estimates of plume height from infrasound for regional volcano monitoring abstract present efforts in volcano monitoring particularly in southeast asia rely on the combination of local data generally gathered at less than 100 km from the volcano and satellite remote sensing while this combination has its strengths there are still weaknesses that the use of ground based remote sensing data such as distant infrasound measurements could help alleviate infrasound offers tools for detecting and characterizing volcanic plumes independent of cloud cover and time of day larger volcanic eruptions generate infrasound that is related to the plume and offers a unique view into eruption dynamics within the context of monitoring past research has demonstrated that infrasound can be used to estimate source parameters such as the rate at which material is ejected from volcanic vents during eruptions these are key input parameters into empirical and numerical models to estimate the height of volcanic plumes atmospheric ash transport and dispersion here we demonstrate the use of remote infrasound in estimating the height of volcanic plumes including a case study on the may 30 2014 plume from the volcano sangeang api in indonesia we were able to determine the plume height using infrasound gathered from 2000 to over 5000 km distance from the volcano during the january 2020 eruption of taal volcano in the philippines this method was applied to remote infrasound recorded 1650 km to the east we show that our workflow can be implemented in near real time offering an effective tool for rapid plume height measurement including associated uncertainties when volcanic clouds are not visible from the ground or space

acoustic source inversion to estimate volume flux from volcanic explosions we present an acoustic waveform inversion technique for infrasound data to estimate volume fluxes from volcanic eruptions previous inversion techniques have been limited by the use of a 1 d green s function in a free space or half space which depends only on the source receiver distance and neglects volcanic topography our method exploits full 3 d green s functions computed by a numerical method that takes into account realistic topographic scattering we apply this method to vulcanian eruptions at sakurajima volcano japan our inversion results produce excellent waveform fits to field observations and demonstrate that full 3 d green s functions are necessary for accurate volume flux inversion conventional inversions without consideration of topographic propagation effects may lead to large errors in the source parameter estimate the presented inversion technique will substantially improve the accuracy of eruption source parameter estimation cf mass eruption rate during volcanic eruptions and provide critical constraints for volcanic eruption dynamics and ash dispersal forecasting for aviation safety application of this approach to chemical and nuclear explosions will also provide valuable source information e g the amount of energy released previously unavailable

theory of the airborne sound field generated in a resonant magma conduit abstract explosive sources triggered inside a magma conduit may excite the conduit into acoustic resonance the acoustic field in the conduit can propagate into the atmosphere through an open vent and ensonify the overlying atmosphere the character of the airborne sound field is determined by a combination of propagation and source effects the resonance of the magmatic conduit and the diffraction of the sound field at the volcanic vent are acoustic propagation effects whereas the explosion pressure signature and the firing rate of the explosions define the source characteristics for wavelengths larger than the conduit radius only the longitudinal resonances of the magmatic conduit are relevant and the open vent radiates like a piston surrounded by an infinite baffle in this case the fluid particle velocities are directed along the axis of the conduit and the sound field may propagate into the surrounding bedrock through the conduit wall displacement induced by the fluid overpressure this coupling may produce seismic signals with banded spectra such as volcanic tremor and long period events the airborne pressure field retains the modal structure of the sound field in the magmatic conduit which contains information on the conduit geometry and geo acoustic properties of the magma the seismic wavefield is driven by the acoustic field in the magma and also contains this information although it may be filtered by propagation effects in the bedrock the theoretical sound field in the magma conduit is used to interpret seismic tremor signals recorded at mt spurr volcano alaska rapid variations in the acoustic impedance of the magma conduit terminations can create systematic changes in the tremor spectra which can be used to monitor changes in the magmatic system the results of the modelling illustrate the difference between source effects and conduit resonance as well as the value of seismoacoustic measurements in volcanic environments

on the relation between infrasound seismicity and small pyroclastic explosions at karymsky volcano 1 ground and atmospheric propagating elastic waves are integrated with digitized video to reconstruct important parameters during the onset of eruptions at karymsky volcano in 1999 muzzle velocities which range from 10 to 55 m s for 34 analyzed explosive events are found to be very well correlated with eruption velocities synthesized from infrasonic trace data acoustic modeling proposed here invokes a linear acoustic source consistent with a 3 m piston that accelerates upwards timing of acoustic arrivals relative to video records of material emission is used to constrain fragmentation sources depths which are assumed to be coincident with infrasound generation these sources are generally shallow with an observed vertical range of about 15 m systematic changes in source depth are observed during two nights of data collection and are attributed to variations in the depth of the magma free surface relative timing of acoustic and seismic arrivals is used to identify the presence of seismicity prior to fragmentation this seismicity is emergent and low intensity but significant because it precedes the presumed fragmentation events by variable amounts up to 4 s the primary short period seismic phases appear coincident with the initiation of fragmentation and infrasound generation because of the complexity of the seismic green s function it is not possible to correlate amplitude from a specific seismic pulse with observed eruption intensity

utilizing the solution of sound diffraction by a thin screen to evaluate infrasound waves attenuated around volcano topography abstract the observation of infrasound signals in the vicinity of volcanoes is a powerful tool to understand the source of explosive volcanic activity although the propagation of infrasound signals is affected by the local topography such effects are often ignored in the analysis leading to potential misinterpretation of the source parameters in this study we propose a simple low cost method of evaluating the attenuation of infrasound signals by topographical barriers in this method the first step approximates the elevation profile between the source and station into one thin screen like barrier then a mathematically exact solution of a sound diffraction problem is adopted to evaluate the attenuation of the infrasound amplitudes to assess the validity of this method the obtained estimates are compared with actual infrasound data observed at sakurajima volcano japan the results show that the estimates of relative amplitude to a reference station are more accurate than those considering only geometrical spreading suggesting that the proposed method provides a useful first order investigation of the attenuation of infrasound signals the spatial distribution of the attenuation in the entire area of the volcano was also estimated revealing a significant contrast between the eastern and western sides of the study area variations in signal attenuation also depend on the radial distance from the crater and were mainly attributed to variations of the relative screen height to the incident wavelength

increased sediment accumulation rates and climatic forcing in the central andes during the late miocene new zircon u pb ages from six volcanic ashes in the subandean foothills provide for the first time well constrained depositional ages of the late cenozoic strata in this region the radiometric ages indicate 12 4 0 5 ma 7 93 0 26 ma and 5 94 0 20 ma depositional ages for the bases of yecua tariquia and guandacay formations respectively we used these zircon ages to determine the accumulation rates of the late cenozoic foreland sediments in the subandes our results show a fourfold increase from 130 to 628 m m y in sediment accumulation rates between ca 7 9 and 6 ma during the deposition of andean derived coarsening and thickening upward sandstone dominated tariquia strata this increased accumulation rate correlates well with monsoon intensification and climate variability in south america which was accompanied by the development of fluvial megafan paleodrainage networks in the central andes this correlation suggests that climate may have been an important factor between the late miocene and pliocene

environmental signal propagation in sedimentary systems across timescales abstract earth surface processes operate across erosionally dominated landscapes and deliver sediment to depositional systems that can be preserved over a range of timescales the geomorphic and stratigraphic products of this source to sink sediment transfer record signals of external environmental forcings as well as internal or autogenic dynamics of the sedimentary system here we evaluate environmental signal propagation across sediment routing systems with emphasis on sediment supply qs as the carrier of up system forcings we review experimental numerical and natural examples of source to sink sediment routing and signal propagation during three timescales 1 historic which includes measurement and monitoring of events and processes of landscape change and deposition during decades to centuries 2 centuries to several millions of years referred to as intermediate timescale and 3 deep time we discuss issues related to autogenic dynamics of sediment transport transient storage and release that can introduce noise lags and or completely mask signals of external environmental forcings we provide a set of conceptual and practical tools for evaluating sediment supply within a source to sink context which can inform interpretations of signals from the sedimentary record these tools include stratigraphic and sediment routing system characterization sediment budgets geochronology detrital mineral analysis e g thermochronology comparative analog approaches and modeling techniques to measure calculate or estimate the magnitude and frequency of external forcings compared to the characteristic response time of the sediment routing systems

investigating spectral distortion of local volcano infrasound by nonlinear propagation at sakurajima volcano japan author s maher s p matoza r s de groot hedlin c d gee k l fee d yokoo a

acoustic multipole source model for volcanic explosions and inversion for source parameters summary volcanic explosions are accompanied by strong acoustic pressure disturbances in the atmosphere with a proper source model these acoustic signals provide invaluable information about volcanic explosion dynamics far field solutions to volcanic infrasound radiation have been derived above a rigid half space boundary and a simple inversion method was developed based on the half space model acoustic monopole and dipole sources were estimated simultaneously from infrasound waveforms stability of the inversion procedure was assessed in terms of variances of source parameters and the procedure was reliable with at least three stations around the infrasound source application of this method to infrasound observations recorded at tungurahua volcano in ecuador successfully produced a reasonable range of source parameters with acceptable variances observed strong directivity of infrasound radiation from explosions at tungurahua are successfully explained by the directivity of a dipole source model the resultant dipole axis in turn shows good agreement with the opening direction of the vent at tungurahua which is considered to be the origin of the dipole source the method is general and can be utilized to study any monopole dipole or combined sources generated by explosions

effect of late cenozoic aridification on sedimentation in the eastern cordillera of northwest argentina angastaco basin this study evaluates the effect of climate on facies grain size and sedimentation rates using sedimentology geochronology and stable isotope geochemistry for miocene pliocene deposits in the angastaco basin eastern cordillera northwest argentina u pb zircon data from ash layers constrain the transition between the finer grained fluvial lacustrine palo pintado formation and the coarser grained fluvial alluvial san felipe formation to ca 5 2 ma and the first deposition of sediment derived from the present day orographic barrier to ca 4 ma 13 c values from pedogenic carbonate nodules range from 15 4 to 10 2 for the palo pintado formation and from 9 5 to 8 2 for the san felipe formation this can be best explained by increased sustained aridity since ca 5 ma the 18 o values range from 9 6 to 5 9 for the palo pintado formation and from 6 1 to 5 2 for the san felipe formation corroborating this interpretation the shift toward more arid conditions correlates with a significant increase in grain size but no significant change in sedimentation rate because aridity precedes the development of an orographic effect we interpret the grain size increase in the angastaco basin since ca 5 ma to be a response of the sedimentary system to aridification resulting from regional climate change

steady sedimentation and lithologic completeness bermejo basin argentina late miocene strata of the bermejo basin argentina 11 7 ma yield a magnetic polarity record of unusually high fidelity three sections spaced along strike over 20 km are firmly correlated with the magnetic polarity time scale all three sections demonstrate high accumulation rates up to 0 88 mm yr and include an interval of normal polarity extending from 7 84 to 7 81 ma that has yet to be resolved on the magnetic polarity time scale the polarity completeness demonstrated by bermejo strata is a result of high accumulation rates as well as environmental factors strata were deposited in an arid setting in which unconfined flows were the primary transporters of sediment shallow flow depths led to low basal shear stresses and thus to little potential for erosion these interpretations are corroborated by field observations steady sedimentation in the bermejo basin is expressed by the low variance short term accumulation rates have from the average long term accumulation rate uniformity of sed

volcanic eruptions lightning and a waterfall differentiating the menagerie of infrasound in the ecuadorian jungle 1 in northeastern ecuador near reventador volcano the airwaves are filled with infrasound here we identify the locations and characterize three distinct sources of local infrasound including two types of infrasonic sources which are not commonly discussed in the literature the first of these novel sources is an intense and continuous radiator with a fixed location corresponding to san rafael waterfall the signal from the river exhibits a tremor like envelope that is well correlated across the 3 element infrasound network beyond the river we also observe and map spatially variable sources corresponding to thunder these transient signals have impulsive onsets but are not well correlated across the network and are attributable to spatially distributed source regions finally we identify plentiful infrasound corresponding to reventador s volcanic vent that is associated with unrest this study demonstrates the utility of dispersed infrasound networks for distinguishing variable sources and improving interpretation of mechanisms of infrasound radiators

statistical significance of minimum of the order parameter fluctuations of seismicity before major earthquakes in japan in a previous publication the seismicity of japan from 1 january 1984 to 11 march 2011 the time of the m9 tohoku earthquake occurrence has been analyzed in a time domain called natural time chi the order parameter of seismicity in this time domain is the variance of chi weighted for normalized energy of each earthquake it was found that the fluctuations of the order parameter of seismicity exhibit 15 distinct minima deeper than a certain threshold 1 to around 3 months before the occurrence of large earthquakes that occurred in japan during 1984 2011 six out of 15 of these minima were followed by all the shallow earthquakes of magnitude 7 6 or larger during the whole period studied here we show that the probability to achieve the latter result by chance is of the order of 10 5 this conclusion is strengthened by employing also the receiver operating characteristics technique

simulation and inversion of harmonic infrasound from open vent volcanoes using an efficient quasi 1d crater model abstract volcanic activity excites low frequency acoustic waves termed infrasound in the atmosphere infrasound observations can be used to provide constraints on eruption properties such as crater geometry and volume flux at open vent volcanoes such as erebus antarctica and villarrica chile the infrasound signal is modulated by the crater properties eruptive activity at the bottom of the crater such as unsteady degassing or explosions can excite the air mass within the crater into resonance leading to infrasound generation with signals possessing clear spectral peaks termed harmonics therefore the effect of the crater on the infrasound signal or crater acoustic response must be accounted for when inverting harmonic infrasound observations for eruption properties at open vent volcanoes here we develop a linearized model of quasi one dimensional 1d wave propagation inside volcanic crater coupled with 3d axisymmetric radiation into the atmosphere from the crater with waves generated by a volumetric flow rate source at the bottom of the crater we perform simulations for a range of volcanic crater geometries temperature profiles gas compositions and source descriptions to explore the influence of these properties on the infrasound signal the observed infrasound signal depends on the flow rate source time function but interference of up and down going waves within the crater selectively amplifies the signal at the resonant frequencies of the crater the crater resonance model presented here is verified by comparison with an established three dimensional 3d infrasound code and is shown to be appropriate for realistic crater geometries when the crater radius is less than approximately one quarter of the acoustic wavelength the model presented here is more computationally efficient and can be used to invert infrasound observations for a range of properties such as crater geometry or volumetric flow rate associated with eruptions we demonstrate the utility of our efficient modeling framework by inverting harmonic infrasound observations for the crater geometry and position of the lava lake at villarrica volcano this technique may be used at other open vent volcanoes to constrain dynamic crater geometry and provide insights about lava lake motions and infrasound producing eruption sources

seismic and acoustic signatures of surficial mass movements at volcanoes abstract surficial mass movements such as debris avalanches rock falls lahars pyroclastic flows and outburst floods are a dominant hazard at many volcanoes worldwide understanding these processes cataloging their spatio temporal occurrence and detecting tracking and characterizing these events would advance the science of volcano monitoring and help mitigate hazards seismic and acoustic methods show promise for achieving these objectives many surficial mass movements generate observable seismic and acoustic signals and many volcanoes are already monitored significant progress has been made toward understanding modeling and extracting quantitative information from seismic and infrasonic signals generated by surficial mass movements however much work remains in this paper we review the state of the art of the topic covering a range of scales and event types from individual rock falls to sector collapses we consider a full variety of volcanic settings from submarine to subaerial shield volcano to stratovolcano finally we discuss future directions toward operational seismo acoustic monitoring of surficial mass movements at volcanoes

the qs problem sediment volumetric balance of proximal foreland basin systems although the stratigraphy of sedimentary basins depends on the balance between the magnitude and grain size characteristics of the sediment supply qs and the spatial distribution of tectonic subsidence generating accommodation x qs is problematical to measure in present day sediment routing systems and formidably difficult to predict in their ancient counterparts this challenge was tackled by treating the sediment discharge from the outlet of mountain catchments as the result of incision by a drainage network with a bulk diffusivity based on the length over which the mean annual rainfall is concentrated the size relief and slope of palaeo catchments acting as feeders for sediment routing systems are used to run simulations of sediment discharge and bulk diffusivity for a range of annual precipitation values a wide range of observable geological phenomena can be used to converge on the most likely solutions for qs including depositional volumes in the basin and bedrock thermochronology and detrital cosmogenic nuclide dating to constrain catchment erosion rates modelled sediment discharges can be checked with estimates derived from global regressions the sediment efflux of mountain catchments serves as a boundary condition for down system sediment transport and deposition variations in the volumetric ratio of sediment supply to available accommodation qs x determines patterns of transverse versus longitudinal axial sediment dispersal the volumetric ratio may change as a result of variations in climatic parameters tectonic uplift rate and catchment expansion an abrupt climate change to higher precipitation values promotes higher qs x but transient landscape response causes a return to values close to the baseline generating a distinctive down system extension of a gravel spike catchment expansion has a similar but more prolonged effect on gravel progradation in contrast a change in tectonic forcing such as an increase in slip rate on a border fault causes little change in qs x because increased subsidence compensates for the increased sediment supply studies of mid eocene oligocene sediment routing systems in the south central pyrenees allow the discrimination of different types of proximal wedge top sedimentary systems on the basis of the volumetric ratio of qs to accommodation x i small steep local fan systems in tectonically ponded underfilled basins supplied by low sediment discharges ii tectonically guided long range axial systems fed by large sediment discharges from widely spaced palaeovalleys and iii large shallow sloping transverse megafans burying underlying defunct or active tectonic structures supplied by high to very high sediment discharges understanding the role of variations in qs helps to explain the syntectonic evolution of proximal foreland basin systems the oligocene miocene north alpine foreland basin switzerland is qualitatively identified as a high qs example the miocene recent northern apennines of italy as a low qs example and the eocene oligocene southern pyrenees of spain as intermediate in character

middle to late miocene stepwise climate cooling evidence from a high resolution deep water isotope curve spanning 8 million years 1 we present high resolution 2 3 kyr benthic foraminiferal stable isotopes in a continuous well preserved sedimentary archive from the west pacific ocean ocean drilling program site 1146 which track climate evolution in unprecedented resolution over the period 12 9 to 8 4 ma we developed an astronomically tuned chronology over this interval and integrated our new records with published isotope data from the same location to reconstruct long term climate and ocean circulation development between 16 4 and 8 4 ma this extended perspective reveals that the long eccentricity 400 kyr cycle is prominently encoded in the 13c signal over most of the record reflecting long term fluctuations in the carbon cycle the 18o signal closely follows variations in short eccentricity 100 kyr and obliquity 41 kyr in particular the obliquity cycle is prominent from 14 6 to 14 1 ma and from 9 8 to 9 2 ma when high amplitude variability in obliquity is congruent with low amplitude variability in short eccentricity the 18o curve is additionally characterized by a series of incremental steps at 14 6 13 9 13 1 10 6 9 9 and 9 0 ma which we attribute to progressive deep water cooling and or glaciation episodes following the end of the miocene climatic optimum on the basis of 18o amplitudes we find that climate variability decreased substantially after 13 ma except for a remarkable warming episode at 10 8 10 7 ma at peak insolation during eccentricity maxima 100 and 400 kyr this transient warming associated with a massive negative carbon isotope shift is reminiscent of intense global warming events at eccentricity maxima during the miocene climatic optimum

effects of miocene pliocene global climate changes on continental sedimentation a case study from the southern central andes national science foundation graduate research fellowship national geographic young explorer s grant 9744 15 geological society of america graduate student research grant

influence of near source volcano topography on the acoustic wavefield and implication for source modeling in near source conditions 5 km the atmosphere is often assumed to be fully transparent to acoustic waves and to have a small effect on the acoustic wavefield as a consequence the propagation of the acoustic waves in the atmosphere near the source is often neglected and waveform is compensated only in amplitude by the inverse of the distance from the source however the amplitude distribution at five infrasonic stations deployed around the active craters of the stromboli volcano reveals anomalous decay up to 11 db larger than expected which cannot be explained in terms of energy loss for geometrical spreading the distribution of amplitude decay changes for different source positions suggesting a strong relationship with the source to receiver path geometry by using 2d fdtd modeling we show that the anomalous amplitude distribution of the acoustic waves at stromboli is not necessarily due to the source radiation pattern but it is strongly influenced by the topography of the ground atmosphere interface diffraction and reflection of topography contaminate the acoustic wavefield and have a strong effect in reducing the amplitude and altering the waveform our work demonstrates that line of sight conditions are quite difficult to be achieved in acoustic experiments and that a detailed knowledge of the topography along the crater receiver path is necessary whenever infrasound waveforms are used to invert for the source process

interpretation and utility of infrasonic records from erupting volcanoes abstract in the most basic seismo acoustic studies at volcanoes infrasound monitoring enables differentiation between sub surface seismicity and the seismicity associated with gas release under optimal conditions complicated degassing signals can be understood relative explosion size can be assessed and variable seismo acoustic energy partitioning can be interpreted the extent to which these points may be investigated depends upon the quality of the infrasonic records a function of background wind noise microphone sensitivity and microphone array geometry and the type of activity generated by the volcano frequency of explosions bandwidth of the signals and coupling efficiency of the explosion to elastic energy to illustrate the features benefits and limitations of infrasonic recordings at volcanoes we showcase acoustic and seismic records from five volcanoes characterized by explosive degassing these five volcanoes erebus in antarctica karymsky in russia and sangay tungurahua and pichincha in ecuador were the focus of seismo acoustic experiments between 1997 and 2000 each case study provides background information about the volcanic activity an overview of visual observations during the period of monitoring and examples of seismo acoustic data we discuss the benefits and utility of the infrasound study at each respective volcano finally we compare the infrasound records and eruptive activity from these volcanoes with other volcanoes that have been the focus of previous seismo acoustic experiments

three dimensional volcano acoustic source localization at karymsky volcano kamchatka russia abstract we test two methods of 3 d acoustic source localization on volcanic explosions and small scale jetting events at karymsky volcano kamchatka russia recent infrasound studies have provided evidence that volcanic jets produce low frequency aerodynamic sound jet noise similar to that from man made jet engines for man made jet noise noise sources localize along the turbulent jet flow downstream of the nozzle discrimination of jet noise sources along the axis of a volcanic jet requires high resolution in the vertical dimension which is very difficult to achieve with typical volcano acoustic network geometries at karymsky volcano an eroded edifice dvor caldera adjacent to the active cone provided a platform for the deployment of five infrasound sensors in july 2012 with intra network relief of 600 m the network was designed to target large scale jetting but unfortunately only small scale jetting and explosions were recorded during the 12 day experiment a novel 3 d inverse localization method srcloc is tested and compared against a more common grid search semblance technique simulations using synthetic signals show that srcloc is capable of determining vertical solutions to within 150 m or better for signal to noise ratios 1 for this network configuration however srcloc locations for explosions and small scale jetting at karymsky volcano show a persistent overestimation of source elevation and underestimation of sound speed the semblance method provides more realistic source locations likely because it uses a fixed realistic sound speed of 340 m s explosion waveforms exhibit amplitude relationships and waveform distortion strikingly similar to those theorized by modeling studies of wave diffraction around the crater rim we suggest that the delay of acoustic signals and apparent elevated source locations are due to raypaths altered by topography and or crater diffraction effects implying that topography in the vent region must be accounted for when attempting 3 d volcano acoustic source localization though the data presented here are insufficient to resolve small scale jet noise sources similar techniques may be successfully applied to large volcanic jets in the future

volcano infrasonic signals and magma degassing first order experimental insights and application to stromboli we demonstrate the rise and expansion of a gas slug as a fluid dynamic source mechanism for infrasonic signals generated by gas puffing and impulsive explosions at stromboli the fluid dynamics behind the rise expansion and burst of gas slugs in the confines of an experimental tube can be characterised into different regimes passive expansion occurs for small gas masses where negligible dynamic gas over pressure develops during bubble ascent and prior to burst meniscus oscillation forms an important infrasonic source with increasing gas mass a transition regime emerges where dynamic gas over pressure is significant for larger gas masses this regime transforms to fully explosive behaviour where gas over pressure dominates as an infrasonic source and bubble bursting is not a critical factor the rate of change of excess pressure in the experimental tube was used to generate synthetic infrasonic waveforms qualitatively the waveforms compare well to infrasonic waveforms measured from a range of eruptions at stromboli assuming pressure continuity during flow through the vent and applying dimensionless arguments from the first order experiments allows estimation of eruption metrics from infrasonic signals measured at stromboli values of bubble length gas mass and over pressure calculated from infrasonic signals are in excellent agreement with those derived by independent means for eruptions at stromboli therefore providing a method of estimating eruption metrics from infrasonic measurement

infrasonic monitoring at stromboli volcano during the 2003 effusive eruption insights on the explosive and degassing process of an open conduit system 1 stromboli is an open conduit volcano characterized by persistent conduit degassing and explosive dynamics during the 2003 effusive eruption we monitored this activity with a five element array deployed at 450 m from the active craters the array allows us to track in real time changes of explosive activity in terms of source position and excess pressure release infrasonic monitoring located the new active vents in the same preeruptive position revealing that the collapse of the crater terrace has not changed the geometry of the shallow feeding system elevation of the infrasonic source is stable at 750 m above sea level coincident with the elevation of the crater terrace this suggests a shallow position of the magma column or if the source is embedded in the conduit diffraction at the crater rim at the end of the eruption back azimuth analysis indicates that explosive activity was progressively reestablished at all of the craters following a ne toward sw direction along the collapsed trench the array detected significant small amplitude 1 pa infrasonic activity occurring at a rate of approximately one pulse every 2 s and generally located in only one vent at a time this persistent activity is not related to strombolian explosion but we infer it is reflecting the overpressurized degassing of the magma column amplitude distribution of 7 million infrasonic signals shows that this degassing is 1 order of magnitude more energetic than the explosions besides infrasonic amplitude distribution presents a decay with a double slope indicating that explosions and degassing are driven by conduit dynamics acting at two different rates

finite difference time domain modeling of transient infrasonic wavefields excited by volcanic explosions 1 numerical modeling of waveform diffractions along the rim of a volcano vent shows high correlation to observed explosion signals at karymsky volcano kamchatka russia the finite difference modeling assumed a gaussian source time function and an axisymmetric geometry a clear demonstration of the significant distortion of infrasonic wavefronts was caused by diffraction at the vent rim edge data collected at karymsky in 1997 and 1998 were compared to synthetic waveforms and variations of vent geometry were determined via grid search karymsky exhibited a wide range of variation in infrasonic waveforms well explained by the diffraction and modeled as changing vent geometry rim diffraction of volcanic infrasound is shown to be significant and must be accounted for when interpreting source physics from acoustic observations

influence of atmospheric structure and topography on infrasonic wave propagation the effects of topography and atmospheric structures on infrasonic wave propagation from a volcanic source were investigated using observations and numerical modeling this paper presents the first long term observational data set showing spatiotemporal variations in patterns of infrasound propagation at distances of up to 60 km from a persistently active infrasound source sakurajima volcano japan the data show that the amplitudes of infrasonic waves received at distant stations relative to those received at a reference station close to the source can vary up to an order of magnitude over short time intervals and short distances and that they do not follow the theoretical geometric decay expected for homogeneous media moreover waveforms also change significantly in both time and space numerical simulations were performed using a two dimensional finite difference time domain 2 d fdtd method effects of atmospheric structure and topography are included in a vertical section parallel to the wave propagation direction the simulation successfully reproduced the variations of amplitudes and waveforms results are interpreted in terms of wave refraction due to sound and wind speed gradients and wave diffraction at topographic barriers our numerical results indicate that both atmospheric and topographic propagation effects are nonnegligible to evaluate the propagation effects and determine source processes in spatially and temporally varying infrasound data atmospheric data with a time resolution higher than is currently available are required if the data are available the present results suggest that the propagation effects could be evaluated using 2 d fdtd modeling at realistic calculation times

neogene deformation of the flat subduction segment of the argentine chilean andes magnetostratigraphic constraints from las juntas la rioja province argentina substantial neogene deformation occurred in the part of the andes mountains and the sierras pampeanas that overlie a subhorizontal segment of the subducting nazca plate in northern argentina the history of the volcanic arc suggests that the nazca plate attained the present low angle inclination between about 17 and 10 ma with the region underlain by the flat nazca plate widening eastward thereafter we compare the history of deformation provided by magnetostratigraphy of miocene strata in foreland and intermontane basins to the history of the subducting plate at las juntas in the precordillera thin skinned thrust belt 4 780 m of neogene nonmarine strata record the initiation and termination of sedimentation in a segment of a foreland basin magnetostratigraphic data complemented by fission track dating of an interbedded tuff indicate that the strata span from 18 to 9 ma the earliest strata correlate to the end of a time of volcanic activity in the magmatic arc and the beginning of reverse faulting in the frontal cordillera subsequently the deformation front migrated eastward generating the precordillera thrust belt and finally the sierras pampeanas basement uplifts the rate of strata accumulation varied systematically as new uplifts arose with a maximum rate exceeding 1 0 mm a between 15 and 12 ma a correlation between the deformational history and the geometric history of the subducted slab suggests that thrusting migrated eastward as the angle of subduction shallowed although large scale factors affecting the plate margin beyond the flat slab segment may have partly induced the compressional deformation this correlation suggests that processes related to flat subduction are of importance in deforming the continental plate

explosions and periodic tremor at karymsky volcano kamchatka russia summary the explosions of karymsky volcano often produce signals containing a sequence of repeating pulses recorded on acoustic and seismic sensors known as chugging the amplitudes of these pulses correlate with the time interval between pulses for a given measured acoustic pressure seismic amplitudes take on arbitrary values up to a specific empirically determined threshold conversely events with a small seismic amplitude yielded acoustic waves with large variations and large amplitude seismic events corresponded to large acoustic waves these observations are not consistent with a source modelled by a resonating conduit rather a model consisting of a sequence of discrete pulses explains the data and provides a framework for understanding the dynamics of degassing at the vent the physical model for chugging involves a time varying narrowing vent where gasses are released in a series of oscillations which appear to be harmonic but instead are modelled as short term transients or discrete pulses suggestive of choked flow

volcanic eruptions observed with infrasound 1 infrasonic airwaves produced by active volcanoes provide valuable insight into the eruption dynamics because the infrasonic pressure field may be directly associated with the flux rate of gas released at a volcanic vent infrasound also enhances the efficacy of volcanic hazard monitoring and continuous studies of conduit processes here we present new results from erebus fuego and villarrica volcanoes highlighting uses of infrasound for constraining quantitative eruption parameters such as eruption duration source mechanism and explosive gas flux

volume flow rate estimation for small explosions at mt etna italy from acoustic waveform inversion this study was supported by nerc grant ne p00105x 1 and by european unions horizon 2020 research and innovation programme under the marie sklodowska curie grant agreement 798480

analysis of gas jetting and fumarole acoustics at aso volcano japan abstract the gas thrust region of a large volcanic eruption column is predominately a momentum driven fluid flow process that perturbs the atmosphere and produces sound akin to noise from jet and rocket engines termed jet noise we aim to enhance understanding of large scale volcanic jets by studying an accessible less hazardous fumarolic jet we characterize the acoustic signature of 2 5 meter wide vigorously jetting fumarole at aso volcano japan using a 5 element infrasound array located on the nearby crater the fumarole opened on 13 july 2015 on the southwest flank of the partially collapsed pyroclastic cone within aso volcano s naka dake crater and had persistent gas jetting which produced significant audible jet noise the array was 220 m from the fumarole and 57 6 from the vertical jet axis a recording angle not typically feasible in volcanic environments array processing is performed to distinguish fumarolic jet noise from wind highly correlated periods are characterized by sustained low amplitude signal with a 7 10 hz spectral peak finite difference time domain method numerical modeling suggests the influence of topography near the vent and along the propagation path significantly affects the spectral content complicating comparisons with laboratory jet noise the fumarolic jet has a low estimated mach number 0 3 to 0 4 and measured temperature of 260 c the strouhal number for infrasound from volcanic jet flows and geysers is not known thus we assume a peak strouhal number of 0 19 based on pure air laboratory jet experiments this assumption leads to an estimated exit velocity of the fumarole of 79 to 132 m s using published gas composition data from 2003 to 2009 the fumarolic vent area estimated from thermal infrared images and estimated jet velocity we estimate total volatile flux at 160 270 kg s 14 000 23 000 t d

blast waves from violent explosive activity at yasur volcano vanuatu 1 infrasonic and seismic waveforms were collected during violent strombolian activity at yasur volcano vanuatu averaging 3000 seismic events showed stable waveforms evidencing a low frequency 0 1 0 3 hz signal preceding 5 6 s the explosion infrasonic waveforms were mostly asymmetric with a sharp compressive 5 106 pa onset followed by a small long lasting rarefaction phase regardless of the pressure amplitude the ratio between the positive and negative phases was constant these waveform characteristics closely resembled blast waves infrared imagery showed an apparent cold spherical front 20 m thick which moved between 342 and 405 m s before the explosive hot gas fragments cloud we interpret this cold front as that produced by the vapor condensation induced by the passage of the shock front we suggest that violent strombolian activity at yasur was driven by supersonic dynamics with gas expanding at 1 1 mach number inside the conduit

explosive volcanic activity at mt yasur a characterization of the acoustic events 9 12th july 2011 abstract volcanic processes occur in a wide range of temporal and spatial scales however a key step of magma ascent is recognizable in the dynamics of gas and magma in the shallow plumbing system where volatiles play a fundamental role in controlling the eruptive style with the aim of investigating shallow degassing processes an experimental setup was deployed at mt yasur an active volcano located in tanna island vanuatu arc from 9th to 12th july 2011 the setup comprised high speed and thermal cameras as well as a microphone capable of recording both in the infrasonic and audible range the analysis of acoustic signals validated by observing images from the high speed and thermal cameras has enabled characterizing the explosive activity during the investigated period two types of explosions distinct for spectral features and waveforms were observed i minor events corresponding to small overpressurized bursts occurring almost continuously ii major events characterizing the strombolian activity at mt yasur by investigating variation in the occurrence rate of the minor events we found that on a short timescale the dynamics responsible for the two types of explosions are decoupled these results together with previous literature data bring additional evidence of the existence of distinct sources of degassing finally major events can be distinguished as emergent events i e long lasting signals corresponding to ash rich explosions and impulsive events featuring shorter duration and larger amplitude

generation and propagation of infrasonic airwaves from volcanic explosions abstract analysis of infrasonic pressure waves generated by active volcanoes is essential to the understanding of volcanic explosion dynamics unlike seismic waves propagating in the earth infrasonic airwaves offer a relatively unfiltered representation of source motions at the vent during an eruption time varying acoustic propagation filters caused by changeable atmospheric conditions are minimal for microphones deployed at intermediate distances johnson et al j volcanol geotherm res in press

strombolian surface activity regimes at yasur volcano vanuatu as observed by doppler radar infrared camera and infrasound abstract in late 2008 we recorded a continuous multi parameter data set including doppler radar infrared and infrasound data at yasur volcano vanuatu our recordings cover a transition in explosive style from ash rich to ash free explosions followed again by a phase of high ash discharge to assess the present paradigm of strombolian behavior in this study we investigate the geophysical signature of these different explosive episodes and compare our results to observations at stromboli volcano italy to this end we characterize yasur s surface activity in terms of material movement temperature and excess pressure the joint temporal trend in these data reveals smooth variations of surface activity and regime like persistence of individual explosion forms over days analysis of all data types shows ash free and ash rich explosive styles similar to those found at stromboli volcano during ash free activity low echo powers high explosion velocities and high temperatures result from the movement of isolated hot ballistic clasts in contrast ash rich episodes exhibit high echo powers low explosion velocities and low temperatures linked to the presence of colder ash rich plumes furthermore ash free explosions cause high excess pressure signals exhibiting high frequencies opposed to low amplitude low frequency signals accompanying ash rich activity to corroborate these findings we compare fifteen representative explosions of each explosive episode explosion onset velocities derived from doppler radar and infrared camera data are in excellent agreement and consistent with overall observations in each regime examination of infrasound recordings likewise confirms our observations although a weak coupling between explosion velocity and excess pressure indicates changes in wave propagation the overall trend in explosion velocity and excess pressure however demonstrates a general correlation between explosive style and explosion intensity and points to stability of the uppermost conduit on timescales shorter than at stromboli volcano