experiments on conduit flow and eruption behavior of basaltic volcanic eruptions multiphase flow in basaltic volcanic conduits is investigated using analog experiments and theoretical approaches depending on gas supply large gas bubbles gas slugs may rise through basaltic magma in regimes of distinct fluid dynamical behavior ascent of single slugs supplied slugs fed from the gas source during ascent and periodic slug flow an annular flow regime commences at the highest gas supply rates a first set of experiments demonstrates that the growth of gas slugs due to hydrostatic decompression does not affect their ascent velocity and that excess pressure in the slugs remain negligible the applicability of theoretical formulae describing slug ascent velocity as a function of liquid and conduit properties is evaluated in a second set of experiments a third set of experiments with continuous gas supply into a cylindrical conduit are scaled to basaltic conditions over morton eotvos reynolds and froude numbers gas flow rate and liquid viscosity are varied over the whole range of flow regimes to observe flow dynamics and to measure gas and liquid eruption rates foam generation by slug bursting at the surface and partial slug disruption by wake turbulence can modify the bubble content and size distribution of the magma at the transition from slug to annular flow when the liquid bridges between the gas slugs disappear pressure at the conduit entrance drops by 60 from the hydrostatic value to the dynamic flow resistance of the annular flow which may trigger further degassing in a stored magma to maintain the annular flow regime until the gas supply is exhausted and the eruption ends abruptly magma discharge may also terminate when magma ascent is hindered by wall friction in long volcanic conduits and the annular gas flow erodes all magma from the conduit supplied slugs are found to reach much higher rise velocities than unsupplied slugs and to collapse to turbulent annular flow upon bursting at the surface a fourth set of experiments uses a conduit partially blocked by built in obstacles providing traps for gas pockets once gas pockets are filled rising gas slugs deform but remain intact as they move around obstacles without coalescence or significant velocity changes bursting of bubbles coalescing with trapped gas pockets causes pressure signals at least 3 orders of magnitude more powerful than gas pocket oscillation induced by passing liquid our experiments suggest a refined classification of strombolian and hawaiian eruptions according to time dependant behavior into sporadically pulsating lava fountains driven by stochastic rise of single slugs periodically pulsating lava fountains resulting from slug flow and quasi steady lava fountains oscillating at the frequency of annular flow turbulence

correlation of changes in gravity elevation and strain in southern california measurements made once or twice a year from 1977 through 1982 show large correlated changes in gravity elevation and strain in several southern california networks precise gravity surveys indicate changes of as much as 25 microgals between surveys 6 months apart repeated surveys show that annual elevation changes as large as 100 millimeters occur along baselines 40 to 100 kilometers long laser ranging surveys reveal coherent changes in areal strain of 1 to 2 parts per million occurred over much of southern california during 1978 and 1979 although the precision of these measuring systems has been questioned the rather good agreement among them suggests that the observed changes reflect true crustal deformation

viscous plugging can enhance and modulate explosivity of strombolian eruptions strombolian activity is common in low viscosity volcanism it is characterised by quasi periodic short lived explosions which whilst typically weak may vary greatly in magnitude the current paradigm for a strombolian volcanic eruption postulates a large gas bubble slug bursting explosively after ascending a conduit filled with low viscosity magma however recent studies of pyroclast textures suggest the formation of a region of cooler degassed more viscous magma at the top of the conduit is a common feature of strombolian eruptions following the hypothesis that such a rheological impedance could act as a viscous plug which modifies and complicates gas escape processes we conduct the first experimental investigation of this scenario we find that 1 the presence of a viscous plug enhances slug burst vigour 2 experiments that include a viscous plug reproduce and offer an explanation for key phenomena observed in natural strombolian eruptions 3 the presence and extent of the plug must be considered for the interpretation of infrasonic measurements of strombolian eruptions our scaled analogue experiments show that as the gas slug expands on ascent it forces the underlying low viscosity liquid into the plug creating a low viscosity channel within a high viscosity annulus the slug s diameter and ascent rate change as it enters the channel generating instabilities and increasing slug overpressure when the slug reaches the surface a more energetic burst process is observed than would be the case for a slug rising through the low viscosity liquid alone fluid dynamic instabilities cause low and high viscosity magma analogues to intermingle and cause the burst to become pulsatory the observed phenomena are reproduced by numerical fluid dynamic simulations at the volcanic scale and provide a plausible explanation for pulsations and the ejection of mingled pyroclasts observed at stromboli and elsewhere

geodetic methods for detecting volcanic unrest a theoretical approach in this paper we study the application of different geodetic techniques to volcanic activity monitoring using theoretical analysis this methodology is very useful for obtaining an idea of the most appropriate and efficient monitoring method mainly when there are no records of geodetic changes previous to volcanic activity the analysis takes into account the crustal structure of the area its geology and its known volcanic activity to estimate the deformation and gravity changes that might precede eruptions the deformation model used includes the existing gravity field and vertical changes in the crustal properties both factors can have a considerable effect on computed deformation and gravity changes topography should be considered when there is a steep slope greater than 10 the case study of teide stratovolcano tenerife canary islands for which no deformation or gravity changes are available is used as a test to avoid considering topography we worked at the lowest level of las canadas and examined a smaller area than the whole caldera or island therefore the results are only a first approach to the most adequate geodetic monitoring system the methodology can also be applied to active areas where volcanic risk is not associated with a stratovolcano but instead with monogenetic scattered centers especially when sites must be chosen in terms of detection efficiency or existing facilities the canary islands provide a good example of this type of active volcanic areas and we apply our model to the island of lanzarote to evaluate the efficiency of the monitoring system installed at the existing geodynamic station on this island topography is not important the results of our study show clearly that the most appropriate geodetic volcano monitoring system is not the same for all different volcanic zones and types and the particular properties of each volcano zone must be taken into account when designing each system

observations of strain accumulation across the san andreas fault near palmdale california with a two color geodimeter two color laser ranging measurements during a 15 month period over a geodetic network spanning the san andreas fault near palmdale california indicate that the crust expands and contracts aseismically in episodes as short as 2 weeks shear strain parallel to the fault has accumulated monotonically since november 1980 but at a variable rate improvements in measurement precision and temporal resolution over those of previous geodetic studies near palmdale have resulted in the definition of a time history of crustal deformation that is much more complex than formerly realized

influence of topography on coseismic displacements induced by the friuli 1976 and the irpinia 1980 earthquakes italy analyzed through a two dimensional hybrid model 1 we investigate the perturbations introduced by the local topography on the coseismic displacement components induced by crustal seismic faults the approach proposed by tinti and armigliato 2002 is applicable to homogeneous two dimensional domains with arbitrary topography of the free surface it uses both analytical results valid for homogeneous spaces and half spaces bounded by a flat free surface ffs and a numerical code solving the equations of equilibrium of linear elasticity through a finite element fe scheme a major characteristic of our hybrid method is that it allows for the correct representation of the displacement components in correspondence with the fault which does not need to be explicitly introduced in the fe mesh we show that in the case of homogeneous domains this makes our approach preferable to pure fe schemes our hybrid approach is here applied to two different disastrous events of the recent italian seismic history for which topography is expected to play an important role namely the 6 may 1976 ms 6 5 friuli and the 23 november 1980 ms 6 9 irpinia basilicata earthquakes for each event we selected hypotheses for the parent fault proposed in the literature and compared the coseismic displacements computed through the widely used analytical models dealing with ffs and through our hybrid approach accounting for the effect of realistic topographies the most relevant effects are observed in the case of the irpinia earthquake depending on the profile chosen the computed misfits can be as high as 19 and 13 for the horizontal and vertical displacements respectively with absolute differences up to 9 and 10 cm

conduit convection driving persistent degassing at basaltic volcanoes abstract the persistent release of gas at basaltic volcanoes where there is a low magma eruption rate can be driven by an exchange flow of magma in the conduit in which gas rich magma ascends degasses and crystallises and then sinks back down the conduit the driving force of the flow is provided by the density difference between the buoyant bubble rich magma at depth and the dense degassed crystallised magma at shallow levels in this study we attempt to constrain the physical and chemical processes driving an exchange flow of magma at stromboli aeolian archipelago italy the model uses a simple cylindrical geometry we define degassing and crystallisation paths of the ascending and descending magmas constrained by gas flux and melt inclusion data given in the literature to produce a three phase model of ascending and descending magmas driving persistent gas fluxes we calculate the viscosity of the three phase magma using end member rheological models for bubble and crystal suspensions combining our modelled magma properties with analogue exchange flow experiments we can relate the regime of magma flow driving persistent degassing to pressure at pressures 90 mpa 3 km the viscosity ratio is 100 and the regime is predicted to be side by side flow with both ascending and descending magmas adjacent to a portion of the conduit wall at pressures 90 mpa 3 km the viscosity ratio between the ascending and descending magma is 100 and the flow is predicted to be core annular flow with the ascending vesiculating magma in the inner core and the more crystalline degassed magma flowing down along the conduit wall by analogy we hypothesise that degassed magma would flow down along the walls in dike like plumbing geometries that have been proposed for the deeper strombolian system analogue experiments suggest that exchange flows do not overturn under conditions of maximum volume flux we use an empirical relationship to characterise the volume flux of the exchange flow and show that the radius of a cylindrical conduit required to account for the observed persistent gas flux at stromboli at 0 1 mpa is 1 m

modelling the rapid near surface expansion of gas slugs in low viscosity magmas the ascent of large gas bubbles slugs in vertical cylindrical conduits and low viscosity magmas is simulated using 1d mathematical and 3d computational fluid dynamic cfd models following laboratory evidence the 1d model defines a constant rise velocity for the slug base and allows gas expansion to accelerate the slug nose through the overlying fluid during ascent the evolution of rapidly expanding gas slugs observed in laboratory experiments is reproduced well and at volcano scales predicts at surface overpressures of several atmospheres without requiring any initial overpressure at depth the near surface dynamics increase slug nose velocities through the overlying magma by a factor of c 2 5 and the gas expansion results in pre burst magma surface velocities of c 35m s21 to examine pressure distributions and the forces exerted on a conduit 3d cfd simulations were carried out at volcano scales the vertical single forces during final slug ascent to the surface are c 106 n two orders of magnitude smaller than those associated with verylong period seismic events at stromboli this supports a previous interpretation of these events in which they are generated by gas slugs flowing through changes in conduit geometry rather than being the direct result of slug eruption processes

automated object based classification of topography from srtm data we introduce an object based method to automatically classify topography from srtm data the new method relies on the concept of decomposing land surface complexity into more homogeneous domains an elevation layer is automatically segmented and classified at three scale levels that represent domains of complexity by using self adaptive data driven techniques for each domain scales in the data are detected with the help of local variance and segmentation is performed at these appropriate scales objects resulting from segmentation are partitioned into sub domains based on thresholds given by the mean values of elevation and standard deviation of elevation respectively results resemble reasonably patterns of existing global and regional classifications displaying a level of detail close to manually drawn maps statistical evaluation indicates that most of classes satisfy the regionalization requirements of maximizing internal homogeneity while minimizing external homogeneity most objects have boundaries matching natural discontinuities at regional level the method is simple and fully automated the input data consist of only one layer which does not need any pre processing both segmentation and classification rely on only two parameters elevation and standard deviation of elevation the methodology is implemented as a customized process for the ecognition software available as online download the results are embedded in a web application with functionalities of visualization and download

some insights into topographic elastic and self gravitation interaction in modelling ground deformation and gravity changes in active volcanic areas surface displacements and gravity changes due to volcanic sources are influenced by medium properties we investigate topographic elastic and self gravitation interaction in order to outline the major factors that are significant in data modelling while elastic gravitational models can provide a suitable approximation to problems of volcanic loading in areas where topographic relief is negligible for prominent volcanoes the rough topography could affect deformation and gravity changes to a greater extent than self gravitation this fact requires the selection depending on local relief of a suitable model for use in the interpretation of surface precursors of volcanic activity we use the three dimensional indirect boundary element method to examine the effects of topography on deformation and gravity changes in models of magma chamber inflation deflation topography has a significant effect on predicted surface deformation and gravity changes both the magnitude and pattern of the geodetic signals are significantly different compared to half space solutions thus failure to account for topographic effects in areas of prominent relief can bias the estimate of volcanic source parameters since the magnitude and pattern of deformation and gravity changes depend on such effects

effects of crystal shape and size modality on magma rheology erupting magma often contains crystals over a wide range of sizes and shapes potentially affecting magma viscosity over many orders of magnitude a robust relation between viscosity and the modality of crystal sizes and shapes remains lacking principally because of the dimensional complexity and size of the governing parameter space we have performed a suite of shear viscosity measurements on liquid particle suspensions of dynamical similarity to crystal bearing magma our experiments encompass five suspension types each consisting of unique mixtures of two different particle sizes and shapes the experiments span two orthogonal subspaces of particle concentration as well as particle size and shape for each suspension type thereby providing insight into the topology of parameter space for each suspension type we determined the dry maximum packing fraction and measured shear rates across a range of applied shear stresses the results were fitted using a herschel bulkley model and augment existing predictive capabilities we demonstrate that our results are consistent with previous work including friction based constitutive laws for granular materials we conclude that predictions for ascent rates of crystal rich magmas must take the shear rate dependence of viscosity into account shear rate dependence depends first and foremost on the volume fraction of crystals relative to the maximum packing fraction which in turn depends on crystal size and shape distribution

analogue experiments on the rise of large bubbles through a solids rich suspension a weak plug model for strombolian eruptions abstract physical interactions between bubbles and crystals affect gas migration and may play a major role in eruption dynamics of crystal rich magmas strombolian eruptions represent an end member for bubble crystal interactions in which large bubbles significantly larger than the crystal size rise through a crystal rich near surface magma indeed volcanoes that produce strombolian eruptions often generate ejecta with 30 vol often 45 vol average crystallinity at stromboli volcano italy average crystallinity can reach 55 vol which is approaching the eruptibility limit for magmas at such high crystallinities the solids interact mechanically with each other and with bubbles this complex rheology complicates the two phase liquid gas slug flow model often applied to strombolian eruptions to examine the effect of crystals on bubble rise we performed analogue experiments in which large bubbles rise in a vertical tube filled with silicone oil and polypropylene particles the particles have a slightly lower density than the oil and therefore form a layer of oil particles at the upper surface we varied surface pressure particle volume fraction length of the particle bearing cap and bubble size to examine the ways in which these parameters influence strombolian type eruptions we show that in experiments suspended solids begin to affect bubble rise dynamics at particle volume fractions as low as 30 vol or when divided by the random close packing value a normalized particle fraction 0 64 bubbles in experiments with higher particle contents deform as they rise and burst through a small aperture generating surface fountains that begin abruptly and decay slowly and longer lasting acoustic signals of lower amplitude than in particle poor experiments particle fractions 38 vol 0 80 generated strong deformations on fast expanding bubbles that applied a high stress on the cap but they trapped bubbles that were less overpressured qualitatively the gas release behavior observed in particle rich experiments is consistent with observations of strombolian eruptions moreover we estimate that the observed crystallinity of pyroclasts at stromboli volcano represents 0 8 from this we suggest a weak plug model for strombolian eruptions that evolves towards a low viscosity equivalent of vulcanian style plug failure with a more crystalline stronger and less permeable plug importantly this model allows the rise of several bubbles in the conduit at the same time and suggests that longer lasting more pulsatory and complex eruptions may reveal an increase in near surface crystallinity shedding some light on changing conduit conditions that could help determine the different gas rise regimes involved in passive degassing puffing and different expressions of strombolian explosions

strain on the san andreas fault near palmdale california rapid aseismic change frequently repeated strain measurements near palmdale california during the period from 1971 through 1980 indicate that in addition to a uniform accumulation of right lateral shear strain engineering shear 0 35 microradian per year across the san andreas fault a 1 microstrain contraction perpendicular to the fault that accumulated gradually during the interval 1974 through 1978 was aseismically released between february and november 1979 subsequently november 1979 to march 1980 about half of the contraction was recovered this sequence of strain changes can be explained in terms of south southwestward migration of a slip event consisting of the south southwestward movement of the upper crust on a horizontal detachment surface at a depth of 10 to 30 kilometers the large strain change in 1979 corresponds to the passage of the slip event beneath the san andreas fault

surficial patterns of debris flow deposition on alluvial fans in death valley ca using airborne laser swath mapping data debris flows are a common event in mountainous environments they often possess the greatest potential for destruction of property and loss of lives in these regions delimiting the spatial extent of potential damage from debris flows relies on detailed studies of the location of depositional zones current research indicates debris flow fans have two distinct depositional zones however the two zones were derived from studies containing detailed analyses of only a few fans high resolution airborne laser swath mapping alsm data is used to calculate profile curvature and surface gradient on 19 debris flow fans on the eastern side of death valley the relationship between these parameters is assessed to 1 identify if debris flow fans are accurately represented by two depositional zones and 2 to assess how these terrain parameters relate to one another at the individual fan scale the results show at least three zones of deposition exist within the sampled fans these zones do not hold consistent when individual fan morphometry is analyzed in conjunction with localized fan surface gradients fans with consistently shallower gradients exhibit numerous depositional zones with more subtle changes in profile curvature steeper gradient fans exhibit significantly fewer zones with more pronounced local changes in profile curvature the surface complexity of debris flow fans is evident from these analyses and must be accounted for in any type of hazard studies related to these features

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

remote sensing as tool for development of landslide databases the case of the messina province italy geodatabase abstract landslide geodatabases including inventories and thematic data today are fundamental tools for national and or local authorities in susceptibility hazard and risk management a well organized landslide geo database contains different kinds of data such as past information landslide inventory maps ancillary data and updated remote sensing space borne and ground based data which can be integrated in order to produce landslide susceptibility maps updated landslide inventory maps and hazard and risk assessment maps italy is strongly affected by landslide phenomena which cause victims and significant economic damage to buildings and infrastructure loss of productive soils and pasture lands in particular the messina province southern italy represents an area where landslides are recurrent and characterized by high magnitude due to several predisposing factors e g morphology land use lithologies and different triggering mechanisms meteorological conditions seismicity active tectonics and volcanic activity for this area a geodatabase was created by using different monitoring techniques including remote sensing e g sar satellite ers1 2 envisat radarsat 1 terrasar x cosmo skymed data and in situ measurements e g gbinsar damage assessment in this paper a complete landslide geodatabase of the messina province designed following the requirements of the local and national civil protection authorities is presented this geo database was used to produce maps e g susceptibility ground deformation velocities damage assessment risk zonation which today are constantly used by the civil protection authorities to manage the landslide hazard of the messina province

slug ascent and associated stresses during strombolian activity with non newtonian rheology strombolian activity is generally assumed to be driven by overpressurized gas slugs that rise through the magma filled volcanic conduit and burst at the surface we develop an analytical model for this process that incorporates a generic depth dependent and non newtonian magma rheology our model also describes the film draining after the burst and allows for the computation of the stresses exerted on the conduit walls using a new analytical solution for the thickness of an annular film flow using stromboli volcano italy as reference it was evaluated with a specifically designed non newtonian rheological model based on petrochemical data the results show the importance of using a realistic magma viscosity model when modeling the slug ascent a 100 kg gas slug attains its maximum overpressure of 2 1 bars about 40 s before it rapidly expands and finally bursts at only 1 4 bars this preburst pressure drop is not reproduced by constant viscosity models the normal stresses on the conduit wall are generally dilatational above and adjacent to the slug and constrictive below it and after the burst in both cases their maximum values exceed 3 bars whereas the shear stresses stay negligible furthermore it was found that the slug needs to start deeper than 25 m to build up its full burst pressure at greater depth the burst pressure decreases because of the adiabatic slug gas finally a viscous plug at the top of the conduit is shown to increase the explosive potential of the volcano significantly

topographic amplification of tectonic displacement implications for geodetic measurement of strain changes correlations of level changes with topography demand an assessment of the effect of an irregular free boundary on surface deformation this is examined through a plane strain elastic model with topography of small slope subjected to a change in the far field horizontal stress to leading order vertical surface displacements due to the topographic perturbation are proportional to the local relief elevationdependent uplift results from a compressional change and downdrop results from a tensional change the model further predicts that the ratio of elevation change to elevation is proportional to and of the same order of magnitude as the regional strain horizontal strains are locally perturbed by topography as well with the magnitude scaling with the local slope the predicted localization of level changes is very small in aseismic regions and cannot contribute significantly to measured correlations a test case in southern california bears this out with strains of order 10 6 accompanied by elevation change to elevation ratios of order 10 4 releveling following the nankaido tonankai earthquakes which induced large coseismic and postseismic strains reveals scattered examples of elevation dependent level changes however when compared to modeled strains the correlations are again at least an order of magnitude larger than the localization effect predicted by the elastic model although the topographic perturbation of vertical displacements appears to be unmeasurably small local variations in horizontal strain or borehole dilatation across steep relief may be discernible with current technology

the impact of refraction correction on leveling interpretations in southern california recent investigations show that the refraction corrections in leveling are large but can be adequately modeled the corrections are proportional to the temperature differences and the square of the sight lengths changes in sight length with time have resulted in apparent crustal movements when non refraction corrected data were used applying refraction corrections to leveling data in southern california significantly alters the size and configuration of the southern california uplift uplift at palmdale and gorman lebec relative to los angeles bm v32 during the 1953 1978 time period is no greater than 10 cm the bulk of the motion about 6 cm occurs as localized motion along the san gabriel fault during the 1953 1964 time period this motion along the san gabriel fault and uplift of 8 cm directly north of the san fernando fault between 1955 and 1968 may represent precursors to the 1971 san fernando earthquake

collection and three dimensional modeling of gps and tilt data at merapi volcano java we study here the deformations associated with the november 1996 to march 1997 eruption period at mount merapi central java one of the most active volcanoes in indonesia this activity period includes a vertical explosion on january 17 and an increase of the lava dome volume by about 3 106 m3 two global positioning system gps campaigns have been carried out on a six benchmark network at the beginning and at the end of the period relative displacements with respect to the reference point show an average subsidence of 6 5 cm a multicomponent tilt station installed on the southeast flank 3 km from the summit recorded a tilt of 11 1 0 7 rad in the tangential direction and 0 9 0 4 rad in the radial direction these data are interpreted using a three dimensional 3 d elastic model based on the mixed boundary element method and a near neighbor monte carlo inversion interpretation of tilt data requires an accurate mesh for discretizing the 3 d topography the final result supports a horizontal elliptic magma source located 8 5 0 4 km below the summit and 2 0 4 km to the east of it in particular the data cannot be consistent with the location of a magma chamber determined from seismic activity analysis i e 2 km below the summit the computed depth depends strongly on the source shape and cannot be constrained properly because of the small amount of data the computed deflation of 11 2 106 m3 is about 3 times larger than the observed increase in the lava dome volume this difference is attributed to rock avalanches and pyroclastic flows on the flanks of the volcano

planar high angle faulting in the basin and range geodetic analysis of the 1983 borah peak idaho earthquake geodetic elevation changes record the broad scale deformation associated with the m 7 0 october 28 1983 borah peak idaho earthquake on the lost river fault the crest of the lost river range rose 0 2 m and adjacent thousand springs valley subsided 1 0 m in relation to reference points 45 km from the main shock epicenter the deformation was modeled by dislocations in an elastic half space a planar fault with uniform dip slip of 2 05 0 10 m dipping 47 o 2osw and extending to a vertical depth of 13 3 1 2 km fits the geodetic data best and is also consistent with the main shock hypocenter and fault plane solution the geodetic moment is 2 6 0 5 x 1019 n m 2 6 0 5 x 1026 dyn cm and the estimated static stress drop is 2 9 0 4 mpa 29 4 bars tests for coseismic slip on listric faults which flatten with depth and on detachments horizontal faults or shear zones showed fits to the geodetic data that are inferior to those for planar high angle faults no detectable coseismic slip occurred on the mesozoic white knob thrust fault although the low angle thrust sheet intersects the south end of lost river fault near the 1983 mainshock epicenter if the high angle lost river fault abuts a flat lying detachment fault or shear zone such a structure must lie at depths of 12 km near the brittle ductile transition where stick slip behavior gives way to creep the depth and geometry of faulting at borah peak is similar to that inferred from seismic and geodetic evidence for the 1954 m 7 2 fairview peak nevada and the 1959 m 7 3 hebgen lake montana events suggesting that if detachments are active at these localities they are deep and most likely slip by creep

object oriented identification of forested landslides with derivatives of single pulse lidar data in contrast to the many studies that use expert based analysis of lidar derivatives for landslide mapping in forested terrain only few studies have attempted to develop semi automatic methods for extracting landslides from lidar derivatives while all these studies are pixel based it has not yet been tested whether object oriented analysis ooa could be an alternative this study investigates the potential of ooa using only single pulse lidar derivatives such as slope gradient roughness and curvature to map landslides more specifically the focus is on both lidar data segmentation and classification of slow moving landslides in densely vegetated areas where spectral data do not allow accurate landslide identification a multistage procedure has been developed and tested in the flemish ardennes belgium the procedure consists of 1 image binarization and multiresolution segmentation 2 classification of landslide parts main scarps and landslide body segments and non landslide features i e earth banks and cropland fields with supervised support vector machines at the appropriate scale 3 delineation of landslide flanks 4 growing of a landslide body starting from its main scarp and 5 final cleaning of the inventory map the results obtained show that ooa using lidar derivatives allows recognition and characterization of profound morphologic properties of forested deep seated landslides on soil covered hillslopes because more than 90 of the main scarps and 70 of the landslide bodies of an expert based inventory were accurately identified with ooa for mountainous areas with bedrock on the other hand creation of a transferable model is expected to be more difficult

spatial characterization resolution and volumetric change of coastal dunes using airborne lidar cape hatteras north carolina the technological advancement in topographic mapping known as airborne light detection and ranging lidar allows researchers to gather highly accurate and densely sampled coastal elevation data at a rapid rate the problem is to determine the optimal resolutions at which to represent coastal dunes for volumetric change analysis this study uses digital elevation models dem generated from lidar data and spatial statistics to better understand dune characterization at a series of spatial resolutions the lidar data were collected jointly by the national aeronautics and space administration nasa the national oceanic and atmospheric administration noaa and the u s geological survey usgs dems of two study sites 100 200 m located in cape hatteras national seashore north carolina were generated using a raster based geographic information system gis changes in the dune volume were calculated for a 1 year period of time fall 1996 1997 at grid cell resolutions ranging from 1 1 to 20 20 m directional statistics algorithms were used to calculate local variance and characterize topographic complexity data processing was described in detail in order to provide an introduction to working with lidar data in a gis results from these study sites indicated that a 1 2 m resolution provided the most reliable representation of coastal dunes on cape hatteras and most accurate volumetric change measurements results may vary at other sites and at different spatial extents but the methods developed here can be applied to other locations to determine the optimum resolutions at which to represent and characterize topography using common gis and database software

numerical investigation of temporal changes in volcanic deformation caused by a gas slug ascent in the conduit abstract strombolian type eruptions are considered to be generated by a sudden release of a large gas slug that migrates upward in the conduit filled with a low viscous basaltic magma we examine volcano deformations caused by such a gas slug to understand the strombolian eruption mechanism from geodetic observation data we model spatio temporal pressure changes in the conduit by using a gas slug ascent model presented by james et al 2008 as a gas slug ascends in the conduit its volume expands because of depressurization hence the magma head lifts up in the conduit and the upper part of the conduit wall is stressed in the conduit magma pressure increases with depth according to the bulk density of magma the gas slug part with a low density is characterized by a small pressure gradient while the other parts consisting of melt are characterized by a large pressure gradient we numerically calculate volcano deformations caused by the spatio temporal changes of magma pressure predicted from the basic equations representing gas slug locations in the conduit simulation results show that the radial and vertical displacements and tilt changes indicate volcano deformations that represent the inflation originating from the stress increase at the upper part of conduit as the gas slug reaches the shallow part of conduit the rate of inflation observed in the radial displacement decreases the vertical displacement starts to move downward and the tilt turns to show down toward the crater these deflation signals are caused by a moving deflation source in the conduit that is formed beneath the gas slug since these predicted features are not observed in the tilt records associated with explosions at stromboli volcano genco and ripepe 2010 it is necessary to modify the gas slug ascent model or to introduce other mechanisms to better understand the magma dynamics of strombolian eruption

rheological behavior of bubble bearing magmas abstract the vesiculation of the rising magma in a volcanic conduit results in a large change in the viscosity of magma understanding the effect of bubbles on the viscous behavior of bubble melt mixtures over a wide range of bubble volume fractions is essential for accurate modeling of the volcanic processes in this study new equations for the relative viscosity of concentrated bubble bearing suspensions are developed using a differential scheme along with the solution of an infinitely dilute suspension of bubbles out of the four models developed in the paper two models predict the relative viscosity to be a function of only two variables capillary number and volume fraction of bubbles there are no adjustable parameters in these models the remaining two models include an additional parameter that is the maximum packing volume fraction of bubbles the proposed models are evaluated using published numerical and experimental data on the relative viscosity of concentrated suspensions of bubbles the viscosity models for bubble bearing suspensions developed in this study are useful in modeling of the volcanic processes

long period seismicity during magma movement at volcan de colima during the period from february to september 2005 volcan de colima produced 30 vulcanian explosions of sufficient magnitude to produce pyroclastic flows of variable size with a total volume of at least 2 5 106 m3 swarms of long period events were associated with each event their duration ranging from about 6 h to 3 days and each swarm containing up to 886 events the characteristics of the swarms have been studied to understand the source mechanism and their relationship with the vulcanian explosions in total 12 548 long period events were analysed using various comparative and statistical methods patterns were not apparent in the data with no correlation between different properties of the swarms duration magnitude or frequency of occurrence of lp events and the magnitude of the associated vulcanian explosion whether recorded by seismicity volume of pyroclastics or altitude of the eruption column this along with other characteristics of the swarms such as the continuation of the swarm after the explosion with an increase in long period event amplitude in some cases suggests that the mechanism is not merely associated with the pressurization under an impermeable cap and resulting pressure differentials between adjacent volumes within the system it is more likely that the production of long period events is dominated by brittle fracturing on the margins of an ascending magma body a model is proposed whereby the unloading above the ascending magma column produced by a vulcanian explosion resulted in an increase in ascent rate reflected in the increasing amplitude of long period events the results reflect the complexity of non linear processes involved during magma ascent degassing crystallization and rupture of the impermeable plug during the vulcanian process at volcan de colima as at many volcanoes long period events represent a useful precursor for eruptive activity for monitoring this paper highlights some useful analyses that can be carried out which could illustrate certain characteristics of an eruptive episode a preliminary model is presented of the conduit processes at work during the cyclic extrusive and explosive activity during 2005

a model for the rheology of particle bearing suspensions and partially molten rocks an edited version of this paper was published by agu copyright 2009 american geophysical union

the first second of volcanic eruptions from the erebus volcano lava lake antarctica energies pressures seismology and infrasound 1 we describe a multiparameter experiment at erebus volcano antarctica employing doppler radar video acoustic and seismic observations to estimate the detailed energy budget of large up to 40 m diameter bubble bursts from a persistent phonolite lava lake these explosions are readily studied from the crater rim at ranges of less than 500 m and present an ideal opportunity to constrain the dynamics and mechanism of magmatic bubble bursts that can drive strombolian and hawaiian eruptions we estimate the energy budget of the first second of a typical erebus explosion as a function of time and energy type we constrain gas pressures and forces using an analytic model for the expansion of a gas bubble above a conduit that incorporates conduit geometry and magma and gas parameters the model consistent with video and radar observations invokes a spherical bulging surface with a base diameter equal to that of the lava lake the model has no ad hoc free parameters and geometrical calculations predict zenith height velocity and acceleration during shell expansion during explosions the energy contained in hot overpressured gas bubbles is freed and partitioned into other energy types where by far the greatest nonthermal energy component is the kinetic and gravitational potential energy of the accelerated magma shell 10 9 j seismic source energy created by explosions is estimated from radar measurements and is consistent with source energy determined from seismic observations for the generation of the infrasonic signal a dual mechanism incorporating a terminally disrupted slug is proposed which clarifies previous models and provides good fits to observed infrasonic pressures a new and straightforward method is presented for determining gas volumes from slug explosions at volcanoes from remote infrasound recordings

a 2 d hybrid technique to model the effect of topography on coseismic displacements application to the umbria marche central italy 1997 earthquake sequence summary we face the problem of modelling the influence of the irregular topography of the earth s crust on coseismic displacements the modelling technique we propose is valid for a homogeneous elastic 2 d domain and is based on a two step approach that uses 1 the traditional analytical results valid for elastic spaces and elastic half spaces with a flat free surface ffs and 2 a finite element fe numerical code to compute the disturbance induced by the local topography attention is particularly focused on 1 the comparison between the results obtained through our method and the analytical formulae valid for ffs geometries which are used extensively today in both forward and inverse modelling even in the presence of irregular topography and 2 the advantages of our hybrid approach over pure fe models after discussing the theoretical experiment of a gaussian topography we present an application to modelling the displacement fields induced by selected events of the earthquake sequence that hit the umbriamarche region in the central apennines italy in 1997 devoting major attention to the effect of the apennines chain topography in the source region in all cases the topography is found to play an important role and to introduce non negligible corrections to the coseismic surface displacement components computed through the ffs approximation the main effect is that topography not only affects the magnitude of the surface signal but it may also lead to highfrequency disturbances that tend to grow with the shallowness of the fault

landslide inventory maps new tools for an old problem landslides are present in all continents and play an important role in the evolution of landscapes they also represent a serious hazard in many areas of the world despite their importance we estimate that landslide maps cover less than 1 of the slopes in the landmasses and systematic information on the type abundance and distribution of landslides is lacking preparing landslide maps is important to document the extent of landslide phenomena in a region to investigate the distribution types pattern recurrence and statistics of slope failures to determine landslide susceptibility hazard vulnerability and risk and to study the evolution of landscapes dominated by mass wasting processes conventional methods for the production of landslide maps rely chiefly on the visual interpretation of stereoscopic aerial photography aided by field surveys these methods are time consuming and resource intensive new and emerging techniques based on satellite airborne and terrestrial remote sensing technologies promise to facilitate the production of landslide maps reducing the time and resources required for their compilation and systematic update in this work we first outline the principles for landslide mapping and we review the conventional methods for the preparation of landslide maps including geomorphological event seasonal and multi temporal inventories next we examine recent and new technologies for landslide mapping considering i the exploitation of very high resolution digital elevation models to analyze surface morphology ii the visual interpretation and semi automatic analysis of different types of satellite images including panchromatic multispectral and synthetic aperture radar images and iii tools that facilitate landslide field mapping next we discuss the advantages and the limitations of the new remote sensing data and technology for the production of geomorphological event seasonal and multi temporal inventory maps we conclude by arguing that the new tools will help to improve the quality of landslide maps with positive effects on all derivative products and analyses including erosion studies and landscape modeling susceptibility and hazard assessments and risk evaluations

an assessment of the accuracy of the geodetic measurements that define the southern california uplift examination of the charge that the geodetic measurements which define the southern california uplift are seriously flawed by height dependent systematic errors indicates that this charge is unfounded our review of those factors designed to minimize the effects of rod error shows that systematic errors attributable to rod miscalibration are trivial and would tend to cancel during the particularly pertinent period 1955 1965 comparisons between the results of measurements in which the correlation between topography and signal is generally poor reveal large aseismic tilts in a number of places within and around the margins of the uplift especially significant in this context are the results of preuplift and postuplift levelings over routes characterized by diverse length topography and atmospheric conditions that produce closely matching temporally equivalent heights for a representative bench mark within the uplift statistical analyses of the short wavelength components of uplift signal and elevation along a frequently repeated survey line indicate variable correlations between the two however the spatial and temporal patterns of these correlations are inconsistent with their attribution to height dependent systematic errors statistically significant short wavelength correlations along this survey line are reasonably explained in part as due to real movement associated with differentially subsiding bench marks and there is a strong likelihood that this movement tends to dominate many of the correlations

computer assisted discrimination of morphological units on north central crete greece by applying multivariate statistics to local relief gradients traditional manual methods have been employed for decades to measure geomorphometric properties from topographic maps such measurement techniques tend to be tedious and time consuming and the designated landform elements cannot be easily overlaid on any digital map and imagery for further applied research this study deals with a new quantitative geomorphometric procedure based on the multivariate statistical analysis of local topographic gradients within a part of northcentral crete this method employs sets of computer algorithms that automatically extract and classify geomorphometric properties from digital elevation models dems this was done by evaluating the morphological setting around each pixel of the dem along the eight azimuth directions isodata unsupervised classification was implemented to generate 10 morphometric classes showing the spatial distribution of areas with a similar geomorphic scenario results revealed that this approach permitted a quick estimation of the spatial distribution of morphologically homogeneous terrain units it also demonstrated the ability of the delineated landform elements to be superimposed on any digital map and imagery for further investigation this became apparent during the examination of the relationship between the geomorphological units and the land cover land use types in the study area both relative association and the dominant land cover land use types in relation to geomorphological units are presented d 2003 elsevier b v all rights reserved

topographic effect on tilt strain and displacement measurements deformation and stress fields are locally modified by the presense of topography an approximate analytical method is used to give simple expressions for the effect of arbitrarily shaped topography on vertical horizontal and surface tilt measurements this provides a means of making corrections to observations without the use of finite element techniques corrections to tilt fields are found to be directly proportional to the local slope of the topography comparison is made between expressions for tilt and those for strain and displacement although the topographic effects on secular tilt strain and vertical displacement are not yet measurable we emphasize that the topographic effect on precision tidal tilt and strain measurements can be significant

evaluating fuzzy operators of an object based image analysis for detecting landslides and their changes abstract this article presents a method of object based image analysis obia for landslide delineation and landslide related change detection from multi temporal satellite images it uses both spatial and spectral information on landslides through spectral analysis shape analysis textural measurements using a gray level co occurrence matrix glcm and fuzzy logic membership functionality following an initial segmentation step particular combinations of various information layers were investigated to generate objects this was achieved by applying multi resolution segmentation to irs 1d spot 5 and alos satellite imagery in sequential steps of feature selection and object classification and using slope and flow direction derivatives from a digital elevation model together with topographically oriented gray level co occurrence matrices fuzzy membership values were calculated for 11 different membership functions using 20 landslide objects from a landslide training data six fuzzy operators were used for the final classification and the accuracies of the resulting landslide maps were compared a fuzzy synthetic evaluation fse approach was adapted for validation of the results and for an accuracy assessment using the landslide inventory database the fse approach revealed that the and operator performed best with an accuracy of 93 87 for 2005 and 94 74 for 2011 closely followed by the mean arithmetic operator while the or and and operators yielded relatively low accuracies an object based change detection was then applied to monitor landslide related changes that occurred in northern iran between 2005 and 2011 knowledge rules to detect possible landslide related changes were developed by evaluating all possible landslide related objects for both time steps

geomorphometric analysis for characterizing landforms in morelos state mexico landforms can be described and quantified into simple relief elements by parametrization of digital elevation model dem in this research we investigate the use of morphometric parameters and a new classification scheme to characterize selected elemental forms associated with landforms we apply and test this methodology on a geomorphologically diverse region located in central mexico these simple elements are known as morphometric classes and include ridge plane channel pit peak and pass these classes correspond to real entities and are of practical significance the morphometric classes were grouped according to their areal parameters ridge plane and channel and pointed parameters pit peak and pass which can be used to form the basis of a system of characterization and classification of landforms landform elements display statistically significant compositional differences with respect to their proportions of morphometric classes this in turn can be plotted onto a diagram of characterization and classification known as a double ternary diagram dtd which comprises both areal and pointed parameters and any combination thereof the dtd is useful for studying geomorphological processes wherein areal and point values and properties have expressions which are topographically quantifiable

viscosity of high crystal content melts dependence on solid fraction 1 the rheological properties of suspensions containing high solid fractions are investigated attention is focused on viscosity of silicate and magmatic melt systems a general empirical equation which describes the relative viscosity of suspensions as a function of suspended solid fraction is proposed in the limit of very dilute solid concentrations it reduces to the einstein equation the proposed relationship is satisfactorily applied to reproduce available experimental data relative to silicate melts moreover the extrapolation of the model to very high concentrations is compared with experimental observations on partially melted granite

object representations at multiple scales from digital elevation models in the last decade landform classification and mapping has developed as one of the most active areas of geomorphometry however translation from continuous models of elevation and its derivatives slope aspect and curvatures to landform divisions landforms and landform elements is filtered by two important concepts scale and object ontology although acknowledged as being important these two issues have received surprisingly little attention this contribution provides an overview and prospects of object representation from dems as a function of scale relationships between object delineation and classification or regionalization are explored in the context of differences between general and specific geomorphometry a review of scales issues in geomorphometry ranging from scale effects to scale optimization techniques is followed by an analysis of pros and cons of using cells and objects in dem analysis prospects for coupling multi scale analysis and object delineation are then discussed within this context we propose discrete geomorphometry as a possible approach between general and specific geomorphometry discrete geomorphometry would apply to and describe land surface divisions defined solely by the criteria of homogeneity in respect to a given land surface parameter or a combination of several parameters homogeneity in its turn should always be relative to scale

expert driven semi automated geomorphological mapping for a mountainous area using a laser dtm in this paper a semi automated method is presented to recognize and spatially delineate geomorphological units in mountainous forested ecosystems using statistical information extracted from a 1 m resolution laser digital elevation dataset the method was applied to a mountainous area in austria first slope angle and elevation characteristics were determined for each key geomorphological unit occurring in the study area second a map of slope classes derived from the laser dtm was used in an expert driven multilevel object oriented approach the resulting classes represent units corresponding to landforms and processes commonly recognized in mountain areas fluvial terrace alluvial fan slope with mass movement talus slope rock cliff glacial landform shallow incised channel and deep incised channel the classification result was compared with a validation dataset of geomorphological units derived from an analogue geomorphological map for the above mentioned classes the percentages of correctly classified grid cells are 69 79 50 64 32 61 23 and 70 respectively the lower values of 32 and 23 are mainly related to inaccurate mapping of rock cliffs and shallow incised channels in the analogue geomorphological map the accuracy increased to 76 and 54 respectively if a buffer is applied to these specific units it is concluded that high resolution topographical data derived from laser dtms are useful for the extraction of geomorphological units in mountain areas

three dimensional indirect boundary element method for deformation and gravity changes in volcanic areas application to teide volcano tenerife canary islands 1 most deformation models of volcanoes assume that the earth is a linear elastic isotropic and homogeneous half space although some volcanic areas are associated with significant relief we investigate the effects of topography on surface deformation and gravity changes caused by a magma intrusion in the earth s crust a three dimensional 3 d indirect boundary element method ibem that incorporates realistic topographic features is developed in order to perform this analysis our results show that the topography alters both the magnitude and pattern of the deformation and gravity signal as an example of realistic topography we consider a spherical source of dilatation located at 4 km depth below teide volcano summit tenerife canary islands in order to simulate the deformation and gravity changes that could be observed at tenerife if a hypothetical intrusion occurred in the volcanic system this approach gives a picture of the 3 d topographic effect at teide that can provide insight in order to improve the geodetic monitoring of the volcano

an analytical model for gas overpressure in slug driven explosions insights into strombolian volcanic eruptions strombolian eruptions common at basaltic volcanoes are mildly explosive events that are driven by a large bubble of magmatic gas a slug rising up the conduit and bursting at the surface gas overpressure within the bursting slug governs explosion dynamics and vigor and is the main factor controlling associated acoustic and seismic signals we present a theoretical investigation of slug overpressure based on magma static and geometric considerations and develop a set of equations that can be used to calculate the overpressure in a slug when it bursts slug length at burst and the depth at which the burst process begins we find that burst overpressure is controlled by two dimensionless parameters v which represents the amount of gas in the slug and a which represents the thickness of the film of magma that falls around the rising slug burst overpressure increases nonlinearly as v and a increase we consider two eruptive scenarios 1 the standard model in which magma remains confined to the vent during slug expansion and 2 the overflow model in which slug expansion is associated with lava effusion as occasionally observed in the field we find that slug overpressure is higher for the overflow model by a factor of 1 2 2 4 applying our model to typical strombolian eruptions at stromboli we find that the transition from passive degassing to explosive bursting occurs for slugs with volume 24 230 m 3 depending on magma viscosity and conduit diameter and that at burst a typical strombolian slug with a volume of 100 1000 m 3 has an internal gas pressure of 1 5 bars and a length of 13 120 m we compare model predictions with field data from stromboli for low energy puffers mildly explosive strombolian eruptions and the violently explosive 5 april 2003 paroxysm we find that model predictions are consistent with field observations across this broad spectrum of eruptive styles suggesting a common slug driven mechanism we propose that paroxysms are driven by unusually large slugs large v

evaluation of current statistical approaches for predictive geomorphological mapping abstract predictive models are increasingly used in geomorphology but systematic evaluations of novel statistical techniques are still limited the aim of this study was to compare the accuracy of generalized linear models glm generalized additive models gam classification tree analysis cta neural networks ann and multiple adaptive regression splines mars in predictive geomorphological modelling five different distribution models both for non sorted and sorted patterned ground were constructed on the basis of four terrain parameters and four soil variables to evaluate the models the original data set of 9997 squares of 1 ha in size was randomly divided into model training 70 n 6998 and model evaluation sets 30 n 2999 in general active sorted patterned ground is clearly defined in upper fell areas with high slope angle and till soils active non sorted patterned ground is more common in valleys with higher soil moisture and fine scale concave topography the predictive performance of each model was evaluated using the area under the receiver operating characteristic curve auc and the kappa value the relatively high discrimination capacity of all models auc 0 85 0 88 and kappa 0 49 0 56 implies that the model s predictions provide an acceptable index of sorted and non sorted patterned ground occurrence the best performance for model calibration data for both data sets was achieved by the cta however when the predictive mapping ability was explored through the evaluation data set the model accuracies of cta decreased clearly compared to the other modelling techniques for model evaluation data mars performed marginally best our results show that the digital elevation model and soil data can be used to predict relatively robustly the activity of patterned ground in fine scale in a subarctic landscape this indicates that predictive geomorphological modelling has the advantage of providing relevant and useful information on earth surface processes over extensive areas such data being unavailable through more conventional survey methods

characterising spectral spatial and morphometric properties of landslides for semi automatic detection using object oriented methods recognition and classification of landslides is a critical requirement in pre and post disaster hazard analysis this has been primarily done through field mapping or manual image interpretation however image interpretation can also be done semi automatically by creating a routine in object based classification using the spectral spatial and morphometric properties of landslides and by incorporating expert knowledge this is a difficult task since a fresh landslide has spectral properties that are nearly identical to those of other natural objects such as river sand and rocky outcrops and they also do not have unique shapes this paper investigates the use of a combination of spectral shape and contextual information to detect landslides the algorithm is tested with a 5 8 m multispectral data from resourcesat 1 and a 10 m digital terrain model generated from 2 5 m cartosat 1 imagery for an area in the rugged himalayas in india it uses objects derived from the segmentation of a multispectral image as classifying units for object oriented analysis spectral information together with shape and morphometric characteristics was used initially to separate landslides from false positives objects recognised as landslides were subsequently classified based on material type and movement as debris slides debris flows and rock slides using adjacency and morphometric criteria they were further classified for their failure mechanism using terrain curvature the procedure was developed for a training catchment and then applied without further modification on an independent catchment a total of five landslide types were detected by this method with 76 4 recognition and 69 1 classification accuracies this method detects landslides relatively quickly and hence has the potential to aid risk analysis disaster management and decision making processes in the aftermath of an earthquake or an extreme rainfall event

gas slug ascent in a stratified magma implications of flow organisation and instability for strombolian eruption dynamics the canonical strombolian paradigm of a gas slug ascending and bursting in a homogeneous low viscosity magma cannot explain the complex details in eruptive dynamics recently revealed by field measurements and textural and geochemical analyses evidence points to the existence of high viscosity magma at the top of the conduit of strombolian type volcanoes acting as a plug here new experiments detail the range of flow configurations that develop during the ascent and burst of a slug through rheologically stratified magma within a conduit end member scenarios of a tube fully filled with either high or low viscosity liquid bracket three main flow configurations 1 a plug sufficiently large to fully accommodate an ascending gas slug 2 a plug that can accommodate the intrusion of low viscosity liquid driven by the gas expansion but not all the slug volume so the slug bursts with the nose in the plug whilst the base is still in the low viscosity liquid 3 gas expansion is sufficient to drive the intrusion of low viscosity liquid through the plug with the slug bursting in the low viscosity layer emplaced dynamically above the plug we show that the same flow configurations are viable at volcanic scale through a new experimentally validated 1d model and 3d computational fluid dynamic simulations applied to stromboli our results demonstrate that the key parameters controlling the transition between each configuration are gas volume plug thickness and plug viscosity the flow processes identified include effective dynamic narrowing and widening of the conduit instabilities within the falling magma film transient partial and complete blockage of the conduit and slug disruption these complexities influence eruption dynamics and vigour promoting magma mingling and resulting in pulsatory release of gas

automated classification of landform elements using object based image analysis this paper presents an automated classification system of landform elements based on object oriented image analysis first several data layers are produced from digital terrain models dtm elevation profile curvature plan curvature and slope gradient second relatively homogenous objects are delineated at several levels through image segmentation these object primatives are classified as landform elements using a relative classification model built both on the surface shape and on the altitudinal position of objects so far slope aspect was not used in classification the classification has nine classes peaks and toe slopes defined by the altitudinal position or the degree of dominance steep slopes and flat gentle slopes defined by slope gradients shoulders and negative contacts defined by profile curvatures head slopes side slopes and nose slopes defined by plan curvatures classes are defined using flexible fuzzy membership functions results are visually analyzed by draping them over dtms specific fuzzy classification options were used to obtain an assessment of output accuracy two implementations of the methodology are compared using 1 romanian datasets and 2 berchtesgaden national park germany the methodology has proven to be reproducible readily adaptable for diverse landscapes and datasets and useful in respect to providing additional information for geomorphological and landscape studies a major advantage of this new methodology is its transferability given that it uses only relative values and relative positions to neighboring objects the methodology introduced in this paper can be used for almost any application where relationships between topographic features and other components of landscapes are to be assessed

gravity induced stresses near topography of small slope topographic modification of gravity induced near surface stresses results in significant departures from a lithostatic state a perturbation scheme provides approximate analytical solutions for plane strain of an elastic half space with an irregularly shaped free surface of small characteristic slope e the leading order effect of the topography is equivalent to that of a distributed normal load on a plane boundary and the correction at order e is due to a distributed shear traction on a plane boundary in the near surface region these two effects contribute at the same order to departures from the lithostatic stress field the contribution of the shearing has been neglected in most previous analyses we present explicit solutions for several particular geometries a symmetric ridge or valley an adjacent ridge and valley a shelf and a sharp crested ridge notable features include 1 for a sufficiently steep ridge the horizontal normal stress is compressive at the crest and decreases possibly becoming tensile with depth 2 large horizontal tension is induced in a valley bottom at greater depth these effects vanish and the stresses approach lithostatic similar analysis is applied to a half space under a far field tectonic compression or tension the result shows that the leading order effect of topography is equivalent to a distributed shear traction on a plane surface regional horizontal compression can be significantly reduced or even change to tension in the neighborhood of a topographic high

physical parameterization of strombolian eruptions via experimentally validated modeling of high speed observations pressurized gas drives explosive volcanic eruptions existing models can predict the amount and pressure of gas in erupting magma but application and testing of such models is currently limited by the accuracy of input parameters from natural systems here we present a new methodology based on a novel integration of 1 high speed imaging and 2 shock tube modeling of volcanic activity in order to derive estimates of sub second variations in the pressure mass and volume of gas that drive the dynamics of unsteady eruptions first we validate the method against laboratoryscale shock tube experiments having validated the method we then apply it to observations of eruptions at stromboli volcano italy finally we use those results for a parametric study of the weight of input parameters on final outputs we conclude that strombolian explosions with durations of seconds result from discrete releases of gas with mass and pressure in the 4 714 kg and 0 10 0 56 mpa range respectively and which occupy the volcano conduit to a depth of 4 190 m these variations are present both among and within individual explosions

the implications of gas slug ascent in a stratified magma for acoustic and ground deformation source mechanisms in strombolian eruptions the interpretation of geophysical measurements at active volcanoes is vital for hazard assessment and for understanding fundamental processes such as magma degassing for strombolian activity interpretations are currently underpinned by first order fluid dynamic models which give relatively straightforward relationships between geophysical signals and gas and magma flow however recent petrological and high speed video evidence has indicated the importance of rheological stratification within the conduit and here we show that under these conditions the straightforward relationships break down using laboratory analogue experiments to represent a rheologically stratified conduit we characterise the distinct variations in the shear stress exerted on the upper sections of the flow tube and in the gas pressures measured above the liquid surface during different degassing flow configurations these signals generated by varying styles of gas ascent expansion and burst can reflect field infrasonic measurements and ground motion proximal to a vent the shear stress signals exhibit timescales and trends in qualitative agreement with the near vent inflation deflation cycles identified at stromboli therefore shear stress along the uppermost conduit may represent a plausible source of near vent tilt and conduit shear contributions should be considered in the interpretation of ground deformation which is usually attributed to pressure sources only the same range of flow processes can produce different experimental infrasonic waveforms even for similar masses of gas escape the experimental data resembled infrasonic waveforms acquired from different vents at stromboli associated with different eruptive styles accurate interpretation of near vent ground deformation infrasonic signal and eruptive style therefore requires detailed understanding of a spatiotemporal magma rheology in the shallow conduit and b shallow conduit geometry as well as bubble overpressure and volume

evolution of a small hydrothermal eruption episode through a mud pool of varying depth and rheology white island nz white island volcano new zealand was a host to multiple hydrothermal eruptive episodes within a mud sulphur pool in 2013 although hydrothermal activity is common at white island past events have largely gone undescribed in favour of the larger phreatomagmatic and magmatic eruptions here we detail the first and longest hydrothermal episode of 2013 lasting from 15 january to 7 february using video and photo analysis from tour operators and staff responsible for monitoring the volcano differences in the dominant bubble burst style across this episode led to the classification of four distinct eruption regimes 1 multiple irregular bursts on the pool surface 2 larger distinct symmetric hemispheres with starbursts and or followed by mud heaves 3 no initial pool surface deformation but a vertical steam jet followed by a sometimes large directed mud heave and 4 no lake and continuous pulsating dry ash and block venting the progression through these regimes is associated with a lowering lake level and a concomitantly increasing viscosity of the pool which initially comprises a low viscosity muddy water and partially evaporates to yield a shallow layer of high viscosity mud that ends with the complete drying up of the mud pool formation of primary mud hemispheres or gas jets is followed by heaves or secondary upheaval events the heights of these heaves are used as a measure of explosivity heights increase from 8 m during regime 1 on 15 january to 102 m during regime 3 on 28 january venting of dry mud during regime 4 developed on 29 january before a regression back to regime 1 took place on 7 february as the pool re established through observations of the shapes of ejected mud clots we propose that the increasing explosivity of higher number regimes is primarily due to increasing slug bubble lengths teamed with increasing mud pool viscosity we attribute a lesser control to the decreasing depth of the pool during its progressive desiccation which may in turn influence the bubble burst depth occasionally visible yellowing of the steam gas plume led us to suggest that elemental sulphur may also be present in the conduit and may also play a role in regulating bubble release dynamics although evidence for magmatic phreatomagmatic eruptions was present during eruptions later in 2013 we found no evidence for juvenile magma in the january february eruption episode described here however we concur with other investigators that magma was probably intruded to shallow levels and may have driven heat and gas flux our explanation for the correlation of pool depth mud viscosity and eruption regime is based on a conceptual model in which a pool is perched above a two phase hydrothermal system and is sensitive to changes in the heat and gas flux from shallow magma the variable release of gas and thermal perturbations in the course of the january february eruptive episode impacted the pool level the water to sediment ratio in the pool and thus its viscosity and in turn modulated the eruption regime the varying degree of explosivity throughout this episode calls for a new consideration of pool properties in assessing eruption hazards at this frequently visited volcano we additionally emphasise that ballistic hazards from small eruptions exist coupled with a range of seismic signals and that the hazard was greatest during infrasound tremor

control of magma flow in dykes on cyclic lava dome extrusion 1 lava dome eruptions are commonly characterized by large fluctuations in discharge rate with cyclic behaviour on time scalesranging from hours to decades examples include bezymianny volcano russia merapi java santiaguito guatemala mt st helens usa mt unzen japan and soufriere hills volcano montserrat previous models have assumed simple cylindrical conduits for magma transport but extrusions are mainly fed by dykes with cylindrical geometries developing only at shallow levels the widths of dykes embedded in an elastic medium are influenced by local magma pressure affecting flow rates and system dynamics strongly we develop a model for magma flow in dykes which predicts intense pulsations of magma extrusion for the case of a constant source pressure the period time scale is determined by the elastic deformation of the dyke walls and the length to width ratio of the dyke the dyke acts like a volumetric capacitor storing magma as pressure increases and then releasing magma in a pulse of extrusion for the soufriere hills volcano cyclic extrusions with time scales of a few weeks are predicted for dykes 300 500 m long and 3 6 m wide matching observations the model explains the sharp onset of tilt pulsations and seismic swarms citation costa a o melnik r s j sparks and b voight 2007 control of magma flow in dykes on cyclic lava dome extrusion geophys res lett 34 l02303 doi 10 1029 2006gl027466

sensitivity test of the geodetic network in las canadas caldera tenerife for volcano monitoring abstract a 17 benchmark geodetic network in the volcanic area of the teide caldera canary islands has been utilised several times since 1982 to detect crustal movements associated with volcanic activity within the network as well as a procedure for solving configuration problems the network is located on the mid western side of the caldera where there are two different morphological zones that both have benchmarks the authors performed a sensitivity test of this geodetic network for volcano monitoring purposes to do so we use a deformation model to calculate surface displacement caused by a dike intrusion in a homogenous half space the depth and location of dike are changed to study the variation of the effects produced displacements the size and location of the intruded dike are found to play a major role in determining both the displacement pattern and magnitude when the dike is close to the surface there is an inversion of the surface displacement pattern and very large surface displacement at certain benchmarks such phenomena can serve as precursors of such dike eruptions our study show a clear need to extend the existing geodetic network to cover the full island for volcano monitoring purposes

application of high resolution interferometric dems to geomorphic studies of fault scarps fish lake valley nevada california usa abstract recent developments in interferometric radar remote sensing provide a method for deriving detailed topographic and slope information for fault scarp detection in october 1996 the airborne topsar instrument ieee trans geosci remote sens 30 1992 933 was flown over southwest nevada and east central california topography calculated from topsar data are in the form of a high resolution 5 m spatial grid digital elevation model dem in this study we focus upon the large steep fault scarps that cut alluvium and alluvial fans in fish lake valley east of the white mountains of nevada california a series of topographic profiles extracted from the dem reveal that the larger fault scarps are greater than 40 m in height and that the average midsection slope angle for all measured scarps is approximately 23 these large scarps are the product of multiple offsets rather than a single event other relevant geomorphic features present in the digital topography include splays and benches along the main fault levees cutbanks gullies incising fault scarp slopes shutterridges offset drainage and small normal faults with scarp heights of only 4 6 m field work corroborated general geomorphologic landforms confirmed fault scarp morphometry and aided the evaluation of the accuracy of the dem we are also able to assess fault segmentation models that divide the fish lake valley fault zone flvfz into discrete segments based upon surface rupture characteristics

an automated approach to the classification of the slope units using digital data abstract digital elevation and remote sensing data sets contain different yet complementary information related to geomorphological features digital elevation models dems represent the topography or land form whereas remote sensing data record the reflectance emittance or spectral characteristics of surfaces computer analysis of integrated digital data sets can be exploited for geomorphological classification using automated methods developed in the remote sensing community in the present study geomorphological classification in a moderate to high relief area dominated by slope processes in southwest yukon territory canada is performed with a combined set of geomorphometric and spectral variables in a linear discriminant analysis an automated method was developed to find the boundaries of geomorphological objects and to extract the objects as groups of aggregated pixels the geomorphological objects selected are slope units with the boundaries being breaks of slope on two dimensional downslope profiles each slope unit is described by variables summarizing the shape topographic and spectral characteristics of the aggregated group of pixels overall discrimination accuracy of 90 is achieved for the aggregated slope units in ten classes

effects of topography on the interpretation of the deformation field of prominent volcanoes application to etna we have investigated the effects of topography on the surface deformation field of volcanoes our study provides limits to the use of classical half space models considering axisymmetrical volcanoes we show that interpreting ground surface displacements with half space models can lead to erroneous estimations of the shape of the deformation source when the average slope of the flanks of a volcano exceeds 20 tilting in the summit area is reversed to that expected for a flat surface thus neglecting topography may lead to misinterpreting an inflation of the source as a deflation comparisons of mogi s model with a three dimensional model shows that ignoring topography may lead to an overestimate of the source volume change by as much as 50 for a slope of 30 this comparison also shows that the depths calculated by using mogi s solution for prominent volcanoes should be considered as depths from the summit of the edifices finally we illustrate these topographic effects by analyzing the deformation field measured by radar interferometry at mount etna during its 1991 1993 eruption a three dimensional modeling calculation shows that the flattening of the deflation field near the volcano s summit is probably a topographic effect

degassing at low magma viscosity volcanoes quantifying the transition between passive bubble burst and strombolian eruption abstract at many volcanoes low magma viscosities allow persistent degassing over a range of styles from explosive strombolian activity to gas puffing and passive degassing it is generally accepted that strombolian eruptions reflect the bursting of large bubbles gas slugs at the magma surface and that relatively quiescent puffing indicates the presence of significantly smaller bubbles or slugs here we address this qualitative range and derive a dimensionless parameter pslim to quantify and distinguish different regimes of burst vigour for pslim 1 passive activity is anticipated and measurable parameters such as infrasonic amplitude will be small for pslim 1 bursting slugs will be energetic and surface effects are anticipated to increase with increasing pslim various physical parameters recorded during laboratory experiments and simulated through numerical models are shown to demonstrate the same trends when parameterised by pslim hence pslim provides a straightforward relationship between changes in measurable surface effects and the system s subsurface physical parameters and for energetic activity of a particular system burst effects are shown to be proportional to the square root of the gas mass involved effect magnitudes are also shown to be a function of atmospheric pressure and application of pslim parameterisation to planetary scenarios produces results in line with our current understanding of planetary volcanism

contemporary plate motion and crustal deformation the measurement of relative plate velocities during the past few years is a signal accomplishment in earth science leading to refinement of the precepts of steady motion of plate interiors and cyclic deformation along plate margins regrettably deformation premonitory to an earthquake has yet to be detected with confidence delineation of the spatial and temporal buildup of strain between earthquakes however has put limits on models of the earthquake cycle a diverse set of fault structures and crustal rheologic conditions can explain the pattern of surface strain accumulation and release along strike slip faults in contrast the geometry of thrusts and normal faults revealed by earthquake deformation has been found to differ markedly from expectations geodetic observations have proved vital to monitor the ascent of magma through the earth s crust and to predict volcanic eruptions at the earth s surface episodic vertical and horizontal deformation in southern california remains a subject of dispute if anything it is less certain than it once seemed

displacements and tilts from dip slip faults and magma chambers beneath irregular surface topography surface displacements and tilts due to buried deformation sources are influenced by topography the leading order corrections due to topography of arbitrary profile but small slope are determined for dip slip faults edge dislocations and magma bodies lines of inflation in a two dimensional elastic medium the vertical displacement correction is simply the product of the topography and the horizontal normal strain due to the source in a flat half space the correction for a normal fault beneath an idealized basin and range topography is a slight increase in the uplift on the range side the effect of topography for a line of inflation beneath a symmetric volcano is to reduce the central uplift failure to account for topographic influences can bias estimates of source depth and geometry