time resolved seismic tomography detects magma intrusions at mount etna the continuous volcanic and seismic activity at mount etna makes this volcano an important laboratory for seismological and geophysical studies we used repeated three dimensional tomography to detect variations in elastic parameters during different volcanic cycles before and during the october 2002 january 2003 flank eruption well defined anomalous low p to s wave velocity ratio volumes were revealed absent during the pre eruptive period the anomalies trace the intrusion of volatile rich 4 weight percent basaltic magma most of which rose up only a few months before the onset of eruption the observed time changes of velocity anomalies suggest that four dimensional tomography provides a basis for more efficient volcano monitoring and short and midterm eruption forecasting of explosive activity

sandstone vs carbonate petroleum reservoirs a global perspective on porosity depth and porosity permeability relationships plots are presented comparing average porosity vs depth for 30 122 siliciclastic petroleum reservoirs and 10 481 carbonate petroleum reservoirs covering all petroleum producing countries except canada however separate plots cover 5534 siliciclastic and 2830 carbonate reservoirs of the alberta basin in canada average permeability vs average porosity is shown for the non canadian reservoirs key similarities and differences between sandstones and carbonates are noted and implications are discussed regarding the dominant factors controlling reservoir quality in each lithology trends of steadily decreasing median and maximum porosity with increasing depth reflect burial diagenetic porosity loss in response to increasing thermal exposure with depth these trends seem inconsistent with the suggestions that both sandstones and carbonates commonly increase in porosity by dissolution during deeper burial carbonate reservoirs have lower values of median and maximum porosity for a given burial depth probably because of greater chemical reactivity of carbonate minerals relative to quartz and the resulting lower resistance to chemical compaction and associated cementation relative paucity of low porosity 0 8 siliciclastic reservoirs at all depths compared with carbonates may reflect the more common occurrence of fractures in carbonates and the effectiveness of these fractures for facilitating economic flow rates in low porosity rock overall carbonate reservoirs do not have lower permeability for a given porosity compared with sandstones but do have strikingly lower proportions of both high porosity and high permeability values the data presented can serve as a general guide for the distribution of reservoir quality that can reasonably be expected in exploration wells drilled to any given depth in the absence of detailed geologic information such as burial and thermal history

gassmann s fluid substitution and shear modulus variability in carbonates at laboratory seismic and ultrasonic frequencies carbonates have become important targets for rock property research in recent years because they represent many of themajoroilandgasreservoirsintheworld someareundergoing enhanced oil recovery most laboratory studies to understand fluid and pressure effects on reservoir rocks have been performed on sandstones but applying relations developed for sandstones to carbonates is problematic at best we measure in the laboratory nine carbonate samples from the same reservoir at seismic 3 3000 hz and ultrasonic 0 8 mhz frequencies samples are measured dry humidified and saturated with liquid butane and brine our carbonate samples showed typical changes in moduli as a function of porosity andfluid saturation however we explore the applicability of gassmann s theory on limestone and dolomite rocks in the context of shear and bulk modulus dispersion andgassmann stheoryassumptions forourcarbonatesetat high differential pressures and seismic frequencies the bulk modulus of rocks with high aspect ratio pores and dolomite mineralogy is predicted by gassmann s relation we also explore in detail some of the assumptions of gassmann s relation especiallyrock framesensitivitytofluidsaturation our carbonate samples show rock shear modulus change from dry to brine saturation conditions and we investigate several rock fluid mechanisms responsible for this change to our knowledge these are the first controlled laboratory experimentsoncarbonatesintheseismicfrequencyrange

temporal variation of seismic velocity and anisotropy before the 2009 mw 6 3 l aquila earthquake italy we describe a set of seismological observations of the foreshock sequence preceding the 6 april 2009 m w 6 3 l9aquila earthquake the dense configuration of the seismic network in the epicenter area and the occurrence of a long foreshock sequence provide the opportunity for a detailed reconstruction of the preparatory phase of the main shock approaching the earthquake we observed clear variations in the seismic wave propagation properties the elastic properties of rocks in the fault region underwent a sharp change about a week before the earthquake from our observations we infer that a complex sequence of dilatancy diffusion processes takes place and that fluids play a key role in the fault failure process

new insights into crustal structure cenozoic magmatism co2 degassing and seismogenesis in the southern apennines and irpinia region from local earthquake tomography we present high resolution vp and vp vs models of the southern apennines italy computed using local earthquakes recorded from 2006 to 2011 with a graded inversion scheme that progressively resolves the crustal structure from the large scale of the apennines belt to the local scale of the normal fault system high vp bodies defined in the upper crust and midcrust under the external apennines are interpreted as extensive mafic intrusions revealing anorogenic magmatism episodes that broadened on the adriatic domain during paleogene under the mountain belt a low vp region annular to the neapolitan volcanic district indicates the existence of a thermal fluid anomaly in the midcrust coinciding with a shallow moho and diffuse degassing of deeply derived co2 in the belt axial zone low vp vs gas pressurized rock volumes under the apulian carbonates correlate to high heat flow strong co2 dominated gas emissions of mantle origin and shallow carbonate reservoirs with pressurized co2 gas caps we hypothesize that the pressurized fluid volumes located at the base of the active fault system influence the rupture process of large normal faulting earthquakes like the 1980 mw6 9 irpinia event and that major asperities are confined within the high vp apulian carbonates this study confirms once more that preexisting structures of the pliocene apulian belt controlled the rupture propagation during the irpinia earthquake the main shock broke a 30 km long ne dipping seismogenic structure whereas delayed ruptures both the 20 s and the 40 s subevents developed on antithetic faults reactivating thrust faults located at the eastern edge of the apulian belt

pore pressure migration along a normal fault system resolved by time repeated seismic tomography in this study we outline the space and time variations of body wave velocities during one of the best documented series of normal faulting earthquakes the 1997 umbria marche sequence in central italy we show the first ever observations of rock fracturing and fluid overpressure propagation along a fault system by using space time resolved variations of vp vs anomalies four dimensional variations that accompany earthquake migration and precede large aftershocks the vp vs increase observed before the mid october earthquakes was related to a pore pressure increase on fluid filled cracks in the volume around the fault we also document that such variations are measurable only by using s and p wave arrival times

do earthquake storms repeat in the apennines of italy terra nova 23 300 306 2011 abstract series of multiple main shocks that develop on adjacent faults is a typical way in which active extension is accommodated in the apennines of italy this behaviour is explained by fault interaction that occurs at a scale ranging from seconds to days yielding a space time clustering of earthquakes termed as earthquake storms we show that the seismic energy released by historical earthquakes in central apennines is clustered into two main small time periods around 600 and 300 years ago during which a great portion of the normal faulting belt failed we favour the hypothesis that clustering results from sudden input of deep fluids into the brittle upper crust the roughly 300 years periodicity and the 3 4 mm year 1 of tectonic extension suggest that earthquake storms need to be taken into account in seismic hazard scenarios

carbon dioxide earth degassing and seismogenesis in central and southern italy 1 we present the first regional map of co2 earth degassing from a large area most of central and south italy derived from the carbon of deep provenance dissolved in the main springs of the region the investigation shows that a globally significant amount of deeply derived co2 10 of the estimated global co2 emitted from subaerial volcanoes is released by two large areas located in western italy the anomalous flux of co2 suddenly disappears in the apennine in correspondence to a narrow band where most of seismicity concentrates here at depth the gas accumulates in crustal traps generating co2 overpressurized reservoirs which induce seismicity

high resolution multi 2d seismic imaging of solfatara crater campi flegrei caldera southern italy from active seismic data abstract a multi 2d imaging of the solfatara crater inside the campi flegrei caldera was obtained by the joint interpretation of geophysical evidences and the new active seismic dataset acquired during the ricen experiment eu project medsuv in 2014 we used a total of 17 894 first p wave arrival times manually picked on pre processed waveforms recorded along two 1d profiles criss crossing the inner solfatara crater and performed a tomographic inversion based on a multi scale strategy and a bayesian estimation of velocity parameters the resulting tomographic images provide evidence for a low velocity 500 1500 m s water saturated deeper layer at west near the outcropping evidence of the fangaia contrasted by a high velocity 2000 3200 m s layer correlated with a consolidated tephra deposit the transition velocity range 1500 2000 m s layer suggests a possible presence of a gas rich accumulation volume thanks to the mutual p wave velocity model we infer a detailed image for the gas migration path to the earth surface the gasses coming from the deep hydrothermal plume accumulate in the central and most depressed area of the solfatara being trapped by the meteoric water saturated layer therefore the gasses are transmitted through the buried fault toward the east part of the crater where the ring faults facilitate the release as confirmed by the fumaroles starting from the eastern surface evidence of the gas releasing in the bocca grande and bocca nuova fumaroles and the presence of the central deeper plume we suggest a fault situated in the central part of the crater which seems to represent the main buried conduit among them plays a key role

p wave attenuation structure in the fault area of the 1995 kobe earthquake the three dimensional 3 d p wave attenuation structure in the kobe epicentral area is determined using aftershock records from the 1995 kobe hyogo ken nanbu earthquake waveform data from both permanent seismic networks and portable stations set up following the kobe mainshock were used the observed p wave amplitude spectra were inverted for the spectral plateau value the source corner frequency and a frequency independent t operator assuming an 2 type source model the calculated t operators were subsequently used for the computation of the 3 d absorption structure using a 3 d velocity model only high quality amplitude spectra were used for the estimation of reliable attenuation parameters resulting in a final data set of 4100 t operators two regions of high absorption were found in the upper part of the crust one is below the northern part of awaji island and reaches down to a depth of 5 km the other region northeast of kobe city is along the arima takatsuki tectonic line and extends along the rokko kashiodani and yamada faults it extends northward to the hokusetsu sanchi area in both regions a high density of fault lineations is mapped and high poisson ratios are known this suggests that partially saturated cracks cause the observed high attenuation

olivine dominated a type asteroids in the main belt distribution abundance and relation to families abstract differentiated asteroids are rare in the main asteroid belt despite evidence for 100 distinct differentiated bodies in the meteorite record we have sought to understand why so few main belt asteroids differentiated and where those differentiated bodies or fragments reside using the sloan digital sky survey sdss to search for a needle in a haystack we identify spectral a type asteroid candidates olivine dominated asteroids that may represent mantle material of differentiated bodies we have performed a near infrared spectral survey with spex on the nasa irtf and fire on the magellan telescope we report results from having doubled the number of known a type asteroids we deduce a new estimate for the overall abundance and distribution of this class of olivine dominated asteroids we find a type asteroids account for less than 0 16 of all main belt objects larger than 2 km and estimate there are a total of 600 a type asteroids above that size they are found rather evenly distributed throughout the main belt are even detected at the distance of the cybele region and have no statistically significant concentration in any asteroid family we conclude the most likely implication is the few fragments of olivine dominated material in the main belt did not form locally but instead were implanted as collisional fragments of bodies that formed elsewhere

multistage strain localisation and fluid assisted cataclasis in carbonate rocks during the seismic cycle insights from the belluno thrust eastern southern alps italy abstract strain localisation in carbonate rocks impacts upon the nucleation and development of structures within the shallow seismogenic crust studying deformed carbonate rocks is thus a key to the refined understanding of the mechanical behaviour of rock successions with high potential to fail coseismically in response to stress accumulation we studied deformation structures and mechanisms of the miocene belluno thrust from the seismically active eastern southern alps italy the thrust contains several structural facies and features pressure soluted and veined lithons cataclasites s c fabrics principal slip surface which make it possible to define a sequence of deformation events in space and through time during thrusting image analysis of cataclasite particle size distribution and morphology supported by cathodoluminescence imaging indicates corrosive wearing as the main comminuting mechanism during cataclasis and repeated ingress of overpressured aqueous fluids promoting carbonate clast dissolution we propose an evolutionary scenario of multiple episodes of fabric formation and rejuvenation that localised and accommodated increasing shear strain into a progressively narrowing fault core we propose that strain localisation in carbonate rocks can be greatly facilitated by cyclic fluctuations between strain hardening and softening conditions punctuated by transient spikes of coseismic failure accommodated by cataclasis during the ingress of overpressured chemically reactive fluids that control carbonate precipitation and dissolution

three dimensional p and s wave velocity structure of redoubt volcano alaska the three dimensional p and s wave structure of redoubt volcano alaska and the underlying crust to depths of 7 8 km is determined from 6219 p wave and 4008 s wave first arrival times recorded by a 30 station seismograph network deployed on and around the volcano first arrival times are calculated using a finite difference technique which allows for flexible parameterization of the slowness model and easy inclusion of topography and source receiver geometry the three dimensional p wave velocity structure and hypocenters are determined simultaneously while the three dimensional s wave velocity model is determined using the relocated seismicity and an initial s wave velocity model derived from the p wave velocity model assuming an average vp vs ratio of 1 78 convergence is steady with approximately 73 and 52 reduction in p and s wave arrival time rms respectively after 10 iterations the most prominent feature observed in the three dimensional velocity models derived for both p and s waves is a relative low velocity near vertical pipelike structure approximately 1 km in diameter that extends from 1 to 6 km beneath sea level this feature aligns axially with the bulk of seismicity and is interpreted as a highly fractured and altered zone encompassing a magma conduit the velocity structure beneath the north flank of the volcano between depths of 1 and 6 km is characterized by large lateral velocity variations high velocities within this region are interpreted as remnant dikes and sills and low velocities as regions along which magma migrates no large low velocity body suggestive of a magma chamber is resolved in the upper 7 8 km of the crust

understanding spaced receiver zonal velocity estimation 1 spaced receiver analysis can be used to estimate the ionospheric zonal irregularity velocity this involves first measuring the scintillation pattern velocity and then estimating the zonal irregularity velocity a straightforward technique involving projection planes has been used to derive a relationship between the satellite position and velocity the irregularities position and velocity and the scintillation pattern velocity this relationship relies on the alignment of the irregularities along the field lines but is independent of the irregularity spectrum when simplified this relationship can be used to estimate the zonal irregularity velocity using either geostationary satellites or global positioning system gps satellites this estimation is straightforward but must be performed in a careful manner an example of zonal irregularity velocity estimation using gps satellites is presented the average zonal irregularity velocity is estimated over a 3 week period in march 2002 at sao luis brazil 3 59 dip angle this hourly average velocity has been compared with the climatological radar observations from jicamarca observatory the spaced receiver zonal velocity agrees well within 8 m s with the radar s observations during postsunset hours

role of fluids in faulting inferred from stress field signatures the stress orientation signature of weak faults containing high pressure fluids has been observed for segments of the san andreas fault system in southern california the inferred lithostatic fluid pressures extend into the surrounding relatively intact rock in a zone scaling with the width of the interseismic strain accumulation repeated strain related fracturing and crack sealing may have created low permeability barriers that seal fluids into the network of currently active fractures

time lapse seismic reservoir monitoring time lapse seismic reservoir monitoring has advanced rapidly over the past decade there are currently about 75 active projects worldwide and more than 100 cumulative projects in the past decade or so the present total annual expenditures on 4 d seismic projects are on the order of 50 100 million us this currently represents a much smaller market than 3 d seismic but the use of 4 d seismic has grown exponentially over the past decade and is expected to continue to do so

sediment dispersed extraterrestrial chromite traces a major asteroid disruption event abundant extraterrestrial chromite grains from decomposed meteorites occur in middle ordovician 480 million years ago marine limestone over an area of 250 000 square kilometers in southern sweden the chromite anomaly gives support for an increase of two orders of magnitude in the influx of meteorites to earth during the mid ordovician as previously indicated by fossil meteorites extraterrestrial chromite grains in mid ordovician limestone can be used to constrain in detail the temporal variations in flux of extraterrestrial matter after one of the largest asteroid disruption events in the asteroid belt in late solar system history

a new seismic tomography of aigion area gulf of corinth greece from the 1991 data set summary an ew three dimensional delay traveltime tomography is performed to image the intermediate structure of the western gulf of corinth a large data set collected in 1991 during a two month passive tomographic experiment has been reanalysed for the reconstruction of detailed vp and vs images an improved tomography method based on an accurate traveltime computation is applied to invert simultaneously delayed p and s first arrival traveltimes for both velocity and hypocentre parameters we perform different synthetic tests to analyse the sensitivity of tomography results to the model parametrization and to the starting 1 d model selection the analysis of the retrieved vp and vs models as well as deduced vp vs and vp vs images allows us to interpret and delineate the distribution of lithological variation porosity crack content and fluid saturation in the upper 9 11 km of the crust beneath the gulf the tomographic models image a rather complex crustal structure which is characterized by a vertical change in both velocity features and seismicity distribution we identify a shallower zone of the crust 0 5 km depth in which velocity distributions seem to be controlled by the still active n s extensional regime and a deeper zone 7 11 km depth which matches the seismogenic zone the correlation between this latter and a specific unit of the hellenic mountain structure the pyllite quartzite series allows us to suggest a possible explanation for seismicity concentration in a narrow band at 7 9 km depth finally the occurrence of clusters showing low angle normal fault mechanisms in areas characterized by high vp vs values indicates a possible role of fluids in triggering brittle creep along the identified low angle normal faults

seismic imaging of a fluid storage in the actively extending apennine mountain belt southern italy a picture of the upper crustal structure of the irpinia active faults system in southern italy was obtained by combining new geological evidences lithological properties and microseismicity distribution p and s wave velocity models indicate high vp vs and low vp vs values suggesting fluid accumulation within a 15 km wide rock volume where intense microseismicity is located the 1980 irpinia ms 6 9 earthquake nucleated within the same fault bounded volume we suggest that concentration of background seismicity is mainly controlled by high pore fluid pressure its increase in fluid filled cracks around major faults leads to earthquakes nucleation seismic pumping along major faults carries fluids through the conduit system represented by the intensely fractured damage zone conversely the cross fault barrier behavior of the low permeability fault core leads to pore fluid pressures building up within the fault bounded block thus producing a positive feedback triggering earthquake nucleation within the volume which behaves as an earthquake reservoir

fault delineation and regional stress direction from the analysis of background microseismicity in the southern apennines italy abstract the present active faults and stress field acting in the southern apennines italy a structurally complex area characterized by high seismic potential are studied by analyzing the background microseismicity m 3 we used a microearthquake data set consisting of 1312 events that occurred from august 2005 to april 2011 by integrating the data recorded at 42 seismic stations of various networks the refined seismicity locations and focal mechanisms delineate a system of northwest southeast striking normal faults along the apenninic chain and an approximately east west oriented strike slip fault transversely cutting the belt the seismicity along the chain does not occur on a single fault but in a volume delimited by the faults activated during the 1980 irpinia m 6 9 earthquake on subparallel predominantly normal faults results show that the recent low magnitude earthquakes belong to the background seismicity and they are likely generated along the major fault segments activated during the most recent earthquakes suggesting that they are still active today 30 years after the mainshock occurrences the stress inversion from the whole data set suggests that a unique anti apenninic extensional regional stress field could explain the two different faulting styles characterizing the earthquakes that occur along the chain and the east west fault dissecting the belt on the other hand the results obtained by separately inverting the irpinia and the potenza clusters indicate a more complex model that would predict a change from a normal faulting regime acting in the inner sector of the chain to a strike slip regime moving eastward and down depth in the potenza area online material seismicity maps and focal mechanisms

a downscaling strategy from fwi to microscale reservoir properties from high resolution images abstract extracting detailed earth information from an ensemble of seismic traces is a challenge facing full waveform inversion so far success on synthetic and real data has been accomplished primarily for the twin purposes of complex structural imaging and geologic interpretation an ongoing issue for the seismic imaging community in addition to building high resolution images is the reliable extraction of acoustic and shear velocities anisotropic parameters quality factors and density such extractions performed at the seismic resolution scale should help greatly with quantitative interpretation and estimation of rock properties a step toward this goal is described here a generic rock physics model is assumed which upscales microscale rock physics properties to mesoscale effective medium poroelastic quantities to be recovered from macroscale estimates of seismic attributes it is shown on simple synthetic examples that quantitative multiparameter reconstruction when it is possible can re

attenuation models qp and qs in three dimensions of the southern california crust inferred fluid saturation at seismogenic depths we analyze high dynamic range waveform spectra to determine t values for both p and s waves from earthquakes in southern california we invert the t values for three dimensional 3 d frequency independent q p and q s regional models of the crust the models have 15 km horizontal grid spacing and an average vertical grid spacing of 4 km down to 22 km depth and extend from the u s mexico border to the coast ranges in the south and sierra nevada in the north in general qp and qs increase rapidly with depth consistent with crustal densities and velocities the 3 d q p and q s models image the major tectonic structures and to a much lesser extent the thermal structure of the southern california crust the near surface low q p and q s zones coincide with major sedimentary basins such as the san bernardino chino san gabriel valley los angeles ventura and santa maria basins and the salton trough in contrast at shallow depths beneath the peninsular ranges southern mojave desert and southern sierras we image high q p and q s zones which correspond to the dense and high velocity rocks of the mountain ranges several clear transition zones of rapidly varying q p and q s coincide with major late quaternary faults and connect regions of high and low q p and q s at midcrustal depths the q p and q s exhibit modest variation in slightly higher and lower qp or qs zones which is consistent with reported crustal reflectivity in general for the southern california crust q s q p is greater than 1 0 suggesting partially fluid saturated crust a few limited regions of q s q p less than 1 0 correspond to areas mostly outside the major sedimentary basins including areas around the san jacinto fault suggesting a larger reduction in the shear modulus compared to the bulk modulus or almost complete fluid saturation

observed spectral properties of near earth objects results for population distribution source regions and space weathering processes abstract we present new visible and near infrared spectroscopic measurements for 252 near earth neo and mars crossing mc objects observed from 1994 through 2002 as a complement to the small main belt asteroid spectroscopic survey smass http smass mit edu combined with previously published smass results we have an internally consistent data set of more than 400 of these objects for investigating trends related to size orbits and dynamical history these data also provide the basis for producing a bias corrected estimate for the total neo population stuart and binzel 2004 icarus 170 295 311 we find 25 of the 26 bus 1999 phd thesis taxonomic types are represented with nearly 90 of the objects falling within the broad s q x and c complexes rare a and e types are more common in the mc than neo population about 5 compared to 3 orbits in terms of possible space weathering effects we see a size dependent transition from ordinary chondrite like q type objects to s type asteroids over the size range of 0 1 to 5 km where the transition is effectively complete at 5 km a match between the average surface age of 5 km asteroids and the rate of space weathering could constrain models for both processes however space weathering may proceed at a very rapid rate compared with collisional timescales in this case the presence or absence of a regolith may be the determining factor for whether or not an object appears space weathered thus 0 1 to 5 km appears to be a critical size range for understanding the processes timescales and conditions under which a regolith conducive to space weathering is generated retained and refreshed

the irpinia italy 1980 earthquake detailed analysis of a complex normal faulting a detailed analysis of near source strong motion and leveling data together with the results of teleseismic waveform modeling by westaway and jackson 1987 and aftershock studies by deschamps and king 1984 allows a satisfactory kinematic description of the complex normal faulting associated with the magnitude ms 6 9 november 23 1980 irpinia earthquake southern italy the three main rupture episodes starting at about 0 20 and 40 s are here associated with better constrained source parameters than in previous studies we first evaluated the triggering time for the 11 closest accelerometers by using the well recorded 40 s strong motion phases this gave the absolute time and location of the dominant episodes of faulting the first rupture propagated mainly toward the northwest on a ne dipping normal fault at a mean velocity close to 3 km s for about 20 km and continued 15 km further on smaller subfaults it was associated with surface breakage in the southeastern part the second rupture started from the southeastern end of the first rupture about 18 s after it and propagated about 20 km toward the southeast on a low angle normal fault dipping 20 ne it was associated with secondary faulting on steeper planes reaching the surface the third and last episode at 39 s nucleated near the first hypocenter at shallower depth and the rupture possibly propagated on a 10 to 15 km long normal fault striking se antithetic to the first activated fault a clear correlation appears between the strength of the geological formations and the existence of surface breakage and shallow aftershock activity

three dimensional velocity structure in northern california coast ranges from inversion of local earthquake arrival times abstract the three dimensional p wave velocity structure in the upper crust in the northern california coast ranges from santa rosa to ukiah is obtained by simultaneous inversion of local earthquake and refraction travel time data for velocity and hypocentral parameters in this region where there are lateral heterogeneities the three dimensional inversion provides important results not found in two dimensional refraction studies the medium is parameterized with velocities at the intersections gridpoints of a nonuniform three dimensional grid travel times are calculated with approximate ray tracing along arcuate paths which are reasonable for lateral distances less than 45 km inversions with 5 to 10 and 2 to 3 km gridspacing achieved 80 per cent decreases in data variance the inversion with 2 to 3 km gridspacing reduced the rms residual level to approximately the level of timing error anomalously low velocities to at least 6 km depth are found along the maacama and healdsburg rodgers creek hrc fault zones the low velocity region is widest at the en echelon junction of the maacama and hrc fault zones low velocities are associated with the clear lake basin where there is a thick sequence of volcanics interbedded with sedimentary deposits there is a high velocity body located southeast of the geysers between the maacama and collayomi fault zones which may be associated with igneous intrusives or high grade metamorphism related to an underlying inferred partial melt body modeled in previous teleseismic travel time studies there is some indication in the vapor dominated geothermal reservoir of lower velocities relative to surrounding water saturated rock as has been shown in some laboratory experiments hypocenter locations obtained in the inversion show little variation from hypocenters obtained through inversion for one dimensional velocity model and station corrections for the inversion with 2 to 3 km gridspacing however some groups of events become more tightly clustered

the taxonomic distribution of asteroids from multi filter all sky photometric surveys abstract the distribution of asteroids across the main belt has been studied for decades to understand the current compositional distribution and what that tells us about the formation and evolution of our solar system all sky surveys now provide orders of magnitude more data than targeted surveys we present a method to bias correct the asteroid population observed in the sloan digital sky survey sdss according to size distance and albedo we taxonomically classify this dataset consistent with the bus and binzel bus s j binzel r p 2002 icarus 158 146 177 and bus demeo et al demeo f e binzel r p slivan s m bus s j 2009 icarus 202 july 160 180 systems and present the resulting taxonomic distribution the dataset includes asteroids as small as 5 km a factor of three in diameter smaller than in previous work such as by mothe diniz et al mothe diniz t carvano j m a lazzaro d 2003 icarus 162 march 10 21 because of the wide range of sizes in our sample we present the distribution by number surface area volume and mass whereas previous work was exclusively by number while the distribution by number is a useful quantity and has been used for decades these additional quantities provide new insights into the distribution of total material we find evidence for d types in the inner main belt where they are unexpected according to dynamical models of implantation of bodies from the outer solar system into the inner solar system during planetary migration levison h f bottke w f gounelle m morbidelli a nesvorn d tsiganis k 2009 nature 460 july 364 366 we find no evidence of s types or other unexpected classes among trojans and hildas albeit a bias favoring such a detection finally we estimate for the first time the total amount of material of each class in the inner solar system the main belt s most massive classes are c b p v and s in decreasing order excluding the four most massive asteroids 1 ceres 2 pallas 4 vesta and 10 hygiea that heavily skew the values primitive material c p types account for more than half main belt and trojan asteroids by mass most of the remaining mass being in the s types all the other classes are minor contributors to the material between mars and jupiter

from velocity and attenuation tomography to rock physical modeling inferences on fluid driven earthquake processes at the irpinia fault system in southern italy we retrieve 3 d attenuation images of the crustal volume embedding the fault system associated with the destructive ms 6 9 1980 irpinia earthquake by tomographic inversion of t measurements a high qp anomaly is found to be correlated with the 1980 fault geometry while the qs model shows regional scale variations related to the ne edge of the uplifted pre tertiary limestone an upscaling strategy is used to infer rock properties such as porosity consolidation type of fluid mixing and relative saturation percentage at 8 10 km fault depth we constrain the porosity and consolidation in the ranges 4 5 and 5 9 respectively with the possible fluid mixes being both brine co2 and ch4 co2 the consolidation parameter range indicates high pore pressures at the same depths these results support the evidence for a fracture system highly saturated in gases and a seismicity triggering mechanism at the fault zone which is strongly controlled by fluid induced pore pressure changes

three dimensional p velocity structure in the region of the ms 6 9 irpinia italy normal faulting earthquake abstract we have calculated the three dimensional velocity structure in the epicentral region of the 1980 irpinia southern italy earthquake using thurber s inversion technique for hypocenter and velocity parameters particular care was given to the evaluation of the resolution of the models because of the poor reading accuracy of the analog stations operating at that time we analyzed the averaging vector for each node of the model in order to estimate the degree of smearing within the final tomographic image this approach is suitable for determining the best parametrization to use i e the minimum grid spacing and for evaluating the region where the computed velocities are meaningful the results show that the main rupture occurred along a sharp nw se trending velocity contrast which probably reflects a crustal discontinuity the velocity variations along the fault probably due to lithological heterogeneities account for the complex character of this earthquake based on the velocity distribution at depth the secondary rupture that started about 40 s after the mainshock is interpreted to be the result of reactivation of an old thrust as a normal fault

accretion rates of meteorites and cosmic dust in the early ordovician abundant fossil meteorites in marine condensed lower ordovician limestones from kinnekulle sweden indicate that accretion rates of meteorites were one to two orders of magnitude higher during an interval of the early ordovician than at present osmium isotope and iridium analyses of whole rock limestone indicate a coeval enhancement of one order of magnitude in the influx rate of cosmic dust enhanced accretion of cosmic matter may be related to the disruption of the l chondrite parent body around 500 million years ago

relationship of e type apollo asteroid 3103 1982 bb to the enstatite achondrite meteorites and the hungaria asteroids visible and near infrared observations confirm that apollo asteroid 3103 1982 bb has a reflectance spectrum consistent with its previous assignment to taxonomic type e it has been generally believed that the e type asteroids are analogous and perhaps even genetically related to the enstatite achondrite meteorites aubrites correlated variations of previously published visible and thermal infrared lightcurves and the lack of rotational color variations in the present data indicate that this is an elongated object with no substantial surface albedo variations apollo asteroid 3103 1982 bb is presently in an orbital resonance 3 5 with earth and appears to be a relatively long lived member of the earthapproaching population its orbit is consistent with both the fall dates and long cosmic ray exposure ages of the aubrites combined with the rarity of e type asteroids in the near earth asteroid population this indicates that 3103 1982 bb is probably either a major or the primary immediate source body of the aubrites the aphelion location and the mineralogy of 3103 1982 bb indicate that it was most probably derived from the hungaria region at the innermost edge 1 9 au of the asteroid belt although the exact dynamical mechanism for producing its present orbit is not clear these results represent the first plausible direct link of a set of meteorites aubrites or enstatite achondrites back to a particular source region in the asteroid belt this link allows the composition of the solar nebula to be constrained at that heliocentric distance during the time interval when the parent assemblage of the aubrites was isolated from contact with the nebular gas by accretion into its parent planetesimal 1992 academic press inc

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

high calcium pyroxene as an indicator of igneous differentiation in asteroids and meteorites our analyses of high quality spectra of several s type asteroids 17 thetis 847 agnia 808 merxia and members of the agnia and merxia families reveal that they include both low and highcalcium pyroxene with minor amounts of olivine 0 4 high calcium pyroxene is a spectrally detectable and petrologically important indicator of igneous history and may prove critical in future studies aimed at understanding the history of asteroidal bodies the silicate mineralogy inferred for thetis and the merxia and agnia family members requires that these asteroids experienced igneous differentiation producing broadly basaltic surface lithologies together with 4 vesta and its smaller vestoid family members and the main belt asteroid 1489 magnya these new asteroids provide strong evidence for igneous differentiation of at least five asteroid parent bodies based on this analysis of a small subset of the near infrared asteroid spectra taken to date with spex at the nasa irtf we expect that the number of known differentiated asteroids will increase consistent with the large number of parent bodies inferred from studies of iron meteorites

source parameter scaling and radiation efficiency of microearthquakes along the irpinia fault zone in southern apennines italy we analyzed the p and s wave displacement spectra of 717 microearthquakes in the moment range 4 109 2 1014 n m recorded at the dense networks operating in southern apennines italy and deployed along the 1980 ms 6 9 irpinia earthquake fault zone source attenuation and site parameters are estimated by using a parametric modeling approach which is combined with a multistep nonlinear inversion strategy we found that in the analyzed frequency band an attenuation model with constant q has to be preferred to frequency dependent q models consistent estimates of the median p and s quality factors q p 167 90 296 and q s 226 114 417 are obtained from two different techniques and relatively high values of qs qp median value 1 3 0 8 2 1 are found in the same depth range where high vp vs and a peak in seismicity distribution are observed this is the evidence for a highly fractured partially or completely fluid saturated medium embedding the irpinia fault zone down to crustal depths of 15 20 km a nearly constant stress drop 1 4mpa 0 4 5 0 and apparent stress a 0 1mpa 0 03 0 4 scaling of p and s corner frequencies and seismic energies is observed above a seismic moment value of about 1011 n m the measured radiation efficiency is low sw 0 06 0 030 13 e g the radiated energy is only a small fraction of the whole energy spent by friction and fracture development a large positive dynamic overshoot high dynamic shear strength can be the dominant mechanism controlling the microearthquake fractures along the irpinia fault zone

the meteorite asteroid connection two olivine rich asteroids two asteroids have clear indications of olivine rich surface petrology without any indication of pyroxene or plagioclase suggesting that the olivine may be quite pure they provide probable examples of mantles of differentiated parent asteroids exposed by fragmentation and are good candidates for the parent bodies of the unusual olivine meteorite brachina or the olivine iron alloy meteorites called pallasites

squirt flow in fully saturated rocks we estimate velocity frequency dispersion and attenuation in fully saturated rocks by employing the squirt flow mechanism of solid fluid interaction in this model pore fluid is squeezed from thin soft cracks into the surrounding large pores information about the compliance of these soft cracks at low confining pressures is extracted from high pressure velocity data the frequency dependence of squirt induced pressure in the soft cracks is linked with the porosity and permeability of the soft pore space and the characteristic squirt flow length these unknown parameters are combined into one expression that is assumed to be a fundamental rock property that does not depend on frequency the appropriate value of this expression for a given rock can be found by matching our theoretical predictions with the experimental measurements of attenuation or velocity the low frequency velocity limits as given by our model are identical to those predicted by gassmann s formula the high frequency limits may sign

soil gas distribution in the main coseismic surface rupture zone of the 1980 ms 6 9 irpinia earthquake southern italy soil gas measurements of different gas species with different geochemical behaviors were performed in the area of the pecore plain a 200 m 300 m sized fault bounded extensional basin located in the northern mount marzano massif in the axial belt of the southern apennine chain the pecore plain area was affected by coseismic surface faulting during the ms 6 9 1980 irpinia earthquake the strongest and most destructive seismic event of the last 30 years in southern italy the collected data and their geostatistical analysis provide new insights into the control exerted by active fault segments on deep seated gas migration toward the surface the results define anomalies that are aligned with the nw se trending coseismic rupture of the 1980 earthquake along the western border of the plain as well as along the southern border of the plain where a hidden e w striking fault is inferred geospatial analysis highlights an anisotropic spatial behavior of 222rn along the main nw se trend and of co2 along the e w trend this feature suggests a correlation between the shape and orientation of the anomalies and the barrier conduit behavior of fault zones in the area furthermore our results show that gas migration through brittle deformation zones occurs by advective processes as suggested by the relatively high migration rate needed to obtain anomalies of short lived 222rn in the soil pores

mercury and other iron rich planetary bodies as relics of inefficient accretion unlike the other terrestrial planets mercury has a relatively thin silicate mantle numerical and statistical models suggest that mercury and other metallic planetary bodies could be survivors of accretion that had their mantles stripped in collisions with larger impactors

evidence for a dynamo in the main group pallasite parent body understanding the origin of pallasites stony iron meteorites made mainly of olivine crystals and feni metal has been a vexing problem since their discovery here we show that pallasite olivines host minute magnetic inclusions that have favorable magnetic recording properties our paleointensity measurements indicate strong paleomagnetic fields suggesting dynamo action in the pallasite parent body we use these data and thermal modeling to suggest that some pallasites formed when liquid feni from the core of an impactor was injected as dikes into the shallow mantle of a 200 kilometer radius protoplanet the protoplanet remained intact for at least several tens of millions of years after the olivine metal mixing event

chondrites as samples of differentiated planetesimals abstract chondritic meteorites are unmelted and variably metamorphosed aggregates of the earliest solids of the solar system the variety of metamorphic textures in chondrites motivated the onion shell model in which chondrites originated at varying depths within a parent body heated primarily by the short lived radioisotope 26 al with the highest metamorphic grade originating nearest the center allende and a few other chondrites possess a unidirectional magnetization that can be best explained by a core dynamo on their parent body indicating internal melting and differentiation here we show that a parent body that accreted to 200 km in radius by 1 5 ma after the formation of calcium aluminum rich inclusions cais would have a differentiated interior and ongoing accretion would add a solid undifferentiated crust overlying a differentiated interior consistent with formational and evolutionary constraints inferred for the cv parent body this body could have produced a magnetic field lasting more than 10 ma this hypothesis represents a new model for the origin of some chondrites presenting them as the unprocessed crusts of internally differentiated early planetesimals such bodies may exist in the asteroid belt today the shapes and masses of the two largest asteroids 1 ceres and 2 pallas can be consistent with differentiated interiors conceivably with small iron cores with hydrated silicate or ice silicate mantles covered with undifferentiated crusts

high precision differential earthquake location in 3 d models evidence for a rheological barrier controlling the microseismicity at the irpinia fault zone in southern apennines

seismological studies at parkfield i simultaneous inversion for velocity structure and hypocenters using cubic b splines parameterization a model for the 3d p and s wave velocity structure at parkfield has been developed by the systematic inversion of arrival times for microearthquakes and surface vibroseis sources recorded by nearby calnet stations and by the local borehole installed 10 station high resolution seismic network there a modification of the linear b splines model parameterization method of thurber 1983 to a cubic b splines formulation through tests inverting synthetic data sets for the parkfield configuration is found to produce smooth velocity distributions that still retain some small scale features application of the method to 953 p wave and 288 s wave arrivals from 111 microearthquakes and 8 vibroseis locations throughout the study area yields a velocity structure having variable resolution a low velocity zone appears to coincide with the creeping segment of the san andreas fault zone northwest of the 1966 parkfield earthquake epicenter an increase of about 15 per cent in seismic velocities is seen from the northeast to southwest across this segment of the fault zone the higher velocities to the southwest apparently correspond to the granitic basement the contrast across the fault is subdued to the southeast along the 1966 rupture zone a high vp vs ratio of 1 9 is seen in a 2 km wide volume near the location of the 1966 main shock hypocenter presumably the nucleation zone for the expected m 6 parkfield earthquake

olivine dominated asteroids and meteorites distinguishing nebular and igneous histories melting models indicate that the composition and abundance of olivine systematically co vary and are therefore excellent petrologic indicators however heliocentric distance and thus surface temperature has a significant effect on the spectra of olivine rich asteroids we show that composition and temperature complexly interact spectrally and must be simultaneously taken into account in order to infer olivine composition accurately we find that most 7 9 of the olivine dominated asteroids are magnesian and thus likely sampled mantles differentiated from ordinary chondrite sources e g pallasites however two other olivine rich asteroids 289 nenetta and 246 asporina are found to be more ferroan melting models show that partial melting cannot produce olivine rich residues that are more ferroan than the chondrite precursor from which they formed thus even moderately ferroan olivine must have non ordinary chondrite origins and therefore likely originate from oxidized r chondrites or melts thereof which reflect variations in nebular composition within the asteroid belt this is consistent with the meteoritic record in which r chondrites and brachinites are rare relative to pallasites