seven years of postseismic deformation following the 1999 m 7 4 and m 7 2 izmit duzce turkey earthquake sequence 1 we report the results of nearly 7 years of postseismic deformation measurements using continuously recorded and survey mode gps observations for the 1999 izmit duzce earthquake sequence resolvable time dependent postseismic changes to the preearthquake interseismic velocity field extend at least as far as the continuous gps station in ankara 200 km southeast of the izmit rupture seven years after the earthquake sequence the relative postseismic velocity across the north anatolian fault naf reaches 10 12 mm a roughly 50 of the steady state interseismic rate with the highest postseismic velocities within 40 km of the coseismic ruptures we use a sequence of logarithmic time functions to fit gps site motions up to three logarithmic terms with decay constants of 1 150 and 3500 days are necessary to fit all the transient motion observed at the continuous gps stations the first term is required for the component of site motion parallel to the naf at near field sites strongly implicating rapid shallow afterslip the intermediate and longer term postseismic velocity components reflect more broadly distributed strain with a symmetric double couple pattern suggestive of either localized deep afterslip or viscoelastic relaxation of the upper mantle and or lower crust in two areas including the marmara sea this pattern is superimposed on north south extension centered on the naf we speculate that this extension may result from aseismic dip slip along coseismically weakened faults driven by the background tectonic stress

izmit earthquake postseismic deformation and dynamics of the north anatolian fault zone 1 we have modeled postseismic deformation from 1999 to 2003 in the region surrounding the 1999 izmit and duzce earthquake ruptures using a three dimensional viscoelastic finite element method our models confirm earlier findings that surface deformation within the first few months of the izmit earthquake is principally due to stable frictional afterslip on and below the izmit earthquake rupture a second deformation process is required however to fit the surface deformation after several months viscoelastic relaxation of lower crust and or upper mantle with a viscosity of the order of 2 to 5 1019 pa s improves the models fit to later gps site velocities however for a linear viscous rheology this range of values is inconsistent with highly localized interseismic deformation around the north anatolian fault zone nafz that was well observed prior to the earthquake sequence the simplest solution to this problem is to assume that the effective viscosity of the relaxing material increases with time after large earthquakes that is that it has a power law or burger s body transient rheology a burger s body rheology with two characteristic viscosities 2 to 5 1019 pa s and at least 2 1020 pa s in the mantle is consistent with deformation around the nafz throughout the earthquake cycle

statistical tests of simple earthquake cycle models a central goal of observing and modeling the earthquake cycle is to forecast when a particular fault may generate an earthquake a fault late in its earthquake cycle may be more likely to generate an earthquake than a fault early in its earthquake cycle models that can explain geodetic observations throughout the entire earthquake cycle may be required to gain a more complete understanding of relevant physics and phenomenology previous efforts to develop unified earthquake models for strike slip faults have largely focused on explaining both preseismic and postseismic geodetic observations available across a few faults in california turkey and tibet an alternative approach leverages the global distribution of geodetic and geologic slip rate estimates on strike slip faults worldwide here we use the kolmogorov smirnov test for similarity of distributions to infer in a statistically rigorous manner viscoelastic earthquake cycle models that are inconsistent with 15 sets of observations across major strike slip faults we reject a large subset of two layer models incorporating burgers rheologies at a significance level of 0 05 those with long term maxwell viscosities m 4 6 1020 pa s but cannot reject models on the basis of transient kelvin viscosity k finally we examine the implications of these results for the predicted earthquake cycle timing of the 15 faults considered and compare these predictions to the geologic and historical record

confirmation of arabia plate slow motion by new gps data in yemen 1 during the last 10 years a network of about 30 gps sites was measured in djibouti east africa additional points were also measured in yemen oman ethiopia iran and on la reunion island merged with data from the available international gps service permanent stations scattered on the different plates in the area eurasia anatolia africa arabia somalia this unique data set provides new insight on the current deformation in the africa somalia arabia triple junction area and on the arabian plate motion here we show that coherent motions of points in yemen bahrain oman and iran allow us to estimate a geodetically constrained angular velocity for the arabian plate 52 59 n 15 74 w 0 461 myr in itrf2000 this result differs significantly from earlier determinations and is based upon our vectors in yemen they provide new additional data and better geometry for angular velocity determination combined with the african and somalian motions this new angular velocity results in predicted spreading rates in the red sea and the gulf of aden which are 15 20 lower than those measured from oceanic magnetic anomalies and thus averaged over the last 3 myr with respect to eurasia the geodetic motion of arabia is also about 30 slower than predicted by nuvel 1a on the basis of the kinematic results presented here and on other evidence for a similar slower geodetic rate of the indian plate we suggest that the whole collision zone between africa arabia india on one hand and eurasia on the other hand has slowed down in the last 3 myr

early holocene and late pleistocene slip rates of the southern dead sea fault determined from 10be cosmogenic dating of offset alluvial deposits 1 two sites located along the wadi araba fault waf segment of the dead sea fault are targeted for tectonic morphological analysis 10be cosmogenic radionuclide crn dating of embedded cobbles is used to constrain the age of offset alluvial surfaces at the first site a 48 7 m offset alluvial fan for which 10be crn model ages average 11 1 4 3 ka yield a slip rate of 5 4 2 7 mm a with conservative bounds of 1 3 16 4 mm a at the second site the scattered distributions of the 10be crn ages from an offset bajada attest to the complex processes involved in sediment transport and emplacement there two offsets were identified the 160 8 m offset of an incised alluvial fan dated at 37 5 ka shows a slip rate of 4 5 0 9 mm a with a conservative minimum value of 3 2 mm a a larger offset 626 37 m is derived from a prominent channel incised into the bajada cobbles from the bajada surface have ages from 33 to 141 ka with a mean of 87 26 ka a slip rate of 8 1 2 9 mm a is derived from the mean age with conservative bounds of 3 8 22 1 mm a these results and other published slip rates along the linear waf segment from gps to geological time scales lack the resolution to fully resolve the question of temporal variations versus consistency of the fault slip rate of the waf yet given the uncertainties they are not inconsistent with each other

late quaternary activity along the lone pine fault eastern california the lone pine fault is a north trending secondary break of the owens valley fault zone 1 4 km west of lone pine california this fault forms an east facing scarp as much as 6 5 m high across an abandoned outwash fan of the tioga latest pleistocene glaciation the fault experienced large right lateral and smaller vertical displacement during the 1872 owens valley earthquake knowledge of the character and amount of slip at this site in and before 1872 is necessary for evaluations of earthquake hazard near owens valley and may help us to understand earthquakes along other parts of the eastern front of the sierra nevada and in the great basin scarp profiles indicate a 1 to 2 m component of dip slip in 1872 thus three 1872 type earthquakes could have created the scarp this number of events is also indicated by desert varnish patterns on boulders in the fault scarp by scarp morphology and by sediments near the fault horizontal offset of a relict channel on the fan is 12 to 18 m 3 earthquakes horizontal offset of a younger debris flow is 10 to 12 m apparently 2 earthquakes average horizontal offset for each earthquake including that of 1872 is 4 to 6 m the age of the fan surface is bracketed by a 21 ka shoreline of former lake owens and by the time of abandonment of the fan about 10 ka an average recurrence interval for 3 earthquakes is 5 000 to 10 500 yr the average recurrence interval combined with the average oblique offset for each event of 4 3 to 6 3 m gives an average late quaternary slip rate of 0 4 to 1 3 mm yr for the lone pine fault if we add the average horizontal slip component for the lone pine fault to the 1872 horizontal slip reported for the adjacent main owens valley trace of 2 7 to 4 9 m the combined 1872 horizontal slip component for the owens valley fault zone is approximately between 7 and 11 m a large value the associated horizontal slip rate for the owens vallev fault zone is 0 7 to 2 2 mm yr

postseismic and interseismic displacements near a strike slip fault a two dimensional theory for general linear viscoelastic rheologies 1 we present an analytic solution for the deformation near an infinite strike slip fault in an elastic layer overlying a linear viscoelastic half space the theory is valid for any linear viscoelastic rheology and any earthquake sequence this is a generalization of the work of j c savage and colleagues which only holds for models with a uniform shear modulus maxwell viscoelastic lower half space and periodic rupture recurrence we demonstrate the theory for models of an elastic layer over a maxwell standard linear solid burgers and triviscous half space for each of these models we calculate example postseismic displacements interseismic displacements in a periodic earthquake sequence and interseismic displacements for a nonperiodic earthquake sequence our solution is for a simple geometry however the model presents an elegant tool to explore the evolution of displacements for relatively complex rheologies and rupture recurrence histories

variable rates of late quaternary strike slip on the san jacinto fault zone southern california three strike slip displacements of strata with known approximate ages have been measured at two locations on the san jacinto fault zone minimum horizontal offset between 5 7 and 8 6 km in no more than 0 73 m y northeast of anza indicates 8 12 mm yr average slip rate since late pleistocene time two measures of more recent displacement are based on trenching studies of stratigraphic offsets on the coyote creek fault in western imperial valley horizontal slip of 1 7 m has been calculated for the youngest sediment of lake cahuilla since its deposition 275 510 yr b p the corresponding slip rate is 2 8 5 0 mm yr right lateral offset of 10 9 m measured on a buried stream channel older than 5060 yr b p but younger than 6820 yr b p yields average slip rates for the intermediate time periods 400 to 6000 yr b p of 1 2 mm yr the average rates of slip for these three time intervals suggest a relatively quiescent period for the san jacinto fault zone from about 4000 b c to about 1600 a d to the extent that long term variations in seismic activity of major strike slip faults elsewhere are known fluctuations in slip rate for the san jacinto fault would not appear to be abnormal if the san jacinto and adjacent segments of the san andreas fault alternately assume dominant roles in absorbing motion between the pacific and american plates perhaps even more recently than 400 yr ago the san andreas fault south of the transverse ranges expressed most of the motion but has since become relatively inactive

holocene slip rate of the north anatolian fault beneath the sea of marmara abstract the north anatolian fault naf is a major continental transform system that extends e w across turkey for over 1600 km separating the anatolian and eurasian plates a portion of its northern branch runs below the sea of marmara this portion constitutes a seismic gap because the last destructive earthquakes occurred at the western 1912 ganos earthquake m 7 4 and eastern 1999 izmit and duzce earthquakes m w 7 4 7 2 edges of the marmara basin it is likely that fault ruptures will fill this gap in the next decades this region of the north anatolian fault is critical to our understanding of fault interactions stress buildup during seismic cycle and seismic hazard in the istanbul area we obtained high resolution acoustic images of the naf in the floor of the eastern marmara sea gulf of izmit and measured fault related offsets of 14 c dated subseafloor channels and paleoshorelines the resulting average slip rate on the fault is 10 mm year for the last 10 kyr this is less than half the total anatolia eurasia relative motion estimated at 24 mm year for the last 10 years from satellite geodetic measurements we conclude that either much of the strike slip motion along this branch of the naf did not occur on the main fault segment or the slip rate increased recently or both these results affect kinematic models of the naf and assessments of seismic hazard for the city of istanbul and the surrounding region

morphology displacement and slip rates along the north anatolian fault turkey 1 geological and geomorphological offsets at different scales are used to constrain the localization of deformation total displacement and slip rates over various timescales along the central and eastern north anatolian fault naf in turkey the naf total displacement is reevaluated using large rivers valleys 80 15 km and structural markers pontide suture 85 25 km tosya vezirkopru basins 80 10 km these suggest a neogene slip rate of 6 5 mm yr over 13 myr the river network morphology shows offsets at a range of scales 20 m to 14 km across the main fault trace and is also used to estimate the degree to which deformation is localized at a smaller scale the morphology associated with small rivers is offset by 200 m along the naf the age of these features can be correlated with the holocene deglaciation and a slip rate of 18 3 5 mm yr is determined this is consistent with a rate of 18 5 mm yr deduced independently from the 14c dating of stream terrace offsets over the short term gps data gives a similar rate of 22 3 mm yr all our results tend to show that most of the deformation between the anatolian and eurasian lithospheric plates has been accommodated along or very close to the active trace of the naf the difference between the neogene and the holocene slip rate may be due to the recent establishment of the current plate geometry after the creation of the naf

an observational heat budget analysis of a coral reef heron reef great barrier reef australia measurements of the surface energy balance the structure and evolution of the convective atmospheric reef layer carl and local meteorology and hydrodynamics were made during june 2009 and february 2010 at heron reef australia to establish the relative partitioning of heating within the water and atmosphere horizontal advection was shown to moderate temperature in the carl and the water having a cooling influence on the atmosphere and providing an additional source or sink of energy to the water overlying the reef depending on tide the key driver of atmospheric heating was surface sensible heat flux while heating of the reef water was primarily due to solar radiation and thermal conduction and convection from the reef substrate heating and cooling processes were more defined during winter due to higher sensible and latent heat fluxes and strong diurnal evolution of the carl sudden increases in water temperature were associated with inundation of warmer oceanic water during the flood tide particularly in winter due to enhanced nocturnal cooling of water overlying the reef similarly cooling of the water over the reef occurred during the ebb tide as heat was transported off the reef to the surrounding ocean while these results are the first to shed light on the heat budget of a coral reef and overlying carl longer term systematic measurements of reef thermal budgets are needed under a range of meteorological and hydrodynamic conditions and across various reef types to elucidate the influence on larger scale oceanic and atmospheric processes this is essential for understanding the role of coral reefs in tropical and sub tropical meteorology the physical processes that take place during coral bleaching events and coral and algal community dynamics on coral reefs

geodetic evidence for a low slip rate in the altyn tagh fault system the collision between india and asia has been simulated with a variety of computational models that describe or predict the motions of the main faults of east asia geological slip rate estimates of 20 30 mm yr 1 suggest that the largest of these faults the 2 000 km long altyn tagh fault system on the northern edge of the tibetan plateau absorbs as much of the indo asian convergence signal as do the himalayas partly by oblique slip and partly by contraction and mountain growth however the predictions of dynamic models for asian deformation and the lower bounds of some geological slip rates estimates 3 9 mm yr 1 refs 7 8 suggest that the altyn tagh system is less active here we report geodetic data from 89 91 degrees e that indicate left lateral shear of 9 5 mm yr 1 and contraction of 3 1 mm yr 1 across the altyn tagh system this result combined with our finding that at 90 degrees e tibet contracts north south at 9 1 mm yr 1 supports the predictions of dynamic models of asian deformation

holocene slip rates along the owens valley fault california implications for the recent evolution of the eastern california shear zone one of the largest historical earthquakes in california occurred in 1872 along the owens valley fault located along the western margin of the eastern california shear zone new paleoseismic and optically stimulated luminescence data are the first to bracket the timing of the pre 1872 rupture to between 3 3 0 3 and 3 8 0 3 ka these data yield an earthquake recurrence interval between 4100 and 3000 yr under the assumption of uniform return and indicate a holocene slip rate between 1 8 0 3 and 3 6 0 2 mm yr our data are broadly consistent with a model proposed for the space time evolution of the eastern california shear zone our holocene slip rate estimates for the owens valley fault are slower than present day slip rates determined from elastic half space models of geodetic data this discrepancy is reduced by using the recurrence interval estimated here and a viscoelastic model of geodetic data or by including geologic slip rates from adjacent faults

evidence for 830 years of seismic quiescence from palaeoseismology archaeoseismology and historical seismicity along the dead sea fault in syria an edited version of this paper was published in earth and planetary science letters by elsevier science elsevier science retains the copyright to this paper copyright 2003 see also http dx doi org 10 1016 s0012 821x 03 00144 4 http atlas geo cornell edu deadsea publications meghraoui2003 epsl htm

late quaternary rate of slip along the san jacinto fault zone near anza southern california the anza section of the san jacinto fault southern california has not experienced a groundbreaking earthquake since at least 1918 and probably since before 1899 leading previous workers to designate this 20 km long fault segment as a seismic gap study of displaced pleistocene and holocene alluvial fan and fluvial deposits across the san jacinto fault near anza california dated using 14c and soil development age control indicates a minimum right lateral slip rate of 9 2 2 mm yr since 9 5 ka and a slip rate of 11 9 5 mm yr since 14 ka 12 9 5 mm yr since 17 ka and 13 10 6 mm yr since 50 ka these estimates agree with a previously determined 700 ka to present minimum slip rate of 10 2 mm yr based on an estimated average slip rate of 12 mm yr from the longer term slip rate estimates about 0 8 m of potential slip has accumulated if the 1918 earthquake broke the anza segment over 1 1 m of potential slip has accumulated if the last earthquake occurred prior to 1899 these data attest to the potential for an earthquake m6 5 for this section of the fault

detection of creep along the philippine fault first results of geodetic measurements on leyte island central philippine geodetic trilateration gps measurements were acquired from experiments conducted in 1991 and 1993 in the central part of the philippine fault on leyte island displacement vectors deduced from two least squares adjustments indicate a mean slip rate of 26 10 mm yr at an azimuth of about n130 e these values are consistent with the tectonic and kinematic data our results indicate that the displacements are 1 almost parallel to the philippine fault and 2 related to creep along the fault because no moderate seismic events occurred between the two observation epochs

measurement of interseismic strain across the haiyuan fault gansu china by insar the haiyuan fault is part of a major left lateral fault system at the northeastern edge of the tibet qinghai plateau two m8 earthquakes 1920 and 1927 occurred along the fault bracketing an unbroken section of the fault identified as the tianzhu seismic gap we use interferometric synthetic aperture radar data from descending orbits of the ers satellites acquired between 1993 and 1998 along two adjacent tracks covering the gap to measure the current surface movements and better understand the present day mechanical behavior of this fault section the analysis of the radar data involves first the combined correction of orbital errors and errors associated with the phase delay through the troposphere a subset of the data is then selected based on the analysis of the residual noise spectra for each pair of data the selected interferograms are stacked and the average phase change rate is converted in fault parallel velocity assuming that the ground movement is horizontal and parallel to the fault velocity maps from both tracks show a zone of high velocity gradient across the fault a few kilometers wide consistent with left lateral slip on the haiyuan fault the average velocity field from the two tracks in their overlapping area is well fit with a single screw dislocation model in an elastic half space the derived fault slip rate at depth 4 2 8 mm yr is consistent with recent gps results the corresponding shallow apparent locking depth 0 4 2 km can be explained by a current low stress accumulation on the fault due to creep almost on the entire fault plane however unless it is transient this creep would be paradoxical with the occurrence of past large earthquakes along this fault section as revealed by paleoseismology an alternative model implying both shallow creep in the brittle upper crust and deep aseismic slip beneath the seismogenic layer separated by a locked section would be consistent with insar observations and with the potential for large earthquakes on the fault as well a two dislocation model with slip at 5 mm yr beneath 15 km and a transient creep rate of 11 mm yr between 2 and 7 km fits the insar data however the width and creep rate of the shallow creeping zone and their possible along strike variations are still poorly resolved with the present data set

dynamic models of interseismic deformation and stress transfer from plate motion to continental transform faults thermal regime on geologic timescales 10 6 10 7 years as well as on timescales of the order of the earthquake recurrence 10 2 years strain localization in the viscoelastic medium results from thermomechanical coupling and power law dependence of strain rate on stress for conditions corresponding to the san andreas fault saf the predicted width of the shear zone in the lower crust is 3 5 km this shear zone accommodates more than 50 of the far field plate motion coupled thermomechanical models predict a single layer lithosphere in case of dry composition of the lower crust and upper mantle and a jelly sandwich lithosphere in case of wet composition deviatoric stress in the lithosphere in our models is relatively insensitive to the water content the far field loading rate and the fault strength and is of the order of 10 2 mpa thermomechanical coupling gives rise to an inverse correlation between the fault slip rate and the ductile strength of the lithosphere we show that our models are broadly consistent with geodetic and heat flow constrains from the saf in northern california models suggest that the regionally elevated heat flow around the saf may be at least in part due to viscous dissipation in the ductile part of the lithosphere

using short term postseismic displacements to infer the ambient deformation conditions of the upper mantle 1 to interpret short term postseismic surface displacements in the context of key ambient conditions e g temperature pressure background strain rate water content creep mechanism we combined steady state and transient flow into a single constitutive relation that can explain the response of a viscoelastic material to a change in stress the flow law is then used to investigate mantle deformation beneath the eastern california shear zone following the 1999 m7 1 hector mine earthquake the flow law parameters are determined using finite element models of relaxation processes constrained by surface displacement time series recorded by 55 continuous gps stations for 7 years following the earthquake results suggest that postseismic flow following the hector mine earthquake occurs below a depth of 50 km and is controlled by dislocation creep of wet olivine diffusion creep models can also explain the data but require a grain size 3 5 mm that is smaller than the inferred grain size 10 20 mm based on the mantle conditions at these depths in addition laboratory flow laws predict dislocation creep would dominate at the stress grain size conditions that provide the best fit to diffusion creep models model results suggest a transient creep phase that lasts 1 year and has a viscosity 10 times lower than subsequent steady state flow in general agreement with laboratory observations the postseismic response is best explained as occurring within a relatively hot upper mantle e g 1200 1300 c at 50 km depth with a long term background mantle strain rate of 0 1 0 2 mstrain yr consistent with the observed surface strain rate long term background shear stresses at the top of the mantle are 4 mpa then decrease with depth to a minimum of 0 1 0 2 mpa at 70 km depth before increasing slowly with depth due to the pressure dependence of viscosity these conditions correspond to a background viscosity of 10 21 pa s within a thin mantle lid that decreases to 5 10 19 pa s within the underlying asthenosphere this study shows the utility of using short term postseismic observations to infer long term mantle conditions that are not readily observable by other means

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

crustal deformation during 1994 1998 due to oblique continental collision in the central southern alps new zealand and implications for seismic potential of the alpine fault the positions of 115 ground marks in a 150 100 km area of oblique continental collision in the central southern alps new zealand have been measured by global positioning system gps two to four times between 1994 and 1998 contemporary velocity and strain rate fields derived from these observations are largely invariant along the northeasterly strike of the mountains and alpine fault across strike more than 60 of the strain occurs within a band from 5 km nw to 20 km se of the alpine fault but significant strain continues at least a further 60 km se to near the edge of the southern alps foothills projections of the fault parallel and fault normal components of velocity onto an alpine faultnormal profile show that about 85 of the nuvel 1a model relative plate motion is observed within the gps network the surface displacements in the high strain rate region are well fit by a model in which stable slip or shearing is occurring at 50 70 of the relative plate rate in a region deeper than about 5 8 km on the down dip extension of the se dipping alpine fault material shallower than this is behaving elastically and thus storing elastic strain in the region of the alpine fault the longer wavelength displacements can be modeled either as distributed deformation beneath the southern alps or by localization of elastic strain around the upper end of a discrete nw dipping fault or shear zone that is slipping stably below about 30 km depth and would outcrop near the se boundary of the mountains if extrapolated to the surface strain determined from a small scale survey network crossing the alpine fault indicates no significant near surface aseismic fault slip on the central alpine fault over the past 25 years our results are consistent with independent geological evidence that the central section of the alpine fault is capable of producing large to great earthquakes

late holocene slip rate for the north anatolian fault turkey from cosmogenic 36cl geochronology implications for the constancy of fault loading and strain release rates geomorphologic mapping and cosmogenic radionuclide 36cl dating of an offset fluvial terrace yield a preferred late holocene slip rate of 20 5 5 5 mm yr for the central part of the north anatolian fault turkey an independent slip rate constrained by 14c ages is 20 5 8 5 mm yr these rates are generally similar to but possibly slightly slower than the short term rate of elastic strain storage of 25 1 measured geodetically across this major strike slip fault reilinger et al 2006 1 suggesting that loading and strain release on this part of the north anatolian fault have been relatively constant when averaged over the past 2 2 5 k y we attribute this consistency to the relatively simple structure of the anatolia eurasia plate boundary in north central turkey where almost all plate boundary strain is accommodated along the north anatolian fault the absence of other moderate to high slip rate faults and the earthquakes they produce leads to a relatively simple stress evolution for the fault dominated by steady tectonic loading 1 ref 10

weak ductile shear zone beneath a major strike slip fault inferences from earthquake cycle model constrained by geodetic observations of the western north anatolian fault zone gps data before and after the 1999 izmit duzce earthquakes on the north anatolian fault zone turkey reveal a preseismic strain localization within about 25 km of the fault and a rapid postseismic transient using 3 d finite element calculations of the earthquake cycle in an idealized model of the crust comprising elastic above maxwell viscoelastic layers we show that spatially varying viscosity in the crust can explain these observations depth dependent viscosity without lateral variations can reproduce some of the observations but cannot explain the proximity to the fault of maximum postseismic velocities a localized weak zone beneath the faulted elastic lid satisfactorily explains the observations if the weak zone extends down to midcrustal depths and the ratio of relaxation time to earthquake repeat time ranges from 0 005 to 0 01 for weak zone widths of 24 and 40 km respectively in the weakened domain and greater than 1 0 elsewhere corresponding to viscosities of 1018 0 3 pa s and greater than 1020 pa s models with sharp weak zone boundaries fit the data better than those with a smooth viscosity increase away from the fault implying that the weak zone may be bounded by a relatively abrupt change in material properties such a change might result from lithological contrast grain size reduction fabric development or water content in addition to any effects from shear heating our models also imply that viscosities inferred from postseismic studies primarily reflect the rheology of the weak zone and should not be used to infer the mechanical properties of normal crust

slip rate and locking depth from gps profiles across the southern dead sea transform 1 the dead sea transform is a major strike slip fault bounding the arabia plate and the sinai subplate on the basis of two gps campaign measurements 6 years apart at 17 sites distributed in israel and jordan complemented by israeli permanent stations we compute the present day deformation across the southern segment of the dead sea transform the wadi araba fault elastic locked fault modeling of fault parallel velocities provides a slip rate of 4 9 1 4 mm a and a best fit locking depth of 12 km this slip rate is slightly higher than previous results based only on israeli permanent gps stations data which are located west of the fault it is in good agreement with results based on offset geomorphologic and geologic features that average longer periods of time 10 ka to 1 ma projection in itrf2000 reference frame allows using our data combined with results published earlier to further study the kinematics between arabia nubia and sinai systematic combination of euler poles available in the literature in addition to our new set of data shows that a wide range of arabia sinai pole positions and angular velocities predict reasonable slip rate on the dead sea fault we highlight uncertainties of calculating such poles due to the small size of the blocks and their slow relative motion along a short and almost straight strand of the transform fault which lead to a large trade off between pole location and angular velocity

late quaternary slip rates and slip partitioning on the alpine fault new zealand abstract published geological data on late quaternary offsets on the alpine fault new zealand have been assembled into a common format and analysed with respect to uncertainties uncertainties arise mainly from measurement of offset features relating apparent offsets to actual fault slip and dating the offset features despite the considerable uncertainties the data form a coherent set consistent with a relatively constant rate of strike slip of 27 5 mm year between milford sound and hokitika this rate represents 70 75 of the fault parallel interplate motion north of the confluence with the hope fault the rate drops substantially dip slip rates on the other hand show considerable variation along strike rising to a maximum of more than 10 mm year in the central section and decreasing to zero at the southern end partitioning of c 25 of the interplate slip on to structures east of the alpine fault occurs in the central section consistent with predictions from critical wedge models the partitioning of all the fault normal component of displacement on to other structures in the south may be related in part to a doubling in width of the deforming wedge to the east most probably however the fault normal displacement is mainly accommodated by underthrusting of the australian plate offshore due to a change in the nature of the crust from continental to oceanic

reconciling viscoelastic models of postseismic and interseismic deformation effects of viscous shear zones and finite length ruptures we have developed a suite of earthquake cycle models for strike slip faults to investigate how finite ruptures and lithosphere scale viscous shear zones affect interseismic deformation in particular we assess whether localized and stationary interseismic deformation and large scale rapidly decaying postseismic transients may be explained with models incorporating either or both of these features models incorporating viscous shear zones give more stationary interseismic deformation than layered half space maxwell viscoelastic models producing similar early postseismic deformation in the near field this tendency is accentuated when the effective viscosity per unit width of the shear zone increases either with depth or with interseismic time models with finite 200 km long ruptures produce time dependent deformation similar to that from models with infinitely long ruptures though with smaller magnitude and somewhat more localized surface velocity fluctuations models incorporating a stiff lithosphere a low viscosity mantle asthenosphere and a crust to lithosphere scale viscous shear zone can replicate postseismic and interseismic deformation typical of large strike slip earthquakes such models require depth dependent power law or transient rheologies for the viscous shear zone material in the crust as long as the effective viscosity per unit shear zone width is approximately 1015 pa s m at crustal depths during the postseismic interval below the moho the shear zone effective viscosity per unit width must be higher throughout the seismic cycle at least over a short depth interval for example if shear zone viscosity per unit width is 5 1016 pa s m in the mantle lithosphere a model with a 50 km thick lithosphere and asthenosphere effective viscosities of 1 to 5 1018 pa s can reproduce reference velocity profiles for both postseismic and later interseismic deformation

time dependent distributed afterslip on and deep below the izmit earthquake rupture surface deformation transients measured with the global positioning system during the 87 days between the 17 august 1999 izmit earthquake and the 12 november 1999 duzce earthquake indicate rapidly decaying aseismic fault slip on and well below the coseismic rupture elastic model inversions for time dependent distributed fault slip using a network inversion filter approach show that afterslip was highest between and below the regions of maximum coseismic slip and propa gated downward to or even below the base of the crust maximum afterslip rates decayed from greater than 2 m yr immediately after the i zmit earthquake to about 1 2 m yr just prior to the duzce earthquake maximum afterslip occurred below the eastern karadere rupture segment and near the i zmit hypocenter afterslip in the upper 16 km decayed more rapidly than that below the seismogenic zone these observations are consistent with a phase of rapid aseismic fault slip concentrated near the base of the seismogenic zone continued loading from the rapid deep afterslip along the eastern rupture zone is a plausible mechanism that helped trigger the nearby mw 7 2 12 november duzce earthquake

rapid slip along the central altyn tagh fault morphochronologic evidence from cherchen he and sulamu tagh consistent with the d 18 o record from the guliya ice cap in the west kunlun the features of interest were all formed by glacial and fluvial processes subsequent to marine isotope stage 5e with the youngest features having formed during the early holocene optimum this near field morphochronological slip rate is averaged over many earthquake cycles and is hence little affected by interseismic strain it is kinematically consistent with other somewhat lower geomorphic slip rate measurements to the east the average rate and lower bounds obtained from alternate interpretational models 18 4 mm yr cannot be reconciled with the most rece geodetic measurements 7 mm yr suggesting that interseismic strain and interactions with adjacent faults may lead to disparate geologic and geodetic rate estimates this late pleistocene holocene morphochronologic rate would imply that at this longitude the altyn tagh fault on the north edge of tibet might absorb almost as much of india s convergence relative to siberia as the himalayan main frontal thrust does on the southern edge of the plateau index terms 1035 geochemistry geochronology 1208 geodesy and gravity crustal movements intraplate 8110 8102 tectonophysics continental contractional orogenic belts 8107 tectonophysics continental neotectonics keywords slip rates cosmogenic dating indo asian collision

evidence of power law flow in the mojave desert mantle studies of the earth s response to large earthquakes can be viewed as large rock deformation experiments in which sudden stress changes induce viscous flow in the lower crust and upper mantle that lead to observable postseismic surface deformation laboratory experiments suggest that viscous flow of deforming hot lithospheric rocks is characterized by a power law in which strain rate is proportional to stress raised to a power n refs 2 3 most geodynamic models of flow in the lower crust and upper mantle however resort to newtonian linear stress strain rate relations here we show that a power law model of viscous flow in the mantle with n 3 5 successfully explains the spatial and temporal evolution of transient surface deformation following the 1992 landers and 1999 hector mine earthquakes in southern california a power law rheology implies that viscosity varies spatially with stress causing localization of strain and varies temporally as stress evolves rendering newtonian models untenable our findings are consistent with laboratory derived flow law parameters for hot and wet olivine the most abundant mineral in the upper mantle and support the contention that at least beneath the mojave desert the upper mantle is weaker than the lower crust

strain accumulation across the carrizo segment of the san andreas fault california impact of laterally varying crustal properties 1 major strike slip faults juxtapose geologically dissimilar terrain which may vary in mechanical properties leading to an asymmetric pattern of strain accumulation we present new gps data on the carrizo segment of the san andreas fault separating the salinian block southwest of the fault from franciscan terrane northeast of the fault to better quantify asymmetric strain accumulation we also present a series of finite element models to investigate the possible role of variable elastic layer thickness and material properties of the upper crust the geodetic data are well fit with a simple model comprising a weak upper crustal zone 10 25 km wide northeast of the fault this model is also consistent with geologic data on the distribution of major rock types and corresponding laboratory data on their material properties as well as paleoseismic seismic and magnetotelluric data using this model we estimate a long term average over several seismic cycles slip rate for the san andreas fault of 36 1 5 2 mm yr in agreement with the known holocene rate within uncertainties and a viscosity for the combined lower crust upper mantle of 2 5 1019 pa s

how do ghost transients from past earthquakes affect gps slip rate estimates on southern california faults 1 in this study we investigate the extent to which viscoelastic velocity perturbations or ghost transients from individual fault segments can affect elastic block model based inferences of fault slip rates from gps velocity fields we focus on the southern california gps velocity field exploring the effects of known large earthquakes for two end member rheological structures our approach is to compute at each gps site the velocity perturbation relative to a cycle average for earthquake cycles on particular fault segments we then correct the scec cmm4 0 velocity field for this perturbation and invert the corrected field for fault slip rates we find that if asthenosphere viscosities are low 3 1018 pa s the current gps velocity field is significantly perturbed by viscoelastic earthquake cycle effects associated with the san andreas fault segment that last ruptured in 1857 mw 7 9 correcting the gps velocity field for this perturbation or ghost transient adds about 5 mm a to the saf slip rate along the mojave and san bernardino segments the gps velocity perturbations due to large earthquakes on the garlock fault most recently events in the early 1600s and the white wolf fault most recently the mw 7 3 1952 kern county earthquake are smaller and do not influence block model inverted fault slip rates this suggests that either the large discrepancy between geodetic and geologic slip rates for the garlock fault is not due to a ghost transient or that un modeled transients from recent mojave earthquakes may influence the gps velocity field

carbon isotope geochemistry of paleozoic oils from big horn basin abstract twenty crude oils from paleozoic reservoirs in the big horn basin wyoming were fractionated into light hydrocarbons saturates monoaromatics diaromatics polyaromatics and polars and asphaltenes amounts and isotopic composition of each fraction were found to be internally consistent with the degree of maturation of the oil confirming the established single source origin for these oils a variation of approximately three per mil in the carbon isotopic composition of the whole oil and individual fraction was explained as being caused by maturation the isotope type curves for these oils the variations in isotopic composition as a function of compound group type were not found to be as simple as commonly believed other alteration processes such as migration and deasphalting might have influenced the pattern of the isotope distributions among fractions the conservative nature of mass balance and subsequent isotope flows among various fractions of crude oil showed that the maturation of crude oil consists of consecutive processes leading from larger and more polar components into smaller and less polar components culminating in natural gas calculations were made to project the amount of condensates associated with the crude oils and the amount of natural gas which had been generated from crude oils of a given maturity

low quaternary slip rate reconciles geodetic and geologic rates along the altyn tagh fault northwestern tibet for more than two decades the slip rate along the active left slip altyn tagh fault of northwestern tibet has been disputed with millennial rates reported to be as much as three times faster than those determined geodetically this problem is significant because the total offset plate boundary length and age of the altyn tagh fault make it the most important single structure accommodating india asia convergence north of the himalayas here we show that the central altyn tagh fault slipped at only 14 9 mm a over the past 4 6 ka by tightly bracketing the age of a displaced fluvial terrace riser at yuemake 88 51 e 38 19 n this result contradicts previous latest quaternary rates and is consistent with those derived from geodetic paleoseismic and geologic measurements and thus resolves the long standing dispute over the latest quaternary slip rate along the longest active strike slip fault in tibet

philippine fault a key for philippine kinematics on the basis of new geologic data and a kinematic analysis we establish a simple kinematic model in which the motion between the philippine sea plate and eurasia is distributed on two boundaries the philippine trench and the philippine fault this model predicts a velocity of 2 to 2 5 cm yr along the fault geologic data from the visayas provide an age of 2 to 4 ma for the fault an age in good agreement with the date of the beginning of subduction in the philippine trench the origin of the philippine fault would thus be the flip of subduction from west to east after the locking of convergence to the west by the collision of the philippine mobile belt with the eurasian margin

a model of the earthquake cycle along the san andreas fault system for the past 1000 years 1 we simulate 1000 years of the earthquake cycle along the san andreas fault system by convolving best estimates of interseismic and coseismic slip with the green s function for a point dislocation in an elastic plate overlying a viscoelastic half space interseismic slip rate is based on long term geological estimates while fault locking depths are derived from horizontal gps measurements coseismic and postseismic deformation is modeled using 70 earthquake ruptures compiled from both historical data and paleoseismic data this time dependent velocity model is compared with 290 present day geodetic velocity vectors to place bounds on elastic plate thickness and viscosity of the underlying substrate best fit models rms residual of 2 46 mm yr require an elastic plate thickness greater than 60 km and a substrate viscosity between 2 1018 and 5 1019 pa s these results highlight the need for vertical velocity measurements developed over long time spans 20 years our numerical models are also used to investigate the 1000 year evolution of coulomb stress stress is largely independent of assumed rheology but is very sensitive to the slip history on each fault segment as expected present day coulomb stress is high along the entire southern san andreas because there have been no major earthquakes over the past 150 300 years animations s1 and s2 of the time evolution of vector displacement and coulomb stress are available as auxiliary material

global positioning system constraints on fault slip rates in southern california and northern baja mexico we use global positioning system gps estimates of horizontal site velocity to constrain slip rates on faults comprising the pacific north america plate boundary in southern california and northern mexico we enlist a simple elastic block model to parameterize the distribution and sum of deformation within and across the plate boundary we estimate a pacific north america relative plate motion rate of 49 3 mm yr one standard deviation consistent with nuvel 1a estimates we are able to resolve robust slip rate estimates for the southernmost san andreas san jacinto and elsinore faults 26 2 9 2 and 6 2 mm yr respectively and for the imperial and cerro prieto faults 35 2 and 42 1 mm yr respectively accounting for about 86 of the total plate motion the remaining 14 appears to be accommodated to the west of these fault systems probably via slip along the san clemente fault and or the san miguel vallecitos rose canyon and newport inglewood fault systems these results are highly consistent with paleoseismic estimates for slip rates implying that off fault strain accumulation within the deforming zone of the plate boundary is largely elastic we estimate that the seismically quiescent southernmost san andreas fault has incurred about 8 2 m of slip deficit over the last few hundred years presumably to be recovered during a future large earthquake

slip rates of the karakorum fault ladakh india determined using cosmic ray exposure dating of debris flows and moraines most recent major glacial advance occurred at 90 15 ka this is consistent with the inference of others that alpine glaciers in this region have not necessarily expanded in concert with northern hemisphere continental ice sheets if features including lateral moraines that liu inferred to have been offset 300 350 m by the karakorum fault date from the same period they too imply a slip rate of 3 4 mm yr 1 this slip rate is comparable to rates of extension across grabens within tibet with recent evidence that slip along the altyn tagh fault occurs at 10 mm yr 1 our rate suggests that slip along the boundaries of tibet is not significantly more rapid than extension within the plateau hence plate tectonics in the strictest sense ought not be applied to tibet because tibet does not behave as a rigid plate index terms 1824 hydrology geomorphology 1625 1035 geochemistry geochronology 9320 information related to geographic region asia 8107 tectonophysics continental neotectonics keywords karakorum fault slip rate cosmic ray exposure age beryllium 10

present tectonic motion across the coast ranges and san andreas fault system in central california geodetic results from very long baseline interferometry vlbi satellite laser ranging slr and the global positioning system gps are used to estimate angular velocities between the sierran microplate pacific plate and north american plate the sierra pacific pole of rotation lies nearer to the san andreas fault than does the pacific north america pole of rotation and leads to different tectonic implications than if the latter is used the angular velocities show that the san andreas fault system and central california coast ranges accommodate motion of 39 2 mm yr mainly by strike slip faulting all confidence limits following signs in this paper are 95 confidence limits fault normal motion is small is mainly convergent at rates up to 3 3 1 0 mm yr and varies along the coast but is divergent at 2 6 1 2 mm yr across san pablo bay and associated topographic lows across which the sierran and central valley watershed drains to the pacific ocean the mountain ranges tend to be larger where the fault normal convergence rates are larger the low convergence rate 0 5 1 8 mm yr normal to the san andreas fault in the carrizo plain differs sharply from that previously inferred 8 2 1 2 mm yr and 4 9 1 6 mm yr by feigl et al 1993 the difference is due to differences between their and our elastic strain accumulation models and between how their and our pacific plate reference frames are defined the ranges in most places require a minimum of 4 2 1 m y of fault normal convergence at the present rate to attain their present cross sectional area if erosion is neglected more if it is not the amount of convergence previously estimated from a balanced cross section across the diablo range in central california requires 10 8 3 m y of convergence at the present rate the former is consistent with widely held views about the onset of the coast range orogeny but the latter is not both are consistent however with the recent plate reconstructions by s cande j stock and colleagues which indicate that pacific plate motion relative to north america changed to a more convergent direction 20 25 clockwise of its prior direction at ca 8 to 6 ma and not at 3 5 ma as had been previously inferred the inferred change in direction of plate motion is large compared with the present angle of convergence across the straight and narrow segment of the san andreas fault of 0 7 4 7 from which we infer that the sierran microplate changed motion relative to north america at the same time ca 8 to 6 ma as did the pacific plate we further infer that the motion accommodated across the great basin must also have changed at the same time we also examine the hypothesis that stable sliding occurs along the san andreas fault and other northwest striking strike slip faults in central california where the fault normal convergence rate is low or negative and that these faults are unstable where the fault normal convergence rate is high such a relationship appears to hold in general but fails in detail in particular there are substantial sections of fault with small inferred rates of fault normal convergence across which the san andreas fault is locked moreover the creeping section of the san andreas fault i e the section between parkfield and the calaveras junction is the locus of greater fault normal convergence 3 2 1 4 mm yr than is the locked part of the fault 0 5 1 8 mm yr south of parkfield thus this hypothesis is at best a partial explanation for the observed distribution of locked and nonlocked sections of the fault

insar observations of low slip rates on the major faults of western tibet two contrasting views of the active deformation of asia dominate the debate about how continents deform i the deformation is primarily localized on major faults separating crustal blocks or ii deformation is distributed throughout the continental lithosphere in the first model western tibet is being extruded eastward between the major faults bounding the region surface displacement measurements across the western tibetan plateau using satellite radar interferometry insar indicate that slip rates on the karakoram and altyn tagh faults are lower than would be expected for the extrusion model and suggest a significant amount of internal deformation in tibet

slip rates and off fault deformation in southern california inferred from gps data and models 1 in southern california fault slip rate estimates along the san andreas fault saf and garlock fault from geodetically constrained kinematic models are systematically at the low end or lower than geologic slip rate estimates the sum of geodetic model slip rates across the eastern california shear zone is higher than the geologic sum however the ranges of reported model and geologic slip rate estimates in the literature are sufficiently large that it remains unclear whether these apparent discrepancies are real or attributable to epistemic uncertainties in the two types of estimates we further examine uncertainties in geodetically derived slip rate estimates on major faults in southern california by conducting a suite of inversions with four kinematic models long term rigid elastic block models constrained by the geologic slip rates cannot fit the present day gps derived velocity field deforming permanent off fault strain elastic block models and viscoelastic earthquake cycle block models constrained by geologic slip rates can fit the present day gps derived velocity field with 28 33 of the total geodetic moment rate occurring as distributed deformation off of the major faults models incorporating viscoelastic mantle flow predict systematically higher slip rates than purely elastic models on many of the major southern california faults with ranges of elastic viscoelastic 29 34 30 37 mm yr for the carrizo saf segment 20 24 20 32 mm yr for the mojave saf segment 14 17 18 22 mm yr for the coachella saf segment 13 19 14 22 mm yr for the san jacinto fault and 5 11 5 11 mm yr for the western garlock fault

the velocity field along the san andreas fault in central and southern california the velocity field within a 100 km broad zone centered on the san andreas fault between the mexican border and san francisco bay has been inferred from repeated surveys of trilateration networks in the 1973 1989 interval the velocity field has the appearance of a shear flow that remains parallel to the local strike of the fault even through such major deflections as the big bend of the san andreas fault in the transverse ranges of southern california across strike profiles of the fault parallel component of velocity exhibit the expected sigmoidal shape whereas across strike profiles of the fault normal component of velocity are flat and featureless no significant convergence upon the fault is observed even along the big bend sector of the fault simple dislocation models can explain most of the features of the observed velocity field but those explanations are not unique about 35 mm yr of relative plate motion is accounted for within the span of the trilateration networks geologic studies indicate that the secular slip rate on the san andreas fault is about 35 mm yr the agreement between these two estimates implies that most of the strain accumulation is elastic and will be recovered in subsequent earthquakes the relative motion observed across the san andreas fault 35 mm yr plus that observed across the eastern california shear zone 8 mm yr accounts for most 43 mm yr of the observed north america pacific relative plate motion 47 mm yr