magnitude scaling of early warning parameters for the mw 7 8 tocopilla chile earthquake and its aftershocks we studied the correlation between the final event magnitude and four parameters obtained from the early portion of p and s phases for a set of high quality subduction events these relationships are used in the framework of earthquake early warning systems for real time magnitude estimation the investigated parameters are thelow pass filteredpeakdisplacement pd theintegralofthevelocitysquared iv2 and the predominant and characteristic periods p and c we created a dataset from the continuous records of the first twoweeks following the 14 november 2007 mw 7 8 tocopilla chile earthquake the dataset includes 69 events with magnitudes greater than 4 among them the main event mw 7 8 the main aftershocks of mw 6 7 occurred on november 15 and 4 events with magnitudegreater than 6 the low pass filtered pd readonshortp phaseands phasewindowsiswellcorrelated withthefinalmagnitude confirming previous results indeed when examining 2 s timewindows of pwaves we didnotobserveanysaturationeffectformagnitudesgreaterthan6 5 however thereisa slope change in the regression curve a similar result is obtained from the integral of squared velocity computed over short windows around p and s waves the character istic and predominant periods are correlated with magnitudes up to mw 6 but they clearly do not scale with the magnitude for the stronger events our observations offer insight into the feasibility of an early warning system in chile

sensitivity of prestack depth migration to the velocity model to get a correct earth image from seismic data acquired over complex structures it is essential to use prestack depth migration a necessary condition for obtaining a correct image is that the prestack depth migration is done with an accurate velocity model in cases where we need to use prestack depth migration determination of such a model using conventional methods does not give satisfactory results thus new iterative methods for velocity model determination have been developed the convergence of these methods can be accelerated by defining constraints on the model in such a way that the method only looks for those components of the true earth velocity field that influence the migrated image in order to determine these components the sensitivity of the prestack depth migration result to the velocity model is examined using a complex synthetic data set the marmousi data set for which the exact model is known the images obtained with increasingly smoothed versions of the true model are compared

the vallo di diano fault system new evidence for an active range bounding fault in southern italy using shallow high resolution seismic profiling range bounding normal faults can presentsignificant challenges for seis mic exploration this is the case of the fault system bounding the vallo di diano the largest intermountain basin in the southern apennines seismic belt industry reflection profiles define the large scale structure of the basin but barely image the shallow fault system due to unfavorable topographic and near surface conditions along the foothills of the eastern range we present two high resolution hr wide aperture profiles recorded attheeastern marginof thebasin acrossunreported scarpsthat affect middle late pleistocene alluvial fans and slope debris the survey is aimed at identifying possible recent faulting across these challenging terrains and at understanding the re lationship between shallow structures and the master range bounding fault at depth common depth point processing of wide aperture reflection data and first arrival tra vel time tomography provide detailed images of the upper 200 300 m and sounding evidence of recent activity along previously unknown splays of the fault system these splays dissect the mesozoic limestone bedrock and alluvial fan sequences affecting theirdepositionalpattern veryhighresolutionvpandreflectivityimagesalsogivehints ofpossiblecoseismicsurfacefaultinginholocenecolluvia theseresultshaverelevant implicationsfortheevaluationoftheseismogenicpotentialoftherange boundingfault systemandforseismichazardassessmentofthedenselyurbanizedvallodidianobasin online material table of acquisition and data processing parameters and figures showing schematic stratigraphy of the vallo di diano basin restoration of fault dis placement along the hr profile and resolution of the p velocity tomographic images for the vhr profile

the recycling of chromitites in ophiolites from southwestern north america abstract podiform chromitites occur in mantle peridotites of the late triassic puerto nuevo ophiolite baja california sur state mexico these are high cr chromitites cr cr cr al atomic ratio 0 61 0 69 that contain a range of minor and trace elements and show whole rock enrichment in ipge os ir ru that are similar to those of high cr ophiolitic chromitites crystallised from melts similar to high mg island arc tholeiites iat and boninites in supra subduction zone mantle wedges crystallisation of these chromitites from s undersaturated melts is consistent with the presence of abundant inclusions of platinum group minerals pgm such as laurite rus2 erlichmanite oss2 osmium and irarsite irass in chromite that yield tma trd model ages peaking at 325 ma thirty three xenocrystic zircons recovered from mineral concentrates of these chromitites yield ages 2263 44 ma to 278 4 ma and hf o compositions hf t 18 7 to 9 1 and 18o values

faulting apparently related to the 1994 northridge california earthquake and possible co seismic origin of surface cracks in potrero canyon los angeles county california apparent southward dipping reverse fault zones are imaged to depths of about 1 5 km beneath potrero canyon los angeles county california based on their orientation and projection to the surface we suggest that the imaged fault zones are extensions of the oak ridge fault geologic mapping by others and correlations with seismicity studies suggest that the oak ridge fault is the causative fault of the 17 january 1994 northridge earthquake northridge fault our seismically imaged faults may be among several faults that collectively comprise the northridge thrust fault system unusually strong shaking in potrero canyon during the northridge earthquake may have resulted from focusing of seismic energy or co seismic move ment along existing related shallow depth faults the strong shaking produced ground surface cracks and sand blows distributed along the length of the canyon seismic reflection and refraction images show that shallow depth faults may underlie some of the observed surface cracks the relationship between observed surface cracks and imaged faults indicates that some of the surface cracks may have devel oped from nontectonic alluvial movement but others may be fault related imme diately beneath the surface cracks p wave velocities are unusually low 400 m sec and there are velocity anomalies consistent with a seismic reflection image of shallow faulting to depths of at least 100 m on the basis of velocity data we suggest that unconsolidated soils 800 rrdsec extend to depths of about 15 to 20 m beneath our datum 25 m below ground surface the underlying rocks range in velocity from about 1000 to 5000 m sec in the upper 100 m this study illustrates the utility of high resolution seismic imaging in assessing local and regional seismic hazards

the vallo di diano and auletta extensional basins in the southern apennines italy a simple model for a complex setting this work has been developed within the 2005 2008 firb project research and development of new technologies for protection and defence of territory from natural risks w p c3 crustal imaging in italy coordinated by p montone funded by the italian ministry of uni versity and research

testing earthquake early warning parameters τpmax τc and pd for rapid magnitude estimation in the sichuan china region abstract to mitigate the potential seismic disasters dominated by the longmen shan fault zone lfz in the sichuan region building up suitable magnitude estimation models for earthquake early warning eew systems is important in this article the records from the mainshocks and aftershocks of the 2008 wenchuan m w 7 9 and 2013 lushan earthquakes m w 6 6 which occurred in the sichuan region were used to develop the maximum predominant and characteristic periods and c and peak ground displacement p d parameters for estimating earthquake magnitude the developed correlations were evaluated and compared with previous studies in other regions the parameter is correlated with magnitudes in the 4 6 and 6 8 ranges whereas c parameter scales are correlated with the entire magnitude range without evident saturation nevertheless the linear slope is slightly lower than the previous studies in other regions show as for p d parameter it is confirmed as a good estimator and performs most similarly with the compared regions with the magnitude of 4 6 range indeed for large magnitude we observe the saturation effect the longer time window length coupled with narrowing the filtering bandwidth can improve the saturation however the linear slope decreases speculatively the different performances can perhaps be attributed to the regional characteristics in the lfz region our works offer an insight into the feasibility of the eew system in sichuan china

large amplitude variations recorded by an on fault seismological station during the l aquila earthquakes evidence for a complex fault induced site effect 1 a station fagn installed on a segment of the fault system that generated the april 2009 l aquila earthquakes shows larger ground motions compared to nearby stations spectral ratios using 304 earthquakes result in a station amplification significantly varying event by event in the frequency band 1 8 hz the resulting pattern of amplitude dependence on causative earthquake location reveals that the strongest up to a factor of 10 amplifications occur for tightly clustered aftershocks aligned with the fault dip beneath fagn thus indicating a fault guided effect fault models are investigated in a grid search approach by varying velocity q width and depth of the fault zone although the problem solution is not unique and there are strong trade offs among the model parameters constraints from observations yield a deep trapping structure model where the most likely values of velocity reduction q and damage zone width are 25 20 and 280 m respectively

simulations of ground motion in the los angeles basin based upon the spectral element method we use the spectral element method to simulate ground motion generated by two recent and well recorded small earthquakes in the los angeles basin simulations are performed using a new sedimentary basin model that is constrained by hundreds of petroleum industry well logs and more than 20 000 km of seismic reflection profiles the numerical simulations account for 3d variations of seismic wave speeds and density topography and bathymetry and attenuation simulations for the 9 september 2001 m w 4 2 hollywood earthquake and the 3 september 2002 m w 4 2 yorba linda earthquake demonstrate that the combination of a detailed sedimentary basin model and an accurate numerical technique facilitates the simulation of ground motion at periods of 2 sec and longer inside the basin model and 6 sec and longer in the regional model peak ground displacement velocity and acceleration maps illustrate that significant amplification occurs in the basin

new frequency based real time magnitude proxy for earthquake early warning the two frequency based magnitude proxies currently employed by earthquake early warning systems in california are the predominant and the characteristic periods these proxies obtained using simple expressions that are valid for noise free monochromatic signals yield erroneous result the log average period log introduced in this study is calculated directly from the actual velocity spectrum of the first few seconds of the seismic record using data from south california and japan consisting of 440 earthquakes whose magnitudes range between 3 and 7 3 it is demonstrated that log is better correlated with the catalog magnitude than the predominant period and provides better magnitude assessment than the characteristic period for small magnitudes m 4 the average prediction error is reduced with increasing the input interval up to 6 s it appears that a single linear scaling describes the relation between log log and the catalog magnitude for the entire magnitude range studied here

fluid percolations in a fault zone a study of fluid inclusion planes in the st sylvestre granite northwest massif central france abstract a method for relating fluid flow evolution direction of fluid percolation to the bulk brittle network microfracture system at each state in a sequence of deformational events is presented fluids percolating through cracks are generally trapped as fluid inclusion planes alignment of fluid inclusions the method involves the use of fluid inclusions not only as a tool for the establishment of the physico chemical conditions under which fluids were entrapped but also as a microstructural marker of the geometry of permeability the study shows that through the determination of the paleopressures for each stage of fluid migration the chronology of the cracks and p t conditions prevailing during each crack formation can be established this methodology has focussed on a granitic example from the french massif central but may be applied to other geological environments

the italian cmt dataset from 1977 to the present abstract the ingv harvard european mediterranean regional centroid moment tensor rcmt catalog collects solutions routinely computed since 1997 for earthquakes with moderate magnitude 4 5 m 5 5 in the mediterranean region the database represents an extension to smaller magnitudes of the harvard global cmt catalog based on analysis of seismograms recorded at regional distance and modeling of intermediate period surface waves the catalog includes about 600 events 200 of which in the italian region this study extends the catalog back in time for the italian region as long as made possible by available digital data i e since 1977 with the same analysis and inversion method used for current seismicity as a result we present here 65 new moment tensors for years between 1977 and 1997 these solutions represent 45 of the total number of events analyzed the existing seismograms being often too scarce to allow a stable solution the new dataset includes events in many seismic zones where moderate seismicity had previously been scarcely documented e g the po plain the central to southern apennines and the adriatic sea the complete dataset including previously determined rcmts and cmts represents the seismic deformation in the italian area during the last 25 years

the influence of nacl h2o fluids on reactions between olivine and plagioclase an experimental study at 0 8 gpa and 800 900 c abstract the lower to middle continental and oceanic crust is dominated by mafic gabbroic rocks which are variably metamorphosed at amphibolite granulite facies conditions forming reaction rims or veins containing secondary pyroxenes amphibole and phlogopite metamorphic fluids in the mid crust are typically nacl rich brines in this study olivine and plagioclase were reacted with varying amounts of fluid 0 2 wt added that had compositions ranging from pure h2o to nacl solutions 0 2 mol in a series of experiments using the piston cylinder apparatus at 0 8 gpa and temperatures from 800 to 900 c coronas of clinopyroxene clinopyroxene amphibole and clinopyroxene phlogopite were formed the thicknesses of reaction rims i e the relative amount of reaction rim products increase with the relative amount of fluid present in the system and are therefore linked to the level of fluid saturation along grain boundaries and interphase boundaries samples with no added h2o show little to no signs of reaction indicating the necessity for fluids in initiating a reaction between olivine and plagioclase the concentration of nacl in the fluid also increases the rates of rim growth at 900 c and 2 wt added fluid cl rich hydrous dacite trachyte melt compositions formed and are similar to low degree partial melts of oceanic crust the cl contents of secondary amphiboles are positively correlated with the feo and k2o contents of the amphibole consumption of fluid during the formation of hydrous rim phases may lead to high cl within transient fluid filled pores along grain boundaries which may lead to locally cl rich amphiboles

p wave attenuation with implications for earthquake early warning several widely implemented and tested earthquake early warning algorithms employ empirical equations that relate earthquake magnitudes with ground motion peak amplitudes and hypocentral distances this approach is effective to the extent that the offline dataset available for setting the fitting coefficients in those equations is of sufficient quality and quantity however to address the problem of having a limited dataset it is instructive to gain physical understanding of the main factors controlling the p wave attenuation in this study theoretical expressions are derived that relate the root mean square rms of the p wave displacement d rms and velocity v rms to the seismic moment stress drop and hypocentral distance the theoretical attenuation laws are then validated against observed attenuation using earthquake data from southern california and japan good agreement is found between observed and predicted ground motions the similar ground motion attenuation in california and japan suggests that the attenuation laws are similarly applicable for the two regions and implies that they may also be implemented in other regions without having to go through a lengthy calibration phase because d rms is more strongly dependent on the seismic moment than v rms use of the attenuation law for d rms yields better magnitude prediction than that of v rms it is shown that the d rms to v rms ratio is proportional to the characteristic length of the rupture and that the stress drop is a function of the seismic moment and the cube of d rms v rms this result paves the way for a new stress drop determination scheme that is totally independent of previously used approaches finally it is shown that the rms of the ground motions are proportional to their peak values

late holocene earthquakes in southern apennine paleoseismology of the caggiano fault although southern apennines are characterized by the strongest crustal earthquakes of central western mediterranean region local active tectonics is still poorly known at least for seismogenic fault recognition is concerned research carried out in the maddalena mts southeast of irpinia the region struck by the mw 6 9 1980 earthquake indicates historical ruptures along a 17 km long n120 normal fault system caggiano fault the system is characterized by a bedrock fault scarp carved in carbonate rocks which continues laterally into a retreating and eroded smoothed scarp affecting the clayey siliciclastic units and by smart scarps and discontinuous free faces in holocene cemented slope debris and in modern alluvial fan deposits the geometry of the structure in depth has been depicted by means of electrical resistivity tomography while paleoseismic analysis carried out in three trenches revealed surface faulting events during the past 7 ky bp 14c age the latest occurred in the past 2 ky bp 14c age and probably during after slope debris deposition related to the little ice age 1400 1800 a d preliminary evaluation accounts for minimum slip rates of 0 3 0 4 mm year which is the same order of rates estimated for many active faults along the apennine chain associated earthquakes might be in the order of mw 6 6 to be compared to the historical events occurred in the area e g 1561 and 1857 p p earthquakes

zoning of phosphorus in igneous olivine we describe p zoning in olivines from terrestrial basalts andesites dacites and komatiites and from a martian meteorite p2o5 contents of olivines vary from below the detection limit 0 01 wt to 0 2 0 4 wt over a few microns with no correlated variations in fo content zoning patterns include p rich crystal cores with skeletal hopper or euhedral shapes oscillatory zoning structures suggesting replacement of p rich zones by p poor olivine and sector zoning melt inclusions in olivines are usually located near p rich regions but in direct contact with low p olivine crystallization experiments on basaltic compositions at constant cooling rates 15 30 c h reproduce many of these features we infer that p rich zones in experimental and natural olivines reflect incorporation of p in excess of equilibrium partitioning during rapid growth and zoning patterns primarily record crystal growth rate variations occurrences of high p phenocryst cores may reflect pulses of rapid crystal growth following delayed nucleation due to undercooling most cases of oscillatory zoning in p likely reflect internal factors whereby oscillating growth rates occur without external forcings but some p zoning in natural olivines may reflect external forcings e g magma mixing events eruption that result in variable crystal growth rates and or p contents in the magma in experimental and some natural olivines al cr and p concentrations are roughly linearly and positively correlated suggesting coupled substitutions but in natural phenocrysts cr zoning is usually less intense than p zoning and al zoning weak to absent we propose that olivines grow from basic and ultrabasic magmas with correlated zoning in p cr and al superimposed on normal zoning in fe mg rapidly diffusing divalent cations homogenize during residence in hot magma al and cr only partially homogenize and delicate p zoning is preserved because p diffuses very slowly this interpretation is consistent with the fact that zoning is largely preserved not only in p but also in al cr and divalent cations in olivines with short residence times at high temperature e g experimentally grown olivines komatiitic olivines groundmass olivines and the rims of olivine phenocrysts grown during eruption p zoning is widespread in magmatic olivine revealing details of crystal growth and intra crystal stratigraphy in what otherwise appear to be relatively featureless crystals since it is preserved in early formed olivines with prolonged residence times in magmas at high temperatures p zoning has promise as an archive of information about an otherwise largely inaccessible stage of a magma s history study of such features should be a valuable supplement to routine petrographic investigations of basic and ultrabasic rocks especially because these features can be observed with standard electron microprobe techniques

combining seismic reflection with multifold wide aperture profiling an effective strategy for high resolution shallow imaging of active faults 1 shallow imaging of fault zones is a challenging task we investigate if this issue can be successfully addressed by combining reflection seismics with non standard multifold wide aperture profiling a strategy pertaining to crustal scale exploration so far near offset reflection and multifold wide aperture data are simultaneously recorded along two profiles in a small basin crossed by an active fault in southern italy imaging consists of multiscale seismic tomography complemented by cdp processing of near offset reflections and of data spanning a large offset range by combining smooth vp and reflectivity images we pinpoint the fault location and yield a valuable picture of the basin performance of each exploration technique strongly varies in the two surveys depending on the local geology thus the combined exploration strategy not only yields complementary images for enhanced interpretation but also allows extending the range of applicability of shallow seismics for fault detection reducing the risk of unsuccessful investigations

a threshold based earthquake early warning using dense accelerometer networks most earthquake early warning systems eews developed so far are conceived as either regional network based or on site stand alone systems the recent implementation of nationwide high dynamic range dense accelerometer arrays makes now available potentially in real time unsaturated waveforms of moderate to large magnitude earthquakes recorded at very short epicentral distances 10 20 km this would allow for a drastic increase of the early warning lead time for example the time between the alert notification and the arrival time of potentially destructive waves at a given target site by analysing strong motion data from modern accelerograph networks in japan taiwan and italy we propose an integrated regional on site early warning method which can be used in the very first seconds after a moderate to large earthquake to map the most probable damaged zones the method is based on the real time measurement of the period c and peak displacement pd parameters at stations located at increasing distances from the earthquake epicentre the recorded values of early warning parameters are compared to threshold values which are set for a minimum magnitude 6 and instrumental intensity vii according to the empirical regression analyses of strong motion data at each recording site the alert level is assigned based on a decisional table with four alert levels defined upon critical values of the parameters pd and c which are set according to the error bounds estimated on the derived prediction equations given a real time evolutionary estimation of earthquake location from first p arrivals the method furnishes an estimation of the extent of potential damage zone as inferred from continuously updated averages of the period parameter and from mapping of the alert levels determined at the near source accelerometer stations the off line application of the method to strong motion records of the m w 6 3 2009 central italy earthquake shows a very consistent match between the rapidly predicted within a few seconds from the first recorded p wave and observed damage zone the latter being mapped from detailed macroseismic surveys a few days after the event the proposed approach is suitable for italy where during the last two decades a dense network of wide dynamic range accelerometer arrays has been deployed by the department of civil protection dpc the istituto nazionale di geofisica e vulcanologia ingv and other regional research agencies

very little water is necessary to make a dry solid silicate system wet the standard rim forming mineral reaction olivine quartz orthopyroxene ol qtz opx has been experimentally performed at very dry conditions i e only 20 wt ppm of water present in the sample container as a fluid and most water was hydrogen dissolved within the solid crystals reaction rates and resulting fabrics at ol qtz interfaces mimic reaction features previously known from water rich conditions tens of thousands ppm our experiment indicates that very small amounts of water tens of ppm of the entire sample are highly effective in facilitating mineral reactions where water acts as a catalyst and creates porosity that might start to migrate from the initial centers of self propagating mineral reaction if rock deformation allows the threshold between dry and wet in granulite and eclogite facies rocks is crossed once the nominally anhydrous minerals are saturated with hydrogen

active normal fault evolution in greece revealed by geomorphology and drainage patterns active normal fault systems in greece are associated with characteristic geomorphology and drainage patterns that are recognizable in satellite images and digital topography some allowance must be made for the nature of the footwall rocks which can exert an important influence on these patterns and we examine the three main types in greece hard mesozoic limestone relatively soft schist volcanic rocks or flysch and very soft neogene sediments drainage and geomorphology can be used to identify active faults that were previously unknown but can also reveal information about plio quaternary fault evolution and interaction that may be inaccessible by other means we illustrate such processes with examples showing the migration of normal fault systems into their hanging walls and the change in normal faulting activity from nw se faults to e w faults both of which are common in greece

p wave seismic velocity structure derived from sonic logs and industry reflection data in the los angeles basin california 1 we present a new three dimensional seismic p wave velocity model of the los angeles basin that is based on more than 150 sonic logs and 7000 stacking velocities from industry reflection profiles the model was developed using kriging techniques implemented in gocad a commercial application specializing in the construction of surfaces the analysis of spatially distributed data and the modeling or simulation of properties and is characterized by a heterogeneous spatial varying velocity gradient with maximum velocities of 5000 m s in the sedimentary section variability of the observed p wave velocities increases with depth reflecting complex structural and sedimentological controls the model contains a new representation of the basin shape as defined by the sediment basement interface which was mapped using well control and seismic reflection profiles our model differs substantially in approach and outcome from previous representations of crustal velocity structure in southern california

high resolution densely spaced wide aperture seismic profiling as a tool to aid seismic hazard assessment of fault bounded intramontane basins application to vallo di diano southern italy abstract seismic hazards in extensional regions are mostly posed by high angle normal faults and deep hanging wall basins that can promote significant ground motion amplifications characterized by strong lateral velocity variations these structures represent challenging targets for seismic exploration in this paper we show that prestack depth migration of high resolution seismic reflection data collected with nonconventional dense wide aperture arrays can effectively assist deterministic seismic hazard assessment of fault bounded basins our high resolution 3 2 km long seismic profile was acquired along vallo di diano the largest fault bounded intramontane basin in the southern apennines seismic belt italy the imaging strategy combines prestack depth migration with an iterative velocity building technique that utilizes results of multiscale refraction tomography in particular migration of steeply dipping reflections is essential in imaging the complex morphology of the basement rocks beneath the basin by combining seismic reflection and v p tomography results we were able to evaluate 1 the structure of the vallo di diano basin along a representative transect from near surface to basement depths 2 the shallow depth geometry of the vallo di diano fault system which bounds the basin to the east 3 the structure of the sediment basement interface and 4 the velocity structure of basement and sediments within the basin these findings are valuable both for understanding the tectonic evolution of the vallo di diano and for developing earthquake shaking scenario studies

magnitude estimation based on integrated amplitude and frequency content of the initial p wave in earthquake early warning applied to tehran iran abstract to optimize magnitude estimation for the earthquake early warning system around the tehran region different amplitude and frequency based parameters that is predominant period characteristic period c log average period log and peak displacement p d were analyzed in this article all parameters were calculated directly from seismic records with an epicentral distance less than 150 km and within the initial 3 s of the p waves the analysis of earthquakes in the 2 4 m l p d and c were underestimated and there was no scaling relationship with the log parameter when combined with the global observations from japan taiwan and italy the results of p d and c for the tehran region produced optimized results

earth science is earthquake rupture deterministic reply rydelek and horiuchi 1 present an analysis of earthquakes in japan whose magnitudes m ranged from 6 0 to 8 0 they determine pmax the peak predominant period for p wave arrival for the five nearest hi net seismic network stations and plot the event averaged pmax versus magnitude they find no statistically significant trend in their data

a mechanism for preferential h 2 o leakage from fluid inclusions in quartz based on tem observations preferential leakage of h2o from fluid inclusions containing multiple gas components has been suspected in natural metamorphic rocks and has been demonstrated experimentally for synthetic h2o co2 rich inclusions in natural quartz knowledge of the physical and chemical characteristics of the leakage mechanism which may be very complex increases the value of natural fluid inclusions to metamorphic geology it is proposed that crystal defects play a major role in nondecrepitative preferential h2o leakage through quartz and remain effective during metamorphism inclusions with either an internal overpressure or underpressure produce strain in the adjacent quartz crystal via the nucleation of many dislocations and planar defects like dauphine twin boundaries these defects allow preferential loss of h2o from h2o co2 rich inclusions at supercritical conditions the transport capacity of this leakage mechanism is enhanced by nucleation of small bubbles on defect structures the nucleation of these bubbles seems to be a recovery process in strained crystals solubility gradients of quartz in water in a crystal with internally underpressurized inclusions may result in optical visible implosion halos in a three dimensional spatial arrangement caused by the growth of small bubbles at the expense of the larger original fluid inclusion natural fluid inclusions from naxos greece are always associated with numerous interlinked dislocations these dislocations may have been produced by plastic derormation or by crystal growth related processes e g crack healing the presence of small bubbles on these dislocations indicates that a similar leakage mechanism for h2o must have occurred in these rocks

test of a threshold based earthquake early warning method using japanese data most of existing earthquake early warning systems are regional or on site systems a new concept is the integration of these approaches for the definition of alert levels and the estimation of the earthquake potential damage zone pdz the key element of the method is the real time simultaneous measurement of initial peak displacement p d and period parameter c in a 3 s window after the first p wave arrival time at accelerometer stations located at increasing distances from the epicenter as for the on site approach the recorded values of p d and c are compared to threshold values which are set for a minimum magnitude m 6 and instrumental intensity i mm vii according to empirical regression analysis of strong motion data from different seismic regions at each recording site the alert level is assigned based on a decisional table with four entries defined by threshold values of the parameters p d and c a regional network of stations provides the event location and transmits the information about the alert levels recorded at near source stations to more distant sites before the arrival of the most destructive phase we present the results of performance tests of this method using ten m 6 japanese earthquakes that occurred in the period 2000 2009 and propose a very robust methodology for mapping the pdz in the first seconds after a moderate to large earthquake the studied cases displayed a very good matching between the rapidly predicted earthquake pdz inferred from initial p peak displacement amplitudes and the instrumental intensity map the latter being mapped after the event using peak ground velocity and or acceleration or from field macroseismic surveys

experimental formation of pyroxenite veins by reactions between olivine and si al ca na and cl rich fluids at 800 oc and 800 mpa implications for fluid metasomatism in the mantle wedge fluids buffered by a plagioclase matrix are experimentally reacted with olivine megacrysts at 800 oc and 800 mpa piston cylinder press caf2 assembly to form secondary veins of orthopyroxene clinopyroxene in the olivine fluids utilized were varied in both amount 0 2 wt and salinity 0 8 m nacl assuming equilibrium with the plagioclase matrix they are presumed enriched in si al ca na and cl and are thereby similar in composition to slab derived fluids the experiments provide controlled multi component analogs of si metasomatism in the mantle wedge above subduction zones the veins are dominated by orthopyroxene with minor clinopyroxene and form complex interconnected networks along fractures in the olivine the reaction is rate limited by interfacial process of dissolution and precipitation porosity is developed throughout the veins and along sub grain boundaries in the olivine megacrysts these veins strongly resemble the textures observed in secondary metasomatic orthopyroxene veins widely reported in upper mantle xenoliths within arc magmas a review of literature data on natural samples and experiments suggests that orthopyroxene clinopyroxene veins primarily form between 750 950 oc and over a large pressure range from 0 8 3 4 gpa the abundance and composition of these metasomatic veins may vary as a function of pressure variances in the fluid rock partition coefficients and or by modification of the metasomatic fluid during the reaction

imaging complex structure in shallow seismic reflection data using prestack depth migration prestack depth migration psdm analysis has the potential to significantly improve the accuracy of both shallow seismicreflectionimagesandthemeasuredvelocitydistributions inastudydesignedtoimagefaultsinthealvordbasin oregon at depths from 25 1000 m psdm produced a detailed reflection image over the full target depth range in contrast poststack time migration produced significant migration artifacts in the upper 100 m that obscured reflection events and limited the structural interpretation in the shallow section additionally an abrupt increase from 2500 to 3000 m s in the psdm velocity model constrained the interpretation of the transition from sedimentary basin fill to basementvolcanicrocks psdmanalysisrevealedacomplex extensional history with at least two distinct phases of basin growthandamidbasinbasementhighthatformsthedivision betweentwomajorbasincompartments

rates of grain boundary diffusion through enstatite and forsterite reaction rims the growth rates of enstatite rims produced by reaction of fo92 and sio2 were determined at 250 1500 mpa and 900 1100 c for a wide range of water contents growth rates were also determined for forsterite rims between mgo and mg2si2o6 and between mgo and sio2 rim growth rates are parabolic indicating diffusion controlled growth of the polycrystalline rims which are composed of 2 m diameter grains rim growth rates were used to calculate the product of the grain boundary diffusion coefficient d a times the effective grain boundary thickness assuming in turn that mgo sio2 and mg2si 1 are the diffusing components coupled diffusion of a cation and oxygen or interdiffusion of mg and si the values for d mgo d and d for enstatite at 1000 c and 700 mpa confining pressure with about 0 1 wt water are about five times larger than the corresponding d a values for samples initially vacuum dried at 250 c most of the increase in d a occurs with the first 0 1 wt water the activation energy for diffusion through the enstatite rims 1100 950 c is 162 30 kj mole the diffusion rate through enstatite rims is essentially unchanged for confining pressures from 210 1400 mpa but the nucleation rate is greatly reduced at low confining pressure for 1 0 wt water present and limits the conditions at which rim growth can be measured the corresponding values for d a through forsterite rims are essentially identical for the two forsterite producing reactions when 0 1 wt water is added and similar to the d a values for enstatite at the same conditions the d a values for forsterite are 28 times larger for samples starting with 0 1 wt water compared to samples that were first vacuum dried thus water enhances these grain boundary diffusion rates by a factor of 5 30 depending on the mineralogy but the total range in d a is only slightly more than an order of magnitude for as wide a range of water contents as expected for most crustal conditions

steep dip seismic imaging of the shallow san andreas fault near parkfield seismic reflection and refraction images illuminate the san andreas fault to a depth of 1 kilometer the prestack depth migrated reflection image contains near vertical reflections aligned with the active fault trace the fault is vertical in the upper 0 5 kilometer then dips about 70 to the southwest to at least 1 kilometer subsurface this dip reconciles the difference between the computed locations of earthquakes and the surface fault trace the seismic velocity cross section shows strong lateral variations relatively low velocity 10 to 30 high electrical conductivity and low density indicate a 1 kilometer wide vertical wedge of porous sediment or fractured rock immediately southwest of the active fault trace

san andreas fault geometry at desert hot springs california and its effects on earthquake hazards and groundwater abstract the mission creek and banning faults are two of the principal strands of the san andreas fault zone in the northern coachella valley of southern california structural characteristics of the faults affect both regional earthquake hazards and local groundwater resources we use seismic gravity and geological data to characterize the san andreas fault zone in the vicinity of desert hot springs seismic images of the upper 500 m of the mission creek fault at desert hot springs show multiple fault strands distributed over a 500 m wide zone with concentrated faulting within a central 200 m wide area of the fault zone high velocity up to 5000 m sec rocks on the northeast side of the fault are juxtaposed against a low velocity m 6 0 earthquakes in the area in 1948 and 1986 occurred at or near the depths 10 to 12 km of the merged san andreas fault large magnitude earthquakes that nucleate at or below the merged fault will likely generate strong shaking from guided waves along both fault zones and from amplified seismic waves in the low velocity basin between the two fault zones the mission creek fault zone is a groundwater barrier with the top of the water table varying by 60 m in depth and the aquifer varying by about 50 m in thickness across a 200 m wide zone of concentrated faulting

late quaternary tectonics of the vallo di diano basin southern apennines italy italian ministry of university and research project firb research and development of new technologies for protection and defence of territory from natural risks w p c3 crustal imaging in italy