a scaling law for slow earthquakes with the availability of the global positioning system and other technical advances a growing number of unusual earthquake phenomena occurring at relatively long periods have been recognized they include deep episodic tremor low frequency earthquakes slow slip events and silent earthquakes based on data chiefly from western japan ide et al report that these slow seismic events follow a unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes a diverse array of unusual earthquake phenomena occurring at relatively long periods slow events follow a unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes indicating that they comprise a new earthquake category recently a series of unusual earthquake phenomena have been discovered including deep episodic tremor1 low frequency earthquakes2 very low frequency earthquakes3 slow slip events4 and silent earthquakes5 6 7 8 9 each of these has been demonstrated to arise from shear slip just as do regular earthquakes but with longer characteristic durations and radiating much less seismic energy here we show that these slow events follow a simple unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes we find that their seismic moment is proportional to the characteristic duration and their moment rate function is constant with a spectral high frequency decay of f 1 this scaling and spectral behaviour demonstrates that they can be thought of as different manifestations of the same phenomena and that they comprise a new earthquake category the observed scale dependence of rupture velocity for these events can be explained by either a constant low stress drop model or a diffusional constant slip model this new scaling law unifies a diverse class of slow seismic events and may lead to a better understanding of the plate subduction process and large earthquake generation

exploring the explosive effusive transition using permanent ultra violet cameras understanding the mechanisms that cause effusive eruptions is the key to mitigating their associated hazard here we combine results from permanent ultra violet uv cameras and from other geophysical observations seismic very long period thermal and infrasonic activity to characterize volcanic so2 flux regime in the period prior during and after stromboli s august november 2014 effusive eruption we show that in the two months prior to effusion onset the so2 flux levels are two times average level we explain this anomalously high so2 regime as primarily determined by venting of rapidly rising pressurized so2 rich gas pockets produced by strombolian explosions being more frequent and intense than usual we develop a procedure to track and count in the uv camera record the so2 flux pulses produced by individual explosions and puffing activity active degassing we find that these so2 pulses are far more numerous 67 47 events hour before the effusion onset than during normal activity 20 15 events hour this observation combined with geophysical evidence demonstrates an elevated gas bubble supply to the shallow conduits causing elevated explosive and puffing activity this increase 0 1 m3s 1 in magma transport rate in the north east feeding conduits finally triggers effusion onset active degassing remains elevated also during the effusive phase supporting the persistence of explosive and puffing activity during the effusive eruption deep in the volcanic conduit our results demonstrate that permanent uv cameras can valuably contribute to monitoring at high sampling frequency gas dynamics and fluxes thus opening the way to direct comparison with more established geophysical observations

an automated so 2 camera system for continuous real time monitoring of gas emissions from kīlauea volcano s summit overlook crater abstract so 2 camera systems allow rapid two dimensional imaging of sulfur dioxide so 2 emitted from volcanic vents here we describe the development of an so 2 camera system specifically designed for semi permanent field installation and continuous use the integration of innovative but largely off the shelf components allowed us to assemble a robust and highly customizable instrument capable of continuous long term deployment at k lauea volcano s summit overlook crater recorded imagery is telemetered to the usgs hawaiian volcano observatory hvo where a novel automatic retrieval algorithm derives so 2 column densities and emission rates in real time imagery and corresponding emission rates displayed in the hvo operations center and on the internal observatory website provide hvo staff with useful information for assessing the volcano s current activity the ever growing archive of continuous imagery and high resolution emission rates in combination with continuous data from other monitoring techniques provides insight into shallow volcanic processes occurring at the overlook crater an exemplary dataset from september 2013 is discussed in which a variation in the efficiency of shallow circulation and convection the processes that transport volatile rich magma to the surface of the summit lava lake appears to have caused two distinctly different phases of lake activity and degassing this first successful deployment of an so 2 camera for continuous real time volcano monitoring shows how this versatile technique might soon be adapted and applied to monitor so 2 degassing at other volcanoes around the world

mantle phase changes and deep earthquake faulting in subducting lithosphere inclined zones of earthquakes are the primary expression of lithosphere subduction a distinct deep population of subduction zone earthquakes occurs at depths of 350 to 690 kilometers at those depths ordinary brittle fracture and frictional sliding the faulting processes of shallow earthquakes are not expected a fresh understanding of these deep earthquakes comes from developments in several areas of experimental and theoretical geophysics including the discovery and characterization of transformational faulting a shear instability connected with localized phase transformations under nonhydrostatic stress these developments support the hypothesis that deep earthquakes represent transformational faulting in a wedge of olivine rich peridotite that is likely to persist metastably in coldest plate interiors to depths as great as 690 km predictions based on this deep structure of mantle phase changes are consistent with the global depth distribution of deep earthquakes the maximum depths of earthquakes in individual subductions zones and key source characteristics of deep events

effect of mantle compressibility on the thermal and flow structures of the subduction zones 1 the heat generated by viscous dissipation is consistently evaluated using a 2 d compressible subduction model with variations of mantle rheology constant as well as pressure and temperature dependent viscosity dip age and velocity of the subducting slab for comparison we also conduct 2 d incompressible subduction calculations with the same conditions and parameters used in the compressible formulation the effect of compressibility on the thermal and flow structures of the subduction zones is relatively small and concentrated along the base of the mantle wedge with temperature differences 100 c and differences in kinematic energy of the mantle wedge 1 between compressible and incompressible models mantle rheology has a stronger effect on thermal and flow structures than mantle compressibility as well as the variations of dip age and velocity of the subducting slab the heat from viscous dissipation in the compressible model increases the slab temperatures over the incompressible model 70 c as a result of additional conduction across the slab surface constant viscosity and thinning of the thermal boundary layer caused by viscosity reduction pressure and temperature dependent viscosity

mirdita zone ophiolites and associated sediments in albania reveal neotethys ocean origin the mirdita ophiolite zone in albania is associated with widespread melanges containing components of up to nappe size we dated matrix and components of the melange by radiolarians conodonts and other taxa the components consist of radiolarites pelagic limestones and shallow water limestones all of triassic age as well as ophiolites triassic radiolarite as a primary cover of ophiolite material proves middle triassic onset of mirdita ocean floor formation the melange contains a turbiditic radiolarite rich matrix radiolaritic flysch dated as late bajocian to early oxfordian it formed as a synorogenic sediment during west directed thrusting of ophiolite and sediment cover nappes representing ocean floor and underplated fragments of the western continental margin the tectonic structures formed during these orogenic events younger kimmeridian or eohellenic orogeny are sealed by late jurassic platform carbonates the geological history conforms with that of the inner dinarides and adjoining areas we therefore correlate the mirdita pindos ophiolite zone with the vardar zone and explain its present position by far distance west directed thrusting

periodic volcanic degassing behavior the mount etna example 1 in contrast to the seismic and infrasonic energy released from quiescent and erupting volcanoes which have long been known to manifest episodes of highly periodic behavior the spectral properties of volcanic gas flux time series remain poorly constrained due to a previous lack of hightemporal resolution gas sensing techniques here we report on so2 flux measurements performed on mount etna with a novel uv imaging technique of unprecedented sampling frequency 0 5hz which reveal for the first time a rapid periodic structure in degassing from this target these gas flux modulations have considerable temporal variability in their characteristics and involve two period bands 40 250 and 500 1200s a notable correlation between gas flux fluctuations in the latter band and contemporaneous seismic root mean square values suggests that this degassing behavior may be generated by periodic bursting of rising gas bubble trains at the magma air interface citation tamburello g a aiuppa a j s mcgonigle p allard a cannata g giudice e p kantzas and t d pering 2013 periodic volcanic degassing behavior the mount etna example geophys res lett 40 4818 4822 doi 10 1002 grl 50924

effects of water transportation on subduction dynamics roles of viscosity and density reduction abstract the effects of water on subduction dynamics e g plate migration rate slab geometry stress field and back arc spreading are investigated by using a 2 d self consistent model for lithosphere subduction and whole mantle convection we solve water transportation coupled with hydrous mineral phase changes mantle flows and water transportation are interactive through constitutive and state equations for hydrous rocks our model has successfully reproduced the water distribution in a mantle wedge and along the slab with sufficient resolution comparable to that of previous models that focus on the mantle wedge structure as a result low density owing to hydration reduces subduction rates back arc spreading and slab stagnation on the phase boundary at 660 km depth whereas low viscosity owing to hydration enhances rapid subduction trench migration and slab stagnation we attribute these results to mechanisms that cause the hydrous buoyancy of subducting plates to reduce the slab pull force and the accompanying tensile stress on overlying lithosphere in addition hydrous weakening diminishes the mechanical coupling of the subducted slab with the wedge mantle and overriding lithosphere thus water is capable of generating two opposite situations in the stress field of the overlying lithosphere and the subduction rate water is therefore expected to be an important mechanism for generating broad styles of the subduction structure and kinematics as observed in actual subduction zones such as tonga and mariana such observed variation in the subduction mode can be caused by variation in buoyancy corresponding to the water content from relatively dry to several thousands of parts per million for the wedge mantle and slab surface whereas the extremely buoyant case does not appear to occur in nature water in the mantle is thus key to better understand the whole mantle scale slab dynamics as well as island arc volcanic processes

coupled effects of phase transitions and rheology in 2 d dynamical models of subduction author s arredondo km billen mi abstract 2017 american geophysical union all rights reserved observations of seismicity and seismic tomography provide a present day constraint on the geometry of slabs within the mantle however it is challenging to directly relate the observed shape of slabs to their time evolution phase transitions modify the buoyancy forces within slabs affecting how slabs deform as they sink into the lower mantle and how forces are transmitted to the surface plates here we show that if the crustal shear zone is sufficiently weak 1020 pa s then the coupled effects of a compositionally dependent phase transition model and a stress dependent rheology lead to oscillatory plate speeds and trench motion in response to buckling and folding of the slab on average subducting plate velocity is 4 cm yr and trench motion is 0 7 cm yr however during folding subducting plate speed and trench motion increases by a factor of 3 and trench motion switches from advance to retreat in models with a higher viscosity shear zone 1021 pa s average plate speed is lower 2 cm yr and there is only trench advance stress dependent weakening due to increasing driving stresses can also cause unexpected changes in plate velocity i e decrease or no change in addition due to the added negative buoyancy from the phase transitions slab breakoff occurs in models with a yield stress 500 mpa because of the oscillatory motion of the trench long flat slabs do not form in the transition zone this suggests that other factors such as interaction of the slab with deep mantle flow may be required to create long flat slabs

applying uv cameras for so2 detection to distant or optically thick volcanic plumes abstract ultraviolet uv camera systems represent an exciting new technology for measuring two dimensional sulfur dioxide so 2 distributions in volcanic plumes the high frame rate of the cameras allows the retrieval of so 2 emission rates at time scales of 1 hz or higher thus allowing the investigation of high frequency signals and making integrated and comparative studies with other high data rate volcano monitoring techniques possible one drawback of the technique however is the limited spectral information recorded by the imaging systems here a framework for simulating the sensitivity of uv cameras to various so 2 distributions is introduced both the wavelength dependent transmittance of the optical imaging system and the radiative transfer in the atmosphere are modeled the framework is then applied to study the behavior of different optical setups and used to simulate the response of these instruments to volcanic plumes containing varying so 2 and aerosol abundances located at various distances from the sensor results show that uv radiative transfer in and around distant and or optically thick plumes typically leads to a lower sensitivity to so 2 than expected when assuming a standard beer lambert absorption model furthermore camera response is often non linear in so 2 and dependent on distance to the plume and plume aerosol optical thickness and single scatter albedo the model results are compared with camera measurements made at kilauea volcano hawaii and a method for integrating moderate resolution differential optical absorption spectroscopy data with uv imagery to retrieve improved so 2 column densities is discussed

geodynamic regimes of subduction under an active margin effects of rheological weakening by fluids and melts the dynamics of subduction under an active margin are analysed by using a 2d coupled petrological thermomechanical numerical model of an oceanic continental subduction system the model includes spontaneous slab bending dehydration of the subducted crust aqueous fluid transport partial melting of both crustal and mantle rocks as well as melt extraction processes resulting in magmatic arc crust growth based on our models the following five geodynamic regimes of subduction which may potentially form at active margins are identified i stable subduction with no backarc spreading centre and without plumes in the mantle wedge ii retreating subduction with a focused backarc spreading centre and without plumes iii retreating subduction with distributed intra arc extension and trans lithospheric sedimentary plumes iv advancing subduction with underplating laterally extending sub lithospheric plumes and v stable to advancing subduction with stationary laterally limited sub lithospheric plumes transitions between these different regimes are mainly caused by the concurrence of rheological weakening effects of i aqueous fluids percolating from the subducting slab into the mantle wedge and ii melts propagating from the partially molten areas formed in the mantle wedge towards the surface the aqueous fluids mainly affect the forearc region strong fluid related weakening promotes plate decoupling and reduces subduction drag and thus results in stacking of sediments in the accretion prism in contrast reduced weakening by fluids results in strong coupling of the plates and leads to advancing collision like subduction with enhanced subduction erosion thickening of the overriding plate and large sedimentary plumes in the mantle wedge are the consequences on the other hand melts extracted from the hot regions above the slab rheologically weaken the lithosphere below the arc which thus controls overriding plate extension and shortening strong rheological weakening by melts in combination with weak plate coupling trigger retreating subduction with a pronounced backarc spreading centre also weakening of the continental lithosphere by melts extracted from trans lithospheric sedimentary plumes generate a weak channel through which these structures may be emplaced into subarc crust if there is insufficient melt related weakening plumes cannot ascend but extend horizontally and thus underplate the lithosphere

quantification of the gas mass emitted during single explosions on stromboli with the so2 imaging camera we performed measurements using an so2 imaging camera of the so2 gas mass emitted during five discrete explosive events on stromboli volcano on 3 october 2006 the so2 gas mass released during discrete explosions was 15 40 kg per explosion producing 3 8 of the total daily so2 gas emission demonstrating that in terms of gas flux strombolian explosions are a second order phenomenon compared with quiescent degassing using the typical gas composition measured with op ftir allows us to determine the total gas mass released during an explosion as 360 960 kg with a volume of 1500 4100 m 3 at 1 bar at the probable source pressure of gas slug formation of 75 mpa this gas amount would occupy a volume equivalent to a sphere with a radius of 0 8 1 m comparable with estimates of stromboli s conduit geometry c 2009 elsevier b v all rights reserved

real time measurement of volcanic so 2 emissions validation of a new uv correlation spectrometer flyspec a miniaturized lightweight and low cost uv correlation spectrometer the flyspec has been devel oped as an alternative for the cospec which has long been the mainstay for monitoring volcanic sulfur dioxide fluxes field experiments have been conducted with the flyspec at diverse volcanic systems including masaya nicaragua po as costa rica stromboli etna and vulcano italy villarica chile and kilauea usa we present here those validation measurements that were made simultaneously with cospec at kilauea between march 2002 and february 2003 these experiments with source emission rates that ranged from 95 to 1 560 t d 1 showed statistically identical results from both instruments so2 path concentrations ranged from 0 to 1 000 ppm m with average correlation coefficients greater than r 2 0 946 the small size and low cost create the opportunity for flyspec to be used in novel deployment modes that have the potential to revolutionize the manner in which volcanic and industrial monitoring is performed

thermal regime of the costa rican convergent margin 1 along strike variations in heat flow from probe measurements and estimated from bottom simulating reflectors the thermal structure of convergent margins provides information related to the tectonics geodynamics metamorphism and fluid flow of active plate boundaries we report 176 heat flow measurements made with a violin bow style probe across the costa rican margin at the middle america trench the probe measurements are collocated with seismic reflection lines these seismic reflection lines show widespread distribution of bottom simulating reflectors bsrs to extend the spatial coverage of heat flow measurements we estimate heat flow from the depth of bsrs comparisons between probe measurements and bsr derived estimates of heat flow are generally within 10 and improve with distance landward of the deformation front together these determinations provide new information on the thermal regime of this margin consistent with previous studies the margin associated with the northern nicoya peninsula is remarkably cool we define better the southern boundary of the cool region the northern extent of the cool region remains poorly determined a regional trend of decreasing heat flow landward of the deformation front is apparent consistent with the downward advection of heat by the subducting cocos plate high wave number variability at a scale of 5 10 km is significantly greater than the measurement uncertainty and is greater south of the northern nicoya peninsula these heat flow anomalies vary between approximately 20 and 60 mw m 2 and are most likely due to localized fluid flow through mounds and faults on the margin simple one dimensional models show that these anomalies are consistent with flow rates of 7 15 mm yr 1 across the margin toe variability is significant and likely due to fluid flow through deformation structures associated with the frontal sedimentary prism

ifit a simple method for measuring volcanic so2 without a measured fraunhofer reference spectrum abstract accurate quantification of the emission rate of sulphur dioxide so2 from volcanoes provides both insights into magmatic processes and a powerful monitoring tool for hazard mitigation the primary method for measuring magmatic so2 is differential optical absorption spectroscopy doas of uv scattered sunlight spectra in which a reference spectrum taken outside the plume is used to quantify the so2 slant column density inside the plume this can lead to problems if the reference spectrum is contaminated with so2 as this will result in a systematic underestimation of the retrieved so2 slant column density and therefore emission rate we present a new analysis method named ifit which retrieves the so2 slant column density from uv spectra by directly fitting the measured intensity spectrum at high spectral resolution 0 01 nm using a literature solar reference spectrum and measured instrument characteristics this eliminates the requirement for a measured reference spectrum providing a point and shoot method for quantifying so2 slant column densities we show that ifit retrieves correct so2 slant column densities in a series of test cases finding agreement with existing methods we propose that ifit is suitable for both traverse measurements and permanent scanning stations and could be integrated into volcano monitoring networks at observatories finally we provide an open source software implementation of ifit with a user friendly graphical interface to allow users to easily utilise ifit

evolution of the molasse basin germany switzerland abstract in the molasse basin 500 1000 m thick mesozoic sediments overlie the variscan basement and locally permo carboniferous grabens containing a largely unknown thickness of clastic sediments the vindelician basement high extended southwestward from the bohemian massif and separated the southern part of the german basin from the tethys shelf triassic early and middle jurassic sediments progressively transgressed over this high which became fully inundated during the late jurassic following a temporary regression sedimentation resumed in the early cretaceous and after another hiatus in the late aptian to campanian during the latest cretaceous to earliest tertiary the area of southern germany became uplifted resulting in a progressive northwestward truncation of cretaceous strata and the late jurassic carbonates at the same time the bohemian massif became upthrusted along northwest striking wrench faults similar faults controlled the upthrusting of the landshut neuoetting high over which some 1 000 m of mesozoic sediments were eroded these wrench and thrust tectonics are part of an extensive compressional deformation in central europe that is supposed to be caused by the latest cretaceous earliest tertiary collision of the adriatic african and european plates during the alpine orogeny the area subsided again during the late eocene and developed into the molasse basin proper in which oligocene to miocene elastics reach a thickness of some 5 000 m near the alpine thrust front subduction and flexuring of the foreland caused numerous essentially basin parallel synthetic and antithetic normal faults the latter form the primary traps for oil and gas accumulations in the molasse basin

using so 2 camera imagery and seismicity to examine degassing and gas accumulation at kīlauea volcano may 2010 abstract so 2 camera measurements at k lauea volcano hawaii in may of 2010 captured two occurrences of lava lake rise and fall within the halema um au crater summit vent during high lava stands we observed diminished so 2 emission rates and decreased seismic tremor similar events at k lauea have been described as the result of sporadic degassing following gas accumulation beneath a mostly impermeable lava lake surface incorporation of so 2 camera data into a multi parameter dataset gives credence to the likelihood of shallow gas accumulation as the cause of these high stand events with accumulated gas release upon lake level drop compensating for the gas deficit reached during accumulation

the importance of serpentinite mylonites for subduction and exhumation of oceanic crust abstract in the ultramafic erro tobbio unit voltri massif western alps a set of overprinting structures in serpentinite mylonites is related to alpine subduction to about 80 km depth and to subsequent exhumation antigorite mylonites are cut by en echelon olivine veins which in turn are dissected by multiple sets of shear bands containing olivine and titanian clinohumite the transition from olivine free to olivine bearing structures indicates recrystallization during prograde metamorphism all structures display the same top to the nw kinematics providing evidence for a continuous non coaxial deformation the serpentinite mylonites surround km scale bodies of pre alpine peridotite which show only minor alpine overprint this indicates that during subduction related deformation recrystallization and fluid flow were strongly localized within serpentinite mylonites olivine bearing discontinuous shear planes with top to the se sense of movement crosscut the prograde structures the inversion of shear sense suggests a change in position of the serpentinites relative to the downgoing slab i e from the subducted slab to the upper plate during accretion thus the shear sense inversion marks the change from burial to exhumation of the serpentinites the low density of antigorite serpentinites 2 75 g cm3 causes strong buoyancy thus providing a mechanism for the exhumation of deeply subducted rocks it is suggested that serpentinites may act as carriers for the uprise of eclogite bodies which have higher densities than the peridotitic upper mantle

volcanological applications of so2 cameras ground based volcanic gas and ash imaging has the potential to revolutionise the way in which volcanoes are monitored and studied the ability to track and quantify volcanic emissions in space and time with unprecedented fidelity opens the door to integration with geophysical measurements allowing breakthroughs in our understanding of the physical processes driving volcanic activity in may 2013 a european science foundation funded plume imaging workshop was conducted in strombolutaly with the objective of bringing the ground based volcanic plume imaging community together in order to examine the state of the art and move towards a best practice for volcanic ash and gas imaging techniques a particular focus was the development of so2 imaging systems or so2 cameras with six teams deploying and testing various designs of ultraviolet and infrared based imaging systems capable of imagining so2 one conclusion of the workshop was that the term so2 camera should be applied to any so2 imaging system regardless of wavelength of radiation used this special issue on volcanic plume imaging is the direct result of the stromboli workshop and together the papers presented here represent the state of the art of ground based volcano plume imaging science and technology in this work we examine in detail the volcanological applications of the so2 camera reviewing previous works and placing the new research contained in this special issue in context the development of the so2 camera and future developments extending imaging to other volcanic gases is one of the most exciting and novel research frontiers in volcanology today c 2014 published by elsevier b v

shallow and deep controls on lava lake surface motion at kīlauea volcano abstract lava lakes provide a rare window into magmatic behavior and lake surface motion has been used to infer deeper properties of the magmatic system at halema uma u crater at the summit of k lauea volcano multidisciplinary observations for the past several years indicate that lava lake surface motion can be broadly divided into two regimes 1 stable and 2 unstable stable behavior is driven by lava upwelling from deeper in the lake presumably directly from the conduit and is an intrinsic process that drives lava lake surface motion most of the time this stable behavior can be interrupted by periods of unstable flow often reversals driven by spattering a shallowly rooted process often extrinsically triggered by small rockfalls from the crater wall the bursting bubbles at spatter sources create void spaces and a localized surface depression which draws and consumes surrounding surface crust spattering is therefore a location of lava downwelling not upwelling stable i e deep upwelling driven and unstable i e shallow spattering driven behavior often alternate through time have characteristic surface velocities flow directions and surface temperature regimes and also correspond to changes in spattering intensity outgassing rates lava level and seismic tremor these results highlight that several processes originating at different depths can control the motion of the lava lake surface and long term interdisciplinary monitoring is required to separate these influences these observations indicate that lake surface motion is not always a reliable proxy for deeper lake or magmatic processes from these observations we suggest that shallow outgassing spattering not lake convection drives the variations in lake motion reported at erta ale lava lake

the thermal structure of the subduction thrust within accretionary and erosive margins abstract we investigate differences in the thermal structure of the subduction thrust between accretionary and erosive margins using a finite element model global averages of plate margin geometries sediment thickness plate age and convergence rate are used to construct generic models of accretionary and erosive margins of these parameters our analysis shows that the largest uncertainty in these models is the geotherm for the incoming oceanic plate despite these uncertainties the subduction thrust of similarly aged accretionary margins is slightly warmer than erosive margins primarily due to the effect of sediment insulating the subduction thrust at accretionary margins if the updip limit of seismicity is thermally controlled warmer accretionary margins suggest shallower seismogenic updip limits counter to the observation that erosional margins are more likely to generate tsunamigenic earthquakes this discrepancy can be reconciled if frictional heat generation at erosive margins is larger than at accretionary margins

heat flow estimated from bsr and iodp borehole data implication of recent uplift and erosion of the imbricate thrust zone in the nankai trough off kumano heat flow values were estimated in the nankai trough fore arc slope region off kii peninsula from the bottom simulating reflector bsr and other data obtained during iodp expeditions 315 and 316 the heat flow has an uncertainty of 20 mainly due to ambiguities in the temperature estimate at the bsr and uncertainties on the thermal conductivity bsrs occur intermittently in the imbricate thrust zone itz they are significantly shallower below anticlines designated anticlinal high zone ahz than in the adjacent synclines basal low zone blz the heat flow in the blz 55 65 mw m2 is consistent with the regional heat flow trend the shallow bsr in the ahz produces an apparent high heat flow anomaly of 70 90 mw m2 and discontinuities are observed across thrust faults the most likely cause is the transient effect of thrust faulting followed by erosion on the hanging wall side a one dimensional time dependent numerical model with latent heat for hydrate and gas transition considered indicates that the relaxation time for the bsr to reequilibrate after such a disturbance is 10 kyr although the possibility that the shallow bsr is a remnant base of hydrate stability zone cannot be ruled out if the shortening has occurred in the recent 10 kyr the convergent rate at the itz would be 30 m kyr which is much larger than the recent horizontal shortening across the megasplay fault and could even exceed the portion of the plate convergence than that accommodated at the frontal thrust

a global synthesis of lava lake dynamics abstract active lava lakes represent a variety of open vent volcanism in which a sizable body of lava accumulates at the top of the magma column constrained by the vent and or crater geometry the longevity of lava lakes reflects a balancing of cooling and outgassing occurring at the surface and input of hot and gas rich magma from below due to their longevity and relative accessibility lava lakes provide a natural laboratory for studying fundamental volcanic processes such as degassing convection and cooling this article examines all seven lakes that existed at the time of writing in 2018 located in the pacific antarctica africa and south and central america these lakes span all tectonic environments and a range of magma compositions we focus on analysis of the lake surface motion using image velocimetry which reveals both similarities and contrasts in outgassing and lake dynamics when comparing the different lakes we identify two categories of lake behavior organized erta ale nyiragongo k lauea after 2011 and erebus and chaotic villarrica masaya marum this division does not map directly to lake size viscosity gas emission rate or temperature instead when examined together we find that the lakes follow a linear relationship between average surface speed and the ratio of total gas flux to lake surface area this relationship points to the combined importance of both flux and lake size in addition to the total volume of gas emission and suggests that a shared deep mechanism controls the supply of heat and gas to all lakes on the other hand the differences between chaotic and organized lakes highlight the important role of the geometry of the conduit lake transition which superimposes a shallow signal on that of the deep circulation the spatial patterns of surface motion we document suggest that the release of gas bubbles at chaotic lakes is more efficient i e bubbles are less likely to be retained and recycled compared with organized lakes in addition the data presented here indicate that the solidified crust of organized lakes plays a role in regulating convection and outgassing in lava lakes

depth of seismic coupling along subduction zones underthrusting at subduction zones can cause large earthquakes at shallow depths but it is always accommodated by aseismic deformation below a certain depth the maximum depth of the seismically coupled zone or seismogenic zone is a transition from unstable to stable sliding along the plate interface we have determined the depth of this stability transition for the circurn pacific subduction zones of honshu kuriles kamchatka aleutians alaska mexico and chile these subduction zones have experienced great interplate earthquakes and the aftershock regions are well located depth estimates of interplate events that are located at the downdip edge of the aftershock regions are used to determine the maximum depth of seismic coupling for an average p wave velocity of 6 7 km s 1 above the plate interface we find that for most subduction zones the stability transition occurs at 40 5 km depth there are however several exceptions at the hokkaido trench junction where the japan trench and the kurile trench intersect seismic coupling is deep and extends down to 52 55 km deep coupling was also found in the coquimbo region in central chile the mexico subduction zone has shallow coupling the transition occurs at 20 30 km depth previous studies of micro earthquakes in honshu hokkaido the aleutians and alaska show that earthquakes within the upper plate extend no deeper than the downdip edge of the coupled zone that we find given our measurements of seismic coupling depth we then explore the mechanism that may determine coupling depth the concept of critical temperature has been used to explain the depth of seismic coupling in other tectonic environments thus we first test whether a critical temperature can explain our results temperatures at the plate interface are dependent on many variables but two that are poorly determined are shear stress and radiogenic heat generation shear stress has been constrained by inversion of heat flow data assuming a crustal radiogenic heat production rate of 3 1 exp z 8 5 wm 3 and a constant coefficient of friction we find two critical temperatures of about 400 c and 550 c the lower critical temperature may be characteristic of regions with a relatively thick continental crust and the higher temperature of regions with a relatively thin continental crust on the other hand one single critical temperature of about 250 c can explain the coupling depths if shear stresses are constant with depth

partial melting of subducting oceanic crust the conditions under which partial melting of subducting oceanic crust occurs can be determined by combining a partial melting model for basaltic compositions with two dimensional thermal models of subduction zones for porosities of 1 containing h20 the amount of partial melt generated at the wet basaltic solidus is limited to 100 mpa can be maintained by rocks close to or above their melting temperatures in the absence of high shear stresses substantial melting of the oceanic crust will only occur during subduction of very young 5 ma oceanic lithosphere partial melting of hydrated basalt amphibolites derived from the mid ocean ridge has been proposed e g 1 3 as being responsible for the generation of certain recent high al andesitic to dacitic volcanic rocks adakites three of these volcanic suites mount st helens southern chile and panama occur in volcanic arcs where oceanic crust 25 ma is being subducted at rates of 1 3 cm yr and the calculated thermal regime is several hundreds of degrees hotter than more typical subduction zone environments however oceanic lithosphere is not currently being subducted beneath baja and new guinea where recent adakites are also present suggesting that some adakite magmas may form by water undersaturated partial melting of underplated mafic lower crust or previously subducted oceanic crust further experimental work on compositions representative of oceanic crust is required to define the depth of possible adakite source regions more accurately

the so2 camera a simple fast and cheap method for ground based imaging of so2 in volcanic plumes 1 so2 flux is widely monitored on active volcanoes as it gives a window into the hidden subsurface magma dynamics we present here a new approach to so2 flux monitoring using ultraviolet imaging of the volcanic plume through carefully chosen filters to produce images of so2 column amount the so2 camera heralds a breakthrough in both our ability to measure so2 flux at unprecedented frequencies 2 hz and at unprecedented accuracy thanks to the application of correlation techniques to determine wind speed directly from the images and the ability to measure the whole profile simultaneously in this paper we detail the commercially available pieces required to construct the so2 camera introduce a retrieval scheme to determine so2 amounts from the images and present results from a field campaign in november 2005 on sakurajima volcano japan

hydration adjacent to a deeply subducting slab the roles of nominally anhydrous minerals and migrating fluids subduction related transport of water into the mantle has significant dynamical and geochemical implications dehydration of hydrous phases within the slab can introduce water into the transition zone and lower mantle potentially hydrating nominally anhydrous minerals nam and impacting the viscosity and density structure of the mantle over a wide area we present models of fluid transport and mantle hydration in the vicinity of a deeply subducting slab focusing on the fate of water released by deep dehydration reaction in the subducted serpentinized mantle a sharp decrease in water storage capacity across the lower boundary of the transition zone may produce secondary dehydration of hydrated nam leading to precipitation of a hydrous fluid and heterogeneous hydration of the transition zone rapid fluid migration relative to the solid flow field can lead to a broad region of diffuse hydration within the upper mantle wedge and the potential for localized melt regions at the top of the transition zone coincident with fluid pathways slower fluid migration instead implies that the fluid phase can be transported deep into the lower mantle water stabilized in nam and as a free fluid can initiate upwelling within and above the transition zone a less abrupt change in water storage capacity across the base of the transition zone leads to high nam water contents in a channel adjacent to the slab where viscosity is reduced however seismic and electromagnetic observations of hydration in the transition zone are most compatible with a sudden drop of water storage capacity

sun photometer and lidar measurements of the plume from the hawaii kilauea volcano pu u o o vent aerosol flux and so2 lifetime 1 aerosol optical depths and lidar measurements were obtained under the plume of hawaii kilauea volcano on august 17 2001 9 km downwind from the erupting pu u o o vent measured aerosol optical depths at 500 nm were between 0 2 0 4 aerosol size distributions inverted from the spectral sun photometer measurements suggest the volcanic aerosol is present in the accumulation mode 0 1 0 5 micron diameter which is consistent with past in situ optical counter measurements the aerosol dry mass flux rate was calculated to be 53 mg d 1 the estimated so2 emission rate during the aerosol measurements was 1450 mg d 1 assuming the sulfur emissions at pu u o o vent are mainly so2 not aerosol this corresponds to a so2 half life of 6 0 hours in the atmosphere

intercomparison of so2 camera systems for imaging volcanic gas plumes abstract so 2 camera systems are increasingly being used to image volcanic gas plumes the ability to derive so 2 emission rates directly from the acquired imagery at high time resolution allows volcanic process studies that incorporate other high time resolution datasets though the general principles behind the so 2 camera have remained the same for a number of years recent advances in ccd technology and an improved understanding of the physics behind the measurements have driven a continuous evolution of the camera systems here we present an intercomparison of seven different so 2 cameras in the first part of the experiment the various technical designs are compared and the advantages and drawbacks of individual design options are considered though the ideal design was found to be dependent on the specific application a number of general recommendations are made next a time series of images recorded by all instruments at stromboli volcano italy is compared all instruments were easily able to capture so 2 clouds emitted from the summit vents quantitative comparison of the so 2 load in an individual cloud yielded an intra instrument precision of about 12 from the imagery emission rates were then derived according to each group s standard retrieval process a daily average so 2 emission rate of 61 10 t d was calculated due to differences in spatial integration methods and plume velocity determination the time dependent progression of so 2 emissions varied significantly among the individual systems however integration over distinct degassing events yielded comparable so 2 masses based on the intercomparison data we find an approximate 1 sigma precision of 20 for the emission rates derived from the various so 2 cameras though it may still be improved in the future this is currently within the typical accuracy of the measurement and is considered sufficient for most applications

depth of the decoupling plate interface and thermal structure under arcs subduction proceeds as thrust movements at the boundary between the subducting plate and the rigid overlying plate at depth below this mechanically decoupling plate interface the subducting plate couples with the overlying mantle and flow is induced in the mantle wedge this induced flow is the main factor that controls thermal structure under arcs depth of this decoupling to coupling transition at the plate interface is estimated from observed surface heat flow in the northeastern japan arc using a two dimensional numerical simulation of thermal structure the estimated depth is about 70 km the termination depth of thrust earthquakes agrees well with the depth of the coupling transition which indicates that these earthquakes occur at the decoupling plate interface the mechanism of this decoupling plate interface is discussed in this paper it is believed that water associated with the subducting oceanic crust reduces the frictional stress at the plate interface and thrust movement thus becomes possible petrological studies show that dehydration reaction in the subducting oceanic crust terminate at about 2 0 gpa and have little temperature dependence termination depths of thrust earthquakes estimated from seismic studies are nearly the same 60 80 km for various arcs this indicates that depth of the decoupling to coupling transition is controlled by the termination depth of dehydration reaction in the subducting oceanic crust across arc heat flow profiles observed in various subduction zones show similar features heat flow is very low in the forearc region and increases steeply at the volcanic front considering that the depth of the slab is about 100 km at the volcanic front for various arcs this heat flow feature is closely related to the depth of the slab thus it is concluded that thermal structure under arcs is mainly controlled by the depth of the pressure dependent dehydration reactions in the subducting oceanic crust

aeromagnetic measurements in the eastern alps the area east of the tauern window abstract the northern margin of the basement complex east of the tauern window is characterized by a particular magnetic signature which connects the penninic systems of rechnitz bernstein with that of the tauern window these partly ophiolitic structures are interpreted as belonging to the penninic and reach depths in the range 3 7 or even more km the ultramafic masses of hochgrossen and larchkogel are considered as exposed penninic remnants the crystalline basement complex east of the tauern window is dominated by anomaly patterns of an entirely different character the anomalies are generally weaker and the locations of the magnetic sources are much shallower representative of this type is the rraubath mass starting from the analysis of the magnetic pattern a model is presented for integrating the area east of the tauern window into an evolutive concept in terms of plate tectonic history

terraferma the transparent finite element rapid model assembler for multiphysics problems in earth sciences we introduce and describe a new software infrastructure terraferma the emph transparent finite element rapid model assembler for the rapid and reproducible description and solution of coupled multiphysics problems the design of terraferma is driven by two computational needs in earth sciences the first is the need for increased flexibility in both problem description and solution strategies for coupled problems where small changes in model assumptions can lead to dramatic changes in physical behavior the second is the need for software and models that are more transparent so that results can be verified reproduced and modified in a manner such that the best ideas in computation and earth science can be more easily shared and reused terraferma leverages three advanced open source libraries for scientific computation that provide high level problem description fenics composable solvers for coupled multiphysics problems petsc and an options handling system spud that allows the hierarchical management of all model options terraferma integrates these libraries into an interface that organizes the scientific and computational choices required in a model into a single options file from which a custom compiled application is generated and run because all models share the same infrastructure models become more reusable and reproducible while still permitting the individual researcher considerable latitude in model construction terraferma solves partial differential equations using the finite element method it is particularly well suited for nonlinear problems with complex coupling between components terraferma is open source and available at http terraferma github io which includes links to documentation and example input files this article is protected by copyright all rights reserved

a community benchmark for subduction zone modeling we have developed a suite of benchmarks to facilitate the comparison of numerical models for the dynamics and thermal structure of subduction zones the benchmark cases are based on a thermomechanical approach in which the slab is prescribed kinematically and the wedge flow is computed dynamically we propose various cases to investigate the influence of boundary conditions and rheology on wedge flow and resulting thermal structure a comparison between the codes suggest that accurate modeling of the thermal field requires a good implementation of the velocity discontinuity along the seismogenic zone and high resolution in the thermal boundary layers a minor modification to the boundary conditions of the wedge flow is also necessary to avoid a pressure singularity that exists in analytical solutions of the cornerflow model

a review of controls on lava lake level insights from halema uma u crater kīlauea volcano the height of the lava column is a fundamental measure of open vent volcanic activity but little continuous long term data exist to understand this parameter the recent 2008 2018 lava lake activity at the summit of k lauea volcano provides an opportunity to track and understand the processes that control lava level over timescales ranging from minutes to years we review recently published data as well as analyze the long term record of lava level at k lauea s summit during 2009 2017 longer timescale fluctuations over days to months have a strong positive linear correlation with ground deformation suggesting they reflect pressure changes in the summit magma reservoir shorter timescale fluctuations over minutes to hours have an inverse relationship with spattering i e outgassing intensity at the lake surface increased outgassing lowers the lake level and vice versa our analysis of the long term lava level data thus confirms that lava level at halema uma u is controlled by these two types of processes 1 those related to magma reservoir pressure changes such as magma supply rate and 2 shallow outgassing fluctuations such as gas pistoning frequency filtering can isolate pressure and outgassing driven components of lava level change time series analysis indicates that there was no large persistent periodicity in the lava level a minor fortnightly oscillation might be related to earth tides but was not continuously present the correlation between lava level and deformation of the summit indicates that the lava lake acts as a reliable piezometer tracking lava level over time may thus provide an indication of flank eruptive potential we show that long term interdisciplinary monitoring is necessary to discriminate the processes that control lava level

a plate tectonic model for the mesozoic and early cenozoic history of the caribbean plate abstract we present a model in which the caribbean plate is an intra american feature formed along the caribbean spreading center as opposed to the current model that considers the caribbean plate as a far travelled crustal segment that formed in the pacific region paleomagnetic data which cover an age range from jurassic through paleocene indicate the ophiolite complexes in costa rica and panama formed in an equatorial position the ophiolites did not fundamentally change their position relative to south america since their origin basaltic rocks of the lower part of the ophiolites are of mid ocean ridge type suggesting formation at a spreading center they are interpreted to have formed as part of the proto caribbean crust at a spreading axis in an intra american position during jurassic and early cretaceous times the upper part of the ophiolites is mainly built up by island arc and intraplate basalts the island arc basalts evolved at the central american landbridge which started in the middle cretaceous the intraplate basalts are related to the caribbean plateau basalt which thickened and stiffened the caribbean crust in middle cretaceous to probably campanian times changes in relative plate motions along the middle american convergent plate margin are reflected by orientations and time sequences of paleostress tensors calculated from fault slip data in southern mexico and costa rica kinematic indicators from mylonite zones display sinistral movement along secondary shear zones within the southern mexican crustal complexes and along the northern boundary of the chortis block in the motagua polochic fault system this reflects the eastward drift of the chortis block since the beginning of the cenozoic at this time the chortis block became part of the caribbean plate which moved more than 1000 km towards the east relative to the north and south american plates during the cenozoic

retrieval of volcanic ash particle size mass and optical depth from a ground based thermal infrared camera abstract volcanoes can emit fine sized ash particles 1 10 m radii into the atmosphere and if they reach the upper troposphere or lower stratosphere these particles can have deleterious effects on the atmosphere and climate if they remain within the lowest few kilometers of the atmosphere the particles can lead to health effects in humans and animals and also affect vegetation it is therefore of some interest to be able to measure the particle size distribution mass and other optical properties of fine ash once suspended in the atmosphere a new imaging camera working in the infrared region between 7 14 m has been developed to detect and quantify volcanic ash the camera uses passive infrared radiation measured in up to five spectral channels to discriminate ash from other atmospheric absorbers e g water molecules and a microphysical ash model is used to invert the measurements into three retrievable quantities the particle size distribution the infrared optical depth and the total mass of fine particles in this study we describe the salient characteristics of the thermal infrared imaging camera and present the first retrievals from field studies at an erupting volcano an automated ash alarm algorithm has been devised and tested and a quantitative ash retrieval scheme developed to infer particle sizes infrared optical depths and mass in a developing ash column the results suggest that the camera is a useful quantitative tool for monitoring volcanic particulates in the size range 1 10 m and because it can operate during the night it may be a very useful complement to other instruments e g ultra violet spectrometers that only operate during daylight

quantitative imaging of volcanic plumes results needs and future trends abstract recent technology allows two dimensional imaging of trace gas distributions in plumes in contrast to older one dimensional remote sensing techniques that are only capable of measuring total column densities the new imaging methods give insight into details of transport and mixing processes as well as chemical transformation within plumes we give an overview of gas imaging techniques already being applied at volcanoes so2 cameras imaging doas ft ir imaging present techniques where first field experiments were conducted led lidar tomographic mapping and describe some techniques where only theoretical studies with application to volcanology exist e g fabry perot imaging gas correlation spectroscopy bi static lidar finally we discuss current needs and future trends in imaging technology

palaeogeography of alpine flysch abstract palaoegeography of alpine basins during times of flysch sedimentation is reconstructed from an approach based upon global tectonic constraints on palinspastic reconstruction from regional geology and on the sedimentalogy of individual flysch sequences the opening of the central atlantic ocean coincident with the formation of the western mediterranean tethys implied left lateral movement between africa and europe during the break up of pangea whereas n s trending margins of this part of oceanic tethys would have been predominantly passive the e w trending northern margin would have been a major transform zone the combination of these broad constraints with detailed palinspastic reconstruction of the area considered provides an approximate early cretaceous palaeogeography of that part of the western mediterranean tethys which was to build the western alps flysch sediments had not yet appeared on the scene the subsequent openings of the south atlantic and the north atlantic oceans together with their spreading rates provide constraints on the movement of africa and therefore adria the southern and eastern margin of the oceanic basin concerned with respect to europe these movements are tied in with the sedimentology of alpine flysch sequences to provide map views of the northern part of the western mediterranean tethys during its closure late cretaceous to palaeogene a number of apparently conflicting views and theories on flysch palaeogeography may be reconciled by this approach

continuous measurements of sif 4 and so 2 by thermal emission spectroscopy insight from a 6 month survey at the popocatepetl volcano abstract the processes linked with the emplacement and growth destruction of a lava dome are of prime importance to understand the stability of such extrusions and assess the associated risks for local populations during the last couple of decades ground and space based spectroscopic techniques have been developed to monitor such processes from a safe distance such approaches significantly improved our knowledge about the relationship between the chemical composition of the volcanic gas plumes and both the deep and shallow volcanic processes leading to the different types of explosive activity the potential of the ground based thermal emission fourier transform infrared spectroscopy ftir remained under exploited due to the difficulty to properly handle the radiative transfer phenomena despite the drawbacks in the complex analytical requirements this method enables to continuously monitor day and night with a high temporal resolution 1 meas 3 min relevant gas species such as so 2 and sif 4 in the volcanic plumes previous studies have related the temporal variations of the sif 4 so 2 ratio in volcanic plumes to the onset of vulcanian explosions this study reports a 6 month so 2 sif 4 and sif 4 so 2 time series from january to june 2015 of the popocatepetl s gas plume obtained from ftir thermal emission spectroscopic measurements the infrared spectra were analyzed using the sfit4 radiative transfer and inverse model which we have adapted for this application we obtained highly variable sif 4 so 2 ratios with a mean value of 3 6 10 4 with the highest values around 3 10 3 measured during the final phase of a lava dome growth february march 2015 the rapid sif 4 so 2 variations were more carefully explored and compared for the first time with the seismic activity a remarkable coincidence between sharp sif 4 so 2 rises and the seismic events are evidenced here

the zone of influence of the subducting slab in the asthenospheric mantle due to the multi disciplinary nature of combined geodynamics and shear wave splitting studies there is still much to be understood in terms of isolating the contributions from mantle dynamics to the shear wave splitting signal even in a two dimensional 2d mantle flow framework this paper investigates the viscous flow development of lattice preferred orientation lpo and predicted shear wave splitting for a suite of buoyancy driven subduction models to shed light on the nature of the slab driven asthenospheric flow field the models show that the spatial dimensions of the slab driven zone of influence in the mantle lpo fabric and resulting synthetic splitting are sensitive to the slab dip and slab strength with the maximum lpo fabric development occurring for models with a moderate initial slab dip and weaker slab the models show that olivine lpo fabric in the asthenosphere generally increases in alignment strength with increased proximity to the slab but can be transient and spatially variable on small length scales the results suggest lpo formed during initial subduction may persist into the steady state subduction regime the vertical flow fields in the asthenosphere can produce shear wave splitting variations with back azimuth that deviate from the predictions of uniform trench normal anisotropy a result that bears on the interpretation of complexity in shear wave splitting observed in real subduction zones furthermore the models demonstrate that the corner flow paradigm should not be equated with a 2d subduction framework

image based correction of the light dilution effect for so2 camera measurements abstract ultraviolet so 2 cameras are increasingly used in volcanology because of their ability to remotely measure the 2d distribution of so 2 in volcanic plumes at a high frequency however light dilution i e the scattering of ambient photons within the instrument s field of view fov on air parcels located between the plume and the instrument induces a systematic underestimation of the measurements whose magnitude increases with distance so 2 content atmospheric pressure and turbidity here we describe a robust and straightforward method to quantify and correct this effect we retrieve atmospheric scattering coefficients based on the contrast attenuation between the sky and the increasingly distant slope of the volcanic edifice we illustrate our method with a case study at etna volcano where difference between corrected and uncorrected emission rates amounts to 40 to 80 and investigate the temporal variations of the scattering coefficient during 1 h of measurements on etna we validate the correction method at popocatepetl volcano by performing measurements of the same plume at different distances from the volcano finally we reported the atmospheric scattering coefficients for several volcanoes at different latitudes and altitudes

degassing processes during lava dome growth insights from santiaguito lava dome guatemala abstract eruptions of intermediate magma may be explosive or effusive the development of open system degassing has been proposed as a pre requisite for effusion of intermediate magma however processes leading to open system degassing are poorly understood to better understand degassing processes during lava dome extrusion we report high temporal resolution so2 emission rate measurements collected with an ultra violet imaging camera at santiaguito guatemala santiaguito is an ideal case study as the dome lava is compositionally very similar to products of the 1902 plinian eruption of the parental santa maria volcano we find that degassing is weak 0 4 1 kg s 1 but continuous and explosions are associated with small increases in emission rates up to 2 3 kg s 1 continuous repose degassing occurs through a shallow cap rock which likely represents a proto crust on the block lava flow which is extruded from the same vent the continual permeability of the upper conduit argues against a mechanism of explosion triggering in which gas pressure builds beneath a viscous cap rock or plug rather we consider degassing data better consistent with a model of shear fracturing at the conduit margins using field constraints we model the viscosity of santiaguito magma as a function of depth and show that conditions for shear fracturing are met from 150 600 m to the surface this is in line with independent estimates of explosion initiation depth we show that repose timescales are orders of magnitude longer than the timescale for shear fracture and suggest that explosions are triggered when a continuous network of smaller scale fractures develops at which point decompression occurs and an explosion is triggered fracture healing occurs by viscous relaxation however near to the surface where viscosity is highest an unconsolidated gouge layer may develop our model implies that the observed explosions are a by product of extrusion shear fracturing can drive open system degassing of crystal rich intermediate magma at shallow levels in the conduit as high magma viscosity is able to overcome the low strain rates associated with slow ascent of magma

temperatures heat flux and frictional stress near major thrust faults we examine the two dimensional advective and conductive transport of heat in a region of thrust faulting both simple theoretical considerations and numerical experiments show that the steady state temperatures near the fault are reduced by a divisor s 1 b z vsin below what they would be with the same heat sources but in the absence of advection in this expression z is the depth to the fault v is the slip rate is the component of the dip of the fault in the direction of underthrusting is thermal diffusivity and b is a dimensionless factor that is essentially equal to one for most forms of heating initial changes in temperatures near the fault are given by t z t t z 0 12vsin t z 0 z these simple formulae are successful because of the neglible influence of lateral conduction of heat at least for slip rates of a few mm yr or more two time constants govern the transition from the initial change in temperature to steady state t1 u v where u is the distance along the fault in the direction of underthrusting from the surface to the depth in question and t2 z 2 2 where z is the depth to the fault when elapsed times exceed the sum of these two time constants temperatures differ from their steady state values by only about 10 percent the numerical experiments indicate that the simple formulae are sufficiently accurate that sophisticiated numerical modeling of temperatures in specific regions is unwarranted putain an application of these simple formulae to measurements of conductive heat flow at island arcs implies that shear stresses at island arcs approach 100 mpa and are greater than 30 mpa calculations of temperatures appropriate for the himalaya suggest that shear stresses of 100 mpa on the main central thrust probably are required to account for the tertiary granites of the region if melting took place after slip began on the thrust similarly the cut off in seismicity at a depth of about 15 km in the himalaya if due to temperatures exceeding 350 to 450 c implies a deviatoric stress close to 100 mpa

plate motions in the alpine region and their correlation to the opening of the atlantic ocean the plate tectonic evolution of the alps is intimately related to the stepwise protrusion of the atlantic ocean to the north the south penninic oceanic basin of the alps is part of the spreading system of the early atlantic ocean in the jurassic in the lower cretacous the north peeninic basin forms as an appendix of the atlantic in its second stage of evolution connected with it via the pyrenees trough and the bay of biscay subduction in the south penninic ocean by convergent motion of the brianconian and the adriatic plates leads to a first continental collision in about mid cretaceous time in the upper cretaceous when the atlantic ocean protrudes between north america and greenland eurasia and africa move divergently and there is relative quiescence in the alps in the tertiary the atlantic ocean spreads between greenland and scandinavia which results in convergent motion between eurasia and africa and important compressional events in the alps

comparison of cospec and two miniature ultraviolet spectrometer systems for so2 measurements using scattered sunlight the correlation spectrometer cospec the principal tool for remote measurements of volcanic so2 is rapidly being replaced by low cost miniature ultraviolet uv spectrometers we compared two of these new systems with a cospec by measuring so2 column amounts at k lauea volcano hawaii the two systems one calibrated using in situ so2 cells and the other using a calibrated laboratory reference spectrum employ similar spectrometer hardware but different foreoptics and spectral retrieval algorithms accuracy signal to noise retrieval parameters and precision were investigated for the two configurations of new miniature spectrometer measurements included traverses beneath the plumes from the summit and east rift zone of k lauea and testing with calibration cells of known so2 concentration the results obtained from the different methods were consistent with each other with 8 difference in estimated so2 column amounts up to 800 ppm m a further comparison between the cospec and one of the miniature spectrometer configurations the flyspec spans an eight month period and showed agreement of measured emission rates to within 10 for so2 column amounts up to 1 600 ppm m the topic of measuring high so2 burdens accurately is addressed for the k lauea measurements in comparing the foreoptics retrieval methods and resultant implications for data quality we aim to consolidate the various experiences to date and improve the application and development of miniature spectrometer systems

protocols for uv camera volcanic so2 measurements abstract ultraviolet camera technology offers considerable promise for enabling 1 hz timescale acquisitions of volcanic degassing phenomena providing two orders of magnitude improvements on sampling frequencies from conventionally applied scanning spectrometer systems this could for instance enable unprecedented insights into rapid processes such as strombolian explosions and non aliased corroboration with volcano geophysical data the uptake of this technology has involved disparate methodological approaches hitherto as a means of expediting the further proliferation of such systems we here study these diverse protocols with the aim of suggesting those we consider optimal in particular we cover choice and set up of hardware calibration for vignetting and for absolute concentrations using quartz so 2 cells the retrieval algorithm and whether one or two filters or indeed cameras are necessary this work also involves direct intercomparisons with narrowband observations obtained with a scanning spectrometer system employing a differential optical absorption spectroscopic evaluation routine as a means of methodological validation

seismic image of the deep crust at the eastern margin of the alps austria indications for crustal extension in a convergent orogen abstract a 39 km long deep seismic reflection profile recorded during two field campaigns in 1996 and 2002 provides a first detailed image of the deep crust at the eastern margin of the eastern alps austria the ese wnw trending low fold seismic line crosses austroalpine basement units and extends approximately from 20 km west of the penninic window group of rechnitz to 60 km sse of the alpine thrust front the explosive source seismic data reveals a transparent shallow crust down to 5 km depth a complexly reflective upper crust and a highly reflective lowermost crust the upper crust is dominated by three prominent west dipping packages of high amplitude subparallel reflections the upper two of these prominent packages commence at the eastern end of the profile at about 5 and 10 km depth and are interpreted as low angle normal shear zones related to the miocene exhumation of the rechnitz metamorphic core complex in the western portion of the upper crust east dipping and less significant reflections prevail the lowermost package of these reflections is suggested to represent the overall top of the european crystalline basement along the western portion of the line the lower crust is characterised by a 6 8 km thick band of high amplitude reflection lamellae typically observed in extensional provinces the moho can be clearly defined at the base of this band at approximately 32 5 km depth due to insufficient signal penetration outstanding reflections are missing in the central and eastern portion of the lower crust we speculate that the result of accompanying gravity measurements and lower crustal sporadic reflections can be interpreted as an indication for a shallower moho in the east preferable at about 30 5 km depth the high reflectivity of the lowermost part of the lower crust and prominent reflection packages in the upper crust the latter interpreted to represent broad extensional mylonite zones emphasises the latest extensional processes in accordance with eastward extrusion

strength of stick slip and creeping subduction megathrusts from heat flow observations subduction faults called megathrusts can generate large and hazardous earthquakes the mode of slip and seismicity of a megathrust is controlled by the structural complexity of the fault zone however the relative strength of a megathrust based on the mode of slip is far from clear the fault strength affects surface heat flow by frictional heating during slip we model heat flow data for a number of subduction zones to determine the fault strength we find that smooth megathrusts that produce great earthquakes tend to be weaker and therefore dissipate less heat than geometrically rough megathrusts that slip mainly by creeping

u th pb systematics of morphologically characterized zircon and allanite a high resolution isotopic study of the alpine rensen pluton northern italy abstract the rensen pluton is a typical member of the tertiary calc alkaline plutonic suite structurally connected to the periadriatic lineament it intrudes the austroalpine polymetamorphic basement of the eastern alps southwest of the tauern window northern italy zircons and allanites from tonalitic quartz dioritic and monzogranitic lithologies were studied systematically on the basis of refined grain by grain microanalytical techniques high resolution isotope analyses show that morphology and u pb systematics of zircon are highly correlated with magma evolution zircons from the main tonalitic part of the intrusion display a gradual increase of u content from early stage s type morphology to late stage g1 type morphology most of the zircon crystals include premagmatic seeds derived from old crustal sources unevolved s type zircons contain inherited components of late proterozoic early paleozoic apparent age whereas late stage g1 type zircons show inheritance of early proterozoic apparent age both types of inherited components are present in zircons from a fine grained tonalitic domain located at the center of the pluton which shows restitic structures the crustal affinity of this rock is corroborated by its relatively low e nd value 6 0 as compared to values obtained for the main tonalite 3 9 and the quartz diorite 3 5 the accuracy of cainozoic zircon ages is affected by initial radioactive disequilibrium in the u pb decay chains particularly uncertain is the fractionation behavior of protactinium which could be enriched in zircon due to the high stability of the pa 5 oxidation state because the th pb system is devoid of long lived intermediate radioactive nuclides the best approximation to the emplacement age of the rensen pluton is given by allanite th pb ages of 31 70 0 25ma 95 c l for the main tonalite and by a slightly younger age of 31 09 0 32ma for quartz diorite

the connection between iron ore formations and mud shrimp colonizations around sunken wood debris and hydrothermal sediments in a lower cretaceous continental rift basin mecsek mts hungary in the early cretaceous the continental rift basin of the mecsek mts hungary was situated on the southern edge of the european plate the opening of the north atlantic ocean created a dilatational regime that expanded to the southern edge of the european plate where several extensional basins and submarine volcanoes were formed during the early cretaceous epoch permanent seaquake activity caused high swell events during which a large amount of terrestrial wood fragments entered into submarine canyons from rivers or suspended woods which had sunk into the deep seafloor these fragments created extended wood fall deposits which contributed large scale flourishing of numerous burrowing thalassinid crustaceans twelve different thalassinid coprolite ichnospecies can be found in the berriasian hauterivian volcano sedimentary formations

shallow degassing events as a trigger for very long period seismicity at kīlauea volcano hawai i the first eruptive activity at k lauea volcano s summit in 25 years began in march 2008 with the opening of a 35 m wide vent in halema uma u crater the new activity has produced prominent very long period vlp signals corresponding with two new behaviors episodic tremor bursts and small explosive events both of which represent degassing events from the top of the lava column previous work has shown that vlp seismicity has long been present at k lauea s summit and is sourced approximately 1 km below halema uma u by integrating video observations infrasound and seismic data we show that the onset of the large vlp signals occurs within several seconds of the onset of the degassing events this timing indicates that the vlp is caused by forces sourced at or very near the lava free surface due to degassing transmitted down the magma column and coupling to the surrounding rock at 1 km depth

relation between single very long period pulses and volcanic gas emissions at mt asama japan 1 multiple volcanic observations conducted at mt asama japan provide evidence of a link between single very long period vlp seismic pulses and volcanic gas emissions so2 flux measurements were conducted on 2 june 2009 when mt asama was producing ash free eruptions with vlp pulses gas bursts from a vent at the crater bottom following the vlp pulses provided an excellent opportunity to examine the relation directly the so2 emission for each eruption was calculated by integrating high temporal so2 flux data obtained by the so2 imaging system and subtracting the contribution from quiescent degassing from fumaroles around the crater bottom a seismic moment of vlp pulse was estimated by the waveform inversion we observed seven eruptions and obtained the proportional relation between vlp pulse moment and so2 emission the relation determined is consistent with the vlp source model these observational results are the first report of a quantitative comparison between single vlp pulse moment and volcanic gas emission

dynamics of the ryukyu izu bonin marianas double subduction system trench motions represent the surface expression of the interaction between subducting plates and the underlying mantle but the inherent dynamics are not fully understood one interesting case is the migration of the izu bonin marianas trench ibm that accommodates the subduction of the pacific beneath the philippine sea plate psp which is in turn subducting beneath the eurasian plate along the ryukyu trench the history of the ibm trench is dominated by fast episodic retreat from 40 to 15 ma however around 10 5 ma the ibm trench reversed its motion from retreat to advance the switch in trench motion occurred soon after the breakoff of the psp slab along the ryukyu trench and the onset of new subduction and represents a fundamental change in the dynamics of the western pacific subduction zones here following the modelling study of ci kova and bina 2015 which suggested a link between ibm trench advance and ryukyu subduction we run 2 d numerical experiments to test the influence of a newly formed ryukyu slab on the established ibm subduction zone we run two dimensional numerical experiments to test the influence of this newly formed ryukyu slab on the ibm subduction zone the results from our geodynamic model compare favourably with the reconstructed trend indicating that the switch in trench motion along the ibm trench may indeed be related to the onset of a new subduction zone along the ryukyu trench our analysis substantiates the idea that advancing trench motions in the western pacific are due to the establishment of a double subduction system further analysis of such dynamics provides insights for the mechanisms controlling subducting plate and trench motions and mantle force transmission

aeromagnetic imaging of the dun mountain ophiolite belt in northern new zealand insight into the fine structure of a major sw pacific terrane suture a new aeromagnetic survey of the junction magnetic anomaly in northern new zealand reveals that it is associated with up to 10 subparallel lineaments the junction magnetic anomaly delineates the dun mountain ophiolite belt a remarkably linear though sigmoidally bent major boundary zone traceable through most of new zealand which separates terranes sutured onto the new zealand gondwana margin in late mesozoic time modelling of the lineaments in conjunction with a new review of structures along the dun mountain ophiolite belt throughout new zealand indicates that the dun mountain ophiolite belt in auckland consists of a number of imbricate slices most of which are likely to dip steeply to the east i e overturned away from the former trench and extend to considerable depth in the crust the source bodies for the central high amplitude magnetic lineaments are interpreted to be serpentinite shear or melange zones cutting a large lensoid body of ultramafic rocks similar to those occurring elsewhere along the length of the dun mountain ophiolite belt our data have revealed that a formerly postulated offset of the dun mountain ophiolite belt in the region instead resembles a duplex or thrust imbricate like bundling of shear zones these shear zones were probably initiated as accretion thrusts but complexities in their pattern indicate subsequent shearing including backfolding to an overturned attitude and possibly strike slip to produce the linear nature of the dun mountain ophiolite belt the outer lineaments mostly mark accretion thrusts in the adjacent terranes this study demonstrates that detailed aeromagnetic surveys can delineate the fine structure in ophiolite complexes and thereby give valuable insights into the effects of micro continental collision on an accretionary margin

drift tectonics the fundamental rhythm of crustal drift and deformation several years of research on deformational history of the alps and their central european foreland led to the development of new models for the driving mechanism of continental drift and intraplate tectonics it was found that a global rhythm of continental drift exists which causes the phases of epeirogeny by regular deformation of lithospheric structures this approach was made possible by the development of a new method of comparing and analysing paleomagnetic and tectonic data

balancing lateral orogenic float of the eastern alps abstract oligocene to miocene post collisional shortening between the adriatic and european plates was compensated by frontal thrusting onto the molasse foreland basin and by contemporaneous lateral wedging of the austroalpine upper plate balancing of the upper plate shortening by horizontal retrodeformation of lateral escaping and extruding wedges of the austroalpine lid enables an evaluation of the total post collisional deformation of the hangingwall plate quantification of the north south shortening and east west extension of the upper plate is derived from displacement data of major faults that dissect the austroalpine wedges indentation of the south alpine unit corresponds to 64 km north south shortening and a minimum of 120 km of east west extension lateral wedging affected the eastern alps east of the giudicarie fault west of the giudicarie fault north south shortening was compensated by 50 to 80 km of backthrusting in the lombardian thrust system of the southern alps the main structures that bound the escaping wedges to the north are the inntal fault system ca 50 km sinistral offset the konigsee lammertal traunsee klt fault 10 km and the salzach ennstal mariazell puchberg semp fault system 60 km these faults as well as a number of minor faults with displacements less than 10 km root in the basal detachment of the alps the thin skinned nature of lateral escape related structures north of the semp line is documented by industry reflection seismic lines crossing the northern calcareous alps nca and the frontal thrust of the eastern alps complex triangle zones with passive roof backthrusts of middle miocene molasse sediments formed in front of the laterally escaping wedges of the northern eastern alps the aim of this paper is a semiquantitative reconstruction of the upper plate of the eastern alps most of the data is published elsewhere

burial and exhumation of corsica france in the light of fission track data 1 the mesozoic and cenozoic exhumation and cooling history of corsica is reconstructed by fission track ft data on basement and sedimentary rocks apatite ages are 105 16 ma zircon ages are 160 145 ma the jurassic and cretaceous ages show that parts of the variscan basement escaped alpine influence the basement was thermally affected by rifting prior to jurassic opening of the ligurian piedmont ocean then it cooled to near surface temperatures in paleocene eocene times subduction buried parts of the basement and overlying flysch to greater depth in the oligocene both collapse of the nappe stack and rifting prior to opening of the ligurian provencal basin affected the apatite ft system of the basement in different partly overlapping areas causing a complex age pattern the study shows that thorough analysis of ft data and thermal modeling allow to assign age populations to distinct cooling processes even when several thermotectonic events contributed to generate an intricate age pattern

an inverted continental moho and serpentinization of the forearc mantle volatiles that are transported by subducting lithospheric plates to depths greater than 100 km are thought to induce partial melting in the overlying mantle wedge resulting in arc magmatism and the addition of significant quantities of material to the overlying lithosphere asthenospheric flow and upwelling within the wedge produce increased lithospheric temperatures in this back arc region but the forearc mantle in the corner of the wedge is thought to be significantly cooler here we explore the structure of the mantle wedge in the southern cascadia subduction zone using scattered teleseismic waves recorded on a dense portable array of broadband seismometers we find very low shear wave velocities in the cold forearc mantle indicated by the exceptional occurrence of an inverted continental moho which reverts to normal polarity seaward of the cascade arc this observation provides compelling evidence for a highly hydrated and serpentinized forearc region consistent with thermal and petrological models of the forearc mantle wedge this serpentinized material is thought to have low strength and may therefore control the down dip rupture limit of great thrust earthquakes as well as the nature of large scale flow in the mantle wedge

the tectono metamorphic history of the valaisan domain from the western to the central alps new constraints on the evolution of the alps petrographic and structural studies on metasedimentary rocks of the valaisan domain from the engadine window switzerland to the petit st bernard france show that this entire domain was subjected to high pressure low temperature conditions during the alpine orogeny the pressure and temperature conditions increased from east to west the metasedimentary rocks of the engadine window and the grisons area are characterized by blueschist facies conditions 12 13 kbar 350 400 c defined by mg carpholite and chloritoid occurrences toward the west in the petit st bernard and versoyen units the metamorphic conditions reached the eclogite facies 15 16 kbar 500 c the shortening direction associated with the high pressure metamorphic event was oriented northwest southeast all over the valaisan domain this direction is compatible with the direction of convergence between the european and apulian plates in early tertiary time 65 35 ma in the eastern and central alps blueschist facies rocks occur below the austroalpine nappes over an area of 300 20 km 2 from the tauern window to the grisons area and have a thickness around 10 km this volume of blueschist facies rocks is in contrast with eclogite facies rocks of western alps that form only a small slice with a thickness of 2 to 5 km we interpret the difference in volume and metamorphic conditions from east to west as being due to a change of the subduction style in the east we assume the formation of a large wedge with a thickness of 40 50 km such that rocks underwent blueschist metamorphism and were exhumed before collision between the european and apulian plates in the west the petit st bernard and the versoyen units were metamorphosed and extruded in a subduction channel above the subducting slab the data further allow us to conclude that the valaisan domain was an ocean that was independent of the piemontese ocean and that had an important place in the youngest phase of the evolution of the alps before the collision

spatially resolved so2 flux emissions from mt etna we report on a systematic record of so2 flux emissions from individual vents of etna volcano sicily which we obtained using a permanent uv camera network observations were carried out in summer 2014 a period encompassing two eruptive episodes of the new south east crater nsec and a fissure fed eruption in the upper valle del bove we demonstrate that our vent resolved so2 flux time series allow capturing shifts in activity from one vent to another and contribute to our understanding of etna s shallow plumbing system structure we find that the fissure eruption contributed 50 000 t of so2 or 30 of the so2 emitted by the volcano during the 5 july to 10 august eruptive interval activity from this eruptive vent gradually vanished on 10 august marking a switch of degassing toward the nsec onset of degassing at the nsec was a precursory to explosive paroxysmal activity on 11 15 august

development of an ultra violet digital camera for volcanic so2 imaging abstract in an effort to improve monitoring of passive volcano degassing we have constructed and tested a digital camera for quantifying the sulfur dioxide so 2 content of volcanic plumes the camera utilizes a bandpass filter to collect photons in the ultra violet uv region where so 2 selectively absorbs uv light so 2 is quantified by imaging calibration cells of known so 2 concentrations images of volcanic so 2 plumes were collected at four active volcanoes with persistent passive degassing villarrica located in chile and santiaguito fuego and pacaya located in guatemala images were collected from distances ranging between 4 and 28 km away with acceptable detection up to approximately 16 km camera set up time in the field ranges from 5 10 min and temporal resolution of up to 6 images per minute is possible which combined with the camera s field of view makes a continuous so 2 dataset attainable variable in plume concentrations can be observed and accurate plume speeds or rise rates can readily be determined by tracing individual portions of the plume within sequential images initial fluxes computed from camera images require a correction for the effects of environmental light scattered into the field of view at fuego volcano simultaneous measurements of corrected so 2 fluxes with the camera and a correlation spectrometer cospec agreed within 25 experiments at the other sites were equally encouraging and demonstrated the camera s ability to detect so 2 under variable background meteorological and environmental conditions this early work has shown great success in imaging so 2 plumes and offers promise for volcano monitoring due to its rapid deployment and data processing capabilities relatively low cost and improved interpretation afforded by synoptic coverage from a range of distances

seismic consequences of warm versus cool subduction metamorphism examples from southwest and northeast japan warm and cool subduction zones exhibit differences in seismicity seismic structure and arc magmatism which reflect differences in metamorphic reactions occurring in subducting oceanic crust in southwest japan arc volcanism is sparse and intraslab earthquakes extend to 65 kilometers depth in northeast japan arc volcanism is more common and intraslab earthquakes reach 200 kilometers depth thermal petrologic models predict that oceanic crust subducting beneath southwest japan is 300 to 500 c warmer than beneath northeast japan resulting in shallower eclogite transformation and slab dehydration reactions and possible slab melting