most and least likely locations of large to great earthquakes along the pacific coast of mexico estimated from local recurrence times based on b values we mapped t l and p l local recurrence time and local probability density respectively for m max 7 2 earthquakes along the plate margin of the pacific coast of mexico in order to test two hypotheses the first is that the minima in t l or maxima in p l extracted probabilistically from the frequency magnitude distribution map asperities the second hypothesis is that recurrence times for characteristic events are estimated more correctly by local recurrence times than by the overall recurrence times of the zone comparing these results to the observed recurrence times for events of m 7 0 we find good agreement the coast of guerrero between longitude west 100 5 and 101 5 and the segment off the coast of southern chiapas show the shortest t l estimated as about 20 yr the location at longitude 98 5 near the boundary of guerrero with oaxaca the ometepec segment follows with estimates of about 30 yr as the next shortest t l along the coast of guerrero between 99 and 100 5 longitude t l is estimated as about 40 yr and finally in the segments off the oaxacan coast near 95 7 and 97 7 longitude t l ranges from 40 to 60 yr these volumes we define as asperities long local recurrence times are observed for the areas offshore from the isthmus of tehuantepec on the pacific plate off the coast of guerrero on land along the coast of most of oaxaca and along the northernmost 40 km of the guerrero coast if our ideas are correct then major moment release should emanate from the volumes we defined as asperities and relatively minor moment release should emanate from the volumes identified by the relatively long local recurrence times

hydrometeor enhanced tephra sedimentation constraints from the 18 may 1980 eruption of mount st helens 1 uncertainty remains on the origin of distal mass deposition maxima observed in many recent tephra fall deposits in this study the link between ash aggregation and the formation of distal mass deposition maxima is investigated through reanalysis of tephra fallout from the mount st helens 18 may 1980 msh80 eruption in addition we collate all the data needed to model distal ash sedimentation from the msh80 eruption cloud four particle size subpopulations were present in distal fallout with modes at 2 2 4 2 5 9 and 8 3 settling rates of the coarsest subpopulation closely matched predicted single particle terminal fall velocities sedimentation of particles 100 m was greatly enhanced predominantly through aggregation of a particle subpopulation with modal diameter 5 9 0 2 19 3 m mammatus on the msh80 cloud provided a mechanism to transport very fine ash particles with predicted atmospheric lifetimes of days to weeks from the upper troposphere to the surface in a matter of hours in this mechanism ash particles initiate ice hydrometeor formation high in the troposphere subsequently the volcanic cloud rapidly subsides as mammatus develop from increased particle loading and cloud base sublimation rapid fallout occurs as the cloud passes through the melting level in a process analogous to snowflake aggregation aggregates sediment en masse and form the distal mass deposition maxima observed in many recent volcanic ash fall deposits this work provides a data resource that will facilitate tephra sedimentation modeling and allow model intercomparisons

holocene tephrochronology of the hualaihue region andean southern volcanic zone 42 s southern chile late glacial and holocene soils and sediments in southern chile contain an important record of explosive volcanic activity since the end of the last glaciation and have considerable potential for

stress changes modelled for the sequence of strong earthquakes in the south iceland seismic zone since 1706 the south iceland seismic zone is roughly speaking situated between two sections of the mid atlantic ridge i e the reykjanes ridge southwest of iceland and the eastern volcanic zone on the island it is a transform zone where earthquakes are expected to occur on e w trending left lateral shear faults equivalent to conjugate n s oriented right lateral rupture planes in fact earthquakes take place on en echelon n s oriented faults which is indicated by the distribution of main shock intensities aftershocks as well as by surface fault traces the stress field continuously generated in the fault zone by opening of the adjacent ridges is computed and superimposed on the stress field changes induced by a series of 13 earthquakes m 6 between 1706 and 2000 the level of the pre seismic stress field is analysed as well as the size of the area under high stress finally the post seismic stress field of june 2000 is analysed to see where high stresses might have accumulated the modelling indicates that the rupture planes located on separated parallel n s striking zones are dense enough to lead to an area wide stress release by the series of events the obtained pre seismic stress level for most events is high and stable with the exception of situations when several strong shocks occur over a time span of several days i e display typical main shock aftershock patterns the size of areas under high stress aside from of the rupture plane i e where no event occurs at the specific time is of medium to small size

locked and creeping patches along the hayward fault california the results of mapping locked and unlocked patches on the hayward fault using the local recurrence time method are compared with models derived from surface creep and geodetic measurements the data used were the m 1 0 earthquakes in the usgs catalog since 1981 0 located within 5 km of the fault trace along the central and southern segments agreement with the other methods is satisfactory the 1868 rupture except for its two ends is classified as a locked segment by our method in the northern part of the hayward fault the data are poor and the results of the three methods differ short local recurrence times in the northern part suggest that an asperity exists there which is capable of an m6 5 class event

comparison of lake and land tephra records from the 2015 eruption of calbuco volcano chile tephra layers in lake sediment cores are regularly used for tephrostratigraphy as isochronous features for dating and recording eruption frequencies however their value for determining volcanic eruption size and style may be complicated by processes occurring in the lake that modify the thickness and grain size distributions of the deposit to assess the reliability of data from lake cores we compare tephra deposited on land during the 2015 eruption of calbuco volcano in chile to records in sediment cores from three lakes of different sizes that are known to have received primary fall deposits in general the thickness and granulometry of the deposit in lake cores and nearby terrestrial sections are very similar as anticipated however cores sampled close to here within 300 m of fluvial inflows were affected by sediment deposition from the lake s catchment they differed from primary deposits not only in their greater thickness and organic content but also in poor sorting and lack of grading cores 850 m away from the inlet were not affected we consider our results in the context of the particle settling regime as well as each lake s location bathymetry and catchment area we find that the particle settling regime is important in more distal settings where the ash particles are small and particle settling occurs in density plumes rather than as individual particles we conclude that lake cores can be useful for physical volcanology providing consideration is given to eruption parameters such as particle size and mass flux as well as lake features such as bathymetry and catchment area

geochemistry and origin of albite gneisses northeastern adirondack mountains new york albite gneisses containing up to 8 7 percent na2o and as little as 0 1 k2o comprise a significant part of the proterozoic lyon mountain gneiss in the ausable forks quadrangle of the northeastern adirondacks new york state two distinct types of albite gneisses are present one is a trondhjemitic leucogneiss lag consisting principally of albite ab95 ab98 and quartz with minor magnetite and locally minor amounts of amphibole or acmiterich pyroxene lag probably originated by metamorphism of a rhyolitie or rhyodacitic ash flow tuff with a type geochemical affinities following post depositional analcitization in a saline or saline alkaline environment the other type is a mafic albite gneiss mag containing albite and pyroxene along with 0 45 percent quartz minor amphibole and titanite mag locally displays pinstripe banding and contains albite ab98 megacrysts up to 5 cm across its precursor may have been a sediment composed of diagenetic analcite or albite dolomite and quartz both types of albite gneiss are interlayered with granitic gneisses lmg of variable composition derived from less altered tuffs a potassium rich up to 9 7 k2o microcline gneiss facies may have had a protolith rich in diagenetic k feldspar we propose that the albite gneisses and associated granitic gneisses are the granulite facies metamorphic equivalent of a bimodal dominantly felsic volcanic suite with minor intercalated sediments probably including evaporites the volcanics were erupted in an anorogenic setting such as an incipient or failed intracontinental rift deposition took place in a closed basin playa lake environment where diagenetic alteration resulted in redistribution of the alkalis and strong oxidation

seismicity patterns are they always related to natural causes by analyzing data from two catalogs of seismicity one local and one regional examples are drawn that demonstrate artificial seismicity patterns which can arise when changes in magnitude reporting or in detection ability are introduced by changes in operating procedures of a seismic network in the first case a catalog which comprises seismic data from guerrero mexico is revised and a correction is applied to magnitudes suspected of being affected by different operative practices next several time windows are analyzed which compare the seismicity rate within the window to that of the total record mapped as a function of space the same procedure is applied to the original i e uncorrected catalog a significant seismic quiescence apparent in the original data set in the center of the seismic network all but disappears in the corrected data indicating that this anomaly is not naturally induced in the second case we investigate the homogeneity of seismicity reporting for the interior of alaska we computed the standard deviate z as a function of time by comparing the overall seismicity rate with the rate in a 3 year window the maps z values were inspected for all times the most outstanding rate change is found around 1992 5 since the b value remained unchanged the most reasonable explanation for the observed rate change around mid 1992 is a decrease in the detection ability of the network in the interior of alaska both case studies demonstrate the usefulness of systematic comparisons of the cumulative and noncumulative frequency magnitude distribution and of spatial and temporal mapping of the seismicity rates as a tool to investigate the homogeneity of earthquake reporting

rare earth element mobility in the roffna gneiss switzerland the roffna gneiss a deformed hercynian granite porphyry within the penninic nappes of eastern switzerland underwent extreme cataclasis with the progressive development of phengite towards the margins of the nappe under conditions of the glaucophane schist to greenschist facies this resulted in the selective mobilization of major and trace elements over distances of 10 s to 100 s of meters and the resetting of the rb sr whole rock isotopic systems some 100 my ago the component ratios and compositionvolume relationships of progressively deformed gneiss samples studied here suggest that this process was essentially isovolumetric the mineralogy of the deformation sequence appears to have been controlled by a reaction involving the breakdown of microcline albite and biotite and the formation of phengite and quartz the fluids introduced mg and h2o promoting the development of phengite and removed the na being released by the breakdown of albite the fluids were most probably derived from the surrounding triassic carbonates and quartzites these relatively high fo2 and carbonate rich fluids also introduced rare earth elements ree into the gneiss the gneiss was progressively enriched in eu up to 60 y up to 40 and yb up to 100 these enrichments are associated with the development of epitaxial xenotime around zircon in the most phengite rich sample while the ree were mobile uranium and thorium were essentially immobile the formation of xenotime was suggested to explain the observed heavy ree enrichment when large differences in the ree contents were found for replicate analyses using hf and then lithium metaborate for dissolution these differences arose because xenotime like monazite can be difficult if not impossible to dissolve in hydrofluoric acid due to the possibility of incomplete sample dissolution we now recommend fusion with lithium metaborate for all ree lu hf or sm nd studies

evidence for a constant b value above magnitude 0 in the southern san andreas san jacinto and san miguel fault zones and at the long valley caldera california the cumulative b value the slope of the gutenberg richter relationship between earthquake occurrence rate and magnitude is commonly found to be constant 1 network catalogues however reveal a decrease at small magnitudes 3 some recent studies have suggested that this decrease in b value is not just an artifact of catalogue incompleteness but that small earthquakes are really not as numerous as a constant b value extrapolated from larger events would predict brune allen 1967 recorded microseismicity in both the san andreas and san jacinto fault zones in southern california calculating that they were complete to magnitude 0 reyes et al 1975 performed a similar study of the san miguel fault zone baja california estimating completeness above magnitude 0 5 we compare the results of these studies with the occurrence rates of earthquakes on the same faults recorded by the southern california and resnor seismic networks the observed microseismicity rates are in good agreement with the rates predicted by extrapolating the b values of the larger earthquakes in a new microseismicity survey at the long valley caldera mammoth lakes california microearthquakes were recorded and counted within 24 km of stations clk and chs this study is estimated to be complete above 0 6 m at clk and 0 9 m at chs and the microseismicity rates are found to be in good agreement with the rate predicted by extrapolating the b value from the local network recorded seismicity the constant b value in the magnitude range 0 to 5 observed in all four areas considered is consistent with a scale invariant earthquake rupture process

local regional and remote seismo acoustic observations of the april 2015 vei 4 eruption of calbuco volcano chile the two major explosive phases of the 22 23 april 2015 eruption of calbuco volcano chile produced powerful seismicity and infrasound the eruption was recorded on seismo acoustic stations out to 1 540 km and on 5 stations is02 is08 is09 is27 and is49 of the international monitoring system ims infrasound network at distances from 1 525 to 5 122 km the remote ims infrasound stations provide an accurate explosion chronology consistent with the regional and local seismo acoustic data and with previous studies of lightning and plume observations we use the ims network to detect and locate the eruption signals using a brute force grid search cross bearings approach after incorporating azimuth deviation corrections from stratospheric cross winds using 3d ray tracing the estimated source location is 172 km from true this case study highlights the significant capability of the ims infrasound network to provide automated detection characterization and timing estimates of global explosive volcanic activity augmenting the ims with regional seismo acoustic networks will dramatically enhance volcanic signal detection reduce latency and improve discrimination capability

physical characterization of explosive volcanic eruptions based on tephra deposits propagation of uncertainties and sensitivity analysis abstract regardless of the recent advances in geophysical monitoring and real time quantitative observations of explosive volcanic eruptions the characterization of tephra deposits remains one of the largest sources of information on eruption source parameters esps i e plume height erupted volume mass mass eruption rate mer eruption duration total grain size distribution tgsd esps are crucial for the characterization of volcanic systems and for the compilation of comprehensive hazard scenarios but are naturally associated with various degrees of uncertainties that are traditionally not well quantified recent studies have highlighted the uncertainties associated with the estimation of esps mostly related to i the intrinsic variability of the natural system ii the observational error and iii the strategies used to determine physical parameters here we review recent studies focused on the characterization of these uncertainties and we present a sensitivity analysis for the determination of esps and a systematic investigation to quantify the propagation of uncertainty applied to two case studies in particular we highlight the dependence of esps on specific observations used as input parameters i e diameter of the largest clasts thickness measurements area of isopach contours deposit density downwind and crosswind range of isopleth maps and empirical constants and wind speed for the determination of mer the highest uncertainty is associated to the estimation of mer and eruption duration and is related to the determination of crosswind range of isopleth maps and the empirical constants used in the empirical parameterization relating mer and plume height given the exponential nature of the relation between mer and plume height the propagation of uncertainty is not symmetrical and both an underestimation of the empirical constant and an overestimation of plume height have the highest impact on the final outcome a 20 uncertainty on thickness measurements area of isopach contours integration limit for the power law fit and deposit density result in esp uncertainties 20 for plume height and erupted volume mass finally a third case study has also been used to explore the sensitivity of the voronoi tessellation strategy for the determination of tgsd and the inversion on both mass area and grain size data for the determination of erupted mass and plume height results confirm the validity of the methods but also the strong dependence on the distribution and number of observations

eruption dynamics of the 22 23 april 2015 calbuco volcano southern chile analyses of tephra fall deposits abstract after 54 years since its last major eruption in 1961 calbuco volcano ensenada southern chile reawakened with few hours of warning on 22 april 2015 at 18 05 local time the main explosive eruption consisted of two eruption pulses lasting 1 5 and 6 h each one on 22 and 23 april producing stratospheric 15 km height eruption columns the erupted materials correspond to porphyritic basaltic andesite 55 wt of sio2 the tephra fall affected mainly the area northeast of the volcano and the finest ash was deposited over southern chile and patagonia argentina we studied the tephra fall deposits of both pulses in terms of stratigraphy distribution volume emplacement dynamics and eruption source parameters here we show field observations that have been made 5 470 km downwind and distinguish five layers layers a b b1 c and d representing different stages of the eruption evolution eruption onset layer a pulse 1 followed by the first paroxysmal event layer b pulse 1 in some places interbedded by layer b1 tentatively representing the sedimentation of a secondary plume during the end of pulse 1 we recognized a second paroxysm layer c pulse 2 followed by the waning of the eruption layer d pulse 2 the total calculated bulk tephra fall deposit volume is 0 27 0 007 km3 0 11 0 13 km3 dense rock equivalent 38 of which was erupted during the first phase and 62 during the second pulse this eruption was a magnitude 4 45 event vei 4 eruption of subplinian type

eruptive parameters and dynamics of the april 2015 sub plinian eruptions of calbuco volcano southern chile we conducted geological and petrological analyses of the tephra fallout and pyroclastic density current pdc products of the 22 23 april 2015 calbuco eruptions the eruptive cycle consisted of two sub plinian phases that generated 15 km height columns and pdcs that travelled up to 6 km from the vent the erupted volume is estimated at 0 38 km3 non dre with approximately 90 corresponding to tephra fall deposits and the other 10 to pdc deposits the erupted products are basaltic andesite 54 55 wt sio2 with minor amounts of andesite 58 wt sio2 despite the uniform composition of the products there are at least four types of textures in juvenile clasts with different degrees of vesicularity and types and content of crystals we propose that the eruption triggering mechanism was either exsolution of volatiles due to crystallization or a small intrusion into the base of the magma chamber without significant magma mixing or with a magma compositionally similar to that of the residing magma in either case the triggering mechanism generated convection and sufficient overpressure to promote the first eruptive phase the start of the eruption decompressed the chamber promoting intense vesiculation of the remaining magma and an increase in eruption rate towards the end of the eruption

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

temporal and three dimensional spatial analyses of the frequency magnitude distribution near long valley caldera california summary the 3 d distribution of the b value of the frequency magnitude distribution is analysed in the seismically active parts of the crust near long valley caldera california the seismicity is sampled in spherical volumes containing n 150 earthquakes and centred at nodes of a grid separated by 0 3 km significant variations in the b value are detected with b ranging from b 0 6 to b 2 0 high b value volumes are located near the resurgent dome and at depths below 5 km at mammoth mountain b values are found to be much lower south of the long valley caldera we interpret this to indicate that an active magma body has advanced from depths below 8 km to depths of 4 to 5 km beneath mammoth mountain in 1989 and that anomalous crust either highly fractured or containing unusually high pore pressure such as is the case in the vicinity of active magma bodies exists north of the seismically active area beneath the resurgent dome at all depths we also investigate the spatial distribution of temporal variations of the frequency magnitude distribution by introducing diverential b value maps b values increased from b 0 8 to b 1 5 underneath mammoth mountain at the onset of the 1989 earthquake swarm and remained high thereafter this suggests that an intrusion permanently altered the average distribution of cracks at 5 10 km depth or that the pore pressure permanently increased we propose that high b values are a necessary but not suycient condition near a magmatic body and therefore spatial b value mapping can be used to aid in the identification of active magma bodies

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

sedimentological analysis of the tephra from the 12 15 august 1991 eruption of hudson volcano the tephra fallout from the 12 15 august 1991 explosive eruption of hudson volcano cordillera de los andes 45 54 s 72 58 w chile was dispersed on a narrow elongated ese sector of patagonia covering an area on land of more than 100 000 km2 the elongated shape of the deposit together with the relatively coarse mean and median values of the particles at a considerable distance from the vent were the result of strong winds blowing to the southeast during the eruption the thickness of the fall deposit decreases up to 250 km ese from hudson volcano where it begins to thicken again secondary maxima are well developed at approximately 500 km from the vent secondary maxima together with grainsize bimodality in individual layers and in the bulk deposit suggest that particle aggregation played an important role in tephra sedimentation the fallout deposit is well stratified with alternating fine grained and coarsegrained layers which is probably a result of strong eruptive pulses followed by relatively calm periods and or changes in the eruptive style from plinian to phreatoplinian the tephra is mostly composed of juvenile material the coarse mode mostly pumice shifts to finer sizes with distance from the volcano the fine mode mostly glass shards is always about 5 6 phi glass shards and pumice are mostly light gray to colorless however considerable amounts of dark poorly vesiculated blocky shards suggest a hydromagmatic component in the eruption a land based tephra volume of 4 35 km3 was estimated and a total volume of 7 6 km3 arose from an extrapolation which took into account the probable volume sedimented in the sea bulk density ranges from 0 9 to 1 10 gr cm3 beyond 110 km from the vent rather uniform density values measured in crushed samples 2 45 2 50 gr cm3 at all distances from the vent reveal a relatively homogeneous composition mean and median sizes decrease rapidly up to 270 km from the vent beyond that point they are more or less constant whereas the maximum size 1 phi shows a steady decrease up to 550 km a concomitant improvement in sorting is observed this is attributed to sorting due to wind transport combined with particle aggregation at different times and distances from the vent the hudson tephra fallout shares some strikingly similar features with the mount st helens 18 may 1980 and quizapu 1932 eruptions

the mechanics of the south iceland seismic zone the south iceland seismic zone appears to act as a transform fault between offset sections of the mid atlantic ridge however there is no morphological expression of a throughgoing transform between the ridges the anticipated throughgoing east west transform is represented by a series of north south strike slip faults we study the mechanics of the south iceland seismic zone using boundary element methods first we examine the implications of the differences between the geometry of an orthogonal ridge transform ridge system and the geometry of the structures observed in iceland then we consider the role of the north south faults in accommodating transform motion in an east west direction we conclude that the north south faults can accommodate deformation if they are longer or more spatially frequent than mapped the south iceland seismic zone is subject to sequences of large earthquakes every 45 112 years in comparing the seismic moment release derived from earthquake magnitudes with that predicted by our models we confirm that the system of north south faults can act as a transform fault the seismic moment release derived from the earthquake magnitudes is 1 4 times greater than that predicted by our models if our application of the moment magnitude relation is correct the above could imply that the brittle layer extends to 14 km rather than the 10 km assumed in our models other possibilities are that the magnitudes of the earthquakes have been slightly overestimated or that the historical seismic record documents a period of seismicity greater than that expected from rates of plate motion inferred from geological and very long baseline interferometry vlbi

pyroclastic deposits and eruptive heterogeneity of volcan antuco 37 s southern andes during the mid to late holocene 7 2 ka abstract volcan antuco 37 24 s 71 22 w 2979 m asl is the 13th ranked high threat volcano in chile with 27 recorded historical eruptions mostly 96 with volcanic explosivity indices vei of 1 2 an older eruptive record has been reconstructed from sections exposed on the western flank and is intimately related to a well documented catastrophic sector collapse at 7 2 cal ka bp however very little is known about antuco s post collapse eruptive history in other sectors especially on the eastern flanks where prevalent westerly winds favor optimal eastward tephra transport and deposition our study reveals a more complete record of activity that has already been indicated from previous work with at least 23 tephra forming explosive eruptions most of them within the last c 7 2 ka including 4 events that have generated pyroclastic density currents that have widely inundated the lower eastern flanks tephra from these eruptive events are typically composed of scoria free crystals and lithics with occasional pumice the composition of juvenile fragments varies between basalt and trachyandesite 50 2 62 2 wt sio2 and show phenocrysts of plagioclase olivine and pyroxene our results show that most of the eruptions of antuco c 79 are strombolian to violent strombolian these eruptions have an estimated longer repose times c 200 year and are likely higher in magnitude than those registered during historical times this study also shows that the composition style and magnitude may change from one eruptive episode to the next this eruptive variability seems in complete accord with recent findings from other centers in the southern volcanic zone exhibiting similar temporal eruptive diversity and ultimately has significant implications with respect to hazard assessment

petrology and phase relations of the kyanite eclogites from eastern turkey eclogites are found as lenses or layers in the precambrian gneiss terrain of the bitlis massif in eastern turkey kyanite eclogites from the region of gablor hill in the bitlis massif exhibit relatively minor alteration and consist of garnet omphacite kyanite zoisite calcic amphibole phengite rutile and quartz in terms of geological setting and mineral compositions gablor eclogites are very similar to eclogites from high grade gneiss terrains metamorphic conditions during the eclogite crystallisation are determined as 625 35 c and 16 3 kbars the coexistence of white mixa omphacite and kyanite constrains a text h text 2 text o between 0 4 and 1 primary calcic amphiboles from the gablor eclogites exhibit conflicting textures indicating stable coexistence with as well as growth from omphacite and garnet this is explained by a buffering reaction between amphibole garnet omphacite zoisite and kyanite during the eclogite crystallisation whereby a text h text 2 text o is controlled and buffered by the mineral assemblage

man made changes of seismicity rates seismicity catalogs contain important information about processes which occur in seismically active regions of the earth many authors have examined these catalogs for patterns and variations in patterns which might reflect changes in these processes we have found that these catalogs include a complex mixture of real and man made changes one must identify and account for the man made changes before the real ones can be identified and understood many man made changes in seismicity catalogs are manifested as changes in seismicity rates and can therefore be identified through careful examination of these rates obvious effects include increases or decreases in the detection and reporting of smaller events which accompany the installation or closure of seismic stations these types of changes can be recognized by examining the distribution of seismicity rate changes in the magnitude domain they are characterized by increases or decreases in the number of small events in the catalog at times when the number of larger events remains constant systematic changes in the magnitudes assigned to events can also be identified by examining seismicity rates because they cause apparent changes in rates of data sets with magnitude cutoffs the sign of the apparent rate change depends on the sign of the magnitude change and the type of cutoff used the effects of detection changes can be easily remedied by using a magnitude cutoff which eliminates the smaller events from consideration the techniques we have developed allow one to determine the optimum cutoff magnitude corrections are necessary for remedying the effects of systematic changes in magnitude estimates these corrections can be determined through modeling of observed rate changes caused by these shifts man made changes are present in all seismicity catalogs whether local regional or teleseismic they must be accounted for if these catalogs are to provide meaningful information on real process changes in the earth

mantle flow induced crustal thinning in the area between the easternmost part of the anatolian plate and the arabian foreland e turkey deduced from the geological and geophysical data abstract eastern anatolia consisting of an amalgamation of fragments of oceanic and continental lithosphere is a current active intercontinental contractional zone that is still being squeezed and shortened between the arabian and eurasian plates this collisional and contractional zone is being accompanied by the tectonic escape of most of the anatolian plate to the west by major strike slip faulting on the right lateral north anatolian transform fault zone natfz and left lateral east anatolian transform fault zone eatfz which meet at karliova forming an east pointing cusp the present day crust in the area between the easternmost part of the anatolian plate and the arabian foreland gets thinner from north ca 44 km to south ca 36 km relative to its eastern eahp and western sides central anatolian region this thinner crustal area is characterized by shallow cpd 12 16 km very low pn velocities

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

comparative study of lahars generated by the 1961 and 1971 eruptions of calbuco and villarrica volcanoes southern andes of chile abstract the villarrica and calbuco volcanoes of the andean southern volcanic zone are two of the most active volcanoes in chile and have erupted several times in the xx century the 1961 eruption at calbuco volcano generated lahars on the north east and southern flanks while the 1971 eruption at villarrica volcano generated lahars in almost all the drainages towards the north west and south of the volcano the deposits from these eruptions in the voipir and chaillupen river villarrica and the tepu river calbuco are studied the 1971 lahar deposits on villarrica volcano show a great number of internal structures such as lamination lenses grading of larger clasts and a great abundance of large floating blocks on top of the deposits the granulometry can be unimodal or bimodal with less than 5 by weight of silt clay material sem images reveal a great variety of forms and compositions of clasts the 1961 lahar deposits on calbuco volcano have a scarce number of internal structures steeper margins and features of hot emplacement such as semi carbonized vegetal rests segregation pipes and a more consolidated matrix the granulometry usually is bimodal with great quantities of silt clay material 10 by weight sem images show a uniformity of composition and forms of clasts differences on deposits reveal different dynamics on both lahars the villarrica lahar was generated by sudden melt of ice and snow during the paroxysmal phase of the 1971 eruption when a high fountain of lava was formed the melted water flowed down on the flanks of the volcano and incorporated sediments to become transition flows highly energetic and were emplaced incrementally dilution of the flows occurs when the lahars reached unconfined and flatter areas in cases where the lahar flow found large water streams dilution is enhanced the calbuco lahars were generated by the dilution of block and ash pyroclastic flows by flowing over the ice or snow or by entering active rivers transforming to debris flows the differences on dynamics of both flows show the importance to understand initiation processes of lahars in order to make better hazard assessment due to laharics flows

recent unrest 2002 2015 imaged by space geodesy at the highest risk chilean volcanoes villarrica llaima and calbuco southern andes abstract villarrica llaima and calbuco volcanoes are the most active and dangerous volcanoes in the southern andes and we use interferometric synthetic aperture radar insar observations from multiple satellites ers 2 envisat alos radarsat 2 cosmo skymed terrasar x sentinel 1a and alos 2 to constrain ground deformation that spans episodes of unrest and eruption at all three volcanoes between 2002 and 2015 we find episodes of ground deformation at each volcano which we invert using analytic elastic half space models to make some of the first geophysical inferences about the source depths of potential magma chambers at llaima we interpret that the vei 2 april 3 2009 eruption was preceded by 6 15 cm of precursory ground uplift one month before from a source 5 km below the surface on the western side of the edifice the vei 2 march 3 2015 villarrica eruption was followed by a short lived uplift of 5 cm in the se part of the volcano from a source depth of 6 km the vei 4 april 22 23 2015 calbuco eruption produced 12 cm of coeruptive subsidence from a source depth 8 11 km and offset 2 km s from the summit importantly we do not find clear evidence that the january 1 2008 the march 3 2015 and april 22 2015 eruptions at llaima villarrica and calbuco volcanoes were preceded by either transient or continuous ground uplift there are several possible explanations for the lack of precursory deformation at each volcano it is possible that any precursory deformation occurred only hours before the eruption e g at calbuco pre eruptive inflation was canceled by co eruptive subsidence as we inferred happened during the april 2009 llaima eruption the pre eruptive deformation was too small to be detectable in areas with persistent topography correlated phase delays pressurized source are deep or that open vent volcanoes like villarrica and llaima do not pressurize at all three volcanoes x and c band interferograms decorrelate in a few weeks due to vegetation snow and ice and have persistent atmospheric phase delays that we find cannot be reliably removed with available global weather models the low number of sar acquisitions therefore makes it challenging to reliably measure unaliased deformation we recommend a multi satellite observing strategy with short repeat periods frequently acquired high resolution digital elevation models and with acquisitions during every satellite overflight that may improve the temporal resolution of measurements

nucleation points of recent mainshocks in southern iceland mapped by b values the earthquake catalog in southern iceland between 20 25 w and 21 3 w is complete down to approximately mw 0 and shows no evidence for mag nitude shifts as a function of time since 1991 this means that 6902 earthquakes m 0 1 depth 20 km are available for studies of seismicity patterns preceding the two ms 6 6 mainshocks in 2000 in their source volumes and vicinity 20 25 w and 20 9 w the power law of the frequency magnitude relationship holds down to m0 detailed mapping including 3d mapping of the b value of the frequency magnitude distribution shows that variations from b 0 6 to 1 4 exist over distances of about 2 km this suggests that the tectonic fabric in southern iceland is hetero geneous on a small scale the hypocenters of the two ms 6 6 mainshocks and one additional m 4 5 mainshock are associated with low b values 0 6 0 8 statistically significantly different from volumes in their vicinity therefore one can expect future mainshocks in southern iceland to also emanate from volumes characterized by low b values however the small dimensions of these asperities may render it difficult to identify them before the mainshocks occur low values of estimated local recur rence times 500 2000 years map the two fault zones that ruptured in 2000 against a background of local recurrence times longer than 5000 years the first of the two m 6 6 mainshocks emanated from a volume of short estimated local recurrence time this supports the hypothesis that asperities with short local recurrence times control locations of major ruptures mapping of b values in cross sections shows anomalies of high b at the bottom of the seismogenic crust correlating with the change of its thickness in the middle of the study area these high b value anomalies and other pockets of such anomalies at shallower depths are best interpreted as caused by high pore pressure because evidence of fluids under high pressure is ubiquitous in this area

determination of the largest clast sizes of tephra deposits for the characterization of explosive eruptions a study of the iavcei commission on tephra hazard modelling the distribution of clasts deposited around a volcano during an explosive eruption typically contoured by isopleth maps provides important insights into the associated plume height wind speed and eruptive style nonetheless a wide range of strategies exists to determine the largest clasts which can lead to very different results with obvious implications for the characterization of eruptive behaviour of active volcanoes the iavcei commission on tephra hazard modelling has carried out a dedicated exercise to assess the influence of various strategies on the determination of the largest clasts suggestions on the selection of sampling area collection strategy choice of clast typologies and clast characterization i e axis measurement and averaging technique are given mostly based on a thorough investigation of two outcrops of a plinian tephra deposit from cotopaxi volcano ecuador located at different distances from the vent these include 1 sampling on a flat paleotopography far from significant slopes to minimize remobilization effects 2 sampling on specified horizontal area sections with the statistically representative sampling area depending on the outcrop grain size and lithic content 3 clast characterization based on the geometric mean of its three orthogonal axes with the approximation of the minimum ellipsoid lithic fragments are better than pumice clasts when present and 4 use of the method of the 50th percentile of a sample of 20 clasts as the best way to assess the largest clasts it is also suggested that all data collected for the construction of isopleth maps be made available to the community through the use of a standardized data collection template to assess the applicability of the new proposed strategy on a large number of deposits and to build a large dataset for the future development and refinement of dispersal models

old magma and a new intrusive trigger using diffusion chronometry to understand the rapid onset calbuco eruption april 2015 southern chile in april 2015 an unpredicted rapid onset eruption occurred at calbuco volcano southern andes of chile this event consisted of two sub plinian eruptions separated by a few hours by analysis of fe ti exchange between ilmenite and titanomagnetite crystals in samples of erupted material we determine timescales of pre eruptive heating experienced at the partially solidified chamber base and constrain the magma residence time for the bulk of the carrier magma analysis of the fe ti oxide pairs from a sample retrieved from a pyroclastic density current deposit cal 160 shows that it was affected by a significant heating event recording 70 220 c of heating while other collected samples did not record this late heating this sample is interpreted to represent a piece of crystal mush located at the bottom of a prolate ellipsoidal mush reservoir mobilised 4 days before the eruption by a triggering pulse of mafic magma considerably hotter than the typical magmatic temperature of the reservoir another two fall deposit samples lapillus cal 149tb and cal 155 of the eruption are interpreted to represent resident eruptible magmas that did not interact with any magma recharge immediately prior to or during the eruption we infer that these magmas had been at eruption temperature for some years based on their extensively equilibrated fe ti oxides

bromine as indicator of source of lacustrine sedimentary organic matter in paleolimnological studies bromine br to organic matter om concentration ratio is studied in lake sediment sequences to provide information on environmental changes modifying om production the sequences studied were extracted from shallow lakes morenito el trebol escondido and portezuelo and deep lakes futalaufquen moreno and traful north patagonia andean range lake morenito a former lake moreno bay until its closure in ad 1960 showed a decrease in br om ratios from 1 38 to 0 74 after lake closure associated with an increase of primary autochthonous productivity attributable to the development of submerged and emerging macrophytes sedimentary sequences from lakes escondido portezuelo and el trebol with large participation of macrophytes in primary productivity and from lakes moreno futalaufquen and traful with little development of littoral macrophytes showed br om ratios consistent with the lake morenito pattern consistently the morphometric parameters mean depth and shoreline development correlate with br om ratios therefore br om ratios can be associated with the composition of primary autochthonous productivity with values of about 0 7 associated to significant macrophyte contributions and higher values associated with more pelagic contributions accordingly br om variations along a sedimentary sequence can be associated with modifications on the composition of the primary autochthonous productivity of the water body providing information on environmental changes

volcanic lightning and plume behavior reveal evolving hazards during the april 2015 eruption of calbuco volcano chile soon after the onset of an eruption model forecasts of ash dispersal are used to mitigate the hazards to aircraft infrastructure and communities downwind however it is a significant challenge to constrain the model inputs during an evolving eruption here we demonstrate that volcanic lightning may be used in tandem with satellite detection to recognize and quantify changes in eruption style and intensity using the eruption of calbuco volcano in southern chile on 22 and 23 april 2015 we investigate rates of umbrella cloud expansion from satellite observations occurrence of lightning and mapped characteristics of the fall deposits our remote sensing analysis gives a total erupted volume that is within uncertainty of the mapped volume 0 56 0 28 km3 bulk observations and volcanic plume modeling further suggest that electrical activity was enhanced both by ice formation in the ash clouds 10 km above sea level and development of a low level charge layer from ground hugging currents

fallout and distribution of volcanic ash over argentina following the may 2008 explosive eruption of chaiten chile 1 the major explosive eruption of chaiten volcano chile in may 2008 provided a rare opportunity to track the long range dispersal and deposition of fine volcanic ash the eruption followed 10 000 years of quiescence was the largest explosive eruption globally since hudson chile in 1991 and was the first explosive rhyolitic eruption since novarupta alaska in 1912 field examination of distal ashfall indicates that 1 6 1011 kg of ash dense rock equivalent volume of 0 07 km3 was deposited over 2 105 km2 of argentina during the first week of eruption the minimum eruption magnitude estimated from the mass of the tephra deposit is 4 2 several discrete ashfall units are identifiable from their distribution and grain size characteristics with more energetic phases showing a bimodal size distribution and evidence of cloud aggregation processes ash chemistry was uniform throughout the early stages of eruption and is consistent with magma storage prior to eruption at depths of 3 6 km deposition of ash over a continental region allowed the tracking of eruption development and demonstrates the potential complexity of tephra dispersal from a single eruption which in this case comprised several phases over a week long period of intense activity

estimating the volume of tephra deposits a new simple strategy volume determination of tephra deposits is necessary for the assessment of the dynamics and hazards of explosive volcanoes several methods have been proposed during the past 40 years that include the analysis of crystal concentration of large pumices integrations of various thinning relationships and the inversion of field observations using analytical and computational models regardless of their strong dependence on tephra deposit exposure and distribution of isomass isopach contours empirical integrations of deposit thinning trends still represent the most widely adopted strategy due to their practical and fast application the most recent methods involve the best fitting of thinning data using various exponential segments or a power law curve on semilog plots of thickness or mass area versus square root of isopach area the exponential method is mainly sensitive to the number and the choice of straight segments whereas the power law method can better reproduce the natural thinning of tephra deposits but is strongly sensitive to the proximal or distal extreme of integration we analyze a large data set of tephra deposits and propose a new empirical method for the determination of tephra deposit volumes that is based on the integration of the weibull function the new method shows a better agreement with observed data reconciling the debate on the use of the exponential versus power law method in fact the weibull best fitting only depends on three free parameters can well reproduce the gradual thinning of tephra deposits and does not depend on the choice of arbitrary segments or of arbitrary extremes of integration

strain release and strain build up in the south iceland seismic zone abstract the south iceland seismic zone is a 70 km long and 10 20 km broad area of land in southern iceland where historically the most destructive earthquakes in iceland have occurred the zone is part of the e w bridge between the mid atlantic ridge and the neovolcanic zone which is an eastward offset of the ridge through iceland the basis for the present study is a historical and an instrumental earthquake catalogue the nature of strain release in earthquakes and as it is revealed in earthquake cracks and observations of aseismic strain release and source propagation the strain build up is modelled as an interplay between the general e w drift across the mid atlantic ridge and stresses caused by the horizontal outflow of upwelling mantle material a complex model of strain release is outlined including seismic as well as aseismic components while seismic strain release plays the dominant role in the eastern and central part of the zone to a depth even below 15 km aseismic slip takes up most of the motion in the western part of the zone and in its continuation in the reykjanes peninsula towards the reykjanes rid e

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

tephra stratigraphy and eruptive volume of the may 2008 chaiten eruption chile on may 1st 2008 mount chaiten southern chile interrupted a long period of quiescence generating a sequence of explosive eruptions and causing the evacuation of chaiten town located a few kilometers south of the volcano the activity was characterized by several explosive events each associated with plumes which reached up to about 19 km above sea level the products were dispersed across a wide area with the finest ash reaching the atlantic coast of argentina our field observations in the proximal medial area 3 25 km from the vent indicate that the may 2008 tephra deposit consists of numerous layers most of which can be correlated with individual eruptive events these layers vary from extremely fine grained ash to layers of lapilli and blocks composed of both juvenile and lithic material here we describe the stratigraphy and physical characteristics of the may 2008 deposits and propose a reconstruction of the timing of the may 2008 events the deposits are mainly associated with the three main explosive phases which occurred on 1st 2nd may 3rd 5th may and 6th may with an estimated bulk tephra volume of 0 5 1 0 km3 integration of both exponential and power law fitting for the 6th may event represented by a layer composed mainly of lithic lapilli and blocks 2 mm an isopleth map was compiled from which a 19 km plume height was determined which is in good agreement with satellite observations

direct injection of water vapor into the stratosphere by volcanic eruptions while theoretical studies show that water vapor wv can be directly injected into the stratosphere during a volcanic eruption few observations of such a phenomenon exist the microwave limb sounder observed stratospheric injection of wv following the 2015 calbuco eruption lower stratospheric mixing ratios exceeded 10 ppmv for a few days downwind of the injection location plume transport is confirmed by back trajectory modelling due to the short duration and limited spatial extent of the enhancement climatic impact is expected to be negligible this letter provides spatiotemporal analysis of a volcanogenic pulse of lower stratospheric wv as it dispersed the inferred mass of stratospheric wv from this eruption of 2 mt and the rapid evanescence of the enhancement is similar to what has been observed for other eruptions suggesting that injection by moderately explosive eruptions is not an effective mechanism for large scale stratospheric hydration

harmonic ionospheric oscillation by the 2010 eruption of the merapi volcano indonesia and the relevance of its amplitude to the mass eruption rate abstract using continuous data from ground based global satellite navigation system gnss receivers in java and sumatra indonesia we studied the response of ionospheric total ionospheric electron content tec to the 2010 nov 5 eruption of the merapi volcano in central java we then compared the results with the case of the 2014 feb 13 eruption of the kelud volcano eastern java the tec showed a quasi periodic oscillation of a frequency 4 mhz with average amplitudes of 0 9 and 1 8 relative to background values lasting for 20 and 120 min for the merapi and kelud eruptions respectively by comparing the two cases together with the 2015 april eruption of the calbuco volcano chile we found the relative tec oscillation amplitude may scale with the mass eruption rate this suggests that the product of such tec oscillation amplitude and the duration provides a new measure for the total volume of the volcanic deposits

an example of enhanced tephra deposition driven by topographically induced atmospheric turbulence spatial variations in the thickness and grain size characteristics of tephra fall deposits imply that tephra depositional processes cannot be fully captured by models of single particle sedimentation from the base of the eruption plume here we document a secondary thickness maximum in a 9 75 ka tephra fall deposit from chaiten volcano chile cha1 eruption this secondary thickness maximum is notably coarser grained than documented historical examples being dominated by medium grained ash and an origin via particle aggregation is therefore unlikely in the region of secondary thickening we propose that high levels of atmospheric turbulence accelerated particles held within the mid to lower troposphere 0 to 6 km towards the ground surface we suggest that this enhancement in vertical atmospheric mixing was driven by the breaking of lee waves generated by winds passing over elevated topography beneath the eruption plume lower atmospheric circulation patterns may exert a significant control on the dispersal and deposition of tephra from eruption plumes across all spatial scales particularly in areas of complex topography

earthquake statistics at parkfield 1 stationarity of b values 1 in this paper paper 1 we quantitatively show that the heterogeneous pattern of b values of the gutenberg richter relation in the parkfield segment of the san andreas fault is to a high degree stationary for the past 35 years this prepares the grounds for paper 2 where we test the hypothesis that our model of spatially varying b values forecasts future seismicity more accurately than the approach in which one assumes a constant b value equal to the average regional value the method we develop to measure stationarity in the presence of spatial heterogeneity consists of the following steps 1 determine the optimal dimensions of the sampling volume by mapping b values with a wide range of radii and selecting the largest radius that gives the most detailed resolution of the b value heterogeneity along the selected fault segment the high data density permits the definition of the dominant dimensions of the seismotectonic fabric which is about 8 10 km 2 map the difference in b value between two periods selecting numerous possible catalog divisions 3 identify significant changes of b values by the utsu test utsu 1992 along the studied fault segment of 110 km length only one patch of radius 5 km showed a significant increase in b from below average to above as a function of time this change in b initiates around 1993 and thus correlates in space and time with a well documented episode of creep at depth using the derived spatial variable b value distributions we find that the highest probability for earthquakes with magnitude m 6 is in the middle mountain asperity where the 1966 parkfield earthquake nucleated and where all m 4 5 events in the data set occurred in contrast if only the regional average b value of 0 92 is used to predict future seismicity the creeping segment north of parkfield should produce major earthquakes most frequently a conclusion that contradicts the observations

representivity of incompletely sampled fall deposits in estimating eruption source parameters a test using the 12 13 january 2011 lava fountain deposit from mt etna volcano italy the southeast crater sec of mt etna italy is renowned for its high activity mainly long lived eruptions consisting of sequences of individual paroxysmal episodes which have produced more than 150 eruptive events since 1998 each episode typically forms eruption columns followed by tephra fallout over distances of up to about 100 km from the vent one of the last sequences consisted of 25 lava fountaining events which took place between january 2011 and april 2012 from a pit vent on the eastern flank of the sec and built a new scoria cone renamed new southeast crater the first episode on 12 13 january 2011 produced tephra fallout which was unusually dispersed toward to the south extending out over the mediterranean sea the southerly deposition of tephra permitted an extensive survey at distances between 1 and 100 km providing an excellent characterization of the tephra deposit here we document the stratigraphy of the 12 13 january fallout deposit draw its dispersal and reconstruct its isopleth map these data are then used to estimate the main eruption source parameters the total erupted mass tem was calculated by using four different methodologies which give a mean value of 1 5 0 4 108 kg the mass eruption rate mer is 2 5 0 7 104 kg s using eruption duration of 100 min the total grain size tgs distribution peaked at 3 phi ranges between 5 and 5 phi and has a median value of 1 4 phi further for the eruption column height we obtained respective values of 6 8 13 8 km by using the method of carey and sparks 1986 and 3 4 0 3 km by using the methods of wilson and walker 1987 mastin et al 2009 and pistolesi et al 2011 and considering the mean value of mer from the deposit we also evaluated the uncertainty and reliability of tem and tgs for scenarios where the proximal and distal samples are not obtainable this is achieved by only using a sector spanning the downwind distances between 6 and 23 km this scenario is typical for etna when the tephra plume is dispersed eastward i e in the prevailing wind direction our results show that if the analyzed deposit has poorer sample coverage than presented in this study the tem 3 4 107 kg is 22 than the tem obtained from the whole deposit the lack of the proximal 6 km deposit may cause more significant differences in the tgs estimations

ash resuspension related to the 2011 2012 cordon caulle eruption chile in a rural community of patagonia argentina abstract the 2011 2012 cordon caulle eruption emitted about 1 km3 of rhyodacitic tephra dominant westerly winds in the region caused most of the primary tephra to deposit in neighboring argentina in addition to the impact of widespread dispersal and fallout of primary tephra during the eruption argentina was also significantly affected by remobilization of the primary ash even several years after the climactic phase of the eruption in this mixed methods study we combine aspects of natural and social sciences to characterize the ash resuspension events associated with the 2011 2012 cordon caulle deposits and assess the impacts on the argentinian farming community of ingeniero jacobacci in the patagonian steppe our findings show the primary importance of wind rainfall and ash availability in controlling the occurrence and persistence of ash resuspension events the role played by these variables was also reflected in the seasonal distribution of events observed regarding the impacts our results complement those of earlier studies and demonstrate that ash resuspension events can exacerbate the negative impact of primary tephra fallout events from the time of deposition to many years after the eruption only after five years has the environment and the farming community begun to show signs of recovery our findings also highlight the importance of assessing ash resuspension events in multi hazard scenarios involving volcanic and hydrometeorologic hazards

aseismic slip in earthquake nucleation and self similarity evidence from parkfield california aseismic slip microearthquakes and moderate earthquakes all take place along the san andreas fault at parkfield california in this letter we discuss the relationship of these slip mechanisms by establishing and modelling the local microearthquake size frequency distribution by examining the effect of background noise on earthquake event detection we show that the distribution is complete for m 0 3 unlike the gutenberg richter law the distribution begins with a relatively small number of very small events further the scaling relation of the distribution changes continuously with event size noting that many parkfield aseismic slip or creep events have moments equivalent to the smaller microearthquakes we show that the nucleation of microearthquakes by this type of slip can account for the size frequency distribution such a model does not require a lower limit to either earthquake or creep event size rather it suggests that at parkfield a transition from creep dominated slip to earthquake dominated slip takes place in the range of moments equivalent to magnitudes close to m 0 9 this is well above the m 0 3 detection limit of the seismic network but right at the limit of current near surface strain instruments

multisatellite multisensor observations of a sub plinian volcanic eruption the 2015 calbuco explosive event in chile a train satellite data acquired during the calbuco volcano chile sub plinian eruption in april 2015 are discussed to explore the complementarity of spaceborne observations in the microwave mw thermal infrared tir and visible wavelengths for both near source plume and distal ash clouds the analysis shows that tir based detection techniques are not suitable near the volcanic vent where rising convective columns are associated with large optical depths detection and parametric estimates of near source tephra mass loading and plume height from mw radiometric data available 69 min after the eruption onset are proposed results indicate a maximum plume altitude of about 21 km above the sea level and an ash mass of 3 65 times 10 10 kg in agreement with mass values obtained from empirical formulas but less than proximal distal mass deposit of 1 86 times 10 11 kg this discrepancy may be explained by extrapolating advanced technology microwave sounder based estimates to 6 h thus obtaining a total mass of about 1 90 times 10 11 kg distal volcanic cloud retrievals are derived from tir imagery and results show a good agreement between moderate resolution imaging spectroradiometer modis and visible infrared imaging radiometer suite viirs retrievals of total mass taking into account the overpass time shift if only the overlapping pixels between modis and viirs are considered the respective estimates are 1 90 times 10 9 kg and 1 80 times 10 9 kg tir radiometric estimates of distal ash cloud height and mass loadings are also compared with cloud aerosol lidar and infrared pathfinder satellite observations lidar retrievals for low to medium optically thick ash cloud average cloud aerosol lidar with orthogonal polarization derived mass loading is about 0 8 g m2 against 0 4 g m2 from viirs and 1 4 g m2 from modis

source and path of magma for volcanoes in the subduction zone of northeastern japan the assumption that the source of magma for volcanoes in subduction zones is located in the mantle immediately above the top of the subducting slab at approximately 100 km depth and straight beneath the volcanoes is incorrect in northeastern japan the combination of evidence from velocity tomography in the mantle wedge above the slab and mapping of earthquake size distribution within it strongly points to a source of fluids at the top of the slab at 140 to 150 km depth from where material rises along an inclined path to the volcanoes

metamorphic feldspathization of metavolcanics and granitoids avnik area turkey in the avnik area of the bingol massif the lower unit consists of basic to felsic metavolcanics ca 450 ma intruded by granitoids ca 350 ma these are unconformably overlain by an upper unit of micaschists and permian marbles both units have been deformed and metamorphosed in alpine time the metavolcanics and granitoids are extensively feldspathized and silicified the granitoids and basic intermediate volcanics are albitized while felsic volcanics are k feldspathized metasomatism has severely modified k rb and rb sr ratios but not ree patterns and is inferred to have occurred at relatively low t nametasomatism of the upper unit micaschists has produced albite porphyroblasts

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

application of independent component analysis to multi temporal insar data with volcanic case studies a challenge in the analysis of multi temporal interferometric synthetic aperture radar insar data is distinguishing and separating volcanic tectonic and anthropogenic displacements from each other and from atmospheric or orbital noise independent component analysis ica is a method for decomposing a mixed signal based on the assumption that the component sources are non gaussian and statistically independent ica has potential as a tool for exploratory analysis of insar data and in particular for testing whether geophysical signals are related or independent this article presents tests of the applicability of ica to insar using synthetic data and application to sentinel 1a archive images from two contrasting examples of volcano deformation co eruptive subsidence associated with the april 2015 eruption of calbuco chile was identified in spatial patterns found by maximising both spatial and temporal independence spatial patterns and rates of lava subsidence were retrieved using ica analysis of interferograms from paricutin lava fields mexico and found to be consistent with previous observations i demonstrate that ica is an appropriate method for the analysis of volcanic signals in the presence of atmospheric noise and propose a strategy for the automatic identification of geophysical displacements using cluster analysis of the spatial patterns of independent components this approach allows the detection of geophysical processes on a range of scales and provides a test of signal independence where multiple displacement sources are active

forecasting volcanic ash dispersal and coeval resuspension during the april may 2015 calbuco eruption abstract atmospheric dispersion of volcanic ash from explosive eruptions or from subsequent fallout deposit resuspension causes a range of impacts and disruptions on human activities and ecosystems the april may 2015 calbuco eruption in chile involved eruption and resuspension activities we overview the chronology effects and products resulting from these events in order to validate an operational forecast strategy for tephra dispersal the modelling strategy builds on coupling the meteorological weather research and forecasting wrf arw model with the fall3d dispersal model for eruptive and resuspension processes the eruption modelling considers two distinct particle granulometries a preliminary first guess distribution used operationally when no field data was available yet and a refined distribution based on field measurements volcanological inputs were inferred from eruption reports and results from an argentina chilean ash sample data network which performed in situ sampling during the eruption in order to validate the modelling strategy results were compared with satellite retrievals and ground deposit measurements results indicate that the wrf fall3d modelling system can provide reasonable forecasts in both eruption and resuspension modes particularly when the adjusted granulometry is considered the study also highlights the importance of having dedicated datasets of active volcanoes furnishing first guess model inputs during the early stages of an eruption

chironomids as indicators of natural and human impacts in a 700 yr record from the northern patagonian andes abstract chironomid communities were studied in a sediment core collected from lake moreno oeste located in nahuel huapi national park a major change in midge assemblages occurred at ad 1760 which was characterized by a decrease of cold taxa including polypedilum sp 2 and dicrotendipes and an increase of warm taxa including apsectrotanypus and polypedilum sp 1 these taxa are likely related to climatic conditions concurrent with the end of a cold period at ad 1500 1700 and the beginning of a drying climate at ad 1740 1900 in northern patagonia coarse tephra layers had low midge diversity however they did not disrupt the climatic trend as the community recovered rapidly after the event since ad 1910 after the increase in suburban housing fish introduction and the construction of a road there was an increase in the relative abundances of taxa typically associated with the littoral zone such as parapsectrocladius riethia apsectrotanypus and some tanytarsini morphotypes the main change in the chironomid community appears to be associated with long term climate change at the beginning of the 20th century other site specific environmental factors catchment change and fish introduction altered the chironomid assemblages making it more difficult to understand the relative importance of each driver of assemblage change

implications for paleomobility studies of the effects of quaternary volcanism on bioavailable strontium a test case in north patagonia argentina abstract strontium isotopes 87sr 86sr are used as geochemical tracers for paleomobility studies because they display predictable and stable patterns in ecosystems primarily controlled by the underlying geological regimes while bedrock geology is stable over thousands of years geomorphological processes can influence the 87sr 86sr in ecosystems over archeologically relevant timescales among these geomorphological processes the deposition and reworking of volcanic sediments over quaternary timescales are little studied but could be an important control of 87sr 86sr variations in many archeological regions north patagonia is a key archeological region to address animal and human movements and an ideal location to test the influence of quaternary volcanism on 87sr 86sr variation as it is located downwind of major volcanic centers in this study we aim to assess the main environmental and geological controls of bioavailable 87sr 86sr and to build a high resolution isoscape using a machine learning regression framework for forthcoming paleomobility studies we sampled several locations and analyzed different types of samples n 94 the ratios show a limited range of variation which is not related to the bedrock geology rather bioavailable 87sr 86sr variations display a progressive increase going eastward away from the andes following dust aerosol deposition and elevation variations r2 0 71 rmse 0 00041 we argue that this trend relates to the deposition and reworking of unradiogenic volcanic sediments by aeolian fluvial and glacial erosion during the quaternary as most of this sediment reworking occurred during glacial periods the current bioavailable 87sr 86sr variations across the study area likely represent a long term average that varied little during the holocene consequently our isoscape provides a solid base for holocene paleomobility studies in north patagonia and underlines the importance of quaternary volcanism processes for interpreting 87sr 86sr data in paleomobility studies in volcanic regions

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

a systematic test of the hypothesis that the b value varies with depth in california we spatially map the shallow to deep b value ratio in the crust in california previous studies of the frequency magnitude distribution as a function of depth for selected crustal regions indicated that b decreases from b 1 1 in the 0 5 km depth range to b 0 8 in the depth range 7 15 km our detailed mapping confirms that this pattern can be established at the 99 significance level for about 32 of the entire seismically active crust about 2 of the crust displays the opposite b gradient one such area is the san francisco bay area we speculate that differences in stress levels are the main factor controlling the depth dependency of b these results confirm that the b value should not always be considered a constant in studies such as seismic hazard estimations

most likely locations of large earthquakes in the kanto and tokai areas japan based on the local recurrence times abstract we examined the hypothesis that minima in local recurrence time tl or equivalently maxima in local probability pl may map asperities in the kanto and tokai areas of japan where the earthquake catalog of the national research institute for earth science and disaster prevention nied is complete at the m 1 5 m1 5 level we mapped tl pl based on the a and b values of the nearest earthquakes within 20 km of every node of a grid spaced 0 01 for m7 target events only earthquakes within the top 33 km were used the b values increase strongly with depth in several areas therefore some of the tl pl anomalies are not revealed if data from the entire crustal seismogenic zone are mixed thus we mapped tl pl separately for the top 15 km and the rest of the depth range as well as for the entire seismogenic crust the resulting tl and pl maps show that approximately 12 of the total area shows anomalously short recurrence times out of six shallow target events with m 6 5 and which occurred since 1890 five are located within the anomalous areas with tl

an example of trondhjemite genesis by means of alkali metasomatism rockford granite alabama appalachians a model for trondhjemite genesis is proposed where granite is transformed to trondhjemite via infiltration by a na rich metamorphic fluid the rockford granite of the northern alabama piedmont serves as the case example for this process and is characterized as a synmetamorphic peraluminous trondhjemite granite suite the major process operative in the conversion of granite to trondhjemite involves cation exchange of na for k in the feldspar and mica phases through a volatile fluid medium whole rock 18o values for the trondhjemites are negatively correlated with atomic proportion k na ratio indicating a partial reequilibration of the altered granitoids with a na and18o rich metamorphically derived fluid biotite decomposition to an al epidote paragonitic muscovite secondary quartz assemblage is also associated with the sodium metasomatism as are apatite replacement by al epidote and secondary zircon crystallization rare albitization of primary magmatic plagioclase and discontinuous grossularite reaction rim growth on magmatic garnet are present in the trondhjemites indicating the mobility of ca during alkali metasomatism the replacement of magmatic phases by me tasomatic phases exemplifies the chemical changes produced during infiltration metasomatism where the trondhjemites are depleted in p2o5 th rb u k2o v sn f mgo pb tio2 feo and li and enriched in cao na2o zr and sr relative to the granites other elements such as cr mno cu zn co ba sio2 ni al2o3 are shown to be relatively immobile during the metasomatism the infiltration metasomatism probably occurred during prograde regional metamorphism when a discrete fluid phase was produced in the surrounding amphibolite grade metasediments foliation planes in the granite apparently served as conduits for fluid flow with reaction enhanced permeability accompanying the 8 molar volume reduction during na for k exchange in the feldspars a source for the na and sr in the metamorphic fluid may have been paragonitic muscovite in the metasedimentary country rocks rubidium and k were probably retained in metasedimentary biotite the silent lake pluton in southeastern ontario is a possible analogue to the alkali metasomatic processes affecting the rockford granite

calbuco volcano and minor eruptive centers distributed along the liquine ofqui fault zone chile 41 42 s contrasting origin of andesitic and basaltic magma in the southern volcanic zone of the andes calbuco volcano is a late pleistocene holocene composite stratovolcano located at 41 20 s in the southern region of the southern volcanic zone of the andes ssvz 37 46 s in contrast to basalt and basaltic andesite which are the dominant lava types on the volcanic front from 37 to 42 s calbuco lavas are porphyritic andesites which contain a wide variety of crustal xenoliths they have sio2 contents in the 55 60 range and have comparatively low k2o rb ba th and lref abundances relative to other ssvz centers incompatible element abundance ratios are similar to those of most ssvz volcanics but 87sr 86sr and 143nd 144nd are respectively higher and lower than those of adjacent volcanic centers basalts from nearby osorno stratovolcano 25 km to the northeast are similar to other basaltic ssvz volcanoes however basalts from several minor eruptive centers mec located east of calbuco and osorno volcano along the liquine ofqui fault zone lofz are enriched in ba nb th and lree and have higher la yb and lower ba la k la and rb la 87sr 86sr and 143nd 144nd in mec basalts are respectively lower and higher than those of osorno and calbuco lavas we suggest that mec basalts were produced by lower extents of mantle melting than basalts from osorno and other ssvz stratovolcanoes probably as a result of lower water content in the source of mec basalts calbuco andesites formed from basaltic parents similar to osorno basalts by moderate pressure crystallization of a hornblende bearing assemblage accompanied by crustal assimilation hornblende stability in the calbuco andesites was promoted by the assimilation of hydrous metasedimentary crustal rocks which are also an appropriate endmember for isotopic trends together with magma storage at mid crustal depths the unique characteristics of calbuco volcano i e the stability of hornblende at andesitic sio2 contents low 143nd 144nd and high 87sr 86sr and abundant crustal xenoliths provide evidence for crustal assimilation that is not apparent at more northerly volcanoes in the ssvz

mapping asperities by minima of local recurrence time san jacinto elsinore fault zones minima of the local recurrence time tl m are correlated with the locations of historical main shocks in the san jacinto sj elsinore e fault zones of southern california we define tl m as the recurrence time calculated from the local b and a values of the frequency magnitude distribution earthquakes within 6 and 10 km from each point in the sj and e fault zones respectively we propose that anomalously low tl m values map asperities out of six historic main shocks 1899 1968 five ruptured substantial parts of four asperities mapped by our method which uses solely the modern earthquake catalog m 1 2 1981 0 1998 8 we estimate the probability for this correlation to occur at random as 10 2 to 10 3 depending on the scenario chosen it appears that the minima in tl m are tied to minima in b values more than to maxima in a values thus locations of low b values can also be used as an indication where asperities may be located and where main shocks are most likely the anza gap a segment of the san jacinto fault with low a values is mapped as an asperity by our method the heterogeneity in b values is strong throughout the study area the b values range from 0 5 to 1 8 over distances of 10 km volumes with approximately constant b values have radii of r 8 6 km our results suggest that detailed mapping of b values and local recurrence times in volumes with a few kilometers radius reveals important information about the local seismic hazard hitherto untapped by conventional seismicity analyses