frequency dependent seismic attenuation in the eastern united states as observed from the 2011 central virginia earthquake and aftershock sequence abstract ground shaking due to earthquakes in the eastern united states eus is felt at significantly greater distances than in the western united states wus and for some earthquakes it has been shown to display a strong preferential direction shaking intensity variation can be due to propagation path effects source directivity and or site amplification in this paper we use s and lg waves recorded from the 2011 central virginia earthquake and aftershock sequence in the central virginia seismic zone to quantify attenuation as frequency dependent q f in support of observations based on shaking intensity we observe high q values in the eus relative to previous studies in the wus with especially efficient propagation along the structural trend of the appalachian mountains our analysis of q f quantifies the path effects of the northeast trending felt distribution previously inferred from the u s geological survey usgs did you feel it data historic intensity data and the asymmetrical distribution of rockfalls and landslides

comparison of different site response estimation techniques using aftershocks of the 1999 izmit earthquake on 17 august 1999 the m w 7 4 izmit earthquake occurred in northwestern turkey a temporary seismic network was installed to improve the geometry of a previously installed network in this study 262 aftershocks of the izmit earthquake with magnitude m l ranging between 0 4 and 4 5 were analyzed using digital recordings from 17 stations of these networks s wave and p wave spectral records corrected for path attenuation function were inverted by means of the generalized inversion technique git the git site responses were compared with those calculated by horizontal to vertical h v ratios applied to both earthquake data and to pre event noise in most cases the h v of the earthquake data provided site responses with shapes consistent with those obtained using git however the level of amplification was occasionally found to be different in general these discrepancies can be explained either by the amplification affecting the vertical component of the ground motion that we detected by git or by the waves having a propagation in almost the vertical direction using the h v ratio applied to noise for most cases we obtained not only the peaks for the fundamental resonance frequencies but site responses with shapes similar to those obtained by git the detected level of amplifications using the h v ratio showed a tendency not to exceed those calculated by the inversion finally amplifications up to a factor 5 are found for stations placed over complex topography for these sites amplifications are not always correctly identified by the h v technique using either earthquakes or noise

lead isotope study of zn pb ore deposits associated with the basque cantabrian basin and paleozoic basement northern spain a total of forty three galena samples from syngenetic and epigenetic pb zn mineralizations emplaced in the lower cretaceous basque cantabrian basin and paleozoic basement of the cinco villas massif in the western pyrenees have been analyzed for pb isotopic composition galena from sedex mineralizations hosted in carboniferous clastic rocks in the cinco villas massif display an homogeneous lead isotopic signature 206pb 2044pb 18 43 207pb 204pb 15 66 208pb 204pb 38 69 suggesting a single lead reservoir these values are slightly more radiogenic than lead from other european hercynian deposits possibly reflecting the influence of a more evolved upper crustal source underlying paleozoic sediments are proposed as lead source for the cinco villas massif ores analyses from twenty six galena samples from the four strata bound ore districts hosted in mesozoic rocks reveal the existence of two populations regarding their lead isotopic composition galena from the western santander districts e g reocin is characterized by more radiogenic isotope values 206pb 204pb 18 74 207pb 204pb 15 67 208pb 204pb 38 73 than those from the central and eastern districts troya legorreta central and western vizcaya 206pb 204pb 18 59 207pb 204pb 15 66 208pb 204pb 38 73 in all districts the most likely source for these mineralizations was the thick sequence of lower cretaceous clastic sediments the existence of two separate lead isotopic populations could be the result of regional difference in the composition of the basement rocks and the clastic sediments derived of it or different evolution histories in both sub basins isotopic ratios indicate an increase in crustal influence as the age of the ores decreases

source radiation invariant property of local and near regional shear wave coda application to source scaling for the mw 5 9 wells nevada sequence 1 this study documents another unique property of local and regional shear wave coda that scattering in the earth s crust averages out source heterogeneities such as focal mechanism and directivity we consider two recent events which exhibited significant source directivity the first an mw 4 2 oakland hills california strike slip event on july 20 2007 resulted in uncharacteristically large amounts of damage in the montclair and south berkeley neighborhoods along strike and north west of the hypocenter but almost no damage to the south east the second event the mw 5 9 wells nevada dip slip event of february 21 2008 was well recorded by the earthscope transportable array usarray and determined to exhibit south west directivity we conclude with an example of corner frequency fc estimates from the wells sequence which showcase the coda s low variance and find that scaling is non self similar suggesting a change in dynamics between the mainshock and aftershocks

high precision isotopic analyses of lead ores from new mexico by mc icp ms implications for tracing the production and exchange of pueblo iv glaze decorated pottery abstract between ca 1275 and 1700 ce pueblo groups in the northern southwest united states produced and exchanged ceramic bowls decorated with lead based glaze paints previous studies of these glaze decorated bowls have used lead isotopic analysis by icp ms to identify the sources of lead used by pueblo potters and investigate how social or economic factors may have influenced resource use among different pueblo communities e g habicht mauche et al 2000 habicht mauche et al 2002 huntley et al 2007 huntley 2008 however interpretations of much of this isotopic data have remained provisional because of overlap among the isotopic ratios of potential sources and because the isotopic composition of many glaze paints do not clearly match any known source here we use multi collector icp ms to re measure the lead isotopic composition of 48 samples of lead sulfide galena and lead carbonate cerussite from sources in new mexico that were potentially utilized by pueblo potters including mines within the cerrillos hills magdalena hansonburg and joyita hills mining districts these results define the isotopic composition of lead ores from these districts with greater precision and accuracy than achieved in previous studies and better distinguish among these mining districts in lead isotope space most significantly we find that galena mineralization within the cerrillos hills only has a modest degree of isotopic variation with 206pb 204pb ratios from 18 508 to 18 753 207pb 204pb ratios from 15 580 to 15 607 and 208pb 204pb ratios from 38 388 to 38 560 these ranges are far narrower than previously reported and should supersede previously published values for this district in total we conclude that isotopic measurements of both ores and glaze paints made by mc icp ms will provide new information about the provenance of lead in glaze paints and allow for more detailed interpretations about resource procurement and exchange in the pueblo world

calculable fluid rock interactions this paper introduces a model of rock deformation anisotropic poro elasticity or ape where the response of fluid saturated rock to changing conditions prior to fracturing can be calculated the driving mechanism for deformation is fluid migration along pressure gradients between neighbouring intergranular microcracks and pores at different orientations to the stress field the parameters that control changes to microcrack geometry also control the splitting birefringence of seismic shear waves so that changes in deformation can be directly monitored by analysing the shear wave splitting which is observed in almost all rocks analysis of shear wave splitting in the earth9s crust and ape modelling show that distributions of mostly intergranular cracks in the crust are always geometrically close to fracturing with the implication that shear wave splitting is sensitive to comparatively minor changes of stress and minor changes of in situ conditions this has important implications for the state of criticality of the rockmass and as a consequence changes in shear wave splitting have been observed before larger earthquakes on those few occasions when suitable source receiver geometry coincides with appropriate seismic activity ape also has implications for monitoring changing conditions in reservoirs during hydrocarbon recovery

complexity of the mw 6 3 2009 l aquila central italy earthquake 2 broadband strong motion modeling 1 near fault strong ground motions 0 1 10 hz recorded during the mw 6 3 2009 l aquila earthquake exhibit great spatial variability modeling the observed seismograms allows linking distinct features of the observed wavefield to particular source and propagation effects and provides insights on strong motion complexity from this moderate magnitude event we utilize a hybrid integral composite approach based on a k square kinematic rupture model combining low frequency coherent and high frequency incoherent source radiation and providing omega squared source spectral decay several source model features proven to be stable by means of an uncertainty analysis in the preceding low frequency 2 hz

control of the 2009 l aquila earthquake central italy by a high velocity structure a receiver function study 1 receiver functions rfs analyzed at two permanent broadband seismic stations operating in the epicentral area of the mw 6 3 2009 l aquila earthquake central italy yield insight on crustal structure along the fault rupture the harmonic decomposition of rfs highlights a subsurface structure in which both isotropic and anisotropic features are present we model the waveforms using recently developed monte carlo methods the retrieved models display a common depth structure between 10 and 40 km depth consistent with the under thrusting of the adria lithosphere underneath the apennines belt along the fault in the uppermost crust the s wave velocity structure is laterally heterogeneous right above the hypocenter we find a 4 6 km thick very high s wave velocity body vs as high as 4 2 km s that is absent in the se portion of the fault where the earthquake propagated the high vs body is coincident with the area of fewer aftershocks and is anticorrelated with the maximum slip patches of the earthquake as modeled by differential interferometric synthetic aperture radar dinsar and strong motion data we interpret this high vs body as a high strength barrier responsible for the high peak ground motion in the near field observed in the l aquila city and surroundings and for the complexity in the rupture evolution the retrieved seismic s wave velocity of this body far exceeds common vs values in the upper crust and it is more compatible with values observed in mafic basement rocks

modelling the compliance of crustal rock ii response to temporal changes before earthquakes summary there have been several claims that seismic shear waves respond to changes in stress before earthquakes the companion paper develops a stress sensitive model ape for the behaviour of low porosity low permeability crystalline rocks containing pervasive distributions of fluid filled intergranular microcracks and this paper uses ape to model the behaviour before earthquakes modelling with ape shows that the microgeometry and statistics of distributions of such fluid filled microcracks respond almost immediately to changes in stress and that the behaviour can be monitored by analysing seismic shear wave splitting the physical reasons for the coupling between shear wave splitting and differential stress are discussed in this paper we extend the model by using percolation theory to show that large crack densities are limited at the grain scale level by the percolation threshold at which interacting crack clusters lead to pronounced increases in rock matrix permeability in the simplest formulation the modelling is dimensionless and almost entirely constrained without free parameters nevertheless ape modelling of the evolution of fluid saturated rocks under stress reproduces the observed fracture criticality and the narrow range of shear wave azimuthal anisotropy in crustal rocks it also reproduces the behaviour of temporal variations in shear wave splitting observed before and after the 1986 m 6 north palm springs earthquake southern california and several other smaller earthquakes the agreement of ape modelling with a wide range of observations confirms that fluid saturated crystalline rocks are stress sensitive and respond to changes in stress by critical fluid rock interactions at the microscale level this means that the effects of changes in stress and other parameters can be numerically modelled and monitored by appropriate observations of seismic shear waves

assessment of the precision and accuracy of lead isotope ratios measured by tims for geochemical applications example of massive sulphide deposits rio tinto spain the true reproducibility of lead isotope measurements by thermal ionization mass spectrometer tims was assessed on both the international standard nbs 982 and sulphide samples from the south iberian pyrite belt sipb lead isotope analyses were made on 21 pyrite and galena samples from rio tinto sulphide orebodies in the spanish part of the sipb independent lead isotope analyses were made in the um2 laboratory montpellier using a vg sector 54 mass spectrometer and at brgm orleans using a finnigan mat 262 mass spectrometer internal precision and reproducibility of the isotope measurements were calculated for lead isotope standards nbs 982 and for pyrite and galena samples the reproducibility 2 is 0 12 for 206pb 204pb 0 16 for 207pb 204pb and 0 22 for 208pb 204pb while the internal precision is on average 0 01 for each isotope ratio 2 m this indicates that the usually adopted errors of between 0 10 and 0 25 are appropriate for geological samples tims has been the most common method for measuring u pb ratios by isotopic dilution but since a few years icp ms has also been used for such determinations we thus checked the reproducibility of u pb ratio measurements by icp ms in order to apply this method to sulphide samples independent measurements 2 to 7 for each of 20 analysed samples showed that the measured average reproducibility for u pb ratios is better than 5 this method is thus suitable for determination of u pb ratios in sulphide samples and most other geological materials lead analyses for the rio tinto deposit were made of the pyritic and orebodies and the stringers this deposit one of the biggest massive sulphides in the world is remarkably homogeneous from a lead isotope viewpoint and no difference can be seen between pyritic and polymetallic orebodies the isotope composition of the deposit can be considered as the average composition of the south iberian crust during the devonian early carboniferous period of crustal fusion

regional moment tensors of the 2009 l aquila earthquake sequence broadband waveform inversion of ground velocities in the 0 02 0 10 hz frequency band is successfully applied to 181 earthquakes with m l 3 of the april 2009 l aquila italy earthquake sequence this was made possible by the development of a new regional crustal velocity model constrained by deep crustal profiles surface wave dispersion and teleseismic p wave receiver functions and tested through waveform fit although all earthquakes exhibit normal faulting with the fault plane dipping southwest at about 55 for the majority of events a subset of events had much shallower dips the issue of confidence in the derived parameters was investigated by applying the same inversion procedure by two groups who subjectively selected different traces for inversion the unexpected difficulty in modeling the regional broadband waveforms of the mainshock as a point source was investigated through an extensive finite fault modeling of broadband velocity and accelerometer data which placed the location of major moment release up dip and about 4 7 s after the initial first arrival hypocentral parameters

isotopic composition of pb in ore deposits of the betic cordillera spain origin and relationship to other european deposits the betic cordillera in southern spain is a complex alpine fold belt that resulted from the cretaceous through cenozoic collision of africa with europe the region is illustrative of one of the characteristics of the alpine mediterranean orogen the occurrence over a limited area of mineral deposits with a wide variety of host rocks mineralization ages and styles the metamorphic basement in the betic zone is characterized by a nappe structure of superimposed tectonostratigraphic units and consists of lower paleozoic to lower triassic clastic metasedimentary rocks this is overlain by middle to upper triassic platform carbonate rocks with abundant strata bound f pb zn ba deposits e g sierra de gador sierra alhamilla cretaceous to paleogene subduction related compression in southeastern spain was followed by miocene postcollisional extension and resulted in the formation of the almeria cartagena volcanic belt and widespread hydrothermal activity and associated polymetallic mineralization typical miocene hydrothermal deposits include volcanic hosted au e g rodalquilar and ag rich base metal e g cabo de gata mazarron deposits as well as complex polymetallic veins mantos and irregular replacement bodies which are hosted by paleozoic and mesozoic metamorphic rocks and neogene sedimentary and volcanic rocks e g cartagena sierra almagrera sierra del aguilon loma de bas lead isotope compositions were measured on sulfide samples from nine ore districts and from representative fresh samples of volcanic and basement rock types of the region the results have been used to evaluate ore forming processes in southeastern spain with emphasis on the sources of metals during a late triassic mineralizing event pb was leached from paleozoic clastic metasedimentary rocks and incorporated in galena in strata bound f pb zn ba deposits 206 pb 204 pb 18 332 or 12 207 pb 204 pb 15 672 or 12 208 pb 204 pb 38 523 or 46 the second episode of mineralization was essentially contemporaneous late miocene throughout the region and did not involve remobilization of less radiogenic triassic ore pb lead isotope data indicate a dominantly paleozoic metasedimentary source for polymetallic vein and manto type deposits that formed by hydrothermal circulation through the betic basement driven by miocene intrusions 206 pb 204 pb 18 747 or 20 207 pb 204 pb 15 685 or 9 208 pb 204 pb 39 026 or 37 lead in au cu te sn ores is isotopically indistinguishable from that of the calc alkalic volcanic host 206 pb 204 pb 18 860 or 9 207 pb 204 pb 15 686 or 8 208 pb 204 pb 38 940 or 27 in contrast the pb in volcanic hosted pb zn cu ag au veins was derived from paleozoic metamorphic and miocene volcanic rocks 206 pb 204 pb 18 786 or 5 207 pb 204 pb 15 686 or 2 208 pb 204 pb 38 967 or 9 a comparison of the pb isotope data from southeastern spain with published data from selected pb zn deposits in southern europe including les malines l argentiere and the alpine iglesiente sulcis and montagne noire districts indicates the importance of a metasedimentary basement as a common source of ore pb

earthquakes as self organized critical phenomena a cellular automation model with threshold elements previously proposed by bak et al 1988 which generates 1 f noise and self organizes into a critical state is studied as a model for earthquake occurrence the model explains some of fractal features of earthquakes such as the power law distribution of the size of the earthquake the model is modified so that every earthquake may trigger aftershocks the modified trigger model explains other fractal features of earthquakes such as the power law decay of aftershock frequency and the power law decay of aftershock frequency and the power law correlation of the hypocenter distribution

the 1997 1998 umbria marche sequence central italy source path and site effects estimated from strong motion data recorded in the epicentral area 1 we apply a nonparametric spectral inversion scheme to calculate source spectra s wave attenuation and site transfer functions from strong motion records in the epicentral region of the 1997 1998 umbria marche seismic sequence central italy we use records from moderate size earthquakes 4 6 ml 5 9 to parameterize the spectral amplitude decay in the distance range from 5 to 40 km we find that the average quality factor q can be approximated by q f 49 f0 9 between 0 5 and 8 hz and the geometrical spreading by r 0 9 at high frequencies f 8 hz the dependence of q on frequency weakens and it takes an approximate constant value of 318 we fit the source spectra to the square model and calculate an average stress drop of 2 1 mpa the average value is consistent with the previous estimates from the weak events 1 4 ml 4 5 of the umbria marche seismic sequence the most remarkable site effects are found in correspondence of large sedimentary basins filled by alternation of sandy clayey deposits the estimated spectral parameters are used to simulate acceleration spectra recorded during several earthquakes of the umbria marche sequence both point source and finite fault effects are considered furthermore attenuation relationships for peak ground velocity and ground acceleration are estimated using synthetic data and compared to existing relationships

the 2009 l aquila central italy seismic sequence as a chaotic process abstract in this paper we demonstrate that the seismic sequence of foreshocks culminating with the recent m w 6 3 main shock on april 6 2009 in l aquila central italy evolved as a chaotic process to do this we apply a nonlinear retrospective prediction to this seismic sequence and look at the temporal behaviour of the error between predicted and actual occurrence of the main shock when gradually increasing parts of the sequence are considered this is a generalisation of the typical nonlinear approach which is quite powerful to detect chaos in relatively short time series the method of prediction is based on the accelerated strain release asr analysis in time and on the nonlinear forecasting approach in a reconstructed phase space we find that i the temporal decay of the prediction error is consistent with an exponential function with a time constant of about 10 days and ii at around 6 days before the main shock asr analysis is quite powerful for anticipating the time of occurrence with an uncertainty of about a day due to its retrospective characteristics the latter result could be affected by changes on some a priori parameters used in the application of the asr technique however we consider these findings together with those obtained from the phase space analysis to be strong evidence that the studied sequence of foreshocks was produced by a physical process dominated by a significant chaotic component characterised by a k entropy 1 of about 0 1 day 1 this result could have important implications for the predictability of the possible main shock for those seismic sequences showing analogous nonlinear chaotic properties

on the characteristics of earthquake stress release variations in japan abstract the amount of stress released during earthquakes is a fundamental characteristic of the earthquake rupture process as such it represents a key parameter for improving our understanding of earthquake source physics and for reliable ground motion prediction large earthquake populations usually show variations in stress release as large as three orders of magnitude but the underlying mechanisms have remained largely elusive and particularly the dependence of stress release on earthquake size is still a matter of debate here i use a unique dataset from japan encompassing earthquakes of a wide magnitude range and spatial coverage to show that stress release variations of crustal earthquakes are strongly correlated with heat flow variations indicating that they are thermally controlled in contrast subcrustal events depict highest stress release in regions of strong subduction interface coupling and overall less pronounced variability as compared with crustal earthquakes stress release is overall only weakly dependent on earthquake size but at local scales i e within individual earthquake sequences the dependence can be very strong and apparently varies with stress regime accounting for these systematic variations reduces the stress release variability on local scale by a factor of two to three as compared with the full earthquake population a finding that is of key significance in the endeavor to reduce the uncertainties in future ground motion predictions

the mw 6 3 2009 l aquila earthquake source path and site effects from spectral analysis of strong motion data summary the strong motion data of 2009 april 6 l aquila central italy earthquake mw 6 3 and of 12 aftershocks 4 1 mw 5 6 recorded by 56 stations of the italian strong motion network are spectrally analysed to estimate the source parameters the seismic attenuation and the site amplification effects the obtained source spectra for s wave have stress drop values ranging from 2 4 to 16 8 mpa being the stress drop of the main shock equal to 9 2 mpa the spectral curves describing the attenuation with distance show the presence of shoulders and bumps mainly around 50 and 150 km as consequence of significant reflected and refracted arrivals from crustal interfaces the attenuation in the first 50 km is well described by a quality factor equal to q f 59f0 56 obtained by fixing the geometrical spreading exponent to 1 finally the horizontal to vertical spectral ratio provides unreliable estimates of local site effects for those stations showing large amplifications over the vertical component of motion

the anatomy of the 2009 l aquila normal fault system central italy imaged by high resolution foreshock and aftershock locations 1 on 6 april 01 32 utc 2009 a mw 6 1 normal faulting earthquake struck the axial area of the abruzzo region in central italy we study the geometry of fault segments using high resolution foreshock and aftershock locations two main sw dipping segments the l aquila and campotosto faults forming an en echelon system 40 km long nw trending the 16 km long l aquila fault shows a planar geometry with constant dip 48 through the entire upper crust down to 10 km depth the campotosto fault activated by three events with 5 0 mw 5 2 shows a striking listric geometry composed by planar segments with different dips along depth rather than a smoothly curving single fault surface the investigation of the spatiotemporal evolution of foreshock activity within the crustal volume where the subsequent l aquila main shock nucleated allows us to image the progressive activation of the main fault plane from the beginning of 2009 the foreshocks activated the deepest portion of the fault until a week before the main shock when the largest foreshock mw 4 0 triggered a minor antithetic segment seismicity jumped back to the main plane a few hours before the main shock secondary synthetic and antithetic fault segments are present both on the hanging and footwall of the system the stress tensor obtained by inverting focal mechanisms of the largest events reveals a ne trending extension and the majority of the aftershocks are kinematically consistent deviations from the dominant extensional strain pattern are observed for those earthquakes activating minor structures

stress forecasting not predicting earthquakes a paradigm shift after 120 years of unsuccessful endeavor a paradigm shift is required before earthquakes can be predicted the most sensitive diagnostic of low level changes of stress in in situ rock variations in microcrack geometry can be monitored by analyzing shear wave splitting the suggested paradigm shift is that instead of investigating the source zone we monitor stress accumulation before earthquakes at possibly substantial distances from the source characteristic temporal variations of shear wave time delays have been observed in retrospect before 14 earthquakes worldwide on one occasion when changes were recognized early enough the time magnitude and fault break of an m 5 earthquake in southwest iceland were successfully stress forecast in a narrow time magnitude window such stress accumulation can be theoretically modeled and is believed to be at least partially understood when sufficient shear wave source earthquakes are available increasing time delays also show an abrupt decrease shortly before the impending earthquake occurs this is not fully understood but is thought to be caused by stress relaxation as microcracks coalesce onto the eventual fault break the new result confirming these ideas and justifying the paradigm shift is that logarithms of the durations of both increases and decreases in time delays are found to be proportional self similar to the magnitudes of impending earthquakes

s wave attenuation characteristics beneath the vrancea region in romania new insights from the inversion of ground motion spectra the s wave attenuation characteristics beneath the vrancea region in romania are analyzed from the spectra frequency range 0 5 20 hz of more than 850 recordings at 43 accelerometric stations of 55 intermediate depth earthquakes m 4 0 7 1 that occurred in the vrancea seismogenic zone the method commonly chosen for this type of investigation in the case of crustal earthquakes is the generalized inversion technique git e g andrews 1986 castro et al 1990 yet the vrancea dataset is entirely different from common crustal datasets because of the strong clustering of the hypocenters within a very small focal volume there are only few crossing ray paths from sources to receivers as a consequence inhomogeneities in the attenuation properties are not averaged out which leads to unphysical results if the standard git approach is adopted the problem is discussed qualitatively by performing tests with synthetic data and solved quantitatively by adapting the git technique in view of these peculiarities with the optimally adapted inversion scheme it is possible to unravel differences in the attenuation characteristics between two or more sets of stations the results show that the attenuation of seismic waves is roughly comparable in the low frequency range 4 5 hz but stronger by up to an order of magnitude at higher frequencies within the carpathian mountain arc as compared with the foreland area modeling this strongly frequency dependent lateral variation of seismic attenuation by a significantly lower q beneath vrancea 1 provides a very good fit of observed strong motion characteristics 2 sheds new light on the distribution of intensities of the previous strong earthquakes 3 will have strong implications for future hazard assessment and 4 is fully compatible with structural models from deep seismic sounding tomography and teleseismic attenuation

stress release and source scaling of the 2010 2011 canterbury new zealand earthquake sequence from spectral inversion of ground motion data the canterbury earthquake sequence beginning with the 2010 m w 7 2 darfield earthquake is one of the most notable and well recorded crustal earthquake sequences in a low strain rate region worldwide and as such provides a unique opportunity to better understand earthquake source physics and ground motion generation in such a tectonic setting ground motions during this sequence ranged up to extreme values of 2 2 g recorded during the february 2011 m w 6 2 event beneath the city of christchurch a better understanding of the seismic source signature of this sequence in particular the stress release and its scaling with earthquake size is crucial for future ground motion prediction and hazard assessment in canterbury but also of high interest for other low to moderate seismicity regions where high quality records of large earthquakes are lacking here we present a source parameter study of more than 200 events of the canterbury sequence covering the magnitude range m w 3 7 2 source spectra were derived using a generalized spectral inversion technique and found to be well characterized by the 2 source model we find that stress drops range between 1 and 20 mpa with a median value of 5 mpa which is a factor of 5 larger than the median stress drop previously estimated with the same method for crustal earthquakes in much more seismically active japan stress drop scaling with earthquake size is nearly self similar and we identify lateral variations throughout canterbury in particular high stress drops at the fault edges of the two major events the m w 7 2 darfield and m w 6 2 christchurch earthquakes

lead isotope systematics of the giant massive sulphide deposits in the iberian pyrite belt lead isotope analyses were performed on 26 polymetallic massive sulphide deposits of the iberian pyrite belt as well as on overlying gossans and associated volcanic rocks all the massive sulphide deposits except for neves corvo and nearly all the volcanic rocks show very similar isotopic compositions grouped around 18 183 206pb 204pb 15 622 207pb 204pb and 38 191 208pb 204pb indicating that most of the ore deposit lead was derived from the same continental crust environment as the associated volcanic rocks the isotopic compositions are representative of the average south iberian crust during the devonian to early carboniferous dinantian and their constancy implies a homogenization of the mineralizing fluids before the deposition of the massive sulphides from hydrothermal fluids circulating through interconnected regional fracture systems this isotopic constancy is incompatible with multiple small independent hydrothermal cells of the east pacific rise type and fits much better with a model of hydrothermal convections driven by magmatic floor heating neves corvo is the only south iberian massive sulphide deposit to have a heterogeneous isotopic composition with in particular a highly radiogenic stanniferous ore 206pb 204pb of the cassiterite is 18 40 a model of lead mixing with three components is proposed to explain these variations 1 one derived from the devonian to early carboniferous dinantian continental crust that generated all the other massive ores 2 an eohercynian stanniferous mineralization partly remobilized during the formation of the massive sulphides but independent of them and 3 a precambrian continental crust component the juxtaposition of three different sources places neves corvo in a specific paleogeographic situation that could also explain its mineralogical specificity the geodynamic context that best explains all the obtained isotopic results is one of an accretionary prism the fact that lead isotope signatures of the gossans are almost identical to those of the underlying massive sulphides means that this technique could be a useful exploration tool for the iberian pyrite belt

observations of stress relaxation before earthquakes summary theory and observations suggest that seismic shear wave splitting caused by fluid saturated stress aligned microcracks directly monitors low level deformation before fracturing faulting and earthquakes occur in the past it had been assumed that the accumulation of stress before earthquakes continued until stress was released by faulting at the time of the earthquake however new data and reappraisal of existing data sets now suggests that the stress begins to relax and cracks close from tens of minutes to months before the earthquake actually occurs with the logarithm of the duration of the relaxation proportional to the magnitude of the impending earthquake the duration of the relaxation appears to be directly correlated with earthquake magnitude and may have implications for the earthquake source process and the ability to predict earthquakes

the scatter of time delays in shear wave splitting above small earthquakes summary measurements of time delays in seismic shear wave splitting above small earthquakes typically display a scatter of often as much as 80 per cent about the mean changes in the average timedelay appear to be related to changes of stress but applications of this potentially powerful tool have been handicapped by the previously inexplicable scatter in time delays above earthquakes in contrast measurements of shear wave time delays in controlled source exploration seismics are typically well controlled and display little scatter previous estimates of possible causes of scatter cannot produce sufficient variation specifically above earthquakes here we show that 90 flips in shear wave polarizations due to fluctuating high pore fluid pressures on seismicallyactive fault planes are the most likely cause of the scatter

retrospective investigation of geomagnetic field time series during the 2009 l aquila seismic sequence abstract this paper reports the analyses of ulf ultra low frequency geomagnetic field observations coming from the geomagnetic observatory of l aquila during the period 2008 2009 this period includes the l aquila 2009 seismic sequence where the main shock of 6 april heavily damaged the medieval centre of the town and its surrounding area causing 308 deaths more than 1000 injuries and about 60 000 displaced people recently several publications have documented the observation of precursory signals which occurred before the 6 april earthquake e g eftaxias et al 2009 2010 while others do not find any pre earthquake anomaly e g villante et al 2010 di lorenzo et al 2011 in light of this the goal of this study is to carry out further retrospective investigations ulf magnetic field data are investigated by means of conventional analyses of magnetic polarization ratio improved magnetic polarization ratio and fractal analysis in addition total geomagnetic field data coming from the ingv central italy tectonomagnetic network have also been investigated using the simple inter station differentiation method within the limits of these methods no magnetic anomalous signal which may be reasonably characterized as a precursor of the l aquila earthquakes has been found

inversion analysis of site responses in the kanto basin using data from a dense strong motion seismograph array abstract we applied nonlinear inversion analysis to estimate site response in the kanto area using data from 19 moderate sized earthquakes observed at the 843 stations constituting strong motion accelerograph networks of the seismic kanto strong motion network sk net k net and kik net we determined the source parameters seismic moment m 0 corner frequency f c for each event and the quality factor q f for the propagation path based on borehole records we also determined the frequency independent and reference independent site responses the resulting seismic moments are in good agreement with those determined by the national research institute for earth science and disaster prevention nied and are proportional to we found a frequency dependent quality factor for the propagation path q f 107 f 0 52 the site responses averaged over 0 5 1 0 hz correlate well with shear wave velocities for the upper 30 m avs30 correlation coefficient of 0 63 and with depth to the seismic basement the shear wave velocity of which is around 3 0 km sec large site responses are found in areas of unconsolidated sediments such as swampy land the predominant frequencies of our site responses roughly agree with those of the horizontal to vertical h v spectral ratio this indicates that the h v ratio is valid for estimating predominant frequencies of s wave amplification

the fracture criticality of crustal rocks summary the shear wave splitting observed along almost all shear wave ray paths in the earth s crust is interpreted as the effects of stress aligned fluid filled cracks microcracks and preferentially oriented pore space once away from the free surface where open joints and fractures may lead to strong anisotropy of 10 per cent or greater intact ostensibly unfractured crustal rock exhibits a limited range of shear wave splitting from about 1 5 to 4 5 per cent differential shear wave velocity anisotropy interpreting this velocity anisotropy as normalized crack densities a factor of less than two in crack radius covers the range from the minimum 1 5 per cent anisotropy observed in intact rock to the 10 per cent observed in heavily cracked almost disaggregated near surface rocks this narrow range of crack dimensions and the pronounced effect on rock cohesion suggests that there is a state of fracture criticality at some level of anisotropy between 4 5 and 10 per cent marking the boundary between essentially intact and heavily fractured rock when the level of fracture criticality is exceeded cracking is so severe that there is a breakdown in shear strength the likelihood of progressive fracturing and the dispersal of pore fluids through enhanced permeability the range of normalized crack dimensions below fracture criticality is so small in intact rock that any modification to the crack geometry by even minor changes of conditions or minor deformation particularly in the presence of high pore fluid pressures may change rock from being essentially intact below fracture criticality to heavily fractured above fracture criticality this recognition of the essential compliance of most crustal rocks and its effect on shear wave splitting has implications for monitoring changes in any conditions affecting the rock mass these include monitoring changes in reservoir evolution during hydrocarbon production and enhanced oil recovery and in monitoring changes before and after earthquakes amongst others

seismicity based earthquake forecasting techniques ten years of progress abstract earthquake fault systems interact over a broad spectrum of spatial and temporal scales and in recent years studies of the regional seismicity in a variety of regions have produced a number of new techniques for seismicity based earthquake forecasting while a wide variety of physical assumptions and statistical approaches are incorporated into the various methodologies they all endeavor to accurately replicate the statistics and properties of both the historic and instrumental seismic records as a result the last ten years have seen significant progress in the field of intermediate and short term seismicity based earthquake forecasting these include general agreement on the need for prospective testing and successful attempts to standardize both evaluation methods and the appropriate null hypotheses here we differentiate the predominant approaches into models based upon techniques for identifying particular physical processes and those that filter or smooth the seismicity comparison of the methods suggests that while smoothed seismicity models provide improved forecast capability over longer time periods higher probability gain over shorter time periods is achieved with methods that integrate statistical techniques with our knowledge of the physical process such as the epidemic type aftershock sequence etas model or those related to changes in the b value for example in general while both classes of seismicity based forecasts are limited by the relatively short time period available for the instrumental catalog significant advances have been made in our understanding of both the limitations and potential of seismicity based earthquake forecasting there is general agreement that both short term forecasting on the order of days to weeks and longer term forecasting over five to ten year periods is within reach this recent progress serves to illuminate both the critical nature of the different temporal scales intrinsic to the earthquake process and the importance of high quality seismic data for the accurate quantification of time dependent earthquake hazard

a successfully stress forecast earthquake summary a m 5 earthquake in iceland has been successfully stress forecast by using variations in time delays of seismic shear wave splitting to assess the time and magnitude at which stress modified microcracking reaches fracture criticality within the stressed volume where strain is released local investigations suggested the approximate location of the forecast earthquake we report the criteria on which this stress forecast was based

comprehensive analysis of earthquake source spectra in southern california we compute and analyze p wave spectra from earthquakes in southern california between 1989 and 2001 using a method that isolates source receiver and path dependent terms we correct observed source spectra for attenuation using both fixed and spatially varying empirical green s function methods estimated brune type stress drops for over 60 000 m l 1 5 to 3 1 earthquakes range from 0 2 to 20 mpa with no dependence on moment or local b value median computed stress drop increases with depth in the upper crust from about 0 6 mpa at the surface to about 2 2 mpa at 8 km where it levels off and remains nearly constant in the midcrust down to about 20 km however the results at shallow depths could also be explained as reduced rupture velocities near the surface rather than a change in stress drop spatially coherent variations in median stress drop are observed with generally low values for the imperial valley and northridge aftershocks and higher values for the eastern transverse ranges and the north end of the san jacinto fault we find no correlation between observed stress drop and distance from the san andreas and other major faults significant along strike variations in stress drop exist for aftershocks of the 1992 landers earthquake which may correlate with differences in main shock slip

isotopic evidence for the provenance of turquoise in the southwestern united states the archaeological record shows that turquoise was widely mined and highly valued by pre hispanic societies in the southwestern united states and it has long been assumed that much of the turquoise noted in ancient mesoamerica was traded from this region however little is understood about the acquisition and exchange of turquoise by native american societies because the geological sources of most turquoise artifacts from archaeological sites in the southwestern u s and mexico are not known we evaluate the potential for pb and sr isotopic ratios to indicate the geological provenance of turquoise artifacts recovered from these regions pb and sr isotopic measurements were made on 137 geological samples of turquoise from 19 mining districts across the southwestern united states and northern mexico these data reveal that isotopic signatures of turquoise deposits vary geographically according to regional and local differences in the geologic settings of turquoise mineralization as an archaeological case study we also report pb and sr isotopic data on 10 turquoise artifacts recovered from three late pre hispanic ca a d 1250 1400 ancestral zuni sites located in the el morro valley of western new mexico these have isotopic signatures uniquely consistent with the turquoise deposits of the cerrillos hills a location identified in zuni traditional history as an ancient source of turquoise these data thus establish pb and sr isotopic measurements as powerful tools for determining the sources of turquoise artifacts and provide a new framework for evaluating the role of turquoise in pre hispanic exchange networks across north america

spectral analysis of k net and kik net data in japan part ii on attenuation characteristics source spectra and site response of borehole and surface stations abstract in this study we apply a nonparametric spectral inversion scheme to a data set of accelerograms recorded by the k net and kik net networks in japan in order to derive attenuation characteristics source spectra and site response for this purpose we use a total of more than 67 000 s wave records from 2178 earthquakes m jma 2 7 8 obtained at 1555 stations at the earth s surface and more than 29 000 records from 1826 events recorded at 637 borehole stations at depths of 100 to 3000 m attenuation characteristics are investigated in five separate regions showing that crustal q depicts lower values in central compared to southern japan and a significant frequency dependence is observed in every region the source spectra follow the 2 model with higher stress drops for subcrustal earthquakes as compared with crustal ones while strong amplification effects dominate the site contributions for the surface sensors those for the borehole sensors are characterized by smaller variability nevertheless consistent with observations from deconvolution of borehole surface recording pairs downgoing wave effects are visible in the site contributions for many borehole stations finally the site amplification functions obtained at the surface are compared with surface to borehole s b and horizontal to vertical h v spectral ratios showing that the s b ratios generally provide better estimates of the horizontal amplification than the h v ratios due to amplification of the vertical component of ground motion

spatial and temporal stress drop variations in small earthquakes near parkfield california 1 we estimate source parameters from spectra of 42367 earthquakes between 1984 and 2005 that occurred in the parkfield segment of the san andreas fault in central california we use a method that isolates the source term of the displacement spectra based on a convolutional model and correct the observed p wave source spectra with a spatially varying empirical green s function egf our brune type stress drop estimates vary from 0 1 to over 100 mpa with a median value of 6 75 mpa which is nearly constant with moment implying self similarity over the ml 0 5 to 3 0 range of our data the corner frequency decreases for earthquakes at shallower depths consistent with slower rupture velocities and reduced shear wave velocities in local velocity models the estimated median stress drops show significant lateral variations we find lower stress drops in the middle mountain asperity and along the creeping fault section and higher stress drops in the hypocentral region of the 2004 m6 0 parkfield earthquake the main shock did not alter the overall pattern of high and low stress drop regions however a statistical test reveals areas with significant changes in computed stress drops after the main shock which we compare to estimated absolute shear stress changes from a main shock slip model by calculating t from the spectral egf ratio we also identify areas with increased attenuation after the main shock and we are able to distinguish source effects and near source attenuation effects in the spectral analysis these results are confirmed independently from spectral ratios of repeating microearthquake clusters

lead isotope analysis as a new method for identifying material culture belonging to the vazquez de coronado expedition abstract archaeological evidence has become an increasingly important component of efforts to identify the route of the francisco vazquez de coronado expedition through northern mexico and the southwestern united states 1540 1542 here we report the first high precision lead isotopic measurements of artifacts from two archaeological sites with strong material evidence for the expedition s presence piedras marcadas pueblo in new mexico and the jimmy owens site in texas the analysis of lead and copper armaments from both sites reveals that many artifacts have overlapping or extremely similar isotopic ratios we propose that the narrow range of lead isotopic ratios measured on these artifacts can be interpreted as a geochemical fingerprint for some of the coronado expedition s surviving material culture and provides evidence that we interpret to suggest the expedition derived lead and copper metal from mexican sources such a geochemical fingerprint presents an empirical method for discriminating between artifacts that belonged to the coronado expedition and those related to subsequent spanish historical or modern activity in the southwest u s thus this method could significantly impact the search for and identification of archaeological sites associated with the coronado expedition

characterization of earthquake induced ground motion from the l aquila seismic sequence of 2009 italy summary based only on weak motion data we carried out a combined study on region specific source scaling and crustal attenuation in the central apennines italy our goal was to obtain a reappraisal of the existing predictive relationships for the ground motion and to test them against the strong motion data peak ground acceleration pga peak ground velocity pgv and spectral acceleration sa gathered during the mw 6 15 l aquila earthquake 2009 april 6 01 32 utc the l aquila main shock was not part of the predictive study and the validation test was an extrapolation to one magnitude unit above the largest earthquake of the calibration data set the regional attenuation was determined through a set of regressions on a data set of 12 777 high quality high gain waveforms with excellent s n ratios 4259 vertical and 8518 horizontal time histories seismograms were selected from the recordings of 170 foreshocks and aftershocks of the sequence the complete set of all earthquakes with ml 3 0 from 2008 october 1 to 2010 may 10 all waveforms were downloaded from the iside web page http iside rm ingv it iside standard index jsp a web site maintained by the istituto nazionale di geofisica e vulcanologia ingv weak motion data were used to obtain a moment tensor solution as well as a coda based moment rate source spectrum for each one of the 170 events of the l aquila sequence 2 8 mw 6 15 source spectra were used to verify the good agreement with the source scaling of the colfiorito seismic sequence of 1997 1998 recently described by malagnini et al 2008 finally results on source excitation and crustal attenuation were used to produce the absolute site terms for the 23 stations located within 80 km of the epicentral area the complete set of spectral corrections crustal attenuation and absolute site effects was used to implement a fast and accurate tool for the automatic computation of moment magnitudes in the central apennines

modeling geometrical spreading and the relative amplitudes of vertical and horizontal high frequency ground motions in eastern north america abstract horizontally layered velocity models were used with point source and finite fault sources to investigate geometrical spreading and the relative amplitudes of vertical and horizontal ground acceleration within 120 km of the source full wave field simulations were done for a range of focal depths and for strike slip and reverse focal mechanisms the attenuation of the geometric mean of randomly oriented horizontal component maximum acceleration amplitudes averaged over all azimuths significantly exceeds the theoretical geometrical spreading for far field body waves in a homogeneous whole space for hypocentral distances less than approximately 60 km the behavior of the vertical component is different from the horizontal vertical attenuation near the epicenter is greater and is more dependent on source mechanism and depth because of the rapid near source decay of the direct s wave reflections from the mid lower crust and moho control the maximum amplitude of the vertical component acceleration in the 60 120 km hypocenter distance range resulting in a flattening of the vertical amplitude distance relation near source vertical maximum amplitudes averaged over all source receiver azimuths tend to be less than the geometric mean horizontal amplitude for strike slip focal mechanisms but near the source for reverse faults the azimuthally averaged vertical component amplitude exceeds that of the geometric mean horizontal the modeling indicates that similar vertical and horizontal component geometrical spreading and approximately constant horizontal vertical amplitude ratios observed in connection with the lg phase at distances greater than approximately 100 km in eastern north america may not hold at smaller distances ground motion prediction models for the vertical component near the source may need to incorporate strong geometrical spreading and dependence on radiation pattern

mechanisms of seismic attenuation in the crust scattering and anelasticity in new york state south africa and southern california the envelopes of high frequency seismograms from earthquakes in new york state south africa and southern california are analyzed to determine how much of the observed attenuation of shear waves in the crust is caused by anelasticity and how much is produced by scattering from small scale heterogeneities for seismograms from new york and south africa there is a systematic enrichment of high frequency energy that develops in the coda relative to the direct s or l sub g waves the author uses the growth with source receiver distance of the high frequency energy in the coda relative to the direct wave to estimate the scattering attenuation of the crust and the relative time decay of high frequency energy in the coda to determine the anelastic attenuation using the estimate of l sub g wave q as a constraint he finds that the scattering q in the crust of new york is either independent of frequency or increases with frequency f slower than f sup 0 3 a similar analysis for south africa indicates that scattering is the major cause of the observed s wave attenuation of high frequency energy 30 hz at local distances 100 km for southern california the extent of the scattering attenuation is unclear from the data more although the relatively steep coda decay of southern california implies that anelastic attenuation is stronger there than in new york or south africa for southern california and new york state the 3 hz coda q taken from the late coda 50 110 s is comparable to the l sub g wave q however the 3 hz coda q for south africa over these lapse times is about 5 times the estimated l sub g wave q for all three areas the frequency dependence of the coda q does not match the frequency dependence of the s wave q and for new york and south africa it changes with lapse time less

isotopic tracing of prehistoric rio grande glaze paint production and trade stable lead isotope analyses using high resolution inductively coupled plasma mass spectrometry icp ms accurately traced the origin of lead ores used in the production of ceramic glaze paints by prehistoric pueblo potters in the american southwest the analyses show that despite the availability of other local sources most potters in north central new mexico during the fifteenth century obtained lead from the cerrillos hills these results suggest that certain strategically located communities may have controlled the distribution of lead within the region thus lead isotope analysis proved an effective technique for examining prehistoric patterns of resource utilisation production and exchange

earthquakes can be stress forecast in 1997 geller et al wrote earthquakes cannot be predicted because scale invariance is ubiquitous in self organized critical systems and the earth is in a state of self organized criticality where small earthquakes have some probability of cascading into a large event physically however large earthquakes can only occur if there is sufficient stress energy available for release by the specific earthquake magnitude this stress dependence can be exploited for stress forecasting by using shear wave splitting to monitor stress accumulation in the rock mass surrounding impending earthquakes the technique is arguably successful but because of the assumed unpredictability requires explicit justification before it can be generally accepted avalanches are also phenomena with self organized criticality recent experimental observations of avalanches in 2 d piles of spherical beads show that natural physical phenomena with self organized criticality such as avalanches and earthquakes can be predicted the key to predicting both earthquakes and avalanches is monitoring the matrix material not monitoring impending source zones

earthquake scaling characteristics and the scale in dependence of seismic energy to moment ratio insights from kik net data in japan 1 we investigate earthquake source characteristics and scaling properties using the results of a spectral inversion of more than 29 000 accelerometric borehole recordings from 1 826 earthquakes mjma 2 7 8 throughout japan we find that the calculated source spectra can be well characterized by the omega square model and show on average self similar scaling over the entire magnitude range with median stress drops of 1 1 and 9 2 mpa for crustal and subcrustal events respectively the seismic energy to moment ratio as theoretically expected if the omega square model is valid shows a strong dependency on stress drop only which in conjunction with data selection practice in some studies to cope with limited recording bandwidth can explain the often observed apparent scale dependence our observations suggest that there is no significant deviation from similarity of the energy radiation in the investigated magnitude range and that the observed scatter is mainly related to the scatter in stress drop

radiography of a normal fault system by 64 000 high precision earthquake locations the 2009 l aquila central italy case study 1 we studied the anatomy of the fault system where the 2009 l aquila earthquake mw 6 1 nucleated by means of 64 k high precision earthquake locations spanning 1 year data were analyzed by combining an automatic picking procedure for p and s waves together with cross correlation and double difference location methods reaching a completeness magnitude for the catalogue equal to 0 7 including 425 clusters of similar earthquakes the fault system is composed by two major faults the high angle l aquila fault and the listric campotosto fault both located in the first 10 km of the upper crust we detect an extraordinary degree of detail in the anatomy of the single fault segments resembling the degree of complexity observed by field geologists on fault outcrops we observe multiple antithetic and synthetic fault segments tens of meters long in both the hanging wall and footwall along with bends and cross fault intersections along the main fault and fault splays the width of the l aquila fault zone varies along strike from 0 3 km where the fault exhibits the simplest geometry and experienced peaks in the slip distribution up to 1 5 km at the fault tips with an increase in the geometrical complexity these characteristics similar to damage zone properties of natural faults underline the key role of aftershocks in fault growth and co seismic rupture propagation processes additionally we interpret the persistent nucleation of similar events at the seismicity cutoff depth as the presence of a rheological i e creeping discontinuity explaining how normal faults detach at depth