late cenozoic geodynamic evolution of eastern indonesia this paper presents an internally and globally consistent model of plate evolution in eastern indonesia from middle miocene to present time it is centered on the banda sea region located in the triple junction area between the pacific philippine australia and south east asia plates the geological and geophysical data available from indonesia were until recently insufficient to define a unique plate tectonic model in this paper the new data taken into account clearly restrict the possible interpretations owing to a great number of geological geophysical and geochemical studies the major plate boundaries the sunda banda subduction zone to the south the tarera aiduna fault zone and the seram thrust to the east and the sorong fault zone and molucca sea collision zone to the north are now clearly identified the age of the major tectonic structures is also better known geodetic measurements well constrain the present time plate kinematics we also consider the deformation history within eastern indonesia where numerous short lived microplates and their related microcontinents successively accreted to the asiatic margin moreover magnetic anomalies identification of the north and south banda sea basins allows a precise kinematic reconstruction of the back arc opening we used the plates software to test the coherency of our model presented as a series of 4 plate reconstruction maps from 13 ma to the present finally the origin of oceanic domains restored by our reconstruction is discussed

crustal structure of the java margin from seismic wide angle and multichannel reflection data seismic investigations across the convergent sunda margin off indonesia provide a detailed image of the crustal architecture of the sunda plate boundary the combined analysis and interpretation of wide angle and reflection seismic data along two coincident profiles across the subduction zone are complemented by additional lines within the forearc domain which yield some three dimensional 3 d constraints on the velocity depth structure across the margin a detailed cross section of the subduction zone is presented which is confirmed by supplementary gravity modeling the sunda convergence zone is a prime example of an accretionary margin where sediment accretion has led to the formation of a massive accretionary prism with a total width of 110 km between the trench and the forearc basin it is composed of a frontal wedge which documents ongoing accretion and a fossil part behind the present backstop structure which constitutes the outer high moderate seismic velocities derived from wide angle modeling indicate a sedimentary composition of the outer high the subducting oceanic slab is traced to a depth of almost 30 km underneath the accretionary prism the adjacent forearc domain is characterized by a pronounced morphological basin which is underlain by a layer of increased seismic velocities and a shallow upper plate moho at 16 km depth we speculate that remnant fragments of oceanic crust might be involved in the formation of this oceanic type crust found at the leading edge of the upper plate beneath the forearc basin

the lamongan volcanic field east java indonesia physical volcanology historic activity and hazards abstract the lamongan volcanic field lvf in east java indonesia consists of up to 61 basaltic cinder or spatter cones a minimum of 29 prehistoric maars and a central compound complex comprising three main vents including the historically active lamongan volcano the field lies on the sunda volcanic arc and abuts onto the currently active tengger caldera semeru complex to the west between 1799 and 1898 lamongan was persistently active and discharged up to 15 lava flows of basaltic to basaltic andesite composition which is probably more than what was erupted by any other indonesian volcano in that period several seismic crises have been recorded in the lvf since lamongan s last eruption there are no existing records of cinder cone or maar forming eruptions in the area despite the possible hazards posed by future activity in the lvf the history and structure of the field have been subject to little scrutiny this contribution presents the results of a detailed morphometric and volumetric investigation of prehistoric vents and historic lava flows in the lvf using field data historic records satellite imagery and modelling of erupted volumes a typical lvf maar is characterised as a crater with a diameter of 450 m generated by an eruption with a model ejecta volume of 0 016 km 3 dense rock equivalent dre and a model juvenile component volume of 0 0096 km 3 dre diameter depth ratios of some maars display a morphological freshness comparable to recently formed phreatomagmatic eruption craters elsewhere the median lvf cinder spatter cone has a basal diameter of 600 m a height of 75 m a volume of 0 009 km 3 and a model total erupted volume of 0 014 km 3 variation in cone basal diameter to height ratios indicates that the age of some prehistoric cones may not exceed a few centuries and morphological classification identifies the youngest prehistoric vents on the northern flanks of the central edifice historic activity from vents on the western flanks of lamongan produced at least 0 05 km 3 of basaltic to basaltic andesite lava resurfacing rates at lamongan in the 19th century imply an age of 900 2100 years for the surface of the volcano the steady state eruptive rate from 1843 1898 is evaluated as 0 025 m 3 s 1 which is low in comparison to estimates from many presently active systems using eruptive rate and volume data the age of the lvf is estimated as between 13 and 40 ka placing it among the youngest dated indonesian volcanoes complex regional tectonics in conjunction with magmatic pressure have probably been the major influences on the distribution of volcanism in the lvf the occurrence of maar forming eruptions may have been controlled by a porous substrate possibly a deposit from the holocene iyang argapura complex to the east volcanic hazards from future eruptions in the lvf include base surges ash flows ashfall and ejected blocks associated with phreatomagmatic activity and ashfall and ejecta from magmatic eruptions

observations of volcanic clouds in their first few days of atmospheric residence the 1992 eruptions of crater peak mount spurr volcano alaska abstract satellite so2 and ash measurements of mount spurr s three 1992 volcanic clouds are compared with ground based observations to develop an understanding of the physical and chemical evolution of volcanic clouds each of the three eruptions with ratings of volcanic explosivity index three reached the lower stratosphere 14 km asl but the clouds were mainly dispersed at the tropopause by moderate to strong 20 40 m s tropospheric winds three stages of cloud evolution were identified first heavy fallout of large 500 m pyroclasts occurred close to the volcano 25 km from the vent during and immediately after the eruptions and the cloud resembled an advected gravity current second a much larger highly elongated region marked by a secondary mass maximum occurred 150 350 km downwind in at least two of the three events this was the result of aggregate fallout of a bimodal size distribution including fine 25 m ash that quickly depleted the solid fraction of the volcanic cloud for the f

magnetic susceptibility of soil an evaluation of conflicting theories using a national data set magnetic susceptibility values for topsoils across england arc combined with data for soil type geochemistry and concentrations of magnetotactic bacteria in order to evaluate different theories for explaining soil magnetism strongly magnetic soils in unpolluted areas are found over weakly magnetic substrates and are dominated by ultrafine superparamagnetic grains magnetotactic bacteria are present in insufficient concentrations to account for strongly magnetic soils and crop burning is discounted as a major factor a small number of samples show high values associated with either airborne magnetic particulates from pollution or residual primary ferrimagnetic minerals from igneous substrates the results are used to construct a new mechanism for the formation of secondary ferrimagnetic minerals that links abiological weathering and biological fermentation processes the fundamental driving force in the mechanism is fe supply which may be linked to climate observed causative associations between climate and the magnetic susceptibility of loess palaeosol sequences are supported by the findings

magnetic properties of a recent parabrown earth from southern germany abstract we report here the analysis of the magnetic properties of a para brown earth from southern germany susceptibility isothermal remanence ratio of anhysteretic to isothermal remanence various hysteresis parameters and viscous remanence were measured in addition some standard pedological parameters were determined ph value content of organic carbon and content of iron hydr oxides for the characterization of the magnetic particles scanning and transmission electron microscope observations were employed we found that it is possible to define a vertical structure in the soil by magnetic measurements and that it reveals details not seen in the general pedological horizons magnetic properties in the topsoil were influenced by the former cultivation of the soil and by the presence of a remarkable amount of strongly magnetic industrial fly ash in the underlying horizons pedogenically formed ferrimagnetic minerals dominate the magnetic properties we could prove that this material forms only in the presence of iron reducing bacteria transmission electron microscopy showed that these magnetite particles have an average grain size of 5 nm we suggest that these grains form clusters as the magnetic properties rather indicate particles that are at the boundary between superparamagnetic and single domain behavior

upper mantle structure and geodynamics of the sumatra subduction zone from 3 d teleseismic p wave tomography abstract teleseismic waveforms from a passive array of 63 seismic stations are applied to image the 3 d p wave velocity structure of the mantle in the sumatra subduction zone in this study 102 teleseisms with good signal to noise ratios were selected in total 1627 p wave relative arrivals have been extracted with high accuracy based on multi channel cross correlation and adaptive stacking methods with this dataset we conducted the 3 d tomographic inversions for the 3 d p wave velocity structure of the upper mantle in the sumatra subduction zone the tomographic results suggest significant lateral variations of p wave velocity in the mantle the trench parallel low velocity features in the upper mantle reveal that there may be a trench parallel flow associated with 3 d mantle flow beneath the subducting slab the subducting indo australian plate is also clearly imaged as a continuous high velocity anomalous zone in the mantle along the sumatra island beneath southern sumatra there could have a lateral detachment of high velocity anomaly from 560 km to the deep part of the slab which may imply the slab tearing if it is true we could infer that this tear in the slab may be terminated around 17 5 ma the advancing speed of the indo australian plate increasing from north sumatra to south sumatra plays a key role in the slab tear which suggests likely that the northeastward subducting of the indo australian plate along the sunda trench and the southeastward clockwise motion of the sunda shelf may form a torque tracing the sumatra island that facilitated the clockwise rotation of the fast moving plate with the oblique subduction of the indo australian plate the asymmetric distribution of stresses along this torque on either side may induce the slab tearing

crustal structure of the central sunda margin at the onset of oblique subduction summary the convergent margin of the central sunda arc in indonesia was the target of a reflection and refraction seismic survey conducted in 1998 and 1999 along two seismic lines across the subduction complex off southern sumatra and off sunda strait coincident multichannel and wide angle data were collected complemented by two refraction strike lines in the forearc basin off sumatra the combined analysis of the acquired data allows us to present a detailed model of the subduction zone where initiation of strain partitioning occurs due to the onset of oblique subduction the dip of the subducted plate is well defined along both dip lines and a lateral increase from 5 to 7 from beneath the outer high off sumatra to sunda strait is supported by complementary gravity modelling the downgoing slab is traced to a depth of more than 30 km on both reflection dip lines a clearly developed backstop structure underlying a trench slope break defines the landward termination of the active accretionary prism and separates it from the outer high active subduction accretion is supported by laterally increasing velocities between the deformation front and the active backstop structure seismic velocities of the outer high are moderate along both lines 5 8 km s 1 at 20 km depth suggesting a sedimentary composition reduced reflectivity beneath a rugged top basement traced along the outer high of both dip lines supports a high degree of deformation and material compaction several kilometres of sediment has accumulated in the forearc domain although a distinct morphological basin is only recognized off southern sumatra and is not developed off sunda strait the bathymetric elevation of the java shelf that is encountered in the southern sunda strait corresponds to increased velocities of a basement high there and is connected to extensional structures of the sunda strait transtensional basin differences observed in the morphology of the forearc domain are also reflected in the lower crustal structure off southern sumatra the velocity depth model clearly indicates a continental type crust underlying the forearc basin whereas lower velocities are found beneath the sunda strait forearc domain off sumatra some 3 d constraint on the upper plate structure is gained from the refraction strike lines which in addition is supported by synthetic data modelling

strain patterns in models of spreading gliding nappes three experiments have been carried out in order to study the progressive and finite strain in nappes where gravitational spreading and gliding occur together these experimental models were made from analogue materials able to collapse under their own weight on an inclined plane throughout most of the models the stretch trajectories in a vertical plane parallel to the flow show a low amplitude sigmoidal pattern consistent with a previous theoretical model other stretch trajectories exist at the front and back ends of each model the kinematic significance of all these trajectories is discussed in detail highest strain intensities are always found next to the base of the model strain paths calculated at different stages of flow indicate clearly that nowhere in the model is the motion simple there is a complex combination in time and space of simple and pure shear except at the base of the model where the motion approximates a simple shearing near the two parallel lateral sides of the model a lateral boundary effect can be observed from the strong curvature of the transverse markers surface grid and vertical layers strain paths have also been estimated in this complex zone where wrench shearing is superimposed upon vertical shortening and thrust shearing the geological implications of these experimental models are discussed in relation to recent theoretical studies and field work

high resolution magnetic survey for soil monitoring detection of drainage and soil tillage effects abstract this paper presents the results of high resolution magnetic cartography realized with a caesium vapor magnetometer on marshland plots in western france this site is interesting because of the clayey substratum homogeneity and the historical knowledge of plot exploitation a wooden truck running on pvc rails allowed acquisition of accurate signals with dynamics of about 2 nt natural grassland presents weak decametric variations correlated to a micro toposequence conversely plots recently tilled show linear magnetic anomalies these anomalies are interpreted as the effect of tractor tyre soil compaction which modify soil properties in addition the study of a drained plot by a wavelet transform reveals the presence of a frequency band close to the drain intervals moreover the magnitude of the linear magnetic anomalies is higher above drains this suggests that the compaction influence on the magnetic carriers is more important in drained hence aerated zones

three dimensional numerical simulation of the subduction dynamics in the sunda arc region southeast asia abstract the sunda arc has been modelled as a test subduction zone with geometrical complexities and varying dynamics we simulated spatially the structural heterogeneities of the subduction zone and carried out our computations by a three dimensional finite element approach the aim is to estimate the lateral variation in the effective horizontal compressive stress in the interplate region which can produce the present day observed seismogenic stress field in our simplified approach the stress field has been modelled by varying the traction ridge push while keeping the age dependent gravitational body force slab pull constant our result suggests that there is a considerable amount of stress dissipation in the decoupled segment of java at sumatra the required traction is much greater than that expected from the age dependency relations in our modelling the transition from the dominance of the horizontal compressive stress to that of the gravitational pull in the regional stress field occurs around a depth range of 150 200 km lateral variation in the subducted slab volume emerges crucial to the seismogenic stress field and the derived pattern of displacement subduction of the lighter oceanic rise material should enhance the stress level the effect of abrupt lateral variation in structure e g sudden changes in the slab dip or slab depth may also be significant on the regional stress field viscoelastic modelling attempted for estimating the temporal variation in subduction dynamics suggests that the thrust level will increase southward of the present day thrust zone in java while strike slip fault type stress field will be developed south of sumatra

the last 40 ka tephrostratigraphic record of lake ohrid albania and macedonia a very distal archive for ash dispersal from italian volcanoes abstract a 1075 cm long core lz1120 was recovered in the south eastern part of the lake ohrid republics of macedonia and albania and sampled for identification of tephra layers magnetic susceptibility investigations show rather high magnetic values throughout the core with peaks unrelated to the occurrence of tephra layers but instead to the relative abundance of detrital magnetic minerals in the sediment naked eye inspection of the core allowed us to identify of two tephra layers at 896 897 cm and 1070 1075 cm laboratory inspection of the grain size fraction 125 m allowed for the identification of a third cryptotephra at 310 315 cm major element analyses on glass shards of the tephra layers at 896 897 cm and 1070 1075 cm show a trachytic composition and indicate a correlation with the regionally dispersed y 3 and y 5 tephra layers dated at ca 30 and 39 cal ka bp the cryptotephra at 310 315 cm has a mugearitic benmoreitic composition and was correlated with the fl eruption of mt etna dated at 3370 70 cal yr bp these ages are in agreement with five 14 c ams measurements carried out on plant remains and macrofossils from the lake sediments at different depths along the core the recognition of distal tephra from italian volcanoes allows us to link the lake ohrid succession to other archives located in the mediterranean area and in eastern europe the benmoreitic mugearitic tephra layer at 310 315 cm is the first recognition in the balkan area of a distal ash deposit from a mid intensity explosive eruption of mt etna as far as 600 km from the source

three dimensional p wave velocity structure beneath the indonesian region abstract we present the p wave seismic tomography image of the mantle to a depth of 1200 km beneath the indonesian region the artb inversion method is applied to a dataset of 118 203 p wave travel times of local and teleseismic events taken from isc bulletins although the resolution is sufficient for detailed discussion in only a limited part of the study region the results clarify the general tectonic framework in this region and indicate a possible remnant seismic slab in the lower mantle structures beneath the philippine islands and the molucca sea region are well resolved and high velocity zones corresponding to the slabs of the molucca sea and philippine sea plates are well delineated seismic zones beneath the manila negros and cotabato trenches are characterized by high velocity anomalies although shallow structures were not resolved the molucca sea collision zone and volcanic zones of the sangihe and philippine arcs are dominated by low velocity anomalies the philippine sea slab subducts beneath the philippine islands at least to a depth of 200 km and may reach depths of 450 km the southern end of the slab extends at least to about 6 n near southern mindanao in the south the two opposing subducting slabs of the molucca sea plate are clearly defined by the two opposing high velocity zones the eastward dipping slab can be traced about 400 km beneath the halmahera arc and may extend as far north as about 5 n unfortunately resolution is not sufficient to reveal detailed structures at the boundary region between the halmahera and philippine sea slabs the westward dipping slab may subduct to the lower mantle although its extent at depth is not well resolved this slab trends n s from about 10 n in the philippine islands to northern sulawesi a ne sw trending high velocity zone is found in the lower mantle beneath the molucca sea region this high velocity zone may represent a remnant of the former subduction zone which formed the sulawesi arc during the miocene the blocks along the sunda and banda arcs are less well resolved than those in the philippine islands and the molucca sea region nevertheless overall structures can be inferred the bowl shaped distribution of the seismicity of the banda arc is clearly defined by a horseshoe shaped high velocity zone the tomographic image shows that the indian oceanic slab subducts to a depth deeper than 300 km i e deeper than its seismicity beneath andaman islands and sumatra and may be discontinuous in northern sumatra along southern sumatra java and the islands to the east the slab appears to be continuous and can be traced down to at least a depth of the deepest seismicity where it appears to penetrate into the lower mantle

probabilistic modeling of tephra dispersal hazard assessment of a multiphase rhyolitic eruption at tarawera new zealand 1 the tarawera volcanic complex comprises 11 rhyolite domes formed during five major eruptions between 17 000 b c and a d 1886 the first four of which were predominantly rhyolitic the only historical event erupted about 2 km3 of basaltic tephra fall a d 1886 the youngest rhyolitic event erupted a tephra fall volume more than 2 times larger and covered a wider area northwest and southeast of the volcano a d 1315 kaharoa eruption we have used the kaharoa scenario to assess the tephra fall hazard from a future rhyolitic eruption at tarawera of a similar scale the plinian phase of this eruption consisted of 11 discrete episodes of vei 4 we have developed an advection diffusion model tephra that allows for grain size dependent diffusion and particle density a stratified atmosphere particle diffusion time within the rising plume and settling velocities that include reynolds number variations along the particle fall simulations are run in parallel on multiple processors to allow a significant implementation of the physical model and a fully probabilistic analysis of inputs and outputs tephra is an example of a class of numerical models that take advantage of new computational tools to forecast hazards as conditional probabilities far in advance of future eruptions three different scenarios were investigated for a comprehensive tephra fall hazard assessment upper limit scenario eruption range scenario and multiple eruption scenario hazard curves and probability maps show that the area east and northeast of tarawera would be the most affected by a kaharoa type eruption

mineralogical analyses and in vitro screening tests for the rapid evaluation of the health hazard of volcanic ash at rabaul volcano papua new guinea the continuous ash and gas emissions from the tavurvur cone in rabaul caldera papua new guinea during 2007 08 raised concerns regarding how exposure would affect the respiratory health of nearby populations and impact on the environment as part of a formal evaluation of the effects of volcanic emissions on public health we investigated the potential health hazard of the ash using a suite of selected mineralogical analyses and in vitro toxicity screening tests the trachy andesitic ash comprised 2 1 6 7 vol respirable sub 4 m diameter particles the crystalline silica content was 1 9 5 0 wt cristobalite in the bulk sample with trace amounts of quartz and or tridymite scanning electron microscopy showed that the ash particles were angular with sparse fibre like particles 3 60 m max diameter observed in some samples which we confirmed to be caso4 gypsum at 6 wt in the bulk samples and not asbestiform fibres the ash specific surface area was low 0 1 2 7 m2 g 1 the leached solution from one of the ash samples was slightly acidic ph 5 6 but did not contain high levels of toxic metals such as f cu zn mn as ni and cd when compared to previously tested volcanic ash leachates ash samples generated potentially harmful hydroxyl radicals through an iron mediated catalytic reaction in the range of 0 15 2 47 mol m 2 after 30 min of reaction however measurement of particle oxidative capacity potential oxidative stress reaction using ascorbic acid and silica like injury to red blood cells erythrolysis assay i e measurement of cell death nevertheless revealed low biological reactivity the findings suggest that acute exposure to the ash would have a limited potential to exacerbate pre existing conditions such as asthma or chronic bronchitis and the potential for chronic exposure leading to silicosis was low

reconstruction of eruption column dynamics on the basis of grain size of tephra fall deposits 1 methods two inversion methods are developed to reconstruct eruption column dynamics from granulometric data of plinian deposits they are based on the steady tephra dispersal model from umbrella clouds which spread as gravity currents the methods provide 1 expansion rate of an umbrella cloud 2 grain size distribution at the top of the eruption column and 3 total amount of ejecta including very fine particles which are extensively dispersed in the atmosphere the first quantity is correlated to the magma discharge rate the second quantity provides information about sorting processes during column rise and hence about deceleration in the gas thrust region of the eruption column and the timing of column collapse the third quantity together with the estimated magma discharge rate provides the effective duration of the eruption the two methods are based on the same dispersal model but use different averaging combining the two methods can provide additional information about eruption dynamics such as minor flow structures of the umbrella cloud and fluctuations of eruption rate the methods are applicable to large scale eruptions where the radial expansion velocity of the umbrella cloud exceeds wind velocity the applicability of the methods is tested from the viewpoint of comparison with real time observations in the companion paper paper 2

a three dimensional eulerian model for transport and deposition of volcanic ashes abstract volcanic ash fallout represents a serious threat to people living near active volcanoes because it can produce several undesirable effects such as collapse of roofs by ash loading respiratory sickness air traffic disruption or damage to agriculture the assessment of such volcanic risk is therefore an issue of vital importance for public safety and its mitigation often requires to evaluate the temporal evolution of the phenomenon through reliable computational models we develop an eulerian model named fall3d for the transport and deposition of volcanic ashes the model is based on the advection diffusion sedimentation equation with a turbulent diffusion given by the gradient transport theory a wind field obtained from a meteorological limited area model lam and the source term derived from by buoyant plume theory it can be used to forecast either ash concentration in the atmosphere or ash loading on the ground model inputs are topography meteorological data given by a lam mass eruption rate and a particle settling velocity distribution a test application to the july 2001 etna eruption is presented

centroid single force inversion of seismic waves generated by landslides the centroid moment tensor cmt waveform inversion method of dziewonski et al 1981 is modified to analyze long period seismic waves generated by single force events such as the gigantic landslides associated with the 1980 eruption of mount st helens we refer to the method as centroid single force csf inversion as the result of the inversion we obtain the spatio temporal centroid and three components of a vector we call the csf vector which is the seismic point source representation of a landslide and whose direction is the opposite of the direction of sliding the sealer magnitude of the csf vector measures the overall size of the landslide and is given by mcsf md where m is the mass of the sliding object and d is the sliding distance we apply csf inversion to the long period surface waves generated by the 1980 mount st helens event the 1975 kalapana earthquake and the 1974 mantaro landslide using seismograms from the gdsn ida and hglp networks the csf solution for the st helens event is remarkably consistent with the actual geological observations and proves the efficacy of csf inversion the csf solution for the kalapana event does not fit the overall waveforms better than the cmt solution does however because the cmt solution does not explain the observed love wave radiation pattern it may be necessary to invoke a combination of both types of mechanism for this event although the geometry of the csf solution the direction of the force for the mantaro event is consistent with the actual landslide mcsf is about 5 times smaller than that expected from the mass and travel distance of the landslide estimated by geological observations this discrepancy may suggest either the relatively aseismic nature of this landslide or that the total volume of the slide was overestimated by analogy to single station cmt inversion single station csf inversion also appears to be stable and useful

petrology and geochemistry of the lamongan volcanic field east java indonesia primitive sunda arc magmas in an extensional tectonic setting new geochemical data are presented from prehistoric and historical multifarious process involving possible inputs from the subducted oceanic lithosphere subducted oceanic sedieruptive products of the lamongan volcanic field lvf east java a region of the sunda arc covering 260 km and containing ments and fluids the asthenospheric and lithospheric portions of the mantle wedge above the subduction zone 90 eruptive vents plus the historically active lamongan volcano lvf lavas include medium k basalts and basaltic andesites from and the arc crust e g tatsumi eggins 1995 following melt generation processes such as crystal fractionation historical eruptions of lamongan and prehistoric eruptions in the eastern lvf along with a high k suite represented by prehistoric accumulation and crustal assimilation during transit to the surface may obscure the true nature of the magma deposits in the western lvf although lacking some of the characteristics of truly primary basalts the least evolved lavas identified source region the effects of these processes on the compositions of erupted lavas must therefore be removed in the lvf have some of the lowest sio2 contents 43 wt sio2 yet reported in sunda arc volcanic rocks mass balance before models of arc magma genesis can be tested for this reason it is desirable to sample magmas that considerations indicate that two chemically distinct lvf magmas may be parental to suites currently being erupted from the neighbouring have suffered minimal modification since segregation from their source region the compositions of the primary volcanoes semeru and bromo lamongan s historical lavas can be related to the medium k andesitic products of semeru by fractional or primitive magmas from different arcs provide a window on the diverse mechanisms of and the components crystallization despite the former s location at the same distance from the trench as bromo a high k volcano extensional tectonics involved in melt production at convergent margins and as such are essential to our understanding of the possibly related to arc segmentation in the region of the lvf creating subduction zone environment conditions that promote the rapid ascent of parental magmas is many studies have highlighted the correlation between probably responsible for this and several other features of the complex extensional tectonics in volcanic arcs and the eruption of lavas with primitive chemical characteristics e g luhr carmichael 1981 knittel oles 1995 bacon et al

modeling tephra dispersal in absence of wind insights from the climactic phase of the 2450 bp plinian eruption of pululagua volcano ecuador the determination of eruptive parameters is crucial in volcanology not only to document past eruptions but also for tephra fallout hazard assessments in most tephra fallout studies eruptive parameters have been determined either by empirical techniques or analytical models but the uncertainty of such parameters is usually not well described we have applied both empirical and analytical models to characterize the climactic phase of the 2450 bp plinian eruption of pululagua bf2 layer and explore the variations in the total erupted mass column height and total grain size distribution both approaches yield comparable results in the total mass of tephra erupted 4 5 1 5 1011 kg while they show some discrepancies for the determination of the column height 36 20 km from empirical techniques and 30 20 km from analytical techniques the total grain size distribution of the bf2 layers varies with the different techniques used for the calculation and significantly affects the outputs of analytical models furthermore the determination of the total grain size distribution depends strongly on the number and spatial distribution of the sample location inverting tephra fallout deposits on the total accumulation or thickness gives a good constraint on the total mass erupted but not on the column height however inverting on individual grain size classes better constrains the possible range of column heights but cannot resolve particle release height results from the inversion on individual grain size classes show that large diffusion coefficients are necessary to model the bf2 layer and might be required to model proximal tephra deposits in order not to overestimate the total erupted mass additionally we used a statistical method smoothed bootstrap approach to quantify the uncertainty in eruptive parameters such as column height and total erupted mass our uncertainty analysis yields a mean total erupted mass of 4 5 0 3 1011 kg and a mean column height of 30 3 km results from the uncertainty analysis compare well with results from other approaches finally although the climactic phase of the 2450 bp plinian eruption of pululagua occurred in relatively calm atmospheric conditions our results show that the dispersion of the bf2 layer was influenced by slight northeasterly wind conditions

enigma of earthquakes at ridge transform fault plate boundaries distribution of non double couple parameter of harvard cmt solutions the distribution of the non double couple parameter of shallow earthquakes reported in the harvard cmt catalogue shows systematic characteristics depending on the epicentral locations and types of fault mechanisms the authors suggest that they can be explained by the presence of subevents with different double couple mechanisms in a single rupture sequence the earthquakes at the ridge transform fault plate boundaries show a particularly interesting pattern it is suggested that two types of faulting expected in the area i e normal faults at ridges and strike slip faults at transform faults tend to occur almost simultaneously although this hypothesis needs to be delineated by careful analyses using bodywave waveforms

proximal tephra hazards recent eruption studies applied to volcanic risk in the auckland volcanic field new zealand abstract auckland new zealand is unique in being a metropolitan area built on an active volcanic field despite the small size and intensity of auckland eruptions the risk from tephra fall is high because of the high density of buildings and lifelines the nature of this threat can be evaluated by comparisons with historical strombolian and hawaiian eruptions which have occurred in non populated areas cone building phases of such eruptions are typically protracted i e weeks to months in duration prolonging the period during which emergency managers will have to fine tune mitigation for numerous parameters such as fluctuations in intensity and wind shifts rapid cone growth during future eruptions will define a region of some 30 to 100 ha where complete destruction will occur on a time scale of hours the cost of this destruction is likely to range between nz 200m and nz 1 4b ca us 130m to us 900m beyond this we have modeled the cumulative long term effect of the build up of a downwind blanket of lapilli and ash by estimating accumulation rates for three phases of the 1959 k lauea iki eruption in hawai i the effect of changing wind direction was evaluated using low level wind data from auckland these results show that intervals between 4 and 100 h will lapse before onset of significant damage to buildings

puff a high resolution volcanic ash tracking model this paper presents a volcanic ash tracking model referred to as puff the model was developed to simulate the movement of airborne ash in near real time following an eruption for the purposes of hazard warning the model tracks particles through a lagrangian formulation of advection fallout and turbulent diffusion using a random walk technique three recent eruption events are simulated using archived data avhrr images from these events are used for comparison and to validate model results

a statistical approach to evaluate the tephra deposit and ash concentration from puff model forecasts abstract in this paper we present a new statistical approach which provides tephra deposit load and ash concentration using puff a lagrangian model widely used to forecast volcanic ash dispersal during volcanic crisis we perform a parametric study in order to analyze the influence of each input parameter on model outputs for this test we simulate two eruptive scenarios similar to the 2001 scenario 1 and 1998 scenario 2 etna eruptions using high resolution weather data and a domain of 170 170 km results show that for both scenarios we are able to calculate the tephra deposit load and ash concentration but the use of millions of particles is required specifically up to 33 and 220 millions of particles were necessary to accurately predict the tephra deposit and ash concentration in air respectively this is approximately two orders of magnitude larger than the values typically considered running puff the parametric study shows that the horizontal diffusion coefficient the time step of the simulations the topography and the standard deviation of the particle distribution greatly affect the model outputs we also validate the model by best fit procedures results show a good comparison between field data of the 2001 etna eruption and puff simulations being inside 5 and 1 5 times the observed data comparable with results of eulerian models this work will allow to reliably outline the areas of contaminated airspace using puff or any other lagrangian model in order to define the no fly zone and ensure the safety aviation operations as required after the eyjafjallajokull eruption

stream functions and complex potentials implications for development of rock fabric and the continuum assumption abstract stream functions may be applied to study the development of ductile deformation patterns in rocks it is demonstrated how to derive the stream function and the associated complex potential from the velocity field of any particular flow finite deformation patterns are subsequently modelled analytically from this mathematical description of flow basic examples discussed are rigid body translation pure shear and composite flows due to simultaneous pure and simple shear a general stream function is obtained to describe the flow regime within a ductile deformation zone deforming by homogeneous plane strain by superposed pure and simple shear components the deformation patterns are visualized using analytical methods only the results are discussed in terms of fabric formation progressive deformation in a simple continuum modelled here mathematically using principles of fluid mechanics is compared with crystalline creep in rocks the validity of the continuum assumption is briefly outlined in view of recent experiments on particular synthetic monocrystalline aggregates octochloropropane ocp deformable at room conditions this provides a method for testing how crystalline deformation compares with an isotropic continuum

computer simulation of transport and deposition of the campanian y 5 ash analyses of grain size and modal composition of the campanian tuff ash layer y 5 from 11 deep sea cores have been carried out this layer represents ash fall that has been correlated with the 38 000 y b p campanian ignimbrite thunell et al 1979 a deposit formed by the largest eruption documented in the mediterranean region during the late pleistocene barberi et al 1978 the bulk deposit is bimodal in grain size and dominated by glass shards the calculated mean grain size of the coarse mode of the individual size distributions decreases with distance from the source and progressively approaches a near constant fine mode of approximately 13 microns distal samples are unimodal in grain size these data combined with a set of vertical profiles of wind 10 year average have been used as input to a computer model that simulates fallout of tephra modelling indicates that the downwind variation of grain size of the coarse mode can be accurately reproduced with transport of ash between 5 and 35 km the observed fine mode of the deposit cannot however be generated by transport of ash as individual particles at these elevations such transport would result in deposition of virtually all of the fine ash beyond the studied area deposition of fine ash within the studied distance of 1600 km from source can only occur by fallout as particle aggregates from a high eruption plume or as individual particles from co ignimbrite ash clouds with a maximum elevation of 3 km the large volume of ash in the fine mode 70 wt and the irregularity in azimuth of low level winds argue against major low level transport of co ignimbrite ash rather the ash may have been derived from both a plinian eruption column and high altitude clouds of co ignimbrite ash with settling of fine ash as particle aggregates

forward modeling of non steady state deformations and the minimum strain path reply structural analyses of shear zones often rely on an assumption of steady state behavior i e that the ratio of pure shear strain rate s to simple shear strain rate s remains fixed throughout deformation however geological deformations are not necessarily steady state non steady state deformation paths can be theoretically modeled if certain deformation parameters such as strain or offset are specified we have analyzed a two dimensional case of specified offset and geometry termed the minimum strain path the minimum finite strain needed to produce a fixed offset across a shear zone is neither simple shear nor pure shear but a combination of the two the minimum strain path if this deformation accumulates with a steady state deformation the kinematic vorticity number w of the minimum strain path varies with the amount of finite offset although w approaches 0 7 at high offset values because of this relation between w and finite offset the minimum strain path is better modeled as a non steady state deformation in which case deformation history starts close to simple shear but rapidly changes to a more pure shear dominated deformation it is expected that the minimum strain path is applicable to geological deformation zones with relaxed boundary conditions such as basal parts of spreading nappes or extensional detachment systems 0 1997 elsevier science ltd

heat flow and seismic observations in the northwestern banda arc results of heat flow measurements in the centers of three basins in the nw banda arc carried out during the indonesian dutch snellius ii expedition in 1985 all show high heat flow values the average heat flow in the north buru basin on the outside of the arc is 161 mw m2 two small ns to nw se elongated subbasins situated in the lucipara basin show heat flow values of 175 and 134 mw m2 respectively the high heat flow measured in both the north buru and lucipara basins is interpreted to be the result of recent ew strike slip movement in the northwestern banda arc

grain size variation of tephra derived from volcanic umbrella clouds the relationships among the thickness and grain size of tephra fall deposits and the volumetric flow rate of their source umbrella clouds are analytically obtained the logarithm of the ratio of the probability distribution function based on grain size inr f in fall deposits at two localities from the vent r 1 and r 2 respectively has a linear relationship with the particle settling velocity v as in 1n r f frac pi r 2 2 r 1 2 nu q 1n a where q is the volumetric flow rate of the umbrella cloud and a is a constant for a given pair of localities the volumetric flow rate of the umbrella cloud can be estimated from granulometric data using this formula generally the thickness distance relationship of tephra fall deposits depends on the initial grain size distribution and the volumetric flow rate of the umbrella cloud the empirical relationship of the exponential thinning behaviour can be extrapolated towards infinite distance only for a specific initial grain size which is similar to a log normal distribution with 2 5 otherwise it holds only in a limited range of distances in applying these results to the 1991 eruption of mt pinatubo it is shown that the volumetric flow rate of the umbrella cloud during the climactic phase of 15 june was approximately 5x1010 m3 s which is fairly consistent with the expansion rate of the umbrella cloud observed in the satellite images

mafalda an early warning modeling tool to forecast volcanic ash dispersal and deposition 1 forecasting the dispersal of ash from explosive volcanoes is a scientific challenge to modern volcanology it also represents a fundamental step in mitigating the potential impact of volcanic ash on urban areas and transport routes near explosive volcanoes to this end we developed a web based early warning modeling tool named mafalda modeling and forecasting ash loading and dispersal in the atmosphere able to quantitatively forecast ash concentrations in the air and on the ground the main features of mafalda are the usage of 1 a dispersal model named vol calpuff that couples the column ascent phase with the ash cloud transport and 2 high resolution weather forecasting data the capability to run and merge multiple scenarios and the web based structure of the procedure that makes it suitable as an early warning tool mafalda produces plots for a detailed analysis of ash cloud dynamics and ground deposition as well as synthetic 2 d maps of areas potentially affected by dangerous concentrations of ash a first application of mafalda to the long lasting weak plumes produced at mt etna italy is presented a similar tool can be useful to civil protection authorities and volcanic observatories in reducing the impact of the eruptive events mafalda can be accessed at http mafalda pi ingv it

perceptions of hazard and risk on santorini abstract santorini greece is a major explosive volcano the santorini volcanic complex is composed of two active volcanoes nea kameni and mt columbo holocene eruptions have generated a variety of processes and deposits and eruption mechanisms pose significant hazards of various types it has been recognized that for major european volcanoes few studies have focused on the social aspects of volcanic activity and little work has been conducted on public perceptions of hazard risk and vulnerability such assessments are an important element of establishing public education programmes and developing volcano disaster management plans we investigate perceptions of volcanic hazards on santorini we find that most residents know that nea kameni is active but only 60 know that mt columbo is active forty percent of residents fear that negative impacts on tourism will have the greatest effect on their community in the event of an eruption 43 of residents would try to evacuate the island by plane ferry residents aged 50 have retained a memory of the effects of the last eruption at the island whereas younger residents have no such knowledge we find that dignitaries and municipal officers those responsible for planning and managing disaster response are informed about the history hazards and effects of the volcanoes however there is no emergency plan for the island and there is confusion between various departments civil defense fire police etc about the emergency decision making process the resident population of santorini is at high risk from the hazards associated with a future eruption

volcanic jets plumes and collapsing fountains evidence from large scale experiments with particular emphasis on the entrainment rate the source conditions of volcanic plumes and collapsing fountains are investigated by means of large scale experiments in the experiments gas particle jets issuing from a cylindrical conduit are forced into the atmosphere at different mass flow rates dense jets high particle volumetric concentration e g c 0 0 01 generate collapsing fountains whose height scales with the squared exit velocity this is consistent with bernoulli s equation which is a good approximation if air entrainment is negligible in this case kinetic energy is transformed into potential energy without any significant loss by friction with the atmosphere the dense collapsing fountain on hitting the ground generates an intense shear flow similar to a pyroclastic density current dilute hot jets low particle volumetric concentration e g c 0 3

particle fallout thermal disequilibrium and volcanic plumes we develop a model of a volcanic eruption column that includes the effects of fallout of pyroclasts and thermal disequilibrium we show that clast fallout with no thermal disequilibrium has only a small effect upon the column however disequilibrium changes column behaviour significantly and can even induce collapse our results may explain the lower plume heights and less widely dispersed fallout of cone forming eruptions contrasted with sheet forming eruptions the model also predicts that the transition from the gas thrust to the convective region in a column results in an inflection in dispersal curves that some features of the stratigraphy common to many fall deposits may result from column velocity structure and that there may exist a region near the volcanic vent in which maximum pyroclast size does not decrease significantly with distance

numerical simulation of spreading nappes sliding against basal friction abstract a numerical method is used to simulate the gravitational spreading of a nappe consisting of newtonian material with high viscosity coefficient the theory is based on maximizing the rate of decline of potential energy which also means maximizing the rate of dissipation due to strain and basal friction as well as maximizing the rate of production of entropy a polynomial stream function is used to describe the velocity field and the displacement field the nappe is permitted to slip against friction at the base a wide variation of friction coefficients being used in the numerical tests a result with great implication is that each nappe has a theoretical critical friction limit crit which chiefly depends upon the aspect ratio the larger the aspect ratio the smaller the friction limit if the true friction coefficient is greater than crit then the potential energy is incapable of making the nappe slip at the base in this case the spreading is solely due to motion within the bulk of the nappe generating a protruding lobe or recumbent fold in the front unless the friction coefficient for natural nappes is considerably less than measured experimentally it is not easy to understand that gravitational spreading is able to make nappes slip at the base if the aspect ratio is say 10 and more however by using stream functions with enough freedom i e of high enough degree and realistic nappe profiles it is found that the foremost sections of nappes may slip along the base pushed by the protruded lobe of the spreading hind portion which is coherent to the base

effect of wind on the rise height of volcanic plumes a theoretical model of a volcanic plume based on applying the equations of motion in a plume centered coordinate system suggests that the interaction between a volcanic plume and wind causes enhanced entrainment of air and horizontal momentum plume bending and a decrease in plume rise height at constant eruption rate because of rapid dilution in the high windspeeds of the polar jet plumes that vary over more than one order of magnitude in mass eruption rate 106 to 107 108 kg s if injected into the polar jet may all attain rise heights only slightly different from that of the core of the jet 10 km as opposed to 17 33 km in a still atmosphere

rheological and tectonic modeling of salt provinces abstract technological improvements and a more rigorous research approach have led the petroleum industry to renew and expand its interest in physical modeling of faulting associated with halokinesis salt tectonics and the formation of structural hydrocarbon traps can be reproduced in models using viscous polymers for the substratum and frictional plastic granular materials for the overburden the fault patterns simulated in these dynamically scaled models are remarkably similar to those in depth converted seismic sections scale models are therefore useful for generating new concepts and for reconstructing the structural evolution of hydrocarbon traps although even unsealed models may help generating ideas the full transfer of quantitative data requires that models be dynamically scaled to their natural prototypes previously published scaling theory for salt tectonics has erroneously assumed fluid behaviour of the overburden this paper provides a sound scaling approach for geological deformations involving brittle overburdens on ductile substrata rheological data from overburden rocks and salt are compiled and compared to model rheologies using dimensions of laboratory analogs and other intrinsic material properties scaling approaches are compared and rules are formulated for achieving dynamic similarity in models of salt tectonics including those with synkinematic sedimentation

sedimentation from turbulent jets and plumes theoretical models are developed for the sedimentation from the margins of a particle laden axisymmetric turbulent buoyant plume in a still environment and for an axisymmetric turbulent momentum jet the models assume that the mass of each individual size fraction of sediment carried in a parcel of fluid decreases exponentially with time for relatively coarse particles the fallout models predict that the sediment deposition beyond a distance r on the ground expressed in log units should decay linearly with distance away from the vent for the momentum jet and should decrease with r1 3 for the buoyant plume the exponential decay constant j is proportional to the terminal fall velocity vt of the particles in both cases and inversely proportional to the square root of the initial momentum flux m0 for the jet fallout jj vtmo 1 2 and to the third power of the initial buoyancy flux fo for the plume fallout jp vtfo 1 3 smaller particles are affected by reentrainment caused by the turbulent eddies sweeping ambient fluid back into the plume or jet and thus reincorporating some particles that were released from the flow at greater heights this is taken into account by introducing a reentrainment coefficient into the theoretical models with the assumption that the coefficient has a constant value for a plume of given strength in new experiments fallout occurs from the margins of particle laden fresh water buoyant jets and plumes in a tank of salty water and sedimentation is measured on the tank floor two experiments were weakly affected by reentrainment and show excellent agreement with the simple theory for smaller particles and increasingly buoyant plumes and strong jets particle reentrainment is important the experimental data are fitted by the new reentrainment theory confirming that values of the reentrainment coefficient are approximately constant for a given flow a settling number is defined as the ratio of the characteristic velocity of the jet or plume to the particle settling velocity for 1 reentrainment seems to reach an equilibrium state for which the reentrainment coefficient is a constant of value 0 1 for jets and 0 4 for plumes irrespective of flow strength or particle size the plume experiments indicate that the value of the reentrainment coefficient is strongly dependent on plume strength and particle size for slightly less than 1 the general principles of sedimentation from turbulent plumes and jets are applied to the fallout of pumice from volcanic eruption columns and of metalliferous particles from black smokers on the ocean floor for volcanic eruptions the results provide an explanation for the near vent overthickening of tephra fall deposits and imply that lithic and pumice fragments from small lapilli up to at least 1 m diameter blocks are efficiently reentrained into eruption columns the size of particles reentrained in hydrothermal plumes is predicted to vary from less than 100 m in weakly buoyant plumes up to over 1000 m in megaplumes

volcanz a volcanic loss model for auckland new zealand abstract volcanz is a probabilistic volcanic loss model developed for the auckland region in new zealand that currently considers tephra fall hazards from the auckland volcanic field avf tuhua volcano okataina volcanic centre taupo volcano tongariro volcanic centre and egmont volcano in this first version of the model structural and non structural damage to residential building envelopes and associated cleanup costs are calculated using monte carlo simulation volcanz assigns a minimum and maximum damage value to groups of buildings for every simulation dependent on tephra thickness a central damage value representing loss as a percentage of total replacement cost is then randomly selected between these limits even with small thickness falls non structural damage is expected to roof and wall coatings air conditioning units aerials and satellite dishes due to the corrosive and abrasive properties of tephra an average loss of 583 attributed to non structural damage was assigned to all residential buildings impacted by any thickness of tephra greater than 0 1 mm the costs of tephra removal from buildings cleaning of building exteriors and tephra transport and disposal are also calculated within the model assuming much of the cleanup process will be carried out by homeowners losses from all simulations are plotted against calculated average recurrence intervals aris to produce loss curves structural damage does not become apparent until aris of approximately 8000 years 1 billion losses due to structural damage occur at about 35 000 years and this increases to about 26 billion at 1 million years loss due to non structural damage is constant at approximately 160 million for aris above about 600 years between 600 and 3000 years cleanup loss is approximately 50 million increasing to over 450 million at a return period of 1 million years at aris between 600 and 3000 years total loss is approximately 210 million increasing to 10 billion at 100 000 years and over 26 billion at 1 million years because we only consider residential building damage and associated cleanup these values greatly underestimate total loss from the next volcanic event to impact auckland loss calculations will be improved by adding additional hazard and loss modules to volcanz resulting in a complete catastrophe loss model

magnetotelluric and geomagnetic modelling reveals zones of very high electrical conductivity in the upper crust of central java abstract we present results of two and three dimensional modelling of magnetotelluric and geomagnetic data from central java indonesia we adopt a hypothesis testing approach where we examine the influence of individual structural elements of competing models on the total model responses the models show that ocean anomalies do not overwhelm the signal due to strong electrical conductivity anomalies within java these highly conducting regions with resistivities of below 1 m are located in the central and northern parts of the island fitting of the geomagnetic data requires that the innermost parts of both regions consist of material with extremely low resistivity 0 2 m young sediments tephra and their alteration products can be responsible for some of the low resistivity regions at shallow depths the two zones of extremely high conductivity however are best explained as consequences of geothermal activity in the vicinity of active volcanism mt merapi in central java and by fluid or graphite enrichment along shear zones in northern java subduction zone related processes in a depth range of 70 400 km cannot be resolved because the highly conductive regions at shallow depths effectively screen deeper structures

p and s wave travel time tomography of the se asia australia collision zone abstract the southeast se asia australia collision zone is one of the most tectonically active and seismogenic regions in the world here we present new 3 d p and s wave velocity models of the crust and upper mantle by applying regional earthquake travel time tomography to global catalogue data we first re locate earthquakes provided by the standard isc reviewed and isc ehb catalogues using a non linear oct tree scheme a machine learning algorithm that clusters earthquakes depending on their spatiotemporal density was then applied to significantly improve the consistency of travel time picks we used the fast marching tomography software package to retrieve 3 d velocity and interface structures from starting 1 d velocity and moho models synthetic resolution and sensitivity tests demonstrate that the final models are robust with p wave speed variations 130 km horizontal resolution generally recovered more robustly than s wave speed variations 220 km horizontal resolution the retrieved crust and mantle anomalies offer a new perspective on the broad scale tectonic setting and underlying mantle architecture of se asia while we observe clear evidence of subducted slabs as high velocity anomalies penetrating into the mantle along the sunda arc banda arc and halmahera arc we also see evidence for slab gaps or holes in the vicinity of east java in the banda arc we image the slab as a single curved subduction zone furthermore a high velocity region in the mantle lithosphere connects northern australia with timor and west papua the s wave model shows broad scale features similar to those of the p wave model with mantle earthquakes generally distributed within high velocity slabs the high velocity mantle connection between northern australia and the eastern margin of the sunda arc is also present in the s wave model while the s wave model has a lower resolution than the p wave model due to the availability of fewer paths it nonetheless provides new and complementary insights into the structure of the upper mantle beneath southeast asia

patterns of stretch trajectories and strain rates within spreading gliding nappes abstract stretch trajectories in vertical flow planes through superficial nappes are thought to be specific for some classical mechanical models so that their recognition in the field is of particular interest in order to find a pattern of stretch trajectories related to a gravitational process a strain factorization is attempted from experimental scale models of nappes where spreading and gliding are combined the strain within this type of nappes is schematically considered as the simultaneous combination of two components a simple shearing component and a pure shearing component spatial and time distribution of these two components is computed from both time and spatial evolution of the strain pattern within the scale models a better understanding of stretch trajectories in spreading gliding nappes is consequently provided strain rates are also computed from scale models and the sudden increase of strain rate from top to bottom is explained finally a mechanical model of spreading gliding nappe is briefly discussed

volcanic ashfall accumulation and loading on gutters and pitched roofs from laboratory empirical experiments implications for risk assessment abstract volcanic ash load is dependent on the migration and accumulation of ash on roofing surfaces and guttering of which limited research has been conducted this study investigates this knowledge gap through the empirical experimental testing of volcanic ash on variably pitched metal sheet roofs with modern pvc gutter systems highlighting the relative importance of accumulation migration remobilization saturation and subsequent load a testing rig delivered ash onto variably pitched roofs pitches 15 25 30 35 and 45 with two 45 tests involving a wet surface with subsequent ashfall and the second of ashfall with periods of wetting followed by wetting until failure in testing dry ash on a dry roof accumulates at pitches up to 35 above this pitch the percentage of ash accumulating reduces with greater percentages infilling guttering and or lost to the ground with the introduction of a wet roof surface at 45 pitch adherence of dry ash greatly increases increasing accumulated ash thickness as compared to dry tests from 8 to 38 for testing involving periods of wetting at 45 roof pitch accumulation percentages further increased to 50 ash migrating from the roof surface filled guttering more rapidly at greater pitches which once full resulted in further migrating ash to spill over the front or back gutter lips collapse of guttering did not occur during testing but deformation and bracket detachment did occur at loads 1 kpa this study provides data on load calculations on roofing and pvc guttering through the quantification and utilization of relationships between ash fate pitch and the influence of water in the development of two scenarios for both roof and gutter these two scenarios then enable the estimation of ash accumulation and thus the load and collapse thresholds for roof and gutter at different roof pitch which could be adopted for volcanic risk modeling or risk management

structure and evolution of lithospheric slab beneath the sunda arc indonesia tomographic imaging reveals seismic anomalies beneath the sunda island arc indonesia that suggest that the lithospheric slab penetrates to a depth of at least 1500 kilometers the sunda slab forms the eastern end of a deep anomaly associated with the past subduction of the plate underlying the mesozoic tethys ocean in accord with previous studies the lithospheric slab was imaged as a continuous feature from the surface to the lower mantle below java with a local deflection where the slab continues into the lower mantle the deep slab seems to be detached from the upper mantle slab beneath sumatra this complex slab structure is related to the tertiary evolution of southeastern asia and the indian ocean region

potential impacts from tephra fall to electric power systems a review and mitigation strategies modern society is highly dependent on a reliable electricity supply during explosive volcanic eruptions tephra contamination of power networks systems can com promise the reliability of supply outages can have signifi cant cascading impacts for other critical infrastructure sectors and for society as a whole this paper summarises known impacts to power systems following tephra falls since 1980 the main impacts are 1 supply outages from insulator flashover caused by tephra contamination 2 dis ruption of generation facilities 3 controlled outages during tephra cleaning 4 abrasion and corrosion of exposed equipment and 5 line conductor breakage due to tephra loading of these impacts insulator flashover is the most common disruption the review highlights multiple instan ces of electric power systems exhibiting tolerance to tephra falls suggesting that failure thresholds exist and should be identified to avoid future unplanned interruptions to ad dress this need we have produced a fragility function that quantifies the likelihood of insulator flashover at different thicknesses of tephra finally based on our review of case studies potential mitigation strategies are summarised specifically avoiding tephra induced insulator flashover by cleaning key facilities such as generation sites and trans mission and distribution substations is of critical importance in maintaining the integrity of an electric power system

a coupled model for dispersal of tephra during sustained explosive eruptions abstract we present a model for fallout of tephra based on approximate analytical solutions of the advection diffusion transport equation as usual the model requires the distribution of mass throughout the eruptive column as a boundary condition an input which is normally imposed ad hoc by means of analytical expressions we propose an alternative way to assess this input based on coupling the model of fallout with already existing simple models for volcanic plumes flow along the volcanic conduit and magma chamber withdrawal the final outcome is a one way coupled model that involves all the spatial domains simultaneously and has a good compromise between physical accuracy and computational efficiency the coupled model outputs not only maps of isopachs but also several relevant eruptive parameters such as column height mass eruption rate or duration of the eruption time dependency is introduced via a quasi steady approach that is considering a succession of steady states we apply the model to simulate the 2 ka subplinian eruption of montana blanca tenerife island

seismic response to recent tectonic processes in the banda arc region abstract internal structure and recent tectonics of the geologically complex banda arc region latitude 1 9 s longitude 124 135 e have been studied by means of the analysis of global seismological data relocated hypocentral determinations of the international seismological center ehb data and fault plane solutions of the global centroid moment tensor project have been used together with previously published information on regional geology and dynamics the analysis considered earthquakes in the lithospheric wedges above subducting slabs and earthquakes in the uppermost portions of the wadati benioff zones focal depth

fine structure beneath the tohoku district northeastern japan arc as derived by an inversion of p wave arrival times from local earthquakes abstract three dimensional p wave velocity structure beneath the tohoku district northeastern japan arc is investigated by an inversion of arrival times from local earthquakes using the method originally due to aki and lee 1976 in the crust 0 32 km depth a low velocity region is found along the volcanic front and its vicinity velocities at depths of 32 65 km are low beneath the regions where many quaternary volcanoes and geothermal areas are distributed in the region deeper than 65 km the subduction of the pacific plate is clearly revealed and the mantle structure above the descending plate is rather uniform these features suggest that volcanic activities have relation to the upper mantle structure the results obtained in this study will be helpful in investigating the mechanism of magma generation in a subduction zone

a new numerical simulation method applied to spreading nappes abstract a numerical method for simulating the temporal evolution of geologic deformation structures is developed and described by using spreading nappes as examples the method is based on maximization of the rate of decline of potential energy which is equivalent to maximizing the rate of dissipation due to strain or maximizing the rate of production of entropy a polynomial stream function is used as the governing equation describing the velocity field of the system the potential energy rate and the strain energy rate are obtained by integration over the profile of the nappe and the maximization procedure determines the coefficients in the stream function which then produces the velocity field and the displacement field the latter displaces the boundary of the nappe and the subsequent integration of energy over the new profile leads to new stream function coefficients which change the velocity field and displace the boundary anew etc by this stepwise procedure the evolution of the nappe can be followed to any final stage velocities and displacements of a number of nappes with different cross section profiles and different aspect ratios are calculated improvement and evolution of the method are discussed in order to apply the method to structures also affected by boundary stresses not related to gravity

a model for the numerical simulation of tephra fall deposits abstract a simple semianalytical model to simulate ash dispersion and deposition produced by sustained plinian and sub plinian eruption columns based on the 2d advection dispersion equation was applied the eruption column acts as a vertical line source with a given mass distribution and neglects the complex dynamics within the eruption column thus the use of the model is limited to areas far from the vent where the dynamics of the eruption column play a minor role vertical wind and diffusion components are considered negligible with respect to the horizontal ones the dispersion and deposition of particles in the model is only governed by gravitational settling horizontal eddy diffusion and wind advection the model accounts for different types and size classes of a user defined number of particle classes and changing settling velocity with altitude in as much as wind profiles are considered constant on the entire domain the model validity is limited to medium range distances about 30 200 km away from the source the model was used to reconstruct the tephra fall deposit from the documented plinian eruption of mt vesuvius italy in 79 a d in this case the model was able to broadly reproduce the characteristic medium range tephra deposit the results support the validity of the model which has the advantage of being simple and fast to compute it has the potential to serve as a simple tool for predicting the distribution of ash fall of hypothetical or real eruptions of a given magnitude and a given wind profile using a statistical set of frequent wind profiles it also was used to construct air fall hazard maps of the most likely affected areas around active volcanoes where a large eruption is expected to occur

total grain size distribution and volume of tephra fall deposits on 17 june 1996 ruapehu volcano new zealand produced a sustained andesitic sub plinian eruption which generated a narrow tephra fall deposit extending more than 200 km from the volcano the extremely detailed data set from this eruption allowed methods for the determination of total grain size distribution and volume of tephra fall deposits to be critically investigated calculated total grain size distributions of tephra fall deposits depend strongly on the method used and on the availability of data across the entire dispersal area the voronoi tessellation method was tested for the ruapehu deposit and gave the best results when applied to a data set extending out to isomass values of 1 g m 2 the total grain size distribution of a deposit is also strongly influenced by the very proximal samples and this can be shown by artificially constructing subsets from the ruapehu database unless the available data set is large all existing techniques for calculations of total grain size distribution give only apparent distributions the tephra fall deposit from ruapehu does not show a simple exponential thinning but can be approximated well by at least three straight line segments or by a power law fit on semi log plots of thickness vs area 1 2 integrations of both fits give similar volumes of about 4 106 m3 integration of at least three exponential segments and of a power law fit with at least ten isopach contours available can be considered as a good estimate of the actual volume of tephra fall integrations of smaller data sets are more problematic

explosive volcanic eruptions v observations of plume dynamics during the 1979 soufriere eruption st vincent summary during the 1979 eruption of the soufritre of st vincent west indies a 14min period of explosive activity occurred on april 22 the first three minutes of this activity were filmed five individual explosions formed distinct plumes which fed an eruption column which eventually ascended to a height of over 18 km the ascent velocities of the fronts of these plumes ranged from 8 5 to 61 7m s the half angle of spreading of the plume fronts ranged from 21 5 to 24 one of the plumes was observed to 8 km height and decelerated steadily from 5 1 5 to 23 m s l the main column fed by individual explosions was however observed to accelerate from 8 5 to 58 m s l in the same height interval a theoretical treatment of volcanic plume motion is presented measurements of dimensions velocities and spreading rates from the film are used to estimate plume parameters such as temperature particle content and volume discharge rate of magma from the theoretical relationships these calculations show that the individual plumes became hotter and richer in juvenile ash with time the acceleration of the main eruption column was the result of being fed by increasingly hotter and more ash rich explosions an average volume discharge rate of 12600m3s is estimated from the analysis of the plume motions this value agrees closely with an estimate of discharge rate based on the heat flux required to form an 18 km high column this agreement suggests that theories of convective motions in plumes can be successfully adapted to the volcanic case as long as the effect of hot entrained ash particles is considered

mesoscale modeling of a cold front and its interaction with a diurnally heated land mass abstract a mesoscale numerical model incorporating a detailed planetary boundary layer scheme including momentum heat and moisture exchange with the lower boundary is used to study the change in structure of a dry summertime front as it moves towards a coastline two dimensional experiments show that the diurnal pressure fall over land causes a trough to form in the coastal region ahead of the approaching front frontogenesis at this mesoscale trough leads to the formation of a new front near the coast giving the appearance of strong acceleration of the original frontal system in the offshore region this process can occur over a wide range of times from early afternoon to late evening but no such acceleration occurs for fronts crossing the coast in the early morning hours these results indicate a tendency for more fronts to cross the coastline in the afternoon early evening period than at other times a statistic which is observed in southeast australia and oregon usa they also imply fronts sho

how the state of stress varies in the wadati benioff zone indications from focal mechanisms in the wadati benioff zone beneath sumatra and java summary this study concentrates on the detailed determination of the state of stress in the wadati benioff zone in the lithosphere subducting under sumatra and java the orientations of p and t axes of earthquake focal mechanisms hcmt are used to define a system of domains in which a uniform state of stress is assumed the method of gephart forsyth is then used to determine the state of stress in each domain we succeeded in delimiting eight domains three si siii in the sumatra region and five ji jv in the java region domains with similar states of stress occur in both regions in similar positions the maximum compression 1 is perpendicular to the trench in domains si sii and jii that is within the depth range 0 165 km the orientation of 1 is almost parallel to the trench in domains siii and jiii depth range 25 225 km the boundary between domains sii and siii and jii and jiii is not distinct covering the depth range 40 165 km it seems that the focal mechanisms belonging to domains sii and siii and similarly to domains jii and jiii occur in different stress layers and that we observe an overlap of earthquakes with different focal mechanisms from two different stress state layers parallel to the wadati benioff zone in domains jiv and jv the states of stress correspond to the stress pattern observed in other subduction zones slab dip parallel extension is observed in domain jiv depth range 225 315 km and slab dip parallel compression is observed in domain jv deeper than 400 km

influence of particle aggregation on deposition of distal tephra from the may 18 1980 eruption of mount st helens volcano the may 18 1980 eruption of mount st helens msh produced an extensive ashfall deposit in washington idaho and montana with a minumum volume of 0 55 km3 tephra an unusual feature of the deposit is the occurrence of a second thickness maximum 325 km ene of msh near ritzville washington grain size and component abundance analysis of samples along the main dispersal axis indicates that ash in this region is very fine grained mean size 22 m poorly sorted polymodal and rich in glass shards and pumice fragments a computer simulation of ash fallout from an atmospherically dispersed eruption plume was developed to evaluate various hypotheses for the origin of the distal ash characteristics particularly the thickness versus distance relationship the model was constrained by observations of the eruption column height elevation of major ash transport lateral spreading of the eruption plume and atmospheric wind structure in the vicinity of msh results of different simulations indicate that the second thickness maximum cannot be attributed to either decreased wind velocities over central washington or injection of fine ash above the horizontal wind velocity maximum near the tropopause for the model to fit the observed characteristics of the deposit significant particle aggregation of ash finer than 63 m must be invoked the best fit occurs when ash less than 63 m is aggregated into particles several hundred microns in diameter with a settling velocity of 0 35 m s support for this process comes from the observation and collection of fragile ash clusters of similar size which fell at pullman washington during the may 18 eruption sorem 1982 the premature fallout of fine ash as particle aggregates is a fundamental process in the origin of the grain size characteristics variations in component abundances and thickness versus distance relationship of the may 18 msh ash fall deposit

an investigation of the relationship between the geology of indonesian sedimentary basins and heat flow density abstract geothermal data collected from 929 wells drilled by oil companies in 20 tertiary basins of indonesia have been related to the geology and tectonics of the area it is found that the thermal conductivity increases with the depth of burial and degree of compaction in both transgressive and regressive sediments but decreases with increases in impurities and heterogeneous grain sizes the temperature gradient is controlled mainly by the depth and temperature of a heat source beneath a basin very high heat flow densities 125 mw m 2 found in central sumatra south sumatra salawati basin and bintuni basin may be caused by relatively shallow magmatic diapirism

the interest of cartography for a better perception and management of volcanic risk from scientific to social representations the case of mt pelee volcano martinique lesser antilles the study develops an innovative gis based integrated approach for the assessment of a comprehensive volcanic risk this is based on a four step methodology which has been developed at mt pelee volcano in martinique a french island in the lesser antilles the first stage of the methodological framework integrates the spatial extent of volcanic hazards for a maximal credible eruptive scenario the second stage covers an assessment of the elements especially the buildings that may be affected in the event of an eruption and defines their level of damages by given volcanic hazards a computerized analysis leads to the definition of an index for the risk of total loss in a 500 meter grid the third stage consists of designing regulative land use maps which should orient and limit the occupation of areas exposed to severe hazards finally the fourth stage based on survey data includes a spatial assessment of collective representations for a future eruption by the surrounding communities these maps turn out to be powerful communication tools which help planners and disaster authorities in mitigating damages from volcanic hazards they can contribute to enhance the perception of volcanic risk in martinique

structural pattern and emplacement mechanism of the neka valley nappe complex eastern alborz iran the neka valley nappe complex is exposed in the south of gorgan county in the eastern alborz fold and thrust belt we use the results of a regional survey of the structural data and their patterns to interpret the mechanisms that emplaced the unmetamorphosed nappes in the foreland fold and thrust belt of the alborz mountains most of the strain magnitudes are low in the study area but increase slightly towards what are probably their proximal ends strain ellipsoid is dominantly oblate with xy aligned along and across the belt or the nappe complex the average kinematic vorticity number w k 0 6 which indicates most of the strain partitioning resulted in a general shear most of flinn s k values and the stretch along the shear plane values are lower than 1 structural indicators such as orthogonal extensional joints pinch and swell structures anastomosing cleavages and listric normal and growth faults developed by push from the rear large scale thrust complexes with opposed dips such as triangle zones as well as k and values 1 are compatible with the shear flow diverging distally and streamlines expected of the rear compression emplacement mechanism together with a later minor brittle deformation these major ductile strains appears to provide a general model suitable for the emplacement of the nappes studied in a thin skinned fold and thrust belt where the sedimentary cover strata shortened and imbricated in the upper crust

strain models within spreading nappes abstract internal strain within nappes and thrust sheets is especially important in the understanding of emplacement mechanisms in this paper strain patterns within spreading nappes are investigated theoretically and experimentally three types of spreading nappe are distinguished using various boundary conditions spreading gliding spreading and extruding spreading nappes each type is placed in its proper natural environment strain components and strain gradients are summarized from the use of scale models performed with analogue materials mathematical computations from experimental modelling allow the calculation of 1 1 the schistosity trajectories in vertical flow planes 2 2 the relationship between stretch and transport direction and 3 3 the spatial distribution of different types of strain ellipsoid these provide some tests which make it possible to demonstrate in the field whether nappes are or are not gravity induced finally some field examples from the central alps and the pyrenees are briefly discussed they provide good support to the strain models presented in the present paper

the effect of total grain size distribution on the dynamics of turbulent volcanic plumes abstract the impact of explosive volcanic plumes on climate and on air traffic strongly depends on the concentration and grain size distribution gsd of pyroclastic fragments injected into the atmosphere accurate and robust modelling of the evolution of gsd during pyroclast transport from the vent to the ash cloud is therefore crucial for the assessment of major volcanic hazards analysis of field deposits from various recent plinian eruptions shows that their total gsd is well described by a power law as expected from the physics of magma fragmentation with an exponent d ranging from 3 0 to 3 9 by incorporating these measured gsd into the initial conditions of a steady state 1d model of explosive eruption columns we show that they have a first order impact on the dynamical behaviour of explosive eruption columns starting from an initial value of d the model tracks the evolution of gsd in the column and calculates the dynamical consequences of particle sedimentation the maximum height reached by the column one of the first order results relevant to aircraft safety changes by 30 for mass fluxes of 10 7 kg s 1 or larger and by 45 85 for mass fluxes between 105 and 10 7 kg s 1 depending on exponent d we compare our predictions to a specially assembled set of geologic field data and remote sensing observations from 10 plinian eruptions for which maximum column height and mass flux are known independently the incorporation of realistic power law gsd in the model greatly improves the predictions which opens new perspectives for estimation of ash load and gsd in volcanic clouds from near real time measurements available from satellite payloads our results also contribute to the improvement of volcanic source term characterization that is required input for meteorological dispersion models

magnetic properties of modern soils and quaternary loessic paleosols paleoclimatic implications the magnetic properties of paleosols developed in quaternary sequences of loess have been used for stratigraphic definition correlation with other terrestrial and deep sea sequences and paleoclimatic paleorainfall reconstruction in some loess paleosol sequences including those of the chinese loess plateau tajikistan and the czech republic maxima in magnetic susceptibility values correspond with the paleosol horizons and minima with the least weathered loess layers in other loess soil sequences including those of siberia alaska and argentina the relationship is completely opposite with susceptibility minima associated with the most developed paleosols to account for these opposite relationships the respective roles of 1 magnetic enhancement and 2 magnetic depletion and or dilution in determining soil magnetic properties are investigated for a range of modern soil types most magnetic enhancement is seen in the upper horizons of well drained cambisols absence or loss of magnetic iron oxides is apparent in acid podsol profiles and waterlogged soils for the cambisol profiles significant correlation is found between susceptibility and organic carbon cation exchange capacity and clay content the mineralogy morphology and grain size of soil magnetic carriers extracted from three modern enhanced soils and a paleosol from the chinese loess plateau are also identified by independent petrographic means microscopy and x ray diffraction of magnetic extracts magnetite and maghemite of ultrafine grain size from 0 4 to 0 001 i m are the major contributors to the magnetically enhanced soils weathering can concentrate detrital magnetic grains especially in the fine silt size fractions of soils the magnetic data from the modern soils indicate that interpretation of paleosol magnetic properties must be done on a site specific basis taking into account the possibilities of pedogenic enhancement pedogenic dilution or depletion and allochthonous inputs of magnetic minerals excessively arid wet or acid soils are unable to form significant amounts of pedogenic ferrimagnets well drained intermittently wet dry soils with reasonable buffering capacity and a substrate source of fe show most magnetic enhancement for those soils which favour magnetic enhancement processes correlation has been found between the maximum value of the pedogenic susceptibility and the annual rainfall the almost unique pedogenic system in the chinese loess plateau where variation in soil forming factors other than climate is reduced to a global minimum allows use of the paleo susceptibility values as proxy paleorainfall values to identify the mechanism of any link between magnetic properties for example susceptibility and climate change the mineralogy and grain size of soil magnetic carriers requires detailed investigation given the prospect of 1 quantitative paleorainfall records from continental loess records 2 predictions of present and future climate change and 3 the value of paleoclimate data for testing of numerical climate models such magnetic investigations can contribute significantly to our understanding of past and future environmental change

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

sedimentation of tephra by volcanic plumes i theory and its comparison with a study of the fogo a plinian deposit sao miguel azores sedimentation of ejecta from volcanic plumes has been studied as a function of distance from the source in the fogo a plinian deposit sao miguel azores the fogo a trachytic pumice deposit is reversely graded and can be divided into two parts on the basis of pumice colour abundance of syenite accessory lithic clasts and distribution the lower syenite poor part was dispersed to the south and was clearly influenced by wind the upper syenite rich part is coarsegrained and has a nearly symmetrical distribution around the vent elongation of isopachs to the east indicate a weak wind influence the grain size variations of lithic and crystal components in the upper coarse part were studied total accumulation and accumulation per unit area expressed in kg m2 show good fits to a gaussian function at distances greater than 7 km for grain diameters less than 2 cm these results agree with a theoretical model for a radially spreading turbulent current moving over a quiescent fluid the gaussian coefficient is shown to be a function of grain size and the flow rate of material into the umbrella region of the eruption column the coefficient is therefore also a function of column height the column height deduced from these data is 21 km which is in broad agrrement with the column height of 27 km deduced from maximum clast dispersal using the method of carey and sparks 1986 the accumulation of clasts larger than 2 cm agrees with a theory for the fallout of clasts from the margins of the ascending eruption column which treats the plume as a succession of large eddies that decrease their mass of particles as an exponential function of time calculations are also presented for the influence of the radial inflow of surrounding air into the column on the deposition of clasts these calculations constrain the wind speed during the later part of the fogo a eruption to be at most a few metres per second the study has allowed four different dynamic categories of clast behaviour to be recognised in eruption columns

seismic history and seismotectonics of the sunda arc historic records of the last 300 years reveal two great interplate earthquakes 1833 mw 8 1861 mw 8 8 which ruptured major segments of the sumatra fore arc in western indonesia a significant percentage of interplate slip along this portion of the plate boundary appears to occur seismically the ends of these rupture zones are coincident with clusters of large ms 7 and moderate 6 ms 7 shocks and with heterogeneities in the plate interface as inferred from geologic and geophysical data the northern extent of the 1833 rupture zone is coincident with a group of moderate and large earthquakes a structural arch in the fore arc and a fracture zone on the subducted plate the southern portion is coincident with a very prominent cluster and the along strike extension of a sediment filled trough on the subducted plate prior to this study sumatra was characterized as relatively aseismic as inferred from the lack of great earthquakes in the instrumental record of this century java and the lesser sunda islands had major ms 6 earthquakes in the historic record but none are of the same magnitude as the great events near sumatra there is no clear evidence that shocks in the java fore arc were interplate events yet geophysical data indicate recent uplift of the trench slope break and a change in strike of the trench axis where the northernmost flank of the roo rise a prominent bathymetrie high appears to be interacting with the fore arc this feature was formed at a ridge crest and is more buoyant and thus more difficult to subduct than the surrounding seafloor there is no increase in seismicity associated with this tectonism however that may indicate a lack of contact between the crystalline portions of the plates at this time we infer that a majority of slip on the plate interface near java occurs aseismically the variation in occurrence of great interplate earthquakes along the sunda arc may be interpreted in terms of a model that attributes variation in interplate coupling to the age of the subducted lithosphere great interplate earthquakes occur near sumatra where the age of the youngest crust is 46 ma the characteristics of the sunda arc and analogies with pacific arcs imply that the entire length of sumatra has the potential to produce great thrust earthquakes its seismic potential should be considered high as there has been no recurrence of the great events of 1833 and 1861 in contrast no such events have been reported off java and the lesser sunda islands where the oldest crust is 152 ma the plate interface near java and the lesser sunda islands should be considered to have low seismic potential

active deformation in eastern indonesia and the philippines from gps and seismicity data in this study we combine global positioning system gps velocities with information on the style of regional seismicity to obtain a self consistent model velocity and strain rate field for the entire eastern indonesia and philippines region in the process of interpolating 93 previously published gps velocities the style and direction of the seismic strain rate field inferred from earthquakes with m0 1 1020 n m from the harvard centroid moment tensor catalog are used as constraints on the style and direction of model strain rates within the plate boundary zones the style and direction of the seismic strain rate field are found to be self similar for earthquakes up to m0 1 1020 n m equivalent to mw 7 3 our inversion result shows the following the java trench which lacks any significant historic seismicity delineates the australian plate au sunda block sunda plate boundary west of the island of sumba east of sumba convergence is distributed over the back arc and banda sea and there is no subduction at the timor trough suggesting that the northern boundary of the au plate runs north of this part of the banda arc through the banda sea in new guinea most motion is taken up as strike slip deformation in the northern part of the island delineating the pacific plate pa au boundary however some trench normal convergence is occurring at the new guinea trench evidence that the strain is partitioned in order to accommodate oblique pa au motion pa au motion is consistent with nuvel 1a direction but 8 mm yr 1 slower than the nuvel 1a estimate for pa au motion the sulawesi trench and molucca sea delineate zones of high strain rates consistent with high levels of active seismicity the sulawesi trench may take up some of the au sunda motion philippine sea plate motion is in a direction slightly northward of the nuvel ia estimate and is partitioned in some strike slip strain rates along the philippine fault and relatively larger trench normal convergence along the philippine trench and on the philippine mainland in the southern philippines and along the manila trench in the northern philippine islands the high level of strain rate along the manila trench is not released by any significant historic seismic activity for the entire eastern indonesia philippines region seismicity since 1963 has taken up 40 of the total moment rate inferred from our model

timber framed building damage from tephra fall and lahar 2015 calbuco eruption chile abstract assessing the damage to buildings from volcanic eruptions is an important aspect of volcanic risk assessment and management however there is a limited empirical evidence base to draw upon when describing the relation between volcanic hazard intensity and resulting physical damage the 2015 subplinian eruption of calbuco volcano chile caused damage to buildings near the volcano because of tephra fall and lahars chilean authorities conducted a damage assessment of 961 properties 990 buildings to inform an assistance programme for property owners affected by the eruption property assessments typically contained observations and classification of damage to a house and in some instances accessory buildings such as sheds garages and exterior storage rooms in this study we used this unique damage data set to adapt damage state frameworks for tephra fall and lahar for classifying and analysing damage observations we developed data quality indicators to provide transparency for how we accounted for data quality issues we assigned a tephra and or lahar damage state to 571 buildings 530 houses and 41 accessory buildings the 419 buildings for which we did not assign a damage state either had too little information or fell outside of tephra and or lahar hazard zones the minimum tephra thickness isopach band that caused complete collapse was 10 to 15 cm dry deposit loading 1 to 1 6 kn m 2 saturated deposit loading 1 6 to 2 4 kn m 2 but most commonly 55 of tephra exposed ds5 houses n 11 this occurred at 15 to 30 cm dry deposit loading 1 5 to 3 3 kn m 2 saturated deposit loading 2 4 to 4 8 kn m 2 lahar damage was typically described as complete ds5 with 26 houses being swept away or destroyed around the blanco south river our results add to the limited evidence base of post eruption tephra and lahar impacts to buildings and contribute to volcanic risk and impact assessment

soil magnetic susceptibility and its relationship with naturally occurring processes and soil attributes in pedosphere in a tropical environment abstract soil magnetic susceptibility has potential to be used as a pedoenvironmental indicator from which mineralogy pedogeochemical pedogeomorphological and pedogenic processes can be inferred it can be used in pedosphere studies as an auxiliary information for appropriate and sustainable soil use and management this research aimed to analyze how pedogenesis and geochemical processes affect the and some of its attributes as well as its potential use in discriminating soil great groups following the digital soil mapping approach the study area is located in sao paulo state brazil soil samples were collected for physical chemical analysis from 79 locations 0 20 cm depth at these sites magnetic susceptibility was measured with a portable field instrument and analyzed in terms of geology relief and soil class the results showed that geology strongly affects mainly in diabase derived soils followed by metamorphosed siltstone and siltstone in fluvial sediments the exhibits different behaviors due to different sediments deposited by the capivari river in less evolved soils such as cambisols lithology is a more important contributor to than pedogenesis in more evolved soils pedogenesis increases whereas argilluviation ferralitization reduces it the values did not decrease significantly or even increase downslope due to the presence of diabase on the lower parts differences in where observed between diabase bedrock located in different parts of the study area indicating more of an influence by geomorphic processes rather than lithology with respect to soil attributes positive correlations between and base saturation cation exchange capacity organic matter and iron and clay content were found whereas a negative correlation was found between and sand content the correlates with changes in lithology and soil class demonstrating its application as a potential tool for the discrimination of soil great groups and digital soil mapping

volcanic risk assessment quantifying physical vulnerability in the built environment abstract this paper presents structured and cost effective methods for assessing the physical vulnerability of at risk communities to the range of volcanic hazards developed as part of the mia vita project 2009 2012 an initial assessment of building and infrastructure vulnerability has been carried out for a set of broadly defined building types and infrastructure categories with the likelihood of damage considered separately for projectile impact ash fall loading pyroclastic density current dynamic pressure and earthquake ground shaking intensities in refining these estimates for two case study areas kanlaon volcano in the philippines and fogo volcano in cape verde we have developed guidelines and methodologies for carrying out physical vulnerability assessments in the field these include identifying primary building characteristics such as construction material and method as well as subsidiary characteristics for example the size and prevalence of openings that may be important in assessing eruption impacts at risk buildings around kanlaon were found to be dominated by timber frame buildings that exhibit a high vulnerability to pyroclastic density currents but a low vulnerability to failure from seismic shaking around fogo the predominance of unreinforced masonry buildings with reinforced concrete slab roofs suggests a high vulnerability to volcanic earthquake but a low vulnerability to ash fall loading given the importance of agriculture for local livelihoods around kanlaon and fogo we discuss the potential impact of infrastructure vulnerability for local agricultural economies with implications for volcanic areas worldwide these methodologies and tools go some way towards offering a standardised approach to carrying out future vulnerability assessments for populated volcanic areas

mantle structure beneath indonesia inferred from high resolution tomographic imaging we investigated mantle structure beneath the indonesian region by means of tomographic inversions of traveltime residuals of direct p and the surface reflected depth phases pp and pwp the hypocentres and phase data used in the inversions were derived from the reprocessing of data reported to international data centres which include data from the australian skippy project we used more than 6 0 10 data from more than 50 000 globally distributed earthquakes recorded at a subset of nearly 3000 seismological stations worldwide the use of depth phases improved the sampling of the upper mantle structure in particular beneath the back arc regions the mapping of distant aspherical mantle structure into the study region was minimized by combining a high resolution regional with a low resolution global inversion the inversion was linearized around the ak135 reference velocity model and a combination of minimum norm and gradient damping was applied to constrain the solution inversion of different subsets of the data and test inversions of synthetic data indicate that resolution is sufficient to substantiate the conclusions pertinent to the complex large scale structure of the subducted slab beneath the indonesian archipelago the tomographic images confirm previous evidence for regional slab penetration into the upper part of the lower mantle but suggest a more complex trajectory of mantle flow beneath indonesia the implied lateral variation in the shape of the upper mantle slab is generally in good agreement with inferences from seismicity the data reveal a seismic anomaly beneath the sunda arc which is detected to at least 1500 km in depth and forms the eastern end of a deep anomaly associated with the past subduction of lithosphere of the mesozoic tethys ocean below java the lithospheric slab is probably continuous from the earth s surface to the lower mantle but beneath sumatra the deep slab seems to be detached from the seismogenic slab the high resolution images suggest that the subducted slab is deflected in the transition zone beneath the banda arc and that the descending slabs form a spoon shaped structure north of the banda sea we detect the two opposing subducted slabs of the molucca sea plate this is consistent with previous studies but our images suggest that the westward subduction has a significantly steeper dip than the eastward subduction slab structure beneath the banda and molucca seas is explained in the context of the continent arc collision between australia and the southeast indonesian island arc and the arc arc collision between sangihe and halmahera inversion of traveltime residuals of direct s phases a novelty for this region largely confirms the inferences from the p wave data even though less detail is resolved

volcanic hazard impacts to critical infrastructure a review abstract effective natural hazard risk assessment requires the characterisation of both hazards and vulnerabilities of exposed elements volcanic hazard assessment is at an advanced state and is a considerable focus of volcanic scientific inquiry whereas comprehensive vulnerability assessment is lacking cataloguing and analysing volcanic impacts provide insight on likely societal and physical vulnerabilities during future eruptions this paper reviews documented disruption and physical damage of critical infrastructure elements resulting from four volcanic hazards tephra fall pyroclastic density currents lava flows and lahars of eruptions in the last 100 years we define critical infrastructure as including energy sector infrastructure water supply and wastewater networks transportation routes communications and critical components common trends of impacts and vulnerabilities are summarised which can be used to assess and reduce volcanic risk for future eruptions in general tephra falls cause disruption to these infrastructure sectors reducing their functionality whilst flow hazards pyroclastic density currents lava flows and lahars are more destructive causing considerable permanent damage volcanic risk assessment should include quantification of vulnerabilities and we challenge the volcanology community to address this through the implementation of a standardised vulnerability assessment methodology and the development and use of fragility functions as has been successfully implemented in other natural hazard fields

an automatic procedure to forecast tephra fallout tephra fallout constitutes a serious threat to communities around active volcanoes reliable short term forecasts represent a valuable aid for scientists and civil authorities to mitigate the effects of fallout on the surrounding areas during an episode of crisis we present a platform independent automatic procedure with the aim to daily forecast transport and deposition of volcanic particles the procedure builds on a series of programs and interfaces that automate the data flow and the execution and subsequent postprocess of fallout models firstly the procedure downloads regional meteorological forecasts for the area and time interval of interest filters and converts data from its native format and runs the calmet diagnostic model to obtain the wind field and other micro meteorological variables on a finer local scale 3 d grid defined by the user secondly it assesses the distribution of mass along the eruptive column commonly by means of the radial averaged buoyant plume equations depending on the prognostic wind field and on the conditions at the vent granulometry mass eruption rate etc all these data serve as input for the fallout models the initial version of the procedure includes only two eulerian models hazmap and fall3d the latter available as serial and parallel implementations however the procedure is designed to incorporate easily other models in a near future with minor modifications on the model source code the last step is to postprocess the outcomes of models to obtain maps written in standard file formats these maps contain plots of relevant quantities such as predicted ground load expected deposit thickness and for the case of or 3 d models concentration on air or flight safety concentration thresholds

the stream function and gauss principle of least constraint two useful concepts for structural geology abstract to the extent that rock deformation can be approximated by a two dimensional newtonian model a powerful stream function simulation method is applicable the significance of stream functions is that velocity strain stress and energy derived from the same stream function satisfy automatically three basic conditions of dynamics 1 1 the condition of continuity 2 2 the navier stokes equations 3 3 conservation of energy hence we state with jaeger if a stream function can be found which satisfies the boundary conditions of a dynamic model the complete solution follows all pertinent bits of dynamic information are implied in the stream function from which they can be directly derived guaranteed so to speak not to violate the basic conditions of dynamics stream functions useful in structural geology are solutions of 4 4 x 4 2 4 x 2 y 2 4 y 4 0 a double polynomial solution of max degree 14 is developed in which the coefficients are related controlled by the 4 0 constraint and their absolute values are determined by the boundary conditions of specific models and by the condition of maximum rate of energy dissipation or maximum rate of decline of potential energy the polynomial stream function is applied to a collapsing viscous nappe consisting of a thin basal layer with low viscosity on which a thicker layer with high viscosity slides due to gravitational spreading the velocity of forward movement depends upon absolute and relative values of the following parameters viscosity thickness the aspect ratio and density the velocity of a variety of nappes with different thicknesses aspect ratios viscosities and densities is determined

mantle structure and seismotectonics of the sunda and banda arcs abstract we have examined the mantle structure and seismotectonic features of the sunda and banda arcs indonesia based on the p wave tomographic images focal mechanism solutions gravity anomaly and heat flow data on the basis of slab morphology and seismicity we can divide the arcs into three parts the western sunda eastern sunda and banda arc the slab like tomographic image penetrates to a depth of about 500 km below the western sunda arc where seismicity does not exceed a depth of 250 km in the eastern sunda arc where a seismic gap exists between 300 and 500 km depths the slab appears to be continuous and to penetrate into the lower mantle beneath the banda arc with seismicity down to a depth of about 650 km the slab dips gently and does not appear to penetrate into the lower mantle the positive gravity anomaly shows a systematic pattern namely the anomaly along the eastern sunda arc is larger than that in the western sunda and the banda arcs along the back arc side of the sunda and banda arcs the heat flow decreases from the west to the east seismic strain release from the shallow earthquakes calculated from the cmt solutions show the strain axes to be oblique to the structural trends the cmt solutions show that the eastern sunda arc is characterized by normal earthquakes along the trench and back arc thrusting earthquakes north of the volcanic line in the western sunda and the eastern sunda arcs earthquakes of the down dip extension type dominate the slab down to a depth of 200 km while down dip compression earthquakes occur below 500 km depth in the banda arc deep earthquakes show down dip extension to a depth of 500 km below this depth the state of stress is not clearly defined

volcanic risk ranking for auckland new zealand ii hazard consequences and risk calculation in a companion paper a methodology for ranking volcanic hazards and events in terms of risk was presented and the likelihood and extent of potential hazards in the auckland region new zealand investigated in this paper the effects of each hazard are considered and the risk ranking completed values for effect are proportions of total loss and as with likelihood and extent are based on order of magnitude

building damage in rabaul papua new guinea 1994 damage information on 173 buildings was collected in the immediate aftermath of the september 1994 eruption which destroyed large sections of rabaul town papua new guinea the extent of damage is presented on a five point scale and related to construction characteristics and tephra load total roof loads in rabaul town ranged from 2 to 16 kn m 2 about 100 to 950 mm tephra thickness most buildings which collapsed completely experienced loads 7 5 kn m 2 but many buildings sustained half this load with little more than cosmetic damage timber framed buildings suffered more than buildings with at least some concrete block walls however some old steel framed buildings experienced severe damage with tephra loads as low as 2 kn m 2 comparisons with tephra loads and building damage elsewhere are limited but suggest that rabaul buildings experiencing roof loads of 2 5 kn m 2 generally survived reasonably well however the comparisons are unsatisfactory because of inadequate data on tephra unit weights roof design building ages the quality of workmanship and the natural variability of construction materials particularly timber the rabaul data suggest that concrete block walls increase building resistance to tephra loads but it is doubtful that conventional residential buildings can be designed to sustain tephra loads exceeding 7 kn m 2 the rabaul experience also indicates that building codes for volcanic areas need to consider mudfills and post eruption corrosion of sheet metal roofs and wall cladding most importantly had the majority of buildings in rabaul survived the september 1994 tephra falls wet season mudflows a few months later would still have made most of the town unsafe and uninhabitable