the role of hydrogeological base level in the formation of sub horizontal caves horizons example from the dead sea basin israel this paper deals with the hydrogeological relationship between base levels of saline lakes and the formation of sub horizontal caves the mechanism presented here suggests that many horizontal cave levels in carbonate sequences are created adjacent to the saline lakes shorelines because of the converging of the groundwater flow above the fresh saline water interface the main factors that control enhanced carbonate dissolution and cave formation are high groundwater flow velocities in the shallow phreatic zone during a relative long steady state of the water table high groundwater flow velocities are evident close to the dead sea due to the convergent fast flows above the shallow interface adjacent to the shoreline the same could prevail in the case of previous paleo lakes that existed in the basin the synergetic combination of the above preconditions for enhanced cave formation seems to be responsible for the formation of elevation controlled alignment of paleo near shore cave levels in the central and southern dead sea portion of the study area these are found on the western fault escarpment and basin margin in different stratigraphic horizons of carbonate lithology many of the cave levels can be linked to late quaternary holocene lake levels obtained from dated lake sediments within the basin the most common cave s elevation was found to be around 200 m below sea level which was the elevation of the lisan lake during part of its history on the other hand the hula basin in the northern part of the dead sea basin was not occupied by saline water bodies since its formation as a base level and thus the above preconditions for enhanced cave formation did not prevail indeed this is evident by the lack of horizontal cave levels on its western carbonate margins unlike the situation in the south

investigation of coseismic and postseismic processes using in situ measurements of seismic velocity variations in an underground mine the in situ mechanical response of a rock mass to a sudden dynamic and static stress change is still poorly known to tackle this question we conducted an experiment in an underground mine to examine 1 the influence of dynamic and static stress perturbations on seismic velocities 2 elastic static stress changes and 3 induced earthquake activity associated with the blast and removal of a portion of hard rock we accurately 0 01 measured seismic velocity variations with ambient seismic noise correlations located aftershock activity and performed elastic static stress modeling overall we observe that the blast induced a sudden decrease in seismic velocities over the entire studied area which we interpreted as the damage due to the passing of strong seismic waves this sudden process is followed by a slow relaxation lasting up to 5 days while seismic activity returns to its background level after 2 days in some locations after the short term effects of the blast have subsided the seismic velocities converge to new baseline levels and permanent changes in seismic velocity become visible after comparing the spatial pattern of permanent seismic velocity changes with elastic static stress modeling we infer that the permanent seismic velocity changes are due to the change in the static volumetric stress induced by the removal of a solid portion of rock by the blast to our knowledge this is the first observation of noise based permanent seismic velocity changes associated with static stress changes

quantifying damage saturation and anisotropy in cracked rocks by inverting elastic wave velocities crack damage results in a decrease of elastic wave velocities and in the development of anisotropy using non interactive crack effective medium theory as a fundamental tool we calculate dry and wet elastic properties of cracked rocks in terms of a crack density tensor average crack aspect ratio and mean crack fabric orientation from the solid grains and fluid elastic properties using this same tool we show that both the anisotropy and shear wave splitting of elastic waves can be derived two simple crack distributions are considered for which the predicted anisotropy depends strongly on the saturation reaching up to 60 in the dry case comparison with experimental data on two granites a basalt and a marble shows that the range of validity of the non interactive effective medium theory model extends to a total crack density of approximately 0 5 considering symmetries up to orthorhombic in the isotropic case kachanov s 1994 non interactive effective medium model was used in order to invert elastic wave velocities and infer both crack density and aspect ratio evolutions inversions are stable and give coherent results in terms of crack density and aperture evolution crack density variations can be interpreted in terms of crack growth and or changes of the crack surface contact areas as cracks are being closed or opened respectively more importantly the recovered evolution of aspect ratio shows an exponentially decreasing aspect ratio and therefore aperture with pressure which has broader geophysical implications in particular on fluid flow the recovered evolution of aspect ratio is also consistent with current mechanical theories of crack closure in the anisotropic cases both transverse isotropic and orthorhombic symmetries were considered anisotropy and saturation patterns were well reproduced by the modelling and mean crack fabric orientations we recovered are consistent with in situ geophysical imaging

shallow perched groundwater a flux of deep co and near surface water rock interaction in northeastern jordan an example of positive feedback and darwin s warm little pond abstract darwin s warm little pond where he envisioned life began was perhaps metaphorical however it included the notion of separation just as the galapagos islands are separated from mainland south america we have studied a location where simple life flourishes far from other abundant life i e a permanently damp surficial zone that is surrounded by stark desert in ne jordan ne jordan is a young basaltic plateau with fresh outcrops however a positive feedback process has produced local weathering at biyar el ghussein in the tulul al ashaqif area calcite smectites and goethite occur with parent minerals water that is inducing this weathering has come from rainfall but the isotopic composition of abundant carbonate veins reveals a deep source i e volcanogenic co 2 a local coincidence of groundwater and rising co 2 is inducing a positive feedback process enhancing a weakly perched water table through weathering of basalt additional perched water dissolves more volcanogenic co 2 accelerating decomposition of the basalt and enlarging the aquiclude

scale dependent seismic velocity in heterogeneous media the measurable traveltimes of seismic events propagating in heterogeneous media depend on the geologic scale the seismic wavelength and the propagation distance in general the velocity inferred from arrival times is slower when the wavelength is longer than the scale of heterogeneity and faster when the wavelength is shorter for normal incidence propagation in stratified media this is the difference between averaging seismic slownesses in the short wavelength limit and averaging elastic compliances in the long wavelength limit in two and three dimensions there is also the path effect shorter wavelengths tend to find faster paths thus biasing the traveltimes to lower values in the short wavelength limit the slowness inferred from the average traveltime is smaller than the mean slowness of the medium when the propagation distance is much larger than the scale of the heterogeneity the path effect causes the velocity increase from long to short wavelengths to be much larger in two dimensions tha

new isotopic evidence for the origin of groundwater from the nubian sandstone aquifer in the negev israel the geochemistry and isotopic composition h o s osulfate c sr of groundwater from the nubian sandstone kurnub group aquifer in the negev israel were investigated in an attempt to reconstruct the origin of the water and solutes evaluate modes of water rock interactions and determine mean residence times of the water the results indicate multiple recharge events into the nubian sandstone aquifer characterized by distinctive isotope signatures and deuterium excess values in the northeastern negev groundwater was identified with deuterium excess values of 16 which suggests local recharge via unconfined areas of the aquifer in the negev anticline systems the d 18 oh2o and d 2 h values 6 5 and 35 4 of this groundwater are higher than those of groundwater in the sinai peninsula and southern arava valley 7 5 and 48 3 that likewise have lower deuterium excess values of 10 based on the geochemical differences between groundwater in the unconfined and confined zones of the aquifer a conceptual geochemical model for the evolution of the groundwater in the nubian sandstone aquifer has been reconstructed the isotopic composition of shallow groundwater from the unconfined zone indicates that during recharge oxidation of pyrite to so4 d 34 sso4 13 d 18 oso4 7 7 and dissolution of caco3 87 sr 86 sr 0 70787 d 13 cdic 3 7 occur in the confined zone of the aquifer bacterial so4 reduction removes a significant part of dissolved so 2

stressing of locked patches along a creeping fault an analysis is presented of the stressing of locked patches along a fault zone which is creeping elsewhere the model consists of strike slip faulted elastic lithospheric plates loaded in a manner equivalent to imposition of a remotely uniform tectonic shear stress the fault zone has an inhomogeneous strength distribution both depth wise and along strike it is modeled as being composed of locked patches and freely slipping parts treated as cracks the solution is given with the use of the line spring model which analyzes the problem by thickness averaged plane stress theory for lithospheric plates which slip along a discontinuity cut at the plate boundary as a boundary condition thickness averaged stress and slip at each local section along the cut was related to one another by the result of an antiplane strain analysis of slip for the crack or crack pair which describes the slipping and locked depth ranges at that section the analysis indicates that the slip distribution along creeping parts of the fault as well as the stress distribution along locked patches depends strongly on the geometry of these zones the model is used to examine stress concentrations associated with a slip deficient seismic gap along strike and to study the effect of local irregularities in the margin of a locked region it is also used to simulate slip and stressing processes associated with the creeping portion of the san andreas fault in central california between the presently locked zones of the great 1906 and 1857 ruptures and to constrain the nature of an apparently locked zone at the southeastern end which ruptures in characteristic parkfield earthquakes near fault creep and broadscale displacement data along the fault since the 1966 parkfield earthquake and inferences from seismicity distributions are used limitations of the modeling procedure at short spatial wavelengths prohibit an accurate description of the parkfield locked patch but results suggest that it may be localized and occupy a small fraction of area of the normal seismogenic zone an effective remote stressing rate of order 0 3 10 6 shear modulus yr is inferred together with a less well constrained 30 to 40 km lithospheric thickness for consistency with the displacement data results enable estimates of stress accumulation along the locked 1857 rupture zone and the build up of fracture energy release capability of order 107 j m2 in 150 yr at its lower margin

propagation of an aseismic dislocation through asperities with smooth borders abstract a 2 d model is presented for the propagation of a somigliana dislocation along a fault with nonuniform friction fault slip is driven by a uniform ambient shear stress slowly increasing with time the dislocation is nucleated in the lowest friction region of the fault plane and is confined by the surrounding higher friction regions asperities the case studied involves asperities which have smooth borders characterized by a constant friction gradient for values of ambient shear stress near to the weak zone friction the propagation of dislocation is slowed down by the presence of asperities only when it goes beyond the border does the dislocation front move at increasing velocity the model shows that at a given value of ambient shear stress the slip amplitude is larger in the case of finite and constant friction gradient than in the case of asperities with sharp borders unlike the propagation velocity slip rate is ever increasing during the dislocation process the model shows to what extent a dislocation is influenced by the distribution of friction on the fault a detailed knowledge of slip rate and slip history is needed to understand the mechanism of frictional instability on faults

paleoclimatic and archeological implications of pleistocene and holocene environments in azraq jordan abstract wetlands are a key archive for paleoclimatic and archeological work particularly in arid regions as they provide a focus for human occupation and preserve environmental information the sedimentary record from ayn qasiyya a spring site on the edge of the azraq qa provides a well dated sequence through the last glacial interglacial transition lgit allowing environmental changes in the present day jordanian desert to be investigated robustly through this time period for the first time results show that the wettest period at the site preceded the last glacial maximum which itself was characterised by marsh formation and a significant early epipaleolithic occupation a sedimentary hiatus between 16 and 10 5 ka suggests a period of drought in the region although seasonal rains and surface waters still allowed seasonal occupation of the azraq region archeological evidence suggests that conditions had improved by the late epipaleolithic about the time of the north atlantic younger dryas the changes between wet and dry conditions at the site show similarities to patterns in the eastern mediterranean and in arabia suggesting the jordan interior was influenced by changes in both these regions through the lgit climatic transition

fracture roughness and gouge distribution of a granite shear band 1 localization of deformation during fracture mechanical tests leads to the development of shear bands we performed triaxial tests using sidobre granite at four different confining pressures from 20 to 80 mpa we compared two sets of tests one set was stopped immediately after the formation of the shear band a second one included additional shear deformation from the analysis of thin sections of these laboratory samples we characterize the typical microstructures in the shear band mode i and ii cracks riedel cracks cataclastic flow statistical properties of rupture surface roughness and gouge grain size reveals scaling invariance using a mechanical profiler the fracture roughness is measured along parallel profiles and shown to be correctly described over up to 3 orders of magnitude by self affine geometry with a roughness exponent close to 0 80 this property is very similar to tensile crack even if local processes are different the influence of the slip is observed fracture surfaces are rougher along the slip direction 0 74 than perpendicular to it 0 80 the confining pressure is shown to have a weak effect on the fracture roughness it smoothes the surface slight increase of the roughness exponent gouge particles extracted from the shear band present a power law distribution with an exponent ranging from 1 44 to 1 91 this exponent appears to increase with the shearing displacement and the confining pressure when a significant shear of the band is combined with a high confining pressure i e impeded dilation of the band the hallmark of fragmentation is observed for the particle distribution and related to a smoothing of the band boundary

development distribution and palaeoenvironmental significance of terrestrial carbonates in the petra region southern jordan abstract terrestrial carbonate deposits are common in both natural and human modified landscapes in petra and its surroundings three broad genetic categories are recognized cementations of pre existing clastics veins crusts cemented cobbles free water deposits massive laminated deposits mld rhizoliths carbonate blisters coatings on archaeological water delivery systems and pedogenic deposits nodules calcrete the oxygen isotopic composition of carbonates suggests mainly precipitation from stored water that reflects the weighted isotopic average of rainfall in the area oxygen and carbon isotope data indicate that a combination of evaporation and co2 degassing are the mechanisms for precipitation depending on the setting and climate at the time of deposition strontium isotopes of carbonates point to an aeolian source from adjacent sources for the calcium the cementations of pre existing clasts are both markers of previous base levels in the case of cemented cobbles and the presence of soil above impermeable bedrock in the case of crusts and veins these types of deposits help to discover previously terraced sites the open water deposits reflect humid pleistocene conditions and their presence inform on the extent and distribution of water resources that may have been available in the late pleistocene and early holocene

the composition and evolution of the continental crust rare earth element evidence from sedimentary rocks the composition of the present day upper crust inferred from the uniformity of sedimentary rock r e e rare earth element patterns is close to that of granodiorite a revised andesite model is used to obtain total crustal composition the lower crust is the composition remaining assuming that the upper crust one third of the total is derived from intracrustal partial melting the upper crustal r e e pattern has pronounced eu depletion eu eu 0 64 the lower crustal pattern has eu enrichment eu eu 1 17 and the total crust has no eu anomaly relative to chondritic abundances the eu depletion in the upper crust is attributed to retention of eu in plagioclase in the lower crust because plagioclase is not stable below 40 km 10 kbar the anomaly is intracrustal in origin the archaean upper crust has a different r e e pattern to that of the present day upper crust being lower in total r e e and la yb ratios and lacking an eu anomaly these data are used to infer the archaean upper crustal composition which resembles that of the present day total crust except that ni and cr contents are higher the archaean crustal composition can be modelled by a mixture of tholeiites and tonalite trondhjemites the latter have steep light r e e enriched heavy r e e depleted patterns consistent with equilibration with garnet and hence probable mantle derivation there is little reason to suppose that the archaean lower crust was different in composition from the upper crust except locally where partial melting episodes occurred the r e e evidence is consistent with isotopic and geological evidence for a low continental growth rate in the early archaean a massive increase to about 70 of the total crust between about 3000 and 2500 ma b p and a slow increase until the present day the change from archaean to post archaean r e e patterns in the upper crust is not isochronous but is reflected in the sedimentary rock r e e patterns at differing times in different continents on the basis of a model composition for the mantle 36 of the potassium 30 of uranium 15 of lanthanum and 3 of ytterbium are concentrated in the present continental crust this enrichment is related to ionic size and valency differences from common mantle cations e g mg fe pre 3 9 ga b p crusts were obliterated by meteorite bombardment no geochemical evidence exists for primordial anorthositic sialic or mafic crusts

oxygen and hydrogen isotopes in the hydrologic cycle changes of the isotopic composition of water within the water cycle provide a recognizable signature relating such water to the different phases of the cycle the isotope fractionations that accompany the evaporation from the ocean and other surface waters and the reverse process of rain formation account for the most notable changes as a result meteoric waters are depleted in the heavy isotopic species of h and o relative to ocean waters whereas waters in evaporative systems such as lakes plants and soilwaters are relatively enriched during the passage through the aquifers the isotope composition of water is essentially a conservative property at ambient temperatures but at elevated temperatures interaction with the rock matrix may perturb the isotope composition these changes of the isotope composition in atmospheric waters surface water soil and groundwaters as well as in the biosphere are applied in the characterization of hydrological system as well as indicators of paleo climatological conditions in proxy materials in climatic archives such as ice lake sediments or organic materials

roughness of fault surfaces over nine decades of length scales 1 we report on the topographic roughness measurements of five exhumed faults and thirteen surface earthquake ruptures over a large range of scales from 50 m to 50 km we used three scanner devices lidar laser profilometer white light interferometer spanning complementary scale ranges from 50 m to 10 m to measure the 3 d topography of the same objects i e five exhumed slip surfaces vuache sillingy bolu corona heights dixie valley magnola a consistent geometrical property i e self affinity emerges as the morphology of the slip surfaces shows at first order a linear behavior on a log log plot where axes are fault roughness and spatial length scale covering five decades of length scales the observed fault roughness is scale dependent with an anisotropic self affine behavior described by four parameters two power law exponents h constant among all the faults studied but slightly anisotropic h 0 58 0 07 in the slip direction and h 0 81 0 04 perpendicular to it and two pre factors showing variability over the faults studied for larger scales between 200 m and 50 km we have analyzed the 2 d roughness of the surface rupture of thirteen major continental earthquakes these ruptures show geometrical properties consistent with the slip perpendicular behavior of the smaller scale measurements our analysis suggests that the inherent non alignment between the exposed traces and the along or normal slip direction results in sampling the slip perpendicular geometry although a data gap exists between the scanned fault scarps and rupture traces the measurements are consistent within the error bars with a single geometrical description i e consistent dimensionality over nine decades of length scales

structure controlled groundwater flow and salinization paths in the bet she an and harod valleys israel the bet she an and harod valleys are regional recipients and mixing zones for groundwater draining to these valleys from a multiple aquifer system this aquifer system includes two different carbonate aquifers several groundwater bearing basalt flows and deep seated pressurized brine the upflow of which causes salinization of fresh groundwater bodies these aquifers drain through two groups of springs due to lack of information on the subsurface structure of the valley the flow paths of groundwater feeding the springs the initial distribution of salinities along the valley and particularly the inflow paths of the brines have never been understood but were assumed to be fault controlled the interpretation of seismic profiles and analysis of gravity anomalies revealed the subsurface structure of the valley and namely the occurrence of a dense network of faults which branch out from those delineating the jordan dead sea rift the faults formed a series of uplifted and down warped horst and graben structures by joint analysis of structural hydrological and geochemical evidence it occurs that groundwater flow paths leading to the springs emerging in the middle of the bet she an valley are determined by structural elements such as major faults and fault controlled structures the penetration of the pressurized ca chloride rift brines and their inflow into fresh groundwater bodies occurs prevalently along the faults outlining the western margins of the dead sea rift valley and at their intersection with outbranching nw se striking faults

imaging along strike variations in mechanical properties of the gofar transform fault east pacific rise a large part of global plate motion on mid ocean ridge transform faults rtfs is not accommodated as major earthquakes when large earthquakes do occur they often repeat quasiperiodically we focus here on the high slip rate 14 cm yr gofar transform fault on the equatorial east pacific rise this fault is subdivided into patches that slip during mw 5 5 6 earthquakes every 5 to 6 years these patches are separated by rupture barriers that accommodate slip through swarms of smaller events and or aseismic creep we performed an imaging study to investigate which spatiotemporal variations of the fault zone properties control this segmentation in mechanical behavior and could explain the specific behavior of rtfs at the global scale we adopt a double difference approach in a joint inversion of active air gun shots and microseismicity recorded for 1 year this data set includes the 2008 mw 6 gofar earthquake the along strike p wave velocity structure reveals an abrupt transition between the barrier area characterized by a damaged fault zone of 10 20 reduced vp and a nearly intact fault zone in the asperity area the importance of the strength of the damage zone on the mechanical behavior is supported by the temporal s wave velocity changes which suggest increased damage within the barrier area during the week preceding the mw 6 earthquake our results support the conclusion that extended highly damaged zones are the key factor in limiting the role of major earthquakes to accommodate plate motion along rtfs

elastic wave velocities and permeability of cracked rocks abstract cracks play a major role in most rocks submitted to crustal conditions mechanically cracks make the rock much more compliant they also make it much easier for fluid to flow through any rock body relying on fracture mechanics and statistical physics we introduce a few key concepts which allow to understand and quantify how cracks do modify both the elastic and transport properties of rocks the main different schemes which can be used to derive the elastic effective moduli of a rock are presented it is shown from experimental results that an excellent approximation is the so called non interactive scheme the main consequences of the existence of cracks on the elastic waves is the development of elastic anisotropy due to the anisotropic distribution of crack orientations and the dispersion effect due to microscopic local fluid flow at a larger scale macroscopic fluid flow takes place through the crack network above the percolation threshold two macroscopic fluid flow regimes can be distinguished the percolative regime close to the percolation threshold and the connected regime well above it experimental data on very different rock types show both of these behaviors

geochemical patterns of groundwater from the palomares carboneras active fault area aquifers se spain determination of a network of sensitive sites indicators of seismic events the aim of this study is to evaluate the hydrogeochemical parameters of the palomares carboneras active fault zones se spain aquifers to establish especially sensitive sampling points that could be indicators of seismic activity in the fault zone we consider these points as a part of a network for this fault area and others in the south of spain with a seasonal and or continuous sampling in the future that may allow us to provide advices of possible seismic events the eastern part of the betic cordillera is a mediterranean semi arid zone with a special sensitivity to climatic fluctuations and human activity a remarkable scarcity in water resources is evident in this region making it difficult to find groundwater sampling points subsequently a network has been designed with 33 water sites selected for availability and proximity to the active fault zones where the physical chemical features and isotope contents of the groundwater have been determined taking into account the geological complexity as well as the different hydrogeological paths recognized in the area three geochemical families of water have been found 1 water with high electrical conductivity up to 14 000 s cm temperatures above 20 c and in some cases traces of boron 2 water with medium electrical conductivity 2 000 3 500 s cm temperatures above 20 c and traces of boron 3 water with electrical conductivity below 1 000 s cm temperatures below 20 c and absence of boron high temperature waters with presence of boron were selected as indicators of deep water circulation processes that can be connected to the seismic activity of the palomares carboneras active fault zones according to this study a selected sensible warning aquifer sites has been established

rare earth elements as geochemical tracers of regional groundwater mixing abstract the rare earth elements ree were analyzed in a groundwater system from south central nevada i e ash meadows national wildlife refuge the spring mountains pahranagat national wildlife refuge and the nevada test site in order to investigate their potential use as tracers of regional groundwater flow previous investigations using conservative tracers e g deuterium and uranium isotopes identified recharge in local mountains as the primary source 60 70 of total discharge for the springs in the regional discharge zone i e ash meadows with the remaining contribution being interbasin flow from the northeast initial mixing calculations for these groundwaters using shale normalized ree patterns agreed well with the previous studies however because the rees are not expected to behave conservatively in natural waters the effect of both solution complexation which acts to enhance the stability of the rees in solution as well as surface complexation responsible for the particle reactive behavior of the rees were examined in subsequent mixing calculations in order to assess the roles of solution and surface complexation relative partitioning coefficients were estimated for each ree in each groundwater by evaluating the ratio of the ionic strength corrected co 3 1 ree co 3 2 ree and co 3 2 f to the first hydrolysis binding constants for the rees the relative partitioning coefficients were then used to calculate ree patterns expected to develop and persist in solution as a consequence of solution and surface complexation the calculated ree values closely resembled the actual measured ree concentrations suggesting that the rees are in fact controlled by solution and surface complexation in these groundwaters the calculated ree concentrations were subsequently used to determine mixing ratios the results of which coincided with the initial calculations as well as the previous studies the results of this study suggest that solution complexation of the rees is sufficient to overcome to a certain degree the affinity of the rees to be adsorbed onto surface sites in the aquifers such that distinctive ree signatures develop and persist in solution in groundwaters from different aquifers the ability of solution complexation to overcome surface complexation is likely related to the formation of the negatively charged dicarbonato complex i e ln co 3 2 where ln is any ree which accounts for significant fractions of each ree in these groundwaters

the structure of the dead sea basin abstract the dead sea basin is located along the left lateral transform boundary between the arabian and sinai plates its structure and history are known from surface geology drilling seismic reflection and other geophysical data the basin comprises a large pull apart almost 150 km long and mostly 8 10 km wide which is flanked by a few kilometres wide zones of normal faulting the basin formed at about 15 ma or earlier close to the beginning of the transform motion and it reached about half its present length before the end of the miocene a strong negative gravity anomaly records a thick sediment basin fill 5 km under half its length reaching a maximum of 10 km the fill includes a few km of salt ca 6 4 ma which forms several diapirs at any one time large parts of the basin subsided simultaneously but the site of fastest subsidence seems to have shifted northward sedimentation rates reached at least hundreds of metres per million years or more in the miocene and 1 km myr in later periods the basin structure is dominated by longitudinal faults intrabasinal faults which delimit the pull apart and which are the extensions of the major strike slip faults north and south of the basin and normal faults which extend along the basin margins the latter faults express a small component of extension across the basin whereas the pull apart resulted from the much larger lateral motion along the basin in addition transverse faults divide the pull apart into several segments with somewhat different histories the pull apart grew by becoming longer parallel to the transform motion at shallow levels this was probably achieved by normal slip on transverse listric faults while the fill between them was little deformed the crust under the basin was stretched and thinned during basin lengthening which caused its subsidence basin formation was accompanied by uplifting of its flanks by 1 km sparse igneous activity occurred along the basin and its flanks its presence suggests a thermal anomaly in the lower lithosphere beneath the basin and adjacent parts of the transform

experimental study of the ultrasonic and mechanical properties of a naturally fractured limestone abstract this study investigates the changes in the ultrasonic and mechanical properties of a rock by means of ultrasonic wave velocity measurements on a brittle limestone containing natural fractures and bedding subjected to uniaxial compression tests the results showed that natural fractures and bedding reduced the velocity of ultrasonic waves and the mechanical strength of the limestone combined with the analysis of x ray ct images of the samples we found that the orientations of the bedding and of the pre existing penetrating fractures affected the direction of subsequent crack propagation under uniaxial compressional loading the initial disturbance factor d and the intactness factor s were calculated through the use of equivalent medium theory and hoek brown strength model the relationship between s and d was empirically characterized by an exponential fitting a parameter b was introduced that can be calculated from the s d relationship this parameter represents a strength index for the pre existing natural fractures based on the value of b the limestones studied were classified into four types fissures and bedding infilled fractures and bedding main infilled fractures and nearly intact

in situ observations of velocity changes in response to tidal deformation from analysis of the high frequency ambient wavefield we report systematic seismic velocity variations in response to tidal deformation measurements are made on correlation functions of the ambient seismic wavefield at 2 8 hz recorded by a dense array at the site of the pinon flat observatory southern california the key observation is the dependence of the response on the component of wave motion and coda lapse time measurements on the vertical correlation component indicate reduced wave speeds during periods of volumetric compression whereas data from horizontal components show the opposite behavior compatible with previous observations these effects are amplified by the directional sensitivities of the different surface wave types constituting the early coda of vertical and horizontal correlation components to the anisotropic behavior of the compliant layer the decrease of the velocity volumetric strain sensitivity s with indicates that this response is constrained to shallow depths the observed velocity dependence on strain implies nonlinear behavior but conclusions regarding elasticity are more ambiguous the anisotropic response is possibly associated with inelastic dilatancy of the unconsolidated low velocity material above the granitic basement however equal polarity of vertical component velocity changes and deformation in the vertical direction indicate that a nonlinear poisson effect is similarly compatible with the observed response pattern peak relative velocity changes at small are 0 03 which translates into an absolute velocity strain sensitivity of s 5 10 3 and a stress sensitivity of 0 5 mpa 1 the potentially evolving velocity strain sensitivity of crustal and fault zone materials can be studied with the method introduced here

discrimination between pressure and fluid saturation changes from time lapse seismic data explicit expressions for computing saturation and pressure related changes from time lapse seismic data have been derived and tested on a real time lapse seismic data set necessary input is near and far offset stacks for the baseline seismic survey and the repeat survey the method has been tested successfully in a segment where pressure measurements in two wells verify a pore pressure increase of 5 to 6 mpa between the baseline survey and the monitor survey estimated pressure changes using the proposed relationships fit very well with observations between the baseline and monitor seismic surveys 27 of the estimated recoverable hydrocarbon reserves were produced from this segment the estimated saturation changes also agree well with observed changes apart from some areas in the water zone that are mapped as being exposed to saturation changes which is unlikely saturation changes in other segments close to the original oil water contact and the top reservoir interface are also estimated and conf

epipalaeolithic settlement dynamics in southwest asia new radiocarbon evidence from the azraq basin a series of radiocarbon dates from two epipalaeolithic sites kharaneh iv and ayn qasiyya in the azraq basin of eastern jordan provide a new perspective on the chronology and settlement patterns of this part of southwest asia during the late pleistocene we discuss the implications to our understanding of the chronology of late pleistocene lithic industries particularly in regard to current hypotheses for the abandonment of eastern jordan s mega sites kharaneh iv and jilat 6 modelling a series of accelerator mass spectrometry dates from kharaneh iv indicates a much shorter span of occupation for the site than previously assumed by the size and density of its deposits given the high density of material accumulated over a relatively short time span we show that kharaneh iv was an aggregation site occupied intensively by a significant number of people providing new perspectives on the east jordanian phenomenon of epipalaeolithic mega sites copyright 2013 john wiley sons ltd

hydrochemistry of aquifers in the southern dead sea area southern jordan the demand for water resources in the area south of the dead sea due to continued development especially at the arab potash company apc works necessitates that water quality in the area be monitored and evaluated based on the local geology and hydrogeology the objective of this paper is to provide information on the past and present status of the main aquifers under exploitation or planned for future development two main aquifers are discussed the safi water field presently being operated and the dhiraa water field which is being developed the aquifer developed in the safi water field is shallow and fed by the hasa fault system which drains a significant portion of the karak mountains this aquifer seems to be well replenished within the core where no obvious long term degradation in water quality can be identified however in the low recharge areas within the distal portions of the alluvial fan there has been a degradation in water quality with time the degradation is caused by the dissolution of the lisan marl which is present at the outskirts of the fan system based on hydrochemistry of water in the wells the dhiraa field is a deep 800 950 m aquifer drilled specifically for the extraction of brackish water present in the kurnub aquifer available data indicate that there are at least three distinct water types within this field these water types are variable in quality and there may be potential for mixing of these waters thus affecting the quality of the freshest waters presently available tritium and oxygen isotope analysis indicate that the water is old and possibly nonrenewable

structural control on drainage network and catchment area geomorphology in the dead sea area an evaluation using remote sensing and geographic information systems in the wadi zerka ma in catchment area jordan the geology of jordan is characterized by fault systems with three major trends 1 nw se the oldest 2 wnw ese and 3 nnw sse the youngest the drainage network of the wadi zerka ma in catchment area located in the middle of the dead sea rift parallels these structural orientations a regional transtensive fault with embedded normal faults bounds the lower and middle part of the catchment area the topographic profile of the zerka ma in river exhibits two major knickpoints where it crosses two major embedded normal faults the second major knickpoint developed as a result of the dramatic lowering of the lisan lake water level a lake that pre dates the dead sea the decreased water level triggered river incision into the clastic sandstone units of wadi zerka ma in we performed a morphotectonic analysis study to investigate how the rock structures control the drainage network and the catchment area geomorphology according to the transverse topographic symmetry factor t the catchment area is highly asymmetric the major basin asymmetry trend is se oriented parallel to the oldest set of fault systems the catchment area displays a convex hypsometric curve indicating a very recent stage in the geomorphologic cycle our study indicates that the lisan lake catchment area shrinkage and structures growth controlled and shaped the wadi zerka ma in catchment area geomorphology the combined use of a geographic information system gis and remote sensing was shown to be very efficient in unraveling the evolution of the drainage network and catchment area geomorphology

breaking of a single asperity rupture process and seismic radiation the problem of spontaneous shear rupture of a single circular asperity on an infinite fault plane is studied initially the fault plane is broken everywhere except at a circular asperity an applied displacement at infinity results in a stress concentration along the bounding edge of the asperity the frictional stress on the broken part of the fault plane is taken to be a constant once a point on the asperity breaks the stress there drops to the same value as on the main fault surface the rupture is started by relaxing the shear stress at a point on the asperity edge and is then allowed to propagate spontaneously using a critical stress level fracture criterion the rupture process is calculated numerically it is found that for asperities of constant strength the rupture first propagates around the edge of the asperity and then inward a phenomenon best described by the well known term of classic military maneuver the double encircling pincer movement in the appendix the expressions for the far field seismic radiation due to the rupture of such an asperity are derived it is shown that the nth cartesian component of the far field displacement at x t for p sv and sh waves using the notation of aki and richards 1980 is given by un x t dni 4 c2r s0 i3 t r c ds thus the far field pulses can be directly found from the stress drops on the fault plane this formula is also true for crack or dislocation problems the directivity function dni for displacement for the asperity problem is found to be that for the double couple modified by some factor in particular the fault plane is a nodal plane for sv waves for the rupturing of asperities on a finite fault these directivity functions are applicable only to the initial part of observed pulses at a receiver provided the receiver is not located on the fault plane outside the broken part of the main crack edge in which case it is inapplicable for all time

seismic anisotropy in sedimentary rocks part 2 laboratory data part one of this paper presents a method for measuring seismic velocities and transverse isotropy in rocks using a single core plug this method saves at least two thirds of the time for preparing core samples and measuring velocities in transversely isotropic ti rocks using this method we have measured velocity and anisotropy of many shale and reservoir rocks from oil and gas fields around the world we present some of the data in this paper which include seismic velocity and anisotropy in 17 brine saturated shale samples 1 gas and brine saturated coal sample 8 brine saturated sands 12 gas saturated sands 32 gas saturated carbonate samples and 25 brine saturated carbonate samples the results show that clays and fine layering in sedimentary rocks are the main causes of seismic anisotropy very little intrinsic anisotropy exists in unfractured reservoir rocks such as sands sandstones and carbonates under reservoir conditions in contrast all shales were found seismically anisotropic anisotr

compressibility of porous rocks four compressibilities are defined for porous rock relating changes in the bulk and pore volumes to changes in the pore and confining pressures using a micromechanical theory based on classical linear elasticity three relations are found between these compressibilities two of these relations are verified experimentally for berea and bandera sandstone bounds are derived for these compressibilities involving only the porosity and the elastic moduli of the rock forming minerals for the strains to be unique functions of the stresses the compressibilities must be functions only of the difference between the confining and pore pressures this dependence is verified for berea bandera and boise sandstone while the strains cannot be expressed as functions of an effective stress regardless of how it is defined the elastic volumetric behavior of porous rocks can be studied through tests conducted at zero pore pressure

geology and hydrochemistry of the deep sandstone aquifers of jordan the deep sandstone aquifer complex of jordan consists of hundreds of meters of paleozoic to lower cretaceous sandstones that extend from the saudi arabian border in the south up to northern jordan in the south this aquifer is known as the disi aquifer and is near the surface well understood and heavily exploited toward the north thick accumulations of later mesozoic and cenozoic sedimentary sequences cover the complex the depth of the aquifer in this area makes it less viable as a water resource thus little is known about its origin movement and chemical evolution a number of exploration and production wells have penetrated this aquifer throughout central and northern jordan the data from these wells can help to draw a reasonable understanding about this aquifer and its water most of the aquifer is under artesian pressure and the piezometric head data point to a general flow north with drainage of the aquifer into the dead sea rift basin stable isotopes show that the water differs from modern meteoric water in the region and thus is possibly late pleistocene in age the water is slightly brackish and according to jordanian standards it can be used for drinking under certain conditions geochemical modeling shows that here is no evidence that the salinity is primarily the result of prolonged water rock interactions but more likely the result of mixing with possibly trapped connate water throughout the complex

damage and recovery of calcite rocks deformed in the cataclastic regime compressional and shear wave velocities have been measured during the experimental deformation of carrara marble and solnhofen limestone in the cataclastic regime both in dry and wet conditions at room temperature measurements were performed under hydrostatic conditions up to 260 mpa confining pressure and 10 mpa pore pressure during triaxial loading at the constant strain rate of 10 s as well as during differential stress relaxation during a full cycle our results show that the seismic velocities first increase as effective mean stress increases however when the stress onset of cataclastic deformation was reached elastic velocities showed rapid decrease due to stress induced damage in the rock during stress relaxation tests we observed an increase of elastic velocities with time which suggested a fast recovery of the microstructure a substantial and rapid drop in the velocities occurred when reloading suggesting that the previous recovery was only transient subsequent relaxation tests showed other marked increases in velocities these experimental results suggest that during the deformation of low porosity calcite rich rocks dilatant crack opening and frictional sliding and compaction micromechanism pore closure compete evolutions of elastic properties mainly sensitive to crack density and macroscopic volumetric strain more sensitive to porosity are therefore not systematically correlated and depend on the strain rate the solid stress conditions and the

earthquakes as self organized critical phenomena a cellular automation model with threshold elements previously proposed by bak et al 1988 which generates 1 f noise and self organizes into a critical state is studied as a model for earthquake occurrence the model explains some of fractal features of earthquakes such as the power law distribution of the size of the earthquake the model is modified so that every earthquake may trigger aftershocks the modified trigger model explains other fractal features of earthquakes such as the power law decay of aftershock frequency and the power law decay of aftershock frequency and the power law correlation of the hypocenter distribution

velocities and quality factors of sedimentary rocks at low and high effective pressures summary techniques for measuring acoustic velocities and quality factors q of sedimentary rocks in the laboratory are sufficiently accurate to establish closely fitting regression curves which represent the variation of these acoustic properties with pressure ultrasonic p and s wave measurements of velocity v v and q q q were made on 16 different water saturated sandstone samples at various effective pressures using an ultrasonic reflection technique and the data were fitted using a simple regression equation containing a constant plus linear and exponential pressure dependent terms the redundancy of the linear term in the regression of q data suggests that microcracks alone govern the pressure variation of q whereas velocities are additionally dependent on another mechanism consistent with the changes in elastic moduli caused by intergranular compression causing small reductions in porosity the implied rates of microcrack closure with increasing effective pressure in all samples were found to be comparable the regression equations describe the data closely enough to enable the extrapolation of acoustic properties to both low and high effective pressures this is of practical use since laboratory techniques can produce uncertain results at low pressures due to coupling problems and low signal strengths whilst high pressures require large confining vessels low pressure and high pressure data are applicable to shallow seismic surveys and hydrocarbon exploration respectively

evidence of deep water inflow in a tectonic window of the northern apennines italy water samples from the river network and from some shallow and brackish springs located in a tectonic window of the northern apennines of italy were studied in the frame of a comprehensive hydrogeological investigation in order to better understand the origin and the mixing processes between the two water types noticed also in previous studies ca hco3 and na cl a sampling campaign covering the drought period during year 2010 was planned to gather electric conductivity temperature and redox potential data along the river network and on groundwater occurrences located inside the tectonic structure additionally eight water samples were collected for hydrochemical major anions and cations na k ca2 mg2 hco3 cl so4 2 and trace ion btot and isotopic 18o 2h 3h analyses and compared with other eighteen samples from shallow and brackish springs collected near the study site during the period 2005 2012 moreover river discharge and water balance estimations were carried out results confirmed the presence of old na cl water with salinity progressively increasing up to 5 5 g l 1 at the northern termination of the tectonic window these values are in agreement with the ions contents of the most mineralized spring macognano spring salinity of 7 6 g l 1 which has been considered as having the deepest and longest flow path stable isotopes and trace ions contents are consistent with rainfall and snowmelt water mixed with brines associated with a hydrocarbon reservoir hosted at depth considering as end member the more mineralized na cl water a cumulate inflow in the range of 12 9 5 9 l s 1 has been estimated this aliquot is released into the river network with different mixing proportions by the groundwater occurrences discharging from the autochthonous flysch unit

climatological signals of the paleogroundwater in jordan abstract isotopic data on paleowaters from various groundwater basins in jordan have been compiled in order to document the various types in terms of age and 18 o d relationships the data indicate that the various types of water can be correlated with the various climatic pluvial phases which have affected the area since the beginning of the wurm period thus the oldest waters 30 ka have d values d d 8 18 o which range from 0 5 to 9 middle to late wurm waters from 8 6 to 17 middle holocene from 13 to 18 and modern precipitation from 21 to 30 moreover the slopes of the regression lines which describe the various suites of data have been decreasing from 9 3 for the oldest waters 8 1 for middle to late wurm waters 6 4 for middle holocene water and 6 2 for modern precipitation the trends of the groundwater isotopic contents with time suggest that although pluvials are part of the climatic cycles in the region there seems to be a significant change in the climatic conditions at the source of the moisture from one pluvial period to the next this change suggests lower relative humidity over the water masses i e the mediterranean sea through time moreover the slopes of the regression lines suggest increasing re evaporation before recharge through time also suggesting lower relative humidity in the areas of precipitation the data suggest that the timing of recharge of waters in the area can be roughly estimated based on the oxygen and deuterium isotopic signature

structural control of groundwater flow regimes and groundwater chemistry along the lower reaches of the zerka river west jordan using remote sensing gis and field methods a hydrogeological study was completed within a sub catchment of the zerka river drainage basin in western jordan the system is characterized by anticlinal bending with an axis trending ssw nne and plunging a few degrees in the ssw direction the anticlinal structure diverts groundwater flow towards the ssw while the strike slipe faults cause the groundwater to diverge where the fault is perpendicular to the groundwater flow lines and to converge where the fault is parallel to the groundwater flow lines a direct relationship was found between the location of springs and the type of groundwater flow with regard to the amount of discharge wherein large spring discharges are located in zones of converging groundwater flow lines in areas where faults are not abundant the groundwater retention time in the aquifers is long and a zonation of the electrical conductivity was detected due to mineral dissolution by controlling groundwater flow the anticlinal setting produces three genetic groups of groundwater flow systems 1 alkaline earth alkaline water which is predominately a bicarbonate type composition 2 alkaline earth alkaline water which is predominately bicarbonate sulfate and 3 alkaline earth alkaline water with a high alkaline component

analysis of peak ground motion in terms of a model of inhomogeneous faulting measurements of peak ground velocity v and acceleration a for earthquakes and mine tremors with local magnitudes ranging from 0 8 to 6 4 have been analyzed in terms of a model of inhomogeneous faulting the fault model involves the failure of a circular asperity of radius ri surrounded by a previously faulted annular region of outer radius r0 the failure of the asperity results in seismic radiation with a characteristic frequency proportional to 1 ri followed by lower frequency radiation proportional to 1 r0 as static equilibrium is regained over the larger region for r0 ri 1 both v and a are associated primarily with the failure of the asperity but also depend on the large scale source parameters specifically v r0 r 0 10 r0 ri 0 15 and a r 0 30 r0 ri 2 0 45 where is the shear wave velocity is the overall stress drop is the modulus of rigidity and is density the terms involving r0 ri correspond to the high frequency radiation associated with the failure of the asperity and the other terms indicate the peak parameters due to the broad scale readjustment observations of peak ground motion for events with seismic moments ranging from 5 1016 to 1026 dyn cm indicate that r0 ri is normally in the range of 1 10 and appears to be independent of earthquake size the inhomogeneous fault model also yields convenient expressions for the small scale displacement and stress drop of the asperity failure as well as for the level of regional stress available to cause slip

groundwater chemistry of strike slip faulted aquifers the case study of wadi zerka ma in aquifers north east of the dead sea wadi zerka ma in catchment area is located to the north east of the dead sea it has two types of aquifers a an upper unconfined aquifer and b a lower confined aquifer the two aquifers are separated by a marl aquiclude a major strike slip fault passes perpendicularly through the two aquifers and the aquiclude layer with embedded normal faults the aim of the study was to specify the effect of the major strike slip fault on the groundwater chemistry the spatial variability of the hydrochemical compositions and physiochemical parameters of the groundwater were investigated it was found that the embedded normal faults of the strike slip fault form conduits that allow groundwater to flow from the lower aquifer to the upper aquifer resulting in mixed groundwater the ratio of mixing was estimated to be 94 groundwater from the upper aquifer and 6 from the lower aquifer since groundwater in the lower aquifer is around three times more saline than the upper aquifer water mixing into the upper water aquifer generates a salinity hazard

geochemistry and pollution of shallow aquifers in the mafraq area north jordan chemical data are used to clarify the hydrogeological regime in the mafraq area in northern jordan as well as to determine the status of water quality in the area groundwater from the shallow aquifer in the mafraq area can be divided into two major groups according to geographical locations and chemical compositions water in the basaltic eastern part of the study area is characterized by the dominance of chloride sulfate sodium and potassium whereas waters in the limestone aquifers in the west are dominated by the same cations but have higher concentrations of bicarbonate stable isotopes show that the shallow aquifers contain a single water type which originated in a distinct climatic regime this water type deviates from the global meteoric water line mwl as well as from the eastern mediterranean meteoric water line the waters are poor in tritium and thus can be considered generally older than 50 years chemical mass balance models suggest that water is moving from the west towards the north of the study area this suggests that waters from the different basins are separated from each other degradation of water quality can be attributed to agricultural fertilizers in most cases although the waste water treatment plant at khirbet es samra is a contributor to pollution in the southwestern part of the study area

penetration of a quasi statically slipping crack into a seismogenic zone of heterogeneous fracture resistance this paper is concerned with some aspects of nonuniform stressing above a deep creeping portion of a fault zone prior to a large crust breaking earthquake the model that we use involves a slipping crack representing the deeper more stably sliding portions of the fault zone which penetrates upward from depth and is blocked in the lower region of the seismogenic zone when conditions are uniform along strike the upward penetration at the crack front is by mode iii in strike slip fault zones but by mode ii in thrust or normal fault zones two major results are reported first we analyze approximately via a linear perturbation formulation how a tectonic crack front encounters and ultimately shears through arrays of localized asperities that are distributed parallel to the crack front and have a toughness which is greater than that of adjoining segments of the fault zone using a fast fourier transform based numerical procedure to simulate crack penetration into asperities we find a notable difference between mode ii and mode iii crack fronts in that the former penetrates approximately twice as far between the asperities as the latter under the same loading level this is interesting because observations of slip distribution in large earthquakes suggest that there is a significant aseismic component to the total slip budget in subduction zone earthquakes which in contrast does not seem to be present in strike slip zone earthquakes and also that the surface slip distribution in continental dip slip faulting is typically much more irregular than for strike slip faulting in a simulation involving multiple rows of periodic asperities we note that the more deeply penetrating mode ii crack front contacts more asperities simultaneously while breaking them at different load levels compared to the less flexible mode iii crack front which simply breaks one row of asperities and jumps unstably to the next the second major result concerns whether a straight crack front in the lithosphere along a strike slip fault zone is configurationally stable that is whether the crack front will tend to remain straight as the crack penetrates upward from depth it is found that for infinitesimal perturbations of the straight front beyond a critical wavelength of the order of the crustal lithosphere thickness the stress intensity factor is higher at the most advanced portions of the crack front rather than at the least advanced the opposite is true at shorter wavelengths when resistance to crack growth is essentially uniform over the fault plane this means that the straight crack front is configurationally unstable at long wavelengths the issue of configurational stability is related to the concept of fault segmentation which is based on the observation that fault zones particularly long ones do not rupture along their entire length during a single earthquake effect of a vertical gradient of fracture resistance is discussed in the appendix where it is shown that a significant upward gradient of resistance to crack growth may completely stabilize the straight crack configuration

ground water origin and movement in the upper yarmouk basin northern jordan the upper yarmouk basin in northern jordan has become an increasingly important groundwater resource in recent years despite this studies of groundwater recharge and movement in the area are limited and mostly parts of larger scale regional data syntheses detailed analysis of the hydrogeology hydrochemistry and isotopic data indicate a more complex system than previously presented whereas earlier studies suggested that groundwater is derived from a single aquifer this study suggests abstraction from multiple aquifers moreover faults and lineaments in the area may be causing segmentation and limited flow within individual aquifers the isotopic and hydrochemical data suggest that local recharge plays a significant role in the hydrogeologic situation in the study area this appears to be mostly happening in the hilly zone in the central part of the study area

crustal earthquake instability in relation to the depth variation of frictional slip properties recent stability studies using constitutive relations of the type found by dieterich ruina and others to describe frictional slip of rocks in the laboratory have provided a new explanation of the depth cutoff of shallow crustal earthquakes the class of friction laws discussed has the property that the sliding stress depends on normal stress temperature slip rate and slip history for sliding at a fixed slip rate v and fixed environment e g normal stress temperature etc the shear strength evolves toward a steady state value ss v stability analysis show that for d ss v dv 0 velocity strengthening implies stable steady state sliding at least for a broad class of constitutive laws more fully described in the paper experiments by dieterich and by tullis and weeks on westerly granite with mature sliding surfaces indicate that d ss v dv is negative at room temperature whereas higher temperature experiments by stesky show that d ss v dv becomes positive above approximately 300 c therefore in the case of the earth where temperature increases with depth the above observations seem to suggest that the depth cutoff of crustal earthquake activity can be understood in terms of the variation of the frictional response with depth from a regime with d ss v dv 0 this is not inconsistent with but rather refines the suggestion by sibson and others that the depth cutoff is due to a transition from brittle friction to ductile flow further our results show definitively that the shallow depth confinement of seismicity is compatible with a model in which deformation is localized to a fault zone extending well below the seismogenic depth the depth confinement does not require a model showing transition to a zone of broadly distributed creep flow beneath the seismogenic zone following mavko a two dimensional quasi static strike slip fault model is analyzed but using different numerical procedures and a depth variation of frictional properties based on the laboratory data mentioned above and the lachenbruch sass depth variation of temperature for the san andreas fault the resulting predictions of such features as the confinement of crustal earthquakes to shallow depths the development of locked patches the recurrence time for the seismic cycle the seismic stress drop and displacement etc are generally in agreement with the observed characteristics of large scale strike slip earthquakes along the san andreas fault calculations based on the laboratory data predict for example that stick slip nucleates around 5 7 km that large seismic motion occurs around the nucleation depth and above but diminishes gradually to zero at 13 15 km depths that rapid postseismic creep occurs over another 3 4 km depth and that at greater depths steady slip consistent with the average plate velocity is only modestly perturbed by the earthquakes occurring above the most uncertain parameter is the slip weakening distance l for evolution of fault surface state we illustrate how features of the predicted earthquake cycles vary with l over the range for which calculations are feasible

microcracking during triaxial deformation of porous rocks monitored by changes in rock physical properties ii pore volumometry and acoustic emission measurements on water saturated rocks abstract we report results from a series of laboratory triaxial deformation experiments performed on samples of darley dale sandstone at servo controlled constant strain rate and constant pore fluid pressure during deformation the volume of water either expelled from the samples during compaction or injected into the samples during dilatancy in order to maintain a constant pore fluid pressure was continuously monitored throughout each experiment in addition the parameters of differential axial stress axial strain and acoustic emission ae characteristics were also recorded complete ae waveforms were also captured and stored by means of a transient recorder and fourier analysis of these waveforms was subsequently carried out the reported experiments were all performed in a conventional high pressure gas medium triaxial cell but with the pore fluid pressure maintained constant using a new servo controlled fluid pressure intensifier and pore volumometer the ae and pore volumometry measurements on water saturated rocks reported in this paper are complementary to the measurements of elastic wave propagation parameters made on dry rocks and reported in a companion paper in this issue the two suites of data have been integrated to infer relations between crack density parameters calculated from elastic wave velocity measurements and the directly measured pore volume during deformation our results show a distinct positive correlation between changes in the axial crack density parameter x and changes in the pore volume during deformation once fluid expulsion due to elastic pore collapse has been corrected for these two parameters have then been combined to obtain an estimate of changes in the mean aspect ratio of propagating dilatant cracks the results suggest that under moderate confining pressures axially aligned dilatant cracks are likely to bow open elastically prior to significant crack extension and growth

attenuation behaviour of tuffaceous sandstone and granite during microfracturing summary laboratory measurements of ultrasonic wave propagation in tuvaceous sandstone kimachi japan and granite iidate japan were performed during increasing fracturing of the samples the fracturing was achieved by unconfined uniaxial compression up to and beyond the point of macrofracture of the specimen using a constant low strain rate the observed variation of wave velocity up to 40 per cent due to the development of micro and macrofractures in the rock is interpreted by rock models relating velocity changes to damage and crack density the calculated density of the newly formed cracks reaches higher values for the sandstone than for the granite using the estimated crack densities the attenuation behaviour is interpreted in terms of diverent attenuation mechanisms that is friction and scattering rayleigh scattering as described by the model of hudson 1981 may explain the attenuation qualitatively if the largest plausible crack dimensions are assumed in modelling

interplay of seismic and aseismic deformations during earthquake swarms an experimental approach observations of earthquake swarms and slow propagating ruptures on related faults suggest a close relation between the two phenomena earthquakes are the signature of fast unstable ruptures initiated on localized asperities while slow aseismic deformations are experienced on large stable segments of the fault plane the spatial proximity and the temporal coincidence of both fault mechanical responses highlight the variability of fault rheology however the mechanism relating earthquakes and aseismic processes is still elusive due to the difficulty of imaging these phenomena of large spatiotemporal variability at depth here we present laboratory experiments that explore in great detail the deformation processes of heterogeneous interfaces in the brittle creep regime we track the evolution of an interfacial crack over 7 orders of magnitude in time and 5 orders of magnitude in space using optical and acoustic sensors we explore the response of the system to slow transient loads and show that slow deformation episodes are systematically accompanied by acoustic emissions due to local fracture energy disorder features of acoustic emission activities and deformation rate distributions of our experimental system are similar to those in natural faults on the basis of an activation energy model we link our results to the rate and state friction model and suggest an active role of local creep deformation in driving the seismic activity of earthquake swarms

hydrological controls on diurnal ice flow variability in valley glaciers 1 this paper uses a combination of field data and three dimensional modeling to investigate the spatial variability in basal conditions required to induce observed fluctuations in diurnal ice velocity at haut glacier d arolla switzerland a network of surface velocity markers was observed at intervals of as little as four hours over diurnal cycles in both winter and late summer winter motion showed limited diurnal variability presumably due to the absence of supraglacial meltwater inputs by contrast diurnal fluctuations in ice motion were recorded in summer across the lower and upper glacier in the lower glacier surface velocities were intimately linked to hydrological forcing in the vicinity of a subglacial channel previously observed diurnal excursions of meltwater away from the channel should reduce areas of basal drag adjacent to the channel thereby impacting on ice dynamics using a first order ice flow approximation we investigated the distribution of basal shear traction adjacent to the channel necessary to replicate the observed surface velocity field during periods of rapid ice motion the modeling suggests that the observed variations in diurnal velocity will only occur with extensive reductions in basal drag across a transverse zone of up to 560 m across well beyond the immediate vicinity and previously observed extent of diurnal excursions of meltwater away from the subglacial channel

lake elji and a geological perspective on the evolution of petra jordan abstract the draining of the herein introduced ancient lake elji and the subsequent erosion of its lacustrine sediments were necessary precursors to the late epipalaeolithic natufian and later settlement of petra this study investigates this geological history and relates it to human occupation of the broader region widespread carbonates consisting of algal mat deposits beach rocks and rhizoliths are consistently present at the 1060 m contour line of what is believed to be the shoreline of lake elji in the petra basin well sorted siliciclastic fluvio lacustrine sediments at lower elevations and human settlement patterns all indicate that a standing body of water once existed in the area stable isotopes of carbon and oxygen as well as the fossil assemblages and the textures of the carbonate deposits suggest that the body of water was an open lake with regular outflows a sill has been identified at ras btahi indicating a southward outflow direction as opposed to the current drainage pattern towards the west the lack of a basin closure towards the west at the time as evidenced by thick low energy sediment accumulations suggest that tectonic movements were responsible for breaching the lake and establishing the current hydrological pattern results obtained from the optical stimulated luminiscence osl in the palaeolake sediments indicate that the basin was closed from at least 100 ka up to approximately 9 ky this timeline is also supported by the distribution of archaeological sites in the area and a previously documented massive erosional event at the end of this period subsequent gradual denudation of the basin sediments allowed for the settlement in the center of petra during the early nabatean period

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

rare earth distributions with a positive ce anomaly in the western north atlantic ocean from the vertical distributions of the rare earth elements ree in the sargasso sea we now report the first profiles of pr tb ho tm and lu in seawater together with profiles for la ce sm eu and yb the first observations of positive ce anomalies in seawater are ascribed to reducing inshore sediments as a source for ce ref 1 all vertical profiles are consistent with adsorption of trivalent rare earths by settling particles possibly siliceous or calcareous followed by their release at or near the sea floor on dissolution of the carriers the very different ce profile demonstrates the additional effects of oxidation reduction reactions

single fractures under normal stress the relation between fracture specific stiffness and fluid flow abstract fracture specific stiffness and fluid flow through a single fracture under normal stress are implicitly related through the geometry of the void space and contact area that comprise the fracture data from thirteen different rock samples each containing a single fracture show that relationships between fracture specific stiffness and fluid flow through a fracture fall into two general classes of behavior fractures either fall on a loosely defined universal curve relating fluid flow to fracture specific stiffness or else the flow is weakly dependent on fracture specific stiffness the second relationship shows that flow decreases slowly with increasing fracture specific stiffness the first relationship shows that flow decreases rapidly for increases in fracture specific stiffness to understand this behavior computer simulations on simulated single fractures were performed to calculate fluid flow fracture displacement and fracture specific stiffness as a function of normal stress simulated fractures with spatially correlated and uncorrelated aperture distributions were studied fractures with spatially uncorrelated aperture distributions tend to exhibit a weak dependence of fluid flow on fracture specific stiffness because these fractures tend to have multiple connected paths across the sample which can support flow with uniformly distributed contact area thus an increment in stress will increase the stiffness of the fracture without greatly reducing the amount of fluid flow on the other hand fractures with spatially correlated aperture distributions tend to belong to the universal relationship because correlated fractures tend to have only one or two dominant flow paths and the contact area is limited to a few regions resulting in a compliant fracture thus an increment in stress on a spatially correlated fracture will result in an increase in stiffness and rapid decrease in fluid flow these spatial correlations in fracture void geometry can be differentiated in the laboratory based on the observed fracture specific stiffness fluid flow relationship for a single fracture under normal loading

dispersion and anisotropy of elastic waves in cracked rocks 1 rocks in the earth s crust contain variable amount of cracks depending on the deviatoric and confining stress levels pore pressure and temperature conditions crack damage results in effects that have been investigated for a long time in particular a decrease in elastic wave velocity and the development of anisotropy in this paper we focus on cracked rocks and develop a method to calculate both the elastic wave anisotropy and the dispersion in a fluid saturated cracked rock we show that analytic expressions can be derived for both properties in terms of the crack density tensor components two fundamental theoretical tools are used in this purpose the first one is the effective medium theory and the second one is the anisotropic poroelastic theory using both it is possible from first principles to predict anisotropy and dispersion results are shown to be valid up to a total crack density of 0 5 the failure threshold appears close to a total crack density of 1 between 0 5 and 1 the model still gives reasonably good results anisotropy can increase up to 60 and dispersion up to 30 depending on the crack distribution these results point out important differences that could exist in fluid saturated rocks between laboratory high frequency data and field low frequency results

crustal deformation in great california earthquake cycles periodic crustal deformation associated with repeated strike slip earthquakes is computed for the following model a depth l h extending downward from the earth s surface at a transform boundary between uniform elastic lithospheric plates of thickness h is locked between earthquakes it slips an amount consistent with remote plate velocity vpl after each lapse of earthquake cycle time tcy lower portions of the fault zone at the boundary slip continuously so as to maintain constant resistive shear stress the plates are coupled at their base to a maxwellian viscoelastic asthenosphere through which steady deep seated mantle motions compatible with plate velocity are transmitted to the surface plates the coupling is described approximately through a generalized elsasser model we argue that the model gives a more realistic physical description of tectonic loading including the time dependence of deep slip and crustal stress buildup throughout the earthquake cycle than do simpler kinematic models in which loading is represented as imposed uniform dislocation slip on the fault below the locked zone parameters of the model are chosen to fit seismic and geologic constraints and the apparent time dependence of surface strain rates along presently locked traces of the 1857 and 1906 san andreas ruptures we fix vpl 35 mm yr tcy 160 years and l 9 11 km based on earthquake nucleation depths the geodetic data are then found to be described reasonably within the context of a model that is locally uniform along strike and symmetric about a single san andreas fault strand by lithosphere thickness h 20 30 km and elsasser relaxation time tr 10 16 years we therefore suggest that the asthenosphere appropriate to describe crustal deformation on the earthquake cycle time scale lies in the lower crust and perhaps crust mantle transition zone and has an effective viscosity between about 2 1018 and 1019 pa s depending on the thickness assigned to the asthenospheric layer predictions based on the chosen set of parameters are also consistent with data on variations of contemporary surface strain and displacement rates as a function of distance from the 1857 and 1906 rupture traces although the fit is degraded by asymmetry relative to the fault and by slip on adjacent fault strands

time dependent recovery of microcrack damage and seismic wave speeds in deformed limestone limestone samples were deformed up to 5 inelastic axial strain at an effective confining pressure peff 50 mpa in the cataclastic flow regime and subsequently maintained under constant static stress conditions either isostatic of triaxial for extended periods of time while elastic wave speeds and permeability were continuously monitored during deformation both seismic wave speeds and permeability decrease with increasing strain due to the growth of subvertical microcracks and inelastic porosity reduction during the static hold period under water saturated conditions the seismic wave speeds recovered gradually typically by around 5 relative to their initial value after 2 days while permeability remained constant the recovery in wave speed increases with increasing confining pressure but decreases with increasing applied differential stress the recovery is markedly lower when the samples are saturated with an inert fluid as opposed to water the evolution in wave speed is interpreted quantitatively in terms of microcrack density which shows that the post deformation recovery is associated with a decrease in effective microcrack length typically of the order to 10 after 2 days the proposed mechanism for the observed damage recovery is microcrack closure due to a combination of backsliding on wing cracks driven by time dependent friction and closure due to pressure solution at contacts between propping particles or asperities and microcrack walls the recovery rates observed in the experiments and the proposed underlying mechanisms are compatible with seismological observations of seismic wave speed recovery along faults following earthquakes

evidence of past environmental conditions during the evolution of a calcretised wadi system in southern jordan using stable isotopes abstract a stratigraphically and temporally ordered sequence of channel calcretes preserved along the wadi dana southern jordan records the quaternary evolution of the formation and infilling of rock cut channels and their subsequent incision in a tectonically subsiding basin it is currently unknown under what palaeoenvironmental conditions these non pedogenic calcretes formed stable isotope analyses have been used to investigate whether any past topographical hydrological vegetational diagenetic and or temporal signatures can be identified from the channel calcretes the results of this research indicate that channel calcrete development is influenced by altitudinal variation affecting vegetation and hydrology within the landscape as well as location within individual wadi channels which has an affect on diagenetic processes the lack of calcretisation of a terrace that is between 1 and 1 5 m above the modern wadi floor supports the idea that the environment is currently too arid for calcrete to develop thus the presence of older wadi dana channel duricrusts suggests wetter conditions when they formed the 18o data of the calcrete implies cooler conditions than today as there is little evidence of a strong evaporative effect any temporal control is limited and mainly a function of stratigraphic position with some numeric dating

seismic velocity changes caused by the earth tide ambient noise correlation analyses of small array data we examine seismic velocity changes due to the earth tide by conducting cross correlation function ccf analyses of ambient seismic noise recorded at a small array composed of seven seismometers in northeastern japan we calculate ccfs for the dilatational and contractional episodes that are predicted from theoretical tidal volumetric strains ccfs of the two episodes are highly correlated but tiny differences are found in their phases the phase differences are explained by seismic velocity changes of 0 19 0 06 at 1 2 hz which are interpreted to be caused by opening closure of cracks or pores in the shallow subsurface due to the tidal strain strain sensitivities of the seismic velocity changes are estimated to be 6 9 104 strain 1 which are almost consistent with those reported in previous studies using artificial sources

linear pressurization method for determining hydraulic permeability and specific storage of a rock sample summary we studied the methodology and applicability of linear pressurization for determining simultaneously hydraulic permeability and specific storage of a rock sample we analytically solved the governing equation for 1 d pressure diffusion through a homogenous isotropic cylindrical rock specimen located between a downstream and an upstream reservoir considering linear pressurization of the upstream fluid as the boundary condition the solution consists of a transient and a steady state for which both differential pressure between the two reservoirs and injection rate at the upstream reservoir assume constant values since the steady state differential pressure is linearly proportional to the compressive storage of the downstream reservoir tests conducted with a systematic variation of the size of the downstream reservoir permit determining permeability and specific storage from the intercept and slope of the linear relationship alternatively simultaneous measurement of differential pressure and fluid injection rate at steady state conditions provides a basis for calculation of the hydraulic properties as previously presented for linear injection experiments were performed on fontainebleau sandstone samples to document the feasibility of the method the determined storage capacity value is used to calculate various poroelastic parameters such as bulk and pore space compressibility skempton and the effective pressure coefficient

preseismic rupture progression and great earthquake instabilities at plate boundaries we present a procedure for modeling the initially quasi static upward progression of a zone of slip from some depth in the lithosphere toward the earth s surface along a transform plate margin culminating in a great crustal earthquake stress transmission in the lithosphere is analyzed with a generalized elsasser model in which elastic lithospheric plates undergo plane stress deformation and are coupled by an elementary foundation model to a maxwellian viscoelastic asthenosphere upward progression of rupture over a finite length of plate boundary corresponding to a seismic gap along strike is analyzed by a method based on the line spring concept whereby a two dimensional antiplane analysis of the upward progression provides the relation between lithospheric thickness averaged stress and slip used as a boundary condition in the generalized elsasser plate model the formulation results in a nonlinear integral equation for the rupture progression as a function of time and distance along strike a simpler approximate single degree of freedom analysis procedure is described and shown to lead to instability results that can be formulated in terms of the slip softening slope at the boundary falling below the elastic unloading stiffness of the surroundings the results also indicate a delay of ultimate seismic instability due to the stiffer short versus long time asthenospheric response and predict a final period of self driven creep toward instability the procedures for prediction of rupture progression and instability are illustrated in detail for an elastic brittle crack model of slip zone advance and parameters of the model are chosen consistently with great earthquake slips and stress drops for example an effective crack fracture energy of the order 4 106 j m2 at the peak 7 to 10 km below surface of a gaussian bell shaped distribution of fracture energy with depth with variance of the order 5 km simulating strength build up in a seismogenic layer leads to prediction of nominal seismic stress drops of 30 to 60 bars and slips of 2 to 5 m in great strike slip earthquake ruptures breaking 100 to 400 km along strike precursory surface straining in the self driven stage is predicted to proceed at a distinctly higher rate over time intervals beginning 3 to 10 months before such an earthquake this interval being greater for longer distances along strike over which the preseismic upward rupture progression takes place

rainfall recharge relationships within a karstic terrain in the eastern mediterranean semi arid region israel δ 18o and δd characteristics annual rainfall variations and processes in the upper vadose zone exert a profound influence on the chemical and isotopic compositions of waters of carbonate aquifers in semi arid climatic zones in order to define these processes we have studied the surface temperatures during rainfall events the isotopic composition of rain infiltrating and groundwaters this study was carried out within a karstic terrain soreq cave israel located in cenomanian dolomitic rocks approximately 40 km inland of the mediterranean sea and 400 m above sea level the climate is typical of the eastern mediterranean semi arid conditions with a rainy winter and dry summer and the average annual rainfall in the area is 500 mm close monitoring indicates that the d and 18o values of individual rainstorm events decrease with increasing rainfall annual average isotopic values of years with rainfall of 500 600 mm do not vary systematically years with extreme rainfall values define a negative covariation between the 18o and rainfall the d 18o relationship of all rain events of more than 20 mm fall on the mediterranean meteoric water line mmwl with a slope of 8 and d excesses of 20 30 these rain events occur when mid winter surface temperatures are 5 to 10 c rainfall events of less than 20 mm mainly occurring at above 10 c have slopes of less than 8 and smaller d excess as a consequence of evaporation processes beneath the clouds two main water types infiltrating into the cave are recognized slow and fast drip slow drip occurs from the tips of stalactites and takes place throughout the year these waters represent seepage water that remains in the upper vadose zone for up to several decades fast drip emanates from fissures in the cave roof during the winter seasons these waters represent vadose flow with a short residence time of less than 1 year the infiltration of the fast drip water into the cave depends on the fracture system of the rock cover and on the intensity of the rainstorms in the inner parts of the cave where the rock cover is thick fast drip starts only after several massive 20 mm rainstorms whereas below a thin roof the response time of fast drip is a few hours to a few days after intensive rainstorms both fast and slow drip water fall on the mmwl indicating that they are derived mainly from the relatively intensive rainstorms that compose about 23 of the annual rainfall although fast dri water represents massive rainstorms their 18o and d values are nonetheless higher by 1 and 10 respectively relative to the average rainwater compisition this indicates that the fast drip water consists predominantly of water derived from intensive rainstorms admixed with a minor component of isotopically 18o and d enriched water which is represented by the slow drip waters the fast drip waters are derived mainly from massive rain events at surface temperatures of 5 to 10 c which thermally equilibrate with the host rock and upon reaching the cave they have already acquired the mean temperature 20 c of the cave

the low temperature brittle ductile transition in a quartzite and the occurrence of cataclastic flow in nature the paper describes the mechanical and microstructural characteristics associated with the brittle to cataclastic flow transition in an orthoquarzite oughtibridge ganister and compares its microstructural development with features of cataclastic deformation of rocks in nature

sudden drop of seismic velocity after the 2004 mw 6 6 mid niigata earthquake japan observed with passive image interferometry 1 passive image interferometry pii is a seismological method employing ambient seismic noise to monitor the temporal evolution of mean shear wave velocity within the earth first the elastic green s tensor between two seismometers is computed from the cross correlation of seismic noise recorded during a certain period second the constructed seismograms of different time periods are treated as earthquake multiplets and small time shifts in their coda are used to invert a relative change in mean shear wave velocity when applied to the source region of the 2004 mw 6 6 mid niigata earthquake japan centroid depth 5 km we used noise recorded at six seismometers located at a distance of less than 25 km from the epicenter daily inversions during the 2 months before and after the earthquake show a sudden drop of mean shear wave velocity of some tenths of a percent at the time of the mid niigata earthquake using noise in two frequency bands 0 1 0 5 hz and 2 8 hz we find similar amplitudes for the velocity drop which indicates that changes are not restricted to the shallow subsurface possible interpretations of this velocity decrease are a decrease of crustal stress after the earthquake a nonlinear site response in the shallow subsurface layer due to strong ground motion or structural weakening due to the creation of new fractures in the source area of the earthquake

seasonal variations of seismic velocities in the san jacinto fault area observed with ambient seismic noise s u m m a r y we observe seasonal seismic wave speed changes dv v in the san jacinto fault area and investigate several likely source mechanisms velocity variations are obtained from analysis of 6 yr data of vertical component seismic noise recorded by 10 surface and six borehole stations we study the interrelation between dv v records frequency dependent seismic noise properties and nearby environmental data of wind speed rain ground water level barometric pressure and atmospheric temperature the results indicate peak to peak seasonal velocity variations of 0 2 per cent in the 0 5 2 hz frequency range likely associated with genuine changes of rock properties rather than changes in the noise field phase measurements between dv v and the various environmental data imply that the dominant source mechanism in the arid study area is thermoelastic strain induced by atmospheric temperature variations the other considered environmental effects produce secondary variations that are superimposed on the thermal based changes more detailed work with longer data on the response of rocks to various known external loadings can help tracking the evolving stress and effective rheology at depth

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

slip patterns and earthquake populations along different classes of faults in elastic solids numerical simulations of slip instabilities on a vertical strike slip fault in an elastic half space are performed for various models belonging to two different categories the first category consists of inherently discrete cellular fault models such are used to represent fault systems made of segments modeled by numerical cells that can fail independently of one another their quasi independence is assumed to provide an approximate representation of strong fault heterogeneity due to geometric or material property disorder that can arrest ruptures at segment boundaries the second category consists of models having a well defined continuum limit these involve a fault governed by rate and state dependent friction and are used to evaluate what types of property heterogeneity could lead to the quasi independent behavior of neighboring fault segments assumed in the first category the cases examined include models of a cellular fault subjected to various complex spatial distributions of static to kinetic strength drops and models incorporating rate and state dependent friction subjected to various spatial distributions of effective stress normal stress minus pore pressure the results indicate that gradual effective stress variations do not provide a sufficient mechanism for the generation of observed seismic response strong and abrupt fault heterogeneity as envisioned in the inherently discrete category is required for the generation of complex slip patterns and a wide spectrum of event sizes strong fault heterogeneity also facilitates the generation of rough rupture fronts capable of radiating high frequency seismic waves the large earthquakes in both categories of models occur on a quasi periodic basis the degree of periodicity increases with event size and decreases with model complexity however in all discrete segmented cases the models generate nonrepeating sequences of earthquakes and the nature of the large quasi periodic events is highly variable the results indicate that expectations for regular sequences of earthquakes and or simple repetitive precursory slip patterns are unrealistic the frequency size fs statistics of the small failure episodes simulated by the cellular fault models are approximately self similar with b 1 2 and ba 1 where b and ba are b values based on magnitude and rupture area respectively for failure episodes larger than a critical size however the simulated statistics are strongly enhanced with respect to self similar distributions defined by the small events this is due to the fact that the stress concentrated at the edge of a rupture expanding in an elastic solid grows with the rupture size when the fault properties e g geometric irregularities are characterized by a narrow range of size scales the scaling of stress concentrations with the size of the failure zone creates a critical rupture area terminating the self similar earthquake statistics in such systems events reaching the critical size become on the average unstoppable and they continue to grow to a size limited by a characteristic model dimension when however the system is characterized by a broad spectrum of size scales the above phenomena are suppressed and the range of apparent self similar fs statistics is broad and characterized by average b and ba values of about 1 the simulations indicate that power law extrapolations of low magnitude seismicity will often underestimate the rate of occurrence of moderate and large earthquakes the models establish connections between features of fs statistics of earthquakes range of self similar regimes local maxima and structural properties of faults dominant size scales of heterogeneities dimensions of coherent brittle zones the results suggest that observed fs statistics can be used to obtain information on crustal thickness and fault zone structure

the correlation between 18o 16o ratios of meteoric water and surface temperature its use in investigating terrestrial climate change over geologic time abstract correlations between mean annual temperature mat and the weighted average oxygen isotope composition of yearly precipitation 18opt are well known but the utility of modern relations to make reliable estimates of temperature change over geological time is uncertain this question has been addressed by using seasonal subsets of the global data base of temperature and isotopic measurements to represent two different climate modes a comparison of middle to high latitude 18opt temperature relations for each climate mode reveals 1 a significant offset between them and 2 a difference in the strength of their correlations the offset in relations is due to differences in temperature and water vapor budget in the tropics and can lead to serious underestimates of temperature change differences in the strength of correlations arise from the influence of climate mode specific non temperature factors on 18opt the overall result is that no single relation can be used in all cases to make unambiguous temperature estimates using a temporal record of 18opt values one way to overcome these problems is to reconstruct 18opt temperature relations for the time periods being investigated if an appropriate proxy for 18opt is available it may also be possible to estimate temperature without relying on 18opt temperature relations a promising alternative to these options is to use records of 18opt to test predictions of global climate models an approach that may allow a reliable and more complete reconstruction to be made of climate change over geologic time

permeability enhancement due to microcrack dilatancy in the damage regime a three dimensional microscopically based permeability model incorporating inelastic deformation has been developed to account for the modification of transport properties due to fracturing the basic hypothesis investigated is that permeability enhancement during brittle deformation is caused by the formation of dilatant microcracks which are associated with friction sliding on a preexisting random population of shear cracks additional dilatancy produced as a result of frictional sliding over asperities is also accounted for by the introduction of a crack roughness parameter linear elastic fracture mechanics is used to calculate the evolution of crack length and crack area as a function of applied stress and fluid pressure after making a geometrical simplification the microcrack parameters derived from the deformation model can be used to calculate the permeability tensor assuming that fluid transport results from poiseuille flow through a connected distribution of cracks the model enables investigation of the macroscopic permeability variation as a function of two loading parameters three constant material parameters and the crack roughness parameter results demonstrate that permeability is a smooth but strongly increasing near power law function of the terzaghi effective stress ratio and is strongly dependent on the initial crack density young s modulus the friction coefficient and the effective confining pressure numerical results are in quantitative agreement with published experimental measurements and display behavior similar to results obtained with a relatively simple analytical model the model enables calculation of the degree of stress induced anisotropy which is shown is be relatively small 10 for resonable effective stress ratios the modeling presented provides a quantitative tool with which the effects of microcrack induced permeability enhancement can be investigated within the broader context of coupled fluid flow and brittle deformation in the crust

hydrogeochemical modeling of the shallow groundwater in the northern jordan valley the reasons for the rapid degradation and salination of the shallow aquifer in the northern jordan valley were investigated shallow groundwater surface water and thermal water were sampled from the study area for this purpose the geochemical mass balance technique was used to quantify the contribution of different sources geochemical processes and rock types to the final water composition applying the netpath software package the isotopic compositions of the water were also investigated the results suggest three potential recharge sources the yarmouk river the jordan river and the mukheibah thermal water evaporation significantly contributes to the current chemistry of the shallow water as is indicated by the geochemical models and the isotopic results tritium analyses indicate that the water is clearly new less than 50 years the relatively high values of nitrate in some wells may be of anthropogenic origin

asymmetric distribution of aftershocks on large faults in california summary we examine the relations between spatial symmetry properties of earthquake patterns along faults in california ca and local velocity structure images to test the hypothesis that ruptures on bimaterial faults have statistically preferred propagation directions the analysis employs seismic catalogues for 25 fault zones in ca we distinguish between clustered and homogeneous parts of each catalogue using a recently introduced earthquake cluster analysis and examine asymmetry of offspring with respect to parent events within the clustered portion of each catalogue the results indicate strong asymmetric patterns along large faults with prominent bimaterial interfaces e g sections of the san andreas fault with enhanced activities in the directions predicted for the local velocity contrasts and absence of significant asymmetry along most other faults assuming the observed asymmetric properties of seismicity reflect the properties of the parent earthquake ruptures the discussed methodology and results can be used to develop refined estimates of seismic shaking hazard associated with individual fault zones

forecast model for great earthquakes at the nankai trough subduction zone an earthquake instability model is formulated for recurring great earthquakes at the nankai trough subduction zone in southwest japan the model is quasistatic two dimensional and has a displacement and velocity dependent constitutive law applied at the fault plane a constant rate of fault slip at depth represents forcing due to relative motion of the philippine sea and eurasian plates the model simulates fault slip and stress for all parts of repeated earthquake cycles including post inter pre and coseismic stages calculated ground uplift is in agreement with most of the main features of elevation changes observed before and after the m 8 1 1946 nankaido earthquake in model simulations accelerating fault slip has two time scales the first time scale is several years long and is interpreted as an intermediate term precursor the second time scale is a few days long and is interpreted as a short term precursor accelerating fault slip on both time scales causes anomalous elevation changes of the ground surface over the fault plane of 100 mm or less within 50 km of the fault trace

landslides along the jordanian dead sea coast triggered by the lake level lowering the level of the dead sea lowers 1 m year and this rate is in acceleration the decline is causing one of the major environmental disasters of the twenty first century the freshwater resources management policy of israel jordan and palestine controls the phenomenon since the 1960s the level of this terminal lake dropped by 28 m and its surface shrunk by one third in the 1990s international builders created major tourist resorts and industrial plants along the jordanian shore while during the same period geological hazards triggered by the level lowering spread out from the very beginning of the year 2000 sinkholes subsidence landslides and river erosion damaged infrastructures more and more frequently dikes bridges roads houses factories pipes crops etc until present scientific articles about this ongoing disaster concerned only sinkholes and subsidence phenomena this paper focuses on the landslides issue along the jordanian coast based on a set of ground observations collected since 1999 the dynamics of the triggering factors in relation to the evolution of the hydro geological setting is discussed it is inferred that the recent industrial and tourist infrastructures never took into consideration the very important geotechnical constraints resulting from the dead sea lowering

palaeoenvironmental inferences from late quaternary sediments of the al jafr basin jordan abstract sedimentological palaeontological and mineralogical analyses of sediments from the endorheic al jafr basin were conducted to better understand the depositional and hydrological conditions on the southern jordan plateau in the late quaternary surficially exposed carbonate rich sediments in the western part of the basin contain ostracod micro crustacean shells of ilyocypris cf bradyi candona neglecta heterocypris salina fabaeformiscandona fabaeformis pseudocandona sp and herpetocypris brevicaudata the shells of these and other more rare species and charophyte and mollusc remains indicate that the sediments were formed in a wetland setting of shallow freshwater to slightly oligohaline ponds streams and swamps the present more northern distribution of some of the recorded taxa implies that climate conditions were probably cooler during the wetland formation radiocarbon age data for biogenic carbonate from two locations suggest that the wetland setting existed during the second half of marine isotope stage mis 3 or possibly earlier a significantly higher water table must have existed in the basin during wetland formation and wetter climate conditions are inferred for the catchment or at least for its highest and most humid westernmost part deflation and local sediment accumulation by wind and occasional sheet wash events apparently prevailed in the region since mis 2 our newly presented data and inferences do not support the reconstruction of a previously reported large and relatively deep pleistocene lake in the al jafr basin however more extensive studies are certainly required for a detailed assessment of the quaternary hydrological conditions in southern jordan

leaching of lisan marl and its consequences on the engineering behavior of dikes studied by finite elements modeling leaching of lisan marl dead sea jordan increased the soil compressibility and cohesion intercept back analysis using the plaxis finite element code was successfully implemented the finite element modeling of dike construction showed a significant increase of total settlement and negligible effect on the strength as calculated by the c reduction method the height of dikes to be constructed on lisan marl as foundation material should be optimized to account for the effect of soluble salts leaching for this to take place an accurate calculation of settlement is crucial