sentinel 1 observation of the 2017 sangsefid earthquake northeastern iran rupture of a blind reserve slip fault near the eastern kopeh dagh abstract new satellites are now revealing insar based surface deformation within a week after natural hazard events quick hazard responses will be more publically accessible and provide information to responding agencies here we used sentinel 1 interferometric synthetic aperture radar insar data to investigate coseismic deformation associated with the 2017 sangsefid earthquake which occurred in the southeast margin of the kopeh dagh fault system the ascending and descending interferograms indicate thrust dominated slip with the maximum line of sight displacement of 10 5 and 13 7 cm respectively the detailed slip distribution of the 2017 sangsefid mw6 1 earthquake inferred from geodetic data is presented here for the first time although the insar interferograms themselves do not uniquely constrain what the primary slip surface is we infer that the source fault dips to southwest by analyzing the 2 5 d displacement field decomposed from the insar observations the determined uniform slip fault model shows that the dip angle of the seimogenic fault is approximately 40 with a strike of 120 except for a narrower fault width than that predicted by the empirical scaling law we suggest that geometric complexities near the kopeh dagh fault system obstruct the rupture propagation resulting in high slip occurred within a small area and much higher stress drop than global estimates the insar determined moment is 1 71 1018 nm with a shear modulus of 3 32 1010 n m2 equivalent to mw 6 12 which is consistent with seismological results the finite fault model the west dipping fault plane reveals that the peak slip of 0 90 m occurred at a depth of 6 3 km with substantial slip at a depth of 4 10 km and a near uniform slip of 0 1 m at a depth of 0 2 5 km we suggest that the sangsefid earthquake occurred on an unknown blind reverse fault dipping southwest which can also be recognised through observing the long term surface effects due to the existence of the blind fault

monitoring volcano slope instability with synthetic aperture radar a review and new data from pacaya guatemala and stromboli italy volcanoes abstract volcano slope instability manifests in many forms ranging from steady state to punctuated movement or shallow erosion to deep seated spreading the interplay of gravity magmatic or hydrothermal fluids and often active tectonics on a volcanic edifice results in complex spatial and temporal variations in deformation kinematics while this makes the recognition assessment and monitoring of volcano slope instability challenging advancements in synthetic aperture radar sar technology have significantly accelerated our knowledge of instability phenomena and our ability to assess their hazards this review discusses the applications and challenges of sar imagery to various slope instabilities at volcanoes around the world sar amplitude images are powerful tools for mapping areas of geomorphological changes these snapshots can be combined using interferometric sar insar to create multi temporal deformation maps that provide unique information on the evolution of slope failures space borne insar has become an economic way to detect changes at volcanoes at very high resolution ground based insar gbinsar can produce frequent sar images on the order of seconds to minutes propelling insar from monitoring to surveillance and early warning applications however interpreting insar derived ground deformation signals related to volcano slope instability is still challenging deformation from magma rise or variations in hydrothermal systems may be inseparable from persistent deep seated flank motion similarly shallow or localized ground motion may occur in overlap with thermal contraction or subsidence of newly emplaced lava or tephra deposits if triggered to failure landslides can vary over several magnitudes from small volume rock falls that pose only a localized hazard to large volume debris avalanches capable of travelling tens of kilometers away from the source these collapses can have cascading hazards if accompanied by directed blasts or tsunamis emphasizing the need for continued advancement of our understanding of these events and their consequences to highlight the utility of sar for measuring and monitoring mass movement two case studies of stromboli italy and pacaya guatemala volcanoes are discussed in detail where recent instability events persistent volcanic activity and ground truth constraints have resulted in excellent case histories in applying sar imagery to understand these potentially hazardous slope instabilities

viscous heating in silicate melts an experimental and numerical comparison 1 the transition from newtonian to non newtonian flow of silicate melts is commonly manifested as shear thinning at conditions of high stress and strain rate shear thinning may strongly influence the dynamics of magmatic flows but the details of its microscopic origins are not fully understood here we consider viscous heating and thermomechanical coupling as a potential cause of shear thinning we compare the results of laboratory uniaxial compression experiments of a silicate melt with the results of thermomechanical numerical simulations corresponding to the experimental setup both the experimental and numerical results concord and indicate that the reduction of the temperature dependent viscosity in flowing silicate melts is a result of viscous heating viscous heating was quantified for glasses with viscosities ranging from 108 to 1011 pa s and strain rates from 10 5 to 100 s 1 the results of 48 compression experiments indicate that the transition from newtonian to non newtonian flow in the silicate melt occurs at a brinkmann number i e ratio of heat gained to heat lost around 1 whereas brittle behavior dominates the melt deformation when the deborah number i e ratio of viscoelastic relaxation time to characteristic deformation time is larger than around 0 01 the observed viscous heating significantly contributes to the viscosity decrease observed in high stress strain rate experiments and questions our current understanding of the non newtonian deformation behavior of silicate melts

fogo volcano cape verde islands seismicity derived constraints on the mechanism of the 1995 eruption seismic data recorded in the vicinity of the active vent of the 1995 fogo eruption global volcanism network bulletin 1995 20 3 2 4 is used to constrain the associated stress field and deformation using the frequency content of the seismograms to distinguish between brittle fracture of cold host rock and deformation in the vicinity of the intruding magma a sub vertical dyke with 060 strike is identified as the feeder of the eruption and delineated down to a depth of about 4 km the local stress field during the eruption is estimated from composite focal mechanisms besides the expected 3 direction normal to the dyke a group of focal solutions point to a stress field with nearly dyke parallel 3 which is interpreted as a re adjustment of the edifice following the eruption maybe partially controlled by gravity this effect may have increased the instability of the steep eastern flank of the island since the deformation detected during the magma drainback is compatible with predominantly dip slip motion on east dipping surfaces

giant quaternary landslides in the evolution of la palma and el hierro canary islands in the past large morphological escarpments in the canaries have been generally related to explosive and or erosive processes recent onshore and offshore investigations drastically changed this interpretation by providing evidence of the importance of giant lateral collapses in the evolution of the islands especially in their earlier stages of growth giant landslide scars and deposits are readily observed both onshore and offshore in the younger western canaries and seem to be a common feature of the development of the entire archipelago at least one catastrophic collapse is apparent on la palma the cumbre nueva giant landslide which occurred about 560 ka ago this collapse removed some 200 km3 of central western la palma forming a large embayment three successive giant landslides and evidence of an aborted attempt at another are seen in the island of el hierro the combined volume of those collapses estimated at about 400 500 km3 considerably exceeds the present subaerial volume of the island about 140 km3 giant landslides and erosion during the past million years have removed more than half of the total subaerial volume of la palma and el hierro

delamination and detachment of a lithospheric root abstract orogens can be formed by shortening of the lithosphere on time scales much shorter than that of thermal diffusion for time scales of a few ma the major part of the uplift of an orogen which may occur during the transition from crustal shortening to extension may be due to delamination of the mantle lithosphere rather than to convective thinning the negative buoyancy forces of a lithospheric root may cause lateral shortening while the lithospheric root delaminates peels off from the crust detaches and is replaced by hot upwelling asthenosphere this provides a large input of heat into the crust geological observations show that the late orogenic phase may be characterized by volcanic activity high temperature low pressure metamorphism extension high heat flow and a rapid within a few ma increase of the topography we present dynamically and thermally consistent numerical models of the evolution of an orogenic root mantle rheology is based on laboratory data of olivine while models with the rheology of olivine do not allow for delamination due to its very high viscosity the incorporation of a quasi brittle rheology is necessary for modelling delamination of the mantle lithosphere successful delamination models are always associated with a rapid change in topography we examined the parameter range of our models and found different regimes of behaviour of the orogenic root of the mantle lithosphere no delamination delamination delamination and full detachment for a fixed viscosity of the upper crust of 1023 pa s delamination occurs for a range of viscosities of 1023 pa s to 1020 pa s for the lower crust depending on the thickness of the lithospheric root but full detachment of the delaminated lithospheric slab only occurs if the viscosity of the lower crust is greater than approximately 1021 pa s hot asthenosphere is welling up into the gap opening during delamination further implications of our models are lithospheric roots or unsupported slabs of at least 100 170 km depth extent are needed to provide sufficient negative buoyancy to allow delamination and detachment in all delamination models significant amounts of lower crustal material are subducted into the mantle in applying our models to selected orogens we argue that mantle delamination may have played an important role in the variscan and the himalayan orogenies

quasi adiabatic instabilities associated with necking processes of an elasto viscoplastic lithosphere abstract necking of the lithosphere involves complex nonlinear thermal mechanical feedback mechanisms in an elasto viscoplastic plate the mode of extension of such plates relies on the mechanical properties of the upper part of the mantle and on the nucleation of ductile faults within the lithosphere our numerical model addresses the key problem of controls of ductile failure of the strongest part in the lithosphere it is found that a small heterogeneity within this strong part can nucleate quasi adiabatic shear bands these develop spasmodically with time as finite amplitude instabilities with increasing temporal and length scales the largest shear zone takes about 100 000 years to propagate through the entire lithosphere and can lead to a thermal instability for an ambient mantle temperature larger than 900 k in our numerical model thermal runaway occurs when the plate is severed the temperature rise of the thermal instability is a function of the creep law exponent n and can be quenched for a lower n and smaller activation energy the model is applicable to the problem of onset of continental break up and holds the key to ductile instabilities in the earth s lithosphere the changing hot surface temperature on venus might also have precipitated lithospheric instabilities in the past

pycnobathic currents over the upper continental slope abstract the dynamic interaction of a sloping seafloor with along isobath density variation is calculated for cases involving a sharp pycnocline and a surface to bottom front pycnocline depth is supposed to vary in the alongshore direction only over a sloping plane seafloor the bottom trace of the surface to bottom front is supposed to cut across isobaths the calculations are diagnostic and make use of linearized equations with a linear bottom friction term the results illustrate the manner in which cross isobath baroclinic flow is converted at the slope into a barotropic flow field with velocities nearly parallel to the isobaths the forward portion of the slope that which lies in the direction of kelvin wave propagation only is affected if there is only one inflow or outflow region however for equal and opposite inflow and outflow a closed circulation pattern arises connecting these two regions accompanied by a secondary closed circulation cell forward of both the inflow and outflow legs

caldera or flank collapse in the fogo volcano what age consequences for risk assessment in volcanic islands abstract the target of this study is the fogo island in cape verde where the hazards caldera and or flank collapse and the timing 120 ka or younger are still controversial using high resolution dem field geological and structural analysis and high precision k ar dating we produced an age calibrated volcanic stratigraphy of fogo s summit cha das caldeiras for the last ca 220 ka from this we infer the following evolution and associated processes 1 the fogo volcano formed during seven stages of construction and partial destruction 2 three flank collapses can be recognised the biggest of which occurred between 60 and 43 ka 3 this collapse occurred retrogressively producing at least two distinct collapse blocks 4 the innermost collapse was only partial forming a flat step where a new volcano pico do fogo grew and formed the cha das caldeiras literally flat of the calderas 5 the removal of the buttressing eastern flank by the outermost collapse can be responsible for the seemingly caldera structure 6 the growing load of the young volcano can produce a new flank failure following the innermost fault 7 the young and closely spaced collapse ages here reported indicate a significant risk for the inhabitants of fogo in particular and for the whole cape verde archipelago and atlantic seaboard if a tsunami is produced by a future catastrophic flank collapse

slip distribution of the 2015 lefkada earthquake and its implications for fault segmentation this work was partially supported by the uk natural environmental research council nerc through ne k011006 1 ne p008828 1 and the centre for the observation and modelling of earthquakes volcanoes and tectonics comet ga 13 m 031 http comet nerc ac uk

inversion of surface deformation data for rapid estimates of source parameters and uncertainties a bayesian approach new satellite missions e g the european space agency s sentinel 1 constellation advances in data downlinking and rapid product generation now provide us with the ability to access space geodetic data within hours of their acquisition to truly take advantage of this opportunity we need to be able to interpret geodetic data in a prompt and robust manner here we present a bayesian approach for the inversion of multiple geodetic data sets that allows a rapid characterization of posterior probability density functions pdfs of source model parameters the inversion algorithm efficiently samples posterior pdfs through a markov chain monte carlo method incorporating the metropolis hastings algorithm with automatic step size selection we apply our approach to synthetic geodetic data simulating deformation of magmatic origin and demonstrate its ability to retrieve known source parameters we also apply the inversion algorithm to interferometric synthetic aperture radar data measuring co seismic displacements for a thrust faulting earthquake 2015 mw 6 4 pishan earthquake china and retrieve optimal source parameters and associated uncertainties given its robustness and rapidity in estimating deformation source parameters and uncertainties our bayesian framework is capable of taking advantage of real time geodetic measurements thus our approach can be applied to geodetic data to study magmatic tectonic and other geophysical processes especially in rapid response operational settings e g volcano observatories our algorithm is fully implemented in a matlab based software package geodetic bayesian inversion software that we make freely available to the scientific community

hotspot volcanism close to a passive continental margin the canary islands the canarian archipelago is a group of volcanic islands on a slow moving oceanic plate close to a continental margin the origins of the archipelago are controversial a hotspot or mantle plume a zone of lithospheric deformation a region of compressional block faulting or a rupture propagating westwards from the active atlas mountains fold belt have been proposed by different authors however comparison of the canarian archipelago with the prototypical hotspot related island group the hawaiian archipelago reveals that the differences between the two are not as great as had previously been supposed on the basis of older data quaternary igneous activity in the canaries is concentrated at the western end of the archipelago close to the present day location of the inferred hotspot this is the same relationship as seen in the hawaiian and cape verde islands the latter archipelago associated with a well defined but slow moving mantle plume shows anomalies in a plot of island age against distance which are comparable to those seen in the canary islands these anomalies cannot therefore be used to argue against a hotspot origin for the canaries individual islands in both archipelagoes are characterized by initial rapid growth the shield building stages of activity followed by a period of quiescence and deep erosion erosion gap which in turn is followed by a post erosional stage of activity the absence of post shield stage subsidence in the canaries is in marked contrast with the major subsidence experienced by the hawaiian islands but is comparable with the lack of subsidence evident in other island groups at slow moving hotspots such as the cape verdes comparison of the structure and structural evolution of the canary islands with other oceanic islands such as hawaii and reunion reveals many similarities these include the development of triple mercedes star rift zones and the occurrence of giant lateral collapses on the flanks of these rift zones the apparent absence of these features in the post erosional islands may in part be a result of their greater age and deeper erosion which has removed much of the evidence for their early volcanic architecture we conclude that the many similarities between the canary islands and island groups whose hotspot origins are undisputed show that the canaries have been produced in the same way

along slope variability of barotropic transport in the nordic seas simplified dynamics tested against observations 1 the present study combines simple geostrophic considerations and observational data to examine the along slope evolution of the barotropic transport following the continental slope in the nordic seas and arctic ocean following geostrophic theory the transport evolution is calculated from bottom densities in five different transects within the nordic seas this theoretically predicted transport evolution is compared with transports estimated directly from velocity measurements between the faroe shetland channel and the svinoy section off southern norway across the fram strait below 800 m and between the fram strait and the greenland sea the agreement is generally good between geostrophic theory and observations this indicates that many aspects of the barotropic flow in these regions are captured by geostrophic dynamics between the eastern and western fram strait above 800 m and between svinoy and the eastern fram strait the observed flow fields differ to a large extent from the flow field predicted by geostrophic dynamics indicating that ageostrophic dynamics play a more important role in these regions the barotropic transport differences between the eastern and western fram strait contain information about the barotropic transport evolution along the entire arctic continental slope the good agreement between observations and theory across the strait below 800 m therefore indicates that the flow along the deeper part of the arctic continental slope is well described by geostrophic dynamics according to our results the noticeably more baroclinic nature of the flow in the western fram strait compared with the eastern strait can then be ascribed to water mass modifications along the arctic continental slope

three dimensional displacement field of the 2015 mw8 3 illapel earthquake chile from across and along track sentinel 1 tops interferometry wide swath imaging has become a standard acquisition mode for radar missions aiming at applying synthetic aperture radar interferometry insar at global scale with enhanced revisit frequency increased swath width compared to classical stripmap imaging mode is achieved at the expense of azimuthal resolution this makes along track displacements and subsequently north south displacements difficult to measure using conventional split beam multiple aperture insar or cross correlation techniques alternatively we show here that the along track component of ground motion can be deduced from the double difference between backward and forward looking interferograms within regions of burst overlap burst overlap interferometry takes advantage of the large squint angle diversity of sentinel 1 1 to achieve subdecimetric accuracy on the along track component of ground motion we demonstrate the efficiency of this method using sentinel 1 data covering the 2015 mw8 3 illapel earthquake chile for which we retrieve the full 3 d displacement field and validate it against observations from a dense network of gps sensors

flank collapse and large scale landsliding in the cape verde islands off west africa large scale landslides occur on the flanks of many volcanic oceanic islands worldwide none have taken place in historical time but their geohazard potential especially their ability to generate tsunamis is large the cape verde islands are a group of 10 large and several smaller volcanic islands off the coast of west africa between 15 and 17 n a single flank landslide has previously been described from the island of fogo but systematic analysis of the cape verde group has until now been lacking this paper describes and interprets a multibeam bathymetry data set covering the slopes of the western cape verde islands including those of the islands with the most recent volcanic activity fogo in the southwest and santo antao in the northwest all of the larger islands show evidence of large flank landslides although only fogo and the southwest part of santo antao have failed in the last 400 ka tope de coroa the volcano at the southwest end of santo antao has been inactive for the past 170 ka and is judged to have a low landslide potential unless volcanic activity resumes in contrast there would seem to be a high probability of a future east directed landslide on fogo from the area of the highly active pico do fogo volcano although it is impossible to predict a timescale for such an event a tsunami generated by such a landslide could have a catastrophic effect on the adjacent island of santiago and possibly even farther afield on the west african coast

the evolution of volcanic systems following sector collapse abstract sector collapses affect volcanic edifices across all tectonic settings and involve a rapid redistribution of mass comparable in scale to the largest magmatic eruptions the eruptive behaviour of a volcano following sector collapse provides a test of theoretical relationships between surface loading and magma storage which imply that collapse driven unloading may lead to changes in eruption rate and erupted magma compositions large sector collapses are infrequent events globally with all historical examples being relatively small in comparison to many of the events documented in the geological record as a result exploration of the impacts of sector collapse on eruptive behaviour requires detailed investigation of prehistoric collapses but this is often hindered by poorly resolved stratigraphic relationships and dating uncertainties nevertheless observations from a number of volcanoes indicate sharp changes in activity following sector collapse here a global synthesis of studies from individual volcanoes in both arc and intraplate settings is used to demonstrate a number of common processes in post collapse volcanism multiple examples from large 5 km3 sector collapses in arc settings show that collapse may be followed by compositionally anomalous large volume and often effusive eruptions interpreted to originate via disruption of a previously stable upper crustal reservoir these anomalous eruptions highlight that magma compositions erupted during periods of typical i e unperturbed by sector collapse volcanism may not be representative of the range of compositions stored within a vertically extensive crustal reservoir if eruptible magma is not present upper crustal reservoirs may rapidly solidify following collapse without further eruption allowing more mafic compositions to ascend to the surface with only limited upper crustal modification resulting in edifice regrowth at temporarily elevated eruption rates subsequent re establishment of an upper crustal reservoir further supports a relationship between surface loading and crustal storage but long term chemical and mineralogical differences between pre and post collapse evolved magmas imply that a newly developed reservoir can overprint the influence of a preceding reservoir forming a spatially and compositionally distinct plumbing system these broad patterns are replicated in intraplate settings despite differences in scale and melting processes current evidence suggests that post collapse evolution of intraplate volcanoes can be explained by unloading induced destabilisation of the magma plumbing system rather than increased melt production what emerges from an apparently diverse set of observations is a systematic behaviour that strongly supports a coupling between edifice growth and magma ascent storage and pressurisation eruption rates erupted compositions and the style of volcanism at any particular system may thus be modulated from the surface and long term shifts in surface behaviour may occur without any changes in the deep parts of magmatic systems observations of sharp post collapse changes in erupted compositions including the ascent of primitive mafic magmas also require a crystal dominated mid to upper crustal reservoir consistent with recent models of crustal magmatic systems

the influence of second scale convection on the thickness of continental lithosphere and crust abstract the effect of sublithospheric convection on the thickness and structure of the continental lithosphere is studied in numerical models assuming different rheologies newtonian non newtonian and temperature and pressure dependent heat fluxes and heating modes bottom versus internal heating the stagnant regions near the top of the models are identified with the lithosphere we distinguish a seismic and thermal lithosphere controlled by temperature an elastic lithosphere controlled by viscosity and a mechanical lithosphere controlled by strain rate strong lateral thickness undulations with a thick lithosphere above the downwelling regions and a thin lithosphere above the upwelling regions develop the thickness of the elastic lithosphere is about two thirds of the mechanical lithosphere while the ratio of the elastic to the thermal lithosphere varies between 0 4 and 0 8 the time dependence of some models with internal heating and a surface heat flow of 20 mw m 2 is characterized by long periods of the order of 1 ga close to steady state and short periods 100 ma of changing cell patterns and lithospheric thicknesses models showing thick lithospheric roots suggest that the mantle beneath some old shields may be associated with cold slowly downwelling convective flow rather than being firmly attached to the lithosphere the missing gravity and topography signals from such regions can be explained by elastic bending of the lithosphere and by dynamic adjustment of the moho observed lithospheric thickness variations in europe and their minimum to maximum spacing agree well with the models suggesting sublithospheric convection to be the cause compared to other observed features thickness undulations of the lithosphere seem to provide the strongest indications for sublithospherical convection relatively low viscosities in the lower crust may lead to a long term decoupling of surface topography from moho topography and mantle dynamics the moho depth is capable of adjusting to mantle stresses within relaxation times of the order of 100 ma while surface topography may flatten out such a mechanism may be important in regions with a deep moho such as fennoscandia or with a shallow moho such as the pannonian basin neither region showing a pronounced surface topography

evidence of multiple strain fields beneath the eastern flank of mt etna volcano sicily italy deduced from seismic and geodetic data during 2003 2004 we carried out a study of the seismicity and ground deformation occurring on mt etna volcano after the end of the 2002 2003 eruption and before the onset of the 2004 2005 eruption data were recorded by the permanent local seismic network run by istituto nazionale di geofisica e vulcanologia sezione di catania and by geodetic surveys carried out in july 2003 and july 2004 on the gps network most earthquakes were grouped in two main clusters located in the northeastern and southeastern sectors of the volcano the areal distribution of seismic energy associated with the recorded earthquakes allowed us to highlight the main seismogenic areas of mt etna in order to better understand the kinematic processes of the volcano 3d seismic locations were used to compute fault plane solutions and a selected dataset was inverted to determine stress and strain tensors the focal mechanisms in the northeastern sector show clear left lateral kinematics along an e w fault plane consistent with events occurring along the pernicana fault system the fault plane solutions in the southeastern sector show mainly right lateral kinematics along a nne and ene fault plane and left lateral kinematics along nw fault planes that together suggest roughly e w oriented compression surface ground deformation affecting mt etna measured by gps surveys highlighted a marked inflation during the same period and exceptionally strong seawards motion of its eastern flank the 2d geodetic strain tensor distribution was calculated and the results show mainly ene wsw extension coupled with wnw ese contraction indicating right lateral shear along a nw se oriented fault plane the different deformation of the eastern sector of the volcano as measured by seismicity and ground deformation must be interpreted by considering the different depths of the two signals seismic activity in the southeastern sector of volcano is located between 3 and 8 km b s l and can be associated with a very strong additional e w compression induced by a pressurizing source just westwards and at the same depth located by inverting gps data ground deformation in contrast is mainly affected by the shallower dynamics of the fast moving eastern flank which produces a shallower opposing e w extension the entire dataset shows that two different processes affect the eastern flank at the same time but at different depths the boundary is clearly located at a depth of 3 km b s l and could represent the decollement surface for the mobile flank

circulation and thermohaline variability of the hanna shoal region on the northeastern chukchi sea shelf we analyzed velocity and hydrographic data from 23 moorings in the northeast chukchi sea from 2011 to 2014 in most years the eastern side of hanna shoal was strongly stratified year round while weakly stratified regions prevailed on the shelf south and west of the shoal stratification differences cause differential vertical mixing rates which in conjunction with advection of different bottom water properties resulted in seasonally varying along isobath density gradients in agreement with numerical models we find that bottom waters flow anticyclonically around the shoal whereas most of the shelf responded barotropically to wind forcing there was a strong baroclinic component to the flow field northeast of hanna shoal resulting in no net vertically integrated transport on average in contrast there is a net eastward transport from west of the shoal which implies convergence north of the shoal convergence and along isobath density gradients may foster cross shelf exchange north of hanna shoal modal analyses indicate that the shelf south of the shoal and barrow canyon responded coherently to local and remote winds whereas the wind current response around hanna shoal was less coherent barotropic topographic waves of 3 day period were generated episodically northeast of the shoal and propagate clockwise around hanna shoal but are blocked from entering barrow canyon and are possibly scattered by the horizontally sheared flow and converging isobaths on the western side of the shoal analysis of water properties on the western side of hanna shoal suggests that these include contributions from the western and southern portions of the chukchi sea

sinking mafic body in a reactivated lower crust a mechanism for stress concentration at the new madrid seismic zone we propose a geodynamic model for stress concentration in the new madrid seismic zone nmsz the model postulates that a high density mafic body situated in the deep crust directly beneath the most seismically active part of the nmsz began sinking several thousands of years ago when the lower crust was suddenly weakened based on the fact that deformation rates in the nmsz have accelerated over the past 9 k y we envision the source of this perturbation to be related to the last north american deglaciation excess mass of the mafic body exerts a downward pull on the elastic upper crust leading to a cycle of primary thrust faulting with secondary strike slip faulting after which continued sinking of the mafic body reloads the upper crust and renews the process this model is consistent with the youth of activity the generation of a sequence of earthquakes and the velocity evolution during interseismic periods which depend upon the density contrast of the mafic body with respect to the surrounding crust its volume and the viscosity of the lower crust

structure composition and age of the small islands of santa luzia branco and raso cape verde archipelago abstract the northern alignment of cape verde archipelago contains three small islands in its central sector santa luzia branco and raso on which there is very scarce geological petrological or geochronological information available the three islands along with the island of sao vicente arise on a continuous underwater relief less than 50 m deep and about 70 km long that formed from separate volcanic edifices the southernmost island raso is formed by accumulation of several tens of lava flows and some remaining strombolian cones an erosion surface covered by sediments allows the separation of two different episodes of growth the lower one older than 2 ma and the upper one between 0 9 and 1 2 ma the smaller island of branco is the remnant of a large stratovolcano about 6 km in radius 1000 m of altitude and between 5 and 6 ma in age santa luzia the northernmost and largest island of this particular group is essentially a remaining rift zone between 4 and 7 ma old at least 600 m high about 10 km long and 7 km wide the se extreme of the island is occupied by rocks of an older partially submarine stage of growth which also include gabbroic intrusions crossed by a dense network of dikes whose age may be estimated in 8 ma or more on the contrary the nw end shows the only remains of late post erosion activity that is of much less volumetric importance and it has been dated between 0 8 and 1 4 ma the three islands as a whole are formed by moderately or strongly alkaline basic and ultrabasic rocks similar to those found in the neighboring island of sao vicente ultraalkaline rocks only appear in raso and differentiate types as trachyandesites and phonolites are exclusively found in santa luzia the similar age found for the main stages of growth recorded in the mentioned four islands and even more in the other two islands santo antao and sao nicolau situated at the end of the barlovento alignment are not easily comprehensible with evolution models implying a simple spatial progression of the volcanic activity from east to west in this array of the archipelago on the other hand the temporal coincidence in periods of quiescence observed in the different islands seems to point to the existence of a cyclical activity for the ensemble

variable viscosity convection and partial melting in the continental asthenosphere convection beneath continents may be associated with the generation of partially molten zones at depth experimentally determined non newtonian temperature and pressure dependent creep laws for olivine were used to model upper mantle convection in the presence and absence of a melt phase in our models convection is chaotic and exhibits a strong time dependence using model dry and water undersaturated solidus relations partially molten regions develop at asthenospheric depths forming low viscosity regions the existence of these regions is linked to convection and consequently varies in space and time with an episodicity of 5 to 10 m y in good agreement with observations based on seismic tomography and the episodicity and volumetric abundance of surface volcanics for an average continental heat flux of about 53 3 mw m2 maximum melt fractions range between 0 and 2 dry solidus and 2 and 4 water undersaturated solidus on the basis of experimental deformation studies we employed an empirical relationship between stress and grain size to assess the grain size variations possible in the upper mantle the grain sizes obtained millimeters to centimeters are in good agreement with grain sizes observed in natural examples the smallest grain sizes occur along narrow zones of high stress within the deepest part of the lithosphere the largest grain sizes are found in the overlying lithosphere and in partially molten asthenospheric regions as our models scale well to natural observations these results appear to preclude diffusion creep n 1 as a viable upper mantle steady state deformation mechanism

grounding line retreat of pope smith and kohler glaciers west antarctica measured with sentinel 1a radar interferometry data we employ sentinel 1a c band satellite radar interferometry data in terrain observation with progressive scans mode to map the grounding line and ice velocity of pope smith and kohler glaciers in west antarctica for the years 2014 2016 and compare the results with those obtained using earth remote sensing satellites ers 1 2 in 1992 1996 and 2011 we observe an ongoing rapid grounding line retreat of smith at 2 km yr 40 km since 1996 an 11 km retreat of pope 0 5 km yr and a 2 km readvance of kohler since 2011 the variability in glacier retreat is consistent with the distribution of basal slopes i e fast along retrograde beds and slow along prograde beds we find that several pinning points holding dotson and crosson ice shelves disappeared since 1996 due to ice shelf thinning which signal the ongoing weakening of these ice shelves overall the results indicate that ice shelf and glacier retreat in this sector remain unabated

constructive and destructive episodes in the building of a young oceanic island la palma canary islands and genesis of the caldera de taburiente the results of new field observations 23 new k ar determinations and sixteen previously published determinations provide the basis for the reconstruction of the subaerial volcanic history of the island of la palma after the seamount activity represented by the materials of the basal complex an eruptive phase between 2 0 and 1 3 ma formed a large shield a period of volcanic quiescence followed until around 1 ma during which a large lateral collapse partly destroyed the former edifice between 1 05 and 0 7 ma activity was renewed in the shield and a n s ridge was built in the southern part of the island around 0 7 ma two new large lateral collapses affected the western part of both edifices and they were followed by eruptions between 0 71 and 0 65 ma which built a new edifice that partly filled the depressions thus created the caldera de taburiente constitutes the eroded remnants of the depression formed in the northern shield from 0 65 ma to present activity has been restricted to the n s ridge which has continued to grow southwards there was a general n s migration of volcanic activity with time but in the shield the trend was northwest to southeast eruptive rates seem to have been fairly constant during the different eruptive phases considered between 0 15 and 0 37 km3 ka a very similar succession of constructive and destructive episodes has been obtained for the neighboring island of hierro but in this case the activity started around 0 8 ma and eruptive rates were about 0 5 km3 ka

the geological history of maio cape verde islands the oldest igneous rocks on maio are pillow lavas of mid ocean ridge pillow basalts character which have been tilted and uplifted about 4 km from the ocean floor to outcrop as a partial ring dipping steeply away from a central plutonic complex made up of pyroxenites essexites syenites and carbonatites the ocean floor volcanic rocks are overlain conformably by a stratigraphically continuous pelagic carbonate succession which demonstrates a shallowing depositional environment from the upper jurassic to upper cretaceous times when tuffaceous beds indicate renewed volcanism the tuffs are associated with rudites demonstrating the emergence of the island and amongst the clasts are plutonics indicating upper cretaceous magmatism and the unroofing of the volcano to a substantial depth deformation under compressive stress resulted in the folding and local repetition by thrusting of this sedimentary cover which together with the plutonic core had been intensively injected by major sills the mesozoic succession has been planed off and overlain with marked unconformity by a largely neogene sequence of volcanic and terrestrial sedimentary rocks there is a hiatus throughout the palaeogene and constructional activity appears to recommence with ankaramitic hyaloclastite and lava deltas and subaerial ankaramitic flows these are overlain by fluvial sediments and tuffs stratigraphically above these is an extensive plateau of silica undersaturated lavas olivine melilitites and nephelinites which rest on a planed and locally lateritized surface at topographically higher levels in the eastern part of the island there are thick ankaramitic lavas and pyroclasts which evidently flowed eastward through valleys cut down into the mesozoic strata and appear to be of pliocene age the subsequent history of the island appears to be non volcanic

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

the diversity of tectonics from fluid dynamical modeling of the lithosphere mantle system abstract numerical modeling of the lithosphere has been carried out from many points of view most popular and prevalent is the use of the kinematic boundary conditions to move the lithosphere about in the dynamics we have approached the numerical modeling of the lithosphere mantle system by treating this as a fluid dynamical system in which crustal and mantle rheologies and thermal and compositional buoyant forces play dominant roles in delivering the dynamics in a self consistent manner we have investigated the development of extensional and compressional tectonic regimes from variations of the crustal density and compare their temporal evolutions in comparing with kinematically driven thickening of the lithosphere we find that the timescales are more self consistently determined in a full fluid dynamical treatment than in kinematic models we emphasize the delicate nature of balancing the chemical buoyancy of the crust with the thermal negative buoyancy of the mantle lithosphere as the modes and associated timescales of the delamination process are controlled critically by their relative importance the role of an actively participating buoyant crust cannot by ignored in the overall lithosphere mantle dynamics

the 2008 eruptive unrest at cerro azul volcano galapagos revealed by insar data and a novel method for geodetic modelling

viscous heating in heterogeneous media as applied to the thermal interaction between the crust and mantle we have studied the effects of viscous heating involving heterogeneous media which occurs in the interaction between the mantle lithosphere crust system with the mantle lithosphere in delamination high rates of viscous heating are found in corner flow regions where the deformation rate of the flow is highest the weak lower crust is sheared between the upper crust and the mantle lithosphere giving rise to a second type of viscous heating with high dissipation values several ten to hundred times the chondritic value greater dissipation rates are found in the shear interaction between heterogeneous media with different non newtonian rheologies than in the shear heating inside a single non newtonian or newtonian homogeneous medium high spatial resolution of at least 2 5 km or finer is needed to resolve the sharp variations of viscous heating near the interface of the two media

coastal oyashio south of hokkaido japan abstract coastal oyashio water cow the cold low salinity water lying along the southeast coast of hokkaido sometimes flows into funka bay on the southwest coast in winter and spring because this water is low in density a density current called the coastal oyashio was assumed to carry cow along these coasts however water property maps for april 1989 february 1992 february 1994 and february 1989 show that only for the latter month did cow extend as far west as cape erimo on the southwest coast steady state flows were calculated using a baroclinic model and the density data collected in april 1989 model results show that the oyashio carries cow southwestward along the continental slope southeast of hokkaido it bifurcates south of cape erimo with a coastal portion turning around the cape but not always reaching the southwest coast because of the density structure along that coast when the oyashio crosses isobaths the joint effect of baroclinicity and bottom relief jebar causes a barotropic

a giant landslide on the north flank of tenerife canary islands the extent of mass wasting along the north flank of tenerife has been mapped using swath bathymetry gloria side scan sonar and 3 5 khz echo sounder data the marine surveys show that north of tenerife a giant landslide is exposed over an area of 5500 km2 of the seafloor more than twice the surface area of the island the landslide truncates an older ridge and valley topography that is associated with the shield building basalts on tenerife we interpret the ridge and valley topography as the result of subaerial erosion the landslide is estimated to have a length of 100 km a width of up to 80 km and a volume of about 1000 km3 it extends onshore into the orotava and icod valleys which have been interpreted as of landslide origin k ar dating of basaltic flows in the steep headwall of orotava suggests an age of formation for the valley is younger than 0 78 ma and may even be younger than 0 27 ma the icod valley is located immediately to the north of the most recent volcano on tenerife las canadas and has been associated with the collapse of its caldera between 1 2 and 0 2 ma a young age for the landslide is supported by the 3 5 khz echo sounder data which show that the landslide is draped by a thin 10 m layer of younger sediment the landslide did not form however during a single catastrophic event but represents the amalgamation of a number of separate landslides the occurrence of the ridge and valley topography in water depths of up to 2 5 km suggests that the shield building basalts have subsided by at least this amount since they formed 3 3 8 0 ma we speculate that this subsidence is caused by some form of stress relaxation that occurs in the underlying lithosphere the giant landslide imaged in our sonar data is associated with the late stages in the development of the most recent volcano on tenerife las canadas which only began at about 1 8 ma thus landsliding may be a particular feature of the time soon after emplacement when because of incomplete isostatic adjustment oceanic volcanoes have their greatest elevations above sea level and therefore are most susceptible to slope failure

layered convection induced by phase transitions we report a systematic study on the conditions under which an endothermic phase transition can enforce layered convection two dimensional numerical calculations of convection in a domain containing a divariant phase change were performed in the framework of the extended boussinesq approximation i e considering the effects of adiabatic gradient latent heat and frictional heating in the energy equation we find that the critical value of the negative clapeyron slope which must be surpassed in order to induce layered convection decreases in magnitude with increasing rayleigh number ra in the range 104 ra 2 106 near the critical clapeyron slope vacillations between double and single layer convection or strongly leaking double layer convection are possible the breakdown into layers is influenced very little by the latent heat release but depends solely on the phase boundary deflection caused by lateral temperature differences the value of the critical clapeyron slope also seems little affected by the width of the transition zone or by its depth a possible superplastic rheology within the transition zone would tend to favor layered convection scaling the model results to the 670 km discontinuity in the earth s mantle as a possible endothermic phase boundary we estimate the critical clapeyron slope to be in the range of 4 to 8 mpa k 40 to 80 bar k the possibility that the spinel perovskite periclase transition is within this range appears to be remote but certainly cannot be neglected

rheological control of oceanic crust separation in the transition zone mineral physics observations suggest that distinct density and rheological differences exist between the crustal component of oceanic lithosphere and the underlying mantle we have conducted numerical experiments to investigate the influence of both density and viscosity on the effectiveness of recycling of oceanic crust into the lower mantle confirming previous results the density inversion at 670 km depth alone is not sufficient to prevent crustal recycling however a soft layer may exist between the strong garnet crust and cold slab interior models employing a simplified newtonian sandwich model show that this thin weak layer can effectively decouple the crust and slab once entrained into the lower mantle the then lighter crust can rise sufficiently fast as a rayleigh taylor instability to avoid further entrainment these results suggest that the crustal component of slabs may be trapped at 670 km depth leading to a garnet enriched transition zone

palaeomagnetic study of a subaerial volcanic ridge sao jorge island azores for the past 1 3 myr evidence for the cobb mountain subchron volcano flank instability and tectonomagmatic implications we present a palaeomagnetic study on 38 lava flows and 20 dykes encompassing the past 1 3 myr on s jorge island azores archipelagonorth atlantic ocean the sections sampled in the southeastern and central western parts of the island record reversed and normal polarities respectively they indicate a mean palaeomagnetic pole 81 3 degrees n 160 7 degrees e k 33 and a95 3 4 degrees with a latitude shallower than that expected from geocentric axial dipole assumption suggesting an effect of non dipolar components of the earth magnetic field virtual geomagnetic poles of eight flows and two dykes closely follow the contemporaneous records of the cobb mountain subchron odp dsdp programs and constrain the age transition from reversed to normal polarity at ca 1 207 0 017 ma volcano flank instabilities probably related to dyke emplacement along an nnwsse direction led to southwestward tilting of the lava pile towards the sea two spatially and temporally distinct dyke systems have been recognized on the island the eastern is dominated by nnwsse trending dykes emplaced before the end of the matuyama chron whereas in the central western parts the eruptive fissures oriented wnwese controlled the westward growth of the s jorge island during the brunhes chron both directions are consistent with the present day regional stress conditions deduced from plate kinematics and tectonomorphology and suggest the emplacement of dykes along pre existing fractures the distinct timing and location of each dyke system likely results from a slight shift of the magmatic source

major changes in volcano behaviour after a sector collapse insights from stromboli italy in recent years increasing numbers of volcanoes are being recognized as having undergone large sector collapses how far such events can change the succeeding behaviour of the volcano is poorly known despite the importance for natural hazards and economic applications by analysing the last 100 kyr geological history of stromboli italy which has involved multiple collapses this paper illuminates the feedback effect between sector collapse and magma upwelling and emplacement the collapsed zone of stromboli is episodically unbuttressed draining magma preferentially with formation of eruptive centres in the collapse amphitheatre and dyking along the collapse shoulders after a collapse there were no further linear eruptions across the cone on opposing middle lower slopes but these occurred again after rebuilding of the cone the time averaged eruption rate increased immediately before the first collapse and remained higher during the succeeding period of frequent collapses

multiparameter monitoring of fogo island cape verde for volcanic risk mitigation fogo island in the cape verde archipelago north atlantic is a stratovolcano of nearly conical shape that rises 2829 m above sea level and v6000 m above the surrounding seafloor with a population of 40 000 the island has known intense historical volcanic activity since ad 1500 with an average interval between eruptions of the order of 20 years twentieth century rates were more subdued with only two flank eruptions in 1951 and 1995 following the 1995 eruption increased awareness of the volcanic hazard affecting the population of the island led to the deployment of the permanent vigil network seismographic stations both broadband and short period tiltmeters and a co2 sensor where installed in fogo together with a telemetry infrastructure to allow remote real time monitoring a broadband seismographic station was installed in neighbour brava island the operation of the network was complemented by the introduction of routine geodetic and microgravity surveying and the operation of an automatic meteorological station in this paper we describe the methodology adopted to monitor the volcanic activity combining real time data analysis volcanotectonic and volcanic earthquakes volcanic tremor and tilt with repeated surveying at intervals of several months gps microgravity examples of data from the first years of operation are presented in particular the data pertaining to a period of anomalous activity in september october 2000 are discussed in the context of the risk mitigation strategy currently being developed

anomalous heat flow and geoid across the cape verde rise evidence for dynamic support from a thermal plume in the mantle summary we describe results from 200 heat flow measurements across the cape verde rise in the north atlantic they show that the heat flow through normal 125 myr old crust is 45 5 3 4mwm 2 close to the prediction for a lithospheric plate model heat flow increases towards the centre of the rise reaching a maximum of 16 4 mw m 2 above the normal oceanic value the concommitant geoid anomaly at the centre of the rise is 7 6 0 3 m and the depth anomaly is 1900 200 m the anomalous heat flow geoid and bathymetric values are used to constrain a variety of theoretical models of hot spot mechanisms lithospheric reheating models alone whether involving transient or sustained thinning of the lithosphere fail to model the broad heat flow anomaly and the long duration of uplift and volcanism observed on the cape verde rise axisymmetric convection models provide a better fit to the observed data and suggest that the swell is a consequence primarily of dynamic uplift generated by an ascending thermal plume in the underlying mantle uplift caused by expansion of the solid lithosphere is of smaller importance the observed geoid bathymetry and heat flow anomalies are reproduced well using convection models with upper mantle viscosities of 2 4 times 1020 pa s and a coefficient of thermal expansion in the range 2 0 2 5 times 10 5 k 1 the effect of melting in the ascending plume is to buffer the heat flow anomalies in the case of the cape verde rise partial melting is minimal but its effect on other hotspots will be to limit observed heat flow anomalies at the surface to less than 20 25 mw m 2

location and orientation of eruptive fissures and feederdykes at mount etna influence of gravitational and regional tectonic stress regimes abstract lava extrusion from fissures on the flanks of the etna volcano is a common feature of recent activity as evidenced by the eruptions of 1971 1981 1983 and 1985 and was of similar importance during prehistoric times we propose here a model within which the location and orientations of the large majority of historic eruptive fissures on etna s flanks together with their feeder dykes are explained within the framework of a gravitational stress regime stress orientations within this regime are controlled largely by the gross morphology of the volcano but are significantly modified by local topographic anomalies we propose that the gravitational stress regime largely supercedes an earlier developed regional tectonic stress regime which still operates in the sub volcanic basement and may remain the dominant control of eruptive fissure and feeder dyke disposition at lower altitudes on the flanks the proposed model is supported by 1 detailed examination of fissure locations and orientations and the relationship between fissure azimuths and topography 2 precise horizontal distance measurement and vertical ground deformation studies of a recent eruption and 3 qualitative physical modelling experiments in which coloured water is injected into solidified gelatine solutions representing variously shaped volcanic constructs a cautious approach is advocated when extrapolating trends of spatially limited fissure segments for the purpose of locating potential sites of magma ascent and implications of the model for hazard analysis are outlined

morphology of pyroclastic cones and tectonics the relationships between morphology and spatial distribution of 1315 quaternary pyroclastic cones and coeval faulting of the volcanic substrate are analyzed in the following regions with different structural settings tepic rift mexico ethiopian rift mexican volcanic belt canary archipelago and mount etna field data and analog experiments of tephra cone emplacement and collapse enable the definition of a number of parameters which can be used to infer the geometry of the fracture feeding the magma to a pyroclastic cone the strike of the feeding plane is directly related to 1 the elongation of cone base and crater 2 the location of depressions on the crater rim and 3 the alignment of pyroclastic cones in relation to a given vent spacing in addition the strike and dip of faults affect the direction of cone breaching these relationships are valid for volcanic substrate topographic surfaces with an inclination of less than 9 and are especially sensitive to fault escarpment and cone height lava and cone density and fault orientation with respect to the dip of the volcanic substrate topography relations 1 and 2 become more pronounced for regions undergoing extensional tectonics where edifices also have a larger dimension whereas breaching in the direction of the fault dip is more widespread in regions under extension breaching along the fault strike as well as the coincidence between fault strike and vent alignment are more frequent in regions with transcurrent or transtensional tectonics

ground deformation due to steam cap processes at reykjanes sw iceland effects of geothermal exploitation inferred from interferometric analysis of sentinel 1 images 2015 2017

fast mechanisms for the formation of new plate boundaries abstract we demonstrate the important role played by non linear feedback in promoting the fast breakup of the continental lithosphere and the formation of new plate boundaries we compare the difference in fluid dynamic and elasto visco plastic approaches and emphasize the advection of stresses in finite element models with large strain lagrangian formulation two types of instabilities were found at multiple time length scales ranging from 100 years and km scale to 0 1 myr and 100 km scale one mechanism relies on the thermo mechanical elasto plastic energy conversion and the other stems from the void volatile interaction elasticity takes on a guiding role in the propagation of shear zones closely followed by a thermal wave which is again followed by a wave of volatiles this last mechanism consolidates the fault zones and establishes the plate boundary for a geological time scale using a fully coupled thermal mechanical approach we obtain for the first time a two dimensional solution which shows that the constant velocity boundary conditions can lead to episodic avalanche type tectonic phases within

toward full exploitation of coherent and incoherent information in sentinel 1 tops data for retrieving surface displacement application to the 2016 kumamoto japan earthquake sentinel 1 s continuous observation program over all major plate boundary regions makes it well suited for earthquake studies however decorrelation due to large displacement gradients and limited azimuth resolution of the terrain observation by progressive scan tops data challenge acquiring measurements in the near field of many earthquake ruptures and prevent measurements of displacements in the along track direction here we propose to fully exploit the coherent and incoherent information of tops data by using standard interferometric synthetic aperture radar insar split bandwidth interferometry in range and azimuth swath burst overlap interferometry and amplitude cross correlation to map displacements in both the line of sight and the along track directions application to the 2016 kumamoto earthquake sequence reveals the coseismic displacements from the far field to the near field by adding near field constraints the derived slip model reveals more shallow slip than obtained when only using far field data from insar highlighting the importance of exploiting all coherent and incoherent information in tops data

viscous heating a potential mechanism for the formation of the ultralow velocity zone abstract the detection of several ultralow velocity zones ulvz on the core mantle boundary cmb together with the recent estimates of the lower mantle solidus would suggest that some sort of melting may occur inside the upwellings in the deep mantle we have studied the possibilities of viscous heating as a mechanism for producing favorable conditions leading to melting inside deep mantle upwellings a two dimensional model in an aspect ratio 3 box with temperature and pressure dependent rheology and two major phase transitions has been employed both viscous and adiabatic heating have been included and various amounts of internal heating have been applied viscous heating can heat up the interior of the deep mantle plumes to around 100 degrees above the cmb temperature this amount of temperature rise is sufficient to cause melting inside upwellings in the deep lower mantle we propose here that viscous heating plays an important role in producing conditions leading to the formation of the ulvz massive melting within rising plumes might have been more prevalent in the past

the 2015 wolf volcano galapagos eruption studied using sentinel 1 and alos 2 data an energetic eruption started on 25 may 2015 from a circumferential fissure at the summit of wolf volcano on isabela island western galapagos further eruptive activity within the wolf caldera followed in mid june 2015 as no geodetic observations of earlier eruptions at wolf exist this eruption provides an opportunity to study the volcano s magmatic plumbing system for the first time here we use interferometric synthetic aperture radar insar data from both the sentinel 1a and alos 2 satellites to map and analyze the surface deformation at four time periods during the activity these data allow us to identify the two eruption phases and reveal strong co eruptive subsidence within the wolf caldera that is superimposed on a larger volcano wide subsidence signal modeling of the surface displacements shows that two shallow magma reservoirs located under wolf at 1 km and 5 km below sea level explain the subsidence and that these reservoirs appear to be hydraulically connected we also suggest that the transition from the circumferential to the intra caldera eruption may have involved ring fault activity

importance of horizontal seafloor motion on tsunami height for the 2011 mw 9 0 tohoku oki earthquake abstract it is now clear that the 2011 tohoku oki earthquake ruptured the subduction interface all the way to the japan trench however there is significant disagreement about just how much slip occurred at the trench with most geodetic studies locating only a small fraction of the maximum slip there whereas broadband seismic studies put the majority of the slip near the trench measurements of seafloor displacement near the trench also imply more slip there than is estimated by the geodetic studies here by means of a joint inversion of displacement measurements and seafloor pressure data we show that it is possible to reconcile geodetic and seismic studies and that a considerable amount of slip indeed occurred at the trench with slip magnitudes reaching 57 74 of the maximum slip the seafloor displacement predicted by our model agrees very well with independent measurements made close to the trench we also find good agreement between our tsunami model and independent measurements of tsunami height in the ocean and on land re running of the inversion without the near field pressure gauge data however leads to underprediction of the flooding on land even when the seafloor geodetic data are still included thus even if the seafloor geodetic measurements had been available in real time they would still not have allowed reliable prediction of near field tsunami inundation close to the trench the dip of the plate interface is shallow which serves to decrease the vertical motion of the sea floor for any given slip however the horizontal motion is conversely larger because the ocean floor slopes steeply near the trench it acted like a giant wedge converting the horizontal motion of the ground into an uplift of the water column and causing the peak initial tsunami wave height to be twice as high as it would have been from vertical displacement alone

ground deformation monitoring at mt etna evidence for dyke emplacement and slope instability ground deformation monitoring at mount etna has successfully enabled the sub surface paths of two shallow feeder dykes to be traced and their dimensional parameters depths and departures from the vertical to be constrained determinations of horizontal movement have recorded the displacement by 3 6 m maximum of a rim segment of the valle del bove flank caldera due to dilation associated with dyke emplacement adjacent to the rim over the period 1981 to 1989 small scale collapse along this rim segment associated with the opening of the 1989 fissure points to increasing slope instability and highlights the potential for major failure and debris avalanche generation

high resolution digital elevation model from tri stereo pleiades 1 satellite imagery for lava flow volume estimates at fogo volcano resolving changes in topography through time using accurate high resolution digital elevation models dems is key to understanding active volcanic processes for the first time in a volcanic environment we utilize very high resolution tri stereo optical imagery acquired by the pleiades 1 satellite constellation and generate a 1 m resolution dem of fogo volcano cape verde the most active volcano in the eastern atlantic region point cloud density is increased by a factor of 6 5 compared to conventional stereo imagery and the number of 1 m2 pixels with no height measurements is reduced by 43 we use the dem to quantify topographic changes associated with the 2014 2015 eruption at fogo height differences between the posteruptive pleiades 1 dem and the preeruptive topography from tandem x give a lava flow volume of 45 83 0 02 106 m3 emplaced over an area of 4 8 km2 at a mean rate of 6 8 m3 s 1

a past giant lateral collapse and present day flank instability of fogo cape verde islands fogo island is a large and extremely steepsided oceanic island volcano in the cape verde archipelago it has a large ca 9 km across east facing summit collapse structure the monte amarelo collapse with a probable volume of at least 150 200 km3 for most of its history the monte amarelo volcano had a small but productive central vent complex and radial rift zones fed by laterally propagating dykes shortly before the collapse the latter were replaced by north south trending arrays of en echelon vertically propagating dykes since the monte amarelo collapse the scar has partly filled with a new volcano the cha das caldeiras volcano the summit cone of this volcano the pico do fogo is a very young feature but has been abandoned in the most recent phase of activity from the 18th century onwards the same period has also seen the abandonment of earlier radial rift zones with laterally propagating dykes and their replacement with en echelon arrays of vents fed by vertically propagating dykes these form an n s trending array within the older collapse structure and are associated with seaward displacement of the eastern flank of the volcano within the old collapse structure the most recent eruptions those of 1951 and 1995 appear to be associated with episodes of flank instability manifested in n s surface fissuring and east facing normal faults these recent structural changes in the volcano parallel those which took place in the monte amarelo volcano prior to its collapse

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

effects of a realistic mantle thermal conductivity on the patterns of 3 d convection abstract a physical model describing the temperature and pressure dependences of mantle thermal conductivity has recently been provided by a m hofmeister science 283 1999 1699 1706 we have studied numerically the influences of such a temperature and pressure dependent thermal conductivity on 3 d constant viscosity convection a large aspect ratio box of 4 4 1 has been taken for rayleigh numbers greater than 104 to 106 the power law index governing the phonon contribution to the thermal conductivity controls the style of convection for silicates the pattern of convection is quite different from that of constant conductivity whereas the pattern of convection associated with conductivity of oxides is close to the case for constant conductivity both boussinesq and extended boussinesq models with viscous and adiabatic heatings have been examined major effects of variable thermal conductivity on mantle convection are 1 heating up of the lower mantle 2 longer wavelength boussinesq convection 3 shorter wavelength for extended boussinesq convection 4 thick stable plumes with large plumeheads 5 thicker thermal boundary layer of around 500 km at the base of the mantle the contributions from the new terms due to the variable conductivity in the energy equation have magnitudes several times that of chondritic heating at the boundary layers a large region of superadiabatic lower mantle with about a 400 to 600 k excess is caused by variable thermal conductivity this finding has an interesting implication on the recent seismic finding of a lighter density in the deep portion of the lower mantle

the flow system in the japan sea caused by a sea level difference through shallow straits we investigate how the current system through the japan sea is driven and what determines the volume transport we suppose that a part of the difference in geopotential anomaly between the subtropical and subpolar gyre is converted into a barotropic sea level difference across the three shallow straits which connect the japan sea with the pacific and that this difference is the primary driving force of the current system then we examine the flow under the condition that there is a constant sea level difference between two oceans connected through a shallow strait we found that the strait acts as a source of arrested shelf waves or steady coastal flows for the timescale beyond the inertial period in the northern hemisphere steady flows are established along the shelves with the coast to the right left in the ocean of low high sea level we apply this notion to the current system through the japan sea the tsushima nearshore branch the tsugaru coastal mode and the soya current can all be interpreted as a coastally trapped flow whose source is the upstream strait further a series of northeastward flows along the south and east china seas shelves should be interpreted as coastally trapped flows whose source is the downstream tsushima strait numerical model experiments incorporating the realistic topography also simulate the observed flow fields the volume flux through each strait being limited geostrophically relations between the sea level difference and volume transport can be represented by simple formulas

an investigation of the dynamics of the east greenland current in fram strait based on a simple analytical model abstract the east greenland current egc in fram strait is examined in summer based on the hydrographic data from the mizex 84 experiment and its dynamics is further analyzed using a simple analytical model from the observed density field the southward geostrophic transport relative to the bottom in the egc is estimated to be about 4 sv sv 106 m3 s 1 at 78 4 n which assuming a ratio 1 1 between the bottom and the relative transports as suggested in the literature allows one to postulate a 4 sv bottom transport the hydrographic data also reveal a northward gradient of potential energy along the east greenland slope between 77 5 n and 80 5 n such a gradient is the prerequisite for the existence of the joint effect of baroclinicity and relief jebar which is here proposed as a driving mechanism for the bottom transport in the egc a model with idealized topography and a density distribution prescribed from the above data is constructed based on a steady state vorticity equation in which the

growth structure instability and collapse of canarian volcanoes and comparisons with hawaiian volcanoes recent onshore and offshore investigations in the canarian archipelago especially in the western islands of la palma and el hierro have greatly improved the understanding of the genesis and evolution of these islands and allow interesting comparisons with other hotspot induced oceanic island volcanoes especially the hawaiian archipelago genesis induced by hotspot activity and consequently shield and post erosional stages of growth allow the definition of similar main stratigraphic units the canarian and hawaiian volcanoes show common constructional and structural features such as rift zones progressive volcano instability and multiple gravitational collapses however the canaries present some important geological differences from the prototypical hotspot volcanoes of the hawaiian islands particularly the absence of significant subsidence the canarian volcanoes remain emergent until completely mass wasted by gravitational collapses and erosion volcanic formations over 20 million years are observable in outcrop in the canaries including the seamount stages of growth in several of the islands

structural features of the 2007 stromboli eruption abstract on 27 february 2007 two ne sw and nnw sse dike fed effusive vents opened to the north at 650 and 400 m above sea level asl of the summit craters at stromboli forming a fissure parallel to the inner walls of the sciara del fuoco sdf sector collapse depression the formation of these vents was soon followed by rapid subsidence of the summit crater area this partly obstructed the central conduit temporarily choking the fissure and increasing the deformation of the upper part of sdf the reactivation of the nnw sse vent and the opening of a new vent located at 500 m asl fed by a second dike released the internal pressure and surface deformation ceased the eruption then continued again from the 400 m vent after a summit explosion on 15 march until ending in early april after a progressive decrease of magma output repeated ne sw dike intrusions have occurred in recent years close to the upper se limit of the sdf in that zone named bastimento the eruptive fractures traced the discontinuities that borders the sdf increasing the risk of triggering new sector collapse whereas the ne sw trending structures lie along the regional volcano structural trend of the aeolian arc through stromboli the nnw sse vents are oblique to this trend and may be controlled by the anomalous stress field within the unstable flank of the sdf another fundamental aspect of the 2007 eruption is the collapse of the central conduit due to the rapid and deep magma drainage linked to the opening of the 400 m vent the intrusion of dikes and development of flank vents during the 2007 eruption could possibly have triggered catastrophic landslides and related tsunami or eruptive paroxysms but the opening of new effusive vents released the internal pressures diminishing the hazard

coastal trapped waves alongshore pressure gradients and the california undercurrent abstractthe california undercurrent cuc a poleward flowing feature over the continental slope is a key transport pathway along the west coast of north america and an important component of regional upwelling dynamics this study examines the poleward undercurrent and alongshore pressure gradients in the northern california current system ccs where local wind stress forcing is relatively weak the dynamics of the undercurrent are compared in the primitive equation navy coastal ocean model and a linear coastal trapped wave model both models are validated using hydrographic data and current meter observations in the core of the undercurrent in the northern ccs in the linear model variability in the predominantly equatorward wind stress along the u s west coast produces episodic reversals to poleward flow over the northern ccs slope during summer however reproducing the persistence of the undercurrent during late summer requires additional incoming energy from sea level variability applied south

application of independent component analysis to multi temporal insar data with volcanic case studies a challenge in the analysis of multi temporal interferometric synthetic aperture radar insar data is distinguishing and separating volcanic tectonic and anthropogenic displacements from each other and from atmospheric or orbital noise independent component analysis ica is a method for decomposing a mixed signal based on the assumption that the component sources are non gaussian and statistically independent ica has potential as a tool for exploratory analysis of insar data and in particular for testing whether geophysical signals are related or independent this article presents tests of the applicability of ica to insar using synthetic data and application to sentinel 1a archive images from two contrasting examples of volcano deformation co eruptive subsidence associated with the april 2015 eruption of calbuco chile was identified in spatial patterns found by maximising both spatial and temporal independence spatial patterns and rates of lava subsidence were retrieved using ica analysis of interferograms from paricutin lava fields mexico and found to be consistent with previous observations i demonstrate that ica is an appropriate method for the analysis of volcanic signals in the presence of atmospheric noise and propose a strategy for the automatic identification of geophysical displacements using cluster analysis of the spatial patterns of independent components this approach allows the detection of geophysical processes on a range of scales and provides a test of signal independence where multiple displacement sources are active

tracking morphological changes and slope instability using spaceborne and ground based sar data abstract stromboli aeolian archipelago italy is an active volcano that is frequently affected by moderate to large mass wasting which has occasionally triggered tsunamis with the aim of understanding the relationship between the geomorphologic evolution and slope instability of stromboli remote sensing information from space born synthetic aperture radar sar change detection and interferometry insar and ground based insar gbinsar was compared with field observations and morphological analyses ground reflectivity and squeesar an insar algorithm for surface deformation monitoring displacement measurements from x band cosmo skymed satellites csk were analysed together with displacement measurements from a permanent sited ku band gbinsar system remote sensing results were compared with a preliminary morphological analysis of the sciara del fuoco sdf steep volcanic flank which was carried out using a high resolution digital elevation model dem finally field observations supported by infrared thermographic surveys irt allowed the interpretation and validation of remote sensing data the analysis of the entire dataset collected between january 2010 and december 2014 covers a period characterized by a low intensity of strombolian activity this period was punctuated by the occurrence of lava overflows occurring from the crater terrace evolving downslope toward sdf and flank eruptions such as the 2014 event the amplitude of the csk images collected between february 22nd 2010 and december 18th 2014 highlights that during periods characterized by low intensity strombolian activity the production of materials ejected from the crater terrace towards the sdf is generally low and erosion is the prevailing process mainly affecting the central sector of the sdf csk squeesar and gbinsar data allowed the identification of low displacements in the sdf except for high displacement rates up to 1 5 mm h that were measured following both lava delta formation after the 2007 eruption and the lava overflows of 2010 and 2011 after the emplacement of the 2014 lava field high displacements in the central and northern portions of the sdf were recorded by the gbinsar device whereas the spaceborne data were unable to detect these rapid movements a comparison between irt images and gbinsar derived displacement maps acquired during the same time interval revealed that the observed displacements along the sdf were related to the crumbling of newly emplaced 2014 lava and of its external breccia detected slope instability after the 2014 flank eruption was related to lava accumulation on the sdf and to the difference in the material underlying the 2014 lava flow i lava flows and breccia layers related to the 2002 03 and 2007 lava flow fields in the northern sdf sector and ii loose volcaniclastic deposits in the central part of the sdf this work emphasizes the importance of smart integration of spaceborne sar derived hazard information with permanent sited operational monitoring by gbinsar devices to detect areas impacted by mass wasting and volcanic activity

applicability of sentinel 1 terrain observation by progressive scans multitemporal interferometry for monitoring slow ground motions in the san francisco bay area 2017 american geophysical union all rights reserved data from the sentinel 1 satellite have already proven useful for investigating seismic and volcanic events since its launch in april 2014 the requirement of ultrahigh coregistration accuracy and the current relatively short time of sentinel 1 acquisitions make its application challenging for studying slow deformation processes such as fault creep and land subsidence here we analyze a set of 14 sar images over the san francisco bay area spanning 1 year from early 2015 to 2016 we show that implementing an existing enhanced spectral diversity algorithm or using precise orbits together with a reference digital elevation model both yield the required coregistration accuracy for making use of the phase measurements in time series analysis of ground deformation following a thorough validation test we update our estimates of hayward fault creep rate and confirm uplift due to recharge of the santa clara valley aquifer system during the final summer of 4 year drought

the 2014 2015 eruption of fogo volcano geodetic modeling of sentinel 1 tops interferometry after 20 years of quiescence fogo volcano erupted in november 2014 the eruption produced fast moving lava flows that traveled for several kilometers and destroyed two villages this event represents the first episode of significant surface deformation imaged by the new european space agency s sentinel 1 satellite in its standard acquisition mode terrain observation by progressive scans tops which differs from that of previous synthetic aperture radar sar missions we perform a bayesian inversion of sentinel 1 tops sar interferograms spanning the eruption and accurately account for variations in the tops line of sight vector when modeling displacements our results show that magma ascended beneath the pico do fogo cone and then moved laterally toward its southwestern flank where the eruptive fissure opened this study provides important insights into the inner workings of fogo volcano and shows the potential of sentinel 1 tops interferometry for geophysical e g volcano monitoring applications

prodigious submarine landslides on the hawaiian ridge the extensive area covered by major submarine mass wasting deposits on or near the hawaiian ridge has been delimited by systematic mapping of the hawaiian exclusive economic zone using the side looking sonar system gloria these surveys show that slumps and debris avalanche deposits are exposed over about 100 000 km2 of the ridge and adjacent seafloor from kauai to hawaii covering an area more than 5 times the land area of the islands some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume ranking them among the largest on earth the slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts culminate near the end of subaerial shield building and apparently continue long after dormancy consequently landslide debris is an important element in the internal structure of the volcanoes the dynamic behavior of the volcanoes can be modulated by slope failure and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems the landslides are of two general types slumps and debris avalanches the slumps are slow moving wide up to 110 km and thick about 10 km with transverse blocky ridges and steep toes the debris avalanches are fast moving long up to 230 km compared to width and thinner 0 05 2 km they commonly have a well defined amphitheater at their head and hummocky terrain in the lower part oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high level wave deposits such as the 365 m elevation hulopoe gravel on lanai that are found on several islands most present day submarine canyons were originally carved subaerially in the upper parts of debris avalanches subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters

investigating collapse structures in oceanic islands using magnetotelluric surveys the case of fogo island in cape verde abstract one of the most remarkable natural events on earth are the large lateral flank collapses of oceanic volcanoes involving volumes of rock exceeding tens of km3 these collapses are relatively frequent in recent geological times as supported by evidence found in the geomorphology of volcanic island edifices and associated debris flows deposited on the proximal ocean floor the island of fogo in the cape verde archipelago is one of the most active and prominent oceanic volcanoes on earth the island has an average diameter of 25 km and reaches a maximum elevation of 2829 m above sea level m a s l at pico do fogo a young stratovolcano located within a summit depression open eastward due to a large lateral flank collapse the sudden collapse of the eastern flank of fogo island produced a megatsunami 73 ky ago the limits of the flank collapse were deduced as well from geomorphologic markers within the island the headwall of the collapse scar is interpreted as either being located beneath the post collapse volcanic infill of the summit depression or located further west corresponding to the bordeira wall that partially surrounds it the magnetotelluric mt method provides a depth distribution of the ground resistivity obtained by the simultaneous measurement of the natural variations of the electric and magnetic field of the earth two n s magnetotelluric profiles were acquired across the collapsed area to determine its geometry and boundaries the acquired mt data allowed the determination of the limits of the collapsed area more accurately as well as its morphology at depth and thickness of the post collapse infill according to the newly obtained mt data and the bathymetry of the eastern submarine flank of fogo the volume involved in the flank collapse is estimated in 110 km3 this volume the first calculated onshore stands between the previously published more conservative and excessive calculations offshore that were exclusively based in geomorphic evidence the model for the summit depression proposing two caldera collapses preceding the collapse of the eastern flank of fogo is supported by the mt data

a network based enhanced spectral diversity approach for tops time series analysis for multitemporal analysis of synthetic aperture radar sar images acquired with a terrain observation by progressive scan tops mode all acquisitions from a given satellite track must be coregistered to a reference coordinate system with accuracies better than 0 001 of a pixel assuming full sar resolution in the azimuth direction such a high accuracy can be achieved through geometric coregistration using precise satellite orbits and a digital elevation model followed by a refinement step using a time series analysis of coregistration errors these errors represent the misregistration between all tops acquisitions relative to the reference coordinate system we develop a workflow to estimate the time series of azimuth misregistration using a network based enhanced spectral diversity nesd approach in order to reduce the impact of temporal decorrelation on coregistration example time series of misregistration inferred for five tracks of sentinel 1 tops acquisitions indicates a maximum relative azimuth misregistration of less than 0 01 of the full azimuth resolution between the tops acquisitions in the studied areas standard deviation of the estimated misregistration time series for different stacks varies from 1 1e 3 to 2e 3 of the azimuth resolution equivalent to 1 6 2 8 cm orbital uncertainty in the azimuth direction these values fall within the 1 sigma orbital uncertainty of the sentinel 1 orbits and imply that orbital uncertainty is most likely the main source of the constant azimuth misregistration between different tops acquisitions we propagate the uncertainty of individual misregistration estimated with esd to the misregistration time series estimated with nesd and investigate the different challenges for operationalizing nesd

a unified description of localization for application to large scale tectonics 1 localized regions of deformation such as faults and shear zones are ubiquitous in the earth s lithosphere however we lack a simple unified framework of localization that is independent of the mechanism or scale of localization we address this issue by introducing the effective stress exponent ne a parameter that describes how a material responds to a local perturbation of an internal variable being tested for localization the value of ne is based on micromechanics a localizing regime has a negative ne indicating a weakening behavior and localization is stronger for more negative 1 ne we present expressions for the effective stress exponent associated with several mechanisms that trigger localization at large scale brittle failure with loss of cohesion elastoplasticity rate and state dependent friction shear heating and grain size feedback in ductile rocks in most cases localization does not arise solely from the relation between stress and deformation but instead requires a positive feedback between the rheology and internal variables brittle mechanisms failure and friction are generally described by ne of the order of 100 shear heating requires an already localized forcing which could be provided by a brittle fault at shallower levels of the lithosphere grain size reduction combined with a transition from dislocation to diffusion creep leads to localization only if the grain size departs significantly from its equilibrium value because either large scale flow moves rocks through different thermodynamic environments or new grains are nucleated when shear heating or grain size feedback produce localization 1 ne can be extremely negative and can control lithospheric scale localization

stratigraphy structure and geochronology of the las canadas caldera tenerife canary islands after a long period of subaerial fissure fed extrusions of basaltic magmas 12 to 3 ma volcanic activity was then concentrated in the central part of tenerife phonolitic magma chambers formed and a central volcanic complex was constructed the las canadas edifice the formation of a large depression the las canadas caldera truncated the top of the edifice the active twin strato cones teide pico viejo are sited in this depression the history of the las canadas caldera and edifice are established from stratigraphy geochronology k ar dates and volcanological studies two different groups are recognized separated by a major unconformity the lower group is dated at 2 to 3 ma and includes the products of several volcanic centres which together represent several cycles the upper group ranges from 1 56 to 0 17 ma and includes three different formations representing three long term 100 to 300 ka volcanic cycles the periods of dormancy between each formation were of 120 to 250 ka duration the las canadas caldera is a multicyclic caldera which formed over the period 1 18 0 17 ma each cycle of activity represented by a formation culminated in caldera collapse which affected different sectors of the las canadas edifice geological observation and geochronology support an origin by collapse into a magma chamber the minimum volume of pyroclastic ejecta is substantially greater than the present caldera depression volume 45 km3 but approaches the inferred volume of the original caldera depression 140 km3 after the formation of the caldera sector collapses could also occur at the northern flank of the volcano causing the disappearance of the northern side of the caldera wall

comparison of observed and model computed low frequency circulation and hydrography on the new england shelf 1 the finite volume coastal ocean model fvcom is configured to study the interannual variability of circulation in the gulf of maine gom and georges bank the fvcom gom system incorporates realistic time dependent surface forcing derived from a high resolution mesoscale meteorological model mm5 and assimilation of observed quantities including sea surface temperature and salinity and temperature fields on the open boundary an evaluation of fvcom gom model skill on the new england shelf is made by comparison of computed fields and data collected during the coastal mixing and optics cmo program august 1996 june 1997 model mean currents for the full cmo period compare well in both magnitude and direction in fall and winter but overpredict the westward flow in spring the direction and ellipticity of the subtidal variability correspond but computed magnitudes are around 20 below observed partially due to underprediction of the variability by mm5 response of subtidal currents to wind forcing shows the model captures the directional dependence as well as seasonal variability of the lag hydrographic results show that fvcom gom resolves the spatial and temporal evolution of the temperature and salinity fields the model computed surface salinity field compares well except in may when there is no indication of the fresh surface layer from the connecticut river discharge noted in the observations analysis of model computed results indicates that the plume was unable to extend to the mooring location due to the presence of a westward mean model computed flow during that time that was stronger than observed overall fvcom gom captures well the dynamics of the mean and subtidal flow on the new england shelf

the spectrum of persistent volcanic flank instability a review and proposed framework based on kīlauea piton de la fournaise and etna abstract persistent motion of the south flank of k lauea volcano hawai i has been known for several decades but has only recently been identified at other large basaltic volcanoes namely piton de la fournaise la reunion and etna sicily thanks to the advent of space geodetic techniques nevertheless understanding of long term flank instability is based largely on the example of k lauea despite the large differences in the manifestations and mechanisms of the process when viewed through a comparative lens for example the rate of flank motion at k lauea is several times that of etna and piton de la fournaise and is accommodated on a slip plane several km deeper than is probably present at the other two volcanoes gravitational spreading also appears to be the dominant driving force at k lauea given the long term steady motion of the volcano s south flank regardless of eruptive intrusive activity whereas magmatic activity plays a larger role in flank deformation at etna and piton de la fournaise k lauea and etna however are both characterized by heavily faulted flanks while piton de la fournaise shows little evidence for flank faulting a helpful means of understanding the spectrum of persistent flank motion at large basaltic edifices may be through a framework defined on one hand by magmatic activity which encompasses both magma supply and edifice size and on the other hand by the structural setting of the volcano especially the characteristics of the subvolcanic basement or subhorizontal intravolcanic weak zones a volcano s size and magmatic activity will dictate the extent to which gravitational and magmatic forces can drive motion of an unstable flank and possibly the level of faulting of that flank while the volcano s structural setting governs whether or not a plane of weakness exists beneath or within the edifice and can facilitate flank slip considering persistent flank instability using this conceptual model is an alternative to using a single volcano as a type example especially given that the example is usually k lauea which defines an extreme end of the spectrum and can provide a basis for understanding why flank motion may or may not exist on other large basaltic volcanoes worldwide

tectonic and anthropogenic deformation at the cerro prieto geothermal step over revealed by sentinel 1a insar the cerro prieto geothermal field cpgf lies at the step over between the imperial and the cerro prieto faults in northern baja california mexico while tectonically this is the most active section of the southern san andreas fault system the spatial and temporal deformation in the area is poorly resolved by the sparse global positioning system gps network coverage moreover interferograms from satellite observations spanning more than a few months are decorrelated due to the extensive agricultural activity in this region here we investigate the use of frequent short temporal baseline interferograms offered by the new sentinel 1a satellite to recover two components of deformation time series across these faults following previous studies we developed a purely geometric approach for image alignment that achieves better than 1 200 pixel alignment needed for accurate phase recovery we construct interferometric synthetic aperture radar time series using a coherence based small baseline subset method with atmospheric corrections by means of common point stacking we did not apply enhanced spectral diversity because the burst discontinuities are generally small 1 4 mm and can be effectively captured during the atmospheric corrections with these algorithms the subsidence at cpgf is clearly resolved the maximum subsidence rate of 160 mm yr due to extraction of geothermal fluids and heat dominates the 40 mm yr deformation across the proximal ends of the imperial the cerro prieto and the indiviso faults

insar observations of the 1995 fogo cape verde eruption implications for the effects of collapse events upon island volcanoes 1 fogo volcano cape verde islands erupted in april 1995 after 43 years of dormancy about 46 106 m3 of lava erupted during 7 5 weeks from vents on the sw flank of pico do fogo into cha das caldeiras interferograms obtained from 1993 1998 ers sar data show ground deformation due to the feeder dike but lack evidence for any volcano wide deformation related to volume changes of a shallow magma reservoir this suggests that fogo is fed from a relatively deep mantle lithospheric source 16 5 km depth consistent with petrological data this supports the concept that cha das caldeiras is the fill of a collapse scar created by a giant landslide and not a collapse caldera overlying a central shallow magma chamber the disturbance of the magmatic system by giant landslides may explain why some oceanic island volcanoes with high magma supply rates currently lack well developed shallow reservoirs

high resolution surface velocities and strain for anatolia from sentinel 1 insar and gnss data measurements of present day surface deformation are essential for the assessment of long term seismic hazard the european space agency s sentinel 1 satellites enable global high resolution observation of crustal motion from interferometric synthetic aperture radar insar we have developed automated insar processing systems that exploit the first 5 years of sentinel 1 data to measure surface motions for the 800 000 km2 anatolian region our new 3d velocity and strain rate fields illuminate deformation patterns dominated by westward motion of anatolia relative to eurasia localized strain accumulation along the north and east anatolian faults and rapid vertical signals associated with anthropogenic activities and to a lesser extent extension across the grabens of western anatolia we show that automatically processed sentinel 1 insar data can characterize details of the velocity and strain rate fields with high resolution and accuracy over large regions these results are important for assessing the relationship between strain accumulation and release in earthquakes