numerical investigation of debris materials prior to debris flow hazards using satellite images abstract the volume of debris flows occurred in mountainous areas is mainly affected by the volume of debris materials deposited at the valley bottom quantitative evaluation of debris materials prior to debris flow hazards is important to predict and prevent hazards at midnight on 7th august 2010 two catastrophic debris flows were triggered by the torrential rain from two valleys in the northern part of zhouqu city nw china resulting in 1765 fatalities and huge economic losses in the present study a depth integrated particle method is adopted to simulate the debris materials based on 2 5 m resolution satellite images in the simulation scheme the materials are modeled as dry granular solids and they travel down from the slopes and are deposited at the valley bottom the spatial distributions of the debris materials are investigated in terms of location volume and thickness simulation results show good agreement with post disaster satellite images and field observation data additionally the effect of the spatial distributions of the debris materials on subsequent debris flows is also evaluated it is found that the spatial distributions of the debris materials strongly influence affected area runout distance and flow discharge this study might be useful in hazard assessments prior to debris flow hazards by investigating diverse scenarios in which the debris materials are unknown

deformations and inferred stress field for ellipsoidal sources at long valley california 1975 1982 ground deformation and seismicity observed from 1975 to the present support the existence of magma beneath the central part of long valley caldera california constraints on the source geometry are obtained from deformation modeling of uplift and trilateration data over the period 1975 1982 the deformation data are modeled with an elastic half space incorporating an ellipsoidally shaped magma chamber under uniform pressure the hilton creek fault and the south moat fault the best fit to the deformation data indicates a nearly spherically shaped source beneath the central part of the caldera at a depth of 9 5 1 km however significant deviations of some horizontal displacement data suggest that movements along the faults are probably more complicated than the assumed dislocations the predicted normal stress on the vertical south moat fault plane varies from weak tension above 4 km depth to strong compression below that depth and the shear stress is right lateral in the eastern half and left lateral in the western half of the fault it is unlikely that such a stress field could trigger slip movement on the fault tangential stress at the surface of the magma chamber has a maximum tension near its intersection with the south moat fault it is possible that the 1983 earthquake swarms in the south moat were triggered by shallow magma intrusions beneath the south moat of the caldera a narrow prolate ellipsoidal source which produces about the same uplift as the spherical source model leads to a horizontal tensile stress that is about 1 order of magnitude higher in the region directly above the source however the crack opening location for magma injection is at the top of the source in this case and would not be related to the seismicity in 1983

a model for deformation in long valley california 1980 1983 geodetic data collected in long valley california from 1975 through 1983 define a pattern of uplift and strain which is evidently associated with a sequence of earthquakes occurring in may 1980 and subsequent swarm activity continuing until the present we have constructed a model to explain the deformation observed since may 1980 in terms of inflation of two subsurface magma chambers faulting in the south moat region of the caldera and slip on the hilton creek fault the most significant new feature of the model is the shallow magma chamber at 5 km depth located a few hundred meters to the east of the casa diablo hot spring area inflation of this chamber causes stresses which show consistency with various aspects of the seismicity in the south moat of the caldera calculations of stress across vertical planes over the magma chamber can be used together with failure criteria to estimate the inflation volume at which the rock layers intervening between the chamber and the surface will fail by extensional fracture

time reverse modelling of acoustic wave propagation in attenuating media summary time reverse modelling trm of acoustic wave propagation has been widely implemented in seismic migration and time reversal source imaging the basic assumption of this modelling is that the wave equation is time invariant in non attenuating media in the earth attenuation often invalidates this assumption of time invariance to overcome this problem i propose a trm approach that compensates for attenuation and dispersion effects during the wave propagation in attenuating media this approach is based on a viscoacoustic wave equation which explicitly separates attenuation and dispersion following a constant q model compensating for attenuation and dispersion during trm is achieved by reversing the sign of the attenuation operator coefficient while leaving the counterpart dispersion parameter unchanged in this viscoacoustic wave equation a low pass filter is included to avoid amplifying high frequency noise during trm i demonstrate the effects of the filter on the attenuation and the phase velocity by comparing with theoretical solutions in a 1 d pierre shale homogeneous medium three synthetic examples are used to demonstrate the feasibility of attenuation compensation during trm the first example uses a 1 d homogeneous model to demonstrate the accuracy of the numerical implementation of the methodology the second example shows the applicability of source location using a 2 d layering model the last example uses a 2 d cross well synthetic experiment to show that the methodology can also be implemented in conjunction with reverse time migration to image subsurface reflectors when attenuation compensation is included i find improved estimation of the source location the excitation timing of the point source the magnitude of the focused source wavelet and the reflectivity image of reflectors particularly for deep structures underneath strongly attenuating zones

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

analysis of dynamics of vulcanian activity of ubinas volcano using multicomponent seismic antennas abstract a series of 16 vulcanian explosions occurred at ubinas volcano between may 24 and june 14 2009 the intervals between explosions were from 2 1 h to more than 6 days mean interval 33 h considering only the first nine explosions the average time interval was 7 8 h most of the explosions occurred after a short time interval

imaging lateral heterogeneity in the northern apennines from time reversal of reflected surface waves summary prominent arrivals in the coda of seismograms from the wider alpine area can be associated with lateral reflections of love waves at the northern apennines mountain chain italy where structural heterogeneity causes an abrupt contrast in phase velocity we discuss an approach to image lateral heterogeneity from reflected surface waves using intermediate period threecomponent coda waveforms as sources for an adjoint wavefield that propagates the reflections backward in time we numerically compute three dimensional sensitivity kernels for the dependence of coda waveforms on p velocity s velocity and density based upon correlations between the adjoint and the regular forward wavefields we consider synthetic coda waveforms for a simplified model of the northern apennines as well as real coda observations from five moderate magnitude earthquakes m w 4 6 5 6 in the southern alps wave propagation is simulated using the spectral element method for which a 3 d regional earth model is used in the case of real data single and combined event sensitivity kernels provide clear images of the reflectivity associated with the northern apennines in kernels for density and s wave speed the kernels show that surface wave reflections occur near the axial zone of the mountain chain apart from the apennines the approach is able to image other smaller reflectivity patches from the coda waveforms like the ivrea zone in the southern alps our coda misfit kernels can be integrated in a gradient based waveform tomography where they could enhance the sharpness of the model at lateral discontinuities

a model for the analysis of rapid landslide motion across three dimensional terrain a new numerical model for the dynamic analysis of rapid flow slides debris flows and avalanches has been developed the model is an extension of an earlier algorithm and is implemented using a nu

numerical modelling of entrainment deposition in rock and debris avalanches abstract rock and debris avalanches as well as debris flows are characterized by peculiar behaviour influenced by geometry of the initial failure surface topography involved materials involved and water content during their motion rock avalanches can entrain large volumes of sediments both in a dry and in a saturated state entrained dry material has generally the consequence to reduce the total landslide runout whereas entrainment of almost saturated material can have more complex consequences we use a finite element code to simulate the motion of a moving landslide mass on materials with different properties and along very sharp topographies erosion and deposition can be modelled as well as interaction with obstacles of different characteristics we present two examples of the modelling problems and capabilities we simulated the runout of a rock avalanche on a ground formed by alluvial material under dry and saturated conditions this material can be entrained and plowed by the impacting and running rock avalanche material sensitivity of the erosion and transport mechanisms has been analysed by performing different analyses the simulated case study is the 6 10 5 m 3 arvel rock avalanche 1922 switzerland for which a reliable set of pre and post failure observations is available final geometry mass redistribution velocities and runup are used to validate the model capabilities and study the effects of different material properties

moment tensor inversion of lp events recorded on etna in 2004 using constraints obtained from wave simulation tests 1 the persistent occurrence of long period lp events at mt etna became apparent with the installation of the first fixed broad band seismic network in late 2003 repeating similar lp events from nov 03 to sept 04 indicate a non destructive source process we perform moment tensor mt inversions on a stacked high s n ratio representative lp signal conducting a grid search for the source geometry and l2 inversion for the source time function results indicate a nnw sse oriented resonating sub vertical crack as the most probable source this result is consistent with deformation and gps observations crucial to this result are constraints imposed by detailed 3d full waveform numerical simulations in a heterogeneous tomographic model with topography and in particular a detailed assessment of the influence of very near surface velocity structure on lp signals pulsating gas injection is hypothesised as the most likely lp trigger

time reversal imaging of seismic sources and application to the great sumatra earthquake the increasing power of computers and numerical methods like spectral element methods allows continuously improving modelization of the propagation of seismic waves in heterogeneous media and the development of new applications in particular time reversal in the three dimensional earth the concept of time reversal hereafter referred to as tr was previously successfully applied for acoustic waves in many fields like medical imaging underwater acoustics and non destructive testing we present here the first application at the global scale of tr with associated reverse movies of seismic waves propagation by sending back long period time reversed seismograms we show that seismic wave energy is refocused at the right location and the right time of the earthquake when tr is applied to the sumatra andaman earthquake 26 dec 2004 the migration of the rupture from the south towards the north is retrieved therefore tr is potentially interesting for constraining the spatio temporal history of complex earthquakes

three fragmentation mechanisms for highly viscous magma under rapid decompression abstract analysis of the behavior of viscous magma under short term tensile stresses demonstrates that the strain rates anticipated in the eruptive stages of collapse related events may be high enough under certain circumstances to provide fragmentation of the melt by brittle failure mechanisms of fragmentation of a highly viscous vesicular magma by the propagation of an unloading wave by layer by layer vesicle bursting fragmentation wave propagation and by rapid filtration gas flow are outlined fragmentation scenarios involving possible combinations of the three fragmentation mechanisms are evaluated for two models of magma with isolated and with connected pores experimental results for magma fragmentation under high decompression rates appear to support such mechanisms these mechanisms of highly viscous magma fragmentation by rapid decompression probably have their greatest application in cases of explosive disintegration of lava domes and cryptodomes caused by collapse events

time reversal imaging of synthetic volcanic tremor sources 1 time reversal of seismic wavefields recorded at active volcanoes may provide images of the source process for long period lp or volcanic tremor events directly independent of assumptions about extent geometry and mechanics of the source time reversal methods involve propagating the original time series from many receiver locations back into the medium the reversed signals then focus at their origin due to constructive interference elucidating the source location extent and radiation pattern in practice focusing may be blurred due to inaccurate earth models or sparse sampling of the wavefield at the surface here we investigate the feasibility of this method for several synthetic volcanic tremor sources and present a gallery of time reversal source images wave propagation is computed numerically in a 2d volcano model with realistic topography our results indicate that time reversal may be applicable in volcanic settings possibly yielding new insights into volcano seismic lp or tremor sources

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

debris avalanche deposits offshore st vincent west indies impact of flank collapse events on the morphological evolution of the island abstract major scarp features have been previously identified on soufriere volcano st vincent lesser antilles and recently interpreted as flank collapse structures although no associated debris avalanche deposits were recognized new offshore high resolution bathymetry and geophysical data have been collected during the caraval cruise n o l atalante february march 2002 offshore of st vincent recent analysis of these data leads us to identify and characterize a debris avalanche deposit on the western flank of soufriere volcano which extends down to the grenada basin the origin of the submarine deposit by submarine slump or flank collapse event is discussed but data analysis tends support the occurrence of a flank collapse event during the evolution of soufriere volcano the collapse volume has been estimated to about 9 km 3 and the age of the event is less than 50 000 years using marine geophysical constraints the origin of the flank collapse can be related to local causes weakening of the flank by intense hydrothermal alteration magmatic injections increase of the load by accumulation of volcanic products and or to regional causes asymmetry of the arc sea level variations induced by climate change that may have an effect on the stability of the volcano taking into account this event we proposed a model for the evolution of soufriere volcano including a new estimation of the magma production rate the estimation indicates that soufriere volcano is one of the most active volcanoes of the arc a future flank collapse event could have catastrophic consequences for the entire area due to the emplacement of voluminous potentially tsunamigenic debris avalanches

earthquake induced chains of geologic hazards patterns mechanisms and impacts large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking most moderate and large magnitude earthquakes trigger landslides ranging from small failures in the soil cover to massive devastating rock avalanches some landslides dam rivers and impound lakes which can collapse days to centuries later and flood mountain valleys for hundreds of kilometers downstream landslide deposits on slopes can remobilize during heavy rainfall and evolve into debris flows cracks and fractures can form and widen on mountain crests and flanks promoting increased frequency of landslides that lasts for decades more gradual impacts involve the flushing of excess debris downstream by rivers which can generate bank erosion and floodplain accretion as well as channel avulsions that affect flooding frequency settlements ecosystems and infrastructure ultimately earthquake sequences and their geomorphic consequences alter mountain landscapes over both human and geologic time scales two recent events have attracted intense research into earthquake induced landslides and their consequences the magnitude m 7 6 chi chi taiwan earthquake of 1999 and the m 7 9 wenchuan china earthquake of 2008 using data and insights from these and several other earthquakes we analyze how such events initiate processes that change mountain landscapes highlight research gaps and suggest pathways toward a more complete understanding of the seismic effects on the earth s surface

time reverse location of seismic long period events recorded on mt etna we present the first application of a time reverse location method in a volcanic setting for a family of long period lp events recorded on mt etna results are compared with locations determined using a full moment tensor grid search inversion and cross correlation method from 2008 june 18 to july 3 50 broad band seismic stations were deployed on mt etna italy in close proximity to the summit two families of lp events were detected with dominant spectral peaks around 0 9 hz the large number of stations close to the summit allowed us to locate all events in both families using a time reversal location method the method involves taking the seismic signal reversing it in time and using it as a seismic source in a numerical seismic wave simulator where the reversed signals propagate through the numerical model interfere constructively and destructively and focus on the original source location the source location is the computational cell with the largest displacement magnitude at the time of maximum energy current density inside the grid before we located the two lp families we first applied the method to two synthetic data sets and found a good fit between the time reverse location and true synthetic location for a known velocity model the time reverse location results of the two families show a shallow seismic region close to the summit in agreement with the locations using a moment tensor full waveform inversion method and a cross correlation location method

seismic anisotropy time variations at mt etna this article has been accepted for publication in geophysical journal international the authors 2020 published by oxford university press on behalf of the royal astronomical society all rights reserved uploaded in accordance with the publisher s self archiving policy

characteristics and management of the 2006 2008 volcanic crisis at the ubinas volcano peru abstract ubinas volcano is located 75 km east of arequipa and ca 5000 people are living within 12 km from the summit this composite cone is considered the most active volcano in southern peru owing to its 24 low to moderate magnitude vei 1 3 eruptions in the past 500 years the onset of the most recent eruptive episode occurred on 27 march 2006 following 8 months of heightened fumarolic activity vulcanian explosions occurred between 14 april 2006 and september 2007 at a time ejecting blocks up to 40 cm in diameter to distances of 2 km ash columns commonly rose to 3 5 km above the caldera rim and dispersed fine ash and aerosols to distances of 80 km between april 2006 and april 2007 until april 2007 the total volume of ash was estimated at 0 004 km 3 suggesting that the volume of fresh magma was small ash fallout has affected residents livestock water supplies and crop cultivation within an area of ca 100 km 2 around the volcano continuous degassing and intermittent mild vulcanian explosions lasted until the end of 2008 shortly after the initial explosions on mid april 2006 that spread ash fallout within 7 km of the volcano an integrated scientific committee including three peruvian institutes affiliated to the regional committee of civil defense for moquegua aided by members of the international cooperation worked together to i elaborate and publish volcanic hazard maps ii inform and educate the population and iii advise regional authorities in regard to the management of the volcanic crisis and the preparation of contingency plans although the 2006 2008 volcanic crisis has been moderate its management has been a difficult task even though less than 5000 people now live around the ubinas volcano however the successful management has provided experience and skills to the scientific community this volcanic crisis was not the first one that peru has experienced but the 2006 2008 experience is the first long lasting crisis that the peruvian civil authorities have had to cope with including attempts to utilize a new alert level scheme and communications system and the successful evacuation of 1150 people lessons learned can be applied to future volcanic crises in southern peru particularly in the case of reawakening of el misti volcano nearby arequipa

analysis of sustained long period activity at etna volcano italy abstract following the installation of a broadband network on mt etna sustained long period lp activity was recorded accompanying a period of total quiescence and the subsequent onset of the 2004 2005 effusive episode from about 56000 events detected by an automatic classification procedure we analyse a subset of about 3000 signals spanning the december 17th 2003 september 25th 2004 time interval lp spectra are characterised by several unevenly spaced narrow peaks spanning the 0 5 10 hz frequency band these peaks are common to all the recording sites of the network and different from those associated with tremor signals throughout the analysed time interval lp spectra and waveforms maintain significant similarity thus indicating the involvement of a non destructive source process that we interpret in terms of the resonance of a fluid filled buried cavity polarisation analysis indicates radiation from a non isotropic source involving large amounts of shear concurrently with lp signals recordings from the summit station also depict very long period vlp pulses whose rectilinear motion points to a region located beneath the summit craters at depths ranging between 800 and 1100 m beneath the surface based on a refined repicking of similar waveforms we obtain robust locations for a selected subset of the most energetic lp events from probabilistic inversion of travel times calculated for a 3d heterogenous structure lp sources cluster in a narrow volume located beneath the summit craters and extending to a maximum depth of 800 m beneath the surface no causal relationships are observed between lp vlp and tremor activities and the onset of the 2004 2005 lava effusions thus indicating that magmatic overpressure played a limited role in triggering this eruption these data represent the very first observation of lp and vlp activity at etna during non eruptive periods and open the way to the quantitative modelling of the geometry and dynamics of the shallow plumbing system

a 3d discrete numerical elastic lattice method for seismic wave propagation in heterogeneous media with topography 1 a three dimensional elastic lattice method for the simulation of seismic waves is presented the model consists of particles arranged on a cubic lattice which interact through a central force term and a bond bending force particle disturbances are followed through space by numerically solving their equations of motion a vacuum free surface boundary condition is implicit in the method we demonstrate that a numerical implementation of the method is capable of modelling seismic wave propagation with complex topography this is achieved by comparing the scheme against a finite difference solution to the elastodynamic wave equation the results indicate that the scheme offers an alternative 3d method for modelling wave propagation in the presence of strong topography and subsurface heterogeneity we apply the method to seismic wave propagation on mount etna to illustrate its applicability in modelling a physical system

magma fragmentation by rapid decompression the processes leading to magma fragmentation and the generation of pyroclastic debris during explosive volcanic eruptions are of fundamental importance in volcanology observations of explosive eruptions1 3 as well as theoretical analyses of the underlying processes4 have raised the question of whether the rapid decompression of highly viscous vesicular magma that results from the collapse of a lava dome or volcanic edifice can in itself produce explosive magma fragmentation and pyroclast formation here we report the results of a laboratory investigation of pyroclast formation following rapid decompression samples of magma from the 1980 eruption of mount st helens when rapidly depressurized from initial pressures of up to 12 mpa and at temperatures in the range 750 825 c fragmented to form pyroclastic products that are in many respects similar to those formed in real eruptions moreover we observe explosive fragmentation at temperatures well below those normally associated with magmatic processes suggesting that even relatively cool magma bodies can be very hazardous when subjected to rapid unloading events

dynamic modelling of entrainment in rapid landslides entrainment of path material is an important feature of many rapid landslides the associated increases in volume and changes in flow character can significantly influence mobility a simple material entrainment algorithm based on the assumption of natural exponential growth with displacement has been incorporated into a new computer model designed to simulate rapid landslide motion across 3d terrain the user controls the growth rate and can also implement a change in rheology at the onset of entrainment a hypothetical example is used to demonstrate the influence of the mass and momentum transfer assumptions a back analysis of the 1999 nomash river landslide is included to show that the simple model is capable of simulating the bulk characteristics of a complex event involving substantial entrainment key words landslides debris flows rock avalanches entrainment erosion dynamic modelling

locating sources of volcanic tremor and emergent events by seismic triangulation application to arenal volcano costa rica 1 we address the issue of locating the sources of volcanic tremor and emergent events with a method requiring a limited amount of equipment a network of several triangular seismic antennas made of vertical sensors is used the slowness vectors are estimated at each array on a sliding window by inverting the time delays between the sensors calculated with the cross spectral method a probabilistic approach is adopted whereby each measure and its error are represented by a probability density function pdf a weighted summation of the pdfs is carried out in which the stable directions of propagation are enhanced the effects of the structural heterogeneities are taken into account by introducing an additional error associated to a robust hyperbolic secant sech type pdf the resulting pdfs of the back azimuth are combined to calculate a pdf of the source location the maximum likelihood of this pdf is taken as an estimate of the source position and its spread is characterized by a covariance analysis data from an experiment carried out at arenal volcano costa rica with four arrays are analyzed the precision and robustness of the method are tested by exploring the influence of the array configuration and other parameters the mean standard deviation on the position of the sources is 600 m for the tremor and 400 m for the explosions and long period lp events several tremors explosions and lp events are analyzed and their sources located the seismogenic zone is located in a 600 m radius area centered on the active crater

long period seismicity in the shallow volcanic edifice formed from slow rupture earthquakes volcanic eruptions are often preceded by long period seismic events that were thought to be generated by the resonance of cracks filled with magmatic fluid analysis and modelling of long period seismicity at volcanoes in italy costa rica and peru shows that it could instead be caused by slow rupture along faults in the upper volcanic edifice

numerical simulation of debris flow behavior incorporating a dynamic method for estimating the entrainment abstract there is a pressing need to estimate debris flow entrainment because several lines of studies have substantiated that the magnitude of a debris flow may grow manyfold due to sediment entrainment in this paper we present a two dimensional numerical model of debris flow behavior for estimating entrainment over complex topography the model is governed by a numerical integration of the depth average motion equations using shallow water approximation the governing equations are numerically solved using the semi lagrangian method in an explicit finite difference grid compared to previous models the presented model highlights the importance of entrainment and incorporates a physically based dynamic method to estimate the entrainment rate the entrainment rate can be predicted using reasonable assumptions regarding the velocity profile of the debris flow and the rapidly changing pore pressure of the bed sediment the stability of the presented model is first illustrated by a hypothesized dam breaking problem the effectiveness of the implemented model entrainment process is subsequently tested on the 2010 yohutagawa debris flow event in japan the test indicates that the presented method can be satisfactorily used to simulate debris flow behavior and the entrainment process a discussion regarding the advantages and limitations of the model concludes the paper

seismo volcano source localization with triaxial broad band seismic array summary seismo volcano source localization is essential to improve our understanding of eruptive dynamics and of magmatic systems the lack of clear seismic wave phases prohibits the use of classical location methods seismic antennas composed of one component 1c seismometers provide a good estimate of the backazimuth of the wavefield the depth estimation on the other hand is difficult or impossible to determine as in classical seismology the use of three component 3c seismometers is now common in volcano studies to determine the source location parameters backazimuth and depth we extend the 1c seismic antenna approach to 3cs this paper discusses a high resolution location method using a 3c array survey 3c music algorithm with data from two seismic antennas installed on an andesitic volcano in peru ubinas volcano one of the main scientific questions related to the eruptive process of ubinas volcano is the relationship between the magmatic explosions and long period lp swarms after introducing the 3c array theory we evaluate the robustness of the location method on a full wavefield 3 d synthetic data set generated using a digital elevation model of ubinas volcano and an homogeneous velocity model results show that the backazimuth determined using the 3c array has a smaller error than a 1c array only the 3c method allows the recovery of the source depths finally we applied the 3c approach to two seismic events recorded in 2009 crossing the estimated backazimuth and incidence angles we find sources located 1000 660 m and 3000 730 m below the bottom of the active crater for the explosion and the lp event respectively therefore extending 1c arrays to 3c arrays in volcano monitoring allows a more accurate determination of the source epicentre and now an estimate for the depth

simulation of rainfall induced debris flow considering material entrainment abstract in order to simulate soil erosion and sedimentation processes of debris flow a depth integrated particle method with soil water mixing model is proposed in the model each numerical particle represents a mixture of soil grains and water with a certain soil volume concentration and can exchange the soil mass with the neighboring particles according to the diffusion equation a unique relationship is also assumed between the soil volume concentration and its critical deposition angle to compute the bottom shear stress acting on the flowing numerical particles therefore the model only contains three major mechanical parameters the classical manning coefficient the critical slope angle for the loose soil deposit at the base of valley and the diffusion coefficient to control the soil water mixing process in addition a two step simulation method is proposed to evaluate the initial distribution of the loose soil deposit in the valley bottom the model is initially validated by a laboratory flume experiment taken from the open literature and adequate values of the mechanical parameters are determined next the model is applied into the case study of the 2010 debris flow event in zhouqu and the simulation results are compared with the field investigation as well as the post event satellite images the affected area the travel distance and the flow velocity statistics exhibit good agreement

automatic classification of volcano seismic signatures the prediction of volcanic eruptions and the evaluation of associated risks remain a timely and unresolved issue this paper presents a method to automatically classify seismic events linked to volcanic activity as increased seismic activity is an indicator of volcanic unrest automatic classification of volcano seismic events is of major interest for volcano monitoring the proposed architecture is based on supervised classification whereby a prediction model is built from an extensive data set of labeled observations relevant events should then be detected three steps are involved in the building of the prediction model i signals preprocessing ii representation of the signals in the feature space and iii use of an automatic classifier to train the model our main contribution lies in the feature space where the seismic observations are represented by 102 features gathered from both acoustic and seismic fields ideally observations are separable in the feature space depending on their class the architecture is tested on 109 609 seismic events that were recorded between june 2006 and september 2011 at ubinas volcano peru six main classes of signals are considered long period events volcanic tremors volcano tectonic events explosions hybrid events and tornillos our model reaches 93 5 0 50 accuracy thereby validating the presented architecture and the features used furthermore we illustrate the limited influence of the learning algorithm used i e random forest and support vector machines by showing that the results remain accurate regardless of the algorithm selected for the training stage the model is then used to analyze 6 years of data

comment on field and seismic evaluation of the block and ash flows emplaced from eruption columns of the 2005 vulcanian explosions at volcan de colima mexico by zobin et al bull volcanol 2016 78 27

positive feedback and momentum growth during debris flow entrainment of wet bed sediment debris flows typically occur when intense rainfall or snowmelt triggers landslides or extensive erosion on steep debris mantled slopes the flows can then grow dramatically in size and speed as they entrain material from their beds and banks but the mechanism of this growth is unclear indeed momentum conservation implies that entrainment of static material should retard the motion of the flows if friction remains unchanged here we use data from large scale experiments to assess the entrainment of bed material by debris flows we find that entrainment is accompanied by increased flow momentum and speed only if large positive pore pressures develop in wet bed sediments as the sediments are overridden by debris flows the increased pore pressure facilitates progressive scour of the bed reduces basal friction and instigates positive feedback that causes flow speed mass and momentum to increase if dryer bed sediment is entrained however the feedback becomes negative and flow momentum declines we infer that analogous feedbacks could operate in other types of gravity driven mass flow that interact with erodible beds the mechanisms by which debris flows acquire mass and momentum as they entrain material are unclear large scale experiments suggest that the pore pressure of wet bed sediment increases as the flow moves over the bed leading to reduced friction and progressive scouring of the base

entrainment of bed material by earth surface mass flows review and reformulation of depth integrated theory earth surface mass flows such as debris flows rock avalanches and dam break floods can grow greatly in size and destructive potential by entraining bed material they encounter increasing use of depth integrated mass and momentum conservation equations to model these erosive flows motivates a review of the underlying theory our review indicates that many existing models apply depth integrated conservation principles incorrectly leading to spurious inferences about the role of mass and momentum exchanges at flow bed boundaries model discrepancies can be rectified by analyzing conservation of mass and momentum in a two layer system consisting of amoving upper layer and static lower layer our analysis shows that erosion or deposition rates at the interface between layers must in general satisfy three jump conditions these conditions impose constraints on valid erosion formulas and they help determine the correct forms of depth integrated conservation equations two of the three jump conditions are closely analogous to rankine hugoniot conditions that describe the behavior of shocks in compressible gasses and the third jump condition describes shear traction discontinuities that necessarily exist across eroding boundaries grain fluid mixtures commonly behave as compressible materials as they undergo entrainment because changes in bulk density occur as the mixtures mobilize and merge with an overriding flow if no bulk density change occurs then only the shear traction jump condition applies even for this special case however accurate formulation of depth integrated momentum equations requires a clear distinction between boundary shear tractions that exist in the presence or absence of bed erosion

stress modeling at long valley california borehole stability near a magma chamber the inversion of surface deformation data at long valley california for magma chamber geometry is not unique an analytical solution in the form of an integral equation was developed to study if the stress variation with depth below the point of maximum uplift on the resurgent dome could constrain the shape and size of various ellipsoidal magma chambers all of which explain the basic surface deformations the integral solution accounts for the magma chamber pressurization interacting with a lithostatic stress field the sensitivity of the results to the far field boundary condition was tested by considering both zero lateral strain and a linearly increasing horizontal stress a wide range of spherical sizes was examined because inversion of the formation data generally limit eccentricities of ellipsoids to a small range 0 2 whereas size is largely unconstrained the center of inflation is well constrained to be at 9 5 km depth the stress at the surface is highly compressive for a 5 km radius spherical chamber and is nearly zero for a 1 km radius chamber when both are centered at 9 5 km depth and produce approximately the same surface deformation the near surface compressive stress for a large chamber greatly exceeds tectonic or lithostatic stresses the compressive stress decreases with depth for the 5 km chamber whereas it increases approximately lithostatically for the 1 km chamber the stress field becomes tensile or nearly tensile as the top of the chamber is approached in all cases the magnitude of the tensile stress is much higher for the 1 km case dike injection is inferred to be much more likely for a smaller chamber the effect of ellipsoid shape is not as significant as size for the small eccentricities allowed by the long valley surface deformations the surface compressive stress due to an oblate source is about 60 mpa larger than for a prolate source when the tops of the chambers are at the same depth part of this difference is due to the larger size of the oblate chamber if the chamber volumes are held constant by allowing the depths to their tops to vary then the difference between the prolate and the oblate cases is reduced to 15 mpa in the absence of other stresses breakouts may occur at 1 km depth for a 5 km radius spherical source if the cohesive strength of the rock is less than 25 mpa borehole stability decreases when tectonic and other stresses are included

waveform inversion of volcano seismic signals assuming possible source geometries 1 we propose an approach to quantify the source of volcano seismic signals assuming possible source geometries such an assumption reduces the number of free parameters in a waveform inversion so we can quantify the source of these signals observed by a small number of seismic stations we test this method by using the synthesized waveforms radiated by a fluid filled crack and with seismic data observed at kusatsu shirane volcano we find that waveform data from 2 to 3 three component seismic stations surrounding the source enable us to estimate the source mechanism and location in the present approach

time reverse modeling of low frequency microtremors application to hydrocarbon reservoir localization 1 time reverse modeling is applied to synthetic and real low frequency microtremors measured at the earth surface with synchronized seismometers in contrast to previous time reverse applications no single event or first arrival time identification is applied for microtremor localization synthetic low frequency microtremors are numerically generated within a small underground area and modeled with a finite difference algorithm simulating two dimensional elastic wave propagation time reverse modeling using synthetic microtremors shows that small underground source areas can be accurately located different source characteristics which emit mainly p waves or s waves vertically influence the localization accuracy time reverse modeling is applied to two real microtremor data sets acquired 16 months apart above known oil reservoirs nearby voitsdorf austria to investigate whether spectral anomalies observed above the reservoirs originate from the reservoirs time reverse modeling indicates that low frequency microtremor signals originate from the reservoir locations and provides a possible method for reservoir localization

destruction of a lava dome observed with photogrammetry acoustic and seismic sensors at volcan de colima mexico abstract during the period december 2016 to march 2017 the lava dome emplaced in september november 2016 at volcan de colima was partially destroyed by vulcanian explosions in particular 10 moderate large explosions were observed with heights of 2 6 8 km from the crater and with the generation of pyroclastic density currents pdcs shock waves and ballistics the acoustic and seismic energies were calculated for each event the values found are similar to other moderate large vulcanian explosions observed at other volcanoes the maximum value of seismic energy was of 1 6 109 j and for acoustic energy 7 5 108 j these values were compared with the height of the eruptive column which resulted in a poor correlation for the acoustic signals the reduced pressure was greater than that commonly reported for vulcanian explosions elsewhere using the time or arrival of the acoustic and seismic signals the depth of the acoustic seismic source was estimated at

flume tests to study the initiation of huge debris flows after the wenchuan earthquake in s w china abstract in the wenchuan area in the southwest of china a huge amount of loose co seismic landslide material was deposited on slopes during the wenchuan earthquake of may 2008 these loose deposits formed the source material for rainfall induced debris flows or shallow landslides in the years after the earthquake on august 13 2010 about 20 large debris flows were triggered by heavy rainfall in the area around the epicenter of the wenchuan earthquake field reconnaissance revealed that the initiation of these post earthquake debris flows was closely related to severe erosion of the loose deposits flume tests were carried out to study the initiation mechanism of these post earthquake debris flows and the related influencing factors the flume was instrumented with ten combination sets of suction and pore pressure sensors these sensors were accompanied by tdr probes to measure the soil water content the flume has a length of 2 5 m and a width of 1 5 m a series of 26 tests was conducted to study the influence of slope gradient and discharge on the initiation mechanism and scale of the debris flows the amount of debris flow discharge was obtained by collecting the washed out deposits every 20 s the experimental results showed that the initiation mechanism of debris flows for gentle slopes and steep slopes was different on steeper slope incision by run off water was very rapid initiating directly the start of a debris flow the debris flow volume increased rapidly by a chain of subsequent cascading processes starting with collapses of the side walls damming and breaching leading to a rapid widening of the erosion channel at gentler slopes less intensive run off incision caused an accumulation of material down slope which after saturation failed as shallow slides transform in a second stage into debris flows it was demonstrated that the slope was the dominant factor in controlling the scale of the debris flows while the effect of discharge on erosion and the size of the debris flows was less clear

migration of seismic activity associated with phreatic eruption at merapi volcano indonesia abstract phreatic activity of merapi started after nearly 2 years of quiescence following the october november 2010 eruption which was the largest in more than 100 years a dozen eruptions identified by visual and or seismic observations took place between august 2012 and april 2014 we present in this work the results of a detailed analysis of the april 20 2014 phreatic eruption we attempted to reconstruct the eruptive process which lasted for over 30 min to this end we determined the wavefield composition by polarization analysis located high frequency earthquakes occurring in the initial part of the eruption process and then determined the seismic source migration of low frequency part of the tremor like signal 0 3 3 hz over time source depth of low frequency signal was obtained by comparing the slowness vector calculated using 3 stations of the seismic antenna with a slowness vector model obtained by ray tracing in the structure taking into account the topography and a 1d velocity model obtained by spatial auto correlation analysis the results allow to distinguish 3 different phases 1 high frequency transients interpreted as the result of a sudden decompression caused by the transition of the volcanic fluid to a gaseous phase that occurred approximately 1 5 km deep this decompression process in the hydrothermal system generated a migration of the low frequency seismic source from 900 m to 1800 m above sea level 2 a second decompression process revealed by high frequency micro seismicity and associated to the migration of the low frequency tremor source which is marked first by a descent phase followed by a sharp ascent until reaching the surface the evolution of the back azimuth during the migration process indicates a slight inclination of the conduit presumably in the orientation of the dome fracture in the nw se direction this direction is consistent with the alignment of regional tectonic structures and with the directivity of eruption deposits 3 the seismic source then remains positioned at the altitude of the dome for over 10 min this phase probably corresponds to the ash emission process the average migration speed of the low frequency seismic source from the starting eruptive process to ash emission is about 5 m s

continuous tracking of volcanic tremor at mount etna italy summary using data from two dense array of short period seismometers we analyse the kinematic properties of volcanic tremor preceding and accompanying the 2004 2005 eruption of etna volcano italy results from slowness analyses indicate the action of at least two distinct sources the first dominates the pre eruptive period and is likely associated with the main plumbing system feeding the summit and southeast craters following the onset of the eruption secondary directions of wave arrival encompass the eruptive fissures located on the lower eastern flank of the southeast crater nonetheless significant energy radiation from this latter source was also occurring prior to the onset of the lava effusion likely suggesting the presence of a resident magma batch in agreement with independent petrologic and geochemical data

experimental study of debris flow entrainment over stepped gradient beds incorporating bed sediment porosity abstract the incorporation of bed sediment by a natural debris flow can cause significant growth in its size and destructive potential in this study the erosion features of debris flows in channels with stepped gradient beds were determined based on field observations and flume experiments field investigations revealed that channel sections with abrupt bed slope variations were eroded more intensely than others a series of small scale flume tests were conducted to study the pore pressure variations in erodible bed sediment and the basal entrainment behaviour of debris flows in channels with stepped gradients reference tests on a uniform bed slope demonstrate that inflection points in the bed longitudinal profile greatly alter the debris mixture flow pattern and accelerate entrainment pore pressure generation in the bed sediment supports debris flow entrainment by reducing basal friction peak pore pressures at concave sites were approximately two times higher than those observed at convex sites likely due to large changes in debris flow dynamics and intense interactions between the flow mixture and bed sediment low bed sediment porosities will increase the interlocking of grain particles promote the formation of clusters and enhance the strength of the grain skeleton suppressing basal entrainment in the flume tests lower peak pore pressures were observed as bed porosity decreased possibly due to fewer connecting channels for pore fluid pressure to transmit in the compacted bed sediment dimensionless analysis indicates that pore pressure fluctuations in the bed sediment were mainly generated by the overriding debris flow a new entrainment formula of debris flow over stepped gradient beds is proposed based on flume tests and theoretical analyses which may aid future debris flow modelling and hazard assessments

a calculation method for predicting the runout volume of dam break and non dam break debris flows in the wenchuan earthquake area abstract the factors affecting debris flow runout volume changed considerably in the wenchuan earthquake area the main characteristic parameters for calculating the debris flow runout volume namely channelized landslide dam volume are first used to establish empirical models a new empirical statistical model is established by applying a multivariate regression analysis to the runout volumes of dam break and non dam break debris flows additionally flo 2d is used to simulate the debris flow runout volumes under the non dam breaking and dam breaking scenarios when the rainfall frequency is p 1 the predicted runout volumes in the huaxi gully are 24 48 104 m3 under the non dam breaking scenario and 43 41 104 m3 under the dam breaking scenario the runout volume in the dam breaking scenario is 6 07 104 m3 more than 1 77 times that in the non dam breaking scenario the predicted runout range of the dam breaking scenario is 1 16 times that of the non dam breaking scenario the predicted alluvial fan areas and average accumulation depths in the dam breaking scenario are larger than those in the non dam breaking scenario the predicted runout volume of the dam breaking scenario is 5 58 104 m3 which is less than the actual surveyed volume 48 99 104 m3 the relative error and accuracy of the numerical simulation results are 11 39 and 88 61 for the dam breaking scenario the new runout volume model was developed in catchments with abundant loose materials in the wenchuan earthquake area and can thus be applied to debris flow gullies in meizoseismal areas with newly fractured regolith and abundant loose material to estimate runout volumes the results of this study will help authorities select safe sites for future rehabilitation and relocation projects and can also be used as an important basis for debris flow risk management

array analysis of the seismic wavefield of long period events and volcanic tremor at arenal volcano costa rica we use wavefield decomposition methods time domain crosscorrelation and frequency domain music to analyze seismic data recorded by a dense small aperture array located 2 km west of arenal volcano costa rica and operated during 2 5 days the recorded wavefield is dominated by harmonic tremor and includes also spasmodic tremor and long period lp events we find that the initial stages of lp events are characterized by three different wave arrivals these arrivals propagate with similar back azimuths pointing to the volcano summit 80 n and increasing apparent slownesses of 0 4 1 1 and 1 7 s km spasmodic tremors can not be regarded as coherent signals on the contrary harmonic tremors are highly coherent characterized by the stability of the apparent slowness vector estimates apparent slownesses lay in the range 1 2 s km back azimuths point in the general direction of the volcano but with a large variability 40 120 n nevertheless there are long term variations and evidences of multiple simultaneous components in the harmonic tremor wavefield these observations suggest that lp events and tremor are generated in a shallow source area near the volcano summit although they do not share exactly the same source region or source processes the tremor source is located in the shallowest part of the plumbing system beneath the lava crust this dynamic region is subject to complex fluctuations of the physical conditions degassing events at different locations of this region might generate variable seismic radiation patterns the effects of topography and heterogeneous shallow structure of the volcano may amplify these variations and produce the wide directional span observed for volcanic tremor on the other hand the lp source seems to be more repeatable lp events are likely triggered by fragmentation of the fluid flow in a slightly deeper portion of the volcanic conduits

multiscale matched field processing for noise source localization in exploration geophysics abstractin the study we investigate the use of ambient noise data to locate microseismic sources at the exploration scale we develop a multiscale matched field processing mfp approach to localize seismic sources at frequencies below 10 hz an application to an actual data set acquired over a hydrocarbon field is presented to determine the reliability of the mfp procedure the data used were continuously recorded over five days at a total of 397 stations on a 1 km per side square seismic network the mfp results show 1 a dominant and stable surface source associated with human activities road and exploration platforms around the reservoir and 2 weaker sources at depth below the seismic network that are related to the injection extraction process

pre explosive conduit conditions of the 1997 vulcanian explosions at soufriere hills volcano montserrat i pressure and vesicularity distributions an authoritative case of vulcanian eruptive dynamics is the series of 88 explosions that occurred between august and october 1997 at soufriere hills volcano on montserrat island the state of the magmatic column just before a vulcanian explosion is still poorly understood but conditions the eruptive style this study establishes such a pre explosive stratigraphy by 1 documenting the textures covering the range of the 1997 products 2 quantitative analysis of h2o content in interstitial glass measured by karl fischer titration and 3 combining these data with a simple model linking pre and post explosive vesicularities the model shows that syn explosive degassing affects greatly the way porosity evolves by decompression during an explosion the stratigraphy reconstruction shows a three part vertical layering of the conduit prior to explosion with overall denser values than those previously suggested a dense and strongly degassed plug caps the column it is underlain by a shallow transition zone featuring complex mingling between vesicular and dense magma up to 10 mpa at higher pressure up to 80 mpa lies a more homogeneous zone of relatively dense 10 20 vol magma which was emplaced under partly open system degassing this conduit stratigraphy gives the vision of a strongly heterogeneous magma column immediately prior to its disruption our analysis suggests that fragmenting such a composite magma cannot happen in a single coherent pulse but rather as stages the transition zone contains heterogeneous amounts of exsolved gas that could explain the pulsatory nature of the vulcanian jets at the beginning of the explosions this contrasts with the nearly constant vesicularities of the deeper part of the pre explosive magma column which are propitious to a general short lived disruption

deformation of long valley caldera between august 1982 and august 1983 geodetic and seismic data collected between july 1982 and august 1983 document an important event in the recent evolution of long valley caldera in january 1983 a substantial change in the pattern of deformation was associated with the most intense seismic swarm since may 1980 the earthquake hypocenters of the january 1983 swarm formed a vertical roughly tabular zone beneath the south moat of the caldera analysis of extensive intracaldera horizontal control data indicates that the shear strain distributed throughout this zone could not all be attributed to slip along any single fault plane the surface deformation of the resurgent dome and caldera floor is temporally associated with the swarm and was caused by an expansion of the upper levels of the residual magma chamber analysis of the 1983 data indicates a pressure distribution 2 5 km shallower than could be fit by analysis of the 1979 1982 caldera deformation the volume of this shallow expansion is 10 15 of the whole chamber expansion that occurred between 1979 and 1982 most of the 1983 deformation occurred between december 14 1982 and january 20 1983 and thus was associated with the january 6 7 1983 swarm though right lateral shear strain continued to accumulate in the south moat through 1983 we conclude that a shallow pressure increase probably occurred within the upper levels of the residual magma chamber of long valley caldera during the 5 week period following december 14 1982 it is not clear however whether this pressure increase preceded or accompanied the january 1983 earthquake swarm

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

well bore breakouts and in situ stress the detailed cross sectional shape of stress induced well bore breakouts has been studied using specially processed ultrasonic borehole televiewer data we show breakout shapes for a variety of rock types and introduce a simple elastic failure model which explains many features of the observations both the observations and calculations indicate that the breakouts define relatively broad and flat curvilinear surfaces which enlarge the borehole in the direction of minimum horizontal compression this work supports the hypothesis that breakouts result from shear failure of the rock where the compressive stress concentration around the well bore is greatest and that breakouts can be used to determine the orientation of the horizontal principal stresses in situ

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

deformation of long valley caldera mono county california from 1975 to 1982 teleseismic and gravity data acquired in 1973 support the existence of a large body of partial melt magma beneath the resurgent dome of long valley caldera in eastern california whereas intermittent reoccupation of vertical and horizontal control networks in and near long valley caldera revealed only very small probably tectonic movements between 1932 and 1979 a leveling survey in september 1980 showed a 250 mm uplift of highway 395 on the west side of the resurgent dome this uplift was apparently related to expansion of the subjacent magma body beginning sometime between july 1979 and september 1980 and may have been coseismic with the mammoth lakes magnitude 6 earthquake sequence of may 25 27 1980 these earthquakes ushered in a period of almost continuous low level seismicity punctuated by relatively severe swarms in the southern moat vertical and horizontal displacements within long valley caldera between 1979 and 1982 define a striking radially symmetric pattern of uplift and horizontal distension that is consistent with expansion of the body of partial melt inferred from teleseismic and gravity data specifically the observed deformation of the caldera floor approximates the theoretical deformation due to expansion of a spherical magma chamber at a depth of at least 7 km the calculated maximum uplift is 430 mm and is located south of the center of the resurgent dome significant deviations from this simple model appear to be associated with either movement of mapped faults within and adjacent to the caldera or folding of weak surface deposits

swelling of a lava plug associated with a vulcanian eruption at sakurajima volcano japan as revealed by infrasound record case study of the eruption on january 2 2007 in order to clarify the time relation of the expansion of a gas pocket and failure of its overlying plug of lava during vulcanian eruptions infrasound records and video images of the vulcanian eruption that occurred at sakurajima volcano on january 2 2007 were analyzed with respect to their origin times weak 3 pa and slowly increasing air pressure preceded the impulsive compression phase by 0 25 0 32 s and a longer period rarefaction phase of infrasound waves was recognized at all microphone stations the velocity of the compression phase was assumed to be supersonic ca 400 m s up to 850 m above the crater bottom from other recent explosions on the other hand the propagation velocity of the preceding weak signal was regarded to be similar to the air sound velocity because the lack of impulsiveness is unlikely to be related to the main compression phase therefore the estimated origin time of the main compression phase was delayed by 0 5 0 7 s from the preceding phase the origin time of the preceding phase coincided with the onset of the isotropic expansion process of the pressurized gas pocket which was obtained by the waveform inversion of the explosion earthquake in contrast the origin time of the main impulsive phase coincided with the time when the expansion rate reached its peak this observation suggests that the volumetric increase of the gas pocket caused swelling of the surface of the crater bottom and its subsequent failure when the expansion velocity exceeded a threshold level the main impulsive compression phase radiated with a high velocity by the sudden releases of the pressurized gases the volumetric change at the source was estimated to be 280 560 m3 from the preceding phase of the infrasound this volume change indicates that the vertical displacement of the swelling ground was on the order of 1 0 m assuming the radius of the lava plug was ca 10 m

inverting the source mechanism of strombolian explosions at mt yasur vanuatu using a multi parameter dataset abstract the source mechanism of strombolian explosions at mt yasur vanuatu is analyzed using a unique data set which enables us to combine different methodologies the novelty of the approach presented here lies in the combination of seismic acoustic and doppler radar data thus using infrasound and doppler radar observations we are able to provide independent estimates of the volume of the eruptive source in the following we show that a correlation exists between source volume and the maximum particle velocity of the expelled volcanic products in order to determine the source location and the associated mechanism and to compare those two methods we use time reversal imaging and moment tensor inversion while the first method also applies to extended sources the latter might be biased by its intrinsic point source approximation we show that time reversal imaging can deliver an estimate of the source depth without any a priori assumptions even in an unfavorable scenario in terms of topography and receiver setup the inverted source mechanism retrieved from moment tensor inversion is found to be largely isotropic with minor deviatoric components the inverted source location points towards an area to the north west of the active craters indicative of a common feeder system of the activity at mt yasur however it is also evident that to fully locate the source of strombolian activity at yasur location precision must be enhanced

initial phases of explosion earthquakes accompanying vulcanian eruptions at lokon empung volcano indonesia abstract we examine the initial phases of explosion earthquakes accompanying vulcanian eruptions at lokon empung volcano in indonesia to reveal the triggering process of explosive eruptions in 2012 2013 56 vulcanian eruptions at lokon empung were observed by our temporary observation network being comprised of four broadband seismometers and two infrasound microphones at 1 6 6 8 km from the active vent the seismic records of each explosion earthquake share almost the same waveform characteristics of initial phases consisting of a small compressional onset p phase and a subsequent large dilatational phase d phase particle orbits of both phases show straight motion from beneath the active vent which suggests that these phases are composed of a longitudinal body wave for each explosion the origin times of the p phase precedes 0 8 2 5 s before the occurrence of an explosion at the vent that are detected by infrasound data since the signal to noise ratio of the p phase is insufficient for a quantitative analysis we analyze the d phase dominating the initial phases our analysis for the signals of 0 2 1 0 hz shows the d phase are well explained by a cylindrical contraction source with a half cosine shaped time function located at 1 0 1 3 km depth beneath the active vent we also recognize that some explosions are followed by a prominent tremor that coincides with continuous ash emission et the seismic amplitudes and intensity of the d phase of events in et are larger than the explosions without accompanying tremor ex the frequency distribution of the time interval from the previous eruption is also different in the events in et and ex the implosion source in the initial phases of explosion earthquakes at several km beneath the active vent has been reported at sakurajima volcano since our result shows considerable agreement with the previous works at sakurajima both lokon empung and sakurajima may share similar initial processes of vulcanian eruptions

simulation of interactions between debris flow and check dams on three dimensional terrain abstract debris flows are rapid gravity driven flows of sediment water mixture which can be greatly destructive due to its huge volume high velocity and large impact force check dam is essential protective structure for controlling debris flow however it is a challenging work to assess the interactions between debris flow and check dam especially when involving complex topography and dam destruction a numerical method was developed in this study to investigate the interactions between debris flow and check dam on three dimensional terrain the debris flow and check dam were simulated by smoothed particle hydrodynamics sph method and finite element method fem respectively the method was validated by a dam break problem and a granular flow flume test an actual debris flow event originated from failure of tailings dams on 19 july 1985 in stava italy was simulated as an example the results indicate that the proposed method is a practical tool to simulate the runout characteristics of debris flow e g flow velocity flow depth impact area and interactions between debris flow and check dam e g impact force destruction of check dam interception by check dam given similar total dam volume increasing the number of dams will improve the hazard mitigation effect moreover it is recommended to construct dams in downstream area with straight channel this study will contribute to a better understanding of the flow structure interaction and is helpful for rational design of check dams

a model to describe precursory material failure phenomena applications to short term forecasting at colima volcano mexico some volcanoes exhibit at times accelerating strain and seismicity before eruptions different authors have used this behavior to predict eruptions and to develop materials science models here a linear kelvin voigt viscoelastic model is proposed to describe the observed behavior this model also has applications to other failure phenomena such as landslides the strain rate of a variety of materials under constant stress after an instantaneous elastic response is found to be well described by a general relaxation law dot varepsilon left t right b over 1 st where b and s are parameters depending on the material and its creep state whether the creep regime is primary or tertiary depends upon the sign of s s 0 corresponds to pseudoviscous flow the creep behavior of the viscoelastic body is analyzed for different load histories it is found that the body has an exponential distribution of retardation frequencies that may or may not converge depending on the sign of s according to the model tertiary creep implies material degradation and a critical weakening of the medium leading to a runaway growth of the strain and seismic energy release rates if tertiary creep is detected time of failure predictions may be done from field data through determination of two model parameters for varying loads the model response compare well with reported examples of pre eruptive volcano behavior and with reported results of landslide experiments the model is tested with the july 1994 in hindsight and november 1998 in foresight colima volcano eruptions although this method provides some guidance in estimating the time over which accelerating volcanic precursors may end in an eruption it is emphasized that eruptions may fail to occur at the estimated time or may not occur at all on the other hand eruptions may not be preceded by such a behavior

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

deformation near the long valley caldera eastern california 1982 1986 annual surveys of trilateration and leveling networks in and around long valley caldera in the 1982 1985 interval indicate that the principal sources of deformation are inflation of a magma chamber beneath the resurgent dome and right lateral strike slip on a vertical fault in the south moat of the caldera the rate of inflation of the magma chamber seems to have been roughly constant 0 02 km3 yr in the 1982 1985 interval but the slip rate on the south moat fault has decreased substantially in addition there is evidence for a shallow source of dilatation possibly dike intrusion beneath the south moat of the caldera in 1983 and less certain evidence for a deep source possibly magma chamber inflation beneath mammoth mountain in the western caldera in 1983 1985 deformation in the 1985 1986 interval as inferred from trilateration alone seems to be similar to that observed in 1984 1985

analysis of seismic body waves excited by the mount st helens eruption of may 18 1980 seismic body waves which were excited by the may 18 1980 eruption of mount st helens and recorded by the global digital seismographic network stations are analyzed to determine the nature and the time sequence of the events associated with the eruption the polarity of teleseismic p waves period 20s is identical at six stations which are distributed over a wide azimuthal range this observation together with a very small s to p amplitude ratio at 20 s suggests that the source is a nearly vertical single force a simple model shows that for seismic radiation a volcanic eruption can be represented by a single force applied in the direction opposite to the blast direction the time history of the vertical force suggests two distinct groups of events about 2 min apart each consisting of several subevents with a duration of about 25 s the magnitude of the force is approximately 2 6 10 12 n this vertical force is in contrast with the long period 150 s southward horizontal single force which has been determined by a previous study and interpreted to be due to the massive landslide an m s 5 2 earthquake initiated the eruption sequence the direction of the p wave first motion of this event observed at two nearby stations is consistent with the radiation pattern expected for the landslide and suggests that it represents the onset of the landslide the ground motions observed at station lon 67 km are dominated by rayleigh waves i e lamb pulse and provide tight constraints on the time sequence of the events

observations of high frequency scattered waves using dense arrays at teide volcano abstract a study of the seismic coda of seven small earthquakes recorded on the teide volcano canary islands spain was carried out using a temporary small aperture 12 station seismic array the purpose was to measure backazimuth apparent velocity and the type of waves that compose the coda in the frequency range 4 to 6 hz we used the zero lag cross correlation zlc method to obtain the components of the wave vector and three component analysis techniques based on the covariance matrix of the signal in the time domain to investigate the polarization properties of the signals the results show that a great part of the coda signals in the analyzed frequency range are almost uncorrelated while a low number of isolated correlated arrivals show an apparent slowness between 2 10 3 and 2 5 10 4 sec m and an almost random distribution of backazimuths the correlated arrivals have been interpreted as generated by strong scatterers probably related to the presence in the study area of surface topography irregularities the volcanic cone and the caldera rim the wave type varies from pure s type waves to mixed surface waves with some rayleigh components

probabilistic source location of explosion quakes at stromboli volcano estimated with double array data data from two dense arrays of short period seismometers are used to retrieve source locations of the explosion quakes at stromboli volcano slowness vectors estimated at both arrays with the zero lag cross correlation technique constitute the experimental data set a probabilistic approach based on a grid search spanning the volcano interior is used to calculate the probability of the source location results depict a shallow source located beneath the crater area at depths not greater than 500 m below the surface results are slightly different from but comparable to those obtained in a companion experiment carried out in the same time period using a broad band seismometer network which show a source shifted some hundreds of meters northwest of the crater area the method is revealed to be effective and useful for future studies having the purpose of real time tracking of the explosion quakes and tremor