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

quartz fabrics in the alpine fault mylonites influence of pre existing preferred orientations on fabric development during progressive uplift strong quartz crystallographic preferred orientations cpos were developed during dislocation creep in the mylonite zone exposed in the hanging wall of the dextral reverse alpine fault zone new zealand the cpos have a consistent asymmetry indicating a high ratio of simple to pure shear strain with a shear sense of dextral up to the nw consistent with the mesoscopic shear sense indicators and with slip on the active fault there is a transition from y maxima and asymmetric single girdles in mylonites and ultramylonites within 300 m of the present fault trace to cross girdle fabrics in the protomylonites further from the fault the strong y maxima or single girdle cpos are ascribed to high ductile shear strains under amphibolite facies conditions while the cross girdle patterns found in the protomylonites are interpreted to represent deformation under lower temperature conditions however the observed fabric transition cannot logically be attributed to variations in temperature during the last increment of deformation the highly oriented y maximum fabrics formed at high temperature contain very few grains suitably oriented for basal slip so that the slip systems activated during subsequent shear at lower temperatures during exhumation were prism or rhomb further from the fault where shear strains under high temperature conditions were lower weaker fabrics developed under these conditions were modified at higher levels in the crust into crossed girdle patterns this interpretation implies that intense localisation of shear strain along the fault zone within the lower crust must have occurred in order for the high temperature fabrics to become sufficiently intense to be preserved this in turn implies that deep seated localised shear was taking place early during the evolution of the current oblique slip plate boundary fault the results of this study also indicate that the current model that operation of certain slip systems in quartz is mostly a function of temperature is incorrect future work should consider the effects of deformation history total strain and the presence of other mineral phases

toward understanding subtle instrumentation effects associated with weak seismic events in the near field abstract broadband observations of small earthquakes at short epicentral distances reveal a mixture of near field effects and instrumental artifacts we investigated these phenomena at a station equipped with an sts 2 and cmg 40t sensor situated almost above shallow m 3 0 to 3 8 events peak ground acceleration 2 10 1 m sec 2 the horizontal components were systematically accompanied by tiltlike disturbances and the tilt obtained from the sts 2 records exceeded more than 10 times the values predicted by the source model we also observed a so far uncommonly recognized type of disturbance whose shape is the first derivative of the tiltlike disturbance the most likely explanation seems to be clipping of high frequency signal peaks within the sensor system a computational model of a broadband feedback velocimeter as a linear dynamic system with saturation proved this interpretation on a qualitative level generally any asymmetry in the transfer of high frequencies in the feedback velocimeter would produce a long period disturbance of this type users of near fault broadband velocigrams may numerically simulate the disturbances without any knowledge of their physical nature and subtract them from the records the decontaminated records still may have a strange bow shaped form related to the near field ramp and the static displacement of the order of 1 10 5 m in this article the effects studied in this article seem to have a general character for apparently any feedback controlled broadband velocimeter

variability of near field ground motion from dynamic earthquake rupture simulations this study investigates near field ground motion variability due to dynamic rupture models with heterogeneity in the initial shear stress ground velocity seismograms are synthesized by convolving the time histories of slip velocity obtained from spontaneous dynamic rupture models with green s functions of the medium calculated with a discrete wavenumber finite element method peak ground velocity pgv estimated on the synthetics generally matches well with an empirically derived attenuation relation whereas spectral acceleration sa shows only an acceptable match at periods longer than 1 sec using the geometric mean to average the two orthogonal components leads to a systematic bias for the synthetics in particular at the stations closest to the fault this bias is avoided by using measures of ground motion that are independent of the sensor orientation the contribution from stress heterogeneity to the overall ground motion variability is found to be strongest close to the fault and in the backward directivity region of unilaterally propagating ruptures in general the intraevent variability originating from the radiation pattern and the effect of directivity is on the same order or larger than the interevent variability the interevent ground motion variability itself is dominated by the hypocenter station configuration and is influenced only to a lesser extent by the differences in the dynamic rupture process due to the stress heterogeneity in our modeling approach the hypocenter location is not picked arbitrarily but is determined to be mechanically consistent with the stress heterogeneity through a procedure emulating tectonic stress loading of the fault and nucleation compared to the peak ground motion recorded during the 2004 parkfield california earthquake our simulated seismograms show enhanced spatial correlation that may be attributed to the simplicity of the assumed crustal model or to an incomplete representation of the spatial heterogeneity of dynamic rupture parameters nevertheless the intraevent pgv variability in the near fault region determined for the parkfield dataset is of the same order of magnitude as for our simulations

exhumational history of the north central pamir 1 the pamir plateau forms a prominent tectonic salient along the western end of the tibet tarim margin despite its tectonic significance relatively little is known about the timing of major cenozoic tectonic events in the pamir here we present new apatite and zircon u th he ages bulk rock geochemistry and al in hornblende barometry results from the karakul graben a prominent north south oriented rift basin located 50 km south of the main pamir thrust although cooling ages do not record the onset of extension graben bounding normal faults provide exposures of otherwise slowly eroding rocks which record two cenozoic thermal events existing geochronology and new results suggest that granitic rocks in the karakul region were shallowly emplaced cooled very quickly through 300 c and have experienced less than 10 km of exhumation since the late triassic a long period of relatively slow exhumation throughout much of the late mesozoic and cenozoic was punctuated by two periods of accelerated exhumation during the middle eocene 50 40 ma and early miocene 25 16 ma we interpret the first period of accelerated exhumation as a result of tectonic uplift and subsequent erosion due to the northward propagation of the india asia collision we attribute the second period of rapid exhumation to a renewed phase of tectonism and plateau uplift in the pamir perhaps related to a break off event along the down going indian plate at 25 ma or to the onset of slip along the nascent karakoram fault

constraining earthquake source inversions with gps data 2 a two step approach to combine seismic and geodetic data sets 1 we present a new method to combine static and wavefield data to image earthquake ruptures our combined inversion is a two step procedure following the work of hernandez et al 1999 and takes into account the differences between the resolutions of the two data sets the first step consists of an inversion of the static field which yields a map of slip amplitude this inversion exploits a special irregular grid that takes into account the resolution of the static data the second step is an inversion of the radiated wavefield it results in the determination of the time evolution of slip on the fault in the second step the slip amplitude is constrained to resemble the static slip amplitude map inferred from the gps inversion using this combined inversion we study the source process of the 2004 m6 parkfield california earthquake we conclude that slip occurred in two main regions of the fault each of which displayed distinct rupture behaviors slip initiated at the hypocenter with a very strong bilateral burst of energy here slip was localized in a narrow area approximately 10 km long the rupture velocity was very fast 3 5 km s and slip only lasted a short period of time 1 s then the rupture proceeded to a wider region 12 20 km northwest of the hypocenter here the earthquake developed in a more moderated way the rupture velocity slowed to 3 0 km s and slip lasted longer 1 2 s the maximum slip amplitude was 0 45 m

contribution of radar interferometry to a two step inversion of the kinematic process of the 1992 landers earthquake we study the rupture process of the 1992 landers earthquake to limit the trade off between slip amplitude and rupture time that affects solutions using only seismological data we adopt a two step approach we first constrain the slip distribution and its uncertainty by independent geodetic data to recover in the second step the temporal details of the rupture propagation the first step consists of an inversion of interferometric data and global positioning system measurements both independently and together to constrain slip distribution on a three segment fault model along both strike and dip direction we use a genetic algorithm to test the uniqueness of the solution and a least squares formulation to find the model which best fits the data we conclude from the results of these geodetic inversions that interferometric data are rich enough to access the slip distribution in the case of the landers earthquake since the surface deformations are more sensitive to shallow slip in our configuration the slip amplitude is better resolved near the surface than at depth the resulting slip distribution is in agreement with geological observations at the surface and confirms the heterogeneous nature of the landers earthquake most of the slip occurs at shallow depths on the homestead valley fault second segment with a maximum value of around 7 m another high slip zone is observed on the johnson valley fault first segment at 8 km depth in the second step we invert strong motion data with the a priori final slip amplitude and its uncertainty deduced from geodetic data to constrain the time history of the rupture process this second step emphasizes a strong variation of the temporal development of the earthquake fast rupture front velocities appear within high slip zones and the rupture slows when it encounters a resistance along the fault on average the rupture front propagates with velocities close to the s wave velocity and terminates about 20 s after initiation the large variations in both slip amplitude and rupture velocity suggest that the rupture process is better described by successively breaking asperities than by a pulse propagating with constant velocity

seismic remote sensing for the earthquake source process and near source strong shaking a case study of the october 16 1999 hector mine earthquake a new methodology to automatically determine the earthquake source process and near source strong ground motions using regional and local distance data was used to study the october 16 1999 hector mine earthquake mw7 1 broadband displacement data were inverted for the seismic moment tensor and to resolve the fault plane ambiguity independent of aftershock location and surface faulting information the identified nnw striking fault plane was used to invert for the distribution of fault slip over a planar surface the slip model was used to predict near fault peak ground velocity which was found to agree well with the trinet shakemap and also with near fault observations that were not available at the time of the initial analysis our method if automated is capable of providing near source strong ground motion information within 30 minutes of the earthquake origin time even in cases where there are few near fault recording instruments

the 2000 tottori earthquake a shallow earthquake with no surface rupture and slip properties controlled by depth the m w 6 8 tottori earthquake japan does not exhibit any surface trace but was particularly well instrumented strong motion displacement records and gps coseismic data are used to constrain the evolution of the slip on the fault plane in time and space we adopt in this study a two plane fault geometry based on aftershock distributions and analysis of close station records in a first step our inversion allowed surface slip the model obtained has a significant surface slip which contradicts the absence of clear surface slip reported by geologists in a second step models with no slip at the surface buried faults compatible with geological observations have been tested the tests with different fault depths show that when slip is allowed to occur close to the surface the fit to seismological and geodetic data is increased these tests confirm that slip actually occurred at shallow depth despite the nonuniqueness of the solution all the inverted source models show 1 a large slip amplitude patch at a depth of about 4 5 km and 2 relatively small slip in the hypocentral area the rupture velocity is about 2750 m s in the asperity region the total rupture duration is about 8 s the slip distribution seems to be controlled by the variation of fault properties with depth another feature that could control the rupture of this earthquake is a fault plane almost perpendicular to the main fault nw of the epicenter which apparently inhibits further rupture propagation

realistic inversions to obtain gross properties of the earthquake faulting process abstract the problem is to find if we are able to determine correctly the average properties of the actual earthquake faulting process which occurs in reality in the earth at microscopic scales from a solution of a feasible inverse problem in order to investigate this we use synthetic accelerograms constructed in the vicinity of a 20 km 5 km dipping thrust fault for a discrete analog of the haskell type of fault model as the data and perform the inversion using much coarser spatial and temporal grids than used in constructing the data and widely used inversion methods we show that we are essentially unable to obtain the proper known results when we use a least squares singular value decomposition method due to the fact that many negative values of moment rate which did not exist in the forward problem are produced though the data are well fit inversions using the svd method together with smoothing constraints or exclusion of small singular values yield an improved solution but the actual values to be used must be obtained by trial and error and do not contribute to our insight as to how to solve the problem with real data finally we show that if we enforce the condition that there are no negative moment rates using in this case the method of linear programming we are able to reproduce many aspects of the original solution better

late cenozoic slip on the talas ferghana fault the tien shan central asia although cenozoic crustal shortening and thickening by thrust faulting have built the present tien shan active right lateral shear on the northwest trending talas ferghana fault appears to be the most rapid localized deformation in the belt ephemeral stream valleys have been offset right laterally tens of metres new and published radiocarbon dates of organic material deposited in depressions blocked by offset ridges place upper bounds on the average holocene slip rate at 18 localities uncertainties allow 14 upper bounds to overlap the range of 8 16 mm yr and 95 confidence limits on such bounds at 11 sites are entirely within this range we infer that the rate of 10 mm yr is not simply an upper bound but applies to the late holocene epoch although the bounds on rates permit more rapid slip in the northwest than the southeast they do not place a useful constraint on variations in slip rate along the fault offsets of paleozoic facies boundaries imply a total right lateral shear of 180 250 km but early cretaceous sedimentary rock appears to have been offset only 60 10 km published paleomagnetic declinations of cretaceous miocene rock demonstrate 20 30 of counterclockwise rotation of the ferghana valley which lies just west of the talas ferghana fault with respect to stable parts of eurasia and 20 11 with respect to the central tien shan east of the fault these declinations are consistent with a maximum northwestward translation of 70 210 km of the ferghana valley at the talas ferghana fault and therefore with a similar maximum horizontal shortening across the chatkal ranges which lie between the ferghana valley and the kazakh platform estimates of crustal thickness beneath the chatkal ranges however permit only 60 100 km of cenozoic shortening if 100 km of slip on the talas ferghana fault accumulated at a constant rate of 10 mm yr it would imply an initiation of slip more recently than ca 10 ma long after india collided with the rest of eurasia

paleomagnetism of cretaceous red beds from tadzhikistan and cenozoic deformation due to india eurasia collision abstract we have carried out structural and paleomagnetic studies in the tadzhik depression in order to evaluate the main features of the alpine tectonics of this area about 340 cores from 43 sites of lower cretaceous red beds were sampled from four different localities in the basin and adjacent ranges a well defined component of magnetization a of normal polarity with high unblocking temperatures up to 650 670 c was isolated from all the sites another component of magnetization b with unblocking temperatures between 650 and 680 c was isolated from only fifteen sites this component is bipolar the fold test is positive for both components we believe that component a was acquired during the cretaceous long interval of normal polarity comparison with eurasian reference data shows significant counterclockwise rotation of a locality close to the pamir wedge r 51 5 and another counterclockwise rotation from the inner part of the basin r 15 5 no significant rotations are observed at the two other localities on the periphery of the tadzhik basin

stochastic model of heterogeneity in earthquake slip spatial distributions summary finite fault source inversions reveal the spatial complexity of earthquake slip or pre stress distribution over the fault surface the basic assumption of this study is that a stochastic model can reproduce the variability in amplitude and the long range correlation of the spatial slip distribution in this paper we compute the stochastic model for the source models of four earthquakes the 1979 imperial valley the 1989 loma prieta the 1994 northridge and 1995 hyogo ken nanbu kobe for each earthquake except imperial valley we consider both the dip and strike slip distributions in each case we use a 1 d stochastic model for the four earthquakes we show that the average power spectra of the raw that is non interpolated data follow a power law behaviour with scaling exponents that range from 0 78 to 1 71 for the four earthquakes we have found that a non gaussian probability law that is the levy law is better suited to reproduce the main features of the spatial variability embedded in the slip amplitude distribution including the presence and frequency of large fluctuations since asperities are usually defined as regions with large slip values on the fault the stochastic model will allow predicting and modelling the spatial distribution of the asperities over the fault surface the values of the levy parameters differ from one earthquake to the other assuming an isotropic spatial distribution of heterogeneity for the dip and the strike slip of he northridge earthquake we also compute a 2 d stochastic model the main conclusions reached in the 1 d analysis remain appropriate for the 2 d model the results obtained for the four earthquakes suggest that some features of the slip spatial complexity are universal and can be modelled accordingly if this is proven correct this will imply that the spatial variability and the long range correlation of the slip or pre stress spatial distribution can be described with the help of five parameters a scaling exponent controlling the spatial correlation and the four parameters of the levy distribution constraining the spatial variability

rupture process of the ms 6 6 superstition hills california earthquake determined from strong motion recordings application of tomographic source inversion abstract we analyze strong motion recordings of the m s 6 6 superstition hills earthquake to determine the timing location spatial extent and rupture velocity of the subevents that produced the bulk of the high frequency 0 5 to 4 hz seismic energy radiated by this shock the earthquake can be characterized by three principal subevents the largest ones occurring about 3 and 10 sec after initiation of rupture timing relationships between pulses on the seismograms indicate that the three subevents are located within 8 km of each other along the northern portion of the superstition hills fault the two largest subevents display different directivity effects we apply a tomographic source inversion to the integrated accelerograms to determine the slip acceleration on the fault as a function of time and distance based on a one dimensional fault model the azimuthal distribution of amplitudes for the second subevent can be largely explained by a rupture that propagated about 2 km to the southeast along the superstition hills fault at a velocity about equal to the p wave velocity an alternative model with rupture propagating to the northeast along a conjugate fault plane can also account for the observed directivity of this subevent but it is not supported by the aftershock distribution the third subevent ruptured to the southeast along an 8 km long portion of the superstition hills fault at about the shear wave velocity this rupture propagation caused the relatively large accelerations and velocities observed in strong motion records for stations southeast of the hypocenter the long time intervals between the subevents and their relative proximity to each other indicate a very slow component to the rupture development the southern half of the superstition hills fault did not generate significant high frequency strong ground motion although it showed substantial co seismic surface displacement the subevents are situated along the same northern portion of the fault where most of the aftershocks are located the locations of the subevents appear to be controlled by bends in the fault mapped at the surface and by changes in basement structure at depth

constraining earthquake source inversions with gps data 1 resolution based removal of artifacts 1 we present a resolution analysis of an inversion of gps data from the 2004 mw 6 0 parkfield earthquake this earthquake was recorded at thirteen 1 hz gps receivers which provides for a truly coseismic data set that can be used to infer the static slip field we find that the resolution of our inverted slip model is poor at depth and near the edges of the modeled fault plane that are far from gps receivers the spatial heterogeneity of the model resolution in the static field inversion leads to artifacts in poorly resolved areas of the fault plane these artifacts look qualitatively similar to asperities commonly seen in the final slip models of earthquake source inversions but in this inversion they are caused by a surplus of free parameters the location of the artifacts depends on the station geometry and the assumed velocity structure we demonstrate that a nonuniform gridding of model parameters on the fault can remove these artifacts from the inversion we generate a nonuniform grid with a grid spacing that matches the local resolution length on the fault and show that it outperforms uniform grids which either generate spurious structure in poorly resolved regions or lose recoverable information in well resolved areas of the fault in a synthetic test the nonuniform grid correctly averages slip in poorly resolved areas of the fault while recovering small scale structure near the surface finally we present an inversion of the parkfield gps data set on the nonuniform grid and analyze the errors in the final model

strong ground motion estimation in the sea of marmara region turkey based on a scenario earthquake we perform a broadband frequency bedrock strong ground motion simulation in the marmara sea region turkey based on several fault rupture scenarios and a source asperity model the technique combines a deterministic simulation of seismic wave propagation at low frequencies with a semi stochastic procedure for the high frequencies to model the high frequencies we applied a frequency dependent radiation pattern model which efficiently removes the effective dependence of the pattern coefficient on the azimuth and take off angle as the frequency increases the earthquake scenarios considered consist of the rupture of the closest segments of the north anatolian fault system to the city of istanbul our scenario earthquakes involve the rupture of the entire north anatolian fault beneath the sea of marmara namely the combined rupture of the central marmara fault and north boundary fault segments we defined three fault rupture scenarios based on the location of the hypocenter selecting a preferred hypocentral location near a fault bend for each case we analysed the effect of location of the asperity within the central marmara fault on the subsequent ground motion as well as the influence of anelasticity on the highfrequency attenuation characteristics the fault and asperity parameters for each scenario were determined from empirical scalings and from results of kinematic and dynamic models of fault rupture we calculated the resulting time series and spectra for ground motion at istanbul and evaluated the sensitivity of the predictions to choice of model parameters the location of the hypocenter is thus shown to be a critical parameter for determining the worst scenario earthquake at istanbul we also found that anelasticity has a significant effect on the regional attenuation of peak ground accelerations our simulated ground motions result in large values of acceleration response spectra at long periods which could be critical for building damage at istanbul during an actual earthquake d 2004 elsevier b v all rights reserved

from earthquake centroid to spatial temporal rupture evolution mw 6 3 movri mountain earthquake june 8 2008 greece 1 we propose a new strategy to reveal the spatial temporal evolution of the earthquake rupture process from near regional data without assuming a constant rupture velocity the approach is based on a conjugate gradient method for which we express analytically the required waveform misfit derivative with respect to slip on the fault the derivative is given by back propagation of residual seismograms towards the source a good initial source approximation is necessary being obtained from hypocenter location and centroid moment tensor solution the iterative approach then gradually reveals major characteristics of the source process as an application we investigate a line source model of a damaging mw6 3 earthquake in greece revealing predominantly unilateral rupture propagation and two or three main slip patches one of which being significantly delayed indicating a temporary rupture arrest the region of largest slip coincides with the region of least abundant aftershocks between hypocenter and centroid the method has application potential for shakemaps emergency response and or aftershock hazard assessment

tomographic imaging of the earthquake rupture process to advance our understanding of the earthquake rupture process we must develop methods that will map observations into the space time variation of seismic moment release on the fault plane while the temporal history of overall moment release is relatively easy to obtain from p waves there has been no objective quantitative method available to directly determine the spatial variation in moment release the theoretical connection between spatially varying moment release and the resultant seismogram is a linear integral relationship specifically a radon transform this paper outlines a linear inverse method that provides a high resolution tomographic image of the space time varying moment density function application of the method to p waves from the large 1976 mindanao earthquake demonstrates the ability of this method to reliably extract coherent pulses of moment release in space and time

a global search inversion for earthquake kinematic rupture history application to the 2000 western tottori japan earthquake 1 we present a two stage nonlinear technique to invert strong motions records and geodetic data to retrieve the rupture history of an earthquake on a finite fault to account for the actual rupture complexity the fault parameters are spatially variable peak slip velocity slip direction rupture time and risetime the unknown parameters are given at the nodes of the subfaults whereas the parameters within a subfault are allowed to vary through a bilinear interpolation of the nodal values the forward modeling is performed with a discrete wave number technique whose green s functions include the complete response of the vertically varying earth structure during the first stage an algorithm based on the heat bath simulated annealing generates an ensemble of models that efficiently sample the good data fitting regions of parameter space in the second stage appraisal the algorithm performs a statistical analysis of the model ensemble and computes a weighted mean model and its standard deviation this technique rather than simply looking at the best model extracts the most stable features of the earthquake rupture that are consistent with the data and gives an estimate of the variability of each model parameter we present some synthetic tests to show the effectiveness of the method and its robustness to uncertainty of the adopted crustal model finally we apply this inverse technique to the well recorded 2000 western tottori japan earthquake mw 6 6 we confirm that the rupture process is characterized by large slip 3 4 m at very shallow depths but differently from previous studies we imaged a new slip patch 2 2 5 m located deeper between 14 and 18 km depth

toward understanding slip inversion uncertainty and artifacts 1 the main concept of seismic source tomography the projection lines along which the observed signals are back projected to the fault is extended to complete wavefields the so called dynamic projection strips dpss are defined and a method to construct the strips from individual waveforms is described in this way each individual station role in the inversion can be better understood synthetic models with two asperities two unilateral and one bilateral rupture scenarios are used as examples they are analyzed using two independent slip inversion methods with similar results bias of the rupture speed for all scenarios and a strong false asperity in the middle of the bilateral fault both artifacts can be explained by the dps analysis as inherent nonuniqueness of the inverse problem due to the joint effect of the two true asperities removal of some slip artifacts by imposing various constraints is discussed but most of the constraints are hardly applicable in practice as such it is recommended to look at least for possible indications of the most significant inversion artifacts this seems to be feasible through combining dpss derived from real data and synthetic models of various rupture scenarios for a given fault and stations the ideas are applied to the movri mountain earthquake in greece mw6 3 8 june 2008 it appears that the earthquake was predominantly unilateral however with a nonunique space time slip pattern few equivalent nonsmooth models all fitting the data equally well are illustrated

petrogenesis of ultramafic xenoliths from the 1800 kaupulehu flow hualalai volcano hawaii the 1800 kaupulehu flow on hualalai volcano hawaii contains abundant xenoliths of dunite wehrlite and olivine clinopyroxenite with minor gabbro troctolite anorthosite and websterite the petrography and mineral compositions of 41 dunite wehrlite and olivine clinopytoxenite xenoliths have been studied and clinopyroxene separates from eight of these have been analyzed for ba k rb sr rare earth elements 87sr 6sr and 143nd 14 nd temperatures of equilibration obtained by olivine spinel and pyroxene geothermometry range from 1000 to 1200 c mineralogical data combined with published fluid inclusion data indicate depths of origin in the range of 8 30 km the rarity of orthopyroxene the presence of fe rich olivine fog 89 and clinopyroxene fs3 2x and the occurrence of high tio2 in spinel 0 9 2 8 wt and clinopyroxene 0 35 1 33 wt all indicate that the xenoliths are cumulates not residues from partial fusion the separated clinopyroxenes have 87sr 6sr 0 70348 0 70367 and nd nd o 51293 o 51299 values that are different from sr and nd isotope ratios of pacific abyssal basalts 0 5130 respectively also clinopyroxenes and spinels in the xenoliths have generally higher tio2 contents o 35 and 0 91 wt respectively than their counterparts in abyssal cumulates 0 40 and 0 70wt respectively these differences indicate that the xenoliths are not a normal component of oceanic crust because the xenoliths and alkalic to transitional hualalai lavas have similar values for cr cr al

late cenozoic tectonic development of the intramontane alai valley pamir tien shan region central asia an example of intracontinental deformation due to the indo eurasia collision 1 the pamir indentor of the northwestern himalayan syntaxis is a first order feature demonstrating partly the northward extent of deformation due to the cenozoic indo eurasia collision the alai valley of kyrgyzstan at the northern end of the indentor is a strategically positioned e w trending intramontane basin that constrains the timing and extent of crustal deformation in this area of the collision zone to quantify the convergence accommodated across the alai valley during the late cenozoic we collected structural and stratigraphic field data reviewed existing soviet literature and analyzed migrated seismic reflection profiles to construct and restore two regional sections crosscutting the basin our study suggests that the development progressive closure and conversion of this formerly marine basin into a terrestrial intramontane basin result from two main deformation events 1 distributed north south contraction took place during the late oligocene early miocene accommodated one third to half of the total shortening and was followed by the formation of a regional erosion surface and 2 n s shortening resumed in the mid miocene and continues today during this second episode the thrust front migrated southward localized along the trans alai ranges and failed to reactivate earlier neogene structures horizontal shortening of about 35 across the alai valley implies relatively low strain rates and displacement rates of about 4 18 4 69 10 16 s 1 and 0 66 0 78 mm yr 1 respectively for the last 25 myr our study confirms other regional observations indicating that contractional deformation occurred far in the interior of the asian continent as early as the late oligocene

the 14 february 2008 earthquake m6 7 sequence offshore south peloponnese greece source models of the three strongest events abstract we investigate the rupture process of the strongest events of the 14 february 2008 sequence which ruptured 30 km of the western hellenic trench three were the strongest events of the sequence the first one m 6 7 occurred on 14 february 2008 at a depth of 30 km on a low angle 10 thrust fault followed within 2 h by an m 6 1 aftershock at a depth of 33 km also on a low angle thrust fault and the third one on 20 feb 2008 of m 6 0 which is characterized as a strike slip event at shallower depth 10 km we used the m 6 1 aftershock as empirical green s function egf to invert for the slip distribution of the strongest m 6 7 event of the sequence we were able to identify the low angle plane strike 288 dip 10 and rake 73 as the fault plane the slip model is dominated by two distinct slip patches which extend towards sse from the hypocenter thus implying rupture directivity toward the island of crete a result which is further supported by our teleseismic waveform inversion results maximum slip is estimated at 270 cm while average slip on the ruptured area area of subfaults of non zero slip was 70 cm most of the slip 95 of total is confined in an area of 34 22 km 2 we attribute the occurrence of the shallow strike slip event just above the interplate thrusting at depth to slip partitioning due to the deflection of slip vectors from the expected plate convergence vector

3d crustal structure from local earthquake tomography around the gulf of arta ionian region nw greece during summer of 1995 local seismicity was recorded in the area around the gulf of arta in northwestern greece by a dense temporary seismic network of the 441 local events observed at 37 stations 232 well locatable events with a total of 2776 p phase readings were selected applying the criteria of a minimum of 6 p observations and an azimuthal gap less than 180 this data set is used to compute a minimum 1d velocity model for the region several tests are conducted to estimate model stability and hypocenter uncertainties leading to the conclusion that relative hypocenter location accuracy is about 500 m in latitude and longitude and 1 km in depth the minimum 1d velocity model serves as initial model in the non linear inversion for three dimensional p velocity crustal structure by iteratively solving the coupled hypocenter velocity problem in a least squares sense careful analysis of the resolution capability of our data set outlines the well resolved features for interpretation the resulting 3d velocity model shows generally higher average crustal velocities in the east and the well resolved area of the eastern gulf of arta exhibits a homogeneous velocity around 6 km s for the whole upper crust a pronounced north south trending zone of low velocities in the upper 5 10 km is observed in the area of the katouna fault zone kfz at greater depths below 10 km the kfz is underlain by high velocity material e w profiles suggest a horst graben structure associated with the kfz