locations of auroral kilometric radiation bursts inferred from multispacecraft wideband cluster vlbi observations 1 description of technique and initial results 1 the cluster wideband data instrument has been used to determine the locations of auroral kilometric radiation akr using very long baseline interferometry the technique involves cross correlating individual akr bursts from all six cluster baselines using time and frequency filtered waveforms the resulting differential delay peaks are used to determine source locations with an uncertainty as small as 500 km in a plane perpendicular to the source spacecraft line of sight or about 200 km when the burst position is projected onto the auroral zone along the magnetic field lines passing through the source the uncertainty along the line of sight is much larger but this is mitigated by assuming that the emission arises from a height corresponding to the electron gyrofrequency we report the locations of over 1700 individual akr bursts during six observing epochs between 10 july 2002 and 22 january 2003 when the cluster constellation was high above the southern or northern hemisphere in general we find that the akr burst locations lie along magnetic field lines which map onto the nighttime auroral zone as expected from previous akr studies for the three observing epochs viewing the northern hemisphere there is a strong tendency for akr burst locations to be centered within the auroral oval and in the evening sector the southern hemisphere burst locations favor magnetic local midnight to early morning and have somewhat higher invariant magnetic latitudes the distribution of akr auroral footprint locations at each epoch had a overall spatial scale between 1000 and 2000 km much larger than the positional uncertainty of an individual akr burst location magnetic footprint but a small fraction of the auroral oval this indicates that on a timescale of 1 3 hours conditions for suitable generation of akr emission are found on only a fraction of all magnetic field lines crossing through the auroral oval for two of the six epochs there was a significant drift in the mean location of akr activity over a period of 1 2 hours the drift was predominantly in latitude at one epoch and in longitude at the other with average drift speed v 80 90 m s 1 at the akr emission location

tectonic evolution of the southern levant margin since mesozoic abstract recognition of syndepositional faults and mechanical analysis of fault slip data are used to reconstruct a high resolution tectonic evolution of israel and to characterize the stress fields associated with the major tectonic deformation events of this area since mesozoic times syndepositional normal faults recognized in mesozoic and paleogene rocks indicate three extensive deformation phases that were active at least during early jurassic campanian and eocene times inversion of fault slip data indicate that a ne sw extension characterizes the two first events whereas orientation of extension during the eocene was n s to nne ssw several scenarios are proposed to explain these newly documented normal faults measured faults also document synchronous strike slip and reverse regimes unambiguous chronological relationships between fault data and bedding attest that a wnw ese to nw se compression is associated with the syrian arc folding event during the late cretaceous times this compression pursued during the development of the dead sea transform plate boundary but its relationship with neogene structures is unclear fault data suggest that folding during the neogene was driven by a regional nnw sse compression a minor ne sw compression was also recognized but no compatible large scale structures were found to date we also show that the post pliocene normal faults developed under a ne sw extension

geometric changes of plate boundaries along part of the northern dead sea transform geochronologic and paleomagnetic evidence the korazim block an elevated pressure ridge along with the faults bounding the sea of galilee and hula pull apart basins are internal structures of the dead sea transform plate boundary k ar dates and paleomagnetic data from basalt flows and sedimentary strata are utilized to determine the stratigraphy and the deformation of the region the integration of the two methods together with structural data yield high resolution age determination of the stratigraphic sequence and provides insight into the timing and style of deformation the korazim block is covered in its southern and central areas by pliocene basalt flows the cover basalt 5 1 3 6 ma and ruman basalt 2 9 2 2 ma formations and in its northern area by basalts yarda basalt 0 9 0 8 ma and sediments 3 0 2 3 and 1 6 0 9 ma of plio pleistocene age the magnetic polarity of a total of 29 lava flows and intercalated sedimentary strata is mixed the mean magnetic declination of the 29 sites shows an anomalous direction which yields 11 4 4 0 counterclockwise rotation with respect to the expected field the mean inclination of 46 0 4 1 does not significantly deviate from the expected field the anomalous declination is interpreted as the consequence of faulting and block rotation accommodating internal deformation this deformation did not begin before late pliocene to early pleistocene probably not before 0 9 ma and may still be active simultaneous right lateral slip of 50 175 m with a small reverse component of 30 90 m along nw trending faults and 11 counterclockwise rotation created internal deformation of the korazim pressure ridge this deformation is the consequence of left lateral slip along the almagor strand of the dead sea transform subparallel to the plate slip vector thus a compression component was formed which presumably led to the internal deformation of the korazim block the recent deformation of the korazim block in relation to the age of adjacent structures and to the age of the dead sea transform permits temporal resolution of geometric changes which must typify transform boundaries such as the dead sea transform internal structures within transforms may change along with the transform internal geometry and become inactive while new structural features may develop

imaging permeability structure within the highly permeable carbonate earth inverse theory and experiment in most oil reservoir rocks the squirt flow characteristic frequency fsq range of 10 100 khz is much less than the biot characteristic frequency f0 range of 1 mhz 1 ghz in contrast carbonate aquifers have very high permeability 10 3000 d and the two characteristic frequencies are reversed f0 from 10 hz to 10 khz and fsq from 1 mhz to 100 mhz the principal objective of this paper is to develop a pilot inverse method for robust imaging of the high permeability structure within carbonate aquifers an analytical approximate model called the super k model is developed the super k model coincides numerically with the combined biot and squirt flow mechanism model when permeability is higher than 100 md and the frequency is lower than 100 khz the super k regime in the super k regime the pore fluid is always relaxed so that the attenuation due to the biot mechanism is roughly four times larger than that of the biot model also empirical equations are developed that relate the stiffness and rigidit

velocity variabilities and other physical properties of marine sediments measured by crosswell acoustic tomography high resolution images of the compressional wave velocity structure within various bottom sediments have been determined from high frequency crosswell acoustic tomography the three dimensional wave number spectra of the velocity variabilities were determined for each measured velocity image the sediment velocity variability spectra are anisotropic in general the variability frequency in the vertical direction is much higher than in the horizontal direction the aspect ratio of the two is found to be approximately 5 0 in addition the major and minor axes of the anisotropy are often tilted from the vertical and the horizontal direction respectively the angle of tilt called dip is found to be as much as 33 deg the measured velocity power spectra approximate a power law the spectral strength depends on the sediment type and the location based on the rock mechanics transformation procedure by yamamoto et al geophysics 59 1530 1541 1994 the sediment porosity density permeability and shear st

high resolution crosswell imaging of a west texas carbonate reservoir part 1 project summary and interpretation a carbon dioxide flood pilot is being conducted in a section of chevron s mcelroy field in crane county west texas prior to co2 injection two high frequency crosswell seismic profiles were recorded to investigate the use of seismic profiling for high resolution reservoir delineation and co2 monitoring these preinjection profiles provide the baseline for time lapse monitoring profile 1 was recorded between an injector well and an offset observation well at a nominal well to well distance of 184 ft 56 m profile 2 was recorded between a producing well and the observation well at a nominal distance of 600 ft 183 m the combination of traveltime tomography and stacked cdp reflection amplitudes demonstrates how high frequency crosswell seismic data can be used to image both large and small scale heterogeneity between wells transmission traveltime tomography is used to image the large scale velocity variations cdp reflection imaging is then used to image smaller scale impedance heterogeneities the

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

crosshole seismic tomography many tomographic interpretations of crosshole seismic traveltimes have approximated the raypaths with straight lines connecting the source and receiver this approximation is valid where the velocity does not vary greatly but in many regions of interest velocity variations of 10 20 percent or more are observed causing significant ray curvature other work has taken this nonlinear effect into account but there do not appear to be many cases of demonstrated success in its application to the crosshole seismic problem we present here an iterative inversion scheme based on two dimensional ray tracing and its successful application to field data the interpretation method iteratively ray traces and then updates the velocity model within each iteration the differences between the data and the current model traveltimes obtained by ray tracing are related to the unknown velocity perturbations through a system of linear equations a damped least squares method solves for the velocity perturbations which updat

the tectonic development of the western margin of the gulf of elat aqaba rift abstract along the western coast of the gulf of elat a 30 km wide shear belt of subparallel faults trending n s to ne sw is developed this shear belt is observed mainly within the precambrian basement terrain sinistral movements on these faults have been recognized based on offsets of magmatic bodies and lithological contacts in rocks of precambrian age the cumulative displacement measured independently at several localities across the belt attains a total of 24 km early neogene volcanism in the form of long dikes trending nw se is known from the eastern desert of egypt of the gulf of suez and along the red sea coast of saudi arabia volcanic bodies of a similar pattern have been identified in eastern sinai these bodies mainly dolerites and basalts intruding mesozoic sediments are parallel to each other and to the gulf of suez they are tens to hundreds of kilometers long and spaced several tens of kilometers apart dating k ar of bodies in sinai saudi arabia and in the eastern desert of egypt suggest an age of 20 22 m y for this extensive volcanism all the dikes are sinistrally displaced by the individual faults of the eastern sinai shear belt the amount of movement recorded using the precambrian markers is identical to movement recorded by offsets of the early neogene dikes this proves that the total 24 km shear of this fault system postdates the 20 22 m y volcanic phase it is assumed that the recorded movements are part of the 105 110 km shear persumed to exist along the gulf of elat which is also younger than 20 22 m y preliminary results suggest that a similar amount of movement is observable along a shear zone developed on the eastern coast of the gulf of elat thus only some 60 km movement are taken up by faults in the gulf itself the evolving model suggests that 1 a the intrusion of very long basaltic dikes in a nw se direction on both sides of the red sea accompanied the initial stage of development of the red sea gulf of suez rift valley 2 b a basic change in the geotectonic regime occurs after the intrusion of this volcanic suite large scale horizontal movements are initiated being recorded as a 105 110 km sinistral movement along the arava jordan rift this movement implies a synchronous opening of the red sea

drainage system reorganization and late quaternary tectonic deformation along the southern dead sea transform the dead sea transform dst accounts for 105 km of left lateral slip between the arabian plate and the sinai subplate since the miocene paleoseismic studies along the arava valley segment of the dst suggest that late quaternary deformation has been primarily concentrated along the axis of the transform valley here we examine late quaternary changes in drainage system characteristics and attribute them to recent tectonic deformation in this region field based geomorphic mapping topographic cross sections and optically stimulated luminescence osl dating of fluvial deposits were used to map and date recent changes in the fluvial characteristics of catchments along the western margin of the southern arava our results reveal coeval migration of channels consistent with tectonically induced surface tilting caused by north south compressional deformation along the western margin of the transform valley osl dating indicates this tilting was initiated in the late pleistocene and continued at least into the mid holocene the late quaternary tectonic deformation along the southern arava segment of the dst is distributed across a wider zone than previously considered and extends out to the margins of the transform valley we associate the inferred wider deformation zone to possible changes in the geometry of motion along the dst

travel time and amplitude analysis in seismic tomography in cross hole tomography straight lines connecting the source and receiver are often used to approximate the true ray paths thus linearizing the inverse problem a recent paper by bregman et al 1989a has shown that this approximation may be very poor in the regions of greatest interest where large velocity gradients cause significant ray curvature the interpretation method presented by bregman et al 1989a iteratively ray traces and updates the velocity model with model perturbations obtained by a damped least squares inversion of the travel time residuals this paper presents a modification of the travel time tomography method so that it may be applied to the inversion of first motion amplitudes for inverse quality factor q 1 after determining the velocity structure using travel time tomography the amplitudes are inverted using a similar scheme no additional ray tracing is required for the amplitude inversions the effect of the velocity structure previously determined through travel time tomography is taken into account so that amplitude variations due to the focusing and defocusing effects of the velocity structure are not interpreted as being due to attenuation structure both the travel time and amplitude tomography methods are applied here to field data from a cross hole experiment in crystalline rock wong et al 1983 the frequency range of the seismograms is 1 6 6 khz allowing resolution of velocity structure on a scale of several meters the resulting velocity image shows good agreement with other geological and geophysical data reversing the model by placing the model boreholes on opposite sides relative to the original reconstruction yields almost identical results indicating that the interpolation scheme used in the forward modeling has not biased the final model synthetic maslov seismograms calculated for the derived velocity model agree well with the waveform data further confirming the validity of the model in addition the amplitude tomography results place absorptive regions in the same location as the most pronounced low velocity features which correlate with fractures in the boreholes highly transmissive regions also correlate well with high velocity regions

porosity permeability shear strength crosswell tomography below an iron foundry crosswell tomography of a sedimentary foundation at an iron foundry was affected by very high background noise nevertheless high resolution velocity images were obtained between wells separated by long distances 120 to 250 m a piezoelectric source in a water filled well used long sequences 4095 cycles of pseudorandom binary codes at high carrier frequencies 1 to 10 khz a 24 channel hydrophone array in another well received the signal beamforming of common source data selected the directions and arrival times of multiple raypaths and tube waves and further enhanced the signal to noise ratio inversion of first arrival times by damped least squares imaged the compressional wave velocities assuming the normal consolidation condition the porosity and shear strength images are predicted from the compressional wave velocity image the direct measurements of porosity and shear strength conducted on the cores and boreholes were used to verify the tomographic predictions the slight differences in the

new age constraints on the evolution of the mt carmel structure and its implications on a late miocene extensional phase of the levant continental margin abstract the mt carmel structure is one of the most prominent topographical elements along the levant continental margin and is the surface expression of a deep tectonic structure the use of 3d seismic data allows us to set new constraints on the uplift of the carmel structure and define the or akiva fault as its southern boundary the or akiva fault was created during a late miocene extensional phase that had also created the carmel fault at the northern edges of mt carmel the different topographic expression across these two boundary faults reflects a change in the post miocene activity where activity along the or akiva fault ceased and its southern side began subsiding whereas its northern side bordered by the carmel fault continued to rise we conclude that the late miocene north south extension previously recognized only along branches of the dead sea transform in northern israel and lebanon affected larger areas than previously thought and can be related to regional kinematic changes during the breakup of arabia from africa and its collision with eurasia

gps measurements of current crustal movements along the dead sea fault 1 a network of 11 continuous gps stations was constructed in israel between 1996 and 2001 to monitor current crustal movements across the dead sea fault dsf analysis of the gps measurements with respect to the itrf2000 reference frame yields time series of daily site positions containing both secular and seasonal variations horizontal secular variations station velocities are evaluated with respect to the main tectonic element in the region the dsf we use six velocity vectors west of the dsf to define the itrf2000 pole of the sinai sub plate and rotate the velocity field for all stations into the sinai reference frame srf the velocity vectors reveal that 1 relative station movements are less than 4 mm yr 2 the nine stations located west of the dsf show no statistically significant motion with respect to the srf and 3 the two stations located in the golan heights katz and elro and a station in damascus syria udmc show 1 7 2 8 mm yr northward motion with respect to sinai indicating a left lateral motion along the dsf using locked fault models we estimate the current slip rate across the dsf as 3 3 0 4 mm yr if we exclude the northern sites elro and udmc which are located adjacent to the compressional jog of mount hermon our estimate increases to 3 7 0 4 mm yr the calculated itrf2000 sinai eurasia and nubia poles and a published pole for arabia allow us to calculate the current relative plate motion of sinai arabia and sinai nubia

stress field fluctuations along the dead sea rift since the middle miocene the dead sea transform dst is the suture between the african and the arabian plates both of which subduct northward under the eurasian plate the collision of these plates with eurasia and their relative motion are the source for their internal deformation especially in the vicinity of the dead sea transform geological observations indicate that two distinct paleostrain regimes operated adjacent to the dead sea rift and in the sinai israel subplate 1 wnw shortening less than 10 and nne extension beginning in the turonian is associated with the development of the syrian arc fold belt and attributed to the syrian arc stress field sas and 2 middle miocene to recent nnw shortening and ene extension associated with the 105 km sinistral displacement along the dead sea transform and the opening of the red sea is attributed to the dead sea stress field dss it was originally suggested that the sas terminated during the middle miocene with initiation of the dss however trend and age analysis of many structures shows that formation of sas compatible structures continued after the middle miocene up to the recent in some middle miocene and younger rocks structures such as faults dikes volcanic lineaments and tectonic stylolites compatible with both stress fields were reported in a few locations structures compatible with both stress fields crosscut each other it is suggested that the movements which resulted in the development of the syrian arc and other sas compatible structures are continuing to the recent and that dss movements are superimposed upon them the overlapping of sas and dss structures adjacent to the dst results from spatial and temporal fluctuations in the overall stress state we propose that such variations could be caused by the superposition of large earthquake stress drops associated with movements along the dst on a steady background plate scale stress regime associated with the sas thus dss compatible structures should form in preseismic activity periods when dst related elastic strain is high on the other hand the sas compatible structures should form during interseismic activity times subsequent to large local stress release along the dst

the onset of the dead sea transform based on calcite age strain analyses the onset and evolution of the dead sea transform are re evaluated based on new in situ u pb dating and strain analyses of mechanically twinned calcites direct dating of 30 syn faulting calcites from 10 different inactive fault strands of the transform indicates that the oceanic to continental plate boundary initiated between 20 8 and 18 5 ma within an 10 km wide distributed deformation zone in southern israel ages from the northern dead sea transform 17 1 12 7 ma suggest northward propagation and the establishment of a well developed 500 km long plate bounding fault in 3 m y the dominant horizontal shortening direction recorded in the dated twinned calcites marks the onset of left lateral motion along the evolving plate boundary the observed changes in the strain field within individual fault strands cannot be simply explained by local weakening effects along strands of the dead sea transform or by gradual changes in the euler pole through time

temporal and spatial relations between large scale fault systems evidence from the sinai negev shear zone and the dead sea fault abstract in the major zones of crustal deformation within the arabia sinai nubia plates the interactions between the sinai negev shear zone snsz and the dead sea fault system dsf shed light on the interplay between neighboring large scale fault systems the snsz is composed of several e w to ene wsw trending mainly normal and dextral strike slip faults that are tens to hundreds of kilometers long these faults form a 120 km wide shear zone in the sinai sub plate on reaching the plate bounding dead sea fault system dsf individual lineaments of the snsz are observed in the arabian plate offset left laterally by 105 km which is the total estimated offset of the dsf in this contribution we review the geologic setting of the snsz and its complex relations with the dsf in light of newly obtained age strain analyses for this we use in situ u pb geochronology in conjunction with twin analysis of syn faulting calcite from both systems the results indicate that the deformation along the snsz initiated in the campanian maastrichtian or earlier as the oldest dates are 73 71 ma the main phase of fault activity began in the late oligocene early miocene 27 22 ma as documented by numerous dates that were obtained along several lineaments of the snsz the activity continued until 10 ma after which no direct ages have been obtained the dominant phase of activity along the snsz at 27 22 ma preceded the timing of initiation of lateral faulting along the dsf at 20 18 ma by a few myr for the overlapping period of activity between 20 and 10 ma episodes of fault activity along the snsz followed by episodes of fault activity along the dsf moreover dominant episodes of activity along one fault system were associated with a decrease in activity along the other system the temporal relations between the snsz and dsf highlight the possibility that these fault systems are mechanically interrelated but the exact mechanism for this fault interaction needs further study we consider the paleo strain or paleo stress that control the evolution and style of the snsz and assess them at the central sinai negev region during the cenozoic we show that the formation of new plate boundaries at the region i e the red sea suez rift and the dsf affected the strain field within the snsz the proximity of the two systems indicates that the dsf related stress originated within the snsz and possibly caused structural and style changes in the latter system syn faulting calcite twins analyses within the snsz show pronounced spatial and temporal variations of the principal strain directions between and along individual faults this observation demonstrates that the imposed stress within the central sinai negev were not uniform over time the high angle 70o between the traces of the snsz and the direction of the dsf related maximum shortening likely suppressed the dextral motion along the snsz post 20 ma field evidence u pb dates and recent seismicity shows that the current snsz is a long lived structure that has been active during the miocene alongside the dominantly dsf and may still be sporadically active today

tomographic inversion for sediment parameters in shallow water this article discusses inversions for bottom geoacoustic properties using broadband acoustic signals obtained from explosive sources the experimental data used for the inversions are sus charge explosions acquired on a vertical hydrophone array during the shelf break primer experiment conducted south of new england in the middle atlantic bight in august 1996 the sus signals were analyzed for their time frequency behavior using wavelets the group speed dispersion curves were obtained from the wavelet scalogram of the sus signals a genetic algorithm ga was used for the inversion of sound speeds in the water column and compressional wave speeds in the sediment layers the variations in the sound speeds in the water column were represented using empirical orthogonal functions eofs a range independent normal mode routine was used to construct the replica fields corresponding to the parameters comparison of group speeds for modes 1 to 9 and for a range of frequencies 8 to 200 hz was used to arrive at the best parameter fit an efficient hybrid optimization scheme using the ga and a levenberg marquardt algorithm is presented linear perturbation methods were also used to fine tune the inversions and to obtain resolution and variance estimates analysis was also done to compute the degree of convergence of each of the parameters by explicitly calculating the hessian matrices numerically a posteriori estimation of mean and covariance was also done to obtain error estimates group speeds for the inverted sound speed fields provide an excellent match to the experimental data the inverted sediment compressional speed profile compares well with in situ measurements

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

intraplate deformation by block rotation and mesostructures along the dead sea transform northern israel combined analysis of mega and meso structures yield the strain inferred stress and tectonic history of the margin of the sinai sub plate in northern israel along the dead sea transform three major stress regimes were developed and have affected the region since the middle miocene one is regional and controlled the left lateral shear along the dead sea transform this one has been active since post early miocene is characterized by 1 trending c 345 and deformed the plate margin by horizontal shear and contemporaneous block rotation this style of deformation is similar to simple shear the second one was local and may be subdivided into distinct stress and strain domains it was characterized by 1 trending e w and 3 trending n s which produced a conjugate set of strike slip faults the region underwent n s elongation by horizontal shear and block rotation similar to the pure shear mechanism this stress regime was active in late miocene to early pliocene time the third and youngest stress regime is extentional with 1 vertical and 3 oriented n s this one has been active since post middle pliocene time producing e w normal faults and minor n s elongation the second and third stress regimes show local distribution and developed as a consequence of the bent geometry of the transform vis a vis the plate slip vector finite element and photoelastic models predict the development of local stress fields and elongation of the plate margin parallel and subparallel to the transform plate boundary the strain of the plate margin in northern israel and southern lebanon indicate remarkable elongation parallel to the dead sea transform by a factor of 1 5 2 1 since the miocene this process of intraplate deformation and the consequent strain is unique to the parts of the plate margin which are adjacent to the bent segment of the transform

analysis of high frequency acoustic scattering data measured in the shallow waters of the florida strait experiments were conducted in the florida strait region of the united states in july 1995 to investigate the contribution of sediment volume scattering to measured acoustic backscatter levels at frequencies of 7 5 and 15 khz five sites were analyzed for bottom backscattering level in the radial and azimuthal directions sediment geophysical parameters were established by a cross well tomographic measurement and used as inputs for modeling both sediment volume and rough interface scattering models were utilized in analyzing the data comparison of model predictions with measured data showed that for grazing angles at the water sediment interface from the critical angle to approximately 60 degrees volume scattering dominated for angles greater than approximately 60 degrees surface roughness scattering consistently dominated in geographic areas where the interface sound speed ratio exceeded one roughness scattering controled the backscattered level for grazing angles less than the critical angle in

structure and paleostresses in the gilboa region western margins of the central dead sea rift abstract the relationships between tectonic paleostresses and major fault systems are analyzed for the gilboa region the gilboa is a folded block on the western margins of the dead sea transform which has been deformed and uplifted at least since the miocene the tectonic paleostresses in the gilboa were determined by inversion of slip striations along small faults measured in the field and from the trends of basaltic dikes one state of stress dominated the gilboa region since the miocene the principal axes of the calculated stress tensor are 1 at 0 122 2 vertical and 3 at 0 032 this stress fits well with the trends of the syrian arc folds in the gilboa and its is compatible with the observed normal slip along the gilboa fault however this stress is incompatible with the either left lateral slip or normal faulting along the dead sea system possible mechanisms to resolve this incompatibility are discussed

evidence for jericho earthquakes from slumped sediments of the jordan river delta in the dead sea seismic reflection data and historical accounts suggest that a large submarine slump in the dead sea was produced by the most recent large earthquake along the dead sea jordan transform plate boundary the m l 6 25 jericho earthquake of july 11 1927 the correlation supports the use of seismically triggered slump landslide and other sediment failures in lakes to infer the timing of paleoearthquakes furthermore the location of the submarine slump adds to evidence that the 1927 earthquake was caused by rupture on a fault segment beneath the north basin of the dead sea this fault rupture implies that the strain accumulation on the jordan fault north of the dead sea is higher than previously recognized older seismically triggered slumps buried beneath the 1927 slump show that a record of ancient jericho earthquakes can also be found in the sedimentary record the estimated number and age range of these slumps suggest a long average earthquake recurrence time

the evolution of barahta rhomb shaped graben mount hermon dead sea transform abstract mount hermon forms part of a ne trending anticlinal structure formed during compression resulting from sinistral movement along the dead sea rift transform at the northern end of the hula valley the dead sea transform branches into five faults one of which the rachaya fault crosses the hermon on its western side with about 1000 m of left lateral displacement the rachaya fault comprises two left stepping segments the southern si on fault and the northern shab a fault as a result of this stepping a rhomb shaped graben was formed two of the bordering faults of the barahta valley are dip slip faults the northern and the western whereas the other two are strike slip faults kinematic calculations reveal that horizontal displacement of about 800 m was transferred from the si on fault to the shab a fault mainly along the eastern diagonal faults the formation of the barahta rhomb shaped graben resulted from a local stress field formed due to the fault configuration and the motion of the arabian block and not due to the regional stress field the structure of the barahta graben can be largely explained by the rotational model rather than by the classic pull apart model it is concluded that stepover of strike slip faults is essential for development of rhomb grabens but the mode of formation is different in each case and depends on the fault configuration and direction of block motion

state of stress from focal mechanisms before and after the 1992 landers earthquake sequence the state of stress in the eastern california shear zone ecsz changed significantly because of the occurrence of the 1992 m w 6 1 joshua tree and the m w 7 3 landers earthquakes to quantify this change focal mechanisms from the 1975 galway lake sequence the 1979 homestead valley sequence background seismicity from 1981 to 1991 and the 1992 landers sequence are inverted for the state of stress in all cases the intermediate principal stress axis s2 remained vertical and changes in the state of stress consisted of variations in the trend of maximum and minimum principal stress axes s 1 and s 3 and small variations in the value of the relative stress magnitudes in general the stress state in the ecsz has s 1 trending east of north and 0 43 to 0 65 suggesting that the ecsz is a moderate stress refractor and the style of faulting is transtensional south of the pinto mountain fault in the region of the 1992 joshua tree earthquake the stress state determined from the 1981 to 1991 background seismicity changed on 23 april and again on 28 june 1992 in the central zone s 1 rotated from n14 5 e to n28 5 e on 23 april and back again to n16 5 e on 28 june thus the landers mainshock in effect recharged some of the shear stress in the region of the m w 6 1 joshua tree earthquake comparison of the state of stress before and after 28 june 1992 along the landers mainshock rupture zone showed that the mainshock changed the stress orientation the s1 trend rotated 7 to 20 clockwise and became progressively more fault normal from south to north along the emerson camp rock faults the variation was so prominent that the focal mechanisms of aftershocks could not be fit by a single deviatoric stress tensor the complex distribution of p and t axes suggests that most of the uniform component of the applied shear stress along the northern part of the rupture zone was released in the mainshock the san bernardino mountains region of the m w 6 2 big bear earthquake has a distinctively different state of stress as compared to the landers region with s 1 trending n3 5 w this region did not show any significant change in the state of stress following the 1992 m w 6 2 big bear sequence

overpressure preventing quartz cementation a reply chemical compaction and the relative importance of the pressure dissolution and illite mica induced dissolution imid models have remained a contentious issue as is the role played by stress in chemical compaction this paper offers further support and evidence as discussed in stricker et al 2016b focusing on the reservoir quality of the triassic skagerrak formation sandstones in the high pressure high temperature hpht central graben north sea the reply discusses alterative reservoir quality interpretations and comments as raised by maast 2016 a series of theoretical and experimental studies as well as field based evidence is presented providing strong support to the important role of stress e g vertical effective stress during chemical compaction the evidence leads to the conclusion that the process of chemical compaction is stress and temperature driven and significantly enhanced by clay minerals playing a catalytic role by increasing the width of diffusion pathway or by modifying the kinetics of the dissolution process

active faulting in the dead sea rift abstract manifestations of late quaternary and holocene faulting were studied in a 500 km long segment of the dead sea transform rift most prominent are left slip faults whose characteristic physiographic features are recognizable along most of the studied segment where these faults bend or are stepped to the left rhomb shaped grabens or pull aparts are produced forming depressions in the reverse situation compressional features such as pressure ridges domes and folds form positive topographic features such structures are combined on a variety of scales ranging from a few hundred meters long to tens of kilometers normal faults sub parallel to the left slip faults produce a trough like valley along much of the dead sea transform but are most prominent along the margins of the large rhomb grabens e g the dead sea trough they apparently record a small component of transverse extension generally their motion is slow young slip did not occur along some segments during the last few 10 4 y elsewhere throws of 10 20 m at least occurred in this period the dead sea transform is seismically active the instrumental and historic records indicate a seismic slip rate of 0 15 0 35 cm y during the last 1000 1500 y while estimates of the average pliocene pleistocene rate are 0 7 1 0 cm y either much creep takes place or the slip rate varies over periods of a few 10 3 y

geological structure of the eastern side of the lower jordan valley dead sea rift reflection seismic evidence abstract interpretation of recently released seismic reflection lines from the shuna eastern jericho basin combined with re analysis of the lithologic logs of the deep jv 1 and jv 2 boreholes provide new insights into the structure of the sedimentary basin that formed along the dead sea transform fault north of the dead sea in jordan we identified four major seismic boundaries in the reflection profiles the upper two were correlated with borehole stratigraphy these reflection boundaries include the top of the pan african basement r4 the base of the mesozoic r3 the base of the cretaceous r2 and the base of the post eocene section r1 the latter records sedimentation during the dead sea transform tectonic regime the total thickness attained by the older sedimentary units late cretaceous through cambrian is apparently less than 2 km we identified a subsurface structure a faulted monocline with a n s trend sub parallel to the strike of the dead sea transform that is named here al kharrar monocline the al kharrar structural ensemble is buried by syntectonic lacustrine and fluviatile sediments of the jordan valley group the structure formed as part of the dead sea transform deformation overprinting the late cretaceous syrian arc folds continued tectonic deformation is evident from the prominent unconformity at the base of post eocene syntectonic deposits that dip nw w and s away from the structural high along the nw flank of the al kharrar monocline syntectonic sediment thickness is generally less than 0 5 km while along the sw flank it thickens rapidly to nearly 1 km at the southern end of the interpreted seismic lines this rapid southern subsidence probably continues into the north end of the dead sea basin the lake s shoreline being located less than 3 km to the south young bifurcating faults with reverse slip components cutting the eastern part of the al kharrar monocline are attributed to a positive flower structure this pattern suggests strike slip with localized active compression northeast of the dead sea it may result from local transpression between fault strands that appear to be a northward continuation of the eastern boundary fault of the dead sea basin

coseismic stress changes induced by the 1989 loma prieta california earthquake earthquake focal mechanisms from before and after the 1989 loma prieta california earthquake are used to infer the coseismic stress change before the main shock most earthquakes correspond to right lateral slip on planes sub parallel to the san andreas fault and imply a generally n s most compressional stress axis and a vertical intermediate stress axis aftershocks within the main shock rupture zone however display almost every style and orientation of faulting implying an extremely heterogeneous stress field this suggests that the main shock relieved most if not all of the shear stress acting on its fault plane aftershocks that lie on the perimeter of the rupture agree with spatially uniform stress states but only when considered in three groups north south and above the main shock rupture area in each of these areas the stress state may reflect stress transfer by the main shock

stress tensor and focal mechanisms along the dead sea fault and related structural elements based on seismological data the dead sea fault is among the largest active strike slip fault of the world this study is focused on the southern part of this fault from the sea of galilee to the gulf of aqaba as monitored mainly by the jordanian and israeli seismic networks the data of arrival times and polarities allowed relocation of earthquakes with a better azimuthal coverage and computation of focal mechanisms this last step has been realized by inverting the polarities to determine a unique stress tensor for the region and the compatible focal mechanisms inversion with different subsets of the data set based on tectonic regionalization has also been performed to evaluate the impact of each cluster of earthquakes on the global solution the population of focal mechanisms is clearly dominated by strike slip events with the notable exception of a cluster of earthquakes south of the dead sea which displays several normal focal mechanisms this last cluster forces 1 to be vertical and 2 to be horizontal a large number of fault planes however are close to the vertical inhibiting the action of the vertical component of the stress tensor and acting like under strike slip stress regime we observed a good agreement between the location of the earthquakes and the active faults based on geological data in addition there is a good agreement between the fault plane solutions and the orientation of the active faults

simultaneous images of the northern and southern auroras from the polar spacecraft an auroral substorm 1 the first simultaneous images of the auroras in the northern and southern hemispheres with a single camera have been gained with the earth camera onboard the polar spacecraft with sufficient angular resolution to provide maps of the intensities an auroral substorm was fortuitously observed on 1 november 2001 when the spacecraft was favorably positioned to observe both auroras the auroral intensities during the onset and the early expansive phase were mapped into corrected geomagnetic coordinates the onset brightening at far ultraviolet wavelengths was first detected in the southern auroras and subsequently seen in the northern auroras about 1 min later on l shells of about 5 re during the early phases of the auroral expansive phase the southern aurora continued to be brighter the unequal auroral intensities in the two hemispheres suggest that there is strong coupling of the ionosphere and magnetosphere the mapping of the auroras revealed that there is a local time difference between the onset positions of about 40 min with the southern auroras positioned to the east relative to those in the north this displacement was also similarly detected in the quiet auroral regions which were not participants in the auroral substorm such displacements may be useful in developing improvements in the accuracy of global magnetic models that are important for determination of the position of the in situ particle and field measurements in the magnetosphere the greater brightness of the northern quiet time auroras by tens of percent as first reported by aircraft observations at visible wavelengths in both hemispheres has been verified by the more global view from the polar spacecraft

some outstanding issues in the geology of lebanon and their importance in the tectonic evolution of the levantine region abstract the concept of pervasive and disruptive late neogene quaternary strike slip tectonics in lebanon has made establishing a satisfactory pre neogene palaeogeographic and palaeotectonic history for the area difficult research has allowed clarification of three fundamental issues that permit the setting of lebanon against its adjacent regions to be more firmly assigned the first issue is the identification of the significance of the 100 km long nne ssw trending monocline of the western lebanon flexure this feature is interpreted as a modified and rejuvenated early mesozoic hinge line that is presumed to be the northern continuation of the carmel sinai hinge line to the south the second issue is the correlation of the mount lebanon bekaa and anti lebanon complex with the adjacent intracontinental palmyride fold belt of syria through recognition in each of common divisions in structural style between a higher northern zone dominated by broadly spaced box folds and a lower southern zone with more numerous closely spaced and more internally complex folds the third issue involves the identification of major two stage late cretaceous to palaeogene syrian arc tectonism within lebanon resolution of these issues suggests a tectonic model for the region whereby the levantine region formed in two main phases the first of these was the multiphase late palaeozoic early mesozoic rifting of the area which imposed a fundamental extensional fabric over much of the region the second tectonic phase was the subsequent inversion of these extensional structures in the two stage syrian arc deformation of senonian and late palaeogene age which gave rise to the main lebanon structures it is this syrian arc tectonism rather than the late cenozoic strike slip that was probably the main structuring agent which affected the lebanon area the transpression from the braided dead sea fault motion although locally complex is an essentially neotectonic overprint on an already existing fabric offset of syrian arc structures in lebanon suggests that the total sinistral motion of the yammouneh fault segment of the dead sea fault is around 47 km

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

soils as a tool for estimating ages of quaternary fault scarps in a hyperarid environment the southern arava valley the dead sea rift israel abstract on the alluvial fan of nahal shehoret in the extremely arid region of the negev desert israel reg soils developed on stable alluvial surfaces in colluvium along terrace risers and in colluvial units on a complex fault scarp were compared the degree of soil profile development provided an age estimate of the surface that was faulted a maximum age estimate of the scarp or terrace riser and an estimate of the maximum recurrence intervals of faulting events irsl dates of the tectonically displaced alluvial surfaces and colluvial units at the same site enabled us to re evaluate the use of reg soils for relative dating the major faulting event started at 34 8 4 3 ka it displaced a late pleistocene surface of the nahal shehoret alluvial fan dated at 56 10 8 ka renewed fluvial activity and deposition of alluvium on the downfaulted block had almost terminated by 13 6 2 3 ka the scarp was formed during the latest pleistocene and was followed by smaller faulting events which had only minor effects on the fault scarp morphology the similarity of age estimates from irsl dating and the degree of soil development in this environment indicates that soils can be used to date surfaces and colluvial units

optical auroral conjugacy viking uv imager south pole station ground data high time resolution satellite uv images of the northern auroral oval are compared with south pole station keogram camera and all sky camera observations to determine the displacement of the south pole conjugate point from its location calculated using the international geomagnetic reference field magnetic field model the results presented extend the study of optical conjugacy to high magnetic latitudes in a solstice period and to sunlit auroral events three high latitude events were analyzed a poleward expansion an arc poleward of the midnight oval and a substantial movement in the afternoon auroral oval they were determined to occur on closed field lines a range of displacement for the south pole conjugate point of 5 3 in latitude and 1 9 hours in mlt was measured

low grazing angle bistatic sea floor scattering on the florida atlantic coastal shelf observations of bistatic scattering at moderate frequencies 3750 hz 7500 hz and 15 000 hz and low grazing angles 2 20 are presented with a geoacoustical description of the site given a source receiver separation of 80 7 m bistatic scattering strengths in the sandy sediments at the measurement site range from 70 to 15 db the observed bistatic scattering at low grazing angles depends primarily on the incident bearing angle bistatic scattering values are highest along the transect between the source and receiver maximum scattering strengths 20 to 15 db appear 30 m from the receiver regions of high scattering 30 db strength are centered along the direct path between the source and receiver the contribution of volume scattering to the observed scattering pattern is not very clear however given the sandy sediments found at the site roughness scattering is expected to be a major contributor to the observed bistatic scattering patterns

long term earthquake clustering a 50 000 year paleoseismic record in the dead sea graben the temporal distribution of earthquakes in the dead sea graben is studied through a 50 000 year paleoseismic record recovered in laminated sediments of the late pleistocene lake lisan paleo dead sea the lisan represents more than 10 times the 4000 years of historical earthquake records it is the longest and most complete paleoseismic record along the dead sea transform and possibly the longest continuous record on earth it includes unique exposures of seismite beds earthquake induced structures associated with slip events on syndepositional faults the seismites are layers consisting of mixtures of fragmented and pulverized laminae the places where the seismites abut syndepositional faults are interpreted as evidence for their formation at the sediment water interface during slip events on these faults thicker sediment accumulation above the seismites in the downthrown blocks indicates that a seismite formed at the water sediment interface on both sides of the fault scarps modern analogs and the association with surface ruptures suggest that each seismite formed during a m l 5 5 earthquake the 230 th 234 u ages of a columnar section obtained by thermal ionization mass spectrometry give a mean recurrence time of 1600 years of m l 5 5 earthquakes in the dead sea graben the earthquakes cluster in 10 000 year periods separated by quiet periods of similar length this distribution implies that a long term behavior of the dead sea transform should be represented by a mean recurrence of at least 20 000 year record this observation has ramifications for seismic hazard assessment based on shorter records

seven million years of strike slip and related off fault deformation northeastern marlborough fault system south island new zealand the marlborough fault system mfs south island new zealand is remarkable for the oblique slip nature of its active faulting and can be placed in a framework of pacific australian pac aus plate motions and geodetic strain new zealand illustrates changing degrees of upper plate slip partitioning in an obliquely convergent margin that varies along strike in crustal type and subduction geometry in this paper we focus on the ne part of this transcurrent fault system especially the awatere fault which is the only marlborough fault to offset a major neogene basin strike slip on an ancestral eastern strand of this fault began after 7 4 6 4 ma later vertical axis rotation may have caused it to be abandoned in favor of the currently active strand since 7 ma at least 34 10 km of dextral slip has accrued on the awatere fault 6 km of slip has accrued on two nearby strands and 4 km has accrued on the currently active coastal strand comparison of miocene with late quaternary offsets suggests that rates of strike slip on the fault have been nearly constant or have possibly decelerated we interpret spatial and temporal patterns of strike slip in the mfs to reflect southward migration of transform motion resulting from increased pac aus plate convergence late neogene to present day shortening directions in ne south island are indicative of a partially slip partitioned margin slip partitioning diminishes southward as the underlying subduction interface becomes strongly coupled suggesting a simple mechanical relationship between these processes

use of 230th u ages of striated carnotites for dating fault displacements crusts of uranium minerals carnotite and tyuyamunite were found along some fault planes in the northern negev israel field microscope and scanning electron microscope sem examinations of the carnotite showed that they crystallized on previously formed faults and then underwent a later deformation this deformation is evidenced by slickensides and striations that developed on the three scales on the crusts the carnotites were dated by the 230th u method and found to be between 123 and 19 ka indicating that the most recent displacement along the faults occurred during late pleistocene to holocene time hence the u series of deformed carnotite is suggested as a method for dating young displacement along faults

holocene seismic and tectonic activity in the dead sea area abstract the dead sea is a large active graben within the dead sea rift which is bounded by two major strike slip faults the jericho and the arava faults we investigated the young tectonic activity along the jericho fault by excavating trenches up to 3 5 m deep across its trace the trenches penetrate through late pleistocene and holocene sediments we found that a zone up to 15 m wide of disturbed sediments exists along the fault these disturbed sediments provide evidence for two periods of intensive activity or more likely for two major earthquakes that occurred during the last 2000 years the earthquakes are evident in small faults vertical throw of a few layers cracks unconformities and wide fissures we further documented evidence for recent sinistral shear along the jericho fault in deformed sediments and damage to an 8th century palace on a subsidiary fault we suggest that the two earthquakes may be correlated with the 31 b c earthquake and the 748 a d earthquake reported by the ancients

pilot experiment for the acquisition of marine sediment properties via small scale tomography system a 3 d high resolution crosswell acoustic tomography system was designed and tested in a shallow water environment this system makes use of a damped least squared inversion technique and is used to construct compressional wave velocity images from measured travel time data use of singular value decomposition allowed checks of the linear inversion confirming the validity of the modeled environment it is shown that when the ratio of width to depth of the cross section is about unity or smaller and the domain has not been overparametrized the inverted image model has sufficiently good figures of merit in resolution and variance to visualize small variations in the magnitude compressional velocity field

imaging the permeability structure of a limestone aquifer by crosswell acoustic tomography a narrow band pseudorandom binary sequence prbs code was used to generate an acoustic pulse that approximates a single laser like frequency measurements of crosswell tomography under a florida limestone aquifer were made using four different prbs frequencies 250 1 000 2 000 and 3 000 hz velocity images created by different prbs frequencies showed different velocity values in the permeable layers but no velocity difference in the impermeable layers for selected source receiver pairs across these layers crosswell experiments were conducted with more prbs frequencies ranging from 200 to 5 000 hz pulse propagation calculations using a layered elastic model indicate that the velocity frequency dispersion is not a result of geometrical dispersion the original procedure to extract porosity permeability and shear strength from seismic velocity images has been extended to the more general case of mixed lithified and unlithified sediments the velocity frequency dispersion data for the limestone layer

young faults in the hula pull apart basin central dead sea transform abstract the geometry and nature of structural features inside the hula pull apart basin at the central dead sea transform are presented here two systems of n s left lateral strike slip faults are located on the east and west sides of the hula basin both fault systems are composed of several segments arranged in a right stepping en echelon pattern the northern end of each segment is bent northeastward and usually merges with the next segment elevated regions and small hills appear on the northern side of each bend the strike slip faults are oblique with both vertical and horizontal components the vertical component may be normal or reverse although the hula valley is subjected to general extension the studied structures indicate local compression inside the basin normal faults striking e w comprise the northern border of the hula basin age determination of displaced travertines and basalts along the faults indicates sub recent tectonic activity and suggests migration of normal faulting towards the inner part of the basin the youngest fault displaces travertine dated at 25 300 years

distinctive diamagnetic fabrics in dolostones evolved at fault cores the dead sea transform abstract we resolve the anisotropy of magnetic susceptibility ams axes along fault planes cores and damage zones in rocks that crop out next to the dead sea transform dst plate boundary we measured 261 samples of mainly diamagnetic dolostones that were collected from 15 stations to test the possible effect of the iron content on the ams we analyzed the fe concentrations of the samples in different rock phases dolostones with mean magnetic susceptibility value lower than 4 10 6 si and iron content less than 1000 ppm are suitable for diamagnetic ams based strain analysis the dolostones along fault planes display ams fabrics that significantly deviate from the primary sedimentary fabric the characteristics of these fabrics include well grouped sub horizontal minimum principal ams axes k 3 and sub vertical magnetic foliations commonly defined by maximum and intermediate principal ams axes k 1 and k 2 axes respectively these fabrics are distinctive along fault planes located tens of kilometers apart with strikes ranging between nnw sse and nne ssw and different senses of motion the obtained magnetic foliations k 1 k 2 are sub parallel within 20 to the fault planes based on rock magnetic and geochemical analyses we interpret the ams fabrics as the product of both shape and crystallographic anisotropy of the dolostones preferred shape alignment evolves due to mechanical rotation of subordinate particles and rock fragments at the fault core preferred crystallographic orientation results from elevated frictional heating 300 c during faulting which enhances c axes alignment in the cement supported dolomite breccia due to crystal plastic processes the penetrative deformation within fault zones resulted from the local fault related strain field and does not reflect the regional strain field the analyzed ams fabrics together with fault plane kinematics provide valuable information on faulting characteristics in the uppermost crust

active tectonics of the yizre el valley israel using high resolution seismic reflection data abstract we present a series of high resolution seismic reflection lines across the yizre el valley which is the largest active depression in israel off the main trend of the dead sea rift the new seismic reflection data is of excellent quality and shows that the valley is dissected into numerous small blocks separated by active faults the yizre el valley is found to consist of a series of half grabens rather than a single half graben or a symmetrical graben the faults are generally vertical and appear to have a dominant strike slip component but some dip slip is also evident a marked zone of compression near megido is associated with the intersection of the two largest faults in the valley the carmel fault and the gideon fault variable trend of the faults reflects the complexity of the local geology along the boundary between the wide nw se trending farah carmel fault zone and the e w trending basins and ranges in the lower galilee this tectonic complexity is likely to result from a highly variable stress pattern modified by the structures inside it normal faulting in the valley occurred at an early stage of its development as a tectonic depression however strike slip motion on the carmel fault and possibly also on some of the other faults appears to have started together with the onset of normal faulting earthquake hazard in the area appears to be uniform as faults are distributed throughout the yizre el valley