active high resolution compressional wave attenuation tomography at newberry volcano central cascade range in this study we use the seismic data from a previous study at newberry to compute its three dimensional compressional wave attenuation structure the data consist of eight explosions recorded on an array of about 120 seismograph stations the shots are located on two concentric circles centered on the caldera with radii of 39 and 85 km attenuation is estimated using spectral ratios to compute t at each station for each shot the data are inverted using a least squares technique our results indicate that regions of inferred boiling water i e two phase pore fluid are correlated spatially with regions of high attenuation not corresponding to low velocities two regions are of particular interest one is underneath the newberry ii drill hole in the central part of the caldera where results from a flow test suggest that two phase fluid conditions existed in the bottom of the hole before the flow test the other region is beneath the west flank of the volcano which has been interpreted as an attractive geothermal prospect because of a shallow conductive anomaly our results are consistent with the suggestion made in an earlier paper by us that two phase geothermal reservoirs can be located within complex three dimensional structures by using jointly interpreted compressional wave velocity and attenuation images

reanalysis of s to p amplitude ratios for gross attenuation structure long valley caldera california because of the strong interest in the magmatism and volcanism at long valley caldera eastern california and because of recent significant improvements in our knowledge of the caldera velocity structure and earthquake locations i have reanalyzed the local earthquake s to p amplitude ratio data of sanders 1984 for the gross three dimensional attenuation structure of the upper 10 km of long valley caldera the primary goals of the analysis are to provide more accurate constraints on the depths of the attenuation anomalies using improved knowledge of the ray locations and an objective inversion procedure the new image of the high s wave attenuation anomaly in the west central caldera suggests that the top of the principal anomaly is at 7 km depth which is 2 km deeper than previously determined because of poor resolution in much of the region some of the data remain unsatisfied by the final attenuation model this unmodeled data may imply unresolved attenuation anomalies perhaps small anomalies in the kilometer or two just above the central caldera anomaly and perhaps a larger anomaly at about 7 km depth in the northwest caldera or somewhere beneath the mono craters the central caldera s wave attenuation anomaly has a location similar to mapped regions of low teleseismic p wave velocity crustal inflation reduced density and aseismicity strongly suggesting magmatic association

an efficient algorithm for double difference tomography and location in heterogeneous media with an application to the kilauea volcano 1 improving our understanding of crustal processes requires a better knowledge of the geometry and the position of geological bodies in this study we have designed a method based upon double difference relocation and tomography to image as accurately as possible a heterogeneous medium containing seismogenic objects our approach consisted not only of incorporating double difference in tomography but also partly in revisiting tomographic schemes for choosing accurate and stable numerical strategies adapted to the use of cross spectral time delays we used a finite difference solution to the eikonal equation for travel time computation and a tarantola valette approach for both the classical and double difference three dimensional tomographic inversion to find accurate earthquake locations and seismic velocity estimates we estimated efficiently the square root of the inverse model s covariance matrix in the case of a gaussian correlation function it allows the use of correlation length and a priori model variance criteria to determine the optimal solution double difference relocation of similar earthquakes is performed in the optimal velocity model making absolute and relative locations less biased by the velocity model double difference tomography is achieved by using high accuracy time delay measurements these algorithms have been applied to earthquake data recorded in the vicinity of kilauea and mauna loa volcanoes for imaging the volcanic structures stable and detailed velocity models are obtained the regional tomography unambiguously highlights the structure of the island of hawaii and the double difference tomography shows a detailed image of the southern kilauea caldera upper east rift zone magmatic complex

volcano tectonic implications of 3 d velocity structures derived from joint active and passive source tomography of the island of hawaii 1 we present a velocity model of the onshore and offshore regions around the southern part of the island of hawaii including southern mauna kea southeastern hualalai and the active volcanoes of mauna loa and kilauea and loihi seamount the velocity model was inverted from about 200 000 first arrival traveltime picks of earthquakes and air gun shots recorded at the hawaiian volcano observatory hvo reconstructed volcanic structures of the island provide us with an improved understanding of the volcano tectonic evolution of hawaiian volcanoes and their interactions the summits and upper rift zones of the active volcanoes are characterized by high velocity materials correlated with intrusive magma cumulates these high velocity materials often do not extend the full lengths of the rift zones suggesting that rift zone intrusions may be spatially limited seismicity tends to be localized seaward of the most active intrusive bodies low velocity materials beneath parts of the active rift zones of kilauea and mauna loa suggest discontinuous rift zone intrusives possibly due to the presence of a preexisting volcanic edifice e g along mauna loa beneath kilauea s southwest rift zone or alternatively removal of high velocity materials by large scale landsliding e g along mauna loa s western flank both locations also show increased seismicity that may result from edifice interactions or reactivation of buried faults new high velocity regions are recognized and suggest the presence of buried and in some cases previously unknown rift zones within the northwest flank of mauna loa and the south flanks of mauna loa hualalai and mauna kea

a reinterpretation of seismicity associated with the january 1983 dike intrusion at kilauea volcano hawaii in january 1983 a dike intrusion fissure eruption generated a swarm of 375 magnitude 1 to 3 earthquakes along a 16 km segment of kilauea s middle east rift zone we searched the hawaiian volcano observatory catalog for multiplets of similar events from this region from 1980 through 1985 and obtained precise relative locations by waveform cross correlation over 150 of the intrusion earthquakes could be grouped into 14 multiplets of five or more events with sufficient similarity for accurate relocation some multiplets were active for only a few minutes during the downrift migration phase of the seismic swarm consistent with generation near the propagating dike tip while others were active for several days the two multiplets nearest the origin of the seismic swarm include events from the preceding days and months most multiplets span only 50 to 100 m following relocation are located at about 3 to 4 km depth and appear to deepen downrift the catalog depths of those earthquakes in multiplets and those not in multiplets are similar suggesting that most of the recorded seismicity may have come from a very limited depth interval despite the fact that the dike breached the surface by analogy with a mechanical model used to explain a similar clustering of background seismicity in the upper east rift in 1991 we infer that the earthquakes are generated in regions of high stress concentration immediately above kilauea s deforming deep rift body this conclusion is consistent with the depth of the top of the deep rift body inferred from geodetic data and with numerical calculations suggesting that a significant ambient differential stress is required for dikes to produce earthquakes larger than magnitude 1

cooling induced strain localization in carbonate mylonites within a large scale shear zone glarus thrust switzerland abstract the glarus thrust switzerland offers a great field example of strain localization under retrograde conditions along the thrust mylonitic microfabrics are characterized by a temperature stress controlled balance of grain size reducing mechanisms and grain growth consequently mean grain sizes decrease along the thrust with decreasing metamorphic conditions and towards the thrust contact in an opposite manner calcite twin densities increase towards the contact cpos are strongest between 0 5 and 15 m away from the thrust but become generally weaker in the last centimeters where also cataclasites occur the cpo weakening and grain size reduction towards the shear zone point to a change from predominant dislocation creep to granular flow finally ending in cataclastic deformation the microfabric changes correlate with a decrease in 13c and 18o towards the thrust contact indicating the presence of fluids during cycles of brittle and plastic deformation based on the microfabric changes variations in stable isotopes and cross cut relationships a subdivision into a low and high temperature shear zone can be made the microfabric modifications resulted from changes in deformation conditions due to ongoing thrusting and exhumation induced cooling promoting further strain localization of an existing high strain shear zone

seismological evidence for magmatic and hydrothermal structure in long valley caldera from local earthquake attenuation and velocity tomography we compare the results of six different tomographic inversions for the three dimensional seismic attenuation and velocity structure in long valley caldera california in order to constrain interpretations on the location and character of magmatic and geothermal structure in the caldera crust p and s wave amplitudes and arrival times obtained in previous studies from seismograms of local earthquakes recorded on vertical and three component seismographis were inverted for q sv 1 q sh 1 q s 1 q p 1 and v p v s in the upper 9 km of teh caldera crust detailed comparisons of the results of the inversions suggest significant locations of high temperatures and perhaps magma and hydrothermal zones in the caldera a region of low q s with locally variable q p and v p v s is imaged in the 7 9 km depth range beneath the resurgent dome overlying and adjacent to this anomaly are significant low q p and low v p v s anomalies as well as smaller zones of low q s and high v p v s together these suggest zones of high temperature magma below and adjacent to zones of supercritical hydrothermal fluids at 4 5 km depth along the southern rim of the caldera just east of mammoth mountain a significant anomaly with relatively low q p and relatively low v p v s is imaged and is interpreted as a supercritical hydrothermal zone poorly resolved relatively low q p and relatively high v p v s are seen at 4 5 km depth beneath the inyo craters suggesting possible high temperatures and perhaps magma because of lack of data in the individual inversions the resultant images have spatially variable error and resolution however by comparing multiple images of different seismic parameters we have improved our ability to determine the significance of an constrain interpretation of seismic structure anomalies

a california statewide three dimensional seismic velocity model from both absolute and differential times abstract we obtain a seismic velocity model of the california crust and uppermost mantle using a regional scale double difference tomography algorithm we begin by using absolute arrival time picks to solve for a coarse three dimensional 3d p velocity v p model with a uniform 30 km horizontal node spacing which we then use as the starting model for a finer scale inversion using double difference tomography applied to absolute and differential pick times for computational reasons we split the state into 5 subregions with a grid spacing of 10 to 20 km and assemble our final statewide v p model by stitching together these local models we also solve for a statewide s wave model using s picks from both the southern california seismic network and usarray assuming a starting model based on the v p results and a v p v s ratio of 1 732 our new model has improved areal coverage compared with previous models extending 570 km in the sw ne direction and 1320 km in the nw se direction it also extends to greater depth due to the inclusion of substantial data at large epicentral distances our v p model generally agrees with previous separate regional models for northern and southern california but we also observe some new features such as high velocity anomalies at shallow depths in the klamath mountains and mount shasta area somewhat slow velocities in the northern coast ranges and slow anomalies beneath the sierra nevada at midcrustal and greater depths this model can be applied to a variety of regional scale studies in california such as developing a unified statewide earthquake location catalog and performing regional waveform modeling

frequency dependent lg q within the continental united states frequency dependent crustal attenuation 1 q is determined for seven distinct physiographic tectonic regions of the continental united states using high quality lg waveforms recorded on broadband stations in the frequency band 0 5 to 16 hz lg attenuation is determined from time domain amplitude measurements in one octave frequency bands centered on the frequencies 0 75 1 0 3 0 6 0 and 12 0 hz modeling errors are determined using a delete j jackknife resampling technique the frequency dependent quality factor is modeled in the form of q q 0 f regions were initially selected based on tectonic provinces but were eventually limited and adjusted to maximize ray path coverage in each area earthquake data was recorded on several different networks and constrained to events occurring within the crust m b 3 5 in size a singular value decomposition inversion technique was applied to the data to simultaneously solve for source and receiver terms along with q for each region at specific frequencies the lowest crustal q was observed in northern and southern california where q is described by the functions q 152 37 f 0 72 0 16 and q 105 26 f 0 67 0 16 respectively the basin and range province pacific northwest and rocky mountain states also display lower q and a strong frequency dependence characterized by the functions q 200 40 f 0 68 0 12 q 152 49 f 0 76 0 18 and q 166 37 f 0 61 0 14 respectively in contrast in the central and northeast united states q functions are q 640 225 f 0 344 0 22 and q 650 143 f 0 36 0 14 respectively show a high crustal q and a weaker frequency dependence these results improve upon previous lg modeling by subdividing the united states into smaller distinct tectonic regions and using significantly more data that provide improved constraints on frequency dependent attenuation and errors a detailed attenuation map of the continental united states can provide significant input into hazard map mitigation both scattering and intrinsic attenuation mechanisms are likely to play a comparable role in the frequency range considered in the study

comparative velocity structure of active hawaiian volcanoes from 3 d onshore offshore seismic tomography abstract we present a 3 d p wave velocity model of the combined subaerial and submarine portions of the southeastern part of the island of hawaii based on first arrival seismic tomography of marine airgun shots recorded by the onland seismic network our model shows that high velocity materials 6 5 7 0 km s lie beneath kilauea s summit koae fault zone and the upper southwest rift zone swrz and upper and middle east rift zone erz indicative of magma cumulates within the volcanic edifice a separate high velocity body of 6 5 6 9 km s within kilauea s lower erz and upper puna ridge suggests a distinct body of magma cumulates possibly connected to the summit magma cumulates at depth the two cumulate bodies within kilauea s erz may have undergone separate ductile flow seaward influencing the submarine morphology of kilauea s south flank low velocities 5 0 6 3 km s seaward of kilauea s hilina fault zone and along mauna loa s seaward facing kao iki fault zone are attributed to thick piles of volcaniclastic sediments deposited on the submarine flanks loihi seamount shows high velocity anomalies beneath the summit and along the rift zones similar to the interpreted magma cumulates below mauna loa and kilauea volcanoes and a low velocity anomaly beneath the oceanic crust probably indicative of melt within the upper mantle around kilauea s submarine flank a high velocity anomaly beneath the outer bench suggests the presence of an ancient seamount that may obstruct outward spreading of the flank mauna loa s southeast flank is also marked by a large anomalously high velocity feature 7 0 7 4 km s interpreted to define an inactive buried volcanic rift zone which might provide a new explanation for the westward migration of mauna loa s current swrz and the growth of kilauea s swrz

p wave attenuation of the yellowstone caldera from three dimensional inversion of spectral decay using explosion source seismic data using explosion source seismic refraction data recorded in the 1978 and 1980 yellowstone snake river plain seismic experiments a three dimensional inversion of differential p wave attenuation was used to assess the relative variations in q 1 in and around the volcanically active 45 km by 70 km yellowstone caldera northwestern wyoming differential attenuation was derived from spectral decay of upper crustal pg phases observed from six explosions and recorded at 90 temporary stations because of the relatively short time windows used to determine the spectral content a maximum entropy technique was employed to estimate the spectra that yielded an optimally small variance differential p wave attenuation was calculated from least squares determinations of the spectral ratios corrected for source and path effects the observed differential attenuation parameters were then inverted using a weighted least squares technique for a discretized 70 105 km three dimensional surface and upper crustal q 1 model of the yellowstone caldera and surrounding region results showed that the surface layer to depths of 2 km within the yellowstone caldera is characterized by relatively high attenuation with low q values less than 30 compared to values of 38 to 50 outside the caldera the higher attenuation in the caldera s surface layer is thought to be associated with quaternary lake sediments highly altered rhyolites and the possible influence of steam in areas of hydrothermal activity in the crystalline upper crust at depths of 2 km to 12 km q values of 40 to 70 were observed in areas of thick sedimentary fill northwest of the caldera and in areas of hydrothermal activity within the caldera upper crustal attenuation generally corresponded to q of 200 in areas that are interpreted to be associated with hot but now solidified granitic material in comparison relatively high attenuation q 40 was observed in the upper crust of the northeastern yellowstone caldera in an area that also corresponds to a 20 reduction in pg velocity a prominent negative bouguer gravity low of 20 mgal near yellowstone s largest area of hydrothermal activity and near a quaternary volcanic resurgent dome on the basis of constitutive models of velocity and density this zone of high attenuation is likely a product of unusual hydrothermal activity highly altered upper crustal rocks a shallow magmatic source or a highly porous steam saturated body outside the caldera the upper crust is relatively unaffected by high temperatures and thermal alteration and the corresponding attenuation is low with q values greater than 200

location and size of the shallow magma reservoir beneath kīlauea caldera constraints from near source vp vs ratios we present high resolution compressional wave to shear wave velocity ratios vp vs beneath k lauea s summit caldera by applying an in situ estimation method using waveform cross correlation data for three similar earthquake clusters we observe high vp vs ratios 1 832 and 1 852 for two event clusters surrounded by the low background vp vs value of 1 412 at 2 1 km depth below the surface these high and low vp vs ratios can be explained by melt and co2 filled cracks respectively based on a theoretical crack model the event cluster with the highest vp vs ratio consists of long period events that followed the 1997 east rift zone eruption indicating their association with fluid and magma movement the depths of the two clusters with high vp vs ratios are consistent with the magma reservoir location inferred from geodetic observations their locations east and north of halema uma u crater suggest a horizontal extent of a few kilometers for the reservoir

sensitivities of seismic velocities to temperature pressure and composition in the lower mantle we calculated temperature pressure and compositional sensitivities of seismic velocities in the lower mantle using latest mineral physics data the compositional variable refers to the volume proportion of perovskite in a simplified perovskite magnesiowustite mantle assemblage the novelty of our approach is the exploration of a reasonable range of input parameters which enter the lower mantle extrapolations this leads to realistic error bars on the sensitivities temperature variations can be inferred throughout the lower mantle within a good degree of precision contrary to the uppermost mantle modest compositional changes in the lower mantle can be detected by seismic tomography with a larger uncertainty though a likely trade off between temperature and composition will be largely determined by uncertainties in tomography itself given current sources of uncertainties on recent data anelastic contributions to the temperature sensitivities calculated using karato s approach appear less significant than previously thought recent seismological determinations of the ratio of relative s to p velocity heterogeneity can be entirely explain by thermal effects although isolated spots beneath africa and the central pacific in the lowermost mantle may ask for a compositional origin 2001 elsevier science b v all rights reserved

inversion for p and s wave attenuation structure long valley caldera california p and s wave amplitude data from digital three component seismograms of local earthquakes recorded on a temporary seismic array have been used to tomographically invert for the three dimensional attenuation structure in the upper crust of long valley caldera california differential attenuation q 1 values are obtained through the use of a spectral ratio technique that minimizes the site effect on the spectral ratios the spectral ratios are inverted for q 1 using the lsqr algorithm zones of high positive p wave q 1 greater p wave attenuation are observed at a depth of 4 5 km beneath the east flank of mammoth mountain and at 6 8 km beneath the southwestern edge of the resurgent dome a region of positive s wave q 1 is seen at 7 8 km beneath the southern edge of the resurgent dome whereas at 6 7 km the s wave results are near average the region of positive s wave q 1 at 7 8 km beneath the resurgent dome may indicate the roof of a magmatic system the positive p wave q 1 at 4 5 km beneath mammoth mountain and 6 8 km beneath the resurgent dome may be due to the presence of a compressible fluid such as supercritical water these zones may represent some of the source regions for the long valley geothermal system

mechanical and microstructural development of carrara marble with pre existing strain variation abstract a series of two stage torsion experiments on carrara marble were conducted to constrain the influence of known prior deformation on rheological response and microstructural evolution comparison with previous experimental data on carrara marble flow and fabric evolution during single stage torsion deformation experiments provided direct insights into the significance of initial deformation at various conditions our experiments were conducted at 727 c temperature and 300 mpa confining pressure while maintaining a constant strain rate of 3 10 4 s 1 on the periphery of the cylindrical samples under these conditions the marble is known to deform in power law n 6 10 ductile flow all torsion experiments were performed with a paterson type gas medium testing machine equipped with a torsion actuator module prior d1 and subsequent d2 deformation are accomplished by two torsion experiments in sequence on same sample segments the effect of d1 strain history is investigated during d2 by applying counter clockwise torsion to a sandwich sample consisting of three segments with different d1 rotation sense d2 samples experienced continued first and reversed shearing deformation in top centre and bottom segments respectively d2 bulk strain was chosen equal to d1 strain in top and bottom segments d1 experiments followed the typical single stage deformation behaviour of carrara marble under the applied experimental conditions yielding was followed by strain hardening until a peak stress was reached at a shear strain around 1 after which work softening occurred weakening gradually evolved into a constant stress regime during hardening a shear microstructure and crystallographic preferred orientation cpo developed afterwards the volume fraction of smaller dynamic recrystallised grains increased continuously resulting in a recrystallisation microstructure and cpo at shear strains of 5 and higher the new d2 experiments displayed a strain variation between homogeneously deformed sample segments that increased with increasing d1 strain the stress strain behaviour of the d2 bulk sandwich samples showed less pronounced work hardening and softening when compared with single stage deformation experiments furthermore constant flow stress was attained at increasingly lower strain with increasing d1 strain in most d2 segments fabric development is equivalent to single stage experiments at corresponding absolute strain the fabrics differed markedly from those in single stage experiments in the case of reversed two stage deformation at moderate strain d1 shear strain 1 and 2 6 experiments show that grain shape by shearing of relict grains is defined by finite strain and thus affected by strain reversal recrystallisation is controlled by absolute strain and not influenced by strain reversal

seismic attenuation beneath northeastern japan constraints on mantle dynamics and arc magmatism we apply a three step approach to estimate three dimensional 3 d p wave attenuation qp 1 structure beneath northeastern japan first corner frequencies of earthquakes are determined using the spectral ratio method for s coda waves then whole path attenuation terms t and site amplification factors are simultaneously estimated by a joint inversion the set of t is finally inverted for 3 d attenuation structure the results show that the mantle wedge has low attenuation in the fore arc and high attenuation in the back arc a depth profile of qp 1 in the back arc mantle is explained by attenuation expected for a two dimensional 2 d thermal model with qp qs 2 and grain sizes of 1 and 3 cm however an inclined high attenuation zone observed in the back arc mantle wedge which is interpreted as an upwelling flow shows higher attenuation than that calculated from the 2 d thermal model the higher seismic attenuation is probably caused by the concentration of partial melt in the upwelling flow a combined interpretation of seismic attenuation and velocity structures further suggests that the degree of partial melt in the upwelling flow varies along the arc and that volcanoes are clustered transverse to the arc below which the upwelling flow contains a higher degree of melt these observations indicate that magmatism is controlled by a mantle wedge process that depends strongly on spatial variations in the degree of partial melt in the upwelling flow our results further imply the breakdown of hydrous minerals in a hydrous layer above the pacific plate at a depth of 120 km

creep and strain dependent microstructures of synthetic anorthite diopside aggregates abstract we investigated plastic deformation of fine grained synthetic diopside and two phase anorthite diopside aggregates in triaxial compression and torsion up to 5 temperature confining pressure and stress ranged between 950 1180 c 200 400 mpa and 5 500 mpa respectively water content of samples ranged between 0 005 0 002 and 0 075 0 025 wt h 2 o all samples deformed in linear viscous creep with a stress exponent of 1 0 0 2 the activation energy ranged between 571 53 and 290 28 kj mol depending on mineralogy and water content sample strength depended on water fugacity with an exponent of 1 55 0 25 samples deformed in torsion and coaxial compression gave similar flow laws in spite of significant differences in the corresponding microstructures scanning and transmission electron microscopy of two phase samples deformed in torsion showed phase mixing cavitation and dislocation processes we suggest that linear viscous creep of fine grained two phase aggregates involved grain boundary sliding accommodated by grain boundary diffusion and significant dislocation accommodation at high strains we also observed that cavity coalescence and microcracking led to sample failure hence dynamic instabilities may exist in high strain shear zones accommodating viscous deformation in the lower continental crust

qp structure of mount etna constraints for the physics of the plumbing system 1 in this study we present the three dimensional qp structure of the mount etna volcano italy obtained by using local earthquake data the attenuation along ray paths t computed from the high frequency decay of velocity spectra is used to reconstruct the deep structure of the volcano down to 15 km depth the tomographic images reveal two broad low qp anomalies at 0 and 3 km depth located to the south and southwest of the summit area and extending at depth to the west of a central high qp anomaly located between 6 and 15 km depth the joint analysis of p wave attenuation and velocity allows us to better constrain the physics of the plumbing system the shallow low qp anomalies are associated with high vp anomalies beneath the top of the volcano and normal low vp toward its western borders we interpret the regions of low qp and normal low vp as shallow volumes where magmatic fluids are stored conversely the low qp high vp region may indicate intensely fractured rock volumes filled by fluids surrounding the magma branches at depth the low qp anomaly defines the path of the magma ascent to the west of an extremely high qp high vp volume located beneath the southeastern side of the summit area the high qp high vp body is interpreted to be the compact solidified high density intrusive body formed by nonerupted material during past volcano activity

seismic velocity variations along the rupture zone of the 1989 loma prieta earthquake california 1 we revisit the rupture zone of the 1989 mw6 9 loma prieta earthquake central california by developing high resolution three dimensional 3 d vp and vp vs models we apply the simul2000 inversion method and algorithm to a set of composite events which have greater number of picks per event and reduced random picking errors compared with traditional master events our final p wave velocity model generally agrees with previous studies showing a high velocity body of above 6 7 km s in the southeast rupture zone of the main shock the 3 dvp vs model however has different features with low vp vs in the upper crust and high vp vs anomalies in deeper layers of the rupture zone we interpret the low vp vs at shallow depths to be granitic rocks whereas at greater depths the areas of higher vp vs around 1 725 1 75 presumably are mafic rocks the resulting 3 d velocity model was used to improve absolute locations for all local events between 1984 and 2010 in our study area we then applied a similar event cluster analysis waveform cross correlation and differential time relocation methods to improve relative event location accuracy over 88 of the seismicity falls into similar event clusters a dramatic sharpening of seismicity patterns is obtained after using these methods the medians of the relative location uncertainties calculated by using the bootstrap approach are 5 m for horizontal and 8 m for vertical differential times from cross correlation are used to estimatein situnear sourcevp vsratio within each event cluster the high resolutionvp vs method confirms the trend of the velocity variations from the tomographic results although absolute values are slightly different

stress control of deep rift intrusion at mauna loa volcano hawaii mauna loa volcano hawaii deforms by a combination of shallow dike intrusions in the rift zones and earthquakes along the base of the volcano but it is not known how the spreading is accommodated in the lower part of the volcanic edifice we present evidence from interferometric synthetic aperture radar data for secular inflation of a dike like magma body at intermediate depth in the southwest rift zone during 2002 to 2005 magma accumulation occurred in a section of the rift zone that was unclamped by previous dikes and earthquakes suggesting that stress transfer plays an important role in controlling subsurface magma accumulation

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

strain localization during high temperature creep of marble the effect of inclusions abstract the deformation of rocks in the earth s middle and lower crust is often localized in ductile shear zones to better understand the initiation and propagation of high temperature shear zones induced by the presence of structural and material heterogeneities we performed deformation experiments in the dislocation creep regime on carrara marble samples containing weak limestone or strong novaculite second phase inclusions the samples were mostly deformed in torsion at a bulk shear strain rate of 1 9 10 4 s 1 to bulk shear strains between 0 02 and 2 9 using a paterson type gas deformation apparatus at 900 c temperature and 400 mpa confining pressure at low strain twisted specimens with weak inclusions show minor strain hardening that is replaced by strain weakening at 0 1 0 2 peak shear stress at the imposed conditions is about 20 mpa which is 8 lower than the strength of intact samples strain progressively localized within the matrix with increasing bulk strain but decayed rapidly with increasing distance from the inclusion tip microstructural analysis shows twinning and recrystallization within this process zone with a strong crystallographic preferred orientation dominated by r and c slip in recrystallization induced weakening starts at local shear strain of about 1 in the process zone corresponding to a bulk shear strain of about 0 1 in contrast torsion of a sample containing strong inclusions deformed at similar stress as inclusion free samples but do not show localization the experiments demonstrate that the presence of weak heterogeneities initiates localized creep at local stress concentrations around the inclusion tips recrystallization induced grain size reduction may only locally promote grain boundary diffusion creep accordingly the bulk strength of the twisted aggregate is close to or slightly below the lower isostress strength bound determined from the flow strength and volume fraction of matrix and inclusions

the intrusive process leading to the mt etna 2001 flank eruption constraints from 3 d attenuation tomography 1 we have analyzed 291 shallow seismic events leading to the july 17 august 9 2001 flank eruption at mt etna volcano to obtain high resolution three dimensional 3 d images of seismic attenuation of p waves qp down to 2 km depth 2293 p wave spectra have been inverted for seismic attenuation to calculate t values considering a frequency independent q and a 2 type source model the 3 d tomographic images reveal an anomalous region of very low qp values between 10 and 30 located in the same place where the 2001 dike emplaced we interpret this anomaly as the effect of fluid intrusion magma rich in gas in the uppermost part of the etna volcano just before the 2001 eruption this confirms that attenuation is a physical parameter sensitive to the thermal state of crustal volumes through which seismic waves travel

thermal structure of the panama basin by analysis of seismic attenuation abstract using recordings of earthquakes on oceanic bottom seismographs and onshore stations on the coastal margins of colombia panama and ecuador we estimate attenuation parameters in the upper lithosphere of the panama basin the tomographic images of the derived coda q values are correlated with estimates of curie point depth and measured and theoretical heat flow our study reveals three tectonic domains where magmatic hydrothermal activity or lateral variations of the lithologic composition in the upper lithosphere can account for the modeled thermal structure and the anelasticity we find that the costa rica ridge and the panama fracture zone are significant tectonic features probably related to thermal anomalies detected in the study area we interpret a large and deep intrinsic attenuation anomaly as related to the heat source at the costa rica ridge and show how interactions with regional fault systems cause contrasting attenuation anomalies

seismicity and seismic structure at okmok volcano alaska abstract okmok volcano is an active volcanic caldera located on the northeastern portion of umnak island in the aleutian arc with recent eruptions in 1997 and 2008 the okmok area had 900 locatable earthquakes between 2003 and june 2008 and an additional 600 earthquakes from the beginning of the 2008 eruption to mid 2009 providing an adequate dataset for seismic tomography to image the seismic velocity structure of okmok we apply waveform cross correlation using bispectrum verification and double difference tomography to a subset of these earthquakes we also perform p wave attenuation tomography using a spectral decay technique we examine the spatio temporal characteristics of seismicity in the opening sequence of the 2008 eruption to investigate the path of magma migration during the establishment of a new eruptive vent we also incorporate the new earthquake relocations and three dimensional 3d velocity model with first motion polarities to compute focal mechanisms for selected events in the 2008 pre eruptive and eruptive periods through these techniques we obtain precise relocations a well constrained 3d p wave velocity model and a marginally resolved s wave velocity model we image a main low vp and vs anomaly directly under the caldera consisting of a shallow zone at 0 2 km depth connected to a larger deeper zone that extends to about 6 km depth we find that areas of low qp are concentrated in the central to southwestern portion of the caldera and correspond fairly well with areas of low vp we interpret the deeper part of the low velocity anomaly 4 6 km depth beneath the caldera as a magma body this is consistent with results from ambient noise tomography and suggests that previous estimates of depth to okmok s magma chamber based only on geodetic data may be too shallow the distribution of events preceding the 2008 eruption suggest that a combination of overpressure in the zone surrounding the magma chamber and the introduction of new material from below were jointly responsible for the explosive eruption magma escaping from the top of the main magma chamber likely reacted with both a smaller shallow pod of magma and groundwater on its way up below the cone d area the earthquakes in the 2008 pre eruptive and eruptive periods are found to have a mixture of strike slip oblique normal and oblique thrust mechanisms with a dominant p axis orientation that is nearly perpendicular to the regional tectonic stress this may indicate that the stresses related to magmatic activity locally dominated regional tectonic forces during this time period

three dimensional seismic velocity structure of mauna loa and kilauea volcanoes in hawaii from local seismic tomography we present a new three dimensional seismic velocity model of the crustal and upper mantle structure for mauna loa and kilauea volcanoes in hawaii our model is derived from the first arrival times of the compressional and shear waves from about 53 000 events on and near the island of hawaii between 1992 and 2009 recorded by the hawaiian volcano observatory stations the vp model generally agrees with previous studies showing high velocity anomalies near the calderas and rift zones and low velocity anomalies in the fault systems the most significant difference from previous models is in v p vs structure the high vp and high v p vs anomalies below mauna loa caldera are interpreted as mafic magmatic cumulates the observed low vp and high v p vs bodies in the kaoiki seismic zone between 5 and 15 km depth are attributed to the underlying volcaniclastic sediments the high vp and moderate to low vp vs anomalies beneath kilauea caldera can be explained by a combination of different mafic compositions likely to be olivine rich gabbro and dunite the systematically low vp and low vp vs bodies in the southeast flank of kilauea may be caused by the presence of volatiles another difference between this study and previous ones is the improved vp model resolution in deeper layers owing to the inclusion of events with large epicentral distances the new velocity model is used to relocate the seismicity of mauna loa and kilauea for improved absolute locations and ultimately to develop a high precision earthquake catalog using waveform cross correlation data 2014 american geophysical union all rights reserved

regional relief characteristics and denudation pattern of the western southern alps new zealand abstract the southern alps of new zealand are the topographic expression of active oblique continental convergence of the australian and pacific plates despite inferred high rates of tectonic and climatic forcing the pattern of differential uplift and erosion remains uncertain we use a 25 m dem to conduct a regional scale relief analysis of a 250 km long strip of the western southern alps wsa we present a preliminary map of regional erosion and denudation by overlaying mean basin relief a modelled stream power erosion index river incision rates historic landslide denudation rates and landslide density the interplay between strong tectonic and climatic forcing has led to relief production that locally attains 2 km in major catchments with mean values of 0 65 0 68 km interpolation between elevations of major catchment divides indicates potential removal of l01 103 km3 or a mean basin relief of 0 51 0 85 km in the larger catchments local relief and inferred river incision rates into bedrock are highest about 50 67 of the distance between the alpine fault and the main divide the mean regional relief variability is 0 5 km local relief valley cross sectional area and catchment width correlate moderately with catchment area and also reach maximum values between the range front and the divide hypsometric integrals show scale dependence and together with hypsometric curves are insufficient to clearly differentiate between glacial and fluvial dominated basins mean slope angle in the wsa 30 is lower where major longitudinal valleys and extensive ice cover occur and may be an insensitive measure of regional relief modal slope angle is strikingly uniform throughout the wsa 38 40 and may record adjustment to runoff and landsliding both and show non linear relationships with elevation which we attribute to dominant geomorphic process domains such as fluvial processes in low altitude valley trains surface runoff and frequent landsliding on montane hillslopes relief dampening by glaciers and rock fall avalanching on steep main divide slopes

distribution of attenuation in the kaoiki hawaii source volume estimated by inversion of p wave spectra a new method to simultaneously invert for q structure and source parameters was used on a set of 635 microearthquakes 0 9 m 2 0 in the kaoiki area of southern hawaii approximately 2800 signals were analyzed which had been recorded by 6 short period vertical seismographs at epicentral distances of a few to 10 km the hypocentral depths ranged from o to 14 km with the bulk of the sources in the 7 5 10 5 km range the hypothesis to be tested was that the source volume of the m 6 6 kaoiki main shock of november 16 1983 may be heterogeneous in attenuation distribution we assumed that the observed p wave displacement spectra could be modelled by a source spectrum with an 2 high frequency decay a single layer resonance filler to account for local site resonances and whole path attenuation along the ray path in a next step the attenuation factor q was constrained by tomographically reconstructing the three dimensional q structure for the source region and using it as starting model for a nonlinear inversion of the corner frequency the seismic moment m0 and a new q value this process was iterated until the results changed less than 0 1 and were accepted as final the average q was approximately constant and very low 105 q 115 between o and 7 km depth it increased to approximately 160 between 9 and 11 km in the depth ranges were the spatial coverage was good 3 9 km the q values in the nw part of the 1983 aftershock volume were larger by approximately 10 15 compared to those in the se part this 12 contrast correlates with other evidence for heterogeneity the nw region shows high coda q no surface faulting medium seismicity rate and medium precursory quiescence while the se region shows low coda q pervasive faulting high seismicity rate strong precursory quiescence and possibly low b values we conclude that the kaoiki source volume is strongly heterogeneous with the contrasting density of cracks controlling the difference in crustal parameters the new simultaneous inversion technique is well suited to derive detailed q structure and source parameter information from microeaithquake spectra recorded at close epicentral distances

tomographic image of p velocity structure beneath kilauea s east rift zone and south flank seismic evidence for a deep magma body we present first results from the analysis of p wave arrival time data recorded from november 11 to december 31 1999 by a temporary 29 station network installed across kilauea volcano s east rift zone erz and south flank sf on hawaii augmented by data from the permanent network of the hawaiian volcano observatory starting with the inversion result for a minimum 1d velocity model we use arrival time data from 135 local earthquakes to invert for the 3d p velocity structure the resulting tomographic image shows evidence for a deep magma body beneath the erz just east of its southward bend and a smaller magma body at about 5 km depth beneath the wnw ese trending segment of the erz we also observe a drastic change in velocities south of the hilina fault system from velocities around 5 5 km s in the west to 6 5 km s to the east

seismic attenuation above 10 hz in southern california from coda waves recorded in the cajon pass borehole we estimate the attenuation around cajon pass southern california for frequencies above 10 hz and we find total q to exhibit only weak frequency dependence ranging from 800 at 10 hz to 1500 at 100 hz the intrinsic attenuation is approximately twice the level of the scattering attenuation measurements are made using earthquake seismograms recorded at 0 3 km depth using the multiple lapse time window method the results are not dependent on receiver depth and are consistent with previous estimates of q made from direct waves recorded at 2 5 km depth our q values are therefore thought to be representative of the seismogenic crust and the technique used is uncontaminated by the highly attenuating near surface at least above 10 hz we also calculate q from surface data between 1 and 10 hz and find a clear change in the frequency dependence of both intrinsic and scattering attenuation at 10 hz q exhibits strong frequency dependence below 10 hz 1 8 consistent with previous studies in active tectonic regions and only weak frequency dependence at higher frequencies 0 34 this change in behavior renders it unwise to extrapolate q measurements outside the frequency range from which they were derived for example in earthquake source studies possible factors responsible for the apparent change in frequency dependence of q are considered further work is required however to resolve the causes of this change

resistivity structure to a depth of 5 km beneath kilauea volcano hawaii from large loop source electromagnetic measurements 0 04 8 hz a deep resistivity study of kilauea volcano using the controlled source electromagnetic csem technique has revealed that the summit region i e the area bounded by the east rift zone the southwest rift zone and the koa e fault zone consists of subhorizontal layers having resistivities ranging from 2 ohm m to greater than several hundred ohm meters the vertical sequence of resistivities is consistent with an increase in temperature from 20 c at the surface to over 1000 c at a depth of about 5 km temperatures beneath the adjacent but inactive area of mauna loa probably do not exceed 300 c at a comparable depth a deep conductor which is indicated by data at five observation locations on kilauea may be magma the source for the csem study is a horizontal wire square approximately 2 km on a side through which a sinusoidal current of about 80 a peak to peak is driven at frequencies between 0 04 and 8 hz

three dimensional velocity structure of the kilauea caldera hawaii high resolution velocity models 0 5 km resolution of the kilauea caldera region are obtained by the tomographic inversion of both p and s wave arrival times data are from the permanent hawaiian volcano observatory hvo seismic network a broadband seismic network and a temporary array of stations centered on the southern boundary of the caldera a low velocity p wave anomaly is imaged centered on the southeastern edge of the caldera with a velocity contrast of about 10 and a volume of 27 km the vp vs model mimics the spatial extent of the p wave anomaly but is partitioned into two discrete anomalous volumes centered on the southern boundary of the caldera and on the upper east rift of the volcano the corresponding poisson s ratio in these zones is high 0 25 0 32 which is consistent with a densely cracked hot volume which may contain partial melt the large scale features of the models are consistent with results obtained from an earlier larger scale 2 km resolution tomographic image of kilauea volcano based on hvo network data

seismic tomography of compressional wave velocity and attenuation structure for makushin volcano alaska abstract located in the central portion of the alaska aleutian subduction zone makushin volcano is among the most active volcanoes in the united states and has been classified as a very high threat by the national volcano early warning system based on its eruptive history and proximity to the city of unalaska and international air routes in 2015 five standalone seismic stations and three mini seismic arrays of 15 stations each were deployed on unalaska island to supplement the alaska volcano observatory permanent seismic network this temporary array was operational for one year taking advantage of the increased azimuthal coverage and the array s increased earthquake detection capability we developed body wave vp and vp vs seismic images of the velocity structure beneath the volcano our results show a complex structure with the upper 4 km of the crust the shallow high vp features possibly delineate remnant magma pathways or conduits low vp regions are found east of the caldera at approximately 4 8 km depth this is in agreement with previous seismic tomographic work and insar based geodetic models which had identified this region as a possible long term source of magma a three dimensional compressional wave attenuation model complemented the velocity models in general we observe regions of corresponding low p wave velocity and high attenuation east of the summit caldera between 5 and 7 km depth supporting the presence of a melt rich zone the absolute vp values 5 5 6 0 km s in this region are consistent with the presence of a magma body with a mafic signature we suggest that a triggering mechanism that involves mafic injections into a more evolved shallow magma chamber is representative of the current magmatic system below the volcano similarly to what petrological studies have inferred for past eruptions

regional three dimensional seismic velocity model of the crust and uppermost mantle of northern california 1 we present a three dimensional 3d tomographic model of the p wave velocity vp structure of northern california we employed a regional scale double difference tomography algorithm that incorporates a finite difference travel time calculator and spatial smoothing constraints arrival times from earthquakes and travel times from controlled source explosions recorded at network and or temporary stations were inverted for vp on a 3d grid with horizontal node spacing of 10 to 20 km and vertical node spacing of 3 to 8 km our model provides an unprecedented comprehensive view of the regional scale structure of northern california putting many previously identified features into a broader regional context and improving the resolution of a number of them and revealing a number of new features especially in the middle and lower crust that have never before been reported examples of the former include the complex subducting gorda slab a steep deeply penetrating fault beneath the sacramento river delta crustal low velocity zones beneath geysers clear lake and long valley and the high velocity ophiolite body underlying the great valley examples of the latter include mid crustal low velocity zones beneath mount shasta and north of lake tahoe

seismic evidence for a crustal magma reservoir beneath the upper east rift zone of kilauea volcano hawaii an anomalous body with low vp compressional wave velocity low vs shear wave velocity and high vp vs anomalies is observed at 8 11 km depth beneath the upper east rift zone of kilauea volcano in hawaii by simultaneous inversion of seismic velocity structure and earthquake locations we interpret this body to be a crustal magma reservoir beneath the volcanic pile similar to those widely recognized beneath mid ocean ridge volcanoes combined seismic velocity and petrophysical models suggest the presence of 10 melt in a cumulate magma mush this reservoir could have supplied the magma that intruded into the deep section of the east rift zone and caused its rapid expansion following the 1975 m7 2 kalapana earthquake

seismic detection of the summit magma complex of kilauea volcano hawaii application of simultaneous inversion of seismic p wave arrival time data to the investigation of the crust beneath kilauea volcano yields a detailed picture of the volcano s heterogeneous structure zones of anomalously high seismic velocity are found associated with the volcano s rift zones a low velocity zone at shallow depth directly beneath the caldera coincides with an aseismic region interpreted as being the locus of kilauea s summit magma complex

s wave attenuation structure in long valley caldera california from three component s to p amplitude ratio data using s to p amplitude ratios measured from three component seismograms we tomographically imaged spatial variations in s wave attenuation in parts of long valley caldera data from seismograms of local earthquakes in the long valley caldera region that occurred during 1984 were employed with the s to p amplitude ratio technique with corrections for source radiation pattern to determine q s resolution is limited throughout most of the model however significant resolution and acceptable error in parts of the model allow meaningful interpretation of the results the primary result is the image of a low q s anomaly at 7 8 km depth beneath the resurgent dome this is independent evidence for high temperatures and possible magma accumulation at this location other regions of anomalously low q s are marginally significant or poorly resolved of these low q s at 4 5 km depth beneath the inyo domes has the most potential significance the similarity of the results from the three component data and from the vertical component data implies that vertical component data which are generally more abundant can be used with confidence

imaging the crustal magma sources beneath mauna loa and kilauea volcanoes hawaii three dimensional seismic p wave traveltime tomography is used to image the magma sources beneath mauna loa and kilauea volcanoes hawaii high velocity bodies 6 4 km s in the upper 9 km of the crust beneath the summits and rift zones of the volcanoes correlate with zones of high magnetic intensities and are interpreted as solidified gabbro ultramafic cumulates from which the surface volcanism is derived the proximity of these high velocity features to the rift zones is consistent with a ridge spreading model of the volcanic flank southeast of the hilina fault zone along the south flank of kilauea low velocity material

new evidence for the serpentinization of the palaeozoic basement of southeastern sicily from joint 3 d seismic velocity and attenuation tomography

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

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

three dimensional attenuation model of the shallow hikurangi subduction zone in the raukumara peninsula new zealand 1 the material properties of the shallow subduction zone are imaged with data from a passive seismic deployment in the raukumara peninsula attenuation images are obtained using t values measured from 2848 spectra of p wave arrivals the t values are inverted for frequency independent three dimensional 3 d qp using a 3 d velocity model linked nodes in a preliminary 2 d inversion are used to obtain the most reliable initial model for 3 d inversions the results show the benefits of obtaining 3 d q in addition to 3 d vp and vp vs q is related to localized permeability and heterogeneity and thus 3 d q is an important tool for interpreting active tectonic regions qp in the shallow overlying plate generally corresponds to the mapped geology two high qp features 600 represent subducted seamounts or cretaceous volcanics within the overlying plate the gradient above the subducting plate is the strongest feature in the qp model with the slab having high qp 600 900 below 20 km depth and above the plate interface there is a zone of 50 decrease in qp and high vp vs about 10 km thick which represents actively subducting sediment and has distributed microearthquake activity associated with active underplating

three dimensional compressional wave attenuation tomography for the crust and uppermost mantle of northern and central california i present a frequency independent three dimensional 3 d compressional wave attenuation model indicated by quality factor qp for the crust and uppermost mantle of northern and central california the tomographic inversion used t values measured from amplitude spectra of 80 988 p wave arrivals of 3247 events recorded by 463 network stations through a 3 d seismic velocity model the model has a uniform horizontal grid spacing of 15 km and the vertical node intervals range between 2 and 10 km down to 45 km depth in general the resulting qp values increase with depth and agree with the surface geology at shallow depth layers the most significant features observed in the qp model are the high qp values in the sierra nevada mountains and low qp anomalies in the western fault zones low qp values are also imaged in owens valley and long valley at shallow depths and the cape mendocino region in the lower crust 25 km depth an overall contrast of qp values across the fault is observed in the creeping parkfield and cholame carrizo sections of the san andreas fault the new 3 d qp model provides an important complement to the existing regional scale velocity models for interpreting structural heterogeneity and fluid saturation of rocks in the study area

seismic velocity and attenuation structure of the east rift zone and south flank of kilauea volcano hawaii it has been proposed that a deep magma body beneath the east rift zone erz of kilauea volcano hawaii must be present in order to explain the observed deformation of the south flank from november 1999 to june 2000 29 iris passcal three component seismographs were operated across kilauea9s erz and south flank using local earthquakes recorded by these stations supplemented with data from the hawaiian volcano observatory stations we investigated the deep structure of the erz and south flank through two approaches seismic velocity tomography and seismic attenuation tomography results along two north northwest south southeast profiles are examined the western profile shows a low velocity region beneath and south of the hilina pali and earthquakes at depth are sandwiched between a high v p v s high q zone and a low v p v s low q zone the velocity and attenuation differences are interpreted to reflect the contrast in material properties between the overlying volcanic pile and the underlying fluid rich ocean sediments and fractured altered ocean crust beneath the south flank thrust fault the eastern profile shows an anomalous feature with low v p low v p v s high q p and low q s at about 7 km depth beneath the erz the low v p v s ratio is inconsistent with the presence of partial melt instead this anomaly is attributed to a trapped reservoir of co 2 our results do not support the existence of a sizable molten or partially molten body at depth beneath the erz if the deep magma body exists it must be relatively small based on synthetic resolution tests an estimated limit on the maximum allowable cross sectional size of the deep magma body is about 2 by 4 km

top down inflation and deflation at the summit of kīlauea volcano hawai i observed with insar 1 we use interferometric synthetic aperture radar insar to study deformation of the summit caldera at k lauea volcano during 2000 2008 which spanned both an east rift zone eruptive event in 2007 and the start of the ongoing summit eruption in 2008 the data set consists of small baseline subset sbas time series generated from 270 acquisitions on three separate beam modes from the radarsat 1 satellite we identify 12 time periods with distinct patterns of displacement that we attribute until late 2003 to secular tectonic driven deformation and from 2004 to 2008 to four different sources in the summit area we model the shallow magmatic system as a spherical reservoir at 1 9 0 1 km depth below the surface to the northeast of halemaumau source 1 and three vertically stacked sills at greater depths in the southern caldera area source 2 at the southern edge of the caldera at 2 9 0 2 km depth source 3 to the south southeast of the caldera at 3 4 0 5 km depth and source 4 south of the caldera at 3 6 0 4 km depth the sequence for filling of and withdrawal from these reservoirs reveals a top down process with sequences of both inflation and deflation initiating in the shallowest source inflation of source 3 is coincident with elevated seismic activity in the upper east rift zone in february 2006 and may 2007 source 4 is elongated toward the southwest rift zone and also shows elevated seismicity that extends toward the southwest rift zone

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

three dimensional compressional attenuation model qp for the salton trough southern california abstract i present a frequency independent 3d seismic attenuation model indicated by for the crust of the salton trough and the adjacent regions in southeastern southern california the simul2000 tomographic algorithm was used to invert the frequency independent attenuation operator t values measured from amplitude spectra of 23 378 p wave arrivals of 1203 events through a recently developed 3d velocity model the q p model has a uniform horizontal grid spacing of 5 km and the vertical node intervals range between 2 and 5 km down to 27 km depth in general the q p values increase with depth and agree with the surface geology in the shallow depth layers low q p values are observed in the imperial valley california which are consistent with the sedimentary deposits and may also reflect the presence of pore fluid in the active fault zones whereas greatly elevated q p values are shown in the surrounding crystalline ranges the new q p model provides an important complement to the existing velocity models for interpreting structural heterogeneity and fluid saturation of rocks in the study area online material figures of checkerboard resolution tests q p versus v p and q p versus heat flow

three dimensional seismic velocity structure and precise earthquake relocations in the salton trough southern california abstract i present a new 3d seismic velocity model and high precision earthquake relocations between 1981 and 2010 near the salton trough and the san jacinto fault zone the simul2000 tomography algorithm is applied to derive the 3d v p and v p v s models using first arrivals of a composite event data set the final v p model correlates with geological features at shallow depths and is more consistent with the refraction studies than the starting 3d regional scale model the v p v s model shows strong variations in the upper crust and is dominated by relatively low values below 1 7 in the middle crust except for the salton trough and the imperial valley the newly resolved model is used to relocate all the seismicity in the study area i then apply the similar event cluster analysis and differential time relocation approach based on waveform cross correlation data to the 3d relocated events a dramatic sharpening of seismicity patterns is obtained after using these methods the new locations are more tightly clustered than the previous catalogs mainly due to the different absolute locations the depth distribution along a basal surface may suggest the existence of a detachment fault from the north end of the salton trough to united states mexico border the fine scale velocity structure and precise earthquake relocations will be helpful for investigating the fault geometry seismicity stress interaction and other seismological studies for southern california online material figures of model resolution tests cross sectional comparisons of different p velocity models and earthquake depth distributions

magmatically triggered slow slip at kilauea volcano hawaii we demonstrate that a recent dike intrusion probably triggered a slow fault slip event sse on kilauea volcano9s mobile south flank our analysis combined models of advanced land observing satellite interferometric dike intrusion displacement maps with continuous global positioning system gps displacement vectors to show that deformation nearly identical to four previous sses at kilauea occurred at far field sites shortly after the intrusion we model stress changes because of both secular deformation and the intrusion and find that both would increase the coulomb failure stress on possible sse slip surfaces by roughly the same amount these results in concert with the observation that none of the previous sses at kilauea was directly preceded by intrusions but rather occurred during times of normal background deformation suggest that both extrinsic intrusion triggering and intrinsic secular fault creep fault processes can lead to sses

absorption band q model for the earth body wave surface wave and normal mode data are used to place constraints on the frequency dependence of q in the mantle with a simple absorption band model it is possible to satisfy the shear sensitive data over a broad frequency range the quality factor qs is proportional to in the band and to and 1 at higher and lower frequencies respectively as appropriate for a relaxation mechanism with a spectrum of relaxation times the parameters of the band are q min 80 0 15 and width 5 decades the center of the band varies from 101 seconds in the upper mantle to 1 6 103 seconds in the lower mantle the shift of the band with depth is consistent with the expected effects of temperature pressure and stress high qs regions of the mantle are attributed to a shift of the absorption band to longer periods to satisfy the gravest fundamental spheroidal modes and the scs data the absorption band must shift back into the short period seismic band at the base of the mantle this may be due to a high temperature gradient or high shear stresses a preliminary attempt is also made to specify bulk dissipation in the mantle and core specific features of the absorption band model are low q in the body wave band at both the top and the base of the mantle low q for long period body waves in the outer core an inner core qs that increases with period and low qp qs at short periods in the middle mantle the short period qs increases rapidly at 400 km and is relatively constant from this depth to 2400 km the deformational q of the earth at a period of 14 months is predicted to be 463

three dimensional velocity structure seismicity and fault structure in the parkfield region central california this study examines the three dimensional velocity structure in a 60 by 80 km region containing the parkfield segment of the san andreas fault we use local earthquake and shot p arrival times in an iterative simultaneous inversion for velocity and hypocentral parameters using the three dimensional model we relocated 5251 events that occurred from 1969 to 1991 as well as the 1966 aftershocks and computed 664 fault plane solutions the san andreas fault saf characterized by a sharp across fault velocity gradient is the primary feature in the velocity solution there is a 5 20 lateral change in velocity over a 4 km width the contrast being sharper where there is better resolution the model also shows significant variations in the velocity and in the complexity of the velocity patterns along the saf the largest across fault velocity difference is below middle mountain where a large volume of low velocity material impinges on the saf from the northeast this material is inferred to be overpressured and may be key to understanding the unusual behavior in the parkfield preparation zone a 20 km long high velocity slice is imaged northeast of the saf near gold hill its along fault length corresponds to the length of the maximum slip in 1966 the relocated seismicity shows that the san andreas fault is a planar vertical fault zone at seismogenic depths ninety percent of the fault plane solutions that are on or near the saf were right lateral strike slip on subvertical fault planes that parallel the saf thus the surface fault complexities do not appear to extend to depth and therefore do not explain the rupture character at parkfield at parkfield variations in material properties play a key role in fault segmentation and deformation style our observations suggest that there may be a general relation between increasing velocity and increasing ability of the rocks to store strain energy and release it as brittle failure

seismic tomography of compressional wave attenuation structure for kilauea volcano hawai i we present a frequency independent three dimensional 3 d compressional wave attenuation model indicated by the reciprocal of quality factor qp for kilauea volcano in hawai i we apply the simul2000 tomographic algorithm to the attenuation operator t values for the inversion of qp perturbations through a recent 3 d seismic velocity model and earthquake location catalog the t values are measured from amplitude spectra of 26708 p wave arrivals of 1036 events recorded by 61 seismic stations at the hawaiian volcanology observatory the 3 d qp model has a uniform horizontal grid spacing of 3 km and the vertical node intervals range between 2 and 10 km down to 35 km depth in general the resolved qp values increase with depth and there is a correlation between seismic activity and low qp values the area beneath the summit caldera is dominated by low qp anomalies throughout the entire resolved depth range the southwest rift zone and the east rift zone exhibit very high qp values at about 9 km depth whereas the shallow depths are characterized with low qp anomalies comparable with those in the summit area the seismic zones and fault systems generally display relatively high qp values relative to the summit the newly developed qp model provides an important complement to the existing velocity models for exploring the magmatic system and evaluating and interpreting intrinsic physical properties of the rocks in the study area

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

high resolution locations of triggered earthquakes and tomographic imaging of kilauea volcano s south flank 1 the spatiotemporal patterns of seismicity beneath kilauea s south flank give insight to the structure and geometry of the decollement on which large tsunamigenic earthquakes have occurred and its relation to slow slip events sses which have been observed every 1 to 2 years since 1997 in order to record earthquakes triggered by a sse that was predicted to occur in march 2007 a temporary network of 20 seismometers was deployed on kilauea s south flank termed the seq network while the sse did not occur until 17 june 2007 theseq network recorded over 3000 earthquakes including those triggered by the sse we relocate hypocenters of volcano tectonic earthquakes and invert for p and s wave velocity structure using waveform cross correlation and double difference tomography using data from the seq network and the permanent hawaii volcano observatory network hvo data with additional data from other previous temporary arrays the best constrained hypocenters recorded by both the seq and hvo networks indicate the decollement as a subhorizontal layer of seismicity at 8 km depth less than 1 km thick in most areas with the western portion of the decollement dipping to the southeast the seismicity triggered by the june 2007 sse includes over 400 earthquakes overlapping with the southern edge of the decollement seismicity a shallower swarm of earthquakes also occurred between 2 and 7 km depth in april 2007 near apua point and may have been indirectly triggered by the mw 8 1 solomon islands earthquake at 6000 km distance which occurred 48 h prior to the beginning of the swarm

the three dimensional structure of kilauea volcano hawaii from travel time tomography a linear travel time tomography study of the most active shield volcano of the world kilauea volcano hawaii was undertaken to determine the lateral heterogeneities produced by its intricate magmatic and tectonic environment kilauea provides an ideal setting to do tomography because of its dense seismograph array and many local earthquakes that allow excellent ray coverage of complex subsurface features local p wave data from 12 295 events were inverted using a one dimensional layered velocity model inversions were done for two cell sizes 5 5 5 km and 1 1 1 km to resolve structural regions on different length scales this study provided a view of the average velocity variations relative to a one dimensional velocity model analysis and interpretation of the tomographic images allowed us to infer the following model the main shallow magma reservoir is delineated by a slow velocity region southeast of the summit from 0 to 2 km depth there is a distinct high velocity region centered northwest of the summit from 0 to 2 km depth that represents a cap of dense intrusive dikes surrounding the magma chamber we suggest that the shallow reservoir is a narrow compartmentalized region of sills and dikes centered just south southeast of halemaumau caldera below the main reservoir the summit is imaged as a slightly fast region from 5 to 10 km in the coarse model indicating that the main conduit is structurally defined by an intrusive dike complex until about 10 km the rift zones of kilauea are imaged as major high velocity entities widening to the south with depth until 6 km these fast anomalies are related to the sheeted dike complexes along the rifts on a finer scale slow anomalies suggest the presence of magma pockets centered at 0 2 km depth beneath mauna ulu makaopuhi and puu oo along the east rift zone erz two significant high velocity regions along the lower erz near kalalua and kaliu are inferred to represent intrusive barriers to magma injection along the shallow 0 4 km erz conduit the southwest rift zone may have an intrusive barrier related to a high velocity region just southwest of mauna iki the hilina and kaoiki fault zones are imaged as slow features at shallow depths 5 km related to the open fractures and scarps along the normal faults the koae fault system is imaged as a slightly fast shallow structure 6 km possibly related to intrusive diking from the adjacent rift zones that fill and may even induce the extensional structures associated with this complex fault zone continued inversions with the immense amount of seismic data collected for hawaiian events will allow the detailed development of a three dimensional structural model for kilauea such a model will be extremely useful to seismologists and petrologists alike for understanding the tectonic growth and magmatic evolution of this dynamic shield volcano

multiple resolution seismic attenuation imaging at mt vesuvius abstract a three dimensional s wave attenuation tomography of mt vesuvius has been obtained with multiple measurements of coda normalized s wave spectra of local small magnitude earthquakes we used 6609 waveforms relative to 826 volcano tectonic earthquakes located close to the crater axis in a depth range between 1 and 4 km below the sea level recorded at seven 3 component digital seismic stations we adopted a two point ray tracing rays were traced in an high resolution 3 d velocity model the spatial resolution achieved in the attenuation tomography is comparable with that of the velocity tomography we resolve 300 m side cubic cells we statistically tested that the results are almost independent from the radiation pattern we also applied an improvement of the ordinary spectral slope method to both p and s waves assuming that the differences between the theoretical and the experimental high frequency spectral slope are only due to the attenuation effects consequently we could check the coda normalization method also comparing the s attenuation image with the p attenuation image the images were obtained inverting the spectral data with a multiple resolution approach results have shown the general coincidence of low attenuation with high velocity zones the joint interpretation of velocity and attenuation images allows us to interpret the low attenuation zone intruding toward the surface until a depth of 500 m below the sea level as related to the residual part of solidified magma from the last eruption in the depth range between 700 and 2300 images are consistent with the presence of multiple acquifer layers no evidence of magma patches greater than the minimum cell dimension 300 m has been found a shallow p wave attenuation anomaly beneath the southern flank of the volcano is consitent with the presence of gas saturated rocks the zone characterized by the maximum seismic energy release cohincides with a high attenuation and low velocity volume interpreted as a cracked medium