provide insight on chemical processes that lead to salinization in the fractured sedimentary bedrock aquifers of this small island major ion chemistry shows that groundwater is recharged locally but mixes with saline waters that occur at depth or near the coast simple mixing is complicated by cation exchange between calcium rich waters and sodium rich exchange sites offered by mudstone beds and results in a spatially variable hydrochemical composition that is dependent on the island topography and geological framework structural sedimentological and glacial in combination with groundwater use patterns sodium present at exchange sites is speculated to be a remnant of ocean water intrusion during the pleistocene when the

hydrochemical and isotopic characterisation of groundwaters to define aquifer type and connectivity in a subtropical coastal setting fraser coast queensland physico chemical parameters major ion chemistry and isotope composition of surface and groundwaters were determined in forested coastal catchments and adjacent coastal plains results showed obvious characterisation related to physical and hydrological setting and highly variable spatial differences reflecting the complexities of these areas all these coastal waters are dominated by na cl and fall on a common dilution line hydrochemical grouping is largely due to anionic differences cl so4 and hco3 although na and mg ratios also vary six major hydrochemical facies were determined for groundwaters compositional differences are largely related to aquifer material and level of confinement for coastal groundwaters important are tidal effects and proximity to the shoreline differentiation for surface waters is mainly by drainage morphology flow regime plus proximity to the coast connectivity between water bodies is reflected by minor base flow to catchment streams including with flood plain wetlands but mostly occurs in low lying zones where there is mixing of fresh and saline water within surface water and subterranean estuaries or by seawater intrusion enhanced by overuse oxygen and hydrogen isotopic data for confined and semi confined groundwaters along the coast indicates local recharge fresh surface waters in the elevated catchments are shown to be sourced further inland plus have experienced evaporation

differentiation of palaeomarine and modern seawater intruded salinities in coastal groundwaters of karaikal and tanjavur india based on inorganic chemistry organic biomarker fingerprints and radiocarbon dating abstract hydrosalinity evolution is examined in the karaikal and tanjavur coastal aquifers situated about 300 km south of madras tamil nadu india ancient and modern sources of solutes in groundwaters have been differentiated using hydro geochemical data environmental radioisotope dates and organic biomarkers results from different techniques show consistently that the pliocene aquifer possesses characteristic palmitoleic and oleic acid biomarkers apparent 14 c ages of more than 20 000 years and high i cl ratio the modern marine estuarine intruded groundwaters in the alluvial aquifer display relatively younger apparent 14 c ages modern to 3000 years enriched potassium ion low i cl ratio and contain vaccenic and hopanoic acid biomarkers and they also tend to display transient changes in chemical characteristics these results have practical importance with regard to identifying and controlling seawater intrusion in coastal areas

analogue experiments of propagation of oblique rifts abstract we present the results of analogue models of oblique rifting which were carried out using a isostatically compensated two layered small scale models the experiments show that structures formed in the brittle layer under oblique extension comprise a series of lenticular rifted basins set en echelon along the axial zone of the experiment box in time the basins propagate lengthways to merge and form a unified composite rift however traces of the initial en echelon rifts expressed in deeper axial basins separated by shallower threshold zones are clearly discernible in the mature rifts both the basins and the threshold zones are located within the composite rift so that the rift margins are abrupt and steep along the basins and more diffuse along the threshold zones the thinning in the brittle layer along the rift is enhanced by diapirs that ascend from the ductile layer and penetrate the rift floor model experiments of nearly orthogonal extension showed a single unified rift which differed conspicuously from the composite oblique rifts the results of the experiments suggest that oblique extension forms en echelon rift segments the axes of which are perpendicular to the extension direction separated by threshold zones therefore there is ground to presume that occurrence of a series of alternating basins and threshold zones inside the axial section of a major rift could suggest a regime of oblique tectonic extension

hydrogeochemical analysis of salinization processes in the coastal aquifer of oropesa castellon spain the coastal aquifer of oropesa is affected by salinization processes undoubtedly associated with intense groundwater exploitation for agriculture supply the aquifer corresponds geologically to a tectonic depression with plioquaternary fill hydrogeologically this aquifer is detrital with intergranular porosity which receives substantial recharge from adjacent mesozoic aquifers contact with the sea in addition to the presence of cultivated soil requiring extreme exploitation of groundwater frequently give rise to processes of seawater intrusion the present research is an attempt to understand the saltwater intrusion in this aquifer using hydrochemical analyses of the behavior of certain minor ions that could help in the characterization process in the case of the oropesa sector groundwater salinization does not appear to be attributable solely to the intrusion of seawater but there are also anomalies related largely to the geology of the sector and its surroundings the type of recharge the hydrodynamic conditions in the specific area etc

hydrogeochemical and isotopic evidence of groundwater salinization in a coastal aquifer a case study in jeju volcanic island korea abstract in order to identify the origin of saline groundwater in the eastern part of jeju volcanic island korea a hydrogeochemical and isotopic study has been carried out for 18 observation wells located in east and southeast coastal regions the total dissolved solid contents of groundwaters are highly variable 77 21 782 mg l oxygen hydrogen sulfur and strontium isotopic data clearly show that the saline water results from mixing of groundwater with seawater strontium isotopic compositions and br cl and i cl ratios strongly suggest that the source of salinity is modern seawater intrusion hydrogeochemical characteristics based on bivariate diagrams of major and minor ions show that changes in the chemical composition of groundwater are mainly controlled by the salinization process followed by cation exchange reactions the highly permeable aquifers at the east coastal region are characterized by low hydraulic gradient and discharge rate and high hydraulic conductivity as compared with other regions these properties enhance the salinization of groundwater observed in the study area based on the cl br and 18 o data seawater was determined to have intruded inland some 2 5 km from the coastline considering the poor correlation of sampling depth and cl concentrations observed the position of seawater freshwater interface is not uniformly distributed in the study area due to heterogeneities of the basaltic aquifers

conceptualization and classification of groundwater surface water hydrodynamic interactions in karst watersheds case of the karst watershed of the coulazou river southern france summary over the last two decades groundwater systems and surface water bodies are being more and more considered as a same entity which constitutes a single resource within the hydrologic system understanding groundwater surface water gw sw interactions is necessary to effectively manage the water resources concepts methods of analysis and classifications of these hydrodynamic interactions have thus been developed mostly in case of porous aquifer today gw sw interactions are still often poorly understood in many watersheds particularly in the case of complex aquifers like karst aquifers this study focuses on the influence of groundwater on the genesis and propagation of surface floods in the case of a highly karstified watershed gw sw hydrodynamic interactions are analysed i at a local scale focussing on hydrodynamic interactions between the karst aquifer in the vicinity of the river and the river and ii at a larger scale focussing on hydrodynamic interactions between a karst spring and sinkholes in the riverbed hydrodynamic time series are described using the karst watershed of the coulazou river western montpellier france as a case study results are used to adapt gw sw classifications that are usually devoted to porous media in case of the studied karst aquifer it is shown that the initial groundwater level may be used to forecast the type of hydraulic connection between the river and the saturated zone during flood however initial water level in the karst aquifer does not give any information about the flow direction gaining or losing stream during a flood the latter is found to be also controlled by the limited discharge capacity of karst conduits a conceptual model of karst river interactions during flood is given with concepts that are derived from the analysis of the coulazou watershed but that can be easily applied to most of the karst watersheds

structure of the dead sea pull apart basin from gravity analyses analyses and modeling of gravity data in the dead sea pull apart basin reveal the geometry of the basin and constrain models for its evolution the basin is located within a valley which defines the dead sea transform plate boundary between africa and arabia three hundred kilometers of continuous marine gravity data collected in a lake occupying the northern part of the basin were integrated with land gravity data from israel and jordan to provide coverage to 30 km either side of the basin free air and variable density bouguer anomaly maps a horizontal first derivative map of the bouguer anomaly and gravity models of profiles across and along the basin were used with existing geological and geophysical information to infer the structure of the basin the basin is a long 132 km narrow 7 10 km and deep 10 km full graben which is bounded by subvertical faults along its long sides the bouguer anomaly along the axis of the basin decreases gradually from both the northern and southern ends suggesting that the basin sags toward the center and is not bounded by faults at its narrow ends the surface expression of the basin is wider at its center 16 km and covers the entire width of the transform valley due to the presence of shallower blocks that dip toward the basin these blocks are interpreted to represent the widening of the basin by a passive collapse of the valley floor as the full graben deepened the collapse was probably facilitated by movement along the normal faults that bound the transform valley we present a model in which the geometry of the dead sea basin i e full graben with relative along axis symmetry may be controlled by stretching of the entire brittle and ductile crust along its long axis there is no evidence for the participation of the upper mantle in the deformation of the basin and the moho is not significantly elevated the basin is probably close to being isostatically uncompensated and thermal effects related to stretching are expected to be minimal the amount of crustal stretching calculated from this model is 21 km and the stretching factor is 1 19 if the rate of crustal stretching is similar to the rate of relative plate motion 6 mm yr the basin should be 3 5 m y old in accord with geological evidence

new evidence of magmatic diapirs in the intermediate crust under the dead sea israel simultaneous inversion of p wave arrivals of 262 local earthquakes recorded in the region of the dead sea was carried out to model the velocity stratification in the underlying crust and uppermost mantle the resulting tomographic model delineates several large magmatic domes rising from the lower crust at depth of approximately 20 km and ascending more than 12 km into the overlying intermediate crust commonly the domal ascent took place along the boundary faults of the dead sea rift the domes are elliptical in shape measuring nearly 5 15 km in diameter and are spaced about 20 km apart earthquake foci are abundant around the diapirs but rare within them the occurrence of these magmatic diapirs under the dead sea implies anomalously high temperatures with metastable stratification in the lower crust and suggests magmatic upwelling

the sinai triple junction revisited abstract this paper is a summary of a more detailed analysis of the kinematics of the sinai triple junction courtillot et al 1987 accurate kinematic data are lacking along the red sea and they can be supplemented by bathymetric topographic and geological data pertaining to the three arms of the entirely continental sinai triple junction motions across the northern red sea and along the gulf of elat are an order of magnitude larger than across the gulf of suez the direction of motion there remains a major uncertainty a possible kinematic model is highlighted in which right lateral strike slip motion and small pull apart basins occur along the gulf of suez in agreement with recent field observations in egypt early miocene is marked by major geodynamical changes all along the northern boundaries of the african and indian plates we suggest that rifting in the arabian sea gulf of aden red sea and gulf of suez was initiated at the end of the first phase of continental extrusion of indochina when the tibetan plateau began to rise and spreading in the south china sea came to a halt

the tectonic style of the southern arava rift margins israel alternating stress fields in wrench rifting processes abstract the arava rift segment of the dead sea transform contains juxtaposed transtensional and transpressional tectonic elements this structural pattern is related to the disposition of individual en echelon faults which accommodate the horizontal slip with respect to the regional stress field a detailed study of mesostructural elements across two transpressional structures at the western margins of the arava rift has established a tectonic sequence and subsequent adjustment of the concurrent drainage systems the studied structures are the shizafon disturbance an array of narrow asymmetric monoclinal and anticlinal folds and the ya alon graben a left lateral branching wrench fault with some downfaulted internal blocks slickensides on small faults small scale rhomb grabens veins with secondary mineralization and tectonic stylolites indicate that during an early compressional phase miocene lower pliocene the main horizontal compressional component 1 trended nw at the shizafon disturbance and nw to nnw at the ya alon graben normal faulting commenced during the middle pliocene and formed antithetic blocks along the rift margins similarly alternating stress fields whereby compression was succeeded by extension are recorded also several hundred kilometres further north along the transform margins the extensive distribution of coeval events along the eastern sinai plate margin calls for a regional stress field most probably a change in the rotation pole of the plates bordering upon the dead sea transform of the sort implied by garfunkel 1981 due to the thin sedimentary cover

onshore scour characteristics around submerged vertical and semicircular breakwaters abstract a laboratory study is presented herein investigating the two dimensional onshore scour along the base of submerged vertical and semicircular breakwaters experiments were conducted with normally incident monochromatic waves breaking at the breakwater on both sloping and horizontal sandy bottoms a principle conclusion of this investigation is that the characteristics of onshore breakwater scour are independent of submerged breakwater shape type it is also concluded that the onshore scour patterns can be divided into two distinct regimes that solely rely on the keulegan carpenter number kc h i w bw wbw breakwater crest width hi incident wave height for kc values larger than the scour forms detached from the breakwater while for kc values smaller than or equal to the scour occurs attached to the onshore breakwater face three important scour characteristics are investigated maximum scour depth smax scour length ls and the distance of smax location from the onshore breakwater face ds smax value is observed to be regime independent and rely on both kc and the mobility number h i t sinh k h 2 g d g reduced gravitational acceleration d median diameter of the sediment k wave number h still water depth t wave period while ls and ds are observed to be regime dependent and rely only on kc semi empirical parameterizations to predict smax ls and ds values for onshore breakwater scour are proposed

punctiform initiation of seafloor spreading in the red sea during transition from a continental to an oceanic rift transition from a continental to an oceanic rift occurs in the red sea by initial emplacement of oceanic crust in regularly spaced hot points which serve as nuclei for axial propagation into segments of oceanic crust accretion and for initiation of seafloor spreading hot points develop above upwelling mantle diapirs caused by density viscosity inversion beneath continental and oceanic rifts

tectonic analysis of the dead sea rift region since the late cretaceous based on mesostructures we have measured the orientations of small faults slickensides tectonic stylolites vein with secondary mineralization small folds and dikes in israel and sinai these structures are indicators of paleo stress or strain and provide the pattern of tectonic deformation data were collected at 130 stations most with tens of separate measurements most stations showed consistent deformation stations were located on exposures ranging from precambrian crystalline rocks to pleistocene sediments we have defined two tectonic stress fields each relatively uniform in both time and space one stress field with dominating maximum horizontal compression trending w to wnw in the late cretaceous to eocene rocks in the folds and plateaus west of the dead sea rift the second field with dominating horizontal extension trending e to ene in all rocks inside the rift and proximal thereto the first stress field is called the syrian arc stress and the second is called the dead sea stress a change in style of tectonic deformation which corresponds to the two stress fields is manifested also in the major structures in israel the late cretaceous to neogene deformation is characterized by long wavelength folds and monoclines whereas the neogene to recent deformation is characterized by normal and strike slip faults and volcanic activity

response of input and output of water and chloride to clearing for agriculture five small forested catchments in the collie river basin in southwest western australia were instrumented to quantify the changes in the input and output of salt and water when land use changed from forest to agriculture the paired catchment approach was used with two adjacent catchments located in high rainfall 1200 mm yr 1 and a group of three located in a lower 800 mm yr 1 rainfall area the treatment of complete clearing was applied to one catchment in the high rainfall zone and to about half of one catchment in the lower rainfall zone after three years of calibration with the uncleared control catchments strategies of partial clearing were applied to the third catchment in the lower rainfall zone the catchment pairs were found to be well matched the yield of water and salt increased immediately after clearing in the higher rainfall catchment streamflow increased about four times to 48 of rainfall salt load increased to fifteen times the mean saltfall measured as chloride ion of 7 g m 2 yr 1 direct runoff increased fourfold to 16 of yearly streamflow due partly to the progressive increase in the area of soil saturated to the surface the perched groundwater system was the major source 77 in 1983 of streamflow though it was the route rather than the source of increased salt to the stream the mottled and pallid clay profile was the dominant source of salt transported by the deep groundwater system into the perched aquifer streamflow became perennial in the first postclearing year absolute increases in streamwater and salt output from partially cleared catchments in the lower rainfall location were about an order of magnitude less than for the higher rainfall catchment though the relative increases were similar the three catchments were found to be accumulating salt in the cleared catchments the rising potentiometric surface would establish a saline groundwater discharge zone in the valley and a net export of salt in all treated catchments reduced interception results in increased water availability at the soil surface for stormflow and infiltration the reduction in transpiration had an added effect in increasing recharge to groundwater a new equlibrium for water had not been achieved eight years after clearing but was estimated to precede the new salt equilibrium

comment on new evidence of magmatic diapirs in the intermediate crust under the dead sea israel by nitzan rabinowitz jean steinberg and yossi mart

video monitoring of sandbar shoreline response to an offshore submerged structure at a microtidal beach abstract in early 2013 an 800 m long and 12 m wide submerged breakwater with its crest in 2 m depth was implemented at the wave dominated barred beach of sete se france to fight against erosion and submersion hazards daily video images from april 2011 to april 2016 covering an alongshore distance of 3 5 km are used to analyse the response of both the sandbar s and the shoreline to the structure implementation results show that the breakwater had a profound impact on the nearshore system both shoreward of the structure and well away from it alongshore a progressive rotation and linearisation of the sandbar was observed shoreward of the submerged breakwater this resulted in the splitting of the sandbar adjacent to the structure during a net offshore sandbar migration event driven by a severe storm in december 2013 the typical formation of a salient or tombolo was not observed instead shoreline coupled to the sandbar geometry which resulted in a slight seaward migration of the shoreline in front of the structure overall this study highlights that the role of the sandbar is critical to shoreline response to the implementation of breakwaters on barred beaches

seismic images of a magma chamber beneath the lau basin back arc spreading centre we present normal incidence seismic reflection profiles from a back arc spreading centre in the southern lau basin which show a bright mid crustal reflector beneath the ridge axis analysis of wide angle seismic data collected simultaneously with the reflection profiles shows that the reflector coincides with the top of a low seismic velocity zone we interpret the reflector as the top surface of a magma chamber the lau basin is one of only two places where a magma body has been clearly imaged beneath a spreading centre the other being the east pacific rise between 9 and 13 n ref 1 the lau basin reflector is imaged beneath an entire 35 km long ridge segment it is also present beneath both ridges and the overlap basin of a small overlapping spreading centre this is the first observation of a widespread magma body beneath an overlapping spreading centre and indicates that the offset here is not related to a break in continuity of the magma chamber

spatial and temporal patterns of shoreline change of a 280 km high energy disrupted sandy coast from 1950 to 2014 sw france abstract a dataset of 15 geo referenced orthomosaics photos was generated to address long term shoreline change along approximately 270 km of high energy sandy coast in sw france between 1950 and 2014 the coast consists of sandy beaches backed by coastal dunes which are only disrupted by two wide tidal inlets arcachon and maumusson a wide estuary mouth gironde and a few small wave dominated inlets and coastal towns a time and spatially averaged erosion trend of 1 12 m year is found over 1950 2014 with a local maximum of approximately 11 m year and a maximum local accretion of approximately 6 m year respectively maximum shoreline evolutions are observed along coasts adjacent to the inlets and to the estuary mouth with erosion and accretion alternating over time on the timescale of decades the two inlet sandspit systems of arcachon and maumusson show a quasi synchronous behaviour with the two updrift coasts accreting until the 1970s and subsequently eroding since then which suggests that shoreline change at these locations is controlled by allocyclic mechanisms despite sea level rise and the well established increase in winter wave height over the last decades there is no capture of significant increase in mean erosion rate this is hypothesized to be partly the result of relevant coastal dune management works from the 1960s to the 1980s after a long period of coastal dune disrepair during and after the second world war this study suggests that long term shoreline change of high energy sandy coasts disrupted by inlets and or estuaries is complex and needs to consider a wide range of parameters including non extensively waves tides inlet dynamics sea level rise coastal dune management and coastal defences which challenges the development of reliable long term coastal evolution numerical models

the northern red sea and the dead sea rift abstract the results of geophysical measurements at sea when combined with mesostructural measurements on land demonstrate systematic extensional features in the region of the northern red sea and the dead sea rift rifts and diapirs were encountered in the northern red sea showing an arcuate trend whereas the faulted continental margins at that region are oriented nw se the rifts and the diapirs changed their trend northwards from nnw sse to n s systems of rifts and diapirs are considered to be extensional features therefore the tectonic extensional axis probably changed its orientation accordingly a series of rifts and diapirs was found also in the gulf of elat trending approximately parallel to the coastlines and is interpreted to be the northern extension of the red sea rift and diapir system mesostructural measurements that were carried out in the western flank of the dead sea rift indicated further evidence for structural extension trending e w to ene wsw in addition to measurements of left lateral offset of approximately 10 km all these data when combined with the geophysical measurements of the characteristics of the earth crust underneath the dead sea rift suggest a tectonic regime of oblique extension in the region of the red sea and the dead sea rift this tectonic regime indicates that the red sea spreading center extends northwards along the dead sea rift and the clockwise change of the axial trend imposed a sinistral offset to the tectonic extension thus it is suggested that the dead sea rift is an incipient oblique spreading center

the role of paleochannels in groundwater seawater exchange relict fluvial channels that are infilled with high permeability sediments act as preferred pathways for groundwater flow and solute transport in coastal regions such paleochannels can provide a hydraulic connection between freshwater aquifers and the sea facilitating saltwater intrusion landward or freshwater discharge offshore although paleochannels have been implicated in several instances of saltwater intrusion there has been little direct study of these channels to confirm their role in this work simulation modeling of a general multi layered coastal plain aquifer setting indicates that when a paleochannel breaches a confining unit offshore submarine groundwater discharge of intermediate salinity occurs this discharge is largely concentrated along the margins of the channel conversely seawater inflow occurs along the channel axis resulting in higher salinity in the middle of the channel relative to the flanks chirp seismic and electromagnetic data collected offshore wrightsville beach nc usa confirm these simulation results and indicate fresher porewater along channel flanks and slightly higher porewater salinity along the channel axis hence paleochannels contribute to the spatial variability in submarine groundwater discharge by serving as conduits of focused fluid exchange simulations also reveal that the freshwater saltwater transition zone is closer to land below paleochannels than in locations with a continuous confining unit this indicates that such channels are likely to be significant modes of saltwater intrusion into confined aquifers when excess freshwater extraction occurs on land

three dimensional velocity structure in northern california coast ranges from inversion of local earthquake arrival times abstract the three dimensional p wave velocity structure in the upper crust in the northern california coast ranges from santa rosa to ukiah is obtained by simultaneous inversion of local earthquake and refraction travel time data for velocity and hypocentral parameters in this region where there are lateral heterogeneities the three dimensional inversion provides important results not found in two dimensional refraction studies the medium is parameterized with velocities at the intersections gridpoints of a nonuniform three dimensional grid travel times are calculated with approximate ray tracing along arcuate paths which are reasonable for lateral distances less than 45 km inversions with 5 to 10 and 2 to 3 km gridspacing achieved 80 per cent decreases in data variance the inversion with 2 to 3 km gridspacing reduced the rms residual level to approximately the level of timing error anomalously low velocities to at least 6 km depth are found along the maacama and healdsburg rodgers creek hrc fault zones the low velocity region is widest at the en echelon junction of the maacama and hrc fault zones low velocities are associated with the clear lake basin where there is a thick sequence of volcanics interbedded with sedimentary deposits there is a high velocity body located southeast of the geysers between the maacama and collayomi fault zones which may be associated with igneous intrusives or high grade metamorphism related to an underlying inferred partial melt body modeled in previous teleseismic travel time studies there is some indication in the vapor dominated geothermal reservoir of lower velocities relative to surrounding water saturated rock as has been shown in some laboratory experiments hypocenter locations obtained in the inversion show little variation from hypocenters obtained through inversion for one dimensional velocity model and station corrections for the inversion with 2 to 3 km gridspacing however some groups of events become more tightly clustered

water and solute transfer between a prairie wetland and adjacent uplands 2 chloride cycle the quality of water in lakes and wetlands depends on the exchange of solutes with adjacent uplands in many prairie wetlands the input of water is dominated by snowmelt runoff and the outputis dominated by groundwater flow we use chloride as a tracer to quantify the mass transfer processes associated with surface runoff and groundwater flow between a wetland in saskatchewan canada and the surrounding upland snowmelt runoff transports 4 5 kg yr 1 of chloride from the upland to the wetland most of this chloride infiltrates under the wetland and moves laterally to the upland with shallow groundwater under the upland chloride moves upward in the vadose zone with soil water and accumulates near the surface as water is consumed by evapotranspiration part of this chloride mixes with snowmelt runoff and moves back to the wetland therefore chloride is cycled between the wetland and the upland at an approximate rate of 5 kg yr 1 the chloride cycle occurs within 5 6 m of the ground surface a small amount of chloride escapes from the cycle with the downward flow of groundwater into the deep aquifer the estimated flux of chloride leaving the cycle is 0 1 0 6 kg yr 1 which is of the same order of magnitude as the rate at which the catchment receives atmospheric deposition of chloride because the atmospheric input is reasonably well known over the prairie region the concentration of chloride in groundwater under recharge wetlands can be used to estimate the recharge rate of deep aquifers

shore protection by oblique seabed bars shore protection by small seabed bars was once considered possible because seafloor undulations strongly reflect surface waves of twice the wavelength by the so called bragg resonance mechanism the idea however proved unreliable when it was realized that a patch of longshore seabed bars adjacent to a reflective shore could result in larger waves at the shoreline than for the case of a flat seabed here we propose to revamp the bragg resonance mechanism as a means of coastal protection by considering oblique seabed bars that divert rather than reflect shore normal incident waves to the shore parallel direction we show via multiple scale analysis supported by direct numerical simulations that the creation of a large protected wake near the shoreline requires a bi chromatic patch to deflect the incident waves to the shore parallel direction with two superposed sets of oblique seabed bars the incident wave energy becomes efficiently deflected far to the sides leaving a wake of decreased wave activity downstream of the patch we demonstrate that the shore protection efficiency provided by this novel arrangement is not affected by reflection of leaked waves at the shoreline and that it is relatively robust against small frequency detuning

geodynamics of the middle east domain since the oligocene research summary several analogue models were merged to link the post oligocene closure of the neotethys seaway with the break up of the gulf of aden and the red sea the seaway closure since the early neogene which was a result of northwards subduction of neotethyan lithosphere under south central eurasia generated two styles of kinematic convergence its western branch forms the tethyan subduction under south central eurasia along the hellenic deformation front generating the break up of the aegean sea and the westward migration of anatolia the eastern branch comprises the oblique convergence of arabia with eastern anatolia and iran along the bitlis zagros suture which gradually shifted from subduction to collision because the velocity of plate collision is slower than that of subduction the subducting section of the underthrust slab moves faster than the colliding segment consequently the underthrust arabian slab rotated counterclockwise and developed detachment zones such extension triggered the resumption of the propagation of the carlsberg ridge into the gulf of aden after being stalled for nearly 30 ma it is presumed further that the break up of the red sea in the mid miocene was superimposed on the regional uplift and exhumation of the arabo nubian massif which was caused by a mantle plume in the oligocene a plume that subsequently affected the ethiopian and the east african plateaux in the neogene

groundwater salinization in pico island azores portugal origin and mechanisms a hydrogeochemical survey was conducted on pico island azores archipelago in order to evaluate the groundwater chemistry patterns and the main mineralization processes samples were from cold waters and corresponded mainly to sodium chloride type conductivity measurements were 82 9790 s cm and suggest the existence of highly mineralized waters in fact 18 had a conductivity 5130 s cm and the total dissolved solid tds value for two of the wells was from the brackish water range the changes in groundwater composition are because of two main processes 1 silicate mineral dissolution especially in a few springs located at high altitude and 2 water salinization in the coastal area as a result of saltwater intrusion and sea salt spraying the salinization process corresponds to a binary mixing system as suggested by the chloride and 18o data and explains the sharp concentration increase in major and minor species detected in several wells

quantification of groundwater seawater interaction in a coastal sandy aquifer system a study from panama sri lanka the panama coastal aquifer system is an important water resource in the southeast coast of sri lanka that provides adequate supplies of water for agriculture and domestic uses one of the biggest threats to these fragile aquifers is the sea water intrusion in this study recharging mechanism and geochemical evaluation of groundwater in the coastal sandy aquifer of panama were evaluated using chemical and stable isotope techniques thirty groundwater samples were collected and analyzed for their major ion concentrations and stable isotope ratios of oxygen 18o 16o and hydrogen d h all studied samples showed a ranking of major anions in the order cl hco 3 so 4 2 n no3 while cations showed a decreasing order of abundance with na ca2 mg2 k dominant groundwater hydrogeochemical types were na cl and mixed ca mg cl results of saturation index calculations indicate that the investigated groundwater body was mostly saturated with respect to calcite dolomite and gypsum in addition stable isotope and geochemical data suggest that fresh groundwater in the aquifer is recharged mainly by local precipitation with slight modification from evaporation and saline water intrusions isotope data suggest that mixing of salt water with freshwater occurs in aquifers which are located towards the lagoon since the communities in the study area depend entirely on groundwater an understanding of the hydrogeochemical characteristics of the aquifer system is extremely important for the better water resource management in the region

effects on catchment water balance from the management of pinus plantations on the coastal lowlands of south east queensland australia a paired catchment study was conducted over a 10 year period on the hydrology of an exotic pinus plantation in the coastal lowlands of south east queensland australia each catchment was instrumented with a stream monitoring station tipping bucket rain gauge and a network of piezometers to monitor the shallow perched water table after a 6 year calibration period a harvest treatment was imposed on one catchment review clearfelling approximately 90 of the catchment area which contained a mature 44 year old pinus elliottii plantation this subsequently was re established with a second rotation plantation of a hybrid of p elliottii p caribaea var hondurensis the control catchment crayfish contained a p elliottii plantation similar to that clearfelled at review the post harvest period was monitored for a further 4 years evapotranspiration was found to be the major output flux with stream flow only a minor component of the study catchments water budget areas with gleyed podzolic soils were found to remain waterlogged for periods up to 7 months following the seasonally high summer rainfall period with other soils having water logging periods of only a few months little change was observed in waterlogging characteristics following harvesting in contrast to stream flow which increased for 3 years but with evidence of a decline after 5 years the perched watertable piezometric surface indicated that its lateral drainage differs from that of surface flows the perched watertable drainage fluxes from the study catchments seem minor and off site movement of solutes e g nutrients and contaminants via them would be limited it was identified that the interaction between the perched and deep aquifers was poorly understood as well as the relative importance of the soil moisture storage of the aquitard clay layer between them it was concluded that there is a need to undertake more detailed analysis using modelling and to obtain additional field data on soil layer properties and piezometric levels of the deep aquifer copyright 2002 john wiley sons ltd

submerged breakwaters for the defence of the shoreline at ostia field experiences comparison an important study case with different defence structures and the results of the monitoring data of are reported field experiences are specially usefull to compare two soft structures used to defend the lido of ostia i e the coastline of rome at the mouth of river tevere tiber

the tectonics of the timna region in southern israel and the evolution of the dead sea rift abstract the timna region is located in the western margin of the southern arava valley at a junction between two regional orthogonal fault systems the dead sea rift and the temed fault the dead sea rift trends n s and extends from the northern red sea to southern anatolia and the temed fault trends e w from the gulf of suez to the arava valley structural analysis of the timna region showed the effects of two tectonic phases that were active there since the miocene the first tectonic phase formed the dextral strike slip temed fault and two systems of secondary faults trending nw se and ne sw the second tectonic phase downfaulted the rift floor and uplifted the rift shoulders simultaneously forming a regional n s trending joint system along the rift shoulder subsequent sinistral strike slip faulting along the rift caused a drag on the eastern part of the timna region and the resulting 2 5 km northward displacement reactivated pre existing faults and formed several rifts and uplifted blocks a correlation of the structural data of the timna region with recently acquired geophysical structural and stratigraphic findings from various places along the dead sea rift indicates that the first tectonic phase in timna is the erythrean phase this phase formed systems of e w trending faults in the negev and northern sinai as well as nw se trending faults in saudi arabia jordan israel and egypt this tectonic phase was active in the miocene and is associated with the first evolutionary phase of the red sea spreading center during this phase the spreading center extended northwards towards the suez rift the second tectonic phase in timna is the levantine phase that formed the dead sea rift and its uplifted shoulders this phase has been active since the pleistocene and is associated with the second tectonic phase of the red sea spreading the structural and geophysical data suggest that the dead sea rift is an incipient spreading center extending from the red sea whereas the suez rift was not reactivated during this phase the change of trend of the northern red sea spreading center from nw se to n s deformed the east shoulder of the southern dead sea rift so that a limited sinistral strike slip displacement occurred recent seismic activity indicates that the evolution of the dead sea rift is presently active

structural geometry and evolution of the dead sea jordan rift system as deduced from new subsurface data abstract analysis of deep drilling data and seismic reflection surveys obtained in recent years permit establishment of a tectonic model of the dead sea jordan rift system that is in part conformable with some of the many often controversial theories on this subject but which also introduces new information negating some concepts that are widely accepted in the literature the dead sea jordan rift system is not a tensional graben between two parallel sets of faults but instead can be best defined as a sinistral transform connecting an incipient oceanic ridge the red sea with an upthrusted collision zone the taurus range the shear is caused by the opening of the red sea and the motion of the arabian sub plate away from the african plate the shearing occurs along a largely south north trending slightly arcuate une consisting of a series of en echelon left stepping left lateral strike slip master faults of varying lengths these faults characteristically die out to the north by bending outward northeast and the movement is taken up by the strike slip faults to the left i e to the west where overlap of the two faults occurs very narrow and very deep grabens have evolved in places the width being equal to the depth the narrowness of these grabens is dictated by the closeness of the overlapping segments of the successive strike slip faults this feature points to the probability that the en echelon strike slip faults have a common root zone at great depth these grabens are not typical leaky pull aparts in that they have no gravimetric magnetic or heat flow anomalies nor are they closed on all four sides by large faults their northern ends are characterized by gradually rising graben floors without major diagonal cross faults the dead sea jordan rift system sensu stricto extends over a distance of 420 km from the northern shore of the gulf of elat to the northern margin of the hula valley southward it is connected with the red sea along the gulf of elat transition zone which has elements of strike slip as well as tensional opening a northern transition zone exists between the hula valley and the taurus arc where diminishing strike slip movement is compensated by several underthrust belts the time of the beginning of the movement along the rift can be established as pre middle miocene because mid miocene sediments overlie an upper cretaceous graben floor rifting has continued intermittently to the present volcanism in the northern fifth of the rift is genetically associated with the seismically active tensional golan hauran jebel drouz wadi sirhan tectonic trend which has a north west southeast orientation and not with the north south trending dead sea jordan rift

experimental and numerical investigation of bed morphology in the lee of porous submerged breakwaters abstract in the present work the evolution of a sandy beach in the lee of a permeable submerged breakwater was studied both experimentally and numerically three dimensional laboratory experiments were performed to investigate regular and irregular wave propagation over a porous submerged structure and the resulting bed morphology evolution down wave of it the tests included normal wave incidence of breaking and non breaking long and shorter waves the measurements were also used to validate a compound numerical model the basic solver relies on enhanced boussinesq type equations extended to simulate wave propagation over porous beds the wave module accounts for the entire nearshore zone from deep water to the swash zone and it is coupled with a sediment transport module including both bed and suspended loads adequate agreement between measurements and model results was achieved in most cases

interaction between shallow groundwater saline surface water and contaminant discharge at a seasonally and tidally forced estuarine boundary this paper presents findings from a 2 year field investigation of a dissolved hydrocarbon groundwater plume flowing towards a tidally and seasonally forced estuarine river system in perth western australia samples collected from transects of multiport wells along the riverbank and into the river enabled mapping of the fine scale 0 5 m vertical definition of the hydrocarbon plume and its longitudinal extent spear probing beneath the river sediments and water table and transient monitoring of multiport wells electrical conductivity was also carried out to define the zone of mixing between river water and groundwater the hyporheic zone and its variability the results showed that groundwater seepage into the estuarine surface sediments occurred in a zone less than 10 m from the high tide mark and that this distance and the hyporheic transition zone were influenced by tidal fluctuations and infiltration of river water into the sediments the dissolved btexn benzene toluene ethylbenzene the xylene isomers and naphthalene distributions indicated the behaviour of the hydrocarbon plume at the groundwater surface water transition zone to be strongly influenced by edge focussed discharge monitoring programs and risk assessment studies at similar contaminated sites should therefore focus efforts within the intertidal zone where contaminants are likely to impact the surface water and shallow sediment environments

the palaeoecology of the callovian and oxfordian strata of majdal shams syria and its implications for levantine palaeogeography and tectonics abstract palaeoecological study of fossils from jurassic strata of majdal shams syria reveals a deepening and shallowing sequence of water conditions from callovian to tithonian time maximum water depth apparently occurred in the lower oxfordian where both fossils and lithology are typical of the deeper water parts of the tethys the contrast with very shallow facies nearby in lebanon is very marked the only acceptable palaeogeographic reconstruction of this region is obtained by accepting the widely proposed post jurassic 110 km sinistral strike slip movement on the dead sea fault on this reconstruction the majdal shams region becomes an extension of the basinal tethys along the nw se trending kishon jezreel graben this is strong evidence for tensional ne sw movements in the levantine area long before the miocene opening of the red sea

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

palynological evidence for the age and rate of sedimentation along the dead sea rift and structural implications abstract pollen diagrams obtained for eight deep boreholes penetrating the thick sequences of the dead sea rift fill correlated with dated marine sequences of the coastal plain in israel enable stratigraphie assignment of the continental deposits to be made the sedimentary units of the rift valley are of two main provenances those deposited in troughs within the rift limits of predominantly lacustrine environment attaining thicknesses in the order of 1 2 km for which the trough is the final erosion base level and those not limited to the rift boundaries but known from wide areas in israel mostly laid down in river systems that crossed the rift region on their way to the sea these fluviatile formations are in the order of hundreds of meters thick in the rift valley region which acted as an intermediate basin the first group of rock units of late miocene through early middle pliocene to glacial pleistocene ages indicate phases of considerable subsidence the earlier termed the erythrean and the later the levantine phase these are predated in the late oligocene through middle miocene by gentle subsidence and separated during the late pliocene preglacial pleistocene by another period of relative quietness in tectonic activity

mechanisms of dilatant en echelon crack formation in bedded chalk abstract this study focuses on various styles of dilatant out of plane en echelon cracks which are associated with bed restricted burial joints that cut slightly deformed sediments in the beer sheva syncline there is a positive linear fit of en echelon crack length to layer thickness r2 0 928 in fringes which were formed by discontinuous breakdowns in joints lithological properties influence the breakdown process the breakdown of joints into en echelon cracks in chalk beds is influenced by both local conditions and remote stresses there are two distinct cases of opposite senses of segment rotation in a single fringe first in a curved fringe and second in a straight fringe the former can best be assigned to local deviations of the minimum principal direction from perpendicularity to the parent joint whereas the latter appears to reflect changes in remote stresses two of the three sets of en echelon segmentation which were distinguished in the beer sheva syncline are correlated with two distinct tectonic associations the k iii k i ratio increases from the layer centre towards the layer boundaries and this is the driving motivation for both the gradual increase of barb overlap from the centre towards the layer boundaries and the en echelon segmentation along the layer boundaries