evidence for an earthquake and tsunami about 3100 3400 yr ago and other catastrophic saltwater inundations recorded in a coastal lagoon new zealand abstract okupe lagoon is 2 02 masl brackish and ponded behind two boulder banks at the northern end of kapiti island new zealand the sediments of the lagoon provide a record of late holocene environmental changes such as tectonic uplift catastrophic saltwater inundation and vegetation change five main events were identified over a 5300 yr record with a sixth representing a re evaluation of previous work an uplift event of 1 5 3 0 m and an associated tsunami are recorded and are inferred to have been caused by a local fault rupture possibly the northern extension of the wairau fault about 3360 40 yr bp two additional tsunami generated by ruptures of either the ohariu or wellington faults 1290 and 1220 ad respectively and either the wellington or alpine faults 1450 ad have been tentatively proposed two catastrophic saltwater inundations csis have also been identified one possibly a tsunami generated by either the wairarapa fault 500 ad or taupo eruption 190 ad the other about 4780 150 yr bp may relate to a local fault rupture however further work is needed to determine whether these are tsunami or storm surge related and they are therefore designated csis the sixth event is the 1855 tsunami recorded from a raised shore platform to the west of okupe lagoon

submarine landforms and shallow acoustic stratigraphy of a 400 km long fjord shelf slope transect kangerlussuaq margin east greenland kangerlussuaq fjord is a relatively uniform steep walled basin whose floor has an almost smooth surface debris is supplied mainly from icebergs from the fast flowing kangerlussuaq glacier sedimentation after iceberg release from multi year sea ice is mainly by rain out of fine grained englacial debris streamlined glacial lineations and drumlins were produced at the sedimentary bed of an ice sheet that expanded into kangerlussuaq trough at the last glacial maximum lgm bedrock channels and crescentic overdeepenings indicate warm based ice and free water beneath parts of the former ice sheet cross cutting iceberg scour marks which characterise outer kangerlussuaq shelf were produced not only during deglaciation but also occasionally through the holocene by deep keeled icebergs from further north in east greenland the outward convex contours of the shelf edge and slope beyond kangerlussuaq trough and debris flows on the slope suggest a glacier influenced high latitude fan the distribution of streamlined subglacial landforms demonstrates that the greenland ice sheet extended throughout kangerlussuaq fjord and reached at least 200 km across the shelf in kangerlussuaq trough at the lgm streamlined landform orientation indicates ice flow from the interior of greenland down the axis of kangerlussuaq trough there is little evidence for discrete sedimentary depocentres in the trough implying that ice probably retreated rapidly from the outer and mid shelf during deglaciation

laboratory earthquakes the sub rayleigh to supershear rupture transition we report on the experimental observation of spontaneously nucleated supershear rupture and on the visualization of sub rayleigh to supershear rupture transitions in frictionally held interfaces the laboratory experiments mimic natural earthquakes the results suggest that under certain conditions supershear rupture propagation can be facilitated during large earthquake events

finite faults and inverse theory with applications to the 1979 imperial valley earthquake abstract using a representation theorem from elastodynamics subsurface slip on a known fault is formulated as the solution to an inverse problem in which recorded surface ground motion is the data two methods of solution are presented the least squares method which minimizes the squared differences between theory and data and the constrained least squares method which simultaneously maintains a set of linear inequalities instabilities in the solution are effectively eliminated in both methods and the sensitivity of the solution to small changes in the data is quantitatively stated the inversion methodology is applied to 77 components of near field ground acceleration recorded during the 15 october 1979 imperial valley earthquake the faulting is constrained to propagate bilaterally away from the epicenter at an average velocity of 90 per cent of the shear wave speed on a vertical fault plane extending from the surface to 10 km depth inequality constraints are used to keep the faulting sequence physically reasonable by maintaining right lateral motion and positive slip velocity the preferred solution is stable and provides a good fit to the data it is also realistic and consistent with observed surface offsets and independent estimates of seismic moment

controls upon the last glacial maximum deglaciation of the northern uummannaq ice stream system west greenland the uummannaq ice stream system uiss was a convergent cross shelf ice stream system that operated in west greenland during the last glacial maximum lgm this paper presents new evidence constraining the geometry and evolution of the northern sector of the uiss and considers the factors controlling its dynamic behaviour geomorphological mapping 21 new terrestrial cosmogenic nuclide tcn exposure ages and radiocarbon dating constrain lgm warm based ice stream activity in the north of the system up to 1400 m a s l intervening plateaux areas either remained ice free or were covered by cold based icefields beyond the inner fjords topography and bathymetry forced ice flow southwards into the uummannaq trough where it coalesced with ice from the south and formed the trunk zone of the uiss deglaciation of the uiss began at 14 9 cal ka bp rapid retreat from the lgm limit was forced by an increase in air temperatures and rising sea level enhanced by the bathymetric over deepening of the uummannaq and igdlorssuit sund troughs ice reached the inner fjord confines in the northern uummannaq area by 11 6 ka and experienced an ice marginal stabilisation in rink karrat fjord for up to 5 ka this was a function of topographic constriction and bathymetric shallowing and occurred despite continued climatic forcing in the neighbouring ingia fjord this did not occur following this period of stability ice within rink karrat fjord retreated reaching the present ice margin or beyond after 5 ka the presence of a major ice stream within a mid fjord setting during the mid holocene and the holocene thermal maximum 11 5 ka is in direct contrast to records of other ice streams throughout west greenland which suggest ice had retreated beyond its present margin by 9 7 ka this demonstrates the potential importance of topographic control on calving margin stability and its ability to override climatic forcing

photo acoustic study of subshear and supershear ruptures in the laboratory abstract we report supershear ruptures observed in spontaneously nucleating laboratory microearthquakes and describe the signature of the associated mach wavefront radiation transducers detect the wavefield both close and at a distance from the fault the rupture velocities are inferred from either photoelastic high speed imaging or using the acoustic recordings both methods yield compatible estimates of sufficient accuracy to discriminate between sub shear and supershear ruptures the acoustic records allow to characterize the mach wavefront radiated from the supershear rupture front in particular its amplitude and decay velocity functions recovered by integrating high frequency accelerometer signals in the case of supershear ruptures consist in a double pulse function a first pulse traveling at supershear velocity followed by a second pulse traveling at the rayleigh wave velocity conversely the sub shear event is characterized by a single pulse finally we perform numerical simulations of our experiment using a prescribed supershear rupture velocity the synthetic waveforms obtained from these simulations including the mach wave amplitude and phase yield a satisfactory fit to the experimental results

variability of kinematic source parameters and its implication on the choice of the design scenario abstract near fault seismic recordings for recent earthquakes chi chi earthquake 1999 and parkfield earthquake 2004 show the high spatial heterogeneity of ground motion this variability is controlled by fault geometry rupture complexity and also by wave propagation and site effects nowadays the number of available records in the near source region is still not enough to infer a robust parameterization of the ground motion and to retrieve multiparametric predictive equations valid at close distances from the fault the use of a synthetic approach may help to overcome this limitation and to study the strong ground motion variability in this article we focus on ground motion dependence on different earthquakes breaking the same fault as it has been rarely recorded by instruments we model seismic scenarios from different rupture models of a fault similar to the 1980 irpinia italy earthquake source m w 6 9 a discrete wavenumber finite element technique is used to compute full wave displacement and velocity time series in the low frequency band up to 2 hz we investigate the variability of the ground motion as a function of different source parameters rupture velocity slip distribution nucleation point and source time function whose values depend on the state of knowledge of the physical model driving the process the probability density functions of the simulated ground motion parameters such as displacement response spectrum and peak ground velocity are used to identify particular scenarios that match specific engineering requests

modelling instantaneous dynamic triggering in a 3 d fault system application to the 2000 june south iceland seismic sequence summary we present a model of seismogenesis on an extended 3 d fault subject to the external perturba tions of coseismic stress changes due to an earthquake occurring on another fault the causative fault as an application we consider the spatio temporal stress redistribution produced on the hvalhnukur fault by the m s 6 6 2000 june 17 mainshock in the south iceland seismic zone sisz the latter is located nearly 64 km from the causative fault and failed 26 s after the main shock with an estimated magnitude m w 5 25 0 25 providing an example of instantaneous dynamic triggering the stress perturbations are computed by means of a discrete wavenumber and reflectivity code the response of the perturbed fault is then analysed solving the truly 3 d fully dynamic or spontaneous problem accounting for crustal stratification in a previous study the response of the hvalhnukur fault was analysed by using a spring slider fault model ss fault model comparing the estimated perturbed failure time with the observed origin time in addition to the perturbed failure time this model can provide numerical estimates of many other dynamic features of the triggered event which can be compared with available observations the rupture history of the whole fault plane its final extent and the seismic mo ment of the induced event we show the key differences existing between a mass spring model and this extended fault model in particular we show the essential role of the load exerted by the neighbouring slipping points of the fault by considering both rate and state dependent laws and non linear slip dependent law we show how the dynamics of the 26 s fault strongly depend on the assumed constitutive law and initial stress conditions in the case of rate and state dependent friction laws assuming an initial effective normal stress distribution that is suitable for the sisz and consistent with previously stated conditions of instantaneous dynamic triggering of the hvalhnukur fault we obtain results in general agreement with observations

spontaneous dynamic rupture propagation beyond fault discontinuities effect of thermal pressurization abstract a range of several fault segments often sequentially ruptures during an earthquake we investigated the effects of thermal pressurization tp on dynamic rupture propagation beyond fault discontinuities by simulating spontaneous rupture propagation on two vertical strike slip fault segments we revealed that a rupture can jump wider stepovers owing to tp and that tp on a primary nucleating fault enables a rupture to jump at deep portions in previous numerical studies on dry fault systems it was found that a rupture sometimes fails to propagate to an unconnected fault which is observed in the case of real earthquakes and a rupture that successfully propagates is usually triggered near the surface of the earth unlike rupture evolution images obtained by seismic waveform modeling tp can explain the inconsistencies between the previous numerical simulations and the observations without depending on the heterogeneity of the initial stress and or friction under depth dependent stress we showed that tp enables a rupture to jump much wider stepovers at deep portions if tp is in effect on faults hydraulic diffusivity along with fault geometry can strongly control the characteristics of rupture propagation at fault discontinuities

new constraints on greenland ice sheet dynamics during the last glacial cycle evidence from the uummannaq ice stream system this paper presents the first assessment of the uummannaq ice stream system uiss in west greenland the uiss drained 6 of the greenland ice sheet gris at the last glacial maximum lgm the onset of the uiss is a function of a convergent network of fjords which feed a geologically controlled trough system running offshore to the shelf break mapping cosmogenic radiogenic nuclide crn dating and model output reveal that glacially scoured surfaces up to 1266 m above sea level asl in fjord head areas were produced by warm based ice moving offshore during the lgm with the elevation of warm based ice dropping westwards to 700 m asl as the ice stream trunk zone developed marginal plateaux with allochthonous blockfields suggest that warm based ice produced till and erratics up to 1200 m asl but crn ages and weathering pits suggest this was pre lgm with only cold based ice operating during the lgm deglaciation began on the outer shelf at 14 8 cal kyrs b p with ubekendt ejland becoming ice free at 12 4 ka the uiss then collapsed with over 100 km of retreat by 11 4 ka 10 8 cal kyrs b p a rapid and complex response to bathymetric deepening trough widening and sea level rise coinciding with rapidly increasing air temperatures and solar radiation but which occurred prior to ocean warming at 8 4 cal kyrs b p local fjord constriction temporarily stabilized the unzipped uiss margins at the start of the holocene before ice retreat inland of the current margin at 8 7 ka

the mechanics of lubricated faults insights from 3 d numerical models 1 the weakening mechanisms occurring during an earthquake failure are of prominent importance in determining the resulting energy release and the seismic waves excitation in this paper we consider the fully dynamic response of a seismogenic structure where lubrication processes take place in particular we numerically model the spontaneous propagation of a 3 d rupture in a fault zone where the frictional resistance is controlled by the properties of a low viscosity slurry formed by gouge particles and fluids this model allows for the description of the fault motion in the extreme case of vanishing effective normal stress by considering a viscous fault response and therefore without the need to invoke in the framework of coulomb friction the generation of the tensile mode of fracture we explore the effects of the parameters controlling the resulting governing law for such a lubricated fault the viscosity of the slurry the roughness of the fault surfaces and the thickness of the slurry film our results indicate that lubricated faults produce a nearly complete stress drop i e a very low residual friction coefficient 0 01 a high fracture energy density eg few 10s of mj m2 and significant slip velocities vpeak few 10s of m s the resulting values of the equivalent characteristic slip weakening distance d0eq 0 1 0 8 m depending on the adopted parameters are compatible with the seismological inferences moreover in the framework of our model we found that supershear ruptures are highly favored in the case of enlarging gap height we can have the healing of slip or even the inhibition of the rupture quantitative comparisons with different weakening mechanisms previously proposed in the literature such as the exponential weakening and the frictional melting are also discussed

how fast is rupture during an earthquake new insights from the 1999 turkey earthquakes we report that during the two devastating 1999 earthquakes in turkey rupture propagated over a large part of the nearly 200km long fault zone at supershear speed approaching 5km s we present observations and modeling which confirm the original inference of supershear rupture during the izmit earthquake and we show that supershear rupture also occurred during the duzce earthquake we show that the rupture velocity measured about 2 times the shear wave velocity is the value predicted by theoretical studies in fracture dynamics we look for clues to explain these observations

the role of lateral drag in the dynamics of ice stream b antarctica the partitioning of resistive force between the bed and sides of ice stream b antarctica is obtained for three large areas that have been measured using repeat aerial photogrammetry problems associated with data errors and local variations in ice strength and velocity are reduced by considering the areally averaged budget of forces for each photo block results indicate that the bed under ice stream b must be very weak and unable to provide muche resistance mechanical control on this ice stream emanates almost entirely from the lateral margins

direct observation of rupture propagation during the 1979 imperial valley earthquake using a short baseline accelerometer array abstract the 1979 imperial valley california earthquake m s 6 9 was recorded on the el centro differential array a 213 m long linear array of 5 three component digital accelerometers 5 6 km from the nearest tectonic surface rupture although absolute time was not recorded on the array elements a relative time base was established using the main shock hypocentral p wave and the p and s waves from a later aftershock a cross correlation technique was used to measure the difference in arrival times of individual seismic waves in a moving 0 6 to 1 2 sec window at each array element which would then be converted into the wave9s slowness 1 velocity along the array when applied to the main shock vertical and horizontal accelerograms results from both components of motion indicated that the early arriving energy came from a source to the south of the array and the source of the energy moved rapidly to the north of the array during the strong shaking the ground motions at the array elements were well correlated for about the first 11 sec of motion these observations suggest that we have observed the initiation of rupture south of the array and its subsequent propagation along the fault to a position north of the array in about 10 sec and that the energy was radiated from a fairly compact region around the rupture front if the observed vertical and horizontal ground motions are assumed to be caused by p and s waves respectively then the observed slownesses show irregularities which can be interpreted as implying that the observed high frequency ground motions originated at irregularly distributed regions on the fault surface or that the rupture velocity was variable or both one possible interpretation of the data suggests that the rupture proceeded at near p wave velocity over a 7 km long section of fault average rupture velocities of about 2 7 to 3 2 km sec at 8 km depth are consistent with the data and 2 8 km sec is weakly preferred under the assumption that rupture propagates at a fixed fraction of the shear velocity the large vertical pulse which had a peak acceleration of 1 7 g at e06 was emitted from the portion of the fault extending 25 to 30 km northwest of the hypocenter near meloland overpass and not from the point on the fault closest to the differential array nothing can be said about fault behavior southeast of the hypocenter

finite difference simulations of seismic scattering implications for the propagation of short period seismic waves in the crust and models of crustal heterogeneity synthetic seismograms produced by the finite difference method are used to study the scattering of elastic and acoustic waves in two dimensional media with random spatial variations in seismic velocity the results of this study provide important insights about the propagation of short period 5 the self similar medium is characterized by a scattering q that is constant with frequency whereas theory predicts that the apparent q in an exponential medium is proportional to frequency these alternative models of crustal heterogeneity can thus be tested by improved measurements of the frequency dependence of crustal q at frequencies greater than about 1 hz assuming that scattering is responsible for most of the attenuation at these frequencies measurements of the time decay of the synthetic coda waves clearly show that the single scattering model of coda decay is not appropriate in the presence of moderate amounts of scattering attenuation scattering q 200 in these cases q values derived from the coda decay rate using the single scattering theory do not correspond to the transmission q of the medium the cross correlation of synthetic waveforms observed for an array of receivers along the free surface is observed to be dependent on the correlation distance of the medium the self similar random medium proposed here for the crust produces waveform variations at high frequencies 15 30 hz similar to those reported for actual small scale seismic arrays with apertures of hundreds of meters

supershear mach waves expose the fault breakdown slip abstract mikumo et al 2003 showed that it is possible to estimate the breakdown slip dc as the slip at the time of the peak slip rate for rupture propagation with subshear speeds cruz atienza et al 2009 later attempted to extend this method to extract information about dc as the displacement at the time of the peak particle velocity from seismic strong motion records however a reasonably accurate estimate of dc was only possible in a narrow zone adjacent to the fault typically on the order of hundreds of meters due to the fast decay with distance from the fault of the seismic energy related to the stress breakdown process when the rupture propagates with supershear speeds on the other hand this energy is carried much farther away from the fault by mach waves in particular rayleigh mach waves when rupture reaches the earth s surface dunham and bhat 2008 here we present a new approach to estimate dc from strong motion records containing mach waves first we show that the method by mikumo et al is valid for supershear rupture propagation this method is then used to estimate dc via an asymptotic approximation of the slip and slip rate time histories from the mach waves using spontaneous rupture simulations we demonstrate that for a visco elastic half space model dc can be estimated within an error of 40 from mach waves that have propagated a distance of at least 3 km from the fault the method is applied to estimate dc for the 2002 mw7 9 denali alaska earthquake 1 5 m and for the 1999 mw7 6 izmit turkey earthquake 1 7 m

a spatial random field model to characterize complexity in earthquake slip 1 finite fault source inversions reveal the spatial complexity of earthquake slip over the fault plane we develop a stochastic characterization of earthquake slip complexity based on published finite source rupture models in which we model the distribution of slip as a spatial random field the model most consistent with the data follows a von karman autocorrelation function acf for which the correlation lengths a increase with source dimension for earthquakes with large fault aspect ratios we observe substantial differences of the correlation length in the along strike a x and downdip a z directions increasing correlation length with increasing magnitude can be understood using concepts of dynamic rupture propagation the power spectrum of the slip distribution can also be well described with a power law decay i e a fractal distribution in which the fractal dimension d remains scale invariant with a median value d 2 29 0 23 while the comer wave number k c which is inversely proportional to source size decreases with earthquake magnitude accounting for larger slip patches for large magnitude events our stochastic slip model can be used to generate realizations of scenario earthquakes for near source ground motion simulations

coherence of mach fronts during heterogeneous supershear earthquake rupture propagation simulations and comparison with observations 1 we study how heterogeneous rupture propagation affects the coherence of shear and rayleigh mach wavefronts radiated by supershear earthquakes we address this question using numerical simulations of ruptures on a planar vertical strike slip fault embedded in a three dimensional homogeneous linear elastic half space ruptures propagate spontaneously in accordance with a linear slip weakening friction law through both homogeneous and heterogeneous initial shear stress fields in the 3 d homogeneous case rupture fronts are curved owing to interactions with the free surface and the finite fault width however this curvature does not greatly diminish the coherence of mach fronts relative to cases in which the rupture front is constrained to be straight as studied by dunham and bhat 2008a introducing heterogeneity in the initial shear stress distribution causes ruptures to propagate at speeds that locally fluctuate above and below the shear wave speed calculations of the fourier amplitude spectra fas of ground velocity time histories corroborate the kinematic results of bizzarri and spudich 2008a 1 the ground motion of a supershear rupture is richer in high frequency with respect to a subshear one 2 when a mach pulse is present its high frequency content overwhelms that arising from stress heterogeneity present numerical experiments indicate that a mach pulse causes approximately an 1 7 high frequency falloff in the fas of ground displacement moreover within the context of the employed representation of heterogeneities and over the range of parameter space that is accessible with current computational resources our simulations suggest that while heterogeneities reduce peak ground velocity and diminish the coherence of the mach fronts ground motion at stations experiencing mach pulses should be richer in high frequencies compared to stations without mach pulses in contrast to the foregoing theoretical results we find no average elevation of 5 damped absolute response spectral accelerations sa in the period band 0 05 0 4 s observed at stations that presumably experienced mach pulses during the 1979 imperial valley 1999 kocaeli and 2002 denali fault earthquakes compared to sa observed at non mach pulse stations in the same earthquakes a 20 amplification of short period sa is seen only at a few of the imperial valley stations closest to the fault this lack of elevated sa suggests that either mach pulses in real earthquakes are even more incoherent that in our simulations or that mach pulses are vulnerable to attenuation through nonlinear soil response in any case this result might imply that current engineering models of high frequency earthquake ground motions do not need to be modified by more than 20 close to the fault to account for mach pulses provided that the existing data are adequately representative of ground motions from supershear earthquakes

does a damaged fault zone mitigate the near field impact of supershear earthquakes application to the 2018 7 5 palu indonesia earthquake the impact of earthquakes can be severely aggravated by cascading secondary hazards the 2018 m w 7 5 palu indonesia earthquake led to devastating tsunamis and landslides while triggered submarine landslides possibly contributed substantially to generate the tsunami the rupture was supershear over most of its length but its speed was unexpectedly slow for a supershear event between the wave velocity v s and eshelby s speed 2v s an unstable speed range in conventional theory here we investigate whether dynamic rupture models including a low velocity fault zone can reproduce such a steady supershear rupture with a relatively low speed we then examine numerically how this peculiar feature of the palu earthquake could have affected the near field ground motion and thus the secondary hazards our findings suggest that the presence of a low velocity fault zone can explain the unexpected rupture speed and may have mitigated the near field ground motion and the induced landslides in palu

evidence of instantaneous dynamic triggering during the seismic sequence of year 2000 in south iceland 1 we analyze the coseismic stress perturbation during the 17 june 2000 south iceland seismic sequence the main shock ms 6 6 was followed by three large events within a few tens of seconds 8 26 and 30 s located within 80 km the aim of this paper is to investigate short term fault interaction and instantaneous triggering this happens when a fault perturbed by a stress change fails before the end of the transient stress perturbation we compute the shear normal and coulomb stress changes as functions of time in a stratified elastic half space by using discrete wave number and reflectivity methods we calculate dynamic stresses caused by the main shock at the hypocenters of these three subsequent events our numerical results show that the onset of the last two events is slightly delayed with respect to the arrival time of the second positive peak of coulomb stress variation while the first event occurred after the first positive stress peak we have also analyzed the response of a spring slider system representing a fault governed by a rate and state dependent friction law perturbed by shear and normal stress variations caused by the main shock the fault response to the computed stress perturbations is always clock advanced we have found suitable constitutive parameters of the modeled fault that allow the instantaneous dynamic triggering of these three earthquakes if the initial sliding velocity is comparable with the tectonic loading velocity we obtained failure times close to the observed origin times for low values of the initial effective normal stress

supershear rupture of the 5 january 2013 craig alaska mw 7 5 earthquake supershear rupture in which a fracture s crack tip expansion velocity exceeds the elastic shear wave velocity has been extensively investigated theoretically and experimentally and previously inferred from seismic wave observations for six continental strike slip earthquakes we find extensive evidence of supershear rupture expansion of an oceanic interplate earthquake the 5 january 2013 mw 7 5 craig alaska earthquake this asymmetric bilateral strike slip rupture occurred on the queen charlotte fault offshore of southeastern alaska observations of first arriving sn and sg shear waves originating from positions on the fault closer than the hypocenter for several regional seismic stations with path calibrations provided by an empirical green s function approach indicate a supershear rupture process several waveform inversion and modeling techniques were further applied to determine the rupture velocity and space time distribution of slip using regional seismic and geodetic observations both theoretical and empirical green s functions were used in the analyses with all results being consistent with a rupture velocity of 5 5 to 6 km s exceeding the crustal and upper mantle s wave velocity and approaching the crustal p wave velocity supershear rupture occurred along 100 km of the northern portion of the rupture zone but not along the shorter southern rupture extension the direction in which supershear rupture developed may be related to the strong material contrast across the continental oceanic plate boundary as predicted theoretically and experimentally the shear and surface wave mach waves involve strongly enhanced ground motions at azimuths oblique to the rupture direction emphasizing the enhanced hazard posed by supershear rupture of large strike slip earthquakes

on the deterministic description of earthquakes 1 the quantitative estimate of earthquake damage due to ground shaking is of pivotal importance in geosciences and its knowledge should hopefully lead to the formulation of improved strategies for seismic hazard assessment numerical models of the processes occurring during seismogenic faulting represent a powerful tool to explore realistic scenarios that are often far from being fully reproduced in laboratory experiments because of intrinsic technical limitations in this paper we discuss the prominent role of the fault governing model which describes the behavior of the fault traction during a dynamic slip failure and accounts for the different and potentially competing chemical and physical dissipative mechanisms we show in a comprehensive sketch the large number of constitutive models adopted in dynamic modeling of seismic events and we emphasize their prominent features limitations and specific advantages in a quantitative comparison we show through numerical simulations that spontaneous dynamic ruptures obeying the idealized linear slip weakening sw equation and a more elaborated rate and state dependent friction law produce very similar results in terms of rupture times peaks slip velocity developed slip and stress drops provided that the frictional parameters are adequately comparable and more importantly that the fracture energy density is the same our numerical experiments also illustrate that the different models predict fault slip velocity time histories characterized by a similar frequency content a feeble predominance of high frequencies in the sw case emerges in the frequency ranges 0 3 1 and 11 50 hz these simulations clearly indicate that even forgiving the frequency band limitation it would be very difficult virtually impossible to discriminate between two different but energetically identical constitutive models on the basis of the seismograms recorded after a natural earthquake

the 14 november 2001 kokoxili tibet earthquake high frequency seismic radiation originating from the transitions between sub rayleigh and supershear rupture velocity regimes seismic array based analysis of the major kokoxili earthquake tibet 14 november 2001 yields an unambiguous reconstruction of the seismic rupture history and relates it to the generated seismic radiation we demonstrate that after a classical sub rayleigh velocity stage the rupture speed has jumped to supershear values close to compressional wave velocity over a 175 km long fault segment before abruptly slowing down in the late part of the earthquake the transition locations between these three phases are correlated with the fault geometry and are associated with the most energetic radiation this observation proves that the rupture velocity changes as theoretically predicted are a primary source of high frequency seismic radiation this result requires reconsidering the origins of seismic damage generally attributed to slip variations

response of a marine terminating greenland outlet glacier to abrupt cooling 8200 and 9300 years ago greenland s largest outlet glacier using 10 be surface exposure ages and 14 c dated lake sediments our chronology of ice margin change demonstrates that jakobshavn isbrae advanced to deposit moraines in response to abrupt cooling recorded in central greenland ice cores ca 8 200 and 9 300 years ago while the rapid dynamically aided retreat of many greenland outlet glaciers in response to warming is well documented these results indicate that marine terminating outlet glaciers are also able to respond quickly to cooling we suggest that short lag times of high ice flux margins enable a greater magnitude response of marine terminating outlets to abrupt

progression of spontaneous in plane shear faults from sub rayleigh to compressional wave rupture speeds we investigate numerically the passage of spontaneous dynamic in plane shear ruptures from initiation to their final rupture speed using very fine grids by carrying out more than 120 simulations we identify two different mechanisms controlling supershear transition for relatively weaker faults the rupture speed always passes smoothly and continuously through the range of speeds between the rayleigh and shear wave speeds the formerly considered forbidden zone of rupture speeds this however occurs in a very short time before the ruptures reach the compressional wave speed the very short time spent in this range of speeds may explain why a jump over these speeds was seen in some earlier numerical and experimental studies and confirms that this speed range is an unstable range as predicted analytically for steady state singular cracks on the other hand for relatively stronger faults we find that a daughter rupture is initiated by the main mother rupture ahead of it the mother rupture continues to propagate at sub rayleigh speed and eventually merges with the daughter rupture whose speed jumps over the rayleigh to shear wave speed range we find that this daughter rupture is essentially a pseudorupture in that the two sides of the fault are already separated but the rupture has negligible slip and slip velocity after the mother rupture merges with it the slip the slip velocity and the rupture speed become dominated by those of the mother rupture the results are independent of grid sizes and of methods used to nucleate the initial rupture

kinematic inversion of the 2004 m 6 0 parkfield earthquake including an approximation to site effects the 2004 m 6 0 parkfield earthquake yielded one of the largest amounts of near source strong ground motion seismic data ever we invert strong motion seismograms to obtain a model for the space time distribution of coseismic slip on the fault to reduce noise in the inversion we take into account local amplifications that affect each station by using records of the 1983 m 6 5 coalinga earthquake site amplification correlates well with large peak ground velocities registered during the 2004 parkfield mainshock the inversion for a kinematic rupture model yields a nonunique solution we therefore analyze various rupture models that explain the data equally well our preferred rupture model identifies a primary zone of high slip surrounding the hypocenter where the maximum slip is 57 cm a secondary slip area over which contours are not well resolved is located northwest of the hypo center the rupture speed is highly heterogeneous we infer an average rupture ve locity of 2 8 km sec close to the hypocenter and of 3 3 km sec in the secondary region of large slip to the northwest of the hypocenter by correlation of our rupture model with both microseismicity and velocity structure we identify six patches on the fault plane that behave in seismically distinct ways online material kinematic rupture model parameters

earthquake triggering by static and dynamic stress changes 1 in this study we aim to understand the effect of static and dynamic stress changes in promoting earthquake failures on secondary faults toward this goal we solve the equation of motion of a spring slider dynamic system including inertia and using rate and state dependent constitutive laws we separately investigate the dynamic response of this fault analog system to a sudden stress change represented either as a stress step or as a stress pulse which are used to model permanent static and transient dynamic stress perturbations the induced earthquake failure does not occur immediately at the application of the coseismic stress change but it is delayed in time we define this time interval as the triggering delay for a given stress perturbation we analyze the dependence of triggering delays on different system conditions and constitutive parameters our results clearly show that the effects of static and dynamic stress changes are quite different while a static stress change is able to advance as well as to delay an induced instability depending on its sign a dynamic stress pulse is only able to promote a nearly instantaneous failure provided its amplitude is positive and large enough with respect to the direct effect of friction in other words dynamic stress changes can only cause nearly instantaneous failures without any relevant triggering delay these results should be considered in interpreting the seismicity rate changes caused by large earthquakes at least as long as seismic events are interpreted as sliding instabilities obeying rate and state dependent friction laws

a new asymptotic method for the modeling of near field accelerograms we study high frequency radiation from a dislocation model of rupture propagation at the earthquake source we demonstrate that in this case all the radiation emanates from the rupture front and by a change of variables that at any instant of time the high frequency waves reaching an observer come from a line on the fault plane that we call isochrone an asymptotic approximation to near source velocity and acceleration is obtained that involves a simple integration along the isochrones for every time step it is shown that wave front discontinuities critical or stopping phases are radiated every time an isochrone becomes tangent to a barrier this leads to what we call the critical ray approximation which is given in a closed form the previous results are compared with discrete wavenumber synthetics obtained by bouchon 1982 for the gilroy 6 recording of the coyote lake earthquake of 1980 the fit between the asymptotic and full numerical method is extremely good the critical ray approximation permits the identification of different phases in bouchon s synthetics and the prediction of the behavior of the signal in the vicinity of their arrival time

three dimensional spontaneous rupture propagation and implications for the earthquake source mechanism summary we consider spontaneous cracks spreading out areally over a fault plane in an infinite medium as a realistic earthquake source model the boundary integral equation technique described in das is used to determine the displacements and stresses everywhere on the crack plane for faults spreading out symmetrically in all four quadrants over infinite planes of constant yield strength we find that the terminal rupture velocity viiicr in the direction of purely anti plane rupture is given by viiicr in the purely in plane direction of rupture propagation we find the terminal rupture velocity viicr to be given by viicr or viicr 0 5 depending on the yield strength we also find that crack propagation in the purely antiplane direction does not influence crack propagation in the purely in plane direction and vice versa for infinitely long shear cracks of finite width the slip at a point is found to grow more slowly after the arrival of a shear wave diffracted from the nearer crack edge the slip virtually ceases after the shear arrival from the further crack edge this implies that for such faults the slip is controlled by the fault width for a rectangular fault in an infinite medium our final dynamic solution is in closer agreement with the static elliptical crack solution of eshelby than with the static rectangular dislocation model solution of chinnery we find the relationship between the average slip and average dynamic stress drop e on such a rectangular fault of half width w to be e c w where c 0 7 the slip at an interior point is again controlled by the fault width for faults that are much longer than wide so that the slip may stop in the region where the fault initiated before the completion of the rupture process this implies that two rectangular faults of varying lengths but of the same width have the same slip for the same average stress drop a fact clearly contradicted by observations that fault slip increases with earthquake size for great earthquakes occurring along the same fault this contradiction is resolved if stress drops are also bigger for bigger earthquakes

analysis of strong motion s wave polarization of the 15 october 1979 imperial valley earthquake abstract this article illustrates the use of near source s wave polarization analyses for constraining some rupture parameters of large earthquakes in the particular case of the 1979 imperial valley mainshock the ten sma1 strong motion records closest to the source have been studied in the 1 to 3 hz frequency range the records were first corrected following the analysis of zollo and bernard 1989 from some anisotropy that produced strong s splitting at a few sites the rotation of the s polarization with time at most of the sites was then interpreted in terms of the northwestward propagation of the rupture we assumed a constant focal mechanism on the fault plane vertical strike slip the polarization data and the absolute times at some stations allowed the identification of a set of subsources their location in space and time assuming a depth of 8 km provided a mean rupture velocity of 3 1 km sec 0 25 km sec i e 90 of the shear velocity the high frequency radiation 3 hz during most of the rupture thus is very likely to have been generated about 1 sec before the beginning of the low frequency radiation 0 5 to 1 hz studied by archuleta 1984 the final rupture model fits the s polarization history well at most sites it also constrains the anisotropy characteristics of the sediments under some sites in particular em0 where it is consistent with the alignment of vertical cracks in the ns stress field applying such a method to other earthquakes requires a careful selection of the distance and frequency range in particular the effect of perhaps pervasive ubiquitous anisotropy in the upper crust must be taken into account which may require the analysis of aftershock records at the same sites

the effect of thermal pressurization on dynamic fault branching s u m m a r y we numerically investigate the effect of thermal pressurization tp on fault branch behaviour during dynamic rupture propagation a situation likely to occur during large earthquakes at subduction interfaces we consider a 2 d mode ii in plane rupture in an infinite medium that propagates spontaneously along a planar main fault and encounters an intersection with a pre existing branching fault the fault system is subjected to uniform external stresses we adopt the values used by kame et al we use the 2 d boundary integral equation method and the slip weakening friction law with a coulomb failure criterion allowing the effective normal stress to vary as pore pressure changes due to tp we reveal that tp can alter rupture propagation paths when the dip angle of the main fault is small the rupture propagation paths depend on the branching angle when tp is not in effect on either of the faults as described by kame et al however the dynamic rupture processes are controlled more by tp than by the branching angle when tp is in effect on the main fault only the rupture propagates along the main fault it propagates along the branch when tp is in effect on both faults finally we considered the case where there is a free surface above the branch fault system in this case the rupture can propagate along both faults because of interaction between the free surface and the branch fault in addition to tp on the main fault

what can physical source models tell us about the recurrence time of earthquakes abstract earthquake prediction no matter what the timescale has been and continues to be a contentious subject and it is indubitably a prominent challenge for modern seismology and earthquake physics indeed few natural events can have the catastrophic consequences of earthquakes earthquakes today account for about 60 of natural fatalities a physical description of an earthquake represents an amenable approach to the prediction but it suffers of some limitations basically due to the notorious ignorance about the initial state of a given fault and about the physical law controlling its traction evolution independent on those intrinsic epistemic limitations the concept of the earthquake recurrence based upon the idea of the cyclic or characteristic earthquake has been often invoked to describe and thus to predict subsequent instability events on a seismogenic structure in this paper by using the simplest analog fault model the one degree of freedom mass spring system we quantitatively show that the concepts of the recurrence time and the earthquake cycle have limitations even making them meaningless we will discuss in a compendious synopsis all the possible physical mechanisms which can dramatically affect the recurrence time our conclusions emphasize again that the competing mechanisms potentially occurring during faulting even in the simplest and idealized condition of an isolated fault can significantly complicate the regular cyclicity of earthquakes predicted by the analog fault system these conclusions can contribute to the debate about the role of the physical modeling of earthquakes in the contest of seismic hazard assessment

rapid early holocene ice retreat in west greenland abstract the possible demise of the greenland ice sheet and its effect on global sea level rank among the most serious climate threats to society to improve our knowledge about the future behaviour of the ice margin we studied the ice sheet s response to early holocene warming in west greenland using 47 cosmogenic 10 be exposure ages 26 optically stimulated luminescence ages as well as 15 new and 28 previously published radiocarbon ages paired bedrock and boulder ages show that the entire area was covered by warm based ice during the last glacial maximum lgm although glacial erosion was insufficient to completely remove the upper rock surface containing 10 be inherited from a previous period of exposure in bedrock samples above an elevation of 800 m our compilation of 10 be and 14 c ages demonstrates that the ice sheet retreated from the outer coast to the present ice margin between c 11 4 and 10 4 cal ka bp in the godthabsfjord system and between 10 7 0 6 and 10 1 0 4 ka ago in buksefjord whereas the coast at sermilik became ice free at c 10 5 cal ka bp we find no significant changes in the retreat rates between the deep godthabsfjord system and the buksefjord sermilik region which is characterized by only a few narrow and shallow fjords however deglaciation was initiated c 700 900 years earlier in the godthabsfjord system indicating that the deep fjords probably triggered land based deglaciation by dynamic ice loss leading to an overall rapid early holocene ice retreat and drawdown of the ice sheet in west greenland these results demonstrate that even if there was a topographic control on the onset of deglaciation fast ice retreat is not restricted to deep fjord systems but may occur independently of the topographic setting

evidence for and implications of self healing pulses of slip in earthquake rupture dislocation time histories of models derived from waveforms of seven earthquakes are discussed in each model dislocation rise times the duration of slip for a given point on the fault are found to be short compared to the overall duration of the earthquake 10 however in many crack like numerical models of dynamic rupture the slip duration at a given point is comparable to the overall duration of the rupture i e slip at a given point continues until information is received that the rupture has stopped propagating alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are 1 the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes 2 earthquakes are composed of a sequence of small dimension short duration events that are separated by locked regions barriers 3 rupture occurs in a narrow self healing pulse of slip that travels along the fault surface evidence is discussed that suggests that slip durations are indeed short and that the self healing slip pulse model is the most appropriate explanation a qualitative model is presented that produces self healing slip pulses the key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity the model has the following features high static strength of materials kilobar range low static stress drops in the range of tens of bars and relatively low frictional stress during slip less than several hundreds of bars it is suggested that the reason that the average dislocation scales with fault length is because large amplitude slip pulses are difficult to stop and hence tend to propagate large distances this model may explain why seismicity and ambient stress are low along fault segments that have experienced large earthquakes it also qualitatively explains why the recurrence time for large earthquakes may be irregular

a constitutive scaling law and a unified comprehension for frictional slip failure shear fracture of intact rock and earthquake rupture 1 it is widely recognized that some of the physical quantities inherent in a rupture are scale dependent and the scale dependence is one of the most no facts and features of rupture phenomena the paper addresses how such scale dependent shear rupture of a broad range from laboratory scale frictional slip failure and shear fracture of intact rock to field scale rupture as an earthquake source can be unified by a single constitutive law noting that the earthquake rupture is a mixed process between frictional slip failure and the shear fracture of intact rock it is concluded that the constitutive law for the earthquake rupture be formulated as a unifying law that governs both frictional slip failure and shear fracture of intact rock it is demonstrated that the slip dependent constitutive law is such a unifying law and a constitutive scaling law is derived from laboratory data on both frictional slip failure and shear fracture of intact rock this constitutive scaling law enables one to provide a consistent and unified comprehension for scale dependent physical quantities inherent in the rupture over a broad range from small scale frictional slip failure and shear fracture in the laboratory to large scale earthquake rupture in the field

effects of supershear rupture speed on the high frequency content of s waves investigated using spontaneous dynamic rupture models and isochrone theory 1 in this paper we achieve three goals 1 we demonstrate that crack tips governed by friction laws including slip weakening rate and state dependent laws and thermal pressurization of pore fluids propagating at supershear speed have slip velocity functions with reduced high frequency content compared to crack tips traveling at subshear speeds this is demonstrated using a fully dynamic spontaneous three dimensional earthquake model in which we calculate fault slip velocity at nine points locations distributed along a quarter circle on the fault where the rupture is traveling at supershear speed in the in plane direction and subshear speed in the antiplane direction this holds for a fault governed by the linear slip weakening constitutive equation by slip weakening with thermal pressurization of pore fluid and by rate and state dependent laws with thermal pressurization the same is also true even assuming a highly heterogeneous initial shear stress field on the fault 2 using isochrone theory we derive a general expression for the spectral characteristics and geometric spreading of two pulses arising from supershear rupture the well known mach wave and a second lesser known pulse caused by rupture acceleration 3 we demonstrate that the mach cone amplification of high frequencies overwhelms the de amplification of high frequency content in the slip velocity functions in supershear ruptures consequently when earthquake ruptures travel at supershear speed a net enhancement of high frequency radiation is expected and the alleged low peak accelerations observed for the 2002 denali and other large earthquakes are probably not caused by diminished high frequency content in the slip velocity function as has been speculated

seismic imaging of the 1999 izmit turkey rupture inferred from the near fault recordings we use near fault accelerograms to infer the space time history of rupture on the fault during the izmit earthquake the records show that the ground displacement and velocity near the fault were surprisingly simple rupture propagated toward the west at a velocity of about 3 km s and toward the east at a remarkably high average velocity of 4 7 km s over a distance of about 45 km before decelerating to about 3 1 km s on the eastern segment slip on the fault is particularly large down to a depth of 20 km on the central portion of the fault where it reaches about 7 m slip is large also below 10 km on the eastern fault segment and this may have contributed to the loading of shear stress on the duzce fault on the western fault segment large slip seems confined to shallow depths

accelerating ice loss from the fastest greenland and antarctic glaciers 1 ice discharge from the fastest glaciers draining the greenland and antarctic ice sheets jakobshavn isbrae ji and pine island glacier pig continues to increase and is now more than double that needed to balance snowfall in their catchment basins velocity increase probably resulted from decreased buttressing from thinning and for ji breakup of their floating ice tongues and from reduced basal drag as grounding lines on both glaciers retreat ji flows directly into the ocean as it becomes afloat and here creep rates are proportional to the cube of bed depth rapid thinning of the pig ice shelf increases the likelihood of its breakup and subsequent rapid increase in discharge velocity results from a simple model indicate that ji velocities should almost double to 20 km a 1 by 2015 with velocities on pig increasing to 10 km a 1 after breakup of its ice shelf these high velocities would probably be sustained over many decades as the glaciers retreat within their long very deep troughs resulting sea level rise would average about 1 5 mm a 1

near source ground motion from steady state dynamic rupture pulses 1 ground motion from two dimensional steady state dynamic ruptures is examined for both subshear and supershear rupture velocities synthetic seismograms demonstrate that coherent high frequency information about the source process rapidly attenuates with distance from the fault for subshear ruptures such records provide almost no resolution of the spatial extent of the stress breakdown zone at supershear speeds s waves radiate away from the fault preserving the full source spectrum and carrying an exact history of the slip velocity on both the fault parallel and fault normal components of motion whose amplitudes are given by a function of rupture speed that vanishes at times the s wave speed the energy liberated from the strain field by the passage of a supershear rupture is partitioned into fracture energy dissipated within the fault zone and far field s wave radiation the partition depends on both the rupture velocity and the size of the breakdown zone

earthquake nucleation on model faults with rate and state dependent friction effects of inertia laboratory studies suggest that earthquake nucleation involves a transition from quasi static slip when inertial effects are negligible to inertia driven dynamic motion this transition occurs via quasi dynamic motion during which the effects of inertia become increasingly important the characteristics of this transition which depend on frictional properties of the fault determine the observability of earthquake nucleation by seismic geodetic or other means by investigating the role of inertia during nucleation we obtain a quantitative definition of the limiting velocity vin which marks the end of quasi dynamic motion and the onset of instability for reasonable friction parameters and fault widths we obtain estimates of vin for crustal faults to study the roles of inertia stiffness and friction parameters on preseismic motion we simulate triggered instabilities in a one dimensional model of a homogeneous fault with rate and state variable friction in most of our simulations triggering is achieved by applying a stress perturbation to an initially creeping fault under steady state friction we also investigate triggering on faults which are initially locked and overstressed compared to their nominal frictional strength due to time dependent healing we study the amount up and duration tp of preseismic slip as a function of system mass m and other model parameters for crustal faults we interpret the relevant mass as a product of density and fault width and find that wider fault zones result in smaller up and larger tp both up and tp are proportional to the system stiffness k the characteristic slip distance dc and the friction constitutive parameter a and inversely proportional to the size of the triggering event we find greater up and tp for constitutive laws which allow strengthening at zero velocity compared to laws that require slip or a combination of slip and aging for state evolution in contrast to quasi static modeling our simulations suggest a minimum stress perturbation criterion for instability which may be interpreted in terms of a strain threshold for triggered seismicity

joint inversion of insar gps teleseismic and strong motion data for the spatial and temporal distribution of earthquake slip application to the 1999 izmit mainshock the space time distribution of slip of the 17 august 1999 izmit earthquake is investigated by inverting synthetic aperture radar sar interferometry and global positioning system gps data together with teleseismic broadband and near field strong motion records surface offsets are used as an added constraint special emphasis is given to analysis of the resolution of the different data sets we use a four segment finite fault model and a nonlinear inversion scheme allowing slip to vary in amplitude direction and duration as well as variable rupture velocity from the inversion of synthetic data we find that the best spatial resolution can be expected in the upper half of the fault model above 12 km where coverage of the interferometric sar data is good western half of the rupture and near the gps and strong motion stations teleseismic data are found to have a lower resolution that is more evenly distributed over the fault model the joint inversion of all the data sets has an increased resolving power compared with the separate inversions and gives a more robust description of the space and time distribution of slip our study shows the importance of resolution tests in evaluating the reliability of earthquake kinematic models and it confirms that an excellent fit of a single kind of data does not necessarily imply a good retrieval of the kinematic properties of an earthquake the izmit rupture which is almost pure right lateral strike slip faulting is dominated by the bilateral breaking of a central asperity located between 29 7 e about 10 km west of the city of golcuk and 30 4 e eastern margin of sapanka lake with slip reaching 6 8 m in the depth range 6 12 km the western termination of the rupture is found near the city of yalova but large slip ends around 29 7 e about 10 km east of hersek delta a second area of large slip is required by all the data sets further east toward the city of duzce between 30 7 e and 31 1 e karadere and duzce faults this eastern slip zone which is separated from the main central asperity by an area of greatly reduced slip is less well constrained by the data however a strong motion station near the city of duzce helps to locate a high slip patch near 31 1 e in the depth range 6 12 km the total seismic moment resulting from the joint inversion is 2 4 1027 dyne cm most of the energy release occurred in a short time less than 15 sec corresponding to the bilateral breaking of the central asperity rupture propagation is relatively uniform and fast toward the west with a rupture velocity close to 3 5 km sec propagation of large slip toward the east is initially slower but it accelerates during a short time interval about 10 sec after rupture nucleation eastward progression then slows down to less than 2 km sec after 15 sec and rupture almost vanishes in amplitude ca 20 sec after initiation rupture propagation then proceeds on the easternmost karadere and duzce fault segments east of 30 7 e from 22 to ca 50 sec supershear rupture propagation is not required for modeling the waveforms considered in this study the hypocenter of the duzce earthquake which occurred 3 months later 12 november 1999 m w 7 2 is located in the immediate vicinity of the easternmost slip patch of the izmit earthquake manuscript received 28 july 2000

dynamic seismic ruptures on melting fault zones 1 we present a physical model that describes the behavior of spontaneous earthquake ruptures dynamically propagating on a fault zone and that accounts for the presence of frictional melt produced by the sliding surfaces first we analytically derive the solution for the temperature evolution inside the melt layer which generalizes previous approximations then we incorporate such a solution into a numerical code for the solution of the elastodynamic problem when a melt layer is formed the linear slip weakening law initially governing the fault and relying on the coulomb friction is no longer valid therefore we introduce on the fault a linearly viscous rheology with a temperature dependent dynamic viscosity we explore through numerical simulations the resulting behavior of the traction evolution in the cohesive zone before and after the transition from coulomb friction and viscous rheology the predictions of our model are in general agreement with the data from exhumed faults we also find that the fault after undergoing the breakdown stress drop controlled by the slip weakening constitutive equation experiences a second traction drop controlled by the exponential weakening of fault resistance due to the viscous rheology this further drop enhances the instability of the fault increasing the rupture speeds the peaks in fault slip velocity and the fracture energy density

stochastic strong ground motion simulation of the 12 november 1999 duzce turkey earthquake using a dynamic corner frequency approach on 12 november 1999 only three months after the 17 august 1999 kocaeli earthquake mw 7 4 an earthquake of mw 7 1 occurred immediately to the east of the kocaeli rupture in northwestern turkey resulting in extensive structural damage in the city of duzce and its surrounding area it was reported to be a right lateral strike slip event on the previously unbroken segment of the north anatolian fault zone with a north dipping fault plane this paper presents stochastic finite fault simulation of near field ground motions from this earthquake at selected near fault stations based on a dynamic corner frequency approach using the computer program exsim motazedian and atkinson 2005 the method requires region specific source path and site characterizations as input model parameters the source mech anism of the 1999 duzce event and regional path effects are well constrained from previous studies of the earthquake the local site effects at the selected stations are studied as a combination of the kappa operator and frequency dependent soil ampli fication the model parameters are validated against recordings and a stress drop value of 100 bars is estimated for the 1999 duzce earthquake the validated model is then used to compute synthetic records around the fault distribution of peak ground motion parameters is observed to be consistent with the building damage dis tribution in the near fault region most affected by the seismic shaking the attenuation of synthetic ground motion parameters is compared with recent ground motion pre diction equations proposed for the region by gulkan and kalkan 2002 ulusay et al 2004 and akkar and bommer 2007 as well as two next generation attenuation models by boore and atkinson 2007 and campbell and bozorgnia 2007 despite discrepancies at several stations stochastic finite fault modeling based on a dynamic corner frequency approach confirms to be a practical tool to reproduce the ground motions of large earthquakes

synthetic source inversion tests with the full complexity of earthquake source processes including both supershear rupture and slip reactivation recent studies in dynamic source modeling and kinematic source inversion show that earthquake rupture may contain greater complexity than we previously anticipated including multiple slipping at a given point on a fault finite source inversion methods suffer from the nonuniqueness of solutions and it may become more serious if we aim to resolve more complex rupture models in this study we perform synthetic inversion tests with dynamically generated complex rupture models including both supershear rupture and slip reactivation to understand the possibility of resolving complex rupture processes by inverting seismic waveform data we adopt a linear source inversion method with multiple windows allowing for slipping from the nucleation of rupture to the termination at all locations along a fault we regularize the model space effectively in the bayesian framework and perform multiple inversion tests by considering the effect of inaccurate green s functions and station distributions we also perform a spectral stability analysis our results show that it may be possible to resolve both a supershear rupture front and reactivated secondary slipping using the linear inversion method if those complex features are well separated from the main rupture and produce a fair amount of seismic energy it may be desirable to assume the full complexity of an earthquake rupture when we first develop finite source models after a major event occurs and then assume a simple rupture model for stability if the estimated models do not show a clear pattern of complex rupture processes

near source ground motions from simulations of sustained intersonic and supersonic fault ruptures we examine the long period near source ground motions from simulations of m 7 4 events on a strike slip fault using kinematic ruptures with rupture speeds that range from subshear speeds through intersonic speeds to supersonic speeds the strong along strike shear wave directivity present in scenarios with subshear rupture speeds disappears in the scenarios with ruptures propagating faster than the shear wave speed furthermore the maximum horizontal displacements and velocities rotate from generally fault perpendicular orientations at subshear rupture speeds to generally fault parallel orientations at supersonic rupture speeds for rupture speeds just above the shear wave speed the orientations are spatially heterogeneous as a result of the random nature of our assumed slip model at locations within a few kilometers of the rupture the time histories of the polarization of the horizontal motion provide a better diagnostic with which to gauge the rupture speed than the orientation of the peak motion subshear ruptures are associated with significant fault perpendicular motion before fault parallel motion close to the fault supershear ruptures are associated with fault perpendicular motion after significant fault parallel motion consistent with previous studies we do not find evidence for prolonged supershear rupture in the long period 2 sec ground motions from the 1979 imperial valley earthquake however we are unable to resolve the issue of whether a limited portion of the rupture approximately 10 km in length propagated faster than the shear wave speed additionally a recording from the 2002 denali fault earthquake does appear to be qualitatively consistent with locally supershear rupture stronger evidence for supershear rupture in earthquakes may require very dense station coverage in order to capture these potentially distinguishing traits

rupture speed and slip velocity what can we learn from simulated earthquakes abstract in this paper we consider a wide catalog of synthetic earthquakes numerically modeled as spontaneous fully dynamic 3 d ruptures on extended faults governed by different friction laws including slip dependent and rate and state dependent equations we analyze the spatial correlations between the peak of fault slip velocity vpeak and the rupture speed vr at which the earthquake spreads over the fault we found that vpeak positively correlates with vr and that the increase of vpeak is roughly quadratic we found that near the transition between sub and supershear regimes vpeak significantly diminishes and then starts to increase again with the square of vr this holds for all the governing models we consider and for both homogeneous and heterogeneous configurations moreover we found that on average vpeak increases with the magnitude of the event vpeak m00 18 our results can be incorporated as constraints in the inverse modeling of faults

near field radiated wave field may help to understand the style of the supershear transition of dynamic ruptures abstract supershear earthquakes are known to leave special signatures in the signals on the fault fault slip velocity dynamic traction evolution energy flux etc and in the ground motions moreover two different styles of supershear transition have been identified in the direct transition dt mechanism the rupture speed continuously increases from the sub rayleigh to the terminal speed of p waves while in the mother daughter md mechanism a forbidden zone of rupture speed exists and a secondary pseudo rupture is generated ahead of the primary rupture front here we found that the off fault signals wavefields generated by these two mechanisms are rather different in that the md case contains an enhanced trailing rayleigh field which has very low amplitudes or it is even practically absent in the dt case and possess higher frequency content therefore we show that it is possible to distinguish the style of the supershear transition from the records of real earthquakes in particular basing on the results of our numerical simulations we can conclude that the denali alaska earthquake was basically controlled by a classical md mechanism

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

off fault damage patterns due to supershear ruptures with application to the 2001 mw 8 1 kokoxili kunlun tibet earthquake 1 we extend a model of a two dimensional self healing slip pulse propagating dynamically in steady state with slip weakening failure criterion to the supershear regime in order to study the off fault stressing induced by such a slip pulse and investigate features unique to the supershear range specifically we show that there exists a nonattenuating stress field behind the mach front that radiates high stresses arbitrarily far from the fault practically this would be limited to distances comparable to the depth of the seismogenic zone thus being capable of creating fresh damage or inducing coulomb failure in known structures at large distances away from the main fault we allow for both strike slip and dip slip failure induced by such a slip pulse we show that off fault damage is controlled by the speed of the slip pulse scaled stress drop and principal stress orientation of the prestress field we apply this model to study damage features induced during the 2001 kokoxili kunlun event in tibet for which it has been suggested that much of the rupture was supershear we argue that an interval of simultaneous induced normal faulting is more likely due to a slip partitioning mechanism suggested previously than to the special features of supershear rupture however those features do provide an explanation for otherwise anomalous ground cracking at several kilometers from the main fault we also make some estimates of fracture energy which for a given net slip and dynamic stress drop is lower than for a sub rayleigh slip pulse because part of the energy fed by the far field stress is radiated back along the mach fronts

a unified source model for the 1906 san francisco earthquake abstract we reconcile two previously discordant source models of the 1906 san francisco earthquake and obtain a model that satisfies both triangulation and seismic data by allowing the rupture velocity to exceed the shear wave velocity employing a projection method to remove the dependence on initial station positions allowed us to make use of a more stable triangulation network including nonrepeated angle observations along the northern san andreas fault this strengthens the case for significant slip over the entire northern segment of the san andreas fault from san juan bautista to cape mendocino during the 1906 earthquake we also found that the teleseismic body wave data can be reconciled with the geodetically derived slip model by allowing supershear rupture this resolves a longstanding conflict between the two previous slip models geodetic and seismic of this earthquake supershear rupture has long been recognized as a theoretical possibility for strike slip faulting and it has been observed in several recent large strike slip earthquakes which raises the prospect that it might be typical for such events supershear rupture leads to substantially different strong ground motion and as a result may need to be taken into account when developing ground motion prediction relations for large strike slip earthquakes our final slip model has a seismic moment of 7 9 10 20 n m which corresponds to a moment magnitude of m w 7 9

dynamic behaviour of mining induced fault slip abstract fault slip bursts induced by mining activities could inflict severe damage to nearby mine developments considering a variety of factors that might exert an influence on the fault slip dynamic numerical analyses are conducted for models having a fault parallel to a tabular ore deposit the results obtained from the analyses show that the maximum dynamic shear displacement increment induced by stope extraction is significantly affected by the friction angle of the fault as well as mining depth and position of fault with respect to the orebody while the stiffness and the dilation angle of the fault do not have as much influence seismic source parameters are computed based on the numerical results and as is the case with the maximum relative shear displacements the position and friction angle of the fault appear to have the strongest influence on seismic moment and energy released by fault slip the limitations of mohr coulomb criterion as applied to the dynamic analysis of fault slip bursts are discussed in light of the results obtained lastly slip rates and rupture velocity are investigated the results show that the maximum slip rates are associated with the maximum increments of relative dynamic shear displacement it is shown that extremely high rupture velocity could be induced by stope extraction this could be the cause for a severe seismic event

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

a faulting model for the 1979 imperial valley earthquake by comparing synthetic particle velocities with the near source strong motion data we have constructed by trial and error a faulting model for the 1979 imperial valley earthquake the calculation of the synthetic seismograms takes into account the vertical inhomogeneity of the elastic parameters in the imperial valley and the spatial variation of the slip rate parameters on the fault plane the independent slip rate parameters are 1 the strike slip rate amplitude 2 the dip slip rate amplitude 3 the duration that slip rate is nonzero the rise time of the slip function and 4 the rupture time which determines when the slip rate is initiated our faulting model has the following principal features 1 faulting occurred on the imperial fault and on the brawley fault rupture on the brawley fault being triggered by rupture on the imperial fault 2 the imperial fault is a plane 35 km long and 13 km wide with a strike of 323 measured clockwise from north and a dip of 80 ne the brawley fault is a 10 km long and 8 km wide plane with a strike of 360 and a dip of 90 3 faulting on the imperial fault is primarily right lateral strike slip with a small component of normal dip slip in the sediments at its northern end the larger strike slip rates are generally confined between depths of 5 and 13 km with maximum values of about 1 0 m s the duration varies on the fault with a maximum of 1 9 s which is considerably shorter than the total time for the rupture to take place 4 the rupture velocity on the imperial fault is highly variable locally it exceeds the shear wave velocity and in one instance the compressional wave velocity the average rupture velocity though is less than the shear wave velocity 5 although the slip on the brawley fault contributes only about 4 of the total moment it greatly affects the ground motion at nearby stations 6 the total seismic moment is 6 7 1018 n m where the imperial fault contributes 6 4 1018 n m and the brawley fault contributes 2 7 1017 n m in the process of trying almost 300 faulting models we found that given the elastic parameters of the medium the synthetic seismograms were most sensitive to the specification of the rupture time although the slip rate amplitudes are linearly related to the data the rupture time and the duration are not the parameterization of the nonlinear variables has a strong effect on the generation of synthetic seismograms from a finite fault

ground motion signatures of supershear ruptures in the burridge andrews and free surface induced mechanisms abstract we analyze the ground motions of supershear ruptures in the burridge andrews bam and free surface induced fsi mechanisms bam supershear ruptures require higher initial shear stress than fsi supershear ruptures thus cause faster rupture speed the supershear slip pulse initiates at the free surface or upper boundary of a fault for fsi and at the hypocenter depth in the in plane direction for bam in homogeneous models both bam and fsi supershear ruptures can generate mach waves and the rayleigh wave field the bam and the faster fsi supershear ruptures can make stronger shear mach waves the shear mach waves show a larger amplitude of negative component for a faster fsi supershear rupture the fsi supershear ruptures make the strongest dilatational wave next to the fault while it is at a distance away from the fault for the bam supershear ruptures the different shapes of supershear rupture front locations of supershear triggered and the rupture speeds contribute to these contrasts and we find that the bam and the faster fsi supershear ruptures can trigger more high frequency radiation due to the sharper and stronger shear mach waves finally the comparisons between the simulated seismograms and the records of ps10 indicate that the 2002 denali earthquake may represent a supershear one with the fsi mechanism and a slow supershear rupture speed

what does control earthquake ruptures and dynamic faulting a review of different competing mechanisms the fault weakening occurring during an earthquake and the temporal evolution of the traction on a seismogenic fault depend on several physical mechanisms potentially concurrent and interacting recent laboratory experiments and geological field observations of natural faults revealed the presence and sometime the coexistence of thermally activated processes such as thermal pressurization of pore fluids melting of gouge and rocks material property changes thermally induced chemical environment evolution elasto dynamic lubrication porosity and permeability evolution gouge fragmentation and wear etc in this paper by reviewing in a unifying sketch all possible chemico physical mechanisms that can affect the traction evolution we suggest how they can be incorporated in a realistic fault governing equation we will also show that simplified theoretical models that idealistically neglect these phenomena appear to be inadequate to describe as realistically as possible the details of breakdown process i e the stress release and the consequent high frequency seismic wave radiation quantitative estimates show that in most cases the incorporation of such nonlinear phenomena has significant often dramatic effects on the fault weakening and on the dynamic rupture propagation the range of variability of the value of some parameters the uncertainties in the relative weight of the various competing mechanisms and the difference in their characteristic length and time scales sometime indicate that the formulation of a realistic governing law still requires joint efforts from theoretical models laboratory experiments and field observations

rock pulverization at high strain rate near the san andreas fault rocks near the san andreas fault are pervasively crushed at distances of up to 400 m from its core laboratory experiments and calculations suggest that the rocks were pulverized at high strain rates 150 s 1 associated with a supershear rupture a rupture propagating at a velocity equal to greater than that of seismic shear waves

dependency of supershear transition and ground motion on the autocorrelation of initial stress abstract theoretical and observational studies show that earthquakes on strike slip faults can have rupture speeds exceeding the shear wave speed due to the close relationship between the rupture velocity and the radiated wave field it is important to understand the conditions leading to supershear ruptures and their effect on the resulting ground motion we compute dynamic strike slip ruptures in a 3d elastic half space using heterogeneous frictional properties on faults that are 60 km long we use a grid spacing of 60 m allowing us to compute ground motion for frequencies from 0 to 5 hz we analyze the resulting ground motion using isochrones to explain phenomena we observe we model the amplitudes of the initial shear stress as a self similar random field with cauchy distributed amplitudes the wavenumber amplitude spectrum of initial stress decays as a power law with exponent that controls the decay and the spatial correlation of the initial stress the faster the decay corresponding to larger value of the more correlated is the stress on the fault i e the stress field appears spatially smoother the strength on the fault is computed under the assumption of a constant s factor where s is the ratio of strength excess over stress drop on a fault with uniform strength and stress drop the s factor has to be less than a critical value for the supershear transition to occur for models with heterogeneous initial stress we find that both the s factor and the value of the spectral decay constant affect the occurrence of supershear rupture we observe that for a given but small enough s factor a smooth model 2 can run at supershear speed while a rough model 1 will rupture at subshear speeds for the same s factor based on the theory of fracture a non dimensional number was introduced to quantify the condition when a transition to supershear rupture velocity can occur during an earthquake transition will occur when exceeds a critical value we introduce a modified dimensionless parameter ac that is based on the original parameter the parameter ac incorporates a length scale w ac that reflects the degree of the autocorrelation of the stress field we compute ac for a large number of available dynamic ruptures that propagate at subshear and supershear speeds and find i there is a critical value ac c below which all ruptures propagate subshear ii for values larger than ac c there is only a finite probability that the rupture goes supershear i e it is a necessary but not a sufficient condition for the occurrence of supershear rupture propagation

evidence for a supershear transient during the 2002 denali fault earthquake elastodynamic considerations suggest that the acceleration of ruptures to supershear velocities is accompanied by the release of rayleigh waves along the fault from the stress breakdown zone these waves generate a secondary slip pulse trailing the rupture front but manifest almost entirely in ground motion perpendicular to the fault in the near source region we construct a spontaneously propagating rupture model exhibiting these features and use it to explain ground motions recorded during the 2002 denali fault earthquake at pump station 10 located 3 km from the fault we show that the initial pulses on both the fault normal and fault parallel components are due to the supershear stress release on the fault whereas the later arriving fault normal pulses result from the trailing subshear slip pulse on the fault online material mpeg movies of rupture history and ground motion

influence of super shear earthquake rupture models on simulated near source ground motion from the 1999 izmit turkey earthquake we numerically simulate seismic wave propagation from the 1999 mw 7 4 earthquake in izmit turkey using a 3d finite difference method based on published finite source models obtained by waveform inversions this earthquake has been reported based on observations at the near fault station skr as an example of supershear rupture propagation toward the east although the modeled ground motion does show a characteristic mach wave from the fault plane it is difficult to identify any particular effects in terms of peak ground velocity pgv an important parameter in earthquake engineering this is because the fault s spatial heterogeneity is strong enough to mask the properties of supershear rupture which has been reported through several numerical simulations mostly based on homogeneous fault conditions this article demonstrates the importance of studying ground motions for known earthquakes through numerical simulations based on finite fault source models