eddy formation near the west coast of greenland abstract this paper extends a bracco and j pedlosky s investigation of the eddy formation mechanism in the eastern labrador sea by including a more realistic depiction of the boundary current the quasigeostrophic model consists of a meridional coastally trapped current with three vertical layers the current configuration and topographic domain are chosen to match as closely as possible the observations of the boundary current and the varying topographic slope along the west greenland coast the role played by the bottom intensified component of the boundary current on the formation of the labrador sea irminger rings is explored consistent with the earlier study a short localized bottom trapped wave is responsible for most of the perturbation energy growth however for the instability to occur in the three layer model the deepest component of the boundary current must be sufficiently strong highlighting the importance of the near bottom flow the model is able to reproduce important features o

constraining the dip of shallow shallowly dipping thrust events using long period love wave radiation patterns applications to the 25 october 2010 mentawai indonesia and 4 may 2018 hawaii island earthquakes constraining precise faulting geometry for shallow shallowly dipping thrust earthquakes is a common challenge plate boundary megathrust faults near the trench and decollement faults beneath volcanic islands and nappes may dip only a few degrees long period point source moment tensor waveform inversions provide limited resolution of shallow fault dip angle the possibility of splay faulting requires precise dip estimation high sensitivity to dip is provided by long period love wave amplitude azimuthal radiation patterns which undergo rapid change from four lobed to two lobed as dip decreases from 10 to 0 modeling variability in love wave nodal amplitudes allows the dip to be determined to within a few degrees this is demonstrated for the 25 october 2010 mentawai m ww 7 8 tsunami earthquake which ruptured the 2 0 5 0 dipping megathrust beneath the shallow sedimentary wedge offshore of indonesia and the 4 may 2018 hawaii island m ww 6 9 thrust earthquake which ruptured the 2 5 7 5 dipping decollement under the island flank

time dependent dike propagation from joint inversion of seismicity and deformation data dike intrusions both deform earth s surface and induce propagating earthquake swarms we develop methods to utilize both deformation and seismicity from brittle volcano tectonic earthquakes to image time dependent dike propagation dieterich s 1994 seismicity rate theory is used to relate dike induced stress changes to seismicity rate and is combined with elastic green s functions relating dike opening to deformation different space time patterns of seismicity develop if earthquakes occur at the same depth as the dike compared to above below the dike in the former seismicity initiates near the dike s leading edges but shuts off as the dike tips pass and seismogenic volumes fall into stress shadows in the latter seismicity continues at a decaying rate after the tips pass we focus on lateral propagation and develop a nonlinear inversion method that estimates dike length and pressure as a function of time the method is applied to the 2007 father s day intrusion in kilauea volcano seismicity is concentrated at 3 km depth comparable to geodetic estimates of dike depth and decays rapidly in time with lateral propagation only and a vertical dike tip line it is difficult to fit both gps data and the rapid down rift jump in seismicity suggesting significant vertical propagation for the events to have occurred below the dike requires a very short aftershock decay time hence unreasonably high background stressing rate the rapid decay is better explained if the dike extends somewhat below the seismicity we suggest that joint inversion is useful for studying the diking process and may allow for improved short term eruption forecasts

impact of labrador sea convection on the north atlantic meridional overturning circulation abstract the overturning and horizontal circulations of the labrador sea are deduced from a composite vertical section across the basin the data come from the late spring early summer occupations of the world ocean circulation experiment woce ar7w line during the years 1990 97 this time period was chosen because it corresponded to intense wintertime convection the deepest and densest in the historical record suggesting that the north atlantic meridional overturning circulation moc would be maximally impacted the composite geostrophic velocity section was referenced using a mean lateral velocity profile from float data and then subsequently adjusted to balance mass the analysis was done in depth space to determine the net sinking that results from convection and in density space to determine the diapycnal mass flux i e the transformation of light water to labrador sea water the mean overturning cell is calculated to be 1 sv 1 sv 106 m3 s 1 as compared with a horizontal gyre of 18 sv the

evolution of dike opening during the march 2011 kamoamoa fissure eruption kīlauea volcano hawai i 1 the 5 9 march 2011 kamoamoa fissure eruption along the east rift zone of k lauea volcano hawai i followed months of pronounced inflation at k lauea summit we examine dike opening during and after the eruption using a comprehensive interferometric synthetic aperture radar insar data set in combination with continuous gps data we solve for distributed dike displacements using a whole k lauea model with dilating rift zones and possibly a deep decollement modeled surface dike opening increased from nearly 1 5 m to over 2 8 m from the first day to the end of the eruption in agreement with field observations of surface fracturing surface dike opening ceased following the eruption but subsurface opening in the dike continued into may 2011 dike volumes increased from 15 to 16 to 21 million cubic meters mcm after the first day eruption end and 2 months following respectively dike shape is distinctive with a main limb plunging from the surface to 2 3 km depth in the up rift direction toward k lauea s summit and a lesser projection extending in the down rift direction toward pu u at 2 km depth volume losses beneath k lauea summit 1 7 mcm and pu u 5 6 mcm crater relative to dike plus erupted volume 18 3 mcm yield a dike to source volume ratio of 2 5 that is in the range expected for compressible magma without requiring additional sources inflation of k lauea s summit in the months before the march 2011 eruption suggests that the kamoamoa eruption resulted from overpressure of the volcano s magmatic system

mechanical response of the south flank of kilauea volcano hawaii to intrusive events along the rift systems abstract increased earthquake activity and compression of the south flank of kilauea volcano hawaii have been recognized by previous investigators to accompany rift intrusions we further detail the temporal and spatial changes in earthquake rates and ground strain along the south flank induced by six major rift intrusions which occurred between december 1971 and january 1981 the seismic response of the south flank to individual rift intrusions is immediate the increased rate of earthquake activity lasts from 1 to 4 weeks horizontal strain measurements indicate that compression of the south flank usually accompanies rift intrusions and eruptions emplacement of an intrusion at a depth greater than about 4 km such as the june 1982 southwest rift intrusion however results in a slight extension of the subaerial portion of the south flank horizontal strain measurements along the south flank are used to locate the january 1983 east rift intrusion which resulted in eruptive activity the intrusion is modeled as a vertical rectangular sheet with constant displacement perpendicular to the plane of the sheet this model suggests that the intrusive body that compressed the south flank in january 1983 extended from the surface to about 2 4 km depth and was aligned along a strike of n66 e the intrusion is approximately 11 km in length extended beyond the january 1983 eruptive fissures which are 8 km in length and is contained within the 14 km long region of shallow rift earthquakes

volcanic subsidence triggered by the 2011 tohoku earthquake in japan the 2011 tohoku earthquake caused high levels of crustal deformation in japan analysis of satellite radar and gps data show that the earthquake caused nearby volcanic regions to subside instantaneously creating elliptical depressions that are parallel to the direction of quake induced crustal extension

laboratory experiments on eddy generation by a buoyant coastal current flowing over variable bathymetry irminger rings are warm core eddies formed off the west coast of greenland recent studies suggest that these eddies which are implicated in the rapid springtime restratification of the labrador sea are formed by an internal instability of the west greenland current wgc triggered by bathymetric variations this study seeks to explore the effect of the magnitude and downstream length scale of bathymetric variations on the stability of a simple model of the wgc in a series of laboratory experiments in which a buoyant coastal current was allowed to flow over bathymetry consisting of piecewise constant slopes of varying magnitude the currents did not form eddies over gently sloping bathymetry and only formed eddies over steep bathymetry if the current width exceeded the width of the sloping bathymetry eddying currents were immediately stabilized if they flowed onto gently sloping topography bathymetric variations that persisted only a short distance downstream perturbed the flow locally but did not lead to eddy formation eddies formed only once the downstream length of the bathymetric variations exceeded a critical scale of about 8 rossby radii these results are consistent with the observed behavior of the wgc which begins to form irminger rings after entering a region where the continental slope abruptly steepens and becomes narrower than the wgc itself in a region spanning about 20 80 rossby radii of downstream distance

decrease in seismic velocity observed prior to the 2018 eruption of kīlauea volcano with ambient seismic noise interferometry the 2018 k lauea eruption was a complex event that included deformation and eruption at the summit and along the east rift zone we use ambient seismic noise interferometry to measure time lapse changes in seismic velocity of the volcanic edifice prior to the lower east rift zone eruption our results show that seismic velocities increase in relation to gradual inflation of the edifice between 1 march and 20 april in the 10 days prior to the 3rd of may eruption onset a rapid seismic velocity decrease occurs even though the summit is still inflating we confirm that intereruptive velocity change is correlated with surface deformation while the velocity decrease prior to eruption is likely due to accumulating damage induced by the pressure exerted by the magma reservoir on the edifice the accumulating damage and subsequent decrease in bulk edifice strength may have facilitated increased transport of magma from the summit reservoir to the middle east rift zone

rapid deformation of kilauea volcano global positioning system measurements between 1990 and 1996 campaign global positioning system gps measurements from 1990 to 1996 are used to calculate surface displacement rates on kilauea volcano hawaii the gps data show that the south flank of the volcano which has generated several large earthquakes in the past 3 decades is displacing at up to 8 cm yr to the south southeast the summit and rift zones are subsiding with maximum subsidence rates of 8 cm yr observed a few kilometers south of the summit caldera elastic dislocation modeling of the gps data suggests that the active sources of deformation include deep rift opening along the upper east and east rift zone fault slip along a subhorizontal fault near the base of the volcano and deflation near the summit caldera a nonlinear optimization algorithm was used to explore the parameter space and to find the best fitting source geometry there is a broad range of model geometries that fit the data reasonably well however certain models can be ruled out including those that have shallow rift opening or shallow fault slip some offshore aseismic slip on a fault plane that dips between 258 north northwest and 88 south southeast is required best fitting slip and rift opening rates are 23 28 cm yr although rates as low as 10 cm yr are permitted by the data

slope failure and volcanic spreading along the submarine south flank of kilauea volcano hawaii 1 new multichannel reflection data and high resolution bathymetry over the submarine slopes of kilauea volcano provide evidence for current and prior landsliding suggesting a dynamic interplay among slope failure regrowth and volcanic spreading disrupted strata along the upper reaches of kilauea s flank denote a coherent slump correlated with the active hilina slump the slump comprises mostly slope sediments underlain by a detachment 3 5 km deep extension and subsidence along the upper flank is compensated by uplift and folding of the slump toe which surfaces about midway down the submarine flank uplift of strata forming papa u seamount and offset of surface features along the western boundary of kilauea indicate that the slump has been displaced 3 km in a south southeast direction this trajectory matches coseismic and continuous ground displacements for the hilina slump block on land and contrasts with the southeast vergence of the rest of the creeping south flank to the northeast slope sediments are thinned and disrupted within a recessed region of the central flank demonstrating catastrophic slope failure in the recent past debris from the collapsed flank was shed into the moat in front of kilauea building an extensive apron seaward sliding of kilauea s flank offscraped these deposits to build an extensive frontal bench a broad basin formed behind the bench and above the embayed flank uplift and back tilting of young basin fill indicate recent and possibly ongoing bench growth the hilina slump now impinges upon the frontal bench this buttress may tend to reduce the likelihood of future catastrophic detachment

stress control of deep rift intrusion at mauna loa volcano hawaii mauna loa volcano hawaii deforms by a combination of shallow dike intrusions in the rift zones and earthquakes along the base of the volcano but it is not known how the spreading is accommodated in the lower part of the volcanic edifice we present evidence from interferometric synthetic aperture radar data for secular inflation of a dike like magma body at intermediate depth in the southwest rift zone during 2002 to 2005 magma accumulation occurred in a section of the rift zone that was unclamped by previous dikes and earthquakes suggesting that stress transfer plays an important role in controlling subsurface magma accumulation

dmodels a matlab software package for modeling crustal deformation near active faults and volcanic centers abstract we have developed a matlab software package for the most common models used to interpret deformation measurements near faults and active volcanic centers the emphasis is on analytical models of deformation that can be compared with data from the global positioning system gps insar tiltmeters and strainmeters source models include pressurized spherical ellipsoidal and sill like magma chambers in an elastic homogeneous flat half space dikes and faults are described following the mathematical notation for rectangular dislocations in an elastic homogeneous flat half space all the expressions have been checked for typographical errors that might have been present in the original literature extended to include deformation and strain within the earth s crust as opposed to only the earth s surface and verified against finite element models a set of gps measurements from the 2006 eruption at augustine volcano alaska is used to test the software package the results show that the best fit source to the gps data is a spherical intrusion v 5 10 4 km3 about 880 m beneath the volcano s summit

dynamics of downwelling in an eddy resolving convective basin the mean downwelling in an eddy resolving model of a convective basin is concentrated near the boundary where eddies are shed from the cyclonic boundary current into the interior it is suggested that the buoyancyforced downwelling in the labrador sea and the lofoten basin is similarly concentrated in analogous eddy formation regions along their eastern boundaries use of a transformed eulerian mean depiction of the density transport reveals the central role eddy fluxes play in maintaining the adiabatic nature of the flow in a nonperiodic region where heat is lost from the boundary current the vorticity balance in the downwelling region is primarily between stretching of planetary vorticity and eddy flux divergence of relative vorticity althougha narrowviscous boundarylayeris ultimately importantin closingtheregionalvorticitybudget this overall balance is similar in some ways to the diffusive viscous balance represented in previous boundary layer theories and suggests that the downwelling in convective basins may be properly represented in lowresolution climate models if eddy flux parameterizations are adiabatic identify localized regions of eddy formations and allow density to be transported far from the region of eddy formations

the use of earthquake rate changes as a stress meter at kilauea volcano stress changes in the earth s crust are generally estimated from model calculations that use near surface deformation as an observational constraint but the widespread correlation of changes of earthquake activity with stress has led to suggestions that stress changes might be calculated from earthquake occurrence rates obtained from seismicity catalogues although this possibility has considerable appeal because seismicity data are routinely collected and have good spatial and temporal resolution the method has not yet proven successful owing to the non linearity of earthquake rate changes with respect to both stress and time here however we present two methods for inverting earthquake rate data to infer stress changes using a formulation for the stress and time dependence of earthquake rates application of these methods at kilauea volcano in hawaii yields good agreement with independent estimates indicating that earthquake rates can provide a practical remote sensing stress meter

thermally driven circulations in small oceanic basins abstract a linear steady model of the circulation of a small f plane oceanic basin driven by heating or cooling at the surface is considered in order to examine the partition of upwelling heating or downwelling cooling between the basin s interior and its boundary layers on the sidewall in which frictional dissipation and lateral temperature diffusion are dominant the basin is rectangular in plan form on three of its lateral sides the basin is insulated to heat exchange on the fourth side the heat added at the surface is shown to be removed through a thin sublayer that also closes the mass balance the temperature is linearized about a basic linear stratification the analytical solution shows that in the case of heating cooling in the basin interior most of the resulting upwelling downwelling near the upper surface actually occurs in narrow boundary layers whose width is on the order of the deformation radius rather than in the interior directly this nonintuitive result is consistent wi

interseismic quiescence and triggered slip of active normal faults of kīlauea volcano s south flank during 2001 2018 the mobile south flank of k lauea volcano hosts two normal fault systems the koa e fault system kfs and the hilina fault system hfs in historical time at least three m 6 5 earthquakes have occurred on the basal detachment of the k lauea volcano s south flank with the most recent being the 4 may 2018 m6 9 earthquake here we analyze kinematic global positioning system data collected from 2001 to 2017 and interferometric synthetic aperture radar data before during and after the 2018 m6 9 earthquake to determine the crustal motion across the hfs and kfs faults our results indicate that the hfs faults did not significantly slip during the interseismic period from 2007 to 2011 despite its substantial magnitude interferometric synthetic aperture radar insar data show that the 2018 m6 9 earthquake triggered subcentimeter level slip along sections of the previously mapped hfs branches up to 20 cm of offset occurred on what appears to be a newly formed or previously unknown fault near the eastern end of the hfs during the 3 months following the m6 9 earthquake up to 30 cm of slip occurred along the kfs which helps accommodate rapid large scale subsidence of k lauea s summit region as large volumes of summit reservoir magma fed the lower east rift zone eruption the hfs appears to activate only in concert with large earthquakes on the basal detachment the kfs on the other hand moves both seismically during small local earthquakes and aseismically in response to nearby earthquakes and caldera subsidence

growth and persistence of hawaiian volcanic rift zones hawaiian volcanic rift zones are modeled by representing the rifts and adjacent volcano flanks as long ridges with the geometry of flattened triangular prisms the intrusion of dikes along the axis of a rift requires a mechanism to generate the appropriate dike trapping stress field within the prism possible factors that affect the state of stress in the prism include multiple dike intrusion along the ridge axis faulting and gravitational sagging of the topography in extreme models with very steep slopes and high poisson s ratio corresponding to the gelatin models of rift zones by fiske and jackson 1972 results of finite element calculations indicate that gravity induced stresses are sufficient to trap a dike into propagating within the prism and parallel to the rift zone as proposed by fiske and jackson however the mechanism does not work for gently sloping flanks or a more acceptable poisson s ratio of about 0 25 additionally trapping stresses in the gravity loading and density stratification models will not persist after a few dike injection episodes therefore in mature hawaiian rift zones with possibly thousands of dikes additional processes must act to control the stresses that permit continued dike intrusion and rift persistence it is proposed that accommodation to dike emplacement occurs by slip on deep faults possibly of the type proposed for the 1975 kalapana hawaii earthquake as suggested by others for this earthquake the faults could coincide with the contact of the volcano with the seafloor within the weak seafloor sediments such faulting not only provides a means for the flanks to adjust continuously to intrusions but also generates the stress patterns needed to constrain future dikes to propagate along the rift axis other possible faulting mechanisms such as shallow gravity slides and normal faulting of the flanks do not appear to favor rift zone persistence in this model the horizontal stress generated by a standing column of magma at the time of dike emplacement the stresses in the ridges and the fault strength are coupled this results in a feedback between the maximum height that magma can rise along the rift fault friction and fault width through this feedback the slope of the volcano flank is controlled by the fault friction when applied to kilauea volcano the model yields an estimate for the coefficient of fault friction as high as 0 39 assuming normal hydrostatic pore fluid pressure an implication of this model supported by other studies is that rift intrusion and lateral spreading could be major contributors to volcano growth

eddy driven buoyancy gradients on eastern boundaries and their role in the thermocline abstract it is demonstrated that eddy fluxes of buoyancy at the eastern and western boundaries maintain alongshore buoyancy gradients along the coast eddy fluxes arise near the eastern and western boundaries because on both coasts buoyancy gradients normal to the boundary are strong the eddy fluxes are accompanied by mean vertical flows that take place in narrow boundary layers next to the coast where the geostrophic constraint is broken these ageostrophic cells have a velocity component normal to the coast that balances the geostrophic mean velocity it is shown that the dynamics in these thin ageostrophic boundary layers can be replaced by effective boundary conditions for the interior flow relating the eddy flux of buoyancy at the seaward edge of the boundary layers to the buoyancy gradient along the coast these effective boundary conditions are applied to a model of the thermocline linearized around a mean stratification and a state of rest the linear model parameterizes the eddy fluxes of buoya

subsidence at southern andes volcanoes induced by the 2010 maule chile earthquake large earthquakes in subduction zones can affect nearby volcanoes analysis of ground deformation following the 2010 earthquake in maule chile shows that some volcanoes subsided by up to 15 cm probably because of quake triggered release of hydrothermal fluids

near surface circulation of the nordic seas as measured by lagrangian drifters in the period june 1991 to august 1993 107 argos tracked drifters drogued to 15 m depth were released in the nordic seas or greenland iceland and norwegian seas the drifter movements revealed the strong and spatially confined current systems along the surface salinity fronts of the iceland faroe frontal zone and of the norwegian coast and along the continental margins and their extensions to the barents sea and spitsbergen the norwegian atlantic current is composed of three distinct streams two continental margin and one coastal branches which join into one single swift mean current west of the lofoten and vesteralen islands where the strongest measured currents are in excess of 110 cm s 1 in addition to the general cyclonic gyre circulation in the nordic seas the drifters indicate smaller cyclonic circulation patterns in all the major subbasins i e the iceland plateau the norwegian the lofoten and the greenland basins no surface signature of the east icelandic current is disclosed by the drifters interpolated and low pass filtered position data were used to construct maps of 15 m depth ensemble mean velocity velocity variability and residence time vigorous eddy fields are dominant in the strong currents and in the lofoten basin eulerian correlations indicate that they tend to propagate to the west in contrast the iceland plateau appears quiescent both in the mean and eddy velocities single particle diffusivities are computed and are found to be in the range 1 7 107 cm2 s 1 the corresponding lagrangian timescale and space scale are 1 3 days and 10 40 km respectively these lagrangian drifter measurements compose the first basin scale accurate near surface velocity data set of the nordic seas

coherent eddies in the labrador sea observed from a mooring abstract during june november 1994 a mooring in the central labrador sea near the former ocean weather station bravo recorded a half dozen anomalous events that prove to be two different types of coherent eddies comparisons with simple analytical models are used to classify these events as coherent eddies on the basis of their velocity signatures the first clear examples of long lived convectively generated eddies are reported these four small radius 5 15 km eddies are exclusively anticyclonic with cold fresh middepth potential temperature and salinity s cores surrounded by azimuthal currents of 15 cm s 1 their s properties identify them unambiguously as the products of wintertime deep convection in the interior labrador sea compared with eddies in other regions these anticyclones are unusual for their strong surface expressions and composite s cores two warm cyclones are also seen these are larger radius 15 km than the anticyclones and about as energetic currents 15 cm s 1

slip model of the 2015 mw 7 8 gorkha nepal earthquake from inversions of alos 2 and gps data we use surface deformation measurements including interferometric synthetic aperture radar data acquired by the alos 2 mission of the japanese aerospace exploration agency and global positioning system gps data to invert for the fault geometry and coseismic slip distribution of the 2015 mw 7 8 gorkha earthquake in nepal assuming that the ruptured fault connects to the surface trace of the main frontal thrust mft fault between 84 34 e and 86 19 e the best fitting model suggests a dip angle of 7 the moment calculated from the slip model is 6 08 1020 nm corresponding to the moment magnitude of 7 79 the rupture of the 2015 gorkha earthquake was dominated by thrust motion that was primarily concentrated in a 150 km long zone 50 to 100 km northward from the surface trace of the main frontal thrust mft with maximum slip of 5 8 m at a depth of 8 km data thus indicate that the 2015 gorkha earthquake ruptured a deep part of the seismogenic zone in contrast to the 1934 bihar nepal earthquake which had ruptured a shallow part of the adjacent fault segment to the east

overthrusting and sediment accretion along kilauea s mobile south flank hawaii evidence for volcanic spreading from marine seismic reflection data a large intermittently active submarine landslide known as the hilina slump has been interpreted along the south flank of kilauea volcano seaward dipping faults on land mark its headwall and an offshore bench may define its uplifted toe geodetic data show that the entire south flank is also moving seaward by a process referred to as volcanic spreading this provides an alternative explanation for the bench i e overthrusting along the edge of the sliding flank the latter interpretation is consistent with new seismic reflection data across the submarine flank a prominent reflection near the top of the oceanic plate suggests the decollement upon which the mobile flank slides landward dipping reflections rise from this horizon and bound packages of bedded strata faulted and imbricated within the bench the absence of correlative seaward dipping faults and rotated strata on the upper flank suggests that the bench is not coupled to a slump moreover kinematic reconstructions of the bench indicate that it has accommodated 15 24 km of displacement this value is consistent with estimates for rift zone extension but too high for shortening at the toe of a slump we interpret the bench to result from overthrusting and accretion of volcaniclastic sediments to the edge of the mobile flank and suggest that morphologic benches develop preferentially where landslide debris has accumulated near the base of the volcano and can be accreted to its sliding edifice

earthquakes triggered by silent slip events on kīlauea volcano hawaii silent earthquakes or slow slip events happen so slowly that they cannot be detected by conventional seismographs but now the availability of gps data means that they can be followed in detail segall et al report on a series of small earthquakes on k lauea volcano hawaii the earthquakes at depths of 7 to 8 km appear to be triggered by otherwise silent slow slips though small triggered earthquakes of this type can be used to help quantify the increased hazard due to slow slip events slow slip events or silent earthquakes have recently been discovered in a number of subduction zones including the nankai trough1 2 3 in japan cascadia4 5 and guerrero6 in mexico but the depths of these events have been difficult to determine from surface deformation measurements although it is assumed that these silent earthquakes are located along the plate megathrust this has not been proved slow slip in some subduction zones is associated with non volcanic tremor7 8 but tremor is difficult to locate and may be distributed over a broad depth range9 except for some events on the san andreas fault10 slow slip events have not yet been associated with high frequency earthquakes which are easily located here we report on swarms of high frequency earthquakes that accompany otherwise silent slips on k lauea volcano hawaii for the most energetic event in january 2005 the slow slip began before the increase in seismicity the temporal evolution of earthquakes is well explained by increased stressing caused by slow slip implying that the earthquakes are triggered the earthquakes located at depths of 7 8 km constrain the slow slip to be at comparable depths because they must fall in zones of positive coulomb stress change triggered earthquakes accompanying slow slip events elsewhere might go undetected if background seismicity rates are low detection of such events would help constrain the depth of slow slip and could lead to a method for quantifying the increased hazard during slow slip events because triggered events have the potential to grow into destructive earthquakes

afterslip and viscoelastic relaxation following the 1999 m 7 4 izmit earthquake from gps measurements summary intensive global positioning system gps monitoring after the 1999 izmit earthquake provides an opportunity to understand the postseismic behaviour of a strike slip fault and the rheology below the brittle upper crust two data sets are available displacements measured during the first 300 days after the izmit earthquake and velocity measurements between 2003 and 2005 using an inversion method and a forward modelling respectively we investigate two mechanisms 1 afterslip on and below the coseismic rupture plane and 2 viscoelastic stress relaxation in the lower crust and upper mantle described by a maxwell or a standard linear solid sls rheology the inversion results show that the first several months following the izmit earthquake were dominated by afterslip at depths shallower than 30 km and the slip amount decayed with time after that apparent afterslip has a very different spatial distribution and is located much deeper for viscoelastic relaxation a model with an elastic upper crust and a maxwell viscoelastic lower crust overlying a maxwell mantle e m m fits the data measured in the first 300 days better in the far field than in the near field however the observed far field 300 day displacement and the long term 2003 2005 displacement which might be dominated by viscoelastic relaxation cannot be described by a maxwell rheological model with constant viscosity the effective viscosity increases over time therefore we have built a refined rheological model an elastic upper crust and an sls lower crust overlying a maxwell viscoelastic mantle e sls m our best solution yields a viscosity for the lower crust of 2 1018 pa s a relaxation strength of 2 3 and a viscosity for the maxwell mantle of 7 1019 pa s finally we explain the data using a composite model consisting of the preferred e sls m model and the afterslip model obtained from the residual displacement after correcting for viscoelastic relaxation for the early time period the residual displacements can be mainly explained by a shallow afterslip whose magnitude decays with time and whose spatial distribution is stable whereas the residual displacements for the later time period require negligible afterslip it indicates that the postseismic deformation in the later time period induced by a deep source can be almost entirely explained by the e sls m model the composite model can generally explain the data in the entire spatial and temporal space

an increment of volcano collapse kinematics of the 1975 kalapana hawaii earthquake abstract earthquakes on kilauea volcano can be even more hazardous than volcanic eruptions the most recent large earthquake was the 1975 kalapana quake which generated a locally damaging tsunami over 8 m of horizontal surface displacement and 3 m of subsidence at the coast the seismic magnitude estimates for this earthquake range from ms 7 2 to mw 7 7 the complexity of the seismic data is matched by the complex surface deformation that was observed with a combination of leveling tilt and electronic distance measurements edm the geodetic data shows evidence of collapse of the caldera due to magma withdrawal localized subsidence over the rift zone normal faulting associated with shallow slumping along the hilina pali and displacement on the basal detachment fault we model the summit caldera rift zones and basal detachment fault as dislocations in an elastic half space to better quantify the sources of deformation related to this devastating event using inversion techniques that allow us to let the data constrain the geometry and magnitude of these sources we find 0 04 km3 of magma withdrawal at the summit between 3 5 m of opening along the rift zone and 7 1 m of slip along the basal detachment at 8 3 km depth models that allow for finer spatial resolution of slip on the detachment show that the largest slip occurred west of the seismically recorded earthquake hypocenter along the region of the fault below the coast and that the majority of the fault slip occurred south of the region of microseismicity our best fitting model has a geodetic moment of 4 1 1020 nm mw 7 7 which is consistent with tsunami models and recent analysis of long period seismic data the residual displacements of sites located in the hanging wall of the hilina pali slump system which were not used in the inversion of the other sources suggest that triggered shallow slumping contributed several meters of horizontal displacement to the coseismic displacement at these sites

volcano monitoring using gps developing data analysis strategies based on the june 2007 kīlauea volcano intrusion and eruption 1 the global positioning system gps is one of the most common techniques and the current state of the art used to monitor volcano deformation in addition to slow several centimeters per year displacement rates gps can be used to study eruptions and intrusions that result in much larger tens of centimeters over hours days displacements it is challenging to resolve precise positions using gps at subdaily time intervals because of error sources such as multipath and atmospheric refraction in this paper the impact of errors due to multipath and atmospheric refraction at subdaily periods is examined using data from the gps network on k lauea volcano hawai i methods for filtering position estimates to enhance precision are both simulated and tested on data collected during the june 2007 intrusion and eruption comparisons with tiltmeter records show that gps instruments can precisely recover the timing of the activity

motion of kilauea volcano during sustained eruption from the puu oo and kupaianaha vents 1983 1991 kilauea erupted almost continuously from january 1983 through 1991 although the summit began subsiding during the rift zone dike intrusion that initiated this eruption remarkably steady ground surface motions began in late 1983 after a magnitude 6 6 earthquake beneath the slopes of nearby mauna loa volcano and continued until the onset of brief upper east rift zone earthquake swarms in late 1990 during these 7 years the summit and upper rift zones subsided up to 10 11 and 4 8 cm yr 1 respectively and summit baselines contracted up to 6 cm yr 1 baselines directed northward from the summit to stations on mauna loa extended at rates up to 7 cm yr 1 and a baseline from south of the summit to mauna loa extended 4 cm yr 1 much of this extension is inconsistent with deformation caused solely by summit magma reservoir collapse and more likely reflects rifting as the south flank of the volcano moved seaward from the summit and rift zones farther from the summit baselines crossing the south flank extended up to 2 cm yr 1 and a south flank tide gauge rose 2 cm yr 1 the lower east rift zone 40 50 km from the summit subsided about 2 cm yr 1 motion on kilauea then is broadly consistent with slip along low angle south flank faults generating subsidence that is focused at the summit and along the rift system behind the faulting and uplift along the coastal south flank ahead of it dislocation models that combine these elements show that much of kilauea s edifice migrated seaward producing ground surface motions along the south flank of up to about 6 cm yr 1 the magnitude 6 1 earthquake of 1989 punctuated these motions along the eastern south flank producing more than 25 cm of seaward displacement and 15 km east of the epicenter up to 24 cm of subsidence south of the lower east rift zone unlike the magnitude 7 2 south flank earthquake of 1975 the 1989 event was preceded neither by summit magma reservoir inflation nor by rift zone dike intrusions and accompanying compression of the south flank deformation was probably caused by the weight of the volcanic overburden and by ongoing dilation and slip within the rift system

fault frictional parameters and material properties revealed by slow slip events at kilauea volcano hawai i 1 we categorize slow slip events at kilauea volcano into two distinct families based on gps measurements of the surface displacement patterns an event correlation filter confirms that eastern and western families are statistically distinguishable with the western family notably self similar the western family exhibits quasi periodicity with regular repeat times while eastern family events are aperiodic or have complicated periodicity if the decollement is the source fault for both families of events it must have varying frictional properties at the 10 km scale of separation the temporal slip and spatial scaling behavior are consistent with a simplistic rate and state dependent frictional formalism provided that the characteristic slip distance for state evolution dc is of the order of millimeters rather than the 10 100 m typically found in lab studies and the shear rigidity is around 2 gpa consistent with fault gouge material

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

pressurized magma reservoir within the east rift zone of kīlauea volcano hawai i evidence for relaxed stress changes from the 1975 kalapana earthquake we use 2000 2012 insar data from multiple satellites to investigate magma storage in k lauea s east rift zone erz the study period includes a surge in magma supply rate and intrusion eruptions in 2007 and 2011 the kupaianaha area inflated by 5 cm prior to the 2007 intrusion and the n pau crater area by 10 cm following the 2011 intrusion for the n pau crater area elastic modeling suggests an inflation source at 5 2 km depth or more below sea level the reservoir is located in the deeper section of the rift zone for which secular magma intrusion was inferred for the period following the 1975 mw7 7 decollement earthquake reservoir pressurization suggests that in this section of the erz extensional stress changes due to the earthquake have largely been compensated for and that this section is approaching its pre 1975 state reservoir pressurization also puts the molten core model into question for this section of k lauea s rift zone

rupture in the 4 may 2018 m w 6 9 earthquake seaward of the kilauea east rift zone fissure eruption in hawaii

january 30 1997 eruptive event on kilauea volcano hawaii as monitored by continuous gps a continuous global positioning system gps network on kilauea volcano captured the most recent fissure eruption in kilauea s east rift zone erz in unprecedented spatial and temporal detail the short eruption drained the lava pond at pueu oeo leading to a two month long pause in its on going eruption models of the gps data indicate that the intrusion s bottom edge extended to only 2 4 km continuous gps data reveal rift opening 8 hours prior to the eruption absence of precursory summit inflation rules out magma storage overpressurization as the eruption s cause we infer that stresses in the shallow rift created by the continued deep rift dilation and slip on the south flank decollement caused the rift intrusion

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

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

geodetic evidence for en echelon dike emplacement and concurrent slow slip during the june 2007 intrusion and eruption at kīlauea volcano hawaii 1 a series of complex events at k lauea volcano hawaii 17 june to 19 june 2007 began with an intrusion in the upper east rift zone erz and culminated with a small eruption 1500 m3 surface deformation due to the intrusion was recorded in unprecedented detail by global positioning system gps and tilt networks as well as interferometric synthetic aperture radar insar data acquired by the envisat and alos satellites a joint nonlinear inversion of gps tilt and insar data yields a deflationary source beneath the summit caldera and an ene striking uniform opening dislocation with 2 m opening a dip of 80 to the south and extending from the surface to 2 km depth this simple model reasonably fits the overall pattern of deformation but significantly misfits data near the western end of an inferred dike like source three more complex dike models are tested that allow for distributed opening including 1 a dike that follows the surface trace of the active rift zone 2 a dike that follows the symmetry axis of insar deformation and 3 two en echelon dike segments beneath mapped surface cracks and newly formed steaming areas the en echelon dike model best fits near field gps and tilt data maximum opening of 2 4 m occurred on the eastern segment beneath the eruptive vent although this model represents the best fit to the erz data it still fails to explain data from a coastal tiltmeter and gps sites on k lauea s southwestern flank the southwest flank gps sites and the coastal tiltmeter exhibit deformation consistent with observations of previous slow slip events beneath k lauea s south flank but inconsistent with observations of previous intrusions slow slip events at k lauea and elsewhere are thought to occur in a transition zone between locked and stably sliding zones of a fault an inversion including slip on a basal decollement improves fit to these data and suggests a maximum of 15 cm of seaward fault motion comparable to previous slow slip events