observation of internal tides in the east china sea with an underwater sliding vehicle detailed structures of internal tides in the east china sea were observed during autumn from 1986 to 1989 using an underwater sliding vehicle that can measure temperature conductivity and depth continuously sliding up and down along a faired cable a variety of structures were observed and are classified with internal froude numbers of the lowest two modes which depend on the barotropic tidal current velocities and the phase speeds of internal waves i e stratification in the central east china sea the second mode waves are most strongly generated at the shelf break and then propagate shoreward onto the east china sea continental shelf since the barotropic tidal current is faster than the phase speed of the second mode waves on the shelf the generation mechanism is consistent with conventional models on the other hand in the southern east china sea the lowest mode response is dominant although the tidal current velocity is slower than the lowest mode phase speed a nonlinear model is proposed for this response

fire ecology of the carboniferous tropical zone abstract fossil charcoal fusain indicating the occurrence of wildfire is common in the carboniferous rocks of north america and europe during the carboniferous these regions lay on the southern margins of the laurasian continent and within the tropical zone this study examines the facies distribution and botanical identity of charcoal in order to investigate the influence of fire on carboniferous tropical ecology new data from charcoal bearing units in eastern canada poland and the british isles are presented and synthesised with previously published data of charcoal occurrence tournaisian visean charcoal bearing strata were deposited in volcanic lacustrine alluvial plain and coastal marine environments in these deposits charred floras are dominated by pro gymnospermous plants whilst uncharred compressed or permineralised floras are dominated by lycopsids uncharred lycopsid remains were probably derived from wetland communities growing close to the depocentres whilst charred gymnospermous remains may have been sourced from well drained extrabasinal settings based on the vertical distribution of charcoal layers in annually laminated lacustrine deposits it is estimated that fires occurred with high frequency approximately every 3 35 years palaeoclimatic analysis indicates that southern laurasia at this time was subject to a seasonal monsoonal tropical climate such environments today are characterised by tropical savannas with high fire frequencies and early carboniferous fire prone gymnospermous plant communities may have represented a comparable vegetation biome namurian stephanian charcoal bearing strata were deposited in alluvial plain coastal plain and coastal marine environments channelised sandstone units interpreted as river channel deposits contain charcoal derived from cordaitaleans and conifers this assemblage records fires in extrabasinal coniferopsid forests mudstone units containing coals are interpreted as the deposits of floodbasins and peat mires hollow uncharred lepidodendrid stumps occur in this facies and contain lepidodendrid charcoal in the stump bases and lepidodendrid pteridosperm coniferopsid and sphenopsid charcoal outside the stumps this assemblage records fires in wetland lepidodendrid dominated forests lepidodendrid trunks comprising of a spongy parenchymatous core surrounded by dense periderm became hollowed out during fire events an estimate of fire frequency based on the vertical spacing of charcoal layers in coals implies that fires occurred every 105 1085 years in the peat mires palaeoclimatic analysis indicates that southern laurasia was subject to a humid tropical climate during the late carboniferous such environments today are characterised by tropical rainforests where fires occur rarely and late carboniferous communities may have represented a comparable biome

statistical analyses and characteristics of volcanic tremor on stromboli volcano italy a study of volcanic tremor on stromboli is carried out on the basis of data recorded daily between 1993 and 1995 by a permanent seismic station str located 1 8 km away from the active craters we also consider the signal of a second station tf1 which operated for a shorter time span changes in the spectral tremor characteristics can be related to modifications in volcanic activity particularly to lava effusions and explosive sequences statistical analyses were carried out on a set of spectra calculated daily from seismic signals where explosion quakes were present or excluded principal component analysis and cluster analysis were applied to identify different classes of spectra three clusters of spectra are associated with two different states of volcanic activity one cluster corresponds to a state of low to moderate activity whereas the two other clusters are present during phases with a high magma column as inferred from the occurrence of lava fountains or effusions we therefore conclude that variations in volcanic activity at stromboli are usually linked to changes in the spectral characteristics of volcanic tremor site effects are evident when comparing the spectra calculated from signals synchronously recorded at str and tf1 however some major spectral peaks at both stations may reflect source properties statistical considerations and polarization analysis are in favor of a prevailing presence of p waves in the tremor signal along with a position of the source northwest of the craters and at shallow depth

cases study of nonlinear interaction between near inertial waves induced by typhoon and diurnal tides near the xisha islands nonlinear interaction between near inertial waves niws and diurnal tides dts after nine typhoons near the xisha islands of the northwestern south china sea scs were investigated using three year in situ mooring observation data it was found that a harmonic wave f d 1 hereafter referred to as fd 1 wave with a frequency equal to the sum of frequencies of niws and dts hereafter referred to as f and d 1 respectively was generated via nonlinear interaction between typhoon induced niws and dts after each typhoon the fd 1 wave mainly concentrates in the subsurface layer and is mainly induced by the first component of the vertical nonlinear momentum term the product of the vertical velocity of dt and vertical shear of near inertial current hereafter referred to as component 1 in which the vertical shear of the near inertial current greatly affects the strength of the fd 1 current the larger the component 1 the stronger the fd 1 currents the background preexisting mesoscale anticyclonic eddy near the mooring site may also enhance the vertical velocity of dt and thus component 1 which subsequently facilitates the nonlinear interaction induced energy transfer to the fd 1 wave and enhances the fd 1 currents after the passage of a typhoon

seismic insight into explosive paroxysms at stromboli volcano italy abstract at stromboli volcano italy continuous seismic monitoring and periodic visual observations of volcanic activity for surveillance purposes began in the mid 1980s since 1985 two eruptions have occurred one lasting from december 1985 until april 1986 and one in may 1993 there have also been two small overflows in 1990 and 1994 since these episodes of lava effusion the persistent strombolian activity of the volcano has had several fluctuations during the past 15 years some episodes climaxed in powerful explosions according to seismic records these paroxysms consisted of a variable number of explosion quakes in rapid succession i e from tens of seconds to a few minutes associated with a notable increment in the amplitude of volcanic tremor throughout these episodes which are called explosive sequences lapilli fragments of old rock and bombs of varying dimensions were ejected affecting an area greater than the crater terrace where the active craters are located in this article we describe the explosive sequences recorded at stromboli between 1985 and 1999 we provide a characterization in terms of reduced displacement and duration for nine episodes occurring in 1998 and 1999 their reduced displacements range from 15 to 124 cm 2 their durations are between 6 and 18 min we find no change in the frequency content of the seismic signal several minutes before and during the sequences considering medium to long term behavior the spectral amplitude of the seismic signal decreases or has low values over several months preceding the occurrence of the paroxysms this feature is common to 20 of the 22 explosive sequences and is indicative of internal conditions that periodically characterize the feeder we surmise that the paroxysms are the result of the partial obstruction of the volcanic conduit when the magma column is low or dropping the onset of the explosive sequence causing the sudden removal of the material which forms the obstruction would trigger a sudden depressurization of the conduit and the rapid rise of magma from depth

tectonic seismicity at stromboli volcano italy from historical data and seismic records abstract we describe the main features of crustal tectonic seismicity in the area of stromboli aeolian islands a volcano known worldwide for its typical strombolian activity we consider data from the italian catalogues of earthquakes along with records of the local seismic network covering the time span from 1885 to 1998 in the historical catalogues we find a low occurrence rate of earthquakes with a small number of seismic events having intensity viii in the mercalli cancani sieberg scale recent instrumental data confirm this finding achieving a maximum magnitude m d 3 7 we explain this low tectonic seismicity as the effect of conditions which allow only a limited storage of stress from a seismic viewpoint the aeolian archipelago shows two different seismogenic domains spatially separated by the aeolian tindari giardini fault system one domain which includes the western and southern parts of the aeolian islands is characterized by crustal seismic activity the second domain which includes the eastern part of the archipelago where stromboli lies has a large number of intermediate and deep earthquakes but little crustal seismicity we surmise that each domain has vertical heterogeneity separating ductile deformation from brittle failure of rock induced by temperature conditions and or hydration dehydration reactions which affect the mechanical strength of the medium

long period events the most characteristic seismicity accompanying the emplacement and extrusion of a lava dome in galeras volcano colombia in 1991 abstract since its reactivation in 1988 the principal eruptions of galeras volcano occurred on may 4 9 1989 july 16 1992 and january 14 march 23 april 3 april 14 and june 7 1993 the initial eruption was a phreatic event which clearly marked a new period of activity a lava dome was extruded within the main crater in october 1991 and subsequently destroyed in an explosive eruption on july 16 1992 the eruptions that followed were all vulcanian type explosions the seismicity accompanying the emplacement extrusion and destruction of the lava dome was dominated by a mix of long period lp events and tremor displaying a variety of waveforms repetitive lp events with dominant periods in the range 0 2 1 s were observed in october and november 1991 and visually correlated with short energetic pulses of gas venting through a crack bisecting the dome surface each lp event was characterized by a weak precursory signal with dominant periods in the range 0 05 0 1 s lasting roughly 7 s using the fluid driven crack model of chouet 1988 1992 we infer that two distinct cracks may have acted as sources for the lp and precursor signals spectral analyses of the data yield the following parameters for the lp source crack length 240 360 m crack width 130 150 m crack aperture 0 5 3 4 mm crack stiffness 100 500 sound speed of fluid 880 m s and excess pressure 0 01 0 19 mpa similar analyses yield the parameters of the precursor source crack length 20 30 m crack width 15 25 m crack aperture 2 3 8 7 mm crack stiffness 5 15 sound speed of fluid 140 m s and excess pressure 0 06 0 15 mpa combined with geologic and thermodynamic constraints obtained from field observations these seismic parameters suggest a gas release mechanism in which the episodic collapse of a foam layer trapped at the top of the magma column subjacent to the dome releases a slug of pressurized gas which escapes to the surface while dilating a preexisting system of cracks in the dome structure accordingly the fracture observed on the crystallized dome body is the surface extension of the lp source crack where lp activity is induced by the rapid emission and expansion of gas flowing through this conduit the width and aperture of the crack estimated in the model are in good agreement with the length and aperture of the fracture estimated from visual observations the source parameters of the precursor signal are suggestive of a nozzle like conduit connecting the lp source crack to the underlying magma reservoir excitation of this conduit segment is attributed to the rapid emission and acceleration of the frothy fluid resulting from the collapse of the foam layer at the top of the reservoir the calculated periodicity of foam collapse events is in agreement with the observed average rate of thirteen lp events per hour

anomalous magmatic degassing prior to the 5th april 2003 paroxysm on stromboli 1 a major explosion occurred at stromboli on april 5 2003 being the most powerful event over a period of exceptional eruptive activity lasting from december to july here we describe results from a network of diffusive tubes set up on the stromboli s summit area aimed at a characterisation of plume composition so2 hcl hf prior to and after april 5 data analysis revealed anomalous sulphur degassing 2 3 days before the event when so2 hcl ratios 9 significantly higher than those typical of quiescent degassing 1 were recorded we interpret this exceptional plume signature as an evidence of s rich magmas ascending in the shallow plumbing system and propose high so2 hcl as a potential precursor of major explosions on the volcano the post april 5 phase was characterised by time decreasing so2 hcl and so2 hf plume ratios ascribed to declining magma feeding as a prelude to restoration of normal strombolian activity

invertebrate trace fossils and agglutinated foraminifera as indicators of marine influence within the classic carboniferous section at joggins nova scotia canada the sea cliffs at joggins nova scotia are the most extensive and continuous carboniferous section in eastern north america although the section has been considered to have formed within a nonmarine depositional basin paleobiological information indicates that parts of the section were deposited in brackish water the occurrence of a trace fossil assemblage which includes cochlichnus kouphichnium and treptichnus is part of an assemblage of biogenic structures that apparently reflects paleodeposition within fluvial systems that may have experienced distal marine influences presence of agglutinated foraminifera characteristic of brackish water environments supports this interpretation this information provides new evidence of brackish water conditions at joggins such as those now being widely recognized in other carboniferous coal bearing sections

shallow velocity structure of stromboli volcano italy derived from small aperture array measurements of strombolian tremor abstract the properties of the tremor wave field at stromboli are analyzed using data from small aperture arrays of short period seismometers deployed on the north flank of the volcano the seismometers are configured in two semi circular arrays with radii of 60 and 150 m and a linear array with length of 600 m the data are analyzed using a spatiotemporal correlation technique specifically designed for the study of the stationary stochastic wave field of rayleigh and love waves generated by volcanic activity and by scattering sources distributed within the island the correlation coefficients derived as a function of frequency for the three components of motion clearly define the dispersion characteristics for both rayleigh and love waves love and rayleigh waves contribute 70 and 30 respectively of the surface wave power the phase velocities of rayleigh waves range from 1000 m sec at 2 hz to 350 m sec at 9 hz and those for love waves range from 800 to 400 m sec over the same frequency band these velocities are similar to those measured near puu oo on the east rift of kilauea volcano hawaii although the dispersion characteristics of rayleigh waves at stromboli show a stronger dependence on frequency such low velocities are consistent with values expected for densely cracked solidified basalt the dispersion curves are inverted for a velocity model beneath the arrays assuming those dispersions represent the fundamental modes of rayleigh and love waves

a co2 rich gas trigger of explosive paroxysms at stromboli basaltic volcano italy in addition to rhythmic slug driven strombolian activity stromboli volcano occasionally produces discrete explosive paroxysms 2 per year on average for the most frequent ones that constitute a major hazard and whose origin remains poorly elucidated partial extrusion of the volatile rich feeding basalt as aphyric pumice during these events has led to consider their triggering by the fast ascent of primitive magma blobs from possibly great depth here i examine and discuss the alternative hypothesis that most of the paroxysms could be triggered and driven by the fast upraise of co2 rich gas pockets generated by bubble foam growth and collapse in the sub volcano plumbing system data for the so2 and co2 crater plume emissions are used to show that stromboli s feeding magma may originally contain as much as 2 wt of carbon dioxide and early coexists with an abundant co2 rich gas phase with high co2 so2 molar ratio 60 at 10 km depth below the vents compared to 7 in time averaged crater emissions pressure related modelling indicates that the time averaged crater gas composition and output are well accounted for by closed system decompression of the basalt gas mixture until the volcano crust interface 3 km depth followed by open degassing and crystallization in the volcano conduits however both the low viscosity and high vesicularity of the basaltic magma permit bubble segregation and bubble foam growth at deep sill like feeder discontinuities and at shallower physical boundaries such as the volcano crust interface where the gas rich aphyric basalt interacts with the unerupted crystal rich and viscous magma drained back from the volcano conduits gas pressure build up and bubble foam collapse at these boundaries will intermittently trigger the sudden upraise of co2 rich gas blobs that constitute the main driving force of the paroxysms deeper sourced gas blobs driving the most powerful explosions will be the richest in co2 and have highest co2 so2 ratios this mechanism is shown to account well for the dynamic seismic and petrologic features of stromboli s paroxysms and hence to provide a potential alternative interpretation for their genesis and their forecasting enhanced bubble foam leakage prior to a paroxysm or foam emptying in several steps should lead indeed to precursory upstream of co2 rich gas and increasing co2 so2 ratio in crater plume emissions the recent detection of such signals prior to two explosions in december 2006 and march 2007 strongly supports this expectation and the model proposed in this study

second mode internal tides in the east china sea deduced from historical hydrocasts and a model during the two year deployment period to obtain temperature t and specific volume anomaly d profiles from t and sea surface temperature sst observed respectively by pies and satellite we constructed multi index gravest empirical mode mi gem fields park et al 2005 using historical hydrocasts however comparison between the mi gem fields and the historical hydrocasts reveals that the mi gem fields fail to capture 44 and 52 of the t and d variance respectively in the p 100 200 dbar layer this may be caused by 2nd or higher mode variations of vertical structure since t is insensitive to all but the lowest baroclinic mode watts and rossby 1977 4 in this study we demonstrate that 2nd mode its in the ecs are responsible for failure of the mi gem fields to captureadequatelytand dvariationsinthep 100 200 dbar layer as seen in historical hydrographic measurements we verify our observations with a numerical simulation of its

evidence for gas influence on volcanic seismic signals recorded at stromboli abstract the meaning of the large variety of seismic waveforms showing different frequencies associated with volcanic activity is still uncertain no definitive model for source dynamics has been proposed yet at present seismic models explaining the origin of the spectral content of the seismic signal are mainly linked to geometrical features of the volcanic conduit and to resonant effects induced by pressure fluctuations in a fluid filled conduit such models assume the physical system to be in a steady state over a long interval of time at stromboli the seismicity produced by each of the three active vents is not stable and can suddenly change in time therefore the application of stable resonator models appears to be unwarranted on the basis of infrared image analyses atmospheric pressure and seismic wavefield signals we show that different frequency contents and different explosive styles occur at stromboli at the same time at different vents moreover we give evidence to support the idea that seismicity and explosivity are both controlled by a variable gas flow regime released during explosions at the top of the magma column we have recognized two main pressure regimes controlling the explositivity at stromboli one is impulsive short and possibly produced by a gas accumulation beneath a cap rock the other has an intermittent regime feature and lasts longer we demonstrate how the first one generates a monochromatic low frequency wavefield while the second shows a high frequency spectrum where the frequency content depends on pressure fluctuations and on pressure gradient we suggest different pressure growth and gas flow in the magma as the common source for both explosive style and seismic wavefield

long term observation of volcanic tremor on stromboli volcano italy a synopsis the features of seismic activity on stromboli are discussed and compared in terms of their relationship with the main changes of volcanic activity from 1990 to 1993

analysis of long period events recorded at mount etna italy in 1992 and their relationship to eruptive activity seismic activity recorded at mount etna during 1992 was characterized by long period lp events and tremor with fluctuating amplitudes these signals were associated with the evolution of the eruptive activity that began on december 14 1991 following the occurrence of numerous volcano tectonic earthquakes at the onset of the eruption lp events dominated the overall seismicity starting in january 1992 the lp activity occurred primarily in swarms which were temporally correlated with episodic collapses of the crater floor in the northeast crater source depths determined for selected lp events suggest a source region located slightly east of northeast crater and extending from the surface to a depth of 2000 m based on the characteristic signatures of the time series four families of lp events are identified each family shares common spectral peaks independent of azimuth and distance to the source these spectral features are used to develop a fluid filled crack model of the source we hypothesize that the locus of the lp events represents a segment of the magma feeding system connecting a depressurizing magma body with a dike extending in the sse direction along the western wall of valle del bove toward the site of the mount etna eruption we surmise that magma withdrawal from the source volume beneath northeast crater may have caused repeated collapses of the crater floor some collapse events may have produced pressure transients in the subjacent dike which acted as seismic wave sources for lp events

seasonal variation of speed and width from kinematic parameters of mode 1 nonlinear internal waves in the northeastern east china sea to better understand the statistical and theoretical characteristics of nonlinear internal waves nliws in the broad continental shelf of the northeastern east china sea ecs historical hydrographic data collected over 50 years between 1962 and 2011 are analyzed to calculate monthly climatology based on kdv and extended kdv models under the two layer approximation i e mode 1 nliws the monthly climatology for propagating speed and characteristic width is constructed ranging from 0 8 to 1 2 m s 1 and from o 102 to o 103 m respectively the result is consistent with a few previous in situ observations in the region when nliws originating in the southeastern slope area approach the shallower regime northwestward propagation they propagate more slowly with neither break nor extinction but with a shorter width since both the iribarren and ostrovsky numbers are small ir 0 45 and os 1 respectively limitations of the two layered kdv type models are discussed e g an importance of mode 2 waves in the context of occasional extension of the low salinity changjiang discharged water onto the area which implies distinct effects on the kinematic parameters of nliws in the ecs

locating the sources of volcanic explosions and volcanic tremor at stromboli volcano italy using beam forming on diffraction hyperboloids abstract the wave field of volcano induced seismic signals at stromboli volcano italy was observed using a network of four broadband seismometers in addition to the standard spectral analysis of the recorded signals new spectral techniques such as wavelet transform and wavelet coherence analysis were also used in order to discriminate between signals related to volcanic tremor and volcanic explosions the common features of these two types of signals are characterised by the maximum of the power spectral density values located in the frequency band 2 0 hz and the main orientation of the principal axes of the particle motion ellipsoids in the frequency bands analysed the seismic signals of the volcanic explosions at stromboli cover the total frequency band whereas the spectral content of the volcanic tremor is restricted to narrow frequency bands ranging from 0 3 5 0 hz in order to localize both types of signals a modified inversion technique was used the result of this beam forming on diffraction hyperboloids of both types of signals reveal a surprisingly shallow source location ranging from 0 2 km 0 7 km above sea level suggesting that the sources of the volcanic explosions as well as of the volcanic tremor are restricted to the uppermost parts of the volcano this is in agreement with several nonseismological observations of this volcano the combination of spectral analysis of volcanic tremor and volcanic explosions with the analysis of ground displacement implies a mechanism which can be described by an ascending bubble of volcanic gas in a nearly closed volcanic system and finally the forced ejection of the material through a narrow channel at the top of the magma column

the 15 march 2007 explosive crisis at stromboli volcano italy assessing physical parameters through a multidisciplinary approach basaltic volcanoes are dominated by lava emission and mild explosive activity nevertheless many basaltic systems exhibit from time to time poorly documented and little understood violent explosions a short lived multiblast explosive crisis paroxysmal explosion occurred on 15 march 2007 during an effusive eruptive crisis at stromboli italy the explosive crisis which started at 20 38 14 ut had a total duration of 5 min the combined use of multiparametric data collected by the permanent instrumental networks seismic acoustic and thermal records and a field survey carried out immediately after the event enabled us to constrain the eruptive dynamics and quantify physical parameters the eruption consisted of three major pulses in the first lithic blocks and ash were ejected at speeds of 100 155 m s and 130 210 m s respectively the high solid load of the eruptive jet resulted in the partial collapse of the column with the formation of a small volume pyroclastic density current the second 12 s long pulse emitted 2 2 2 7 107 kg of tephra mass discharge rate 1 9 2 3 106 kg s forming a 3 km high convective plume dispersing tephra up to the west coast and a dilute density current with limited dispersal downslope of the craters a final 30 s long phase formed a scoria flow with a volume of 1 5 1 7 104 m3 mass discharge rate 5 9 6 7 105 kg s a total runout of 200 m and a velocity of 45 m s the total gas volume involved in the explosion was 1 3 1 9 104 m3 with an initial overpressure of 7 9 0 4 mpa we compared the 15 march 2007 event with historical paroxysms in particular with that of 5 april 2003 which was remarkably similar

chronology of the 2007 eruption of stromboli and the activity of the scientific synthesis group abstract on 27 february 2007 at 12 49 gmt a new eruption of stromboli took place with the effusion of a lava flow from a fracture cutting the flank of the ne cone which rapidly reached the sea the eruption had been heralded by an increase in the amplitude of tremor and flank movement since at least the 14th of february short term precursors were an increase in the rate of occurrence of small landslides within the sciara del fuoco scar on the north western flank of the volcano a new effusive vent opened at 18 30 gmt on the sciara del fuoco at an height of 400 m asl the new lava emission caused the sudden termination of the summit flow and initiated a period of non stationary lava outpouring which ended on 2 april 2007 the eruption has been characterized by a rapid decrease in the eruption rate after the first days and subsequently by episodic pulse increases on the 15th of march the increase in lava outpouring monitored by a thermal camera heralded by 9 min the occurrence of a violent paroxysmal explosion with the formation of an impulsive eruption column and the emission of small pumices mingled with black scoriae the pumice had a bulk composition similar to that of the lava and of the black scoriae but with a distinct lower content of phenocrysts a similar feature has been repeatedly observed during the major explosive paroxysms of stromboli short term precursors of the paroxysm were recorded by strainmeter and tiltmeter stations the volcano monitoring activity has been made by a joint team of researchers from the ingv sections of catania napoli palermo and rome along with researchers from the universities of florence pisa roma tre and palermo the scientific activity was coordinated by a synthesis group made up by scientists responsible for the different monitoring techniques of ingv and universities and by the volcanic experts of commissione nazionale grandi rischi of the prime minister office civil protection department the group made a daily evaluation of the state of the volcano and transmitted its recommendations to the civil protection department dpc several prevention measures were adopted by dpc the main of which were the evacuation of the coast zone when strong acceleration of the sciara del fuoco slope motion occurred twice could led to a dangerous tsunami by flank collapse as last occurred on 30 december 2002 and four days before the 15 march paroxysm when access was prohibited to the part of the volcano above 290 m asl

observations of volcanic tremor at mount st helens volcano digital recordings of ground motion during tremor episodes accompanying eruptions at mount st helens volcano in the state of washington on august 7 and october 16 18 1980 are studied the spectra of the vertical component waveforms contain at least two dominant peaks at 1 0 and 1 3 hz for all events recorded during both eruptions that were studied spectra of horizontal ground motion show peaks at 0 9 and 1 1 hz the relative amplitude of the two peaks changes between tremor episodes and during single tremor episodes and shows no consistent relation to amplitude of ground motion spectra of long period earthquakes are very similar to those of tremor events suggesting that tremor is composed of many long period earthquakes that occur over a period of time the unique waveform of tremor events observed at mount st helens must be due to a source effect since the relative amplitude of the two dominant peaks changes during tremor episodes the path effect on tremor waveforms is small since there are no peaks in the spectra of waveforms recorded during tectonic earthquakes occurring in the vicinity of mount st helens the consistency of the location of the spectral peaks for the wide range of tremor amplitudes means that there must be a physical length at the source that is constant independent of the amplitude of motion at the source variations in amplitude of motion generated during tremor events must be due to variations in the force driving the tremor amplitudes of ground motion varies between 0 11 and 4 7 m seismic moment rates during the two eruptions are calculated using the model of aki et al 1977 and found to vary between 6 1018 and 1 1020 dynes cm s 1 which are larger than values found by aki et al 1977 who studied amplitudes of shallow tremor events recorded during the october 1963 eruption of kilauea volcano in hawaii study of tremor amplitudes recorded at corvallis oregon leads to the conclusion that tremor accompanying the cataclysmic may 18 1980 eruption was at least one order of magnitude larger in amplitude than tremor during august and october

three dimensional numerical simulation of m2 internal tides in the east china sea the east china sea and adjacent seas are one of the most significant generation regions of the m 2 internal tide in the world s oceans in the present study we investigate the distribution and energetics of the m 2 internal tide around the continental shelf edge in the east china sea using a three dimensional numerical model the numerical experiment shows that m 2 internal tides are effectively generated over prominent topographic features such as the subsurface ridges in the bashi luzon and tokara straits the ridges along the ryukyu island chain and the continental shelf slope in the east china sea the former particularly so all of these topographic features are characterized by steep slopes at the depth of the thermocline onto which the m 2 barotropic tide is almost normally incident the m 2 internal tides propagating away from these multiple source regions interfere with each other to create a complicated wave pattern it is found that the calculated pattern of the m 2 internal tide agrees well with topex poseidon altimeter observations the conversion rate from m 2 barotropic to baroclinic energy over the whole analyzed model domain is estimated to be 35 gw roughly 10 of the energy in the m 2 surface tide incident on the prominent topographic features is converted to the m 2 internal tide although about half of the m 2 internal tidal energy is subject to local dissipation in close proximity to the generation sites

observations of flow variability through the kerama gap between the east china sea and the northwestern pacific the kerama gap near the middle of the ryukyu island chain is the deepest channel with a sill depth of 1050 m connecting the east china sea ecs to the northwestern pacific we measured the flow through the kerama gap from june 2009 to june 2011 the 2 year mean transport 2 0 0 7 sv is into the ecs from the northwestern pacific it contributes about 11 of the mean kuroshio transport in the ecs at the pn line subtidal standard deviation of the transport through the kerama gap is 3 2 sv comparable to that of the pn line kuroshio transport 4 0 sv suggesting a significant effect of kerama gap transport on temporal variability of the kuroshio transport in the ecs comparison with time series of satellite measured sea surface height maps reveals that temporal variability of the kerama gap transport is related to the arrival of mesoscale eddies from the east high low transport into the ecs is associated with the presence of a cyclonic anticyclonic eddy south of the kerama gap

stromboli 2007 eruption deflation modeling to infer shallow intermediate plumbing system 1 during the effusive phase of the stromboli 2007 eruption the gps and tilt stations recorded small but significant changes which for the first time at this volcano clearly indicated a deflation we modeled the deflation inferring a depressurizing vertically elongated source with centre under the volcano edifice about 2 8 km below sea level the model whose position is above the magma source region inferred by petrological studies and the associated rapid deflation suggest a near free pathway for magma ascent from this source to the upper shallow conduit

interaction of seismic and air waves recorded at stromboli volcano explosion quake seismograms recorded at stromboli show that seismic phases with a high amplitude and high frequency content propagate with a velocity of approximately 330 m s the sound speed the analysis of seismograms recorded at a distance of 500 m from one of the three active vents shows for the first onset a low frequency and particle motion characteristic of a p wave which loses its longitudinal polarization with the onset of the air wave recording the explosion quakes simultaneously with a microphone we could ascertain that the high frequency onset coincided with the air wave s in order to better understand the seismic wavefield generated by the atmospheric pressure we performed a controlled source experiment at stromboli using a seismic gun seismograms with the same two phases and particle motions comparable with the volcano seismic data were obtained a second experiment demonstrated that the air wave propagates at least in the uppermost 1 m of the ground we suggest that the seismic source of the corresponding seismograms is an explosion at the top of the magma column and conclude that the p and air waves are both generated in the same point and at the same time

new integrated geodetic monitoring system at stromboli volcano italy stromboli is a composite volcano forming the northernmost island of the aeolian archipelago volcanic arc tyrrhenian sea on december 28th 2002 lava flows outpoured from the northern wall of the ne crater and descended into the sciara del fuoco sdf a deep depression marking the nw flank of the volcano edifice on december 30th 2002 two landslides occurred on the northern part of the sdf they moved a mass in the order of tens of millions of cubic meters both above and below sea level the landslide produced a tsunami causing significant damage to the eastern coast of the island reaching the other aeolian islands and the sicilian and southern italian coasts this event led to the upgrading of the ground deformation monitoring system already existing on the island the new requirement was the real time detection of the deformations related to potential slope failures of the sdf to this end a remotely controlled monitoring system based both on gps and geodetic techniques was planned and set up in a few months the new monitoring system allowed to continuously measure the ground deformations occurring on the sdf by integrating both terrestrial and satellite geodetic techniques although this system was severely damaged during the 7 month long eruption it allowed to monitor important eruptive phases for the first time an accurate data set on the actual mass movements of the sdf and the crater area was available it provided data that significantly supported the civil protection authorities in making decisions and constrains theories related to landslide movements and volcanic activity after the end of the eruption the system was overhauled in order to optimize the instruments and set up a monitoring system aimed at measuring deformations forecasting other flank collapses

observed upper ocean response to typhoon megi 2010 in the northern south china sea typhoon megi passed between two subsurface moorings in the northern south china sea in october 2010 and the upper ocean thermal and dynamical response with strong internal tides present was examined in detail the entire observed water column 60 360 m was cooled due to strong ekman pumped upwelling up to 50 m in the thermocline by megi with maximum cooling of 4 2 c occurring in thermocline a relatively weak maximum amplitude of 0 4 m s 1 and quickly damped e folding time scale of 2 inertial periods near inertial oscillation nio was observed in the mixed layer power spectrum and wavelet analyses both indicated an energy peak appearing at exactly the sum frequency fd1 with maximum amplitude up to 0 2 m s 1 of nio f and diurnal tide d1 indicating enhanced nonlinear wave wave interaction between f and d1 during and after typhoon numerical experiments suggested that energy transfer from nio to fd1 via nonlinear interaction between f and d1 may have limited the growth and accelerated the damping of mixed layer nio generated by megi the occurrence of fd1 had a high correlation with nio the vertical nonlinear momentum term associated with the vertical shear of nio and vertical velocity of d1 or vertical shear of d1 and vertical velocity of nio was more than 10 times larger than the horizontal terms and was responsible for forcing fd1 after megi surface layer diurnal energy was enhanced by up to 100 attributed to the combined effect of the increased surface layer stratification and additional megi forced diurnal current

role of evaporite withdrawal in the preservation of a unique coal bearing succession pennsylvanian joggins formation nova scotia the pennsylvanian joggins formation in the cumberland group of nova scotia is widely regarded as the world s best exposure of coal bearing carboniferous strata this 1 5 km thick coal bearing unit is famous for upright fossil lycopsid trees and is preferentially preserved in the athol syncline in the western cumberland basin new seismic profiles show that the athol syncline is atop a salt weld and that the joggins formation thins on the flanks of adjacent evaporite cored anticlines these observations indicate that during deposition of the joggins formation at least 1 km of syndepositional subsidence was facilitated by flow of underlying salt into the adjacent anticlines in contrast halo kinesis was mainly active during the mississippian in the eastern cumberland basin tatamagouche syncline minibasins were filled by mabou group sediments whereas the cumberland group is thin and lacks significant coals this basinwide comparison shows that much of the subsidence responsible for the preservation of the coal bearing joggins formation was the result of salt withdrawal at depth

model estimates of m2 internal tide energetics at the hawaiian ridge 1 a primitive equation model is used to examine the structure and energetics of m 2 internal tides generated at the hawaiian ridge recent estimates based on altimeter data suggest that 20 gw of barotropic tidal dissipation occurs at the ridge with conversion to internal tides believed to be the dominant dissipation mechanism the model simulates an internal tide that accounts for 9 7 gw of radiated energy away from the ridge in the northeast and southwest directions the strongest generation occurs at three sites where enhanced barotropic currents flow across elongated topographic features the depth integrated baroclinic energy flux and energy densities at these sites are on the order of 10 4 w m 1 and 10 4 j m 2 respectively a modal decomposition indicates that 62 of the outgoing energy flux is accounted for by the first internal mode 15 is accounted for by the second mode and less than 5 is accounted for by each subsequent higher mode the tidal dissipation due to bottom friction along the ridge is estimated to be 0 1 gw the level of turbulent dissipation near the ridge owing to tidal energy conversion remains to be determined to assess fully the barotropic baroclinic energy budget

the shallow plumbing system of stromboli island as imaged from 1 hz instantaneous gps positions 1 the stromboli volcano aeolian islands italy erupted suddenly on 28 december 2002 after a 17 year period of typically persistent but moderate eruptive activity followed two days later by a tsunamigenic landslide on its nw flank sciara del fuoco felt in the coastal areas of southern italy three continuous gps stations were quickly deployed near the volcano s rim sampling at 1 hz with instantaneous positions computed relative to a fourth station on its flank we report on two deformation episodes a vent migration on 16 17 february 2003 caused significant displacements at only one site and contributed to the decision not to issue a warning of an impending tsunamigenic landslide the second episode on 5 april 2003 a paroxystic explosion from the summit crater allowed us to model for the first time with geodetic data the shallow magma chambers that give rise to strombolian explosive activity

observed enhanced internal tides in winter near the luzon strait seasonal characteristics and nonlinear interaction of internal tides its near the luzon strait in the northeastern south china sea are investigated using 285 day in situ observation data it is found that its which are dominated by the first mode wave throughout the year are the strongest in subsurface layer baroclinic incoherent diurnal semidiurnal variance accounts for about 85 7 78 3 of diurnal semidiurnal its the amplitude and seasonal variation of the diurnal its are more prominent than those that are semidiurnal e g the largest kinetic energy densities of diurnal and semidiurnal baroclinic tidal currents are 2 81 and 0 83 kj m2 in winter respectively it is considered that there are two reasons for the significantly enhanced its in winter 1 it may be due to the kuroshio intrusion and 2 the enhanced diurnal its may be due to the enhanced diurnal barotropic tidal currents while the enhanced semidiurnal its may be caused by the strong nonlinear interaction between diurnal it constituents o1 and k1 due to their high vertical shears in subsurface layer thus harmonic semidiurnal constituent d2 with a similar frequency of constituent m2 is induced it subsequently enhances the semidiurnal its in this subsurface layer and the associated energy is carried downward to enhance the semidiurnal its in the upper and lower layers

observations of kuroshio flow variations in the east china sea 1 kuroshio velocity structure and transport in the east china sea ecs were investigated as part of a 23 month study using inverted echo sounders and acoustic doppler current profilers adcps along the regularly sampled pn line flow toward the northeast is concentrated near the continental shelf with the mean surface velocity maximum located 30 km offshore from the shelf break taken as the 170 m isobath there are two regions of southwestward flow a deep countercurrent over the continental slope beneath the kuroshio axis and a recirculation offshore which extends throughout the whole water column there is a bimodal distribution to the depth of maximum velocity with occurrence peaks at the surface and 210 dbar when the maximum velocity is located within the top 80 m of the water column it ranges between 0 36 m s and 2 02 m s when the maximum velocity is deeper than 80 m it ranges between 0 31 m s and 1 11 m s the 13 month mean net absolute transport of the kuroshio in the ecs is 18 5 0 8 sv standard deviation 4 0 sv the mean positive and negative portions of this net flow are 24 0 0 9 sv and 5 4 0 3 sv respectively

architecture of coastal and alluvial deposits in an extensional basin the carboniferous joggins formation of eastern canada abstract the joggins formation was deposited in the cumberland basin which experienced rapid mid carboniferous subsidence on bounding faults a 600 m measured section of coastal and alluvial plain strata comprises cycles tens to hundreds of metres thick the cycles commence with coal and fossiliferous limestone siltstone intervals interpreted as widespread flooding events these intervals are overlain by coarsening upward successions capped by planar based sandstone mounds up to 100 m in width that represent the progradation of small river generated delta lobes into a standing body of open water developed during transgression the overlying strata contain sand rich heterolithic packages 1 8 m thick that are associated with channel bodies 2 3 m thick and 10 50 m wide drifted plant debris calamites groves and erect lycopsid trees are preserved within these predominantly green grey heterolithic sediments which were deposited on a coastal wetland or deltaic plain traversed by channel systems the cycles conclude with red siltstones containing calcareous nodules that are interbedded with thin sandstones and associated with both single storey channel bodies 1 1 5 m thick and 2 3 m wide and larger multistorey channels 3 6 m thick with incised margins numerous channel bodies at the same level suggest that multiple channel anastomosed river systems were developed on a well drained floodplain many minor flooding surfaces divide the strata into parasequences with dominantly progradational and aggradational stacking patterns multistorey channel bodies are relatively thin fine grained and modestly incised and palaeosols are immature and cumulative the abundance and prominence of flooding surfaces suggests that base level rise was enhanced whereas the lack of evidence for abrupt basinward stepping of facies belts coupled with the absence of strong fluvial incision and mature palaeosols suggests that base level fall was suppressed these architectural features are considered to reflect a tectonic architectural signature in accordance with the high subsidence basinal setting evidence for restricted marine influence and variation in floral assemblages suggests modulation by eustatic and climatic effects although their relative importance is uncertain

generation mechanism of internal waves by tidal flow over a sill the generation mechanism of internal waves by relatively strong tidal flow over a sill is clarified analytically special attention is directed to the role of the tidal advection effect which is examined by use of characteristics an internal wave which propagates upstream is gradually formed over the sill through the interference among infinitesimal amplitude internal waves elementary waves emanated from the sill at each instant of time in the accelerating decelerating stage of tidal flow the effective amplification of an internal wave takes place as the froude number exceeds falls below unity because during this period the internal wave slowly travels downstream upstream crossing over the sill where elementary waves are efficiently superimposed when the strength of the tidal advection effect is appropriate the internal wave formed in the accelerating stage ac wave and that formed in the decelerating stage dc wave overlap so that the resultant wave height becomes very large since the relative position of ac and dc waves varies depending on the strength of the tidal advection effect the resultant internal wave form is strongly affected by it when the tidal advection effect is strong the ac wave is carried too far downstream to interfere with the dc wave and hence the resultant wave form consists of two crests and two troughs when the tidal advection effect is moderate the optimum interference between ac and dc waves occurs and the resultant wave form consists of one crest and one trough with its horizontal scale approaching that of the sill when the tidal advection effect is weak the internal wave height becomes very small since elementary waves propagate almost freely in the tidal flow without coming close together and the resultant wave form approaches a sinusoidal wave of tidal frequency

late carboniferous and early permian drainage patterns in atlantic canada paleoflow data have been compiled for late carboniferous late westphalian a to early permian alluvial deposits over a large area of atlantic canada the data which include more than 36 000 measurements of large scale trough cross strata indicate a predominantly northeasterly paleoflow and suggest that a major source area lay to the southwest of the region throughout the 30 ma period represented uplands within the basin deflected paleoflow and probably formed important local drainage and sediment sources tectonostratigraphic analysis suggests that the drainage originated in the fold and thrust belt of the central appalachians and parts of the northern appalachians rivers probably followed northeast oriented structural lineaments through the older acadian mountains of the northern appalachians a considerable proportion of the rising orogen s drainage and probably detritus may have traversed basins along the strike of the mountain belt a situation analogous to that of the modern himalayas

eruptive sequence and seismic activity of llaima volcano chile during the 2007 2009 eruptive period inferences of the magmatic feeding system abstract llaima volcano one of the most active volcanoes in south america has experienced intense activity during the last 100 years the most recent eruptive activity occurred during the period 2007 2009 with at least six energetic eruptions the january 1st 2008 vei 3 being the strongest episode most of the paroxysmal activity was characterized by a rapid increase in seismic energy minutes to hours and the absence of precursory signals as well as by an accelerated drop of the seismic energy and eruption intensity at the end moreover subtle changes in the increase of low energy long period lp seismicity and the occurrence of minor explosive activity six months before the onset of the eruptive cycle were the only remarkable changes observed in advance this is the first study that includes a detailed description of the 2007 2009 eruptive period and is based on a temporal analysis of the seismic records technical reports from the monitoring network and 2000 photos this set allows a characterization of the coeval eruptive styles including strombolian and hawaiian activity morphological changes of the active vents inside the main crater and two fractures located in the sw and se flanks ten phases were identified based on the eruptive style volcanic explosivity index vei and the salient features of the seismic events the seismicity that accompanied the eruptive phases was characterized by the predominance of a continuous tremor tr and discrete lp events and a remarkable absence of volcano tectonics vt earthquakes a waveform cross correlation analysis of lp events showed an overall low similarity between them which suggests multiple sources our observations and analysis suggest that the plumbing system is composed of multiple independent structures some of which reached the surface during this eruptive period indicating that the upper part of the cone could be an unstable and essentially weak zone the activity and seismicity observed are characteristic of an open vent system in which the magma can ascend rapidly from several km depth with little to no clear precursory activity these results are in agreement with petrological studies of the products of these eruptions

a two dimensional gravest empirical mode determined from hydrographic observations in the subantarctic front abstract south of australia where the baroclinicity in the subantarctic front extends almost to the seafloor the geopotential height of the sea surface and the vertical acoustic travel time exhibit a tight empirical relationship to each other and to the entire vertical structure of temperature t p salinity s p and specific volume anomaly p measurements of provide proxy estimates of the profiles tg p sg p and g p based on a two dimensional gravest empirical mode gem representation of the vertical structure fitted to 212 hydrographic stations a seasonal model was fitted in the near surface layers using additional historical data at each depth in the range 150 3000 dbar more than 96 of the variance in both the t and fields is captured by the gem representation during the subantarctic flux and dynamics experiment mar 1995 mar 1997 inverted echo sounders ies and current meters were moored in a 2d array along the woce sr3 transect south of australia at each i

polarization analyses of broadband seismic data recorded on stromboli volcano italy from 1996 to 1999 1 we analyze broadband seismic data recorded at a single station deployed on stromboli island from 1996 to 1999 in order to determine basic parameters of the seismic wavefield and study their relationship with volcanic activity in addition to a characterization in the frequency domain we apply polarization analysis and study long term variations of these parameters possibly reflecting also changes in source properties our analysis is twofold first we focus on a meaningful reduction of the data to selected parameters i e azimuth and incidence angle which can be correlated with volcanic activity secondly we investigate if there is maintenance of the correlations over long time spans we observe statistically significant long term changes from several months to year in the wavefield parameters considered we interpret such changes as possibly being caused by the enhanced strength of a deep source potentially by supply of fluids from a low part of the magma feeder between the end of 1997 and the first months of 1998

variability of internal tides and near inertial waves on the continental slope of the northwestern south china sea structure and variability of internal tides it and near inertial waves niw on the continental slope of the northwestern south china sea were investigated based on 9 month moored current observations from autumn to early summer in 2008 and 2009 the diurnal it kinetic energy dominant over that of semidiurnal tides is found to exhibit apparent seasonal variability strongest in summer and weakest in winter whereas the semidiurnal variance remained nearly uniform throughout the observation period moreover the diurnal it were more coherent i e phase locked to the astronomical forcing than the semidiurnal constituents coherent diurnal variance accounts for about 40 of diurnal motions but semidiurnal tides contain a much smaller fraction 10 of coherent motions further analysis demonstrates that the diurnal it are dominated by the first mode whereas the semidiurnal tides show a variable multimodal structure the second mode is dominant in summer and comparable to the first mode in spring and autumn but the first mode predominates in winter multimodal semidiurnal it are more influenced by varying stratification structures and background currents and thus exhibit highly incoherent and intermittent behavior which may wash out seasonal variability during their long propagation from the generation source the observed niw are seasonally independent and comparable to the semidiurnal motions during the passage of typhoon hagupit however the niw became the most energetic component of the inertia gravity waveband motions niw energy and shear were significantly enhanced and exceeded tidal counterparts by a factor of 2 to 3 in the upper layer

metalliferous coals of the westphalian a joggins formation cumberland basin nova scotia canada petrology geochemistry and palynology abstract five coals of westphalian a early middle pennsylvanian age were sampled from the joggins formation section exposed along chignecto bay at joggins nova scotia coal beds along the bay were mined beginning in the early 17th century yet there have been few detailed published investigation of the coal beds of this classic section the lowermost coal the upper coal 28 upper fundy is a high vitrinite coal with a spore assemblage dominated by arboreous lycopsid spores with tree ferns subdominant the upper portions of the coal bed have the highest ratio of well preserved to poorly preserved telinite of any of the coals investigated coal 19 clam coal has 88 total vitrinite but unlike the fundy coal bed the telinite has a poor preservation ratio and half the total vitrinite population comprises gelocollinite and vitrodetrinite the latter coal bed is directly overlain by a basin wide limestone bed the lower kimberly coal shows good preservation of vitrinite with relatively abundant telinite among the total vitrinite the middle kimberly coal which underlies the tetrapod bearing lycopsid trees found by lyell and dawson in 1852 exhibits an upward decrease in arboreous lycopod spores and an upward increase in the tree fern spore punctatisporites minutus telinite preservation increases upwards in the middle kimberly but overall is well below the preservation ratio of the upper fundy coal bed the coals all have high sulfur contents yielding up to 13 7 total sulfur for the lower lithotype of the upper fundy coal bed the kimberly coals are not only high in total and pyritic sulfur but also have high concentrations of chalcophile elements zinc ranging up to 15 000 ppm ash basis is present as sphalerite in fusain lumens arsenic and lead each exceed 6000 ppm ash basis in separate lithotypes of the kimberly coals together these data are consistent with elevated ph in planar mires the source of the elemental enrichment in this presumed continental section is enigmatic

multimodal structure of the internal tides on the continental shelf of the northwestern south china sea based on the moored current and temperature observations during the summer of 2005 the vertical structure of the internal tides on the continental shelf of the northwestern south china sea scs is studied the vertical structure of the internal tides was found to differ greatly between semidiurnal and diurnal constituents generally the diurnal constituents are dominated by the first mode motions which are consistent with the overwhelming first mode signals in the northeastern scs in contrast the semidiurnal internal tides unlike the predomination of the first mode variations in the northeastern area exhibit a higher modal structure with dominate second mode signals in the observational region moreover although the diurnal internal tides are much stronger than the semidiurnal component the shear caused by the latter over various scales was found to be significant compared to that induced by the diurnal tides probably due to the superposition of the first mode and higher mode smaller scale semidiurnal variations further analysis demonstrates that the shear induced by the diurnal internal tides is larger than that induced by the semidiurnal variations around 45 m depth where the first mode current reversal in the vertical happens while below 45 m depth higher mode semidiurnal internal tides generally produce larger shear than that by the diurnal component the northwest propagating semidiurnal internal tides of higher mode with small vertical scale probably do not originate from a distant source like luzon strait but were likely generated near the experiment site c 2011 elsevier ltd all rights reserved

observations of seismic volcanic signals at stromboli volcano italy abstract digital recordings of ground motion during a seismic operation organized at stromboli volcano italy from may 31 1986 to june 26 1986 have been studied the amplitude of background seismic noise is greater at the summit than at the base of the volcano and the spectra calculated on different days are dominated by at least two frequencies 2 0 and 6 0 hz with subdominant frequencies at 4 1 4 8 and 8 hz according to their waveform and their spectral content three types of discrete volcanic signals are distinguishable the first type is characterized by a dominant frequency at 2 hz and a subdominant frequency at 4 1 hz the second type also has a dominant peak frequency at 2 hz with two important subdominant frequencies at 5 and 8 hz the type 3 has a sharp dominant frequency at 6 hz and subdominant frequency at 3 2 hz the frequencies observed for discrete signals and ground noise suggest that they are produced by the same repeated mechanism which probably has a volcanic origin the discrete signals are linked to explosions at the active vents within the craters

upland ecology of some late carboniferous cordaitalean trees from nova scotia and england abstract permineralised logs and charcoal fragments composed of dadoxylon type wood and derived from cordaitalean trees are described from the upper carboniferous westphalian of nova scotia and england they exclusively occur in sandstone bodies interpreted as the deposits of braided meandering and anastomosing river channels the architecture and ecology of this type of cordaitalean has not yet been satisfactorily described estimates of tree height using an allometric approach suggest that the largest trees attained an approximate height of ca 45 m the absence of true growth rings in the logs indicate that they grew under non seasonal humid tropical conditions however the presence of charred wood fragments implies that droughts of sufficient intensity to permit wildfire did occasionally occur the charcoal fragments are usually associated with incised poorly sorted chaotically bedded channel facies interpreted as flood deposits dramatic increases in runoff and sediment discharge are known to follow the destruction of vegetation in modern wildfire events and the high energy charcoal bearing channel facies described may represent a similar geomorphic response to cordaitalean vegetation fires geomorphic sensitivity to fire is greatest for steeply sloping terrains and it is therefore probable that the cordaitaleans described in this paper occupied upland settings this palaeoecological interpretation is supported by occurrence of the cordaitalean remains in river channel deposits immediately downstream of regions of palaeo upland and by the palynological record the presence of upland forests in late carboniferous times has important implications for numerical modelling of global geochemical cycles

regional stress field in the area of stromboli italy insights into structural data and crustal tectonic earthquakes abstract crustal tectonic seismicity on stromboli is here discussed along with the regional tectonic and geodynamic context of the aeolian archipelago italy the aim of this paper is to contribute to the reduction of the crucial gap in information concerning the tectonic activity originating at the volcano stromboli in the last decade it is indeed well known that strombolian eruptions related to the persistent state of activity on this volcano allow a fast collection of seismic data which are mainly represented by explosion quakes and tremor however only some sporadic information concerns tectonic earthquakes due to their low occurrence rate a catalog of 150 crustal tectonic earthquakes recorded at stromboli from 1985 to 1996 is presented here the analyses of the seismograms were carried out on the basis of the records of the station str located in the southwestern part of the island the magnitude considered ranged from 1 5 to 3 7 hypocentral location indicates foci at less than 12 km although for the majority of the earthquakes which are not recorded at the seismic stations deployed on the other islands of the aeolian archipelago a shallower within a few kilometers depth can be hypothesized the strain release associated with the 150 tectonic earthquakes of our catalog was also evaluated the low levels of occurrence and seismic energy release reached throughout the ca twelve years analyzed here confirm the minor role played by processes of brittle failure of rocks this aspect of seismic activity is nevertheless important as it can provide a contribution to the knowledge of the dynamics of this volcano the focal mechanisms available integrated with data from the literature show the t axes oriented about ne sw and nw se these findings are consistent with the deformative and tectonic characteristics of this volcanic edifice and of the aeolian archipelago which shows the same two directions of extension this is in agreement with subduction which is very old or which passively evolves towards the final stages and is controlled by the transform activity of the aeolian tindari giardini fault system

sliding episodes during the 2002 2003 stromboli lava effusion insights from seismic volcanic and statistical data analysis 1 repeated phenomena of flank instability accompanied the 28 december 2002 to 21 july 2003 eruption of stromboli volcano the major episodes were two tsunamigenic landslides on 30 december 2002 2 d after the volcano unrest after 30 december sliding processes remodeled the area affected by slope instability we propose analyses of 565 sliding episodes taking place from december 2002 to february 2003 we try to shed light on their main seismic features and links with the ongoing seismic and volcanic activity using variogram analysis as well a characterization of the seismic signals in the time and frequency domains is presented for 185 sliding episodes their frequency content is between 1 hz and 7 hz on the basis of the dominant peaks and shape of the spectrum we identify three subclasses of signals one of which has significant energy below 2 hz low frequency signatures were also found in the seismic records of the landslides of 30 december which affected the aerial and submarine northwestern flank of the volcano accordingly we surmise that spectral analysis might provide evidence of sliding phenomena with submarine runouts we find no evidence of sliding processes induced by earthquakes additionally a negative statistical correlation between sliding episodes and explosion quakes is highlighted by variogram analysis variograms indicate a persistent behavior memory of the flank instability from 5 to 10 d we interpret the climax in the occurrence rate of the sliding processes between 24 and 29 january 2003 as the result of favorable conditions to slope instability due to the emplacement of nw se aligned dike fed vents located near the scarp of the landslide area afterward the stabilizing effect of the lava flows over the northwestern flank of the volcano limited erosive phenomena to the unstable loose slope not covered by lava

seasonal variation of semidiurnal internal tides in the east japan sea the seasonal variation of semidiurnal internal tides in the east japan sea was investigated using 25 month long output from a real time ocean forecasting system the z coordinate eddy resolving high resolution numerical model called the riam ocean model incorporates data assimilation that nudges temperature and salinity fields together with volume transport through the korea strait to produce realistic oceanic currents and stratification in addition to atmospheric forcing it includes tidal forcing of 16 major components along open boundaries the model generates energetic semidiurnal internal tides around the northern entrance of the korea strait energy conversion from barotropic to baroclinic internal tides varies seasonally with maxima in september ranging 0 48 0 52 gw and minima in march ranging 0 11 0 16 gw this seasonal variation is induced by the seasonality in stratification near the southwestern east japan sea the propagation distance of the internal tides is associated with generation intensity and wavelength from late summer to early winter the semidiurnal internal tides travel relatively far from the generation region due to stratification changes its energy dissipates less as a result of longer wavelengths our results suggest that spatiotemporal variation of internal tide induced mixing due to the seasonality in the generation propagation and dissipation of internal tides should be considered for a more realistic simulation of water masses and circulation in models of the east japan sea

the pennsylvanian tropical biome reconstructed from the joggins formation of nova scotia canada the pennsylvanian langsettian joggins formation contains a diverse fossil assemblage first made famous by lyell and dawson in the mid 19th century collector curves based on c 150 years of observation suggest that the joggins fossil record is relatively complete a key feature of the site is that fossils occur in par autochthonous assemblages within a narrow time interval