seasonal cycles of particle and solute transport processes in nearshore sediments 222rn226ra and 234th238u disequilibrium at a site in buzzards bay ma radiochemical measurements leading to the estimation of particle mixing rates and irrigation rates in the sediments of a site in buzzards bay massachusetts have been made over two nearly full seasonal cycles both particle mixing and sediment irrigation show significant seasonal variability at this site the variability is consistent with biologically driven transport mechanisms 234th238u disequilibrium measurements were used to estimate particle mixing rates based on three cores taken from december through march and four taken from june through october a cold season average mixing rate of 5 6 cm2 yr and a warm season average rate of 17 cm2 yr were found excess 234th inventories in the upper 5 cm of the sediments also varied seasonally with a cold season average value of 1 8 dpm cm2 significantly less than both the warm season value of 3 4 dpm cm2 and the predicted average value for buzzards bay 3 dpm cm2 222rn226ra disequilibrium in sediment pore waters was used to estimate sediment irrigation based on a total of seven cores three seasonal groupings of results were made 1 december through march when 222rn deficits could be explained by vertical molecular diffusion alone 2 early summer june when irrigation was important to at least 20 cm the maximum depth of the sampled region and 3 early fall when irrigation was important to about 10 cm a nonlocal exchange vertical molecular diffusion model emersonet al 1984 was used to obtain quantitative estimates of irrigation rates when the exchange parameter was allowed to vary exponentially with depth below the sediment water interface model rn deficit profiles fit measured profiles quite well

the attenuation of seismic shear waves in quaternary alluvium in santa clara valley california we used shear waves generated by an air powered source at the ground surface and recorded in a borehole to estimate the shear wave quality factor at strong motion station gilroy no 2 we find similar values of q using both the decay of the spectra with depth and the slope of the spectral ratio at two depths we find no evidence of a frequency dependence of q the mean value of q over the depth range 10 to 115 m is close to 10 the use of this value over the depth of the borehole and the observed travel time of 0 358 sec gives a cumulative attenuation factor t of 0 036 sec for the upper 180 m of the quaternary alluvium this is comparable to the differential decay between gilroy no 2 and a rock site 1 9 km away gilroy no 1 as measured from the decay of the high frequency spectra of accelerograms from large earthquakes plotted on a log linear scale t 0 05 0 04 and 0 03 sec for the 1979 coyote lake 1984 morgan hill and 1989 loma prieta earthquakes respectively the similarity between the attenuations measured from the low strain surface source and those from the larger amplitude earthquake sources suggests that increases of damping due to nonlinear wave propagation effects are limited

intraplate extensional tectonics of the eastern basin range inferences on structural style from seismic reflection data regional tectonics and thermal mechanical models of brittle ductile deformation the general lack of a correlation between earthquakes and surface faulting in the interior of the western u s cordillera has motivated our efforts to evaluate the geometry structural style and mechanism of normal faulting characteristic of this region of intraplate extension to address the problem we have interpreted over 1500 km of seismic reflection data and constructed detailed cross sections of the upper crust rheological models of the continental crust were calculated to examine the possibility of shallow quasi plastic flow and its influence on faulting in the eastern basin range the western colorado plateau and the middle rocky mountains our data and interpretations have revealed the following styles of cenozoic deformation 1 steep to low angle dip normal faulting along the wasatch fault 2 low angle dip and listric normal faulting possibly associated with movement on preexisting thrusts 3 the occurrence of asymmetric mostly eastward tilted tertiary basins that are bounded by low to moderate dipping planar and listric faults and 4 at least three vertically stacked en echelon low angle reflections in the mid to upper crust that dip gently westward from 3 km beneath the wasatch plateau to over 15 km at the utah nevada border these reflections are interpreted as normal detachment faults the structural style of the pervasive low to moderate angle dipping faults cannot be easily reconciled with classic brittle failure theory but the interpreted termination of normal faults at or above the deeper low angle reflections suggests the presence of shallow zones of ductile deformation that may have accommodated slip an important observation based on interpretations of seismic reflection profiles is that normal fault zones dip more gently in the subsurface than their associated scarps in unconsolidated surficial deposits segment boundaries of the wasatch fault zone apparently coincide with the positions of east trending displacement transfer structures in thrust sheets and the position of the precambrian uinta aulacogen suggesting that preexisting crustal structure partly controls the geometry of extension to examine the influence of ductile deformation quasi plastic flow was modeled for appropriate geotherms of the basin range and colorado plateau crusts these models provide constraints on the depth to the frictional quasi plastic transition that occurs as shallow as 8 km in the eastern basin range this depth also corresponds to the approximate depth above which most accurately determined earthquake foci for small earthquakes m 5 5 appear to nucleate at 10 15 km in or near the brittle ductile transition the rheological modeling suggests that a thermally deforming continental lithosphere plays an important role in the evolution of this extending intraplate region large scale low angle reflections may represent decollements and normal faults at the top of upper crustal zones of reduced shearing strength and higher ductility

seismic wave attenuation from borehole and surface records in the top 2 5km beneath the city of basel switzerland summary we investigate attenuation q 1 of sediments of 2 5 3 5 km thickness underneath the city of basel switzerland we use recordings of 195 induced events that were obtained during and after the stimulation of a reservoir for a deep heat mining project in 2006 and 2007 the data set is ideally suited to estimate q as all events are confined to a small source volume and were recorded by a dense surface network as well as six borehole sensors at various depths the deepest borehole sensor is positioned at a depth of 2 7 km inside the crystalline basement at a mean hypocentral distance of 1 8 km this allows us to measure q for frequencies between 10 and 130 hz we apply two different methods to estimate q first we use a standard spectral ratio technique to obtain q and as a second measure we estimate q in the time domain by convolving signals recorded by the deepest sensor with a q operator and then comparing the convolved signals to recordings at the shallower stations both methods deliver comparable values for q we also observe similar attenuation for p and s waves qp qs as expected q increases with depth but with values around 30 50 it is low even for the consolidated permian and mesozoic sediments between 500 and 2700 m

folding of mylonitic zones in cordilleran metamorphic core complexes evidence from near the mylonitic front metamorphic core complexes of north america are asymmetric when viewed perpendicular to the direction of tectonic transport on one side mylonitic fabrics and the overlying detachment fault dip gently in the direction of upper plate transport and the mylonitic rocks have a down dip sense of shear on the opposite side the mylonitic zone rolls over to a dip opposed to the direction of upper plate transport diverges downward from the detachment fault and dies out upward across a mylonitic front new kinematic data show that the backdipping mylonitic zone in most complexes is a downfolded continuation of the main mylonitic zone folding of the mylonitic zone was accompanied by the formation of antithetic shear zones and occurred during the late stages of mylonitization

rock deformation studies in the mineral mountains and sevier desert of west central utah implications for upper crustal low angle normal faulting the cave canyon detachment a low angle normal fault that crops out in the mineral mountains west central utah has been interpreted as a hanging wall splay of a much larger structure the sevier desert detachment that was influential in development of the idea that low angle normal faults play a role in crustal extension the cave canyon detachment provides expectations for the deformational features that might be expected along the hypothesized sevier desert detachment which is not exposed in outcrop and is inferred to exist primarily on the basis of seismic reflection data the footwall of the cave canyon detachment is characterized by a 200 m thick granite cataclasite which exhibits a clear decrease in grain size and increase in microfracture density as the fault surface is approached undulatory extinction in quartz and feldspar and abundant quartz deformation lamellae at distances more than 200 m from the fault surface are interpreted as related to cooling of the miocene granite rather than to normal faulting although mylonitic textures have previously been described in the granite we found no evidence for mylonitization in the footwall rocks the hanging wall of the detachment is characterized by 9 m of deformed partially dolomitized limestone with a 2 m thick carbonate mylonite at the contact deformation features include dynamic recrystallization grain size reduction development of twinning with a strong preferred orientation some grain size layering and undulatory extinction close to the fault static recrystallization overprints fossils and ooids at distances greater than 9 m drill cuttings and some core recovered at similar distances above and below the hypothesized sevier desert detachment show no evidence for localized deformation arco hole in the rock no 1 arco meadow federal no 1 and argonaut energy federal no 1 wells fossils and ooids are undeformed in paleozoic carbonate rocks within 3 m below the contact and sandstone and conglomerate with rounded clasts lacking more than background levels of microfracturing are found in samples within 3 m above the contact these features contrast markedly with those of the cave canyon detachment which was active at a considerably shallower and cooler level in the crust 5 km and 300 c than is implied for paleozoic rocks beneath the sevier desert once hanging wall rocks are restored along the hypothesized detachment 9 14 km and 280 425 c at the locations studied the very different character of the two surfaces reinforces our earlier suggestion that beneath much of the sevier desert basin the base of the tertiary section is an unconformity rather than a low angle normal fault

the use of radon 222 as a tracer of sediment irrigation and mixing on the washington continental shelf abstract observations of the natural radioisotope rn 222 were used in conjunction with radiochemical biological and sedimentological techniques to investigate the irrigation and mixing of sediment at three sites about 90 m water depth along the washington continental shelf the rn 222 deficit difference between observed and predicted concentrations within the seabed was greatest near the columbia river during the summer molecular diffusion at most locations and times could account for only a portion of the deficit irrigation and mixing of the seabed explain the remainder biological mixing bioturbation and physical irrigation wave and tidal pumping have relatively little effect on the rn 222 deficit physical mixing erosion and deposition has a significant effect soon after a major erosion event storm however no such event occurred prior to the observations the conclusion is that biological irrigation and molecular diffusion are the primary causes of the rn 222 deficit and that biological irrigation is responsible for the observed spatial and temporal variations in the deficit therefore biological irrigation is greatest near the columbia river during the summer the spatial increase of irrigation near the columbia is probably due to a relatively large population of tube dwelling filter feeding polychaetes the temporal increases of irrigation during the summer is probably due to annual growth cycles of the benthic community and is not due to water temperature changes

detachment faults evidence for a low angle origin the origin of low angle normal faults or detachment faults mantling metamorphic core complexes in the southwestern united states remains controversial if sigma sub 1 is vertical during extension the formation of or even slip along such low angle normal faults is mechanically implausible no records exist of earthquakes on low angle normal faults in areas currently undergoing continental extension except from an area of actively forming core complexes in the solomon sea papua new guinea in light of such geophysical and mechanical arguments w r buck and b wernicke and g j axen proposed models in which detachment faults originate as high angle normal faults but rotate to low angles and become inactive as extension proceeds these models are inconsistent with critical field relations in several core complexes the rawhide fault an areally extensive detachment fault in western arizona propagated at close to its present subhorizontal orientation late in the tertiary extension of the region neither the wernicke and axen nor buck models predict such behavior in fact both models preclude the operation of low angle normal faults the authors recommend that alternative explanations or modifications of existing models are needed to explain the evidence that detachment faults form and operate with gentle dips

microseismicity at the north anatolian fault in the sea of marmara offshore istanbul nw turkey 1 the north anatolian fault zone nafz below the sea of marmara forms a seismic gap where a major earthquake is expected to occur in the near future this segment of the fault lies between the 1912 ganos and 1999 izmit ruptures and is the only nafz segment that has not ruptured since 1766 to monitor the microseismic activity at the main fault branch offshore of istanbul below the cinarcik basin a permanent seismic array pires was installed on the two outermost prince islands yassiada and sivriada at a few kilometers distance to the fault in addition a temporary network of ocean bottom seismometers was deployed throughout the cinarcik basin slowness vectors are determined combining waveform cross correlation and p wave polarization we jointly invert azimuth and traveltime observations for hypocenter determination and apply a bootstrap resampling technique to quantify the location precision we observe seismicity rates of 20 events per month for m 2 5 along the basin the spatial distribution of hypocenters suggests that the two major fault branches bounding the depocenter below the cinarcik basin merge to one single master fault below 17 km depth on the basis of a cross correlation technique we group closely spaced earthquakes and determine composite focal mechanisms implementing recordings of surrounding permanent land stations fault plane solutions have a predominant right lateral strike slip mechanism indicating that normal faulting along this part of the nafz plays a minor role toward the west we observe increasing components of thrust faulting this supports the model of nw trending dextral strike slip motion along the northern and main branch of the nafz below the eastern sea of marmara

the surface rupture and slip distribution of the 17 august 1999 izmit earthquake m 7 4 north anatolian fault the 17 august 1999 izmit earthquake occurred on the northern strand of the north anatolian fault zone the earthquake is associated with a 145 km long surface rupture that extends from southwest of duzce in the east to west of hersek delta in the west detailed mapping of the surface rupture shows that it consists of five segments separated by releasing step overs herein named the hersek karamursel golcuk izmit sapanca lake sapanca akyazi and karadere segments from west to east respectively the hersek segment which cuts the tip of a large delta plain in the western end of the rupture zone has an orientation of n80 the n70 80 e trending karamursel golcuk segment extends along the linear southern coasts of the izmit gulf between karamursel and golcuk and produced the 470 cm maximum displacement in golcuk the northwest southeast striking golcuk normal fault between the karamursel golcuk and izmit sapanca segments has 2 3 m maximum vertical displacement the maximum dextral offset along the izmit sapanca lake segment was measured to be about 3 5 m and its trend varies between n80 e and east west the sapanca akyazi segment trends n75 85 w and expresses a maximum displacement of 5 2 m the karadere segment trends n65 e and produced up to 1 5 m maximum displacement the karadere and sapanca akyazi segments form fan shape or splaying ruptures near their eastern ends where the displacement also diminished

s wave attenuation in the marmara region northwestern turkey the frequency dependent attenuation of shear waves in the crust is estimated by using two different methods based on the rate of time decay of coda wave amplitude qc 1 and the rate of decay of the s wave to coda wave amplitude ratio with distance qs 1 the epicentral distances of selected earthquakes range between 20 and 110 km and magnitudes are around 3 the quality factors qc are calculated at frequencies of 1 5 3 6 12 and 24 hz and lapse times of 40 50 60 and 70 s estimated qc values show a dependence on frequency and lapse time we observed the similarity in the frequency dependency of qc 41 1 07 f1 08 0 03 and qs 50 1 7 f1 09 0 05 for a lapse time of 50 s indicating that the attenuation mechanism for coda waves is similar to that of the direct s waves

crustal anisotropy in the eastern sea of marmara region in northwestern turkey abstract the north anatolia fault zone nafz is a transform zone 1600 km in length representing the plate boundary between the westward moving anatolian plate and stable eurasia almost the entire fault zone has failed during the last century except for the sea of marmara section which is located in direct vicinity to the city of istanbul in this study we investigate the crustal anisotropy along the eastern marmara section of the nafz based on shear wave splitting we measure seismic anisotropy parameters namely the fast polarization direction pd and time delay td by analyzing local seismicity recorded at selected seismographs operated throughout the eastern sea of marmara region our shear wave splitting sws observations indicate a predominant northwest southeast oriented pd which is sub parallel to both the orientation of the regional s hmax in northwest turkey and the local nafz strike along the princes islands segment toward the south at the armutlu peninsula we find a different pd pattern reflecting local fault strikes s hmax as well as strain asymmetry between different crustal blocks across the fault zone applying strict quality criteria enables us to identify robust preferred fast pds which suggests that initially observed pd heterogeneities are sometimes caused by second order effects in the data rather than by varying pds comparing td and hypocentral depth distribution we find the depth extent of the anisotropy is confined to the uppermost 10 km depth of crust we combine our sws results with those from previous studies conducted along the san andreas fault saf and nafz in order to investigate the relation of angular deviations of the pds from regional s hmax and local fault strikes with fault zone distance we find that fast pds are mainly controlled by the local fault structure in close proximity to a fault zone 5 and 10 km while they are controlled by crustal stress at off fault locations 5 and 10 km

magmatic structural and hydrothermal evolution of the mineral mountains intrusive complex utah the mineral mountains intrusive complex records the interaction since oligocene time between magmatic structural and hydrothermal processes these processes continue to the present as exemplified by the roosevelt hot springs geothermal system which is structurally controlled and driven by a pluton emplaced during the pleistocene the intrusive rocks of the complex show changes in composition from an early calc alkaline suite oligocene to a slightly alkaline main intrusive sequence miocene that makes up most of the range at about 9 ma the intrusive activity was associated with low angle faulting the oldest volcanic rocks are dated at 7 ma volcanic activity continued in the region until 0 5 ma and may be active still examples of the youngest volcanism include a sequence of rhyolite flows domes and pyroclastic deposits that were erupted along the crest of the range between 0 8 and 0 5 ma minor basaltic flow and pyroclastic eruptions also were localized in the northern part of the range a major low angle detachment fault containing as much as 200 m of cataclasite is preserved in the southern mineral mountains this fault separates lithologies of the mineral mountains intrusive complex from an overlying paleozoic sedimentary sequence we propose that this zone developed at the brittle ductile transition and has been exposed because of the extreme uplift of the range the range also preserves a series of listric faults which may sole into a major low angle fault at depth high angle normal faults strike both north and east both sets have important controls on the flow of fluid in the roosevelt hot springs geothermal field the east west structures are presently seismically active hydrothermal activity has been associated with all intrusive events in the mineral mountains base metal mineralization accompanied the older events whereas precious metal mineralization accompanied the younger we propose an evolution of the intrusive complex involving the interaction of magmetic structural and hydrothermal components from oldest to youngest each phase of activity reflects emplacement of magma into progressively higher levels of the crust uplift reflected by this progression has been quite rapid at times as shown by fission track dating as a consequence the mineral mountains constitute a profound structural high in the region this extreme uplift probably was caused by diapiric rise of this area under the influence of repeated magmatic intrusion

bargen continuous gps data across the eastern basin and range province and implications for fault system dynamics we collected data from a transect of continuous global positioning system gps sites across the eastern basin and range province at latitude 39 n from 1997 2000 intersite velocities define a region 350 km wide of broadly distributed strain accumulation at 10 nstr yr 1 on the western margin of the region site egan 10 km north of ely nevada moved at a rate of 3 9 0 2 mm yr 1 to the west relative to site cast which is on the colorado plateau velocities of most sites to the west of ely moved at an average rate of 3 mm yr 1 relative to cast defining an area across central nevada that does not appear to be extending significantly the late quaternary geological velocity field derived using seismic reflection and neotectonic data indicates a maximum velocity of egan with respect to the colorado plateau of 4 mm yr 1 also distributed relatively evenly across the region the geodetic and late quaternary geological velocity fields therefore are consistent but strain release on the sevier desert detachment and the wasatch fault appears to have been anomalously high in the holocene previous models suggesting horizontal displacement rates in the eastern basin and range near 3 mm yr 1 which focused mainly along the wasatch zone and intermountain seismic belt may overestimate the holocene wasatch rate by at least 50 per cent and the quaternary rate by nearly an order of magnitude while ignoring potentially major seismogenic faults further to the west

infaunal burrow ventilation and pore water transport in muddy sediments the ventilation of burrows by tube dwelling benthos is understood to be important in determining rates of exchange of solutes between the sediment and overlying water however few models have attempted to link the burrow ventilation behavior of tube dwelling organisms with their geochemical consequences the classic cylinder model of bioirrigation in muddy sediments aller r c 1980 quantifying solute distributions in the bioturbated zone of marine sediments by defining an average microenvironment geochimica et cosmochimica acta 44 1955 1965 links pore water processes and burrow sizes and distributions in the sediment by assuming that burrows are fully flushed the equivalence between the cylinder model and the more commonly used one dimensional non local exchange model depends upon this assumption however this assumption has seldom been tested in the field we have extended the cylinder model of bioirrigation to include burrow ventilation activities of organisms burrow ventilation is modeled as a simple non local exchange of burrow water with overlying water model simulations indicate that burrow ventilation has a large effect on vertical profiles and fluxes of solute tracers we collected data on burrow geometry in the field by ct scanning freshly collected sediment cores at the same study sites we measured activity profiles of 222 rn a naturally occurring radionuclide tracer of pore water transport with model geometry independently constrained we tested the model by comparing our model predicted profiles with measured profiles our results demonstrate that burrows in the field are not fully flushed our estimated burrow ventilation rates compare favorably with previous laboratory measurements the inclusion of realistic burrow ventilation in this pore water transport model strongly affects modeled solute profiles and fluxes we demonstrate how model parameters can be determined from field samples and present a model that more realistically simulates pore water transport processes in muddy sediments

the use of short lived radionuclides to quantify transitional bed material transport in a regulated river we investigate the use of the short lived fallout radionuclide beryllium 7 7be t1 2 53 4 days as a tracer of medium and coarse sand 0 25 2 mm which transitions between transport in suspension and as bed load and evaluate the effects of impoundment on seasonal and spatial variations in bed sedimentation we measure 7be activities in approximately monthly samples from point bar and streambed sediments in one unregulated and one regulated stream in the regulated stream our sampling spanned an array of flow and management conditions during the annual transition from flood control in the winter and early spring to run of the river operation from late spring to autumn sediment stored behind the dam during the winter quickly became depleted in 7be activity this resulted in a pulse of dead sediment released when the dam gates were opened in the spring which could be tracked as it moved downstream measured average sediment transport velocities 30 80 metres per day m d 1 exceed those typically reported for bulk bed load transport and are remarkably constant across varied flow regimes possibly due to corresponding changes in bed sand fraction results also show that the length scale of the downstream impact of dam management on sediment transport is short c 1 km beyond this distance the sediment trapped by the dam is replaced by new sediment from tributaries and other downstream sources copyright 2006 john wiley sons ltd

seismic hazard in the marmara sea region following the 17 august 1999 izmit earthquake on 17 august 1999 a destructive magnitude 7 4 earthquake occurred 100 km east of istanbul near the city of izmit on the north anatolian fault this 1 600 km long plate boundary 1 2 slips at an average rate of 2 3 cm yr 1 refs 3 5 and historically has been the site of many devastating earthquakes 6 7 this century alone it has ruptured over 900 km of its length 6 models of earthquake induced stress change 8 combined with active fault maps 9 had been used to forecast that the epicentral area of the 1999 izmit event was indeed a likely location for the occurrence of a large earthquake 9 10 here we show that the 1999 event itself significantly modifies the stress distribution resulting from previous fault interactions 9 10 our new stress models take into account all events in the region with magnitudes greater than 6 having occurred since 1700 ref 7 as well as secular interseismic stress change constrained by gps data 11 these models provide a consistent picture of the long term spatio temporal behaviour of the north anatolian fault and indicate that two events of magnitude equal to or greater than the izmit earthquake are likely to occur within the next decades beneath the marmara sea south of istanbul

inversion of borehole weak motion records observed in istanbul turkey summary the estimation of shear wave velocity and attenuation in near surface geology is of primary importance in engineering seismology in fact such knowledge is essential for site response studies when preparing improved seismic hazard scenarios in this study we propose a linear inversion of the spectra of a deconvolved wavefield collected by a borehole array in istanbul turkey the spectra are calculated using as a reference the recordings collected by a sensor at the surface this allows us to minimize the effect of the deconvolution filter on the peaks amplitudes the feasibility of the proposed inversion scheme and the parametrization of the velocity and attenuation models were tested and assessed using synthetic data the real data inversion is carried out using observation from three weak motion events several starting models are used for each event changing the values of the quality factor qs whereas the starting vs profiles are fixed to what was obtained by the analysis of the deconvolved wavefield in the time domain our results showed that fairly well constrained vs models can be obtained while the variability of the qs profile both between different inversions of the same data set and between the inversions of different data sets might be large this indicates that qs variations observed in models derived by strong motion data inversions should be considered with care however the high agreement of the estimated soil profiles in the uppermost layer both when using different events and different starting models suggests that any variation in the s wave velocity that might be estimated when using strong motion data should be reliable

factors controlling normal fault offset in an ideal brittle layer we study the physical processes controlling the development and evolution of normal faults by analyzing numerical experiments of extension of an ideal two dimensional elastic plastic brittle layer floating on an inviscid fluid the yield stress of the layer is the sum of the layer cohesion and its frictional stress faults are initiated by a small plastic flaw in the layer we get finite fault offset when we make fault cohesion decrease with strain even in this highly idealized system we vary six physical parameters the initial cohesion of the layer the thickness of the layer the rate of cohesion reduction with plastic strain the friction coefficient the flaw size and the fault width we obtain two main types of faulting behavior 1 multiple major faults with small offset and 2 single major fault that can develop very large offset we show that only two parameters control these different types of faulting patterns 1 the brittle layer thickness for a given cohesion and 2 the rate of cohesion reduction with strain for a large brittle layer thickness 22 km with 44 mpa of cohesion extension always leads to multiple faults distributed over the width of the layer for a smaller brittle layer thickness the fault pattern is dependent on the rate of fault weakening a very slow rate of weakening leads to a very large offset fault and a fast rate of weakening leads to an asymmetric graben and eventually to a very large offset fault when the offset is very large the model produces major features of the pattern of topography and faulting seen in some metamorphic core complexes

the mechanical interaction between the propagating north anatolian fault and the back arc extension in the aegean we use fracture mechanics concepts to analyse the large scale deformation of anatolia and the aegean our purpose is to characterize the process of propagation of the north anatolian fault naf our approach incorporates long term geological constraints in dislocation modelling of present day gps velocities that allows for internal deformation in regions between major structures unravelling the superposition of two deformation fields now interacting in the aegean propagating naf and back arc extension permits us to characterise the large scale damage zone at the western end of the naf and to determine slip rates for the main structures the contemporary slip rate profile of the naf shows that it apparently behaves like a transform fault for 75 of its length the process zone corresponds to a rapid southwestward tapering of the naf slip rate modelling slip rate distributions for the naf under stress free conditions shows that the development of the process zone depends on the boundary conditions imposed at the hellenic arc our stress free modelling suggests a scenario for the evolution of the naf 1 at an earlier stage before the naf had reached the aegean it was not under the influence of hellenic arc pull its slip rate profile is modelled to have a half elliptical shape corresponding to a crack in elastic solid and an elastically strained anatolian lithosphere 2 the present day naf penetrates the aegean and a large process zone has developed due to interaction with the aegean extension and the hellenic arc pull elastic strains in the anatolian lithosphere are relaxed and the naf resembles a transform fault the models that we present suggest that changes in subduction zone behaviour should influence all of the boundaries associated with anatolian extrusion

timing of detachment faulting in the bullfrog hills and bare mountain area southwest nevada inferences from 40ar 39ar k ar u pb and fission track thermochronology crustal extension in the bullfrog hills and bare mountain area of southwest nevada is associated with movement along a regional detachment fault normal faulting in the upper plate and rapid cooling denudation of the lower plate were coeval with miocene silicic volcanism and with west northwest transport along the detachment fault a west northwest progression of tilting along upper plate normal faults is indicated by ages of the volcanic rocks in relation to angular unconformities near the breakaway tilting in the upper plate occurred between 12 7 and 11 6 ma continued less strongly past 10 7 ma and was over by 8 2 ma ten to 20 km west of the breakaway tilting occurred between 10 7 and 10 33 ma continued less strongly after 10 33 ma and was over by 8 1 ma the cooling histories of the lower plate metamorphic rocks were determined by thermochronologic dating methods k ar and ar 40 39 a on muscovite biotite and hornblende ar 40 39 a on k feldspar u pb on apatite zircon and sphene and fission track on apatite zircon and sphene lower plate rocks 10 km west of the breakaway cooled slowly from early cretaceous lower amphibolite facies conditions through 350 50 degrees to 300 50 degrees c between 57 and 38 ma then cooled rapidly from 205 50 degrees to 120 5o degrees c between 12 6 1 6 and 11 1 1 9 ma lower plate rocks 20 km west of the breakaway cooled slowly from early cretaceous upper amphibolite facies conditions through 500 50 degrees c at 78 67 ma passed through 350 50 degrees to 300 50 degrees c between 16 3 0 4 and 10 5 0 3 ma then cooled rapidly from 285 50 degrees to 120 50 degrees c between 10 2 and 8 6 ma upper plate tilting and rapid cooling denudation of the lower plate occurred simultaneously in the respective areas the early slow cooling part of the lower plate thermal histories was probably related to erosion at the earth s surface which stripped off about 9 km of material in 50 to 100 m y the results indicate an initial fault dip greater than or equal to 30 degrees and a 12 mm yr 1 west northwest migration of the locus of rapid tilting in the upper plate

submarine fault scarps in the sea of marmara pull apart north anatolian fault implications for seismic hazard in istanbul earthquake scarps associated with recent historical events have been found on the floor of the sea of marmara along the north anatolian fault naf the marmarascarps cruise using an unmanned submersible rov provides direct observations to study the fine scale morphology and geology of those scarps their distribution and geometry the observations are consistent with the diversity of fault mechanisms and the fault segmentation within the north marmara extensional step over between the strike slip ganos and izmit faults smaller strike slip segments and pull apart basins alternate within the main step over commonly combining strike slip and extension rapid sedimentation rates of 1 3 mm yr appear to compete with normal faulting components of up to 6 mm yr at the pull apart margins in spite of the fast sedimentation rates the submarine scarps are preserved and accumulate relief sets of youthful earthquake scarps extend offshore from the ganos and izmit faults on land into the sea of marmara our observations suggest that they correspond to the submarine ruptures of the 1999 izmit mw 7 4 and the 1912 ganos ms 7 4 earthquakes while the 1999 rupture ends at the immediate eastern entrance of the extensional cinarcik basin the 1912 rupture appears to have crossed the ganos restraining bend into the sea of marmara floor for 60 km with a right lateral slip of 5 m ending in the central basin step over from the gulf of saros to marmara the total 1912 rupture length is probably about 140 km not 50 km as previously thought the direct observations of submarine scarps in marmara are critical to defining barriers that have arrested past earthquakes as well as defining a possible segmentation of the contemporary state of loading incorporating the submarine scarp evidence modifies substantially our understanding of the current state of loading along the naf next to istanbul coulomb stress modeling shows a zone of maximum loading with at least 4 5 m of slip deficit encompassing the strike slip segment 70 km long between the cinarcik and central basins that segment alone would be capable of generating a large magnitude earthquake mw 7 2 other segments in marmara appear less loaded

flexural rotation of normal faults a conceptual model is proposed for the generation of low angle normal faults in metamorphic core complexes the model is based on three assumptions 1 the isostatic response to normal fault motion is of regional extent 2 when a fault segment is significantly rotated from the optimum angle of slip relative to the crustal stress field it is replaced by a new planar fault oriented in the optimum direction and 3 the fault cuts the entire upper crust and fault motion always nucleates in the same region at the base of the upper crust the stress field is considered to be uniform through the crust and the regional isostatic response of the crust to loads is computed using the thin plate flexure approximations active low angle normal faults are difficult to reconcile with rock mechanics theories earthquake focal mechanism studies and geochronologic results indicating rapid cooling of core complex rocks the model does not require active fault slip on low angle faults the flexural response to normal faulting is shown to be significantly affected by anelastic behavior of the crust and by loading due to sedimentation the anelastic response to large bending stresses results in significant reduction in the effective elastic rigidity of the upper crust this can explain the observed short wavelength of topographic response to normal fault loads the model results in 1 a nearly flat lying abandoned normal fault or detachment below slices of upper plate rocks and sedimentary infill 2 a strong contrast in metamorphic grade across the abandoned detachment 3 rapid movement of lower plate rocks from midcrustal depths to shallower depths these results are qualitatively in agreement with geologic observations for core complexes

recalculated probability of m 7 earthquakes beneath the sea of marmara turkey 1 new earthquake probability calculations are made for the sea of marmara region and the city of istanbul providing a revised forecast and an evaluation of time dependent interaction techniques calculations incorporate newly obtained bathymetric images of the north anatolian fault beneath the sea of marmara le pichon et al 2001 armijo et al 2002 newly interpreted fault segmentation enables an improved regional a d 1500 2000 earthquake catalog and interevent model which form the basis for time dependent probability estimates calculations presented here also employ detailed models of coseismic and postseismic slip associated with the 17 august 1999 m 7 4 izmit earthquake to investigate effects of stress transfer on seismic hazard probability changes caused by the 1999 shock depend on marmara sea fault stressing rates which are calculated with a new finite element model the combined 2004 2034 regional poisson probability of m 7 earthquakes is 38 the regional time dependent probability is 44 18 and incorporation of stress transfer raises it to 53 18 the most important effect of adding time dependence and stress transfer to the calculations is an increase in the 30 year probability of a m 7 earthquake affecting istanbul the 30 year poisson probability at istanbul is 21 and the addition of time dependence and stress transfer raises it to 41 14 the ranges given on probability values are sensitivities of the calculations to input parameters determined by monte carlo analysis 1000 calculations are made using parameters drawn at random from distributions sensitivities are large relative to mean probability values and enhancements caused by stress transfer reflecting a poor understanding of large earthquake aperiodicity index terms 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics 8150 tectonophysics plate boundary general 3040 keywords earthquake probability sea of marmara seismic hazard turkey stress interaction north anatolian fault

detachment and rotation of a metamorphic core complex during extensional deformation palaeomagnetic study of the catalina rincon core complex basin and range province arizona abstract the catalina rincon complex exposes a metamorphic core of mid crustal rocks exhumed by extensional tectonism along a major detachment exposed along the southeast side of the catalina rincon mountains near tucson arizona the juxtaposition of core complexes against high level crust segmented into rotated and tilted fault blocks is an important component to models for crustal extension and key questions surround the way s that cores are exhumed we report palaeomagnetic results from rocks beneath the detachment in the catalina rincon core and additional data from lavas and tuffs in adjoining hanging wall rocks immediately above the detachment magnetic remanence in the metamorphic core is carried predominantly by magnetite with a dominant wnw ese dual polarity direction a1 d i 288 50 n 59 components r 55 60 95 4 6 this remanence is interpreted to have been acquired through a broadened blocking temperature spectrum during protracted exhumation and cooling in oligocene times since the magnetic inclination accords with the mid cenozoic field it is difficult to explain this magnetization in terms of large later tilting and it appears to be the record of near vertical axis ccw rotation of 63 5 relative to cratonic north america although magnetic inclination identifies no significant horizontal axis rotation this could be fortuitous and hide the influence of magnetic anisotropy and resultant inclination shallowing to assess this contribution both anisotropy of magnetic remanence amr and anisotropy of magnetic susceptibility ams have been investigated ams resolves only weak fabrics comparable with the top ne mylonite deformational fabric near the detachment which probably dates from a mid eocene high temperature event amr shows that deflections of magnetic remanence of up to several tens of degrees into the foliation may be anticipated although weak alignment of the magnetite is likely to reduce this effect the full importance of horizontal axis tilting remains unresolved although a possible relict component in the core a2 d i 269 9 n 24 components r 22 91 95 6 6 is rotated 20 more ccw than a1 and also of presumed mid cenozoic cooling related origin it suggests that segments of middle crust comprising the exposed core might have been rotated by large amounts into their present position highly faulted early oligocene pantano formation volcanic rocks in the hanging wall immediately above the detachment zone appear to have rotated by a much smaller amount ccw on the south west side d i 161 45 6 sites and by larger variable amounts on the northeast side movements of the upper plate immediately above the detachment are difficult to resolve with precision due to complex fault block rotations although the underlying core complex has clearly undergone large differential slip relative to these cover rocks the magnitude of inferred vertical axis rotation of the catalina rincon core implies that it is not rooted into adjoining crust as proposed in classical simple shear models instead the core exposed below the detachment may be part of a fault carapace that has decoupled and rotated over a ductile lower crust

the atakoy vertical array turkey insights into seismic wave propagation in the shallow most crustal layers by waveform deconvolution summary a vertical array of accelerometers was installed in atak oy western istanbul with the longterm aim of improving our understanding of in situ soil behaviour to assess the modelling and parametric uncertainties associated with the employed methodologies for strong motion site response analysis and for shallow geological investigations geotechnical and geophysical investigations were carried out to define the subsoil structure at the selected site data associated with 10 earthquakes 2 7 m 4 3 collected during the first months of operation of the array were used to image the upgoing and downgoing waves by deconvolution of waveforms recorded at different depths results have shown that the velocity of propagation of the imaged upgoing and downgoing waves in the borehole is consistent with that of s or p waves depending on the component of ground acceleration analysed but independent of the chosen signal window in particular an excellent agreement was found between the observed upgoing and downgoing wave traveltimes and the ones calculated using a model derived by seismic noise analysis of array data the presence of a smaller pulse on the waveforms obtained by deconvolution of the horizontal components suggests both internal s wave reflection and s to p mode conversion as well as a not normal incidence of the wavefield the presence of a pulse propagating with s wave velocity in the uppermost 25 m in the waveforms obtained by the deconvolution of the vertical components suggests p to s mode conversion these evidences imply that even when site amplification is mainly related to 1 d effects the standard practice in engineering seismology of deconvolving the surface recording down to the bedrock using an approximate s wave transfer function generally valid for vertical incidence of sh waves might lead to errors in the estimation of the input ground motion required in engineering calculations finally downgoing waves with significant amplitudes were found down to 70 m and even to 140 m depth this result provides a warning about the use of shallow borehole recordings as input for the numerical simulation of ground motion and for the derivation of ground motion prediction relationships

field tests of rolling hinges existence mechanical types and implications for extensional tectonics in rolling hinge models a locus of isostatic footwall uplift migrates together with the withdrawing hanging wall of a large displacement tens of kilometers normal fault a fault bend fold that migrates through the footwall results causing progressive deactivation of the updip part of the fault as it is tilted to a lower dip rolling hinge migration should leave a discernible geologic record but compelling tests are difficult to design because predictions of rolling hinge models are nonunique and alternative models commonly can explain individual data sets field tests based on thermochronology paleomagnetism and structural analysis are typically applied to footwall rocks whereas sedimentology geochronology of volcanic rocks and structural analysis are typically applied to upper plate rocks we review existing theoretical models and case studies in 14 detachment terranes some negative results are reasonably compelling but positive tests as yet tend to permit rather than demand a rolling hinge locally both positive and negative conclusions have been reached about the passage of a hinge within the same terrane such differences in interpretation may depend more on the scale of observation or on the specific model considered than on the geological development of the area subvertical simple shear and flexural failure mechanisms with or without significant induced flow of lower crustal material are thought to dominate hinge related footwall deformation in individual sites although rolling hinge models offer an alternative to low initial fault dips hinge related deformation does not demand a steep initial fault dip few areas in which rolling hinge tectonics are permissible had initially steep faults 35 rather where the evidence most strongly favors a rolling hinge detachment faults had initial dips 35 in the future conclusive results are most likely to be obtained if diverse tests are applied to both the upper and lower plates of detachment terranes where other geological sources of ambiguity are minimal at best the rolling hinge mechanism does not universally explain the observation that earthquakes are rare on low angle normal faults nor solve the mechanical problems of frictional slip on such faults

plutonism and the origin of metamorphic core complexes the formation of metamorphic core complexes may be triggered by plutonic activity during episodes of continental extension pulses of ductile deformation have taken place during short lived thermal events initiated by the heat input from intruded plutons sills or dikes such intrusions may be the underlying cause for differential uplift of the footwall during tectonic denudation of metamorphic core complexes fast cooling inferred from 40 ar 39 ar apparent ages may have taken place after periods of magma arrival and need not be the result of rapid erosional or tectonic denudation heterogeneity of 40 ar 39 ar apparent ages can be explained by rapid cooling of deforming mylonites formed at shallow crustal levels in the thermal aureoles of intruded sills or sill swarms under such circumstances apparently isothermal decompression paths may actually link pressure temperature points set during periods of transient mineral growth during and after periods of igneous activity

spatiotemporal earthquake clusters along the north anatolian fault zone offshore istanbul we investigate earthquakes with similar waveforms in order to characterize spatiotemporal microseismicity clusters within the north anatolian fault zone nafz in northwest turkey along the transition between the 1999 izmit rupture zone and the marmara sea seismic gap earthquakes within distinct activity clusters are relocated with cross correlation derived relative travel times using the double difference method the spatiotemporal distribution of microearthquakes within individual clusters is resolved with relative location accuracy comparable to or better than the source size high precision relative hypocenters define the geometry of individual fault patches permitting a better understanding of fault kinematics and their role in local scale seismotectonics along the region of interest temporal seismic sequences observed in the eastern sea of marmara region suggest progressive failure of mostly nonoverlapping areas on adjacent fault patches and systematic migration of microearthquakes within clusters during the progressive failure of neighboring fault patches the temporal distributions of magnitudes as well as the number of events follow swarmlike behavior rather than a mainshock aftershock pattern

an advection diffusion model for222rn transport in near shore sediments inhabited by sedentary polychaetes abstract a porewater solute transport model is proposed to explain the dissolved radon distributions in four profiles from a near shore marine site the macro infauna at the site is dominated by clymenella torquata a sedentary deposit feeding polychaete that actively irrigates its burrow the model includes both an advective component that takes into account the e g c torquata mechanism of burrow irrigation as well as enhanced diffusion like transport brought about by mobile infauna because it explains the existence of subsurface radon minima with a constant source function and is based on the known irrigations habits of c torquata the model provides good fit to observed radon profiles and may be applicable to other solutes that display depth dependent minima sediment advection velocities individual burrow irrigation rates and enhanced diffusion coefficients are estimated based on a minimization of chi squared for model fits to the 222 rn data of each profile the net advection velocity ranged from 0 19 to 0 91 cm d 1 and enhanced diffusion ranged from 13 to 30 times effective molecular diffusion these values are comparable to those determined by previous investigators using other transport models in similar sediments the range of burrow irrigation rates 0 16 0 78 ml h individual is somewhat lower than the average rate for c torquata that had been determined in the laboratory

structural evolution of the 40 km wide araguainha impact structure central brazil the 40 km wide araguainha structure in central brazil is a shallowly eroded impact crater that presents unique insights into the final stages of complex crater formation the dominant structural features preserved at araguainha relate directly to the centripetal movement of the target rocks during the collapse of the transient cavity slumping of the transient cavity walls resulted in inward verging inclined folds and a km scale anticline in the outer ring of the structure the folding stage was followed by radial and concentric faulting with downward displacement of kilometer scale blocks around the crater rim the central uplift records evidence for km scale upward movement of crystalline basement rocks from the transient cavity floor and lateral moment of sedimentary target rocks detached from the cavity walls much of the structural grain in the central uplift relates to structural stacking of km scale thrust sheets of sedimentary strata onto the core of crystalline basement rocks outward plunging radial folds indicate tangential oblate shortening of the strata during the imbrication of the thrust sheets each individual sheet records an early stage of folding and thickening due to non coaxial strains shortly before sheet imbrication we attribute this folding and thickening phase to the kilometer scale inward movement of the target strata from the transient cavity walls to the central uplift the outer parts of the central uplift record additional outward movement of the target rocks possibly related to the collapse of the central uplift an inner ring structure at 10 12 km from the crater center marks the extent of the deformation related to the outward movement of the target rocks

source parameters of small earthquakes recorded at 2 5 km depth cajon pass southern california implications for earthquake scaling a 2 5 km deep triaxial seismometer at cajon pass in southern california has recorded several hundred earthquakes ml4 0 occurring within the san andreas fault system at 2 5 km seismic background noise is below amplifier sensitivity and the 2 250 hz spectral range of recorded seismic motion is wider and higher than that of most natural event catalogs compared with downhole recorded motion seismic amplitudes at the surface are amplified below 10 hz and severely attenuated above 30 hz we estimate that qs is at least 1000 for wave motion at 2 5 km and below and qp is over 2000 the range of source dimensions in the downhole recorded catalog is 10 m to 70 m ml 2 0 mo 108 nm to ml 2 7 mo 1013 nm the plot of log source radius vs log moment has a straight line trend compatible with earthquake scaling at constant stress drop inferred stress drops are scattered between 1 and 500 bars there is no evidence in the catalog for the proposed minimum source dimension at 100 m when the cajon pass borehole catalog containing some of the smallest recorded natural earthquakes is combined with 800 larger events from previous studies the moment radius trend suggests that natural earthquakes are self similar over a magnitude range m 2 to 8 we suggest that inferences of minimum source dimension are more likely due to bias in bandlimited individual catalogs than to properties of the seismic crust

miocene unroofing of the canyon range during extension along the sevier desert detachment west central utah this is the published version copyright 2001 american geophysical union all rights reserved

cenozoic and mesozoic structure of the eastern basin and range province utah from cocorp seismic reflection data cocorp seismic reflection data collected from the eastern basin and range in west central utah provide information on cenozoic extensional tectonics mesozoic thrusting and their interrelationships those data show a series of remarkably continuous low angle reflectors that extend more than 120 km perpendicular to strike and can be traced as deep as 15 20 km over that distance none of these events are significantly cut by any high angle normal faults a major detachment beneath the sevier desert can be traced from a surface zone of normal faulting to a depth of 12 15 km with a regional apparent westward dip of 12 tentative correlation of upper and lower plate events suggests 30 60 km of extensional displacement on this detachment whether this structure is a reactivated mesozoic thrust is uncertain west steepening splays off the end of the detachment reach depths of 20 km and may represent a major mesozoic ramp or zones of distributed ductile shearing during extension some events are interpreted to be mesozoic thrusts of which at least one beneath the house range has been reactivated during the cenozoic the snake range decollement dips gently east and has a sense of cenozoic displacement opposite to that of other cenozoic detachments farther east deep events are most numerous beneath the east side of the sevier desert where they occur to depths of 30 km at the top of or perhaps partly within the anomalously low velocity upper mantle

mode i microfracturing and fluid flow in damage zones the key to distinguishing faults from slides abstract we have examined the distribution of microfractures in arenites and the evolution of vein forming fluids in the matrix of carbonate breccias within the damage zones of large detached blocks in order to characterize their modes of emplacement previous studies of microfractures in the damage zone associated with tectonic faulting have shown a clear pattern of increasing density as the fault is approached previous studies of carbonate breccia within damage zones of tectonic faults typically document evidence of multiple fluid events representing repeated rupture healing processes however in this study we find no change in the microfracture density with distance from the 45 km displaced gravity driven slide block at heart mountain wyoming in a previous study of the same massive slide block there was no evidence of multiple fluid infiltration events related to emplacement we interpret these observations as indicating the absence of rupture cycling that would be expected in the development of a process zone instead being consistent with catastrophic emplacement of gravity driven slide blocks we use this distinct pattern of microfracture density and fluid infiltration to demonstrate that several large 1 km2 detached blocks in the basin and range previously thought to be allochthons related to hyperextension detachment faults are actually slide blocks whose detachment surfaces represent no crustal extension

broad band power law spectra of well log data in japan summary for the purpose of revealing the statistical characteristics of p wave velocity s wave velocity and density in the uppermost part of the crust we analysed well log data obtained from five deep wells in different tectonic regions in japan three wells through the mainly sedimentary rocks in the kanto plain and two wells in the kuju volcano group in kyushu island in the kanto plain the power spectral density of fractional fluctuation of p wave velocity and that of density are proportional to a power of the spatial wavelength from a few metres to 100 m where the power index slope of the power spectral density at double logarithmic scale is 1 1 1 3 at the kuju volcano group that of p and s wave velocity and density also obey a power law with a power index of 1 3 1 6 for wavelengths from a few metres to few hundred metres correcting the effect of the moving box car observation window which corresponds to the separation of two receivers of the logging tool we find that the power law characteristics hold for wavelengths down to a few tens of centimetres the 1 d sections of the elastic inhomogeneities follow a kind of band limited self affine random process comparing the power spectral densities we find smaller values of the power index in stable areas and larger values in tectonically active areas the difference in the power index arises from long wavelength components

downhole geophysical observatories best installation practices and a case history from turkey downhole sensors of different types and in various environments provide substantial benefit to signal quality they also add the depth dimension to measurements performed at the earths surface sensor types that particularly benefit from downhole installation due to the absence of near surface noise include piezometers seismometers strainmeters thermometers and tiltmeters likewise geochemical and environmental measurements in a borehole help eliminate near surface weathering and cultural effects installations from a few hundred meter deep to a few kilometer deep dramatically reduce surface noise levels the latter noticeably also reduces the hypocentral distance for shallow microearthquakes the laying out of a borehole network is always a compromise of local boundary conditions and the involved drilling costs the installation depth and procedure for a long term downhole observatory can range from time limited installations with a retrieval option to permanently cemented sensors permanently cemented sensors have proven to be long term stable with non deteriorating coupling and borehole integrity however each type needs to be carefully selected and planned according to the research aims a convenient case study is provided by a new installation of downhole seismometers along the shoreline of the eastern marmara sea in turkey these stations are being integrated into the regional net for monitoring the north anatolian fault zone here we discuss its design installation and first results we conclude that despite the logistical challenges and installation costs the superior quality of downhole data puts this technique at the forefront of applied and fundamental research

determination of shallow shear wave attenuation in the mississippi embayment using vertical seismic profiling data abstract we used vertical seismic profiling vsp data collected in four shallow boreholes about 40 to 60 m deep to study the shear wave attenuation in the mississippi embayment in southwestern tennessee the source was an air powered hammer that produces repeatable sh waves that were recorded by monitor geophones deployed on the surface very close to the source the spectral ratio method was used to estimate the shear wave quality factor q s the method assumes that the amplitudes of the seismic waves decay exponentially in the frequency domain the spectral ratio was computed using a vsp trace at a certain depth and the corresponding monitor trace using the source monitor trace as reference eliminates possible artifacts that may be introduced by changes in the source ground coupling the slope of a least square line fitted to the logarithm of the spectral ratio versus frequency gives the attenuation coefficient z for that depth then a straight line is fitted to z as a function of z and the slope of this line is used to estimate an average value of q s for the four sites shelby farms covington brownsville and jackson the q s values are 25 3 2 6 18 6 3 4 18 4 7 6 and 16 4 2 6 respectively to assess the reliability of these results synthetic vsp data were generated from the first cycles of the monitor traces recorded in the four sites and these q s values except for brownsville good matches with correlation coefficients equal to 96 99 were obtained between the synthetic vsps and the actual vsps indicating that the q s values we obtained are reliable in addition these values are also consistent with recent results obtained by others using seismic data generated by small earthquakes recorded by the japanese strong motion network kiban kyoshin kik net

seismic wave propagation in shallow layers at the gonaf tuzla site istanbul turkey using the first dataset available from the downhole geophysical observatory of the north anatolian fault we investigated near surface seismic wave propagation on the tuzla peninsula istanbul turkey we selected a dataset of 26 seismograms recorded at tuzla at sensor depths of 0 71 144 215 and 288 m to determine near surface velocities and attenuation structures the waveforms from all sensors were pairwise deconvolved and stacked this produced low noise empirical green s functions for each borehole depth interval from the green s functions we identified reflections from the free surface and a low velocity layer between 90 and 140 m depth the presence of a low velocity zone was also confirmed by a sonic log run in the borehole this structure plus high near surface p and s wave velocities of 3600 4100 and 1800 m s lead to complex interference effects between upgoing and downgoing waves as a result the determination of quality factors q with standard spectral ratio techniques was not possible instead we forward modeled the green s functions in the time domain to determine effective q values and to refine our velocity estimates the effective q p values for the depth intervals of 0 71 0 144 0 215 and 0 288 m were found to be 19 35 39 and 42 respectively for the s waves we obtained an effective q s of 20 in the depth interval of 0 288 m considering the assumptions made in our modeling approach it is evident that these effective quality factors are biased by impedance contrasts between our observation points our results show that even after correcting for a free surface factor of 2 the motion at the surface was found to be 1 7 times greater than that at 71 m depth our efforts also illustrate some of the difficulties of dealing with site effects in a strongly heterogeneous subsurface online material plots of resistivity and caliper logs and the spectra of all 26 events

rupture processes of the 1999 august 17 izmit and november 12 duzce turkey earthquakes summary we derive the rupture history of the 1999 august 17 izmit mw 7 4 and 1999 november 12 duzce mw 7 1 earthquakes in turkey from teleseismic body waves using broad band data of the global seismograph network aftershock locations and mapped surface breaks the centroid solutions indicate strike slip mechanisms for both events the izmit earthquake was characterized by rupture propagating predominantly eastwards it consisted of a main rupture lasting about 25 s followed within 1 min by two more events of mw 6 9 and mw 7 0 with the teleseismic data we could not resolve the westward extent of rupture into the marmara sea however an upper bound of the seismic moment release west of the epicentre of the izmit event is estimated to be 1 9 1019 n m the duzce earthquake lasted about 14 s and was characterized by a bilateral mode of rupture in excellent agreement with mapped surface breaks and aftershock locations

estimating near surface shear wave velocities in japan by applying seismic interferometry to kik net data 1 we estimate shear wave velocities in the shallow subsurface throughout japan by applying seismic interferometry to the data recorded with kik net a strong motion network in japan each kik net station has two receivers one receiver on the surface and the other in a borehole by using seismic interferometry we extract the shear wave that propagates between these two receivers applying this method to earthquake recorded data at all kik net stations from 2000 to 2010 and measuring the arrival time of these shear waves we analyze monthly and annual averages of the near surface shear wave velocity all over japan shear wave velocities estimated by seismic interferometry agree well with the velocities obtained from logging data the estimated shear wave velocities of each year are stable for the niigata region we observe a velocity reduction caused by major earthquakes for stations on soft rock the measured shear wave velocity varies with the seasons and we show negative correlation between the shear wave velocities and precipitation we also analyze shear wave splitting by rotating the horizontal components of the surface sensors and borehole sensors and measuring the dependence on the shear wave polarization this allows us to estimate the polarization with the fast shear wave velocity throughout japan for the data recorded at the stations built on hard rock sites the fast shear wave polarization directions correlate with the direction of the plate motion

characterization of aftershock fault plane orientations of the 1999 izmit turkey earthquake using high resolution aftershock locations 1 joint inversion for hypocentral parameters and the velocity field is nowadays a state of the art tool to obtain high resolution images of seismically active regions in this study we focus on the location accuracy of aftershocks of the 1999 mw 7 4 izmit nw turkey earthquake we obtained a new velocity model for the region and depicted its improvement on absolute locations in terms of uncertainty and misfit two well developed aftershock clusters located in the akyazi area and karadere duzce region were analyzed in detail based on a waveform cross correlation approach that allowed improving the location accuracy by a factor of 6 relocation results reveal that hypocenters form narrow planes of activity that can be correlated with focal mechanisms of the larger aftershocks as well as nearby clouds of activity with no internal structure down to the resolved scale of 300 m

kinetically limited isotope exchange in a shallow level normal fault mineral mountains utah we have conducted a stable isotope and geochemical study of the corral canyon fault zone a shallow level low angle normal fault on the west flank of the mineral mountains in southwest utah our stable isotope and geochemical data document the infiltration of local meteoric water during brittle deformation and hydrothermal alteration of the shear zone during tertiary basin and range extensional faulting within the fault zone 18o depletion correlates with progressive hydrothermal alteration and cataclasis demonstrating that the processes of fluid infiltration hydrothermal alteration fracturing comminution of grains and 18o exchange took place concurrently interpretation of our data using a model of combined fluid flow and kinetically limited isotope exchange leads us to conclude that the exposed fault zone was infiltrated by isotopically unevolved fluids from the wall rock adjacent to the fault zone and that an important component of fluid flow in this fault was between the wall rock and the fault zone rather than strictly within the fault plane we propose that the rate of isotopic alteration in shallow level fault zones is enhanced by comminution and recrystallization of grains during deformation so that fluids in the wall rock because of the relatively coarser grain size remain relatively unevolved until they infiltrate the fault zone where they rapidly become isotopically evolved due to exchange with cataclasized grains we present a general model for calculating the duration of isotopic alteration in flow systems characterized by kinetically limited isotope exchange calculated exchange durations for the corral canyon fault zone are short on the order of thousands to a few hundreds of thousands of years compared to the likely duration of deformation of millions of years the geologically short duration of isotope exchange leads us to suggest that the fluid flow responsible for the isotopic alteration was episodic of short duration and possibly related to discrete seismic events this result corroborates diverse lines of evidence that support a model of alternating fluid flow and permeability sealing by hydrothermal precipitation within fault zones

particle mixing rates in deep sea sediments determined from excess 210pb and 32si profiles particle mixing rates have been determined for 5 south atlantic antarctic and 3 equatorial pacific deep sea cores using excess 210 pb and 32 si measurements radionuclide profiles from these siliceous calcareous and clay rich sediments have been evaluated using a steady state vertical advection diffusion model in antarctic siliceous sediments 210 pb mixing coefficients 0 04 0 16 cm 2 y are in reasonable agreement with the 32 si mixing coefficient 0 2 or 0 4 cm 2 y depending on 32 si half life in an equatorial pacific sediment core however the 210 pb mixing coefficient 0 22 cm 2 y is 3 7 times greater than the 32 si mixing coefficient 0 03 or 0 07 cm 2 y the difference in 210 pb and 32 si mixing rates in the pacific sediments results from 1 non steady state mixing and differences in characteristic time and depth scales of the two radionuclides 2 preferential mixing of fine grained clay particles containing most of the 210 pb activity relative to coarser particles large radiolaria containing the 32 si activity or 3 the supply of 222 rn from the bottom of manganese nodules which increases the measured excess 210 pb activity relative to 226 ra at depth and artificially increases the 210 pb mixing coefficient based on 32 si data and pore water silica profiles dissolution of biogenic silica in the sediment column appears to have a minor effect on the 32 si profile in the mixed layer deep sea particle mixing rates reported in this study and the literature do not correlate with sediment type sediment accumulation rate or surface productivity based on differences in mixing rate among three antarctic cores collected within 50 km of each other local variability in the intensity of deep sea mixing appears to be as important as regional differences in sediment properties

unusual features of the distribution of radon 222 in the bottom waters of the continental slope of the mid atlantic bight hydrodynamic implications abstract 222rn was measured in the near bottom waters of the continental slope of the mid atlantic bight separate measurements of the 222rn supported by dissolved 226ra allowed the excess 222rn that is derived from the underlying sediments to be distinguished measurements of production of 222rn by the sediments were used to calculate fluxes of 222rn from sediments that would be expected as a result of molecular diffusion on the upper slope and on the lower slope excess 222rn standing crops were respectively greater than and consistent with fluxes of radon from sediments by molecular diffusion as are typical of most ocean environments on the middle slope however observed excess 222rn concentrations and standing crops were significantly lower than what would be expected from the calculated fluxes from the underlying sediments this unusual feature of low radon concentrations on the middle slope is referred to as the low radon zone lrz this lrz was always present over several years and seasons but was variable in intensity excess radon concentration and standing crop and in location on the slope low concentrations of suspended particulate matter and low current velocities observed by others in the same region are consistent with low mixing as a possible cause of the lrz radon profile shapes and recent work by others on near bottom mixing due to interactions between topography and internal waves however suggest that high mixing due to internal waves is a more likely cause of the lrz

comparison of empirical and numerical site responses at the tito test site southern italy the town of potenza southern italy is one of the test sites for preparing ground motion scenarios within the framework of the italian dipartimento protezione civile instituto nazionale di geofisica e vulcanologia dpc ingv 2004 2006 pro jects an area in the neighboring village of tito was selected to evaluate different techniques for estimating site effects involving a 40 m deep instrumented borehole this two sensor vertical array records teleseismic regional and local seismicity close to the borehole three seismological microarrays utilizing short period sen sors and digitizers with a high dynamic range were installed in may 2005 to record seismic noise differing acquisition geometries allowed the checking of any depen dency in the derived dispersion curves based on the adopted analysis method ex tended spatial autocorrelation esac and frequency wave number f k in gen eral the esac method appears to provide more reliable results in the low frequency range furthermore the soil velocity profiles obtained from the microarray data were compared with the s wave velocity profile derived from down hole measurements a good agreement was observed in the depth range well constrained by the data finally empirical site responses were compared with those calculated numerically from the s wave velocity profiles obtained from the microarray data although this comparison did not resolve a preference among the derived models it showed the importance of downgoing waves in modifying the site response at the tito site

interferometry by deconvolution part 2 theory for elastic waves and application to drill bit seismic imaging deconvolution interferometry successfully recovers the impulse response between two receivers without the need for an independent estimate of the source function here we extend the method of interferometry by deconvolution to multicomponent data in elastic media as in the acoustic case elastic deconvolution interferometry retrieves only causal scattered waves that propagate between two receivers as if one acts as a pseudosource of the point force type interferometry by deconvolution in elastic media also generates artifacts because of a clamped point boundary condition imposed by the deconvolution process in seismic while drilling swd practice the goal is to determine the subsurface impulse response from drill bit noise records most swd technologies rely on pilot sensors and or models to predict the drill bit source function whose imprint is then removed from the data interferometry by deconvolution is of most use to swd applications in which pilot records are absent or provide unreliable estimates of bit excitation with a numerical swd subsalt example we show that deconvolution interferometry provides an image of the subsurface that cannot be obtained by correlations without an estimate of the source autocorrelation finally we test the use of deconvolution interferometry in processing swd field data acquired at the san andreas fault observatory at depth safod because no pilot records were available for these data deconvolution outperforms correlation in obtaining an interferometric image of the san andreas fault zone at depth

modes of tilting during extensional core complex development crustal extension and formation of the mineral mountains core complex utah involved tilting of the mineral mountains batholith and associated faults during hanging wall and footwall deformation the batholith was folded in the hanging wall of the beaver valley fault between 11 and 9 million years ago yielding about 45 of tilt subsequently the batholith was unroofed along the cave canyon detachment fault and the batholith and fault were tilted approximately 40 during footwall uplift recognition of deformed dikes beneath the detachment fault establishes the importance of footwall tilt during formation of extensional core complexes and demonstrates that footwall rebound can be an important process during extension

significant groundwater input to a coastal plain estuary assessment from excess radon a submarine groundwater discharge zone was identified through the investigation of persistent excess radon in the delaware river and bay estuary this zone the excess radon maximum erm was located approximately 82 km upstream from the mouth of the delaware bay water column radon activity at the erm was elevated relative to the radon activity observed outside of this zone and was as high as 2 73 dpm l 1 a radon budget model developed to assess the contribution of multiple radon sources to the erm indicated that simple molecular diffusion from sediments could not support the observed excess radon activity an additional source of radon is required to sustain the excess radon activity in the erm a groundwater flux of 14 to 29 m 3 s 1 from the two aquifers that subcrop on the delmarva peninsula immediately west of the erm can support the excess radon observed in the water column the stratigraphy and hydrology of these aquifers makes them likely sources of the groundwater discharge that results in the erm the calculated submarine groundwater discharge flux is equivalent to the surface water discharge of the second and third largest tributary rivers of the delaware estuary 2003 elsevier science b v all rights reserved

stress and structure induced shear wave anisotropy along the 1999 izmit rupture northwest turkey abstract we perform a shear wave splitting analysis using seismograms of aftershocks following the 1999 m w 7 4 izmit earthquake to delineate between stress and structure controlled anisotropic mechanisms in the upper crust beneath the northwest north anatolian fault zone nafz the splitting analysis is performed on direct shear wave arrivals using a cross correlation technique to calculate the fast shear wave polarization and the delay time between fast and slow shear wave arrivals five stations located both within 1 km the nafz yield a combined 333 quality shear wave splitting measurements the shear wave splitting measurements indicate that it is occasionally possible to delineate between the two anisotropic mechanisms stations greater than 1 km from the nafz tend to have dominant fast shear wave polarizations parallel or subparallel to the regional strike of the maximum horizontal compressive stress which suggests a stress controlled anisotropic mechanism the single station within 1 km of the nafz yields a bimodal dominant fast shear wave polarization that is both parallel and perpendicular to the strike of the nearby mudurnu fault we interpret the fault parallel mode as representing a structure controlled anisotropic mechanism from the mudurnu fault the average delay time for all earthquakes is 0 038 0 031 s and anisotropic intervals do not appear to extend below 8 km the fast shear wave polarizations and delay times suggest a heterogeneous anisotropic distribution within the recording array and that the physical properties of the upper crust vary between the nafz and surrounding area

palaeomagnetic evidence for large magnitude low angle normal faulting in a metamorphic core complex controversy exists over whether large magnitude extensional deformation can occur along low angle master detachment normal faults1 16 large amounts of cenozoic extension occurred in the basin and range province of the western united states and master detachment faults related to this extension are currently exposed as subhorizontal structures along crustal arches known as metamorphic core complexes mccs 10 11 17 one set of models suggests that mccs represent crustal scale blocks bounded by originally high angle normal faults which have tilted to sub horizontal attitudes1 6 more dynamic models propose isostatically induced flexural tilting of an initial subhorizontal fault to an active high angle fault to final abandonment as a subhorizontal structure7 9 these models require mcc detachment faults and their footwalls to have been tilted by 30 60 alternatively mcc detachment faults may have originated as subhorizontal or low angle structures10 16 here we test these models with palaeomag netic data from undeformed portions of the south mountains a typical cenozoic mcc in the southern basin and range province18 24 comparison with time averaged expected directions of the geomagnetic field25 27 yields no evidence for tilting of the footwall we conclude that the south mountains master detachment fault was active as a low angle extensional structure with a dip of 10

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

the determination of the seismic quality factor q from vsp data a comparison of different computational methods1 ten methods for the computation of attenuation have been investigated namely amplitude decay analytical signal wavelet modelling phase modelling frequency modelling rise time pulse amplitude matching technique spectral modelling and spectral ratio in particular we have studied the reliability of each of these methods in estimating correct values of q using three synthetic vsp seismograms for plane p waves with different noise contents the investigations proved that no single method is generally superior rather some methods are more suitable than others in specific situations depending on recording noise or geology the analytical signal method has been demonstrated to be superior if true amplitude recordings are available otherwise spectral modelling or in the noise free case the spectral ratio method is optimal finally two field vsps in sediments are investigated only in the case of the highest quality vsp can significant information be deduced from the computed attenuation

istanbul s earthquake hot spots geodetic constraints on strain accumulation along faults in the marmara seismic gap during the past century a series of predominantly westward migrating m 7 earthquakes broke an 1000 km section of the north anatolian fault naf the only major remaining seismic gap along the fault is under the sea of marmara main marmara fault mmf we use 20 years of gps observations to estimate strain accumulation on fault segments in the marmara sea seismic gap we report the first direct observations of strain accumulation on the princes islands segment of the mmf constraining the slip deficit rate to 10 15 mm yr in contrast the central segment of the mmf that was thought to be the most likely location for the anticipated gap filling earthquakes shows no evidence of strain accumulation suggesting that fault motion is accommodated by fault creep we conclude that the princes islands segment is most likely to generate the next m 7 earthquake along the sea of marmara segment of the naf

determination of shallow s wave attenuation by down hole waveform deconvolution a case study in istanbul turkey summary the estimation of shear wave velocity and attenuation in near surface geology is of primary importance in engineering seismology in fact their knowledge is essential for site response studies when preparing improved seismic hazard scenarios in this study we propose two approaches for estimating the average shear wave quality factor qs by using recordings of a vertical array of accelerometers the methods are mainly based on the deconvolution of the wavefield recorded in a borehole with that recorded at the surface the first method requires the fourier transform of the deconvolved wavefield to be fitted with a theoretical transfer function valid for the vertical or nearly vertical in the case at hand up to 30 incidence angle propagation of s waves the second method is based on the spectral fitting of the fourier transform of only the acausal part of the deconvolved wavefield with a theoretical transfer function both methods can be applied without any prior knowledge of the subsoil structure since they are based on empirical data analysis and do not require a precise knowledge of the azimuthal orientation of the sensors in the boreholes which is seldom available first we describe the theoretical framework of the proposed methodologies for qs estimation which are based on the assumption that the structure in the borehole is weakly heterogeneous in the vertical direction i e no large impedance contrast exists between the borehole sensor and the surface second by using synthetic accelerograms we verify that in a realistic subsoil structure the assumption of vertical homogeneity can hold and we investigate the robustness and the suitability of the proposed methods finally only the method that was shown to provide the more stable results based on fitting the borehole to surface spectral ratio with a theoretical function is applied to earthquakes signals recorded by a vertical array of accelerometers installed in atak oy western istanbul results show that using borehole data provides a fair and robust estimate of an average qs of about 30 46 and 99 for the 0 50 0 70 0 140 m depth ranges respectively that can be used for numerical simulations of ground motion