continuing inflation at three sisters volcanic center central oregon cascade range usa from gps leveling and insar observations uplift of a broad area centered 6 km west of the summit of south sister volcano started in september 1997 onset estimated from model discussed in this paper and was continuing when surveyed in august 2006 surface displacements were measured whenever possible since august 1992 with satellite radar interferometry insar annually since august 2001 with gps and leveling surveys and with continuous gps since may 2001 the average maximum displacement rate from insar decreased from 3 5 cm yr during 1998 2001 to 1 4 cm yr during 2004 2006 the other datasets show a similar pattern i e surface uplift and extension rates decreased over time but deformation continued through august 2006 our best fit model to the deformation data is a vertical prolate spheroidal point pressure source located 4 9 5 4 km below the surface the source inflation rate decreased exponentially during 2001 2006 with a 1 e decay time of 5 3 1 1 years the net increase in source volume from september 1997 to august 2006 was 36 5 41 9 x 106 m3 a swarm of 300 small mmax 1 9 earthquakes occurred beneath the deforming area in march 2004 no other unusual seismicity has been noted similar deformation episodes in the past probably would have gone unnoticed if as we suspect most are small intrusions that do not culminate in eruptions

applicability of insar to tropical volcanoes insights from central america measuring volcano deformation is key to understanding the behaviour of erupting vol canoes and detecting those in periods of unrest satellite techniques provide the opportunity to do so on a global scale but with some notable exceptions the deformation of volcanoes in the tropics has been understudied relative to those at higher latitudes largely due to technical difficulties in applying interferometric synthetic aperture radar insar we perform a systematic survey of the central american volcanic arc to investigate the appli cability of interferometric synthetic aperture radar insar to volcanoes in the tropics volcano characteristics that may prevent insar measurement include 1 dense vegetation cover 2 per sistent activity and 3 steep slopes measurements of deformation are further inhibited by atmos pheric artefacts associated with 4 large changes in topographical relief we present a systematic method for distinguishing between water vapour artefacts and true deformation our data show a linear relationship c 2 cm km between the magnitudes of water vapour artefacts and volcano edifice height for high relief volcanoes e g fuego guatemala 3763 m a s l above sea level errors are of the order of 4 5 cm across the volcano s edifice but are less than 2 cm for lower relief e g masaya nicaragua 635 m a s l examples such as arenal atitlan and fuego illustrate that satellite acquisition strategies incorporating ascending and descending tracks are particularly important for studying steep sided volcanoes poor coherence is primarily associated with temporal decorrelation which is typically more rapid in southern central america where evergreen broadleaf vegetation dominates land use classification is a better predictorof decorrelation rate thanvegetationindex comparisonof coher ence for different radar wavelengths match expectations high resolution x band radar is best suited to local studies where high resolution digital elevation models dems exist while l bandwavelengths are necessary for regional surveys however this is the first time that relation ships between phase coherence and time perpendicular baseline radar wavelength and land use have been quantified on the scale of a whole volcanic arc

magma supply dynamics at westdahl volcano alaska modeled from satellite radar interferometry 1 a group of satellite radar interferograms that span the time period from 1991 to 2000 shows that westdahl volcano alaska deflated during its 1991 1992 eruption and is reinflating at a rate that could produce another eruption within the next several years the rates of inflation and deflation are approximated by exponential decay functions having time constants of about 6 years and a few days respectively this behavior is consistent with a deep constant pressure magma source connected to a shallow reservoir by a magma filled conduit an elastic deformation model indicates that the reservoir is located about 6 km below sea level and beneath westdahl peak we propose that the magma flow rate through the conduit is governed by the pressure gradient between the deep source and the reservoir the pressure gradient and hence the flow rate are greatest immediately after eruptions pressurization of the reservoir decreases both the pressure gradient and the flow rate but eventually the reservoir ruptures and an eruption or intrusion ensues the eruption rate is controlled partly by the pressure gradient between the reservoir and surface and therefore it too decreases with time when the supply of eruptible magma is exhausted the eruption stops the reservoir begins to repressurize at a high rate and the cycle repeats this model might also be appropriate for other frequently active volcanoes with stable magma sources and relatively simple magma storage systems

magma intrusion and effusion at sinabung volcano indonesia from 2013 to 2016 as revealed by continuous gps observation abstract we analyzed continuous global positioning system gps data from sinabung to capture and model the migration of magma from the pre eruptive and syn eruptive time period between june 2013 and january 2016 we divided this time into four periods of significant deformation two extensional stages followed by two contractional stages using a grid search method we determined the location and volume change of a mogi source for each deformation stage cumulative volume changes during the contraction periods were approximated by an exponentially decaying function with time period 1 began in june 2013 with slight extension for which an inflation source was modeled at a depth of 3 8 km below sea level bsl and a volume change of 0 3 1 8 mm3 seismicity in period 1 was marked by a notable increase in deep high frequency volcano tectonic earthquakes vts beginning in july 2013 and shallow vts in september 2013 period 2 began in late october 2013 with accelerated extension with at least 1 cm extension in the baseline length during period 2 the modeled inflation source ascended to a shallower depth of 0 9 0 4 2 1 km below sea level bsl beneath sinabung with a change in volume of 0 39 0 18 0 60 mm3 and with accelerated rates of volume increase during the time period when the magma migrated to the surface seismicity during period 2 was marked first by an increase in the incidence of shallow volcano tectonic vt earthquakes and later by repetitive self similar hybrid events as the magma migrated to the surface period 3 began in january 2014 after the appearance of the lava dome and was marked by rapid steady contraction of 3 cm through march 2014 the modeled source located at 8 4 7 4 9 9 km bsl beneath the eastern flank of sinabung with a volume change of 20 51 26 89 to 14 12 mm3 period 4 began in april 2014 with decelerating contraction and the modeled deformation center shifted to the northeast reaching a depth of 12 2 10 1 14 8 km bsl between sinabung and sibayak volcanoes and a change in volume of 88 26 123 87 to 52 66 mm3 approximately 2 3 of the total volume change related to contraction occurred between january 2014 and may 2016 and the current activity of sinabung is expected to decrease gradually and almost terminate in the early 2020s assuming no new intrusion or deformation rate changes both of the eruptions at sinabung in 2010 and unzen in 1991 1995 show characteristics of ground inflation and subsequent deflation indicating magma migration and effusion processes similar to the current sinabung activity the inflation before the 2010 sinabung eruptions likely started before 2007 and is an indication of magma intrusion before the 2010 and 2013 eruptions

tracking magma volume recovery at okmok volcano using gps and an unscented kalman filter 1 changes beneath a volcano can be observed through position changes in a gps network but distinguishing the source of site motion is not always straightforward the records of continuous gps sites provide a favorable data set for tracking magma migration dense campaign observations usually provide a better spatial picture of the overall deformation field at the expense of an episodic temporal record combining these observations provides the best of both worlds a kalman filter provides a means for integrating discrete and continuous measurements and for interpreting subtle signals the unscented kalman filter ukf is a nonlinear method for time dependent observations we demonstrate the application of this technique to deformation data by applying it to gps data collected at okmok volcano seven years of gps observations at okmok are analyzed using a mogi source model and the ukf the deformation source at okmok is relatively stable at 2 5 km depth below sea level located beneath the center of the caldera which means the surface deformation is caused by changes in the strength of the source during the 7 years of gps observations more than 0 5 m of uplift has occurred a majority of that during the time period january 2003 to july 2004 the total volume recovery at okmok since the last eruption in 1997 is 60 80 the ukf allows us to solve simultaneously for the time dependence of the source strength and for the location without a priori information about the source

the postseismic response to the 2002 m 7 9 denali fault earthquake constraints from insar 2003 2005 summary insar is particularly sensitive to vertical displacements which can be important in distinguishing between mechanisms responsible for the postseismic response to large earthquakes afterslip viscoelastic relaxation we produce maps of the surface displacements resulting from the postseismic response to the 2002 denali fault earthquake using data from the canadian radarsat 1 satellite from the periods summer 2003 summer 2004 and summer 2005 a peak to trough signal of amplitude 4 cm in the satellite line of sight was observed between summer 2003 and summer 2004 by the period between summer 2004 and summer 2005 the displacement rate had dropped below the threshold required for observation with insar over a single year the insar observations show that the principal postseismic relaxation process acted at a depth of 50 km equivalent to the top of the mantle however the observations are still incapable of distinguishing between distributed viscoelastic relaxation and localized afterslip deformation the imposed coseismic stresses are highest in the lower crust and assuming a maxwell rheology a viscosity ratio of at least 5 between lower crust and upper mantle is required to explain the contrast in behaviour the lowest misfits are produced by mixed models of viscoelastic relaxation in the mantle and shallow afterslip in the upper crust profiles perpendicular to the fault show significant asymmetry which is consistent with differences in rheological structure across the fault

oscillatory nature of the okmok volcano s deformation abstract the time dependent deformation of volcanic edifices can help one understand the dynamics of pre eruptive overpressure build up in magma chambers thus geodetic time series recorded at the okmok volcano in alaska show a pattern of fast and short inflations referred to as pulses followed by either slower and longer deflations or time intervals with no deformation this pattern is superimposed onto a longer period inflation a rapid inflation occurred just before the 2008 eruption which suggests that the underlying process may lead to eruptions it is crucial to understand whether such a behavior is driven by external forcing such as melt supply variations or whether it can develop spontaneously within the volcano s plumbing system here we model the observed oscillations 2004 2008 as resulting from the hydraulic interaction between two shallow magma chambers fed by a deeper source region a geometry that is consistent with geochemical petrological and geophysical data the model shows that episodes of periodic fast inflations occur i when a viscosity gradient is present in the vertical pipe for instance as the result of a temperature gradient and ii when the flux supplying the shallower chamber lies between two bounds that we derive analytically the deformation pulses observed at okmok can therewith be fully explained by the internal variability of the magmatic system and do not require time variable external forcing the proposed model can also be seen as an improvement upon the classic hydraulic models regularly used to explain a commonly observed pattern of volcanic deformations i e exponential inflation

rapid changes in magma storage beneath the klyuchevskoy group of volcanoes inferred from time dependent seismic tomography abstract we present the results of time dependent local earthquake tomography for the kluchevskoy group of volcanoes in kamchatka russia we consider the time period from 1999 to 2009 which covers several stages of activity of kluchevskoy and bezymianny volcanoes the results are supported by synthetic tests that recover a common 3d model based on data corresponding to different time windows throughout the period we observe a robust feature below 25 km depth with anomalously high v p v s values up to 2 2 we interpret this feature as a channel bringing deep mantle materials with high fluid and melt content to the bottom of the crust this mantle channel directly or indirectly determines the activity of all volcanoes of the kluchevskoy group in the crust we model complex structure that varies over time during the pre eruptive period we detected two levels of potential magma storage one in the middle crust at 10 12 km depth and one close to the surface just below kluchevskoy volcano in 2005 a year of powerful eruptions of kluchevskoy and besymiyanny volcanoes we observe a general increase in v p v s throughout the crust in the relaxation period following the eruption the v p v s values are generally low and no strong anomalous zones in the crust are observed we propose that very rapid variations in v p v s are most likely due to abrupt changes in the stress and deformation states which cause fracturing and the active transport of fluids these fluids drive more fracturing in a positive feedback system that ultimately leads to eruption we envision the magma reservoirs beneath the kluchevskoy group as sponge structured volumes that may quickly change the content of the molten phases as fluids pulse rapidly through the system

deformation associated with the 1997 eruption of okmok volcano alaska 1 okmok volcano located on umnak island in the aleutian chain alaska is the most eruptive caldera system in north america in historic time its most recent eruption occurred in 1997 synthetic aperture radar interferometry shows deflation of the caldera center of up to 140 cm during this time preceded and followed by inflation of smaller magnitude the main part of the observed deformation can be modeled using a pressure point source model the inferred source is located between 2 5 and 5 0 km beneath the approximate center of the caldera and 5 km from the eruptive vent we interpret it as a central magma reservoir the preeruptive period features inflation accompanied by shallow localized subsidence between the caldera center and the vent we hypothesize that this is caused by hydrothermal activity or that magma moved away from the central chamber and toward the later vent since all historic eruptions at okmok have originated from the same cone this feature may be a precursor that indicates an upcoming eruption the erupted magma volume is 9 times the volume that can be accounted for by the observed preeruptive inflation this indicates a much longer inflation interval than we were able to observe the observation that reinflation started shortly after the eruption suggests that inflation spans the whole time interval between eruptions extrapolation of the average subsurface volume change rate is in good agreement with the long term eruption frequency and eruption volumes of okmok

simulation of the supersar multi azimuth synthetic aperture radar imaging system for precise measurement of three dimensional earth surface displacement the supersar imaging system a novel multi azimuth synthetic aperture radar sar system capable of detecting earth surface deformation in three dimensions from a single satellite platform has recently been proposed in this paper we investigate the feasibility of detecting precise 3 d surface displacement measurements with the supersar imaging system using a point target simulation from this simulation we establish both a relationship between the interferometric sar phase and the across track displacement and a relationship between the multiple aperture interferometry phase and the along track displacement based on the supersar imaging geometry the theoretical uncertainties of the supersar measurement are analyzed in the across and along track directions and the theoretical accuracy of the 3 d displacement measurement from the supersar system is also investigated according to both the decorrelation and the squint and look angles in the case that the interferometric coherence is about 0 8 and that five effective looks are employed the theoretical 2 d measurement precision values are about 3 67 and 6 35 mm in the across and along track directions respectively and the theoretical 3 d measurement precision values for 3 d displacement are about 4 05 4 56 and 3 45 mm in the east north and up directions respectively the result of this study demonstrates that the supersar imaging system is capable of measuring the 3 d surface displacement in all directions with subcentimeter precision

multidimensional time series analysis of ground deformation from multiple insar data sets applied to virunga volcanic province summary a novel multidimensional small baseline subset msbas methodology is presented for integration of multiple interferometric synthetic aperture radar insar data sets for computation of 2 or 3 d time series of deformation the proposed approach allows the combination of all possible air borne and space borne sar data acquired with different acquisition parameters temporal and spatial sampling and resolution wave band and polarization the produced time series have improved temporal resolution and can be enhanced by applying either regularization or temporal filtering to remove high frequency noise we apply this methodology to map 2003 2010 ground deformation of the virunga volcanic province vvp north kivu democratic republic of congo the horizontal and vertical time series of ground displacement clearly identify lava compaction areas long term deformation of mt nyamuragira and 2004 2006 and 2010 pre and coeruptive deformation providing that enough sar data is available the method opens new opportunities for detecting ground motion in the vvp and elsewhere

post emplacement cooling and contraction of lava flows insar observations and a thermal model for lava fields at hekla volcano iceland lava flows contract as they cool causing progressive subsidence of the flow surface here we study this process by measuring and modelling the deformation of emplaced lava flows and the surrounding substrate the temporal trend of vertical lava movements was investigated using interferometric analysis of synthetic aperture radar insar images from the 1991 and 2000 hekla eruptions covering periods of 23 and 12 years respectively data from six tracks from three satellites including both ascending and descending passes were used to create 99 interferograms from which trends of accumulated subsidence and subsidence velocities were derived subsidence rates are similar for both lava flows and decay approximately exponentially from about 20 mm year five years after emplacement to about 2 mm year 15 years after emplacement a one dimensional semi analytical model was fitted to the observed subsidence rates with subsidence due to phase change calculated analytically and subsidence due to thermal contraction calculated numerically using dilatometic constraints obtained experimentally the initial thicknesses of the 1991 and 2000 lava fields d1991 and d2000 scaled thermal expansivity and thermal diffusivity are the crucial parameters influencing lava subsidence and subsidence rate inversion for these parameters reveal linear correlations between them best fitting results of inversions for d1991 range from 10 m to 27 m for d2000 from 10 m to 30 m 9 24 10 6k 1 and 1 7 10 7m2s 1

mapping ground surface deformation using temporarily coherent point sar interferometry application to los angeles basin abstract multi temporal interferometric synthetic aperture radar insar is an effective tool to detect long term seismotectonic motions by reducing the atmospheric artifacts thereby providing more precise deformation signal the commonly used approaches such as persistent scatterer insar psinsar and small baseline subset sbas algorithms need to resolve the phase ambiguities in interferogram stacks either by searching a predefined solution space or by sparse phase unwrapping methods however the efficiency and the success of phase unwrapping cannot be guaranteed we present here an alternative approach temporarily coherent point tcp insar tcpinsar to estimate the long term deformation rate without the need of phase unwrapping the proposed approach has a series of innovations including tcp identification tcp network and tcp least squares estimator we apply the proposed method to the los angeles basin in southern california where structurally active faults are believed capable of generating damaging earthquakes the analysis is based on 55 interferograms from 32 ers 1 2 images acquired during oct 1995 and dec 2000 to evaluate the performance of tcpinsar on a small set of observations a test with half of interferometric pairs is also performed the retrieved tcpinsar measurements have been validated by a comparison with gps observations from southern california integrated gps network our result presents a similar deformation pattern as shown in past insar studies but with a smaller average standard deviation 4 6 mm compared with gps observations indicating that tcpinsar is a promising alternative for efficiently mapping ground deformation even from a relatively smaller set of interferograms

post eruptive deformation associated with the 1986 87 and 1989 lava flows of etna detected by radar interferometry we analysed 92 interferograms produced using ers1 sar images taken on etna between may 1992 and october 1993 nineteen show a local subsidence in the eastern flank of the volcano correlated with the location of the 30 october 1986 1 march 1987 and 27 september 9 october 1989 lava flows using fringe unwrapping and data gridding techniques and assuming that over the sampled time window deformation was a linear function of time we derive a map of along range rate of motion the correlation between the deformation field and the area covered by recent lavas suggests that compaction of the lava flows continues several years after the eruptions the area of maximum subsidence 47 mm yr is localised at the narrowing of the 1989 flow between 1500 and 1700 m a s l we observe that subsidence extends outside the lava flows accounting for at least 12 mm yr assuming a relaxation process of the substrate in response to loading produced by recent lavas a simple 1d maxwell visco elastic model predicts a maximum subsidence rate of 25 mm yr and a relaxation time of about 3 5 years the relaxation time agrees with those derived from post eruptive displacements observed by levelling on etna and piton de la fournaise after several eruptions we conclude that at the time of our measurements 25 to 50 of the deformation was related to relaxation of the substrate and the other part due to compaction of the lava flows

anisotropy repeating earthquakes and seismicity associated with the 2008 eruption of okmok volcano alaska 1 we use shear wave splitting sws analysis and double difference relocation to examine temporal variations in seismic properties prior to and accompanying magmatic activity associated with the 2008 eruption of okmok volcano alaska using bispectrum cross correlation a multiplet of 25 earthquakes is identified spanning five years leading up to the eruption each event having first motions compatible with a normal fault striking ne sw cross correlation differential times are used to relocate earthquakes occurring between january 2003 and february 2009 the bulk of the seismicity prior to the onset of the eruption on 12 july 2008 occurred southwest of the caldera beneath a geothermal field earthquakes associated with the onset of the eruption occurred beneath the northern portion of the caldera and started as deep as 13 km subsequent earthquakes occurred predominantly at 3 km depth coinciding with the depth at which the magma body has been modeled using geodetic data automated sws analysis of the okmok catalog reveals radial polarization outside the caldera and a northwest southeast polarization within we interpret these polarizations in terms of a magma reservoir near the center of the caldera which we model with a mogi point source sws analysis using the same input processing parameters for each event in the multiplet reveals no temporal changes in anisotropy over the duration of the multiplet suggesting either a short term or small increase in stress just before the eruption that was not detected by gps or eruption triggering by a mechanism other than a change of stress in the system

the effects of topography on magma chamber deformation models application to mt etna and radar interferometry we have used a three dimensional elastic finite element model to examine the effects of topography on the surface deformation predicted by models of magma chamber deflation we used the topography of mt etna to control the geometry of our model and compared the finite element results to those predicted by an analytical solution for a pressurized sphere in an elastic half space topography has a significant effect on the predicted surface deformation for both displacement profiles and synthetic interferograms not only are the predicted displacement magnitudes significantly different but also the map view patterns of displacement it is possible to match the predicted displacement magnitudes fairly well by adjusting the elevation of a reference surface however the horizontal pattern of deformation is still significantly different thus inversions based on constant elevation reference surfaces may not properly estimate the horizontal position of a magma chamber we have investigated an approach where the elevation of the reference surface varies for each computation point corresponding to topography for vertical displacements and tilts this method provides a good fit to the finite element results and thus may form the basis for an inversion scheme for radial displacements a constant reference elevation provides a better fit to the numerical results

thermal deformation and degassing remote sensing time series ce 2000 2017 at the 47 most active volcanoes in latin america implications for volcanic systems

dome growth at mount cleveland aleutian arc quantified by time series terrasar x imagery synthetic aperture radar imagery is widely used to study surface deformation induced by volcanic activity however it is rarely applied to quantify the evolution of lava domes which is important for understanding hazards and magmatic system characteristics we studied dome formation associated with eruptive activity at mount cleveland aleutian volcanic arc in 2011 2012 using terrasar x imagery interferometry and offset tracking show no consistent deformation and only motion of the crater rim suggesting that ascending magma may pass through a preexisting conduit system without causing appreciable surface deformation amplitude imagery has proven useful for quantifying rates of vertical and areal growth of the lava dome within the crater from formation to removal by explosive activity to rebirth we expect that this approach can be applied at other volcanoes that host growing lava domes and where hazards are highly dependent on dome geometry and growth rates

slope failures on the flanks of the western canary islands abstract landslides have been a key process in the evolution of the western canary islands the younger and more volcanically active canary islands el hierro la palma and tenerife show the clearest evidence of recent landslide activity the evidence includes landslide scars on the island flanks debris deposits on the lower island slopes and volcaniclastic turbidites on the floor of the adjacent ocean basins at least 14 large landslides have occurred on the flanks of the el hierro la palma and tenerife the majority of these in the last 1 million years with the youngest on the northwest flank of el hierro as recent as 15 thousand years in age older landslides undoubtedly occurred but are difficult to quantify because the evidence is buried beneath younger volcanic rocks and sediments landslides on the canary island flanks can be categorised as debris avalanches slumps or debris flows debris avalanches are long runout catastrophic failures which typically affect only the superficial part of the island volcanic sequence up to a maximum thickness of 1 to 2 km they are the commonest type of landslide mapped in contrast slumps move short distances and are deep rooted landslides which may affect the entire thickness of the volcanic edifice debris flows are defined as landslides which primarily affect the sedimentary cover of the submarine island flanks some landslides are complex events involving more than one of the above end member processes individual debris avalanches have volumes in the range of 50 500 km3 cover several thousand km2 of seafloor and have runout distances of up to 130 km from source overall debris avalanche deposits account for about 10 of the total volcanic edifices of the small relatively young islands of el hierro and la palma some parameters such as deposit volumes and landslide ages are difficult to quantify the key characteristics of debris avalanches include a relatively narrow headwall and chute above 3000 m water depth on the island flanks broadening into a depositional lobe below 3000 m debris avalanche deposits have a typically blocky morphology with individual blocks up to a kilometre or more in diameter however considerable variation exists between different avalanche deposits at one extreme the el golfo debris avalanche on el hierro has few large blocks scattered randomly across the avalanche surface at the other icod on the north flank of tenerife has much more numerous but smaller blocks over most of its surface with a few very large blocks confined to the margins of the deposit icod also exhibits flow structures longitudinal shears and pressure ridges that are absent in el golfo the primary controls on the block structure and distribution are inferred to be related to the nature of the landslide material and to flow processes observations in experimental debris flows show that the differences between the el golfo and icod landslide deposits are probably controlled by the greater proportion of fine grained material in the icod landslide this in turn relates to the nature of the failed volcanic rocks which are almost entirely basalt on el hierro but include a much greater proportion of pyroclastic deposits on tenerife landslide occurrence appears to be primarily controlled by the locations of volcanic rift zones on the islands with landslides propagating perpendicular to the rift orientation however this does not explain the uneven distribution of landslides on some islands which seems to indicate that unstable flanks are a weakness that can be carried forward during island development this may occur because certain island flanks are steeper extend to greater water depths or are less buttressed by the surrounding topography and because volcanic production following a landslide my be concentrated in the landslide scar thus focussing subsequent landslide potential in this area landslides are primarily a result of volcanic construction to a point where the mass of volcanic products fails under its own weight although the actual triggering factors are poorly understood they may include or be influenced by dyke intrusion pore pressure changes related to intrusion seismicity or sealevel climate changes a possible relationship between caldera collapse and landsliding on tenerife is not in our interpretation supported by the available evidence

measurement of three dimensional surface deformation by cosmo skymed x band radar interferometry application to the march 2011 kamoamoa fissure eruption kīlauea volcano hawai i abstract three dimensional 3d surface deformation is retrieved for the march 6 10 2011 utc dates kamoamoa fissure eruption along the east rift zone of k lauea volcano hawai i through the integration of multi temporal synthetic aperture radar sar interferometry insar and multiple aperture interferometry mai measurements from the cosmo skymed x band sar the measurement accuracies of 1 the individual and multi stacked mai interferograms and 2 the 3d deformation which is measured from cosmo skymed data are assessed using continuous gps stations the root mean square rms errors of individual mai interferograms for descending and ascending data are 2 97 0 6 cm and 3 20 0 62 cm respectively the mai interferograms stacked from multi temporal observations can produce better results by emphasizing surface deformation signals with the rms errors of 1 06 and 1 24 cm for descending and ascending data respectively the empirical equations for measurement uncertainties are determined with respect to interferometric coherence for individual and stacked mai interferograms an assessment of the 3d components of deformation was performed as well and rms errors of 0 75 0 83 and 0 68 cm were estimated in the east north and up directions a performance test of magma source model parameter estimations was carried out by using the insar and 3d measurements from the 3d deformation field we found that the magma chamber source at the k lauea caldera should be modeled by the spheroid source rather than the simple point source the performance comparison between the insar and 3d modeled results showed that the 3d deformation field allows for precise model parameter estimation

evaluating links between deformation topography and surface temperature at volcanic domes results from a multi sensor study at volcan de colima mexico abstract dome building activity is common at many volcanoes and due to the gravitational instability a dome represents one of the most hazardous volcanic phenomena shallow volcanic processes as well as rheological and structural changes of the dome affecting the fluid transport have been linked to transitions in eruptive activity also hydrothermal alteration may affect the structural integrity of the dome increasing the potential for collapse however mapping the deformation and details of fluid escape at the summit of steep sloped volcanoes and integrating these with other types of data is challenging due to difficult access and poor coverage here we present for the first time the near vertical and near horizontal surface deformation field of a quiescent summit dome and the relationships with degassing and topographic patterns our results are derived from high resolution satellite radar interferometry insar time series based on a year of terrasar x spotlight acquisitions and structure from motion sfm processing of overflight infrared data at volcan de colima mexico the identified deformation is dominated by localized heterogeneous subsidence of the summit dome exceeding rates of 15 cm yr and strongly decreasing over the year 2012 up to the renewal of explosive and extrusive activity in early 2013 we tentatively attribute the deformation to the degassing cooling and contraction of the dome and shallow conduit material we also find that the results strongly differ depending on the chosen insar time series method which potentially overprints the true physical complexities of small scale shallow deformation processes the combined interpretation of the deformation and infrared data reveals a complex spatial relationship between the degassing pathways and the deformation while we observe no deformation across the crater rim fumaroles discontinuities in the deformation field are more commonly observed around the dome rim fumaroles and occasionally on the dome upper surface we propose that the deformation pattern is also linked to processes controlling the fumarole formation and distribution topography permeability and volcanic activity and the lack of direct relationships may be explained by how the influence of these processes varies across the volcanic summit the presented work provides a new approach for safely monitoring the activity and stability of internal dome structures as well as for constraining and validating models of dome degassing pathways and densification processes

the 1997 eruption of okmok volcano alaska a synthesis of remotely sensed imagery abstract okmok volcano in the eastern aleutian islands erupted in february and march of 1997 producing a 6 km long lava flow and low level ash plumes this caldera is one of the most active in the aleutian arc and is now the focus of international multidisciplinary studies a synthesis of remotely sensed data airsar derived dems landsat mss and etm data avhrr ers jers radarsat has given a sequence of events for the virtually unobserved 1997 eruption elevation data from the airsar sensor acquired in october 2000 over okmok were used to create a 5 m resolution dem mosaic of okmok volcano avhrr nighttime imagery has been analyzed between february 13 and april 11 1997 landsat imagery and sar data recorded prior to and after the eruption allowed us to accurately determine the extent of the new flow the flow was first observed on february 13 without precursory thermal anomalies at this time the flow was a large single lobe flowing north according to avhrr band 3 and 4 radiance data and ground observations the first lobe continued growing until mid to late march while a second smaller lobe began to form sometime between march 11 and 12 this is based on a jump in the thermal and volumetric flux determined from the imagery and the physical size of the thermal anomalies total radiance values waned after march 26 indicating lava effusion had ended and a cooling crust was growing the total area 8 9 km 2 thickness up to 50 m and volume 1 54 10 8 m 3 of the new lava flow were determined by combining observations from sar landsat etm and airsar dem data while the first lobe of the flow ponded in a pre eruption depression our data suggest the second lobe was volume limited remote sensing has become an integral part of the alaska volcano observatory s monitoring and hazard mitigation efforts studies like this allow access to remote volcanoes and provide methods to monitor potentially dangerous ones

source model for the mw 6 7 23 october 2002 nenana mountain earthquake alaska from insar 1 the 23 october 2002 nenana mountain earthquake mw 6 7 occurred on the denali fault alaska to the west of the mw 7 9 denali earthquake that ruptured the same fault 11 days later we used 6 interferograms constructed using radar images from the canadian radarsat 1 and european ers 2 satellites to determine the coseismic surface deformation and a source model data were acquired on ascending and descending satellite passes with incidence angles between 23 and 45 degrees and time intervals of 72 days or less modeling the event as dislocations in an elastic half space suggests that there was nearly 0 9 m of right lateral strike slip motion at depth on a near vertical fault and that the maximum slip in the top 4 km of crust was less than 0 2 m the nenana mountain earthquake increased the coulomb stress at the future hypocenter of the 3 november 2002 denali earthquake by 30 60 kpa

precursory inflation of shallow magma reservoirs at west sunda volcanoes detected by insar 1 we use 2006 2009 alos interferometric synthetic aperture radar data over the entire west sunda arc indonesia home of 13 of the world s active volcanoes to derive arc wide time dependent ground deformation data we present unambiguous evidence of inflation at six volcanoes three of which erupted after the observation period we show that these volcanoes have shallow magma reservoirs at 1 3 km depth below the average regional elevation a global comparison of reservoir depths at arc volcanoes suggests that volcanoes in extensional and strike slip settings west sunda can develop shallow reservoirs whereas volcanoes in compressional settings may lack them thus magma ascend through the upper crust could be influenced by intra arc tectonic settings

later stages of volcanic evolution of la palma canary islands rift evolution giant landslides and the genesis of the caldera de taburiente the islands of la palma and el hierro form the western end of the hotspot induced canary islands chain both islands are at present in the earliest and fastest shield building stage of growth and show many similarities with the hawaiian islands la palma shows two very distinct phases of volcanic construction 1 a pliocene submarine volcanic and intrusive series interpreted as an uplifted seamount at least 1500 m above present sea level and 2 a subaerial volcanic series erupted in the past 2 m y taburiente volcano initially formed the northern part of the island and then extended to the south forming a ridge cumbre nueva ridge that was partially destroyed about 560 ka by a giant lateral collapse the cumbre nueva collapse possibly involving 180 200 km 3 of subaerial volcanic material the northwest boundary of the cumbre nueva collapse formed a vertical scarp that enlarged by headward erosion formed the spectacular depression of caldera de taburiente cumbre vieja volcano a north south elongated rift forms the southern half of la palma and constitutes its last stage of growth including all eruptive activity in the past 125 k y detailed field observations mapping and high precision radiometric dating have allowed reconstruction of the growth and structural changes of the cumbre vieja volcano interactions between eruption rates coastal erosion and glacio eustatic sea level change allow stratigraphic subdivision of the edifice the structure of the volcano has been controlled for most of its history by a rift system with a clearly dominant north south and less distinct north east and north west volcanic rift zones the rift reorganization of the volcano to a single north south rift since 7 ka and the opening of faults during the 1949 eruption probably reflect increasing instability of the west flank of the volcano

interferometric synthetic aperture radar study of okmok volcano alaska 1992 2003 magma supply dynamics and postemplacement lava flow deformation 1 okmok volcano located in the central aleutian arc alaska is a dominantly basaltic complex topped with a 10 km wide caldera that formed circa 2 05 ka okmok erupted several times during the 20th century most recently in 1997 eruptions in 1945 1958 and 1997 produced lava flows within the caldera we used 80 interferometric synthetic aperture radar insar images interferograms to study transient deformation of the volcano before during and after the 1997 eruption point source models suggest that a magma reservoir at a depth of 3 2 km below sea level located beneath the center of the caldera and about 5 km northeast of the 1997 vent is responsible for observed volcano wide deformation the preeruption uplift rate decreased from about 10 cm yr 1 during 1992 1993 to 2 3 cm yr 1 during 1993 1995 and then to about 1 2 cm yr 1 during 1995 1996 the posteruption inflation rate generally decreased with time during 1997 2001 but increased significantly during 2001 2003 by the summer of 2003 30 60 of the magma volume lost from the reservoir in the 1997 eruption had been replenished interferograms for periods before the 1997 eruption indicate consistent subsidence of the surface of the 1958 lava flows most likely due to thermal contraction interferograms for periods after the eruption suggest at least four distinct deformation processes 1 volcano wide inflation due to replenishment of the shallow magma reservoir 2 subsidence of the 1997 lava flows most likely due to thermal contraction 3 deformation of the 1958 lava flows due to loading by the 1997 flows and 4 continuing subsidence of 1958 lava flows buried beneath 1997 flows our results provide insights into the postemplacement behavior of lava flows and have cautionary implications for the interpretation of inflation patterns at active volcanoes

seismicity and seismic structure at okmok volcano alaska abstract okmok volcano is an active volcanic caldera located on the northeastern portion of umnak island in the aleutian arc with recent eruptions in 1997 and 2008 the okmok area had 900 locatable earthquakes between 2003 and june 2008 and an additional 600 earthquakes from the beginning of the 2008 eruption to mid 2009 providing an adequate dataset for seismic tomography to image the seismic velocity structure of okmok we apply waveform cross correlation using bispectrum verification and double difference tomography to a subset of these earthquakes we also perform p wave attenuation tomography using a spectral decay technique we examine the spatio temporal characteristics of seismicity in the opening sequence of the 2008 eruption to investigate the path of magma migration during the establishment of a new eruptive vent we also incorporate the new earthquake relocations and three dimensional 3d velocity model with first motion polarities to compute focal mechanisms for selected events in the 2008 pre eruptive and eruptive periods through these techniques we obtain precise relocations a well constrained 3d p wave velocity model and a marginally resolved s wave velocity model we image a main low vp and vs anomaly directly under the caldera consisting of a shallow zone at 0 2 km depth connected to a larger deeper zone that extends to about 6 km depth we find that areas of low qp are concentrated in the central to southwestern portion of the caldera and correspond fairly well with areas of low vp we interpret the deeper part of the low velocity anomaly 4 6 km depth beneath the caldera as a magma body this is consistent with results from ambient noise tomography and suggests that previous estimates of depth to okmok s magma chamber based only on geodetic data may be too shallow the distribution of events preceding the 2008 eruption suggest that a combination of overpressure in the zone surrounding the magma chamber and the introduction of new material from below were jointly responsible for the explosive eruption magma escaping from the top of the main magma chamber likely reacted with both a smaller shallow pod of magma and groundwater on its way up below the cone d area the earthquakes in the 2008 pre eruptive and eruptive periods are found to have a mixture of strike slip oblique normal and oblique thrust mechanisms with a dominant p axis orientation that is nearly perpendicular to the regional tectonic stress this may indicate that the stresses related to magmatic activity locally dominated regional tectonic forces during this time period

nonlinear estimation of geometric parameters in fems of volcano deformation integrating tomography models and geodetic data for okmok volcano alaska 1 the internal structure loading processes and effective boundary conditions of a volcano control the deformation observed at the earth s surface using finite element models fems we simulate the response due to a pressurized magma chamber embedded in a domain having a distribution of elastic material properties we present the pinned mesh perturbation method pmp to automate the mesh generation process in response to perturbations of the position of a simulated magma chamber within an fem domain using insar observed deformation for the 1997 eruption of okmok volcano alaska as an example we combine pmp with nested monte carlo methods to estimate a set of linear and nonlinear parameters that characterize the depressurization and location of the magma chamber beneath okmok s caldera the three dimensional fems used in the pmp method simulate the distribution of material properties of tomography models and account for the irregular geometry of the topography and bathymetry the estimated depth of an assumed spherical magma chamber is 3527 54 55 m below sea level and is sensitive to the distribution of material properties this depth is consistent with lithostatic pressure constraints and very long period tremor observations the fit of this fem to the insar data is a significant improvement at the 95 confidence level compared to the fit of a corresponding fem having homogeneous material properties the methods presented here allow us to construct deformation models that integrate tomography models with geodetic observations in an effort to achieve a deeper understanding of active volcanoes

recurrent large scale landsliding on the west flank of la palma canary islands a large area of debris avalanche deposits has been discovered on the western submarine flanks of the island of la palma multibeam bathymetry and its derivative backscatter data towed ocean bottom instrument tobi sidescan sonar images and 3 5 khz and airgun seismic reflection data have been used to identify at least two and possibly as many as four major landslide events the youngest of the events the cumbre nueva debris avalanche extends onshore into the valleys bounded by the caldera de taburiente and cumbre nueva ridge which mark the degraded collapse scars radiometric dating of the volcanic flows in the headwall indicate an age of between 536 and 125 ka for this landslide the debris avalanche covers an area of 780 km2 has a maximum thickness of 500 m and has an estimated volume of 95 km3 older deposits collectively referred to as the playa de la veta debris avalanche complex are probably as the name indicates an amalgamation of at least two or three events rather than the result of a single catastrophic failure the playa de la veta debris avalanche complex is associated onshore with an unconformity dated as late matuyama 1 ma to 800 ka it covers an area of 1200 km2 has a maximum thickness of 1300 m and may represent a total volume of up to 650 km3 the greater thicknesses and limited areas occupied by debris avalanches on the western flank of la palma compared to other landslides in the canary archipelago suggest that the la palma landslide masses have relatively low mobility the different debris avalanche lobes formed by each landslide event are separated by channels 2 2 5 km wide the clear relationship between channel position and the boundaries of each debris avalanche lobe indicates that debris avalanches control later channel formation and pathways the relief of the submarine flanks of the la palma volcanoes in the areas of island slope unaffected by landslides is mainly the result of constructional volcanic processes however the older submarine slopes such as in the northern taburiente volcano may also have been modified by smaller scale submarine mass wasting and sediment flows

a two magma chamber model as a source of deformation at grimsvotn volcano iceland grimsvotn volcano is the most active volcano in iceland and its last three eruptions were in 1998 2004 and 2011 here we analyze the displacement around grimsvotn during these last three eruptive cycles using 10 gps stations the observed displacements in this region generally contain a linear component of tectonic and glacio isostatic origin in agreement with the previously estimated values of plate motions and vertical rebound larger amplitude deformation observed close to grimsvotn at the gfum continuous gps station clearly reflects a major volcanic contribution superimposed on a tectonic component we estimate and subtract the tectonic trend at this station using regional observed displacement the direction and pattern of the residual volcanic displacement for coeruptive and intereruptive periods are consistent for all three of these eruptive cycles the posteruptive inflation is characterized by an exponential trend followed by a linear trend in this study we explain this temporal behavior using a new analytic model that has two connected magma chambers surrounded by an elastic medium and fed by a constant basal magma inflow during the early posteruptive phase pressure readjustment occurs between the two reservoirs with replenishment of the shallow chamber from the deep chamber afterward due to the constant inflow of magma into the deep reservoir the pressurization of the system produces linear uplift a large deep reservoir favors magma storage rather than surface emission based on displacement measured at gfum station we estimate an upper limit for the radius of the deep reservoir of 10 km

ground surface deformation patterns magma supply and magma storage at okmok volcano alaska from insar analysis 2 coeruptive deflation july august 2008 1 a hydrovolcanic eruption near cone d on the floor of okmok caldera alaska began on 12 july 2008 and continued until late august 2008 the eruption was preceded by inflation of a magma reservoir located beneath the center of the caldera and 3 km below sea level bsl which began immediately after okmok s previous eruption in 1997 in this paper we use data from several radar satellites and advanced interferometric synthetic aperture radar insar techniques to produce a suite of 2008 coeruption deformation maps most of the surface deformation that occurred during the eruption is explained by deflation of a mogi type source located beneath the center of the caldera and 2 3 km bsl i e essentially the same source that inflated prior to the eruption during the eruption the reservoir deflated at a rate that decreased exponentially with time with a 1 e time constant of 13 days we envision a sponge like network of interconnected fractures and melt bodies that in aggregate constitute a complex magma storage zone beneath okmok caldera the rate at which the reservoir deflates during an eruption may be controlled by the diminishing pressure difference between the reservoir and surface a similar mechanism might explain the tendency for reservoir inflation to slow as an eruption approaches until the pressure difference between a deep magma production zone and the reservoir is great enough to drive an intrusion or eruption along the caldera ring fracture system

statistical tests for closure of plate motion circuits the standard method of testing whether data describing the relative motion of three plates meeting at a triple junction are consistent with rigid plate tectonics uses the condition of plate circuit closure the euler vectors or angular velocities describing the relative motion of each plate pair must sum to zero deviations from closure suggest that the data are systematically in error or that the plate boundaries have been identified incorrectly or that the plates are non rigid we examine two methods one based on a chi square test and the other based on an f ratio test of testing whether plate motion circuits close we find the latter test is useful but the former is of limited value because of the common practice of systematically overestimating errors in plate motion data we apply the f ratio test to minster and jordan s data for the boundaries dividing the pacific cocos and nazca plates which prove consistent with plate circuit closure application of the test to their data for the boundaries dividing the australian antarctic and african plates shows nonclosure even after deletion of data from the carlsberg ridge which recently has been suggested to divide the african plate from an indo arabian plate this nonclosure suggests systematic errors in the data or internal deformation of one or more of the plates meeting at the indian ocean triple junction

some thoughts on the use of insar data to constrain models of surface deformation noise structure and data downsampling repeat pass interferometric synthetic aperture radar insar provides spatially dense maps of surface deformation with potentially tens of millions of data points here we estimate the actual covariance structure of noise in insar data we compare the results for several independent interferograms with a large ensemble of gps observations of tropospheric delay and discuss how the common approaches used during processing of insar data affects the inferred covariance structure motivated by computational concerns associated with numerical modeling of deformation sources we then combine the data covariance information with the inherent resolution of an assumed source model to develop an efficient algorithm for spatially variable data resampling or averaging we illustrate these technical developments with two earthquake scenarios at different ends of the earthquake magnitude spectrum for the larger events our goal is to invert for the coseismic fault slip distribution for smaller events we infer the hypocenter location and moment we compare the results of inversions using several different resampling algorithms and we assess the importance of using the full noise covariance matrix

ground surface deformation patterns magma supply and magma storage at okmok volcano alaska from insar analysis 1 intereruption deformation 1997 2008 eruption magma storage had increased by 3 7 5 2 1 0 7 m 3 or 85 100 of the 1997 eruption volume we propose that the supply rate decreased in response to the diminishing pressure gradient between the shallow storage zone and a deeper magma source region eventuallytheeffectsofcontinuingmagmasupplyandvesiculationofstoredmagmacaused acriticalpressurethresholdtobeexceeded triggeringthe2008eruption asimilarpatternof initially rapid inflation followed by oscillatory but generally slowing inflation was observed prior to the 1997 eruption in both cases withdrawal of magma during the eruptions depressurized the shallow storage zone causing significant volcano wide subsidence and initiating a new intereruption deformation cycle

locating magma reservoirs using insar and petrology before and during the 2011 2012 cordon caulle silicic eruption abstract we combine petrological and insar observations to probe the origin of deformation of cordon caulle volcano in southern chile before and during the 2011 2012 eruption the erupted rhyodacite is crystal poor and was stored at about 900 c with ca 4 wt h2o and 220 ppm co2 in the melt corresponding to a storage depth of about 6 7 km in addition to a previously documented 2007 2008 deformation episode we find three pre eruptive deformation episodes the first between 2008 and 2009 that covers 400 km2 with a maximum uplift of 18 5 cm the second between february and march 2010 that covers 20 km2 with a maximum uplift of 10 cm and the third between march and may 2011 that covers 40 km2 with a maximum uplift of 6 cm modeling of the 2008 2009 deformation episode suggests source depths of about 5 9 km consistent with the petrologically determined magma storage depth the sum of modeled source volume changes from 2007 to 2009 is about 12 times smaller than the observed erupted volume our calculation of magma compressibility shows that there must have been a significant volume of pre existing magma in the reservoir to account for this difference co eruptive subsidence shows evidence for three distinct magma sources and pre eruptive inflation is seen at two of the three sources modeled deformation sources are located 2 10 km from the 2011 2012 eruptive vent and coincide with the vents from previous historical eruptions 1921 22 1960 and with the neighboring puyehue volcano this implies the existence of an interconnected magma plumbing system that allows for pressure transfer and which covers an area of at least 20 km2 thus the deformation and geochemical characteristics of cordon caulle resemble those of a large silicic caldera system the presence of a mafic crystal clot demonstrates the existence of basaltic melts in the silicic reservoir but we find that the mafic magmas reached the reservoir at least several hundred years before eruption therefore if the pre eruptive deformation was caused by replenishment to a shallow reservoir the new magma was silicic and similar to the pre existing magma and or there was no interaction between the two we find that pre eruptive deformation can occur in pulses and reach its peak years before eruption and thus lack of deformation does not necessarily imply that eruption is not imminent

rapid reinflation following the 2011 2012 rhyodacite eruption at cordon caulle volcano southern andes imaged by insar evidence for magma reservoir refill cordon caulle is a large fissural volcano that has erupted rhyodacitic magma of the same composition in its past three historical eruptions in 1921 1960 and 2011 2012 there was significant ground deformation observed before and during the 2011 2012 eruption here we use c and x band insar time series results to document post eruptive uplift up to 0 8 m between march 2012 and may 2015 with los rates up to 45 cm yr that have been largely aseismic along with subsidence in the 2011 2012 lava flow the 2012 uplift rate is one of the largest for silicic systems and was likely produced by the intrusion of 0 125 km3 of magma in the same tectonically controlled plumbing system that has been active during the historical eruptions nevertheless the uplift ended before the reservoir refilled with the erupted volume maybe due to a change in the pressure gradient produced by the 2011 2012 eruption

mechanism of the 1996 97 non eruptive volcano tectonic earthquake swarm at iliamna volcano alaska a significant number of volcano tectonic vt earthquake swarms some of which are accompanied by ground deformation and or volcanic gas emissions do not culminate in an eruption these swarms are often thought to represent stalled intrusions of magma into the mid or shallow level crust real time assessment of the likelihood that a vt swarm will culminate in an eruption is one of the key challenges of volcano monitoring and retrospective analysis of non eruptive swarms provides an important framework for future assessments here we explore models for a non eruptive vt earthquake swarm located beneath iliamna volcano alaska in may 1996 june 1997 through calculation and inversion of fault plane solutions for swarm and background periods and through coulomb stress modeling of faulting types and hypocenter locations observed during the swarm through a comparison of models of deep and shallow intrusions to swarm observations we aim to test the hypothesis that the 1996 97 swarm represented a shallow intrusion or failed eruption observations of the 1996 97 swarm are found to be consistent with several scenarios including both shallow and deep intrusion most likely involving a relatively small volume of intruded magma and or a low degree of magma pressurization corresponding to a relatively low likelihood of eruption

interferometric synthetic aperture radar atmospheric correction using a gps based iterative tropospheric decomposition model abstract atmospheric effects represent one of the major error sources of repeat pass interferometric synthetic aperture radar insar and could mask actual displacements due to tectonic or volcanic deformation the tropospheric delays vary both vertically and laterally and can be considered as the sum of i a vertically stratified component highly correlated with topography and ii a turbulent component resulting from turbulent processes in the troposphere varying both in space and time in this paper we outline a framework to routinely use pointwise gps data to reduce tropospheric effects on satellite radar measurements an iterative tropospheric decomposition itd model is used and further developed to separate tropospheric stratified and turbulent signals and then generate high resolution correction maps for sar interferograms cross validation is employed to assess the performance of the itd model and act as an indicator to users of when and where correction is feasible tests were carried out to assess the impact of gps station spacing on the itd model insar correction performance which provides insights into the trade off between station spacing and the achievable accuracy the application of this framework to sentinel 1a interferograms over the southern california usa and southern england uk regions shows approximately 45 78 of noise reduction even with a sparse 50 80 km station spacing gps network and or with strong and non random tropospheric turbulence this is about a 50 greater improvement than previous methods it is believed that this framework could lead to a generic insar atmospheric correction model while incorporating continuous and global tropospheric delay datasets e g numerical weather models

monitoring changes in seismic velocity related to an ongoing rapid inflation event at okmok volcano alaska okmok is one of the most active volcanoes in the aleutian arc in an effort to improve our ability to detect precursory activity leading to eruption at okmok we monitor a recent and possibly ongoing gps inferred rapid inflation event at the volcano using ambient noise interferometry ani applying this method we identify changes in seismic velocity outside of okmok s caldera which are related to the hydrologic cycle within the caldera we observe decreases in seismic velocity that are associated with the gps inferred rapid inflation event we also determine temporal changes in waveform decorrelation and show a continual increase in decorrelation rate over the time associated with the rapid inflation event the magnitude of relative velocity decreases and decorrelation rate increases are comparable to previous studies at piton de la fournaise that associate such changes with increased production of volatiles and or magmatic intrusion within the magma reservoir and associated opening of fractures and or fissures notably the largest decrease in relative velocity occurs along the intra station path passing nearest to the center of the caldera this observation along with equal amplitude relative velocity decreases revealed via analysis of intra caldera autocorrelations suggest that the inflation source may be located approximately within the center of the caldera and represent recharge of shallow magma storage in this location importantly there is a relative absence of seismicity associated with this and previous rapid inflation events at okmok thus these ani results are the first seismic evidence of such rapid inflation at the volcano

the importance of subsurface lithology in controlling magma storage v eruption an example from offshore southern australia the volumetric relationship between the intrusive and extrusive components of volcanic fields is difficult to constrain this is because either the erupted products are commonly eroded or the intrusions are concealed by overburden three dimensional seismic data therefore offer a unique opportunity to study ancient volcanic provinces as these datasets can image both components without the need for erosional dissection this study is based on 3d seismic data from the bight basin igneous complex bbic a volcanic province constructed within a sedimentary basin offshore southern australia we demonstrate that the bbic contains abundant sills and laccoliths emplaced within deltaic sediments the intrusions have a total volume of 92 111 km 3 and the lava flows and volcanoes have a combined volume of 66 76 km 3 dense rock equivalent this indicates that the ratio of intrusive extrusive products for the bbic is between 1 1 and 2 1 the architecture of the bbic contrasts markedly with the neighbouring newer volcanics province nvp which lacks abundant sills and laccoliths because lava flows and volcanoes in the nvp were dominantly fed by dykes hosted in basement rock we suggest that subsurface lithology plays an important role in causing sill formation and determining the total volume of magma stored in the subsurface

estimating lava volume by precision combination of multiple baseline spaceborne and airborne interferometric synthetic aperture radar the 1997 eruption of okmok volcano alaska interferometric synthetic aperture radar insar techniques are used to calculate the volume of extrusion at okmok volcano alaska by constructing precise digital elevation models dems that represent volcano topography before and after the 1997 eruption the posteruption dem is generated using airborne topographic synthetic aperture radar topsar data where a three dimensional affine transformation is used to account for the misalignments between different dem patches the preeruption dem is produced using repeat pass european remote sensing satellite data multiple interferograms are combined to reduce errors due to atmospheric variations and deformation rates are estimated independently and removed from the interferograms used for dem generation the extrusive flow volume associated with the 1997 eruption of okmok volcano is 0 154 spl plusmn 0 025 km sup 3 the thickest portion is approximately 50 m although field measurements of the flow margin s height do not exceed 20 m the in situ measurements at lava edges are not representative of the total thickness and precise dem data are absolutely essential to calculate eruption volume based on lava thickness estimations this study is an example that demonstrates how insar will play a significant role in studying volcanoes in remote areas

spatial and temporal patterns of deformation at the tendaho geothermal prospect ethiopia abstract observations of ground deformation in east africa have been fundamental for unveiling the tectonics of continental rifting assessing the seismic and volcanic hazard to development and identifying geothermal resources here we investigate the active natural and anthropogenic processes in the tendaho graben afar using interferometric synthetic aperture radar insar collected by the envisat satellite in 2004 2010 we used the poly interferometric rate and time series estimation rate method to calculate displacement in satellite line of sight and a least square inversion to decompose the line of sight displacement into vertical and rift perpendicular components we observe two zones of deformation a 20 km wide circular region of subsidence located 10 km northeast of the town of semera with a maximum displacement rate of 5 cm yr and elongated zone 50 km of subsidence in the area of the geothermal prospect maximum rate of 4 cm yr the temporal characteristics of subsidence varies between these zones with an increase in subsidence rate observed in the circular region in august 2008 we used a bayesian inversion to find the best fitting source models and compared this to locations of seismicity and other geophysical observations the pattern of deformation is consistent with a combination of magmatic and geothermal processes but there does not appear to be a direct link to a sequence of dyke intrusions during 2005 2010 at manda hararo graben 60 km away but dynamic stress changes or deep crustal flow could account for the observations

shallow seismicity triggered seismicity and ambient noise tomography at the long dormant uturuncu volcano bolivia using a network of 15 seismometers around the inflating uturuncu volcano from april 2009 to 2010 we find an average rate of about three local volcano tectonic earthquakes per day and swarms of 5 60 events a few times per month with local magnitudes ranging from 1 2 to 3 7 the earthquake depths are near sea level more than 10 km above the geodetically inferred inflation source and the altiplano puna magma body the mw 8 8 maule earthquake on 27 february 2010 triggered hundreds of earthquakes at uturuncu with the onset of the love and rayleigh waves and again with the passage of the x2 x3 overtone phases of rayleigh waves this is one of the first incidences in which triggering has been observed from multiple surface wave trains the earthquakes are oriented nw se similar to the regional faults and lineaments the b value of the catalog is 0 49 consistent with a tectonic origin of the earthquakes we perform ambient noise tomography using love wave cross correlations to image a low velocity zone at 1 9 to 3 9 km depth below the surface centered slightly north of the summit the low velocities are perhaps related to the hydrothermal system and the low velocity zone is spatially correlated with earthquake locations the earthquake rate appears to vary with time a seismic deployment from 1996 to 1997 reveals 1 5 earthquakes per day whereas 60 events day were seen during 5 days using one seismometer in 2003 however differences in analysis methods and magnitudes of completeness do not allow direct comparison of these seismicity rates the rate of seismic activity at uturuncu is higher than at other well monitored inflating volcanoes during periods of repose the frequent swarms and triggered earthquakes suggest the hydrothermal system is metastable

interpretation of recent alpine landscape system evolution using geomorphic mapping and l band insar analyses abstract alpine landscapes are typically characterized by inherited features of past glaciations and for the more recent past by the interplay of a multitude of types of geomorphic processes including permafrost creep rockfalls debris flows and landslides these different processes usually exhibit large spatial and temporal variations in activity and velocity the understanding of these processes in a wide alpine area is often hindered by difficulties in their surveying in this study we attempt to disentangle recent changes in an alpine landscape system using geomorphic mapping and l band dinsar analyses alos palsar in the zermatt valley swiss alps geomorphic mapping points to a preferential distribution of rock glaciers on north facing slopes whereas talus slopes are concentrated on south facing slopes field based interpretation of ground deformation in rock glaciers and movements in talus slopes correlates well with the ratio of insar images showing potential ground deformation moraines formed during the little ice age rock glaciers and talus slopes on north facing slopes are more active than landforms on south facing slopes implying that the presence of permafrost facilitates the deformation of these geomorphic units such deformations of geomorphic units prevail also at the elevation of glacier termini for rock cliffs the ratio of images indicating retreat is affected by slope orientation and elevation linkages between sediment supply from rock cliffs and sediment transport in torrents are different among tributaries affected by relative locations between sediment supply areas and the channel network we conclude that the combined use of field surveys and l band dinsar analyses can substantially improve process understanding in steep high mountain terrain

the 2007 8 volcanic eruption on jebel at tair island red sea observed by satellite radar and optical images we use high resolution optical images and interferometric synthetic aperture radar insar data to study the september 2007 january 2008 jebel at tair eruption comparison of pre and post eruption optical images reveals several fresh ground fissures a new scoria cone near the summit and that 5 9 0 1 km2 of new lava covered about half of the island decorrelation in the insar images indicates that lava flowed both to the western and to the northeastern part of the island after the start of the eruption while later lavas were mainly deposited near the summit and onto the north flank of the volcano from the insar data we also estimate that the average thickness of the lava flows is 3 8 m resulting in a bulk volume of around 2 2 107 m3 we observe no volcano wide pre or post eruption uplift which suggests that the magma source may be deep the co eruption interferograms on the other hand reveal local and rather complex deformation we use these observations to constrain a tensile dislocation model that represents the dike intrusion that fed the eruption the model results show that the orientation of the dike is perpendicular to the red sea rift implying that the local stresses within the volcanic edifice are decoupled from the regional stress field

repeated magmatic intrusions at el hierro island following the 2011 2012 submarine eruption abstract after more than 200 years of quiescence in july 2011 an intense seismic swarm was detected beneath the center of el hierro island canary islands culminating on 10 october 2011 in a submarine eruption 2 km off the southern coast although the eruption officially ended on 5 march 2012 magmatic activity continued in the area from june 2012 to march 2014 six earthquake swarms indicative of magmatic intrusions were detected underneath the island we have studied these post eruption intrusive events using gps and insar techniques to characterize the ground surface deformation produced by each of these intrusions and to determine the optimal source parameters geometry location depth volume change source inversions provide insight into the depth of the intrusions 11 16 km and the volume change associated with each of them between 0 02 and 0 13 km 3 during this period 20 cm of uplift was detected in the central western part of the island corresponding to approximately 0 32 0 38 km 3 of magma intruded beneath the volcano we suggest that these intrusions result from deep magma migrating from the mantle trapped at the mantle lower crust discontinuity in the form of sill like bodies this study using joint inversion of gps and insar data in a post eruption period provides important insight into the characteristics of the magmatic plumbing system of el hierro an oceanic intraplate volcanic island

deformation patterns magma supply and magma storage at karymsky volcanic center kamchatka russia 2000 2010 revealed by insar abstract under a complex geological region influenced by the subduction of the pacific plate kamchatka peninsula is one of the most active volcanic arcs in the pacific rim due to logistical difficulty in instrumentation shallow magma plumbing systems beneath some of the kamchatkan volcanoes are poorly understood insar offers a safe and quick method for monitoring volcanic deformation with a high spatial resolution in this study a group of satellite radar interferograms that span the time interval from 2000 to 2010 shows eruptive and non eruptive deformation at karymsky volcanic center kvc kamchatka russia all the interferograms provide details of the activity around the kvc during 2000 2010 as follows 1 from 2000 to 2004 the karymsky an akademia nauk area deflated and the ms maly semyachik area inflated 2 from 2004 to 2006 the karymsky an area deflated with ongoing eruption while the ms area subsided without eruption 3 from 2006 to 2008 as with 2000 2004 the karymsky an area deflated and the ms area inflated 4 from 2008 to 2010 the karymsky an area inflated up to 3 cm and the ms area subsided point source models suggest that two magma reservoirs provide a good fit to the observed deformation one source is located beneath the area between karymsky and an at a depth of approximately 7 0 km and the other one is situated beneath ms at a depth of around 5 8 km synchronous deformation patterns suggest that two magma systems are fed from the same deep magma source and connected by a fracture zone the insar results are consistent with gps ground deformation measurements seismic data and petrological constraints

magma flux at okmok volcano alaska from a joint inversion of continuous gps campaign gps and interferometric synthetic aperture radar 1 volcano deformation is usually measured using satellite geodetic techniques including interferometric synthetic aperture radar insar campaign gps and continuous gps differences in the spatial and temporal sampling of each system mean that most appropriate inversion scheme to determine the source parameters from each data set is different most studies either compare results from independent inversions or subsample the data sets to the lowest common factor it is unclear whether differences in the solution reflect differences in source behavior differences in measurement bias or differences in inversion technique here we develop a single inversion procedure that captures the benefits of each system especially the daily sampling of continuous gps and the high spatial resolution of insar okmok volcano alaska is an ideal target for such a test because a long series 15 years of insar and continuous gps measurement exists and the source is almost continuously active and in a stable location

turbidite depositional architecture across three interconnected deep water basins on the north west african margin the moroccan turbidite system mts on the north west african margin extends 1500 km from the head of the agadir canyon to the madeira abyssal plain making it one of the longest turbidite systems in the world the mts consists of three interconnected deep water basins the seine abyssal plain sap the agadir basin and the madeira abyssal plain map connected by a network of distributary channels excellent core control has enabled individual turbidites to be correlated between all three basins giving a detailed insight into the turbidite depositional architecture of a system with multiple source areas and complex morphology large volume 100 km3 turbidites sourced from the morocco shelf show a relatively simple architecture in the madeira and seine abyssal plains sandy bases form distinct lobes or wedges that thin rapidly away from the basin margin and are overlain by ponded basin wide muds however in the agadir basin the turbidite fill is more complex owing to a combination of multiple source areas and large variations in turbidite volume a single very large turbidity current 200 300 km3 of sediment deposited most of its sandy load within the agadir basin but still had sufficient energy to carry most of the mud fraction 500 km further downslope to the map large turbidity currents 100 150 km3 of sediment deposit most of their sand and mud fraction within the agadir basin but also transport some of their load westwards to the map small turbidity currents 35 km3 of sediment are wholly confined within the agadir basin and their deposits pinch out on the basin floor turbidity currents flowing beyond the agadir basin pass through a large distributary channel system individual turbidites correlated across this channel system show major variations in the mineralogy of the sand fraction whereas the geochemistry and micropalaeontology of the mud fraction remain very similar this is interpreted as evidence for separation of the flow with a sand rich erosive basal layer confined within the channel system overlain by an unconfined layer of suspended mud large volume turbidites within the mts were deposited at oxygen isotope stage boundaries during periods of rapid sea level change and do not appear to be specifically connected to sea level lowstands or highstands this contrasts with the classic fan model which suggests that most turbidites are deposited during lowstands of sea level in addition the three largest turbidites on the map were deposited during the largest fluctuations in sea level suggesting a link between the volume of sediment input and the magnitude of sea level change

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

pre eruption deformation caused by dike intrusion beneath kizimen volcano kamchatka russia observed by insar abstract interferometric synthetic aperture radar insar images reveal a pre eruption deformation signal at kizimen volcano kamchatka russia where an ongoing eruption began in mid november 2010 the previous eruption of this basaltic andesite to dacite stratovolcano occurred in 1927 1928 insar images from both ascending and descending orbital passes of envisat and alos palsar satellites show as much as 6 cm of line of sight shortening from september 2008 to september 2010 in a broad area centered at kizimen about 20 cm of opening of a nearly vertical dike provides an adequate fit to the surface deformation pattern the model dike is approximately 14 km long 10 km high centered 13 km beneath kizimen and strikes ne sw time series analysis of multi temporal interferograms indicates that 1 intrusion started sometime between late 2008 and july 2009 2 continued at a nearly constant rate and 3 resulted in a volume expansion of 3 2 107 m3 by september 2010 i e about two months before the onset of the 2010 eruption earthquakes located above the tip of the dike accompanied the intrusion eventually magma pressure in the dike exceeded the confining strength of the host rock triggering the 2010 eruption our results provide insight into the intrusion process that preceded an explosive eruption at a pacific rim stratovolcano following nearly a century of quiescence and therefore have implications for monitoring and hazards assessment at similar volcanoes elsewhere

consequences of volcano sector collapse on magmatic storage zones insights from numerical modeling abstract major volcano flank collapses strongly affect the underlying magmatic plumbing system here we consider the magma storage zone as a liquid pocket embedded in an elastic medium and we perform numerical simulations in two dimensional axisymmetric geometry as well as in three dimensions in order to evaluate the consequences of a major collapse event we quantify the pressure decrease induced within and around a magma reservoir by a volcano flank collapse this pressure reduction is expected to favor replenishment with less evolved magma from deeper sources we also estimate the impact of the magma pressure decrease together with the stress field variations around the reservoir on the eruptive event associated with the edifice failure we show that for a given magma reservoir geometry the collapse of a large strato volcano tends to reduce the volume of the simultaneous eruption destabilization of large edifices may even suppress magma emission resulting in phreatic eruptions instead this effect is greater for shallow reservoirs and is more pronounced for spherical reservoirs than for vertically elongated ones it is reduced for compressible magmas containing a large amount of volatiles over a longer time scale the modification of pressure conditions for dyke initiation at the chamber wall may also explain an increase in eruption rate as well as an apparent change of magma storage location

interpretation of ground surface changes prior to the 2010 large eruption of merapi volcano using alos palsar aster tir and gas emission data abstract understanding precursory signals is essential to forecast eruptions hazards and mitigate risks satellite observations have been shown to increasingly contribute to this goal we use differential inteferometric synthetic aperture radar d insar and sar backscattering intensity data from alos palsar to define a time series of ground surface displacements for the 2006 2010 inter eruptive period at merapi volcano we correlate trends in the displacement data to trends for summit temperature determined using data from the aster sensor and to gas emission data we show that processing of the satellite data must be performed carefully before meaningful interpretations can be drawn for example after careful removal of the topographic effect on phase delays we detect only subtle inter eruptive episodes of cyclic deformation in the d insar and sar backscattering data these small mostly sub centimeter displacements contrast with meter scale pre eruptive displacements along an electronic distance measurement edm line on the south flank of the volcano we suggest that this difference is a consequence of localized movement within the summit area a result that has important implications for understanding merapi s structure for monitoring network design and for eruption forecasting although small merapi s inter eruptive deformation cycles are also seen in thermal data from aster and gas emissions accordingly we interpret these cycles as the result of successive movement of individual magma batches migrating upward from deeper to shallower storage systems located along a ne dipping conduit in view of magma migration prior to eruptions these cycles may also serve as a precursory signal for large eruptions at merapi such as the one that took place in early november 2010

dynamic deformation of seguam island alaska 1992 2008 from multi interferogram insar processing abstract we generated a time series of ers 1 2 and envisat interferometric synthetic aperture radar insar images to study ground surface deformation at seguam island from 1992 to 2008 we used the small baseline subset sbas technique to reduce artifacts associated with baseline uncertainties and atmospheric delay anomalies and processed images from two adjacent tracks to validate our results seguam island comprises the remnants of two late quaternary calderas one in the western caldera of the island and one in the eastern part of the island the western caldera subsided at a constant rate of 1 6 cm yr throughout the study period while the eastern caldera experienced alternating periods of subsidence and uplift 5 cm year uplift during january 1993 october 1993 stage 1 1 6 cm year subsidence during october 1993 november 1998 stage 2 2 0 cm year uplift during november 1998 september 2000 stage 3 1 4 cm year subsidence during september 2000 november 2005 stage 4 and 0 8 cm year uplift during november 2005 july 2007 stage 5 source modeling indicates a deflationary source less than 2 km below sea level bsl beneath the western caldera and two sources beneath the eastern caldera an inflationary source 2 5 6 0 km bsl and a deflationary source less than 2 km bsl we suggest that uplift of the eastern caldera is driven by episodic intrusions of basaltic magma into a poroelastic reservoir 2 5 6 0 km bsl beneath the caldera cooling and degassing of the reservoir between intrusions result in steady subsidence of the overlying surface although we found no evidence of magma intrusion beneath the western caldera during the study period it is the site pyre peak of all historical eruptions on the island and therefore cooling and degassing of intrusions presumably contributes to subsidence there as well another likely subsidence mechanism in the western caldera is thermoelastic contraction of lava flows emplaced near pyre peak during several historical eruptions most recently in 1977 and 1992 93

monitoring crater wall collapse at active volcanoes a study of the 12 january 2013 event at stromboli crater wall collapses are fairly frequent at active volcanoes and they are normally studied through the analysis of their deposits in this paper we present an analysis of the 12 january 2013 crater wall collapse occurring at stromboli volcano investigated by means of a monitoring network comprising visible and infrared webcams and a ground based interferometric synthetic aperture radar the network revealed the triggering mechanisms of the collapse which are comparable to the events that heralded the previous effusive eruptions in 1985 2002 2007 and 2014 the collapse occurred during a period of inflation of the summit cone and was preceded by increasing explosive activity and the enlargement of the crater weakness of the crater wall increasing magmastatic pressure within the upper conduit induced by ascending magma and mechanical erosion caused by vent opening at the base of the crater wall and by lava fingering are considered responsible for triggering the collapse on 12 january 2013 at stromboli we suggest that the combination of these factors might be a general mechanism to generate crater wall collapse at active volcanoes

catastrophic collapse of the volcanic island of hierro 15 ka ago and the history of landslides in the canary islands landslides play an important role in the evolution of many volcanic islands producing huge fields of blocky volcanic debris on their submarine slopes sidescan sonar images presented in this paper provide evidence for a large debris avalanche el golfo on the northern flank of hierro island in the canary islands angular blocks as much as 1 2 km across and 200 m high cover the debris avalanche surface el golfo avalanche is related to both the canary debris flow and a volcaniclastic turbidite found in the madeira abyssal plain 600 km west of the canaries dating of the turbidite and the failure scarp onshore indicates that the failure probably occurred between 13 and 17 ka there appears to be a general correlation between volcaniclastic turbidites in the abyssal plain sequence and landslides in the canaries during the past 750 ka tentatively this correlation suggests that seven major landslides have affected the canaries in that time

data assimilation strategies for volcano geodesy abstract ground deformation observed using near real time geodetic methods such as insar and gps can provide critical information about the evolution of a magma chamber prior to volcanic eruption rapid advancement in numerical modeling capabilities has resulted in a number of finite element models targeted at better understanding the connection between surface uplift associated with magma chamber pressurization and the potential for volcanic eruption robust model data fusion techniques are necessary to take full advantage of the numerical models and the volcano monitoring observations currently available in this study we develop a 3d data assimilation framework using the ensemble kalman filter enkf approach in order to combine geodetic observations of surface deformation with geodynamic models to investigate volcanic unrest the enkf sequential assimilation method utilizes disparate data sets as they become available to update geodynamic models of magma reservoir evolution while the enkf has been widely applied in hydrologic and climate modeling the adaptation for volcano monitoring is in its initial stages as such our investigation focuses on conducting a series of sensitivity tests to optimize the enkf for volcano applications and on developing specific strategies for assimilation of geodetic data our numerical experiments illustrate that the enkf is able to adapt well to the spatial limitations posed by gps data and the temporal limitations of insar and that specific strategies can be adopted to enhance enkf performance to improve model forecasts specifically our numerical experiments indicate that 1 incorporating additional iterations of the enkf analysis step is more efficient than increasing the number of ensemble members 2 the accuracy of the enkf results are not affected by initial parameter assumptions 3 gps observations near the center of uplift improve the quality of model forecasts 4 occasionally shifting continuous gps stations to provide variability in the locations of observations results in better model predictions than utilizing fixed locations when the number of available instruments is limited 5 spotty insar data coverage on the flanks of a volcano due to topographic shadows and or atmospheric interference does not adversely impact the effectiveness of enkf if the available coverage is 50 and 6 snow or glacial obstruction in the center of uplift can adversely impact enkf forecasts by utilizing these strategies we conclude that the enkf is an effective sequential model data fusion technique for assimilating multiple geodetic observations to forecast volcanic activity at restless volcanoes

changes in the magma system during the 2008 eruption of okmok volcano alaska based on gps measurements 1 the 2008 eruption of okmok volcano was preceded by 6 7 months of immediate precursory inflation which followed 3 years of quiescence during which no significant magma was intruded at shallow depth although gps data for the precursory period are too sparse to derive a unique source model the data show that either the center of pressurization shifted from its 1997 2005 location during the immediate precursory time interval or the shape of the pressure source changed from a sphere to something else deflation during the eruption resulted from a decrease in pressure from a source estimated to be at 2 1 km below sea level using a mogi model although source depth estimates from a mogi model can be biased due to elastic layering or heterogeneity the gps data require the 2008 eruptive source to be shallower than the preeruptive inflation source during the eruption the gps time series indicate three distinct pulses of deflation rather than a single smoothly decaying process with the initial pulse being the largest reinflation of the volcano commenced within at most 3 weeks after the end of ash emissions and was evident at a near source site while a far field site continued to deflate for an additional 4 5 weeks the asynchronous transition from deflation to inflation controlled by the distance of the site from the source indicates that paired deep deflation and shallow inflation is required to explain the observations

deformation and seismicity in the coso geothermal area inyo county california observations and modeling using satellite radar interferometry interferometric synthetic aperture radar insar data collected in the coso geothermal area eastern california during 1993 1999 indicate ground subsidence over a 50 km 2 region that approximately coincides with the production area of the coso geothermal plant the maximum subsidence rate in the peak of the anomaly is 3 5 cm yr 1 and the average volumetric rate of subsidence is of the order of 10 6 m 3 yr 1 the radar interferograms reveal a complex deformation pattern with at least two irregular subsidence peaks in the northern part of the anomaly and a region of relative uplift on the south we invert the insar displacement data for the positions geometry and relative strengths of the deformation sources at depth using a nonlinear least squares minimization algorithm we use elastic solutions for a prolate uniformly pressurized spheroidal cavity in a semi infinite body as basis functions for our inversions source depths inferred from our simulations range from 1 to 3 km which corresponds to the production depths of the coso geothermal plant underpressures in the geothermal reservoir inferred from the inversion are of the order of 0 1 1 mpa except a few abnormally high underpressures that are apparently biased toward the small source dimensions analysis of the insar data covering consecutive time intervals indicates that the depths and or horizontal extent of the deformation sources may increase with time this increase presumably reflects increasing volumes of the subsurface reservoir affected by the geothermal exploitation we show that clusters of microearthquakes associated with the geothermal power operation may result from perturbations in the pore fluid pressure as well as normal and shear stresses caused by the deflation of the geothermal reservoir

interferometric synthetic aperture radar study of recent eruptive activity at shrub mud volcano alaska abstract shrub mud volcano is one of three large mud volcanoes that comprise the klawasi group in the copper river basin of southcentral alaska except for minor discharges in the mid 1950s when the group was first described shrub was dormant prior to its reactivation in summer 1996 from 1997 to 1999 shrub vigorously erupted more than 5 105 m3 of saline mud and co2 rich gas at temperatures as high as 54 c thereafter activity waned but continued at least through 2015 we analyzed 192 interferograms derived from 106 synthetic aperture radar sar images acquired by the jers 1 l band ers 1 2 c band radarsat 1 c band and alos palsar l band satellites to characterize ground deformation at shrub before during and after its reactivation collectively the interferograms span 1992 2000 and 2006 2011 we fit the observations with two deformation sources a deflating steeply dipping pipe like body under the summit area and an inflating shallow dipping sill like body under the southwest flank both sources are shallow with centroids less than 1 km beneath the summit prior to reactivation the flank source inflated 0 35 105 m3 yr from july 1992 to may 1996 during eruptive activity the summit source deflated at higher rates that peaked at 8 71 105 m3 yr during may november 1997 and continued at 0 95 105 m3 yr during the 2006 2011 observation window cumulative source volume loss is comparable to the volume of mud erupted we interpret the summit source as the volcano s feeder conduit that pressurized prior to the first sar observation in 1992 also before 1992 the conduit ruptured to feed a lateral intrusion of mud under the southwest flank perhaps along a bedding plane in underlying glaciolacustrine deposits the growing sill caused the southwest flank to inflate while it accommodated the mud supply from depth which explains why we observed pre eruptive inflation of the flank but not the summit the summit began deflating when the conduit ruptured to the surface at the onset of eruptive activity the flank source did not deflate concurrently because the weight of the thin overburden was insufficient to collapse the sill there is a suggestion in the modern topography that lateral intrusions under shrub s southwest flank are a common feature of activity there

magma compressibility and the missing source for some dike intrusions 1 dike intrusions are often accompanied by localized deflation interpreted as depressurizing magma chambers feeding the dike in some cases the inferred volume decrease is a factor of 4 or 5 less than the volume increase of the dike here we explore whether this discrepancy can be explained by compressibility of the magma combined with the fact that cracks are much more compliant than equidimensional magma chambers if pressure changes are small the magma compressibility m is constant and the dike ends up in hydrostatic equilibrium with an ellipsoidal magma chamber at the same depth the ratio rv of the volume of the crack to the volume lost by the chamber is rv 1 4 m 3 1 where is the host rock rigidity for gas poor magmas m 0 6 2 10 10 pa 1 and 3 25 gpa we find 1 2 rv 7 7 large changes in magma compressibility due to gas exsolution increase rv

hydrothermal and magmatic reservoirs at lazufre volcanic area revealed by a high resolution seismic noise tomography we determine here for the first time the geometry and location of the hydrothermal and magmatic reservoirs in the lazufre volcanic area this furthers the understanding of the origin of one of the largest worldwide volcanic uplift regions both in space and amplitude the exact locations and shapes of the sources generating a double wide uplift region in the lazufre found by past deformation data insar and gps and generating hydrothermal and magmatic fluids found by geochemical gas analysis have not been well delimited in this study we use seismological data to perform a 3 d high resolution s wave velocity model which allows defining better the locations and shapes of the sources of the deformations and the hydrothermal and magmatic reservoirs we find three anomalies two of them with s wave velocity of about 1 2 1 8 km s are located below the lastarria volcano the shallow one 1 km below the volcano base has a funnel like shape the deeper one is located between a depth of 3 and 6 km below the volcano base both are strongly elliptical in an ew direction and separated by a 2 3 km thick zone with vs of 1 5 2 km s as far as these anomalies are located under the hydrothermal activity of lastarria volcano they are interpreted as a double hydrothermal the shallow part and magmatic source the deeper part the latter can feed the former this double hydrothermal and magmatic source is in agreement with previous geochemical deformation gps and insar and magneto telluric studies in particular it explains the double origin of the gases hydrothermal and magmatic the third low velocity zone with s wave velocity of about 2 3 km s located at 5 km depth and deeper is centered beneath an area of surface uplift as determined by insar data we compare the seismic tomography and insar results to propose that this low velocity zone is at the top of a large reservoir hosting hydrothermal fluids and possibly also magma

surface movements of emplaced lava flows measured by synthetic aperture radar interferometry lava flows continue to move after they have been emplaced by flow mechanisms this movement is largely vertical and can be detected using differential synthetic aperture radar sar interferometry there are three main components to this motion 1 movement of surface scatterers resulting in radar phase decorrelation 2 measurable subsidence of the flow surface due to thermal contraction and clast repacking and 3 time dependent depression of the flow substrate these effects act in proportion to the thickness of the lava flow and decay with time although there is a time lag before the third component becomes significant we explore these effects using sar data from the ers satellites over the etna volcano sicily phase decorrelation on young thick a a lava flows persists for a few years and probably results from surface block rotations during flow contraction maximum measured subsidence rates of the 1991 1993 lava flow over a period of 70 days are about 0 7 mm day 1 but are potentially greater in areas of data decorrelation these rates fall to 2 7 10 2 mm day 1 after about 20 years in flows about 50 m thick sooner for thinner flows comparison with measured subsidence rates on kilauean lava lakes suggests that thermal contraction only accounts for about one third of the observed subsidence the remaining motion is thought to come from surface clast repacking during cooling and from creep mechanisms in the flow substrate measurements of postemplacement surface movement provide new constraints on the thermomechanical properties of lava flows and have cautionary implications for the interpretation of interferometric sar data of volcanoes 2001 american geophysical union

correlation between rate of sea level change and frequency of explosive volcanism in the mediterranean volcanic activity has frequently been linked to quaternary environmental change either by driving climate modification1 2 or in response to environmental changes3 although a link has been established between large explosive eruptions and small 0 5 c brief 1 2 years falls in global temperatures4 both the evidence and mechanisms responsible for longer episodes of eruption induced planetary cooling remain questionable1 2 5 6 in contrast recent research based on ice core data suggests that rapid climate changes during the past 110 000 years increased explosive volcanic activity7 here we present a statistical analysis relating the frequency of explosive activity of mediterranean volcanoes based on dated8 9 10 11 tephra layers in deep sea sediment cores to the rate of late quaternary sea level change the nonlinear correlation between the two is tentatively explained in terms of dynamic responses of the volcanoes to stress related influences on various spatial scales the correlation supports a mechanism or mechanisms by which the climate driven growth and decay of large ice sheets can influence the eruptive chronologies of distant volcanic edifices via changes in global sea level