high resolution velocity structure beneath mount vesuvius from seismic array data 1 a high resolution p wave image of mt vesuvius edifice has been derived from simultaneous inversion of travel times and hypocentral parameters of local earthquakes land based shots and small aperture array data the results give details down to 300 500 m the relocated local seismicity appears to extend down to 5 km below the central crater distributed in a major cluster centered at 3 km below the central crater and in a minor group with diffuse hypocenters inside the volcanic edifice the two clusters are separated by an anomalously high vp region at around 1 km depth a zone with high vp vs in the upper layers is interpreted as produced by the presence of intense fluid circulation the highest energy quakes up to m 3 6 are located in the deeper cluster in a high p wave velocity zone our results favor an interpretation in terms of absence of shallow magma reservoirs

joint inversion for vp vs and vp vs at safod parkfield california we refined the three dimensional 3 d vp vs and vp vs models around the san andreas fault observatory at depth safod site using a new double difference dd seismic tomography code tomoddps that simultaneously solves for earthquake locations and all three velocity models using both absolute and differential p s and s p times this new method is able to provide a more robust vp vs model than that from the original dd tomography code tomodd obtained simply by dividing vp by vs for the new inversion waveform cross correlation times for earthquakes from 2001 to 2002 were also used in addition to arrival times from earthquakes and explosions in the region the vp values extracted from the model along the safod trajectory match well with the borehole log data providing in situ confirmation of our results similar to previous tomographic studies the 3 d structure around parkfield is dominated by the velocity contrast across the san andreas fault saf in both the vp and vs models there is a clear low velocity zone as deep as 7 km along the saf trace compatible with the findings from fault zone guided waves there is a high vp vs anomaly zone on the southwest side of the saf trace that is about 1 2 km wide and extends as deep as 4 km which is interpreted to be due to fluids and fractures in the package of sedimentary rocks abutting the salinian basement rock to the southwest the relocated earthquakes align beneath the northeast edge of this high vp vs zone we carried out a 2 d correlation analysis for an existing resistivity model and the corresponding profiles through our model yielding a classification that distinguishes several major lithologies

tomographic imaging of seismic velocity structure in and around the onikobe volcanic area northeastern japan implications for fluid distribution abstract we estimated three dimensional p vp and s wave velocity vs and vp vs structures in and around the onikobe volcanic area northeastern japan by local travel time tomography we used travel time data from source and receiver pairs located within and outside the study area which plays an important role in obtaining the optimum ray coverage and in elucidating the deeper structure more accurately detailed information on deeper structures is essential for imaging the complete volcanic system from the magmatic source zone through areas of shallow hydrothermal circulation more than 50 000 travel time data for the p waves and 35 000 for the s waves were used to image the velocity structure our results show the following dominant features 1 two conduits in the upper crust with low vp and low vs indicative of h2o rich fluid pathways one lying beneath naruko volcano the other beneath the focal area of the 1962 northern miyagi earthquake m6 5 2 an underlying broad region in the lower crust with low vp low vs and high vp vs suggestive of a zone of partial melt from which the fluids in 1 are derived and 3 low vp vs areas near the surface of the sanzugawa and onikobe calderas suggesting a diffuse vapor saturated cap

experimental measurements of seismic attenuation in microfractured sedimentary rock ultrasonic compressional and shear wave attenuation in water saturated carrara marble increase with increasing crack density and decreasing effective pressure between 0 4 and 1 0 mhz empirical linear relationships between 1 q and crack density cd were found to be cd 1 96 or 0 63 x 1 q for compressional waves andcd 6 7 or 1 5 x 1 q for shear waves

upper mantle structure in the south central chilean subduction zone 30 to 36 s 1 regional p and s wave travel time data were used to obtain three dimensional seismic tomography models for vp vs and vp vs above the subducting slab in central chile and argentina in this region there is an abrupt change from a normal subduction geometry south of 33 s to a flat subduction geometry to the north we find low vp low vs and high vp vs ratios in the southern half of our study area directly beneath the modern active volcanic arc which we interpret as localized pockets of melt in the northern half of our study area above where the subducting nazca plate flattens at 100 km depth we find low vp high vs and low vp vs ratios these unusual results point to a lack of melt or hydrated mineralogies such as serpentine both of which are characterized by high vp vs values the only mantle rocks that have low vp vs and high vs are mg rich compositions such as dehydrated serpentinite or orthopyroxenite we suggest that significant portions of the mantle overlying the flat slab consist of orthopyroxenite formed by a transient fluxing of silica rich fluids such fluids may have come from sediments that were subducted during the initiation of flat subduction at this latitude at 10 ma this would imply that the hydration of mantle material above a flat slab can be a transient phenomenon which leaves little residual free water behind but significantly alters the mantle chemistry

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

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

three dimensional seismic velocity structure and earthquake relocations at katmai alaska abstract we invert arrival time data from local earthquakes occurring between september 2004 and may 2009 to determine the three dimensional 3d upper crustal seismic structure in the katmai volcanic region waveforms for the study come from the alaska volcano observatory s permanent network of 20 seismic stations in the area predominantly single component short period instruments plus a densely spaced temporary array of 11 broadband 3 component stations the absolute and relative arrival times are used in a double difference seismic tomography inversion to solve for 3d p and s wave velocity models for an area encompassing the main volcanic centers the relocated hypocenters provide insight into the geometry of seismogenic structures in the area revealing clustering of events into four distinct zones associated with martin mageik trident novarupta and mount katmai the seismic activity extends from about sea level to 2 km depth all depths referenced to mean sea level beneath martin is concentrated near 2 km depth beneath mageik and lies mainly between 2 and 4 km depth below katmai and trident novarupta many new features are apparent within these earthquake clusters in particular linear features are visible within all clusters some associated with swarm activity including an observation of earthquake migration near trident in 2008 the final velocity model reveals a possible zone of magma storage beneath mageik but there is no clear evidence for magma beneath the katmai novarupta area where the 1912 eruptive activity occurred suggesting that the storage zone for that eruption may have largely been evacuated or remnant magma has solidified

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

three dimensional vp vs variations for the coso region california recent seismological studies of the coso region of southeastern california document both low p wave velocities and abnormal sv attenuation in indian wells valley south of the pleistocene volcanics of the coso range in order to learn more about the physical nature of these colocated anomalies a tomographic inversion for the three dimensional variations of vp vs the ratio of compressional to shear velocity was performed iterative back projection of 2966 shear and compressional wave travel time residuals from local earthquakes recorded on vertical instruments reveals that vp vs is generally high at the surface and decreases systematically to 10 km depth superimposed on this trend are several large anomalies near devil s kitchen in the coso geothermal area vp vs values are very low near the surface consistent with measured values for steam dominated geothermal systems abnormally high values of vp vs are observed in portions of indian wells valley and also below the cactus peak rhyolite dome from 2 to 5 km in depth in indian wells valley the co occurrence of low p velocities low s velocities high vp vs and anomalous sv attenuation are indicative of subsurface partial melt because the inversion is based on vertical data only however the results cannot be considered conclusive only suggestive

the augustine magmatic system as revealed by seismic tomography and relocated earthquake hypocenters from 1994 through 2009 1 we incorporate 14 years of earthquake data from the alaska volcano observatory with data from a 1975 controlled source seismic experiment to obtain the three dimensional p and s wave velocity structure and the first high precision earthquake locations at augustine volcano to be calculated in a fully three dimensional velocity model velocity tomography shows two main features beneath augustine a narrow high velocity column beneath the summit extending from 2 km depth to the surface and elevated velocities on the south flank our relocation results allow a thorough analysis of the spatio temoral patterns of seismicity and the relationship to the magmatic and eruptive activity background seismicity is centered beneath the summit at an average depth of 0 6 km above sea level in the weeks leading to the january 2006 eruption of augustine seismicity focused on a nw se line along the trend of an inflating dike a series of drumbeat earthquakes occurred in the early weeks of the eruption indicating further magma transport through the same dike system during the six months following the onset of the eruption the otherwise quiescent region 1 to 5 km below sea level centered beneath the summit became seismically active with two groups of earthquakes differentiated by frequency content the deep longer period earthquakes occurred during the eruption and are interpreted as resulting from the movement of magma toward the summit and the post eruptive shorter period earthquakes may be due to the relaxation of an emptied magma tube the seismicity subsequently returned to its normal background rates and patterns

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

seismic image of the mount spurr magmatic system the three dimensional p wave velocity structure of mount spurr is determined to depths of 10 km by tomographic inversion of 3 754 first arriving p wave times from local earthquakes recorded by a permanent network of 11 seismographs results show a prominent low velocity zone extending from the surface to 3 4 km below sea level beneath the southeastern flank of crater peak spatially coincident with a geothermal system p wave velocities in this low velocity zone are approximately 20 slower than those in the shallow crystalline basement rocks beneath crater peak an approximately 3 km wide zone of relative low velocities correlates with a near vertical band of seismicity suggestive of a magmatic conduit no large low velocity zone indicative of a magma chamber occurs within the upper 10 km of the crust these observations are consistent with petrologic and geochemical studies suggesting that crater peak magmas originate in the lower crust or upper mantle and have a short residence time in the shallow crust earthquakes relocated using the three dimensional velocity structure correlate well with surface geology and other geophysical observations thus they provide additional constraints on the kinematics of the mount spurr magmatic system

preeruptive inflation and surface interferometric coherence characteristics revealed by satellite radar interferometry at makushin volcano alaska 1993 2000 1 pilot reports in january 1995 and geologic field observations from the summer of 1996 indicate that a relatively small explosive eruption of makushin one of the more frequently active volcanoes in the aleutian arc of alaska occurred on 30 january 1995 several independent radar interferograms that each span the time period from october 1993 to september 1995 show evidence of 7 cm of uplift centered on the volcano s east flank which we interpret as preeruptive inflation of a 7 km deep magma source v 0 022 km3 subsequent interferograms for 1995 2000 a period that included no reported eruptive activity show no evidence of additional ground deformation interferometric coherence at c band is found to persist for 3 years or more on lava flow and other rocky surfaces covered with short grass and sparsely distributed tall grass and for at least 1 year on most pyroclastic deposits on lava flow and rocky surfaces with dense tall grass and on alluvium coherence lasts for a few months snow and ice surfaces lose coherence within a few days this extended timeframe of coherence over a variety of surface materials makes c band radar interferometry an effective tool for studying volcano deformation in alaska and other similar high latitude regions

three dimensional p wave velocity structure derived from local earthquakes at the katmai group of volcanoes alaska abstract the three dimensional p wave velocity structure beneath the katmai group of volcanoes is determined by inversion of more than 10 000 rays from over 1000 earthquakes recorded on a local 18 station short period network between september 1996 and may 2001 the inversion is well constrained from sea level to about 6 km below sea level and encompasses all of the katmai volcanoes martin mageik trident griggs novarupta snowy and katmai caldera the inversion reduced the average rms travel time error from 0 22 s for locations from the standard one dimensional model to 0 13 s for the best three dimensional model the final model from the 6th inversion step reveals a prominent low velocity zone 3 6 5 0 km s centered at katmai pass and extending from mageik to trident volcanoes the anomaly has values about 20 25 slower than velocities outboard of the region 5 0 6 5 km s moderately low velocities 4 5 6 0 km s are observed along the volcanic axis between martin and katmai caldera griggs volcano located about 10 km behind northwest of the volcanic axis has unremarkable velocities 5 0 5 7 km s compared to non volcanic regions the highest velocities are observed between snowy and griggs volcanoes 5 5 6 5 km s relocated hypocenters for the best 3 d model are shifted significantly relative to the standard model with clusters of seismicity at martin volcano shifting systematically deeper by about 1 km to depths of 0 to 4 km below sea level hypocenters for the katmai caldera are more tightly clustered relocating beneath the 1912 scarp walls the relocated hypocenters allow us to compare spatial frequency size distributions b values using one dimensional and three dimensional models we find that the distribution of b is significantly changed for martin volcano which was characterized by variable values 0 8 b b b b b b values indicating the robustness of the observations the strong high b value region at mageik volcano is mainly associated with an earthquake swarm in october 1996 that possibly indicates a shallow intrusion or influx of gas the new velocity and spatial b value results in conjunction with prior gravity bouguer anomalies up to 40 mgal and interferometry several cm uplift data provide strong evidence in favor of partially molten rock at shallow depths beneath the mageik katmai novarupta region moderately low velocities beneath martin and katmai suggest that old mostly solidified intrusions exist beneath these volcanoes higher relative velocities beneath the griggs and snowy vents suggest that no magma is resident in the shallow crust beneath these volcanoes

high resolution 3 d p wave attenuation structure of the new madrid seismic zone using local earthquake tomography a three dimensional 3 d high resolution p wave seismic attenuation model for the new madrid seismic zone nmsz is determined using p wave path attenuation t values of small magnitude earthquakes md 3 9 events were recorded at 89 broadband and short period seismometers of the cooperative new madrid seismic zone network and 40 short period seismometers of the portable array for numerical data acquisition experiment the amplitude spectra of all the earthquakes are simultaneously inverted for source path t and site parameters the t values are inverted for qp using local earthquake tomography methods and a known 3 d p wave velocity model for the region the four major seismicity arms of the nmsz exhibit reduced qp higher attenuation than the surrounding crust the highest attenuation anomalies coincide with areas of previously reported high swarm activity attributed to fluid rich fractures along the southeast extension of the reelfoot fault the qp results are consistent with previous attenuation studies in the region which showed that active fault zones and fractured crust in the nmsz are highly attenuating

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

observations of deep long period dlp seismic events beneath aleutian arc volcanoes 1989 2002 abstract between october 12 1989 and december 31 2002 the alaska volcano observatory avo located 162 deep long period dlp events beneath 11 volcanic centers in the aleutian arc these events generally occur at mid to lower crustal depths 10 45 km and are characterized by emergent phases extended codas and a strong spectral peak between 1 0 and 3 0 hz observed wave velocities and particle motions indicate that the dominant phases are p and s waves dlp epicenters often extend over broad areas 5 20 km surrounding the active volcanoes the average reduced displacement of aleutian dlps is 26 5 cm2 and the largest event has a reduced displacement of 589 cm2 or ml 2 5 aleutian dlp events occur both as solitary events and as sequences of events with several occurring over a period of 1 30 min within the sequences individual dlps are often separated by lower amplitude volcanic tremor with a similar spectral character occasionally volcano tectonic earthquakes that locate at similar depths are contained within the dlp sequences at most aleutian volcanoes dlps appear to loosely surround the main volcanic vent and occur as part of background seismicity a likely explanation is that they reflect a relatively steady state process of magma ascent over broad areas in the lower and middle portions of the crust at mount spurr dlp seismicity was initiated by the 1992 eruptions and then slowly declined until 1997 at shishaldin volcano a short lived increase in dlp seismicity occurred about 10 months prior to the april 19 1999 eruption these observations suggest a link between eruptive activity and magma flux in the mid to lower crust and uppermost mantle

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

seismic observations of redoubt volcano alaska 1989 2010 and a conceptual model of the redoubt magmatic system abstract seismic activity at redoubt volcano alaska has been closely monitored since 1989 by a network of five to ten seismometers within 22 km of the volcano s summit major eruptions occurred in 1989 1990 and 2009 and were characterized by large volcanic explosions episodes of lava dome growth and failure pyroclastic flows and lahars seismic features of the 1989 1990 eruption were 1 weak precursory tremor and a short 23 hour long intense swarm of repetitive shallow long period lp events centered 1 4 km below the crater floor 2 shallow volcano tectonic vt and hybrid earthquakes that separated early episodes of dome growth 3 13 additional swarms of lp events at shallow depths precursory to many of the 25 explosions that occurred over the more than 128 day duration of eruptive activity and 4 a persistent cluster of vt earthquakes at 6 to 9 km depth in contrast the 2009 eruption was preceded by a pronounced increase in deep lp dlp events at lower crustal depths 25 to 38 km that began in mid december 2008 two months of discontinuous shallow volcanic tremor that started on january 23 2009 a strong phreatic explosion on march 15 and a 58 hour long swarm of repetitive shallow lp events the 2009 eruption consisted of at least 23 major explosions between march 23 and april 5 again accompanied by shallow vt earthquakes several episodes of shallow repetitive lp events and dome growth continuing until mid july increased vt earthquakes at 4 to 9 km depth began slowly in early april possibly defining a mid crustal magma source zone magmatic processes associated with the 2009 eruption seismically activated the same portions of the redoubt magmatic system as the 1989 1990 eruption although the time scales and intensity vary considerably among the two eruptions the occurrence of precursory dlp events suggests that the 2009 eruption may have involved the rise of magma from lower crustal depths based on the evolution of seismicity during the 1989 1990 and 2009 eruptions the redoubt magmatic system is envisioned to consist of a shallow system of cracks extending 1 to 2 km below the crater floor a magma storage or source region at roughly 3 to 9 km depth and a diffuse magma source region at 25 to 38 km depth close tracking of seismic activity allowed the alaska volcano observatory to successfully issue warnings prior to many of the hazardous explosive events that occurred in 2009

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