very high rate 10 hz gps seismology for moderate magnitude earthquakes the case of themw6 3 l aquila central italy event accepted for publication in journal of geophysical research copyright 2010 american geophysical union

haskell 1935 revisited the haskell 1935 value of 1021 pa s for mantle viscosity is a classic and enduring constraint on the rheology of the earth s interior we revisit this inference using spherically symmetric self gravitating maxwell viscoelastic earth models our inference is based on both forward and inverse analyses of decay times associated with uplift at two sites considered by haskell angerman river sweden and oslo norway rather than the raw relative sea level rsl data at these sites we demonstrate that predictions of the decay time associated with the angerman river data are insensitive to variations in both the late pleistocene ice load history and the lithospheric thickness of the earth model the predictions at oslo are sensitive to both these inputs and hence decay times at this site provide a remarkably robust constraint on mantle viscosity we derive a constraint on the average viscosity of the mantle of 0 65 1 10 1021 pa s where the average resolved by the data encompasses a region which extends from the base of the lithosphere to a depth of near 1400 km this indicates that many previous analyses which have invoked the haskell value of 1021 pa s as a constraint on the average upper mantle i e above 670 km depth viscosity alone have misinterpreted the resolving power of the inference furthermore our analysis indicates that a number of apparently contradictory inferences of viscosity based on fennoscandian data satisfy the new rigorous interpretation of the haskell constraint finally we demonstrate how the ambiguity in the upper mantle lower mantle viscosity contrast associated with the haskell average may be reduced by invoking decay time constraints estimated from rsl curves in hudson bay a preliminary inversion of decay times at angerman river and richmond gulf in hudson bay suggests a contrast of approximately an order of magnitude between the average viscosities of the upper mantle and the top 1000 km of the lower mantle however a conclusive analysis in this regard must await the determination of consistent decay time estimates for the hudson bay region

performance of high rate gps waveforms at long periods moment tensor inversion of the 2003 mw 8 3 tokachi oki earthquake abstract we present a comparison of long period 30 t m w 8 3 with both very broadband seismograms and synthetic waveforms we show that gps provides valuable waveform data between 40 and 160 s periods especially in the near field of the earthquake where seismograms are saturated there are no long period broadband seismic data available in the near field of large earthquakes 100 km for earthquakes m w 7 and 500 km for earthquakes m w 8 the comparison with synthetic seismic displacement waveforms shows that the gps waveforms are performing well at periods of 40 80 s at epicentral distances between 150 and 600 km and at periods of 80 160 s at epicentral distances between 150 and 400 km at longer periods and larger epicentral distances the amplitudes do not always exceed the noise level 2 3 mm but we still observe at selected gps sites that the phase and the amplitude of the surface waves are of good quality up to 1200 km we conclude that gps waveforms in the near field of a large event can be used for seismological applications in this article we recover the focal mechanism of the tokachi oki event by inverting the gps data recorded within 300 km of the epicenter

peak ground velocity shakemaps derived from geodetic slip models summary we develop a methodology to derive fast and reliable peak ground velocity pgv shakemaps from kinematic finite source models of earthquake rupture inferred from geodetic static displacements the temporal variations in slip on the fault are based on the simple assumption that larger slip takes longer time to accumulate assuming constant rupture and slip velocities slip is distributed in time to produce a variable rise time model sensitivity tests on finite source models of the 1994 mw 6 7 northridge california earthquake show that distribution of peak ground velocities derived using 3 0 km s 1 rupture velocity and 76 8 cm s 1 slip velocity matches to a large extent observed pgv suggesting that rapid assessment of strong ground motions derived from geodetic data can aid emergency response particularly in areas with sparse seismic station coverage

effects of lateral variations in lithospheric thickness and mantle viscosity on glacially induced surface motion on a spherical self gravitating maxwell earth abstract the effects of lateral variations in lithospheric thickness and mantle viscosity on surface motions on a spherical self gravitating incompressible viscoelastic earth are investigated using the coupled laplace finite element method the ice 4g deglaciation model is used together with gravitationally self consistent sea levels in realistic oceans to describe the load lateral variations in mantle viscosities and lithospheric thickness are inferred from seismic tomography model s20a using well known scaling relationships the laterally homogeneous background viscosity has viscosity increases across 670 km and 1330 km depths and is a simplification of peltier s vm2 model the effect of interaction between ice complexes in north america greenland eurasia and antarctica are investigated and found to be significant for tangential motion the predicted motion in laurentide and antarctica are also compared with results obtained with flat earth models and found that there is general agreement between the two types of modeling although spherical earth models are more realistic because they take into account the interaction between ice complexes and there is no problem with edge effects the effects of lateral heterogeneity on uplift rate are found to be large enough to be resolved by current gps technology it confirms that the effect of the reverse viscosity contrast in the transition zone under the laurentian and fennoscandian craton may mask the effect of lateral heterogeneity in the neighboring layers on uplift rate for tangential motion lateral heterogeneity is found to be able to overprint the divergent motion from the centers of rebound predicted in laterally homogeneous models this finding is new for laurentide and is due to the contribution from the deep part of the lower mantle although the contribution from the upper mantle is also important on tangential motion its effects are compromised by the effects from the other layers

long period ground motion prediction equations for moment magnitude estimation of large earthquakes in japan we developed long period 5 30 s ground motion prediction equations gmpes for peak ground velocities pgvs and peak ground displacements pgds for crustal interplate and intraplate earthquakes we used strong motion data from kik net downhole stations located in layers with shear wave velocities equal to or greater than 2000 m s the data set consisted of 20 earthquakes of 6 m w 9 1 that occurred in and around japan including the 2011 tohoku earthquake two stage regression analyses were performed to derive the long period gmpes we fitted the data with bilinear regression lines bending at m w 7 5 although additional factors such as focal depth and earthquake type were found to enhance the fitting with the observed data the developed equations indicated that long period pgvs and pgds are larger for crustal earthquakes than for interplate and intraplate earthquakes the attenuation coefficients indicated that long period pgvs and pgds increase with increasing depth we estimated the moment magnitude by fitting the observed pgvs and pgds in the 5 30 s period range with the long period gmpes we obtained estimates of the magnitudes of 23 earthquakes recorded by kik net downhole accelerometers and the results were consistent with the moment magnitudes obtained from the global centroid moment tensor project the described method was proven useful for estimating the moment magnitude of great earthquakes offering the potential for rapid estimation of moment magnitude if information from the source area is available

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

the potential of high rate gps for strong ground motion assessment abstract we show that high rate global positioning system gps can have a vital role to play in near real time monitoring of potentially destructive earthquakes we do this by investigating the potential of gps in recording strong ground motions from earthquakes in switzerland and japan the study uses finite fault stochastic ground motion simulation based on fourier amplitude spectra and duration models previously developed for both countries allowing comparisons in terms of both fourier and time domain characteristics here the peak ground velocity pgv we find that earthquakes of magnitude m w 5 8 can be recorded by gps in real time at 10 km distance that is their fourier spectrum exceeds the noise of the instruments enough to be used in strong motion seismology postprocessing of gps time series lowers the noise and can improve the minimum observable magnitude by 0 1 0 2 as gps receivers can record at higher rates 10 hz we investigate which sampling rate is sufficient to optimally record earthquake signals and conclude that a minimum sampling rate of 5 hz is recommended this is driven by recording events at short distances below 10 km for magnitude 6 events and below 30 km for magnitude 7 events furthermore the maximum ground velocity derived from gps is compared with the actual pgv for synthetic signals from the stochastic simulations and the 2008 m w 6 9 iwate earthquake the proposed model confirmed by synthetic and empirical data shows that a reliable estimate of pgv for events of about magnitude 7 and greater can be basically retrieved by gps in real time and could be included for instance in shakemaps for aiding postevent disaster management

gps seismology application to the 2002 mw 7 9 denali fault earthquake abstract the 2002 denali fault alaska earthquake m w 7 9 caused one or more components of most broadband seismometers in western canada to clip yet did not trigger strong motion instruments thus leaving a substantial gap in the seismic record of this event however the large amplitude surface waves generated by this event were well recorded by the global positioning system gps in the same region out to epicentral distances of more than 3000 km in this article we explore the capabilities of gps seismology specifically how the relative strengths of gps and seismic data sets can be exploited in order to more effectively study earthquake source characteristics and wave propagation effects high rate 1 hz gps data from 23 stations throughout western north america have been analyzed to derive displacement waveforms for this event and the impact of instrumentation gps receiver model and error reduction strategy modified sidereal and spatial filtering on the noise characteristics of displacement time series at each gps site was assessed after applying error reduction methods to gps displacements the final average noise floors of 0 5 cm in the horizontal and 1 5 cm in the vertical indicate that large dynamic displacements are observable by gps we validate the gps displacements by comparing broadband seismic recordings integrated to displacement with gps recordings for four effectively colocated sets of instruments we show excellent agreement between the unclipped seismic and gps recordings of the surface waves from the denali earthquake over the period range of 10 50 sec and for ground displacements exceeding about 1 0 cm thus a large gps displacement data set is now available for western north america an area where records of this event were previously missing or incomplete the final gps seismograms are archived at incorporated research institutions for seismology iris for public use in future studies of the 2002 denali earthquake

effects of nonlinear rheology on degree 2 harmonic deformation in a spherical self gravitating earth 1 the effect of non linear rheology on surface displacements gravitational potential perturbation and tj2 or j2 dot for a self gravitating spherical earth is studied using a finite element code coupled to poisson s equation four earth models investigated are a model with uniform linear rheology throughout the mantle and three others containing nonlinear rheology in the whole mantle upper mantle and lower mantle respectively the effect of self gravitation is shown to be non negligible the effects of nonlinear rheology in different parts of the mantle on surface displacements and potential have also been shown to be large tj2 due to cyclic glaciation of the laurentian fennoscandian barents sea and antarctic ice sheets over realistic oceans is also computed for all four rheology models the model with nonlinear lower mantle cannot be ruled out by the observed data

modeling the rupture process of the 2003 september 25 tokachi oki hokkaido earthquake using 1 hz gps data received 10 september 2004 accepted 3 october 2004 published 3 november 2004 1 high rategpshasthepotentialtorecoverbothdynamic and static displacements accurately we analyze 1 hz gps data recorded during the 2003 tokachi oki earthquake the 1 hz gps displacement waveforms show good agreement with integrated accelerometer records except for low frequency noise that are inherently present in integrated seismic records the gps waveforms were inverted to model the spatio temporal evolution of the fault slip during the rupture the slip is found to propagate downdip in the subduction zone with largest moment release 50 km northwest of the hypocenter the region of largest slip agrees in general with traditional seismic studies indicating that 1 hz gps can be used for finite fault studies the 1 hz gps slip model shows clearer contrast with afterslip distributions than those inferred from strong motion data possibly because 1 hz gps is more sensitive to cumulative slip distribution index terms 1294 geodesy and gravity instruments and techniques 7209 seismology earthquake dynamics and mechanics 7212 seismology earthquake ground motions and engineering citation miyazaki s k m larson k choi k hikima k koketsu p bodin j haase g emore and a yamagiwa 2004 modeling the rupture process of the 2003 september 25 tokachi oki hokkaido earthquake using 1 hz gps data geophys res lett 31 l21603 doi 10 1029 2004gl021457

attenuation of seismic shear wave energy in switzerland summary modelling the attenuation of shear wave energy is an important component of seismic hazard analysis previous studies have shown how attenuation particularly in the uppermost layers of the crust is regionally dependent the impact of this is that the decay of energy radiating from an earthquake will vary from place to place to quantify the regional attenuation in switzerland we model the fourier spectral amplitude of small to moderate earthquakes recorded on the local seismic networks high frequency decay is parametrized by q and while apparent geometrical spreading models account for the frequency independent decay of energy we analyse ground motion encompassing the significant duration of shaking to provide models that are useful for the purpose of seismic hazard analysis two methods are used to estimate the whole path attenuation parameter t first a simultaneous fit of the source model and attenuation effects across the entire spectral bandwidth for earthquakes with m 2 and secondly a linear fit of an attenuation model to the high frequency part of the spectrum for earthquakes with m 3 5 the t parameter is found to vary with hypocentral distance consistent with a weakly attenuating crust and strongly attenuating uppermost layer 1 d tomographic inversions indicate a profile of increasing q with depth down to the moho frequency independent decay is parametrized using a three part model which allows for the inclusion of moho reflection phases in the spectrum in the range of 20 140 km in the swiss foreland and from 70 to 140 km in the swiss alps

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

detection of ground motions using high rate gps time series monitoring surface deformation in real time help at planning and protecting infrastructures and populations manage sensitive production i e seveso type and mitigate long term consequences of modifications implemented we present rt shake an algorithm developed to detect ground motions associated with landslides sub surface collapses subsidences earthquakes or rock falls rt shake detects first transient changes in individual gps time series before investigating for spatial correlation s of observations made at neighbouring gps sites and eventually issue a motion warning in order to assess our algorithm on fast seconds to minute large from 1cm to meters and spatially consistent surface motions we use the 1hz geonet gnss network data of the tohoku oki mw9 0 2011 as a test scenario we show the delay of detection of seismic wave arrival by gps records is of 10 seconds with respect to an identical analysis based on strong motion data and this time delay depends on the level of the time variable noise nevertheless based on the analysis of the gps network noise level and ground motion stochastic model we show that rt shake can narrow the range of earthquake magnitude by setting a lower threshold of detected earthquakes to mw6 5 7 if associated with a real time automatic earthquake location system

liquidus temperatures of the skaergaard magma the liquidus temperatures of the skaergaard intrusion can be estimated for the layered series from plagioclase compositions plagioclase saturation in one atmosphere melting experiments on evolved north atlantic basalts is a function of an content mol and can be described by an empirical linear relationship t c 899 3 6 an 1 20 c this relationship predicts a total crystallization interval for the intrusion of 150 c plagioclase crystallized in the hidden zone an 71 at 1155 c at the base of the lower zone an 66 at 1137 c and finally in the sandwich horizon an 30 at 1007 c these temperatures are in good agreement with previous estimates based on melting studies of suitable chilled margin rocks and gabbros from the skaergaard intrusion and liquid line of descent modeling our temperature estimates however are markedly lower by up to 60 c than recent temperature estimates based on an extrapolation of high pressure experimental data for the kiglapait intrusion to skaergaard emplacement conditions proposed variations in magmatic pressure during skaergaard evolution and reasonable estimates of magmatic water contents do not alter these conclusions

earthquake magnitude calculation without saturation from the scaling of peak ground displacement gps instruments are noninertial and directly measure displacements with respect to a global reference frame while inertial sensors are affected by systematic offsets primarily tilting that adversely impact integration to displacement we study the magnitude scaling properties of peak ground displacement pgd from high rate gps networks at near source to regional distances 10 1000 km from earthquakes between mw6 and 9 we conclude that real time gps seismic waveforms can be used to rapidly determine magnitude typically within the first minute of rupture initiation and in many cases before the rupture is complete while slower than earthquake early warning methods that rely on the first few seconds of p wave arrival our approach does not suffer from the saturation effects experienced with seismic sensors at large magnitudes rapid magnitude estimation is useful for generating rapid earthquake source models tsunami prediction and ground motion studies that require accurate information on long period displacements

instantaneous geodetic positioning with 10 50 hz gps measurements noise characteristics and implications for monitoring networks 1 recent earthquake recordings from high rate 1 hz continuous gps stations in california indicate that even higher temporal resolution provided by modern gps receivers is desirable we measured seven baselines during time intervals devoid of detectable transient signals at sampling rates of 1 50 hz with geodetic receivers from four manufacturers to investigate the noise characteristics of these data our tests over short distances meters to typical station spacing tens of kilometers of regional gps networks show no loss of spatial resolution compared to 1 hz samples measurement noise is red with the typical ramp profile of log log spectra below about 0 5 hz above this frequency noise is essentially white low pass filtering of high rate positions achieves improved spatial resolution compared to decimated raw samples averaging 20 hz measurements to 2 hz samples on a 40 km baseline for example yields about 0 5 mm horizontal and about 3 4 mm vertical accuracy at high frequencies these estimates are a factor of 2 2 5 better than for 2 hz raw samples the improvements in spatial resolution due to averaging at high frequencies are substantial and approach the theoretical square root of n expectation for independent samples however since noise spectral densities rise rapidly below about 0 5 hz low pass filtering is only effective above this frequency these results have important implications for the design of continuous gps networks for crustal deformation and structural monitoring and for positioning and attitude determination of dynamic platforms

assessment of site effects in alpine regions through systematic site characterization of seismic stations abstract in the framework of the renewal project of the swiss strong motion network ssmnet a procedure for site characterization has been established the aim of the procedure was to systematically derive realistic 1d velocity profiles at each station it is mainly based on the analysis of surface waves particularly from passive experiments and includes cross checks of the derived amplification functions with those obtained through spectral modeling of recorded earthquakes the systematic use of three component surface wave analysis allowing the derivation of both rayleigh and love dispersion curves also contributes to the improvement of the quality of the retrieved profiles the procedure is applied to the 30 ssmnet stations installed on various site types within the project covering different aspects of seismic risk the characterization of these 30 sites gives an overview of the variety of possible effects of surface geology on ground motion in the alpine area such effects ranged from deamplification at hard rock sites to amplification up to a factor of 15 in lacustrine sediments with respect to the swiss reference rock velocity model the derived velocity profiles are shown to reproduce observed amplification functions from empirical spectral modeling although many sites are found to exhibit 1d behavior the procedure allows the detection and qualification of 2d and 3d effects the sites are therefore classified with respect to the occurrence of 2d 3d resonance and edge generated surface waves in addition to the large and deeply incised alpine valleys of the rhone the rhine and the aar smaller structures such as local alpine valleys and alluvial fans are shown to exhibit 2d 3d behavior

using 1 hz gps data to measure deformations caused by the denali fault earthquake the 3 november 2002 moment magnitude 7 9 denali fault earthquake generated large permanent surface displacements in alaska and large amplitude surface waves throughout western north america we find good agreement between strong ground motion records integrated to displacement and 1 hertz global positioning system gps position estimates collected 140 kilometers from the earthquake epicenter one hertz gps receivers also detected seismic surface waves 750 to 3800 kilometers from the epicenter whereas these waves saturated many of the seismicinstruments in the same region high frequency gps increases the dynamic range and frequency bandwidth of ground motion observations providing another tool for studying earthquake processes

earthquake ground motion prediction equations for eastern north america new earthquake ground motion relations for hard rock and soil sites in eastern north america ena including estimates of their aleatory uncertainty vari ability have been developed based on a stochastic finite fault model the model incorporates new information obtained from ena seismographic data gathered over the past 10 years including three component broadband data that provide new in formation on ena source and path effects our new prediction equations are similar to the previous ground motion prediction equations of atkinson and boore 1995 which were based on a stochastic point source model the main difference is that high frequency amplitudes f 5 hz are less than previously predicted by about a factor of 1 6 within 100 km because of a slightly lower average stress parameter 140 bars versus 180 bars and a steeper near source attenuation at frequencies less than 5 hz the predicted ground motions from the new equations are generally within 25 of those predicted by atkinson and boore 1995 the prediction equations agree well with available ena ground motion data as evidenced by near zero average residuals within a factor of 1 2 for all frequencies and the lack of any significant residual trends with distance however there is a tendency to positive residuals for moderate events at high frequencies in the distance range from 30 to 100 km by as much as a factor of 2 this indicates epistemic uncertainty in the prediction model the positive residuals for moderate events at 100 km could be eliminated by an increased stress parameter at the cost of producing negative residuals in other magnitude distance ranges adjustment factors to the equations are provided that may be used to model this effect

parental liquids of the skaergaard intrusion cumulates petrogenetic relationships between compositions advocated as possible liquids parental to the skaergaard layered series cumulates have been investigated using equations for the prediction of liquidus temperature and liquid path followed during fractional crystallization given a suitably defined sequence of primocryst mineral assemblages a variation of the fractionation scheme provides a new method for the calculation of the parent liquid composition

5hz gps seismology of the el mayor cucapah earthquake estimating the earthquake focal mechanism summary high rate 5hz gps records observed in the near field following the magnitude 7 2 el mayor cucapah earthquake that occurred in northern mexico on 2010 april 4 are compared with broad band seismograms the high rate gps displacement records are consistent with the twice integrated strong motion seismic records in the near field where broad band seismograms are clipped due to strong shaking agreement degrades at distances greater than about 150 km from the epicentre where displacement amplitudes approach the noise level of gps seismograms using high rate gps data the focal mechanism of the main shock is estimated and is shown to be consistent with teleseismic estimates the result is seen as confirmation that high rate gps observed at near field stations can be applied together with teleseismic seismometers to yield better information about earthquake rupture properties and parameters

coseismic and early postseismic slip for the 2003 tokachi oki earthquake sequence inferred from gps data 1 early afterslip following the 2003 tokachi oki earthquake is investigated using subdaily gps time series afterslip results are compared with the coseismic slip for the m8 mainshock and the m7 4 aftershock afterslip between those two earthquakes is inferred at the southwestern adjacent region of the mainshock between two epicentral regions which possibly triggered the aftershock in the southwest subsequently deeper slip occurs the afterslip loci are distinct from the rupture regions the non uniform propagation of afterslip may reflect the depth dependence of the effective normal stress and the distance between the closest unstable slip patches

application of real time gps to earthquake early warning 1 we explore the use of real time high rate gps displacement data for earthquake early warning using 1 hz displacement waveforms from the april 4 2010 mw 7 2 el mayor cucapah earthquake we compare these data to those provided by the broadband velocity and accelerometer instrumentation of the southern california seismic network the unique information provided by the gps based displacement timeseries is the permanent static displacement using a simple algorithm that can be applied in real time we extract the static offset shortly after the s wave arrival around the time of the observed peak shaking at the same site and before shaking at more distant locations these data can be used as they become available to provide a robust estimate of the earthquake magnitude which ranges from 6 8 to 7 0 in this case we therefore conclude that real time high rate gps can provide a useful and independent assessment of earthquake magnitude for the purpose of earthquake early warning and real time earthquake information systems in general including tsunami warning systems

a predictive equation for the vertical to horizontal ratio of ground motion at rock sites based on shear wave velocity profiles from japan and switzerland abstract ratios of vertical to horizontal v h ground motion are important for the computation of scenario compatible vertical design spectra they are therefore a crucial aspect of seismic hazard analysis we characterize the v h ratio at rock sites in terms of the recording site s average quarter wavelength velocity a predictive equation is presented which can be used for reconstructing the expected v h ratio of the 5 damped response and fourier spectra for rock sites given a known shear wave velocity profile the equation is based on the regression analysis of two datasets one from switzerland and one from japan the two datasets allow us to analyze well characterized hard rock sites in switzerland using small earthquakes m w 2 while the magnitude range is increased up to events of m w 7 3 using strong motion recordings from japan s kik net seismic network it is shown that a correlation exists between the quarter wavelength velocity at a given frequency and the v h ground motion ratio small differences possibly due to velocity measurement bias or topographical and basin effects existed when analyzing the individual regional datasets apart from near source distances r v h no clear magnitude or distance dependence of the v h ratios is present in either of the datasets of earthquake recordings we show that the same correlation exists for response spectra and fourier spectra of recorded ground motion a similar correlation was derived for ambient vibrations recorded at swiss station sites resulting in larger values of v h at a given frequency and thereby indicating that v h is sensitive to the composition of the wave field finally uncertainties in the v h models are presented we separate the sources of uncertainty into source and site specific components and present the single site sigma uncertainty measure for site specific hazard analyses

regional stochastic gmpes in low seismicity areas scaling and aleatory variability analysis application to the french alps we generate stochastic ground motion prediction equations gmpes for a wide magnitude range m w 3 8 that are adapted to the french alps based on inversions of source path and site terms from weak motion accelerometric data drouet et al 2010 we build seismological stochastic models to use in conjunction with the simulation program stochastic method simulation smsim to stochastically simulate ground motion response spectral amplitudes all the input parameters are considered random variables and the uncertainty is propagated through simulations by random sampling of the corresponding distributions constant and magnitude dependent stress parameter models are compared with variable large magnitude stress levels stochastic simulations are performed for periods between 0 01 and 3 s m w from 3 to 8 epicentral distances from 1 to 250 km and two site conditions rock v s 30 800 m s and hard rock v s 30 2000 m s these synthetic data are then regressed to produce stochastic gmpes using an up to date regression form the parameterization of which can be defined in terms of different distance metrics i e epicentral hypocentral joyner boore or rupture distance the impact of the uncertainty on each input parameter on the gmpe standard deviation is determined through sensitivity analysis the major contributors to the uncertainty are the site model both v s 30 and the high frequency parameter which affect the within event standard deviation and the uncertainty on the stress parameter which affects the between event term the gmpes are compared to real data using statistical analysis of residuals two sets of strong motion data are considered the reference database for seismic ground motion in europe resorce and the worldwide next generation attenuation databases as well as weak motion data recorded in france the results show that the magnitude dependent stress parameter models for magnitudes below 4 6 fit the french data better and a large magnitude constant stress parameter of 10 mpa gives a better fit to strong motion data online material tables of ground motion prediction equation coefficients

the differentiation of the skaergaard intrusion mcbirney and naslund have missed the two central points that we reiterate for clarity first the composition of the cotectic cumulate extract for the lzc best estimated from the average composition of adcumulate rocks had a substantially lower silica content than any conceivable basaltic liquid so silica enrichment is unavoidable this is true of all the dyke compositions reported by brooks and nielsen even the anomalous rock e with sio2 46 second it is the normal behaviour of tholeiite basaltic magma to produce increasingly iron rich cumulate extracts with little change in silica until feti oxide precipitation occurs when silica enrichment and compositional divergence begins such divergence between equivalent cumulate plutonic and fractionated volcanic rocks hads been widely documented skaergaard magmas do have some uncommon features however similar assemblages exist in volcanic rocks as in the andesitic to rhyolitic glasses of the loch ba ring dyke mull sparks 1988 it is also a basic principle that elements enriched in cumulate rocks often become depleted in the corresponding liquids iron enrichment in the skaergaard cumulates is complementary to iron depletion in liquids

millimeter level ultra long period multiple earth circling surface waves retrieved from dense high rate gps network abstract high rate gps networks have proven to be capable of continuously recording strong ground motion which is valuable for studying earthquake rupture processes and seismic hazard mitigation previous studies of high rate gps usually resolved dynamic ground displacements of some major seismic phases stronger than a few millimeters in this study we explore the feasibility of retrieving much weaker ground motions sub millimeter in long duration records by stacking high rate gps network we processed data of the 2011 tohoku oki earthquake recorded by more than 600 high rate gps stations of the plate boundary observatory pbo and analyzed kinematic displacement results with seismic array methods from these high rate gps seismograms we identified abundant seismic phases not only including clear body waves such as multiple s waves s ss sss ssss traveling along minor major great circle arc and ssssss beyond 360 degrees but also the r1 r5 rayleigh waves and g1 g6 love waves some of which travel around the earth multiple times many of these seismic phases have not been reported by previous high rate gps studies the group velocity dispersion curves extracted from multiple earth circling love waves of high rate gps are consistent with those of broadband seismic records in the period from 150 to 600 s which can sample the mantle structure down to top of the lower mantle thus important for understanding interaction between upper mantle and lower mantle so the dense high rate gps networks should be useful for deep mantle research as an additional valuable dataset with the development of multi system gnss and the more precise modeling of error sources high rate gnss data should have great potential for accurately detecting more geodynamic processes with much wider bandwidth in geoscience studies

attenuation relations of strong ground motion in japan using site classification based on predominant period a spectral acceleration attenuation model for japan is presented in the present study the data set includes a very large number of strong ground motion records up to the 2003 off tokach main and aftershocks site class terms instead of individual site correction terms are used the site classes of recording stations are from a recent study on site classification for strong motion recording stations in japan according to a classification scheme that has been used in japanese engineering design the use of site class terms enables tectonic source type effects to be identified and accounted for in the present model the effects of a faulting mechanism for crustal earthquakes also are accounted for for crustal and interface earthquakes a simple form of an attenuation model with respect to distance is able to capture the main strong motion characteristics and achieves unbiased estimates for subduction slab events a simple distance modification factor is employed to achieve plausible and unbiased predictions the effects of source depth tectonic source type and faulting mechanism of crustal earthquakes are significant the need for magnitude squared terms is evaluated and the use of magnitude squared terms reduces the interevent error further

a stochastic earthquake ground motion prediction model for the united kingdom low seismicity regions such as the united kingdom uk pose a challenge for seismic hazard analysis in view of the limited amount of locally recorded data available in particular ground motion prediction is faced with the problem that most of the instrumental observations available have been recorded at large distances from small earthquakes direct extrapolation of the results of regression on these data to the range of magnitudes and distances relevant for the seismic hazard analysis of engineered structures generally leads to unsatisfactory predictions the present study presents a new ground motion prediction equation gmpe for the uk in terms of peak ground acceleration pga peak ground velocity pgv and 5 damped pseudospectral acceleration psa based on the results of numerical simulations using a stochastic point source model calibrated with parameters derived from local weak motion data the predictions from this model are compared with those of previous gmpes based on uk data other gmpes derived for stable continental regions scrs as well as recent gmpes developed for the wider european area

derivation of a reference shear wave velocity model from empirical site amplification abstract the definition of a reference bedrock condition representative of a region of interest is of great significance in seismic hazard assessment it is highly beneficial when ground motion prediction equations are referenced to a specific site condition particularly in the case of site specific seismic hazard analyses when known the effect of any given site with respect to the reference can then be applied to the predicted ground motion however the choice of a reference velocity profile is not straightforward mainly due to the high variability of the velocity structure in the shallower layers a new method to define the regional reference rock profile is proposed the method relates quarter wavelength average velocity at a site to frequency dependent amplification a reference bedrock velocity profile can then be directly defined in relation to expected amplification characteristics over a number of sites we compare 27 quarter wavelength velocity profiles from seismic station locations in switzerland with empirical amplification functions derived from spectral modeling from this comparison a set of frequency dependent calibration relationships is established assuming that the reference profile is defined by a lack of any relative amplification the quarter wavelength velocity profile that corresponds to unitary spectral amplification can be extracted the reference velocity profile can then be obtained through an inversion procedure and defines the reference for the ground motion prediction equation gmpe the proposed reference velocity profile is compared with previous reference velocity profiles a good agreement is found between the different methods additionally an estimation of the transfer function for the swiss reference rock condition is provided this can be used to correct recorded or estimated spectral amplitudes for the local response of the reference site finally it is shown that the coefficients from the aforementioned correlations can be used to estimate a generic amplification function at any site with a known quarter wavelength velocity profile

postglacial sealevels on a spherical self gravitating viscoelastic earth effects of lateral viscosity variations in the upper mantle on the inference of viscosity contrasts in the lower mantle abstract previous studies of lateral viscosity variations on postglacial rebound often neglect the spherical shape of the earth and the self gravity of the solid earth and oceans in this paper the consistent sealevel equation is solved by the coupled laplace finite element method for a spherical self gravitating incompressible maxwell earth it confirms the importance of self gravity in the oceans on sealevel computation near the ice margin where the data are most sensitive to the existence of lateral variations in lithospheric thickness and asthenospheric viscosity the effects of lateral variations in lower mantle viscosity asthenospheric viscosity and lithospheric thickness are investigated this paper confirms the finding of earlier investigations the combined effect of lateral viscosity variations in the lower mantle with reverse viscosity contrasts in the upper mantle is also investigated for sealevel data near the center of rebound the effect of lateral viscosity contrast in the lower mantle can be masked by the existence of a reverse lateral viscosity contrasts in the upper mantle however this is not the case for sealevel data just outside the ice margin

slip distribution of the february 27 2010 mw 8 8 maule earthquake central chile from static and high rate gps insar and broadband teleseismic data 1 the shallow depth underthrust earthquake of february 27 2010 mw 8 8 ruptured the subduction plate interface in central chile between 34 s and 38 s we retrieve the spatial and temporal distribution of slip during this mega earthquake through a joint inversion of teleseismic records insar and high rate gps hrgps data additionally our model is shown to agree with broadband surface waves rupture initiated at about 32 km depth and propagated bilaterally resulting in two main slip zones located ssw and nne of the hypocenter nucleation did not take place within or at the edge of one of these main asperities but in between during the first 30s slip propagated predominantly southwards later on the rupture evolved more slowly and more symmetrically eventually the northern asperity became predominant with maximum slip reaching about 20 m most of the seismic moment was released within 110s a relatively short time explained by the bilateral propagation the overall average rupture velocity is 2 6 km s but propagation occurred initially faster towards the south 3 2 km s large slip did not reach the trench a result consistent with the moderate size of the tsunami down dip rupture stopped at about 50 km depth in agreement with the lower limit of the locked zone inferred by ruegg et al 2009 from pre seismic gps data

viscous gravitational relaxation summary this paper is concerned with a detailed examination of the response of maxwell models of the planet to surface mass loads particular attention is devoted to an examination of the factors which determine the isostatic response since the understanding of this response is crucial in a number of different geodynamic problems one particular example which we discuss in detail is concerned with the prediction of free air gravity anomalies produced by large scale deglaciation events using the methods developed here we are able to provide the first direct assessment of the importance of initial isostatic disequilibrium on the observed relative sea level variations and free air gravity anomalies forced by the melting of the laurentide ice sheet we are therefore able to estimate the extent to which such initial disequilibrium might influence the inference of mantle viscosity from isostatic adjustment data our calculations establish that free air gravity data although they are sensitive to the degree of initial disequilibrium provide an extremely high quality constraint upon the viscosity of the lower mantle

lateral asthenospheric viscosity variations and postglacial rebound a case study for the barents sea the effect of lateral asthenospheric viscosity variations on observable signatures related to postglacial rebound in the barents sea is studied using a finite element approach to discretize the problem a comparison between a laterally homogeneous reference earth model and a laterally heterogeneous earth model is performed the results indicate that a change in asthenospheric viscosity of about three orders of magnitude influences predictions of land uplift up to 10 20 m present day velocities up to 0 5 1 5 mm a and present day gravity anomalies up to 0 4 0 8 mgal in the northwestern part of the barents sea region

ability of 1 hz gps data to infer the source process of a medium sized earthquake the case of the 2008 iwate miyagi nairiku japan earthquake 1 we demonstrate the ability of 1 hz global positioning system gps data to infer a medium sized m6 class earthquake source process through an inversion study of the 2008 iwate miyagi nairiku japan earthquake m 6 9 1 hz gps waveforms for this earthquake are compared and show good agreement with strong motion waveforms ground motions are well recorded at a sufficient number of gps stations in and around source region allowing us to perform waveform inversion using 1 hz gps data only the 1 hz gps inversion result shows fairly good agreement with a joint inversion of geodetic and strong motion data such as the seismic moment mw 6 9 cumulative slip distribution and rupture propagation such agreements demonstrate that 1 hz gps is able to infer the dynamic features of the rupture process as well as permanent or static slip even for a m6 class medium sized earthquake

developing an application specific ground motion model for induced seismicity abstract a key element of quantifying both the hazard and risk due to induced earthquakes is a suite of appropriate ground motion prediction equations gmpes that encompass the possible shaking levels due to such events induced earthquakes are likely to be of smaller magnitude and shallower focal depth than the tectonic earthquakes for which most gmpes are derived furthermore whereas gmpes for moderate to large magnitude earthquakes are usually derived to be transportable to different locations and applications taking advantage of the limited regional dependence observed for such events the characteristics of induced earthquakes warrant the development of application specific models a preliminary ground motion model for induced seismicity in the groningen gas field in the netherlands is presented as an illustration of a possible approach to the development of these equations the gmpe is calibrated to local recordings of small magnitude events and captures the epistemic uncertainty in the extrapolation to larger magnitude considered in the assessment of the resulting hazard and risk

effects of lateral variations in lithospheric thickness and mantle viscosity on glacially induced surface motion in laurentia abstract the effects of lateral variations in lithospheric thickness and mantle viscosity on surface motions in laurentia are investigated using the finite element method both a simple axisymmetric ice model and a more realistic ice deglaciation model ice4g are used to investigate the effects of lateral heterogeneity beside the laterally homogeneous reference model six laterally heterogeneous models are used the lateral heterogeneity in the lithosphere upper mantle transition zone and lower mantle are inferred from seismic tomographic model s20a in general the magnitude of the effect of lateral heterogeneity is found to depend on the deglaciation history and the relative position between the ice center and the lateral heterogeneity it is shown that lateral heterogeneity does affect horizontal motion in laurentia however because the effects of lateral heterogeneity from different depths give different orientations to the incremental velocity vector the total effect is not large enough to overwhelm the divergent motion but just weaken it in southern laurentia for land uplift rate the effect of lateral viscosity variation in the transition zone between 425 and 700 km depth is opposite to that of the upper or lower mantle thus the net effect of lateral heterogeneity on uplift rate is not very large but enough to change the shape of the uplift pattern

reference s wave velocity profile and attenuation models for ground motion prediction equations application to japan defining the reference rock or soil condition related to ground motion prediction is an important aspect of seismic hazard analysis in a previous study by the authors a method was proposed to establish a reference rock profile for switzerland through the comparison of empirical amplification functions with shear wave velocity profiles at 27 selected sites of the swiss national seismic network the retrieved velocity profile served as reference for a regional ground motion prediction equation however a lacking piece of information remained the anelastic attenuation for such a reference profile reference attenuation is essential to correctly model and interpret amplification at high frequencies in the present study we extended our approach to simultaneously model both the reference shear wave velocity profile and the corresponding attenuation for japan we compared site specific attenuation measurements with quarter wavelength average velocities at 36 soil and rock sites from the japanese kik net strong motion network the selected sites are characterized by a lack of observed resonance phenomena in order to avoid trade off between amplification and attenuation effects we establish a parametric model through regression analysis the resulting model gives us the possibility to estimate anelastic attenuation of a rock site with a given velocity profile and provides the base for host to target adjustments of real or modeled ground motion

coseismic and postseismic elastic wave velocity variations caused by the 2008 iwate miyagi nairiku earthquake japan 1 we analyze coseismic and postseismic velocity variations caused by the june 13 2008 iwate miyagi nairiku earthquake mw 6 9 using passive image interferometry pii seismic noise is correlated in order to reconstruct the green s function between two sensors shear wave velocity changes are determined by relating the coda parts of the daily green s functions to a long term reference green s function our study extends from january 2008 to august 2010 and includes the correlations for 190 station pairs in three different frequency ranges from 0 125 to 1 0 hz we show that combining the 9 different component cross correlation functions stabilizes the velocity change estimation and increases analysis resolution the observed velocity change curves can be fitted by model time series consisting of a coseismic velocity drop followed by logarithmic postseismic recovery and seasonal velocity variations the coseismic velocity drops are stronger at higher frequencies and are concentrated in the southern part of the fault zone a tomography algorithm was developed to reproject the observed velocity variations of the different sensor pairs onto the single sensors the depth distribution of coseismic changes was modeled for the three stations with the largest velocity drops at two stations the coseismic velocity changes are located in the upper several hundred meters the third station shows indications for deeper changes in the order of kilometers postseismic recovery takes significantly longer than the analyzed two year period seasonal velocity variations with periods of one year are observed at all analyzed frequencies for most station pairs

lateral viscosity variations and post glacial rebound effects on present day vlbi baseline deformations by means of a finite element algorithm we investigate the effects of lateral viscosity variations upon the horizontal motions currently detected by vlbi techniques in europe our axisymmetric flat models appropriate to describe the rebound due to the melting of the fennoscandia ice sheet are characterized by a layered compressible mantle with linear maxwell rheology we have first computed the time evolution of theoretical baselines characterized by a simple geometry in agreement with previous results the rates of horizontal deformation have been found to be greatly sensitive to both lateral viscosity variations and deep mantle stratification especially for baselines located in the vicinity of the ice sheet margin to complete our study we have compared our numerical results with the observed time evolutions of relevant european baselines onsala wettzell and onsala eflsberg are fitted by a laterally varying asthenosphere and sharp viscosity increase in the lower mantle longer baselines connecting these sites to medicina northern italy indicate that post glacial rebound is responsible only for a fraction of the vlbi observations the residual being thus attributable to continental collision in the mediterranean sea

a stochastic ground motion model for switzerland abstract we present a stochastic ground motion model for switzerland a model for the far field fourier amplitude spectra of earthquakes is first proposed constrained by ground motions observed from small local and regional earthquakes in addition to macroseismic intensities observed from large damaging events in switzerland we then use this model in a stochastic simulation technique to generate predictions of peak ground acceleration and velocity and 5 damped response pseudo spectral acceleration we facilitate the prediction of ground motions from finite fault sources through the use of the r eff distance metric and show that magnitude and distance scaling behavior of events up to m w 7 5 is broadly consistent with next generation attenuation and japanese models ground motion prediction uncertainty is described in terms of between and within event uncertainties through residual analysis of response spectra finally single station sigma is derived accounting for the prediction uncertainty at a given site without the ergodic assumption consistency of the model is emphasized through its compatibility with other seismic hazard products the model is referenced to a generic rock profile that was developed by utilizing velocity profiles of the sites of seismic stations and is calibrated at higher magnitudes to the swiss regional macroseismic intensity prediction model furthermore the model is based on moment magnitudes from the recently developed earthquake catalogue of switzerland 2009 ecos09 the well defined reference for the model means that it can easily be adapted for a site specific application for instance through the use of proxies such as quarter wavelength velocity and travel time average shear wave velocity in the upper 30 m v s 30