reply to comment from liotta and rizzo on evolution of co2 so2 hcl and hno3 in the volcanic plumes from etna by voigt et al geophys res lett 41 doi 10 1002 2013gl058974 editor s note the following comment and reply arise from an article published in geophysical research letters by voigt et al 2014 the article addresses a volcanology topic and the commenters take issue with some conclusions and offer an analysis of their own voigt and co authors have responded why is this comment and reply being published in the bulletin it is because geophysical research letters is one of a number of journals that do not offer any published forum for discussion of the papers they publish this is a matter of editorial policy and a decision for each journal the bulletin of volcanology does provide a forum for discussion of articles published when contacted by marcello liotta with the request that the bulletin consider hosting a discussion of the voigt et al volcanology article in grl i agreed to do so if the grl authors were willing to engage with the comment voigt and co authors were willing to do so and have been allowed a small amount of additional space to summarize for bulletin readers the key points of the grl paper under discussion before responding directly to the comment from liotta and rizzo i hope that bulletin readers find the discussion and reply of interest

acoustic multipole logging in transversely isotropic poroelastic formations the properties of the modes generated by multipole sources in a fluid filled borehole embedded in radially layered formations that include transversely isotropic poroelastic layers are investigated these layers are modeled following biot s and homogenization theories under the assumption that the principal axes of symmetry of both the transversely isotropic skeleton and the complex permeability tensor are parallel to the vertical axis of the borehole a general formulation based on the thomson haskell method accounts for any combination of fluid elastic and poroelastic layers either isotropic or transversely isotropic the investigation is achieved through the computation of dispersion and attenuation curves and frequency dependent sensitivity coefficients with respect to the parameters in the presence of a fast or slow radially semi infinite transversely isotropic poroelastic formation with an impermeable borehole wall the shear wave transverse isotropy of the skeleton can be determined using t

simulation of multipole acoustic logging in cracked porous formations abstractrocks in the earth s crust usually contain pores and cracks we developed a cracked porous medium elastic wave theory by modifying biot s poroelastic wave theory to include the effects of cracks adding the crack density and aspect ratio as two important parameters to the original theory the new theory was applied to model multipole acoustic wave propagation along a borehole surrounded by a cracked porous formation the modeling results showed that the multipole acoustic waveforms were significantly affected by the presence of cracks even when the formation had low permeability and porosity particularly cracks can cause the monopole p and stoneley waves and the dipole flexural wave to have significant sensitivity to hydrocarbon saturation suggesting use of the waveform characteristics for hydrocarbon detection in tight formations

deposits flow characteristics and landscape change resulting from the september 2009 south pacific tsunami in the samoan islands the september 29th 2009 tsunami caused widespread coastal modification within the islands of samoa and northern tonga in the south pacific preliminary measurements indicate maximum runup values of around 17 m okal et al 2010 and shore normal inundation distances of up to 620 m jaffe et al 2010 geological field reconnaissance studies were conducted as part of an unesco ioc international tsunami survey team survey within three weeks of the event in order to document the erosion transport and deposition of sediment by the tsunami data collected included a general morphology and geological characteristics of the coast b evidence of tsunami flow inundation flow depth and direction wave height and runup c surficial and subsurface sediment samples including deposit thickness and extent d topographic mapping and e boulder size and location measurements four main types of sedimentary deposits were identified a gravel fields consisting mostly of isolated cobbles and boulders b sand sheets from a few to 25 cm thick c piles of organic mostly vegetation and man made material forming debris ramparts and d surface mud deposits that settled from suspension from standing water in the tsunami aftermath tsunami deposits within the reef system were not widespread however surficial changes to the reefs were observed

spectroscopic evidence for a lava fountain driven by previously accumulated magmatic gas the eruption of mount etna in 2000 was notable for an exceptional series of 64 periodic lava fountains propelling lava fragments to heights of up to 900 metres it has been difficult to determine which of two suggested sources of power gas release from the magma itself during its rapid ascent or a build up of pressure from gas accumulated at depth is the driving force for these dramatic jets but one of the etna fountains provided volcanologists with the opportunity to use remote sensing not that remote see picture on the following page to determine the infrared spectra of the gas phase this revealed the chemical composition of the gas that powered this fountain as consistent with an origin in an accumulated gas layer lava fountains are spectacular continuous gas jets propelling lava fragments to heights of several hundred metres which occasionally occur during eruptions of low viscosity magmas1 2 3 4 5 whether they are generated by the effervescent disruption of fast rising bubbly melt2 3 4 5 or by the separate ascent of a bubble foam layer accumulated at depth6 7 still remains a matter of debate8 no field measurement has yet allowed firm discrimination between these two models a key insight into the origin of lava fountains may be gained by measuring the chemical composition of the driving gas phase this composition should differ markedly depending on whether the magma degassing occurs before or during eruption9 10 here we report the analysis of magmatic gas during a powerful 250 600 m high lava fountain measured with fourier transform infrared spectroscopy11 12 13 14 on mount etna sicily the abundances of volcanic gas species determined from absorption spectra of lava radiation reveal a fountain gas having higher co2 s and s cl ratios than other etnean emissions14 15 16 17 18 and which cannot derive from syn eruptive bulk degassing of etna basalt19 20 instead its composition suggests violent emptying of a gas bubble layer previously accumulated at about 1 5 km depth below the erupting crater

fracture responses of conventional logs in tight oil sandstones a case study of the upper triassic yanchang formation in southwest ordos basin china fractures are the main fluid flow pathways in tight oil sandstones and they have a significant influence on tight oil distribution exploration and development cores and image logs are commonly unavailable because of their high costs so employing conventional logs for fracture detection is imperative for tight oil sandstones we compared the fracture response characteristics of conventional logs based on two data sets one from 8 cored wells with fracture intensities greater than 1 m 1 3 3 ft 1 and the other from 11 cored wells with fracture intensities less than 0 5 m 1 1 6 ft 1 with a case study of the upper triassic yanchang formation in southwest ordos basin china the results indicate that when tight oil sandstones are more intensely fractured the caliper log acoustic log compensated neutron log density log dual induction logs and laterolog 8 present fracture responses to some extent however it is difficult to make a distinction between fractured and nonfractured zones using conventional logs in sandstones with smaller fracture intensities the fracture response intensities of conventional logs are weak and they are influenced by fracture abundance fracture occurrence fracture scale and mineral filling degree moreover lithology fluids and rock physical properties can cause fracturelike responses hence some ambiguity exists when using conventional logs to directly identify fractures accompanying fracture sensitive conventional logs with some methods to enhance fracture response intensity and eliminate nonfracture influence could enable fracture identification in tight oil sandstones

chlorine isotope composition of volcanic gases and rocks at mount etna italy and inferences on the local mantle source abstract we present the first chlorine isotope compositional data for gases and lavas from mount etna italy and to our knowledge of active mediterranean volcanism we investigated lavas erupted and gases discharged during 2008 2011 from a high temperature fumarole ht 300 c and plume gases from both north east and central craters most of the samples vary in a narrow range of chlorine isotope composition 37 cl values 0 0 7 with gases partially overlapping with rocks only ht gases sampled in 2009 have been clearly affected by secondary processes 37 cl values 15 9 resulting in partial removal of chlorine and isotopic fractionation producing a 37 cl enrichment in the residual gaseous hcl these secondary processes also affect although to a lesser extent plume gases from north east crater nec although post magmatic processes are able to modify the chlorine isotope composition 37 cl values are not affected by magma degassing for residual fractions 0 3 in the melt or any effect is within our data variability finally 37 cl values and cl k ratios of magmatic chlorine constrain the etnean source to be compatible with depleted mantle dmm contaminated by altered oceanic crust aoc in agreement with indications from more common isotopic tracers of mantle processes

lack of suitable coastal plains likely influenced lapita 2800 cal bp settlement of sāmoa evidence from south eastern upolu between 3050 and 2700 years ago humans first colonized the islands of south west remote oceania a region stretching from vanuatu to s moa these colonists created a dense archaeological record of lapita pottery and other artefacts on island coastlines across the region there is one striking exception to this pattern s moa with only a single lapita pottery colonization site dating to approximately 2800 years ago there are two competing explanations for the unique s moan colonization record first there was a dense lapita colonization record now displaced through sedimentation and coastal subsidence second there were few coastal plains suitable for settlement 2800 years ago resulting in the lack of colonization sites this article describes the first archaeological and geological research designed to systematically test these explanations the research focuses on the south eastern coastal plain of upolu island an area where previous geological research and mid holocene sea level indicators predi

coral reefs as buffers during the 2009 south pacific tsunami upolu island samoa abstract the coral reef bordering the coastline of samoa affected by the 29 september 2009 tsunami provides a variety of ecosystem services from nurseries for fisheries and inshore source of food for local communities to aesthetics for tourists and the width of the lagoon may have been a factor in reducing the onshore wave height to understand the complex interactions between the onshore human population and the offshore coral we formed an interdisciplinary survey team to document the effects the tsunami had on the nearshore coral reef and how these changes might affect local inhabitants the scale of reef damage varied from severe where piles of freshly killed coral fragments and mortality were present to areas that exhibited little impact despite being overrun by the tsunami we found that many coral colonies were impacted by tsunami entrained coral debris which had been ripped up and deposited on the fore reef by repeated cyclones and storm waves in other places large surface area tabular coral sustained damage as the tsunami velocity increased as it was funneled through channels areas that lacked debris entrained by the waves as well as areas in the lee of islands came through relatively unscathed with the exception of the delicate corals that lived on a sandy substrate in the lagoon on the south coast with its steep topography coral colonies were damaged by tsunami generated debris from onshore entrained in the backwash despite the potential for severe tsunami related damage there were no noticeable decreases in live coral cover between successive surveys at two locations although algal cover was higher with the increased nutrients mobilized by the tsunami while there was an immediate decrease in fish takes in the month following the tsunami when supporting services were likely impacted both volume and income have rapidly increased to pre tsunami levels long term monitoring should be implemented to determine if nursery services were affected

evolution of co2 so2 hcl and hno3 in the volcanic plumes from etna the volcanic plumes from degassing etna italy were extensively probed with instruments onboard the deutsches zentrum fur luft und raumfahrt research aircraft falcon during the contrail volcano and cirrus experiment concert on 29 30 september 2011 up to 10 4 ppmv so2 and 0 3 ppmv hcl were detected with the atmospheric chemical ionization mass spectrometer aims at 3 1 km altitude and 20 km distance to the summit hno3 is the dominant reactive nitrogen component in the plumes linking aircraft and ground based observations by hybrid single particle lagrangian integrated trajectory dispersion modeling we identify two crater plumes with different compositions primarily injected by the bocca nuova and north east craters uniquely we follow their chemical evolution up to 5 h plume age our results show that co2 so2 and so2 hcl molar ratios are stable in the ageing plumes hence conversion of so2 to h2so4 and partitioning of hcl in acidic plume particles play a minor role at dry tropospheric conditions thus these trace gases allow monitoring volcanic activity far from the crater

comment on evolution of co 2 so 2 hcl and hno 3 in the volcanic plumes from etna by voigt et al geophys res lett 41 doi 10 1002 2013gl058974 editor s note the following comment and reply arise from an article published in geophysical research letters by voigt et al 2014 the article addresses a volcanology topic and the commenters take issue with some conclusions and offer an analysis of their own voigt and co authors have responded why is this comment and reply being published in the bulletin it is because geophysical research letters is one of a number of journals that do not offer any published forum for discussion of the papers they publish this is a matter of editorial policy and a decision for each journal the bulletin of volcanology does provide a forum for discussion of articles published when contacted by marcello liotta with the request that the bulletin consider hosting a discussion of the voigt et al volcanology article in grl i agreed to do so if the grl authors were willing to engagewith the comment voigt and co authors were willing to do so and have been allowed a small amount of additional space to summarize for bulletin readers the key points of the grl paper under discussion before responding directly to the comment from liotta and rizzo i hope that bulletin readers find the discussion and reply of interest james d l white executive editor bulletin of volcanology

coral reefs reduce tsunami impact in model simulations 1 significant buffering of the impact of tsunamis by coral reefs is suggested by limited observations and some anecdotal reports particularly following the 2004 indian ocean tsunami here we simulate tsunami run up on idealized topographies in one and two dimensions using a nonlinear shallow water model and show that a sufficiently wide barrier reef within a meter or two of the surface reduces run up on land on the order of 50 we studied topographies representative of volcanic islands islands with no continental shelf but our conclusions may pertain to other topographies effectiveness depends on the amplitude and wavelength of the incident tsunami as well as the geometry and health of the reef and the offshore distance of the reef reducing the threat to reefs from anthropogenic nutrients sedimentation fishing practices channel building and global warming would help to protect some islands against tsunamis

the 2009 samoa tonga great earthquake triggered doublet great earthquakes having seismic magnitudes of at least 8 usually involve abrupt sliding of rock masses at a boundary between tectonic plates such interplate ruptures produce dynamic and static stress changes that can activate nearby intraplate aftershocks as is commonly observed in the trench slope region seaward of a great subduction zone thrust event1 the earthquake sequence addressed here involves a rare instance in which a great trench slope intraplate earthquake triggered extensive interplate faulting reversing the typical pattern and broadly expanding the seismic and tsunami hazard on 29 september 2009 within two minutes of the initiation of a normal faulting event with moment magnitude 8 1 in the outer trench slope at the northern end of the tonga subduction zone two major interplate underthrusting subevents both with moment magnitude 7 8 with total moment equal to a second great earthquake of moment magnitude 8 0 ruptured the nearby subduction zone megathrust the collective faulting produced tsunami waves with localized regions of about 12 metres run up that claimed 192 lives in samoa american samoa and tonga overlap of the seismic signals obscured the fact that distinct faults separated by more than 50 km had ruptured with different geometries with the triggered thrust faulting only being revealed by detailed seismic wave analyses extensive interplate and intraplate aftershock activity was activated over a large region of the northern tonga subduction zone

determining formation s wave transverse isotropy from borehole flexural wave dispersion data abstractmany earth formations are characterized as transversely isotropic ti media in acoustic logging through a vertical borehole the s wave ti property has traditionally been determined from borehole monopole stoneley wave measurements but the feasibility of shear ti estimation from dipole flexural waves has not been fully investigated we have developed a methodology to determine the ti parameters from borehole dipole flexural wave data our analysis shows that the stoneley wave is sensitive to the ti property mainly in an acoustically slow formation and the sensitivity diminishes when the formation becomes faster the advantage of the flexural wave over the stoneley wave is that the former wave is sensitive to the ti property in the slow and fast formations provided the wave measurement is made in a broad frequency range in which the flexural wave dispersion characteristics from low to high frequencies can be used by calculating the theoretical flexural wave dispersion curve for the ti formati

active alkaline traps to determine acidic gas ratios in volcanic plumes sampling techniques and analytical methods in situ measurements have been the basis for monitoring volcanic gas emissions for many years and being complemented by remote sensing techniques still play an important role to date concerning in situ techniques for sampling a dilute plume an increase in accuracy and a reduction of detection limits are still necessary for most gases e g co2 so2 hcl hf hbr hi in this work the raschig tube technique rt is modified and utilized for application on volcanic plumes the theoretical and experimental absorption properties of the rt and the drechsel bottle db setups are characterized and both are applied simultaneously to the well established filter packs technique fp in the field on stromboli island and mount etna the comparison points out that fps are the most practical to apply but the results are error prone compared to rt and db whereas the rt results in up to 13 times higher analyte concentrations than the db in the same sampling time an optimization of the analytical procedure including sample pretreatment and analysis by titration ion chromatography and inductively coupled plasma mass spectrometry led to a comprehensive data set covering a wide range of compounds in particular less abundant species were quantified more accurately and iodine was detected for the first time in stromboli s plume simultaneously applying multiaxis differential optical absorption spectroscopy max doas the chemical transformation of emitted bromide into bromine monoxide bro from stromboli and etna was determined to 3 6 and 7 respectively within less than 5 min after the gas release from the active vents

sulfur isotopic compositions of fumarolic and plume gases at mount etna italy and inferences on their magmatic source 1 here we report new data on the sulfur isotopic compositions 34s of fumarolic and plume gases collected at mount etna volcano during 2008 2009 while low temperature fumaroles are affected by postmagmatic processes that modify the pristine isotopic signature high temperature and plume gases allow establishment of a 34s range of 0 1 for magmatic so2 we compared our data with those from s dissolved in primitive melt inclusions from 2002 lava and in whole rocks that erupted during the past two thousand years such a comparison revealed that 34s is systematically lower for magmatic gases than for sulfur dissolved in the melt we modeled how isotopic fractionation due to magma degassing process may vary 34s value in both the melt and gaseous phases this modeling required assessment of the fractionation factor gas melt the most recent measurements on the oxidation state of sulfur in basaltic melt inclusions indicate that nearly all s is dissolved as sulfate s6 which would be possible in oxidized magmatic systems nno 1 under these conditions the exsolved gaseous phase is depleted with respect to the melt and the proposed model fits both gas and melt data and constrains the etnean magmatic 34s to 1 0 1 5 it is remarkable that the assessed redox conditions which are significantly more oxidizing than previously thought are able to explain why the dominant sulfur species measured in the etnean plume is so2

a review of the discrete wavenumber method we present a review of the discrete wavenumber dwn method the method introduced by bouchon and art 1977 allows the simple and accurate calculation of the complete green s functions for many problems in elastodynamics

local and global fluid effects on sonic wave modes abstractmost subsurface formations of value to exploration contain a heterogeneous fluid filled pore space where local fluid pressure effects can significantly change the velocities of passing seismic waves to better understand the effect of these local pressure gradients on borehole wave propagation we combined chapman s squirt flow model with biot s poroelastic theory we applied the unified theory to a slow and fast formation with permeable borehole walls containing different quantities of compliant pores these results are compared with those for a formation with no soft pores the discrete wavenumber summation method with a monopole point source generates the wavefields consisting of the p s leaky p stoneley and pseudo rayleigh waves the resulting synthetic wave modes are processed using a weighted spectral semblance wss algorithm we found that the resulting wss dispersion curves closely matched the analytical expressions for the formation compressional velocity and solutions to the peri

high precision u th dating of storm transported coral blocks on frankland islands northern great barrier reef australia abstract high energy storm transported coral blocks are widespread on the reef flats of the great barrier reef gbr australia and have the potential to be used as proxies for reconstructing past storm cyclone events prior to historical or instrumental records in this study samples from 42 individual transported coral blocks were collected from the inshore frankland islands northern gbr for high precision mc icpms u th dating with their surface mortality ages recording the timing of individual storms or cyclones responsible for their uplift from their original growth position the dated mortality ages were found to match well with known historical storm cyclone events in the last century with 80 of them falling within episodes of increased storm activity 1910 1915 1945 1950 1955 1960 1975 1990 1995 2000 ad captured by instrumental historic records confirming that transported coral blocks on inshore reefs can be used as proxies for past storm cyclone occurrences using this approach this study also identified 17 additional storm cyclone events that occurred before european settlement in the 1850s including three oldest events at 758 4 3 7 777 9 4 9 and 985 2 4 8 ad respectively our results despite still preliminary suggest that the storm cyclone activity in this region tends to broadly correlate with the positive modes of the pacific decadal oscillation pdo during the last millennium in addition there appears to be a decreasing age trend from the shore to the reef edge from 758 4 3 7 ad to 1988 3 1 6 ad which can be attributed to sea level fall and or reef island progradation over the last 2000 years

ancestral heritage saves tribes during 1 april 2007 solomon islands tsunami 1 the 1 april 2007 magnitude ms 8 1 earthquake off the new georgia group in the solomon islands generated a tsunami that killed 52 with locally focused run up heights of 12 m local flow depths of 5 m as well as tectonic uplift up to 3 6 m and subsidence down to 1 5 m a reconnaissance team deployed within one week investigated 65 coastal settlements on 13 remote islands the ancestral heritage run to high ground after an earthquake passed on to younger generations by survivors of smaller historic tsunamis triggered an immediate spontaneous self evacuation containing the death toll

seismic signatures of permeability in heterogeneous porous media in homogeneous poroelastic systems the permeability tensor practically does not influence propagating seismic waves in the low frequency range 0 1000 hz see e g schmitt 1989 gelinsky and shapiro 1996 in this paper we show that this situation changes in heterogeneous systems such as layered or fractured sediments due to the heterogeneities of poroelastic structures the attenuation of p waves is influenced by the permeability in an enhanced way we show however that such a seismic permeability can differ very strongly from the hydraulic permeability

borehole flexural modes in anisotropic formations a perturbation method of solution is an efficient way of analyzing elastic wave propagation along a borehole in anisotropic formations the perturbation model allows us to calculate changes in the modal dispersion curves caused by the differences in elastic constants between the anisotropic formation of interest and a reference or unperturbed isotropic formation the equivalent isotropic constants in the reference formation are obtained from the appropriate compressional and shear wave velocities for the selected propagation and polarization directions of the flexural mode this choice of the unperturbed solution means that the required perturbation is minimal resulting in enhanced accuracy of the perturbed solution computational results are presented for the dispersion curves of borehole flexural waves in a transversely isotropic ti formation as a function of borehole deviation from the ti symmetry axis in addition radial distributions of displacement and stress fields associated with the flexura

prediction of fracture density using genetic algorithm support vector machine based on acoustic logging data the existing methods of well logging interpretation cannot be applied accurately to the exploration and evaluation of carbonate reservoirs because of the fracture development based on the fracture density obtained by core analysis in a carbonate reservoir located in the ordos basin the west of china three types of fracture density low medium and high fracture density of the target formation were identified we investigated the effect of fractures on acoustic logging signals in time and frequency domain by hilbert huang transform hht and extracted 11 features in time domain and 9 features in frequency domain then we reduced the features in time and frequency domain to three principal components by principal component analysis pca finally a new prediction model of ga svm method based on hilbert huang transform of acoustic logging data was reported to predict the fracture density the results show that fracture density has a greater effect on the attenuation of imf2 and imf3 components for thre

laboratory experiments of tsunami runup on a circular island laboratory experiments of a 7 2 m diameter conical island were conducted to study three dimensional tsunami runup the 62 5 cm tall island had 1 on 4 side slopes and was positioned in the center of a 30 m wide by 25 m long flat bottom basin solitary waves with height to depth ratios ranging from 0 05 to 0 20 and source lengths ranging from 0 30 to 7 14 island diameters were tested in water depths of 32 and 42 cm twenty seven capacitance wave gages were used to measure surface wave elevations at incident and four radial transects on the island slope maximum vertical runup measurements were made at 20 locations around the perimeter of the island using rod and transit a new runup gage was located on the back or lee side of the island to record runup time series

unravelling the processes controlling gas emissions from the central and northeast craters of mt etna abstract we measured volcanic gas emissions from the northeast crater nec and central crater cc of mount etna on 21st july 2008 and 3rd and 31st august 2009 using a novel lightweight open path fourier transform infrared spectrometry op ftir in active mode with a portable infrared lamp contemporaneously we measured the so2 flux of the total gas emission released by the combined summit craters 14 km downwind and the so2 flux emitted by the nec measured at the summit combining these data we determined the flux of the major volcanic components h2o co2 so2 hcl and hf emitted individually from cc and nec craters the results reveal similar so2 hcl ratios but distinct co2 so2 ratios 1 3 and 10 9 for nec and cc respectively and an order of magnitude greater co2 flux from the cc compared with the nec a simple model in which the nec branches from a central feeding conduit at a depth of 2 km can reproduce these observations we highlight that in such a system short term variations in co2 so2 ratios at each crater can occur due to minor variations in the magma gas flux entering each conduit at the branch without an overall change in magma supply co2 so2 variations measured at individual craters may therefore be unrepresentative of the volcanic system and require cautious interpretation monitoring of the total co2 and so2 fluxes emitted from each crater is on the contrary an optimal monitoring strategy and can be achieved using a combination of co2 so2 instruments and so2 imaging cameras

palaeotsunamis and their influence on polynesian settlement the 11 march 2011 t hoku oki tsunami caused widespread devastation to coastal communities in japan this event however was merely the latest yet largest of several similar occurrences in the pacific that include the 2007 solomon islands 2009 south pacific and 2010 chilean tsunamis all have had their predecessors and a growing data base of palaeotsunamis in the pacific suggests recurrent events comparable with and of larger magnitude than their recent historical counterparts here we show that evidence for regional palaeotsunamis provides an opportunity to re evaluate hypotheses used to explain the punctuated history of human settlement patterns across the pacific in particular the almost two millennia long pause in eastward migration and the abandonment of long distance sea voyaging in the 15th century may be related to palaeotsunamis with potential sources including the tectonically active tonga kermadec trench the kuwae caldera collapse and the more distant pacific wide ring of fire

borehole flexural modes in transversely isotropic formations low frequency asymptotic velocity dipoleacousticloggingiswidelyusedforinsitumeasurement of formation shear velocity this technique is based on the theoretical result in isotropic formations that the velocity ofthedispersiveflexuralmodeapproachestheshearvelocity at the low frequency limit transversely isotropic ti formations frequently are encountered in petroleum engineering so it is necessary to determine if shear velocity along the borehole can be determined from the low frequency flexural wave in ti cases the flexural wave in a borehole parallel to thesymmetryaxisofatiformationisinvestigated theborehole acoustic field is formulated in the frequency wavenumber domain as the sum of a direct field from the source and a reflected field from the borehole wall poles and branch points of the reflection coefficient are analyzed and component waves contributed by those singularities are calculated thedispersionfeatureoftheflexuralmodeinsometiformationsdiffersfromisotropiccases thelow frequencylimitof flexural mode velocity trends to a value lower than the shear velocity when parameters of the formation satisfy c44 2c33 where and arethomsenparametersandc33 and c44 are the elastic moduli that asymptotic value corresponds to a newly found branch point of the reflection function numerical results show that the low frequency flexural wave travels slower than the shear wave in the synthetic full waveforms in mesaverde clayshale 5501 extracting the shearvelocityfromtheflexuralarrivalleadstoinaccuracyon theorderof10 inthisformation

a cracked porous medium elastic wave theory and its application to interpreting acoustic data from tight formations rocks in the earth s crust usually contain pores and cracks typical examples include tight sandstone and shale rocks that have low porosity but contain abundant microcracks by extending the classic biot s poroelastic wave theory to include the effects of cracks we obtain an elastic wave theory for porous rocks containing cracks adding crack density and aspect ratio as two important parameters to the original theory because the flat or narrow shaped cracks can easily deform under acoustic wave excitation the acoustic property of a cracked porous rock is quite different for different saturation conditions the predicted fluid sensitivity is used to interpret acoustic velocity log data from tight sand and shale gas formations in both scenarios the new theory correctly predicts the trend of velocity variation with gas saturation the results confirm that the presence of cracks in tight rocks can give rise to significant hydrocarbon signature in the acoustic measurement data allowing for identifying hydrocarbons from the data

coastal plain stratigraphy records tectonic environmental and human habitability changes related to sea level drawdown upolu sāmoa coastal plain stratigraphy is often over looked in paleo sea level reconstructions because carbonate sediments do not precisely constrain former sea level pacific island sedimentology provides an invaluable record of geomorphic and environmental consequences of coastal evolution in response to changes in sea level and local tectonics a series of coastal auger cores obtained from eastern upolu reveal a subsurface carbonate sand envelope predominately composed of coral and coralline algae derived from the reef framework coupling the sedimentological record with geophysical models of holocene sea level we identify a critical value 0 3 1 0 m during the falling phase of the sea level high stand 1899 2103 cal yr bp that represents the transition from a transgressive to a regressive environment and initiates coastal progradation correlating the critical value with time we observe nearly a millennium of coastal plain development is required before a small human population is established our findings support previous studies arguing that s moa was colonized by small and isolated groups as post mid holocene drawdown in regional sea level produced coastal settings that were morphologically attractive for human settlement as future sea level approaches mid holocene high stand values lessons learned from pacific island sedimentological records may be useful in guiding future decisions related to coastal processes and habitat suitability

permeability and borehole stoneley waves comparison between experiment and theory we performed laboratory experiments to evaluate theoretical models of borehole stoneley wave propagation in permeable materials a berea sandstone and synthetic samples made of cemented glass beads were saturated with silicone oils we measured both velocity and attenuation over a frequency band from 10 khz to 90 khz our theoretical modeling incorporated biot theory and deresiewicz skalak boundary conditions into a cylindrical geometry and included frequency dependent permeability by varying the viscosity of the saturating pore fluid we were able to study both low frequency and high frequency regions of biot theory as well as the intermediate transition zone in both low frequency and high frequency regions of the theory we obtained excellent agreement between experimental observations and theoretical predictions velocity and attenuation 1 q are frequency dependent especially at low frequencies also at low frequencies velocity decreases and attenuation increases with increasing fluid mobility permeability viscosity more complicated behavior is observed at high frequencies these results support recent observations from the oil field suggesting that stoneley wave velocity and attenuation may be indicative of formation permeability

total volatile flux from mount etna 1 the total volatile tv flux from mount etna volcano has been characterised for the first time by summing the simultaneously evaluated fluxes of the three main volcanogenic volatiles h2o co2 and so2 so2 flux was determined by routine doas traverse measurements while h2o and co2 were evaluated by scaling multigas sensed h2o so2 and co2 so2 plume ratios to the uv sensed so2 flux the time averaged tv flux from etna is evaluated at 21 000 t day 1 with a large fraction accounted for by h2o 13 000 t day 1 h2o dominates 70 the volatile budget during syn eruptive degassing while co2 and h2o contribute equally to the tv flux during passive degassing the co2 flux was observed to be particularly high prior to the 2006 eruption suggesting that this parameter is a good candidate for eruption prediction at basaltic volcanoes

elastic wave propagation in a fluid filled borehole and synthetic acoustic logs the propagation and dispersion characteristics of guided waves in a fluid filled borehole are studied using dispersion curves and modeling full wave acoustic logs by synthetic microseismograms the dispersion characteristics of the pseudo rayleigh reflected and stoneley waves in a borehole with and without a tool in the center are compared effects of different tool properties are calculated the effect of a rigid tool is to make the effective borehole radius smaller as an approximation dispersion characteristics of the guided waves in a borehole with a tool can be calculated as a purely fluid filled borehole with a smaller effective radius theoretical waveforms microseismograms of elastic waves propagating in a borehole are calculated using a discrete wavenumber integration with an appropriate choice of parameters our results look similar to the acoustic waveforms recorded in a limestone and a shale formation several factors affect the shape of an acoustic log microseismogram the effective rad

insights into magma and fluid transfer at mount etna by a multiparametric approach a model of the events leading to the 2011 eruptive cycle 1 since the second half of the 1990s the eruptive activity of mount etna has provided evidence that both explosive and effusive eruptions display periodic variations in discharge and eruption style in this work a multiparametric approach consisting of comparing volcanological geophysical and geochemical data was applied to explore the volcano s dynamics during 2009 2011 in particular temporal and or spatial variations of seismicity volcano tectonic earthquakes volcanic tremor and long period and very long period events ground deformation gps and tiltmeter data and geochemistry so2 flux co2 flux co2 so2 ratio were studied to understand the volcanic activity as well as to investigate magma movement in both deep and shallow portions of the plumbing system feeding the 2011 eruptive period after the volcano deflation accompanying the onset of the 2008 2009 eruption a new recharging phase began in august 2008 this new volcanic cycle evolved from an initial recharge phase of the intermediate shallower plumbing system and inflation followed by i accelerated displacement in the volcano s eastern flank since april 2009 and ii renewal of summit volcanic activity during the second half of 2010 culminating in 2011 in a cyclic eruptive behavior with 18 lava fountains from new southeast crater nsec furthermore supported by the geochemical data the inversion of ground deformation gps data and the locations of the tremor sources are used here to constrain both the area and the depth range of magma degassing allowing reconstructing the intermediate and shallow storage zones feeding the 2011 cyclic fountaining nsec activity

three years of so2 flux measurements of mt etna using an automated uv scanner array comparison with conventional traverses and uncertainties in flux retrieval 1 sviluppo di sistemi di monitoraggio dipartimento di protezione civile della regione sicilia 2 ingv istituto nazionale di geofisica e vulcanologia sezione di catania italy 3 novac network for observation of volcanic and atmospheric change eu funded sixth framework programme project 18354 4 uk nerc national centre for earth observation via the dynamic earth and geo hazards