seismic reflectors beneath the central cones of aso volcano kyushu japan abstract the subsurface structure of aso volcano central kyushu japan has been imaged down to 10 km below sea level and notable features of subsurface structure in the central cones were revealed by a 3 d seismic reflection analysis the 3 d reflection analysis included reflection enhancements and 3 d migration the reflection enhancements and the nmo correction were applied on waveform data from the seismic experiment aso98 the 3 d migration with a kirchhoff integral was processed for 1397 nmo corrected traces to calculate the reflectivity at about 60 000 image points in an approximately 7 km by 7 5 km square region the results of the 3 d migration show that the subsurface structure beneath the central cones can be divided into three parts the western part the eastern part and the northwestern part bright reflectors appear in most of them and a significant discontinuity is inferred the reflector horizon at 2 km below sea level spreads beneath the western and the eastern part and is probably the top surface of the pre aso volcanic rocks or the basement rocks reflection voids appear in the western part and just beneath the active crater the reflector void in the western part implies a hot region and is most probably the known seismic anomalies such as low velocity region or attenuation region another reflector void beneath the active crater can also be associated with a hot region apparently surrounding the conduit system of the current volcanic craters the major discontinuity is located beneath the northwest flank of the central cones this discontinuity divides the northwest region with weak reflectors from other parts the discontinuity may be the trace of the oita kumamoto tectonic line which is the major tectonic line in central kyushu crossing the aso caldera

temperature changes at depths to 150 metres near the active crater of aso volcano preliminary analysis of seasonal and volcanic effects abstract two holes were drilled to depths of 150 m and 70 m from the surface about 200 m from the active crater of aso volcano and quartz thermometers were installed in the holes at depth intervals of 30 m and 35 m respectively this series of observations is one of the first measurements of temperature at depth so close to an active crater the ground temperature at a depth of 2 m had an annual variation with a range of about 10 c as expected clearly corresponding to the atmospheric temperature variation but delayed by about 1 month temperatures measured at depths from 30 m to 70 m had very small annual temperature variations the range of temperature at 30 m depth was about 0 04 c the temperature at a depth of 60 m however was particularly stable probably because at this depth the hole is in the middle of a massive lava flow at depths of 70 m or more small less than 0 2 c annual temperature variations were again observed these variations are probably due to the effects of surface water descending to these levels through cracks and fissures at 120 m depth the average temperature is about 17 5 c over 5 c above the surface average temperature and the annual temperature variation has a range of about 2 c out of phase with the atmospheric changes this is probably due to the interaction of rainfall descending from the surface with convecting hotter fluids from below the temperature gradient below 100 m depth is very high with the average temperature at a depth of 150 m being about 31 c the temperature variations at this depth are dominated by long period variations with a steady decline after a peak in november december 1989 overlain by a rather irregular seasonal variation with a range of about 0 5 c october 1989 was the time of most active volcanic activity with strombolian eruptions depositing ash to a distance of 50 km from the crater accompanied by very high amplitude volcanic tremor so the temperature changes at 150 m seem to be mainly the result of volcanic activity the maximum temperature at this depth occurred 1 or 2 months after the peak of observed volcanic activity so it is likely that the temperature variations show a delayed influence of the level of volcanic activity these results show that in the unconsolidated materials often found by active volcanic craters the effects of seasonal atmospheric variations are carried to substantial depths by groundwater flows so that at aso volcano only at the maximum depth of 150 m are the temperature variations clearly dominated by the level of volcanic activity

geochemistry hydrology and mineralogy of the sand bulge area laguna madre flats south texas abstract the sand bulge area of the laguna madre flats is a silicoclastic coastal sabkha lying between padre island and the intracoastal waterway on the gulf coast of southwest texas the sabkha is sporadically inundated by wind tidal flooding of water from an adjacent lagoon laguna madre saline interstitial brines are formed by infiltration of partially evaporated ponded flood water manometric data indicate that the brine seeps downward through the sabkha and laterally west toward the intracoastal waterway icww some of the brine may flow seaward east through incised pleistocene stream valleys most of the sabkha in this area is covered with blue green algal mat precipitation of microcrystalline mg calcite algal micrite in brine ponds or within the algal mat induced by algal or bacterial action removes much of the calcium from recharge water before it reaches the sabkha watertable thus though brine salinities reach 240 per mil low calcium concentrations prevent the precipitation of gypsum and thermodynamic calculations indicate that the brines are undersaturated with respect to gypsum gypsum does not presently occur in the sabkha sediments in this area contrary to earlier observations fisk 1959 it is suggested that emplacement of the icww altered the rate and direction of water flow through the sabkha leading to less saline brines and possibly to the dissolution of previously formed gypsum

oxygen and carbon isotopes of early permian cold water carbonates tasmania australia abstract the permian carbonates of tasmania formed at a paleolatitude near 80 s during the gondwanan ice age contain abundant dropstones and are associated with glaciomarine sediments a shallow marine carbonate depositional model with floating icebergs calved from an adjacent ice shelf grading into an ice sheet has been proposed as the sea level rose during relatively warmer periods large volumes of melt waters mixed with marine waters retarding limestone deposition and causing deposition of shales siltstones these phases are preserved in the stratigraphic record as interbedded units australian permian brachiopods and molluscs are characterized by unusually light o18 pdb values and heavier c13 pdb values than those that occur in many modern cool temperate to subpolar cold water carbonates tasmanian permian whole rock o18 pdb values fall at the edge of the normal marine limestone field of keith and weber 1964 and range towards lighter values down to 16 9 pdb the o18 values of cements 7 6 to 25 6 pdb in the tasmanian early permian limestones partly overlap with those o18 values obtained for fresh water cements in the early permian continental tillites from antarctica and south africa gondwanaland indicating that the early permian sea was diluted by isotopically light melt waters during warming phases the o18 values of permian fauna if one assumes no diagenetic equilibration give unrealistic paleotemperatures because of this variable melt water dilution of the permian sea however calculated o18 values corresponding to marine c13 values of brachiopods and eurydesma and extrapolated from a model based on the linear trend of c13 o18 in modern and last glacial cold water carbonates give reasonable estimates of australian permian temperatures of up t 15 c with the coldest waters of less than 4 c around tasmania the sequential deviation lines of o18 c13 of both cements and the fauna associated with these cements indicate that the original o18 value of fauna was as high as 6 pdb this calculated original o18 value indicates an average seawater temperature for tasmania in the early permian of 1 8 c similar to the present average 1 9 c water temperature near ice shelves around antarctica the o18 values of ements suggest that the tasmanian limestones reacted with subfreezing melt waters during early diagenesis the o18 composition of the early permian sea is inferred to have been about 1 2 pdb similar to that observed during the pleistocene glaciations and was diluted by melt water as light as o18 smow 31 at 5 c 26 pdb in variable amounts it is unlikely that the o18 composition of the wellmixed open permian sea ever reached a value as light as o18 pdb 6 it is suggested that the permian sea c13 value was about 2 pdb heavier than that of modern and pleistocene seawater

an attenuating structure beneath the aso caldera determined from the propagation of seismic waves the attenuation of amplitude is seen in seismic waves which pass through the central region of the aso caldera in kyushu japan it is also recognized from spectral analysis of seismic waves that the higher frequencies of the p wave are reduced in the waves which pass through the central region of the caldera it is shown that the relative attenuation increases remarkably for the frequency range of 5 to 10 hz the specific attenuation factor q of the p wave train is about 100 from the surface projection of the ray paths with low q values through the aso caldera to each station the attenuating region is located beneath the center of the caldera extending to the north of the central cones in conjunction with the low q value of the p wave and the decreases of s wave amplitudes the relative p wave residual times have comparatively large values for seismic waves passing through the central region beneath the caldera in order to attempt to provide additional information on the depth configuration of the attenuating material the ray paths of p wave s first arrivals are located in three dimensional space it indicates that the low velocity material is located beneath the center of the caldera at depths of about 6 to 9 km however lowvelocity anomalies above the depth of 6 km and below the depth of 15 km were not able to be detected because most of the available seismic ray paths had crossed the caldera at depths of about 6 to 15 km furthermore the relative residual times have numerous errors resulting from incorrect hypocenter locations origin times inhomogeneities in the structure and uncertainty of the velocity structure at shallow depths in the aso caldera refraction or reflection studies are required for an accurate estimate of the structure and more detailed properties of the attenuating material

detection of a crack like conduit beneath the active crater at aso volcano japan to constrain the source of long period tremors lpts we deployed a very dense broadband seismic network consisting of totally twenty four stations around the active crater of aso volcano in kyushu japan the spatial variation of the observed signal amplitudes reveals that the source of lpts consists of an isotropic expansion contraction and an inflation deflation of an inclined tensile crack with a strike almost parallel to the chain of craters the detected crack has a dimension of 1 km and its center is located a few hundred meters southwest of the active crater at a depth of about 1 8 km the extension of the crack plane meets the crater chain including the active fumarole at the surface suggesting that the crack has played an important role in transporting gasses and or lava to the craters from below this work also demonstrates a powerful usage of broadband seismometers as geodetic instruments to constrain subsurface structures at active volcanoes

effect of compaction pressure on consolidation behaviour of unsaturated silty soil the effect of compaction pressure on subsequent soil behaviour during isotropic consolidation has been investigated by conducting controlled suction triaxial tests on samples of an unsaturated compacted silty soil a comprehensive set of laboratory experiments was carried out in a double walled triaxial apparatus on samples of unsaturated soil that were prepared using two different compaction pressures the axis translation technique was used for creating the desired suctions in the samples in the experiments the soil samples were subjected to isotropic consolidation under constant suctions the results show that different compaction pressures produce different fabrics in a soil and therefore affect the behaviour of the soil the results also show that the value of yield stress and the location of the loading collapse lc yield curve are functions of soil fabric furthermore it is shown that the slopes of normal consolidation lines for densely and loosely compacted samples differ in unsaturated condit

influence of compaction procedure on the mechanical behaviour of an unsaturated compacted clay part 1 wetting and isotropic compression the influence of compaction pressure compaction water content and type of compaction static or dynamic on subsequent soil behaviour during wetting and isotropic loading has been investigated by conducting controlled suction tests on samples of unsaturated compacted speswhite kaolin the results are interpreted within the context of an elastoplastic framework for unsaturated soils to examine which compaction induced effects can be explained simply by variation in the initial state of the soil and which require that soils produced by different compaction procedures are modelled as fundamentally different materials the compaction pressure influences initial state by affecting the initial position of the yield surface but it also influences to a limited degree the positions of the normal compression lines for different values of suction the compaction water content influences the initial suction but also has a significant influence greater than does compaction pressure on the positions of the nor

diffraction problems of 3d seismic imaging migration is essential to seismic imaging it is carried out by backward extrapolation of the wavefield registered on the observation surface the quality of images depends on the accuracy of the wavefield reconstruction at interior subsurface points from the theory based on the exact solution of the scalar wave equation it is known that for accurate wave extrapolation data must be obtained from an infinite observation surface limiting of migration apertures which is inevitable in practice leads to artefacts in extrapolated fields the distortion they cause in 2d and 3d imaging is different in 2d migration the artefacts known as truncation effects are much weaker than the signals being extrapolated and for this reason attract no special attention in 3d migration diffractions caused by an aperture edge are stronger and may create serious problems for a circular aperture their amplitudes are comparable to the amplitudes of the signals themselves the study of aperture diffractions is intended to help in the search for ways of either suppressing them efficiently or deliberately utilizing them in order to improve imaging in optics diffractions by an aperture play a constructive role in image making this research shows that the same may take place in seismic imaging

influence of compaction procedure on the mechanical behaviour of an unsaturated compacted clay part 2 shearing and constitutive modelling the influence of compaction pressure compaction water content and type of compaction static or dynamic on subsequent soil behaviour was investigated by conducting controlled suction triaxial tests on samples of unsaturated compacted speswhite kaolin compaction pressure influences initial state by determining the initial position of the yield surface thus affecting among other things the shape of stress strain curves during shearing compaction pressure also influences to a limited degree the positions of the normal compression lines for different values of suction but it has no effect on critical state relationships the effect of compaction pressure can probably be modelled solely in terms of initial state if an anisotropic elastoplastic model incorporating rotational hardening is employed whereas the parameters defining the slopes and intercepts of the normal compression lines for different values of suction require adjustment with variation of compaction pressure if a conventional isotropic

petrologic and geochemical constraints on the origin of subsurface dolomite enewetak atoll an example of dolomitization by normal seawater dolomite is present 1 250 1 400 m below sea level in eocene strata of enewetak atoll petrographically the deep enewetak dolomite postdates brittle compaction of rigid grains in the host eocene strata the 87 sr 86 sr ratio of these dolomites 0 70865 0 70901 indicates that they formed at one or more times between the middle miocene and the present since the top of the lower miocene is more than 900 m above the deep dolomitic interval the dolomite must have formed at a minimum burial depth of 900 m stable oxygen isotope determinations suggest dolomite precipitation from cold marine water lower miocene and eocene carbonate strata on the atoll are apparently in open communication with cold modern ocean water suggesting that those same strata were in open communication with ocean water during dolomitization at a depth of about 1 000 m modern pacific ocean water becomes undersaturated with respect to calcite but is still supersaturated with respect to dolomite therefore it is proposed that the deep enewetak dolomite precipitated from cold deep ocean water undersaturated with respect to calcite at a burial depth of more than 900 m

experimental observations of the stress regime in unsaturated compacted clay when laterally confined construction processes often involve reformation of the landscape which will inevitably encompass compaction of artificially placed soils a common application of fill materials is their use as backfill in many engineering applications for example behind a retaining wall the post construction behaviour of clay fills is complex with respect to stresses and deformation when the fills become saturated over time heavily compacted fills swells significantly more than the lightly compacted fills this will produce enhanced lateral stresses if the fill is laterally restrained the work presented in this paper examines how the stress regime in unsaturated clay fills changes with wetting under laterally restrained conditions specimens of compacted kaolin with different initial conditions were wetted to various values of suction under zero lateral strain at constant net overburden pressure which allowed the concept of k0 the ratio between the net horizontal stress and the net vertical stress to be examined

the 2016 kumamoto mw 7 0 earthquake a significant event in a fault volcano system the 2016 kumamoto earthquake sequence occurred on the futagawa hinagu fault zone near the aso volcano on kyushu island the sequence was initiated with two major m w 6 0 foreshocks and the mainshock m w 7 0 occurred 25 h after the second major foreshock we combine gps strong motion synthetic aperture radar images and surface offset data in a joint inversion to resolve the kinematic rupture process of the mainshock and coseismic displacement of the foreshocks the joint inversion results reveal a unilateral rupture process for the mainshock involving sequential rupture of four major asperities the slip area of the foreshocks and mainshock and the aftershock loci form a detailed complementary pattern the mainshock rupture terminates near the rim of the caldera leaving a 10 km long gap of aftershocks this area is characterized by high temperature and low shear wave velocity density and resistivity which may be related to the partially melted geothermal condition ductile material property near the volcano may act as a material barrier to the dynamic rupture topographic weight of the caldera increases compressional normal stress on the fault plane which may behave as a stress barrier long term seismic hazard and deformation behaviors related to these two types of barriers are discussed in terms of the associated frictional mechanism significant postseismic creeps observed near the volcano area indicates a velocity strengthening frictional behavior near the rupture termination which confirms that the material barrier mechanism is likely the dominant rupture termination mechanism

diagenesis of ordovician carbonates from the north east michigan basin manitoulin island area ontario evidence from petrography stable isotopes and fluid inclusions middle to late ordovician subtidal carbonates in the manitoulin island area of ontario are predominantly limestone in composition but non ferroan and ferroan dolomite is a common cement as well as a selective or locally pervasive replacement phase integration of field petrographic geochemical 6i3c 6 o and fluid inclusion data indicates that lithification of these carbonates occurred during burial diagenesis with much of the alteration controlled by regional fracturing and hydrothermal influences aqueous type 1 fluid inclusions in early calcite pre dolomite and dolomite are saline 29 wt nacl eq solutions with ca and or mg in excess of na and display homogenization temperatures with modes of 95 and 101 c respectively these temperatures can be explained by significantly more burial than can be accounted for either by the available stratigraphic information or by an unusually high palaeogeothermal gradient which also is not well supported the fluid inclusion temperatures are interpreted to have resulted from hydrothermal fluids which circulated during the burial diagenesis of these strata type 1 inclusions in late post dolomite calcite are less saline 19 wt nacl eq and have a bimodal distribution of homogenizatign temperatures with a relatively well defined low temperature peak similar to those in early calcite and dolomite and a broad higher temperature grouping with a mode at 183 c a small proportion of methane and light hydrocarbon bearing fluid inclusions type 2 are present in all stages of carbonate dolomitizing fluids were derived from burial compaction of argillaceous sediments in the more central parts of the michigan basin and the updip migration of these brines along fractures to the basin margin where the carbonates of the manitoulin island area were dolomitized alternatively migration of dolomitizing brines downward from the overlying pervasively dolomitized silurian sequence into fractures in the ordovician carbonates may have occurred integration of the aqueous fluid inclusion data into the diagenetic history of these carbonates remains equivocal because most of the inclusions are secondary or indeterminate in origin nevertheless high salinities resulting from interaction with evaporitic strata and hydrothermal effects are clearly implicated although the origin of the latter remains unclear the alteration styles of the ordovician carbonates in the manitoulin area are similar to those of ordovician hydrocarbon reservoirs described from other parts of the michigan basin they indicate that fracture related diagenesis occurred on a basin wide scale and that hydrothermal effects were important

devonian dolomites from the holy cross mts poland a new concept of the origin of massive dolomites based on petrographic and isotopic evidence a new model based on the effective hydrothermal pump was invoked for the middle and lower upper devonian dolomites from the holy cross mountains wietokrzyskie mts mid southern poland the hybridized seawater was recycled periodically through the deep seated quasi rifted fault system up to the floor of the basin during the eifelian through lower frasnian time bringing about the massive dolomitization of carbonate sediments apart from the dolomites stratified and irregular concentrations of clay minerals iron and manganese oxides and hydroxides with admixtures of pyrite and occasionally barite formed during that time numerous dolomite structural forms connected with various hydrothermal pulses were recorded the delta 13 c and delta 18 o of dolomites range from 1 61 to 6 30 0 and from 0 52 to 10 74 0 respectively the delta 13 c shift in the dolomites is characteristic of that for the associated limestones distinct fluctuation in trace element compositions

dolomitization of permian reef carbonates in a jurassic subduction complex central japan abstract a 100 m thick sequence of dolomite occurs within reef carbonates of the permian nabeyama formation central japan analyses of sediments fossils minerals and geochemical ingredients of a dolomitized sequence reveal that dolomitization was the consequence of active seawater circulation through the carbonate column stable carbon and oxygen isotopic data precluding dolomitizing fluids of freshwater or hybridized seawater origin provide arguments for atoll dolomitization by seawater thermal gradients between the atoll and the underlying volcanic structure caused the convection flow of interstitial water upwelling oceanic water supersaturated with dolomite but undersaturated with respect to calcite was subjected to thermal convection through the porous and permeable sediment column leading to massive dolomitization of the oceanic atoll

a framework for unsaturated soil behaviour a framework is put forward which explains the shear behaviour of an unsaturated soil in terms of the total stresses and suctions acting within the soil it is based on the critical state model for

the measurement of soil stiffness in the triaxial apparatus this paper describes a simple technique for accurately measuring the mean local axial strains of triaxial samples over a central gauge length the technique makes use of an axial displacement gauge which is a development of one devised by burland symes 1982 which makes use of electrolytic levels the device can resolve to less than 1 m over a range of 15 mm is simple to mount on the specimen and is not damaged when the sample is taken to failure the results of undrained triaxial tests are presented for a wide spectrum of soil types ranging from sands through intact reconstituted and remoulded low plasticity till undisturbed london clay to intact unweathered chalk the test results show that conventional external measurements of displacement contain errors which are frequently so large that their use in the determination of soil stiffness at working levels of stress is invalid the errors mainly result from tilting of the sample bedding at the end platens and the effects of compliance in the app

reply to narkiewicz 2017 comment on thermal evolution of paleozoic successions of the holy cross mountains poland abstract in this paper we reply to the criticisms advanced by narkiewicz 2017 on the paper by schito et al 2017 we clarify the issues related to the stratigraphic and thermal maturity constraints used for reconstructing burial and thermal models of the two blocks of the holy cross mountains we also show how geological evidences brought by narkiewicz 2017 as a proof of elevated variscan heat flow are not conclusive or at least suggest the occurence of a localized thermal anomaly only along the area of the holy cross fault in the end we performed new burial and thermal models in the kielce region demonstrating that stratigraphic thickness variations between schito et al 2017 and narkiewicz et al 2010 produce only negligible differences in levels of thermal maturity of paleozoic rocks in addition we outline that levels of thermal maturity for silurian rocks can be matched only by using constant heat flow values through the paleozoic and point to a decisive role for the absence of regional high variscan heat flow in the area

three dimensional seismic velocity structure beneath aso volcano kyushu japan tomographic results for p and s wave velocity structure beneath the active aso volcano kyushu japan using 800 well recorded earthquakes and ten shots recorded by an eight station seismic network are presented a 68 variance reduction was achieved upon simultaneous inversion for hypocenter and velocity structure well resolved velocity anomalies associated with the active crater reveal heterogeneity up to 26 slower and 18 faster in p velocity and up to 31 slower and 22 faster in s velocity than the one dimensional model the largest anomaly is seen over the upper 11 km in the central and northern parts beneath the central cones two low velocity regions are imaged the first region a 10 15 km region encompassing the upper 3 km centered near the caldera wall at tateno valley is characterized by p velocities up to 19 slower 20 for s the second low velocity region is associated with the central cones and active magma conduit system at 6 km depth velocities as low as 4 3 km s up to 26 in p and 2 km s 31 slower in s characterize the 7 km wide volume the magma chamber is roughly spherical in shape centered at 6 km depth flattens at 10 km depth and is located between mt kishima mt eboshi and mt naka the present focus of magmatism a sharp velocity contrast at the depth of 3 km with high velocities to the southwest and lower velocities to the northeast characterizes different abutting structures associated with the oita kumamoto tectonic line

steady subsidence of a repeatedly erupting caldera through insar observations aso japan the relation between unrest and eruption at calderas is still poorly understood aso caldera japan shows minor episodic phreatomagmatic eruptions associated with steady subsidence we analyse the deformation of aso using sar images from 1993 to 2011 and compare it with the eruptive activity although the dataset suffers from limitations e g atmospheric effects coherence loss low signal to noise ratio we observe a steady subsidence signal from 1996 to 1998 which suggests an overall contraction of a magmatic source below the caldera centre from 4 to 5 km depth we propose that the observed contraction may have been induced by the release of the magmatic fluids feeding the eruptions if confirmed by further data this hypothesis suggests that degassing processes play a crucial role in triggering minor eruptions within open conduit calderas such as at aso our study underlines the importance of defining any eruptive potential also from deflating magmatic systems with open conduit

geochemistry of brachiopods oxygen and carbon isotopic records of paleozoic oceans abstract combined trace element and isotope studies of 319 brachiopods covering the ordovician to permian time span show that 13c and 18o in well preserved specimens varied during the paleozoic the overall 13c secular trend is in accord with the previously published observations but its details are obscured by vital isotopic fractionation effects at generic level nonetheless the results suggest that the negative correlation between marine 13ccarbonate and 34ssulphate deteriorates at time scales of 106 years due to the long residence time and thus slow response of so42 in the ocean for oxygen isotopes all devonian and older specimens have 18o of 4 while the well preserved permian samples have near present day 18o of about 1 pdb this isotopic dichotomy is probably not due to post depositional phenomena salinity or biogenic fractionation effects this leaves open the perennial arguments for a change in 18 o 16 o of sea water versus warmer ancient oceans the present data are difficult to explain solely by the temperature alternative the coincidence of the proposed shift in 18o with the large late paleozoic changes in marine 87 sr 86 sr 13 c 12 c 34 s 32 s and sea level stands argues for a tectonic cause and for a change in 18 o 16 o of sea water although such explanation is difficult to reconcile with global balance considerations and with isotopic patterns observed in alteration products of ancient basalts and ophiolites whatever the precise cause or combination of causes the implications for tectonism and or paleoclimatology are of first order significance

a framework for the behaviour of unsaturated expansive clays the paper presents a framework for describing the mechanical behaviour of unsaturated expansive clays it is an extension of an existing formulation developed for unsaturated soils of low activity the extended framework is based on the distinction within the material of a microstructural level where the basic swelling of the active minerals takes place and a macrostructural level responsible for major structural rearrangements by adopting simple assumptions concerning the coupling between the two levels it is possible to reproduce major features of the behaviour of unsaturated expansive clays some selected qualitative comparisons between model predictions and experimental results reported in the literature are presented despite the simplified hypotheses made a very encouraging agreement is obtained key words capillarity clay model unsaturation suction expansive soils

holocene dolomitization of supratidal sediments by active tidal pumping sugarloaf key florida abstract sugarloaf key is an area where holocene dolomitization is occurring calcium rich dolomite is found in a 0 25 to 10 cm thick surface crust which transgresses a thin layer of carbonate mud overlying the karsted pleistocene miami oolite radiocarbon ages of the crust range from 160 years b p to 1420 years b p with a corresponding increase in dolomite content from 0 to 80 the relatively high permeability of the underlying pleistocene oolite and low permeability of the holocene carbonate mud results in a tidal lag between surface water and the partly confined aquifer consequently seawater is pumped upward and downward through the holocene sediment during spring tides the highest concentration of dolomite is found in areas where the sediment layer is thinnest and tidal pumping is most effective limited analyses of surface and subsurface water taken at intervals throughout the pumping cycle suggest that the dolomitizing fluid is essentially florida bay water the earliest diagenesis is caused by precipitation of dolomite cement which occurs as 0 1 to 0 3 micron subrounded crystallites that show no distinct crystal form during further cementation and somewhat later during replacement of preexisting crystallites poorly ordered dolomite forms as 1 to 5 micron euhedral rhombs x ray diffraction data indicate that the crystallized dolomite is better ordered and less calcium rich than the dolomite composed of crystallites

mechanical behaviour of unsaturated kaolin with isotropic and anisotropic stress history part 1 wetting and compression behaviour over the last 40 years considerable progress has been made in understanding the complex behaviour of unsaturated soils research using constitutive modelling has extended the critical state framework and the concept of yielding in saturated soils to encompass unsaturated soils experiencing suction however validation testing of the framework for unsaturated soils has shown disagreement with the basic propositions the main reason for this disparity is the anisotropic properties of the soil specimens tested as a result of preparation using one dimensional compaction the paper describes the detailed testing carried out to justify this statement as part of the work presented samples of unsaturated kaolin were prepared using isotropic compression the suctions in these samples were reduced to predefined values by wetting under low isotropic loading the pore size distributions the pressure volume relationships and yielding under subsequent isotropic loading are compared with tests on samples prepared by

low velocity zones in the crust beneath aso caldera kyushu japan derived from receiver function analyses aso volcano in central kyushu island in southwest japan has a large caldera 18 25 km that formed by the ejection of more than 600 km3 of deposits 89 thousand years ago we calculated receiver functions from teleseismic waveform data obtained from densely distributed stations in and around the caldera we estimated the crustal s wave velocity structure from the receiver functions by using genetic algorithm inversion we detected a low velocity zone vs 2 2 km s at a depth of 8 15 km beneath the eastern flank of the central cones a sill like deformation source has been detected at a depth of 15 5 km by analyses of gps data and a swarm of low frequency earthquakes exists at depths of 15 25 km just beneath this low velocity zone magma may be newly generated and accumulated in this low velocity zone as a result of hot intrusions coming from beneath it except for the region beneath the eastern flank of the central cones a second low velocity zone vs 1 9 km s extends in and around the caldera at a depth of 15 23 km although phenomena representing intrusions have not been detected below it from the estimated velocity structure these low velocity zones are interpreted to contain a maximum of 15 melt or 30 water

formation of fossil hydrothermal chimneys and mounds from silvermines ireland sulphur isotope analyses reveal that the fossil hydrothermal pyrite mound and tubes at silvermines were produced by the reaction of hydrothermal fe ii with bacteriogenically reduced sulphur species 34s range 18 4 to 42 5 this took place in a brine pool dominated by hyper saline carboniferous seawater this is in contrast to their modern but considerably larger morphological counterparts forming by direct precipitation of hydrothermal sulphides on the east pacific rise at 21 n

elastic plastic modelling of unsaturated soil using results from a new triaxial test with controlled suction this paper examines the constitutive behaviour of a compacted highly plastic sand clay mixture three series of tests evaluated components of a possible elastic plastic constitutive model for unsaturated stress strain behaviour the tests examined the influence of suction on yield stress under external isotropic loading and the influence of suction on shear strength the results examine the behaviour of highly plastic clay subjected to generalised triaxial stresses that include shear isotropic and suction loading the data represent an important new resource of information on a densely compacted strongly expansive sand bentonite mixture that was loaded independently by external stresses and internal suctions the suctions were also measured by sensors buried in the specimens they have been interpreted in an elastic plastic framework to produce values for some of the material properties needed for the model the results and associated discussion provide new insights into the behaviour of unsaturated

characteristics of isolated hybrid tremor hbt during a calm activity period at aso volcano isolated type tremors having two events with different dominant frequencies are characteristic seismological phenomena observed during the fumarolic activity stage at aso volcano these isolated tremors are called hybrid tremors hbt and comprise two parts an initial part named the hf part with a dominant frequency in the high frequency region approximately 10 hz and the following part named the lf part with a dominant frequency in the low frequency region approximately 2 hz the lf part is observed after the hf part and the hbt is accompanied by a long period tremor lpt hypocenters and source parameters are estimated using seismograms recorded at 64 stations around nakadake crater the amplitude distributions of all hf parts have almost similar trends similarly the amplitude distributions of all lf parts have almost similar trends however the amplitude distributions of hf and lf parts are not similar from these results we proposed that the hypocenters and source parameters of hf and lf parts are not common but each of them have common hypocenters and source parameters the hypocenter region of hf parts was estimated to be just beneath the fumarole region south of the 1st crater the volume fluctuation is the major source factor the hypocenter region of lf parts is estimated to be at a depth of approximately 300 m beneath the first crater the strike slip component is the major source parameter the hypocentral depth of lf parts is located at the upper end of the crack estimated to be the source of the lpts the lpts and hbts are observed almost simultaneously we consider that volcanic fluid is involved in the source mechanisms of both hbt and lpt

dolomitization of atolls by sea water convection flow test of a hypothesis at niue south pacific the core of the former atoll on niue island south pacific is extensively dolomitized a detailed stable isotope study reveals that the dolomites are uniformly enriched in 18o and 13c 18o 2 8 0 5 13c 2 0 0 3 relative to their carbonate precursor the sr isotope ratios are equally constant with depth yielding 87sr 86sr values between 0 70912 and 0 70916 the observed isotopic compositions point to sea water as the dominant dolomitizing fluid the sr age of the dolomites is younger than the biostratigraphic age mid to late miocene placing the dolomitization event at plio pleistocene time a model of sea water convection is proposed for atoll dolomitization on the basis of a thermal gradient between the atoll and the ambient ocean water sea water is drawn through the atoll margin and transferred upward by convective flow delivering mg to the sites of dolomite precipitation transported with the sea water are volcano derived metals fe cu zn mn as evidenced by the chemical gradient in

a preparation zone for volcanic explosions beneath naka dake crater aso volcano as inferred from magnetotelluric surveys abstract the 1st crater of naka dake aso volcano is one of the most active craters in japan and known to have a characteristic cycle of activity that consists of the formation of a crater lake drying up of the lake water and finally a strombolian type eruption recent observations indicate an increase in eruptive activity including a decrease in the level of the lake water mud eruptions and red hot glows on the crater wall temporal variations in the geomagnetic field observed around the craters of naka dake also indicate that thermal demagnetization of the subsurface rocks has been occurring in shallow subsurface areas around the 1st crater volcanic explosions act to release the energy transferred from magma or volcanic fluids measurement of the subsurface electrical resistivity is a promising method in investigating the shallow structure of the volcanic edifices where energy from various sources accumulates and in investigating the behaviors of magma and volcanic fluids we carried out audio frequency magnetotelluric surveys around the craters of naka dake in 2004 and 2005 to determine the detailed electrical structure down to a depth of around 1 km the main objective of this study is to identify the specific subsurface structure that acts to store energy as a preparation zone for volcanic eruption two dimensional inversions were applied to four profiles across the craters revealing a strongly conductive zone at several hundred meters depth beneath the 1st crater and surrounding area in contrast we found no such remarkable conductor at shallow depths beneath the 4th crater which has been inactive for 70 years finding instead a relatively resistive body the distribution of the rotational invariant of the magnetotelluric impedance tensor is consistent with the inversion results this unusual shallow structure probably reflects the existence of a supply path of high temperature volcanic gases to the crater bottom we propose that the upper part of the conductor identified beneath the 1st crater is mainly composed of hydrothermally altered zone that acts both as a cap to upwelling fluids supplied from deep level magma and as a floor to infiltrating fluid from the crater lake the relatively resistive body found beneath the 4th crater represents consolidated magma these results suggest that the shallow conductor beneath the active crater is closely related to a component of the mechanism that controls volcanic activity within naka dake