combining local and remote infrasound recordings from the 2009 redoubt volcano eruption abstract the explosive phase of the 2009 redoubt volcano eruption produced predominantly short duration high amplitude infrasound signals recorded up to 4500 km away all 19 numbered explosive events were recorded at a local microphone dfr 12 km as well as at an infrasound array in fairbanks alaska i53us 547 km most with high signal to noise ratios the local microphone provides an estimate of the source parameters and comparison between the two datasets allows the unique opportunity to evaluate acoustic source term estimation at a remote array high waveform similarity between dfr and i53us occurs during much of the explosive phase due to strong stratospheric ducting permitting accurate source constraints inferred from i53us data cross correlation analysis after applying a hilbert transform to the i53us data shows how the acoustic energy has passed through a single caustic as predicted by ray theory similar to previous studies significant low frequency infrasound from redoubt recorded at i53us is coincident with high altitude ash emissions the largest events also produced considerable energy at greater than 50 s periods likely related to the initial oscillations of the volcanic plume or jet many of the explosive events have emergent onsets somewhat unusual for explosive short duration eruptions comparison of the satellite derived so2 emissions with the relative amount of acoustic energy at i53us shows a very high statistically significant correlation this study reiterates the utility of using remote infrasound arrays for detection of hazardous emissions and characterization of large volcanic eruptions and demonstrates how under typical meteorological conditions remote infrasound arrays can provide an accurate representation of the acoustic source

slip system domains 2 kinematic aspects of fabric development in polycrystalline aggregates abstract in the first paper of the present series cobbold and gapais 1986 we develop theoretical models of plane strain domainal deformation by slip along inextensible and indestructible fibres for such extreme mechanical conditions we show that deformation is largely controlled by kinematic factors we use our models to explain domainal patterns of natural slip systems including bedding and foliation planes faults ductile shear zones and lattice planes the present paper focusses on kinematic aspects of fabric development in polycrystalline aggregates a three dimensional kinematic model is developed it reveals that common quartz fabrics may develop domainally by reorientation and selection of inextensible slip directions a axes or slip planes with initially random orientation stable orientations of slip directions are close to both surfaces of no finite extension and orientations of large amount of shear we explain 1 1 common patterns of quartz a and c axis fabrics e g small circles and crossed girdles 2 2 characteristic differences between fabric patterns according to the shape of the finite strain ellipsoid 3 3 development of asymmetric fabrics during non coaxial deformation histories this last process involves selective destruction or replacement of certain orientation domains so that a preferred orientation of slip lines develops close to the bulk shear direction rotation recrystallization is shown to be an efficient natural selection mechanism the models also account for many microstructural features found in oriented polycrystalline rocks especially 1 1 alternating band like or kink like domains of twinned preferred orientations 2 2 individual grains or clusters of grains with retort like shapes and extensive recrystallisation at boundaries 3 3 small scale shear bands formed by strain partitioning and shear localization

infrasonic tremor in the diffraction zone 1 volcanic tremor signals recorded by an infrasound array 12 5 km from the active vent of k lauea volcano show clear diurnal amplitude variations and originate from a well defined direction pointing to the active pu u crater complex spectral amplitudes between 0 02 0 3 hz a proxy for wind speed increase when the wind speeds increase during the daytime spectral amplitudes between 0 5 3 hz where infrasonic tremor is concentrated increase when the wind speeds decrease at night power spectrum analysis shows that when ambient noise levels drop infrasonic tremor amplitudes rise array processing confirms this relationship and reveals tremor detections and amplitudes decrease during the day these changes in infrasonic tremor spectral amplitude and coherence are most likely due to diurnal variations in atmospheric boundary layers affecting infrasonic propagation within the diffraction zone recognition of these regional atmospheric patterns is necessary to permit robust infrasonic remote sensing of volcanic processes

strain path partitioning within thrust sheets microstructural and petrofabric evidence from the moine thrust zone at loch eriboll northwest scotland abstract quartz c axis fabrics and microstructures have been investigated within a suite of quartzites collected from the loch eriboll area of the moine thrust zone and are used to interpret the detailed processes involved in fabric evolution the intensity of quartz c axis fabrics is directly proportional to the calculated strain magnitude a correlation is also established between the pattern of c axis fabrics and the calculated strain symmetry two kinematic domains are recognized within one of the studied thrust sheets which outcrops immediately beneath the moine thrust within the upper and central levels of the thrust sheet coaxial deformation is indicated by conjugate mutually interfering shear bands globular low strain detrital quartz grains whose c axes are aligned sub parallel to the principal finite shortening direction z and quartz c axis fabrics which are symmetric both in terms of skeletal outline and intensity distribution with respect to mylonitic foliation and lineation non coaxial deformation is indicated within the more intensely deformed and recrystallized quartzites located near the base of the thrust sheet by single sets of shear bands and c axis fabrics which are asymmetric with respect to foliation and lineation tectonic models offering possible explanations for the presence of kinematic strain path domains within thrust sheets are considered

eruption chronologies plume heights and eruption styles at tungurahua volcano integrating remote sensing techniques and infrasound article i nfo satellite remote sensing allows volcanic ash plumes to be detected and tracked and routinely aids in hazard mitigation especially to the aviation community although satellite imagery provides valuable information about volcanic plume processes i e plume heights plume composition and plume transport it has its limitations in addition to the observational gaps produced by meteorological clouds as well as temporal and spatial resolution restrictions large volcanic clouds often obscure the vent during an eruption therefore some key information about eruption dynamics and processes are impossible to obtain from satellite images in this paper we investigate four eruptions at tungurahua volcano ecuador during the 2006 2008 time period we integrate satellite derived eruption chronologies plume heights and plume aspect ratios with infrasound data primarily acoustic power and hand held thermal imagery when available integrating these datasets allows us to identify accurate eruption onsets durations and cessations as well as define different types of eruption styles ranging from plinian to weak vulcanian transitions between the different eruption styles were also documented results show that there is a positive correlation between plume height and acoustic power we conclude that combining the two datasets allows better constraints on eruption processes and source parameters using these methods in real time monitoring will allow more accurate eruption monitoring and ash hazard mitigation

an evaluation of criteria to deduce the sense of movement in sheared rocks some of the most useful criteria for the deduction of the sense of shear are summarized for use in areas where unequivocal field evidence is lacking apparently conflicting evidence from rotated pressure shadow regions around porphyroclasts and porphyroblasts is clarified the use of quartz crystallographic fabric asymmetry to deduce the shear sense in the bulk rock should be treated with caution and used only together with detailed microstructural observations

strombolian explosions 1 a large bubble breaking at the surface of a lava column as a source of sound strombolian activity consists of a series of explosions caused by the breaking of large overpressurized bubbles at the surface of the magma column acoustic pressure has been measured for 36 explosions at stromboli we propose that sound is generated by the vibration of the bubble before it bursts oscillations are driven by an initial overpressure inside the bubble assumed to be initially at rest just below the magma air interface inertia effects cause the bubble to overshoot its equilibrium radius then the bubble becomes underpressurized and contracts because of gas compressibility these oscillations are only slightly damped by viscous effects in the magma layer above the bubble the bubble cannot complete more than one cycle of vibration because of instabilities developing on the magma layer that lead to its breaking near the minimum radius assuming a simple geometry we model this vibration and constrain the radius and length of the bubble and the initial overpressure by fitting a synthetic waveform to the measured acoustic pressure the fit between synthetic and observed waveforms is very good both for frequency 60 rad s 1 and amplitude the initial bubble radius is 1 m and the length varies between several and a few tens of meters from the initial overpressure approximately 105 pa we calculate the maximum radial velocity of ejecta 30 m s 1 the generally good agreement between data and predictions of our model leads us to suggest that acoustic measurements are a powerful tool for the understanding of eruption dynamics

the reliability of asymmetric c axis fabrics of quartz to determine sense of vorticity abstract asymmetric c axis fabrics of quartz are commonly used to determine sense of vorticity in ductile shear zones this method seems to work if the fabric pattern resembles a model fabric proposed by lister and hobbs 1980 usually however c axis fabrics are rather vague the reliability of such vague fabrics was tested in a major shear zone with known sense of vorticity only 62 of the c axis fabrics predict the correct sense great care should therefore be taken in applying this method to determine sense of vorticity

microfabrics as energy minimisers rotation recrystallisation as an example abstract microfabrics are discussed as features that minimise helmholtz energy in a system undergoing deformation and metamorphism the energy minimisation process leads to inhomogeneous deformations and hence the formation of microfabrics at a number of scales this process together with the requirement for compatibility both with the imposed deformation and local gradients in deformation means the microfabric must refine on smaller and smaller scales in a self similar manner leading to fractal geometries nine independent levels of refinement are necessary to match the nine independent components of a general imposed deformation gradient the process of rotation recrystallisation is proposed as one example of self similar refinement so that crystallographic preferred orientations cpo associated with rotation recrystallisation are presented as fractals whose fractal dimensions reflect the conditions of deformation compatibility also has implications for the formation of other microstructures such as non rational deformation lamellae the evolution and orientations of microfabrics that minimise energy are related to the history of the imposed deformation gradient as was originally proposed by sander and not the strain tensor as is commonly assumed as examples possible models for cpo development in deformed quartz aggregates by rotation recrystallisation and the development of deformation lamellae in deformed quartz grains are presented

microfabrics of uhp metamorphic granites in the dora maira massif western alps no evidence of deformation at great depth in the dora maira massif western alps essentially undeformed ultrahigh pressure uhp metamorphic granites brossasco granite are embedded in and locally grade into granite gneisses or augengneisses and mylonites in this study the quartz microfabrics of the undeformed granites are compared against the augengneisses and mylonites in a representative number of samples from several locations in the undeformed granites the fine grained quartz aggregates that formed from coesite upon decompression are characterized by a foam structure and random crystallographic orientation in the deformed granites the quartz microstructures and the crystallographic preferred orientation cpo indicate deformation by dislocation creep most of the deformation of the granites if not all must have happened at a late stage during exhumation after transformation of coesite to quartz at greenschist facies conditions in the middle crust the deformed granites provide no evidence of deformation during subduction at u hp metamorphic conditions and in the earlier stages of exhumation the diameter of internally undeformed slices of continental crust subducted to and exhumed from about 100 km can exceed that of the presently exposed brossasco granite i e it can be on the kilometre scale

tracing the differences between vulcanian and strombolian explosions using infrasonic and thermal radiation energy abstract eruptive plume dynamics is a direct expression of explosive style where duration and altitude of eruptive clouds and dispersion of erupted products is proportional to the degree of fragmentation we present an analysis of infrasonic and thermal records for explosions at villarrica chile stromboli italy santiaguito and fuego guatemala volcanoes across these four systems magma composition spans from basaltic to dacitic and explosive activity is typically described as ranging from strombolian to vulcanian we use this analysis to provide a quantitative geophysically based description of and discrimination between the different explosive styles that characterize the four volcanoes while infrasound is directly related to the emission of over pressurized gas and thus solely reflects the plume emission both plume emission and ascent are detected thermally thus the two data sets together provide a complete description of the plume dynamics in particular while infrasound solely reflects the gas thrust phase driving plume emission thermal radiation energy is also affected by buoyancy during plume ascent thermal radiation energy estimated for explosions at stromboli and villarrica 10 4 10 7 j is lower than that for events at santiaguito and fuego 10 8 10 9 j but infrasonic energies overlap this suggests a greater contribution of buoyancy for eruptive clouds at santiaguito and fuego when compared with stromboli and villarrica we further investigated the plume dynamics by comparing infrasonic energy which reflects gas thrust e gt with the difference between thermal radiation and infrasonic energies which mostly reflects buoyancy e b our data distribution reveals two separate clusters explosions at stromboli and villarrica share low values of buoyancy pointing to a gas thrust dominated emission efficient coupling of the infrasonic source to the atmosphere and a strombolian type source process to generate a plume rich in coarse fragments in contrast explosions at santiaguito and fuego share large buoyancy e b and are consistent with vulcanian type events in which a large part of infrasonic energy is spent in magma fragmentation leading to ascent of buoyant ash rich plumes we demonstrate that the comparison between thermal radiation and infrasonic energies of explosions allows a quantitative discrimination between and characterization of strombolian and vulcanian type explosions which leads us to suggest that such an approach may be used as an index to further and quantitatively discriminate between eruptive styles

the mechanism of flow and fabric development in mechanically anisotropic trachyte lava anisotropy of magnetic susceptibility ams and electron back scattered diffraction ebsd of magnetite and sanidine fabrics throughout an eroded trachyte lava dome in tertiary volcanic province of the nw czech republic revealed two fabric types the high degree of ams fabric is associated with sanidine textural domains similar to normal kink bands type i fabric and occupies the whole body except the sw margin folded fabric and low anisotropy of ams also in the sw margin reveals sanidine alignment domains resembling reverse kink bands type ii fabric the flow of trachyte lava occurred via simultaneous slip of sanidine crystals along their 010 planes and also by readjustment of the textural domain boundaries according to the fibre slip theory this microfabric study suggests that the type ii fabrics resulted from collapse of vertically anisotropic trachyte crystal mush above the feeding conduit type i fabric is interpreted to originate from type ii fabrics by further stretching of highly attenuated fold limbs asymmetric type i fabrics along margins of the dome are related to outflow of trachyte lava away from the conduit region due to divergent flow the trachyte fabric zonality is interpreted to reflect the process of successive emplacement of progressively rotated trachyte lava lobes within a lava dome that locally preserves the collapsed and folded vertical fabrics

relative partitioning of acoustic and seismic energy during strombolian eruptions the relative elastic energy partitioning during strombolian eruptions can be estimated from acoustic pressure and seismic velocity records we outline methods for determining acoustic and seismic energies for sensors deployed within several kilometers of erupting vents we use these energies to introduce the concept of the volcano acoustic seismic ratio g or vasr which is the ratio of elastic energy propagated through the atmosphere and into the earth eruption vasr is a physical diagnostic of explosive degassing that is appropriate for comparing eruption mechanisms at individual and between various volcanoes here we assess acoustic and seismic energies and corresponding vasr for discrete strombolian explosive events at karymsky and erebus volcanoes we attribute the relatively high and stable vasr at erebus g 8 standard deviation 41 to repeatable source conditions occurring at the surface of a persistent lava lake with accompanying strong coupling to the atmosphere lower and more variable vasr at karymsky g 0 18 in 1998 to g 1 51 in 1991 with standard deviations of 93 and 313 respectively is attributed to changing conditions within a narrow partially choked conduit variable seismoacoustic energy partitioning for karymsky as manifested by the large vasr standard deviation suggests that conduit conditions affecting vasr which include magma properties conduit obstruction or fragmentation depths can evolve both during the course of an explosion and between successive events d 2005 elsevier b v all rights reserved

the 3d quantitative lattice and shape preferred orientation of a mylonitised metagranite from monte rosa western alps combining neutron diffraction texture analysis and synchrotron x ray microtomography abstract two complementary 3d techniques neutron diffraction and synchrotron x ray microtomography sxr ct were used to compare the shape and lattice preferred orientations of a mylonitised metagranite from the monte rosa unit western alps italy the goal of using these techniques was to obtain two different orientation distribution functions although the two functions describe relatively independent characteristics of the rock fabric nonetheless they also exhibit close relationships to macroscopic fabrics and may be complementarily used to quantify rock fabrics and microstructures thereby highlighting 3d features that cannot be obtained with either technique if used independently we describe an approach that can be potentially useful in various disciplines e g structural geology rock mechanics tectonics and geophysics when a complete data set of preferred orientations and size distribution is needed micas display a strong orthorhombic symmetry between mesoscopic lineation and microscopic spo and lpo whereas quartz and feldspars are characterised by a monoclinic symmetry between mesoscopic lineation and lpo these observations suggest a rheological decoupling between the weak phase mica layers and the stronger quartz feldspar layers this mechanical decoupling occurred during the alpine subduction collision when the monte rosa unit was part of the insubric line system and accommodated large vertical strain

a critical assessment of the tectono thermal memory of rocks and definition of tectono metamorphic units evidence from fabric and degree of metamorphic transformations

infrasound radiated by the gerdec and chelopechene explosions propagation along unexpected paths summary infrasound propagation paths through the atmosphere are controlled by the temporally and spatially varying sound speed and wind speed amplitudes because of the complexity of atmospheric acoustic propagation it is often difficult to reconcile observed infrasonic arrivals with the sound speed profiles predicted by meteorological specifications this paper provides analyses of unexpected arrivals recorded in europe and north africa from two series of accidental munitions dump explosions recorded at ranges greater than 1000 km two explosions at gerdec albania on 2008 march 15 and four explosions at chelopechene bulgaria on 2008 july 3 the recorded signal characteristics include multiple pulsed arrivals celerities between 0 24 and 0 34 km s 1 and some signal frequency content above 1 hz often such characteristics are associated with waves that have propagated within a ground to stratosphere waveguide although the observed celerities extend both above and below the conventional range for stratospheric arrivals however state of the art meteorological specifications indicate that either weak or no ground to stratosphere waveguides are present along the source to receiver paths by incorporating realistic gravity wave induced horizontal velocity fluctuations into time domain parabolic equation models the pulsed nature of the signals is simulated and arrival times are predicted to within 30 s of the observed values 1 per cent of the source to receiver transit time modelling amplitudes is highly dependent upon estimates of the unknown acoustic source strength or equivalent chemical explosive yield current empirical explosive yield relationships derived from infrasonic amplitude measurements from point source chemical explosions suggest that the equivalent chemical yield of the largest gerdec explosion was of the order of 1 kt and the largest chelopechene explosion was of the order of 100 t when incorporating these assumed yields the parabolic equation simulations predict peak signal amplitudes to within an order of magnitude of the observed values as gravity wave velocity perturbations can significantly influence both infrasonic arrival times and signal amplitudes they need to be accounted for in source location and yield estimation routines both of which are important for explosion monitoring especially in the context of the comprehensive nuclear test ban treaty

observations of infrasound from surf in southern california 1 we observe 10 000 s of infrasound signals annually in the frequency range from 1 5 hz at the i57us infrasound array in southern california 75 of these signals arrive at i57us at azimuths between 260 and 320 degrees there is a good correlation between the amplitudes of signals from 260 320 and wave height measurements offshore southern california providing firm evidence that the signals from these azimuths are caused by surf action by modeling the propagation of infrasound for specific time periods using 3d ray tracing and up to date atmospheric models we show that amplitudes of signals recorded at i57us are also dependent upon atmospheric winds the modeled rays that return in the stratosphere fit observations more closely than modeled rays that return in the troposphere suggesting the signals are from stratospheric returns our findings are the first observations of surf infrasound at a long range from the source region this suggests that surf signals might serve as a probe of the atmosphere much like microbarom signals are used to probe the atmosphere at greater range

deformation path partitioning within a transpressive shear zone marble cove newfoundland detailed study of the structures in marble cove newfoundland indicates that they formed during a single transpressional event during which deformation was partitioned between dominantly strike slip and dominantly dip slip domains marble cove exhibits steeply dipping foliations steeply to shallowly plunging stretching lineations greenschist facies mineral assemblages and abundant quartz veins within the broad domain where stretching lineations plunge steeply sense of shear indicators and asymmetry of quartz c axis distributions in mylonitized quartz veins indicate dominantly reverse motion with a component of dextral shear adjacent greenschists exhibit orthorhombic symmetry and apparently accommodated pure shear the abrupt transition to a narrow high strain domain of shallowly plunging stretching lineations is accommodated by a rheologically distinct serpentinite body shear bands in this domain indicate dextral strike slip movement with a reverse component smaller conjugate shear bands are evident in thin section indicating a component of pure shear sense of shear indicators and asymmetry of c axis distributions in mylonitized quartz veins also record dextral strike slip and reverse shear with a component of pure shear crenulations and asymmetric folds in foliation overprint all other fabrics in marble cove and record a final phase of reverse shear with a dextral component with partitioning of this kind structures recording strike slip movement may be limited in areal extent and therefore less likely to be exposed than structures recording dip slip motion such partitioning within transpressional shear zones may therefore impede recognition of strike parallel motions within orogenic belts

the effect of the basal prism mechanism switch on fabric development during plastic deformation of quartzite abstract blacic described a transition from basal a to prism c dislocation glide systems as temperature increased or strain rate decreased in sequences of experiments involving deformation of single crystals of quartz in this paper theoretical aspects of competition between these systems during plastic deformation are discussed it is concluded that the basal prism mechanism switch should have important consequences for the development of crystallographic fabrics during plastic deformation of quartzite and the taylor bishop hill analysis is used in an attempt to predict expected fabric transitions

prism c slip in the quartzites of the oakhurst mylonite belt california abstract quartz c axis fabrics from 21 amphibolite facies quartzites of the oakhurst mylonite belt california suggest that prism c prism a and basal a slip systems were activated during deformation qualitative two dimensional kinematic models consistent with meso and microscopic shear criteria are constructed based on a regime of combined pure and simple shear in this kinematic framework most of the observed c axis fabric patterns of the oakhurst mylonite belt can be explained if prism c slip was dominant during the early increments of deformation until a transition to dominant basal a slip occurred an apparent relationship between grain size and type of crystallographic fabric is interpreted as resulting from some quartz syntectonic vein quartz having recorded only the latest increments of deformation comparison with the metamorphic evolution of fault zones of similar tectonic origin in california suggests that prism c slip was enhanced by the circulation of hot fluids which hydrolytically weakened quartz and allowed prism c slip to occur at relatively low temperature

strain and shape fabric variations associated with ductile shear zones abstract the foliated and compositionally banded granitic orthogneisses in the central core of the maggia nappe a lower pennine basement nappe of the central swiss alps are shown to be the sheared equivalent of late hercynian age granitic intrusions these ductile shear zones show mineral assemblages in amphibolite facies are alpine in age and form an anastomosing network enclosing remnant lozenge shaped pods of relatively undeformed rock the foliation developed within the shear zones concomitantly with a change in shape of quartz grain aggregates from initially equidimensional through tear drop shapes to ribbon like aggregates these shape changes occurred by intracrystalline glide together with intercrystalline slip on deformation induced planar surfaces

late precambrian thrust and wrench zones in northern brittany france abstract brioverian units of northern brittany armorican massif france were deformed and metamorphosed during a late precambrian tectonic episode the cadomian orogeny kinematic study strain and displacement in the st cast st brieuc area shows that this tectonic episode was characterized by the obduction of a back arc basin over a continental margin around 580 590 ma ago strain pattern analysis reveals a constant interaction between ssw directed imbricated thrust zones and ductile sinistral wrench zones trending n 50 e the arcuate pattern of cadomian structures in this area results from such an interaction thickening as a result of the thrusts induced migmatization and the development of a high temperature belt around 540 ma in the st malo guingamp area

tectonic significance of fault slip data abstract the statistical analysis of populations of minor faults is commonly used by structural geologists working in areas of brittle rock it is based on measurements of fault attitude direction and sense of slip at individual sampling localities results are classically interpreted as indicators of stress or strain rate fields assuming a homogeneous stress or strain rate tensor respectively however fault patterns are expected to vary with time because of displacements rigid rotations and internal strains which generally occur along boundaries of fault bounded blocks as deformation proceeds thus in the general situation where early faults accumulate displacements and rigid rotations and where new faults develop during progressive deformation fault slip data can be rather complex and variable in space and reflect neither local stress or strain rate tensors nor finite strains and finite rotations in a simple way we use two examples of faulted regions to illustrate the spatial variability of fault slip data this can be due to local complications at the edges of fault blocks or to complex kinematic conditions at regional boundaries such complications may make it difficult to deduce a consistent and simple pattern of either stresses or strain rates instead our results suggest that information contained in fault slip data can be pertinent to finite deformation in particular the principal axes that we have deduced from the analysis of fault slip data are consistent with the finite displacements at block boundaries that we have calculated by numerical restoration

infrasonic observations of the june 2009 sarychev peak eruption kuril islands implications for infrasonic monitoring of remote explosive volcanism abstract sarychev peak sp located on ostrov matua kurils erupted explosively during 11 16 june 2009 whereas remote seismic stations did not record the eruption we report atmospheric infrasound acoustic wave 0 01 20 hz observations of the eruption at seven infrasound arrays located at ranges of 640 6400 km from sp the infrasound arrays consist of stations of the international monitoring system global infrasound network and additional stations operated by the korea institute of geoscience and mineral resources signals at the three closest recording stations is44 643 km petropavlovsk kamchatskiy kamchatka krai russia is45 1690 km ussuriysk russia and is30 1774 km isumi japan represent a detailed record of the explosion chronology that correlates well with an eruption chronology based on satellite data terra noaa mtsat the eruption chronology inferred from infrasound data has a higher temporal resolution than that obtained with satellite data atmosphere corrected infrasonic source locations determined from backazimuth cross bearings of first arrivals have a mean centroid 15 km from the true location of sp scatter in source locations of up to 100 km result from currently unresolved details of atmospheric propagation and source complexity we observe systematic time variations in trace velocity backazimuth deviation and signal frequency content at is44 preliminary investigation of atmospheric propagation from sp to is44 indicates that these variations can be attributed to solar tide variability in the thermosphere it is well known that additional information about active volcanic processes can be learned by deploying infrasonic sensors with seismometers at erupting volcanoes this study further highlights the significant potential of infrasound arrays for monitoring volcanic regions such as the kurils that have only sparse seismic network coverage

using lightning observations as a volcanic eruption monitoring tool lightning commonly occurs in the eruption columns produced by explosive volcanic eruptions there are several different kinds of lightning detection instruments that could be employed to help monitor volcanoes each with their own advantages and disadvantages very low frequency vlf instruments have the ability to detect lightning at long ranges but tend to have low sensitivity due to network geometry and typically can provide only the time and 2 d location of a cloud to ground return stroke or similar high amplitude pulse produced by an intracloud discharge low frequency lf and medium frequency mf instruments typically have more sensitivity than a vlf network but can only be used for detection on a regional scale very high frequency vhf lightning mapping instruments also provide only regional coverage but detect all lightning within their range during the 2009 eruption of redoubt volcano alaska usa each of these types of instruments detected lightning from redoubt s ash plume the vhf system consistently detected lightning before the other two during each distinct explosive event and also detected more lightning than the others by one or two orders of magnitude lightning observations could be used to confirm and in some cases detect explosive volcanic activity the rapid response provided by lightning monitoring is a valuable tool for fast identification of potentially hazardous ash clouds

networking of shear zones at the brittle to viscous transition cap de creus ne spain a crustal scale shear zone network at the fossil brittle to viscous transition exposed at cap de creus ne spain evolved by coeval fracturing and viscous mylonitic overprinting of an existing foliation initial fracturing led to mylonitic shearing as rock softened in ductilely deformed zones surrounding the fractures mylonitic shear zones widened by lateral branching of fractures from these shear zones and by synthetic rotation of the existing foliation between the fractures and shear zones shear zones lengthened by a combination of fracturing and mylonitic shearing in front of the shear zone tips shear zones interconnected along and across their shearing planes separating rhomb shaped lozenges of less deformed rock lozenges were subsequently incorporated into the mylonitic shear zones by widening in the manner described above in this way deformation became homogeneous on the scale of initial fracturing metre to decametre scale in contrast the shear zone network represents localisation of strain on a decametre length scale the strength of the continental crust at the time of coeval fracturing and viscous shearing is inferred to have decreased with time and strain as fracturing evolved to mylonitic shearing and as the shear zones coalesced to form a through going network subparallel to the shearing plane crustal strength must therefore be considered as strain and scale dependent

detecting hidden volcanic explosions from mt cleveland volcano alaska with infrasound and ground coupled airwaves 1 in alaska where many active volcanoes exist without ground based instrumentation the use of techniques suitable for distant monitoring is pivotal in this study we report regional scale seismic and infrasound observations of volcanic activity at mt cleveland between december 2011 and august 2012 during this period twenty explosions were detected by infrasound sensors as far away as 1827 km from the active vent and ground coupled acoustic waves were recorded at seismic stations across the aleutian arc several events resulting from the explosive disruption of small lava domes within the summit crater were confirmed by analysis of satellite remote sensing data however many explosions eluded initial automated analyses of satellite data due to poor weather conditions infrasound and seismic monitoring provided effective means for detecting these hidden events we present results from the implementation of automatic infrasound and seismo acoustic eruption detection algorithms and review the challenges of real time volcano monitoring operations in remote regions we also model acoustic propagation in the northern pacific showing how tropospheric ducting effects allow infrasound to travel long distances across the aleutian arc the successful results of our investigation provide motivation for expanded efforts in infrasound monitoring across the aleutians and contributes to our knowledge of the number and style of vulcanian eruptions at mt cleveland

volcanic tremor and plume height hysteresis from pavlof volcano alaska the march 2016 eruption of pavlof volcano alaska produced an ash plume that caused the cancellation of more than 100 flights in north america the eruption generated strong tremor that was recorded by seismic and remote low frequency acoustic infrasound stations including the earthscope transportable array the relationship between the tremor amplitudes and plume height changes considerably between the waxing and waning portions of the eruption similar hysteresis has been observed between seismic river noise and discharge during storms suggesting that flow and erosional processes in both rivers and volcanoes can produce irreversible structural changes that are detectable in geophysical data we propose that the time varying relationship at pavlof arose from changes in the tremor source related to volcanic vent erosion this relationship may improve estimates of volcanic emissions and characterization of eruption size and intensity

fabric asymmetry and shear sense in movement zones asymmetry between lattice preferred orientation and shape fabrics is commonly observed in microstructural studies of many deformed mineral aggregates e g ice carbonate rocks peridotites and quartzites theoretical predictions are limited by the nature of the models available and more can be gained by discussion of the mechanisms which give rise to such asymmetry in specific natural and experimental situations

infrasound observations of the 2008 explosive eruptions of okmok and kasatochi volcanoes alaska 1 the recent explosive eruptions of okmok and kasatochi volcanoes provide an opportunity to use seismic local infrasound distant infrasound array and remote sensing data in concert to better monitor volcanoes in the aleutian arc and to better understand the source processes the eruption of okmok volcano began on 12 july 2008 and included a seismically active phase that lasted continuously for about 10 h in contrast the eruption of kasatochi which began on 7 august 2008 consisted of five explosive events that lasted from 26 to 68 min each and had a cumulative duration of 3 4 h given the event times by local seismic stations the corresponding infrasound signals were found in the data recorded by local infrasound sensors and by distant infrasound arrays signals from the okmok eruption were detected by three international monitoring system ims arrays as far away as 4400 km signals from the kasatochi eruption were detected at greater distances up to 5200 km away by seven infrasound arrays including the ones that detected the event at okmok volcano back azimuth propagation and a simple acoustic wave propagation model in unison with known event times were used to confirm that the planar acoustic signals recorded at the arrays had originated from the eruptions the infrasound array data reflected the differences in eruption styles between okmok and kasatochi as the signals from kasatochi were of shorter duration of greater amplitude and detected over greater distances the infrasound array data were also able to distinguish between two types of tremor episodes that occurred at kasatochi volcano based on atmospheric disturbance

application of an updated atmospheric model to explore volcano infrasound propagation and detection in alaska abstract winds and temperature gradients greatly affect the long range propagation of infrasound the spatio temporal variability of these parameters must therefore be accurately characterized to correctly interpret recorded infrasound at long distances specifically to differentiate between source and propagation effects here we present the first results of an open source reanalysis model termed alaska volcano observatory ground to space avo g2s constructed to accurately characterize the atmosphere and model long range infrasound propagation from volcanic eruptions in alaska we select a number of case studies to examine recent eruptions of alaskan volcanoes whose ash emissions posed a threat to air traffic including the two most recent eruptions of pavlof volcano and two typical explosions from cleveland volcano strong tropospheric ducting and low noise at the station during the 21 july 2015 explosion of cleveland volcano led to an automated detection of the explosion at an infrasound array 992 km away whereas low signal to noise ratio for the 6 november 2014 cleveland volcano explosion helps explain the non detection in real time of a predicted strong stratospheric arrival for the november 2014 pavlof eruption discrepancies between local seismic data and a distal infrasound array 460 km away cannot be solely explained by changes in atmospheric conditions though some features of the complex propagation predictions follow the trends in long range infrasound signals the most recent eruption of pavlof volcano in march 2016 shows minimal changes in propagation conditions throughout the eruption and therefore indicates that the signals detected at long range primarily reflect source processes these results show how detailed examination of the acoustic propagation conditions provides insight into detection capability and eruption dynamics future work will implement avo g2s and high resolution long range infrasound propagation modeling in real time for alaskan volcanoes of interest

global morphology of infrasound propagation i atmospheric sound waves in the 0 02 10 hz region also known as infrasound exhibit long range global propagation characteristics measurable infrasound is produced around the globe on a daily basis by a variety of natural and man made sources as a result of weak classical attenuation 0 01 db km 1 at 0 1 hz these acoustic signals can propagate thousands of kilometers in tropospheric stratospheric and lower thermospheric ducts to model this propagation accurately detailed knowledge of the background atmospheric state variables the global winds and temperature fields from the ground to 170 km is required for infrasound propagation calculations we have developed a unique atmospheric specification system g2s that is capable of providing this information using acoustic ray tracing methods and detailed g2s atmospheric specifications we investigate the major aspects of the spatiotemporal variability of infrasound propagation characteristics

construction of crossed girdles by superposing four subfabrics each with a single maximum commonly basal glide is the predominant deformation mechanism of quartz in tectonites therefore local deformation is probably mostly progressive simple shear rotating the sheared domains as well as deforming them

loess caves a special kind of geo hazard on loess plateau northwestern china abstract the loess caves developed on chinese loess plateau are not only a typical phenomenon of soil and water loss but also a special kind of geological hazard many loess dilapidations collapses and medium to small sized landslides are related to the loess caves to understand the characteristics and the geo disasters induced by loess caves the loess caves developed on chinese loess plateau were rigorously investigated based on a long term field surveys on about 800 fixed points in gansu ningxia and northern shaanxi the classifications and characterization of loess caves in chinese loess plateau are discussed in detail moreover the regionally developmental regularity hierarchical development regularity of loess cave and its characteristics are studied in this paper which show that the density of loess caves on the northwestern loess plateau is higher than that in the southeastern loess plateau than that in the southeast in china and the main control factors affecting the development of loess caves are analyzed interestingly the development of the caves is related to the loess layer land characteristics geologic structure including the joints and the fracture system micro topography hydro geological factors and climatic conditions

the development of shear zones in polycrystalline camphor urai j l and humphreys f j 1981 the development of shear zones in polycrystalline camphor in g s lister h j behr k weber and h j zwart editors the effect of deformation on rocks tectonophysics 78 677 685 thin polycrystalline specimens of rhombohedral camphor have been deformed in pure shear in the temperature range 283 343k the deformation processes dynamic recrystallization and the development of microstructure were followed by transmission polarized light microscopy when the stress distribution in the specimens was favourable shear zones were initiated the development of microstructure changed drastically above 310320k the shape of the dynamically recrystallized grains which was equiaxed below this temperature became strongly elongated this change probably due to the development of a marked anisotropy in grain boundary mobilities and the activation of new slip systems made the development of shear zones a more frequently occurring phenomenon above 310 320k

an overview of volcano infrasound from hawaiian to plinian local to global abstract volcano infrasound is an increasingly useful technique for detecting locating characterizing and quantifying eruptive activity and can be used to constrain eruption source parameters in recent years studies of infrasound data from active volcanoes have shown clear progress towards mitigating volcanic hazards and understanding volcanic source processes volcano acoustic sources are shallow or aerial thus volcano infrasound data provide valuable information on eruption dynamics and are readily combined with direct and remote observations of gas ash and other eruptive phenomena the infrasound signals produced by volcanoes are indicative of the eruption style and dynamics here we review the diversity of infrasound signals generated by a wide variety of volcanic eruptions from hawaiian to plinian and the physical processes inferred to produce them we place particular emphasis on regional 15 250 km distance and global 250 km distance volcano infrasound studies as recent work in this area has made significant advances in monitoring and characterizing remote and difficult to monitor eruptions long range infrasonic detection of explosive volcanic eruptions is possible due to the energetic source mechanisms involved minor atmospheric attenuation at low frequencies and the existence of waveguides in the atmosphere however accurate characterization of the atmosphere and its spatiotemporal variability is required for reliable long range sound propagation modeling and correct interpretation of global infrasound recordings conversely because volcanic explosions are energetic and sometimes repetitive infrasound sources they can be used to validate atmospheric and acoustic propagation models

clast based kinematic vorticity gauges the effects of slip at matrix clast interfaces clast based methods for estimating the mean kinematic vorticity number wm are compromised by strain localization at the clast margins localization increases with modal matrix mica content as determined with samples from the sandhill corner mylonite zone a crustal scale high strain strike slip shear zone in maine using these samples we estimate wm with the oblique quartz shape preferred orientation and rigid clast rotation methods the rigid clast rotation method yields much lower values for wm than the quartz method to investigate whether or not slip at the matrix clast interface can explain the discrepancy in calculated wm we conducted numerical modeling of rigid clasts enveloped by a low viscosity layer both embedded within a shearing viscous matrix within this dynamic framework we carried out numerical sensitivity analyses in which we varied the viscosity ratio between the lubricating layer and the surrounding matrix the thickness of the lubricating layer and the kinematic vorticity number of the bulk flow our data and numerical results succeed in explaining why wm estimates from clast based rotational methods are typically lower than estimates from other methods and this has implications for testing hypotheses related for example to vorticity partitioning in oblique convergent settings crustal scale extrusion or channel flow and exhumation of ultra high pressure rocks all of which rely on robust estimates of wm the relation between the shape preferred orientations of clasts and modal mica content lead to the hypothesis that mica is the cause of the lubrication at clast matrix interfaces if so then we surmise that mica fish should be self lubricating and would therefore form an end member shape preferred orientation regardless of matrix modal mica content the unique role of mica allows us to speculate about the bounds on viscosity contrast between the matrix and lubricated clast interfaces

infrasound generated by the 2016 2017 shallow submarine eruption of bogoslof volcano alaska the 2016 2017 shallow submarine eruption of bogoslof volcano produced numerous infrasound signals over 9 months that were recorded on six alaska volcano observatory avo arrays at ranges of 59 to over 800 km from the volcano the lack of geophysical monitoring near bogoslof and the repeated production of volcanic clouds to flight levels made monitoring by remote infrasound critical during the eruption for the first time avo relied extensively on automated infrasound detections from regional arrays to dispatch timely notifications of the ongoing activity most of the 70 eruptive events were detected on at least one array but no array detected all of the events mainly because atmospheric conditions were highly variable during the eruption acoustic propagation modeling helps explain some of the variation in array detections but also highlights limitations in regional propagation models to our knowledge this is the first example of well recorded infrasound from an explosive eruption occurring in shallow seawater providing extensive insights into eruption dynamics in this unique environment the dominance of low frequency infrasound 0 1 1 hz is attributed to eruptions occurring beneath tens of meters of seawater higher frequency infrasound signals were mostly limited to eruptions where the vent was isolated from major interaction with seawater or in several cases where a lava dome grew above sea level

pluton accommodation at high strain rates in the upper continental crust the example of the central extremadura batholith spain abstract emplacement in the tensional bridge of a stepped dextral shear zone system is proposed for the central extremadura batholith spain the country rocks show a pervasive anisotropy that conditioned the style of the structures developed as a consequence of the transference of displacement from the stepped shear zones to the releasing area the kinematic evolution of the resulting megakink fold provided the volume increase necessary for the granite emplacement thermal and kinematic models suggest that the growth of individual plutons took place in periods of no more than several hundred to a few thousand years fast strain rates 10 10 10 11 s 1 must concentrate in local structures e g initiation of kink folds even in zones deforming as a whole under typical strain rates 10 14 1 s 1 granite plutons might be used as strain rate gauges for syn plutonic structures

deformation around rigid particles the influence of slip at the particle matrix interface abstract theoretical and previous experimental studies of rigid particle structures have only considered the behaviour of rigid particles for which the interface between particle and matrix is coherent in natural rocks the boundary behaviour may cover the whole range from free slip to complete coherence examples where slip may be promoted include crack seal deformation during the development of pressure shadows core mantle structures where the mantle is composed of much weaker fine recrystallized material and crystallizing magmas or partially molten rocks where grain boundaries are lubricated by the melt phase analogue scale model experiments have been performed under pure shear and simple shear conditions to compare the particle rotation and the flow in the matrix for both slipping and non slipping particle matrix interfaces when slip does occur particles rotate faster in pure shear and slower in simple shear than for non slip leading to the more rapid development of a shape preferred orientation the preferred orientation tends to be bimodal in simple shear flow the flow and finite strain patterns in the matrix are also strongly influenced by slip at the interface and porphyroclast systems can develop geometries with ambiguous or contradictory shear senses dependent on the original particle orientation in multi particle experiments slip on the interfaces enhances strong strain localization in non linear viscous material to produce patterns very similar to natural s c fabrics

the concept of steady state foliation abstract a steady state foliation is thought of as a foliation with constant orientation and intensity in a rock undergoing steady state flow the problem discussed is whether such straininsensitive foliations exist in rocks and how they might be distinguished from the more familiar strain sensitive foliations steady state foliations would be useful indicators of stress or of strain rate yet misleading if used as indicators of finite strain one requirement for maintenance of steady state foliations is operation of processes that locally weaken grain shape preferred orientation or reduce grain aspect ratios or destroy lithological layering during flow these are the inverses of the processes normally discussed in connection with foliation development many such processes are known though the details of how and when they operate efficiently enough to stabilize a foliation are unknown there is however a tendency for some of them to operate more efficiently at high strains high temperatures and in flow regimes with high vorticity natural and experimental high temperature shear zones are accordingly one environment in which steadystate foliations may be encountered an experiment is described in which a thin specimen of para dichlorobenzene was given a large shearing deformation at 90 of its absolute melting point a steady state foliation was not produced but the technique is a promising one for further microstructural studies where in situ observation of material undergoing large deformations is desirable

strain compatibility and shear zones is there a problem in analyzing deformation in rocks it is important to ensure that the solutions obtained satisfy strain compatibility this creates a challenge to understanding patterns of strain associated with shear zones in which measured strain may appear incompatible with the strain in the shear zone walls flattening strains are common in natural shear zones with locally straight and parallel boundaries to satisfy compatibility conditions such strains require volume loss across the shear zone or deviations from plane strain with or without discontinuities between the shear zone and the wall rock in the case of shear zones for which there is no evidence of volume loss or discontinuities along the shear zone walls problems of strain compatibility may be resolved if individual shear zones are linked together in an appropriate fashion shear zones commonly occur in anastomosing arrays and simple configurations of such arrays and the strains associated with them are examined it is shown that local transpression with strain compatibility can be accounted for in this way quite complex local strain patterns can develop in simple arrays

hydroacoustic infrasonic and seismic monitoring of the submarine eruptive activity and sub aerial plume generation at south sarigan may 2010 abstract explosive submarine volcanic processes are poorly understood due to the difficulties associated with both direct observation and continuous monitoring in this study hydroacoustic infrasound and seismic signals recorded during the may 2010 submarine eruption of south sarigan seamount marianas arc are used to construct a detailed event chronology the signals were recorded on stations of the international monitoring system which is a component of the verification measures for the comprehensive nuclear test ban treaty numerical hydroacoustic and infrasound propagation modelling confirms that viable propagation paths from the source to receivers exist and provide traveltimes allowing signals recorded on the different technologies to be associated the eruption occurred in three stages separated by three hour periods of quiescence 1 a 46 h period during which broadband impulsive hydroacoustic signals were generated in clusters lasting between 2 and 13 min 95 of the 7602 identified events could be classified into 4 groups based on their waveform similarity the time interval between clusters decreased steadily from 80 to 25 min during this period 2 a five hour period of 10 hz hydroacoustic tremor interspersed with large amplitude broadband signals associated infrasound signals were also recorded at this time 3 an hour long period of transient broadband events culminated in two large amplitude hydroacoustic events and one broadband infrasound signal a speculative interpretation consistent with the data suggests that during phase 1 transitions between endogenous dome growth and phreatomagmatic explosions occurred with the magma ascent rate accelerating throughout the period during phase 2 continuous venting of fragmented magma occurred and was powerful enough to breach the sea surface during the climactic phase 3 discrete powerful explosions occurred and sufficient seawater was vaporised to produce the contemporaneous 12 km altitude steam plume

boundary migration and kinking in sheared naphthalene abstract deformation of melt grown anisotropic crystal aggregates of naphthalene with strong b axis crystallographic preferred orientations produces two distinct microstructural features the crystals grown in thin sections have been constrained to deform in simple shear at t 0 9 t m with the b axis oblique to the shear direction in the shortening field the microstructure evolves through crystal kinking with migration of the kink band boundaries in the stretching field migration of boundaries induces the development of brittle ductile shear bands kinking and grain boundary migration complement the dominant b intracrystalline slip in order to accommodate the imposed simple shear at the crystal scale and are similar to the accommodation processes involved in a polycrystal when grain boundary sliding is inactive

volcano infrasound a review abstract exploding volcanoes which produce intense infrasound are reminiscent of the veritable explosion of volcano infrasound papers published during the last decade volcano infrasound is effective for tracking and quantifying eruptive phenomena because it corresponds to activity occurring near and around the volcanic vent as opposed to seismic signals which are generated by both surface and internal volcanic processes as with seismology infrasound can be recorded remotely during inclement weather or in the dark to provide a continuous record of a volcano s unrest moreover it can also be exploited at regional or global distances where seismic monitoring has limited efficacy this paper provides a literature overview of the current state of the field and summarizes applications of infrasound as a tool for better understanding volcanic activity many infrasound studies have focused on integration with other geophysical data including seismic thermal electromagnetic radiation and gas spectroscopy and they have generally improved our understanding of eruption dynamics other work has incorporated infrasound into volcano surveillance to enhance capabilities for monitoring hazardous volcanoes and reducing risk this paper aims to provide an overview of volcano airwave studies from analog microbarometer to modern pressure transducer and summarizes how infrasound is currently used to infer eruption dynamics it also outlines the relative merits of local and regional infrasound surveillance highlights differences between array and network sensor topologies and concludes with mention of sensor technologies appropriate for volcano infrasound study

airwaves generated by an underwater explosion implications for volcanic infrasound 1 a shallow explosion in a fluid is one of the fundamental processes of airwave generation in volcanic eruptions to better understand the mechanism of the airwave generation underwater explosion experiments were conducted although the underwater explosions have been intensely studied over the last century airwaves have received little attention in this study pressure waves were measured in air and under water and the corresponding motion of the water surface was captured by a high speed video camera airwaves and associated styles of the surface motion show similarities determined by the scaled depth defined as the depth divided by the cubic root of the explosion energy the air waveforms are quite different from the pressure waves measured in the water and cannot be completely explained by linear transmission of pressure waves from water to air the mechanism of airwave generation is a combination of wave transmission and dynamics of the interface boundary the first mechanism directly reflects the explosion source and the same source is also observed as the underwater pressure waves on the other hand the second is not necessarily visible in the underwater pressure waves but will provide information on the mechanical properties and behavior of the material above the explosion source each mechanism is analyzed in the experiments

slip system domains i plane strain kinematics of arrays of coherent bands with twinned fibre orientations abstract slip system in rocks often occupy domains each of uniform slip system orientation examples are conjugate faults shear zones folded bedding and crystal lattices domainal behaviour in plane strain is modelled as simple shearing along inextensible fibres an array of alternating band domains with coherent boundaries can undergo a uniform bulk strain with local perturbations in the domains if 1 domain boundaries are planes of mirror symmetry with respect to fibre attitude and 2 domains have alternating fractional widths a and 1 a motion in the models is shown to be a combination of three independent modes plus a bulk rigid motion during mode 1 motion domain boundaries stretch but do not migrate during mode 2 they do not stretch but migrate by lateral translation during mode 3 they migrate by translation and rotation orientation distribution functions odfs are defined by assigning frequencies a and 1 a to orientations and changes in are shown to be due to mode 1 alone changes in a to mode 2 alone mode 3 has no effect on an odf combinations of modes 1 2 and 3 can be used to accommodate an imposed bulk motion two examples are discussed a bulk simple shear and a rigid motion large amounts of simple shear are possible if fibres are on average parallel to the imposed shear direction if modes 1 and 2 are operative the resulting odf has a maximum peak close to the shear direction this may explain the asymmetry of preferred lattice orientations and the occurrence of unique fault sets in rocks that have undergone a progressive simple shear

characterization of the 2008 kasatochi and okmok eruptions using remote infrasound arrays 1 the 2008 plinian eruptions of kasatochi and okmok volcanoes were recorded by six remote international monitoring system infrasound arrays high amplitude infrasound at these stations combined with remote sensing permits insight into important volcanic source parameters such as origin times durations and source characteristics infrasound from the 7 8 august kasatochi eruption consists of three well defined eruption pulses with the first two steam rich and the last ash rich pulse 2 is the most energetic and impulsive okmok produced over 9 h of continuous infrasound on 12 13 july acoustic propagation modeling for the okmok eruption and first kasatochi pulse predict thermospheric ducting and origin times consistent with seismic and satellite observations however theoretical acoustic origin times of pulses 2 3 are predicted to occur 15 min earlier than the seismic stratospheric ducting for these later pulses provides more consistent origin times although both volcanoes ejected ash into the stratosphere 15 km kasatochi produced higher amplitude infrasound than okmok previous studies have shown sustained infrasound with frequencies 2000 km and does not seem to be appreciably affected by changes in ash content between the eruption pulses

remote sensing of volcanoes and volcanic processes integrating observation and modelling introduction volcanoes are often remote and have footprints that may extend across many hundreds or thousands of square kilometres they are generally inaccessible during eruption and may continue to be inaccessible for extended periods of time after eruption while their products can be scattered or dispersed over regional or global scales consequently since direct measurement can only provide us with part of the picture of many volcanic processes remote sensing is now playing an increasingly important role in advancing understanding of the science underlying volcanic behaviour on this planet and beyond e g mouginis mark et al 2000 sparks et al 2012 satellite airborne and ground based remote sensing are increasingly vital tools for monitoring active or potentially active volcanoes and assessing their likely real time or time averaged impact fig 1 at the same time the synoptic scale surveys that are often well suited to remote sensing techniques allow us to address questions about the fundamental processes that control volcano behaviour in a way that is not necessarily possible from individual case studies new research is often driven by technological advancements in the development of novel sensors or launching of new platforms meaning that the space agencies are increasingly involved in identifying scientific questions and priorities e g ferruci et al 2012 multiple and complementary data streams are increasingly being used both to monitor active volcanoes and advance volcanological science the key geophysical parameters that comprise monitoring data streams typically include the categories of i seismicity ii surface deformation iii thermal measurements and iv gas flux and composition data as major components while measurements of seismicity remain the domain of ground based seismometers remote sensing techniques have made major contributions in each of the others this special publication volume is concerned with the use of remote sensing at volcanoes it is split into three parts roughly arranged from the subsurface to the surface and then further afield as volcanic products are injected and dispersed into the atmosphere the papers span a range of applications of remote sensing techniques to monitor and understand a surface deformation b surface thermal anomalies and c gas fluxes as well as tracking ash and gas plumes from eruptions to gain insights into the extent of a volcano s impacts volcanology is driven in part by the operational concerns surrounding volcano monitoring and hazard and crisis management but the goal of volcanological science is at its heart to understand the processes that underlie volcanic activity this special publication is also concerned with how we go from observations to this deeper understanding including the progress that can be made by integrating observations and modelling while this volume focuses mainly on satellite based remote sensing integrating datasets from different platforms is also of vital importance and so papers on airborne remote sensing and measurement from both manned and unmanned aircraft are also included

infrasound from tungurahua volcano 2006 2008 strombolian to plinian eruptive activity abstract strombolian to plinian activity from tungurahua volcano ecuador has been recorded by the autonomous infrasound arrays of the acoustic surveillance for hazardous eruptions ashe project since early 2006 our studies suggest that acoustic energy release during large eruptions does appear to broadly scale with eruption intensity this manuscript provides a detailed chronology and characterization of tungurahua s eruptive activity between 2006 and 2008 and demonstrates the ability to constrain source parameters of significant eruptions such as onset duration and escalation at regional distances by combining infrasound and remote sensing techniques the ashe system in ecuador automatically detected over 20 000 volcanic explosions at an array 37 km from tungurahua and was successful at notifying the onset escalation and cessation of a hazardous february 2008 eruption with a latency of 5 min elevated infrasonic energy from sustained and intense tungurahua eruptions correlates well with ash column heights and their lateral extent during the study period the spectra of these sustained explosive eruptions appear to be recurrent readily recognizable and indicative of volcanic jetting and significant atmospheric ash injection the paroxysmal plinian phase of the august 2006 eruption produced an ash cloud that extended well into the stratosphere 24 km coinciding with a shift of the dominant jetting frequency from 0 25 hz to below 0 1 hz and radiation of over 5 107 w of acoustic power transient explosions were often marked by minor or no ash release and are presumed to be more gas rich a change in the acoustic spectrum of volcanic jetting was also detected in the transition from a sustained to collapsed eruption column at the end of the july 14 2006 eruption the jetting spectrum at tungurahua during a period of sustained pyroclastic density current production changes from a typical double peaked to a single peaked spectrum suggesting remote acoustic monitoring can help ascertain the stability and dynamics of an eruptive column

kinematic and mechanical discontinuity at a coherent interface abstract across a coherent interface displacements are continuous but some components of large strain rotation stretching spin stress and rheology need not be so this accounts for refraction of cleavage and other geological structures the general theory of deformation and motion is used to analyze how discontinuities develop a measure of discontinuity in total deformation gradients strain and rotation is the ratio k of amounts of shear above and below the interface and in directions parallel to it it is shown that k is equal to the ratio of simple shearings above and below the interface provided i the latter ratio is constant in time and ii no volume changes occur these kinematic conditions are shown to hold in newtonian fluids and incompressible neo hookean solids where k is exactly equal to the inverse viscosity ratio or to the inverse rigidity ratio the conditions do not hold in general in reiner rivlin fluids in power law fluids the ratio of simple shearings is constant for two special classes of motion one with little simple shearing along the interface the other with simple shearing alone therefore the rheological contrast can be determined the theoretical results can be used to determine rheological contrasts in nature or experiment provided there is some knowledge of the nature of the flow laws that operate under these conditions an interface is an inbuilt rheometer

fabric domains in quartz mylonites localized three dimensional analysis of microstructure and texture fabric domains of a quartz vein deformed under greenschist facies conditions arc analysed with domainal x ray texture goniometry optical microscopy computer integrated polarization microscopy cip and shape analysis in two mutually perpendicular sections the analysed domains consist of large non recrystallized deformed clast fragments prolate non recrystallized ribbon grains and prolate recrystallized domains in terms of texture monomaximal and polymaximal domains have been distinguished pronounced partitioning of deformation is observed between these domains this strain partitioning asks for caution when making kinematic inferences for fault zones based on a study of domainal fabrics domains persist as fabric elements up to high strains this emphasizes the often neglected role of a non random initial fabric neighbouring domains with alternating c axis orientations and grain boundary preferred orientations indicating opposing senses of shear occur in both sections the bulk texture is controlled by clast and ribbon domains rather than being strictly deformation induced we infer that prolate elongation of clasts and ribbons is achieved mainly by combined prism and basal slip recrystallized domains are characterized by different textures they are deformed by intracrystalline slip combined with grain boundary migration and sliding inclined preferred grain boundary orientations are continuously maintained by grain boundary migration copyright 0 1996 elsevier science ltd

the himalayan main central thrust pile and its quartz rich tectonites in central nepal as a consequence of the india asia collision a deeply rooted crustal slice has been moved southwards over the northern boundary of the indian plate at the present level of observation the main central thrust pile a rock pile of several kilometers thickness is affected by shear deformation which imprinted a flat foliation and a constant n s trending lineation these tectonites were deformed under a wide range of metamorphic conditions grading from lower greenschists up to the sillimanite field the m c t shear zone is studied from the view point of the quartz rich rocks over 100 samples helped to define a microstructural zonation roughly parallel to the thermal one 35 samples particularly rich in quartz have been used for the preferred orientation study of their c axes and a few of them for their a axes strong lattice orientations when undisturbed by mainly secondary recrystallization attest to large plastic strains in quartz the c axes are mostly distributed along unequally populated crossed girdles which may evolve into an inclined single girdle the a axes concentrate perpendicular to the more populated girdle concerning quartz the following is suggested 1 1 the deformation has a dominant shear component responsible for the dominant stretching lineation it could be simple shear in case of inclined single girdles 2 2 one set of a axes line up parallel to the shear direction slip on various planes in the a direction may be an important deformation mechanism 3 3 asymmetry in the lattice preferred orientations could be used to predict the sense of shear for the himalayan thrusting in more than 80 of cases

quantitative texture analysis of glaucophanite deformed under eclogite facies conditions sesia lanzo zone western alps comparison between x ray and neutron diffraction analysis

bubble development in explosive silicic eruptions insights from pyroclast vesicularity textures from raoul volcano kermadec arc critical to understanding explosive eruptions is establishing how accurately representative pyroclasts are of processes during magma vesiculation and fragmentation here we present data on densities and vesicle size and number characteristics for representative pyroclasts from six silicic eruptions of contrasting size and style from raoul volcano kermadec arc we use these data to evaluate histories of bubble nucleation coalescence and growth in explosive eruptions and to provide comparisons with pumiceous dome carapace material density vesicularity distributions show a scarcity of pyroclasts with 65 75 vesicularity however pyroclasts closest to this vesicularity range have the highest bubble number density bnd values regardless of eruptive intensity or style clasts with vesicularities greater than this 65 75 pivotal vesicularity range have decreasing bnds with increasing vesicularities interpreted to reflect continuing bubble growth and coalescence clasts with vesicularities less than the pivotal range have bnds that decrease with decreasing vesicularity and preserve textures indicative of processes such as stalling and open system degassing prior to vesiculation in a microlite rich magma or vesiculation during slow ascent of degassing magma bubble size distributions bsds and bnds show variations consistent with 65 75 representing the vesicularity at which vesiculating magma is most likely to undergo fragmentation consistent with the closest packing of spheres we consider that the observed vesicularity range may reflect the development of permeability in the magma through shearing as it flows through the conduit these processes can act in concert with multiple nucleation events generating a situation of heterogeneous bubble populations that permit some regions of the magma to expand and bubbles to coalesce with other regions in which permeable networks are formed fragmentation preserves the range in vesicularity seen as well as any post fragmentation pre quenching expansion which may have occurred we demonstrate that differing density pyroclasts from a single eruption interval can have widely varying bnd values corresponding to the degree of bubble maturation that has occurred the modal density clasts the usual targets for vesicularity studies have likely undergone some degree of bubble maturation and are therefore may not be representative of the magma at the onset of fragmentation

the hazards of eruptions through lakes and seawater abstract eruptions through crater lakes or shallow seawater referred to here as subaqueous eruptions present hazards from hydromagmatic explosions such as base surges lahars and tsunamis which may not exist at volcanoes on dry land we have systematically compiled information from eruptions through surface water in order to understand the circumstances under which these hazards occur and what disastrous effects they have caused in the past subaqueous eruptions represent only 8 of all recorded eruptions but have produced about 20 of all fatalities associated with volcanic activity in historical time excluding eruptions that have resulted in about a hundred deaths or less lahars have killed people in the largest number of historical subaqueous eruptions 8 followed by pyroclastic flows excluding base surges 5 tsunamis 4 and base surges 2 subaqueous eruptions have produced lahars primarily on high 1000 m steep sided volcanoes containing small

granite emplacement during contemporary shortening and normal faulting structural and magnetic study of the veiga massif nw spain abstract the veiga massif belongs to the calc alkaline series of hercynian granitic rocks of the ibero armorican arc the veiga granodiorite intruded during the upper carboniferous into the core of the wnw ese n verging ollo de sapo antiform formed by precambrian and palaeozoic metasediments internal fabrics show that magma intrusion was contemporary with shortening measurements of feldspars orientations and anisotropy of magnetic susceptibility ams throughout the granite are consistent and indicate a foliation striking wnw ese parallel to folding with a constant dip of 75 85 n the zonation of bulk low field susceptibility is related to mineral content and indicates a more basic composition at the southern and western borders the difference in elevation between outcrops more than 600 m allows us to infer the three dimensional attitude of granite fabrics throughout the massif syn magmatic fabric folds are preserved in the inner part of the igneous body the highest degree of magnetic anisotropy is observed in areas located near the bottom and top of the intrusion at the scale of the massif foliation is convergent toward the bottom of the intrusion along a line located at its northern border where the magma source is interpreted to be located in the western border of the massif the presence of c and s structures indicates that magma cooling was coeval with movement of the chandoiro fault a n s striking normal fault with a n290e hanging wall displacement direction these results indicate that emplacement of the veiga granite is coeval with nne ssw shortening and with an wnw ese extension direction parallel to the trend of the late folds

crystal rotation by mechanical interaction between plastically anisotropic crystals abstract in polycrystalline material minerals with pronounced plastic anisotropy may experience inhomogeneous deformation and significant mechanical interaction between neighboring crystals to study the effect of crystal interaction on preferred orientation pure shear of a polycrystalline material with identical orthogonal slip systems was modeled two dimensionally by the finite element method such a material is non ductile in the formal von mises sense because it lacks five independent slip systems as a result each crystal has highly anisotropic strength because a homogeneous irrotational strain history in a two dimensional crystal with identical orthogonal slip systems does not cause lattice rotation rotation caused by crystal interaction is readily observed in the finite element models slip planes rotate toward a preferred orientation parallel to maximum shear stress 45 to shortening and extension directions mechanical interaction between neighboring crystals produces this preferred orientation by rigid body rotation of crystals or parts of crystals not favorably oriented for slip

evanescent wave coupling in a geophysical system airborne acoustic signals from the mw 8 1 macquarie ridge earthquake atmospheric low frequency sound i e infrasound from underwater events has not been considered thus far due to the high impedance contrast of the water air interface making it almost fully reflective here we report for the first time on atmospheric infrasound from a large underwater earthquake mw 8 1 near the macquarie ridge which was recorded at 1325 km from the epicenter seismic waves coupled to hydroacoustic waves at the ocean floor after which the energy entered the sound fixing and ranging channel and was detected on a hydrophone array the energy was diffracted by a seamount and an oceanic ridge which acted as a secondary source into the water column followed by coupling into the atmosphere the latter results from evanescent wave coupling and the attendant anomalous transparency of the sea surface for very low frequency acoustic waves

crustal structure of central japan and its petrological implications the crustal structure of central honshu japan has been influenced by several tectonic events a series of collision processes during the late tertiary extensive faulting highly compressive deformation and quaternary volcanism the southern part of the study area is covered by various granitic rocks which intrude into old palaeozoic formations quaternary volcanoes occupy the northern part and cover the basement which is mainly composed of granitic rocks and tertiary formations a traveltime inversion for velocity and interface depth was applied to the seismic data together with constraints from amplitude forward modelling to produce a seismic velocity model of the crust in central honshu in this experiment both refracted p and s waves are clearly recorded along a 110 km profile these provide constraints on the 2 d p and s wave velocity structure down to a depth of about 10 km moreover clear p wave reflections from intracrustal interfaces provide constraints on deeper parts of the crust down to about 25 km for the p wave velocity model the velocities of near surface layers show large lateral variations from 3 7 to 4 4 km s 1 increasing towards the south underlying layers have velocities ranging from 4 85 to 5 6 km s 1 velocities in the range 5 85 6 2 km s 1 characterize the upper crust that extends to a depth of about 15 km for the s wave velocity model the near surface layer velocities change from 1 7 to 2 55 km s 1 showing remarkable lateral heterogeneity whilst the upper crust is characterized by velocities of 3 4 3 6 km s 1 the deeper parts are modelled by two prominent reflectors in the mid crust the shallower one which delineates the bottom of the upper crust dips southwards from 14 to 16 km the deeper reflector lies between 20 and 24 km depth and dips northwards the velocity in this mid crustal layer is 6 35 km s 1 at the top and 6 7 km s 1 at the bottom the crustal thickness under the profile could not be determined because of a lack of pn and or pm p phases this study also presents the vp vs ratio and the poisson s ratio distribution and gives the probable composition of the upper crust poisson s ratio varies from 0 29 to 0 34 which can be ascribed to a porous and water saturated structure for the near surface layers in the northern part of the region poisson s ratios of about 0 24 0 25 in the southern part and 0 22 0 24 in the upper crust together with the geological data show that the upper crust has a felsic content and is formed by granite granodioritic rocks with a high quartz content the changes in the quartz content explain the lateral variations of vp vs and poisson s ratio in the model the higher velocities in the middle crust suggest a more mafic structure probably composed of diorites