sinking cities in indonesia alos palsar detects rapid subsidence due to groundwater and gas extraction abstract we use interferometric synthetic aperture radar insar time series analysis of alos l band sar data to resolve land subsidence in western indonesia with high spatial and temporal resolution the data reveal significant subsidence in nine areas including six major cities at rates up to 22 cm year land subsidence is detected near lhokseumawe in medan jakarta bandung blanakan pekalongan bungbulang semarang and in the sidoarjo regency the fastest subsidence occurs in highly populated coastal areas particularly vulnerable to flooding we correlate the observed subsidence with surface geology and land use despite the fact that subsidence is taking place in compressible deposits there is no clear correlation between subsidence and surface geology in urban areas we find a correlation between rapid patchy subsidence and industrial land use and elsewhere with agricultural land use this suggests that the subsidence is primarily caused by ground water extraction for industrial and agricultural use respectively we also observe subsidence associated with exploitation of gas fields near lhokseumawe and in the sidoarjo regency a continuation of these high rates of subsidence is likely to put much of the densely populated coastal areas below relative sea level within a few decades

volcanic conduit controls on effusive explosive transitions and the 2010 eruption of merapi volcano indonesia abstract individual volcanoes can produce both effusive and explosive eruptions a transition between these two eruption styles dramatically changes the hazards and can occur either between distinct eruption events or within one eruption episode the causes of these transitions are difficult to determine due to the number of system parameters that can influence whether or not magma fragments in a runaway process we apply a numerical model of magma ascent in a volcanic conduit to isolate and test the effects of key parameters related to magma rheology and system geometry we find that for a given volcanic system parameters that control magma viscosity such as initial water mass fraction initial crystal volume fraction and temperature have the greatest influence on whether or not magma fragments during ascent and erupts explosively we also define a critical condition for the full set of initial parameters under which a transition in eruption style from effusive to explosive or the reverse is more likely to occur under these conditions small heterogeneities in the water or crystal content of the magma or small perturbations to the conduit pressure gradient due to magma chamber overpressure or dome growth or collapse can disrupt the magmatic conditions and cause a transition in eruption style the 2010 vei 4 eruption of merapi volcano included both effusive and explosive phases and was larger by an order of magnitude than its eruptions during the previous century we constrain our model for the merapi system using published literature values and show that between the previous eruption in 2006 and the 2010 eruption the shallow magmatic system at merapi reached critical conditions due to the ascent from depth of a large hotter more volatile rich magma under these critical conditions and according to our model results small changes in the volatile content of the magma small dome collapses subtle changes in degassing rate or the addition of co2 to the magma through decarbonation of the bedrock are all feasible mechanisms for triggering rapid transitions between effusive and explosive activity during the 2010 eruption period

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

deflection of dykes into sills at discontinuities and magma chamber formation abstract many rift zones contain composite volcanoes central volcanoes most of which are supplied with magma from shallow crustal magma chambers volcanotectonic studies of eroded rift zones such as in iceland as well as geophysical studies indicate that many shallow magma chambers evolve from sills here i provide field description of sills and extinct magma chambers in the quaternary and tertiary palaeorift zones of iceland focusing on the felsic pluton of slaufrudalur southeast iceland as a fine example of a magma chamber developed through the injection of sills in this paper i review analyse and develop further two related mechanisms for the deflection of dykes into sills and thus the potential initiation of a magma chamber namely a cook gordon debounding delamination and b stress barriers and propose a third mechanism c favourable material toughness ratios due to elastic mismatch difference in young s moduli or stiffnesses of layers in contact in the cook gordon mechanism a weak contact opens up as a result of dyke induced tensile stress this mechanism is likely to operate primarily at shallow depths as is supported by field observations and numerical models a stress barrier is a layer where the local stress is unfavourable to a particular type of rock fracture here a dyke field observations and numerical models show that on meeting a stress barrier a dyke either changes into a sill or becomes arrested the material toughness mechanism indicates that when the upper layer at a contact has the same or less stiffness than the lower layer hosting the dyke there is little tendency for the dyke to become deflected into the contact however when the upper layer is stiffer such as when a stiff basaltic lava flow is on the top of a soft pyroclastic layer the dyke tends to become deflected into the contact to form a sill field results suggest that all these mechanisms may cause dyke deflection into sills and may operate together particularly where the rock consists of alternating soft and stiff layers since the quaternary lava pile in iceland has many more soft hyaloclastite layers than the tertiary lava pile these mechanisms were probably very efficient in generating sills and by implication shallow magma chambers during the quaternary this may be one reason why in comparison with the tertiary lava pile the quaternary lava pile contains so many sills and extinct plutons and active shallow magma chambers

ground deformation before the 2015 eruptions of cotopaxi volcano detected by insar cotopaxi volcano started a period of volcanic unrest in april 2015 that led to a series of eruptions between august and november 2015 we use cosmo skymed interferometric synthetic aperture radar supported by continuous gps observations spanning the period of 2014 2016 to obtain time dependent ground deformation data over cotopaxi volcano related to the period of unrest and onset of eruptions we find evidence of precursory deformation with a maximum uplift on the western flank of 3 4 cm from april to august 2015 deformation is explained by an inclined sheet intrusion located a few km southwest of the summit with an opening volume of 6 8 106 m3 extending from a depth of 12 1 km and shallowing to 5 5 km below the summit that contributed to internal edifice growth the temporal coincidence of deformation prior to the eruptions potentially suggests that short term eruptions at cotopaxi are partly controlled by episodic edifice growth

regional controls on magma ascent and storage in volcanic arcs understanding the controls for magma ascent and storage depth is important for volcanic hazard assessment regional differences in the depths of magma storage between volcanic arcs suggest that the settings of subduction zones and of overriding plates influence how magma ascends through the crust here we use a compilation of data for 70 volcanoes in 15 volcanic regions to better understand the geodynamic controls on magma storage we describe the subduction system which consists of the subducting slab the mantle wedge and the upper plate with 12 parameters encompassing the kinematics of the subduction the structure and geometry of the slab the timing of the subduction the thermal structure of the slab the upper plate crustal structure its stress regimes and its thermal structure we find that the magma reservoir depths correlate with the upper plate crustal structure and with the stress regimes shallow reservoirs 45 km similarly shallow magma reservoirs are 33 69 more common in extensional and strike slip stress regimes that in compressional regimes this illustrates the effect of buoyancy for magma ascent as well as the importance of stress regime and preexisting structures

kinematic setting and structural control of arc volcanism abstract the evaluation of the kinematic setting and the structural control of volcanic arcs are important in defining the tectono magmatic processes along convergent plate boundaries however our knowledge is fragmented and the available data highlight different behaviours this study analyzes the kinematic setting the structural control and the volcanic productivity of 16 arcs these arcs are characterized by predominant extensional compressional strike slip or oblique motions there is an overall coupling between the normal vs parallel motions along the arc and those of the underlying slab therefore the higher the trench normal or parallel component of the subduction rate the higher is the amount of arc normal or parallel motion this relation confirms that strain partitioning is in general feasible at many convergent settings involving also the volcanic arc portion the arc normal motion may be characterized by extension or compression as a function of the increase in the trench normal convergence or subduction velocity the lack of an evident relation between the subduction rate or convergence rate and the volcanic productivity of the arc is partly inconsistent with previous studies which highlight a relation between the subduction rate and melt production below arcs this discrepancy mainly suggests that different processes control the generation rise and eruption of magma at different depths varying the intrusive extrusive ratio along arcs the structure of the arc does not control the distribution of the volcanoes however it does control the volcanic output through different processes even though regional or local extension associated with strike slip or compressive structures is the ultimate requisite in any setting in general the higher the amount of extension the higher is the output rate along the arc

subsidence in the paricutin lava field causes and implications for interpretation of deformation fields at volcanoes abstract assessment of volcanic hazards includes interpretation of ground deformation signal which at polygenetic volcanoes often results from the superposition of deformation due to pressure changes in the magmatic system and due to surficial processes such as cooling of emplaced lava the deformation signal associated with emplaced lava is sometimes considered negligible if fields are decades old but if the lava thickness is great deformation may still be occurring possibly leading to misinterpretation of the observed deformation here i evaluate the 2007 2011 ground motion of the 1943 1952 lava field of the paricutin monogenetic cinder cone mexico interferometric synthetic aperture radar insar time series reveal patchy subsidence restricted to the lava field and following linear rates up to 5 5 cm year there is a clear correlation between subsidence rates and topography suggesting a causal relationship with deposits or lava thickness i estimate these thicknesses in the subsiding areas using pre and post eruption topographic maps and show that they reach up to 200 m a numerical model for lava flow cooling was developed considering radiation and convection from the surface conductive transfer inside the flow and to the ground and vesiculation and latent heat generation at the top and bottom of the flow the model shows that compaction induced by cooling of the thick deposits emplaced 60 years ago explains the observed subsidence when conductive transfer to the ground is considered these results demonstrate that thick deposits can keep deforming significantly even decades after their emplacement emphasizing the importance of considering cooling processes when interpreting deformation fields at polygenetic volcanoes producing massive lava fields

surface creep rate and moment accumulation rate along the aceh segment of the sumatran fault from l band alos 1 palsar 1 observations

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

multiscale and multitemporal surface temperature monitoring by satellite thermal infrared imagery at mayon volcano philippines abstract mayon volcano on eastern luzon island is the most active volcano in the philippines the high level of vulnerability to volcanic hazards is apparent since mayon is surrounded by eight cities and municipalities with a total population of approximately one million inhabitants thus there is an urgent need to develop and expand reliable and affordable long term methods in volcano monitoring despite abundant open access satellite dataset archives satellite remote sensing has been underutilized in mayon s hazard mapping and monitoring system here we perform monitoring analysis on a nineteen year time series of land surface temperature lst obtained from satellite thermal infrared images both aster advanced spaceborne thermal emission and reflection radiometer thermal imagery with 90 m spatial resolution and modis moderate resolution imaging spectroradiometer lst products 1 km spatial resolution are used for the analysis the ensemble empirical mode decomposition eemd is applied as the decomposition tool to extract components of different timescales from the lst time series physical interpretation of decomposed lst components at various periods are explored and compared with mayon s eruption records specifically the lst annual period component is compared to regular annual cycle air temperature results show that lst annual period component tends to lose its regularity following an eruption the dissimilarity of the two time series has been taken as an indicator of volcanic restlessness trends of different timescales based on lst components have been constructed which all indicate the rising trend this means that mayon volcano will remain restless in the future decades this study presents the advantages and effectiveness of satellite remote sensing on volcanic monitoring

calculation of dike trajectories from volcanic centers 1 patterns of dike swarms around volcanic centers or above mantle plumes are interpreted by a mechanical analysis of regional and dike induced stresses in which dike emplacement is controlled and guided by the stress state comparisons of dike patterns with patterns of principal stress trajectories caused by a source and a regional stress system are commonly used to infer paleostresses however dike trajectories are determined by a complex interaction between dike induced stresses and the source regional stress system we present numerical calculations based on a novel boundary integral formulation which examines the simultaneous effects of regional stresses magma pressure and dike injection on the local stress state around a continuously curving dike dike paths are calculated from the condition that dikes propagate by mode i failure our results suggest that the magnitude of the regional stresses would be 2 5 times higher than previous estimates based on principal stress trajectory analysis

land subsidence in central mexico detected by alos insar time series abstract massive groundwater extraction is common throughout mexico and is well known to result in land subsidence however most land subsidence surveys focus on one single city mainly mexico city and thus fail to reveal the regional extent of the problem here we use 2007 2011 interferometric synthetic aperture radar insar time series analysis of alos data to resolve land subsidence in the entire central mexico region we identify land subsidence in 21 areas including 17 cities linear vertical rates over 30 cm yr are observed in mexico city while in the other locations rates of 5 10 cm yr are detected we define 3 main categories of subsidence using the averaged velocity maps in conjunction with previously published structural surface geology and land use mapping 1 rapid large scale subsidence 2 rapid local scale subsidence and 3 slow patchy subsidence the correlation between subsidence and land use confirms that groundwater extraction mainly for agricultural and urban activities is the main cause of land subsidence we observe that the boundaries of the subsiding areas are typically characterized by high velocity gradients often coinciding with pre existing faults motion on these faults being driven by water extraction rather than by tectonic activity regional surveys of this type are necessary to understand the spatial and temporal evolution of land subsidence to constrain the distribution and connectivity of water bearing units and ultimately to reach better hazard mitigation plans

gas and ash emissions associated with the 2010 present activity of sinabung volcano indonesia abstract sinabung volcano sumatra indonesia awoke from over 1200 years of dormancy with multiple phreatic explosions in 2010 after a period of quiescence sinabung activity resumed in 2013 producing frequent explosions lava dome extrusion and pyroclastic flows from dome and lava flow collapses becoming one of the world s most active volcanoes and displacing over 20 000 citizens this study presents a compilation of the geochemical datasets collected by the indonesian center for volcanology and geological hazard mitigation cvghm from 2010 current 2016 which provides insights into the evolution of the eruption based on observations of so2 emissions ash componentry ash leachate chemistry and bulk ash geochemistry the eruption can be split into six distinct geochemical phases the initial stage of phreatic summit explosions phase a occurred from august september 2010 during which background so2 emissions averaged 550 180 t d 1 s d an eruptive pause phase b starting in october 2010 abruptly ended in september 2013 with a resumption of conduit clearing eruptions phase c this third phase had a relatively modest background so2 emission rate avg 430 310 t d and produced ash consisting of accidental ejecta with high s cl leachate molar ratios 12 0 8 2 max 34 suggestive of deep sourced magma and or the incorporation of hydrothermal sulfur bearing phases lava extrusion at the summit phase d began in mid december 2013 and was accompanied by relatively low so2 emission rates 360 200 t d and lower but variable s cl leachate ratios 6 3 8 5 the most intense phase of the eruption phase e occurred from mid january to late february 2014 following a major lava dome collapse this period included increased lava extrusion rates dozens of large eruptions per day high so2 emission rates average 1680 1070 t d peak 3800 t d and a dramatic drop in s cl ash leachates to ratios average 1 4 0 5 consistent with increased degassing from shallow magma and the clearing out of sulfurous phases from the old hydrothermal system from march 2014 through the time of writing september 2016 sinabung settled into a relatively steady state of lower activity phase f ash emissions now consist of dominantly juvenile andesitic dacitic material with low s cl leachate ratios average 1 1 0 6 in august 2016 so2 emissions started being measured in a continuous manner using a network of permanent scanning doas instruments background so2 emission rates average 450 290 t d for the entirety of phase f but have been progressively decreasing to an average of 250 300 t d since june 2016 this long term gradual decline in so2 emission rates at sinabung since early 2014 is consistent with an apparent decrease in magma supply and lava effusion rates our conceptual degassing model suggests that large explosions and pyroclastic flows could continue in the near term owing to conduit plugging and dome collapses remaining a major threat until the magma supply rate decreases further and the eruption ends

surface deformation of the barren island volcano andaman sea 2007 2017 constrained by insar measurements evidence for shallow magma reservoir and lava field subsidence abstract barren island situated in the andaman sea is the northernmost active volcano of the sunda arc the oldest known eruption of the volcano was during the period 1787 1832 after about 150 years of quiescence volcanic activity resumed in 1991 and continues since then the magmatic plumbing system of this volcano is largely unknown due to lack of geophysical experiments owing to its remote location we report for the first time time series surface deformation measurements of barren island volcano from interferometric synthetic aperture radar insar during epochs 2007 2011 and 2015 2017 line of sight los deformation of 50 mm yr during 2007 2011 at the cinder cone is interpreted as the co eruptive pressure changes associated with the 2008 2010 eruptions bayesian inversion suggests a shallow magma reservoir at a depth of 578 100 300 m below the summit the depth of the magma reservoir is shallower than that of other volcanoes of the sunda arc probably due to the extensional stress regime imposed by the oblique subduction based on the present studies and previous works we propose a plausible source model for barren island volcano we also discuss potential biases in the present source parameter estimation due to the lack of high quality insar data from both ascending and descending directions significant deformation 15 to 150 mm yr observed along the lava delta of barren island volcano for both the epochs are interpreted as post emplacement subsidence of the lava flow further we characterise the lava flow including volcanic deposits by mapping its spatial extent and elevation changes during 1979 2000 and 2000 2017 periods using geodetic measurements

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

thermomechanics of shallow magma chamber pressurization implications for the assessment of ground deformation data at active volcanoes abstract in this study we utilize thermomechanical models to investigate how magma chambers overpressurize as the result of either magmatic recharge or volatile exsolution by implementing an adaptive reservoir boundary condition we are able to track how overpressure dissipates as the magma chamber expands to accommodate internal volume changes we find that the size of the reservoir greatly impacts the resultant magma chamber overpressure in particular overpressure estimates for small to moderate sized reservoirs 1 10 km 3 are up to 70 lower than previous analytical predictions we apply our models to santorini volcano in greece where recent seismic activity and ground deformation observations suggested the potential for eruption the incorporation of an adaptive boundary condition reproduces mogi flux estimates and suggests that the magma reservoir present at santorini may be quite large furthermore model results suggest that if the magma chamber is 100 km 3 overpressures generated due to the high magma flux may not exceed the strength of the host rock thus requiring an additional triggering mechanism for eruption although the adaptive boundary condition approach does not calculate the internal evolution of the magma reservoir it represents a fundamental step forward from elastic mogi models and fixed boundary solutions on which future investigations of the evolution of the magma can be built

fracture control on type morphology and distribution of parasitic volcanic cones an example from mt etna italy abstract this paper uses a coupled morphometric and stratigraphic analysis of several tens of parasitic pyroclastic cones of the se flank of mt etna volcano italy to explain the structure of a poorly understood actively deforming zone of the volcano moreover we present a new general classification of pyroclastic cones based on the parameterisation of coeval eruption points along the same magma feeding fracture each cone has been studied in detail in order to define its stratigraphic position morphometric characteristics growth evolution in relation to fracture distribution and orientation stress field and morphology of the substratum end members of this classification are at one side a simple circular or elongated edifice that grew around a single eruption point and can be related to a magma feeding fracture constrained by a relatively high confining stress in the substratum or a low magma pressure the other end member is a multiple rifted strongly elongated cone formed along multiple eruption points of a magma feeding fracture constrained by a relatively low confining stress or a high magma pressure lithostratigraphic and historical analyses demonstrate that the cones in this area developed between 15 ka bp and historical times the most recent one in 1669 ad testifying to a high rate of lateral eruption occurrence in the area these cones show n s elongated maximum crater axes n s trending axis of the depressed points of the crater rim and southward and southeastward breaching directions while coeval cones are n s aligned these morphometric characteristics reflect the geometry of n s magma feeding fractures the area can be regarded as a transitional weakness zone between the n s rift and the releasing system represented by the transtensional trecastagni and mascalucia faults indicating an e w oriented local component of extension possibly related to the interplay between the regional timpe fault system and the eastward gravitational spreading of the volcano the azimuth of breaching is controlled by magma feeding fracture orientation and substrate morphology especially in the eastern part of the area where it is influenced by the scarps related to the timpe regional fault system but it is also sensitive to cone development

dynamics of volcanic systems in iceland example of tectonism and volcanism at juxtaposed hot spot and mid ocean ridge systems volcanic systems are swarms of tectonic fractures and basalt volcanoes formed as a result of plate pull as the plates are pulled apart associated with the mid ocean ridges and the magma dynamics of the iceland mantle plume most systems are 40 150 km long 5 20 km wide and develop a central volcano they supply magma to all eruptions in iceland data obtained in the last few years have greatly improved our knowledge of their volcanotectonic environment as a result the geometry of the plume is better constrained and the crust previously considered thin 10 km is now modeled as thick 20 40 km depending on the location of the volcanic systems their activity either decreases or increases faulting in the two main seismic zones from this we can infer that emplacement of the feeder dike to the largest historical eruption in iceland that of laki in 1783 increased shear stress in the south iceland seismic zone and almost certainly triggered the largest m 7 1 in 1784 historical earthquake in ic

the prevalence and significance of offset magma reservoirs at arc volcanoes determining the spatial relations between volcanic edifices and their underlying magma storage zones is fundamental for characterizing long term evolution and short term unrest we compile centroid

locally distributed ground deformation in an area of potential phreatic eruption midagahara volcano japan detected by single look based insar time series analysis abstract although it is difficult to monitor the spatial extent and temporal evolution of local and small magnitude ground inflation this information is vital to assess the potential for phreatic eruption herein we demonstrate the detection of locally distributed ground deformation preceding the enhancement of geothermal activity in the midagahara volcano japan through the application of single look based interferometric synthetic aperture radar analysis in the jigoku dani geothermal area the ground deformation proceeded at a low speed of 4 cm year at most with a spatial extent of 500 m in the east west direction and 250 m in the north south direction the deformation can be recognized to progress from 2007 at the latest to 2010 after which the geothermal activity increased with the collapse of sulfur towers and the appearance of active fumaroles and boiling water on the ground surface the most deformed area corresponds to the geothermal area with the highest activity observed on the ground surface assuming a sill opening model the deformation source is estimated to be located at a depth of 50 m from the surface with a speed of 7 cm year at most which is consistent with the depth of the highly conductive medium inferred from magnetotelluric analyses this may suggest that volcanic fluid and or heat was injected into the fluid rich medium from depth and caused the ground inflation our results demonstrate that high spatial resolution deformation data can be an effective tool to monitor subsurface pressure conditions with pinpoint spatial accuracy during the build up to phreatic eruptions

a large magmatic sill complex beneath the toba caldera an understanding of the formation of large magmatic reservoirs is a key issue for the evaluation of possible strong volcanic eruptions in the future we estimated the size and level of maturity of one of the largest volcanic reservoirs based on radial seismic anisotropy we used ambient noise seismic tomography below the toba caldera in northern sumatra to observe the anisotropy that we interpret as the expression of a fine scale layering caused by the presence of many partially molten sills in the crust below 7 kilometers this result demonstrates that the magmatic reservoirs of present non eroded supervolcanoes can be formed as large sill complexes and supports the concept of the long term incremental evolution of magma bodies that lead to the largest volcanic eruptions

volcano geodesy recent developments and future challenges abstract ascent of magma through earth s crust is normally associated with among other effects ground deformation and gravity changes geodesy is thus a valuable tool for monitoring and hazards assessment during volcanic unrest and it provides valuable data for exploring the geometry and volume of magma plumbing systems recent decades have seen an explosion in the quality and quantity of volcano geodetic data new datasets some made possible by regional and global scientific initiatives as well as new analysis methods and modeling practices have resulted in important changes to our understanding of the geodetic characteristics of active volcanism and magmatic processes from the scale of individual eruptive vents to global compilations of volcano deformation here we describe some of the recent developments in volcano geodesy both in terms of data and interpretive tools and discuss the role of international initiatives in meeting future challenges for the field

accuracy and resolution of alos interferometry vector deformation maps of the father s day intrusion at kilauea we assess the spatial resolution and phase noise of interferograms made from l band advanced land observing satellite alos synthetic aperture radar sar data and compare these results with corresponding c band measurements from european space agency remote sensing satellite ers based on cross spectral analysis of phase gradients we find that the spatial resolution of alos interferograms is 1 3times better than ers interferograms the phase noise of alos i e line of sight precision in the 100 5000 m wavelength band is 1 6times worse than ers 3 3 mm versus 2 1 mm in both cases the largest source of error is tropospheric phase delay vector deformation maps associated with the june 17 2007 father s day intrusion along the east rift zone of the kilauea volcano were recovered using just four alos sar images from two look directions comparisons with deformation vectors from 19 continuous gps sites show rms line of site precision of 14 mm and rms azimuth precision flight direction of 71 mm this azimuth precision is at least 4times better than the corresponding measurements made at c band phase coherence is high even in heavily vegetated areas in agreement with previous results this improved coherence combined with similar or better accuracy and resolution suggests that l band alos will outperform c band ers in the recovery of slow crustal deformation

recent unrest 2002 2015 imaged by space geodesy at the highest risk chilean volcanoes villarrica llaima and calbuco southern andes abstract villarrica llaima and calbuco volcanoes are the most active and dangerous volcanoes in the southern andes and we use interferometric synthetic aperture radar insar observations from multiple satellites ers 2 envisat alos radarsat 2 cosmo skymed terrasar x sentinel 1a and alos 2 to constrain ground deformation that spans episodes of unrest and eruption at all three volcanoes between 2002 and 2015 we find episodes of ground deformation at each volcano which we invert using analytic elastic half space models to make some of the first geophysical inferences about the source depths of potential magma chambers at llaima we interpret that the vei 2 april 3 2009 eruption was preceded by 6 15 cm of precursory ground uplift one month before from a source 5 km below the surface on the western side of the edifice the vei 2 march 3 2015 villarrica eruption was followed by a short lived uplift of 5 cm in the se part of the volcano from a source depth of 6 km the vei 4 april 22 23 2015 calbuco eruption produced 12 cm of coeruptive subsidence from a source depth 8 11 km and offset 2 km s from the summit importantly we do not find clear evidence that the january 1 2008 the march 3 2015 and april 22 2015 eruptions at llaima villarrica and calbuco volcanoes were preceded by either transient or continuous ground uplift there are several possible explanations for the lack of precursory deformation at each volcano it is possible that any precursory deformation occurred only hours before the eruption e g at calbuco pre eruptive inflation was canceled by co eruptive subsidence as we inferred happened during the april 2009 llaima eruption the pre eruptive deformation was too small to be detectable in areas with persistent topography correlated phase delays pressurized source are deep or that open vent volcanoes like villarrica and llaima do not pressurize at all three volcanoes x and c band interferograms decorrelate in a few weeks due to vegetation snow and ice and have persistent atmospheric phase delays that we find cannot be reliably removed with available global weather models the low number of sar acquisitions therefore makes it challenging to reliably measure unaliased deformation we recommend a multi satellite observing strategy with short repeat periods frequently acquired high resolution digital elevation models and with acquisitions during every satellite overflight that may improve the temporal resolution of measurements

interpreting coseismic deformation using holocene coastal deposits wellington new zealand abstract eight holocene palaeoshorelines ps1 ps8 are recognised on miramar peninsula and rongotai isthmus wellington new zealand coseismic uplift cu1 of ps1 by 1 35 1 50 m occurred in 1855 associated with a magnitude 8 1 8 2 earthquake centred on the wairarapa fault some 20 km east of the study area the other palaeoshorelines ps2 ps8 are inferred to represent earlier coseismic uplift events with a total uplift of 8 1 m over the past 6500 years these coseismic uplift events numbered cu2 cu8 have estimated ages in cal bp of 7290 5730 years cu8 and cu7 5970 5730 years cu6 5400 4890 years cu5 3410 2740 years cu4 and cu3 and 940 260 years cu2 only four coseismic uplift events at miramar cu8 cu6 cu4 and cu1 are likely to have been caused by movement on the wairarapa fault the others probably relate to movements of other active faults in the wellington area

monitoring forecasting collapse events and mapping pyroclastic deposits at sinabung volcano with satellite imagery abstract during the ongoing 2013 present eruption of sinabung volcano north sumatra we have routinely used a variety of satellite remote sensing data to observe and forecast lava dome and lava flow collapse events to map the resulting pyroclastic deposits and to estimate effusion rates in this paper we focus on the first two years of the current eruption september 2013 december 2015 and we summarize major events in 2016 we divide the eruption into 5 major phases 1 phreatomagmatic july 2013 18 december 2013 2 first dome growth and collapse 18 december 2013 10 january 2014 3 lava flow 10 january 2014 mid september 2014 4 second lava dome and collapse mid september 2014 july 2015 5 lava dome collapse and ash explosion phase august 2015 present throughout the eruption remotely sensed information has been instrumental in assessing the stability of the lava dome and flow and to forecast collapse events that produce pyroclastic density currents pdcs block and ash flows co ignimbrite surges and blasts forecasts based on remote sensing data in combination with seismic geodetic and gas monitoring data have also helped inform decisions related to alert levels and evacuations relatively unusual aspects of the sinabung eruption include the transition from dome to flow morphology phase 2 to phase 3 transition and the frequent occurrence during phase 3 of collapses from the lava flow front and flow margins collapses that produced extensive pyroclastic density currents by analogy to the well known merapi type collapses and pyroclastic deposits we propose that lava flow front and flow margin collapses with associated pdcs be known as sinabung type although detailed study of deposits has not been possible due to continuing hazards our observations suggest that the transition from lava dome to lava flow and the occurrence of flow front and flow margin collapses reflect a particular combination of lava viscosity and steepness of slope our observations also show clear evidence of at least one slope parallel high velocity and dilute pdc a blast that emanated from a lava margin collapse site 500 m downslope from the vent this 1 february 2014 blast downed and singed a forest out to at least 3 9 km from the collapse site and killed 16 people we also use a combination of field and remotely sensed data to map the distribution of sinabung deposits we estimate eruptive volumes and extrusion rates by combining sequential measurements of lava surface and pyroclastic flow areas with thickness estimates derived from simple geometric assumptions oblique photographs and digital elevation models dems derived from remotely sensed data our estimates of short term effusion rates vary widely on a daily to weekly basis from 20 m3 s 1 in a few cases periods of increased extrusion precede lava flow front collapses by a few days to a week suggesting delays in transmittance of effusion pulses as lava moves from vent to flow front we find that as of 1 january 2016 the total area of deposits is 107 m2 and their approximate deposit volume is about 0 3 km3 equivalent to 0 2 km3 dense rock equivalent dre we anticipate that our deposit maps will be valuable in the future as a framework for the study of the magmatic and textural evolution of eruptive products through time

diagenesis of titaniferous minerals in jurassic sandstones from the norwegian sea abstract ti oxides anatase and in some cases rutile that attain various textures and modes of occurrence are minor yet very common authigenic minerals in the jurassic sandstones of the haltenbanken oil field offshore central norway these ti oxides pyrite commonly occur as pseudomorphs after detrital fe ti oxides usually ilmenite titanomagnetite and titanohematite pseudomorphs comprised of ti oxides as well as quartz and or calcite are believed to result upon alteration of detrital sphene ti oxides have also resulted upon kaolinization of detrital biotite and less significantly muscovite authigenic sphene occurs in very small amounts in some of the jurassic sandstones at burial depths 2000 m it displays three major crystallization habits 1 as almond shaped crystals that have most commonly crystallized on authigenic calcite 2 as discrete rhombic crystals that have crystallized adjacent to altered fe ti oxides and biotite and 3 as aggregates of euhedral and subhedral crystals these crystallization habits suggest that sphene has been formed by reaction of si and ti ions with calcite crystallization from pore fluids and replacement of fe ti oxides respectively microprobe analyses of authigenic sphene revealed that al and fe 3 substitute ti in appreciable amounts average 0 08 and 0 04 moles per 5 oxygen atoms respectively whereas substitutions of ca by mn k and na and of ti by mg are negligible

a survey of volcanic deformation on java using alos palsar interferometric time series of the hundreds of volcanic centers throughout the indonesian archipelago few are adequately monitored for pre eruptive activity due to socioeconomic and logistical barriers with the result that volcanic hazards in the region are not well quantified the advent of satellite borne l band synthetic aperture radar provides an opportunity for detection and measurement of volcanic deformation over broad regions in heavily vegetated tropical island arcs we use data from the palsar instrument on the japanese alos satellite to conduct a comprehensive survey of volcanic deformation on the indonesian island of java over a time period of two years 2007 2008 to obtain the most complete temporally continuous record of ground deformation we use a temporally overlapping set of short time interval radar image pairs to produce a deformation time series consistent with previous results from other regions our survey suggests that volcanoes experiencing small eruptions are typically fed by magma bodies too small and or too shallow or deep to produce a recognizable insar signal however we identified a deformation event at lamongan volcano which is likely linked to a magmatic intrusion at several kilometers depth and a second one at slamet volcano at a shallower depth that may have been related to a subsequent eruption this initial test of a broad application of l band data allowed us to better define the satellite imaging criteria required for successful observation as well as developing a useful methodology for monitoring deformation over a wide region

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

emplacement of dikes sills and crustal magma chambers at divergent plate boundaries abstract a model of dike emplacement at divergent plate boundaries is developed which predicts that below the uppermost 1 3 km of the oceanic crust the number and lengths of dikes in any particular swarm should increase but that the thickness should decrease with depth in the crust these predictions are supported by field observations it is proposed that rapid injections of dikes at divergent plate boundaries may temporarily alter the normal stress field in such a way that at a certain level in the crust subsequent dikes change into sills such sills may develop into crustal magma chambers either when many nearby sills combine into a large one or when an initial sill absorbs the magma of many dikes that enter it in a rapid succession while the sill is liquid for the fastest spreading ridges the initial thickness of a sill that is to develop into a crustal chamber need only attain 20 m whereas at the slowest spreading ridges the initial thickness must exceed 170 m because thin sills are much more likely to form than thick sills the probability of sills developing into crustal chambers increases with dike intrusion frequency hence with spreading rate furthermore the model predicts first that with increasing spreading rate the length of the chamber along the ridge axis should increase and second that the most likely site for magma chambers is at depths of 2 4 km both these predictions are supported by available data

3 d seismic tomographic study of sinabung volcano northern sumatra indonesia during the inter eruptive period october 2010 july 2013 abstract we estimated 3d p wave velocity vp s wave velocity vs and vp vs tomographic structures in and around the sinabung volcano area northern sumatra indonesia during the intereruptive period between october 2010 and july 2013 using high quality p and s wave phases from 600 local volcano tectonic vt earthquakes and 5000 phase picks we used the iterative damped least squares method of simulps12 to simultaneously invert for the velocity structure and hypocenter relocations we find that the majority of the vt earthquakes locate beneath sinabung volcano to depths of about 8 km with distal hypocenters dominantly to the north and northwest of the summit we find six anomalous regions with the most notable including an area of low seismicity high vp vs and low vp at depths of around 5 km slightly south of the summit we believe this anomaly most likely represents hot material with some partial melt that may be the source for the 2010 phreatic eruptions and continued unrest throughout the study period we also find a region below the summit with high seismicity high vp high vs and low vp vs that we believe likely represents old intrusive material that has been fractured by the processes of the 2010 phreatic eruptions other shallow anomalous values of vp vs and vp vs are consistent with the known geology of sinabung anomalies of high vp and vs likely represent old well consolidated rock and are observed to the sw and ne of sinabung while low vp low vs and high vp vs likely represent increased fracture densities temperatures or gas contents in geothermal features to the west of the summit finally we compare our results to those of the tomographic study of the october to november 2013 eruptive period in nugraha et al 2019 and find evidence that suggests magma rose from the lower region imaged in our study to within a few kilometers of the surface

modification of the regional stress field by magma intrusion and formation of tabular granitic plutons granitic intrusions typically have large aspect ratios with an horizontal major axis about 4 8 times the vertical one combined structural and geophysical gravity data allows distinction between two main types of plutons flat floored plutons the most represented are rather thin 3 4 km and extend in every horizontal direction with a gently dipping floor toward several root zones these contrast with the thick 10 km wedge shaped plutons more elongated in one direction with a few root zones we interpret the shape of flat floored plutons as the result of a switch in the stress pattern caused by the emplacement of magma magma is preferentially emplaced into the plane 1 2 perpendicular to the least principal stress component 3 this plane is initially vertical except for compressional conditions this dilation causes a local re organization of the stress field by increasing the minor and intermediate principal stress components when they overcome the lithostatic load a drastic change in the orientation of the opening plane results switching from vertical to horizontal this constitutes a change from vertically oriented dike shaped intrusions to sub horizontal laccoliths crustal anisotropies vertical faults or horizontal zones of different rheology also contribute to modify the shape of the intrusions the continual exchange of the intermediate stress components also explains the rounded shape of intrusions in strongly extended regions our analysis suggests that the concept of magmas rising to a level of neutral buoyancy is not applicable to many settings rather we suggest that the feedback between displacements resulting from magma intrusion and the local stress pattern controls the geometry of magma emplacement

igneous sills record far field and near field stress interactions during volcano construction isle of mull scotland abstract sill emplacement is typically associated with horizontally mechanically layered host rocks in a near hydrostatic far field stress state where contrasting mechanical properties across the layers promote transitions from dykes or inclined sheets to sills we used detailed field observations from the loch scridain sill complex isle of mull uk and mechanical models to show that layering is not always the dominant control on sill emplacement the studied sills have consistently shallow dips 1 25 and cut vertically bedded and foliated metamorphic basement rocks and horizontally bedded cover sedimentary rocks and lavas horizontal and shallowly dipping fractures in the host rock were intruded with vertical opening in all cases whilst steeply dipping discontinuities within the sequence i e vertical fractures and foliation in the basement and vertical polygonal joints in the lavas were not intruded during sill emplacement mechanical models of slip tendency dilation tendency and fracture susceptibility for local and overall sill geometry data support a radial horizontal compression during sill emplacement our models show that dykes and sills across mull were emplaced during nw se horizontal shortening related to a far field tectonic stress state the dykes generally accommodated phases of ne sw horizontal tectonic extension whereas the sills record the superposition of the far field stress with a near field stress state imposed by emplacement of the mull central volcano we show that through detailed geometric characterisation coupled with mechanical modelling sills may be used as an indication of fluctuations in the paleostress state

geothermal systems on the island of java indonesia abstract this paper presents an overview of the geothermal systems on the island of bali indonesia physicochemical data of hot springs and shallow geothermal wells were collected from four geothermal locations penebel batur banjar and banyuwedang the concentrations for the three main anions varied significantly indicating a different geothermal history the values for cl ranged from 0 1 to 1000 mg l for hco3 from 20 to 2200 mg l and for so42 from 0 1 to 500 mg l although the island of bali is underlain by carbonate rocks a carbonate host rock for the geothermal reservoirs could not be confirmed because the ca2 mg2 hco3 molar ratios were approximately 0 4 well below 1 0 and the k mg ratios were approaching those of a calc alkaline rock reservoir the hco3 of the thermal waters correlated with ca2 mg2 sr2 and k indicating water rock interaction in the presence of carbonic acid phase separation was inferred for the bedugul and banjar geothermal systems because of relatively high b cl ratios boron isotopes were determined for selected samples with values ranging from 11b of 1 3 to 22 5 nbs 951 the heavy 11b of 22 5 together with a low b cl ratio indicated seawater input in the banyuwedang geothermal system the hydrogen and oxygen isotopic composition of the thermal water plotted along the global meteoric water line gmwl and close to the mean annual value for precipitation in jakarta indicating a meteoric origin of the geothermal water comparison of the si na k na k ca and na li geothermometers with actual reservoir temperature measurements and physicochemical considerations led to the conclusion that the na li thermometer provided most reliable results for the determination of geothermal reservoir temperatures on bali using this thermometer the following reservoir temperatures were calculated 1 penebel bedugul from 235 to 254 c 2 batur 240 c and 3 banjar 255 c due to seawater input this thermometer could not be applied to the banyuwedang geothermal system there application of a sio2 thermometer indicated a reservoir temperature below 100 c

physical controls and depth of emplacement of igneous bodies a review the formation and growth of magma bodies are now recognised as involving the amalgamation of successive discrete pulses such as sills sills would thus represent the building blocks of larger plutons sensu lato mechanical and thermal considerations on the incremental development of these plutons raise the issue of the crustal levels at which magma can stall and accumulate as sills reviewing the mechanisms that could a priori explain sill formation it is shown that principal physical controls include rigidity contrast where sills form at the interface between soft strata overlaid by comparatively stiffer strata rheology anisotropy where sills form within the weakest ductile zones and rotation of deviatoric stress where sills form when the minimum compressive stress becomes vertical comparatively the concept of neutral buoyancy is unlikely to play a leading control in the emplacement of sills although it could assist their formation these different controls on sill formation however do not necessarily operate on the same length scale the length scale associated with the presence of interfaces separating upper stiffer layers from lower softer ones determines the depth at which rigiditycontrolled sills will form on another hand the emplacement depths for rheology controlled sills is likely to be determined by the distribution of the weakest ductile zones whereas the emplacement depth of stress controlled sills is determined by a balance between the horizontal maximum compressive stress which favours sill formation and the buoyancy of their feeder dykes which drives magma vertically ultimately the depth at which a sill forms depends on whether crustal anisotropy or stress rotation is the dominant control i e which of these processes operates at the smallest length scale using dimensional analysis it is shown that sill formation controlled by remote stress rotation would occur on length scales of hundreds of meters or greater this therefore suggests that crustal heterogeneities and their associated anisotropy are likely to play a larger role than remote stress rotation in controlling sill emplacement unless these heterogeneities are several hundred meters or more apart this also reinforces the role of local stress barriers owing to interactions between deviatoric stress and crustal heterogeneities in the formation of sills

copper enrichment in arc magmas controlled by overriding plate thickness the characteristics of magmas typically associated with porphyry copper deposits are thought to be imparted in the mantle statistical assessment of over 40 000 geochemical analyses of magmatic rocks formed in subduction zones worldwide however shows that the characteristics of these magmatic rocks are systematically controlled by the thickness of the arc crust

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

structural control on late miocene to quaternary volcanism in the ne honshu arc japan 1 volcanological and structural field data are used to define the tectonic control on the n s volcanic arc of ne honshu japan since late miocene during late miocene pliocene bimodal products were mainly erupted from along arc and ne sw aligned and elongated calderas the deformation pattern mostly consisted of n s dextral faults and subordinate ne sw extensional structures produced by ne sw compression this pattern because of the indentation of the kuril sliver is similar to that of oblique convergence settings magma rose and extruded along ne sw areas of localized extension created by the dextral faults these extensional areas were uncoupled with regard to those e w trending inferred to have focused the rise of melts from the subducting slab in the mantle during quaternary a larger amount of andesite was mainly erupted from along arc and e w aligned and elongated stratovolcanoes the deformation pattern mostly consisted of n s thrust faults and subordinate e w extensional structures produced by e w compression resulting from orthogonal convergence due to the variation in the absolute motion of the pacific plate the e w extensional structures are the shallowest expression of e w trending hot mantle fingers suggesting mantle crust coupling for the rise of magma such a coupling ensures 1 higher extrusion and 2 mixing between a deeper mafic and a shallower felsic magma generating the andesites the significantly larger volumes ma 1 200 km 1 of length of the arc of magma erupted during quaternary show that pure convergence conditions do not necessarily hinder the rise and extrusion of magma

the tectonic framework of the sumatran subduction zone the great aceh andaman earthquake of december 26 2004 and its tragic consequences brought the sumatran region and its active tectonics into the world s focus the plate tectonic setting of sumatra has been as it is today for tens of millions of years and catastrophic geologic events have likely been plentiful the immaturity of our understanding of great earthquakes and other types of geologic hazards contributed to the surprise regarding the location of the 2004 earthquake the timing however is probably best understood simply in terms of the inevitability of the infrequent events that shape the course of geologic progress our best hope is to improve understanding of the processes involved and decrease our vulnerability to them

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

characterization of open and closed volcanic systems in indonesia and mexico using insar time series 1 we use 2007 2011 advanced land observing satellite alos data to perform an arc wide interferometric synthetic aperture radar insar time series survey of the trans mexican volcanic belt tmvb and to study time dependent ground deformation of four indonesian volcanoes selected following the 2007 2009 study of chaussard and amelung 2012 our objectives are to examine whether arc volcanoes exhibit long term edifice wide cyclic deformation patterns that can be used to characterize open and closed volcanic systems and to better constrain in which cases precursory inflation is expected we reveal deformation cycles at both regularly active and previously inactive indonesian volcanoes but we do not detect deformation in the tmvb reflecting a lower activity level we identify three types of relationships between deformation and activity inflation prior to eruption and associated with or followed by deflation kerinci and sinabung inflation without eruption and followed by slow deflation agung and eruption without precursory deformation merapi colima and popocatepetl at merapi no significant deformation is detected even during eruption the first two cases correspond to closed volcanic systems and suggest that the traditional model of magmatic systems and eruptive cycles do apply to andesitic volcanoes i e inflation and deflation episodes associated with magma accumulation or volatile exsolution in a crustal reservoir followed by eruptions or in situ cooling in contrast the last case corresponds to open volcanic systems where no significant pressurization of the magmatic reservoirs is taking place prior to eruptions and thus no long term edifice wide ground deformation can be detected we discuss these results in terms of insar s potential for forecasting volcanic unrest

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

the mechanics of unrest at long valley caldera california 1 modeling the geometry of the source using gps leveling and two color edm data we surveyed 44 existing leveling monuments in long valley caldera in july 1999 using dual frequency global positioning system gps receivers we have been able to tie gps and leveling to a common reference frame in the long valley area and computed the vertical deformation by differencing gps based and leveled orthometric heights the resurgent dome uplifted 74 7 cm from 1975 to 1999 to define the inflation source we invert two color edm and uplift data from the 1985 1999 unrest period using spherical or ellipsoidal sources we find that the ellipsoidal source satisfies both the vertical and horizontal deformation data whereas the spherical point source cannot according to our analysis of the 1985 1999 data the main source of deformation is a prolate ellipsoid located beneath the resurgent dome at a depth of 5 9 km 95 bounds of 4 9 7 5 km this body is vertically elongated has an aspect ratio of 0 475 95 bounds are 0 25 0 65 and a volume change of 0 086 km3 95 bounds are 0 06 0 13 km3 failure to account for the ellipsoidal nature of the source biases the estimated source depth by 2 1 km 35 and the source volume by 0 038 km3 44

effect of mechanical heterogeneity in arc crust on volcano deformation with application to soufriere hills volcano montserrat west indies 1 analyses of volcano surface deformation are commonly based on models that assume mechanical homogeneity of rocks surrounding the causative pressure source here we present a detailed study that shows the differences in deduced surface deformation caused by source pressurization accounting for either mechanical homogeneity or mechanical heterogeneity of encasing rocks in a volcanic arc setting using finite element models accounting for crustal heterogeneity from seismic data we test for a range of source geometries and intermediate crustal depths and explore the misfits of deduced source parameters from the two families of models in the second part of this study we test the results from the generic study against cgps data from two deformation periods the 2003 2005 ground inflation and the 2005 2007 ground deflation at soufriere hills volcano montserrat west indies to inform on source parameters accounting for a variable crustal rigidity with depth as deduced by seismic analysis beneath montserrat we find the data to be best explained by pressurization and depressurization of a slightly prolate midcrustal magma chamber that is centered between 11 5 and 13 km below sea level about 640 m ne of the active vent considering source dimension and source pressure changes we demonstrate that magma compressibility and viscoelasticity of host rocks considerably affect dynamics in the midcrustal magmatic system of soufriere hills volcano and need to be accounted for as first order effects in geodetic data analyses and modeling

an experimental investigation of sill formation and propagation in layered elastic media a series of experiments are described where dyed water a magma analogue was intruded into solid gelatine a crustal analogue to investigate the formation of sills we considered a layered gelatine system with contrasting adjacent layers by varying the density and rigidity of the gelatine we found that experimental sills form when the upper layer is more rigid than the lower layer with intrusion occurring in a plane directly below the interface experimental dykes were observed to propagate to the surface when the young s modulus ratio of upper to lower gelatine layers was less than one experimental dyke arrest occurred when the upper layer was more rigid and the interface was strong two varieties of experimental sill formed when the upper layer was more rigid than the lower layer and the interface was sufficiently weak the form of the intrusion depends on the balance of driving pressures and the young s modulus ratio of contrasting adjacent layers when the rigidity ratio is high and there is a large driving pressure the experimental feeder dyke completely converts to propagate as a sill however when the rigidity ratio and driving pressure are both close to one a dyke sill hybrid forms under these conditions the experimental sill formation is accompanied by contemporaneous dyke intrusion into the overlying more rigid layer during sill propagation deformation structures such as faults and en echelon fractures are formed into the lower layer experimental sill propagation dynamics are controlled by viscous dissipation along the length of the sill causing acceleration with increasing length our study suggests that rigidity contrasts may play a major role in the location of sills and development of igneous complexes in ancient cratonic areas the moho is a suitable site for the preferential formation of sills with higher rigidity continental crust overlying weaker mantle mantle plumes impacting ancient continents provide a situation in which large sills can form to fractionate prior to eruption of flood basalts the boundary between the upper and lower crust conrad discontinuity may provide a preferential focus for the emplacement of sheets of silicic magma at continental arcs where the lower crust is weakened by prolonged heating and possible hydration

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

an insar based survey of volcanic deformation in the southern andes we use interferometric synthetic aperture radar insar to search for surface deformation in the southern andes 40 s 46 s and 49 s 53 s associated with magmatic processes although the available data are not optimal we can constrain the amount of volcanic deformation at about 27 holocene volcanoes between the years 1993 1999 we detect inflation of cerro hudson volcano following its 1991 eruption and use spherical and non spherical models to constrain the source of deformation to be between 4 and 8 km below sea level we measure the rate of deformation to be about 5 cm year in the radar line of sight and infer that the maximum deformation could exceed 10 cm year in the center of the caldera within the errors of the measurements the rate of deformation is constant from 1993 1998 10 30 10 6 m 3 year at this rate 100 200 years is required to accumulate the volume of material erupted in 1991