extracting time domain green s function estimates from ambient seismic noise 1 it has been demonstrated experimentally and theoretically that an estimate of the green s function between two seismic stations can be obtained from the time derivative of the long time average cross correlation of ambient noise between these two stations this tdgf estimate from just the noise field includes all tensor components of the green s function and these green s function estimates can be used to infer earth structure we have computed cross correlations using 1 to 30 continuous days of ambient noise recorded by over 150 broadband seismic stations located in southern california the data processing yielded thousands of cross correlation pairs for receiver separations from 4 500 km which clearly exhibit coherent broadband propagating dispersive wavetrains across frequency band 0 1 2 hz

the turbulent oscillator a mechanism of low frequency variability of the wind driven ocean gyres intrinsic low frequency variability is studied in the idealized quasigeostrophic midlatitude wind driven ocean gyres operating at large reynolds number a robust decadal variability mode driven by the transient mesoscale eddies is found and analyzed the variability is a turbulent phenomenon which is driven by the competition between the eddy rectification process and the potential vorticity anomalies induced by changes of the intergyre transport

long period 12 sec volcanic tremor observed at usu 2000 eruption seismological detection of a deep magma plumbing system 1 from a temporal deployment of a broadband seismic network at usu volcano japan we observed long period 12 sec volcanic tremors during the first few weeks of the eruptive activity which started in the end of march 2000 the source of these long period tremors are located relatively deep at a depth of 5 km and their amplitude variation well correlates with the uplift rate of the eruption area we thus attribute these long period tremors to the flow induced vibration of a magma chamber and its outlet located around the source region of the long period tremors this may be the first seismological detection of long period 10 sec vibrations of a deep magma plumbing system

fluid dynamics of oceanic thermocline ventilation abstract a flux form of the potential vorticity pv equation is applied to study the creation and transport of potential vorticity in an ocean gyre generalized pv fluxes j vectors and the associated pv flux fines are used to map the creation by buoyancy forcing of pv in the mixed layer and its transport as fluid is subducted through the base of the mixed layer into the thermocline the pv flux lines can either close on themselves recirculation or begin and end on the boundaries ventilation idealized thermocline solutions are diagnosed using j vectors which vividly illustrate the competing process of recirculation through western boundary currants and subduction from the surface potential vorticity flux vectors are then used to quantify the flux of mass passing invisidly through a surface across which potential vorticity changes discontinuously but at which potential density and velocity are continuous such a surface might be the base of the oceanic mixed layer or in a meteorological context

modeling of surface deformation in volcanic areas the 1970 1972 and 1982 1984 crises of campi flegrei italy campi flegrei is a densely inhabited volcanic area within a caldera 12 14 km in diameter immediately west of naples italy in 1970 1972 and in 1982 1984 campi flegrei experienced considerable ground surface deformation producing a bulge about 3 5 m high at its peak in the two inflation episodes the point of maximum uplift did not change coinciding with the caldera center about which the displacements exhibited radial symmetry the 1982 1984 uplift was accompanied by considerable seismic activity gravity changes have been interpreted as reflecting the occurrence of a subvertical magmatic intrusion volcanological petrological and geophysical data point to the existence of a shallow magma chamber just beneath the center of the caldera we assume that the observed surface displacements are the response of an essentially elastic medium to a pressure increase in the magma chamber static deformation is calculated by using a finite element method assuming axial symmetry around a vertical axis through the caldera center the role played by various components of the model geometry boundary conditions elastic properties is analyzed it is shown that models assuming uniform elasticity are inadequate therefore the major volcanotectonic features as well as the influence of temperature and pressure on the elastic properties are taken into account the results of various more complex models are presented it is suggested that a progressively fractured zone whose size and shape depend also on the possible occurrence of magmatic intrusions may explain the observed surface displacements and the other data collected at campi flegrei it is suggested that the 1970 1972 uplift was possibly accompanied by larger scale changes in the stress field

insar bias and uncertainty due to the systematic and stochastic tropospheric delay we quantify the bias and uncertainty of interferometric synthetic aperture radar insar displacement time series and their derivatives the displacement velocities by analyzing the systematic and stochastic components of the temporal variation of the tropospheric delay the biases due to the systematic seasonal delay depend on the sar acquisition times whereas the uncertainties depend on the standard deviation of the random delay the number of acquisitions the total time span covered and the covariance of the time series of the stochastic delay between a pixel and the reference we study the contribution of the wet delay to the insar observations along the western india plate boundary using i moderate resolution imaging spectroradiometer precipitable water vapor ii stratified tropospheric delay estimated from the era i global atmospheric model and iii seven envisat insar swaths our analysis indicates that the amplitudes of the annual delay vary by up to 10 cm in this region equivalent to a maximum displacement bias of 24 cm in insar line of sight direction between two epochs assuming envisat is6 beam mode the stratified tropospheric delay correction mitigates this bias and reduces the scatter due to the stochastic delay for 7 years of envisat acquisitions along the western india plate boundary the uncertainty of the insar velocity field due to the residual stochastic wet delay after stratified tropospheric delay correction using the era i model is in the order of 2 mm yr over 100 km and 4 mm yr over 400 km we discuss the implication of the derived uncertainties on the full variance covariance matrix of the insar data

insar observations of post rifting deformation around the dabbahu rift segment afar ethiopia summary increased displacement rates have been observed following manylarge earthquakes and mag matic events although an order of magnitude smaller than the displacements associated with the main event the post seismic or post rifting deformation may continue for years to decades after the initial earthquake or dyke intrusion due to the rare occurrence of subaerial rifting events thereareveryfewobservationstoconstrainmodelsofpost riftingdeformation in2005 september a 60 km long dyke was intruded along the dabbahu segment of the nubia arabia plate boundary afar ethiopia marking the beginning of an ongoing rifting episode con tinued activity has been monitored using satellite radar interferometry and data from global positioning system instruments deployed around the rift in response to the initial intrusion using multiple satellite passes we are able to separate the rift perpendicular and vertical displacement fields around the dabbahu segment rift perpendicular and vertical rates of up to 180 and 240 mm yr 1 respectively here we show that models of viscoelastic relaxation alone are insufficient to reproduce the observed deformation field and that a large portion of the observed signal is related to the movement of magma within the rift segment our models suggest upper mantle viscosities of 10 18 19 pas overlain by an elastic crust of between 15 and 30km to fit the observations inflation and deflation of magma chambers in the centre of the rift and to the south east of the rift axis is required at rates of 0 13 and 0 08km 3 yr 1

satellite radar interferometry 1993 1999 suggests deep accumulation of magma near the crust mantle boundary at the krafla volcanic system iceland 1 deep magma accumulation near the crust mantle boundary 21 km depth at the krafla volcanic system is suggested from insar observations a best fit model derived from four interferograms covering 1993 1999 comprises an opening dike representing plate spreading and post rifting deformation and two mogi sources a mogi source deflating at a rate of 0 3 106 m3 yr coincides with the shallow krafla magma chamber while a deeper inflating mogi source further north at 21 km depth inflates at a rate of 26 106 m3 yr the inflating source is at or near the crust mantle boundary as identified by seismic studies and is interpreted as accumulating magma

localized deformation at miyakejima volcano based on jers 1 radar interferometry 1992 1998 1 stacked radar interferograms at miyakejima volcano japan between 1992 and 1998 showed two localized significantly deforming areas with a magnitude of 4 6 mm yr in the radar line of sight one area is close to the 1983 eruption vent and using a simple closed analytical formulation the deformation is interpreted as due to a thermoelastic contraction of a formerly intruded magma the other one detected in the previous caldera is explained by a depressurization source whose depth 500 m coincides with that of a low resistivity zone interpreted as a hydrothermal reservoir also our computed co2 flux is consistent with in situ measurement data the reservoir volume is significantly less than the collapsed volume in 2000 and its depth is much shallower than the void detected prior to the collapse hence the depressurization would not directly induce the caldera collapse in 2000

the eruptive history and magmatic evolution of aluto volcano new insights into silicic peralkaline volcanism in the ethiopian rift the silicic peralkaline volcanoes of the east african rift are some of the least studied volcanoes on earth here we bring together new constraints from fieldwork remote sensing geochronology and geochemistry to present the first detailed account of the eruptive history of aluto a restless silicic volcano located in a densely populated section of the main ethiopian rift prior to the growth of the aluto volcanic complex before 500 ka the region was characterized by a significant period of fault development and mafic fissure eruptions the earliest volcanism at aluto built up a trachytic complex over 8 km in diameter aluto then underwent large volume ignimbrite eruptions at 316 19 ka and 306 12 ka developing a 42 km2 collapse structure after a hiatus of 250 ka a phase of post caldera volcanism initiated at 55 19 ka and the most recent eruption of aluto has a radiocarbon age of 0 40 0 05 cal ka bp during this post caldera phase highly evolved peralkaline rhyolite lavas ignimbrites and pumice fall deposits have erupted from vents across the complex geochemical modelling is consistent with rhyolite genesis from protracted fractionation 80 of basalt that is compositionally similar to rift related basalts found east of the complex based on the style and volume of recent eruptions we suggest that silicic eruptions occur at an average rate of 1 per 1000 years and that future eruptions of aluto will involve explosive emplacement of localised pumice cones and effusive obsidian coulees of volumes in the range 1 100 106 m3

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

3 d surface deformation of the 2000 usu eruption measured by matching of sar images a subpixel level offset estimation technique was applied to sar synthetic aperture radar images of usu volcano japan using radarsat sar amplitude images acquired from ascending and descending orbits we generated a map of three dimensional displacement vectors showing ground deformation associated with criptdome formation in april 2000 moreover displacement velocities and volume changes were estimated from april 3 29 inflation was observed with vertical and horizontal displacements each exceeding 20m during the period of major activity from april 3 5 uplift and n s spreading velocities reached 3 3m day and 2 7m day respectively while volume change was 3 4 106 m day although this technique is less precise than other methods and is not very sensitive to local deformations it provides several key advantages including 1 personnel are not required to enter hazardous areas 2 it provides wide spatial coverage and 3 it does not depend on coherence making it more widely applicable than insar

recent advances in sar interferometry time series analysis for measuring crustal deformation abstract synthetic aperture radar sar interferometry is a technique that permits remote detection of deformation at the earth s surface and has been used extensively to measure displacements associated with earthquakes volcanic activity and many other crustal deformation phenomena analysis of a time series of sar images extends the area where interferometry can be successfully applied and also allows detection of smaller displacements through the reduction of error sources here we review recent advances in time series sar interferometry methods that further improve accuracy this is particularly important when constraining displacements due to processes with low strain rates such as interseismic deformation we include examples of improved algorithms applied to image deformation associated with the 2010 eruption of eyjafjallajokull volcano in iceland slow slip on the guerrero subduction zone in mexico and tectonic deformation in western anatolia turkey

post eruptive volcanic dome evolution as revealed by deformation and microgravity observations at usu volcano hokkaido japan abstract usu volcano hokkaido japan is a dacitic volcano known for its high production rate of lava domes and crypto domes it is thus a good target to study processes of volcanic dome evolution upheaval and or relaxation we carried out repeated gps and microgravity surveys on the three most recent domes of mt usu 1910 meiji shinzan 1943 1945 showa shinzan and 1977 1982 usu shinzan the repeat period was 1 to 2 months and extended from october 1996 to june 1997 we also compare new data with results from former studies more than 20 years after the start of usu shinzan dome growth there is still subsidence at a maximum rate of about 7 to 8 cm year the reasons for this subsidence are discussed repeated gravity surveys revealed an increase of gravity on the domes about 60 10 microgal year for usu shinzan about 15 microgal at showa shinzan and 10 to 20 microgal for meiji shinzan this gravity increase exceeds that expected due to subsidence we discuss and interpret the excess gravity change in terms of a density increase in the edifice caused by a combination of processes contraction of the edifice water level change devesiculisation cooling and magma intrusion quantification of these processes at usu volcano may help to understand the processes of evolution at domes on other volcanoes such as merapi indonesia unzen japan or montserrat west indies

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

diagnosing the observed seasonal cycle of atlantic subtropical mode water using potential vorticity and its attendant theorems analyzed fields of ocean circulation and the flux form of the potential vorticity equation are used to map the creation and subsequentcirculation of lowpotential vorticity waters known as subtropical mode water stmw in the north atlantic novel mapping techniques are applied to i render the seasonal cycle and annual mean mixed layer vertical flux of potential vorticity pv through outcrops and ii visualize the extraction ofpv from the mode water layer in winter over and to the south of the gulf stream both buoyancy loss and wind forcing contributetotheextractionofpv buttheauthorsfindthattheformergreatlyexceedsthelatter thesubsequent path of stmw is also mapped using bernoulli contours on isopycnal surfaces

homogenization of potential vorticity in planetary gyres the mean circulation of planetary fluids tends to develop uniform potential vorticity q in regions where closed time mean streamlines or closed isolines of mean potential vorticity exist this state is established in statistically steady flows by geostrophic turbulence or by wave induced potential vorticity flux at the outer edge of the closed contours the expelled gradients of q are concentrated beyond this transition lies motionless fluid or a different flow regime in which the planetary gradient of q may be dominant the homogenized regions occur where direct forcing by external stress or heating within the closed isoline is negligible upon the potential density surface under consideration in the stably stratified ocean such regions are found at depths greater than those of direct wind induced stress or penetrative cooling in channel models of the atmosphere we again find constant q when mesoscale eddies cause the dominant potential vorticity flux in the real atmosphere the results here can apply only where internal heating is negligible the derivations given here build upon the prandtl batchelor theorem which applies to non rotating steady two dimensional flow supporting evidence is found in numerical circulation models and oceanic observations

effects of the submesoscale on the potential vorticity budget of ocean mode waters abstractnonconservative processes change the potential vorticity pv of the upper ocean and later through the subduction of surface waters into the interior affect the general ocean circulation

nyamulagira s magma plumbing system inferred from 15 years of insar nyamulagira located in the east of the democratic republic of congo on the western branch of the east african rift is africa s most active volcano with an average of one eruption every 3 years since 1938 owing to the socio economical context of that region the volcano lacks ground based geodetic measurements but has been monitored by interferometric synthetic aperture radar insar since 1996 a combination of 3d mixed boundary element method and inverse modelling taking into account topography and source interactions is used to interpret insar ground displacements associated with eruptive activity in 1996 2002 2004 2006 and 2010 these eruptions can be fitted by models incorporating dyke intrusions and some namely the 2006 and 2010 eruptions require a magma reservoir beneath the summit caldera we investigate inter eruptive deformation with a multi temporal insar approach we propose the following magma plumbing system at nyamulagira by integrating numerical deformation models with other available data a deep reservoir c 25 km depth feeds a shallower reservoir c 4 km depth proximal eruptions are fed from the shallow reservoir through dykes while distal eruptions can be fed directly from the deep reservoir a dyke like conduit is also present beneath the upper southeastern flank of nyamulagira

active tectonics in central italy constraints from surface wave tomography and source moment tensor inversion abstract we investigate the lithosphere asthenosphere structure and active tectonics of central italy with emphasis on the umbria marche area by means of surface wave tomography and seismic moment tensor inversion the data include a large number of short period local and regional group velocity measurements sampling the umbria marche apennines and the adria margin respectively incorporation of published phase velocity measurements sampling italy and surroundings results from deep seismic soundings which go through the umbria marche area the local group velocity maps covering the area reactivated by the 1997 1998 umbria marche earthquake sequence suggest an intimate relationship between the lateral earth structure variations and the distribution of the active fault systems and related sedimentary basins the upper crustal models reveal the importance of inherited compressional tectonics on the recent extensional deformation and associated seismic activity source inversion studies of the main events of the 1997 earthquake sequence show the dominance of normal faulting mechanisms whereas selected aftershocks between the fault segments at the step over reveal that the prevailing deformation is of strike slip faulting type at the regional scale the crust exhibits clear layering and varies in thickness from about 25 km below the tuscan metamorphic complex tmc to about 30 km below the val tiberina extensional thick sedimentary basin and reaches about 35 km below the umbria marche geological domain umd the lithospheric mantle lid is thin about 30 km below tmc while it is about 70 km thick below umd a lithospheric root about 120 km wide between the tmc and umd reaches a depth of at least 130 km a low velocity zone defined mantle wedge vs less than 4 2 km s in the uppermost mantle overlying the high velocity lid is detached this wedge is about 20 km thick and decouples the underlying lid from the crust the retrieved crust and upper mantle structure beneath central italy is in agreement with bouguer anomaly and heat flow data and supports a delamination process the high velocity upper mantle underlying the mantle wedge is inferred to be subcrustal lithospheric material delaminated from the overlying crust

imaging the upper crust of the korean peninsula by surface wave tomography cross correlation of seismic background motions campillo and paul 2003 shapiro et al 2005 is applied to observations from the korean meteorological administration seismic network to estimate the short period rayleigh and love wave dispersion characteristics of the region standard processing procedures are applied to the cross correlation except that signal whitening is used in place of one bit sampling to equalize power in signals from different times multiple filter analysis is used to extract the group velocities from the estimated green s functions which are then used to image the spatially varying dispersion at periods between 0 5 and 20 sec the tomographic inversion technique used inverts all periods simultaneously to provide a smooth dispersion curve as a function of period in addition to the usual smooth spatial image for a given period the gyeongsang basin in the southeastern part of the peninsula is clearly resolved with lower group velocities

rayleigh wave tomography of china and adjacent regions 1 this paper presents a tomographic study on the s wave velocity structure of china and adjacent regions group velocity dispersions of fundamental rayleigh waves along more than 4000 paths were determined with frequency time analysis the study region was divided into a 1 1 grid and velocities in between grid nodes were calculated by bilinear interpolation the occam s inversion scheme was adopted to invert for group velocity distributions this method is robust and allows us to use a fine grid in model parameterization and thus helps to restore a more realistic velocity pattern checkerboard tests were carried out and the lateral resolution was estimated to be 4 6 in china and its eastern continental shelves the resulting group velocity maps from 10 to 184 s showed good correlation with known geological and tectonic features the pure path dispersion curves at each node were inverted for shear wave velocity structures the three dimensional velocity model indicates thick lithospheres in the yangtze and tarim platforms and hot upper mantles in baikal and western mongolia coastal area and continental shelves of eastern china and indochina and south china sea regions the tibetan plateau has a very thick crust with a low velocity zone in its middle beneath the crust a north dipping high velocity zone mimicking a subducting plate reaches to 200 km in depth and reaches to the kunlun mountains northward in northern tibet a low velocity zone immediately below the moho extends eastward then turns southward along the eastern edge of the plateau until it connects to the vast low velocity area in indochina and the south china sea

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

group velocity tomography and regionalization in italy and bordering areas abstract more than 200 group velocity dispersion curves 109 new dispersion data and 101 collected from literature of the fundamental mode of rayleigh waves in the period range from 10 to 35 s have been processed to obtain tomographic maps for the italian peninsula and bordering areas we compute average dispersion relations over a 1 1 grid and since the lateral resolving power of our data set is of about 200 km we group the cells of the grid according to their dispersion curves in this way and without any a priori geological constraints we define seven different regions each characterised by a distinctive mean group velocity dispersion curve the resulting regionalization can be easily correlated with the main tectonic features of the study area and mimics a recently proposed structural sketch average models of the shear wave velocity in the crust and in the upper mantle for a few selected regions are presented the very low s wave velocity values found in the uppermost upper mantle of the southern tyrrhenian basin are consistent with a large percentage of partial melting in agreement with the presence of the vavilov magnaghi and marsili huge volcanic bodies

pressure sources versus surface loads analyzing volcano deformation signal composition with an application to hekla volcano iceland the load of lava emplaced over periods of decades to centuries induces a gradual viscous response of the earth resulting in measurable deformation this effect should be considered in source model inversions for volcanic areas with large lava production and flow emplacement in small centralized regions if deformation data remain uncorrected constructive load and pressure source interference may result in an overestimate of depth and volume of a magma reservoir whereas destructive signal interference may cause these values to be underestimated in both cases the source geometry preference could be biased the ratio of horizontal and vertical displacements aids the identification of composite signals we provide a method to quantify and remove the lava load deformation signals using deformation at hekla volcano iceland as an example

estimating source parameters from deformation data with an application to the march 1997 earthquake swarm off the izu peninsula japan we have applied two monte carlo optimization techniques simulated annealing and random cost to the inversion of deformation data for fault and magma chamber geometry these techniques involve an element of randomness that permits them to escape local minima and ultimately converge to the global minimum of misfit space we have tested the monte carlo algorithms on two synthetic data sets we have also compared them to one another in terms of their efficiency and reliability we have applied the bootstrap method to estimate confidence intervals for the source parameters including the correlations inherent in the data additionally we present methods that use the information from the bootstrapping procedure to visualize the correlations between the different model parameters we have applied these techniques to gps tilt and leveling data from the march 1997 earthquake swarm off of the izu peninsula japan using the two monte carlo algorithms we have inferred two sources a dike and a fault that fit the deformation data and the patterns of seismicity and that are consistent with the regional stress field

source model for the 1997 zirkuh earthquake mw 7 2 in iran derived from jers and ers insar observations summary we present the first detailed source model of the 1997 m7 2 zirkuh earthquake that ruptured the entire abiz fault in east iran producing a 125 km long bended and segmented fault trace using sar data from the ers and jers 1 satellites we first determined a multisegment fault model for this predominately strike slip earthquake by estimating fault segment dip slip and rake values using an evolutionary optimization algorithm we then inverted the insar data for variable slip and rake in more detail along the multisegment fault plane we complement our optimization with importance sampling of the model parameter space to ensure that the derived optimum model has a high likelihood to detect correlations or trade offs between model parameters and to image the model resolution our results are in an agreement with field observations showing that this predominantly strike slip earthquake had a clear change in style of faulting along its rupture in the north we find that thrust faulting on a westerly dipping fault is accompanied with the strike slip that changes to thrust faulting on an eastward dipping fault plane in the south the centre part of the fault is vertical and has almost pure dextral strike slip the heterogeneous fault slip distribution shows two regions of low slip near significant fault step overs of the abiz fault and therefore these fault complexities appear to reduce the fault slip furthermore shallow fault slip is generally reduced with respect to slip at depth this shallow slip deficit varies along the zirkuh fault from a small deficit in the north to a much larger deficit along the central part of the fault a variation that is possibly related to different interseismic repose times

modeling long term ground deformation due to the cooling of a magma chamber case of basiluzzo island aeolian islands italy 1 we estimate the long term vertical deformation of basiluzzo island located in the volcanic arc of the aeolian islands italy by inferring the subsidence of a roman age submerged wharf dated 2000 50 years ago we model the crustal deformation that produced this displacement as a cooling magma chamber emplaced during the formation of the island this is the first attempt to model crustal deformation using the subsidence of a submerged archaeological structure nowadays the top of the wharf which can be considered an unconventional leveling benchmark is located near punta levante at an average depth of 3 20 0 10 m below actual sea level and it is still in good conservation its present location is due to combined effect of sea level rise and volcanic and tectonic activity that occurred since it was built taking into account the architectural features of the wharf and that the mean sea level rise of the mediterranean sea has been estimated as 0 45 m during the last 2000 years flemming and webb 1986 we estimate a total subsidence of 3 75 0 10 m at a rate of about 1 87 mm yr 1 anzidei et al 2002 we propose a possible mechanism for the long term subsidence which occurred on a timescale of thousands of years by considering the earth s crust as a maxwell body we assume that the magmatic source is located directly beneath basiluzzo dome and underwent progressive solidification and subsequent volume reduction since its emplacement 50 000 years ago

a seismic refraction experiment in the tyrrhenian sea summary we present the results of two 100 km long reversed seismic refraction lines shot in the tyrrhenian sea using explosive sources and oceanbottom receivers the results have been interpreted using ray tracing through laterally varying structures the more easterly line t2 was shot in the central part of the tyrrhenian abyssal plain in a water depth of 3 5 km the crust here is shown to be oceanic in character but to exhibit significant lateral heterogeneity the upper part of the crust layer 2 contains a steep velocity gradient from about 4 to over 6 km s l at a depth of typically 2 km the lower part of the crust layer 3 contains a smaller velocity gradient from 6 6 to 6 9 km s l at the base of the crust total crustal thickness is between 6 and 8 km the other line t1 carried out in the cornaglia basin in 2 7 km of water reveals a more complicated velocity structure we conclude that its southern half is underlain by oceanic crust similar to that observed at t2 however its northern half appears to be underlain by crust of similar thickness but in which seismic velocities increase slowly with depth from 4 9 km s l immediately below the superficial sediments to 6 3 km s l at the moho we interpret this latter structure as thinned continental crust surprisingly neither the seafloor topography nor the depth to moho reflect the transition from oceanic to continental crust we infer from these results that although the southern and eastern parts of the tyrrhenian basin were formed primarily by seafloor spreading much of the basin north of about 40 n and probably including some areas with water depths in excess of 3 km is underlain by thinned continental crust the evolution of the northern part of the tyrrhenian basin must therefore have occurred chiefly through a process of continental extension which in some areas has reduced crustal thickness to as little as 6 8 km south of 40 n

thermal and mechanical aspects of magma emplacement in giant dike swarms we consider the thermal history and dynamics of magma emplacement in giant feeder dikes associated with continental flood basalts for driving pressure gradients inferred for giant dike swarms thicknesses of 10 m would enable dikes to transport magma laterally over the distances observed in the field up to thousands of kilometers without suffering thermal lock up using time dependent numerical solutions for the thermal evolution of a dike channel under laminar and turbulent flow conditions in the presence of phase transitions we investigate the possibility that the observed dike thicknesses of the order of 100 m result from thermal erosion of the country rocks during dike emplacement this implies that the observed range of dike widths in giant dike swarms may reflect variations in the source volume and not the excess magma pressure it is found that the total volume of intruded magma required to produce an order of magnitude increase in dike width via wall rock melting broadly agrees with the estimated volumes of individual flows in continental flood basalts the presence of chilled margins and apparently low crustal contamination characteristics of some giant dikes may be consistent with turbulent magma flow and extensive melt back during dike emplacement in this case measurements of the anisotropy of magnetic susceptibility most likely indicate magma flow directions during the final stages of dike intrusion shear stresses generated at the dike wall when the dike starts to freeze strongly decrease with increasing dike width which implies that thicker dikes may have less tendency to produce consistent fabric alignment our results suggest that if the dike was propagating downslope off a plume related topographic swell the mechanism responsible for flow termination could possibly have been related to underpressurization and collapse implosion of the shallow magma plumbing system feeding the intrusion radial dikes that erupted at the periphery of the topographic uplift might have increased rather than decreased extensional stresses in the crust within the topographic uplift upon their solidification

wind energy input to the ekman layer wind stress energy input through the surface ageostrophic currents is studied the surface ageostrophic velocity is calculated using the classical formula of the ekman spiral with the ekman depth determined from an empirical formula the total amount of energy input over the global oceans for subinertial frequency is estimated as 2 4 tw averaged over a period from 1997 to 2002 or 2 3 tw averaged over a period from 1948 to 2002 based on daily wind stress data from ncep ncar thus in addition to the energy input to the near inertial waves of 0 5 0 7 tw reported by alford and by watanabe and hibiya the total energy input to the ekman layer is estimated as 3 tw this input is concentrated primarily over the southern ocean and the storm track in both the north pacific and north atlantic oceans

magma prospecting in usu volcano hokkaido japan using magnetotelluric soundings abstract we carried out magnetotelluric mt soundings across usu volcano hokkaido japan which has been active since 1663 the objective was to image an intrusion expected below the formation of 180m high cryptodomes formed during the 1977 78 eruption a ne sw two dimensional resistivity model has been obtained from the inversion in the frequency range from 0 01 to 10 000 hz the major features of the resistivity section are as follows 1 a 50 m thick surficial resistive 1000 10 000 m layer corresponding to the lava layer 2 a relatively conductive 10 1000 m layer from the surface to 200 m depth corresponding to quaternary sedimentary and volcanic rocks 3 beneath the quaternary formations a thick 2 4 km conductive 1 500 m layer of altered tertiary volcanics distributed widely in the volcanic edifice 4 a resistive block 500 1 000 m in the tertiary layer from 200 to 400 m in depth beneath the summit crater forming a striking contrast to the rest of the conductive tertiary layer and probably indicating a cooling intrusion at shallow depth 5 pre tertiary formations consisting of a high resistivity 1000 10 000 m layer overlying a conductive layer with the top of the pre tertiary becoming shallow to the northeast and 6 no deep conductive anomalies corresponding to a magma chamber inferred from petrological studies

quasi static thermoelastic deformation in an elastic half space theory and application to insar observations at izu oshima volcano japan summary we derive closed analytical solutions for quasi static thermoelastic deformation in response to instantaneous point and spherical heat sources in an elastic half space since we can take advantage of the solutions for an infinite medium the derivation of solutions for a semi infinite medium is straightforward we examine the spatial and temporal evolution of thermoelastic deformation for point and spherical heat sources we applied the solution to a radar interferometric observation of post eruptive deformation associated with the 1986 fissure eruption at izu oshima volcano japan assuming a spherical heat source at a depth of 240 m with a volume of 1 15 10 7 m 3 and a temperature step 10 3 k the predicted rate of post eruptive ground movement agrees with the observed rate within observational errors also the same parameter values allow us to compute the co eruptive ground displacement by the effect of mass intrusion whose amplitude is consistent with the observed height 45 m of the newly formed cone the derived solutions can be applied to transient ground displacements observed at active volcanoes and allow us to evaluate the heat amount of magma intruded at very shallow depths

inter eruptive volcanism at usu volcano micro earthquakes and dome subsidence abstract post eruptive crustal activity after the 2000 eruption of usu volcano was investigated by seismic and geodetic field observations remarkable features of the magmatic eruptions that occur almost every 30 years include lava dome formation and strong precursory earthquakes on the other hand rapid dome subsidence was observed by electronic distance meter edm measurement after the 1977 1982 summit eruption since the 2000 eruption seismic activity at a shallow part under the summit crater has remained at a high level relative to that after the 1977 1982 eruption although eruption occurred at the western foot of the volcano during the 2000 eruption to reveal the shallow crustal activity in the inter eruptive period around the summit area seismicity and crustal deformation have been investigated since 2006 dense temporary seismic observations and hypocenter relocation analysis using a three dimensional velocity structure model revealed that the focal area is localized along the u shaped fault that developed in the dome forming stage of the 1977 1982 eruption three major focal clusters are distributed on the southwestern side of usu shinzan cryptodome which was built up during the 1977 1982 eruption for the seven major events with magnitudes larger than 1 the focal mechanism was a large dip slip component which suggests the subsidence of usu shinzan cryptodome interferomatetric satellite aperture radar insar image analysis and repeated gps measurements revealed subsidence of the summit dome which is almost centered at the usu shinzan cryptodome the area of rapid deformation is restricted to a small area around the summit crater the estimated rate of dome subsidence relative to the crater floor is about 3 cm year these results strongly suggest that subsidence of usu shinzan is associated with the small earthquakes along the u shaped fault that surrounds the cryptodome according to prior seismic and geodetic studies it is thought that most of the magma rising under the summit crater during the 2000 eruption stopped around a depth of 2 km below sea level which is sufficiently deep relative to the focal area of the present seismicity a part of the magma intruded under the western foot and contributed to the 2000 eruption we conclude that the 2000 eruption scarcely affected the shallow crustal activity under the summit crater and that usu shinzan cryptodome is continuing to subside just as it was before the 2000 eruption the shallow volcanic earthquakes that began increasing from 1995 are closely related to the successive subsidence of the summit domes temporal change in fumarole temperature suggests a relationship between the shallow earthquakes and cooling of the magma that intruded under usu shinzan during the 1977 1982 eruption

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

on the cause of abrupt vegetation collapse in north africa during the holocene climate variability vs vegetation feedback the abrupt desertification over the northern africa in the mid holocene is studied in both a complex and a simple coupled climate vegetation model in contrast to the previous mechanism that relies on strong positive vegetation climate feedback and the resulted multiple equilibria we propose a new mechanism in which the abrupt desertification is caused by low frequency climate variability rather than a positive vegetation climate feedback the implication of this new mechanism to modelling and observation is also discussed

three dimensional interface modelling with two dimensional seismic data the alpine crust mantle boundary summary we present a new approach to determine the 3 d topography and lateral continuity of seismic interfaces using 2 d derived controlled source seismic reflector data the aim of the approach is to give the simplest possible structure consistent with all reflector data and error estimates we define simplicity of seismic interfaces by the degree of interface continuity i e shortest length of ovsets and by the degree of interface roughness least surface roughness the method is applied to structural information of the crust mantle boundary moho obtained from over 250 controlled source seismic reflection and refraction profiles in the greater alpine region the reflected and refracted phases from the moho interface and their interpretation regarding crustal thickness are reviewed and their reliability weighted weights assigned to each reflector element are transformed to depth errors considering fresnel volumes the 2 d derived reflector elements are relocated in space 3 d migration and interpolation is performed between the observed reflector elements to obtain continuity of model parameters interface ovsets are introduced only where required according to the principle of simplicity the resulting 3 d model of the alpine crust mantle boundary shows two ovsets that divide the interface into a european an adriatic and a ligurian moho with the european moho subducting below the adriatic moho and with the adriatic moho underthrusting the ligurian moho each sub interface depicts the smoothest possible i e simplest surface fitting the reflector data within their assigned errors the results are consistent with previous studies for those regions with dense and reliable controlledsource seismic data the newly derived alpine moho interface however surpasses earlier studies by its lateral extent over an area of about 600 km by 600 km by quantifying reliability estimates along the interface and by obeying the principle of being consistently as simple as possible

three dimensional p wave velocity structure of mt etna italy the three dimensional p wave velocity structure of mt etna is determined to depths of 15 km by tomographic inversion of first arrival times from local earthquakes recorded by a network of 29 permanent and temporary seismographs results show a near vertical low velocity zone that extends from beneath the central craters to a depth of 10 km this low velocity region is coincident with a band of steeply dipping seismicity suggesting a magmatic conduit that feeds the summit eruptions the most prominent structure is an approximately 8 km diameter high velocity body located between 2 and 12 km depth below the southeast flank of the volcano this high velocity body is interpreted as a remnant mafic intrusion that is an important structural feature influencing both volcanism and east flank slope stability and faulting

surface wave array tomography in se tibet from ambient seismic noise and two station analysis i phase velocity maps summary empirical green s functions egfs between pairs of seismographs can be estimated from the time derivative of the long time cross correlation of ambient seismic noise these egfs reveal velocity dispersion at relatively short periods which can be used to resolve structures in the crust and uppermost mantle better than with traditional surface wave tomography we combine rayleigh wave dispersion estimates from egfs and from traditional two station ts analysis into a new approach to surface wave array tomography with data from dense receiver arrays we illustrate the methodology with continuous broad band recordings from a temporary seismographic network on the southeastern part of the tibetan plateau in sichuan and yunnan provinces sw china the egfs are robust under temporal changes in regional seismicity and the use of either ambient noise approximated by records without signal from events with magnitude mb 5 or 4 or surface wave coda produces similar results the egfs do not strongly depend on the presence of large earthquakes but they are not reciprocal for stations aligned in the n s direction this directionality reflects the paucity of seismicity to the north of the array using a far field representation of the surface wave green s function and an image transformation technique we infer from the egfs the rayleigh wave phase velocity dispersion in the period band from 10 30 s a classical ts approach is used to determine rayleigh wave phase velocity dispersion between 20 120 s together they constrain phase velocity variations for t 10 120 s which can be used to study the structure from the crust to the upper mantle beneath se tibet short and intermediate period 10 80 s phase velocities are prominently low suggesting that the crust and upper mantle beneath se tibet is characterized by slow shear wave propagation

shear wave attenuation in the lithosphere beneath italy and surrounding regions tectonic implications more than 700 waveforms produced by 51 shallow earthquakes and recorded at regional distances 250 1400 km by the italian seismic network have been analyzed to characterize the amplitude and frequency contents of the crustal and uppermost mantle shear waves lg and sn respectively the crustal phase lg efficiently propagates through the relatively stable adriatic continental crust while it is not observed along propagation paths crossing major physiographic features like the apennine chain and the basinal domain of the tyrrhenian and ionian seas similar to lg efficient sn propagation is observed in the uppermost mantle beneath the po plain and the adriatic sea efficient sn transmission is also observed across the northern ionian sea and sicily and in the area between sardinia and the northern coasts of africa sn are efficiently transmitted across the sicily channel and rather efficient sn propagate beneath the ligurian sea on the contrary inefficient sn transmission characterizes the uppermost mantle beneath the apennines the western margin of the italian peninsula and the southern tyrrhenian sea shear wave attenuation suggests the presence of asthenospheric material in the uppermost mantle probably related to the present day extension along the apennine chain and in the tyrrhenian basin this interpretation is consistent with the presence of extensive neogene and quaternary volcanic activity in these areas and related high heat flow proposed lithospheric delaminatioh processes beneath the apennines and subduction beneath the tyrrhenian sea can reasonably explain the observed high attenuation zones in the uppermost mantle in contrast a high strength mantle lid is inferred to underlay the po plain the adriatic sea and the northern ionian sea the available waveforms also indicate that a continuous mantle lid is present beneath sicily and the extensional domain of the sicily channel as well as in the marine area south of sardinia

destruction of potential vorticity by winds the destruction of potential vorticity pv at ocean fronts by wind stress driven frictional forces is examined using pv flux formalism and numerical simulations when a front is forced by downfront winds that is winds blowing in the direction of the frontal jet a nonadvective frictional pv flux that is upward at the sea surface is induced the flux extracts pv out of the ocean leading to the formation of a boundary layer thicker than the ekman layer with nearly zero pv and nonzero stratification the pv reduction is not only active in the ekman layer but is transmitted through the boundary layer via secondary circulations that exchange low pv from the ekman layer with high pv from the pycnocline extraction of pv from the pycnocline by the secondary circulations results in an upward advective pv flux at the base of the boundary layer that scales with the surface nonadvective frictional pv flux and that leads to the deepening of the layer at fronts forced by both downfront winds and a destabilizing atmospheric buoyancy flux f b the critical parameter that determines whether the wind or the buoyancy flux is the dominant cause for pv

3d density modeling with gravity and muon radiographic observations in showa shinzan lava dome usu japan we performed three dimensional density modeling of showa shinzan lava dome usu japan by joint inversion of the gravity anomaly and recently obtained muon radiography data our multilayer emulsion muon detector significantly reduces the background noise in our measurements of the muon flux through the dome the high quality muon data enables us to more accurately reconstruct the density structure of the lava dome compared with our own previous work we find that the lava dome consists of a cylindrical column of massive lava with a diameter of 300 m and that there is no evidence of magma intrusion in the shallow part of the plateau located east of the dome

volume and potential vorticity budgets of eighteen degree water abstractmode waters are a distinctive baroclinic feature of the world ocean characterized by relatively weak vertical stratification they correspond dynamically to low potential vorticity pv in the north atlantic subtropical gyre the mode waters have become known as eighteen degree water their dynamics involves air sea interaction diapycnal and isopycnal mixing and subduction understanding mode water dynamics is therefore both challenging and important since it connects several aspects of the ocean circulation mass and pv budget of the mode water s core evaluated in a realistic primitive equation north atlantic model are used to characterize mode water maintenance it is shown that the surface pv flux has very little impact on mode water the surface buoyancy flux in combination with eddy mass flux is the most important control on mode water structure a mean pv formalism is used to show that the pv and water mass formation budgets are intrinsically linked a decomposition of the budget demons

temperature dependent viscoelastic modeling of ground deformation application to etna volcano during the 1993 1997 inflation period abstract we used the finite element method fem for modeling time dependent ground deformation due to volcanic pressure sources embedded in a viscoelastic medium especially in volcanic areas the presence of heterogeneous materials and high temperatures produce a lower effective viscosity of the earth s crust that calls for considering the thermal regime of crustal volume surrounding the magmatic sources we propose a thermo mechanical numerical model for evaluating the temperature dependency of the viscoelastic solution both temperature distributions and ground deformation are evaluated by solving an axi symmetric problem to estimate the effects of thermo viscoelastic response of the medium the thermo mechanical model permits to evidence that viscoelastic relaxation is responsible for significant time dependent variations in long term deformation these effects may be relevant for the interpretation and quantitative assessments of the pressure changes within magmatic sources with this in mind we reviewed the ground deformation observed on etna volcano during the 1993 1997 inflation period by setting up a fully 3d temperature dependent viscoelastic model since 1993 different geodetic measurements edm gps sar and leveling data identified an inflationary phase characterized by a uniform and continuous expansion of the overall volcano edifice that was not perturbed by eruptive activity the numerical model including significant viscoelastic material and reduced crustal rigidity around the magmatic source enables to produce deformation comparable with those obtained from elastic model requiring a significantly lower pressure for a purely elastic model with the same geometry and rigidity the pressure change necessary to describe the 1993 through 1997 inflation is around 320 mpa whereas for the viscoelastic model a pressure increase of about 200 mpa is required

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

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

palaeomagnetic study of the holocene and upper pleistocene sediments from lake barombi mbo cameroun first results abstract the analyses of the stable deposition and post depositional remanent magnetization carried by the lacustrine sediments contained in a 24 m sequence collected from the bottom of the maar lake barombi mbo cameroun yield well defined declination and inclination oscillations which can be attributed to palaeosecular variations of the local geomagnetic field the transformation to a time scale based on the interpolation and extrapolation of 14 c ages allows comparison of this record with contemporaneous records obtained in other parts of the world the successive inclination peaks can be individually identified with those found in western europe in spite of small chronological discrepancies which are in the range of the standard deviation of the ages normalization of the nrms by anhysteretic magnetization provides a profile of relative palaeointensities which shows similarities with that reconstructed from the same time interval in a sequence from western europe although an important phase shift appears

surface wave tomography from ambient seismic noise of accelerograph networks in southern korea 1 an efficient and robust cross correlation technique for estimation of surface wave green s function between two locations is applied to a set of ambient noise data recorded by accelerograph networks in the southern korea we have estimated 1843 group velocities of rayleigh waves in the period band of 2 4 seconds from correlation pairs of 91 accelerograph stations relatively dense and uniform coverage of the pairs provides us with high resolution tomographic image of surface wave group velocities in the region the resulting group velocity distribution correlates well with the characteristic features of geological map of the region displaying low velocities for the sedimentary basins and regions of volcanic and metasedimentary rocks and high velocities for the regions where granitoid basement rocks outcrop the short period information from the accelerograph network can enhance resolution of the subsurface structures at depths within a few kilometers which may be predominantly responsible for simulation results of strong ground motions

surface deformation of long valley caldera and mono basin california investigated with the sbas insar approach abstract we investigate the surface deformation of the eastern california area that includes long valley caldera and mono basin we apply the sar interferometry insar algorithm referred to as small baseline subset sbas approach that allows us to generate mean deformation velocity maps and displacement time series for the investigated area the results presented in this work represent an advancement of previous insar studies of the area that are mostly focused on the deformation affecting the caldera in particular the proposed analysis is based on 21 sar data acquired by the ers 1 2 sensors during the 1992 2000 time interval and demonstrates the capability of the sbas procedure to identify and analyze displacement patterns at different spatial scales for the overall area spanning approximately 5000 km2 two previously unreported localized deformation effects have been detected at paoha island located within the mono lake and in the mcgee creek area within the sierra nevada mountains a zone to the south of the long valley caldera in addition a spatially extended uplift effect which strongly affects the caldera has been identified and analyzed in detail the insar results clearly show that the displacement phenomena affecting the long valley caldera have a maximum in correspondence of the resurgent dome and are characterized by the sequence of three different effects a 1992 1997 uplift background a 1997 1998 unrest phenomenon and a 1998 2000 subsidence phase moreover the analysis of the retrieved displacement time series allows us to map the extent of the zone with a temporal deformation behavior highly correlated with the detected three phases deformation pattern background uplift unrest subsidence we show that the mapped area clearly extends outside the northern part of the caldera slopes accordingly we suggest that future inversion models take this new evidence into account the final discussion is dedicated to a comparison between the retrieved insar measurements and a set of gps and leveling data confirming the validity of the results achieved through the sbas insar analysis

seismological significance of the 1977 1978 eruptions and the magma intrusion process of usu volcano hokkaido abstract an earthquake swarm and the major pumice eruptions in august 1977 which followed marked the start of the dacitic doming activity of usu volcano in southwestern hokkaido japan the sequence of magma intrusion processes was investigated in detail by means of seismological and other geophysical data the distribution of the abundant hypocenters shows clearly an earthquake free zone beneath the summit crater the hypocenters migrated in a manner consistent with the development of the observed asymmetrical surface deformations considered due to magma intrusion into this earthquake free zone the earthquake mechanism solutions are mostly of dip slip type and are interpreted in terms of the doming deformations the existence of earthquake families earthquakes with similar waveforms is the main cause of the peculiar occurrence of earthquakes in space time and magnitude the concept of scattered barriers of different sizes and strengths can explain well the distinct characteristics of the occurrence of the swarm and the observed episodic deformations

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

broadband ambient noise surface wave tomography across the united states 1 this study presents surface wave dispersion maps across the contiguous united states determined using seismic ambient noise two years of ambient noise data are used from march 2003 through february 2005 observed at 203 broadband seismic stations in the us southern canada and northern mexico cross correlations are computed between all station pairs to produce empirical green functions at most azimuths across the us coherent rayleigh wave signals exist in the empirical green functions implying that ambient noise in the frequency band of this study 5 100 s period is sufficiently isotropically distributed in azimuth to yield largely unbiased dispersion measurements rayleigh and love wave group and phase velocity curves are measured together with associated uncertainties determined from the temporal variability of the measurements a sufficient number of measurements 2000 is obtained between 8 and 25 s period for love waves and 8 and 70 s period for rayleigh waves to produce tomographic dispersion maps both phase and group velocity maps are presented in these period bands resolution is estimated to be better than 100 km across much of the us from 8 40 s period for rayleigh waves and 8 20 s period for love waves which is unprecedented in a study at this spatial scale at longer and shorter periods resolution degrades as the number of coherent signals diminishes the dispersion maps agree well with each other and with known geological and tectonic features and in addition provide new information about structures in the crust and uppermost mantle beneath much of the us

potential vorticity budgets in the north atlantic ocean abstractthis paper focuses on potential vorticity pv budgets in the north atlantic with an emphasis on the wind driven subtropical gyre since pv is the key dynamical variable of the wind driven circulation these budgets are important to understand pv is a conservative quantity on isopycnals and can only enter or exit through the boundaries like the lateral topography or the surface the latter fluxes are diagnosed and tested against the evolution of the pv content in an isopycnal layer the former are computed using the bernoulli function the essential result is found for all the tested isopycnals and the dominant feature of pv is recirculation with very little added at the surface or the boundaries density coordinates are well suited to understanding pv circulation a novel technique for computing the bernoulli function is proposed the bernoulli function is governed by a simple elliptic equation and the solutions demonstrate the dominant contribution of pv advection

entry flux and exit of potential vorticity in ocean circulation the flux form of the potential vorticity pv equation is employed to derive simple expressions for the boundary and interior flux of pv in ocean circulation using bernoulli functions the formulas are discussed and physically interpreted and used to map the flux of pv through a model of ocean circulation

crustal structures in the central eastern alpine sector a revision of the available dss data abstract in the alpine sector east of the giudicarie line the investigation of crustal structure is less developed than in the western and central sectors because seismic near vertical reflection nvr profiles are not yet available however it is felt that a revision by a complete homogeneous reinterpretation of several refraction wide angle reflection profiles or deep seismic soundings dss recorded during different phases of the early exploration will help in defining a model of the deep crust and of the moho boundary in the whole area from the central to the eastern alps six interpretative cross sections are proposed as the final output of the seismic modelling as well as a map of the crust mantle boundary the main results of this investigation are the following the lower crust and the moho beneath the northern alps show a fairly homogeneous structure the seismic velocity of the european lower crust is anomalously low while in the north the southward dip of the bottom of the european crust is of about 12 in the center of the investigated area its dip is reduced to about 6 in this zone of flatter moho a complex crust mantle transition is observed the northern strip of the adriatic crust appears highly fragmented into small blocks each block dipping in different directions n ne nw as far as the relationship between the surface tectonic features and the deep crustal structure is concerned it is found that while the edge of the adriatic moho is fairly coincident with the periadriatic lineament in its western sector tonale line it appears to be strongly displaced in the eastern one pustertal line also in the eastern alps in agreement with the interpretation of the european geotraverse crossing eastern swiss alps and lombardian southern alps a wedge of the adriatic lower crust overrides the more ductile european crust protruding northwards beyond the edge of the adriatic moho these results can help to better investigate the complex interactions between the european and adriatic plates as well as to study the relationships between deep and surface structures

surface wave tomography from microseisms in southern california received 5 april 2005 revised 23 may 2005 accepted 9 june 2005 published 26 july 2005 1 since it has already been demonstrated that point topoint seismic propagation green functions can be extracted from seismic noise it should be possible to image earth structure using the ambient noise field seismic noise data from 148 broadband seismic stations in southern california were used to extract the surface wave arrival times between all station pairs in the network the seismic data were then used in a simple but densely sampled tomographic procedure to estimate the surface wave velocity structure within the frequency range of 0 1 0 2 hz for a region in southern california the result compares favorably with previous estimates obtained using more conventional and elaborate inversion procedures this demonstrates that coherent noise field between station pairs can be used for seismic imaging purposes citation sabra k g p gerstoft p roux w a kuperman and m c fehler 2005 surface wave tomography from microseisms in southern california geophys res lett 32 l14311 doi 10 1029 2005gl023155

a retrospective look at the february 1993 east rift zone intrusion at kīlauea volcano hawaii abstract the february 1993 dike intrusion in the east rift zone erz of k lauea volcano hawai i was recognized from tilt and seismic data but ground based geodetic data were too sparse to constrain the characteristics of the intrusion analysis of interferometric synthetic aperture radar insar from the japan aerospace exploration agency jaxa jers 1 satellite reveals a maximum of 30 cm of line of sight los displacement occurring near makaopuhi crater in the middle erz of k lauea we model this deformation signal as a subvertical dike using a 3d mixed boundary element method 3d mbem paired with a nonlinear inversion algorithm to find the best fit model the best fit dike is located just to the west of makaopuhi crater striking n50 w extends to within 100 m of the surface is 1 3 km in length by 4 2 km in width along strike and has a total volume of 7 4 106 m3 in addition a post intrusion interferogram from jers 1 spanning 1993 1997 was analyzed guided by previous results our model for the 4 year period consists of opening of the deep rift zones by about 0 5 m at 3 8 5 km depth beneath the southwest rift zone swrz erz and the summit a sub horizontal detachment fault is connected to the seaward side of the vertical dike like source to mimic the decollement known to exist beneath the volcano we classify the 1993 dike intrusion as a passive intrusion similar to those that occurred in 1997 and 1999 passive intrusions lack precursory inflation at k lauea s summit and the likely triggering mechanism is persistent deep rift opening combined with seaward motion of the south flank along the basal decollement passive intrusions make forecasting and hazard assessment difficult since they are not preceded by inflation nor by large increases in seismicity

a natural and controlled source seismic profile through the eastern alps transalp abstract the combined passive and active seismic transalp experiment produced an unprecedented high resolution crustal image of the eastern alps between munich and venice the european and adriatic mohos em and am respectively are clearly imaged with different seismic techniques near vertical incidence reflections and receiver functions rfs the european moho dips gently southward from 35 km beneath the northern foreland to a maximum depth of 55 km beneath the central part of the eastern alps whereas the adriatic moho is imaged primarily by receiver functions at a relatively constant depth of about 40 km in both data sets we have also detected first order alpine shear zones such as the helvetic detachment inntal fault and sub tauern ramp in the north apart from the valsugana thrust receiver functions in the southern part of the eastern alps have also observed a north dipping interface which may penetrate the entire adriatic crust adriatic crust interface aci deep crustal seismicity may be related to the aci we interpret the aci as the currently active retroshear zone in the doubly vergent alpine collisional belt

seismic tomography of the crust underneath the etna volcano sicily abstract a new tomographic inversion of the velocity structure and hypocenter parameters has been carried out in the etna area using a remarkably larger seismic dataset than used in the previous investigations the obtained v p and v p v s space distributions allow us to detail the already known structural features and to find new velocity anomalies a major aseismic high velocity body is recognized in the upper 10 km beneath the central crater area and the southeastern flank of the volcano interpreted as high strength magmatic rocks such as cumulites dike structures etc a high level of seismic activity and low v p values are found immediately to the west and the east of the high velocity body suggesting the presence of highly fractured weakness zones which also taking into account the local distribution of seismogenic stress can be supposed to include paths for magma rising and stationing clear evidence is also found of a shallow aseismic low velocity zone beneath the volcano s southwestern flank corresponding to the volume where previous investigators hypothesized the presence of a magma chamber on the grounds of geodetic data and seismic b value mapping

ambient noise rayleigh wave tomography in western sichuan and eastern tibet abstract we perform rayleigh wave tomography in western sichuan and eastern tibet by applying the ambient noise method to broadband data recorded at 49 stations from the sichuan digital seismic network cross correlations of vertical component ambient noise data are computed in one hour segments and stacked over 7 months from june to december 2007 then rayleigh wave group dispersion curves from 6 to 48 s were measured using the multiple filter analysis method group velocity maps at periods from 8 to 44 s were inverted the resulting group velocity maps generally show good correlations with tectonic features the sichuan basin is clearly resolved with lower group velocities at the short periods 8 to 20 s due to thick sedimentary layers and a prominent low velocity zone exhibits in the middle crust beneath the eastern margin of the tibetan plateau the longmen shan thrust belt marks not only the rapid lateral velocity variation between the topographically high tibetan plateau and low elevation sichuan basin but also the transition from the thick crust beneath the tibetan plateau to the normal continental crust beneath the sichuan basin

surface wave dispersion measurements from ambient seismic noise analysis in italy summary we present the surface wave dispersion results of the application of the ambient noise method to broad band data recorded at 114 stations from the istituto nazionale di geofisica e vulcanologia ingv national broad band network some stations of the mediterranean very broadband seismographic network mednet and of the austrian central institute for meteorology and geodynamics zamg vertical component ambient noise data from 2005 october to 2007 march have been cross correlated for station pairs to estimate fundamental mode rayleigh wave green s functions cross correlations are calculated in 1 hr segments stacked over periods varying between 3 months and 1 5 yr rayleigh wave group dispersion curves at periods from 8 to 44 s were determined using the multiple filter analysis technique the study region was divided into a 0 2 0 2 grid to invert for group velocity distributions checkerboard tests were first carried out and the lateral resolution was estimated to be about 0 6 the resulting group velocity maps from 8 to 36 s show the significant difference of the crustal structure and good correlations with known geological and tectonic features in the study region the po plain and the southern alps evidence lower group velocities due to soft alluvial deposits and thick terrigenous sediments our results also clearly showed that the tyrrhenian sea is characterized with much higher velocities below 8 km than the italian peninsula and the adriatic sea which indicates a thin oceanic crust beneath the tyrrhenian sea

year to year reoutcropping of eighteen degree water in an eddy resolving ocean simulation abstractwinter outcropping of the eighteen degree water edw and its subsequent dispersion are studied using a eddy resolving simulation of the family of linked atlantic modeling experiments flame outcropped edw columns in the model simulations are detected in each winter from 1990 to 1999 and particles are deployed in the center of each outcropped edw column subsequently the trajectories of these particles are calculated for the following 5 yr the particles slowly spread away from the outcropping region into the nonoutcropping subducted edw region south of 30 n and eventually to the non edw region in the greater subtropical gyre approximately 30 of the particles are found in non edw waters 1 yr after deployment after 5 yr only 25 of the particles are found within edw the reoutcropping time is defined as the number of years between when a particle is originally deployed in an outcropping edw column and when that particle is next found in an outcropping edw column of the particles 66 ar

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

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

high resolution teleseismic tomography of upper mantle structure using an a priori three dimensional crustal model summary the effect of an a priori known 3 d crustal model in teleseismic tomography of upper mantle structure is investigated we developed a 3 d crustal p wave velocity model for the greater alpine region encompassing the central and western alps and the northern apennines to estimate the crustal contribution to teleseismic traveltimes the model is constructed by comparative use of published information from active and passive seismic surveys the model components are chosen to represent the present large scale alpine crustal structure and for their significant effect on the propagation of seismic wavefields they are first order structures such as the crust mantle boundary sedimentary basins and the high velocity ivrea body teleseismic traveltime residuals are calculated for a realistic distribution of azimuths and distances by coupling a finite difference technique to the iasp91 traveltime tables residuals are produced for a synthetic upper mantle model featuring two slab structures and the 3 d crustal model on top of it the crustal model produces traveltime residuals in the range between 0 7 and 1 5 s that vary strongly as a function of backazimuth and epicentral distance we find that the non linear inversion of the synthetic residuals without correcting for the 3 d crustal structure erroneously maps the crustal anomalies into the upper mantle correction of the residuals for crustal structure before inversion properly recovers the synthetic slab structures placed in the upper mantle we conclude that with the increasing amount of high quality seismic traveltime data correction for near surface structure is essential for increasing resolution in tomographic images of upper mantle structure

repressurization following eruption from a magma chamber with a viscoelastic aureole i analyze an approximate solution for spherical magma chambers radius r1 surrounded by maxwell viscoelastic shells radius r2 in elastic half spaces following a sudden decrease in pressure mass flux into the chamber is proportional to the pressure difference between a deep source and chamber p p t solutions depend on r2 r1 c m c where m c are magma and chamber compressibilities the relaxation time tr and the recharge time for the elastic system without recharge the system exhibits either post eruptive deflation or for incompressible magmas partial reinflation more generally immediate post eruptive inflation is favored by large tr and small r2 r1 with short tr and large the time for magma chamber pressure to recover increases significantly post eruptive creep increases the chamber pressure decreasing the pressure gradient driving recharge delaying pressure recovery following eruption the hoop stresses which are initially compressive relax toward the radial stress causing them to go through a local relative tension maximum the magma pressure in excess of the dike normal compression at the chamber wall can recover to pre eruptive values well before the chamber pressure or erupted mass recovers this suggests that dikes could nucleate at the chamber margin well before sufficient pressure has recovered to drive them far from the chamber for some parameters co eruptive deflation has not fully recovered when the magma overpressure relative to hoop stress in the elastic region is restored to pre eruptive values a condition assumed to be sufficient for eruption

observations of entry and exit of potential vorticity at the sea surface abstract although potential vorticity pv is central to many theories of the oceanic circulation the entry exit of pv at the sea surface has not been thoroughly discussed from an observational perspective after clarifying the notion of pv entry and exit and the mechanisms responsible for it a climatology of this quantity for the northern hemisphere is presented it is found that surface pv loss over western boundary current regions and their interior extension is a robust feature over the north pacific and atlantic basins at high latitudes mechanical and diabatic effects act in concert in the north atlantic to drive the net pv exit in the pacific however these effects oppose each other and the net entry exit of pv is more uncertain at low latitudes surface winds are found to be particularly important in setting the surface pv exit in the pacific equatorward of the intertropical convergence zone

tomographic constraints on the geodynamic evolution of the italian region in this paper we present p wave tomographic images of the mantle beneath italy obtained by inverting 6000 teleseismic p and pkp wave arrival times accurately repicked recorded in the time period 1988 1994 by the stations of the national seismic network of the istituto nazionale di geofisica we pay great attention in the data selection and picking procedure of seismic phases to obtain a very high quality data set the data were inverted with the well established aki christofferson husebye tomographic technique different reference models and residuals computation have been tried to verify the stability of the results the high quality of the repicked arrival times allows us to enhance the definition of the deep structures beneath both the alps and the apennines looking for their lateral and vertical continuity down to 800 km depth the main finding of this study is a continuous high velocity body located between 250 and 670 km depth beneath the entire apenninic system dipping toward the tyrrhenian area which continues upward segmented in two main anomalies in the northern apenninic and the calabrian arcs we interpret this high velocity feature as the subducted oceanic lithosphere between the eurasian and african plates dipping down to the upper lower mantle boundary beneath the tyrrhenian sea the retrieved images of the lithosphere subducting beneath apennines are reliable in terms of thickness about 80 90 km and p wave velocity contrast 2 4 higher than the normal mantle furthermore our tomographic images which focus on the deep geometry and continuity of the velocity structures provide new keys to understanding the geodynamic evolution of the italian region the segmentation of the high velocity slab upward suggests a complex evolution of the arc trench system and the initially continuous subduction of the ionian adriatic plate progressively developed in subordinate arcs probably due to lateral heterogeneity of the subducting lithosphere

eucrust 07 a new reference model for the european crust 1 we present a new digital model eucrust 07 for the crust of western and central europe and surroundings 35n 71n 25w 35e available results of seismic reflection refraction and receiver functions studies are assembled in an integrated model at a uniform grid 15 0 15 0 the model consists of three layers sediments and two layers of the crystalline crust besides depth to the boundaries we provide average p wave velocities in the upper and lower parts of the crystalline crust the new model demonstrates large differences in the moho depth compared to previous compilations over 10 km in some specific areas e g the baltic shield furthermore the velocity structure of the crust is much more heterogeneous than in previous maps eucrust 07 offers a starting point for numerical modeling of deeper structures by allowing correction for crustal effects beforehand and to resolve trade off with mantle heterogeneities citation tesauro m m k kaban and s a p l cloetingh 2008 eucrust 07 a new reference model for the european crust geophys res lett 35 l05313 doi 10 1029 2007gl032244

tomography of the alpine region from observations of seismic ambient noise we use correlations of the ambient seismic noise to study the crust in western europe cross correlation of 1 year of noise recorded at 150 three components broadband stations yields more than 3 000 rayleigh wave group velocity measurements these measurements are used to construct rayleigh group velocity maps of the alpine region and surrounding area in the 5 80 s period band in the 5 10 s period band the seismic noise recorded in europe is dominated by surface waves originating from the northern atlantic ocean this anisotropy of the noise and the uneven station distribution affect the azimuthal distribution of the paths where we obtain reliable group velocity measurements as a consequence our group velocity models have better resolution in the northeast direction than in the southwest direction finally we invert the resulting rayleigh wave group velocity maps to determine the moho depth our results are in good agreement with the result of the numerous active experiments in the alps and provide a continuous image of the alpine structure