size distributions and failure initiation of submarine and subaerial landslides abstract landslides are often viewed together with other natural hazards such as earthquakes and fires as phenomena whose size distribution obeys an inverse power law inverse power law distributions are the result of additive avalanche processes in which the final size cannot be predicted at the onset of the disturbance volume and area distributions of submarine landslides along the u s atlantic continental slope follow a lognormal distribution and not an inverse power law using monte carlo simulations we generated area distributions of submarine landslides that show a characteristic size and with few smaller and larger areas which can be described well by a lognormal distribution to generate these distributions we assumed that the area of slope failure depends on earthquake magnitude i e that failure occurs simultaneously over the area affected by horizontal ground shaking and does not cascade from nucleating points furthermore the downslope movement of displaced sediments does not entrain significant amounts of additional material our simulations fit well the area distribution of landslide sources along the atlantic continental margin if we assume that the slope has been subjected to earthquakes of magnitude 6 3 regions of submarine landslides whose area distributions obey inverse power laws may be controlled by different generation mechanisms such as the gradual development of fractures in the headwalls of cliffs the observation of a large number of small subaerial landslides being triggered by a single earthquake is also compatible with the hypothesis that failure occurs simultaneously in many locations within the area affected by ground shaking unlike submarine landslides which are found on large uniformly dipping slopes a single large landslide scarp cannot form on land because of the heterogeneous morphology and short slope distances of tectonically active subaerial regions however for a given earthquake magnitude the total area affected by subaerial landslides is comparable to that calculated by slope stability analysis for submarine landslides the area distribution of subaerial landslides from a single event may be determined by the size distribution of the morphology of the affected area not by the initiation process

the 25 september 2007 eruption of mount ruapehu new zealand directed ballistics surtseyan jets and ice slurry lahars abstract at 20 26 nzdt on 25 september 2007 a moderate gas driven eruption beneath the summit crater lake of mt ruapehu new zealand generated a directed ballistic fallout apron and surtseyan jet that impacted an area of c 2 5 km2 to the north of the vent two climbers were caught in the blast at a hut 600 m from the vent primary ice slurry lahars were generated in two catchments draining the summit region including a flow that entered a commercial ski field the ejecta consists of blocks of andesitic lava and scoria erupted during previous volcanic episodes a variety of mineral cemented lake floor sediments vent fill debris and rare glassy material interpreted to be derived from a fresh batch of magma a minority of clasts contain formerly molten elemental sulphur indicating that vent temperatures at the base of the lake were in excess of 119 c the ballistic deposit is confined to a c 40 wide swath directed northwards that extends up to 2 km from the inferred vent location beneath crater lake the strong directionality of the jetted deposits and ballistic free shadow zones sheltered by intervening topography all point to a relatively low angle directed blast previous similar eruptions at ruapehu also show preferred deposit orientations that are here correlated with an inclined and off centre vent beneath crater lake the 25 september 2007 eruption appears to have resulted from failure of a relatively shallow hydrothermal seal composed of elemental sulphur and other mineral precipitates developed in the vent breccia which breached following overpressurization by a pulse of magmatic gases released from deeper in the conduit this event highlights the potential hazard from relatively minor gas driven eruptions at ruapehu that can occur with little or no warning improved understanding of the eruption mechanism for this style of eruption will inform future risk assessments for ruapehu and other similar volcanoes worldwide

the effects of sediment supply and concentrations on the formation timescale of martian deltas abstract we used a comprehensive 2 d and 3 d basin filling morphodynamical model to explore the effects of changing hydrologic and sedimentary conditions on delta formation under martian conditions spatial and temporal deposition of sediment into a body of standing water was simulated using event based time stepping e g seasons river and sediment discharge were calculated using the darcy weisbach equation for width and depth averaged flow velocity and well known and tested terrestrial sediment transport predictors modified for application to martian flows a range in sediment grain sizes was determined from both landers and orbiting spacecraft data in order to include grain sizes typical of mars and yet representative of the martian deltas several different scenarios of seasonal river discharge and sediment supply were explored to encompass a range of possible formation conditions with the ability to track sediment as it is transported throughout the basin it is apparent that non negligible amounts of material are moved beyond the delta forming region this loss of sediment increased with river discharge increasing the gap between the calculated and modeled formation timescales these results have important implications for the formation timescales of the deltas and the small number of identifiable deltas on mars today formation timescales that consider only the supply of sediment to the system and do not take into account factors affecting deposition and delta formation are underestimates of the actual amount of time needed to form the deposits the lack of identifiable deltas in many paleolakes is likely a result of significant sediment transport beyond the channel mouth causing the expected delta deposit to be draped throughout the basin

a facies model for a quaternary andesitic composite volcano ruapehu new zealand ruapehu composite volcano is a dynamic volcanic sedimentary system characterised by high accumulation rates and by rapid lateral and vertical change in facies four major cone building episodes have occurred over 250 ka from a variety of summit flank and satellite vents eruptive styles include subplinian strombolian phreatomagmatic vulcanian and dome related explosive eruptions and extrusion of lava flows and domes the volcano can be divided into two parts a composite cone of volume 110 km3 surrounded by an equally voluminous ring plain complementary portions of ruapehu s history are preserved in cone forming and ring plain environments cone forming sequences are dominated by sheet and autobrecciated lava flows which seldom reach the ring plain the ring plain is built predominantly from the products of explosive volcanism both the distal primary pyroclastic deposits and the reworked material eroded from the cone much of the material entering the ring plain is transported by lahars either generated directly by eruptions or triggered by the high intensity rain storms which characterise the region ring plain detritus is reworked rapidly by concentrated and hyperconcentrated streams in pulses of rapid aggradation immediately following eruptions and more gradually in the longer intervals between eruptions

advances in the numerical modeling of sediment failure during the development of a continental margin abstract the sedflux model is modified to more realistically simulate the distributions of seafloor geotechnical parameters during the growth of a seismically active continental margin alternative methods are provided for the prediction of the coefficient of consolidation remolded shear strength internal friction angle sediment cohesion dynamic viscosity and excess pore pressure the new methods improve simulations of the architecture of basin deposits through the dynamics within the slope stability and debris flow modules the new formulation shows sediment failures to be more frequent but smaller in size and to occur at larger water depths however the overall architecture is not significantly different sedflux is then used to examine the role of global sea level fluctuations on the location and dimensions of sediment failure and the subsequent transport of sediment to the deep ocean more sediment failures are predicted to occur during periods of falling or low sea level conditions and to be confined to the upper continental slope 500 250 m water depth the shallower failures are more characteristic of the period represented by the last two episodes of low sea level i e during the late pleistocene affected by the magnitude of the sea level fluctuation most of the predicted failures have thickness

stratigraphic variability due to uncertainty in model boundary conditions a case study of the new jersey shelf over the last 40 000 years abstract prediction of stratigraphy by numerical sedimentary models is influenced by a series of geological boundary conditions paleo bathymetry sediment supply sea level ocean storm climate and tectonics these boundary conditions evolve non linearly over time and have considerable uncertainty this study explores the impact of the uncertainty of complex boundary conditions on stratigraphic prediction two numerical models are sequentially run the climate driven hydrological model hydrotrend generates a time series of discharge and sediment load at the river mouth which then feed into the process based stratigraphic model sedflux 2d sedflux disperses sediment in the fluvio marine domain the bedload fluxes drive floodplain and mouthbar deposition while suspended sediment is dispersed in the ocean through hypopycnal plumes seafloor sediment is reworked by ocean storms failures and subsequent transport as sediment gravity flows sedflux records the thickness of the deposited sediment and the grain size preserved over time along a longitudinal profile one base case simulation and 20 sensitivity tests of the new jersey shallow margin over the last 40 000 yr serve to explore the impact of uncertain boundary conditions initially the shelf is exposed and arctic conditions prevail in the drainage area paleo temperature and precipitation estimates differ significantly between different community climate system model realizations impacting river sediment flux predictions subsequently high sediment supply from the rivers draining the melting laurentide ice sheet has a dominant impact on the shelf stratigraphy drainage basin characteristics are strongly controlled by the hard to define details of the laurentide ice sheet dynamics over the last 10 000 yr the shelf becomes sediment starved and storm dominated but the paleo storm conditions are uncertain and thus require a wide range of values shallow seismic data have been used to validate the large scale deposited thicknesses of the sedflux prediction the base case sedflux prediction for the sedimentary architecture of the new jersey shelf is consistent with the acoustically observed distribution of major sediment wedges due to the strong forcing of the relatively well constrained sea level changes the range in thickness predictions over the sensitivity tests is well within the lateral variations reconstructed from the observed seismic data sedflux predictions and a data set of 654 seafloor samples taken on the new jersey shelf between 50 and 150 m water depth shows a subtle fining towards deeper water sedflux systematically overpredicts the component of fine sediments at the seafloor likely because the model does not predict shell hash paleo storm climate is found to have a high uncertainty and strongly impacts the predicted grain size distributions we advocate a modeling approach which couples a series of sensitivity experiments to a predicted base case experiment in that way the stratigraphic variability caused by uncertainty in the boundary conditions is evident for later users

pattern recognition applied to seismic signals of the llaima volcano chile an analysis of the events features abstract this paper proposes a computer based classifier to automatically identify four seismic event classes of the llaima volcano one of the most active volcanoes in the southern andes situated in the araucania region of chile a combination of features that provided good recognition performance in our previous papers concerning the llaima and villarica located 100 km south of llaima volcanoes is utilized in order to train the classifiers these features are extracted from the amplitude frequency and phase of the seismic signals unlike the previous works where fixed length windows were used to obtain the seismic signals this paper employs signals of variable lengths that span the entire seismic event the classifiers are implemented using support vector machines a confidence analysis is also included to improve reliability of the classification results indicate that the features used for recognition of the events of villarica volcano also provide good recognition results for the llaima volcano yielding classification exactitude of over 80

monitoring of phreatic eruptions using interferometry on retrieved cross correlation function from ambient seismic noise results from mt ruapehu new zealand abstract since the last major eruption in 1995 96 mt ruapehu has erupted twice on 4 october 2006 and on 25 september 2007 these events occurred without any clear precursors and were mostly phreatic explosions the technique of interferometry on retrieved cross correlation function from ambient seismic noise irccasn is used to monitor subtle temporal changes of mt ruapehu s elastic properties the computation of cross correlation functions of seismic noise recorded at several stations around the volcano allowed us to observe variations during the 2006 eruption period the comparison between a reference cross correlation function and a current cross correlation function allows us to infer relative seismic velocity variations a 0 8 decrease of relative seismic velocity in the edifice starting two days before the 2006 eruption was observed this drop is due to a reversible and ephemeral effect which can be attributed to a pressurization of a magma pocket beneath the east flank of ruapehu due to new magma entering a small reservoir this pressure increase produced an inflation of the east flank of ruapehu and opened fractures in this area leading to a localised drop of seismic velocity we conducted the same analysis for the 2007 eruption but no significant seismic velocity variation was observed this difference is possibly due to the varying time scales of pressurization for the two events and also the irccasn time resolution an analysis of the seismicity before these two eruptions allows us to propose a conceptual model which explains the velocity drop for the 2006 eruption and the lack of velocity variations for the 2007 eruption since there was no surface deformation recorded by the geonet gps network we modelled the maximum radius and pressure change for a simple mogi point source at 5 km depth that produced no deformation we inferred the maximum fresh magma volume of 0 0017 km 3 entering the reservoir as a detectability threshold for gps ground deformation measurements

the coulomb critical taper theory applied to gravitational instabilities the critical coulomb wedge theory has been widely applied to the structural evolution of accretionary wedges and fold and thrust belts but it also predicts the spreading of a wedge under gravity this solution may be applied to the formation of gravitational spreading and gliding along passive margins where elevated pore fluid pressure is common following the initial hypotheses of the theory we provide an alternative expression of the exact solution for a noncohesive wedge better suited to slope instabilities our formulation allows a direct calculation of the fluid pressure required for the system to deform and predicts two kinds of gravitational deformation shallow slumping and or deep gravitational spreading rooting on the basal detachment to verify the predictions of the model we performed scaled experiments with pore pressure under conditions close to the critical taper hypotheses the good agreement between our experimental results and the theory confirms the applicability of the critical taper model to the formation of gravitational structures in sedimentary wedges subjected to pore fluid pressure

frequency and timing of landslide triggered turbidity currents within the agadir basin offshore nw africa are there associations with climate change sea level change and slope sedimentation rates abstract older sequence stratigraphic models suggested that submarine landslide and turbidite activities are greatest during sea level lowstands however growing evidence indicates that many turbidite systems are also active during sea level transgressions and highstands the moroccan turbidite system comprises three depocentres of which agadir basin is closest to the moroccan slope and canary archipelago the very large volumes of sediment transported by individual sediment flows in this system suggest that they are triggered by landslides extensive core coverage and dating control for the agadir basin deposits have provided an excellent opportunity to derive accurate records of turbidite and associated landslide frequency for the last 600 ka previous studies in the more distal madeira abyssal plain depocentre have indicated that large volume 50 km 3 turbidites occurred at oxygen isotope stage ois boundaries this study of agadir basin confirms that two major turbidites beds a5 and a12 occurred during glacial interglacial transitions associated with ois4 and ois6 however this association is based on just two examples and two other large volume turbidites beds a7 and a11 did not occur at a stage boundary the main conclusion of this study is that 90 of turbidites and landslides occurred during rising and high sea level which represents 40 of the total time during the last 600 ka only 10 of the turbidites and landslides occurred during glacials 40 of the time with a paucity of turbidites and landslides at peak glacial lowstands a comparison to sediment accumulation rates in the source area of the turbidite suggests that landslides did not occur preferentially during periods of more rapid sedimentation rate although sedimentation rates in this area only varied from 4 to 6 g cm 2 ka 1

failure of marine deposits and their redistribution by sediment gravity flows sedflux simulates the fill of sedimentary basins and can be used to examine the location and attributes of sediment failure on continental margins and the runout of their associated sediment gravity flows numerical experiments show how the evolving boundary conditions of sea level fluctuations floods storms tectonic and other relevant processes control the rate and size of slope instabilities by tracking deposit properties pore pressures grain size bulk density porosity a finite slope factor of safety analysis of marine deposits examines failure potential a decider routine is used to determine whether the failed material will travel down slope as turbidity current or a debris flow examples provided insight into i why fjords dominated by turbidity current deposition often contain debris flow deposits ii how glaciated margins prograde seaward through shallow failures of low yield strength material and iii how large scale basin subsidence can control the onset of canyon formation across continental slopes

seismo acoustic evidence for an avalanche driven phreatic eruption through a beheaded hydrothermal system an example from the 2012 tongariro eruption abstract the 6 august 2012 te maari eruption comprises a complex eruption sequence including multiple eruption pulses a debris avalanche that propagated 2 km from the vent and the formation of a 500 m long arcuate chasm located 300 m from the main eruption vent the eruption included 6 distinct impulses that were coherent across a local infrasound network marking the eruption onset at 11 52 18 all times utc an eruption energy release of 3 1012 j was calculated using a body wave equation for radiated seismic energy a similar calculation based on the infrasound record shows that 90 of the acoustic energy was released from three impulses at onset times 11 52 20 20 of total eruption energy 11 52 27 50 and 11 52 31 20 these energy impulses may coincide with eyewitness accounts describing an initial eastward directed blast followed by a westward directed blast and a final vertical blast pre eruption seismic activity includes numerous small unlocatable micro earthquakes that began at 11 46 50 two larger high frequency earthquakes were recorded at 11 49 06 and 11 49 21 followed directly by a third earthquake at 11 50 17 the first event was located within the scarp based on an arrival time location from good first p arrival times and probably represents the onset of the debris avalanche the third event was a tornillo characterised by a 0 8 hz single frequency resonance and has a resonator attenuation factor of q 40 consistent with a bubbly fluid filled resonator this contrasts with a similar tornillo event occurring 2 5 weeks earlier having q 250 1000 consistent with a dusty gas charged resonator we surmise from pre eruption seismicity and the observed attenuation change that the debris avalanche resulted from the influx of fluids into the hydrothermal system causing destabilisation and failure the beheaded hydrothermal system may have then caused depressurisation frothing of the remaining gas charged system leading to the onset of explosive activity

phenotypic evolution in the fossil record numerical experiments abstract stratophenetic data document phenotypic changes in a fossil lineage and play a vital role in reconciling contemporary microevolution with long term paleontological patterns however stratophenetic series represent multiscale geological and biological interactions defying simple analysis and interpretation a numerical model is presented that simulates stratophenetic series in shallow marine siliciclastic deposits the model is driven by predictions of water depth substrate properties and sedimentation rate from a high resolution sedimentary basin fill model species abundance is modeled as a probability density peaked with respect to environmental preferences the price equation is used to model phenotypic evolution based on phenotype fitness covariance and drift preservation is a poisson process controlled by population size preservation probability and sedimentation numerical experiments are used to investigate 1 the effects of sampling and depositional architecture on observed patter

effects of ambient currents and waves on gravity driven sediment transport on continental shelves abstract observations from several shelf environments show that down slope gravity driven transport may constitute an important mode of suspended sediment dispersal across shelves and highlight the influence of ambient waves and currents on gravity induced sediment flux the phenomena discussed here involve high concentrations of suspended sediment mixed with seawater and thus differ in genesis from hyperpycnal plumes released directly from sediment laden rivers the field sites examined are the gulf of bohai off the mouth of the yellow river huanghe the northern california shelf off the mouth of the eel river and the louisiana shelf west of the mouths of the mississippi river off the yellow river rapid down slope transport over distances of a few km occurred when frictional resistance induced by strong along shelf currents was temporarily relaxed more prolonged down slope motion over longer distances occurred following floods of the eel river when wave and current agitation provided turbulence to sustain gravity driven transport of fluid mud on the louisiana inner shelf the down slope gravity force was much weaker but observations suggest that thin gravity flows may still have occurred in the presence of waves a simple analytical theory is developed that incorporates the influence of ambient shelf currents on gravity driven transport of suspended sediment this theory is quantitatively consistent with the observations from the three sites if the supply of easily suspended sediment is less than the capacity of ambient currents including waves to carry sediment then intense turbulence limits gravity induced sediment transport by increasing the drag at the base of the flow when ambient currents abruptly cease rapid down slope transport can then occur over short distances until the sediment settles such flows do not remain intensely turbulent because the slope of the continental shelf is too gentle to induce shear instability within the gravity flow the maximum sustained rate of gravity induced sediment transport occurs when ambient currents are strong but the supply of easily suspended sediment exceeds the resuspension capacity of the ambient currents feedback then leads to values of the gradient richardson number ri within the flow that are near the critical value of 1 4 this partially damps bottom drag but still allows the generation of sufficient turbulence to maintain sediment in suspension observations also indicate systematic relationships among ri the supply of easily suspended sediment and the bottom drag coefficient acting on the gravity flow

analysis of phreatic events at ruapehu volcano new zealand using a new som approach abstract we apply self organising maps som to assess the low level seismic activity prior to small scale phreatic events at ruapehu volcano new zealand the som approach allows an automatic pattern recognition virtually independent from a priori knowledge volcanic tremor spectra are randomly presented to the network in a competitive iterative training process followed by a hierarchical clusterization of the som nodes spectra are then projected ordered by time to clusters on the map a coherent time evolution of the data through the clusters can highlight the existence of different regimes and the transitions between them two ruapehu events were examined a phreatic event on 4 october 2006 which displaced the crater lake producing a 4 m high wave on the lake edge and the more energetic 25 september 2007 phreatic eruption the som analysis provides a classification of tremor spectral patterns that clusters into three regimes that we label by colours the pattern for both eruptions is consistent with a pre eruption spectral pattern including enhanced spectral energy in the range of 4 to 6 hz labelled green tremor this gives way to spectra having broader energy between 2 and 6 hz the so called red tremor just prior to the eruption the post eruption pattern includes spectral peaks at generally lower frequencies of 2 to 4 hz the so called blue tremor clusterization into only three groups yields highly non unique solutions which cannot explain the variety of processes operating at ruapehu over long time periods regardless the approach highlights noteworthy similarities that may be explained by a pattern of slow pressurisation under a hydrothermal or magmatic seal green followed by seal failure red and subsequent de pressurisation blue for the two events studied although the application shown here is limited we think it demonstrates the power of this classification approach

fluorescent growth bands in irradiated bitumen nodules evidence of episodic hydrocarbon migration minute rims of solid bitumen 40 50 m thick surround detrital radioactive grains in the permian triassic sandstones and arranoo member of the kockatea shale from the northern perth basin australia the bitumen formed as th and u bearing minerals monazite xenotime zircon thorite irradiated and immobilized fluid hydrocarbons coming within range of alpha particle emissions using transmitted light and scanning electron microscopy the rims appear compositionally homogeneous but under blue violet epifluorescent illumination the bitumen displays complex concentric and contorted banding these fluorescent textures indicate that multiple influxes of hydrocarbons passed through the reservoir sandstones following radiation induced immobilization of hydrocarbons from the first oil influx the bitumen nodules grew through a process of swelling and expansion outward from the mineral core during subsequent oil

thermal seismic and infrasonic evidences of variable degassing rates at stromboli volcano abstract during june 1999 we measured the amplitude and rate number of events per second at which gas exited the vent at stromboli volcano as discrete gas bursts or puffs this allowed us to identify two styles of gas burst puffing activity the first is characterized by frequent rapidly rising puffs the second by less frequent slowly rising puffs each style persisted over 5 40 min long durations and was associated with a high and low number of strombolian explosions per hour respectively each period was also associated with characteristic delay times between the arrival of the infrasonic and thermal signals during strombolian explosions the delays were longer during vigorous puffing periods to explain our observations we propose a model in which the degassing process cycles between vigorous and weak degassing phases during vigorous degassing phases bubble layers ascend the conduit at a frequency of 0 5 1 0 s 1 this high degassing level reflects a gas rich magma column and leads to an increased rate in the formation of shallow foams and hence an increase in puffing and explosive activity as well as a higher free surface level and or gas jet velocity during weak phases bubble layers ascend the conduit at a reduced frequency of 0 2 0 3 s 1 during such times the magma column is poor in gas this leads to a decreased rate of foam layer formation and hence a reduction in puffing and explosive activity as well as a lower free surface level and or gas jet velocity variations in puffing activity can thus be used to track changes in the rate at which the shallow system is supplied by fresh gas rich magma our observations indicate that the two degassing styles last from 5 to 40 min and that the switch from one to the other occurs over a matter of minutes

inverse modeling of post last glacial maximum transgressive sedimentation using 2d sedflux application to the northern adriatic sea abstract a coupled simulation of the hydrologic model hydrotrend and the stratigraphic model 2d sedflux is applied to transgressive deposits in the north adriatic sea area over the last 21 000 years synthetic sediment discharge from the po river which increases more than 70 during late pleistocene compared to those during holocene due to glacier melt and enlarged drainage area is employed in the simulation of sediment deposition by the process based forward model 2d sedflux paleo morphology is reconstructed in a pseudo inverse manner by comparing the predicted deposit distribution and the modern morphology accommodation for thick prograding deposits in the modern po delta and the po lowstand delta are created by drawing back the modern bathymetric profile the bathymetric profile is then adjusted for aggradational deposits these sequential simulations produced a likely profile of the paleo morphology which had accommodation matching with the sediment supply evaluation of effects of waves however suggested that the predicted rate of sediment input was too low to produce a prograding delta a good match with the observation of the modern po delta was achieved when further adjustments in basin width was properly made

seismic characteristics of variable convection at erta ʻale lava lake ethiopia abstract the active summit lava lake of erta ale volcano ethiopia offers a unique opportunity to study magma convection in february 2002 we collected a multiparametric set of seismic thermal and video data these data indicate that the lake cycled between periods characterized by low 0 01 0 08 m s 1 and high 0 1 0 4 m s 1 convection rates typically lasting tens to hundreds of minutes three seismometers placed around the active crater recorded continuous tremor with a dominant frequency of 2 hz and energy at frequencies from 0 8 to 12 hz here we characterize the seismic signature of each regime by its spectral content wavefield polarization and tremor source location for both regimes the wavefield is mostly rectilinear azimuths and incidence angles are consistent with p waves originating in one of two locations the north edge of the active lava lake or a region 100 150 m ene of the lava lake because both regimes are dominated by a low frequency rectilinearly polarized wavefield we investigate the source location using a method that solves for location and isotropic source power by a weighted least squares amplitude based inversion of seismic data we find that tremor source regions are unique to each convective regime although some location overlap exists when tremor is located in short time windows wavefield composition suggests that the convective phases may share a common source process but their differing locations indicate that either the source region is non stationary or a second source skews the location during the high convective phase tremor polarization and location suggests that the low frequency tremor is caused by bubble coalescence and bursting in a conduit whose surface is the lava lake the higher frequency signal associated with the high convective regime is associated with a scattered more complex wavefield superimposed on the low frequency background tremor caused by bubble bursting and cracking of cooled crust at the lava lake surface

evaluation of the global oxygen isotope curve as a proxy for quaternary sea level by modeling of delta progradation patterns of delta progradation in rapidly subsiding basins have been used previously as a proxy for quaternary sea level change major transgression surfaces and maximum lowstand positions are readily recognizable in seismic reflection profiles quaternary sea level change can be approximated by stacked and tuned oxygen isotope records but significant departures from this proxy result from variation in isotopic composition of ice sheets temperature variations in the deep sea and the effect of bioturbation in degrading the isotopic record we analyze the influence of rapid quaternary sea level change on delta progradation in the eastern mediterranean using delta a multi process sediment transport model subsidence rates and sediment inputs may vary through time but compared to quaternary sea level change such variations were minor and had little effect on model results for a variety of geologically reasonable sediment inputs and subsidence rates the delta architecture observed in seismic profiles could not be reproduced when the sea level estimates were taken directly from a scaled global oxygen isotopic curve however when this sea level curve was corrected to include independent estimates of sea level from geological data elsewhere in the world previously used sediment inputs and subsidence rates invariably predict the general form of the observed architecture the difference between isotopic and geological estimates of sea level for the last 200 ka follows a linear trend that was applied to previous glacial interglacial cycles producing a corrected sea level history for the last 540 ka using delta over this time span the sea level history based directly on the oxygen isotope curve was again less able to reproduce the observed delta architecture compared with a corrected sea level history this study shows the importance of modeling delta progradation as an avenue for testing and exploring quaternary sea level history

identification of variable convective regimes at erta ale lava lake abstract during february 17 19 2002 we collected a combined thermal and seismic data set for persistent lava lake activity at erta ale volcano ethiopia these data indicate that the lake cycled between periods characterized by low 0 01 0 08 m s 1 and high 0 1 0 4 m s 1 surface velocities typically lasting tens to hundreds of minutes these periods of high and low velocity motion define periods of vigorous and sluggish convection respectively spectral analysis revealed that vigorous convection periods were characterized by high frequencies and energies in the thermal data and an increased presence of high frequency energy in the seismic data the data show that vigorous periods were characterized by formation of hot short lived plastic crusts and sluggish periods by cooler longer lived brittle crusts here the higher transit velocity across the lake surface from upwelling zones of crust formation to downwelling zones of crust destruction during the vigorous periods decreases the crust lifetime this in turn decreases the total cooling and thickening experienced by a plate of crust moving across the lake surface two scenarios can be envisaged to explain such convection cycles the first relates variable convection rates to changes in the volume flux and rheology of magma entering the lake in the second cyclic convection is set up by the generation of convective instabilities within the lake in this case cooling of a surface layer generates a slow moving viscous increasingly dense convection layer at the lake surface which is consumed and replaced during overturn

discriminating seismic events of the llaima volcano chile based on spectrogram cross correlations abstract the surveillance of active volcanoes around the world has become a critical security issue for many countries requiring a continuous monitoring of seismic signals by analyzing such signals we intend to understand volcanic activities e g explosions eruptions and depressurization and take decisions to reduce the effects and damages to the economy and society of nearby regions active volcanoes constantly produce signals which may then be characterized as data streams making impractical the presence of specialists to monitor and label every activity to overcome this drawback we present a new and straightforward approach to discriminate volcano seismic signals using spectrogram cross correlations spcc in conjunction with the k nearest neighbors algorithm a supervised machine learning strategy experiments were performed on signals collected from the llaima volcano chile and results confirmed the ability of our approach to discriminate events with a sensitivity over 95 for three out of the five classes considered

detecting imminent eruptive activity at mt etna italy in 2007 2008 through pattern classification of volcanic tremor data abstract volcano monitoring aims at the recognition of changes in instrumentally observable parameters before hazardous activity in order to alert governmental authorities among these parameters seismic data in general and volcanic tremor in particular play a key role recent major explosive eruptions such as okmok aleutians and chaiten chile in 2008 and numerous smaller events at mt etna italy have shown that the period of premonitory seismic activity can be short only a few hours which entails the necessity of effective automatic data processing near on line here we present a synoptic pattern classification analysis based on self organizing maps and fuzzy cluster analysis which is applied to volcanic tremor data recorded during a series of paroxysmal eruptive episodes and a flank eruption at etna in 2007 2008 in total eight episodes were analyzed in six of these significant changes in the dynamic regime of the volcano were detected up to 9 h prior to the onset of eruptive activity and long before changes in volcanic tremor amplitude and spectral content became evident in classical analysis in two cases the state transition was

unsupervised neural analysis of very long period events at stromboli volcano using the self organizing maps we have implemented a method based on an unsupervised neural network to cluster the waveforms of very long period vlp events associated with explosive activity at the stromboli volcano southern italy stromboli has several active vents in the summit area producing together more than 200 explosions day we applied this method to investigate the relationship between each vent and its associated vlp explosive waveform we selected 147 vlp events recorded between november and december 2005 when digital infrared camera recordings were available from a visual inspection of the infrared camera images we classified the vlps on the basis of which vent produced each explosion we then applied the self organizing map som an unsupervised neural technique widely applied in data exploratory analysis to cluster the vlps on the basis of their waveform similarity our analysis demonstrates that the most recurrent vlp waveforms are usually generated by the same vent some exceptions occurred however in which different waveforms are associated with the same vent as well as different vents generating similar waveforms this suggests that the geometry of the upper conduit vent system plays a role in shaping the recurring vlp events whereas occasional modest changes in the source process dynamics produce the observed exceptions

spectro temporal features applied to the automatic classification of volcanic seismic events abstract feature extraction and selection are very relevant processes in the design of automatic classifiers in the context of volcanic seismic signal classification most of the features presented in the literature have been extracted separately from a single domain such as time or frequency however spectrograms which combine time and frequency information are widely used by experts during the classification of manual seismic events this paper proposes to evaluate the performance of classifiers trained with features extracted from the spectro temporal domain individually or combined with other conventional features the parameters were extracted from the spectrogram based on a curve which combines the high energy components and the frequency bandwidth information through the duration of the event the tests were performed at the llaima volcano and seismic events were classified into four classes long period tremor volcano tectonic and tectonic using a database of signals recorded between the years 2009 and 2017 the main achievements of this study were the reduction of more than 70 of the error and false positive rates and also a reduction of approximately 30 of the number of features compared with a baseline established in previous studies thus the inclusion of spectro temporal information was considered relevant to complement the conventional features and to support classification

oil bearing co2 ch4 h2o fluid inclusions oil survival since the palaeoproterozoic after high temperature entrapment the 2 45 ga fluvial quartz arenites and conglomerates of the matinenda formation at elliot lake canada contain evidence for two episodes of oil migration with entrapment of oil bearing fluid inclusions the first episode was during diagenesis the second during a subsequent sub greenschist facies metamorphic event at ca 2 2 ga at temperatures exceeding 250 c remnants of the migrating hydrocarbon fluids are preserved as radiogenic pyrobitumen nodules occupying former inter granular pore spaces and as complex fluorescing oil bearing fluid inclusions the latter include two dominant types 1 aqueous oil inclusions with a minor oil phase located within original detrital grains and clasts and within rare quartz overgrowths and 2 aqueous carbonic inclusions with a minor oil phase light hydrocarbons and solids located within microfractures in detrital quartz grains and clasts the majority of type 1 inclusions were trapped with a high salinity fluid up to 25 wt nacl equivalent at relatively low temperatures between 80 and 200 c and pressures of less than 2 kbar early in the burial history of the matinenda formation type 2 inclusions were trapped during metamorphism with a much lower salinity aqueous carbonic fluid 1 2 to 17 wt nacl equivalent at temperatures between 280 and 350 c and pressures between 1 and 1 5 kbar under these conditions oil may have been miscible in the mixed fluid 13c of 25 5 and 24 9 for the pyrobitumen nodules and fluid inclusion hydrocarbon gas indicate a biogenic origin for the petroleum 13c of 16 2 for the bulk inclusion gas suggests a value of 12 for the carbonic phase hence a mix of inorganic co2 and organic co2 from either thermal alteration of organic matter or in situ chemical oxidation of hydrocarbons this study has implications for the depth and temperature at which oil may be present suggesting that deep old reservoirs may not be completely barren of petroleum the fact that hydrocarbons in the matinenda formation fluoresce indicates that aromatic compounds are able to survive temperatures of up to 350 c in a suitable geological environment

cyclic processes and factors leading to phreatic eruption events insights from the 25 september 2007 eruption through ruapehu crater lake new zealand abstract a dangerous block ash eruption occurred without warning from ruapehu crater lake on 25 september 2007 ending a 6 month period of temperature decline in the lake the northerly directed blast sent ballistics of up to 2 m diameter more than 2 km from the source the ejecta comprised a variety of volcano lacustrine lithologies many showing evidence of intense hydrothermal alteration petrographic studies of the ballistics reveal numerous examples of pores vesicles being filled with assemblages of elemental sulphur anhydrite pyrite and natroalunite and many ballistics exuded liquid sulphur from their pores during cooling at atmospheric pressure up to 5 of the ash was comprised of fine grained juvenile glass material confirming the presence of magma in the shallow vent environment a long recognised characteristic of this volcano is the thermal cycling behaviour of the crater lake behaviour which has remained effectively unchanged through two magmatic eruption events in 1945 and in 1995 96 airborne measurements of co2 and so2 flux from the volcano since 2003 show a strong positive correspondence with temperature cycling in the lake pointing to a definitive link between heat and mass discharge through the system low so2 emission rates and c s mole ratios 30 were typical of the period 2003 to early 2007 and appear to reflect vigorous scrubbing of s gases in the hydrothermal system during this time to better understand the chemical and physical processes operating in this very dynamic volcanic hydrothermal system and its propensity to develop potentially dangerous hydrothermal seals we have developed an integrated finite difference tough2 heat mass transport simulation of the hydrothermal environment the model which is constrained by observed heat and mass flux characteristics of the volcano demonstrates the transient nature of the heating cycles on the vent lake system of particular interest is the role of co2 as a relatively inert pressure transmitting medium in the hydrothermal environment seal formation was simulated using the reactive transport code x1t which showed that condensation of magmatic vapour into a highly porous medium of andesitic composition leads to rapid formation of an elemental sulphur anhydrite natroalunite mineral assemblage and a drastic reduction in permeability we suggest that since the 1995 96 vent clearing eruptions a shroud of elemental sulphur and other alteration phases formed along the margins of the 2 phase liquid vapour region enclosing the conduit this effectively seals the upper portion of the vent from the adjacent hydrostatically controlled environment and allows for development of pressurised vapour static gas columns beneath the northern and central vents

the heat source of ruapehu crater lake deductions from the energy and mass balances abstract regular observations of temperature outflow rates and water chemistry of crater lake mt ruapehu new zealand have been made for the last 25 years these data have been used to derive a model of the dynamics of the lake and determine the input of energy mass and chloride from the volcano to the crater lake the recent relatively quiescent state of the volcano when virtually no heat has been input to the lake has also enabled an assessment to be made of the surface heat loss characteristics which play an important role in the model of the lake the modelling suggests that since about 1982 the ratio of the volcanic heat to mass added to the base of the lake is about 6 mj kg which is not compatible with heating of the lake by magmatic steam alone thus only about 50 of the heating has been by magmatic steam it is suggested that heat could be transferred from a magmatic source to the region below the lake by a heat pipe mechanism commonly associated with geothermal systems the simultaneous upward movement of vapour phase and downward movement of liquid phase from condensed vapour allows efficient heat transfer without overall mass transfer the permeability necessary to supply the required heat is of the order of 10 darcy and is consistent with a rubble filled vent for at least the last five years there has been a characteristic pattern in the crater lake temperature record with alternate heating and cooling phases the heating phase generally lasts for one or two months while the cooling phase lasts for six months to a year a possible explanation for this cyclic behaviour is the presence of a layer of liquid sulphur under crater lake acting as a partial barrier between the heat pipe and the lake the unusual variations of the viscosity of liquid sulphur with temperature will mean that at temperatures greater than 160 c the layer of sulphur becomes highly viscous and would block any upwards steam flow and hence stop the heat input to crater lake so producing a cooling phase this blockage would last until the heating from below raised the temperature of the sulphur beyond the high viscosity region so gases could again pass through the sulphur

oil preserved in fluid inclusions in archaean sandstones oil is generally thought to be geologically young as it is thermodynamically unstable when subjected to elevated temperatures over long periods in open systems1 2 indeed almost all petroleum production comes from rocks younger than 400 million years ref 3 although the oldest known oil occurs in rocks 1 650 myr old4 suitable source rocks were abundant in older geological successions5 and circumstantial evidence suggests that some of these generated hydrocarbons early in their history6 here we report the discovery of oil preserved in fluid inclusions in sandstones dating back 3 000 myr most inclusions lie within healed microfractures confined to individual detrital quartz grains indicating that their oil was emplaced before archaean or palaeoproterozoic metamorphism sealed all voids and thus came from older in some cases archaean sources the fluid inclusions apparently acted as inert pressure vessels that protected the oil from subsequent degradation by circulating fluids and mineral catalysts because of its great age this oil can potentially yield valuable information about the size and diversity of the early biosphere particularly if it contains molecular fossils biomarkers of the primordial organisms from which it was derived

ambrym vanuatu july august 2000 spectral and dynamical transitions on the hours to days timescale abstract ambrym is a large basaltic volcano with a 12 km wide 1900 year old caldera located in the vanuatu archipelago formerly known as new hebrides two cones are currently active in the caldera marum and benbow each with several active vents that hosted visible lava lakes until 1999 on 26 november 1999 an earthquake m w 7 5 located near the northern part of the island caused important changes to the vent morphology during july 2000 we installed a short period seismic station on the eastern rim of benbow crater in the western side of the caldera the station acquired continuous data for about 1 month during this period volcanic tremor was permanently recorded together with discrete events in this paper first results from these data are discussed focusing attention on the existence of significant transitions in the long term volcano dynamics studied both with spectrally derived dominant and average frequencies and more properly dynamical embedding dimensions and delay time parameters during the observation period on 9 august 2000 another significant earthquake was recorded m b 6 3 about 65 km north of the volcano the influence of this and other regional tectonic events on the volcano dynamics are discussed

tracking volcanic and geothermal activity in the tongariro volcanic centre new zealand with shear wave splitting tomography abstract we apply a simplified two dimensional tomographic inversion of recorded delay times of shear wave splitting and a spatial averaging of fast direction of anisotropy to data from temporary seismic deployments in the tongariro volcanic centre in order to identify regions of changing seismic anisotropy we observe a region of strong anisotropy 0 025 s km greater than the surrounding area centered on mt ruapehu in 1995 the time of a major magmatic eruption this is interpreted to be due to an increase in fluid filled fractures during the eruption we also observe strong anisotropy 0 018 s km greater than the surrounding area and a change in fast direction 80 at mt tongariro in 2008 and examine the temporal evolution of this anomaly using clusters of earthquakes and permanent seismic stations in operation since 2004 this anomaly is attributed to a change in the geothermal system a pronounced and unchanging feature is observed at waiouru even when the source and receiver locations differ we therefore conclude that the transient features of strong anisotropy associated with volcanic and geothermal activity detected with this method are also robust

pattern recognition applied to seismic signals of llaima volcano chile an evaluation of station dependent classifiers abstract automatic pattern recognition applied to seismic signals from volcanoes may assist seismic monitoring by reducing the workload of analysts allowing them to focus on more challenging activities such as producing reports implementing models and understanding volcanic behaviour in a previous work we proposed a structure for automatic classification of seismic events in llaima volcano one of the most active volcanoes in the southern andes located in the araucania region of chile a database of events taken from three monitoring stations on the volcano was used to create a classification structure independent of which station provided the signal the database included three types of volcanic events tremor long period and volcano tectonic and a contrast group which contains other types of seismic signals in the present work we maintain the same classification scheme but we consider separately the stations information in order to assess whether the complementary information provided by different stations improves the performance of the classifier in recognising seismic patterns this paper proposes two strategies for combining the information from the stations i combining the features extracted from the signals from each station and ii combining the classifiers of each station in the first case the features extracted from the signals from each station are combined forming the input for a single classification structure in the second a decision stage combines the results of the classifiers for each station to give a unique output the results confirm that the station dependent strategies that combine the features and the classifiers from several stations improves the classification performance and that the combination of the features provides the best performance the results show an average improvement of 9 in the classification accuracy when compared with the station independent method

eruption source processes derived from seismic and acoustic observations of the 25 september 2007 ruapehu eruption north island new zealand abstract mt ruapehu erupted on 25 september 2007 at 20 26 pm nzdt 8 26 ut generating a steam column to about 15 000 ft 4600 m a directed ballistic and surge deposit of coarse blocks and ash to the north of the crater lake and initiated lahars in the whangaehu catchment and whakapapa ski field the eruption was recorded on three broadband seismometers and two acoustic pressure sensors which indicated broadly coherent waveform characteristics across the network the eruption had a duration of less than 1 min as indicated by strong seismic and acoustic pulses the acoustic wave coincided with observed very long period vlp seismic signal 2 25 s period the acoustic pulse had a positive pressure indicating an explosion and travelled at a velocity of 320 m s the syn eruptive vlp was composed of surface waves having strong radial and transverse components the immediate aftermath of the eruption produced about 4 min of continued high amplitude spasmodic tremor signals that probably resulted from post explosion phase associated vent backfill stabilisation the eruption was preceded by minor volcano tectonic earthquakes and tremor bursts which began 10 min before the main eruption two smaller vlp signals were associated with these tremor pulses at 20 17 and 20 25 these pre eruptive vlp signals had particle motions indicating body and surface waves from a sub surface source region modelling of the vlp sources using a 3d finite difference method shows that that the pre eruption vlp signals are consistent with a volume fluctuation at 3 7 km depth from a radially symmetric source the main eruption vlp was consistent with a south and downward directed single force in response to a northward directed jet and northward directed ballistic deposits

a fluid dynamics approach to modelling the 18th march 2007 lahar at mt ruapehu new zealand lahars are water sediment mass flows from a volcanic source they can be triggered by a variety of mechanisms and span a continuum of flow rheology and hydraulic properties even within the same event lahars are extremely powerful landscaping agents and represent a considerable hazard potential however this highly dynamic character and a lack of direct measurements has made modelling lahars difficult this study therefore applies a fluid dynamics model delft3d to analyse the 18th march 2007 dam break lahar at mount ruapehu new zealand the modelled lahar routed through the whangaehu gorge in 30 min crossed the whangaehu fan in 60 min and then over a further 3 h travelled an additional 22 km distance along the whangaehu river to the tangiwai bridge the modelled mean frontal velocity was 6 5 m s 1 along the gorge although peak velocity reached up to 19 6 m s 1 the modelled lahar flow front progressively slowed across the fan but along the river it accelerated from 2 1 3 3 m s 1 calculated peak velocity along the river was 4 5 m s 1 these results generally compare well with gauged records with historical records and with other modelling approaches however discrepancies in frontal velocity and time to peak stage arise due to 1 specifying roughness which arises from slope variations between adjacent computational nodes and which is stage dependant and 2 due to rapid topographic changes that produce frequent hydraulic jumps which are inadequately accommodated in the numerical scheme the overall pattern of discharge attenuation and of relationships between topographic and hydraulic variables is similar to that calculated for lahars on other volcanoes this modelling method could be applied at other similar sites where a likely source hydrograph and high resolution topographic data are available these results have important implications for hazard management at ruapehu and for examining geomorphic and sedimentary impacts of this lahar

can tectonic events change volcanic tremor at stromboli 1 besides the well known strombolian activity stromboli shows the presence of a continuous volcanic tremor tectonic events in the area are rare and no evidence of a local tectonic event changing the characteristics of the tremor was previously known in april and may 2006 a swarm of tectonic events was recorded located very close to the island of stromboli possibly within the same volcanic edifice in this paper we analyse the time evolution of several dynamical parameters computed on the volcanic tremor and show examples where abrupt transitions can be associated to the occurrence of such local tectonic events this suggests that these events may be related to the volcanic activity i e be proper volcano tectonic events