seismic tomography a window into deep earth abstract the goal of this paper is to provide an overview of the current state of the art in seismic tomography and trace its origins from pioneering work in the early 1970s to its present status as the pre eminent tool for imaging the earth s interior at a variety of scales due to length limitations we cannot hope to cover every aspect of this diverse topic or include mathematical derivations of the underlying principles rather we will provide a largely descriptive coverage of the methodology that is targeted at readers not intimately familiar with the topic the relative merits of local versus global parameterization ray tracing versus wavefront tracking backprojection versus gradient based inversion and synthetic testing versus model covariance are explored a variety of key application areas are also discussed including body wave traveltime tomography surface wave tomography attenuation tomography and ambient noise tomography established and emerging trends many of which are driven by the ongoing rapid increases in available computing power will also be examined including finite frequency tomography full waveform tomography and joint tomography using multiple datasets several practical applications of seismic tomography including body wave traveltime attenuation and surface waveform are presented in order to reinforce prior discussion of theory

new constraints on the 3d shear wave velocity structure of the upper mantle underneath southern scandinavia revealed from non linear tomography abstract we analyse travel times of shear waves which were recorded at the magnus network to determine the 3d shear wave velocity vs structure underneath southern scandinavia the travel time residuals are corrected for the known crustal structure of southern norway and weighted to account for data quality and pick uncertainties the resulting residual pattern of subvertically incident waves is very uniform and simple it shows delayed arrivals underneath southern norway compared to fast arrivals underneath the oslo graben and the baltic shield the 3d upper mantle vs structure underneath the station network is determined by performing non linear travel time tomography as expected from the residual pattern the resulting tomographic model shows a simple and continuous vs perturbation pattern a negative vs anomaly is visible underneath southern norway relative to the baltic shield in the east with a contrast of up to 4 vs and a sharp w e dipping transition zone reconstruction tests reveal besides vertical smearing a good lateral reconstruction of the dipping vs transition zone and suggest that a deep seated anomaly at 330 410 km depth is real and not an inversion artefact the upper part of the reduced vs anomaly underneath southern norway down to 250 km depth might be due to an increase in lithospheric thickness from the caledonian southern scandes in the west towards the proterozoic baltic shield in sweden in the east the deeper seated negative vs anomaly 330 410 km depth could be caused by a temperature anomaly possibly combined with effects due to fluids or hydrous minerals the determined simple 3d vs structure underneath southern scandinavia indicates that mantle processes might influence and contribute to a neogene uplift of southern norway

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

carbon dioxide reaction processes in a model brine aquifer at 200 c and 200 bars implications for geologic sequestration of carbon the reactive behavior of supercritical co2 under conditions relevant to geologic storage and sequestration of c is largely unknown experiments were conducted in a flexible cell hydrothermal apparatus to determine the extent of fluid rock reactions in addition to carbonate mineral precipitation that may occur in a brine aquifer aquitard system that simulates a saline aquifer storage scenario the system was held at 200 c and 200 bars for 59 days 1413 h to approach steady state then injected with co2 and allowed to react for another 80 days 1924 h in addition to magnesite precipitation silicate minerals quartz plagioclase microcline and biotite in the aquifer and the aquitard display textures etch pits mineralization indicating significant reaction changes in elemental abundances in the brine following addition of co2 include ph decrease and enrichment in cl partly due to supercritical co2 desiccation of the brine geologic sequestration systems have potential for geochemical reactions that extend beyond simple aqueous dissolution of co2 and precipitation of carbonate these reactions may produce geochemical and geotechnical consequences for sequestration and provide important characteristics for monitoring and evaluation of stored co2 a n understanding of multi phase equilibrium relationships between supercritical co2 and aquifer brine systems also raises new questions for a variety of geologic systems multi phase fluid equilibria may for example account for the large amounts and heterogeneous distributions of calcite cement in a wide variety of geologic systems particularly in sedimentary basin sandstones published by elsevier science ltd

free surface effects on the propagation of dynamic rupture dynamic rupture of reverse and normal fault intersecting the surface are investigated in the case of a normal fault nucleating at depth and propagating upwards coupling of rupture radiated stress and free boundary conditions at the surface may induce a shallow secondary nucleation anticipating up to a few seconds the arrival of the main rupture front indeed the free surface induces normal stress fluctuations modifying the fault frictional strength no significant effect on rupture velocity is observed in the case of reverse faulting these incidences are explained by a stress analysis and illustrated by some numerical simulations in the case of dynamic normal faulting in a homogeneous half space the described effects could explain some observations of high frequency radiation close to the surface in documented shallow earthquakes like in kalamata 1986 bouin 1994

role of initial stress rotations in rupture dynamics and ground motion a case study with implications for the wenchuan earthquake 1 motivated by observations in the 2008 mw 7 9 wenchuan earthquake we study effects of systematic changes in the principal stress orientation along the fault strike on rupture dynamics and ground motion using a 3 d finite element method based on anderson s theory of faulting we set up the initial stress field with rotations in stress orientations along strike for a dynamic rupture model of a shallow dipping fault we find that initial stress rotations along strike can cause dramatic changes in rupture speed and produce distinct patterns in slip distribution and peak ground motion when a mismatch unfavorable for faulting between fault geometry and initial stress orientations is encountered rupture can spontaneously stop some first order features in the wenchuan event may be partially caused by rotations in the principal stress orientation along strike such as the rupture arrest at the northeast end and two severe destruction zones in the observed seismic intensity distribution these results may have important implications for assessing seismic hazards imposed by faults with changes in the initial stress field along strike worldwide

experimental evidence that thrust earthquake ruptures might open faults many of earth s great earthquakes occur on thrust faults these earthquakes predominantly occur within subduction zones such as the 2011 moment magnitude 9 0 eathquake in tohoku oki japan or along large collision zones such as the 1999 moment magnitude 7 7 earthquake in chi chi taiwan notably these two earthquakes had a maximum slip that was very close to the surface this contributed to the destructive tsunami that occurred during the tohoku oki event and to the large amount of structural damage caused by the chi chi event the mechanism that results in such large slip near the surface is poorly understood as shallow parts of thrust faults are considered to be frictionally stable here we use earthquake rupture experiments to reveal the existence of a torquing mechanism of thrust fault ruptures near the free surface that causes them to unclamp and slip large distances complementary numerical modelling of the experiments confirms that the hanging wall wedge undergoes pronounced rotation in one direction as the earthquake rupture approaches the free surface and this torque is released as soon as the rupture breaks the free surface resulting in the unclamping and violent flapping of the hanging wall wedge our results imply that the shallow extent of the seismogenic zone of a subducting interface is not fixed and can extend up to the trench during great earthquakes through a torquing mechanism

deep structure of fennoscandia from fundamental and higher mode dispersion of rayleigh waves abstract surface wave dispersion for the baltic shield area has been investigated through analysis of phase velocities up to periods of about 250 s for the fundamental rayleigh mode and about 80 s for the first two higher modes this has enabled investigation of the lithosphere asthenosphere system and deeper regions down to about 400 km the shear wave velocitydepth relationship obtained from the inversion of dispersion data for the paths cop kev cop krk can be considered as representative of an average model for the baltic shield moreover the inversion of dispersion data supplemented by previous results from the scandinavian area suggest the presence of significant lateral heterogeneity down to depths of about 350 km moving from the older precambrian shield cop kev cop krk to the peripheral area nur cop models with small if any differences in average shear velocity are consistent with the data in the depth range 350 450 km for the regions studied

mapping the lithosphere asthenosphere boundary through changes in surface wave anisotropy abstract the alignment of olivine crystals is considered as the dominant source of seismic anisotropy in the subcrustal lithosphere and asthenosphere different components of large scale anisotropy can be traced in depth distributions of the radial and azimuthal anisotropy of surface waves we propose a global model of the lithosphere asthenosphere boundary lab as a transition between a frozen in anisotropy in the lithosphere to anisotropy in the sublithospheric mantle related to the present day flow due to different orientations of velocity maxima in the anisotropic subcrustal lithosphere and the asthenosphere the velocity contrast related to the lab can increase in particular directions because of their long wavelengths and horizontal propagation surface waves suffer from poor lateral resolution however surface waves with various wavelengths allow us to map gross features of the lab with a good vertical resolution we estimate depths to the lab to be between 200 and 250 km for the precambrian shields and platforms around 100 km for the phanerozoic continental regions and 40 70 km beneath oceans from the world wide depth distribution of the radial and azimuthal anisotropy of surface waves

inelastic surface deformation during the 2013 mw 7 7 balochistan pakistan earthquake comprehensive quantification of the near field deformation associated with an earthquake is difficult due to the inherent complexity of surface ruptures the a d 2013 m w 7 7 balochistan pakistan earthquake dominated by left lateral motion with some reverse component ruptured a 200 km long section of the hoshab fault we characterize the coseismic rupture in detail along its entire length optical and radar satellite images are combined to derive the full three dimensional far field displacement 115 m pixel size and the high resolution 2 5 m pixel horizontal displacement field resulting from the earthquake we show that the vertical deformation is significant in several locations the high resolution near field horizontal displacement 1 km around the rupture reveals inelastic shortening at the fault surface significantly larger than expected from simple elastic modeling a zone of extension in the hanging wall as much as 1 km wide concentrating numerous tensile cracks visible in submeter scale optical images compensates for this excess shortening

high resolution body wave tomography beneath the svekalapko array ii anomalous upper mantle structure beneath the central baltic shield high resolution body wave tomography beneath the svekalapko array ii anomalous upper mantle structure beneath the central baltic shield

archean continental assembly in the southeastern superior province of canada between 1988 and 1993 seismic reflection and refraction surveys were acquired across the medium to high grade opatica plutonic gneiss belt the low grade abitibi greenstone belt and the pontiac metasedimentary belt all of which form part of the late archean superior province shallowly north dipping reflections define a structural style consistent with the northward underthrusting and accretion over about 30 ma of various exotic terranes against a backstop provided by the opatica belt this rapid southward growth of the archean protocraton was driven by at least one north dipping subduction zone as revealed by north dipping reflections that extend to 65 km depth in the upper mantle below the opatica belt in contrast to the mainly orthogneissic opatica and pontiac belts the midcrust of the abitibi belt comprises metasedimentary and igneous rocks plus imbricated units of unknown affinity relict midcrustal accretionary complexes of substantial size whieh are indicative of primary suture zones are interpreted near the northern and southern limits of the abitibi belt an interpreted basal decollement and significantly older ages in the north suggest that the upper crustal greenstone rocks are allochthonous evidence of large scale extension appears to be confined to the southern volcanic zone of the abitibi which developed into a half graben as the original suture zone was reactivated in extension unusually high seismic p wave velocities 7 5 8 2 kms 1 are present in the lower 8 km of the abitibi crust and they correlate well with a downward reduction in seismic reflectivity attributable to late modification of the deepest part of the crust crustal xenolith studies suggest that this process may be linked to early proterozoic magmatism

the three dimensional dynamics of dipping faults recent two dimensional dynamic simulations of dip slip faulting niel sen 1998 oglesby et al 1998 2000 shi et al 1998 have shown that the asym metric geometry of dip slip faults that intersect the free surface can have large effects on the dynamics of earthquake rupture the nonvertical dip angle of such faults leads to larger motion on the footwall than the hanging wall as well as much larger motion from thrust reverse faults than from normal faults with the same geometry and stress magnitudes in the present work we perform full three dimensional simulations of thrust reverse normal and strike slip faults and show that the same effects exist in three dimensions strike slip fault motion is either in between or lower than the motion of both dip slip faults additional three dimensional effects include strong rake rotation at the free surface the results confirm the findings of the previous studies and further elucidate the dynamic effects of the free surface on fault rupture slip and ground motion they are also borne out by early analyses of the 1999 chi chi taiwan thrust earthquake which displayed higher motion on the hanging wall than on the footwall and a strong oblique component of motion at the surface

the sorgenfrei tornquist zone as the mantle edge of baltica lithosphere new evidence from three dimensional seismic anisotropy joint analysis of shear wave splitting parameters and directional dependence of teleseismic p residuals based on data from the seismic experiment tor across the trans european suture zone suggest that the sorgenfrei tornquist zone stz in northern denmark forms the south western margin of baltica in the upper mantle different lithosphere thickness and different orientation of seismic anisotropy in the mantle lithosphere identify three domains separated by the stz between denmark and southern sweden and the thor suture between northern germany and denmark we suggest that the anisotropy reflects frozen in olivine fabrics most probably created during early stages of the evolution of the european continent the middle danish block might represent a microplate caught in between avalonia and baltica before the caledonian orogeny

novel anisotropic teleseismic body wave tomography code anitomo to illuminate heterogeneous anisotropic upper mantle part ii application to data of passive seismic experiment lapnet in northern fennoscandia seismic anisotropy provides a unique constraint on the past and present dynamics of the lithosphere and sublithospheric mantle to contribute to studies of large scale tectonic fabric we have developed code anitomo for regional anisotropic tomography anitomo allows us to invert simultaneously relative traveltime residuals of teleseismic p waves for 3 d distribution of isotropic velocity perturbations and velocity anisotropy in the upper mantle weak hexagonal anisotropy with the symmetry axis oriented generally in 3 d is considered the first application of novel code anitomo to data from passive seismic experiment lapnet results in a model of anisotropic velocities of the upper mantle beneath northern fennoscandia we have opted for northern fennoscandia for the first application because it is a tectonically stable precambrian region with a thick anisotropic mantle lithosphere without significant thermal heterogeneities we carefully analyse the distribution of the rays to limit the fully anisotropic inversion only to the volume with the sufficient directional ray coverage capability of the given inversion setup to reveal large scale anisotropic structures in the upper mantle is documented by a series of synthetic tests the strongest anisotropy and the largest velocity perturbations concentrate at depths corresponding to the mantle lithosphere while in deeper parts of the tomographic model the lateral variations are insignificant we delimit regions of laterally and vertically consistent anisotropy in the mantle lithospheric part of the model we attribute the retrieved domain like anisotropic structure of the mantle lithosphere in northern fennoscandia to preserved fossil fabrics of the archean microplates accreted during the precambrian orogenic processes

the lithosphere asthenosphere boundary in the north west atlantic region abstract a detailed knowledge of the thickness of the lithosphere in the north atlantic is an important parameter for understanding plate tectonics in that region we achieve this goal with as yet unprecedented detail using the seismic technique of s receiver functions clear positive signals from the crust mantle boundary and negative signals from a mantle discontinuity beneath greenland iceland and jan mayen are observed according to seismological practice we call the negative phase the lithosphere asthenosphere boundary lab the seismic lithosphere under most of the iceland and large parts of central greenland is about 80 km thick this depth in iceland is in disagreement with estimates of the thickness of the elastic lithosphere 10 20 km found from postglacial rebound data in the region of flood basalts in eastern greenland which overlies the proposed iceland plume track the lithosphere is only 70 km thick about 10 km less than in iceland which is located directly above the proposed plume at the western greenland coast the lithosphere thickens to 100 120 km with no indication of the iceland plume track identified below jan mayen the lithospheric thickness varies between 40 and 60 km

seismic anisotropy of the mantle lithosphere beneath the swedish national seismological network snsn body wave analysis shear wave splitting and p travel time residuals detect anisotropic structure of the upper mantle beneath the swedish part of fennoscandia geographic variations of both the

summary of project tor delineation of a stepwise sharp deep lithosphere transition across germany denmark sweden project tor teleseismic tomography across the tornquist zone in germany denmark sweden is now producing results we are able to detect very significant deep lithosphere differences and we can now discuss the sharpness laterally in 1996 1997 our 120 seismographs constituted the largest seismic antenna ever in europe the tor area was chosen along a well studied crustal profile of an earlier project and the inversion efforts are concentrated on the deep lithosphere and asthenosphere differences to depths around 300 km the tor investigation can be called two and a half dimensional as it has a 900 km profile length with 100 km width plus a few seismographs off the profile the tor data have been subjected to p wave travel time tomography surface wave and receiver function analysis as well as anisotropy and scattering measurements through ray tracing in a compiled crustal model and subtraction of the modelled travel time anomalies the influence of the lower lithosphere asthenosphere on the seismic rays from distant earthquakes is being established travel time tomography results confirm very large lateral lithosphere differences of 4 6 in p wave velocity for several events of the large data base it is demonstrated that the observed p wave travel time anomalies of 1 2 s can be divided almost equally between known crustal effects and lower lithosphere asthenosphere differences which then must account for about 1 s of the travel time differences the transition is interpreted to be sharp and steep in two places it goes all the way through the lithosphere at the northern rim of the tornquist zone near the border between sweden and denmark and here the lithosphere difference is large a smaller lithosphere difference is found near the southern edge of the ringkobing fyn high just north of the border between denmark and germany also this transition is sharp and steep and goes all through the lithosphere these two sharp transitions divide the tor region into three different lithosphere structures distinguishable in p wave travel time tomography surface wave dispersion p and s wave anisotropy and partly in p wave scattering

complex lithospheric structure under the central baltic shield from surface wave tomography complex lithospheric structure under the central baltic shield from surface wave tomography

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

seismic anisotropy a key to resolve fabrics of mantle lithosphere of fennoscandia abstract by merging different regional sets of body wave data we compile a relief of the lithosphere asthenosphere boundary in one of the oldest continental regions on the planet the fennoscandian shield a maximum lithospheric thickness of 200 220 km is observed in the central part of the shield and a significant thinning at its margins particularly in the southwest at the trans european suture zone fabric of the mantle lithosphere is modelled from independent sets of anisotropic parameters relative p residual spheres and shear wave splitting the mantle lithosphere of fennoscandia consists of several domains consistent olivine fabrics of dipping foliations in 3d anisotropic models of the proterozoic lithosphere or predominantly dipping lineations in models of the archean lithosphere the strength of seismic anisotropy agrees with findings from mantle xenoliths we interpret the anisotropic domains as fragments of mantle lithosphere retaining an old fossil olivine fabric which was created before these micro continents assembled we envisage an early form of plate tectonic processes such as successive subduction episodes stacking of oceanic plates and accretion of magmatic arcs such processes could create the generally observed fossil dipping fabrics of the thick precambrian mantle lithosphere starting as early as the archean

non linear body wave teleseismic tomography along the tor array summary the tor project investigates the lithosphere asthenosphere structure under the tornquist zone between denmark and sweden around 150 seismic stations 108 short period 28 broadband and 14 other permanent stations were employed in a rectangular array along a 900 km long by 100 km wide strip across the tornquist zone from july 1996 to august 1997 the results obtained based on a non linear teleseismic tomography algorithm reveal significant p velocity variations up to 5 per cent along the tor array from northern germany to southern sweden distinct lithospheric blocks are also recognized in the inversion results two inverse methods singular value decomposition and a quadratic programming method were implemented in order to investigate whether or not the lithospheric blocks and major boundaries in the inversion are required by the data or are artefacts of the inversion according to the results the lithosphere under northern germany is thin but reaches to intermediate thicknesses of about 120 km in the tornquist zone area farther north in the baltic shield more than 200 km of continental lithosphere is recognized in the model abrupt lateral p velocity changes maximum 5 per cent are seen at both the southern and northern sides of the tornquist zone

attenuation of radiated ground motion and stresses from three dimensional supershear ruptures 1 radiating shear and rayleigh waves from supershear ruptures form mach waves that transmit large amplitude ground motion and stresses to locations far from the fault we simulate bilateral ruptures on a finite width vertical strike slip fault of width w and half length l with l w breaking the surface of an elastic half space and focus on the wavefield out to distances comparable to l at distances much smaller than w two dimensional plane strain slip pulse models i e models in which the lateral extent of the slip zone is unbounded accurately predict the subsurface wavefield amplitudes in the shear mach wedge of those models are undiminished with distance from the fault when viewed from distances far greater than w rupture is accurately modeled as a moving point source that produces a shear mach cone and on the free surface rayleigh wave mach fronts geometrical spreading of the shear mach cone occurs radially and amplitudes there decrease with the inverse square root of distance the transition between these two asymptotic limits occurs at distances comparable to w similar considerations suggest that rayleigh mach waves suffer no attenuation in the ideally elastic medium studied here the rate at which fault strength weakens at the rupture front exerts a strong influence on the off fault fields only in the immediate vicinity of the fault for both sub rayleigh and supershear ruptures and at the mach fronts of supershear ruptures more rapid weakening generates larger amplitudes at the mach fronts

velocity modelling of the lithosphere beneath south finland abstract the seismic structure of the upper lithosphere beneath southern finland area was investigated by a series of seismic refraction and reflection surveys during the 1980s and 1990s the resulting two dimensional models of the crust from the deep seismic sounding dss profiles were combined to image the region as a three dimensional structure by interpolating and smoothing although these models are reasonably accurate the velocity structure between the profiles is truly unknown in this study the seismograms of the dss shots at permanent seismic stations are used to estimate new depth points of reflections from the moho between the profiles the relief of the moho boundary is reinterpolated by combining our depths with estimates along the dss profiles the detailed crustal model is discussed together with the geology and gravity anomalies of the area the contradiction between the variation of the crust thickness in our model and the bouguer anomaly support previously presented idea of mass surplus compensation a simple three dimensional seismic p wave velocity model is also constructed and presented as vertical and horizontal cross sections the variations of velocity in the upper crust correlate with surface geology unlike in the deeper crust the velocity of the lithosphere beneath south finland varies smoothly from 5 6 6 2 km s on the surface to 7 8 8 6 km s below the moho

lithospheric and sublithospheric anisotropy beneath the baltic shield from surface wave array analysis abstract we report measurements of radial and azimuthal anisotropy in the upper mantle beneath southern and central finland which we obtained by array analysis of fundamental mode rayleigh and love waves azimuthally averaged phase velocities were analysed in the period range 15 to 190 s for rayleigh waves and 15 to 100 s for love waves the azimuthal variation of the rayleigh wave phase velocities was obtained in the period range 20 to 100 s the limited depth resolution of fundamental mode surface waves necessitated strong damping constraints in the inversion for anisotropic parameters we investigated the effects of non unicity on the final model by experimenting with varying model geometries the radial anisotropy beneath finland can be explained by a lithosphere at least 200 km thick predominantly 50 by volume composed of olivine crystals having their a axes randomly distributed in the horizontal plane on the contrary the measured lithospheric azimuthal anisotropy is small this can be reconciled with body wave observations made in the area that indicate a complex pattern of rapidly varying anisotropy below 200 250 km depth that is below the petrologic lithosphere as revealed by xenolith analyses conducted in the area the magnitude of the azimuthal anisotropy increases and would be compatible with a mantle containing 15 20 by volume of olivine crystals whose a axes are coherently aligned in the n ne direction the alignment of the a axes is off the direction of present day absolute plate motion in either the no net rotation or hot spot reference frame currently n55 n60 we interpret this mismatch as evidence for a complex convective flow pattern of the mantle beneath the shield which by inference is decoupled from the overlying lithosphere

anisotropy across the sorgenfrei tornquist zone from shear wave splitting abstract during the tor 1 passive seismic experiment in 1996 97 a maximum of 139 temporary seismograph stations were operating over the sorgenfrei tornquist zone stz in an area extending from northern germany through denmark to central sweden one of the objectives was to study horizontal anisotropy directions in the subcrustal lithosphere and asthenosphere across the trans european suture zone to achieve this goal broad band and intermediate period 5 s data of the tor 1 stations and additional stations of permanent networks grsn geofon were analysed for splitting of sks and skks phases as a result of the relatively dense station spacing the method offers good lateral resolution of anisotropy preliminary results suggest that the directions of the fast horizontal s wave velocity are affected by the stz in central europe and southern sweden far away from the stz fast s wave directions are approximately e w while they turn more northerly closer to the stz where they are approximately parallel to the trend of the stz no significant shear wave splitting was observed north of 57 n and east of 14 e small delay times between 0 2 and 0 5 s observed at the northernmost tor 1 station t40s and t60s may be controlled by anisotropy in a thickened crust the mantle contribution of horizontal anisotropy within the stz is probably constrained to an approximately 60 km thick zone in the depth range between 70 and 300 km the observations are consistent with a model where azimuthal anisotropy is not governed by present day mantle flow in the asthenosphere but rather is frozen into the subcrustal lithosphere during the last episode of tectonic activity

an olivine fabric database an overview of upper mantle fabrics and seismic anisotropy we present a unique database of 110 olivine petrofabrics and their calculated seismic properties the samples come from a variety of the upper mantle geodynamic environments ophiolites subduction zones and kimberlites with a wide range of micro structures a phenomenological relationship is established between p and s wave seismic anisotropy and the degree of crystal alignment fabric strength seismic anisotropy increases rapidly at low fabric strength before reaching a near saturation level of 15 to 20 for p waves and 10 to 15 for s waves despite a large variation in the symmetry of fabric patterns the average seismic properties of the different fabric micro structural and geodynamic settings have similar anisotropies in both magnitude and symmetry hence it would seem possible to determine some measure of fabric strength from seismic anisotropy if the dimensions of the anisotropic region are known but not geodynamic environment or details of the petrofabric pattern a simple pattern of seismic anisotropy characterises the average sample of the database which has the following features the polarisation plane of the fastest s wave is parallel or sub parallel to the foliation plane the maximum shear wave splitting is parallel to the y structural direction in foliation plane and normal to the lineation the maximum of the p wave velocity is parallel to the high concentration of 100 axes which is sub parallel to the lineation the 100 orientation distribution has the greatest influence on the p wave seismic anisotropy the 100 and 001 orientation distributions have the greatest influence on the symmetry of s wave anisotropy although the magnitude of anisotropy is influenced by the distribution of all three principal axes although the database only contains olivine petrofabrics this statistical study clearly shows that seismic anisotropy can be used to deduce the orientation of the structural frame in the upper mantle 1998 elsevier science b v all rights reserved

the deep structure of the scandes and its relation to tectonic history and present day topography abstract we review the results of the toposcandiadeep project a component of the topoeurope project in which we have studied the crustal and upper mantle structures of southern norway in relation to its high topography the scandinavian mountain chain the scandes is an intracontinental mountain chain at the western edge of the baltic shield and has its southern part located in southern norway the timing as well as the processes causing the formation of the scandes are disputed we bring new geophysical constraints to this issue by providing crustal and mantle seismic models for the area and by integrated modeling of the lithosphere and its potential deformation new maps of moho depth and crustal seismic velocities have been compiled using data from refraction lines p receiver functions and noise cross correlation these results show a thickening of the crust from southwest to northeast and a small crustal root not directly located below the topographic high p s and surface wave tomography infer seismic mantle velocities lower than in normal shield structure with a possible sharp boundary close to the oslo graben these low velocities are imaged in the lithosphere and in the underlying mantle down to the 410 km discontinuity integrated modeling of seismic models and gravity data shows that the low velocities below southern norway are compatible with a change in lithosphere thickness from c 100 km under southern norway to nearly 200 km under southern sweden with possible additional differences in composition the study also indicates that the topography can be isostatically sustained by the density distribution in the crust and lithospheric mantle we argue that the lithospheric lateral variation has been present for at least 300 my and has had a significant influence on the localization of the topography independently of the mechanism for uplift

european mantle lithosphere assembled from rigid microplates with inherited seismic anisotropy abstract we have modelled three dimensional seismic anisotropy of the mantle lithosphere from anisotropic parameters of teleseismic body waves we invert jointly shear wave splitting parameters and p residual spheres based on data from dense networks of temporary and permanent stations in four european regions ranging from the variscan belt to the baltic shield changes in orientation of the large scale anisotropy caused by systematic preferred orientation of olivine identify boundaries of domains of mantle lithosphere individual domains are characterized by a consistent large scale orientation of anisotropy approximated by hexagonal or orthorhombic symmetry with generally inclined symmetry axes the domains are separated by mapped tectonic boundaries sutures which cut the entire lithosphere besides the change of anisotropy orientation at domain boundaries we often observe a change of the lithosphere and or crust thicknesses we do not detect any fabric of the mantle lithosphere which could have been produced by a collision of microcontinents in a volume detectable by large scale seismic anisotropy the observations of consistent anisotropy within individual blocks of the mantle lithosphere reflect frozen in olivine preferred orientation most probably formed prior to the assembly of microcontinents that created the modern european landmass therefore our findings support a plate tectonic view of the continental lithosphere as a mosaic of rigid blocks of the mantle lithosphere with complicated but relatively sharp contact zones these contacts are blurred by the easily deformed overlying crust terranes

joint interpretation of upper mantle anisotropy based on teleseismic p travel time delays and inversion of shear wave splitting parameters abstract we inverted shear wave splitting parameters and simultaneously analysed delays of teleseismic longitudinal waves to obtain a self consistent three dimensional 3 d image of the anisotropic upper mantle beneath the continents efficiency of the simultaneous 3 d analyses of p residual spheres and shear wave polarizations is demonstrated on data from two regions southern sweden and the western usa the anisotropic inferences of the subcrustal lithosphere are to a first approximation represented by homogeneous hexagonal or orthorhombic media with plunging symmetry axes

the dynamics of thrust and normal faults over multiple earthquake cycles effects of dipping fault geometry we perform dynamic simulations of thrust and normal faults over multiple earthquake cycles our goal is to explore effects of asymmetric fault geometry on the long term seismicity and dynamics of dipping faults a dynamic finite element method is used to model the interseismic and coseismic processes with a dynamic relaxation technique for the former the faults are loaded by stable sliding along the downward continuation of the faults the asymmetric fault geometry of dipping faults with respect to the free surface cause changes in normal stress during the interseismic and coseismic periods these changes are of opposite sign in the two periods resulting in a stabilization of the normal and shear stresses over many earthquake cycles both faults develop relatively stable event patterns in which a large event that ruptures the entire fault is preceded by a number of small events with various rupture lengths a strong asymmetry in fault and ground motion exists between thrust and normal faults and between the hanging wall and the footwall of both faults on faults dipping less than 70 in both normal and thrust faults the horizontal component of ground motion dominates on the footwall while the vertical component dominates on the hanging wall the above results may have implications in seismic hazard analysis and building design in regions where dip slip faults predominate

pulse like and crack like ruptures in experiments mimicking crustal earthquakes theoretical studies have shown that the issue of rupture modes has important implications for fault constitutive laws stress conditions on faults energy partition and heat generation during earthquakes scaling laws and spatiotemporal complexity of fault slip early theoretical models treated earthquakes as crack like ruptures but seismic inversions indicate that earthquake ruptures may propagate in a self healing pulse like mode a number of explanations for the existence of slip pulses have been proposed and continue to be vigorously debated this study presents experimental observations of spontaneous pulse like ruptures in a homogeneous linear elastic setting that mimics crustal earthquakes reveals how different rupture modes are selected based on the level of fault prestress demonstrates that both rupture modes can transition to supershear speeds and advocates based on comparison with theoretical studies the importance of velocity weakening friction for earthquake dynamics

receiver function analysis of the crust and upper mantle from the north german basin to the archaean baltic shield summary two passive seismic experiments have been carried out across the trans european suture zone tesz from northern germany to southern sweden tor and across the proterozoicarchaean suture in finland svekalapko to improve our understanding of the processes involved in the creation of the european continent teleseismic earthquakes recorded by the two networks and stations of the grsn and geofon permanent networks have been used for studies of the crust mantle and upper mantle seismic discontinuities with the receiver function method along the tor network the depth to the moho increases from 30 km at the southern edge of the profile to 40 km at the elbe line between the elbe line and tesz the moho branches off and whereas the deeper branch continues at 40 km depth to the tesz a second branch appears at 30 35 km depth the upper branch descends north of the tesz to below 55 km under the northern end of the tor profile the crustal thickening north of the tesz is accompanied by an increase in average vp vs values appearance of intracrustal conversion zones and north dipping features which we interpret as remnants of the subduction and subsequent collision between avalonia and baltica in southern finland beneath the svekalapko network the moho starts in the south at the depth of 40 45 km plunges to about 65 km depth south of the archaean proterozoic suture this deepening of the moho is coincident with a north dipping intracrustal structure apparently related to the subduction and collision and of the proterozoic and archaean provinces in proterozoic north of the line of the suture the moho rises smoothly to 45 50 km depth in the archaean province along the tor profile 410 and 660 discontinuities were hard to detect however manyfold stacking of receiver functions revealed that the conversions from the two discontinuities arrive more or less according to iasp91 predicted time across the svekalapko network 410 and 660 discontinuities arrive markedly earlier than iasp91 theoretical arrival times in particular north of the archaean proterozoic suture in finland the 410 and 660 km conversions arrive about 2 s earlier indicating about 5 per cent higher average upper mantle velocities and lower temperatures than what iasp91 global model predicts

s and p velocity heterogeneities within the upper mantle below the baltic shield abstract upper mantle structure beneath the baltic fennoscandian shield is investigated using non linear tomographic inversion of relative arrival time residuals 52 selected teleseismic earthquakes recorded by 45 broadband stations of the swedish national seismological network snsn provide 1532 good quality s wave relative arrival times sv and sh arrival time residuals were initially analyzed independently providing two separate models these reveal several consistent major features many of which are also consistent with p wave results lateral velocity variations of 3 4 are observed to depths of at least 470 km the correlation between the sh and sv models is investigated and shows a pattern of minor but significant differences down to around 150 200 km depth below which the models are essentially similar direct cell by cell comparison of the model velocities reveals a similar pattern with velocity differences between the models of up to 4 numerical tests show that differences in the two s wave models can only be partially attributed to noise and limited resolution and some features are attributed to the effect of large scale anisotropy one of the significant and sharp discrepancies between the s models coincides with a presumed boundary between archean and proterozic domains suggesting different anisotropic characteristics in the two regions

contrasts in lithospheric structure within the australian craton insights from surface wave tomography abstract contrasts in the seismic structure of the lithosphere within and between elements of the australian craton are imaged using surface wave tomography new data from the wacraton and tigger experiments are integrated with re processed data from previous temporary deployments of broad band seismometers and permanent seismic stations the much improved path coverage in critical regions allows an interpretation of structures in the west of australia and a detailed comparison between different cratonic regions improvements to the waveform inversion procedure and a new multi scale tomographic method increase the reliability of the tomographic images in the shallowest part of the model 75 km a region of lowered velocity is imaged beneath central australia and confirmed by the delayed arrival times of body waves for short paths within the cratonic lithosphere there is clearly structure at scale lengths of a few hundred kilometres resolution tests indicate that path coverage within the continent is sufficient to reveal features of this size in the upper part of our model in western australia differences are seen beneath and within the archaean cratons at depths greater than 150 km faster velocities are imaged beneath the yilgarn craton than beneath the pilbara craton in the complex north australian craton a fast wavespeed anomaly continuing to at least 250 km is observed below parts of the craton suggesting the possibility of archaean lithosphere underlying areas of dominantly proterozoic surface geology

forsterite dissolution and magnesite precipitation at conditions relevant for deep saline aquifer storage and sequestration of carbon dioxide the products of forsterite dissolution and the conditions favorable for magnesite precipitation have been investigated in experiments conducted at temperature and pressure conditions relevant to geologic carbon sequestration in deep saline aquifers although forsterite is not a common mineral in deep saline aquifers the experiments offer insights into the effects of relevant temperatures and pco2 levels on silicate mineral dissolution and subsequent carbonate precipitation mineral suspensions and aqueous solutions were reacted at 30 c and 95 c in batch reactors and at each temperature experiments were conducted with headspaces containing fixed pco2 values of 1 and 100 bar reaction products and progress were determined by elemental analysis of the dissolved phase geochemical modeling and analysis of the solid phase using scanning electron microscopy infrared spectroscopy and x ray diffraction the extent of forsterite dissolution increased with both increasing temperature and pco2 the release of mg and si from forsterite was stoichiometric but the si concentration was ultimately controlled by the solubility of amorphous silica during forsterite dissolution initiated in deionized water the aqueous solution reached supersaturated conditions with respect to magnesite however magnesite precipitation was not observed for reaction times of nearly four weeks magnesite precipitation was observed in a series of experiments with initial solution compositions that simulated extensive forsterite dissolution the precipitation of magnesite appears to be limited by the process of nucleation and nucleation requires a critical saturation index between 0 25 and 1 14 at 95 c and 100 bar pco2 magnesite precipitation is fastest in the presence of an initial magnesite seed although magnesite precipitates do form on the surfaces of forsterite particles the presence of the forsterite surface does not significantly accelerate magnesite precipitation relative to solid free systems

rupture modes in laboratory earthquakes effect of fault prestress and nucleation conditions seismic inversions show that earthquake risetimes may be much shorter than the overall rupture duration indicating that earthquakes may propagate as self healing pulse like ruptures several mechanisms for producing pulse like ruptures have been proposed including velocity weakening friction interaction of dynamic rupture with fault geometry and local heterogeneity and effect of bimaterial contrast we present experimental results on rupture mode selection in laboratory earthquakes occurring on frictional interfaces which were prestressed both in compression and in shear our experiments demonstrate that pulse like ruptures can exist in the absence of a bimaterial effect or of local heterogeneities we find a systematic variation from crack like to pulse like rupture modes with both 1 decreasing nondimensional shear prestress and 2 decreasing absolute levels of shear and normal prestress for the same value of nondimensional shear prestress both pulse like and crack like ruptures can propagate with either sub rayleigh or supershear rupture speeds our experimental results are consistent with theories of ruptures on velocity weakening interfaces implying that velocity weakening friction plays an important role in governing the dynamic behavior of earthquake ruptures we show that there is no measurable fault normal stress decrease on the fault plane due to the nucleation procedure employed in experiments and hence this is not a factor in the rupture mode selection we find that pulse like ruptures correspond to the levels of nondimensional shear prestress significantly lower than the static friction coefficient suggesting that faults hosting pulse like ruptures may operate at low levels of prestress compared to their static strength

connectivity of earthquake triggered landslides with the fluvial network implications for landslide sediment transport after the 2008 wenchuan earthquake evaluating the influence of earthquakes on erosion landscape evolution and sediment related hazards requires understanding fluvial transport of material liberated in earthquake triggered landslides the location of landslides relative to river channels is expected to play an important role in postearthquake sediment dynamics in this study we assess the position of landslides triggered by the mw 7 9 wenchuan earthquake aiming to understand the relationship between landslides and the fluvial network of the steep longmen shan mountain range combining a landslide inventory map and geomorphic analysis we quantify landslide channel connectivity in terms of the number of landslides landslide area and landslide volume estimated from scaling relationships we observe a strong spatial variability in landslide channel connectivity with volumetric connectivity ranging from 20 to 90 for different catchments this variability is linked to topographic effects that set local channel densities seismic effects including seismogenic faulting that regulate landslide size and substrate effects that may influence both channelization and landslide size altogether we estimate that the volume of landslides connected to channels comprises 43 9 7 of the total coseismic landslide volume following the wenchuan earthquake fine grained 90 of the total landslide volume may be more significantly affected by landslide locations

quantitative visualization methods for continuous evolution of three dimensional discontinuous structures and stress field in subsurface rock mass induced by excavation and construction an overview abstract discontinuous structures such as pores fractures joints and faults govern the physical and mechanical behavior of subsurface rock masses in underground engineering applications the excavation of subsurface energy resources and construction activities extensively change the discontinuous structures and stress distribution in the surrounding rock masses these hidden and dynamic changes are extremely difficult to detect and characterize using conventional methods and techniques and this has greatly impeded the study of the intrinsic mechanisms governing the deformation and failure of rock masses in the past few years discontinuous rock structure imaging methods and three dimensional printing 3dp technology have been successfully applied to replicate rock mass samples for geological and geophysical research purposes the combination of these methods has led to innovative ways to investigate the behavior of complex rock and guide underground engineering applications this review focuses on the characterization and visualization of 1 the interior discontinuities of rock masses and 2 the stress distribution and its continuous evolution in the discontinuous rock masses recent progress in experimental and computational methods in identifying and characterizing the discontinuous structures are presented in particular we discuss the development and process of integrating computed tomography ct 3dp technology transparent rock models and optical mechanics methods to quantitatively and visually present the interior structures and stress evolution inside rock masses

seismic anisotropy of the lithosphere around the trans european suture zone tesz based on teleseismic body wave data of the tor experiment abstract a passive teleseismic experiment tor traversing the northern part of the trans european suture zone tesz in germany denmark and sweden recorded data for tomography of the upper mantle with a lateral resolution of few tens of kilometers as well as for a detailed study of seismic anisotropy a joint inversion of teleseismic p residual spheres and shear wave splitting parameters allows us to retrieve the 3d orientation of dipping anisotropic structures in different domains of the sub crustal lithosphere we distinguish three major domains of different large scale fabric divided by first order sutures cutting the whole lithosphere thickness the baltic shield north of the sorgenfrei tornquist zone stz is characterised by lithosphere thickness around 175 km and the anisotropy is modelled by olivine aggregate of hexagonal symmetry with the high velocity ac foliation plane striking nw se and dipping to ne southward of the stz beneath the norwegian danish basin the lithosphere thins abruptly to about 75 km in this domain between the stz and the so called caledonian deformation front cdf the anisotropic structures strike ne sw and the high velocity ac foliation dips to nw to the south of the cdf beneath northern germany we observe a heterogeneous lithosphere with variable thickness and anisotropic structures with high velocity dipping predominantly to sw most of the anisotropy observed at tor stations can be explained by a preferred olivine orientation frozen in the sub crustal lithosphere beneath northern germany a part of the shear wave splitting is probably caused by a present day flow in the asthenosphere

identifying the unique ground motion signatures of supershear earthquakes theory and experiments the near field ground motion signatures associated with sub rayleigh and supershear ruptures are investigated using the laboratory earthquake experiment originally developed by rosakis and co workers xia et al 2004 2005a lu et al 2007 rosakis et al 2007 heterodyne laser interferometers enable continuous high bandwidth measurements of fault normal fn fault parallel fp and vertical v particle velocity ground motion records at discrete locations on the surface of a homalite 100 test specimen as a sub rayleigh or a supershear rupture sweeps along the frictional fault photoelastic interference fringes acquired using high speed digital photography provide a synchronized spatially resolved whole field view of the advancing rupture tip and surrounding maximum shear stress field the first phase of experimental investigations examine and verify the ground motion signatures of supershear ruptures experimental results demonstrate that a shear mach front produced by a stable supershear rupture is characterized by a dominant fp velocity component the situation is shown to reverse in the sub rayleigh rupture speed regime whereby the fn particle velocity component dominates the ground motion record additional distinguishing particle velocity signatures consistent with theoretical and numerical predictions and repeatedly observed in experimental records are 1 a pronounced peak in the fp velocity record induced by the leading dilatational field which sweeps the measurement station in advance of the shear mach front and 2 a pronounced velocity swing in the fn record associated with the arrival of a trailing rayleigh sub rayleigh secondary rupture which follows the arrival of the shear mach front analysis of the particle velocity records also confirms 2d steady state theoretical predictions pertaining to the separation attenuation and radiation partitioning of the shear and dilatational portions of the rupture velocity field components the second phase of our experimental investigations re examine the 2002 mw7 9 denali fault earthquake and the remarkable set of near source ground motion records obtained at ps10 located approximately 85 km east of the epicenter and just 3 km north of the fault along the alaska pipeline motivated by the analysis and interpretation of these records by ellsworth et al 2004 dunham and archuleta 2004 2005 we attempt to mimic the denali strike slip rupture scenario and replicate the ps10 ground motion signatures using a laboratory earthquake experiment the experiments feature a left to right west to east propagating right lateral rupture within a homalite 100 test specimen with particle velocity data collected at a near field station situated just above north of the fault both sub rayleigh and supershear laboratory earthquake experiments are conducted using the denali ps10 configuration in order to compare and contrast the resulting particle velocity signatures supershear laboratory records capture all of the prominent features displayed within the ps10 ground motion records noted velocity signatures are correlated to the location of the rupture fronts and their noted arrival times in the synchronized photoelastic image sequence scaling relationships are also presented which transform the laboratory records through six orders of magnitude in time to match the scale of the ps10 ground motion records the strong correlation between the scaled experimental records and the actual ps10 ground motion records support the hypothesis that the denali strike slip fault exhibited a supershear burst finally we present a 2d steady state stress velocity formulation that relates the fp and fn particle velocity records measured close to the fault to the evolution of the stress tensor at the same location a locally steady state condition is assumed within a restricted time interval in order to invoke these relationships and estimate the dynamic stresses xx t and t at the near fault station dynamic stress measurements enable a new class of friction investigations using the laboratory earthquake configuration experimental findings are presented which capture the temporal and spatial distributions of xx and evolution of the dynamic friction coefficient and velocity weakening behavior of a supershear slip pulse

integrated geophysical modelling of a lateral transition zone in the lithospheric mantle under norway and sweden summary the scandinavian mountain chain the scandes exhibits characteristics that are unusual for an old palaeozoic mountain belt these include renewed neogene uplift in a passive margin setting and the lack of a pronounced crustal root we investigate the influence of present day thermal compositional and geometric structures in the crust and mantle on the topography of the southern scandes and the resulting implications for the tectonic history of fennoscandia a self consistent 3 d subsurface model of southern norway and sweden is constructed from recent geophysical data sets that constrain the crustal architecture lithosphere geometry density distributions and thermal properties recent seismological studies show evidence for a relatively abrupt transition from seismically slower lithospheric mantle underneath southern norway to seismically faster lithospheric mantle underneath southern sweden we find that a transition from thin subcontinental lithospheric mantle sclm underneath southern norway to a significantly thicker sclm beneath southern sweden can explain this velocitytrend adifferenceincompositionbetweenthetwosclmdomains owingtodifferent depletion refertilization is required to satisfy the gravity field and isostatically compensated topography but contributes only slightly to the observed velocity contrast such a lateral transition zone constituting a major change in the lithospheric structure in southwestern fennoscandia can be related to several major proterozoic and phanerozoic tectonic events such as the sveconorwegian orogeny the permian oslo rift and perhaps even the opening of the atlantic

effects of the hanging wall and footwall on ground motions recorded during the northridge earthquake abstract systematic differences in ground motion on the hanging wall and footwall during the northridge earthquake are evaluated using empirical data an empirical model for the hanging wall effect is developed for the northridge earthquake this empirical model results in up to a 50 increase in peak horizontal accelerations on the hanging wall over the distance range of 10 to 20 km relative to the median attenuation for the northridge earthquake in contrast the peak accelerations on the footwall are not significantly different from the median attenuation over this distance range recordings from other reverse events show a similar trend of an increase in the peak accelerations on the hanging wall indicating that this systematic difference in hanging wall peak accelerations is likely to be observed in future reverse events

an array study of lithospheric structure across the protogine zone varmland south central sweden signs of a paleocontinental collision abstract a small seismological array was installed on both sides of the protogine zone pz in varmland south central sweden to study the structure of the mantle lithosphere and lateral variations of its anisotropy no distinct isotropic velocity anomalies were detected by tomography in the upper mantle around the pz the observed velocity variations depending on the direction of propagation can be explained by anisotropy within the subcrustal lithosphere on both sides of the suture the best solution of a joint analysis of anisotropic inferences from teleseismic p residual spheres and an inversion of shear wave splitting parameters resulted in 3d self consistent anisotropic models of blocks of the subcrustal lithosphere the anisotropic structures within the lithosphere are approximated by hexagonal models k p 5 with low velocity symmetry axes the high velocity planes dip to the e in a region westward of the pz and to the nw eastward of the pz the pz can be interpreted as a steep and narrow suture cutting the whole lithosphere and separating the two anisotropic blocks of different origin

surface characterization of acid leached olivines by x ray photoelectron spectroscopy abstract x ray photoelectron spectroscopy was used to study the surface alteration of olivines fayalite and forsterite during acid dissolution 0 05 mol 1 1 h 2 so 4 at room temperature for one day the abundances of fe and mg relative to si in the near surface of olivines decreased after acid dissolution the divalent cations in the fayalite were removed more readily than those in the forsterite after acid dissolution the si 2s and o 1s spectra of fayalite were deconvoluted to contributions from unleached and leached phases the si 2s and o 1s binding energies were higher for the leached phase relative to the unleached phase and comparable to those of silicon dioxide quartz and silica gel indicating that sio 2 n h 2 o formed on the mineral surface scanning electron micrographs of the leached olivine grains showed a harshly etched structure for fayalite and a locally etched structure for forsterite indicating that the dissolution proceeded heterogeneously

direct effects of co2 and temperature on silicate weathering possible implications for climate control a critical uncertainty in models of the global carbon cycle and climate is the combined effect of organic activity temperature and atmospheric co2 on silicate weathering here we present new dissolution rates of anorthite and augite which indicate that silicate weathering in organic rich solutions is not directly affected by soil co2 but is very sensitive to temperature apparently co2 accelerates silicate weathering indirectly by fertilizing organic activity and the production of corrosive organic acids the weathering dependencies highlight the ability of silicate weathering to act as a global thermostat and damp out climate change when used as input in steady state carbon cycle and climate models

seismic anisotropy beneath stable continental interiors a robust knowledge of seismic anisotropy beneath the continents is essential to our understanding of plate tectonic theory as anisotropy provides a unique constraint on the character of past and present deformation in the lithosphere and sublithospheric mantle this review paper summarizes the range of techniques currently available to image seismic anisotropy with passive source seismic data and addresses current issues surrounding the observation and interpretation of continental seismic anisotropy to this end we present case studies for four regions where seismic anisotropy has been extensively investigated in recent years eastern north america the canadian shield australia and southern africa based on this full suite of results we infer that stable continental regions generally contain seismic anisotropy that is clearly located within both the lithosphere and the sublithospheric mantle usually to depths of at least 200 km and perhaps more an implication of these results is that tectonic plates are at most only partially coupled to the underlying mantle the results from these case studies also demonstrate that while remarkable progress in seismic anisotropy imaging has been achieved in recent years it is clear that much more work will be required to adequately understand the origin of continental seismic anisotropy we suggest that a more robust characterization of anisotropic parameters can only be achieved by integrating complementary seismic datasets and by incorporating constraints from key related datasets from mineral physics magnetotellurics gravity and geodesy

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

fault geometry and the dynamics of the 1999 chi chi taiwan earthquake the 1999 m 7 6 chi chi taiwan earthquake produced a data set of unparalleled size and quality particularly in the near source region where data have been previously quite scarce the large amount of near source data allows the verification of many predictions of thrust fault behavior for faults that intersect the surface of the earth through rigorous three dimensional dynamic models of the chi chi earthquake it can be shown that many aspects of the observed near source ground motion in this event are direct effects of the asymmetrical dipping fault geometry these effects include the hanging wall moving more than the footwall with strongly peaked velocities right at the fault trace and a transition from predominantly thrust motion in the south of the fault to largely left lateral motion in the north building on the work of oglesby and day 2001 the current work helps to delineate the effects of fault geometry nonuniform prestress and dynamic waves on the physics of the chi chi earthquake and dip slip faults in general in particular we find that a completely homogeneous prestress pattern still fits the gross features of the near source ground motion quite well additionally the strike slip component of motion near the fault trace is seen to be a combination of dynamic and static effects finally dynamic overshoot is seen to be much larger for dip slip faults than for otherwise identical vertical faults the results emphasize the necessity of rigorous models that correctly account for both the effects of fault geometry and dynamic waves in the rupture and slip processes manuscript received 31 july 2000

shear wave splitting measurements problems and solutions abstract we compare sensitivity and reliability of three basic techniques of shear wave splitting analysis cross correlation of wave components minimization of covariance matrix eigenvalues and minimizing energy on the transverse component of both synthetic and real data point out some problems and propose solutions we discuss major difficulties of evaluating shear wave splitting parameters which are not always obvious in routine processing and can sometimes lead to false results and wrong interpretations we describe effects of pre processing of digital records of shear waves e g filtering and setting lengths of analyzed signals and discuss reliability of results to minimize outliers in evaluated splitting parameters for reliable evaluation of splitting of medium quality sks wave forms which are valuable mainly in temporary deployments of stations we recommend a careful band pass filtering of the signal using a window length not shorter than the dominant period inspecting the signal noise ratio on t component and the particle motion the transverse minimization method provides usually more robust and stable solutions than the other two methods in the conclusion we suggest how to proceed in evaluation of splitting parameters to ensure reliable solutions even for medium or low quality shear waveforms recorded frequently during temporary field measurements

isostatic constraints on the assembly stabilization and preservation of cratonic lithosphere cratonic uplift or subsidence as recorded geologically by erosion or deposition indicates the net change in lithospheric buoyancy density change is primarily controlled by temperature change such that the geologic record reveals the net lithospheric heating or cooling our modeling shows that thermal stabilization of lithosphere can occur in 100 m y largely determined by the time for crustal radioactivity to warm the entire lithosphere longer term thermal evolution 350 400 m y is controlled by the feedback between isostatic and thermal responses crustal heat production is the dominant factor for evolution of crustal geo therms whereas the detailed initial thermal structure is less important the fact that many cratons are eroded to only modest depths indicates that they have a history of warming slightly since their formation implying a rather cool 700 1000 c for initial lithospheric mantle this is consistent with the growth of cratonic lithosphere by progressive thickening during continental assembly and or subduction stacking of oceanic lithosphere relatively warm early lithosphere due to elevated crustal heat production or higher initial lithospheric mantle temperatures may have had a lower preservation potential due to preferential deformation and destruction study of the proterozoic orogen of the southwestern united states indicates that the distinct thermal and isostatic records of adjacent crustal blocks are compatible with observed differences in crustal heat production but also with similar initial lithospheric mantle temperatures

experimental investigation of strong ground motion due to thrust fault earthquakes thrust fault earthquakes are studied in a laboratory earthquake setup previously used to investigate analog strike slip seismic events dynamic mode ii ruptures are generated along preexisting faults in an analog material homalite h 100 and their interaction with the free surface is studied for both sub rayleigh and supershear rupture speeds high speed digital photography and laser velocimeter diagnostics are used synergistically to identify and study the ground velocity signatures caused by the various features of the generated ruptures the obtained surface normal motions of both sub rayleigh and supershear ruptures show substantial asymmetry between the hanging and footwall with the hanging wall experiencing much larger velocity amplitudes the main features of the surface velocity traces at various stations can be explained by the calculated arrivals of various waves and fronts mach cones pand s waves and sub rayleigh features in both the sub rayleigh and supershear cases the arrival of the rupture tip generates a prominent rayleigh wave traveling along the simulated earth s surface supershear events feature larger amplitudes of ground shaking profiles all signatures in the surface motion records attenuate and broaden with increasing distance from the fault trace the signatures corresponding to the arrival of the mach fronts attenuate with distance at a slower rate than those from sub rayleigh ruptures the arrival of the updip supershear rupture at the free surface creates a downdip propagating slip feature with its own mach cone these additional mach fronts further amplify ground shaking on the hanging and footwalls

high resolution body wave tomography beneath the svekalapko array i a priori three dimensional crustal model and associated traveltime effects on teleseismic wave fronts summary assessment of contributions from shallow lithosphere to teleseismic wave front distortion is a prerequisite for high resolution regional teleseismic tomography several methods have been proposed in the past for the correction of these effects e g application of station correction terms we propose an approach that is independent of the subsequent inversion and uses the available a priori knowledge of the crustal structure to calculate crustal traveltime effects of teleseismic wave fronts our approach involves the construction of a 3 d crustal model based on controlled source seismology data and calculation of the associated traveltime anomalies for incoming teleseismic wave fronts the model for central fennoscandia shows a maximum crustal thickness of 64 km and includes a high velocity lower crust as derived for parts of the study area by previous authors traveltimes calculated using finite differences for teleseismic waves travelling through this crustal model are compared with those from the standard reference model iasp91 and the residuals are used to correct observed teleseismic arrival times at the svekalapko array to test the performance of this approach in a second part of the study a synthetic traveltime data set is obtained by tracing wave fronts through a mantle structure with known velocity anomalies and the 3 d crustal model this data set is inverted with and without correction for crustal effects the 3 d crustal effects alone with a homogeneous mantle are also inverted and the results show that the crustal effects propagate down to 450 km the comparison of the inversion results demonstrates the need to apply appropriate 3 d crustal corrections in high resolution regional tomography for upper mantle structure beneath the baltic shield

a tomographic crustal velocity model of the central fennoscandian shield summary in this paper local seismic tomographic method is used to find the terrane distribution within the central parts of the accretionary svecofennian orogen this study presents a crustal pwave velocity model and for the first time the s wave velocity and vp vs ratio model of svekalapko area that is 700 800 km 2 in southern and central finland the 3 d model is presented as p and s wave velocity as well as vp vs ratio depth slices and vertical sections the data set comprised of several subsets of crustal pg and sg wave traveltime data from local events recorded by the svekalapko seismic tomography array in 1998 1999 from older controlled source shots recorded at portable stations as well as at permanent stations and from non controlled chemical explosions recorded at permanent seismic stations from 300 local explosions a total of 10 404 pg wave and 9361 sg wave arrival times were inverted to create independent 3 d vp and vs tomographic models from which the vp vs ratio was calculated according to sensitivity tests the optimal horizontal resolution of recognizable velocity structures in the central study area is at least 60 km down to depths of 40 km in the final model the seismic velocities vary smoothly the lateral variations are larger for vp 5 9 6 6 km s 1 than for vs 3 5 3 8 km s 1 in the upper 20 km of the crust at depths of 20 40 km vp varies from 6 5 to 7 2 km s 1 and vs from 3 7 to 4 1 km s 1 the vp vs ratio varies spatially more distinct than p and s wave velocities usually from 1 70 to 1 74 in the upper crust and from 1 72 to 1 78 in the lower crust schist belts and their continuations at depth are associated with lower velocities and lower vp vs ratios vp 6 2 6 8 km s 1 vs 3 6 3 9 km s 1 vp vs 1 68 1 73 than the granitoid areas vp 6 3 7 4 km s 1 vs 3 6 4 2 km s 1 vp vs 1 72 1 78 the svecofennian orogen was accreted from crustal blocks ranging in size from 100 100 km 2 to 200 200 km 2 in cross sectional area the intervening sedimentary belts have ca 0 2 km s 1 lower p and s wave velocities and ca 0 04 lower vp vs ratios tomographic model supports the idea that the thick svecofennian crust was accreted from several crustal terranes some hidden and that the crust was later modified by intra and underplating

lithospheric growth at margins of cratons abstract deep seismic reflection profiles collected across proterozoic archean margins are now sufficiently numerous to formulate a consistent hypothesis of how continental nuclei grow laterally to form cratonic shields this picture is made possible both because the length of these regional profiles spans all the tectonic elements of an orogen on a particular cratonic margin and because of their great depth range key transects studied include the lithoprobe snorcle 1 transect and the babel survey crossing the slave and baltic craton margins respectively in most cases the older archean block appears to form a wedge of uppermost mantle rock embedded into the more juvenile proterozoic block by as much as 100 200 km at uppermost mantle depths and archean lithosphere is therefore more laterally extensive at depth than at the surface particularly bright reflections along the moho are cited as evidence of shear strain within a weak low viscosity lower crustal channel that lies along the irregular top of the indenting wedge the bottom of the wedge is an underthrust subduction zone and associated late reversal in subduction polarity beneath the craton margin emerges as a common characteristic of these margins although related arc magmatism may be minor

earthquakes on dipping faults the effects of broken symmetry dynamic simulations of earthquakes on dipping faults show asymmetric near source ground motion caused by the asymmetric geometry of such faults the ground motion from a thrust or reverse fault is larger than that of a normal fault by a factor of 2 or more given identical initial stress magnitudes the motion of the hanging wall is larger than that of the footwall in both thrust reverse and normal earthquakes the asymmetry between normal and thrust reverse faults results from time dependent normal stress caused by the interaction of the earthquake generated stress field with earth s free surface the asymmetry between hanging wall and footwall results from the asymmetric mass and geometry on the two sides of the fault

shear wave splitting as a diagnostic of variable anisotropic structure of the upper mantle beneath central fennoscandia abstract we analyze splitting of shear waves recorded during the svekalapko passive seismic experiment in south central finland to study fabrics of the mantle lithosphere of the precambrian region and thus to bring information into a debate on existence of plate tectonics or its forms in the early stage of continent formation geographical variations of the splitting parameters and their distinct dependence on direction of wave propagation through the upper mantle allow us to identify six domains of the central fennoscandian mantle lithosphere including the proterozoic archean transition and to model their fabrics by joint inversion of body wave anisotropic parameters fabrics of the archean mantle lithosphere can be approximated by a peridotite aggregate with lineation a dipping to the ne on the other hand anisotropy of the proterozoic mantle lithosphere is weaker and we model its fabric by the a c foliations dipping to the se we present a 3d self consistent anisotropic model of the proterozoic and archean upper mantle along the sw ne profile in the south central finland boundaries of inter growing wedges of the proterozoic and archean mantle lithospheres explain the longitudinal and shear wave propagation and polarization mantle xenolith ages surface wave tomography and location of the upper mantle reflectors we interpret the six anisotropic domains as fragments of mantle lithosphere retaining an old fossil olivine fabric which was created before these micro continents assembled

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

space and time evolution of rupture and faulting during the 1999 izmit turkey earthquake we use the records of the ground motion obtained at near fault accelerometers to study the space and time evolution of rupture and faulting during the izmit earthquake we find that the rupture propagated at the sub rayleigh speed of about 3 km sec on the western and eastern segments of the fault but that the central segment izmit sapanca lake sakarya nearly 50 km long broke at the supershear speed of about 4 8 km sec this value within the range of uncertainties is the one theoretically predicted sqrt 2 v mathrm s in fracture dynamics for stable shear crack growth at intersonic speed we infer an average fault slip of about 2 9 m over a total rupture length of about 150 km with the largest values of up to 6 m occurring in the golcuk area to the west and in the sakarya region to the east the strong motion data also indicate that the slip diminished gradually to the west beyond the hersek peninsula over about 30 km whereas it stopped abruptly at depth at the termination of the eastern karadere segment the slip duration is between 2 and 4 sec except in the hypocentral area which slipped in about 1 sec the seismic moment inferred is about 2 5 10 20 n m

rupture dynamics on a bimaterial interface for dipping faults dip slip faulting may juxtapose different geologic materials with differ ent properties such that a strong material contrast will naturally tend to form both the material contrast across a fault and dip slip motion on a nonvertical fault lead to normal stress variations during earthquake rupture this normal stress variation will significantly affect dynamic rupture propagation to demonstrate this we model dynamic rupture propagation on two dimensional 2d reverse and normal faults 30 45 and 60 dipping with 20 material contrasts for predominantly up dip rupture propagation we find that normal stress variations due to the free surface and material contrast can either reinforce or counteract each other depending on the configuration for reverse faults we find a larger strength drop for a more com pliant hanging wall and a lower strength drop for a more compliant footwall for normal faults we find a larger strength drop for a more compliant footwall and a lower strength drop for a more compliant hanging wall for both reverse and normal faults ground motion will be more symmetric between the hanging wall and footwall with compliant material on the footwall and more asymmetric if more compliant materials are on the hanging wall our results have important implications for the dynamics of crustal and perhaps subduction zone earthquake faulting where strong bimaterial contrasts across dipping faults are possible in continental settings reverse faulting will tend to advect rigid materials from greater depth onto the hanging wall such that the effects of fault dip and material contrast will counteract one another in subduction zones the hanging wall is likely to be more compliant and hence the material and geometric effects may reinforce one another

three dimensional crustal structure beneath the tor array and effects on teleseismic wavefronts abstract the temporary seismic station array tor was designed to study the lithosphere asthenosphere system across the northwestern part of the trans european suture zone tesz by teleseismic tomography teleseismic wavefronts when propagating through complex crustal structure undergo severe distortion that may result in travel time residual anomalies of significant amplitude the inversion of teleseismic travel time residuals for deep structures without accounting for such crustal related anomalies may erroneously map these travel time anomalies into features at greater depth in this study we apply a three dimensional 3 d technique to estimate effects of a priori known 3 d crustal structure on travel times of teleseismic waves observed at the tor seismic array across the tesz to correct for these effects in future tomographic studies a uniform 3 d crustal model is developed by use of published two dimensional crustal models from previous active seismic surveys the parameterization of this 3 d crustal model is designed to adequately represent those crustal structures that mostly influence the propagation of teleseismic wavefronts the 3 d model includes lateral variation in velocity structure moho topography and large and deep sedimentary basins the teleseismic forward problem for this local 3 d model is solved by calculation of travel times to the base of the model using a standard whole earth model and by subsequent propagation of spherical wavefronts using finite difference methods travel time calculations for an event near japan reveal significant lateral variations in the range between 0 3 s and 0 5 s due to crustal structures being able to obtain the full travel time field at the surface of the model has the additional advantage of improving the identification and timing of seismic phases observed at the tor seismic array

supershear rupture in the 24 may 2013 mw 6 7 okhotsk deep earthquake additional evidence from regional seismic stations zhan et al 2014a reported supershear rupture during the m w 6 7 aftershock of the 2013 m w 8 3 sea of okhotsk deep earthquake relying heavily on the regional station pet which played a critical role in constraining the vertical rupture dimension and rupture speed here we include five more regional stations and find that the durations of the source time functions derived from these stations are consistent with zhan et al s supershear rupture model furthermore to reduce the nonuniqueness of deconvolution and combine the bandwidths of different stations we conduct a joint inversion of the six regional stations for a single broadband moment rate function mrf the best fitting mrf which explains all the regional waveforms well has a smooth shape without any temporal gaps the m w 6 7 okhotsk deep earthquake is more likely a continuous supershear rupture than a dynamically triggered doublet

europe from the bottom up a statistical examination of the central and northern european lithosphere asthenosphere boundary from comparing seismological and electromagnetic observations abstract the lithosphere asthenosphere boundary lab is a fundamental boundary in the plate tectonic paradigm it is the most pervasive on the planet yet comparatively it is one we know little about defined initially on the basis of the mechanical response of the earth to loading its usage has become ubiquitous across the geosciences but the natural differences in its definition due to differences in thermal physical and chemical parameters cause confusion to advance this debate comparisons are made both qualitatively and quantitatively between the delineation of the lab for europe based on seismological and electromagnetic observations we examine statistically using robust methods the labs derived from independent datasets and methods essentially all definitions of the lab as an impedance contrast from receiver functions slabrf a seismic anisotropy change slaba and an increase in conductivity from magnetotellurics elab are consistent with a deeper lab beneath precambrian europe and a shallower lab beneath phanerozoic europe with some exceptionally deep regions in phanerozoic europe such as the alps all three labs increase in depth significantly and rapidly at a location consistent with the surface expression of the trans european suture zone tesz which separates precambrian europe to the north and east from phanerozoic europe in the centre two of the definitions slabrf and elab are consistent for phanerozoic europe with mean values of 90 100 km compared to an average slabrf of 135 km a different two slaba and slabrf are consistent for precambrian europe with mean values of 170 180 km compared to an elab mean of 250 km the deeper elab depths for precambrian europe are more consistent with body wave and surface wave tomography models than are the slaba and slabrf ones suggesting that the lower lithosphere beneath precambrian europe between 170 to 250 km is responding to shearing on the base of the lithosphere from plate driving forces taken together the definitions provide strong constraints on the nature of the lab for example the electrical elab beneath the tesz is anomalously thick to possibly the transition zone whereas slaba and slabrf seismological definitions would place it at far shallower depths given the sensitivity of electrical conductivity to partial melt and water content the thick elab beneath the tesz excludes interpretation of the seismic lab in that location in terms of a thermal structure that would induce partial melting or of hydration

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

images of a lower crustal oceanic slab direct evidence for tectonic accretion in the archean western superior province the archean western superior province in canada is the type area for proposed archean plate tectonics seismic images from this region provide direct evidence for assembly of the craton by terrane accretion and for a large slab of remnant oceanic crust preserved at the base of the crust this slab with inferred garnet amphibolite composition adds a critical piece of evidence to previous suggestions that archean subduction was at a shallow angle and that some neoarchean tonalite trondhjemite granodiorite suites distinct from most modern day suprasubduction magmas are melts primarily derived directly from subducted slabs

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

interpretation of geoid anomalies in the contact zone between the east european craton and the palaeozoic platform ii modelling of density in the lithospheric mantle summary we present analysis of lateral variations of density in the upper mantle in the area of contact of the precambrian east european craton eec and the palaeozoic platform pp in poland obtained by analysis of the gravimetric geoid undulations a precise 3 d density model of the crust in the study area down to a depth of 50 km discussed in the first part of this paper majdanski et al in press did not explain all features of the observed geoid this suggests that these features can be due to density inhomogeneities in the upper mantle to estimate them we performed inversion of a residual between the observed geoid and undulations caused by the 3 d density distribution in the crust basing on the assumption of local isostatic compensation and pratt hayford isostasy model the density distribution in the upper mantle was parametrized as a 40 km thick layer located above the assumed compensation depth of 140 km and subdivided into irregular blocks the boundaries of the blocks were defined according to boundaries of major tectonic units in the study area and position and shape of the most pronounced anomalies in the residual geoid a series of sensitivity tests calculated for such density heterogeneities in the upper mantle showed that they can produce geoid undulations of the order of several metres the density values in each unit were taken as model parameters for the inversion procedure and inverse problem was solved using global optimization with constraints the density variations in the upper mantle in the final model correlate well with the surface heat flow this suggests that these variations can be due to diversity in mantle temperature the trans european suture zone tesz which is a major suture separating the eec from the pp is not observed as a distinct unit in the mantle instead our study suggests continuation of the lithosphere of the eec beneath the pp and confirms subdivision of the tesz into terranes with distinctly different evolution a simple calculation shows that condition of local isostatic equilibrium is almost achieved at the assumed compensation depth with the exception of several small scale units however different loads and mass deficiencies in the lithosphere are compensated at different depth levels this proves that the lithosphere is alternation of mechanically strong and weak layers both in the crust and upper mantle and that different loads can be compensated at different depth however the total compensation of all lithospheric loads occurs in the upper mantle

structure of the crust and uppermost mantle beneath southern finland revealed by analysis of local events registered by the svekalapko seismic array abstract in 1998 1999 a large scale seismic array was deployed in finland as a part of the europrobe svekalapko subproject involving 14 european universities and research institutes the objective of the project was to map the deep lithosphere structure and thickness beneath the fennoscandian shield by means of teleseismic events in addition about 580 local seismic events were registered during the data acquisition period among them only eight local earthquakes were recorded the rest being quarry blasts from mining sites in russia finland estonia and sweden in this study we present the analysis of the seismic wave field from the strongest local events registered by the majority of the stations of the svecofennian karelian lapland kola transect svekalapko array with the aim of mapping the structure of the upper mantle beneath the array for this purpose we selected the events corresponding to a single source type and compared these recordings with those from wide angle reflection and refraction experiments in the area to identify the regional phases the record sections of selected events demonstrate strong reflections pmp from the moho boundary the refracted pn phases can be seen as first arrivals at distances of about 200 400 km from the source at offsets of about 400 800 km phases reflected from inhomogeneities in the uppermost mantle p1 and double reflections from the moho boundary pmppmp were recorded results from 2d forward ray trace modeling of reflected and refracted p waves along four profile swathes from svekalapko stations demonstrate that the mantle reflections originate from two different groups of boundaries beneath the array one group of phases arrive from subhorizontal and gently dipping reflectors below the moho boundary at a depth of 70 90 km while the other group are phases originating from a depth of 100 to 130 km based on the irregular character of the first group of reflections their different spatial orientation and correlation with the moho offsets we interpret the boundaries of this group as relicts of ancient subduction and collision processes the second group of reflections can be explained by a transition from mechanically strong to mechanically weak lithosphere

sharp contrast in lithospheric structure across the sorgenfrei tornquist zone as inferred by rayleigh wave analysis of tor1 project data abstract this work is a part of the tor1 project 1996 1997 and is devoted to determining the lithospheric structure across the sorgenfrei tornquist zone in northern europe for the first time in europe a very dense seismic broadband array has offered the possibility of determining very sharp lateral variations in the structure of the lithosphere at small scales using surface wave analysis we measure phase velocities for rayleigh waves with periods ranging between 10 and 100 s both within arrays with apertures of 40 50 km small compared to the wavelength and along long profiles of at least 100 km dispersion curves are then inverted and shear wave velocity models down to the depth of 200 km are proposed we show that the sorgenfrei tornquist zone is a major tectonic feature within the whole lithosphere north east of this feature in sweden beneath the baltic shield no lithosphere asthenosphere boundary is observed to exist to depths of 200 km south west of the sorgenfrei tornquist zone beneath denmark we find a lithospheric thickness of 120 20 km the transition across the sorgenfrei tornquist zone is sharp and determined to be very steeply dipping to the south west we also demonstrate the existence of a sharp discontinuity between the lithospheres beneath denmark 120 20 km thick and beneath germany characterized by thicknesses of 50 10 km in the northernmost part and 100 20 km in the southwest this discontinuity is most likely related to the trans european fault at the surface

dynamics of thrust faulting 2d lattice model particle motions in a foam rubber model of shallow angle thrust faulting show many features different from those commonly assumed in dislocation models of subduction thrusts brune 1996 as a complement to a physical foam rubber experiment we have carried out dynamic simulation using a 2d lattice numerical model the model is constructed as a triangular block sliding over a rectangular elastic block it consists of a 2d set of particles interacting with each other by nonlinear hooke s forces and obeying newton s equations of motion rough surfaces are introduced on the contact plane of the two blocks to simulate realistic friction the numerical simulations demonstrate several key features of thrust faulting including stick slip fault opening and strong breakout and shaking at the hanging wall toe the wedge shaped tip of the outcropping hanging wall block of the thrust fault all consistent with the foam rubber experiments the stick slip motion shows an approximate time and slip repeatable behavior each slip event is characterized by a self healing pulse associated with fault opening and frictional locking the rupture pulse propagates steadily along the fault when rupture reaches the toe of the fault outcrop the hanging wall breaks away from the foot wall and creates a large opening vibration of the hanging wall the peak acceleration observed at the hanging wall toe of the fault outcrop is about 3 to 4 times the peak acceleration in the center part of the fault and about 2 to 3 times the motion of the foot wall such a large increase in peak acceleration at the toe is caused mainly by multiply reflecting stress waves trapped in the wedge shaped hanging wall of the fault the strong asymmetry of the particle velocity between the hanging wall and foot wall is an important feature of the results consistent with the foam rubber model but different from standard dislocation models this dynamic result illustrates the important effects of thrust faulting geometry on fault slip and ground motion

lithospheric structure of the mid norwegian margin comparison between the more and voring margins the lithospheric structure across the more margin has been studied by integrating regional elevation gravity geoid and heat flow data together with available seismic and geological data our results show that the moho depth varies from 42 km beneath the caledonides to 20 15 km beneath the basin and to 13 16 km in the oceanic domain the lithosphere thins in a step like manner from 160 km inland to 60 80 km in the oceanic domain a comparison with the voring margin reveals that both margins have similar crustal and lithospheric structures major dissimilarities are 1 the volume of underplating beneath the ocean continent boundary 2 the lithospheric thickness beneath the caledonian front 3 the lithospheric thickness beneath the distal parts of the margins the heat transfer across the voring transform margin the secular variation of lithospheric thickness with age and the jump of the aegir spreading ridge are responsible for these differences

structure of the scandes lithosphere from surface to depth abstract in this review we give an overview of geophysical data and models available for the scandinavian mountains and adjacent areas as they are of relevance to the debate about the existence and cause of neogene uplift emphasis is given to potential field and petrophysical data of which the earth science communities of norway and sweden have a long tradition of acquisition and interpretation this is reflected in the wealth and dense coverage of data available the topography of the scandes mountain chain correlates to a large degree with a bouguer gravity low which suggests isostatic compensation but comparison with magnetic and petrophysical data shows that the gravity low is partly influenced by the trans scandinavian igneous belt signals due to the effects of surface geology can be further eliminated by considering the near surface density distribution as provided by petrophysical sampling to illuminate the entire lithospheric structure active and passive seismic and magnetotelluric data can be used recent and ongoing experiments are aimed at improving the existing models of the lithosphere integration of these different geophysical data sets allows the structure of the lithosphere of the scandes and its surroundings to be addressed seismic models show no pronounced crustal root below the scandes which could provide isostatic compensation but instead an increase of crustal thickness towards the central fennoscandian shield from the integrated model isostatic compensation is inferred to be largely controlled by the density distribution of the crust and that a high density lower crust to the east of the scandes is necessary to achieve isostatic equilibrium on a regional scale we demonstrate the typical crustal structure with profiles crossing from the scandes into the shield and a combined onshore offshore basement map

the lithosphere in central europe seismological and petrological aspects abstract the lithosphere thickness in the variscan belt of central europe varies between about 60 and 150 km with typical values of 100 120 km our estimates derived from directionally independent representative p wave residuals are in good agreement with magnetotelluric determinations of a layer with increased conductivity in the upper mantle the large scale anisotropies of the subcrustal lithosphere beneath four seismological stations determined from spatial variations of relative p residuals vary between 6 5 and 15 2 for p velocities the s wave anisotropies determined from sks polarizations vary between 2 2 and 6 7 these values are in reasonable agreement with the anisotropies of peridotites determined in laboratory systematic spatial variations of the directional terms of relative residuals in dependence on azimuths and incidence angles suggest the existence of large dipping anisotropic structures in the subcrustal lithosphere the residual patterns at most stations in the saxothuringicum rhenohercynicum and in the massif central imply northwesterly orientated dips of the anisotropic structures while stations in the moldanubicum the alpine foredeep and most of the alps north of the insubric line suggest southeasterly orientated dips in our interpretation the dipping anisotropic structures may represent paleosubductions which retain olivine preferred orientations originating from an ancient oceanic lithosphere the variscides of central europe may thus represent a collision zone characterized by two systems of paleosubductions divergent relative to the suture between the moldanubicum and the saxothuringicum

upper mantle structure of the baltic shield below the swedish national seismological network snsn resolved by teleseismic tomography summary upper mantle structure under the baltic shield is studied using non linear high resolution teleseismic p phase tomography observed relative arrival time residuals from 52 teleseismic earthquakes recorded by the swedish national seismological network snsn are inverted to delineate the structure of the upper mantle the network consists of 47 currently working three component broad band stations located in an area about 450 km wide and 1450 km long in order to reduce complications due to possible significant three dimensionality of earth structure events chosen for this study lay close to in line with the long axis of the array 30 results indicate p wave velocity perturbations of 3 per cent down to at least 470 km below the network the size of the array allows inversion for structures even at greater depths and lateral variations of velocity at depths of up to 680 km appear to be resolved below the central part of the array 60 64 n where ray coverage is best the data reveals a large region of relatively low velocity at depths of over about 300 km at depths less than about 250 300 km the models include a number of features including an apparent slab like structure dipping gently towards the north