agronomic impact of tephra fallout from the 1995 and 1996 ruapehu volcano eruptions new zealand eruptions from ruapehu volcano on 11 and 14 october 1995 and 17 june 1996 distributed at least 36 106 m3 of sulphur s rich tephra over the central and eastern north island of new zealand the tephras added between 30 1500 kg ha 1 s to at least 25 000 km2 of land in primary production smaller but beneficial amounts of selenium se and in some areas potassium and magnesium were also supplied addition of s to the soils in the form of sulphate and elemental s resulted in a drop in soil ph and an increase in pasture s contents within seven weeks of the eruptions the soils affected by the tephra are naturally low in s and se but following the eruptions s was not required in fertilizer applications in many areas the strongest and longest lasting effects of s and se deposition were in high anion retention soils particularly hapludands moist moderately weathered soils derived from volcanic ash soluble fluorine concentrations within the tephras were low compared to historic icelandic and chilean examples however pastoral livestock deaths were apparently caused by fluorosis in addition to starvation when tephra covered feed the ruapehu tephra contained very low concentrations of other soluble toxic elements

a fractal model for crustal deformation abstract we hypothesize that crustal deformation occurs on a scale invariant matrix of faults for simplicity we consider a two dimensional pattern of hexagons on which strike slip faulting occurs the behavior of the system is controlled by a single parameter the fractal dimension deformation occurs on all scales of faults the fractal dimension determines the fraction of the total displacement that occurs on the first order or primary faults the value of the fractal dimension can be obtained from the frequency magnitude relation for earthquakes our results are applied to the san andreas fault system in central california earthquake studies give d 1 90 we associate the main strand of the san andreas fault with the primary faults of our fractal system we predict that the relative velocity across the main strand is 2 93 cm yr the remainder of the relative velocity of 5 5 cm yr between the pacific and north american plates occurs on higher order faults the predicted value is in reasonably good agreement with the value 3 39 0 29 cm yr obtained from geological studies

three dimensional velocity imaging of the kachchh seismic zone gujarat india abstract to understand the causative mechanism of the continued occurrence of earthquakes in kachchh gujarat for the last six years we estimated high resolution three dimensional vp vs and vp vs structures in the aftershock zones of the 2001 mw7 7 bhuj and 2006 mw5 6 gedi earthquakes we used 13 862 p and 13 736 s wave high quality arrival times collected from the seismograms of 2303 aftershocks recorded at 5 18 three component seismograph stations during 2001 06 seismic images revealed a marked spatial variation in the velocities from 20 to 14 in vp from 12 to 13 in vs and from 12 to 12 increase in vp vs in the 0 34 km depth range beneath the bhuj aftershock zone relatively more increase in vp than vs resulting in an increase in vp vs in the crust beneath the seismically active causative fault north wagad fault nwf zone of 2001 bhuj mainshock suggests a rigid mafic crust beneath the region they also delineate an increase of 8 in vp and 14 in vs and a decrease of 4 in vp vs in the almost vertical rupture zone of the 2006 gedi earthquake extending up to 12 km depth this high velocity body associated with the gedi mainshock is inferred to be a gabbroic intrusive the banni region and the wagad uplift are found to be associated with high velocity intrusive bodies inferred to be mafic extending from 5 to 35 km depth which might have intruded during the rifting in early jurassic 160 ma aftershock activity is mainly confined to the zones characterized by high vp high vs and low vp vs ratio which might be representing the strong competent and brittle parts of the fault zone intrusive bodies that could accumulate large strain energy for generating aftershocks for more than six years it is inferred that the crustal stress concentrations associated with the intrusive bodies are contributing significant perturbation to the crustal stress regime to generate the intraplate earthquakes in the kachchh rift zone a few patches of slow vp and vs and high vp vs between 10 to 30 km depth have also been detected on the causative 45 south dipping north wagad fault nwf for the 2001 mainshock which may be attributed to the fluid filled fractured rock matrix interestingly the 2001 bhuj mainshock hypocenter is found to be associated with such a low velocity patch thus it is inferred that the occurrence of 2001 bhuj mainshock might have facilitated by the presence of fluids at hypocentral depth

fractal structure of spatial distribution of microfracturing in rock summary a constant stress fracture experiment of oshima granite was carried out at the confining pressure of 40mpa hypocentres of 2064 acoustic emissions were located during the experiment using the correlation integral we found that the spatial distribution of hypocentres of acoustic emission is a fractal and that the fractal dimension decreases with the evolution of rock fracturing the spatial distribution of earthquake s hypocentres reveals fractals ranging from regional to worldwide distribution if we extrapolate from laboratory measurements it is possible to predict the occurrence of large earthquakes by the decrease in the fractal dimension

shallow vent architecture during hybrid explosive effusive activity at cordon caulle chile 2011 12 evidence from direct observations and pyroclast textures in june 2011 an eruption of rhyolite magma began at the puyehue cordon caulle volcanic complex southern chile by january 2012 explosive activity had declined from sustained pyroclastic plinian to sub plinian fountaining to mixed gas and ash jetting punctuated by vulcanian blasts this explosive activity was accompanied by synchronous effusion of obsidian lava in a hybrid explosive effusive eruption fortuitous climatic conditions permitted ground based observation and video recording of transient vent dynamics as well as real time collection of proximal juvenile ash as it sedimented from the active plume the main eruptive vent complex and site of lava effusion was represented by two loci of vulcanian blasts within a single tephra cone containing a pancake shaped proto lava dome these blast loci each consisted of clusters of sub vents that expressed correlated shifts in eruption intensity indicating the presence of partially connected and or branching zones of high permeability within the upper conduit pyroclast textures were examined by x ray computed microtomography and their permeability was modeled by lattice boltzmann simulations the porosity 39 to 67 and darcian permeability 3 1x10 15 m2 perpendicular to fabric to 3 8x10 11 m2 parallel to fabric of fine ash emitted during ash jetting indicates that the permeable zones comprised highly sheared tube like bubbly magma and contrast with the low porosity 17 and nul permeability of bombs ejected to hundreds of metres from the vent in vulcanian blasts residual h2o content of ash 0 14 wt and two bombs 0 2 0 25 wt determined by karl fischer titration indicate degassing of this pyroclastic material to near atmospheric pressures ash textures and simple degassing vesiculation models indicate the onset of permeability by ductile processes of shear enhanced bubble coalescence in the upper 1 to 1 5 km of the conduit repeated ash jetting and vulcanian blasts indicate that such ductile processes were not sufficiently effective to accommodate all degassing requirements and additional brittle e g fragmentation events transiently assisted in maintaining an open system degassing regime that permitted long lived hybrid explosive effusive activity the eruption at cordon caulle has provided an excellent opportunity to closely observe key processes of silicic volcanism

accelerated melting of himalayan snow and ice triggers pronounced changes in a valley peatland from northern india 1 the himalayan region of northern india depends on monsoon rains together with snow and glacial melt to supply life sustaining water to one of the world s most densely populated areas here we provide high resolution pollen and diatom evidence from a peat deposit in the pinder valley that shows a synchronous and abrupt ecosystem turnover toward a wetter state in the last two centuries that exceeded changes recorded over the last three millennia contrary to expectations there was no relationship between recent proxy changes and summer monsoon precipitation strong relationships however were found with winter climate data we link this recent unprecedented wetness to marked warming at higher elevations resulting in increased seasonal runoff and associated climatic feedbacks in this snow and ice melt dominated region in contrast to the expected desiccation and decomposition of most peat systems with warming this site has instead become the wettest in its ca 3500 year history

change in the probability for earthquakes in southern california due to the landers magnitude 7 3 earthquake the landers earthquake in june 1992 redistributed stress in southern california shutting off the production of small earthquakes in some regions while increasing the seismicity in neighboring regions up to the present this earthquake also changed the ratio of small to large events in favor of more small earthquakes within about 100 kilometers of the epicenter this implies that the probabilistic estimate for future earthquakes in southern california changed because of the landers earthquake the location of the strongest increase in probability for large earthquakes in southern california was the volume that subsequently produced the largest slip in the magnitude 7 1 hector mine earthquake of october 1999

seismic imaging of the aftershock zone of the 2001 mw 7 7 bhuj earthquake india 1 detailed seismic tomography reveals that the 2001 mw 7 7 bhuj earthquake was associated with a 10 14 increase in vp and vs and a 10 decrease in vp vs in the 10 to 35 km depth range covering a 2750 km2 area beneath the aftershock zone this anomaly could be attributed to the existence of a lithological heterogeneity or a pluton of mafic composition that might have intruded during the rifting in early jurassic 160 ma the banni basin and the wagad uplift are found to be associated with high velocity intrusive bodies extending from 5 to 35 km depth a few patches of low vp and vs and high vp vs between 10 to 30 km depth have also been detected on the causative 45 south dipping north wagad fault nwf for the 2001 mainshock which may be attributed to a fluid filled fractured rock matrix

spatiotemporal variation of fractal properties in the source zone of the 2001 mw 7 7 bhuj earthquake the kachchh seismic zone ksz in gujarat india has been experiencing earthquakes since the occurrence of the 2001 m w 7 7 bhuj mainshock which led to a homogeneous catalog of 2808 earthquakes of m w 3 0 between 2001 and 2011 this enabled us to investigate the spatiotemporal variation of fractal dimensions d b values and seismic velocities in the ksz through 3d mapping of these three independent parameters the estimated fractal dimensions for the gedi fault gf events range from 0 7 to 1 0 whereas those of north wagad fault nwf events vary from 1 2 to 2 4 the b values for gf events also show smaller values in comparison to the nwf events the d values associated with events occurring in the main rupture zone mrz of the 2001 mainshock vary from 1 6 to 2 1 whereas those associated with events occurring in the surrounding unrifted zones show a wider range of variation from 1 2 to 2 4 we also observe that events associated with the nwf satisfy the aki s relationship d 2 b aki 1981 whereas events associated with gf do not follow this relationship both b and d values tend to increase with an increase in the earthquake density which could be connected with the process of disintegration of crustal rocks in the mrz where large material heterogeneities in terms of low and high seismic velocity patches are being mapped through local earthquake velocity tomography through examining the temporal changes in b and d values we notice several episodes of abnormally low b and d values associated with the occurrences of bursts of seismic activity in 2001 2005 2006 2008 and 2010 this decrease in b and d values is attributed to a reduction in rock friction in the causative fault zone at 10 35 km depths probably due to the presence of metamorphic fluids or volatile co2 thereby enhancing the probability of occurrence of stronger earthquakes

statistical physics seismogenesis and seismic hazard the scaling properties of earthquake populations show remarkable similarities to those observed at or near the critical point of other composite systems in statistical physics this has led to the development of a variety of different physical models of seismogenesis as a critical phenomenon involving locally nonlinear dynamics with simplified rheologies exhibiting instability or avalanche type behavior in a material composed of a large number of discrete elements in particular it has been suggested that earthquakes are an example of a self organized critical phenomenon analogous to a sandpile that spontaneously evolves to a critical angle of repose in response to the steady supply of new grains at the summit in this stationary state of marginal stability the distribution of avalanche energies is a power law equivalent to the gutenberg richter frequency magnitude law and the behavior is relatively insensitive to the details of the dynamics here we review the results of some of the composite physical models that have been developed to simulate seismogenesis on different scales during 1 dynamic slip on a preexisting fault 2 fault growth and 3 fault nucleation the individual physical models share some generic features such as a dynamic energy flux applied by tectonic loading at a constant strain rate strong local interactions and fluctuations generated either dynamically or by fixed material heterogeneity but they differ significantly in the details of the assumed dynamics and in the methods of numerical solution however all exhibit critical or near critical behavior with behavior quantitatively consistent with many of the observed fractal or multifractal scaling laws of brittle faulting and earthquakes including the gutenberg richter law some of the results are sensitive to the details of the dynamics and hence are not strict examples of self organized criticality nevertheless the results of these different physical models share some generic statistical properties similar to the universal behavior seen in a wide variety of critical phenomena with significant implications for practical problems in probabilistic seismic hazard evaluation in particular the notion of self organized criticality or near criticality gives a scientific rationale for the a priori assumption of stationarity used as a first step in the prediction of the future level of hazard the gutenberg richter law a power law in energy or seismic moment is found to apply only within a finite scale range both in model and natural seismicity accordingly the frequency magnitude distribution can be generalized to a gamma distribution in energy or seismic moment a power law with an exponential tail this allows extrapolations of the frequency magnitude distribution and the maximum credible magnitude to be constrained by observed seismic or tectonic moment release rates the answers to other questions raised are less clear for example the effect of the a priori assumption of a poisson process in a system with strong local interactions and the impact of zoning a potentially multifractal distribution of epicentres with smooth polygons the results of some models show premonitory patterns of seismicity which could in principle be used as mainshock precursors however there remains no consensus on both theoretical and practical grounds on the possibility or otherwise of reliable intermediate term earthquake prediction

temporal variations in the fractal properties of seismicity in the north anatolian fault zone between 31 e and 41 e we investigate the nature of temporal variations in the statistical properties of seismicity associated with the north anatolian fault zone between longitudes 31 41 e during the instrumental period 1900 1992 temporal variations in the seismicb value and the fractal correlation dimensiondc of earthquake epicenters are examined for earthquakes of magnitudems 4 5 using sliding windows of 100 consecutive events b varies temporally between 0 6 and 1 0 anddc between 0 6 and 1 4 both representing significant fluctuations above the errors in measurement technique a strong negative correlation r 0 85 is observed betweenb anddc consistent with previous observation of seismicity in japan and southern california major events early in this century ms 7 are associated with lowb and highdc respectively consistent with greater stress intensity and greater spatial clustering of epicenters both implying a greater degree of stress concentration at this time

a simple fracture mechanical model for the evolution of seismicity a simple model is presented in which a fault is represented by a one dimensional array of elements to which a remote stress is applied the fracture toughnesses of the fault elements are initially generated by a random walk function but the fracture system quickly becomes organized into a fractal set characterised by a box counting fractal dimension the slope b of the frequency magnitude distribution and the fractal dimension of the crack population are measured at each step and found to vary in a similar manner to the seismic b value and fractal dimension of earthquake epicentres the model also predicts the observed variation of b value of acoustic emissions in laboratory experiments

self organized fractal seismicity and b value of aftershocks of the 2001 bhuj earthquake in kutch india the devastating intraplate earthquake of m w 7 7 of 26 january 2001 took place along the south dipping reverse fault in the lower crust 23 km of kutch gujarat india obliterating some 14 000 people the aftershock activity has ensued for three years we analyzed 997 aftershocks of m 3 0 to study the b value and fractal correlation dimensions in time and space the b value is found to be 0 8 0 03 from the gutenberg richter relation and 0 76 0 02 from the maximum likelihood suggesting a typical value for the intraplate region the spatial correlation is 1 71 0 02 indicating that events are approaching a two dimensional region further the temporal correlation dimension is estimated to be 0 78 0 02 confirming the structure is mono fractal in time domain the depth section of b value shows a peak at 15 35 km depth range coinciding with the maximum occurrence of aftershocks 47 which is inferred as a fluid filled highly fractured rock matrix with fractures of high density it will be important to note that tomographic results also suggest a low vp low vs and a large poisson s ratio for the same depth range further confirming this inference additionally we have studied the variation of d2 s and b value with time during the first two months of aftershock activity the results show a marked negative correlation between spatial correlation dimension d2 large and b value low indicating the predominance of large events associated with weak clustering the negative correlation means the stress release along faults of a larger surface area after two months the fractal dimension d2 s and b value suggests a positive correlation implying more numerous smaller shocks with stress release along faults of a smaller surface area this would indicate a reduced probability of large magnitude earthquakes due to fragmentation of the fault zone

the identification of mantle reflections below hungary from deep seismic profiling abstract in the 1970 s the eotvos lorand geophysical institute performed seismic reflection deep sounding experiments with multiple coverage in several parts of the pannonian basin posgay 1975 one of the most interesting results was that arrivals were received in the time range corresponding to the depth of the asthenosphere they were interpreted as reflections posgay et al 1981 conspicuous arrivals from the time range of the asthenosphere 15 20 s were also received along the pannonian geotraverse in 1987 in the majority of sections published in other countries the upper mantle seems to be transparent the present paper discusses investigations and preliminary results which lead to the conclusion that this apparent transparency is due to the frequency range below 10 hz being neglected in both signal generation and recording in most deep continental reflection surveys the seismogeological conditions of the pannonian basin are certainly favourable for reflection studies of the upper mantle the correctness of the assumption that arrivals from the time range of the asthenosphere are primary reflections is subjected to further investigation and conclusions are made concerning the structure of the asthenosphere

surface area porosity and water adsorption properties of fine volcanic ash particles our understanding on how ash particles in volcanic plumes react with coexisting gases and aerosols is still rudimentary despite the importance of these reactions in influencing the chemistry and dynamics of a plume in this study six samples of fine ash 500 a all the specimens had similar pore size distributions with a small peak centered around 50 a these findings suggest that fine ash particles have relatively undifferentiated surface textures irrespective of the chemical composition and eruption type adsorption isotherms for water vapour revealed that the capacity of the ash samples for water adsorption is systematically larger than predicted from the nitrogen adsorption a s values enhanced reactivity of the ash surface towards water may result from i hydration of bulk ash constituents ii hydration of surface compounds and or iii hydroxylation of the surface of the ash the later mechanism may lead to irreversible retention of water based on these experiments we predict that volcanic ash is covered by a complete monolayer of water under ambient atmospheric conditions in addition capillary condensation within ash pores should allow for deposition of condensed water on to ash particles before water reaches saturation in the plume the total mass of water vapour retained by 1 g of fine ash at 0 95 relative water vapour pressure is calculated to be 10 2 g some volcanic implications of this study are discussed

from pull apart to the rifting process the formation of the pannonian basin abstract during the middle and the late miocene intra carpathian basins have developed south and west of the carpathian arc these basins are bounded by normal faults and connected by conjugate shear zones sinistral strike slip fault systems trend ne sw whereas dextral ones trend nw se by means of geometrical analyses of fault system and paleostress tensor determinations it has been possible to consistently reconstruct the succession of tectonic events in the hungarian mountains the two main stages in the structural development of the intra carpathian basins are 1 1 the initiation of pull apart basins along conjugate shear zones in a n s compressional and e w extensional regime and 2 2 the development of these basins in a tectonic regime characterized by a dominant e w trending extension

fractal dimensions of blocks using a box counting technique for the 2001 bhuj earthquake gujarat india several destructive earthquakes have occurred in the kachchh region of gujarat during the past two centuries among them allah bund earthquake m7 8 in 1819 anjar earthquake m6 in 1956 and the recent bhuj earthquake m7 6 in 2001 the anjar earthquake was on kmf kachchh mainland fault and the recent bhuj events were caused by a hidden fault north of kmf the present study discusses the fractal analysis of tectonics governing seismic activity in the region the region has been divided into five blocks and the fractal dimension of each block has been calculated using the box counting technique the results show significantly low value of fractal dimension of the kachchh rift block consisting of the kmf compared to the other surrounding blocks which also contain faults and rifts of higher fractal dimension this indicates that the cause of earthquakes in this block may be asperities and barriers however the predominance of aftershocks over foreshocks signifies that barriers may be the main cause the other results such as the lower value of dimension of fault clustering show that the kachchh rift block has faults which are distributed in a clustered manner in this context the seismicity of this block seems to be high

ash storms impacts of wind remobilised volcanic ash on rural communities and agriculture following the 1991 hudson eruption southern patagonia chile tephra fall from the august 1991 eruption of volcan hudson affected some 100 000 km 2 of patagonia and was almost immediately reworked by strong winds creating billowing clouds of remobilised ash or ash storms the immediate impacts on agriculture and rural communities were severe but were then greatly exacerbated by continuing ash storms this paper describes the findings of a 3 week study tour of the diverse environments of southern patagonia affected by ash storms with an emphasis on determining the impacts of repeated ash storms on agriculture and local practices that were developed in an attempt to mitigate these impacts ash storms produce similar effects to initial tephra eruptions prolonged for considerable periods these have included the burial of farmland under dune deposits abrasion of vegetation and contamination of feed supplies with fine ash these impacts can then cause problems for grazing animals such as starvation severe tooth abrasion gastrointestinal problems corneal abrasion and blindness and exhaustion if sheep fleeces become laden with ash in addition ash storms have led to exacerbated soil erosion human health impacts increased cleanup requirements sedimentation in irrigation canals and disruption of aviation and land transport ash deposits were naturally stabilised most rapidly in areas with high rainfall 1 500 mm year through compaction and enhanced vegetation growth stabilisation was slowest in windy semi arid regions destruction of vegetation and

cenozoic active margin and shallow cascades structure cocorp results from western oregon two deep seismic reflection profiles totaling 98 km were recorded by the consortium for continental reflection profiling cocorp in western oregon in 1984 providing some of the first onshore deep seismic reflection data from the forearc and arc of an active convergent margin these data are of lower quality than most cocorp data but when combined with other geological and geophysical data they provide some useful insights into the subduction zone beneath oregon and into extensional structures in the cascades line 1 crossed the eocene sediments and underlying pillow basalts of the coast range and western willamette valley reflections from the willamette valley clearly define the lower and western boundary of flat lying rhythmically bedded eocene sediments these sediments appear to be underlain by as much as 8 km of seismically transparent eocene pillow basalts layered reflections at depths of 8 16 km may indicate a remnant crust upon which the eocene pillow basalts were erupted east dipping reflections at depths of 35 40 km may represent the decollement above the subducting juan de fuca plate oregon line 2 crosses the cenozoic volcanic arc terrains of the western and high cascades interpretation of cocorp seismic data suggests modification of existing models for normal faulting that postulate a symmetric graben or grabens in the cascades of oregon in the high cascades along cocorp oregon line 2 reflections suggest a large gently west dipping half graben with major offset only on the west side of the range the seismic reflection data along with other geological and geophysical data suggest that the high cascades were built on a series of blocks rather than a single graben the blocks were differentially faulted during the pliocene seismic data from the western cascades indicate several normal faults with down to the east offset including a major previously unidentified fault of probable miocene age

seismic imaging of the 2001 bhuj mw7 7 earthquake source zone b value fractal dimension and seismic velocity tomography studies abstract we use precisely located aftershocks of the 2001 mw7 7 bhuj earthquake 2001 2009 to explore the structure of the kachchh seismic zone by mapping the 3 d distributions of b value fractal dimension d and seismic velocities from frequency magnitude analysis we find that the catalog is complete above mw 3 0 thus we analyze 2159 aftershocks with mw 3 0 to estimate the 3 d distribution of b value and fractal dimensions using maximum likelihood and spatial correlation dimension approaches respectively our results show an area of high b d and vp vs ratio values at 15 35 km depth in the main rupture zone mrz while relatively low b and d values characterize the surrounding rigid regions and gedi fault gf zone we propose that higher material heterogeneities in the vicinity of the mrz and or circulation of deep aqueous fluid volatile co2 is the main cause of the increased b d and vp vs ratio values at 15 35 km depth seismic velocity images also show some low velocity zones continuing in to the deep lower crust supporting the existence of circulation of deep aqueous fluid volatile co2 in the region probably released from the eclogitasation of olivine rich lower crustal rocks the presence of number of high and low velocity patches further reveals the heterogeneous and fractured nature of the mrz interestingly we observe that aki 1981 s relation d 2b is not valid for the spatial b d correlation of the events in the gf d2 1 2b zone however the events in the mrz d2 1 7b show a fair agreement with the d 2b relationship while the earthquakes associated with the remaining parts of the aftershock zone d2 1 95b show a strong correlation with the aki 1981 s relationship thus we infer that the remaining parts of the aftershock zone are probably behaving like locked un ruptured zones where larger stresses accumulate we also propose that deep fluid involvement may play a key role in generating seismic activity in the mrz therefore a similar episode of deep fluid inflow could play a crucial role in causing the next strong earthquakes in the surrounding blocks of nwf

on varying b values with depth results from computer intensive tests for southern california summary the gutenberg richter b value is thought to reflect the stress conditions in the crust therefore spatial and or temporal variations of the b value can provide important information regarding crustal tectonics we investigate the variation of b value with depth in seven selected areas of southern california a previous study provided a detailed mapping of the variations of b with depth in california our study is less systematic than this study our approach is more similar to the regional one used by mori abercrombie in comparison to these previous studies our investigation indicates that the variability of b is often not statistically significant and that the decrease of b with depth should be interpreted with caution the seismic catalogues used are subsets of a set of about 100 000 seismic events recorded by the southern california seismic network scsn and relocated by richards dinger shearer we study the performance of utsu s test compared to bootstrap tests for comparison of b values the results of our investigation also raise the question of the relevancy of utsu s test when comparing b values both simulations and real cases show that the utsu s test is biased towards rejection of the null hypothesis in favour of the hypothesis that b values are significantly different

environmental hazards of fluoride in volcanic ash a case study from ruapehu volcano new zealand abstract the vent hosted hydrothermal system of ruapehu volcano is normally covered by a c 10 million m3 acidic crater lake where volcanic gases accumulate through analysis of eruption observations granulometry mineralogy and chemistry of volcanic ash from the 1995 1996 ruapehu eruptions we report on the varying influences on environmental hazards associated with the deposits all measured parameters are more dependent on the eruptive style than on distance from the vent early phreatic and phreatomagmatic eruption phases from crater lakes similar to that on ruapehu are likely to contain the greatest concentrations of environmentally significant elements especially sulphur and fluoride these elements are contained within altered xenolithic material extracted from the hydrothermal system by steam explosions as well as in residue hydrothermal fluids adsorbed on to particle surfaces in particular total f in the ash may be enriched by a factor of 6 relative to original magmatic contents although immediately soluble f does not show such dramatic increases highly soluble naf and casif6 phases demonstrated to be the carriers of available f in purely magmatic eruptive systems are probably not dominant in the products of phreatomagmatic eruptions through hydrothermal systems instead slowly soluble compounds such as caf2 alf3 and ca5 po4 3f dominate fluoride in these phases is released over longer periods where only one third is leached in a single 24 h water extraction this implies that estimation of soluble f in such ashes based on a single leach leads to underestimation of the f impact especially of a potential longer term environmental hazard in addition a large proportion of the total f in the ash is apparently soluble in the digestive system of grazing animals in the ruapehu case this led to several thousand sheep deaths from fluorosis

neogene extensional collapse in the western mediterranean betic rif alpine orogenic belt implications for the genesis of the gilbraltar arc and magmatic activity the betic rif orogenic belt crops out in the western mediterranean and constitutes the westernmost part of the alpine edifice the building up of this belt by compressional nappe tectonics occured during a series of alpine deformational episodes subsequent neogene extension resulted from the collapse of the previous compressional edifice through major extensional detachment systems this episode was accompanied by cafe alkaline to shoshonitic and lamproitic volcanism tectonic denudation of metamorphic core complexes and emplacement of peridotite bodies as a final consequence of the evolution of detachment systems furthermore we relate the generation of the gibraltar arc and the opening of the alboran sea to this major extensional event finally two main stages of tectonic denudation of these detachment systems are defined 1 nevado filabride stage with ex humation of metamorphic core complexes and 2 ronda beni boussera stage with a more advanced degree of denudation leading to the exhumation of upper mantle peridotites which may be tentatively termed mantle core complexes

assessment of leachable elements in volcanic ashfall a review and evaluation of a standardized protocol for ash hazard characterization abstract volcanic ash presents a widespread and common hazard during and after eruptions complex interactions between solid ash surfaces and volcanic gases lead to the formation of soluble salts that may be mobilized in aqueous environments a variety of stakeholders may be concerned about the effects of ash on human and animal health drinking water supplies crops soils and surface runoff as part of the immediate emergency response rapid dissemination of information regarding potentially hazardous concentrations of soluble species is critical however substantial variability in the methods used to characterize leachable elements makes it challenging to compare datasets and eruption impacts to address these challenges the international volcanic health hazard network www ivhhn org organized a two day workshop to define appropriate methods for hazard assessment the outcome of this workshop was a consensus protocol for analysis of volcanic ash samples for rapid assessment of hazards from leachable elements which was subsequently ratified by leading volcanological organizations the purpose of this protocol is to recommend clear standard and reliable methods applicable to a range of purposes during eruption response such as assessing impacts on drinking water supplies and ingestion hazards to livestock and also applicable to research purposes where possible it is intended that the methods make use of commonly available equipment and require little training to evaluate method transferability an interlaboratory comparison exercise was organized among six laboratories worldwide each laboratory received a split of pristine ash and independently analyzed it according to the protocol for a wide range of elements collated results indicate good repeatability and reproducibility for most elements thus indicating that the development of this protocol is a useful step towards providing standardized and reliable methods for ash hazard characterization in this article we review recent ash leachate studies report the outcomes of the comparison exercise and present a revised and updated protocol based on the experiences and recommendations of the exercise participants the adoption of standardized methods will improve and facilitate the comparability of results among studies and enable the ongoing development of a global database of leachate information relevant for informing volcanic health hazards assessment

mapping the b value anomaly at 100 km depth in the alaska and new zealand subduction zones a positive anomaly in the frequency magnitude distribution b value is detected at approximately 90 100 km depth in two subduction zones the b value in this anomalous zone is 40 higher than in adjacent volumes we use regional catalogs with a magnitude of completeness of 2 6 central alaska and cook inlet 2 0 shumagin islands and 3 5 new zealand to resolve the b value as a function of space in more detail we project all earthquakes onto planes perpendicular to the strike of the slab these cross section views of the b value distribution locate the high b value anomalies at a depth of 90 100 km on the upper surface of the wadati benioff zone at these depths slab dehydration may increase pore pressure thus lowering the effective stress and increasing the b value increased pore pressure would also lower the liquidus in the overlying asthenosphere giving rise to the volcanism that occurs directly above this zone

variations in the frequency magnitude distribution with depth in two volcanic areas mount st helens washington and mt spurr alaska the frequency magnitude distribution of earthquakes characterized using the b value is examined as a function of space beneath mount st helens 1988 1996 and mt spurr 1991 1995 at mount st helens two volumes of anomalously high b b 1 3 can be observed at depths of 2 6 3 6 km below the crater floor and below 6 4 km these anomalies coincide with 1 the depth of vesiculation of ascending magma and 2 the suggested location of a magma chamber at mount st helens study of mt spurr reveals an area of high b value b 1 3 at a depth of about 2 3 4 5 km below the crater floor of the active vent crater peak we propose that the higher material heterogeneity in the vicinity of a magma chamber or conduit due to vesiculation of the ascending magma is the main cause of the increased b value at shallow depths alternatively interaction of magma with groundwater may have increased pore pressure and lowered the effective stress the deeper anomaly at mount st helens is likely caused by high thermal stress gradients in the vicinity of the magma chamber our results indicate that detailed mapping of the frequency magnitude distribution can be used as a tool to trace vesiculation and locate active magma chambers

thermal models of the middle america trench at the nicoya peninsula costa rica 1 we present thermal models of the 24 ma cocos plate subducting under the caribbean plate at the nicoya peninsula costa rica our modeling incorporates the effect of hydrothermal cooling of the seafloor and the absence of an accretionary prism initial geotherms of the incoming plate representing different effective cooling depths of hydrothermal circulation affect the thermal structure and temperatures along the main subduction thrust excluding the deforming prism results in a higher heat flow immediately landward of the trench than previous models and therefore significant frictional heating is not required conductive plate cooling over predicts heat flow across the frontal forearc with no or very low frictional heating models with hydrothermal cooling to depths of 2 km under predicts the heat flow comparisons with recently determined hypocenter locations indicate that the updip limit of seismicity is consistent with temperatures between 100 150 c but there are large along strike variations in both the seismicity and thermal regime

complex dynamics of small moderate volcanic events the example of the 2011 rhyolitic cordon caulle eruption chile after decades of repose puyehue cordon caulle volcano chile erupted in june 2011 following a month of continuously increasing seismic activity the eruption dispersed a large volume of rhyolitic tephra over a wide area and was characterized by complex dynamics during the initial climactic phase of the eruption 24 30 h on 4 5 june 11 14 km high plumes dispersed most of the erupted tephra eastward towards argentina reaching as far as the atlantic ocean this first eruptive phase was followed by activity of lower intensity leading to the development of a complex stratigraphic sequence mainly due to rapid shifts in wind direction and eruptive style the resulting tephra deposits consist of 13 main layers grouped into four units each layer was characterized based on its dispersal direction sedimentological features and on the main characteristics of the juvenile fraction texture density petrography chemistry the lowest part of the eruptive sequence unit i corresponding to the tephra emitted between 4 and 5 june is composed of alternating lapilli layers with a total estimated volume of ca 0 75 km3 these layers record the highest intensity phase during which a bent over plume dispersed tephra towards the southeast east with negligible up wind sedimentation products emitted during 5 6 june unit ii signaled an abrupt shift in wind direction towards the north leading to the deposition of a coarse ash deposit in the northern sector ca 0 21 km3 in volume followed by a resumption of easterly directed winds a third phase unit iii began on 7 june and resulted in tephra deposits in the eastern sector and ballistic bombs around the vent area a final phase unit iv started after 15 june and was characterized by the emission of fine grained white tephra from ash charged plumes during low level activity and the extrusion of a viscous lava flow timing and duration of the first eruptive phases were constrained based on comparison of the dispersal of the main tephra layers with satellite images showing that most of the tephra was emitted during the first 72 h of the event the analyzed juvenile material tightly clusters within the rhyolitic field with negligible chemical variations through the eruptive sequence textural observations reveal that changes in eruption intensity and consequently in magma ascent velocity within the conduit and complex interactions between gas rich and gas depleted magma portions during ascent resulted in vesicular clasts with variable degrees of shear localization and possibly in the large heterogeneity of the juvenile material

research into the multifractal of earthquake spatial distribution abstract the spectra dq of the henon map are calculated and analyzed using the extended g p method the key problems such as the scaling range determination data sample selection and the calculation method are also discussed results show that the scaling radius r should be less than about 1 3 of the diameter of the research object e g the earthquake region for reducing the boundary effect and a sample volume of 500 may be sufficient for the small absolute of the q value we also calculate and study the whole multifractal spectra dq of available seismic data for example the catalogue of earthquakes which have the occurred in tangshan region north china the results show that there is a multifractal in the data and that the dq value showed a remarkable variation with time before the large tangshan earthquake of july 1976

remobilized cordon caulle 2011 tephra deposits in north patagonian watersheds resedimentation at deltaic environments and its implications abstract the argentinean side of the andean north patagonia is drained by several fluvio lacustrine systems flowing eastwards from their headwaters at the andes mountains towards large glacial lakes these watersheds are recurrently affected by the deposition of tephra erupted from the many active andean volcanos located in the southern volcanic zone this research focusses on two fluvial systems pireco and totoral pt located in nahuel huapi national park which were severely impacted by the cordon caulle 2011 eruption cc2011 we investigate particularly the resedimentation of pyroclastic materials on their lacustrine deltas and its potential implications considering 1 the deltas morphology and 2 mass wasting processes developing at the delta fronts original tephra fall deposits were registered at nahuel huapi national park in 2011 based on the isopach map we performed a gis based volume estimation of the deposit for the studied watersheds delta plain progradation from 2011 to 2017 was analyzed from satellite images we studied the temporal evolution of the subaqueous morphology and mass wasting processes at the delta fronts using high resolution bathymetric grids registered in 2011 2014 and 2017 during june 2011 the studied watersheds received a tephra input of 72 x 106m3 the significant progradation experienced by both deltas especially during the first month of the eruption was favored by 1 abundant precipitation at the watersheds concomitant to heavy tephra deposition and 2 the pre existing subaqueous morphology characterized by a wide shallow terrace bordering pt delta plains about six years after the beginning of cc2011 6 of the tephra fallen over the entire basins had been resedimented at the delta environments terrace and delta front totalizing 3 x 106t evidence of pre eruption and or co eruptive mass wasting processes occurring at pt delta fronts was found on november 2011 up to 30 m thick pyroclastic deposits were accumulated at pt delta fronts since november 2011 burying mass wasting features at the upper delta fronts a suspended sediment collector installed at the prodelta in 2012 detected hyperpycnal currents transporting pyroclastic materials these currents probably explain the development of mass movements at high depths such as the one that displaced and filled up the bottom sediment trap this frontally confined landslide initiated at a depth of 60 m and involved tephra and organic materials deposited at the lower part of totoral delta front because of their recent deposition and loose consolidation we propose that fresh tephra deposits at pt delta fronts could become particularly unstable and represent a potential hazard to failure especially if a strong earthquake affects the study area in the next years a landslide induced tsunami wave generated at these deltas would impact rural settlements located along the coasts of brazo rincon and probably reach the coastal city of villa la angostura

earth science microseismicity data forecast rupture area on 28 september 2004 there was an earthquake of magnitude 6 0 at parkfield california here we show that the size distribution of the micro earthquakes recorded in the decades before the main shock occurred allowed an accurate forecast of its eventual rupture area applying this approach to other well monitored faults should improve earthquake hazard assessment in future

mapping active magma chambers by b values beneath the off ito volcano japan the b value of the frequency magnitude relation and thus the mean magnitude in the off ito volcanic area is not uniform based on detailed b value tomography using about 10 000 events in an area of 10 km radius and in the upper 15 km of the crust a high b value anomaly b 15 below 7 km depth and with a radius of about 2 km located below the coast southeast of ito contrasts with lower values of typically b 0 7 north of it and at shallower depths on the basis of surface deformations a tensile crack dislocation source was located above 7 km depth thus we surmise that the magma chamber in the off ito area was located below 7 km depth the correlation of a high b value anomaly with this model supports our hypothesis that active magma chambers may be mapped by high b value anomalies the magma body may be described as consisting of two parts a lower well established chamber below 11 km depth and a shallower part 11 7 km depth the b value in the volume surrounding the magma chamber increased from 0 7 during the 1980s to 1 5 during the earthquake swarms of the 1990s this may reflect a trend of increasing crack density due to the intrusion activity

sedimentation of long lasting wind affected volcanic plumes the example of the 2011 rhyolitic cordon caulle eruption chile sedimentation processes and fragmentation mechanisms during explosive volcanic eruptions can be constrained based on detailed analysis of grain size variations of tephra deposits with distance from vent and total grain size distribution tgsd grain size studies strongly rely on deposit exposure and in case of long lasting eruptions can be complicated by the intricate interplay between eruptive style atmospheric conditions particle accumulation and deposit erosion the 2011 cordon caulle eruption chile represents an ideals laboratory for the study of long lasting eruptions thanks to the good deposit accessibility in medial to distal area all layers analyzed are mostly characterized by bimodal grain size distributions with both the modes and the fraction of the coarse subpopulation decreasing rapidly with distance from vent and those of the fine subpopulation being mostly stable due to gradually changing wind direction the two subpopulations characterizing the deposit of the first 2 days of the eruption are asymmetrically distributed with respect to the dispersal axis the tgsd of the climactic phase is also bimodal with the coarse subpopulation representing 90 wt of the whole distribution polymodality of individual samples is related to size selective sedimentation processes while polymodality of the tgsd is mostly related to the complex internal texture e g size and shape of vesicles of the most abundant juvenile clasts the most representative tgsd could be derived based on a combination of the voronoi tessellation with a detailed analysis of the thinning trend of individual size categories finally preferential breakage of coarse pumices on ground impact was inferred from the study of particle terminal velocity

environmental effects of ashfall in argentina from the 2008 chaiten volcanic eruption analyses of air water and vegetation samples collected in june 2008 offer new insights into the environmental effects of the may 2008 chaiten eruption on argentina which was subject to significant ashfall between 42 s and 46 s results from air filtration in the ash affected town of esquel with samples analysed by gravimetry and scanning electron microscopy show the total mass of resuspended ash in the air is well correlated with traffic activity however this variation is primarily related to varying amounts of the largest particles with little variation in the amounts of fine ash particles i e d results from water and vegetation sampling with samples analysed by inductively coupled plasma mass spectrometry and ion chromatography indicate that ashfall resulted in significant compositional changes in ephemeral lakes and coiron grass festuca pallescens for b cd zn tl cu and ni there are strong linear correlations between concentrations and ash thickness where 2 mm in both datasets these results suggest that the eruption of chaiten led to significant changes in the concentrations of trace volatile elements within the environment analysis of vegetation samples collected in january 2009 indicates that the elevated element concentrations in coiron grass persisted for 8 months these results offer insights into the environmental fate of volatile trace elements emitted during volcanic eruptions

volcanic ash leachate compositions and assessment of health and agricultural hazards from 2012 hydrothermal eruptions tongariro new zealand abstract after almost 80 years of quiescence the upper te maari vent on mt tongariro erupted suddenly at 2352 h nz time on 6 august 2012 the short lived hydrothermal eruption distributed a fine ash of minor volume 5 10 5 m 3 over 200 km from source the threat of further eruptions prompted an investigation of the possible health and agricultural impacts of any future eruptions from this volcano particularly since the most recent large scale ash falls in new zealand in 1995 1996 had generated significant agricultural problems including livestock deaths deposited ash was sampled between 5 and 200 km from the volcano as soon as possible after the eruption two sub lobes of ash were identified from different vent areas and displayed subtly different leaching properties the first was an initial small lobe directed nne likely formed from drifting low level clouds associated with the initial lateral explosive blast and surges the main fall lobe directed eastward was sourced from a short lived vertical plume that rose up to c 8 km ash from the initial fall lobe had higher concentrations of f and al in single step leaches as well as in the totals of three sequential extractions further the initial lobe showed a higher proportion of soluble f and al extracted in the first leach compared to totals a linear relationship between concentrations of al and f in single leaches from the 6 august eruption was highly significant pearson correlation coefficient r 0 987 for 1 20 leaching ratios and r 0 971 for 1 100 suggesting the presence of soluble alumino fluoride complexes alf x 3 x an even more significant 1 1 ratio is displayed for the largest concentration leached ions of ca and so 4 which correspond to the presence of crystalline gypsum throughout the newly excavated hydrothermal system although no fresh magma was erupted in this event a shallow intrusion prior to the hydrothermal explosion apparently provided significant contents of volcanic gas that was dissolved within the hydrothermal fluids and adhering to ejected particles this and the ubiquitous presence of gypsum dominated the soluble components of these ash deposits leading to a complex leaching profile the leaching study carried out here showed that agricultural and human health hazard assessment particularly of f and s is not straightforward particularly because f solubility may be complex and not well characterised by simple leaching studies in the case of s which is agriculturally important saturation effects are apparent using normal leaching protocols and also imply a need for modification of standard methods

spatial analysis of mount st helens tephra leachate compositions implications for future sampling strategies tephra particles in physically and chemically evolving volcanic plumes and clouds carry soluble sulphate and halide salts to the earth s surface ultimately depositing volcanogenic compounds into terrestrial or aquatic environments upon leaching of tephra in water these salts dissolve rapidly previous studies have investigated the spatial and temporal variability of tephra leachate compositions during an eruption in order to gain insight into the mechanisms of gas tephra interaction which emplace those salts however the leachate datasets analysed are typically small and may poorly represent the natural variability and complexity of tephra deposits here we have conducted a retrospective analysis of published leachate analyses from the 18 may 1980 eruption of mount st helens washington analysing the spatial structure of the concentrations and relative abundances of soluble ca cl na and s across the deposits we have identified two spatial features 1 concentrated tephra leachate compositions in blast deposits to the north of the volcano and 2 low s cl and na cl ratios around the washington idaho border by reference to the bulk chemistry and granulometry of the deposit and to current knowledge of gas tephra interactions we suggest that the proximal enrichments are the product of pre eruptive gas uptake during cryptodome emplacement we speculate that the low s cl and na cl ratios reflect a combination of compositional dependences on high temperature so2 uptake and preferential hcl uptake by hydrometeor tephra aggregates manifested in terrestrial deposits by tephra sedimentation and fallout patterns however despite our interrogation of the most exhaustive tephra leachate dataset available it has become clear in this effort that more detailed insights into gas tephra interaction mechanisms are prevented by the prevalent poor temporal and spatial representativeness of the collated data and the limited characterisation of the tephra deposits future leachate studies should aim to extensively sample across tephra deposit limits whilst simultaneously characterising deposit stratigraphy and tephra chemistry mineralogy and granulometry taking steps to ensure the quality and comparability of collected leachate datasets

eruptive history geochronology and magmatic evolution of the puyehue cordon caulle volcanic complex chile forty three 40 ar 39 ar age determinations of lava flows domes ignimbrites and dikes plus 14 c dates from seven distal tephra layers combined with stratigraphy geochemistry and sr and th isotope data establish an eruptive chronology for the puyehue cordon caulle volcanic complex at 40 5 s in the andean southern volcanic zone svz the complex preserves 131 km 3 of lava and tephra that erupted from numerous vents widely separated in time and space approximately 80 of the total volume consists of basaltic to andesitic lava that formed two broad shield volcanoes between 314 and 70 ka the modern puyehue stratovolcano was built on the southerly shield during the past 69 k y following a hiatus of 25 k y puyehue has erupted 15 km 3 of basaltic to rhyolitic magma that spans the entire compositional range found in the southern svz and evolved via at least six phases including 1 basaltic andesitic to dacitic lavas between 69 and 32 ka 2 a shift to bimodal magma compositions that is first expressed by a rhyodacite mingled with inclusions of mgo rich basaltic andesite at 34 ka 3 dacitic to rhyolitic flows and domes from 19 to 12 ka 4 basaltic to basaltic andesitic flows between 15 and 12 ka 5 subsequent rhyolitic dome growth in several effusive and explosive stages between 7 and 5 ka followed by 6 a powerful series of phreatomagmatic and sub plinian eruptions at ca 1 1 ka that obliterated the preceding rhyolite domes and formed the present 2 5 km diameter 280 m deep summit crater along the cordon caulle fissure zone 5 km 3 of rhyodacitic to rhyolitic lavas domes and cones have formed during the past 16 5 k y including explosive and effusive eruptions in 1921 1922 and 1960 eruptive rates were nonuniform over time with background growth at 0 04 km 3 k y or less punctuated by spurts at up to 0 90 km 3 k y the time averaged rate 0 42 km 3 k y is nearly double that at the tatara san pedro complex 500 km to the north during the past 300 k y these findings indicate that within a single arc the magmatic and eruptive fluxes at individual frontal volcanoes can be highly variable the last three stratocone building events on puyehue began during periods of deglaciation suggesting a relationship between unloading of ice and ease of magma ascent puyehue basalt exhibits subtle changes in 238 u 230 th 87 sr 86 sr and trace element composition over time that signal shifts in the composition and degree of melting of the mantle wedge or the extent to which basalt was modified by assimilation of heterogeneous crustal melts the complex has become exceptionally bimodal and more explosive over time with recent rhyolites evolving by extreme crystal fractionation of mafic magma and lesser volumes of andesite and dacite created via mixing of rhyolite and basalt despite the high flux of basalt during the past 300 k y no large silicic magma reservoir formed in the upper crust instead 238 u 230 th data favor rapid ascent of several small bodies of basaltic and silicic magma from the lower crust promoted perhaps by conduits that reflect strike slip faulting beneath the complex

potential impacts of tephra fallout from a large scale explosive eruption at sakurajima volcano japan we present an exposure analysis of infrastructure and lifeline to tephra fallout for a future large scale explosive eruption of sakurajima volcano an eruption scenario is identified based on the field characterization of the last subplinian eruption at sakurajima and a review of reports of the eruptions that occurred in the past six centuries a scenario based probabilistic hazard assessment is performed using the tephra2 model considering various eruption durations to reflect complex eruptive sequences of all considered reference eruptions a quantitative exposure analysis of infrastructures and lifelines is presented primarily using open access data the post event impact assessment of magill et al earth planets space 65 677 698 2013 after the 2011 vei 2 eruption of shinmoedake is used to discuss the vulnerability and the resilience of infrastructures during a future large eruption of sakurajima results indicate a main eastward dispersal with longer eruption durations increasing the probability of tephra accumulation in proximal areas and reducing it in distal areas the exposure analysis reveals that 2300 km of road network 18 km2 of urban area and 306 km2 of agricultural land have a 50 probability of being affected by an accumulation of tephra of 1 kg m2 a simple qualitative exposure analysis suggests that the municipalities of kagoshima kanoya and tarumizu are the most likely to suffer impacts finally the 2011 vei 2 eruption of shinmoedake demonstrated that the already implemented mitigation strategies have increased resilience and improved recovery of affected infrastructures nevertheless the extent to which these mitigation actions will perform during the vei 4 eruption presented here is unclear and our hazard assessment points to possible damages on the sakurajima peninsula and the neighboring municipality of tarumizu

a reinterpretation of the precursory seismic b value anomaly from fracture mechanics summary a new model is presented which can explain the major temporal fluctuations in seismic b value in terms of the underlying physical processes of time varying applied stress and crack growth under conditions of constant strain rate the model predicts two minima in the b value separated by a temporary maximum of inflexion point a corollary being that a single broad maximum would be expected in scattering attenuation these fluctuations in b value are consistent with reported intermediate term and short term earthquake precursors separated by a period of seismic quiescence we present preliminary results from controlled laboratory experiments and report recent field observations both of which are consistent with the predicted form and in particular exhibit the distinctive second short term anomaly which reaches a value bc 0 5 during the critical phase

3 d spatial variation of b values of magnitude frequency distribution beneath the kanto district japan summary a method is developed for estimation and interpolation of 6 values in space a 3 d spline function is considered for the logarithm of the 6 value at each location in the space since many parameters for the spline coefficients are required to obtain a sensible estimate of the spatial variation of 6 values we consider the penalized log likelihood with the standard roughness penalties for the spline function further the error bands of the b value estimation at each location can be calculated using the current method the spatial distribution of 6 values beneath the kanto district down to the depth of 100km is determined based on hypocentral data of microearthquakes from the kanto tokai observational network of the national research center for disaster prevention the stability of the estimated pattern is checked by comparing with the results using alternative cut off magnitudes this is further ensured by comparison with the result obtained by an alternative model using equally divided blocks on the whole the vertical change in 6 value is greater than the horizontal one it is high in the crust of the eurasian plate especially above the upper boundary of the subducting pacific plate and in the northwest part or the volcanic area in the kanto district a steep decrease of the 6 values is seen to take place in perpendicular direction to the subducting pacific plate boundary also a similar change is seen in the boundary between the eurasian and phillippine sea plates especially beneath the southern part of the kanto plain the 6 value is low in the upper boundary of the subducting plates but high in the lower plane of the double seismic zone in the pacific plate it appears that even within a narrow area of aftershocks the 6 value can change significantly it is also found that the variation of the 6 value estimate is in good agreement with the structure of seismic wave fractional velocity perturbations the regions of high and low 6 values correspond respectively to the lower and higher parts of the p wave velocity the similar relationship is seen with the spatial structure of the seismic wave attenuation

discussion of origins of hinterland basins to the rif betic cordillera and carpathians abstract the hinterland basins of the rif betic cordillera western alboran sea and the carpathians pannonian basin are in part composed of a thick in excess of 3 4 km thermal sag basin sequence the underlying crust has been thinned to 25 km in parts of the pannonian basin and to 15 km in parts of the alboran sea modern tectonic models for these areas envision tectonic collision and thickening of the crust followed by crustal thinning either by gravitational collapse back arc extension or a combination of the two contemporaneous with thrusting basin and range type extension has been envisioned for parts of these extensional collapse systems extensional features are common and they interact in a complex way with strike slip systems flexural cantilever modelling agrees with earlier mckenzie type pure shear modelling of the extensional systems in suggesting that extension alone cannot generate sufficient thermal decay to explain the great thickness of the sag basins associated with the alboran sea and pannonian basin consequently it is suggested that uplift of the asthenosphere accompanying subduction roll back is an important factor in the evolution of these basins roll back of the mantle lithosphere permits hot asthenospheric mantle to upwell and lie close to the base of the crust initially uplift and erosion of the crust overlying the asthenosphere occurs as the thermal perturbation cools the crust thermally subsides to produce a large sag basin

the immediate environmental effects of tephra emission the earth s history is punctuated by large explosive eruptions that eject large quantities of magma and silicate rock fragments into the atmosphere these tephra particles can sometimes be dispersed across millions of square kilometres or even entire continents the interaction of tephra with or in receiving environments may induce an array of physical chemical and biological effects the consequences for affected systems and any dependent communities may be chronic and localised in the event of frequent small eruptions while larger and rarer events may have acute regional scale impacts it is therefore necessary to document the range of possible impacts that tephra may induce in receiving environments and any resulting effects in interconnected systems we collate results from many studies to offer a detailed multidisciplinary and interdisciplinary review of the immediate post eruptive effects of tephra emission into the atmosphere onto vegetation soil or ice snow surfaces and in aquatic systems we further consider the repercussions that may be induced in the weeks to years afterwards in the atmosphere tephra can influence cloud properties and air chemistry by acting as ice nuclei in or by offering sites for heterogeneous reactions respectively tephra on vegetation causes physical damage and sustained coverage may elicit longer term physiological responses tephra deposits on soils may alter their capacity to exchange gas water and heat with the atmosphere or may have a specific chemical effect such as nutrient input or acidification on sensitive soils tephra deposition onto snow or ice may affect ablation rates rivers and lakes may experience turbidity increases and changes in their morphology as a result of fallout and prolonged months or years erosion from the tephra covered catchment in the first weeks after deposition tephra leaching may affect river chemistry the abundance and speciation of phytoplankton populations in lakes may be altered by tephra induced changes in water chemistry or sediment water nutrient cycling in the oceans tephra deposition may fertilise fe limited waters with potential impacts on the global carbon cycle embracing the full complexity of environmental effects caused by tephra fall demands a renewed investigative effort drawing on interdisciplinary field and laboratory studies combined with consideration of the interconnectivity of induced impacts within and between different receiving environments

volcanic ash leachates a review and recommendations for sampling methods tephra in plumes can scavenge and thereby rapidly deposit volatiles including sulphur halogen and metal species these may then be leached e g by rainfall potentially releasing heavy loadings to soils and water bodies several eruptions have resulted in contamination of pasture sometimes with serious impacts on livestock water quality has also been an issue in some areas affected by tephra fall this work synthesises the literature on volcanic ash leachates and considers the controls on volatile adsorption general trends emerge for basaltic intermediate and silicic tephra as well as for variable particle size and transport distance the applications of ash leachate data to plume gas geochemistry calculation of volatile budgets and environmental impact assessment are evaluated comparisons for different eruptions are hampered by disparities in leachate analysis techniques a standardised methodology is therefore proposed to facilitate future health impact assessment and volcanological interpretation of results from different sites

sediment thicknesses and qs vs qp relations in the kachchh rift basin gujarat india using sp converted phases delineation of the top sedimentary structure and its qs vs qp relationship using the travel time difference of direct s and converted sp phase is key to understanding the seismic hazard of any sedimentary basin area we constructed filtered displacement waveforms from local etna episensor acceleration recordings as well as local velocity recordings of aftershocks of the 2001 bhuj earthquake recorded by the kachchh seismological network of the national geophysical research institute ngri hyderabad india during 2001 2004 stations are within 15 70km of epicenters and the resulting displacement waveforms are generally simple displaying prominent p sp and s wave pulses particle motion of p and s waves suggest near vertical raypaths consistent with preliminary depth estimates the direct s wave on the horizontal component is characterized by lower frequency content than the converted sp phase on the vertical component this difference in frequency content between s and sp phases can be explained in terms of different attenuation effects for p and s waves in the unconsolidated sediments the sp phase is generated by s to p phase conversion at the base of mesozoic sediments of the kachchh basin travel time inversion velest of 2565 p and 2380 s arrivals from 658 well located aftershocks recorded at 8 14 three component local seismic stations led to 1 d velocity models indicated very slow sediments in the upper 0 2 km depth range vp 2 92 km s and vs 0 90 km s and an increasing trend of velocities with depth at 2 40 km depth the estimated sediment thicknesses beneath 12 accelerograph and 6 seismograph sites from the estimated velocity model and the travel time difference between s and converted sp phases reaches a maximum of 1 534 0 117 km beneath bandri near the location of 2001 bhuj mainshock and attains a minimum sediment thickness of 0 858 0 104 km beneath ramvav and burudia the spectral ratios between sp and s from 159 three component accelerograms have been used to study seismic wave attenuation in the kachchh rift basin the estimated qs vs qp relations for 12 accelerograph sites vary from qs 0 184 qp at chobari to qs 0 505 qp at dudhai for stations chobari chopdwa jahawarnagar vondh and tapar the spectral ratio slopes and hence the calculated qs vs qp relations are effectively the same and the correlation coefficients are quite high 0 91 0 93 stations adhoi manfara new dudhai dudhai and sikara have similar qs vs qp relationships to each other and also have high correlation coefficients 0 78 0 87 the spectral ratios for stations anjar and ramvav are small and poorly constrained resulting in less reliable qs vs qp relations this could be due to noisy data fewer available waveforms or scattering due to velocity heterogeneities and or interface irregularities

fractal geometry in the san andreas fault system it has been noted that the spatial distribution of earthquakes and the mode of strain release in the san andreas fault system is related to the complexity of fault geometry because of their rough appearance over many length scales faults can be regarded as fractal surfaces direct estimates of fractal dimension d of portions of the san andreas fault system between the northern gabilan range and the salton sea including the postulated extent of the great 1857 fort tejon earthquake are obtained from measured fault lengths analogous to the lengths of coastlines as discussed by mandelbrot regions characterized by complicated fault geometry are associated with larger values of d based on fault traces mapped at a scale of 1 750 000 d is 1 3 for this reach of the fault defined as a 30 km wide band about a main fault trace for that part near parkfield which could be associated with the nucleation of the 1857 earthquake d is 1 1 at this same scale d is 1 4 for the san andreas and related faults near san bernardino where the 1857 rupture stopped compared to 1 2 for the san andreas san juan fault segments near the point of arrest of the 1966 parkfield earthquake at finer map scales 1 24 000 and 1 62 500 critical lengths of 500 m and 1 km are identified which might relate to the extent of off san andreas fault offsets the critical lengths also suggest that fault geometry is not self similar if this fractal geometry persists through the seismic cycle it may be possible to use a quantitative measure of complexity to explain the occurrence of great and characteristic earthquakes along a given reach of fault

a correlation between the b value and the fractal dimension from the aftershock sequence of the 1999 chi chi taiwan earthquake summary we analyse large number of aftershock events from the 1999 chi chi taiwan earthquake m l 7 3 recorded around the epicentre area of the main shock in central taiwan where events can be precisely located due to dense coverage of modern seismometers the seismicity is characterized by the b value of the gutenberg richter relation and the fractal correlation dimension d of earthquake hypocenters calculated from sliding windows containing more than 100 events over a span of 6 months after the main shock we find a positive correlation between b and d from the aftershock sequence our result thus suggests that aki s relation d 3b c could be possibly applied to one single fracturing process and its related aftermath

leaching experiments in recent tephra deposits from talang volcano west sumatra indonesia abstract tephra deposits are prone to leaching because of their high contents of easily weatherable primary minerals rapid weathering of pristine tephra results in soil solutions becoming saturated with soluble cations such as calcium magnesium and potassium which are major nutrient elements essential for plant growth determining cations and phosphate leached from tephra deposits is important for understanding the geochemical weathering of the volcanic materials mt talang erupted on april 12 2005 depositing basalto andesitic ash over portions of the solok district in west sumatra indonesia a leaching study was conducted to examine the chemical fluxes of cations from these tephra deposits in closed batch reaction vessels the tephra samples were leached with de ionized water organic citric and oxalic and inorganic nitric and sulfuric acids for 60 days in the laboratory at temperatures of 10 27 and 40 c respectively the leachates were collected after 24 h and after 10 30 and 60 days up to 30 days leaching of the tephra samples with water decreased leachate ph from 6 75 to 4 51 leachate ph was also noticed to decrease from 3 85 to 3 11 3 25 to 2 71 3 20 to 2 71 and 3 03 to 2 39 due to leaching with citric acid oxalic acid nitric acid and sulfuric acid respectively after 60 days leaching with water has decreased the ph by 0 9 2 9 units whereas that with citric and sulfuric acids by 0 06 0 24 units however leaching with oxalic and nitric acids has increased the ph by 0 16 1 38 units the release of cations from the mt talang tephra was in the decreasing order of ca mg k na the rate of initially dissolved calcium was very high in contrast the amount of dissolved k and na were low in the beginning but increased sharply after 10 days over the next 2 months there was a distinct decrease in the concentration of ca and mg the amount of p released by water citric nitric sulfuric and oxalic acid after 24 h was 237 349 681 964 and 1057 mg of p 2 o 5 kg 1 respectively at the low temperature of 10 c but the values tended to increase with increasing temperature it was noticed that the amount of dissolved p decreased exponentially with time of leaching which was highly correlated when using oxalic and sulfuric acid at the end of the incubation period dissolved p accounted for less than 36 mg of p 2 o 5 kg 1 higher amounts of total dissolved p were obtained when using inorganic sulfuric and nitric acids compared with those of organic oxalic and citric acids

the b value as an earthquake precursor a systematic study of b values in new zealand has shown that within the vicinity of forthcoming large earthquakes there is initially an increase in b and then a return to normal the caracas and san fernando earthquakes show the same phenomenon which is related to that of seismic gaps

characterization of the causative fault system for the 2001 bhuj earthquake of mw 7 7 abstract precise hypocenters erh m w 2 0 5 3 delineate a east west trending blind thrust dipping 45 towards south named as north wagad fault nwf about 25 km north of kachchh main land fault kmf as the causative fault for the 2001 bhuj earthquake of m w 7 7 the aftershock zone involves a crustal volume of 60 40 35 km 3 lying between kmf and nwf the waveform inversion of 45 aftershocks of m 3 0 5 3 suggest that the e w trending south dipping reverse faulting mainly characterizes the aftershock zone however some reverse faulting along nw se as well as ne sw planes and some strike slip faulting along nw se trending vertical plane are also noticed the estimated p axes point on an average towards n s while t axes orient in e w agreeing well with the prevailing regional plate tectonic stress directions the estimated velocity model from one dimensional inversion of 8000 p and 5000 s travel times from 600 aftershocks deciphers a detailed crustal structure of the region upper 0 6 km on an average suggests a low velocity zone characterizing the jurassic and younger sediments the depth range 6 42 km is characterized on an average by larger values of v p 6 31 to 6 98 km s with an average of 6 71 km s v s 3 64 to 4 05 km s with an average of 3 85 km s and v p v s 1 69 to 1 81 with an average of 1 75 the high crustal velocities can be attributed to the existence of a high velocity mafic intrusive rift pillow structure beneath the region probably emplaced during the rifting time this brittle competent high velocity zone beneath the epicentral area in response to the compression due to the northward movement of the indian plate could induce sufficient local stress perturbation for generating large intraplate earthquakes of m w 7 5 in the lower crust further within the overall higher velocity depth range a layer characterized by large values of v p 6 98 km s v s 3 854 km s and v p v s 1 81 is found in the depth range of 20 5 30 km which is inferred to be fractured and saturated high crack density and probably fluid filled presence of numerous fractures in this layer is confirmed by a high b value 0 75 1 1 in this layer this layer might have facilitated the nucleation process of the 2001 bhuj earthquake the major rupture and 47 of the aftershocks have occurred within this layer

seismicity analysis of the kachchh aftershock zone and tectonic implication for 26 jan 2001 bhuj earthquake abstract we have carried out a detailed analysis of seismicity in the vicinity of the 26 jan 2001 bhuj earthquake mw 7 7 from the depth sections of 24 parallel profiles and from the b value cross section we claim the existence of a hidden fault which conjugates to the major rupture fault i e north wagad fault of the 2001 bhuj earthquake the proximity of the intersection of these faults to the focus suggests a close association bhuj main shock generation a circular pattern in the profiles also provides evidence for the existence of an intrusive consistent with earlier findings from gravity magnetic modeling and tomography studies the location of the fault intersection within the intrusive support a model where both play a significant role in the earthquake generation the intersection of the conjugate faults acts as a stress concentrator while their presence within a big pluton possibly will facilitate the stress amplification this mechanism might explain the occurrence of two mw 7 7 earthquakes in a relatively short time span of 182 years in the kachchh rift the b value cross section displays high and low b value patches along the two intersecting faults this suggests a model of a faulted block that consists of two kinds of segment the locked and the unlocked locked segments do not easily participate in creeping and therefore generate strong magnitude aftershocks m 3 while unlocked segments easily creep and result in only weak aftershocks m

fate and agricultural consequences of leachable elements added to the environment from the 2011 cordon caulle tephra fall abstract the june 2011 eruption of cordon caulle volcano chile dispersed tephra over 350 000 km 2 including productive agricultural land this resulted in the death of nearly one million livestock two distinct environments were affected a proximal temperate andean setting and the semi arid argentine steppe farther from the volcano the purpose of this study was to better understand the fate and agricultural consequences of leachable elements added to the environment by this large silicic tephra fall tephra soil and surface water samples across the depositional area were collected both immediately after the eruption tephra and water and nine months afterwards tephra soil and water tephra samples were analysed following a new hazard assessment protocol developed by the international volcanic health hazard network ivhhn water extractable element concentrations in freshly collected tephra were very low to low compared to other eruptions and showed no trends with distance from the volcano surface water analyses suggested short term changes to water composition due to the release of elements from tephra no effect on the fertility of soils underlying tephra was apparent after nine months water extractable fluorine f in freshly collected tephra ranged from 12 to 167 mg kg with a median value of 67 mg kg based on parallels with the 11 12 october 1995 eruption of ruapehu volcano new zealand we conclude that f toxicity was a possible contributing factor to the large scale livestock deaths as well as to chronic fluorosis widely reported in wild deer populations across the cordon caulle tephra depositional area finally we recommend that effective response to widespread tephra fall over agricultural areas should include 1 rapid statistically representative field sampling of tephra soils surface water supplies and forage crops 2 analysis using appropriate and reliable laboratory methods 3 modelling both short and long term impacts on the ecosystem especially for elements that may generate chronic hazard 4 timely dissemination of results to agricultural agencies 5 longitudinal sampling and monitoring to adapt impact models and 6 developing reliable animal fatality diagnoses through autopsies and chemical analysis

mapping the frequency magnitude distribution in asperities an improved technique to calculate recurrence times we hypothesize that highly stressed asperities may be defined by mapping anomalously low b values along the san andreas fault near parkfield the asperity under middle mountain with its b 0 46 can be distinguished from all other parts of the fault surface likewise along the calaveras fault the northern asperity of the morgan hill 1984 m6 2 rupture can be identified by its low b of 0 5 as a high stress patch along the fault we add further evidence to the observations that the b value of the frequency magnitude relationship of earthquakes is inversely proportional to stress by showing that it decreases with depth in the parkfield segment of the san andreas and along the calaveras fault in both of these areas b values above and below 5 km depth are 1 2 and 0 8 respectively we propose that probabilistic recurrence times tr based on the seismicity parameters a and b should be calculated from their values within asperities only instead of from the values of the entire rupture area of the maximum expected earthquake the strong patches on faults control the time of rupture because they are capable of accumulating larger stresses than the rest of the fault zone which slips along passively when an asperity breaks therefore no information on tr is contained in the passive fault segments only in the asperities at parkfield the probabilistic estimates of tr derived from the data in the whole rupture and in the asperity only are 72 18 24 and 23 12 18 years respectively compared to the historically observed repeat time of 22 years at morgan hill the tr estimates are 122 46 76 and 78 47 110 years respectively compared to the observed repeat time of 72 years

the 2001 bhuj earthquake tomographic evidence for fluids at the hypocenter and its implications for rupture nucleation 1 the january 26 2001 bhuj earthquake mw 7 6 is one of the most catastrophic indian earthquakes we have investigated the 3 d seismic velocity and poisson s ratio structures of the bhuj source area to understand the probable cause of triggering the earthquake we used 1948 p and 1865 s wave high quality arrival times from 331 aftershocks recorded at a temporary seismic network significant variations up to 5 in velocity and 10 in poisson s ratio are revealed in the aftershock area the mainshock is located in a distinctive zone characterized by high vp low vs and high poisson s ratio in the depth range of 20 to 30 km and extending 15 to 30 km laterally this feature is very similar to that of the 1995 kobe earthquake zhao et al 1996 the anomaly may be due to a fluid filled fractured rock matrix which might have contributed to the initiation of the bhuj earthquake

seismicity in north eastern brazil fractal clustering and the evolution of the b value summary we analyse a catalogue of earthquakes recorded near joao camara brazil an intraplate area with a simple velocity structure and low attenuation the evolution of seismicity is characterized by the seismic b value and the fractal dimension of earthquake epicentre locations measured from sliding 100 event windows the events are divided into a number of spatial clusters using a nearest centroid sorting technique and two of these clusters are examined in detail one cluster characterized by intense activity shows a clear negative correlation between b value and fractal dimension of epicentre locations as has been predicted from simple mechanical models a second cluster shows a weak positive correlation and it is suggested that this might be explained in terms of fluid flow in the fault zone

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

physical modeling of the formation and evolution of seismically active fault zones acoustic emission ae in rocks is studied as a model of natural seismicity a special technique for rock loading has been used to help study the processes that control the development of ae during brittle deformation this technique allows us to extend to hours fault growth which would normally occur very rapidly in this way the period of most intense interaction of acoustic events can be studied in detail characteristics of the acoustic regime ar include the gutenberg richter b value spatial distribution of hypocenters with characteristic fractal correlation dimension d hurst exponent h and crack concentration parameter pc the fractal structure of ar changes with the onset of the drop in differential stress during sample deformation the change results from the active interaction of microcracks this transition of the spatial distribution of ae hypocenters is accompanied by a corresponding change in the temporal correlation of events and in the distribution of event amplitudes as signified by a decrease of b value the characteristic structure that develops in the low energy background ae is similar to the sequence of the strongest microfracture events when the ar fractal structure develops the variations of d and b are synchronous and d 3b this relation which occurs once the fractal structure is formed only holds for average values of d and b time variations of d and b are anticorrelated the degree of temporal correlation of ar has time variations that are similar to d and b variations the observed variations in laboratory ae experiments are compared with natural seismicity parameters the close correspondence between laboratory scale observations and naturally occurring seismicity suggests a possible new approach for understanding the evolution of complex seismicity patterns in nature

large scale control on the patagonian climate abstractpatagonia located in southern south america is a vast and remote region holding a rich variety of past environmental records but a small number of meteorological stations precipitation over this region is mostly produced by disturbances embedded in the westerly flow and is strongly modified by the austral andes uplift on the windward side leads to hyperhumid conditions along the pacific coast and the western slope of the andes in contrast downslope subsidence dries the eastern plains leading to arid highly evaporative conditions the authors investigate the dependence of patagonia s local climate precipitation and near surface air temperature year to year variability on large scale circulation anomalies using results from a 30 yr long high resolution numerical simulation variations of the low level zonal wind account for a large fraction of the rainfall variability at synoptic and interannual time scales zonal wind also controls the amplitude of the air temperature annual cycle by changi