ultrasonic velocity and attenuation during co2 injection into water saturated porous sandstone measurements using difference seismic tomography we undertook laboratory based seismic measurements with dense sensor array at ultrasonic frequencies during the injection of co2 into a water saturated sandstone specimen the resulting high quality seismic data enabled detailed determination of the relative velocity and attenuation coefficient of the compressional wave using difference seismic tomography which directly inverses time lapse changes in rock properties from time lapse changes in observed data co2 migration and water displacement were clearly mapped using tomographic images of relative velocity and the attenuation coefficient the final and largely stabilised volume fraction of co2 in the pore space of the sample is about 30 40 on average the p velocity fell by 7 5 12 and 14 5 and the attenuation coefficient q 1 increased by factors of 3 3 2 7 and 3 7 as a result of the replacement of water with co2 during the injection of gaseous liquid and supercritical co2 respectively as a function of gas saturation both the velocity and attenuation data are in good agreement with results obtained using the white and dutta ode model for partial saturation indicating that viscous losses due to fluid diffusion are of significant importance for compressional waves travelling at ultrasonic frequencies in porous rocks

wave attenuation in partially saturated porous rocks new observations and interpretations across scales abstract seismic waves propagating in porous rocks saturated with two immiscible fluids can be strongly attenuated predicting saturation effects on seismic responses requires a sound understanding of attenuation and velocity dependencies on the fluid distribution decoding these effects involves interpreting laboratory experiments analyzing well log data and performing numerical simulations despite striking differences among scales flow regimes and frequency bands some aspects of wave attenuation can be explained with a single mechanism wave induced pressure diffusion different facets of wave induced pressure diffusion can be revealed across scales

global positioning system measurements of present day crustal movements in the arabia africa eurasia plate collision zone we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1994 at 54 sites extending east west from the caucasus mountains of southern russia georgia and armenia to the aegean coast of turkey and north south from the southern edge of the eurasian plate pontus block to the northern edge of the arabian platform viewed from a eurasia fixed reference frame sites on the northern arabian platform move n38 13 w at 20 3 mm yr roughly consistent with the velocity implied by nuvel 1a circuit closure n23 7 w at 24 2 mm yr the motion of arabia appears to be transferred directly to the region of turkey north of the suture however eastern turkey is characterized by distributed deformation while central western turkey is characterized by coherent plate motion involving westward displacement and counterclockwise rotation of the anatolian plate internal deformation within the central part of the anatolian plate is less than 2 mm yr the anatolian plate is decoupled from eurasia along the right lateral strike slip north anatolian fault naf this different response in eastern and western turkey to the collision of arabia may result from the different boundary conditions the hellenic arc forming a free boundary to the west and the asian continent and oceanic lithosphere of the black and caspian seas forming a resistant boundary to the north and east we derive a best fitting euler vector for anatolia eurasia motion of 29 2 0 8 n 32 9 0 4 1 3 0 1 m y the mapped surface trace of the naf corresponds well to a small circle about this pole the new euler vector implies an upper bound for naf slip rate of 30 2 mm yr i e assuming all relative motion is accommodated along the naf using the nuvel 1a euler vector for arabia eurasia and the gps euler vector for anatolia eurasia we determine an arabia anatolia euler vector of 31 2 n 45 2 e 0 9 0 1 m y and an upper bound on the east anatolian fault slip rate of 15 3 mm yr the aegean trough region of western turkey deviates significantly from coherent plate rotation in addition to rotating with anatolia this region shows roughly n s extension at a rate of 14 5 mm yr taken together with satellite laser ranging results along the hellenic arc the contemporary pattern of deformation indicates increasing motions toward the arc suggesting that the westward displacement and counterclockwise rotation of anatolia is driven both by pushing from the arabian plate and by pulling or basal drag associated with the foundering african plate along the hellenic subduction zone

structure and mechanical properties of faults in the north anatolian fault system from insar observations of coseismic deformation due to the 1999 izmit turkey earthquake 1 we study the structure and mechanical properties of faults in the north anatolian fault system by observing near fault deformation induced by the 1999 mw 7 4 izmit earthquake turkey we use interferometric synthetic aperture radar insar and global positioning system observations to analyze the coseismic surface deformation in the near field of the izmit rupture the overall observed coseismic deformation is consistent with deformation predicted by a dislocation model assuming a uniform elastic crust previous insar studies revealed small scale changes in the radar range across the nearby faults of the north anatolian fault system in particular the mudurnu valley and iznik faults e g wright et al 2001 we demonstrate that these anomalous range changes are consistent with an elastic response of compliant fault zones to the stress perturbation induced by the izmit earthquake we examine the spatial variations and mechanical properties of fault zones around the mudurnu valley and iznik faults using three dimensional finite element models in these models we include compliant fault zones having various geometries and elastic properties and apply stress changes deduced from a kinematic slip model of the izmit earthquake the best fitting models suggest that the inferred fault zones have a characteristic width of a few kilometers depth in excess of 10 km and reductions in the effective shear modulus of about a factor of 3 compared to the surrounding rocks the characteristic width of the best fitting fault zone models is consistent with field observations along the north anatolian fault system ambraseys 1970 our results are also in agreement with insar observations of small scale deformation on faults in the eastern california shear zone in response to the 1992 landers and 1999 hector mine earthquakes fialko et al 2002 fialko 2004 the inferred compliant fault zones likely represent intense damage and may be quite commonly associated with large crustal faults

ionospheric signatures of dayside magnetopause transients a case study using satellite and ground measurements a case study is presented of coordinated ground and space measurements featuring a set of transient auroral fragments located on the poleward side of a stable cusp cleft arc optical ground data from ny alesund svalbard and heiss island franz josef land were combined with dmsp f9 satellite measurements to examine the characteristics of these auroral features a stable red arc stretched across most of the dayside auroral zone in a region dominated by westward convection in accordance with the orientation of the imf poleward of the red arc were several westward moving auroral jets having characteristics similar to midday auroral breakup events such events may be ground signatures of transitory magnetic merging at the dayside magnetopause if so the driven convective motion of these structures should contribute to the polar cap potential within this limited data set we find that although the transitory structures have an inherent potential associated with the motion of the optical signatures the structures on the whole contribute a small fraction of the total polar cap potential

a complex seismogenic shear zone the duzce segment of north anatolian fault turkey abstract this work highlights how surface geological data can integrate and complete a fault characterization including its seismogenic depth we investigated the area struck by the november 1999 mw 7 1 earthquake that ruptured the duzce segment of the north anatolian fault zone nafz after the august 1999 mw 7 4 izmit earthquake to explore the persistency or evolution of the active fault setting at the surface we compared detailed coseismic surface expressions with the long term morphology and structural architecture of the duzce zone we identified a simple 1999 coseismic fault trace cft and an older complex fault system rfs involving a wider zone of deformation two different parts of the duzce segment were recognized a western section presents a staircase trajectory of the coseismic fault trace that reactivated part of the older fault system an eastern section presents a straight coseismic fault trace that cross cuts the older and complex fault system the western duzce fault segment splays out from the izmit counterpart of the nafz forming a releasing fault junction by comparing a model of its coseismic surface deformation field with the long term morphology we observed that the present topography of this western section results from the nafz activity by repeating coseismic deformations like those in 1999 the mechanical interaction in the release fault junction produces local transtension across the western duzce fault and justifies its stable complexity it does not evolve into a straight trace the surface boundary between the duzce fault sections also separates at depth two fault sections one with low slip to the west and another with a big asperity to the east thus the izmit duzce interaction 1 may produce an unfavorable setting for a build up of asperities in the western duzce segment and 2 could delay the propagation of the izmit rupture along the duzce segment that nucleates mainshocks only on its eastern section in other words the arrangement of the fault junction may permanently control how the two sections of the duzce fault behave and rupture

direct laboratory observation of patchy saturation and its effects on ultrasonic velocities maximizing the recovery of known hydrocarbon reserves is one of the biggest challenges facing the petroleum industry today optimal production strategies require accurate monitoring of production induced changes of reservoir saturation and pressure over the life of the field time lapse seismic technology is increasingly used to map these changes in space and time however until now interpretation of time lapse seismic data has been mostly qualitative in order to allow accurate estimation of the saturation it is necessary to know the quantitative relationship between fluid saturation and seismic characteristics elastic moduli velocity dispersion and attenuation the problem of calculating acoustic properties of rocks saturated with a mixture of two fluids has attracted considerable interest gist 1994 mavko and nolen hoeksema 1994 knight et al 1998 for a comprehensive review of theoretical and experimental studies of the patchy saturation problem see toms et al 2006

gps phase scintillation at high latitudes during the geomagnetic storm of 17 18 march 2015 the geomagnetic storm of 17 18 march 2015 was caused by the impacts of a coronal mass ejection and a high speed plasma stream from a coronal hole the high latitude ionosphere dynamics is studied using arrays of ground based instruments including gps receivers hf radars ionosondes riometers and magnetometers the phase scintillation index is computed for signals sampled at a rate of up to 100 hz by specialized gps scintillation receivers supplemented by the phase scintillation proxy index obtained from geodetic quality gps data sampled at 1 hz in the context of solar wind coupling to the magnetosphere ionosphere system it is shown that gps phase scintillation is primarily enhanced in the cusp the tongue of ionization that is broken into patches drawn into the polar cap from the dayside storm enhanced plasma density and in the auroral oval in this paper we examine the relation between the scintillation and auroral electrojet currents observed by arrays of ground based magnetometers as well as energetic particle precipitation observed by the dmsp satellites equivalent ionospheric currents are obtained from ground magnetometer data using the spherical elementary currents systems technique that has been applied over the ground magnetometer networks in north america and north europe the gps phase scintillation is mapped to the poleward side of strong westward electrojet and to the edge of the eastward electrojet region also the scintillation was generally collocated with fluxes of energetic electron precipitation observed by dmsp satellites with the exception of a period of pulsating aurora when only very weak currents were observed

comparison of p wave attenuation models of wave induced flow abstract wave induced oscillatory fluid flow in the vicinity of inclusions embedded in porous rocks is one of the main causes for p wave dispersion and attenuation at seismic frequencies hence the p wave velocity depends on wave frequency porosity saturation and other rock parameters several analytical models quantify this wave induced flow attenuation and result in characteristic velocity saturation relations here we compare some of these models by analyzing their low and high frequency asymptotic behaviours and by applying them to measured velocity saturation relations specifically the biot rayleigh model considering spherical inclusions embedded in an isotropic rock matrix is compared with white s and johnson s models of patchy saturation the modeling of laboratory data for tight sandstone and limestone indicates that by selecting appropriate inclusion size the biot rayleigh predictions are close to the measured values particularly for intermediate and high water saturations

effect of sub core scale heterogeneities on acoustic and electrical properties of a reservoir rock a co2 flooding experiment of brine saturated sandstone in a computed tomography scanner the effect of sub core scale heterogeneity on fluid distribution pattern and the electrical and acoustic properties of a typical reservoir rock was studied by performing drainage and imbibition flooding tests with co2 and brine in a laboratory moderately layered rothbach sandstone was used as a test specimen two core samples were drilled one perpendicular and the other parallel to the layering to allow injection of fluids along and normal to the bedding plane during the test 3d images of fluid distribution and saturation levels were mapped by an industrial x ray ct scanner together with simultaneous measurement of electrical resistivity ultrasonic velocities as well as amplitudes the results showed how the layering and the flooding direction influenced the fluid distribution pattern and the saturation level of the fluids for a given fluid saturation level the measured changes in the acoustic and electrical parameters were affected by both the fluid distribution pattern and the layering orientation relative to the measurement direction the p wave amplitude and the electrical resistivity were more sensitive to small changes in the fluid distribution patterns than the pwave velocity the change in amplitude was the most affected by the orientation of the layering and the resulting fluid distribution patterns in some instances the change due to the fluid distribution pattern was higher than the variation caused by the change in co2 saturation as a result the gassmann relation based on uniform or patchy saturation pattern was not suitable to predict the p wave velocity variation overall the results demonstrate the importance of core imaging to improve our understanding of fluid distribution patterns and the associated effects on measured rock physics properties

complex geometry and segmentation of the surface rupture associated with the 14 november 2001 great kunlun earthquake northern tibet china abstract the 14 november 2001 kunlun china earthquake with a moment magnitude m w 7 8 occurred along the kusai lake kunlun pass fault of the kunlun fault system we document the spatial distribution and geometry of surface rupture zone produced by this earthquake based on high resolution satellite landsat etm aster spot and ikonos images combined with field measurements our results show that the surface rupture zone can be divided into five segments according to the geometry of surface rupture including the sun lake buka daban hongshui river kusai lake hubei peak and kunlun pass segments from west to east these segments each 55 to 130 km long are separated by step overs the sun lake segment extends about 65 km with a strike of n45 75 w between 90 05 e 90 50 e along the previously unrecognized west sun lake fault a gap of about 30 km long exists between the sun lake and buka daban peak where no obvious surface ruptures can be observed either from the satellite images or field observations the buka daban hongshui river kusai lake hubei peak and kunlun pass segments run about 365 km striking n75 85 w along the southern slope of the kunlun mountains between 91 07 e 94 58 e this segmentation of the surface rupture is well correlated with the pattern of slip distribution measured in the field detailed mapping suggest that these five first order segments can be further separated into over 20 second order segments with a length of 10 30 km linked by smaller scale step overs or bends our result also shows that the total coseismic surface rupture length produced by the 2001 kunlun earthquake is about 430 km excluding the 30 km long gap which is the longest coseismic surface rupture for an intracontinental earthquake ever recorded finally we suggest a multiple bilateral rupture propagation model that shows the rupture process of the 2001 m w 7 8 earthquake is complex it consists of westward and eastward rupture propagations and interaction of these bilateral rupture processes

a laboratory study of the dependence of elastic wave velocities on pore scale fluid distribution laboratory data have been collected during a continuous imbibition drainage experiment that show a clear dependence of elastic wave velocities on the details of the pore scale distribution of water and air in a sandstone compressional wave velocity vp was measured at a frequency of 1 mhz shear wave velocity vs was measured at a frequency of 600 khz during the experiment vp showed little variation with the level of water saturation sw during increasing sw through imbibition until sw 0 80 at which point vp increased dramatically when sw was decreased pronounced saturation induced hysteresis was observed in the region 03 0 4 as a simple model we consider the imbibition process as producing a partially saturated state in all pores i e all pores contain both air and water the drainage process in contrast favors the existence of either air filled or water filled pores as elastic wave velocities are very sensitive to the saturation state in the smaller crack like pores these variations in fluid distribution cause related variations in velocities

the sea of marmara a plate boundary sea in an escape tectonic regime abstract the sea of marmara is dissected by two major fault systems the first consists of two east west striking transtensional boundary faults and a number of secondary faults subparallel to them the second is made up of ne sw trending subvertical strike slips and their conjugates oriented nw se that offset the first system these fault systems segment the deep marmara sea into 5 blocks that are either rhomboidal lazy z or wedge shaped three of these blocks may be interpreted as pull apart basins characterized by transtension while the other two sill areas which separate the basins are transpressional push up structures the blocks are subjected to rapid episodic subsidence but they also undergo pervasive vertical motions and possible rotations relative to one another the sedimentary column above the acoustic basement mapped within the sea of marmara can be divided into 3 seismic units a folded and truncated pre transform unit and two syn transform units the lower thick syn transform unit exhibits 3 distinct seismic facies a well stratified basin fill facies cut by subvertical growth faults a push up facies with a contorted or chaotic internal configuration and a slump facies the observed neotectonic and sedimentary regimes result from compressional movement between eurasia and africa which has led to major dextral transform movements along the north anatolian fault zone escape tectonics and from the fact that this fault zone splinters into two overlapping right stepping oblique master faults at the eastern and western border of the sea of marmara respectively

ionospheric scintillation over antarctica during the storm of 5 6 april 2010 on 5 april 2010 a coronal mass ejection produced a traveling solar wind shock front that impacted the earth s magnetosphere producing the largest geomagnetic storm of 2010 the storm resulted in a prolonged period of phase scintillation on global positioning system signals in antarctica the scintillation began in the deep polar cap at south pole just over 40 min after the shock front impact was recorded by a satellite at the first lagrangian orbit position scintillation activity continued there for many hours on the second day significant phase scintillation was observed from an auroral site 81 degrees s during the postmidnight sector in association with a substorm particle data from polar orbiting satellites provide indication of electron and ion precipitation into the antarctic region during the geomagnetic disturbance total electron content maps show enhanced electron density being drawn into the polar cap in response to southward turning of the interplanetary magnetic field the plasma enhancement structure then separates from the dayside plasma and drifts southward scintillation on the first day is coincident spatially and temporally with a plasma depletion region both in the dayside noon sector and in the dayside cusp on the second day scintillation is observed in the nightside auroral region and appears to be strongly associated with ionospheric irregularities caused by e region particle precipitation

surface ruptures of the 17 august and 12 november 1999 izmit and duzce earthquakes in northwestern anatolia turkey their tectonic and kinematic significance and the associated damage the 17 august izmit kocaeli and 12 november duzce earthquakes m w 7 4 and 7 1 respectively represent the most recent two of a series of large earthquakes along the north anatolian fault a highly active right lateral strike slip fault that crosses the anatolian peninsula in turkey from one end to the other the first earthquake rupture apparently initiated at a small step over along a relatively inconspicuous fault strand following the southern coast of the izmit bay and propagated to the west and to the east for a distance of 125 150 km the western segment enters the bay in both directions after attaining the largest surface slip of about 5 m at the town of golcuk the eastern extension of the surface rupture associated with the izmit earthquake is composed of five major segments with the maximum slip magnitudes from 3 to 4 4 5 0 5 1 4 and 0 1 m from west to east respectively the segment with 0 5 m slip trends n70 w the segment with 1 4 m slip trends n70 e and the easternmost segment with minor slip trends east west again the surface manifestation of the duzce earthquake is an extensively segmented rupture trace with dominant transtensional deformation it has a normal slip component of more than 3 7 m and a right lateral slip close to 1 4 m along the western part that showed minor rupture during the first earthquake the central part has a transpressional character with about 1 m reverse slip and about 3 m right lateral slip the highest right lateral slip nearly 5 m occurs at the central part the eastern part of the rupture displays a typical strike slip deformation with less than about 3 m right lateral slip and minor local vertical slip that exhibits changing polarity the varying orientations of the rupture segments reflect the fault mosaic of the broader region and the interaction between neighboring faults the temporal and spatial characteristics of the rupture segments as well as the significance of the nearly 3 month time period between the first and second earthquakes pose highly challenging mechanical problems regarding the rupture initiation propagation and termination processes the main surface rupture zone although unusually narrow 2 5 6 m left a path of death and destruction manuscript received 1 june 2000

present day kinematics of the middle east and eastern mediterranean the middle east and eastern mediterranean regions contain three major strike slip fault zones the dead sea fault zone dsfz and the north and east anatolian fault zones nafz and eafz these accommodate northward motion of the african and arabian plates relative to eurasia and westward motion of the small turkish plate this study deduces an internally consistent solution for the present day kinematics of these plates which is accurate to better than 20 and applicable throughout time since 5 ma by constraining the slip senses and rates on these strike slip fault zones the 7 0 5 mm yr 1 left lateral slip rate on the dsfz is associated with counterclockwise rotation of arabia relative to africa at 0 33 m y 1 around an eulcr pole near 33 n 23 e the nafz takes up counterclockwise rotation of the turkish plate relative to eurasia at 0 83 m y 1 13 around a pole at 31 n 35 5 e with right lateral slip rate 15 mm yr 1 the resulting prediction for the eafz involves 14 mm yr 1 left lateral motion and 2 mm yr 1 of shortening between arabia and turkey the triple junction of africa arabia and turkey is near the city of kahramanmaras this locality contains a narrow promontory bounded by ssw trending left lateral faults at the edges of the arabian and turkish plates which is loosely attached to the african plate moving westward relative to its interior at 4 mm yr 1

relationship between polar cap patches and field aligned irregularities as observed with an all sky airglow imager at resolute bay and the polardarn radar at rankin inlet 1 simultaneous two dimensional observations of airglow enhancement and radar backscatter from field aligned irregularities fais associated with polar cap patches were conducted the spatial structure of 630 nm airglow from polar cap patches was imaged using an all sky airglow imager at resolute bay canada while backscatter echoes from decameter scale fais were observed using the newly constructed hf polar dual auroral radar network polardarn radar at rankin inlet canada both the airglow enhancement and the radar backscatter appeared within a structured region with the spatial extent of about 500 1000 km the decameter scale fais were found to extend over the entire region of airglow enhancement associated with polar cap patches indicating that the polar patch plasma became almost fully structured soon after initiation within approximately 20 25 min these findings imply that some rapid structuring process of the entire patch area is involved in addition to the primary gradient drift instabilities

day night coupling by a localized flow channel visualized by polar cap patch propagation we present unique coordinated observations of the dayside auroral oval polar cap and nightside auroral oval by three all sky imagers two super dual auroral radar network superdarn radars and defense meteorological satellite program dmsp 17 this data set revealed that a dayside poleward moving auroral form pmaf evolved into a polar cap airglow patch that propagated across the polar cap and then nightside poleward boundary intensifications pbis superdarn observations detected fast antisunward flows associated with the pmaf and the dmsp satellite whose conjunction occurred within a few minutes after the pmaf initiation measured enhanced low latitude boundary layer precipitation and enhanced plasma density with a strong antisunward flow burst the polar cap patch was spatially and temporally coincident with a localized antisunward flow channel the propagation across the polar cap and the subsequent pbis suggests that the flow channel originated from dayside reconnection and then reached the nightside open closed boundary triggering localized nightside reconnection and flow bursts within the plasma sheet

slip distribution along the north anatolian fault associated with the large earthquakes of the period 1939 to 1967 abstract between 1939 and 1967 six large fault ruptures formed a westward migrating sequence of events along a 900 km long nearly continuous portion of the north anatolian fault for these events the 1939 erzincan 1942 niksar erbaa 1943 tosya 1944 bolu gerede 1957 abant and 1967 mudurnu valley earthquakes i have compiled a record of dextral slip which contains nearly 100 points these data indicate that the amount of slip is irregularly distributed along the 1939 to 1967 rupture zone the maximum slip 7 5 m occurred during the 1939 earthquake in the eastern 150 km of the 900 km long rupture zone dextral offsets diminish very abruptly eastward but very gradually westward the rate of westward decrease in the 1939 to 1967 offsets is only slightly greater than the rate of westward decrease of post miocene displacement along the north anatolian fault this suggests that westward decrease in slip can be expected to be a general characteristic of earthquake ruptures along the north anatolian fault in the future nevertheless within the 1939 to 1967 slip distribution there are three regions that had less slip than the neighboring regions these i interpret as possible sites of large future earthquakes one of these seismic gaps has already experienced another earthquake in 1951 and subsequent creep

velocity saturation relation in partially saturated rocks modelling the effect of injection rate changes the relationship between p wave velocity and fluid saturation in a porous medium is of importance for reservoir rock characterization forced imbibition experiments in the laboratory reveal rather complicated velocity saturation relations including rollover like patterns induced by injection rate changes poroelasticity theory based patchy saturation models using a constant fluid patch size are not able to describe these velocity saturation relations therefore we incorporate a saturation dependent patch size function into two models for patchy saturation this recipe allows us to model observed velocity saturation relations obtained for different and variable injection rates the results reveal an increase in patch size with fluid saturation and show a reduction in the patch size for decreasing injection rate this indicates that there can exist a distinct relation between patch size and injection rate we assess the relative importance of capillarity on velocity saturation relations and find that capillarity stiffening impairs the impact of patch size changes capillarity stiffening appears to be a plausible explanation when a decrease in the injection rate is expected to boost the importance of capillarity

seismic attenuation in porous rocks with random patchy saturation saturation of porous rocks with a mixture of two fluids has a substantial effect on seismic wave propagation in particular partial saturation causes significant attenuation and dispersion of the propagating waves due to the mechanism of wave induced fluid flow such flow arises when a passing wave induces different fluid pressures in regions of rock saturated by different fluids most models of attenuation and dispersion due to mesoscopic heterogeneities imply that fluid heterogeneities are distributed in a regular way however recent experimental studies show that mesoscopic heterogeneities have less idealized distributions and that the distribution itself affects attenuation and dispersion based on an approximation for the coherent wavefield in random porous media we develop a model which assumes a continuous distribution of fluid heterogeneities as this continuous random media approach assumes that there will be a distribution of different patch sizes it is expected to be better suited to modelling experimental data we also show how to relate the random functions to experimentally measurable parameters

seismicity distribution in conjunction with spatiotemporal variations of coseismic slip and postseismic creep along the combined 1999 izmit duzce rupture abstract the north anatolian fault zone nafz in nw turkey as one of the most active and best studied strike slip faults provides a unique opportunity to study earthquake related relaxation processes through analyzing co and postseismic deformation we study the spatial and temporal distributions of seismicity related to the two consecutive 1999 m 7 izmit and duzce earthquakes a high resolution aftershock catalogue including 10 000 hypocenters extending along the combined rupture zone and extending from prior to the izmit event to after the duzce event is studied spatial and temporal distributions of events allow to identify distinct seismically active and inactive fault patches their location is related to the co and postseismic deformation within and below the seismogenic layer respectively four seismically inactive patches extending 30 50 km along the rupture zone and down to 10 km depth are identified with a systematic spatial shift between them introduced by the duzce mainshock the cumulative distribution of sub areas hosting coseismic slip aftershock clusters and postseismic creep shows that the entire upper seismogenic and lower ductile portions of the crust along the combined izmit and duzce rupture zone are activated between rupture initiation and a two year postseismic period this observation was only achieved due to the subsequent occurrence of two adjacent m 7 strike slip earthquakes in combination with a distinct local seismic and geodetic monitoring our findings suggest that a coseismically introduced lateral and vertical slip deficit is systematically compensated postseismically in both the brittle and ductile portions of the crust

high resolution observations of the small scale flow pattern associated with a poleward moving auroral form in the cusp 1 in this paper we present high resolution observations by the eiscat svalbard radar of the localized ionospheric flow response due to one single flux transfer event and the relative location of a poleward moving auroral form in a fast scan mode the radar was tracking a 50 60 km wide channel of westward flow in the cusp region this flow channel was surrounded by flow running in the opposite direction at the poleward edge of the narrow flow channel a poleward moving auroral form was situated consistent with the auroral form being the signature of an upward birkeland current filament our observations can be interpreted in terms of the southwood 1985 1987 flux transfer model and the fte twin cell flow pattern appears to be a ripple onto the larger scale background convection

severe and localized gnss scintillation at the poleward edge of the nightside auroral oval during intense substorm aurora in this paper we study how gps glonass and galileo navigation signals are compromised by strong irregularities causing severe phase scintillation 1 in the nightside high latitude ionosphere during a substorm on 3 november 2013 substorm onset and a later intensification coincided with polar cap patches entering the auroral oval to become auroral blobs using global navigation satellite systems gnss receivers and optical data we show severe scintillation driven by intense auroral emissions in the line of sight between the receiver and the satellites during substorm expansion the area of scintillation followed the intense poleward edge of the auroral oval the intense auroral emissions were colocated with polar cap patches blobs the patches did not contain strong irregularities neither before entering the auroral oval nor after the aurora had faded signals from all three gnss constellations were similarly affected by the irregularities furthermore two receivers spaced around 120km apart reported highly different scintillation impacts with strong scintillation on half of the satellites in one receiver and no scintillation in the other this shows that areas of severe irregularities in the nightside ionosphere can be highly localized amplitude scintillations were low throughout the entire interval

low free field accelerations of the 1999 kocaeli earthquake the august 17 1999 kocaeli earthquake ruptured the earth s surface along 145 km and produced a magnitude of m w 7 4 as expected for such an event modified mercalli intensities of typically ix and x in the vicinity of the fault were determined yet the observed accelerations at the five near fault sites remained amazingly small with horizontal pga values of 0 14 g to 0 4 g we attempt to resolve the enigma by modeling surface ground motion with a finite difference algorithm utilizing two different rupture and slip histories derived from the strong motion observations and translate the computed horizontal motion in intensity values we can show that a in a given simple crustal velocity model different slip distributions result in significantly different ground motion distributions in the vicinity of the fault even though both slip distributions fit the observed accelerometer data quite well b both slip distributions project high ground motion into areas adjacent to the fault where no accelerometer was located c both slip distributions are not fully compatible with observed intensity observations around the fault although this could be partly attributed to the lack of knowledge regarding to the crustal structure in the light of our results it would thus be misleading if the few strong motion observations around the kocaeli earthquake fault were taken as typical or representative for the entire area and for potential future events

poleward moving hf radar flow bursts in the cusp transient changes in flow speed or direction poleward moving line of sight velocity flow bursts have been observed in the cusp by two southern hemisphere superdarn hf radars with overlapping fields of view this has allowed the estimation of unambiguous two dimensional velocity vectors in the vicinity of the flow bursts rather than showing enhancements in the flow magnitude the velocity vectors suggest that the line of sight velocity enhancements are a result of a change in the direction of the flow associated with latitudinal motion of the convection reversal boundary these observations may have important implications for understanding the ionospheric footprint of flux transfer events and also illustrate that caution is needed when interpreting line of sight velocity data from single radars

seismotectonic setting of the karadere duzce branch of the north anatolian fault zone between the 1999 izmit and duzce ruptures from analysis of izmit aftershock focal mechanisms abstract we investigate aftershock focal mechanisms along the eastern part of the izmit mw 7 4 august 17 1999 rupture zone during the time period august 22 1999 october 17 1999 two spatial clusters of aftershock activity are analyzed representing the karadere fault kf and the duzce area da based on an aftershock hypocenter catalogue restricted to events with horizontal and vertical errors 10 km events north and east of the easternmost end of the karadere fault we observe a high variance in stress field orientation correlated with lower b values while the karadere fault reflects a predominant dextral strike slip regime with normal faulting components the duzce area further to the east that also hosted the forthcoming mw 7 2 mainshock 87 days after the izmit earthquake can be subdivided into a dominantly ne sw extensional normal faulting regime below the duzce basin db and a first order strike slip regime along the western duzce fault df we conclude that the duzce basin was set under tension by the izmit rupture and partly released the slip deficit by extensional faulting on karadere fault parallel to the coseismic displacement at the same time this area and in particular the duzce fault that bounds the duzce basin to the south reflects mostly strike slip events representing a major asperity along the north anatolian fault zone nafz before initiating the duzce rupture 87 days after the izmit event

scintillation and irregularities from the nightside part of a sun aligned polar cap arc in this paper we study the presence of irregularities and scintillation in relation to the nightside part of a long lived sun aligned transpolar arc on 15 january 2015 the arc was observed in dmsp uv and particle data and lasted at least 3 h between 1700 and 2000 ut the arc was more intense than the main oval during this time from all sky imagers on svalbard we were able to study the evolution of the arc which drifted slowly westward toward the dusk cell the intensity of the arc as observed from ground was 10 17 kr in 557 7 nm and 2 3 5 kr in 630 0 nm i e significant emissions in both green and red emission lines we have used high resolution raw data from global navigation satellite systems gnss receivers and backscatter from super dual auroral radar network superdarn radars to study irregularities and scintillation in relation to the polar cap arc even though the literature has suggested that polar cap arcs are potential sources for irregularities our results indicate only very weak irregularities this may be due to the background density in the northward imf polar cap being too low for significant irregularities to be created

westward propagation of the north anatolian fault into the northern aegean timing and kinematics we present new evidence for the propagation processes of the north anatolian fault folding in the dardanelles straits region allows us to document the timing of the deformation preceding and the finite displacement after the passage of the propagating tip of the fault the accuracy of the observations is due to interplay between deformation and the sea level changes in the mediterranean the well known messinian regression followed by the pliocene transgression the long term kinematics around the sea of marmara pull apart total displacement of about 85 km over the past 5 m y is similar to the present day kinematics deduced from space geodesy at a larger scale westward propagation of the north anatolian fault over nearly 2000 km in the past 10 m y appears to be associated with strain recovery suggesting that the continental lithosphere retains long term elasticity

gps scintillation and irregularities at the front of an ionization tongue in the nightside polar ionosphere in this paper we study a tongue of ionization toi on 31 october 2011 which stretched across the polar cap from the canadian dayside sector to svalbard in the nightside ionosphere the toi front arrived over svalbard around 1930 ut we have investigated gps scintillation and irregularities in relation to this toi front this is the first study presenting such detailed multi instrument data of scintillation and irregularities in relation to a toi front combining data from an all sky imager the european incoherent scatter svalbard radar the super dual auroral radar network hankasalmi radar and three gps scintillation and total electron content tec monitors in longyearbyen and ny alesund we observe bursts of phase scintillation and no amplitude scintillation in relation to the leading gradient of the toi spectrograms of 50hz phase measurements show highly localized and variable structuring of the toi leading gradient with no structuring or scintillation within the toi or ahead of the toi

stress coupling between earthquakes in northwest turkey and the north aegean sea we have investigated the coulomb stress interactions of 29 earthquakes m s greater than or equal to 6 0 that have occurred in the region of northwest turkey and north aegean sea since 1912 of these events 23 may be related to earlier events and 16 are clearly related to earlier events all events after 1967 are related to previous events events in the early part of our time interval that show no correlation could be related to historical events as yet unidentified in some cases faults that have received a stress reduction from earlier events are prepared for an event by an earthquake occurring a few years before that creates a local coulomb stress rise thus regions of coulomb stress shadow can become regions where a damaging earthquake may occur the relation between smaller events and the coulomb stress distribution is less clear but may be related to poor data quality and practical limitations of our modeling technique nonetheless there are 4 times as many events per unit area in regions of enhanced stress than where stress is reduced we discuss the contemporary distribution of coulomb stress and argue that it is possible to identify the likely locations of future damaging earthquakes including identifying the most likely candidate faults

in situ measurement of a newly created polar cap patch 1 the investigation of cusp irregularities 2 sounding rocket was launched 5 december 2008 at 1035 ut we present an overview of the associated solar wind and auroral conditions and we look in detail at the relationship between poleward moving auroral forms pmafs and the creation of polar cap patches using ground based optical and radar data as well as in situ data from the rocket payload the solar wind was found to be dominated by a stable interplanetary magnetic field imf bz 0 situation the aurora was characterized by a series of pmafs throughout the period of interest associated with each pmaf were polar cap patches seen to emerge from the most poleward location of the pmafs on the basis of the available data we present a conceptual model explaining the creation of the polar cap patches under the given solar wind and ionospheric conditions

seismic wave attenuation and dispersion resulting from wave induced flow in porous rocks a review one major cause of elastic wave attenuation in heterogeneous porous media is wave induced flow of the pore fluid between heterogeneities of various scales it is believed that for frequencies below 1 khz the most important cause is the wave induced flow between mesoscopic inhomogeneities which are large compared with the typical individual pore size but small compared to the wavelength various laboratory experiments in some natural porous materials provide evidence for the presence of centimeter scale mesoscopic heterogeneities laboratory and field measurements of seismic attenuation in fluid saturated rocks provide indications of the role of the wave induced flow signatures of wave induced flow include the frequency and saturation dependence of p wave attenuation and its associated velocity dispersion frequency dependent shear wave splitting and attenuation anisotropy during the last four decades numerous models for attenuation and velocity dispersion from wave induced flow have been developed with varying degrees of rigor and complexity these models can be categorized roughly into three groups according to their underlying theoretical framework the first group of models is based on biot s theory of poroelasticity the second group is based on elastodynamic theory where local fluid flow is incorporated through an additional hydrodynamic equation another group of models is derived using the theory of viscoelasticity though all models predict attenuation and velocity dispersion typical for a relaxation process there exist differences that can be related to the type of disorder periodic random space dimension and to the way the local flow is incorporated the differences manifest themselves in different asymptotic scaling laws for attenuation and in different expressions for characteristic frequencies in recent years some theoretical models of wave induced fluid flow have been validated numerically using finite difference finite element and reflectivity algorithms applied to biot s equations of poroelasticity application of theoretical models to real seismic data requires further studies using broadband laboratory and field measurements of attenuation and dispersion for different rocks as well as development of more robust methods for estimating dissipation attributes from field data

inverting for slip on three dimensional fault surfaces using angular dislocations the increasing quality of geodetic data synthetic aperture radar interferometry insar dense global positioning system gps arrays now available to geophysicists and geologists are not fully exploited in slip inversion procedures most common methods of inversion use rectangular dislocation segments to model fault ruptures and therefore oversimplify fault geometries these geometric simplifications can lead to inconsistencies when inverting for slip on earthquake faults and they preclude a more complete understanding of the role of fault geometry in the earthquake process we have developed a new three dimensional slip inversion method based on the analytical solution for an angular dislocation in a linear elastic homogeneous isotropic half space the approach uses the boundary element code poly3d that employs a set of planar triangular elements of constant displacement discontinuity to model fault surfaces the use of triangulated surfaces as discontinuities permits one to construct fault models that better approximate curved three dimensional surfaces bounded by curved tiplines shapes that commonly are imaged by three dimensional reflection seismic data and inferred from relocated aftershock data we demonstrate the method s ability to model three dimensional rupture geometries by inverting for slip associated with the 1999 hector mine earthquake the resulting model avoids displacement anomalies associated with the overlapping rectangular dislocations used in previous models improving the fit to the geodetic data by 32 and honors the observed surface ruptures thereby allowing more direct comparisons between geologic and geodetic data on slip distributions online material hector mine input files and file format description

first in situ measurements of hf radar echoing targets 1 the sounding rocket investigation of cusp irregularities 2 ici 2 was launched into the cusp ionosphere over svalbard to investigate the production of decameter scale irregularities in the electron plasma associated with hf radar backscatter the main mission objective was to obtain high resolution measurements of decameter scale electron plasma irregularities and to quantify the growth rate for the gradient drift instability gdi at the 5 7 khz sampling rate of the absolute density measurements ici 2 has provided the first documentation in terms of absolute electron density measurements of how 10 m structures are located on km scale electron density gradients ici 2 traversed a cusp electron density structure created by ongoing soft precipitation 10 m scale irregularities were generated at km scale density gradients the estimated growth time for the gdi process was 10 50 seconds

faulting characteristics of supershear earthquakes article i nfo recent observations of large continental strike slip earthquakes show that different fault segments may rupture at different speeds and that rupture may propagate faster than the shear wave velocity of surrounding rocks we report that all the documented occurrences of supershear rupture are associated with faults which have simple geometry the surface trace of these faults is described in the field or seen on satellite images as remarkably linear continuous and narrow segmentation features along these segments are small or absent and the deformation is highly localized as theoretically predicted supershear is clearly associated with mode ii rupture

stratification of east west plasma flow channels observed in the ionospheric cusp in response to imf by polarity changes 1 during a period of predominantly north westward flow for imf bz negative and imf by positive a sequence of three distinct negative excursions of imf by resulted in a train of three eastward directed flow channels interleaved by westward flow enhancements propagating into the polar cap the high resolution of the eiscat svalbard radar data enables us to track formation and movement of the flow channels which are interpreted as a sequence of intermittent reconnection alternating between different reconnection sites our observations are consistent with the view that a new region of reconnected flux manifests as development of a distinct flow channel near the polar cap boundary and that successive events stay separated while pushing each other into the polar cap each flow channel will remain separated from neighboring channels mapping to different reconnection sites as long as the magnetic tension force with its associated field aligned current systems is maintained

gps signal corruption by the discrete aurora precise measurements from the mahali experiment measurements from a dense network of gps receivers have been used to clarify the relationship between substorm auroras and gps signal corruption as manifested by loss of lock on the received signal a network of nine receivers was deployed along roadways near the poker flat research range in central alaska with receiver spacing between 15 and 30 km instances of large amplitude phase fluctuations and signal loss of lock were registered in space and time with auroral forms associated with a sequence of westward traveling surges associated with a substorm onset over central canada the following conclusions were obtained 1 the signal corruption originated in the ionospheric e region between 100 and 150 km altitude and 2 the gps links suffering loss of lock were confined to a narrow band 20 km wide along the trailing edge of the moving auroral forms the results are discussed in the context of mechanisms typically cited to account for gps phase scintillation by auroral processes

acoustic signatures of partial saturation the relationship between elastic wave velocities and water saturation in a water gas reservoir depends strongly on whether saturation is heterogeneous patchy or homogeneous heterogeneity in saturation may result from lithologic heterogeneity because under conditions of capillary equilibrium different lithologies within a reservoir can have different saturations depending on their porosities and permeabilities we investigate this phenomenon by generating models of a reservoir in which we control the distribution of lithologic units and theoretically determine the corresponding velocity saturation relationship we assume a state of capillary equilibrium in the reservoir and determine the saturation level of each region within the reservoir from the corresponding capillary pressure curve for the lithologic unit at that location the velocities we calculate for these models show that saturation heterogeneity caused by lithologic variation can lead to a distinct dependence of velocity on saturation in a water gas saturated reservoir a patchy distribution of the different lithologic units is found to cause p wave velocity to exhibit a noticeable and almost continuous velocity variation across the entire saturation range this is in distinct contrast to the response of a homogeneous reservoir where there is only a large change in velocity at water saturations close to 100

modeling forced imbibition processes and the associated seismic attenuation in heterogeneous porous rocks quantifying seismic attenuation during laboratory imbibition experiments can provide useful information towards the use of seismic waves for monitoring injection and extraction of fluids in the earth s crust however a deeper understanding of the physical causes producing the observed attenuation is needed for this purpose in this work we analyze seismic attenuation due to mesoscopic wave induced fluid flow wiff produced by realistic fluid distributions representative of imbibition experiments to do so we first perform two phase flow simulations in a heterogeneous rock sample to emulate a forced imbibition experiment we then select a sub sample of the considered rock containing the resulting time dependent saturation fields and apply a numerical upscaling procedure to compute the associated seismic attenuation by exploring both saturation distributions and seismic attenuation we observe that two manifestations of wiff arise during imbibition experiments the first one is produced by the compressibility contrast associated with the saturation front whereas the second one is due to the presence of patches containing very high amounts of water that are located behind the saturation front we demonstrate that while the former process is expected to play a significant role in the case of high injection rates which are associated with viscous dominated imbibition processes the latter becomes predominant during capillary dominated processes that is for relatively low injection rates we conclude that this kind of joint numerical analysis constitutes a useful tool for improving our understanding of the physical mechanisms producing seismic attenuation during laboratory imbibition experiments

transformation of high latitude ionospheric f region patches into blobs during the march 21 1990 storm discrete f region electron density enhancements of a factor of 2 or more have been observed in the high latitude ionosphere these enhancements have been termed patches if they occur within the polar cap and blobs if they occur outside of the polar cap it is important to understand the formation and evolution of these structures because they are associated with large phase and amplitude scintillation in transionospheric radio signals blobs are generally thought to result from the breakup of patches as they exit the polar cap however this process has not previously been observed detailed study of high latitude ionospheric plasma transport is generally difficult because of the sparseness spatial and temporal of electron density and velocity observations in this paper we present electron density enhancements measured from the qaanaaq digisonde the millstone hill incoherent scatter radar and the dmsp f8 satellite during a 5 hour interval of the march 21 1990 storm period and show definitively how a patch is transformed into a blob we present a new trajectory analysis package that is capable of using ionospheric convection patterns to determine the motion of ionospheric plasma over a period of several hours the new package uses convection patterns from the assimilative mapping of ionospheric electrodynamics amie technique to track the motion of observed patches from one site to another and thus determines where the measured electron density enhancements originated and where they went after being observed the trajectory analysis also establishes that there is a direct connection between the enhancements observed by the different instruments at different locations in this case within 4 hours plasma observed by a digisonde near the pole is convected through 35 of latitude to the northeastern united states where it is observed by the millstone hill radar then roughly equal portions are transported westward to alaska and eastward to scandinavia where they are observed by the dmsp satellite this study demonstrates that the changing convection pattern can significantly distort the patch shape and trajectory and illustrates the high degree of mixing of ionospheric plasma by convection the changing convection pattern leads to the simultaneous existence of a boundary blob and a subauroral blob which are both observed by the millstone hill radar this work is very relevant to our future ability to specify and forecast ionospheric conditions at high latitudes it represents a critical step from a merely qualitative ability to model the evolution of patches and blobs to a quantitative ability

seismic hazard evaluation in western turkey as revealed by stress transfer and time dependent probability calculations western turkey has a long history of destructive earthquakes that are responsible for the death of thousands of people and which caused devastating damage to the existing infrastructures and cultural and historical monuments the recent earthquakes of izmit kocaeli on 17 august 1999 m w 7 4 and duzce m w 7 2 on 12 november 1999 which occurred in the neighboring fault segments along the north anatolian fault naf were catastrophic ones for the marmara region and surroundings in nw turkey stress transfer between the two adjacent fault segments successfully explained the temporal proximity of these events similar evidence is also provided from recent studies dealing with successive strong events occurrence along the naf and parts of the aegean sea in that changes in the stress field due to the coseismic displacement of the stronger events influence the occurrence of the next events of comparable size by advancing their occurrence time and delimiting their occurrence place in the present study the evolution of the stress field since the beginning of the twentieth century in the territory of the eastern aegean sea and western turkey is examined in an attempt to test whether the history of cumulative changes in stress can explain the spatial and temporal occurrence patterns of large earthquakes in this area coulomb stress changes are calculated assuming that earthquakes can be modeled as static dislocations in elastic half space taking into account both the coseismic slip in large m 6 5 earthquakes and the slow tectonic stress buildup along the major fault segments the stress change calculations were performed for strike slip and normal faults in each stage of the evolutionary model the stress field is calculated according to the strike dip and rake angles of the next large event whose triggering is inspected and the possible sites for future strong earthquakes can be assessed a new insight on the evaluation of future seismic hazards is given by translating the calculated stress changes into earthquake probability using an earthquake nucleation constitutive relation which includes permanent and transient effects of the sudden stress changes

one dimensional random patchy saturation model for velocity and attenuation in porous rocks porous rocks encountered in hydrocarbon reservoirs are often saturated with a mixture of two or more fluids generation of synthetic seismograms as well as interpretation of in situ attenuation measurements require a theoretical understanding of the relation between the heterogeneous distribution of fluid patches and the acoustic properties of rocks thus the problem of calculating acoustic properties of rocks saturated with a mixture of two fluids has attracted considerable interest white 1975 murphy 1982 gist 1994 mavko and mukerji 1998 pride et al 2004 at the same time this problem is also interesting from the theoretical point of view because partially saturated rocks represent a particularly interesting situation when the effects of dynamic poroelasticity may be significant at seismic or sonic frequencies indeed it is a radical departure from the situation with a porous material fully saturated with a single fluid such a fully saturated material exhibits frequency dependent effects only at frequencies comparable with biot9s characteristic frequency bourbie et al 1987 c f where f is the fluid density is fluid viscosity is permeability and is porosity for frequencies much lower than c the dynamic effects can be ignored and gassmann theory applies

measurements of seismic attenuation and transient fluid pressure in partially saturated berea sandstone evidence of fluid flow on the mesoscopic scale s u m m a r y a novel laboratory technique is proposed to investigate wave induced fluid flow on the mesoscopic scale as a mechanism for seismic attenuation in partially saturated rocks this technique combines measurements of seismic attenuation in the frequency range from 1 to 100 hz with measurements of transient fluid pressure as a response of a step stress applied on top of the sample we used a berea sandstone sample partially saturated with water the laboratory results suggest that wave induced fluid flow on the mesoscopic scale is dominant in partially saturated samples a 3 d numerical model representing the sample was used to verify the experimental results biot s equations of consolidation were solved with the finite element method wave induced fluid flow on the mesoscopic scale was the only attenuation mechanism accounted for in the numerical solution the numerically calculated transient fluid pressure reproduced the laboratory data moreover the numerically calculated attenuation superposed to the frequency independent matrix anelasticity reproduced the attenuation measured in the laboratory in the partially saturated sample this experimental numerical fit demonstrates that wave induced fluid flow on the mesoscopic scale and matrix anelasticity are the dominant mechanisms for seismic attenuation in partially saturated berea sandstone

scintillation and loss of signal lock from poleward moving auroral forms in the cusp ionosphere we present two examples from the cusp ionosphere over svalbard where poleward moving auroral forms pmafs are causing significant phase scintillation in signals from navigation satellites the data were obtained using a combination of ground based optical instruments and a newly installed multiconstellation navigation signal receiver at longyearbyen both events affected signals from gps and global navigation satellite system glonass when one intense pmaf appeared the signal from one gps spacecraft also experienced a temporary loss of signal lock although several polar cap patches were also observed in the area as enhancements in total electron content the most severe scintillation and loss of signal lock appear to be attributed to very intense pmaf activity this shows that pmafs are locations of strong ionospheric irregularities which at times may cause more severe disturbances in the cusp ionosphere for navigation signals than polar cap patches

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

surface rupture at a fault bend the 28 june 1992 landers california earthquake mapping of surface rupture associated with the 28 june 1992 landers earthquake along a portion of the north central emerson fault permits us to characterize the fractures and to interpret them in terms of a contractional bend in the fault trace the main rupture exhibits right lateral and reverse slip and is localized in a zone about 50 m wide along the present day trace of the emerson fault the surface deformation within its northeastern block the hanging wall is accommodated by a dome structure about 2 km long and 0 5 km wide and a complex assemblage of fractures the complexity of the fracture pattern around the fault bend results in part from 1 interaction between the main rupture and many shorter subparallel faults 2 the initiation and propagation of fractures at geometric complexities such as fault segment tips and fault bends and 3 bedding plane faulting both geological data and rupture kinematics indicate that uplift and shortening are associated with the fault bend the state of stress around the emerson fault bend is determined for co seismic conditions fault slip boundary conditions and interseismic conditions the remote applied stress and frictional fault boundary conditions using both displacement discontinuity boundary element and dislocation methods respectively we also investigate a possible fault propagation path at an idealized bend using the maximum distortional strain energy density criterion results of the theoretical analyses provide support for an understanding of the location and the asymmetry of the dome structure and the mechanisms for some of the observed fracture systems in terms of the state of stress and fault propagation paths around the fault bend and other smaller scale complexities along the fault trace

active faults and evolving strike slip basins in the marmara sea northwest turkey a multichannel seismic reflection study abstract the north anatolian fault is a 1200 km long transform fault forming the boundary between the anatolian and eurasian plates near its western end it strikes through the marmara sea and is responsible for the creation of three deep marine depressions the north anatolian fault system and the linked basins in the eastern marmara sea were studied using newly acquired multi channel seismic reflection data in the marmara sea the north anatolian fault consists of a main strand and a few subsidiary branches the main strand is made up of the ganos 15 km long central marmara 105 km and north boundary 45 km fault segments the north boundary fault joins in the east to the izmit segment which was ruptured during the m s 7 4 earthquake on 17 8 1999 the north boundary fault is highly oblique to the regional displacement vector which results in the generation of a symmetrical fault wedge basin this cinarcik basin is a wedge shaped deep marine depression south of istanbul it is about 50 km long up to 20 km wide and 1250 m deep and is filled with pliocene to quaternary sediments over 3 km thick the north boundary fault joins in the west to the transpressional central marmara fault around the restraining segment boundary the syntransform sediments are being deformed into a large anticlinorium the cinarcik basin started to form when the westward propagating north anatolian fault intersected a northwest trending pre existing fault zone during the pliocene and bifurcated into nw and sw trending segments forming a transform transform transform type triple junction dextral strike slip movement along the arms of the triple junction led to the development of the cinarcik basin the present fault geometry in the marmara region was achieved later during the mid pliocene following the termination of the triple junction geometry south of the main north anatolian fault system there is a second active strike slip fault in the marmara sea made up of several segments a highly asymmetrical fault bend basin comprising pliocene quaternary sediments over 2 5 km thick is forming along a releasing fault segment of this south boundary fault system

strike slip fault geometry in turkey and its influence on earthquake activity the geometry of turkish strike slip faults has been reviewed and described from this data set it appears that fault geometry the distribution of discontinuities such as bends and stepovers along the main fault trace plays an important role in controlling the location of large earthquake rupture segments along the fault zones large earthquake ruptures generally do not propagate past individual stepovers that are wider than 5 km or bends that have angles greater than about 30 more important than the size of each discontinuity however is the total geometric pattern i e the distribution of adjacent bends and stepovers based not only on distance from one another but also on relative discontinuity size certain geometric patterns restraining single or double bends are particularly common and can be viewed as responsible for strain accumulation along portions of the fault zone fault geometry not only plays a role in the extent of earthquake rupture but also in characteristics of earthquake behavior for example large earthquake epicenters often occur near restraining bends or double bends furthermore aftershocks and swarm activity can often be associated with releasing areas areas along the strike slip fault that are undergoing a relatively large amount of extension

gps and geologic estimates of the tectonic activity in the marmara sea region nw anatolia a dense network of 52 global positioning system gps sites is used to determine the velocity field and strain rate pattern at the western end of the north anatolian fault zone nafz in the marmara sea region nw anatolia based on four gps campaigns carried out biannually between 1990 and 1996 the detailed kinematic field of crustal motion is calculated the southernmost station shows an average rate of 22 3 mm yr oriented westward relative to istanbul eurasia this value is indicative of the dextral strike slip motion of nw anatolia relative to the black sea the gps velocity field reveals that the sites located on the thrace black sea block show negligible motion relative to istanbul the gps based deformation pattern of three sections crossing the westward prolongation of the nafz is compared with neotectonic data both the gps and the neotectonic data give clear evidence that most of the deformation occurs along a relatively narrow e w oriented zone this belt extends from the single fault trace of the nafz through the gulf of izmit the marmara sea the arkoy region and the gulf of saros into the north aegean trough nat in addition the cross sections show the increasing influence of the n s oriented extension in the aegean sea region from the comparison of the directions and rates of shear and normal strain deduced from gps data with geologic and seismic observations we conclude that the most active zone of dextral shear follows a line along mudurnu valley the northern marmara sea and the saros trough where it joins the nat

forced imbibition into a limestone measuring p wave velocity and water saturation dependence on injection rate quantitative interpretation of time lapse seismic data requires knowledge of the relationship between elastic wave velocities and fluid saturation this relationship is not unique but depends on the spatial distribution of the fluid in the pore space of the rock in turn the fluid distribution depends on the injection rate to study this dependency forced imbibition experiments with variable injection rates have been performed on an air dry limestone sample water was injected into a cylindrical sample and was monitored by x ray computed tomography and ultrasonic timeof flight measurements across the sample the measurements show that the p wave velocity decreases well before the saturation front approaches the ultrasonic raypath this decrease is followed by an increase as the saturation front crosses the raypath the observed patterns of the acoustic response and water saturation as functions of the injection rate are consistent with previous observations on sandstone the results confirm that the injection rate has significant influence on fluid distribution and the corresponding acoustic response the complexity of the acoustic response that is not monotonic with changes in saturation and which at the same saturation varies between hydrostatic conditions and states of dynamic fluid flow may have implications for the interpretation of time lapse seismic responses

new constraints on recent large earthquakes along the xidatan dongdatan segment of the kunlun fault western china field investigation and paleoseismic study constrain the offset and timing of recent large earthquakes on the xidatan dongdatan segment of the strike slip kunlun fault northern tibet displaced terrace risers and gullies preserved on the lowest and youngest terrace in the central part of the xidatan dongdatan valley indicate that the offset produced by the most recent earthquake is 3 6 m which is much smaller than what has been previously estimated however it is consistent with the slip of historical earthquakes along the kunlun fault and recent well recorded large earthquakes on other strike slip faults accumulated offsets on higher terraces indicate repeated seismic activity of the kunlun fault we assume a 150 20 km long surface rupture for the most recent event based on roughly continuous linear features on remote sensing images and distinct mole tracks in the field the lack of seismicity records in the region earlier than 100 years ago led us to carry out paleoseismic investigation samples collected from the faulted upper layer show that the most recent large event on the xidatan dongdatan segment is not older than 663 yr b p at least three prehistoric events are identified on the trench wall due to a lower constraint on the offset produced by the most recent earthquake it would be necessary to reevaluate the seismic behavior of the xidatan dongdatan segment

rupture progression along discontinuous oblique fault sets implications for the karadere rupture segment of the 1999 izmit earthquake and future rupture in the sea of marmara abstract large earthquakes in strike slip regimes commonly rupture fault segments that are oblique to each other in both strike and dip this was the case during the 1999 izmit earthquake which mainly ruptured e w striking right lateral faults but also ruptured the n60 e striking karadere fault at the eastern end of the main rupture it will also likely be so for any future large fault rupture in the adjacent sea of marmara our aim here is to characterize the effects of regional stress direction stress triggering due to rupture and mechanical slip interaction on the composite rupture process we examine the failure tendency and slip mechanism on secondary faults that are oblique in strike and dip to a vertical strike slip fault or master fault for a regional stress field well oriented for slip on a vertical right lateral strike slip fault we determine that oblique normal faulting is most favored on dipping faults with two different strikes both of which are oriented clockwise from the strike slip fault the orientation closer in strike to the master fault is predicted to slip with right lateral oblique normal slip the other one with left lateral oblique normal slip the most favored secondary fault orientations depend on the effective coefficient of friction on the faults and the ratio of the vertical stress to the maximum horizontal stress if the regional stress instead causes left lateral slip on the vertical master fault the most favored secondary faults would be oriented counterclockwise from the master fault for secondary faults striking 30 oblique to the master fault right lateral slip on the master fault brings both these secondary fault orientations closer to the coulomb condition for shear failure with oblique right lateral slip for a secondary fault striking 30 counterclockwise the predicted stress change and the component of reverse slip both increase for shallower angle dips of the secondary fault for a secondary fault striking 30 clockwise the predicted stress change decreases but the predicted component of normal slip increases for shallower angle dips of the secondary fault when both the vertical master fault and the dipping secondary fault are allowed to slip mechanical interaction produces sharp gradients or discontinuities in slip across their intersection lines this can effectively constrain rupture to limited portions of larger faults depending on the locations of fault intersections across the fault intersection line predicted rakes can vary by 40 and the sense of lateral slip can reverse application of these results provides a potential explanation for why only a limited portion of the karadere fault ruptured during the izmit earthquake our results also suggest that the geometries of fault intersection within the sea of marmara favor composite rupture of multiple oblique fault segments