extracting time domain green s function estimates from ambient seismic noise 1 it has been demonstrated experimentally and theoretically that an estimate of the green s function between two seismic stations can be obtained from the time derivative of the long time average cross correlation of ambient noise between these two stations this tdgf estimate from just the noise field includes all tensor components of the green s function and these green s function estimates can be used to infer earth structure we have computed cross correlations using 1 to 30 continuous days of ambient noise recorded by over 150 broadband seismic stations located in southern california the data processing yielded thousands of cross correlation pairs for receiver separations from 4 500 km which clearly exhibit coherent broadband propagating dispersive wavetrains across frequency band 0 1 2 hz

evidence from precise earthquake hypocenters for segmentation of the san andreas fault in san gorgonio pass we use precise hypocenter patterns and focal mechanisms to investigate the presence or absence of a continuous strike slip fault at depth connecting the san bernardino strand of the san andreas fault with the coachella valley segment of the banning fault we inverted 560 000 arrival times from 23 000 earthquakes 1981 1993 for high quality hypocenters and three dimensional p wave velocity structure in a 1 by 2 area centered on the san gorgonio pass cross sectional plots of relocated earthquakes reveal an abrupt 5 to 7 km high step in the maximum depth of hypocenters the step riser defines a near vertical locally curved surface that extends westerly more than 60 km from the coachella valley segment of the san andreas fault to the san jacinto fault a hypothetical continuous vertical san andreas fault through san gorgonio pass would cross the step at an oblique angle we suggest that the step is the expression of the contact between different basement rock types juxtaposed by large scale right slip motion on the ancestral san andreas fault south of the step in peninsular ranges type basement intrusives brittle failure occurs down to about 20 km depth while north of the step in san bernardino type basement pelona schist brittle failure occurs to only about 13 km depth the step provides a piercing plane that should be offset about 3 km right laterally by an active continuous vertical san andreas fault within the resolution of our mapping the step is not offset in this manner implying either that there has not been a throughgoing vertical fault at depth that a throughgoing fault has not experienced enough slip to offset the step or that a throughgoing fault is not vertical and dips north over the top of the step hypocentral patterns and focal mechanisms indicate distributed deformation thrust normal and strike slip faulting over a large volume in the san gorgonio pass region there is no evidence of hypocenter or slip vector alignments that would indicate a throughgoing continuous near vertical san andreas fault in summary we find no evidence indicating a continuous fault at seismogenic depth connecting the san bernardino strand and coachella valley segment of the san andreas fault zone we speculate that this is because the 3 km of right slip on the san bernardino stand of the san andreas fault and coachella valley segment of the banning fault has not been sufficient to form a single new structure through the 15 to 20 km gap between the two previously unconnected segments this implies that large earthquake rupture on the san andreas fault may be inhibited from propagating through san gorgonio pass thus limiting the maximum magnitudes on the southern san andreas fault

what do data used to develop ground motion prediction equations tell us about motions near faults a large database of ground motions from shallow earthquakes occurring in active tectonic regions around the world recently developed in the pacific earthquake engineering center s nga west2 project has been used to investigate what such a database can say about the properties and processes of crustal fault zones there are a relatively small number of near rupture records implying that few recordings in the database are within crustal fault zones but the records that do exist emphasize the complexity of ground motion amplitudes and polarization close to individual faults on average over the whole data set however the scaling of ground motions with magnitude at a fixed distance and the distance dependence of the ground motions seem to be largely consistent with simple seismological models of source scaling path propagation effects and local site amplification the data show that ground motions close to large faults as measured by elastic response spectra tend to saturate and become essentially constant for short periods this saturation seems to be primarily a geometrical effect due to the increasing size of the rupture surface with magnitude and not due to a breakdown in self similarity

evaluation of the role of cambrian granites in the genesis of world class vhms deposits in tasmania abstract an analysis of the distribution composition and alteration zonation of cambrian granites which intrude the mt read volcanics of western tasmania provides evidence that there may have been a direct input of magmatic fluids containing fe cu au and p to form the copper gold volcanic hosted massive sulphide vhms mineralisation in the mt lyell district interpretation of regional gravity and magnetic data indicates that a narrow discontinuous body of cambrian granite 2 4 km wide extends along the eastern margin of the mt read volcanic belt for over 60 km the cambrian granites are altered magnetite series types which show enrichment in barium and potassium and contrast markedly with the fractionated ilmenite series devonian granites related to tin mineralisation elsewhere in the dundas trough copper mineralisation occurs in a linear zone above the apex of the buried cambrian granite body at the southern end of the belt from mt darwin to the mt lyell district over a strike length of 25 km gold and zinc mineralisation are concentrated higher in the volcanic stratigraphy more distant from the granite overlapping zones of alteration extend from the granite into the surrounding volcanic rocks an inner zone of k feldspar alteration is overprinted by chlorite alteration which passes outwards into sericite alteration magnetite pyrite chalcopyrite apatite mineralisation is concentrated in the chlorite alteration zone as veins and low grade disseminations the mt lyell copper gold stringer and disseminated mineralisation is hosted in felsic volcanic rocks 1 to 2 km west of the interpreted buried granite position magnetite apatite pyrite veins in the prince lyell deposit at mt lyell are very similar to the veins in the halo of the granite further south and provide evidence for magmatic fluid input during the formation of the copper gold vhms deposits a model involving deeply penetrating convective seawater mixing with a magmatic fluid released from the cambrian granites best explains the features of vhms mineralisation in the mt lyell district

ground motion prediction equations in the san jacinto fault zone significant effects of rupture directivity and fault zone amplification we present a new set of ground motion prediction equations gmpes for horizontal peak ground acceleration peak ground velocity and 5 damped pseudo spectral acceleration psa developed for the san jacinto fault zone sjfz area besides using these equations to quantify seismic shaking in the area the results allow us to examine the physics and local properties controlling the observed ground motions the analyzed dataset includes 30 000 observations from 800 events spanning a magnitude range of 1 5 m 6 0 and recorded by up to 140 stations at epicentral distances ranging from essentially zero to 150 km the local gmpe is developed for the sjfz by applying classical regression techniques with predictive variables that include first distance and magnitude and then site characteristics rupture directivity and fault zone amplification the significance of these effects is determined by measuring the uncertainty reduction of the gmpe due to each factor the results show that in contrast to many regional studies traditional site characteristic has a relatively minor effect on peak amplitudes in our study area however rupture directivity is a significant factor controlling the amplitudes of ground motion even for small events the dense seismic network and newly developed directivity tool enable us to extract efficiently directivity effects with statistical significance using the ground motion dataset during the regression analysis process the obtained rupture directivities are consistent with the main focal mechanism orientations and surface trace orientations known from other studies and predictions for bimaterial ruptures in the trifurcation area of the sjfz fault zone amplification is a second important factor showing strong impact on the peak ground motion values with increasing role for the lower frequency range 10 hz examined in the 5 damped psa values we also observe signatures of large amplitude variances which indicate additional source related control on the distribution of amplitudes besides rupture directivity for aftershocks close in time and location to the m l 5 1 earthquake of march 2013 using the full set of records we present the most complete set of gmpes for the sjfz area including a higher amplitude prediction for regions in the direction of rupture

fault zone architecture of the san jacinto fault zone in horse canyon southern california a model for focused post seismic fluid flow and heat transfer in the shallow crust abstract we report results of a new study of the architecture of the san jacinto fault zone in horse canyon california where stream incision has exposed a nearly continuous outcrop of the fault zone at 0 4 km depth the fault zone at this location consists of a fault core transition zone damage zone and tonalitic wall rocks we collected and analyzed samples for their bulk and grain density geochemical data clay mineralogy and textural and modal mineralogy progressive deformation within the fault zone is characterized by mode i cracking subsequent shearing of already fractured rock and cataclastic flow grain comminution advances towards the strongly indurated cataclasite fault core damage progression towards the core is accompanied by a decrease in bulk and grain density and an increase in porosity and dilational volumetric strain palygorskite and mixed layer illite smectite clay minerals are present in the damage and transition zones and are the result of hydrolysis reactions the estimated percentage of illite in illite smectite increases towards the fault core where the illite smectite to illite conversion is complete suggesting elevated temperatures that may have reached 150 c chemical alteration and elemental mass changes are observed throughout the fault zone and are most pronounced in the fault core we conclude that the observed chemical and mineralogical changes can only be produced by the interaction of fractured wall rocks and chemically active fluids that are mobilized through the fault zone by thermo pressurization during and after seismic events based on the high element mobility and absence of illite smectite in the fault core we expect that the greatest water rock ratios occur within the fault core these results indicate that hot pore fluids circulate upwards through the fractured fault core and into the surrounding damage zone though difficult to constrain we speculate that the site studied during this investigation may represent the top of a narrow ephemeral hydrothermal circulation cell that dissipates heat generated from rupture events at deeper levels 4 km

geological observations of damage asymmetry in the structure of the san jacinto san andreas and punchbowl faults in southern california a possible indicator for preferred rupture propagation direction we present new in situ observations of systematic asymmetry in the pattern of damage expressed by fault zone rocks along sections of the san andreas san jacinto and punchbowl faults in southern california the observed structural asymmetry has consistent manifestations at a fault core scale of millimeters to meters a fault zone scale of meters to tens of meters and related geomorphologic features the observed asymmetric signals are in agreement with other geological and geophysical observations of structural asymmetry in a damage zone scale of tens to hundreds of meters in all of those scales more damage is found on the side of the fault with faster seismic velocities at seismogenic depths the observed correlation between the damage asymmetry and local seismic velocity structure is compatible with theoretical predictions associated with preferred propagation direction of earthquake ruptures along faults that separate different crustal blocks the data are consistent with a preferred northwestward propagation direction for ruptures on all three faults if our results are supported by additional observations asymmetry of structural properties determined in field studies can be utilized to infer preferred propagation direction of large earthquake ruptures along a given fault section the property of a preferred rupture direction can explain anomalous behavior of historic rupture events and may have profound implications for many aspects of earthquake physics on large faults

crustal structure and seismicity distribution adjacent to the pacific and north america plate boundary in southern california new three dimensional 3 d v p and v p v s models are determined for southern california using p and s p travel times from local earthquakes and controlled sources these models confirm existing tectonic interpretations and provide new insights into the configuration of geological structures at the pacific north america plate boundary the models extend from the u s mexico border in the south to the southernmost coast ranges and sierra nevada in the north and have a 15 km horizontal grid spacing and an average vertical grid spacing of 4 km down to 22 km depth the heterogeneity of the crustal structure as imaged by v p and v p v s models is larger within the pacific plate than the north american plate similarly the relocated seismicity deepens and shows more complex 3 d distribution in areas of the pacific plate exhibiting compressional tectonics the models reflect mapped changes in the lithology across major geological terranes such as the mojave desert the peninsular ranges and the transverse ranges the interface between the shallow mono of the continental borderland and the deep moho of onshore california forms a broad zone to the north beneath the western transverse ranges ventura basin and the los angeles basin and a narrow zone to the south along the peninsular ranges the near surface increase in velocity from the surface to up to 8 km depth is rapid and has a logarithmic shape for stable blocks and mountain ranges but is slow with a linear shape for sedimentary basins at midcrustal depths a rapid increase in v p is imaged beneath the sediments of the large sedimentary basins while beneath the adjacent mountain ranges the increase is small or absent

regional alteration systems associated with volcanogenic massive sulfide mineralization at panorama pilbara western australia outstanding exposure across the panorama district of the archean pilbara block of western australia reveals a cross section through a ca 3 24 ga massive sulfide bearing volcanic pile and an underlying coeval subvolcanic intrusion in an area of low metamorphic grade and very low strain this has provided a rare opportunity to map a complete regional scale hydrothermal alteration system associated with volcanogenic massive sulfide mineralization and to assess the role of a subvolcanic intrusion in driving such a system four major alteration facies can be defined in the panorama district these are feldspar bearing background alteration and feldspar sericite quartz alteration and completely feldspar destructive sericite quartz and chlorite quartz alteration these alteration facies affect all of the volcanic pile and the upper parts of the underlying subvolcanic intrusion regional semiconformable alteration zones which are predominantly feldspar bearing are crosscut by broad corridors of transgressive feldspar destructive alteration a convective hydrothermal model is invoked to explain this distribution of alteration facies where semiconformable alteration zones represent seawater recharge and transgressive feldspar destructive alteration zones mark the path of evolved seawater discharging back to the sea floor the interpreted discharge sites are coincident with base metal sulfide deposits at the top of the volcanic pile geologic relationships and the distribution of alteration zones clearly implicate the strelley granite as the subvolcanic intrusion which drove the hydrothermal alteration systems granophyric textures and miarolitic cavities in the upper parts of the intrusion suggest that a magmatic fluid phase was exsolved early in its crystallization history granite hosted copper zinc tin veins near the top of the intrusion are interpreted to be a product of this magmatic fluid this raises the possibility of a substantial contribution of magmatically derived metal to the overlying volcanogenic massive sulfide hydrothermal alteration systems

alteration zonation and short wavelength infrared swir characteristics of the honghai vms cu zn deposit eastern tianshan nw china abstract the honghai vms cu zn deposit is located in the dananhu tousuquan arc eastern tianshan northwestern china orebodies of the honghai deposit are buried 300 m underground and hosted by the middle ordovician upper silurian daliugou formation felsic to intermediate volcanic sedimentary rocks at the footwall and hanging wall of the massive sulfide lens intensive and pervasive phyllic alterations were found detailed drill core logging petrographic study and electron microprobe analyses had delineated six alteration mineralization zones namely from top to bottom zone i chlorite albite white mica carbonate ii epidote chlorite albite white mica carbonate iii quartz white mica pyrite iv massive sulfide v chlorite pyrite white mica and vi chlorite quartz white mica our new data supported the sub seafloor replacement influence for the honghai vms deposit as evidenced by the presence of 1 sulfide breccias in the immediate host rocks 2 rapid emplacement of host rocks 3 strong phyllic alteration in the immediate hanging wall 4 replacement textures of the massive sulfides 5 barite as gangue minerals moreover intensive chlorite and epidote alterations and vein mineralization are present in the hanging wall which are comparable with porphyry related propylitic alteration besides different mineralogy and mineral chemistry are present between chlorites from the hanging wall and footwall at honghai which probably suggested porphyry style alteration and mineralization overprinting at honghai short wavelength infrared swir spectral analysis had identified mainly white mica chlorite and epidote and minor montmorillonite calcite gypsum kaolinite and prehnite the wavelengths of the aloh absorption feature for white mica range from 2194 to 2221 nm suggesting compositions from paragonite through muscovite to phengite the wavelengths of feoh absorption feature for chlorite range from 2249 to 2261 nm indicating compositions from mg rich to fe rich chlorite according to swir measurements and electron microprobe analyses empa areas proximal to the massive sulfides are characterized by short wavelength of the aloh absorption feature and high alvi content of white mica petrography and empa showed that chlorite in the ore proximal zones are more mg rich than that in ore distal zones these findings indicated high temperature for the white mica formation and more seawater influx during the chlorite formation in areas near the massive sulfides this study suggested that swir analysis supported by petrographic study and empa can serve as an effective tool in alteration mapping and mineral geochemical variations are potential deposit scale exploration vectoring tools

san andreas fault geometry through the san gorgonio pass california three dimensional numerical models are needed to investigate the role of nonvertical strike slip fault segments on the deformation within restraining bends numerical models simulate geologic deformation of two alternative three dimensional present day configurations for the san andreas fault through the restraining bend within the san gorgonio pass region sgpr in southern california both models produce decreasing strike slip rates southward along the san bernardino strand of the san andreas fault similar to geologic data the north dipping san andreas fault model better matches the available strike slip data as well as the geologic uplift data for the southern san bernardino mountains than the vertical san andreas fault model we conclude that a north dipping fault configuration is preferred for models of the san andreas fault in the sgpr the complexity of the active fault geometry at the sgpr promotes the transfer of strike slip from the san andreas fault to the nearby but unconnected san jacinto fault slip rates and uplift patterns are sensitive to fault geometry within strike slip restraining bends

a 21 event 4 000 year history of surface ruptures in the anza seismic gap san jacinto fault and implications for long term earthquake production on a major plate boundary fault paleoseismic work completed at hog lake on the san jacinto fault sjf near anza california indicates that at least 21 surface ruptures have occurred in the anza seismic gap over the past 4 000 years the ages of the ruptures are constrained by 111 radiocarbon dates 97 of which fall in stratigraphic order the average recurrence interval for all ruptures for this period is about 185 105 years although some ruptures such as occurred in the april 1918 earthquake caused only minor displacement we rate the expression of each interpreted event in each of the twelve developed field exposures presented in this work by assigning numeric values for the presence of different criteria that indicate rupture to a paleo ground surface weakly expressed ruptures for example the deformation we interpret to be the result of the historical 1918 earthquake received low scores and are interpreted as smaller earthquakes from this analysis we infer that at least fifteen of the identified ruptures are indicative of large earthquakes similar to the penultimate earthquake inferred to be the m w 7 3 22 november 1800 earthquake the adjusted recurrence interval for large earthquakes lengthens to approximately 254 years comparison with the rupture history at the mystic lake paleoseismic site on the claremont strand indicates that it is plausible that several of the large ruptures identified at hog lake could have jumped the hemet step over at mystic lake and continued on the claremont strand or vice versa but most of the event ages do not match between the two sites indicating that most ruptures do not jump the step finally comparison with san andreas fault ruptures both to the north and south of its juncture with the sjf suggest that some northern sjf ruptures identified at mystic lake may correlate with events identified at wrightwood but that these northern ruptures have no match at hog lake and can not indicate rupture of the entire sjf onto the saf

diagenesis and reservoir quality in high resolution sandstone sequences an example from the middle jurassic ravenscar sandstones yorkshire coastuk abstract a section of the middle jurassic ravenscar sandstones exposed between cloughton wyke and burniston bay was studied to understand fine scale variation in reservoir quality that can affect flow properties at the reservoir scale the study has identified two 3rd order depositional sequences consisting of twelve 4th order high resolution sandstone sequences deposited mostly in a lower delta plain although these sandstones exhibit a narrow range in porosity values however a sharp disparity exists in their permeability which can have implications at the scale of reservoir development diagenetic studies have revealed that mechanical compaction produced the same effect for most of these sandstones however dissolution and cementation vary hence are mostly responsible for the sharp contrast in their reservoir quality the distributary channel sandstones developed during normal regression of the area in the fs9 sequence are considered the best reservoir sand bodies however these lst sandstones are compartmentalised by authigenic illite quartz and kaolin into two reservoir segments the upper portion lacks illite with resultant higher permeability values above 1100 md ave 2217 md and classified as reservoir group 4 in contrast the lower part contains illite with relatively lower permeability values in the range of 300 1100 md ave 879 md and classified as reservoir group 3 together with the transgressive crevasse channel sandstones in the fs11 sequence the presence of illite cement in these sandstones is linked to the occurrence of k feldspar hence facilitated illitization of kaolin in contrast to group 4 which lacks this mineral the other transgressive sandstones deposited in interdistributary bay crevasse delta back barrier lagoon lagoon and estuarine environments which form reservoir groups 1 and 2 have permeability values in the range of 0 50 md ave 6 md and 50 300 md ave 184 md respectively these sandstones have complex styles of diagenetic cement with variable higher volumes of total authigenic cement consisting of quartz kaolin illite chlorite and calcite than reservoir groups 3 and 4 hence have significantly reduced their reservoir potential therefore for effective reservoir development of these sandstone reservoirs in the north sea and elsewhere in the world with a similar geological setting detailed reservoir characterisation involving linking lithofacies sequence stratigraphy and diagenesis at high resolution are essential for understanding the distribution of reservoir flow properties

pleistocene brawley and ocotillo formations evidence for initial strike slip deformation along the san felipe and san jacinto fault zones southern california abstract we examine the pleistocene tectonic reorganization of the pacific north american plate boundary in the salton trough of southern california with an integrated approach that includes basin analysis magnetostratigraphy and geologic mapping of upper pliocene to pleistocene sedimentary rocks in the san felipe hills these deposits preserve the earliest sedimentary record of movement on the san felipe and san jacinto fault zones that replaced and deactivated the late cenozoic west salton detachment fault sandstone and mudstone of the brawley formation accumulated between 1 1 and 0 6 0 5 ma in a delta on the margin of an arid pleistocene lake which received sediment from alluvial fans of the ocotillo formation to the west southwest our analysis indicates that the ocotillo and brawley formations prograded abruptly to the east northeast across a former mud dominated perennial lake borrego formation at 1 1 ma in response to initiation of the dextral oblique san felipe fault zone the 25 km long

late quaternary rate of slip along the san jacinto fault zone near anza southern california the anza section of the san jacinto fault southern california has not experienced a groundbreaking earthquake since at least 1918 and probably since before 1899 leading previous workers to designate this 20 km long fault segment as a seismic gap study of displaced pleistocene and holocene alluvial fan and fluvial deposits across the san jacinto fault near anza california dated using 14c and soil development age control indicates a minimum right lateral slip rate of 9 2 2 mm yr since 9 5 ka and a slip rate of 11 9 5 mm yr since 14 ka 12 9 5 mm yr since 17 ka and 13 10 6 mm yr since 50 ka these estimates agree with a previously determined 700 ka to present minimum slip rate of 10 2 mm yr based on an estimated average slip rate of 12 mm yr from the longer term slip rate estimates about 0 8 m of potential slip has accumulated if the 1918 earthquake broke the anza segment over 1 1 m of potential slip has accumulated if the last earthquake occurred prior to 1899 these data attest to the potential for an earthquake m6 5 for this section of the fault

dynamic rupture on a material interface with spontaneous generation of plastic strain in the bulk abstract we discuss 2d simulations of in plane ruptures on a fault between different solids in a model that includes dynamic generation of plastic strain off the fault the fault is governed by a regularized friction with a gradual response to abrupt changes of normal stress while plastic strain in the bulk is governed by a coulomb yielding criterion the occurrence of off fault damage stabilizes the slip velocity on the fault stable self sustaining ruptures propagate on the material interface as narrow unidirectional pulses in the direction of slip on the more compliant side of the fault plastic strain is generated only on the stiffer side of the fault the tensional quadrant in the direction of rupture propagation in a strip of approximately constant width that is correlated with the slip velocity on the fault simulations for various values of confining normal stress material contrast and cohesion in the bulk suggest that significant generation of off fault damage is limited to conditions that correspond to the top few kilometers of the crust the results are compatible with field observations of shallow asymmetric damage patterns in the structure of several large faults

geodetic slip rates in the southern san andreas fault system effects of elastic heterogeneity and fault geometry 1 we use high resolution interferometric synthetic aperture radar and gps measurements of crustal motion across the southern san andreas fault system to investigate the effects of elastic heterogeneity and fault geometry on inferred slip rates and locking depths geodetically measured strain rates are asymmetric with respect to the mapped traces of both the southern san andreas and san jacinto faults two possibilities have been proposed to explain this observation large contrasts in crustal rigidity across the faults or an alternate fault geometry such as a dipping san andreas fault or a blind segment of the san jacinto fault we evaluate these possibilities using a two dimensional elastic model accounting for heterogeneous structure computed from the southern california earthquake center crustal velocity model cvm h 6 3 the results demonstrate that moderate variations in elastic properties of the crust do not produce a significant strain rate asymmetry and have only a minor effect on the inferred slip rates however we find that small changes in the location of faults at depth can strongly impact the results our preferred model includes a san andreas fault dipping northeast at 60 and two active branches of the san jacinto fault zone in this case we infer nearly equal slip rates of 18 1 and 19 2mm yr for the san andreas and san jacinto fault zones respectively these values are in good agreement with geologic measurements representing average slip rates over the last 10 10 years implying steady long term motion on these faults

seismic tomography of the southern california crust based on spectral element and adjoint methods we iteratively improve a 3 d tomographic model of the southern california crust using numerical simulations of seismic wave propagation based on a spectral element method sem in combination with an adjoint method the initial 3 d model is provided by the southern california earthquake center the data set comprises three component seismic waveforms i e both body and surface waves filtered over the period range 2 30 s from 143 local earthquakes recorded by a network of 203 stations time windows for measurements are automatically selected by the flexwin algorithm the misfit function in the tomographic inversion is based on frequency dependent multitaper traveltime differences the gradient of the misfit function and related finite frequency sensitivity kernels for each earthquake are computed using an adjoint technique the kernels are combined using a source subspace projection method to compute a model update at each iteration of a gradient based minimization algorithm the inversion involved 16 iterations which required 6800 wavefield simulations the new crustal model m 16 is described in terms of independent shear v s and bulk sound v b wave speed variations it exhibits strong heterogeneity including local changes of 30 per cent with respect to the initial 3 d model the model reveals several features that relate to geological observations such as sedimentary basins exhumed batholiths and contrasting lithologies across faults the quality of the new model is validated by quantifying waveform misfits of full length seismograms from 91 earthquakes that were not used in the tomographic inversion the new model provides more accurate synthetic seismograms that will benefit seismic hazard assessment

the san andreas fault revisited through seismic noise and surface wave tomography 1 we present here surface wave tomography results for the san andreas fault in the parkfield area california usa that were extracted from microseismic noise in the 0 15 hz to 0 35 hz frequency band using passive seismic correlation techniques using directive noise incoming from the pacific ocean passive seismic noise tomography was performed using three component sensors from a dense seismic network a rotation algorithm was applied to the nine component noise correlation tensor that optimally forced each station pair to re align in the noise direction a necessary condition to extract unbiased travel times from passive seismic processing after the rotation was performed an optimal surface wave tensor is obtained from which love waves were extracted for tomography inversion dispersion curves were then inverted to obtain a three dimensional shear velocity map showing vertical geological structures and a 1 3 km wide low seismic velocity dip which are in agreement with previous tomography studies in the same area

quantitative measurements of shear wave polarizations at the anza seismic network southern california implications for shear wave splitting and earthquake prediction we analyze shear wave polarizations from local earthquakes recorded by the anza network in southern california using an automated method which provides unbiased and quantitative measurements of the polarization and the duration of linear motion following the shear wave arrival the linearity interval initial shear wave particle motions are strongly aligned at four stations a feature that is not predicted by focal mechanisms the particle motion alignment is most likely caused by shear wave splitting due to anisotropy beneath these stations a result supported by the clear shear wave splitting seen in a borehole recording near one of the anza stations these results are consistent with an earlier analysis of these data by peacock et al 1988 however our analysis does not support claims by crampin et al 1990 that shear wave splitting delay times at station knw exhibit temporal variations which can be correlated with the occurrence of the north palm springs earthquake ml 5 6 of july 8 1986 automatically determined linearity intervals scatter widely from 0 02 to 0 15 s and exhibit no clear temporal trends we find a correlation between earthquake moment and the linearity interval possibly a result of longer effective source time functions for the larger events the inability to identify a distinct slow quasi shear wave pulse for the vast majority of these events indicates that scattering strongly affects the particle motion even in the very early shear wave coda analysis of earthquake clusters with similar waveforms recorded at knw shows that seismic green functions are stable throughout the observational period and that most linearity interval variation is due to source and ray path differences between events if shear wave splitting is causing the observed delay times between horizontal components the waveform stability for events in these clusters restricts any temporal changes in shear wave splitting delay times to less than 5 10

oxygen isotope alteration in the noranda mining district abitibi greenstone belt quebec a regional whole rock oxygen isotope survey carried out in the noranda district shows how oxygen isotope alteration can be used to guide exploration for massive sulfide deposits the survey is based on 588 outcrop whole rock oxygen isotope determinations from 478 sites in a approximately 35 by 50 km area between the destor porcupine and cadillac larder lake breaks from east of the horne mine to west of the magusi river mine the mean isotopic composition of all samples is 7 4 or 2 per mil smow nested analysis of variance of 478 isotopic determinations from 371 of these sites shows that 74 percent of the total variance in whole rock delta 18 o r r whole rock is associated with outcrop location 21 percent with outcrop sampling and 5 percent with sample analysis an analysis of 259 determinations indicates that rock type is statistically no more important than outcrop sampling the statistical analysis indicates that isotopic variations greater than or 1 per mil can be used to map the hydrothermal circulation responsible for massive sulfide mineralization specific traverses visually confirm the lack of 18 o dependence on rock type and the utility of a 2 per mil interpretive band the large scale pattern of isotopic alteration in the noranda district is dominated by a nearly continuous 2 to 3 km wide annulus at the margins of the flavrian pluton of delta 18 o r 18 o r 18 o r depletion is surrounded up section by a approximately 10 km wide band of patchy but intense 18 o enrichment 8 5 14ppm the combined pattern of concentric light and heavy alteration has a diameter of approximately 30 km the clericy intrusion shows a similar pattern of isotope alteration on a smaller 10 km diam scale the lake dufault pluton seems to have been isotopically altered by continuing convection driven by the flavrian hydrothermal system modeling suggests that the 18 o depletion is produced by water circulating toward and along the edges of an intrusion and that the surrounding heavy alteration is produced either by seawater recharge or limited hydrothermal discharge the large scale and coherency of the alteration pattern centered on the flavrian pluton is remarkable and indicates that this pluton drove a major long lived approximately 10 m y hydrothermal system in which convection penetrated to an 8 kin depth the intensity and coherency of the 18 o depletion correlates with the tonnage of associated massive sulfide mineralization oxygen isotope depletion may in general mark the margins of plutons that have driven sufficient hydrothermal circulation to produce economic massive sulfide deposits up section it may be possible to screen plutons for up section massive sulfide exploration potential by collecting and isotopically analyzing approximately 50 samples from five traverses across a pluton9s margins additional samples may provide details light fingers that guide exploration to particular deposits

characterization of fault zones there are currently three major competing views on the essential geometrical mechanical and mathematical nature of faults the standard view is that faults are possibly segmented and heterogeneous euclidean zones in a continuum solid the continuum euclidean view is supported by seismic gravity and electromagnetic imaging studies by successful modeling of observed seismic radiation geodetic data and changes in seismicity patterns by detailed field studies of earthquake rupture zones and exhumed faults and by recent high resolution hypocenter distributions along several faults the second view focuses on granular aspects of fault structures and deformation fields the granular view is supported by observations of rock particles in fault zone gouge by studies of block rotations and the mosaic structure of the lithosphere which includes the overall geometry of plate tectonics by concentration of deformation signals along block boundaries by correlation of seismicity patterns on scales several times larger than those compatible with a continuum framework and by strongly heterogeneous wave propagation effects on the earth s surface the third view is that faults are fractal objects with rough surfaces and branching geometry the fractal view is supported by some statistical analysis of regional hypocenter locations by long range correlation of various measurements in geophysical boreholes by the fact that observed power law statistics of earthquakes are compatible with an underlying scale invariant geometrical structure by geometrical analysis of fault traces at the earth s surface and by measurements of joint and fault surfaces topography

a special issue on alteration associated with volcanic hosted massive sulfide deposits and its exploration significance this special issue on alteration associated with the spectrum of volcanic hosted massive sulfide deposits and its exploration significance largely reports the results of a three year 1995 1998 collaborative research project p439 between the centre for ore deposit research at the university of tasmania and the australian mineral industry research association amira volcanic hosted massive sulfide deposits vhms provide a significant contribution to world zinc copper lead silver and gold production some australian deposits have been very profitably mined because of their particularly high polymetallic grades high precious metal values and large size for example rosebery que river and hellyer were mainstays of the tasmanian mining industry for several decades although vhms targets have recently gone out of favor fallen off the radar screens for many large base metal exploration companies they continue to be favorable targets for small to medium size mining companies due to the geological complexity of ancient submarine volcanic terranes new vhms deposits are extremely difficult to discover especially those deposits buried more than a few tens of meters below the surface the research team at the centre for ore deposit research and mineral explorers through amira recognized that an improved understanding of alteration zonation was needed to enhance vhms discovery rates in mature exploration districts extensive previous research in submarine volcanic terranes in australia north america japan and europe has documented the mineralogy and geochemistry of various styles of hydrothermal alteration which are related spatially and genetically to vhms deposits figure 1 illustrates the spatial relationships of seven major alteration styles in vhms districts as they were recognized at the beginning of this project these are summarized below 1 footwall alteration pipes exist below most major mound style vhms deposits and result from focused upward flow of hydrothermal fluids to the sea floor previous studies e g shirozu 1974 riverin and hodgson

depositional setting and structural evolution of the archean perseverance volcanogenic massive sulfide deposit matagami mining district quebec canada the perseverance volcanogenic massive sulfide deposit 5 1 mt at 15 8 zn 1 24 cu 29 4 g t ag 0 4 g t au matagami district abitibi greenstone belt consists of four pipelike orebodies discordant to local bedding in a shallow dipping portion of the south flank volcanic succession most of the ore is hosted by rhyolitic lavas of the watson unit 2725 9 0 8 ma and is overlain by a thinly laminated tuffaceous unit known as the key tuffite as well as by rhyodacitic lavas of the dumagami unit 2725 4 0 7 ma the presence of sulfide zones predominantly hosted in the footwall rhyolite relicts of key tuffite within the ore and intricate sulfide replacement of the laminated tuff are all features consistent with the formation of most of the deposit via subseafloor replacement the permeability of steep synvolcanic structures likely controlled the migration of metal bearing fluids and simultaneously allowed the downward infiltration of seawater causing mixing cooling and sulfide deposition in the subseafloor environment stratigraphic relationships suggest that massive sulfide formation was active at perseverance while tuffaceous sedimentation was ongoing on the seafloor progressive growth of the massive sulfides along subvertical structures was accompanied by the development of pipelike sericite chlorite talc alteration halos both the hanging wall and the footwall units are characterized by significant mgo mass gains k 2 o na 2 o mass losses and high alteration index values e g chlorite carbonate pyrite index alteration index however these geochemical changes are less intense and widespread in the hanging wall than in the footwall the record of a decreasing alteration above the orebodies was likely caused by the emplacement of the rhyodacite while massive sulfide deposition and hydrothermal activity were still ongoing primary relationships between mineralization and the host lithofacies were overprinted by intense deformation during the main event of compression induced by regional north south shortening deformation is controlled by contrasting rheologies within the sulfide assemblage and between the orebodies and their host rocks structural modifications include the transposition of sulfide ores subparallel to the main foliation the formation of piercement veins at the interface with the host rocks and the generation of a series of secondary textures within the orebodies including a vertical mineralogical banding the distribution of cu in the deposit is interpreted to be affected by the mechanical remobilization of chalcopyrite during deformation whereas the zonation of zn is likely primary hydrothermal alteration halos adjacent to the orebodies have accommodated significant strain as indicated by the presence of tight folds in the key tuffite unit and a marked schistosity strain localization in the vicinity of the deposit highlights the relative ductility of the ore assemblage with respect to the host volcanic succession and resulted in a spatial association between hydrothermal alteration and deformation despite the lack of a genetic relationship

complexities of the san andreas fault near san gorgonio pass implications for large earthquakes 1 geologic relationships and patterns of crustal seismicity constrain the three dimensional geometry of the active portions of san andreas fault zone near san gorgonio pass southern california within a 20 km wide contractional stepover between two segments of the fault zone the san bernardino and coachella valley segments folds and dextral reverse and dextral normal faults form an east west belt of active structures the dominant active structure within the stepover is the san gorgonio pass garnet hill faults a dextral reverse fault system that dips moderately northward within the hanging wall block of the san gorgonio pass garnet hill fault system are subsidiary active dextral and dextral normal faults these faults relate in complex but understandable ways to the strike slip faults that bound the stepover the pattern of crustal seismicity beneath these structures includes a 5 8 km high east west striking step in the base of crustal seismicity which corresponds to the downdip limit of rupture of the 1986 north palm springs earthquake we infer that this step has been produced by slip on the linked san gorgonio pass garnet hill coachella valley banning sgp gh cvb fault this association enables us to construct a structure contour map of the fault plane the large step in the base of seismicity downdip from the sgp gh cvb fault system probably reflects a several kilometers offset of the midcrustal brittle plastic transition u th he thermochronometry supports our interpretation that this south under north thickening of the crust has created the region s 3 km of topographic relief we conclude that future large earthquakes generated along the san andreas fault in this region will have a multiplicity of mostly specifiable sources having dimensions of 1 20 km two tasks in seismic hazard evaluation may now be attempted with greater confidence first the construction of synthetic seismograms that make useful predictions of ground shaking and second theoretical investigations of the role of this complexity in retarding the propagation of future seismic ruptures

district scale alteration associated with massive sulfide deposits in the mount read volcanics western tasmania the distribution of secondary mineral assemblages in six mineralized areas of the mount read volcanics defines a district wide zonation which is subconformable with massive sulfide host horizons and the contacts of sill like granitoids where present the relationships between alteration patterns and elements of cambrian geology strongly suggest that the alteration is related to cambrian hydrothermal circulation responsible for massive sulfide mineralization there is a later greenschist facies metamorphic overprint the major components of the principal assemblages are quartz albite chlorite epidote quartz albite chlorite calcite quartz sericite chlorite and quartz k feldspar chlorite several complex assemblages involving the above minerals biotite magnetite pyrite and tourmaline are characteristic of granite contacts secondary biotite is also present sporadically in the rosebery area probably related to devonian granitoids at depth there is a districtwide zonation of sodic or calcic versus nonsodic noncalcic assemblages in felsic volcanic rocks in preore volcanics nonsodic noncalcic assemblages occur immediately beneath the host horizon and may persist several hundred meters before passing into a zone including granite contacts where calcium minerals and albite occur sporadically the nonsodic noncalcic assemblages are predominantly sericitic but assemblages with prominent k feldspar occur locally in postore volcanics sericitic non sodic noncalcic assemblages may persist up to 200 m above the ore horizon before passing into relatively fresh volcanics with common albite and calcic greenschist minerals preore assemblages probably largely reflect downward circulation upwelling zones are characterized by intense sericite chlorite or chlorite development with or without k feldspar lateral spreading of solutions immediately beneath the ore horizon is common chlorite compositions preserve local patterns due to cambrian hydrothermal processes but they do not vary systematically with alteration assemblages throughout the province chlorite mg to fe ratios appear to have been preserved through metamorphism a combination of structural and alteration data is useful to mapping in the mount read volcanics this approach indicates that most syngenetic deposits and sedimentary lenses in the rosebery hercules area may lie on a single host horizon and suggests a continuity of geology from mount farrell through red hills to mount sedgwick

australian volcanic hosted massive sulfide deposits features styles and genetic models the cambro ordovician period has yielded the major development of volcanic hosted massive sulfide vhms deposits in australia resulting in about 12 million metric tons of contained metal copper lead and zinc concentrated in the mount read volcanics tasmania and the mount windsor volcanics queensland the archean 4 million metric tons of metal and the silurian 3 5 million metric tons of metal constitute the next important episodes while the devonian and permian have produced isolated deposits the deposits range from cu type to zn cu type to zn pb cu type the zn cu type deposits are restricted to the archean and silurian whereas the cu type and zn pb cu type occur sporadically throughout the time span from early archean to permian in general terms the major vhms bearing districts are calc alkaline in character and display a thick basal pile of rhyolitic volcanics 1 3 km thick including lavas epiclastics and subvolcanic intrusions which is overlain by a polymodal sequence containing various proportions of rhyolite dacite andesite basalt and sediments the major deposits are commonly located at the top contact of the rhyolite pile or within the lower part of the overlying polymodal sequence there is a wide range in variability of styles of australian vhms deposits including mounds pipes sheets layered deposits stacked deposits stockwork and disseminated deposits distal reworked deposits and cyclic layered deposits although these various styles show a range of features there is a consistent theme across the spectrum of metal zonation alteration mineralogy alteration chemistry sulfur isotopes macrotextures microtextures and host volcanic relationships which strongly suggests that they all belong to the one genetic group of ore deposit the classic mound style deposits such as hellyer have a series of key features subsets of which are represented in the other deposit styles the mound deposits are considered to form from deposition of metal sulfides on the sea floor immediately around the hydrothermal vent growth of the mound occurs by upward replacement of sulfide assemblages stable at higher fluid temperatures leading to zone refining and lead zinc silver gold enrichment in the outer and upper parts of the mound departure from the classic mound style of deposit is related principally to three key factors the chemistry of the ore fluid salinity temperature f02 and ah2s the nature permeability and chemistry of the volcanic pile and the sea hoor environment sea hoor topography and seawater depth these factors control the aspect ratio of the deposit the extent of stringer zone development the degree of subsea floor replacement mineralization the nature and spatial development of footwall alteration and the development and style of related distal mineralization sulfur isotope studies of australian vhms deposits indicate that reduced seawater sulfate is a major source of sulfur in the deposit whereas lead and strontium isotope results are compatible with the metals being derived by seawater convection and leaching from the volcanic pile and basement rocks this conclusion is supported by the application of various leaching models which demonstrate the availability of an adequate source of both base and precious metals in the footwall volcanic sequences the input of metals directly from volcanic magma chambers is not precluded by the available data and one likely scenario involves the contribution of gold and copper from a magmatic vapor plume rising to mix with convective seawater fluids which contribute lead zinc silver and gold leached from the footwall volcanics and basement rocks the relative importance of the magmatic input compared with the seawater convective input may help to explain the spectrum of deposit styles arid their spatial relationship to volcanic centers or adjacent sedimentary basins

application of high resolution dem data to detect rock damage from geomorphic signals along the central san jacinto fault abstract we analyze geomorphic properties extracted from lidar and srtm shuttle radar topography mission data to test whether the damage zone along the central san jacinto fault sjf zone can be resolved with remotely sensed data in a quantitative fashion the sjf is one of the most active faults in southern california with well expressed geomorphology and a fast slip rate as seen in the geology and by gps we use arcmap and the taudem toolbox to compare several morphometric parameters including drainage density dd on both sides of the fault using a 1 km and a 5 km buffer for the lidar and srtm data respectively we also analyze the spatial patterns of dd near the fault using two different definitions of spatial dd the high resolution of the lidar data allows us to focus on a single fault eliminating the effects of parallel nearby faults from the lidar data we find that the highest dd values occur in areas between two fault strands followed generally by rocks on the northeast side of the fault with the lowest dd values occurring on the southwest side of the fault the srtm data shows a band of high dd values centered on the main fault trace with 1 km width our results indicate that there is a strong correlation between drainage density and proximity to the fault with zones of structural complexity along the fault displaying the highest dd we interpret this to largely be an effect of degree of rock damage as these are areas that are expected to be more damaged and field observations support this contention if we are correct then it appears that the northeast side of the sjf is generally more damaged south of the trifurcation area there is evidence that the signal is reversed on the larger scale with more damage on the southwest side of the fault inferred from the srtm data possibly caused by extension between the coyote creek and clark faults the implications of the observed asymmetry could be geological evidence for rupture propagation direction because a preferred propagation direction is predicted to produce asymmetric damage structure that would be recorded in the volume of rock surrounding a fault

a three dimensional crustal seismic velocity model for southern california from a composite event method we present a new crustal seismic velocity model for southern california derived from p and s arrival times from local earthquakes and explosions to reduce the volume of data and ensure a more uniform source distribution we compute composite event picks for 2597 distributed master events that include pick information for other events within spheres of 2 km radius the approach reduces random picking error and maximizes the number of s wave picks to constrain absolute event locations and shallow velocity structure we also use times from controlled sources including both refraction shots and quarries we implement the simulps tomography algorithm to obtain three dimensional 3 d v p and v p v s structure and hypocenter locations of the composite events our new velocity model in general agrees with previous studies resolving low velocity features at shallow depths in the basins and some high velocity features in the midcrust using our velocity model and 3 d ray tracing we relocate about 450 000 earthquakes from 1981 to 2005 we observe a weak correlation between seismic velocities and earthquake occurrence with shallow earthquakes mostly occurring in high p velocity regions and midcrustal earthquakes occurring in low p velocity regions in addition most seismicity occurs in regions with relatively low v p v s ratios although aftershock sequences following large earthquakes are often an exception to this pattern

stress induced upper crustal anisotropy in southern california 1 we use an automated method to analyze shear wave splitting from local earthquakes recorded by the southern california seismic network between 2000 and 2005 the observed fast directions of upper crustal anisotropy generally are consistent with the direction of maximum horizontal compression hmax suggesting that one major mechanism of anisotropy in the top 20 km of crust under southern california is regional stress however at other stations fast directions are aligned with the trends of regional faulting and local alignment of anisotropic bedrock splitting delay times range widely within 0 2 s these upper crustal anisotropy observations together with previous studies of sks shear wave splitting surface waves and receiver functions suggest different mechanisms of anisotropy at different depths under southern california anisotropy in the upper crust appears to be in response to the current horizontal maximum compression hmax which differs from the cause of anisotropy in the lower crust and mantle we also explore possible temporal variations in upper crustal anisotropy associated with preearthquake stress changes or stress changes excited by surface waves of great earthquakes but do not observe any clear temporal variations in fast directions or time delays

seismic tomography of the southern california plate boundary region from noise based rayleigh and love waves we use cross correlations of ambient seismic noise between pairs of 158 broadband and short period sensors to investigate velocity structure over the top 5 10 km of the crust in the southern california plate boundary region around the san jacinto fault zone sjfz from the 9 component correlation tensors associated with all station pairs we derive dispersion curves of rayleigh and love wave group velocities the dispersion results are inverted first for rayleigh and love waves group velocity maps on a 1 5 1 5 km2 grid that includes portions of the sjfz the san andreas fault saf and the elsinore fault we then invert these maps to 3d shear wave velocities in the top 7 km of the crust the distributions of the rayleigh and love group velocities exhibit 2 azimuthal anisotropy with fast directions parallel to the main faults and rotations in complex areas the reconstructed 3d shear velocity model reveals complex shallow structures correlated with the main geological units and strong velocity contrasts across various fault sections along with low velocity damage zones and basins the sjfz is marked by a clear velocity contrast with higher v s values on the ne block for the section se of the san jacinto basin and a reversed contrast across the section between the san jacinto basin and the saf velocity contrasts are also observed along the southern parts on the saf and the elsinore fault with a faster southwest block in both cases the region around the salton trough is associated with a significant low velocity zone strong velocity reductions following flower shape with depth are observed extensively around both the sjfz and the saf and are especially prominent in areas of geometrical complexity in particular the area between the sjfz and the saf is associated with an extensive low velocity zone correlated with diffuse seismicity at depth and a similar pattern including correlation with deep diffuse seismicity is observed on a smaller scale in the trifurcation area of the sjfz these results augment local earthquake tomography images that have low resolution in the top few km of the crust and provide important constraints for studies concerned with behavior of earthquake ruptures generation of rock damage and seismic shaking hazard in the region

surface wave tomography from microseisms in southern california received 5 april 2005 revised 23 may 2005 accepted 9 june 2005 published 26 july 2005 1 since it has already been demonstrated that point topoint seismic propagation green functions can be extracted from seismic noise it should be possible to image earth structure using the ambient noise field seismic noise data from 148 broadband seismic stations in southern california were used to extract the surface wave arrival times between all station pairs in the network the seismic data were then used in a simple but densely sampled tomographic procedure to estimate the surface wave velocity structure within the frequency range of 0 1 0 2 hz for a region in southern california the result compares favorably with previous estimates obtained using more conventional and elaborate inversion procedures this demonstrates that coherent noise field between station pairs can be used for seismic imaging purposes citation sabra k g p gerstoft p roux w a kuperman and m c fehler 2005 surface wave tomography from microseisms in southern california geophys res lett 32 l14311 doi 10 1029 2005gl023155

the scuddles cu zn prospect an archean volcanogenic massive sulfide deposit golden grove district western australia the scuddles volcanogenic massive sulfide prospect together with the nearby gossan hill golden grove prospect constitute the largest known potentially economic cu zn sulfide deposits in the archean yilgarn block of western australia enclosed in a submarine sequence of felsic to intermediate volcanics epiclastics and exhalative chemical sediments the scuddles deposit lies in a regionally extensive mineralized horizon this horizon is up to 80 m thick and is dominated by sulfidic and cherty exhalites and epiclastics a sequence of felsic to intermediate lavas pyroclastics and epiclastics lies above the mineralized horizon with felsic pyroclastics and epiclastics beneath pyroclastic rocks may have been resedimented by mass flow processes the entire sequence has sustained the effects of hydrothermal alteration and regional metamorphism and dips steeply to the west lying on the east limb of a major synclinal structure due to alteration major element values of the rocks are not an accurate guide to their primary composition however abundances of ti zr y nb and v are commonly unaffected and confirm an andesitic to rhyolitic spectrum zoning of ore metals in the scuddles mineralized horizon is typical of that in many precambrian felsic volcanic associated exhalative sulfide deposits the top is defined by a laminated magnetite bearing iron formation enriched in fe mn and base metals which conformably overlies several lenses of massive fe zn sulfides in places containing significant pb ag au and cu grading downward into pyritic sulfides in turn the massive sulfides overlie a zone of epigenetic stockwork stringer and disseminated cu fe sulfides in the middle and lower portions of the mineralized horizon massive to disseminated exhalative sulfides are in places accompanied by quartz chlorite talc and other silicates carbonates and magnetite also interpreted to be at least partly exhalative in origin the lower cu fe sulfide zone is considered to have formed immediately below the sea floor perhaps occupying an extensive feeder system for hot springs the upper zn fe sulfide zone may have formed by precipitation out of hydrothermal plumes as they vented into and mixed with seawater ore mineral deposition was attended by the development of a volumetrically large 10 km long several hundred meters thick strata bound zone of hydrothermal alteration well represented in the footwall and mineralized horizon upper hanging wall rocks are little altered but elsewhere the sequence displays moderate to intense feldspar destructive development of quartz chlorite sericite and locally abundant carbonate talc and sulfides these mineralogical changes are accompanied by pervasive depletion of na ca and sr and locally k the mineralized horizon and much of the footwall is enriched in fe mg mn base and precious metals as s co 2 and h 2 o interpreted to be the result of addition from exhalative sources the strata bound alteration zone represents a volume of hydrothermal flux in which major sites of sulfide deposition at scuddles and gossan hill were focused zones of fe mg base metal enrichment below and adjacent to positions of submarine metal bearing exhalations precipitation of exhalites occurred under relatively quiescent conditions in the mineralized horizon however the stratigraphic sequence indicates that at other times active mass flow deposition was taking place

layered azimuthal anisotropy of rayleigh wave phase velocities in the european alpine lithosphere inferred from ambient noise abstract passive seismic imaging of the earth is a rapidly developing field of study recent advances in noise cross correlation techniques allow imaging of isotropic surface wave and shear wave velocities in areas where earthquake numbers and distributions are insufficient to implement traditional earthquake based tomography furthermore advances in the theory underpinning surface wave inversion have led to depth dependent mapping of seismic anisotropy in the lithosphere and upper asthenosphere we show that by merging these two rapidly advancing fields we can invert noise based phase velocity measurements for azimuthally anisotropic phase speed thereby providing a highly resolved image of layered azimuthal anisotropy in continental crust we apply this new algorithm in the western alps an area of complex lithospheric structure alpine crustal thickening results from continental collision indentation of the ivrea mantle into the middle crust of the european plate rollback of the european lithospheric mantle and crustal slicing we find that anisotropy beneath the central alps is stratified in two layers one with an orogen parallel fast direction above 30 km depth and another with a strong orogen perpendicular fast direction at greater depth although our resolution is reduced outside the central alps we map orogen parallel anisotropy in the crust of the northern alpine foreland we interpret the results in the central alps as first order evidence for a model of azimuthal anisotropy in which 1 near vertical emplacement of crustal slices following detachment of the lithospheric mantle from the crust gives rise to orogen parallel fast directions of wave propagation in the crust and 2 dominantly horizontal tectonics in the thickened crustal root and uppermost mantle yield orogen perpendicular fast directions at greater depth

the murchison gorge tasmania a possible cross section through a cambrian massive sulfide system the murchison gorge northeast of rosebery in tasmania is believed to expose a section through the main elements of an inferred volcanogenic massive sulfide forming system the top of the steeply dipping section is dominated by shallow marine siltstones of the farrell slates which host several sulfide bodies the farrell slates conformably overlie an altered succession of rhyodacitic and dacitic tuffs and lavas the murchison volcanics a sill like monzonitic quartz monzonitic body the murchison granite is emplaced in the murchison volcanics about 2 to 3 km stratigraphically below the farrell slates the sulfide deposits in the farrell slates are of devonian age but sulfur isotope studies and comparisons with the cambrian massive sulfide horizons at red hills and rosebery suggest that the slates are a local cambrian mineralized horizon the murchison granite and the murchison volcanics appear to be comagmatic and coeval and are similar to calc alkaline intrusions and volcanics of orogenic continental margins both the volcanics and the granite are extensively altered the granite has been subject to potassic alteration chloritization and late calcite epidote alteration minor greisenization was also noted there is a vertical zonation of alteration mineralogy in the volcanics between the farrell slates and the top of the granite as follows top sericite zone a sericite quartz b sericite quartz calcite k feldspar chlorite hematite chalcopyrite pyrite c sericite quartz chlorite calcite hematite k feldspar albite chlorite zone chlorite sericite albite calcite hematite magnetite epidote zone epidote chlorite calcite magnetite allanite potassic zone chlorite epidote calcite k feldspar pyrite magnetite the increasing predominance of hematite over magnetite toward the top of the section is consistent with an increase in fluid f sub o 2 away from the granite chlorites from the four zones lie in fairly clear fields on an mgo vs feo plot trends of decreasing mgo and increasing feo up the section are consistent with decreasing temperature sulfide delta 34 s values increase from about 9 per mil within the granite through 10 to 14 per mil in the overlying volcanics to 17 per mil in the farrell slates the high values suggest cambrian seawater sulfate 30 35ppm as the dominant sulfur source in the system the up section variation is ascribed to varying degrees of mixing between cambrian seawater derived sulfur and lighter magmatic sulfur

a new perspective on the geometry of the san andreas fault in southern california and its relationship to lithospheric structure the widely held perception that the san andreas fault saf is vertical or steeply dipping in most places in southern california may not be correct from studies of potential field data active source imaging and seismicity the dip of the saf is significantly nonvertical in many locations the direction of dip appears to change in a systematic way through the transverse ranges moderately southwest 55 75 in the western bend of the saf in the transverse ranges big bend vertical to steep in the mojave desert and moderately northeast 37 65 in a region extending from san bernardino to the salton sea spanning the eastern bend of the saf in the transverse ranges the shape of the modeled saf is crudely that of a propeller if confirmed by further studies the geometry of the modeled saf would have important implications for tectonics and strong ground motions from saf earthquakes the saf can be traced or projected through the crust to the north side of a well documented high velocity body hvb in the upper mantle beneath the transverse ranges the north side of this hvb may be an extension of the plate boundary into the mantle and the hvb would appear to be part of the pacific plate

fault slip rates effects of elastic heterogeneity on geodetic data and the strength of the lower crust in the salton trough region southern california 1 in southernmost california the salton trough sedimentary basin lies between the subparallel san jacinto and san andreas faults that together with the elsinore fault accommodate 80 of the 50 mm yr of pacific north american relative motion the slip rates on the san andreas and san jacinto faults have been a matter of recent debate and one source of uncertainty has been the influence of crustal strength heterogeneity due to elastically weak basin sediments on geodetic data to evaluate these effects we have modeled regional kinematics with elastic and viscoelastic finite element models that incorporate laterally and vertically varying crustal material properties we find that in general the effects of the sedimentary basin on surface deformation are relatively small and that to explain the geodetic velocity data the slip rate on the san andreas must be higher than that on the san jacinto fault consistent with traditional geologic estimates we also conclude that a relatively strong lower crust of viscosity 5 x 10 19 pa s exists in this region

stratigraphy structure and volcanic hosted mineralization of the mount windsor subprovince north queensland australia the mount windsor subprovince contains a major belt of mineralized cambro ordovician subaqueous volcanogenic rocks at the northern end of the tasman orogenic belt the base of the stratigraphic sequence is a thick continent derived siliciclastic package intruded by alkali andesites typical of intraplate settings this is overlain by massive subaqueous rhyolitic units and then by a mixed association of basaltic andesitic dacitic and rhyolitic volcanics and volcaniclastics containing numerous small elongate pods of quartz hematite or magnetite exhalite the cessation in active volcanism is marked by a change to a sandstone siltstone unit dominated by volcanic sources the majority of volcanics form a coherent group of low to medium k calc alkaline lavas similar to those in modern island arc settings extensional growth faults produced local variation in the stratigraphic thickness the largest growth fault in the area is close to the reward highway and handcuff deposits the sequence has been multiply folded and faulted in the paleozoic but the large scale structure remains relatively simple volcanic hosted massive sulfide vhms deposits occur at the top of the massive rhyolite and in the mixed volcanic package above it with the exception of the reward pyrite pipe the mineralization occurs as blanketlike deposits with low thickness lateral extent ratios the thalanga reward and waterloo deposits are copper rich whereas agincourt magpie liontown handcuff and warrawee are zinc rich and copper poor with a significant barite component