the accommodation of the south flank s motion by the koa e fault system kīlauea hawai i insights from the june 2012 earthquake sequence

analysis of shuttle multispectral infrared radiometer measurements of the western saudi arabian shield during the november 12 14 1981 mission of the space shuttle columbia the shuttle multispectral infrared radiometer smirr recorded radiances in ten channels along a 100 m wide groundtrack across the western saudi arabian shield the ten channels are located in the 0 5 to 2 4 m region with five positioned between 2 0 and 2 40 m for measuring absorption features that are diagnostic of oh bearing and co3 bearing minerals this exceptionally well exposed area consists of late proterozoic metamorphic intermediate to silicic intrusive and interlayered clastic sedimentary and intermediate silicic volcanic rocks that have not been studied previously using smirr data plots or traces of unnormalized smirr channel ratios were examined before field studies to locate areas with high spectral contrast especially in the 2 0 m to 2 40 m channels reflectance spectra were measured in the laboratory for rock and soil samples collected in these areas and the mineralogic causes of the main absorption features w

what are the best radar wavelengths incidence angles and polanzations for discrimination among lava flows and sedimentary rocks a statistical approach linear discriminant analysis of multifrequency and multipolarization radar scatterometer data of lava flows and sedimentary rocks indicates that the lava flows sampled at the snake river plain idaho and the sedimentary formations sampled at the san rafael swell utah can be discriminated from one another the necessary radar backscatter data and optimum wavelengths polarizations and incidence angles among those available for these problems are indicated by the discriminant analysis program for separation of the lava flows shorter wavelengths and smaller incidence angles are best for the sedimentary rocks conversely the longer wavelengths and somewhat larger incidence angles are preferred separation among the lava flows was slightly better using horizontally polarized data while vertical polarization gave better separation with the sedimentary rocks the method developed here may provide a rationale for user selection tion of operating parameters for advanced radar systems such as the shuttle imaging radar c sir c and that proposed for the earth observation system eos the analysis is being extended to other study sites for which we have scatterometer data to determine the generality of the results reported here

quiescent explosive transitions during dome forming volcanic eruptions using seismicity to probe the volcanic processes leading to the 29 july 2008 vulcanian explosion of soufriere hills volcano montserrat

deep magma body beneath the summit and rift zones of kilauea volcano hawaii a magnitude 7 2 earthquake in 1975 caused the south flank of kilauea volcano hawaii to move seaward in response to slippage along a deep fault since then a large part of the volcano s edifice has been adjusting to this perturbation the summit of kilauea extended at a rate of 0 26 meter per year until 1983 the south flank uplifted more than 0 5 meter and the axes of both the volcano s rift zones extended and subsided the summit continues to subside these ground surface motions have been remarkably steady and much more widespread than those caused by either recurrent inflation and deflation of the summit magma chamber or the episodic propagation of dikes into the rift zones kilauea s magmatic system is therefore probably deeper and more extensive than previously thought the summit and both rift zones may be underlain by a thick near vertical dike like magma system at a depth of 3 to 9 kilometers

automatic approach for increasing the location accuracy of slow moving landslide endogenous seismicity the apoloc method seismological observations offer valuable insights on the stress strain states the physical mechanisms and the possible precursory signs of activation of various earth surface processes i e volcanoes glaciers and landslides comprehensive catalogues of the endogenous landslide seismicity that is corresponding to seismic sources generated by the unstable slope from either mechanical or hydrological origins should include the typology and an estimate of the source parameters location magnitude of the event these advanced catalogues constitute a strong basis to better describe the slope deformation and its time evolution and better understand the controlling factors because the number of seismic events in landslide catalogues is generally large automatic approaches must be considered for defining both the typology and the location of the sources we propose here a new location approach called automatic picking optimization and location method apoloc for locating landslide endogenous seismic sources from seismological arrays located at close distance the approach is based on the automatic picking of the p waves arrivals by optimizing the intertrace correlations the method is tested on calibration shots realized at the super sauze landslide southeast french alps and compared to other location approaches by using a realistic velocity model obtained from a seismic tomography campaign apoloc reduces the epicentre errors to 23 m on average compared to ca 40 m for the other approaches apoloc is then applied for documenting the endogenous seismicity i e slopequakes and rockfalls at the landslide

granitic terrains viewed remotely by shuttle infrared radiometry some compositional predictions ratios of intensities of near infrared spectral bands measured in reflectance quantitatively predict the iron content of granitic rocks such data from the 1 60 and 1 05 m bands of the shuttle multispectral infrared radiometer have been used to study granitic rocks along orbits crossing baja california mexico and the eastern desert of egypt both regions are arid and relatively to essentially free of vegetation and there is no indication in the spectra that surface chemical alteration masks the true composition of the unweathered rock predicted values of iron are consistent with known compositional types of most of the rocks along the orbital paths results demonstrate that the near infrared method used is a powerful technique to average the variability of these rocks on the scales of meters to kilometers

frequency dependent site amplification factors using the s wave coda for the island of hawaii abstract the coda method has been utilized to determine the seismic response at various sites on the island of hawaii using data from the hawaiian volcano observatory hvo seismic network site amplification factors are calculated using spectral ratios of s wave coda amplitude measured for many events and lapse times between 33 and 59 sec for frequencies between 1 5 and 15 0 hz we find that these site amplification factors vary by factors of as much as 12 for a given frequency due to differences in absorption and or impedance properties beneath the site similar to results from japan central california and long valley the coda site amplification factors showed strong correlation with station residuals for magnitude determined by johnson unpublished results for the hvo network between 1 5 and 6 0 hz johnson unpublished results made an independent determination of event magnitudes and station site corrections by measuring averaged windowed amplitudes of the s wave and its coda using a method previously tested with data from the southern california seismic network johnson 1979 station calibrations were simultaneously determined and included the effects of instrument gain and site effect after correcting johnson9s unpublished results results for the instrument gain provided by hvo we obtain correlations similar to the previous works with the best correlation appearing at 3 0 hz despite the complex subsurface structures on the island of hawaii the frequency dependence of our coda site amplification factors displays a remarkable regional trend in some cases plausible causes related to the underlying geologic structures can explain the similar frequency dependence in other cases the similarity cannot be explained or may be coincidental similar frequency dependences among stations accompanied by a large variability in the absolute level of the site effect may be due to inaccurate instrument calibrations

source amplitudes of volcano seismic signals determined by the amplitude source location method as a quantitative measure of event size article i nfo the amplitude source location asl method which uses high frequency amplitudes under the assumption of isotropic s wave radiation has been shown to be useful for locating the sources of various types of volcano seismic signals we tested the asl method by using synthetic seismograms and examined the source amplitudes determined by this method for various types of volcano seismic signals observed at different volcanoes our synthetic tests indicated that although asl results are not strongly influenced by velocity structure and noise they do depend on site amplification factors at individual stations we first applied the asl method to volcano tectonic vt earthquakes at taal volcano philippines our asl results for the largest vt earthquake showed that a frequency range of 7 12 hz and a q value of 50 were appropriate for the source location determination using these values we systematically estimated source locations and amplitudes of vt earthquakes at taal we next applied the asl method to long period events at cotopaxi volcano and to explosions at tungurahua volcano in ecuador we proposed a practical approach to minimize the effects of site amplifications among different volcano seismic networks and compared the source amplitudes of these various volcano seismic events with their seismic magnitudes we found a proportional relation between seismic magnitude and the logarithm of the source amplitude the asl method can be used to de termine source locations of small events for which onset measurements are difficult and thus can estimate the sizes of events over a wider range of sizes compared with conventional hypocenter determination ap proaches previously there has been no parameter widely used to quantify the sources of volcano seismic signals this study showed that the source amplitude determined by the asl method may be a useful quan titative measure of volcano seismic event size

spatiotemporal model of kīlauea s summit magmatic system inferred from insar time series and geometry free time dependent source inversion k lauea volcano hawai i island has a complex magmatic system including summit reservoirs and rift zones kinematic models of the summit reservoir have so far been limited to first order analytical solutions with pre determined geometry to explore the complex geometry and kinematics of the summit reservoir we apply a multitrack wavelet based insar interferometric synthetic aperture radar algorithm and a novel geometry free time dependent modeling scheme to map spatiotemporally distributed surface deformation signals over k lauea s summit we process sar data sets from two overlapping tracks of the envisat satellite including 100 images during the period 2003 2010 following validation against global positioning system gps data we invert the surface deformation time series to constrain the spatiotemporal evolution of the magmatic system without any prior knowledge of the source geometry the optimum model is characterized by a spheroidal and a tube like zone of volume change beneath the summit and the southwest rift zone at 2 3 km depth respectively to reduce the model dimension we apply a principal component analysis pca scheme which allows for the identification of independent reservoirs the first 3 pcs explaining 99 63 8 28 5 and 6 6 respectively of the model include six independent reservoirs with a complex interaction suggested by temporal analysis the data and model presented here in agreement with earlier studies improve the understanding of k lauea s plumbing system through enhancing the knowledge of temporally variable magma supply storage and transport beneath the summit and verify the link between summit magmatic activity seismicity and rift intrusions

source mechanism of volcanic tremor low frequency 10 hz volcanic earthquakes originate at a wide range of depths and occur before during and after magmatic eruptions the characteristics of these earthquakes suggest that they are not typical tectonic events physically analogous processes occur in hydraulic fracturing of rock formations low frequency icequakes in temperate glaciers and autoresonance in hydroelectric power stations we propose that unsteady fluid flow in volcanic conduits is the common source mechanism of low frequency volcanic earthquakes tremor the fluid dynamic source mechanism explains low frequency earthquakes of arbitrary duration magnitude and depth of origin as unsteady flow is independent of physical properties of the fluid and conduit fluid transients occur in both low viscosity gases and high viscosity liquids a fluid transient analysis can be formulated as generally as is warranted by knowledge of the composition and physical properties of the fluid material properties geometry and roughness of the conduit and boundary conditions to demonstrate the analytical potential of the fluid dynamic theory we consider a single phase fluid a melt of mount hood andesite at 1250 c in which significant pressure and velocity variations occur only in the longitudinal direction further simplification of the conservation of mass and momentum equations presents an eigenvalue problem that is solved to determine the natural frequencies and associated damping of flow and pressure oscillations for a simple constant pressure reservoir conduit orifice fluid system a change in orifice size can cause the source signal duration due to a single disturbance to change from several seconds to in excess of an hour fluid kinematic viscosity 0 412 m2 s is both included and neglected in the analysis to illustrate its effect upon system damping tremor magnitude is related to the magnitude of the conduit wall motion occurring in response to oscillating fluid pressures the entire volcanic fluid system does not generally experience a transient flow condition at a given time closed end and constant pressure fluid system boundaries reflect pressure waves and isolate components of the fluid system total fluid movement may not be accurately monitored by tremor data alone since steady state and slowly changing flows are aseismic

monitoring velocity variations in the crust using earthquake doublets an application to the calaveras fault california we present a technique that greatly improves the precision in measuring temporal variations of crustal velocities using an earthquake doublet or pair of microearthquakes that have nearly identical waveforms and the same hypocenter and magnitude but occur on different dates we compute differences in arrival times between seismograms recorded at the same station in the freqency domain by cross correlation of short windows of signal a moving window analysis of the entire seismograms including the coda gives t the difference in arrival times versus running time along the seismogram the time resolution of the method is an order of magnitude better than the digitization interval the t technique is illustrated with a pair of microearthquakes m 1 7 and 2 0 that occurred before and after the coyote lake california earthquake m 5 9 of august 6 1979 and on the same segment of the calaveras fault that ruptured during the earthquake the coda wave arrivals for some stations are progressively delayed for the second earthquake in the doublet so that its seismogram appears as a stretched version of the earlier event we interpret this systematic variation in t along the coda as a change in the average s velocity in the upper crust in the time interval between the two doublets s wave velocities appear to have decreased by 0 2 in an oblong region 5 10 km in radius at the south end of the aftershock zone

deep fault plane geometry inferred from multiplet relative relocation beneath the south flank of kilauea dense microearthquake swarms occur in the upper south flank of kilauea providing multiplets composed of hundreds of events the similarity of their waveforms and the quality of the data have been sufficient to provide accurate relative relocations of their hypocenters a simple and efficient method has been developed which allowed the relative relocation of more than 250 events with an average precision of about 50 m horizontally and 75 m vertically relocation of these events greatly improves the definition of the seismic image of the fault that generates them indeed relative relocations define a plane dipping about 6 northward although corresponding absolute locations are widely dispersed in the swarm a composite focal mechanism built from events providing a correct spatial sampling of the multiplet also gives a well constrained northward dip of about 5 to the near horizontal plane this technique thus collapses the clouds of hypocenters of single event locations to a plane coinciding with the slip plane revealed by previous focal mechanism studies we cannot conclude that all south flank earthquakes collapse to a single plane there may locally be several planes perhaps with different dips and depths throughout the south flank volume the 6 northward dipping plane we found is too steep to represent the overall flexure of the oceanic crust under the load of the island of hawaii this plane is probably an important feature that characterizes the basal slip layer below the upper south flank of kilauea volcano differences in seismicity rate and surface deformations between the upper and lower south flank could be related to the geometry of this deep fault plane the present work illustrates how high precision relative relocations of similar events in dense swarms combined with the analysis of geodetic measurements can help to describe deep fault plane geometry systematic selection and extensive relative relocation of similar earthquakes could be attempted in other well instrumented highly seismic areas to provide reliable basic information especially useful for understanding of earthquake generation processes

seismic source mechanism of degassing bursts at kilauea volcano hawaii results from waveform inversion in the 10 50 s band the current march 2008 to february 2009 summit eruptive activity at kilauea volcano is characterized by explosive degassing bursts accompanied by very long period vlp seismic signals we model the source mechanisms of vlp signals in the 10 50 s band using data recorded for 15 bursts with a 10 station broadband network deployed in the summit caldera to determine the source centroid location and source mechanism we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous medium that takes topography into account the vlp signals associated with the bursts originate in a source region 1 km below the eastern perimeter of halemaumau pit crater the observed waveforms are well explained by the combination of a volumetric component and a vertical single force component for the volumetric component several source geometries are obtained which equally explain the observed waveforms these geometries include 1 a pipe dipping 64 to the northeast 2 two intersecting cracks including an east striking crack dike dipping 80 to the north intersecting a north striking crack another dike dipping 65 to the east 3 a pipe dipping 58 to the northeast intersecting a crack dipping 48 to the west southwest and 4 a pipe dipping 57 to the northeast intersecting a pipe dipping 58 to the west southwest using the dual crack model as reference the largest volume change obtained among the 15 bursts is 24 400 m3 and the maximum amplitude peak to peak of the force is 20 gn each burst is marked by a similar sequence of deflation and inflation trailed by decaying oscillations of the volumetric source the vertical force is initially upward synchronous with source deflation then downward synchronous with source reinflation followed by oscillations with polarity opposite to the volumetric oscillations this combination of force and volume change is attributed to pressure and momentum changes induced during a fluid dynamic source mechanism involving the ascent expansion and burst of a large slug of gas within the upper 150 m of the magma conduit as the slug expands upon approach to the surface and more liquid becomes wall supported by viscous shear forces the pressure below the slug decreases inducing conduit deflation and an upward force on the earth the final rapid slug expansion and burst stimulate vlp and lp oscillations of the conduit system which slowly decay due to viscous dissipation and elastic radiation consideration of the fluid dynamic arguments leads us to prefer the dual crack vlp source model as it is the only candidate model capable of producing plausible values of length scales and pressure changes the magnitudes of the vertical forces observed in the 15 bursts appear consistent with slug masses of 104 to 106 kg

spatial extent of a hydrothermal system at kilauea volcano hawaii determined from array analyses of shallow long period seismicity 2 results we present a probabilistic method to locate the source of seismic events using seismic antennas the method is based on a comparison of the event azimuths and slownesses derived from frequency slowness analyses of array data with a slowness vector model several slowness vector models are considered including both homogeneous and horizontally layered half spaces and also a more complex medium representing the actual topography and three dimensional velocity structure of the region under study in this latter model the slowness vector is obtained from frequency slowness analyses of synthetic signals these signals are generated using the finite difference method and include the effects of topography and velocity structure to reproduce as closely as possible the behavior of the observed wave fields a comparison of these results with those obtained with a homogeneous half space demonstrates the importance of structural and topographic effects which if ignored lead to a bias in the source location we use synthetic seismograms to test the accuracy and stability of the method and to investigate the effect of our choice of probability distributions we conclude that this location method can provide the source position of shallow events within a complex volcanic structure such as kilauea volcano with an error of 200 m

inferred attenuation from site effect corrected t phases recorded on the island of hawaii coda site amplification factors are used to eliminate the site effect from records of three circum pacifict phases recorded by the hawaiian volcano observatory hvo network on the island of hawaii observedt phase amplitudes across the island generally decrease with increasing distance from the conversion point where acoustic waves in the sofar channel become seismic waves propagating through the crust however the decay of the observedt phase signal across the island is not regular in regions of dense station coverage in particular the kilauea caldera region we divide the maximum observedt phase amplitudes at a given station by the coda site amplification factor obtained for the same station and frequency band 3 0hz the distribution of these amplitudes reveals a smooth pattern over the entire island the distance over which the site effect correctedt phase amplitude decreases by one half combined with the apparent velocity of propagation oft phases across the island allows for an approximate determination of near surfaceq over much of the island of hawaii we found a region of lowq in the kilauea summit area q 30 and east rift zone q 60 with considerably higherq in the kaoiki and northern portions of the island q 150 to 200 the lowq values obtained in the kilauea summit region and east rift zone are significantly lower than estimates of codaq in the same region suggestingt phases may be sampling the earth s near surface properties

multiplets their behavior and utility at dacitic and andesitic volcanic centers 1 multiplets or groups of earthquakes with similar waveforms are commonly observed at volcanoes particularly those exhibiting unrest using triggered seismic data from the 1980 1986 mount st helens msh eruption we have constructed a catalog of multiplet occurrence our analysis reveals that the occurrence of multiplets is related at least in part to the viscosity of the magma we also constructed catalogs of multiplet occurrence using continuous seismic data from the 2004 eruption at msh and 2007 eruption at bezymianny volcano russia prior to explosions at msh in 2004 and bezymianny in 2007 the multiplet proportion of total seismicity mpts declined while the average amplitudes and standard deviations of the average amplitude increased the life spans of multiplets time between the first and last event were also shorter prior to explosions than during passive lava extrusion dome forming eruptions that include a partially solidified plug like msh 1983 1986 and 2004 2008 often possess multiplets with longer life spans and mpts values exceeding 50 conceptually the relatively unstable environment prior to explosions is characterized by large and variable stress gradients brought about by rapidly changing overpressures within the conduit we infer that such complex stress fields affect the number of concurrent families mpts average amplitude and standard deviation of the amplitude of the multiplets we also argue that multiplet detection may be an important new monitoring tool for determining the timing of explosions and in forecasting the type of eruption

analysis of long period events recorded at mount etna italy in 1992 and their relationship to eruptive activity seismic activity recorded at mount etna during 1992 was characterized by long period lp events and tremor with fluctuating amplitudes these signals were associated with the evolution of the eruptive activity that began on december 14 1991 following the occurrence of numerous volcano tectonic earthquakes at the onset of the eruption lp events dominated the overall seismicity starting in january 1992 the lp activity occurred primarily in swarms which were temporally correlated with episodic collapses of the crater floor in the northeast crater source depths determined for selected lp events suggest a source region located slightly east of northeast crater and extending from the surface to a depth of 2000 m based on the characteristic signatures of the time series four families of lp events are identified each family shares common spectral peaks independent of azimuth and distance to the source these spectral features are used to develop a fluid filled crack model of the source we hypothesize that the locus of the lp events represents a segment of the magma feeding system connecting a depressurizing magma body with a dike extending in the sse direction along the western wall of valle del bove toward the site of the mount etna eruption we surmise that magma withdrawal from the source volume beneath northeast crater may have caused repeated collapses of the crater floor some collapse events may have produced pressure transients in the subjacent dike which acted as seismic wave sources for lp events

location of long period events below kilauea volcano using seismic amplitudes and accurate relative relocation 1 we present methods for improving the location of long period lp events deep and shallow recorded below kilauea volcano by the permanent seismic network lp events might be of particular interest to understanding eruptive processes as their source mechanism is assumed to directly involve fluid transport however it is usually difficult or impossible to locate their source using traditional arrival time methods because of emergent wave arrivals at kilauea similar lp waveform signatures suggest the existence of lp multiplets the waveform similarity suggests spatially close sources while catalog solutions using arrival time estimates are widely scattered beneath kilauea s summit caldera in order to improve estimates of absolute lp location we use the distribution of seismic amplitudes corrected for station site effects the decay of the amplitude as a function of hypocentral distance is used for inferring lp location in a second stage we use the similarity of the events to calculate their relative positions the analysis of the entire lp seismicity recorded between january 1997 and december 1999 suggests that a very large part of the lp event population both deep and shallow is generated by a small number of compact sources deep events are systematically composed of a weak high frequency onset followed by a low frequency wave train aligning the low frequency wave trains does not lead to aligning the onsets indicating the two parts of the signal are dissociated this observation favors an interpretation in terms of triggering and resonance of a magmatic conduit instead of defining fault planes the precise relocation of similar lp events based on the alignment of the high energy low frequency wave trains defines limited size volumes

littoral survey using the jers ops multispectral sensor example of the mont saint michel bay normandy france a jers 1 ops j p a anese earth renwte sensing satellite optical sensor image was used to make a method ological survey of the mont saint michel foreshore west of france the main objective was to test different procedures for processing m spectral data hetw een 520 nm and 2400 nm so as to re ne the information acquired from other sensor y such as spot xs and landsat tm w hich have a lower spectral and spatial discrimination potential the use of m spectral satellite data enables a rapid reconnaissance of the zone where both sedimen tological and morphological evolution occur according to the tides the ops sensor appears able to detect carbon ate responses channel 6 especially in suspension in the turbid plume of the estuary water jers ops distinguished clearly between clays vegetation and the eflect of phenomena likely to perturb their response mainly moisture characteri ed by channel 5

properties of the near field term and its effect on polarisation analysis and source locations of long period lp and very long period vlp seismic events at volcanoes abstract seismicity that originates within volcanic magmatic and hydrothermal plumbing systems is characterised by wavelengths that are often comparable to or longer than the source receiver distance the effect of such a near field configuration must be explored when analysing these signals herein we summarise properties of near field observations for both a single force and moment tensor seismic sources we show radiation patterns of the near intermediate and far field terms for the source types that are most likely candidates for long lp and very long period vlp volcanic seismicity including a single force compensated linear vector dipole clvd a tensile crack and a pipe like source we find that the deviation of the first motion polarisation from the radial direction is significant in all planes except one whose normal is parallel to the symmetry axis if there is one of the source mechanism however this deviation is less pronounced or even negligible when there is a considerable volumetric component in the source as in the case of a tensile crack or pipe our location test shows that the accuracy of locations obtained using the semblance or cross correlation techniques is very significantly affected by the near field geometry this effect is especially pronounced for shallow sources such as often encountered on volcanoes and decreases with increasing source depth hence in practical applications on volcanoes 3d full waveform numerical simulation including topography and structural heterogeneities should be used in order to both validate location techniques and as an interpretational aid to reduce misinterpretations of location results

seismic monitoring and modeling of an active volcano for prediction we describe seismic monitoring and modeling of an active volcano for the purpose of predicting the magma transport process in real time we selected the piton de la fournaise which has been monitored by an observatory since the early 1980s and is active with 28 eruptions from 1980 until august 1992 it erupted on march 9 1998 after an unusually long quiet period the eruption lasted until september 21 1998 before the march eruption we completed the initial construction of a model of a magma system based primarily on long period lp events and coda localization we found that lp events are associated with the lateral movement of magma to the rift zone and not with the vertical movement to the summit we also found that the source of 2 hz lp events is located below that of 1 hz lp events the coda localization is a newly discovered phenomenon that helped to locate a magma body this model was used for interpreting the incoming information from the precursory seismic crisis and the eruption tremor during the 6 months of the eruption the simultaneous monitoring and modeling of an active volcano led us to a quantitative simulation of the eruption process computing excess pressure and flow rate in a system of reservoirs connected by channels

new insights into kilauea s volcano dynamics brought by large scale relative relocation of microearthquakes 1 we investigated the microseismicity recorded in an active volcano to infer information concerning the volcano structure and long term dynamics by using relative relocations and focal mechanisms of microearthquakes there were 32 000 earthquakes of the mauna loa and kilauea volcanoes recorded by more than eight stations of the hawaiian volcano observatory seismic network between 1988 and 1999 we studied 17 000 of these events and relocated more than 70 with an accuracy ranging from 10 to 500 m about 75 of these relocated events are located in the vicinity of subhorizontal decollement planes at a depth of 8 11 km however the striking features revealed by these relocation results are steep southeast dipping fault planes working as reverse faults clearly located below the decollement plane and which intersect it if this decollement plane coincides with the pre mauna loa seafloor as hypothesized by numerous authors such reverse faults rupture the pre mauna loa oceanic crust the weight of the volcano and pressure in the magma storage system are possible causes of these ruptures fully compatible with the local stress tensor computed by gillard et al 1996 reverse faults are suspected of producing scarps revealed by kilometer long horizontal slip perpendicular lineations along the decollement surface and therefore large scale roughness asperities and normal stress variations these are capable of generating stick slip large magnitude earthquakes the spatial microseismic pattern observed in the south flank of kilauea volcano and hilina type instabilities rupture intersecting the decollement surface causing its large scale roughness may be an important parameter controlling the growth of hawaiian volcanoes

modeling the three dimensional structure of macroscopic magma transport systems application to kilauea volcano hawaii we report the results of modeling the three dimensional internal structure of kilauea s magmatic passageways the approach uses a clear plexiglass model containing equally spaced levels upon which well located seismic hypocenters are plotted application of constraining geologic and geophysical criteria to this distributed volume of earthquakes permits the interpretation of seismic structures produced by fracturing in response to locally high fluid pressures four magma transport and storage structures have been identified within and beneath kilauea 1 primary conduit the conduit transporting magma into kilauea s summit storage reservoir rises from the model base 14 6 km to the 6 5 km depth level it is a zone of intense fracturing and inferred intrusion whose horizontal sections are elliptical in planform over its height the average major axis of the component horizontal sections is 3 3 km with an average minor axis of 1 7 km this yields an aspect ratio of 0 52 at the 14 6 km level the strike of the major axis is n67 e during passage from the upper mantle through the oceanic crust this axis rotates in a right handed sense until the strike is n41 w at the 6 5 km level 2 magma chamber complex floor the interval from 6 5 to 5 7 km immediately over the primary conduit is aseismic this suggests differentially high fluid to rock ratios and relatively weak pathways for further vertical transport into higher levels of the storage complex as well as lateral leakage eastward into the mauna ulu staging area for later vertical ascent beneath the upper east rift zone seismicity within the immediately subjacent rocks that form the top of the primary conduit at 6 5 km suggests that this inferred magma rich horizon forms the effective floor of the summit storage complex 3 magma chamber crown intense seismicity over the 1 1 1 9 km depth interval defines an elliptical region in plan view the top of this region has a broad apex with an average major axis of 1 5 km and an average minor axis of 1 1 km producing an aspect ratio of 0 73 this region coincides with the epicentral position of summit vertical displacement maxima during inflationary deformation and is interpreted as a region of intense diking crowning the summit storage complex 4 upper east rift zone pipe from a depth of 5 7 km a cylindrical region of seismicity rises beneath the upper east rift zone to the 1 9 km level where it merges with the subhorizontal upper east rift zone duct this pipe like zone has a mean diameter of 1 4 km and a vertical axis that pierces the surface of the volcano at the intersection of the koae fracture system and the upper east rift zone we suggest this pipe forms a principal connection between the base of the summit storage reservoir and near surface storage compartments and ducts in the upper east rift zone in this role the pipe is suggested to have contributed heavily to mauna ulu s magma supply during 1969 1974 the model of magma transport and storage thus constructed provides a context in which other types of data e g ground deformation and electrical conductivity may be interpreted as well as a means of refining petrological inferences based on lava chemistry

the shallow structure of kīlauea caldera from high resolution bouguer gravity and total magnetic anomaly mapping insights into progressive magma reservoir growth 1 we conducted total magnetic field and bouguer gravity measurements to investigate the shallow structure beneath the summit caldera of k lauea volcano hawai i two significant and distinctive magnetic anomalies were identified within the caldera one is interpreted to be associated with a long lived prehistoric eruptive center the observatory vent located 1 km east of the hawaiian volcano observatory the second magnetic anomaly corresponds to a set of eruptive fissures that strike northeast from halema uma u crater suggesting this is an important transport pathway for magma the bouguer gravity data were inverted to produce 3 d models of density contrasts in the upper 2 km beneath k lauea the models detect 3 0 km3 of material denser than 2800 kg m 3 beneath the caldera that may represent an intrusive complex centered northeast of halema uma u recent temporal gravity studies indicate continual addition of mass beneath the caldera during 1975 2008 centered west of halema uma u and suggest this is due to filling of void space the growth of a large intrusive complex apparent cyclical caldera formation and continual mass addition without inflation however can also be explained by extensional rifting caused by the continual southward movement of k lauea s unstable south flank

evolution of the december 14 1989 precursory long period event swarm at redoubt volcano alaska abstract the intermittency pattern and evolution in waveforms of long period lp seismic events during the intense 23 h swarm that preceded the december 14 1989 eruption of redoubt volcano are investigated utilizing cross correlation to exploit the high degree of similarity among waveforms a substantially more complete event catalog is generated than was available from near realtime detection based on short term long term amplitude ratios which was saturated by the high rate of activity the temporal magnitude distribution of the predominant lp events is found to have an unusual banded structure in which the average magnitude of each band slowly increases and then decreases through time a bifurcation that appears in the uppermost band shortly after the peak in magnitudes is characterized by a quasi periodicity in intermittency and magnitude that is reminiscent of one of the classic routes to chaotic behavior in some non linear systems the waveforms of the predominant events evolve slowly but unsteadily through time these gradual changes appear to result from variations in the relative amplitudes of spectral peaks that remain stable in frequency which suggests that they are due to differential excitation of a single resonant source two other previously unrecognized repetitive waveforms are also identified but the signals from these secondary events are not clearly recorded at distances beyond the closest station similarities among the spectra of the predominant and secondary events suggest that the signals from these events also could represent different modes of exciting the same source significant changes in the rates and the sizes of the largest of these secondary events appear to coincide with the peak in the size distribution of the predominant lps at least some of the non repetitive lp waveforms in the swarm appear to be the result of the superposition of signals from the rapid repetition of predominant lp source thus placing a constraint on the repeat time of the triggering mechanism for this source a lone hybrid event which has a waveform character intermediate between the predominant lp events and high frequency volcano tectonic events was also identified in the swarm the occurrence of this event provides important evidence that the low frequency character of the lp events is a source rather than a path or site effect

characterization of scattered seismic wavefields simulated in heterogeneous media with topography 1 we performed numerical simulations of seismic waveforms with frequencies up to 10 hz in heterogeneous media with topography to investigate the effects of topography and structural heterogeneity on seismic scattering we used the simulated waveforms to test the source location method assuming isotropic radiation of s waves for long period events and tremor at volcanoes the assumption of isotropic radiation has been shown previously to be valid in a high frequency band because of the path effect caused by the scattering of seismic waves our simulation results showed that distortion of the wavefields increased as the correlation distance of structural heterogeneity a decreased as the frequency increased and as the travel distance increased topography alone considerably distorted the wavefields however we found that strong scattering due to topography was suppressed if the correlation distance of structural heterogeneity was longer than the s wave wavelength isotropic radiation of s waves by scattering due to topography was not achieved in our simulations our results indicated that scattering due to structural heterogeneity becomes stronger than that due to topography at ka 1 and a 50 m where k is the wave number of the s waves this suggests that strong short scale structural heterogeneity is required to achieve isotropic radiation of s waves although we could not reproduce isotropic radiation our results support the validity of the assumption of isotropic radiation in the source location method

recurrent slow slip events as a barrier to the northward rupture propagation of the 2016 pedernales earthquake central ecuador the northern ecuador segment of the nazca south america subduction zone shows spatially heterogeneous interseismic coupling two highly coupled zones 0 4 s 0 35 n and 0 8 n 4 0 n are separated by a low coupled area hereafter referred to as the punta galera mompiche zone pgmz large interplate earthquakes repeatedly occurred within the coupled zones in 1958 mw 7 7 and 1979 mw 8 1 for the northern patch and in 1942 mw 7 8 and 2016 mw 7 8 for the southern patch while the whole segment is thought to have rupture during the 1906 mw 8 4 8 8 great earthquake we find that during the last decade the pgmz has experienced regular and frequent seismic swarms for the best documented sequence december 2013 january 2014 a joint seismological and geodetic analysis reveals a six week long slow slip event sse associated with a seismic swarm during this period the microseismicity is organized into families of similar earthquakes spatially and temporally correlated with the evolution of the aseismic slip the moment release 3 4 1018 nm mw 6 3 over a 60 40 km area is considerably larger than the moment released by earthquakes 5 8 1015 nm mw 4 4 during the same time period in 2007 2008 a similar seismic aseismic episode occurred with higher magnitudes both for the seismic and aseismic processes cross correlation analyses of the seismic waveforms over a 15 years long period further suggest a 2 year repeat time for seismic swarms which also implies that sses recurrently affect this area such sses contribute to release the accumulated stress likely explaining why the 2016 pedernales earthquake did not propagate northward into the pgmz

theoretical basis of the amplitude source location method for volcano seismic signals the source location method using high frequency seismic amplitudes based on the assumption of isotropic radiation of s waves has been used successfully to locate seismic events and tremor at volcanoes this amplitude source location asl method overcomes the limitations of traditional hypocenter determination methods that use onset arrival times and has great potential to improve volcano seismic monitoring and the investigation of source processes of volcano seismic signals however theoretical justification of the basic assumption used in the asl method has not been provided in previous studies in this study we tested the asl method by using seismic waveforms simulated with a finite difference method in realistic heterogeneous volcanic structures with intrinsic attenuation and topography our results showed that asl determinations were successful when using waveforms characterized by multiple scattering that can be approximated by the diffusion model we found that the energy solution of the diffusion model provided an amplitude distance relation that is similar to that used in the asl method our results suggest that the asl method is applicable to high frequency seismograms in highly heterogeneous media with transport mean free paths of 103 m or smaller and strong intrinsic attenuation these medium parameters are consistent with those estimated at various volcanoes our study validates the basic assumption of the asl method and justifies its use to locate the sources of high frequency seismic signals observed at volcanoes

high precision relative locations of earthquakes at mount st helens washington several earthquake sequences have occurred at mount st helens as clusters of shallow events with nearly identical waveforms multiplets we present a technique that allows the relative relocation of events within a multiplet to at least an order of magnitude higher precision than is typically possible with traditional techniques a multiplet is studied in pairs of events called doublets each doublet is made up of a reference event and one other event from the multiplet the cross spectrum of a short window beginning just before the p arrival is used to compute differences in arrival times between seismograms from the same station for each doublet these time differences computed with a precision of 1 2 ms are then used to locate each earthquake relative to the reference event engineering explosions with well known locations are used to test the relocation technique explosions can be relocated with accuracy better than 20 m for events within 250 m of the reference explosion the relocation technique is applied to earthquakes preceding the september 10 1984 and the may june 1985 dome building eruptions of mount st helens forty events that occurred during a 12 hour period in september 1984 are located in a volume approximately 30 m in diameter beneath the lava dome the earthquakes following the extrusion do not occur in multiplets and appear to be distributed over a much larger volume in the may june 1985 eruption we recognize three multiplet sets that took place successively in time the multiplets are interpreted as repeated failure or slip within a relatively small volume due to high strain rates around the magma supply conduit

shallow magma accumulation at kīlauea volcano hawai i revealed by microgravity surveys for vertical displacement at the summit of about 1 3 m and 160 gal respectively the volume of magma lost based on grav ity data and assuming a reasonable magma density exceeded the volume of summit col lapse suggesting the creation of 40 90 10 6 abstract using microgravity data collected at k lauea volcano hawai i united states between november 1975 and january 2008 we document signifi cant mass increase beneath the east margin of halema uma u crater within k lauea s summit caldera surprisingly there was no sustained uplift accompanying the mass accumulation we propose that the positive grav ity residual in the absence of signifi cant uplift is indicative of magma accumulation in void space probably a network of interconnected cracks which may have been created when magma withdrew from the summit in response to the 29 november 1975 m 7 2 south fl ank earthquake subsequent refi lling documented by gravity represents a gradual recovery from that earthquake a new eruptive vent opened at the summit of k lauea in 2008 within a few hundred meters of the positive gravity residual maximum probably tapping the reservoir that had been accumulating magma since the 1975 earthquake

fluctuations in surface height of active lava lakes during 1972 1974 mauna ulu eruption kilauea volcano hawaii an active lava lake is one that forms directly on top of a magma column as opposed to an inactive one formed by passive ponding of lava within a preexisting crater two active lava lakes operating within summit craters of newly constructed volcanic shields at mauna ulu and alae were the longest lived of any observed in a hawaiian rift zone to date small scale fluctuations a few to 20 m in the height of lake surfaces are typically associated with degassing gas piston activity larger fluctuations as great as 200 m reflect major changes in eruptive activity measurements of surface height fluctuations of mauna ulu lake show gross positive correlation with variation in summit tilt which in turn reflects the inflation deflation state of kilauea s summit magma reservoir a more tenuous conclusion is that a sympathetic variation possibly exists between surface heights of the mauna ulu and alae lakes collectively these observations 1 require the existence of a fully engorged connected open and hydraulically efficient magma conduit system linking the summit reservoir with the lava lakes 2 provide additional evidence for the postulated regime of quasi steady state magma transfer that characterized much of the eruption 3 imply that fluctuations in lake surface reflect variation in magma supply rate to the reservoir and or outflow rate from the mauna ulu alae vents and 4 suggest undetected episodes of magma intrusion or storage in kilauea s east rift zone during 1973

swarms of similar long period earthquakes in the mantle beneath mauna loa volcano abstract we present analyses of two swarms of long period lp earthquakes at 30 km depth that accompanied the geodetically observed 2002 2005 mauna loa intrusion the first lp earthquake swarm in 2002 consisted of 31 events that were precursory and preceded the start of mauna loa inflation the second lp swarm of two thousand events occurred from 2004 2005 the rate of lp earthquakes slowed significantly coincident with the occurrence of the december 26 2004 m w 9 3 sumatra earthquake suggesting that the seismic waves from this great earthquake may have had a dynamic triggering effect on the behavior of mauna loa s deep magma system using waveform cross correlation and double difference relocation we find that a large number of earthquakes in each swarm are weakly similar and can be classified into two families the relocated hypocenters for each family collapse to compact point source regions almost directly beneath the mauna loa intrusion we suggest that the observed waveform characteristics are compatible with each family being associated with the resonance of a single fluid filled vertical crack of fixed geometry with differences in waveforms between events being produced by slight variations in the trigger mechanism if these lp earthquakes are part of the primary magma system that fed the 2002 2005 intrusion as indicated by the spatial and temporal associations between mantle seismicity and surface deformation then our results raise the possibility that this magma system may be quite focused at these depths as opposed to being a diffuse network it is likely that only a few locations of mauna loa s deep magma system met the geometric and fluid dynamic conditions for generating lp earthquakes that were large enough to be recorded at the surface and that much of the deep magma transfer associated with the 2002 2005 intrusion occurred aseismically

time space variation of volcano seismic events at la fossa vulcano aeolian islands italy new insights into seismic sources in a hydrothermal system we investigated the relationship between volcano seismic events recorded at la fossa crater of vulcano aeolian islands italy during 2004 2006 and the dynamics of the hydrothermal system during the period of study three episodes of increasing numbers of volcano seismic events took place at the same time as geothermal and geochemical anomalies were observed these geothermal and geochemical anomalies have been interpreted as resulting from an increasing deep magmatic component of the hydrothermal fluids three classes of seismic events long period high frequency and monochromatic events characterised by different spectral content and various similarity of the waveforms have been recognised these events clustered mainly below la fossa crater area at depths of 0 5 1 1 km b s l were space distributed according to the classes based on their features we can infer that such events at vulcano are related to two different source mechanisms 1 fracturing processes of rocks and 2 resonance of cracks or conduits filled with hydrothermal fluid in the light of these source mechanisms the increase in the number of events at the same time as geochemical and geothermal anomalies were observed was interpreted as the result of an increasing magmatic component of the hydrothermal fluids implying an increase of their flux indeed such variation caused an increase of both the pore pressure within the rocks of the volcanic system and the amount of ascending fluids increased pore pressures gave rise to fracturing processes while the increased fluid flux favoured resonance and vibration processes in cracks and conduits finally a gradual temporal variation of the waveform of the hybrid events one of the subclasses of long period events was observed likely caused by heating and drying of the hydrothermal system

mineral discrimination using a portable ratio determining radiometer the instrument has ten bands in the visible and near infrared portion of the spectrum 0 5 2 4 mu m measurements and statistical analyses were performed on 66 samples which were characterized by microscopic and x ray diffraction analyses on the ability to discriminate between 16 mineralogical groups 91 percent classification accuracy was achieved modified journal abstract

anisotropic scattering and travel time delay analysis in kilauea volcano hawaii earthquake coda waves we study the s wave coda of microearthquake multiplets earthquakes showing similar seismograms recorded on the kilauea volcano and we analyze the direction of emission for wavelets composing the coda our data set consists of 71 small magnitude well relocated clustered events that occurred in an area of about 1 km2 in the southern flank of kilauea recorded at hypocentral distances of 10 to 20 km for each station we apply a cross spectral moving window technique to each pair of multiplet records to estimate the travel time delays due to source location offsets these delays are computed for consecutive windows starting at the p wave arrival time and ending at 4 times the s wave travel time they are next used to estimate the slowness vector for each window along the seismograms our analysis shows 1 that scattered waves are emitted anisotropically along some preferred directions as late as 4 times the s wave travel time and 2 that for some stations the azimuthal plane rotates during the seismogram with a clear travel time delay signature our analysis shows that travel time delay variation in the coda can be purely due to geometrical propagation effects this conclusion is of special interest when trying to use travel time delays to infer temporal changes in the crust our results do not support a coda diffracted isotropically in the crust in the magnitude range and at the hypocentral distances we investigated

broadband seismic monitoring of active volcanoes using deterministic and stochastic approaches 1 we systematically used two approaches to analyze broadband seismic signals for monitoring active volcanoes one is waveform inversion of very long period vlp signals assuming possible source mechanisms the other is a source location method of long period lp events and tremor using their amplitudes the deterministic approach of the waveform inversion is useful to constrain the source mechanism and location but is basically only applicable to vlp signals with periods longer than a few seconds the source location method assumes isotropic radiation of s waves and uses seismic amplitudes corrected for site amplifications this simple approach provides reasonable source locations for various seismic signals such as a vlp event accompanying lp signals an explosion event and tremor associated with lahars and pyroclastic flows observed at five or fewer stations our results indicate that a frequency band of about 5 12 hz and a q factor of about 60 are appropriate for the determination of the source locations in this frequency band the assumption of isotropic radiation may become valid because of the path effect caused by the scattering of seismic waves the source location method may be categorized as a stochastic approach based on the nature of scattering waves systematic use of these two approaches provides a way to better utilize broadband seismic signals observed at a limited number of stations for improved monitoring of active volcanoes

precursory swarms of long period events at redoubt volcano 1989 1990 alaska their origin and use as a forecasting tool abstract during the eruption of redoubt volcano from december 1989 through april 1990 the alaska volcano observatory issued advance warnings of several tephra eruptions based on changes in seismic activity related to the occurrence of precursory swarms of long period lp seismic events dominant period of about 0 5 s the initial eruption on december 14 occurred after 23 years of quiescence and was heralded by a 23 hour swarm of lp events that ended abruptly with the eruption after a series of vent clearing explosions over the next few days dome growth began on december 21 another swarm with lp events similar to those of the first began on the 26th and ended in a major tephra eruption on january 2 eruptions continued over the next two weeks and then ceased until february 15 when a large eruption initiated a long phase of repetitive dome building and dome destroying episodes that continued into april warnings were issued before the major events on december 14 and january 2 but as the eruptive sequence continued after january 2 the energy of the swarms decreased and forecasting became more difficult a significant but less intense swarm preceded the february 15 eruption which was not forecast this eruption destroyed the only seismograph on the volcanic edifice and stymied forecasting until march 4 when the first of three new stations was installed within 3 km of the active vent from march 4 to the end of the sequence on april 21 there were eight eruptions six of which were preceded by detectable swarms of lp events although weak these swarms provided the basis for warnings issued before the eruptions on march 23 and april 6 the initial swarm on december 13 had the following features 1 short duration 23 hours 2 a rapidly accelerating rate of seismic energy release over the first 18 hours of the swarm followed by a decline of activity during the 5 hours preceding the eruption 3 a magnitude range from 0 4 to 1 6 4 nearly identical lp signatures with a dominant period near 0 5 s 5 dilatational first motions everywhere and 6 a stationary source location at a depth of 1 4 km beneath the crater this occurrence of long period events suggests a model involving the interaction of magma with groundwater in which magmatic gases steam and water drive a fixed conduit at a stationary point throughout the swarm the initiation of that sequence of events is analogous to the failure of a pressure relief valve connecting a lower supercharged magma dominated reservoir to a shallow hydrothermal system a three dimensional model of a vibrating fluid filled crack recently developed by chouet is found to be compatible with the seismic data and yields the following parameters for the lp source crack length 280 380 m crack width 140 190 m crack thickness 0 05 0 20 m crack stiffness 100 200 sound speed of fluid 0 8 1 3 km s compressional wave speed of rock 5 1 km s density ratio of fluid to rock 0 4 and ratio of bulk modulus of fluid to rigidity of rock 0 03 0 07 the fluid filled crack is excited intermittently by an impulsive pressure drop that varies in magnitude within the range of 0 4 to 40 bar such disturbance appears to be consistent with a triggering mechanism associated with choked flow conditions in the crack

precise relocation of earthquakes following the 15 june 1991 eruption of mount pinatubo philippines 1 the 15 june 1991 climactic eruption of mount pinatubo philippines was followed by intense seismicity that remained at a high level for several months we located 10 839 events recorded between 1 july and mid december 1991 in contrast to the preeruptive seismicity which was focused in two groups below the summit area posteruptive events were widely distributed below and around the volcano the classification of the events indicates the presence of several large multiplets and the application of relative relocation techniques to the similar events by calculating high precision delays between traces outlines a number of clear seismogenic structures we used different methods to confirm the validity of our results these tests indicate that reliable features can be detected with a small monitoring network while the main cluster of activity can be attributed to an intrusive process starting from below the 15 june crater the volcanic origin of the seismic activity in the other areas is more difficult to establish away from the summit relocations define streaks or planes which are oriented predominantly southwest northeast with in several cases the presence of northwest southeast conjugate structures most of the composite focal mechanisms that we could determine indicate predominantly strike slip right lateral faulting our results indicate that most of the seismicity that occurred after the 15 june eruption is related to the east west regional compressional stress field related to the subduction we suggest that the regional stress field induces seismicity along new or preexisting faults in the medium surrounding the volcano where the stress field was locally disturbed by the volcanic eruption

mantle fault zone beneath kilauea volcano hawaii relocations and focal mechanism analyses of deep earthquakes 13 kilometers at kilauea volcano demonstrate that seismicity is focused on an active fault zone at 30 kilometer depth with seaward slip on a low angle plane and other smaller distinct fault zones the earthquakes we have analyzed predominantly reflect tectonic faultingin the brittle lithosphere rather than magma movement associated with volcanic activity the tectonic earthquakes may be induced on preexisting faults by stresses of magmatic origin although background stresses from volcano loading and lithospheric flexure may also contribute

a spherical source model for low frequency volcanic earthquakes a resonant magma chamber is modeled by a spherically symmetric whole space consisting of a small gas filled chamber surrounded by magma which is encased in country rock source boundary conditions are specified on the cavity boundary simulating a possible sudden gas expansion in the magma the simplicity of this model leads to an analytical closed form solution for the fourier transform of radial displacement which predicts a peaked spectrum and an oscillating decaying seismogram for physically reasonable values of the rock and magma elastic properties and dimensions of the model the dominant frequency of the signal is in the range of 1 to 5 hz near the values observed for low frequency volcanic earthquakes and volcanic tremor furthermore the seismograms and spectra bear resemblance to those observed for low frequency earthquakes the fundamental mode of oscillation is a pure radial breathing mode which has markedly different properties from single cavity solutions the fundamental frequency is insensitive to the magma chamber boundary radius when both the inner and outer radii are greater than specified values this may help to explain the apparent similarity of the dominant frequency of volcanic earthquakes over a wide range of physical situations the presence of an inner effective bubble of a certain minimum size is necessary for the existence of the dominant low fundamental frequency spectral peak although highly idealized we believe that this fundamental fluid solid cavity mode may provide an explanation for the observations of tremor and low frequency volcanic earthquakes

high precision relocation of long period events beneath the summit region of kilauea volcano hawai i from 1986 to 2009 long period 0 5 5 hz lp seismicity has been recorded for decades in the summit region of kilauea volcano hawai i and is postulated as linked with the magma transport and shallow hydrothermal systems to better characterize its spatiotemporal occurrence we perform a systematic analysis of 49 030 seismic events occurring in the kilauea summit region from january 1986 to march 2009 recorded by the 50 station hawaiian volcano observatory permanent network we estimate 215 437 p wave spectra considering all events on all stations and use a station averaged spectral metric to consistently classify lp and non lp seismicity we compute high precision relative relocations for 5327 lp events 43 of all classified lp events using waveform cross correlation and cluster analysis with 6 4 million event pairs combined with the source specific station term method the majority of intermediate depth 5 15 km lps collapse to a compact volume with remarkable source location stability over 23 years indicating a source process controlled by geological or conduit structure

locating hydrothermal acoustic sources at old faithful geyser using matched field processing in 1992 a large and dense array of geophones was placed around the geyser vent of old faithful in the yellowstone national park to determine the origin of the seismic hydrothermal noise recorded at the surface of the geyser and to understand its dynamics old faithful geyser ofg is a small scale hydrothermal system where a two phase flow mixture erupts every 40 to 100 min in a high continuous vertical jet using matched field processing mfp techniques on 10 min long signal we localize the source of the seismic pulses recorded at the surface of the geyser several mfp approaches are compared in this study the frequency incoherent and frequency coherent approach as well as the linear bartlett processing and the non linear minimum variance distorsionless response mvdr processing the different mfp techniques used give the same source position with better focalization in the case of the mvdr processing the retrieved source position corresponds to the geyser conduit at a depth of 12 m and the localization is in good agreement with in situ measurements made at old faithful in past studies

excitation of a buried magmatic pipe a seismic source model for volcanic tremor recent observations of seismic events at various volcanoes suggest that harmonic tremor results from the sustained occurrence of so called long period or low frequency events accordingly we can view the long period volcanic event as the elementary process of tremor and interpret it as the impulse response of the tremor generating system we present a seismic model in which the source of tremor is the acoustic resonance of a fluid filled volcanic pipe triggered by excess gas pressure the model consists of three elements namely a triggering mechanism a resonator and a radiator for simplicity we assume a hemispherical trigger cylindrial resonator and circular radiator set in a vertical configuration with the trigger capping the top of the pipe and the disk shaped radiator shutting off its bottom considering the simple case of a source buried in a homogeneous half space we then apply the discrete wave number method to obtain a complete representation of the ground motion response at near and intermediate distances the results demonstrate that the displacement attributed to the pipe dominates the near field motion while that due to the disk is representative of the intermediate and far fields the trigger itself has a smaller contribution mainly limited to the field in the proximity of the source the characteristics displayed by the free surface response evolve from a strong impulsive signature in the immediate vicinity of the epicenter to a well developed harmonic wave train dominated by rayleigh waves at larger distances no clear shear arrival can be detected in the synthetic seismograms the displacement spectrum reflects the organ pipe modes of the conduit and the bandwidth associated with the dominant spectral peak of motion is controlled by the combined losses due to viscous attenuation in the fluid and elastic radiation into the solid in the case of the cylindrical magma column considered the radiation loss is proportional to the square of the pipe radius while the loss related to viscous damping is inversely proportional to the same factor indicating that the relative importance of the two loss mechanisms is critically dependent on the geometry of the magma reservoir the relative importance of the pipe and disk elements likewise is a function of the conduit cross section this suggests the possibility of determining the geometry of the source as well as the radiation loss and in situ magma viscosity from a comparison of near and far field observations

magma degassing triggered by static decompression at kīlauea volcano hawai i 1 during mid june 2007 the summit of k lauea volcano hawai i deflated rapidly as magma drained from the subsurface to feed an east rift zone intrusion and eruption coincident with the deflation summit so2 emission rates rose by a factor of four before decaying to background levels over several weeks we propose that so2 release was triggered by static decompression caused by magma withdrawal from k lauea s shallow summit reservoir models of the deflation suggest a pressure drop of 0 5 3 mpa which is sufficient to trigger exsolution of the observed excess so2 from a relatively small volume of magma at the modeled source depth beneath k lauea s summit static decompression may also explain other episodes of deflation accompanied by heightened gas emission including the precursory phases of k lauea s 2008 summit eruption hazards associated with unexpected volcanic gas emission argue for increased awareness of magma reservoir pressure fluctuations

the role of volatiles in magma chamber dynamics many andesitic volcanoes exhibit effusive eruption activity1 with magma volumes as large as 107 109 m3 erupted at rates of 1 10 m3 s 1 over periods of years or decades during such eruptions many complex cycles in eruption rates have been observed with periods ranging from hours to years2 3 4 5 6 7 longer term trends have also been observed and are thought to be associated with the continuing recharge of magma from deep in the crust and with waning of overpressure in the magma reservoir here we present a model which incorporates effects due to compressibility of gas in magma we show that the eruption duration and volume of erupted magma may increase by up to two orders of magnitude if the stored internal energy associated with dissolved volatiles can be released into the magma chamber this mechanism would be favoured in shallow chambers or volatile rich magmas and the cooling of magma by country rock may enhance this release of energy leading to substantial increases in eruption rate and duration

the low frequency earthquake swarms at mount pinatubo philippines implications for magma dynamics abstract mount pinatubo s intense low frequency lf earthquake swarms in 1992 provide insight into the volcano s shallow plumbing system and into the possible magmatic process that generate these unusual earthquakes lf waveforms are remarkably uniform with spectral peaks at about 1 hz recorded at pinatubo 1 week prior to the june 1991 cataclysmic eruption lf events reappeared 1 year later and a day before a new dome began to grow in the volcano s freshly formed caldera seismicity with at least 23 000 lf events accompanied the 1992 dome growth and both simultaneously ceased after 4 months the magnitude range of the thousands of lf events is narrow at only 1 6 units and show a more restricted range in size during any particular period within the crisis defining a group magnitude during two lf earthquake swarms the group magnitude gradually varied indicating a pervasive process affecting the mechanism of lf earthquake generation hypocenters of pinatubo s lf earthquakes define a vertical pipe extending from the crater floor to 4 2 km below sea level coinciding with the column formed by high frequency hf earthquakes prior to the 1991 cataclysmic eruption a dike intrusion along the nw trending maraunot fault is also suggested by the hypocenters the temporal amplitude and waveform features and hypocenter location of pinatubo s lf earthquakes are distinctly different from those of hf events and indicate a close affinity of lf earthquakes to one another lf events appear to be caused by interactions between more fluid magma intruding semi ductile materials confined within the volcano s shallow plumbing system this source mechanism can account for the occurrence of lf earthquakes as swarms and multiplets the limited magnitude range of the events the temporally changing group magnitudes the obscurity of s phase the existence of hybrid lf hf earthquakes and the close relationship of lf earthquakes with dome extrusions the 1992 lf seismicity at pinatubo trails the 1991 paroxysmal eruption residual melt left in the shallow conduit following the 1991 eruption may have reached density and viscosity contrasts that allowed fluid fractions to intrude more viscous but still ductile part of the magma this process may have produced the small sized 1992 dome by analogy we suggest that the 1991 pre eruptive dome and lf events may have involved viscous materials left by the 500 year bp eruption and intruded by the then ascending melt

source geometry from exceptionally high resolution long period event observations at mt etna during the 2008 eruption during the second half of june 2008 50 broadband seismic stations were deployed on mt etna volcano in close proximity to the summit allowing us to observe seismic activity with exceptionally high resolution 129 long period events lp with dominant frequencies ranging between 0 3 and 1 2 hz were extracted from this dataset these events form two families of similar waveforms with different temporal distributions event locations are performed by cross correlating signals for all pairs of stations in a two step scheme in the first step the absolute location of the centre of the clusters was found in the second step all events are located using this position the hypocentres are found at shallow depths 20 to 700 m deep below the summit craters the very high location resolution allows us to detect the temporal migration of the events along a dike like structure and 2 pipe shaped bodies yielding an unprecedented view of some elements of the shallow plumbing system at mount etna these events do not seem to be a direct indicator of the ongoing lava flow or magma upwelling

effects of topography and crustal heterogeneities on the source estimation of lp event at kilauea volcano summary the main goal of this study is to improve the modelling of the source mechanism associated with the generation of long period lp signals in volcanic areas our intent is to evaluate the effects that detailed structural features of the volcanic models play in the generation of lp signal and the consequent retrieval of lp source characteristics in particular effects associated with the presence of topography and crustal heterogeneities are here studied in detail we focus our study on a lp event observed at kilauea volcano hawaii in 2001 may a detailed analysis of this event and its source modelling is accompanied by a set of synthetic tests which aim to evaluate the effects of topography and the presence of low velocity shallow layers in the source region the forward problem of green s function generation is solved numerically following a pseudo spectral approach assuming different 3 d models the inversion is done in the frequency domain and the resulting source mechanism is represented by the sum of two time dependent terms a full moment tensor and a single force synthetic tests show how characteristic velocity structures associated with shallow sources may be partially responsible for the generation of the observed long lasting ringing waveforms when applying the inversion technique to kilauea lp data set inversions carried out for different crustal models led to very similar source geometries indicating a subhorizontal cracks on the other hand the source time function and its duration are significantly different for different models these results support the indication of a strong influence of crustal layering on the generation of the lp signal while the assumption of homogeneous velocity model may bring to misleading results

relocation of long period lp seismic events reveals en echelon fractures in the upper edifice of turrialba volcano costa rica swarms of long period lp events were recorded on turrialba volcano costa rica during a seismic field experiment in 2009 families of lp events were previously identified and located using a joint inversion for source location and mechanism however the spatial resolution of the obtained locations was not sufficient for imaging the structures on which they occur using a waveform similarity based location method we take advantage of the joint location mechanism inversion by relocating events around the obtained familial location the location method is successfully tested on a synthetic data set and is then applied to the turrialba lp data set the relocated events are jointly interpreted with their source mechanisms and reveal an en echelon structure within the upper edifice of the volcano this can be interpreted as a response of a shearing band with high fluid pressure inducing tensile fractures at unconsolidated rock layer interfaces within the upper edifice of the volcano

implications of deflation inflation event models on kīlauea volcano hawaiʻi abstract surface deformation of volcanic areas can reveal information about subsurface magma reservoirs and how magma is transported between them which is an important part of volcano monitoring for hazard mitigation one prominent style of deformation observed at k lauea volcano hawai i is episodic deflation inflation di events which are recorded in surface deformation data and characterized by deflation of the summit region over hours to days followed by rapid re inflation the exact cause of di events is unknown however a commonly proposed explanation is that a temporary blockage occurs in the conduit connecting the south caldera magma reservoir to the shallower halema uma u reservoir thus interrupting the influx of magma this model is investigated by testing the hypothesis that during the deflationary phase of a di event the volume of magma blocked from reaching the halema uma u reservoir is added to the south caldera reservoir using a mass balance approach and deformation modeling the expected deformation tilt pattern was predicted for the reservoirs and compared to tilt observations from 16 large 4 rad magnitude di events between 2010 and 2012 while the predicted tilts due to inflation from the south caldera reservoir are strong enough to be detected this signal is not seen in the tilt observations we also explore the possibility that the blockage occurs below the south caldera reservoir as well as alternative configurations that include a direct connection between the south caldera reservoir and the eruption site none of the simple two reservoir models we test are able to adequately satisfy the observations selected di events show that tilt vectors change in both magnitude and azimuthal direction over the course of deflation we conclude that the portion of the summit storage and plumbing system active during these di events is more complicated than two connected chambers and that it is more likely that these summit reservoirs have their own source conduits connecting in some complex way to the deep magma source

ground motion in the near field of a fluid driven crack and its interpretation in the study of shallow volcanic tremor we present a study of the motion of the ground in the near field of a fluid driven tensile crack embedded in a layered half space the source that we consider is the jerky opening of a channel connecting two fluid filled cracks and the cause of this opening is the excess pressure of fluid in one of the cracks we make a complete representation of the three components of ground motion in the space time and frequency domains and analyze the effects of fluid compressibility source depth and medium structure on the ground response the calculations show the presence of a dominant frequency of motion which depends not only on the source geometry and bulk modulus of the fluid but also on medium characteristics receiver position and the component of motion being considered using this source model we view an episode of volcanic tremor as a continuous sequence produced by numerous jerky openings of channels occurring randomly in time along a chain of cracks our results are applied to the october 5 6 1963 east rift eruption of kilauea volcano hawaii and found to be compatible with available seismic data suggesting that magma is transported through an ensemble of cracks with the area of 1 1 km each pair of cracks constituting an individual dike segment which opens in discrete increments at a rate of 1 s we obtain the following parameters for each dike segment opening increase in cavity volume 40 m3 stress drop 0 004 bar seismic moment 1019 dyn cm and force applied by the fluid to open the dike 1014 dyn the total moment integrated over the entire duration of tremor for the eruption is 0 5 1024 dyn cm roughly equivalent to a single magnitude m 5 earthquake the seismic source parameters and other field observations offer constraints on the process of mass transport and are compatible with the excess pressure and viscosity of magma of about 40 bars and 102 p respectively

source location of long period seismicity at volcan de colima mexico this paper presents an analysis of seismicity associated with the volcanic activity of volcan de colima mexico and recorded in the period november 2005 april 2006 during a field survey by the istituto nazionale di geofisica e vulcanologia ingv osservatorio vesuviano the observatorio vulcanologico de colima of colima university and the instituto andaluz de geofisica university of granada three different types of volcanic earthquakes have been identified on the basis of their spectral properties type a 0 3 1 hz type b 1 5 hz and type c 3 4 hz results of polarization analysis applied to type a events show a predominance of radial motion indicating that the wavefield comprises compressional waves p and shear waves polarized in the vertical plane sv while the signal always begins with a negative polarity type a b and c earthquakes have been located using both a flat layered model and a 3d model including topography hypocentre distributions indicate that the source of type a signals is very shallow and confined to a small volume lying about 1 km below the crater in contrast the source of type b and c events is significantly deeper with most hypocentres located in a volume of about 1 km3 centred at 2 5 3 km depth a cluster analysis based on the cross correlation among the waveforms of different events recorded at the same station was applied to type a earthquakes only two clusters which include only a small percentage of events were found indicating that earthquake families were uncommon during the period of our survey

families of similar events and modes of oscillation of the conduit at yasur volcano vanuatu abstract we examined one year of seismic recordings collected in 2008 during a temporary experiment at yasur volcano vanuatu the volcano has a permanent strombolian activity that was at a relatively high level during most of our experiment with commonly at least one explosion per minute associated with this activity the network recorded intense seismicicity with hundreds of transients per day video recordings indicate that most of the high frequency transients are directly related to the strombolian explosions they also outline the presence of fewer signals which are not accompanied by any surface activity the classification of transient events recorded at a station close to the summit indicates that a significant part of the events exhibit waveform similarity this technique allows the identification of characteristic repeating events among the hundreds of thousands of transients recorded during the experiment most of the families of similar events are groups of explosion quakes eqs but a few are groups of long period events related to deeper processes by scanning the 9 months of continuous data available at the summit station with master events extracted from these families we reconstruct their temporal evolution our results show that several families dominate the activity with a few of them lasting for several months we show that their temporal evolutions can be used to probe changes in the structure or activity of the volcano we observe that a major change was induced by a m 7 3 subduction earthquake which occurred on april 9 2008 about 80 km from the volcano while this event did not change significantly the surface morphology of the volcano nor the intensity of the eruptive activity it interrupted the families as none of them is present both before and after the event this change in the waveforms can be explained by a drop in the seismic velocity of the volcano caused by the distal event numerous other transitions between families are observed sudden or progressive these can be interpreted as representative of changes in the eruptive dynamics the presence of similar eqs especially for impulsive explosions indicates that the source mechanism is reproducible and has a stable location for some periods this favors a source process based on the oscillation of the conduit or oscillation of the edifice in response to the explosive decompression of gas slugs at the free surface of the conduit our results suggest that the seismic activity of yasur is characterized by the presence of dominant modes of resonance of the conduit which may be influenced both by external and internal factors

a late pleistocene glacial chronology for the southern brooks range stratigraphic record and regional significance radiocarbon dates from 11 measured sections in the koyukuk region provide a chronology of the last pleistocene glaciation glaciers were advancing strongly by 24 000 yr ago they built moraines near the south flank of the brooks range retreated briefly about 22 000 to 20 000 yr b p then readvanced at least one more time into their terminal zones glaciation was accompanied by alluviation of the koyukuk and kobuk drainage systems and by periglacial processes that resemble those taking place today farther north and at higher altitudes moraines near the south flank of the range were being revegetated by 13 500 yr b p a strong final readvance into end moraine belts of some northern valleys occurred about 13 000 to 12 500 yr ago and this event may be synchronous with less extensive glacier readvances in upper valleys of the koyukuk region upper valleys were largely deglaciated by 11 800 yr b p dated stratigraphic sections from the northern alaska range show similar ages for initiation and close of glaciation and also suggest a possible interstadial episode about 20 000 yr ago scanty records of fluctuations during ice wastage probably reflect the general scarcity of datable wood peat and organic soils between about 19 500 and 13 500 yr ago the brooks range and alaska range chronologies closely approximate glacial successions determined else where in eastern beringia and in siberia advance and retreat of glaciers throughout this region evidently were associated with widespread climatic changes that also controlled the late wisconsin history of the laurentide ice sheet the itkillik ii and late itkillik phases of former usage are part of a single glaciation that was entirely separate from the preceding itkillik i ice advance for this reason the local term walker lake glaciation is here extended to the last major glaciation of the entire southern brooks range and use of itkillik phases should be discontinued the term itkillik glaciation is hereby restricted to the next older ice advance in accord with its original definition cold and dry conditions during the last glaciation of eastern beringia are indicated by 1 relatively small mountain glaciers 2 slight 200 m depression of glaciation limits below modern values 3 periglacial features indicating severe frost action on slopes with little protective plant cover 4 widespread accretion of eolian sand 5 low pollen influx rates 6 scarcity of radiocarbon datable organic remains and 7 general absence of carbonaceous paleosols plant growth may have been much more restricted than generally believed with relatively low capacity to support grazing animals and human hunting bands