seismic study of pull apart induced sedimentation and deformation in the northern gulf of aqaba elat abstract new multichannel seismic and bathymetric data are presented which clarify the plio quaternary evolution of the northern gulf of aqaba elat and the dead sea transform dst the seismic data reveal two main seismic sequences a lower pretectonic and an upper syntectonic unit separated by a prominent unconformity these units are each linked to a distinct tectonic phase in the history of the dst parallel horizons and an undisturbed internal structure point to a tectonic quite time or pure strike slip without extension or compression during the first pretectonic phase the second syntectonic phase which begins in the early pliocene is characterized by a major change in the activity of the dst the pretectonic sedimentary unit subsided and consequently dips southward with a supplementary inclination to the east the coeval sedimentation of the syntectonic unit is recorded by the divergent reflection pattern and onlap terminations on the unconformity the apparent fault system seems to be rearranged in the second phase the stepover of the main strand of the dst from the eastern side of the elat deep to the western side of the northern gulf of aqaba was mapped in detail for the first time the very smooth shape of the stepover and the apparent lack of extensional tectonics do not fit with the classical pull apart basin model for the elat deep and point to a decoupling of the crystalline basement from the sedimentary overburden comparisons of the new geophysical findings with analog models support this assertion

co seismic deformation during the mw7 3 aqaba earthquake 1995 from ers sar interferometry the m w 7 3 1995 aqaba earthquake is the largest instrumental earthquake along the dead sea fault we complement previous seismological studies by analyzing co seismic ground displacement from differential interferometry computed from ers images spanning 3 different areas they are compared with a synthetic model derived from seismological study only far field deformation related to the main sub event could be revealed because the near field area lies within the gulf the interferometric data imply a 56 km long and 10 km wide fault segment connecting the elat deep to the aragonese deep which strikes n195 e and dips 65 to the west with 2 1 m left lateral slip and a 15 5 rake indicating a slight normal component the geodetic moment compares well with the seismic moment

seismic potential of the dead sea fault in the northern gulf of aqaba elat new evidence from liquefaction seismic reflection and paleoseismic data abstract the cities of elat israel and neighboring aqaba jordan are major economic cultural and seaport centers they are located on the northern shore of the gulf of aqaba elat gae directly on the dead sea transform yet the precise location of the fault trace and its tectonic activity are lacking the interpretation of seismic reflection profiles across the gae beach and paleoseismic trench data located 2 2 km north of the shoreline provide evidence that the active offshore mapped avrona fault extends onland along the eastern side of the elat sabkha mudflat where three prominent fault strands crosscut the sedimentary fill mismatch of reflector geometry across the faults and flower structures indicate strike slip faulting with a normal slip component subsurface data from two trenching sites provide evidence for a minimum of two surface ruptures and two paleoliquefaction events faulting is constrained by radiocarbon dating for an event 1 between 897 and 992 ce and event 2 after 1294 ce we suggest that the historically documented 1068 ce and at least one later earthquake in 1458 or 1588 ce ruptured the elat sabkha site based on fault mapping we suggest a minimum value of m 6 6 for the 1068 ce earthquake whereas no surface rupture was observed for the 1212 ce historical earthquake fluidized strata radiocarbon dated to before 1269 1389 ce identified as paleoliquefaction may be attributed to it two liquefaction sand blows mapped in the trench likely formed after 1337 ce and before 1550 ce which possibly occurred at the same time as in the second faulting event our data suggest that no large event occurred along the avrona segment in the past 430 550 years given a 5 mm yr slip rate we conclude that a significant period of time passed since the last surface rupturing on the avrona fault increasing its seismic potential

active faulting in the gulf of aqaba new knowledge from the mw 7 3 earthquake of 22 november 1995 abstract on 22 november 1995 the largest earthquake instrumentally recorded in the area with magnitude m w 7 3 occurred in the gulf of aqaba the main rupture corresponding to the strike slip mechanism is located within the gulf of aqaba which forms the marine extension of the levantine fault also known as the dead sea fault the levantine fault accommodates the strike slip movement between the african plate and the arabian plate the gulf of aqaba itself is usually described as the succession of three deep pull apart basins elongated in the n s direction concerning historical seismicity only two large events have been reported for the last 2000 years but they are still poorly constrained the seismicity recorded since installation of regional networks in the early 1980s had been characterized by a low background level punctuated by brief swarmlike activity a few months in duration three swarms have already been documented in the gulf of aqaba in 1983 1990 and 1993 with magnitudes reaching at most 6 1 m w we suggest that the geometry of the rupture for the 1995 event is related to the spatial distribution of these previous swarms body wave modeling of broadband seismograms from the global network along with the analysis of the aftershock distribution allow us to propose a well constrained model for the rupture process northward propagation of the rupture has been found we have demonstrated that three successive subevents are necessary to obtain a good fit between observed and synthetic wave forms the total seismic moment released was 7 42 10 19 n m the location of the subsevents shows that the three stages of the rupture involve three different segments within the gulf substantial surface breakage showing only normal motion up to 20 cm affecting beachrock was observed along the egyptian coast we show that these ruptures are only a secondary feature and are in no case primary ruptures the stress tensor derived from striations collected in quaternary sediments shows radial extension this result supports landsliding of the beach terraces under the action of the earthquake shaking

imaging crustal discontinuities and the downgoing slab beneath western crete the migration of teleseismic receiver functions yields high resolution images of the crustal structure of western crete data were collected during two field campaigns in 1996 and 1997 by networks of six and 47 short period three component seismic stations respectively a total of 1288 seismograms from 97 teleseismic events were restituted to true ground displacement within a period range from 0 5 to 7 s the application of a noise adaptive deconvolution filter and a new polarization analysis technique helped to overcome problems with local coda and noise conditions the computation and migration of receiver functions results in images of local crustal structures with unprecedented spatial resolution for this region the crust under crete consists of a continental top layer of 15 20 km thickness above a 20 30 km thick subducted fossil accretionary wedge with a characteristic en echelon fault sequence the downgoing oceanic moho lies at a depth of 40 60 km and shows a topography or undulation with an amplitude of several kilometres as a consequence of slab depth and distribution of local seismicity the mediterranean ridge is interpreted as the recent accretionary wedge

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

data driven seismic hazard models prepared for a seismic risk assessment in the dead sea region abstract we derive a probabilistic seismic hazard model for the dead sea region to allow for seismic risk estimation which will be part of a subsequent study this hazard model relies as much as possible on data driven approaches utilizing a seismic catalog compiled for the region by integrating data from different sources we derive seismicity models using two different smoothing approaches and estimate a hypocentral depth distribution from historical observations we do not include paleoseismological evidence apart from the observed seismicity because ground motion records are sparse in the region we formulate the model in the european macroseismic intensity scale from 1998 however the collected macroseismic intensity data are still too few to derive a local intensity prediction equation ipe thus we choose among existing equations derived for different regions and combine them in a logic tree here motivated by scherbaum et al 2010 we propose a two step approach to select the ipes for the logic tree first we cluster a set of 10 candidate ipes to identify groups of models that can be considered similar with respect to the distribution of the predicted values for a selection of the explanatory variables i e magnitude and distance using a k mean approach steinhaus 1956 then we apply different ranking techniques scherbaum et al 2009 kale and akkar 2013 to identify within each cluster the most suitable model to be included in the logic tree the resulting hazard models are consistent with existing probabilistic seismic hazard models for the region we estimate a moderate to high hazard of intensity grade vii viii with 10 probability of exceedance within 50 years in close vicinity to the dead sea transform fault the dominant seismogenic structure in this region

a coupled fluid fracture approach to propagation of clastic dikes during earthquakes abstract the propagation of clastic dikes was studied in ami az plain where hundreds of clastic dikes cross cut the soft rock of the late pleistocene lacustrine lisan formation within the seismically active dead sea basin two analytic models were established to estimate the dike propagation velocities the dike emplacement duration and the driving pressures that were associated with dike propagation either under laminar or turbulent flow conditions these models depend on the host rock and fluid properties dike width and length based on these properties and field limitations the results indicate that the dikes were propagated under turbulent flow conditions and propagation velocities of 4 65 m s the emplacement duration of the clastic dikes is between 0 8 and 2 s which is similar to the order of the acoustic wave duration that passes through the soft rock during an earthquake event this implies that the propagation of dikes could form during the passing acoustic waves and may thus be considered as an earthquake induced impact structures the calculated driving pressures that were generated during the earthquake events near the surface are 1 2 mpa one order of magnitude larger than the pressure due to the overburden on the source layer

structural framework of the gulf of elat aqaba northern red sea the gulf of elat aqaba occupies the southern part of the dead sea rift the rift is considered to be a plate boundary of the transform type partially leaky which connects seafloor spreading in the red sea with the sagros taurus zone of continental collision the deep water in the gulf of elat up to 1850 m provides a rare opportunity to examine the process of continental rifting by marine geophysical techniques the bathymetry alone provides much information about fault patterns in this area the fragmentation of the once continuous arabian african platform is a complicated process it shapes the structure of the gulf which has developed through continuing tectonism primarily consisting of faulting recent geophysical and geological studies of the gulf of elat including bathymetry bottom photographs continuous seismic profiles seismic refraction gravity magnetics heat flow and coring provide new information about the shallow and deep crustal structure of this important segment of the world rift system the shallow structure of the gulf is dominated by three elongated en echelon basins which strike n20 25 e undulations in the floors of the basins produce several distinct deeps these basins are interpreted as pullaparts the new data from the gulf suggest that classical models for the formation of these structures should be modified only one of the longitudinal faults of each depression is a strike slip fault while the other is predominantly a normal fault the situation with the other two sides of the basin which are supposed to be composed of normal faults may also be more complex than previously thought at least in one case one such boundary is composed of a strike slip fault while the other has no significant fault crustal models of the gulf of elat based on gravity data indicate that the basins are rather shallow and do not extend into the lower crust the fill of the basins extends to about 5 km below the seafloor in the northern and southern basins and less in the central basin most significant magnetic anomalies in the gulf of elat extend from land into the sea none of them however extends from one coast to another across the gulf this supports the geological evidence for a shear between the arabia and sinai plates the magnetic field over the southern third of the gulf is rather smooth and markedly different from that of the other parts the nature of the magnetics the crustal structure of the western margin and the heat flow values indicate a thinner crust and different tectonic processes in the southern part of the gulf overall it seems that within the southern gulf of elat a transition occurs between crustal spreading that takes place in the red sea to a rifting without spreading that takes place along the dead sea transform spreading activity propagates from south to north the most active place is the central basin which is being propagated northward into the shallow northern basin

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

seismic moments local magnitudes and coda duration magnitudes for earthquakes in central california onscale seismograms recorded at stations in the u s geological survey s usgs central california seismic network calnet have been used to estimate the seismic moment m and local magnitude ml for earthquakes of 1 ml 4 located on the san juan bautista and parkfield sections of the san andreas fault the coyote lake section of the calaveras fault the sargent fault and near livermore these data together with m and ml estimates for 4 ml 6 earthquakes in these areas cannot be fit with a single linear log m versus ml relation rather the data are consistent with log m 1 5 ml 16 for 3 ml 6 with log m 1 2 ml 17 for 1 1 2 ml 3 1 2 and with a slope of to 1 fro 1 2 ml 1 1 2 whereas usgs coda duration magnitude md is consistent with ml for 1 1 2 ml 3 md is larger than ml at ml 1 1 2 and smaller than ml at ml 3 log m can be estimated to a precision of 0 2 for 1 md 3 1 2 earthquakes in central california by applying log m 1 2 md 17 to the md that have been routinely published by the usgs

micro and macroseismicity of the dead sea rift and off coast eastern mediterranean abstract the seismicity of israel has been evaluated from documented earthquake records of the present century and two years of routine monitoring of microearthquake activity by means of eleven stations spreading from the gulf of elat to northern galilee the dead sea rift asserts itself as the tectonic feature that accounts for the seismicity of our region the activity peaks at zones where the fault branches sideways or at a junction with other fault systems in particular the crescent fault of wadi faria seems to be a zone of high strain accumulation this is probably the site of many historical earthquakes which caused inland and coastal damage it is thus found that the most active fault today which constitutes the greatest seismic risk to israeli metropolitan areas extends along the dead sea rift from 31 2 n to 33 4 n the seismicity around the dead sea conforms with the proposed movement along en echelon faults while the southwest segment is presently inactive most of the seismic activity there is limited to the neighbourhood of its eastern shore with extreme seismicity at its southern tip near the prehistorical site of bab a dara a the seismicity of the arava is much lower than the jordan dead sea section the seismicity of the israeli coast was found to be somewhat higher than that of the arava

intrabasin paleoearthquake and quiescence correlation of the late holocene dead sea 1 a comprehensive multisite paleoseismic archive of the late holocene dead sea basin past 2500 years is established by constructing two age depth chronological models of two sedimentary sections exposed at the retreating shores of the modern dead sea two new paleoseismic study sites studied are the ein feshkha nature reserve outcrop located at the northern part of the basin and close to an active underwater transverse fault and the east ze elim gully outcrop at the southern part of the basin age depth regression models are calculated for these sections based on atmospheric radiocarbon ages of short lived organic debris calibrated with a bayesian model the uncertainties on individual model ages are smaller than 100 years the new chronological records are compared to a laminae counting study of the ein gedi core migowski et al 2004 located at the central dead sea basin the ein feshkha outcrop yielded the largest number of seismites in the studied time interval n 52 while lower numbers of seismites are recovered from the ze elim outcrop and ein gedi core n 15 and 36 respectively the seismites show no strong dependence on the limnological sedimentological conditions in the particular sampling sites they coappear in both shallow and deep water environments and in different sedimentary facies during time intervals when the chronologies are comparable it appears that the number of seismites is significantly larger in the northern part of the basin ein gedi and ein feshkha seismic quiescence intervals are apparent at all three sites from 2nd 4th century a d and at 500 150 b c at ze elim and ein gedi several synchronous seismites appear in all sections termed here the intrabasin seismites ibs among them 1927 1293 1202 1212 749 551 419 and 33 a d and 31 and mid 2nd century b c the recurrence time of the ibs from the 2nd century b c to the 14th century a d is 200 years compared with 100 years for all earthquakes on a diagram of epicentral distance versus magnitude historic earthquakes that are correlated with ibs plot in a field of high local intensity the farther and stronger ibs earthquakes require lower local intensities to be recorded this study demonstrates that a painstaking effort is still needed for unraveling the seismic history of the dead sea basin the results also indicate that such a study will likely be highly rewarding

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

the northern edge of the gulf of elat abstract the gulf of elat aqaba is located at the southern portion of the dead sea transform three large sedimentary basins exist within the gulf the northern edge of the gulf of elat the gulf s head forms the divide between the northern sedimentary basin of the gulf the elat deep basin and the on land sedimentary basins of the southern arava valley at this location the gulf of elat narrows considerably a transverse fault zone separates the elat deep basin from the gulf s head this fault zone is highly deformed and consists of numerous distinct faults and subbottom structures several structural elements within this zone extend westward into a graben on the sinai peninsula which is older than the gulf of elat the transverse fault zone connects two large strike slip faults segments of the dead sea transform the southern segment borders the elat deep on the east and the northern segment borders the gulfs head on the west some left lateral displacement is also occurring along the transverse fault zone the transverse fault zone is thus part of the main dead sea transform and not a secondary fault as is found at the southern end of the elat deep it is associated with a magnetic anomaly which is one of the largest recorded in the gulf of elat the existence of such an anomaly possibly indicates basaltic intrusion along this zone other instances where transverse faults extend away from the basinal areas like at the northern boundary of the elat deep can be recognized along the dead sea rift these structures may suggest that the longitudinal dimension of several of the basins is determined during early stages of their formation

seismicity of the eastern mediterranean region perspective from the sinai subplate we conducted a comprehensive study of the seismicity of the eastern mediterranean and examined its relation to the regional plate tectonics based on various published catalogs we have constructed a new list of ml 4 earthquakes which were recorded during the years 1900 1991 and represents most of the seismic moment released in the area over this period b values are 1 02 1 0 and 1 07 for the whole sinai subplate the dead sea transform and the cypriot arc respectively seismic efficiency of the dead sea transform is very low about 7 stressing the role of aseismic deformation in that plate border most of the major and moderate events ml 5 occur in belts associated with the geologically documented borders of the sinai subplate the cypriot convergent arc in the north the dead sea transform in the east and the rift of suez in the southwest the latter like the gulf of eilat aqaba was considered aseismic during the first half of the century the northwestern border however could not be delineated low level activity appears within the subplate especially north of latitude 32 n reflecting the breakdown of this part of sinai as it approaches the cypriot convergence zone though most of the seismic moments tend to concentrate along the subplate borders some moderate activity spreads out in wide belts which reflect the complexity of deformation accompanying motion along the subplate borders

simulation of seismic wave propagation through geometrically complex basins the dead sea basin abstract the dead sea transform dst is the source for some of the largest earthquakes in the eastern mediterranean the seismic hazard presented by the dst threatens the israeli palestinian and jordanian populations alike several deep and structurally complex sedimentary basins are associated with the dst these basins are up to 10 km deep and typically bounded by active fault zones the low seismicity of the dst the sparse seismic network and limited coverage of sedimentary basins result in a critical knowledge gap therefore it is necessary to complement the limited instrumental data with synthetic data based on computational modeling in order to study the effects of earthquake ground motion in these sedimentary basins in this research we performed a 2d ground motion analysis in the dead sea basin dsb using a finite difference code cross sections transecting the dsb were compiled for wave propagation simulations results indicate a complex pattern of ground motion amplification affected by the geometric features in the basin to distinguish between the individual contributions of each geometrical feature in the basin we developed a semiquantitative decomposition approach this approach enabled us to interpret the dsb results as follows 1 ground motion amplification as a result of resonance occurs basin wide due to a high impedance contrast at the base of the uppermost layer 2 steep faults generate a strong edge effect that further amplifies ground motions 3 sub basins cause geometrical focusing that may significantly amplify ground motions and 4 salt diapirs diverge seismic energy and cause a decrease in ground motion amplitude

episodic behavior of the jordan valley section of the dead sea fault inferred from a 14 ka long integrated catalog of large earthquakes the continuous record of large surface rupturing earthquakes along the dead sea fault brings unprecedented insights for paleoseismic and archaeoseismic research in most recent studies paleoseismic trenching documents the late holocene faulting activity while tectonic geomorphology addresses the long term behavior 10 ka with a tendency to smooth the effect of individual earthquake rupture events m w 7 here we combine historical archaeological and paleoseismic investigations to build a consolidated catalog of destructive surface rupturing earthquakes for the last 14 ka along the left lateral jordan valley fault segment the 120 km long fault segment limited to the north and the south by major pull apart basins the hula and the dead sea respectively is mapped in detail and shows five subsegments with narrow stepovers width 3 km we conducted quantitative geomorphology along the fault measured more than 20 offset drainages excavated four trenches at two sites and investigated archaeological sites with seismic damage in the jordan valley our results in paleoseismic trenching with 28 radiocarbon datings and the archaeoseismology at tell saydiyeh supplemented with a rich historical seismic record document 12 surface rupturing events along the fault segment with a mean interval of 1160 yr and an average 5 mm yr slip rate for the last 25 ka the most complete part of the catalog indicates recurrence intervals that vary from 280 yr to 1500 yr with a median value of 790 yr and suggests an episodic behavior for the jordan valley fault our study allows a better constraint of the seismic cycle and related short term variations late holocene versus long term behavior holocene and late pleistocene of a major continental transform fault

the gulf of aqaba earthquake swarm of 1983 january april summary in the period 1983 january 21 april 20 more than 500 local earthquakes ml 4 85 occurred in the gulf of aqaba area between latitudes 29 00 and 29 25 and longitudes 34 30 and 34 45 most of the activity including the largest shocks was restricted to the area between latitudes 29 07 and 29 15 and longitudes 34 33 and 34 42 where the nw atiya regional dyke crosses the area and is horizontally displaced by ne strike slip faults the first motion directions of four large shocks including the largest at both unj and hlw stations are in agreement with a strike slip mechanism at a ne trending fault in this area the b value showed a temporal increase with time from 0 43 to 0 69 this together with other geological and geophysical observations may indicate that subsurface magmatic activity has affected the stressed crustal rocks thus triggering earthquake activity this swarm and historical information indicate that the gulf of aqaba dead sea jordan transform is characterized by both swarm and foreshock aftershock types of seismic activity and therefore the relatively large proportion of non seismic slip along the southern part of this transform may actually be higher if swarm type activities are considered

seismicity and aeromagnetic features of the gulf of aqaba elat region recent seismicity in the gulf of aqaba region has been examined in relation to pull apart tectonics and structures indicated by bathymetry surface geology and new analyses of aeromagnetic data forty earthquakes occurring in the region from 1985 to 1989 were located using data from a network of five telemetered seismographs in the midyan region of saudi arabia east of the gulf of aqaba and from a network north of the gulf in israel interpretation of aeromagnetic data from the gulf of aqaba and the adjacent midyan region confirms previous estimates of offsets across the zone of transform faulting in the gulf aeromagnetic anomaly patterns obtained by reduction to the pole techniques and earthquake locations provide evidence for continuation of the faulting regime from the gulf northeastward into the midyan region the vicinity of the elat deep primarily the southwest flank probably is undergoing active normal faulting other seismicity and first motion polarity data confirm the regional pattern of nne trending sinistral strike slip faulting

quaternary tectonic evolution of the northern gulf of elat aqaba along the dead sea transform the northern gulf of elat aqaba is located in the transition between the deep marine basins of the gulf and the shallow onland basins of the arava valley interpretation of 500 km of high resolution seismic reflection data collected across the northern shelf reveals the tectonic structure and evolution of this transition six nne trending faults and one e w trending transverse fault are mapped slip rates are calculated based on measured offsets and age determination based on a radiocarbon calibrated sedimentation rate and a quaternary age model the most active fault is the evrona fault that absorbs most of the left lateral slip within the basin with an average sinistral slip rate of 0 7 0 3 mm yr through the late pleistocene and 2 3 3 4 mm yr during the holocene two intrabasin faults east of the evrona fault that have been inactive for the last several tens of thousands of years were mapped and motion from these faults has likely transferred to the evrona fault the basin is flanked on the west by the elat fault and on the east by the aqaba fault both faults are marked by large bathymetric escarpments based on displaced seismic reflectors we calculate a holocene vertical slip rate of 1 0 0 2 and 0 4 0 1 mm yr for the elat and aqaba faults respectively the geometry slip rates and slip history of the northern gulf of elat aqaba faults show that during the late pleistocene several intrabasin faults became dominant across the basin but that during the holocene the evrona fault accommodates most of the strike slip

coseismic deformation associated with the november 1995 mw 7 1 nuweiba earthquake gulf of elat aqaba detected by synthetic aperture radar interferometry the november 22 1995 mw 7 1 nuweiba earthquake occurred along one of the left stepping segments of the dead sea transform in the gulf of elat aqaba although it was the largest earthquake along this fault in the last few centuries little is yet known about the geometry of the rupture the slip distribution along it and the nature of postseismic deformation following the main shock in this study we examine the surface deformation pattern during the coseismic phase of the earthquake in an attempt to better elucidate the earthquake rupture process as the entire rupture zone was beneath the waters of the gulf and there is very little global positioning system gps data available in the region for the period spanning the earthquake interferometric synthetic aperture radar insar provides the only source of information of surface deformation associated with this earthquake we chose four synthetic aperture radar sar scenes of about 90 90 km each spanning the rupture area imaged by the ers 1 and ers 2 satellites the coseismic interferograms show contours of equal satellite to ground range changes that correspond to surface displacements due to the earthquake rupture interferograms that span the earthquake by 1 week show similar fringe patterns as those that span the earthquake by 6 months suggesting that postseismic deformation is minor or confined to the first week after the earthquake a high displacement gradient is seen on the western side of the gulf 20 40 km south of elat and aqaba where the total satellite to ground range changes are at least 15 cm the displacement gradient is relatively uniform on the eastern side of the gulf and the range changes are less than 10 cm to interpret these results we compare them to synthetic interferograms generated by elastic dislocation models with a variety of fault parameters although selecting the best fit fault parameters is nonunique we are able to generate a group of simplified model interferograms that provide a reasonable fit to the coseismic interferogram and serve to constrain the location of the fault the present analysis shows that if the rupture reached the gulf bottom surface the mean sinistral slip along the fault is constrained to about 1 4 m if surface rupture did not occur the average sinistral slip is constrained to the range of 1 4 3 m for a fault patch buried 0 4 km below the gulf bottom surface respectively with a minor normal component

quaternary stratigraphy of the prophet river northeastern british columbiathis article is one of a selection of papers published in this special issue on the theme geology of northeastern british columbia and northwestern alberta diamonds shallow gas gravel and glaciers exposures in the prophet river valley in northeast british columbia provide a unique glimpse into the quaternary history of the northwest canadian boreal plains the region shows evidence of late wisconsinan laurentide glaciation in the form of widespread till containing abundant erratic clasts derived from the canadian shield vertical sections along the prophet river expose non glacial and advance glacial sediments below this till pre late wisconsinan non glacial or interglacial floodplain sediments are interbedded with fluvial gravels at many sites macrofossils within horizontally laminated organic rich black clay and silt indicate deposition on the floodplain of the paleo prophet river within an oxbow lake the climate during deposition is interpreted to be similar to present supporting a dominantly spruce forest wood obtained from eight sites provided non finite radiocarbon ages and one sample provided an age of 49 300 2000 bp which is also considered non finite glaciolacustrine clays and s

source parameters and scaling relationships of earthquakes in israel abstract determination of earthquake dynamic source parameters such as the seismic moment stress drop and rupture area are often based purely on theoretical considerations in reality however some of the corrected coefficients utilized in the computations should preferably be defined empirically in the present study 39 earthquakes of ml between 3 0 and 6 7 are used to define the correction coefficients associated with distance geometric and unelastic attenuation and ratios between zero frequency spectral amplitides of s waves recorded by vertical and horizontal seismographs these are used in turn to determine the seismic moment m0 and the empirical correlation between log m0 and ml magnitudes for that region the validity of using constant stress drop assumption and correlation between moment and corner frequency is also discussed

microseismicity of three locations along the jordan rift abstract from september 1981 until june 1984 a portable seismograph station array was in operation at three different locations along the jordan rift system covering a the dead sea area b the hula valley area and c the southern part of the arava valley based on the seismological data obtained by these arrays a comparison of the microseismic activity in these areas is made these observations are also compared with the data from the countrywide network issn some preliminary conclusions regarding the seismicity of the investigated areas and the performance of the arrays are suggested

aftershock decay of three recent strong earthquakes in the levant aftershock sequences are studied from three recent strong earthquakes in the levant the mw 7 1 earthquake of 22 november 1995 and the ml 5 8 earthquake of 3 august 1993 both in the gulf of aqaba and the mw 6 8 earthquake of 9 october 1996 off the southwest coast of cyprus the modified omori s law provides a good fit to the decay of aftershock activity for both events the two sequences from the gulf of aqaba have rather low p values 0 90 in 1993 and 0 75 in 1995 reflecting slow decay of the aftershock activity this may be attributed to low heat flow close to the epicenters for the cyprus sequence the p value is 1 09 similar to that of many other sequences around the globe

the afar depression interpretation of the 1960 2000 earthquakes summary we studied the seismic activity of the afar depression ad and adjacent regions during the period 1960 2000 we define seven distinct seismogenic regions using geological tectonic and seismological data based on the frequency magnitude relationships we obtain b values of about 1 for the different regions the pattern of the distribution of the location of epicentres fits with the known active fault zone in the ad and the axial volcanic ridges the bab el mandab area and the danakil aysha a blocks are less active for 125 intermediate to strong earthquakes the seismic moment and source parameters were calculated the results of the fault plane solutions for the afar depression indicate mainly strike slip and normal sense of movement originating from fault planes striking nw se these results indicate a clockwise block rotation described previously as a bookshelf model in central ad there are a few rightlateral faults east of massawa with e w striking fault planes at the southern red sea north of the danakil block the mixed focal mechanisms with axial plane striking nw se comprise several reverse faulting strike slip motion and normal faulting right lateral movement was also calculated for a cluster of seismic events between the manda hararo and alyata volcanic ridges along nw se striking faults along the n s striking faults in the escarpment at the western afar margins there are two distinct clusters of epicentres the strong earthquakes at the southern cluster exhibit normal or strike slip motions the intermediate to small earthquakes in the northern cluster exhibit reverse and strike slip motions mainly normal faults were calculated along ne sw striking faults of the ethiopian east african rift estimates of the seismic efficiency suggest that the maximal values are about 50 per cent or less implying that most of the motion is taken aseismically

heat flow and continental breakup the gulf of elat aqaba heat flow measurements were made at five sites in the major basins of the gulf of elat aqaba northern red sea the gulf is located at the southern portion of the dead sea rift which is a transform plate boundary vertical temperature gradients were measured with a probe which allows multiple penetration of the bottom during a single deployment and thermal conductivities were determined by needle probe measurements on sediment cores a mean heat flux of about 80 mwm 2 was found and the values tend to increase from north to south this latitudinal gradient corresponds to the general trend of gradual thinning of the continental crust of the gulf toward the red sea where oceanic crust exists the heat flow data together with other geophysical data are consistent with a propagation of rifting from the red sea northward along the dead sea rift where the fractures are primarily shear the gulf forms a transition between these two tectonic regimes extensional red sea to the south and transform dead sea to the north

determination of earthquake energy release in the eastern mediterranean region summary seismic energy radiated by earthquakes in the eastern mediterranean region is estimated using the short period 50 samples per second seismic recordings made by the israel seismic network during 1990 1997 our data set is the whole s wave window from sn until lg falls to less than twice the noise level from 133 earthquakes with a high signal to noise ratio we obtained the attenuation function 1 850 0 005 log r 0 00460 0 00005 r log e 0 05 where the distance range is 50 r 1500 km we tested the dependence of the attenuation function on the azimuth and the distance despite the different propagation paths of the waves travelling through the continental crust of the arabian shield to the east or the intermediate crust of the mediterranean sea to the west we show that from a statistical point of view the attenuation functions are similar the energy estimation involves time domain integration of the squared ground motion velocity assuming that the attenuation is known following the method of kanamori et al 1993 for the magnitude range 3 0 mb 6 2 magnitude determined by the national earthquake information service neis we obtained the magnitude energy relationship log e0 2 09 0 10 mb 8 86 0 42 comparison of the seismic energy and the seismic moment suggests that e m00 19 and that orowan s stress drop increases as m00 19 a refinement of the results is expected with the application of the method of mayeda walter 1996 for energy estimation from coda envelopes using a large data set of broad band observations

three dimensional elastic earthquake modelling based on integrated seismological and insar data the mw 7 2 nuweiba earthquake gulf of elat aqaba 1995 november summary the nuweiba earthquake 1995 november 22 m w 7 2 the largest seismic event along the dead sea transform dst in at least 160 yr ruptured 45 50 km along the aragonese segment of the left stepping strike slip fault system occupying the gulf of elat aqaba southern segment of the dst the rupture initiated in a partly normal low slip first subevent near the southern end of the fault and propagated unilaterally north northeastward as a high slip nearly pure sinistral second subevent which was responsible for over 90 per cent of the total seismic moment the source mechanism and slip distribution derived from inversion of teleseismic broad band waveforms are used to construct a 3 d elastic model of the earthquake based on the boundary elements method resulting in the full 3 d displacement and stress fields induced by the earthquake in the absence of sufficient global positioning system data the only other constraints on the geometry and slip distribution of the rupture are provided by interferometric synthetic aperture radar insar measurements spanning the coseismic and early post seismic period we calculate simulated interferograms by transforming the calculated surface displacement field into the satellite coordinate system and comparing them with the observed interferograms the model parameters are then iteratively modified until a best fitting model is obtained providing a refined set of static source parameters for the mainshock this model is then used to calculate the static coulomb stress changes induced by the mainshock on the step over faults suggesting that the major m w 5 aftershocks in the first eight post seismic months were triggered by small changes 1 bar in the left lateral coulomb stress with effective friction coefficient not higher than 0 2 aftershock distribution and mechanisms indicate that the available coulomb stress dropped below the frictional strength of the fault but was not complete

coseismic horizontal slip revealed by sheared clastic dikes in the dead sea basin despite the hazard caused by near surface destructive horizontal displacements during earthquakes field evidence for coseismic slip along horizontal discontinuities is exceptionally rare mainly due to the lack of adequate exposure and markers however within the seismically active dead sea basin the late pleistocene lisan formation contains vertical clastic dikes that are sheared laterally at maximum depths of 15 m and thereby provide unique profiles of such horizontal displacement in order to investigate how coseismic horizontal shearing is distributed near the surface we document an 1 m thick brittle shear zone consisting of up to 11 slip surfaces that can be traced for tens of meters in the lisan formation displacements along individual slip surfaces are up to 0 6 m and the total displacement across the shear zone is up to 2 0 m displacement profiles and gradients indicate that the brittle shear zone formed by simple shear and deformation was associated with slip partitioning and transfer between primary and secondary slip surfaces evidence for concurrent displacement along slip surfaces during a single event indicates that the brittle shear zone was formed during a coseismic event subsequent to 30 ka we consider the mechanical effect of seismic wave related transient stress which when added to the initial static effective stress may result in concurrent horizontal shear failure along detrital rich layers in the lisan formation the exceptional quality of exposures and markers enables us to document for the first time the details of near surface horizontal shearing and indicates that displacement along horizontal bedding planes is a viable mechanism to absorb coseismic deformation in well bedded near surface strata

variable slip rate and slip per event on a plate boundary fault the dead sea fault in northern israel abstract we resolved displacement on buried stream channels that record the past 3400 years of slip history for the jordan gorge jgf section of the dead sea fault in israel based on three dimensional 3d trenching slip in the past millennium amounts to only 2 7 m similar to that determined in previous studies whereas the previous millennium experienced two to three times this amount of displacement with nearly 8 m of cumulative slip indicating substantial short term variations in slip rate the slip rate averaged over the past 3400 years as determined from 3d trenching is 4 1 mm yr which agrees well with geodetic estimates of strain accumulation as well as with longer term geologic slip rate estimates our results indicate that 1 the past 1200 years appear to significantly lack slip which may portend a significant increase in future seismic activity 2 short term slip rates for the past two millennia have varied by more than a factor of two and suggest that past behavior is best characterized by clustering of earthquakes from these observations the earthquake behavior of the jordan gorge fault best fits is a weak segment model where the relatively short fault section 20 km bounded by releasing steps fails on its own in moderate earthquakes or ruptures with adjacent segments

velocities and driving pressures of clay rich sediments injected into clastic dykes during earthquakes summary we studied the velocities and driving pressures associated with clastic dyke formation in the ami az plain where hundreds of clastic dykes cross cut the soft rock of the late pleistocene lacustrine lisan formation within the seismically active dead sea basin flow of clastic material into fractures and opening of the fractures are two mechanisms that occur during earthquake induced clastic dyke emplacement two analytic models were established based on field observations and experimental viscosity tests to estimate the velocities and driving pressures that were associated with dyke emplacement a a channel flow for upward injection of a clay water mixture and b a profile of fracture dilation based on the elastic theory analysis the two models predict that pressures between 1 and 10 mpa are generated in the source layer and dykes in the last stage of the injection process in addition the channel flow model predicts that the injection velocity reaches metres to tens of metres per second and the emplacement time of the clastic dykes is on a scale of seconds it is suggested that the high pressure values represent the static stress drop during earthquake events or represent dynamic stresses resulting from the seismic waves which passed through the soft lacustrine rocks in both cases the predicted high pressure values indicate that the clastic dyke was emplaced in close proximity of an active segment of the dead sea fault during the late pleistocene holocene

seismic observations of the 22 11 1995 gulf of aqaba earthquake sequence abstract we analyzed the aftershock sequence of the gulf of aqaba earthquake recorded by short period and broad band stations between november 1995 and december 1996 the seismicity pattern reveals significant activity often confined to known surface traces of active faults or within local grabens most of the aftershock activity is concentrated north of the main shock in the aragonese and eilat basins while the activity is diffused south of the main shock in the dakar and tiran basins most of the moderate to strong aftershocks of the whole aftershock sequence occurred in the aragonese basin mainly in the first 100 days following the main shock the eilat basin is characterized by a larger number of aftershocks composed mainly of small magnitude implying a slower decay rate assuming a detection level of ml 3 2 we obtain b values of 1 01 1 15 and 0 89 for the whole gulf of aqaba and eilat and aragonese basins respectively in good agreement with recent studies of the dead sea fault following omori s law we obtained a decay parameter of 0 94 0 88 and 0 96 for the aftershock sequences in the whole gulf of aqaba and the eilat and aragonese basins respectively correlative with regions of low heat flow for 1630 events in the local magnitude range of 0 6 ml 6 2 we found seismic moment estimates m0 of 5 1018 m0 7 7 1026 dyn cm and brune stress drop estimates between 1 and 200 bars with a characteristic value of 90 bars in the eilat and aragonese basins for m0 5 1021 dyn cm these characteristics are comparable to those for events occurring on the main dead sea jordan fault most of the moment release in the basins occurred shortly after the occurrence of the main shock the total moment release in the eilat and aragonese basins is only a fraction of the moment release of the main shock suggesting an almost complete stress release

evidence from the northern red sea on the transition from continental to oceanic rifting abstract the northern red sea is an active rift in the last stages of continental rifting which is beginning to undergo the transition to oceanic seafloor spreading the rift can be divided into two distinct regions the marginal areas consist of a series of bathymetric terraces and as indicated by geophysical data are underlain by a series of rotated fault blocks the axial depression which forms the axis of deep water is a continuous region 10 to 25 km wide near the center of the sea which is characterized by high heat flow a large gravity minimum and very deformed sediments both regions are divided along strike into segments roughly 60 km long by cross trending transfer zones the presently active tectonics are characterized by the concentration of extension and deformation in the axial depression and by the emplacement of a number of large intrusions the intrusions occur at distinct sites located at the intersection of transfer zones with the faults bounding the rotated blocks in the marginal areas and at deeps located in the axial depression halfway between transfer zones although extension is becoming concentrated in the axial depression geophysical data imply that at least the upper few kilometers of the crust in that region consists of non magnetic continental type material and that this ca apace has been ruptured by large intrusions only at the deeps a wide range of crustal seismic velocities has been observed in the northern red sea including velocities normally associated with oceanic crust the velocity variations appear spatially related to corresponding large variations in basement rock type observed on shore in the eastern desert of egypt the northern red sea is in an intermediate stage between a continental rift valley and a young ocean basin and delineation of its structure and tectonics allows a model to be developed for the evolution of a rifted continental margin rifting starts in a series of linked half grabens 50 60 km long and formed over detachment surfaces which probably penetrate no deeper than the mid or lower crust this style of rifting can accommodate at least the amcunt of extension represented by the gulf of suez 35 km at some greater amount of extension the rift acquires a more symmetric shape probably through the development of antithetically faulted blocks in the hanging wall extension in this stage is still distributed throughout the rift and is accommodated in the upper crust by rotation of fault blocks at the stage represented by the northern red sea extension becomes concentrated in an axial depression and begins to be partially accommodated by large intrusions which form deeps the position of the deeps is controlled by the transfer zones established in the earliest stages of rifting with further extension the deeps serve as nucleation points that develop into small discrete cells of seafloor spreading these cells grow and coalesce to form a continuous mid ocean ridge spreading center such as is found in the southern red sea

what controls thickness of sediments and lithospheric deformation at a pull apart basin we present a simplified three dimensional thermomechanical model of a pull apart basin formed at an overstepping of an active continental transform fault the modeling shows that for a given strike slip displacement and friction on the faults the major parameter that controls basin length thickness of sediments and deformation pattern beneath the basin is the thickness of the brittle layer the unusually large length and sediment thickness of the dead sea basin the classical pull apart basin associated with the dead sea transform can be explained by 100 km of strike slip motion and a thick 20 22 km up to 27 km locally brittle part of the cold lithosphere beneath the basin the thinner sedimentary cover in the gulf of aqaba basin located at the southernmost part of the dead sea transform close to the red sea rift is probably due to a thinner brittle part 15 km of the warmer lithosphere the modeling also suggests no more than 3 km of moho uplift beneath narrow 10 15 km pull apart basins formed in cold lithosphere such as the dead sea basin we also infer that a pull apart basin may only form if a several kilometer thick ductile detachment zone exists between the brittle crust and upper mantle modeling shows that this would not be the case for the dead sea basin if the surface heat flow there were indeed as low as 40 mw m 2 as previously reported we consider this result as an indication that the surface heat flow at the dead sea might have been underestimated

internal tides in the southwestern japan east sea abstract this paper investigates the internal tidal energy distribution in the southwestern japan east sea using vertical round trip travel time data from 23 pressure sensor equipped inverted echo sounders pies the records are analyzed by bandpass filtering to separate time dependent variability of the semidiurnal and diurnal bands the semidiurnal internal tides exhibit a horizontal beam pattern of high energy propagating into the open basin they originate from a restricted portion of the shelf break where the korea strait enters the ulleung basin the generation appears to occur at 200 m water depth near 35 5 35 7 n and 130 131 e where the slope of bottom topography matches that of the wave characteristics coinciding with the location where the semidiurnal barotropic cross slope tidal currents are strongest maximum vertical displacement of the thermocline interpreted as a long wave first baroclinic mode from the measured is about 25 m near the generation region annual and monthly var

constraints on the thermal history of the dead sea graben as revealed by coal ranks in deep boreholes abstract coal ranks have been studied by vitrinite reflectance measurements in three boreholes zuk tamrur 1 and zohar 8 on the judea desert plateau adjacent to the graben margin and amiaz 1 on a down faulted block at the southwest dead sea graben in the plateau boreholes time temperature index tti calculations reveal that the coalification profile probably evolved under a late cretaceous thermal event with a thermal gradient of 35 38 c km followed by gradual decay to the present level c 20 c km by miocene time in amiaz 1 the highest coal rank encountered 0 5 ro is marginal for independent tti calculations however some constraints on thermal history can be inferred stratigraphic and structural relationships between the 0 5 ro isoreflectance in amiaz 1 and the plateau boreholes reveals that most of the coalification measured in amiaz 1 pre dates the formation of the graben and that an additional 3 4 km of miocene holocene graben fill barely affected the coalification cessation of coalification despite increasing burial indicates that the post miocene thermal gradient in the amiaz block could not have exceeded 20 23 c km this finding is consistent with present day heat flow and other geophysical information tectonic models for the evolution of the dead sea graben requiring a high thermal regime are inconsistent with the presented data this raises questions as to the mechanism involved in the formation of rhomb shaped grabens in general on the one hand and for the hypothesis of the leaky nature of the dead sea transform north of the gulf of elat on the other

12 000 year long record of 10 to 13 paleoearthquakes on the yammouneh fault levant fault system lebanon we present results of the first paleoseismic study of the yammouneh fault the main on land segment of the levant fault system within the lebanese restraining bend a trench was excavated in the yammouneh paleolake where the fault cuts through finely laminated sequences of marls and clays first order variations throughout this outstanding stratigraphic record appear to reflect climate change at centennial and millennial scales the lake beds are offset and deformed in a 2 m wide zone coinciding with the mapped fault trace ten to thirteen events are identified extending back more than 12 kyr reliable age bounds on seven of these events constrain the mean seismic return time to 1127 135 yr between 12 ka and 6 4 ka implying that this fault slips in infrequent but large m 7 5 earthquakes our results also provide conclusive evidence that the latest event at this site was the great a d 1202 historical earthquake and suggest that the yammouneh fault might have been the source of a less well known event circa a d 350 these findings combined with previous paleoseismic data from the zebadani valley imply that the parallel faults bounding the beqaa release strain in events with comparable recurrence intervals but significantly different magnitudes our results contribute to document the clustering of large events on the levant fault into centennial episodes such as that during the eleventh through twelfth centuries separated by millennial periods of quiescence and raise the possibility of a m 7 event occurring on the yammouneh fault in the coming century such a scenario should be taken into account in regional seismic hazard assessments and planned for accordingly

seismic activity along fault branches of the dead sea jordan transform system the carmel tirtza fault system abstract about 550 earthquakes 1 0 m l 5 3 along the carmel tirtza fault a branching fault of the jordandashdead sea transform system recorded by the israel seismograph network isn between 1984 and 1994 were analyzed the seismicity pattern reveals significant activity often confined to known surface traces of active faults or within local grabens earthquake clusters are also observed the seismicity pattern within the mediterranean seems more diffuse possibly due to observational inaccuracies and insufficient knowledge of how the carmel tirtza fault system extends towards the northwest the seismicity along the carmel tirtza fault system since the beginning of this century is characterized by a b value of about 0 9 for 15 events with 3 1 m l 5 3 we found seismic moment estimates m 0 of 0 7 10 14 m 0 10 17 nm and brune stress drop estimates between 0 9 and 16 4 mpa these characteristics are comparable to those for events occurring on the main dead sea jordan transform fault ten individual earthquake focal mechanisms and three joint focal mechanisms for earthquake clusters have been obtained towards the northeastern part of the carmel tirtza fault system a left lateral motion seems to dominate while the seismicity pattern and the focal mechanism solutions near the branching of the carmel tirtza fault and the dead sea jordan rift suggest the present day existence of a complicated tectonic regime stress inversion assuming one stress tensor for the whole region indicates nne ssw extension and wnw ese compression

thermal history of the eastern margin of the gulf of suez i reconstruction from borehole temperature and organic maturity measurements abstract the gulf of suez is a tertiary continental rift associated with prominent flank uplift despite numerous studies which focused mainly on the western and central parts of the graben the thermo mechanics controlling the tectonic evolution of the gulf of suez is still enigmatic we have integrated borehole temperatures and organic maturity measurements in the eastern margin of the gulf of suez in order to study rift related paleothermometry and the present day thermal regime the data obtained suggest that the present thermal regime represents the maximum heat flow and temperatures for the sedimentary section in the basin furthermore lateral distributions of geothermal gradient and heat flow in the gulf of suez do not correlate mainly because of extensive variability in lithology and thermal conductivity rift related heat flow increases systematically and subparallel to the rift axis from about 60 mw m2 in the darag subbasin in the north to about 80 mw m2 in the ras garra area in the south both values are higher than 45 mw m2 the average heat flow assumed for the pre rift stage and the characteristic level for the present day heat flow away from the rift the north to south increase in heat flow probably reflects the southward increase of extension as well as lateral transfer of heat flow from the red sea this latter conclusion is supported by the fact that heat flow in the southern gulf of suez recorded by the paleothermometric reconstructions and borehole temperature data is somewhat higher than that estimated by model calculations for the extension derived from structural and subsidence reconstruction

source inversion of the 1993 and 1995 gulf of aqaba earthquakes abstract the teleseismic body waves of two earthquakes were inverted to their sources so as to obtain a rupture process for each the events of august 3 1993 m s 6 1 and november 22 1995 m s 7 2 took place at the southern end of the dead sea fault system dsfs which has been seismically quiet for the last few centuries the inversion results show that the rupture of the 1995 event originated in the vicinity of the 1993 event and propagated to the north where the major moment release of two subevents took place the first being 20 km and the second being 40 km away the seismic moment of the first and second subevents were m o 7 4 10 18 nm and m o 38 10 18 nm respectively despite their proximity they show completely different focal mechanisms the first subevent has a predominantly normal faulting mechanism like the 1993 event which probably took place on the faults forming the pull apart basins beneath the gulf of aqaba the major subevent shows a predominantly left lateral strike slip mechanism which clearly identifies the dsfs as accommodating the motion between africa and arabia we attribute the abrupt change of the mechanisms of the 1993 and 1995 events to segmentation of the dsfs beneath the gulf of aqaba which probably gave rise to an extensional regime the locations of the 1993 and 1995 earthquakes their aftershock distribution and the spatial distribution of the subevents of the 1995 earthquake show end to end migration of sources from south to north taking into account the long seismic quiescence of the dsfs and the source inversion results one may conclude that the area to the north of the rupture zone of the 1995 event is prone to a large earthquake