the thermal and mineral springs of aitoloakarnania prefecture function mechanism and origin of groundwater the study area is located in the northwestern part of greece in aitoloakarnania prefecture in this region where no volcanic activity exists thermal springs such as kremasta and kokkino stefani well known for their healing properties occur the objective of this study was the investigation of these springs as well as the study of the chemical composition and origin of water relationships between these springs were also examined the geological setting of the area comprises sedimentary rocks of the pindos gavrovo tripolis and ionian geotectonic zones deformed by orogenic movements followed by neogene extensional tectonism the thermal and mineral springs were classified into three main groups the first group is characterized by ca hco3 water type and low water temperatures it corresponds to the springs that are hosted in the ionian zone and their possible enrichment in so4 is mainly attributed to the evaporites the other two groups consist of alkaline thermal water mainly hosted in the formations of gavrovo tripolis zone in these two groups the very strong reducing conditions that prevail are expressed by high amounts of nh3 and h2s moreover na f li sr and ba display elevated concentrations the second includes mineral waters of ca na hco3 type that are depleted in calcium their residence time is rather long and they originate from deep water circulation through siliceous rocks the third group includes thermal waters of ca mg na hco3 water type of higher water temperatures that reveal characteristics of deep circulation directly associated with the underlain limestones

extracting time domain green s function estimates from ambient seismic noise 1 it has been demonstrated experimentally and theoretically that an estimate of the green s function between two seismic stations can be obtained from the time derivative of the long time average cross correlation of ambient noise between these two stations this tdgf estimate from just the noise field includes all tensor components of the green s function and these green s function estimates can be used to infer earth structure we have computed cross correlations using 1 to 30 continuous days of ambient noise recorded by over 150 broadband seismic stations located in southern california the data processing yielded thousands of cross correlation pairs for receiver separations from 4 500 km which clearly exhibit coherent broadband propagating dispersive wavetrains across frequency band 0 1 2 hz

geochemical evolution of groundwater beneath mexico city abstract the geochemical evolution of groundwaters along a 24 km flow beneath central mexico city path from the sierra de las cruces towards lake texcoco has been investigated using stable isotopes radiocarbon and major and trace elements to determine the natural baseline conditions the extent of any contamination and the effectiveness of the overlying aquitard seal modern groundwaters of low salinity 1 are found up to 11 km from the outcrop area and groundwater ages of up to 6000 yr bp occur in the middle part of the section groundwater stable isotope ratios 18 o and 2 h lie close to the global meteoric water line indicating that the groundwater originates from local rainfall the groundwater chemistry may be interpreted as the result of inputs from the source area with progressive water rock interaction down the horizontal flow gradient a redox boundary is found at 9 km along the line of section coincident with the start of the confined section relatively low nitrate concentrations below 9 mg l 1 no 3 n are found in the aerobic waters low concentrations of no 3 in the aerobic waters and low cl reflect inputs prior to the modern development some elements cr u as se sb increase their concentration with distance time as far as the redox boundary but low concentrations occur in the reducing aquifer section the chemistry of several major ions mg na cl k as well as trace elements such as li rb ba reflect the weathering of the basaltic mineral assemblage feldspars and mafic minerals and their increases are generally proportional to residence time phosphate f and i concentrations indicate a probable source from apatite in the basaltic or rhyolitic rocks a borehole in the east of the city some 17 km downgradient intercepted thermal water si geothermometry indicates 163 c at depth this water gives a distinctive composition indicating possible addition of metamorphic co 2 which has then reacted with the igneous rocks increases in b and cl are derived from volatiles trapped in the glass or vesicular basalt a thermal anomaly found in the middle section of the heavily pumped aquifer is interpreted as the up coming of warmer water from medium to greater depth mainly from basalts rhyolites and possibly limestones the geochemistry indicates that groundwater beneath mexico city is of good quality and there is no obvious evidence of leakage of inorganic compounds from surface sources of contamination through the aquitard the younger groundwater drawn from the western outcrop area is generally of good inorganic quality increased drawdowns in the confined aquifer have induced flow of warmer water with higher cl from depth the resources in the aquifer represent an important reserve of good quality water which need to be properly managed as a high quality resource as part of integrated plans for the city s future supplies

implications of felt area magnitude relations for earthquake scaling and the average frequency of perceptible ground motion abstract observed relations between felt area and moment magnitude m for stable continental regions scr and california earthquakes can be explained by a simple model with geometrical spreading attenuation q 1 and earthquake stress drops that remain constant from m 4 to 8 differences in the slopes of the observed felt area m relations between scr and california earthquakes are consistent with differences in q between these tectonic settings fitting the felt area m data to the model yields an estimate of f q where f is the average frequency of minimum perceptible ground motion using fits to the data and instrumentally derived values of q i find that f is between about 2 and 4 hz i present an estimate of the spectral acceleration level associated with the lower limit of perceptibility

robust empirical relationships for estimating the carbonate system in the southern california current system and application to calcofi hydrographic cruise data 2005 2011 1 the california current system ccs is expected to experience the ecological impacts of ocean acidification oa earlier than most other ocean regions because coastal upwelling brings old co2 rich water relatively close to the surface ocean historical inorganic carbon measurements are scarce so the progression of oa in the ccs is unknown we used a multiple linear regression approach to generate empirical models using oxygen o2 temperature t salinity s and sigma theta as proxy variables to reconstruct ph carbonate saturation states carbonate ion concentration co32 dissolved inorganic carbon dic concentration and total alkalinity ta in the southern ccs the calibration data included high quality measurements of carbon oxygen and other hydrographic variables collected during a cruise from british columbia to baja california in may june 2007 all resulting empirical relationships were robust withr2values 0 92 and low root mean square errors estimated and measured carbon chemistry matched very well for independent data sets from the calcofi and imecocal programs reconstructed ccs ph and saturation states for 2005 2011 reveal a pronounced seasonal cycle and inter annual variability in the upper water column deeper in the water column conditions are stable throughout the annual cycle with perennially low ph and saturation states over sub decadal time scales these empirical models provide a valuable tool for reconstructing carbonate chemistry related to ocean acidification where direct observations are limited however progressive increases in anthropogenic co2 content of southern ccs water masses must be carefully addressed to apply the models over longer time scales

geochemistry genesis and health implications of fluoriferous groundwaters in the upper regions of ghana the most appropriate and widely used source of drinking water for the populations of the upper regions of ghana is groundwater in general groundwater quality is acceptable except for some parts of the bolgatanga and bongo districts where there are occurrences of elevated levels of natural groundwater fluoride concentrations of groundwater fluoride in excess of the world health organization who maximum guideline value 1 5 mg l in the bongo area have been known since 1978 however the effect of fluoride on people ingesting the water did not receive public and medical attention until october 1993 when health personnel were asked to investigate the cause of stained teeth in school children the investigation established that 62 of the total population of school children in the bongo area had dental fluorosis against this background a study was initiated to understand the geochemistry genesis and distribution of fluoride in relation to the geology of the area groundwater fluoride in the upper regions ranges from 0 11 to 4 60 ppm with the highest concentrations associated with the fluorine enriched bongo coarse grained hornblende granite and syenite suite the source of groundwater fluoride within the bongo granitoids is dissolution of the mineral fluorite and dissolution of and anion exchange with micaceous minerals and their clay products applying the who recommended guideline values for fluoride in drinking water reveals that 49 of wells in the area deliver water below the optimum level of 0 5 mg l f these populations are thus prone to dental caries twenty eight percent of the wells fall within the optimum interval for good dental health 0 5 1 5 mg l f twenty three percent of the wells have concentrations above the recommended maximum guideline limit of 1 5 mg l f this population is susceptible to dental and possibly skeletal fluorosis climatic conditions of the area suggest that the individual water consumption is in the order of 3 to 4 l which is higher than the who estimate of 2 l adult day in addition dietary intake for the upper region population is probably higher than who baseline values 0 2 0 5 mg day this implies that a much higher population is susceptible to developing dental and skeletal fluorosis than originally suspected geochemical symbol plot maps help geochemists understand factors controlling the distribution and uptake of fluoride in the upper regions but they are of minimal value to health officials responsible for planning epidemiological studies and dental health education programs in the region by casting fluoride data into contoured geochemical health risk maps using intake interval guidelines more closely aligned to regional climatic and dietary conditions health officals can better judge the impacts regional and population based of fluoride on segments of the population such as various sex and age groups

site amplifications observed in the gubbio basin central italy hints for lateral propagation effects abstract in this study we investigate the site amplification effects observed in the gubbio plain central italy the recordings of 140 local earthquakes 1 2 ml 4 7 observed by two linear arrays installed along the longitudinal and perpendicular basin axis are analyzed both in the time and frequency domains to determine the spatial variation of the local site effects in the basin the time series recorded in the gubbio plain are characterized by locally generated surface waves which cause a significant increase in both ground motion duration and amplitude with respect to a nearby reference station on a rock site in the middle of the basin where the sedimentary cover is thickest ca 600 m the peak ground velocity is amplified on average by a factor of 5 with respect to the reference station installed on rock and the duration is increased by a factor of about 2 the analyses in the frequency domain show that the spectral energy of the basin generated waves is mainly distributed over the range 0 4 2 hz and affects both horizontal and vertical components the site responses estimated by applying two reference site methods show that the overall shape of the amplification functions is similar for the sites located inside the basin with a difference in the amplification levels which can reach values as high as 30 in the middle of the valley amplifications up to a factor of 10 affect the vertical component of ground motion over a broad frequency range for nearly all basin sites with the maximum amplifications occurring at around 1 hz finally although the horizontal to vertical spectral ratios were found to provide a reliable estimation of the fundamental resonance frequency of the site they fail to estimate the shape of the site transfer function

deformation of western greece during neogene clockwise rotation and collision with apulia following an early miocene phase of n s extension affecting the entire hellenides 50 clockwise rotation affected western greece modern gps analyses show rapid southwestward motion in southwestern greece over subducting oceanic lithosphere and no motion in the northwest where greece collided with apulia we aim to identify the deformation history of western greece associated with the rotation and the collision with apulia the timing of the various phases of deformation is constrained via detailed analysis of vertical motions based on paleobathymetry evolution of sedimentary sequences overlying the evolving structures the results show that accompanying the onset of rotation compression was re established in western greece in the early langhian around 15 ma subsequently western greece collided with the apulian platform leading in the late miocene to a right lateral strike slip system running from the aliakmon fault zone in northern greece via the kastaniotikos fault and the thesprotiko shear zone to the kefallonia fault zone offshore western greece ne sw compression and uplift of the ionian islands was accompanied by ne sw extension in southwestern greece associated with faster southwestward motion in the south than in the north this led in the middle pliocene around 3 5 ma to collision without further shortening in northwestern greece from then onward nw se to n s extension east of apulia and gradually increasing influence of e w extension in the south accommodated motion of the hellenides around the apulian platform as a result curved extensional basin systems evolved including the gulf of amvrakikos sperchios basin gulf of evia system and the gulf of corinth saronic gulf system

strong shaking in los angeles expected from southern san andreas earthquake 1 the southernmost san andreas fault has a high probability of rupturing in a large greater than magnitude 7 5 earthquake sometime during the next few decades new simulations show that the chain of sedimentary basins between san bernardino and downtown los angeles form an effective waveguide that channels love waves along the southern edge of the san bernardino and san gabriel mountains earthquake scenarios with northward rupture in which the guided wave is efficiently excited produce unusually high long period ground motions over much of the greater los angeles region including intense localized amplitude modulations arising from variations in waveguide cross section

modeling and validation of a 3d velocity structure for the santa clara valley california for seismic wave simulations a 3d seismic velocity and attenuation model is developed for santa clara valley california and its surrounding uplands to predict ground motions from scenario earthquakes the model is developed using a variety of geologic and geophysical data our starting point is a 3d geologic model developed primarily from geologic mapping and gravity and magnetic surveys an initial velocity model is constructed by using seismic velocities from boreholes reflection refraction lines and spatial autocorrelation microtremor surveys this model is further refined and the seismic attenuation is estimated through waveform modeling of weak motions from small local events and strong ground motion from the 1989 loma prieta earthquake waveforms are calculated to an upper frequency of 1 hz using a parallelized finite difference code that utilizes two regions with a factor of 3 difference in grid spacing to reduce memory requirements cenozoic basins trap and strongly amplify ground motions this effect is particularly strong in the evergreen basin on the northeastern side of the santa clara valley where the steeply dipping silver creek fault forms the southwestern boundary of the basin in comparison the cupertino basin on the southwestern side of the valley has a more moderate response which is attributed to a greater age and velocity of the cenozoic fill surface waves play a major role in the ground motion of sedimentary basins and they are seen to strongly develop along the western margins of the santa clara valley for our simulation of the loma prieta earthquake

secondary processes determining the ph of alkaline waters in crystalline rock systems abstract the understanding of the main hydrogeochemical processes controlling the features and behaviour of crystalline rock environments considered for the deep geological storage of spent nuclear fuel is a key issue for the improvement of our knowledge and management of these systems and for a more accurate prediction of their future evolution in this paper some of the most important irreversible processes cooling mixing and co 2 exchange are studied and their effects quantified by combining classical geochemical calculations and geochemical modelling this methodology is applied to an alkaline thermal water system developed in crystalline rocks the caldas de boi groundwater system ne spain analogous to the deep geological environments expected for nuclear waste storage one of the most remarkable results obtained in this study is related to the high ph buffering capacity exhibited by these alkaline thermal waters during the mixing processes with colder and shallower waters taking place during the uprising of the hot waters from the deep reservoir even for high mixing proportions of cold water up to 60 the final ph remains as alkaline as in the thermal and deep end member although the rest of the physicochemical parameters including temperature change consistently with mixing another important secondary ph determining process detected in this study is the conductive cooling of the thermal waters suffered during their rise to surface conditions which is clearly responsible for a ph increase which enhances the typical alkaline character of these waters finally the existence of external inputs of edaphic or biogenic co 2 to the groundwater system producing a ph decrease in some of the springs has been proven to play a key role in their behaviour and evolution

the west andean thrust the san ramon fault and the seismic hazard for santiago chile 1 the importance of west verging structures at the western flank of the andes parallel to the subduction zone appears currently minimized this hampers our understanding of the andes altiplano one of the most significant mountain belts on earth we analyze a key tectonic section of the andes at latitude 33 5 s where the belt is in an early stage of its evolution with the aim of resolving the primary architecture of the orogen we focus on the active fault propagation fold system in the andean cover behind the san ramon fault which is critical for the seismic hazard in the city of santiago and crucial to decipher the structure of the west andean thrust wat the san ramon fault is a thrust ramp at the front of a basal detachment with average slip rate of 0 4 mm yr young scarps at various scales imply plausible seismic events up to mw 7 4 the wat steps down eastward from the san ramon fault crossing 12 km of andean cover to root beneath the frontal cordillera basement anticline a range 5 km high and 700 km long we propose a first order tectonic model of the andes involving an embryonic intracontinental subduction consistent with geological and geophysical observations the stage of primary westward vergence with dominance of the wat at 33 5 s is evolving into a doubly vergent configuration a growth model for the wat altiplano similar to the himalaya tibet is deduced we suggest that the intracontinental subduction at the wat is a mechanical substitute of a collision zone rendering the andean orogeny paradigm obsolete

evaluation of site effects on strong motion records in concepcion during the 2010 maule chile earthquake in the 2010 maule chile earthquake m w 8 8 many high rise buildings in downtown concepcion conc sustained severe damage the accelerogram observed at conc had large amplitudes and long periods the spectra contained strong peaks with periods around 2 s whereas the spectra from a neighboring site ccsp did not exhibit strong peaks because conc and ccsp are located in the concepcion basin and at the edge of the basin respectively these observations suggest that the spectral differences are due to site geological effects to quantitatively evaluate site effects microtremor array observations were conducted as a subsurface structure survey in concepcion the s wave velocity profiles were estimated from the inversion of the rayleigh wave phase velocity and the horizontal to vertical ratio the different spectral characteristics of the records at conc and ccsp could be explained by the theoretical amplification factors computed from the velocity profiles further studies on seismic microzoning of the city with an emphasis on the subsurface structure should improve disaster planning in concepcion

simulated ground motion in santa clara valley california and vicinity from m 6 7 scenario earthquakes abstract models of the santa clara valley scv 3d velocity structure and 3d finite difference software are used to predict ground motions from scenario earthquakes on the san andreas saf monte vista shannon south hayward and calaveras faults twenty different scenario ruptures are considered that explore different source models with alternative hypocenters fault dimensions and rupture velocities and three different velocity models ground motion from the full wave field up to 1 hz is exhibited as maps of peak horizontal velocity and pseudospectral acceleration at periods of 1 3 and 5 sec basin edge effects and amplification in sedimentary basins of the scv are observed that exhibit effects from shallow sediments with relatively low shear wave velocity 330 m sec scenario earthquakes have been simulated for events with the following magnitudes 1 m 6 8 7 4 calaveras sources 2 m 6 7 6 9 south hayward sources 3 m 6 7 monte vista shannon sources and 4 m 7 1 7 2 peninsula segment of the saf sources ground motions are strongly influenced by source parameters such as rupture velocity rise time maximum depth of rupture hypocenter and source directivity cenozoic basins also exert a strong influence on ground motion for example the evergreen basin on the northeastern side of the scv is especially responsive to 3 5 sec energy from most scenario earthquakes the cupertino basin on the southwestern edge of the scv tends to be highly excited by many peninsula and monte vista fault scenarios sites over the interior of the evergreen basin can have long duration coda that reflect the trapping of seismic energy within this basin plausible scenarios produce predominantly 5 sec wave trains with greater than 30 cm sec sustained ground motion amplitude with greater than 30 sec duration within the evergreen basin

the thermal springs of jordan the thermal springs alongside wadi araba dead sea and jordan valley jordan were investigated and sampled in a comprehensive field study of 2 weeks conventional physicochemical properties were measured in situ dissolved solids and isotopic composition were analyzed two main spring locations on the east side of the dead sea were mapped it became evident that the hottest springs are among the closest to prominent faults some springs are controlled by gas lift jordan s hot springs are described by means of a broad hydrochemical and physicochemical data set and several figures are presented based on their hydrochemistry the thermal springs are classified into four thermal provinces water genesis is discussed several geothermometers are applied to estimate reservoir temperatures observed discharge rate water temperature and isotopic composition are compared with data from the literature although discharge and water temperature are reported to be constant over the last decades groundwater overexploitation led to a shift of the isotopic composition what is documented for the first time in jordan thus the effect of groundwater mining on jordan s hot springs can be stated as a fact

basin shear wave velocities beneath seattle washington from noise correlation rayleigh waves tomography with short period rayleigh waves extracted using noise interferometry can refine s wave velocity v s models in urban areas with dense arrays of short period and broadband instruments we apply this technique to the seattle area to develop a new shallow v s model for use in seismic hazard assessment continuous data from the seismic hazards in puget sound ships array and local broadband stations have interstation distances of 90 km or less this spacing allows us to extract rayleigh waves with periods between 2 and 10 s that are sensitive to shallow basin structure this new v s model for the seattle basin is constructed using direct observations rather than using p wave velocity v p observations and a v p v s ratio as all previous 3d models at this scale have been constructed our results reveal greater detail in the upper 3 5 km than previous models earthquake simulations calculated using our new model better predict peak ground velocities pgv at periods between 1 and 2 s for two local earthquakes than the previous model used to calculate seattle s seismic hazard map frankel et al 2007 we collected data from two local earthquakes and ran finite difference simulations using our new velocity model as well as the previous velocity model used in development of the seattle seismic hazard maps to assess how well our model predicts ground motions relative to the previous model with a recent deployment of netquakes strong motion stations by the pacific northwest seismic network pnsn and the u s geological survey we are now able to make more comprehensive assessments of the predictions for recent events

shallow ambient noise 3d tomography in the concepcion basin chile implications for low frequency ground motionsshallow ambient noise 3d tomography in the concepcion basin chile

mixing hydrology and chemical equilibria in bakreswar geothermal area eastern india abstract a group of alkaline thermal springs of bakreswar having varying temperatures 45 71 c and identical compositions emerges through a nearly n s trending fault in the gneissic basement the thermal springs are of na cl so 4 type and are rich in sio 2 and f contrary to the local groundwaters which are mostly of ca hco 3 type the springs undergo mild to moderate dilution by local groundwater which does not significantly affect their original compositions agnikund the main spring with the highest temperature mild dilution consistent composition and negligible tritium discharges almost pure deep seated thermal water original thermal water is at equilibrium with quartz in the deep reservoir and attains surface temperature largely by conductive cooling with no significant loss of dissolved sio 2 certain ionic ratios coupled with very low tritium contents in the springs are indicative of prolonged subsurface circulation of the original water xrd results of the spring site sediments and the bore hole rocks fairly corroborate the predicted saturation state of thermal water with respect to quartz feldspar calcite fluorite etc which is believed to control the major chemical compositions of the springs a geothermal reservoir having probable temperature of about 100 5 c and possibly occurring at a depth of 1 km is the source of thermal water for the springs the present study is aimed at understanding the mixing trend between thermal springs and local groundwaters as well as the water rock equilibria

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

occurrence of aragonite corrosive water in the north yellow sea near the yalu river estuary during a summer flood abstract to understand seawater caco3 saturation state arag for aragonite and cal for calcite dynamics in river dominated ocean margins we investigated the carbonate system and ancillary parameters in the north yellow sea near the yalu river estuary during and after a summer flood august and september 2013 respectively during the flood period nearshore arag ranged from 0 76 to 1 61 and cal ranged from 1 22 to 2 53 aragonite undersaturation values were associated with quite low salinity of 14 58 25 18 and a broad dissolved oxygen saturation range from 58 to 102 a week after the flood period aragonite undersaturated waters together with the estuarine plumes disappeared based on field data analyses and simplified model simulation we suggest that net community respiration remineralization and the dilution of riverine water discharge both contributed to the low caco3 saturation states

simulations of strong ground motion and 3d amplification effect in the taipei basin by using a composite grid finite difference method we perform full elastic wave field simulations within the taipei basin by using a three dimensional 3d discontinuous finite difference method the 3d taipei basin model is determined from a seismic reflection study two major subsurfaces the songshan formation surface soil layer and the basin basement are constituted in the model a parallel based composite grid technique a containing scalene grid and a discontinuous grid is developed in this study to deal with the possible numerical prob lem of thin depth and low velocity of the songshan formation taking advantage of the composite grid the resolution of the subsurface structure can be reached to 20 m and a higher frequency up to 3 hz of the synthetic waveform can be achieved in our strong ground motion simulations we assume a constant velocity in each subsurface three different types of models are considered in the study the songshan formation with a basement structure model a basin basement model and a layered half space model results indicate that only the model with both the songshan formation and the basement structure can produce the apparent basin amplification effects first the surface wave generated after the primary s wave is trapped at the shallow part of the basin then when the wave propagates through the deepest part of the basin most of the energy is reflected from the boundary and focused back into the basin in addi tion part of the seismic wavefront turns and follows the shallow basin edge resulting in further amplification our study indicates that the complex taipei basin geometry and fairly low velocity of the songshan formation dominate the amplification and wave propagation behavior that result in extraordinary strong shaking patterns in the taipei metropolitan region

the combined effects of ocean acidification mixing and respiration on ph and carbonate saturation in an urbanized estuary puget sound is a large estuary complex in the u s pacific northwest that is home to a diverse and economically important ecosystem threatened by anthropogenic impacts associated with climate change urbanization and ocean acidification while ocean acidification has been studied in oceanic waters little is known regarding its status in estuaries anthropogenically acidified coastal waters upwelling along the western north american continental margin can enter puget sound through the strait of juan de fuca in order to study the combined effects of ocean acidification and other natural and anthropogenic processes on puget sound waters we made the first inorganic carbon measurements in this estuary on two survey cruises in february and august of 2008 observed ph and aragonite saturation state values in surface and subsurface waters were substantially lower in parts of puget sound than would be expected from anthropogenic carbon dioxide co2 uptake alone we estimate that ocean acidification can account for 24e49 of the ph decrease in the deep waters of the hood canal sub basin of puget sound relative to estimated pre industrial values the remaining change in ph between when seawater enters the sound and when it reaches this deep basin results from remineralization of organic matter due to natural or anthropogenically stimulated respiration processes within puget sound over time however the relative impact of ocean acidification could increase significantly accounting for 49e82 of the ph decrease in subsurface waters for a doubling of atmospheric co2 these changes may have profound impacts on the puget sound ecosystem over the next several decades these estimates suggest that the role ocean acidification will play in estuaries may be different from the open ocean published by elsevier ltd

reactive transport modeling of calcite dissolution in the fresh salt water mixing zone abstract dissolution of calcite in the saltwater mixing zone of coastal carbonate aquifers has been the subject of numerous studies they conclude that dissolution is driven by mixing of freshwater and saltwater which may lead to undersaturation even if both end members are saturated however as transport in the mixing zone is rather complex a fully coupled reactive transport model is needed to properly understand the interplay between transport and chemistry we perform 1 and 2d simulations to gain insight into the processes controlling dissolution rate exploring its sensitivity to the chemistry of end members and the dispersivity of the medium we conclude that the results of sanford and konikow sanford w e konikow l f 1989 simulation of calcite dissolution and porosity changes in saltwater mixing zones in coastal aquifers water resources research 25 655 667 which used a two step method solely transporting the amount of calcite dissolved are essentially correct but their solution is essentially kinetic with a rate dependent on the time increment used the 1d simulations allow us to show that maximum dissolution rates do occur neither at the location nor for the end members of maximum undersaturation for non reactive mixing in the 1d case enhanced transport at the freshwater end causes dissolution to concentrate there however in the 2d case representative of coastal aquifers maximum dissolution occurs at the saline side near the discharge zone because of a very active convection cell that develops there which enhances mixing and thus reaction rates this mechanism may explain observations at blue holes and should display a positive feedback with dissolution causing an increase in permeability that would lead to increased seawater flux and mixing thus enhancing further dissolution

sedimentological response to neotectonics and sea level change in a delta fed complex graben gulf of amvrakikos western greece abstract the gulf of amvrakikos is one of several e w grabens developed in the middle quaternary almost orthogonal to the tectonic grain of the external hellenides in western greece and is critically located at the termination of the kefallinia transform fault linking the hellenic subduction zone to the adriatic dinaride collision lineament the tectonic evolution of the gulf and the response of sedimentation have been investigated based on 3 5 khz and sparker profiles the holocene stratigraphy results from rising eustatic sea level breaching the tectonic sill north of preveza and inundating the braid plain of the arachthos river which then prograded across the northern gulf following the formation of the maximum flooding surface older major transgressive surfaces are recognised in sparker profiles interpretation of these transgressions in terms of eustatic sea level changes allows a chronology to be established and estimates to be made of neotectonic rates of subsidence two sets of neotectonic faults are present reactivated nne trending mid tertiary thrusts of the ionian zone and more active e w trending faults the sedimentary succession in the gulf of amvrakikos is the result of a complex interplay between eustatic sea level changes the neotectonic creation of accommodation and autocyclic delta distributary switching the details of this process are resolved for the holocene and the general sedimentation pattern established back to marine isotope stage mis 8 245 300 ka in general mis 8 shows greater evidence of terrestrial deposition compared with mis 6 130 190 ka and especially mis 2 4 10 80 ka when there was lacustrine deposition and some marine incursions at intermediate eustatic sea levels this implies that regional subsidence has been taking place at least since mis 8 in addition changing sediment supply plays a role in overall sediment architecture but is only well resolved for the holocene with higher rates of fluvial supply recognised in the mid holocene

3 d simulations of surface wave propagation in the kanto sedimentary basin japan part 2 application of the surface wave bem abstract the 3 d surface wave boundary element method is applied to the same set of strong motion records as those of part 1 kato et al 1993 namely the long period strong motion with periods around 8 sec recorded at the jma japan meteorological agency stations in yokohama and tokyo during the 1980 izu hanto toho oki earthquake this method simulates exact love and rayleigh waves in a laterally heterogeneous medium including 3 d basin structures the needed computer memory and cpu time are made manageable by assuming the inside and outside of the basin to consist of horizontal flat layers in addition vertical interfaces are assumed between the basin and the outside bedrock for simplicity in this study after checking the range of validity of the flat layer approximation for the kanto sedimentary basin the generation and propagation of surface waves in the basin are numerically investigated in particular our investigation places special emphasis on the cause of the observed long duration which could not be explained in part 1 using the surface wave gaussian beam method when the bedrock outside the western margin of the kanto basin is incorporated into the model the observed long duration at the tokyo station is successfully reproduced this can be explained by the strong surface waves generated by the surface wave to surface wave conversion at the margin and appearing in tokyo after the direct surface waves from the epicenter this result agrees with kinoshita et al 1992 who studied records from an array of seismographs in tokyo moreover when a sedimentary basin of sagami bay is included as was done in part 1 the simulations are greatly improved particularly at the yokohama station which corresponds to the node in the radiation pattern of the source this is due to the fact that the radiation pattern is strongly affected by the near source heterogeneity of the sagami basin all these results together with direct comparisons to 2 d modelings clearly show the strong 3 d effects of the basin structures on the generation and propagation of surface waves for this earthquake

shallow crustal structures of the tehran basin in iran resolved by ambient noise tomography in this study we present an application of the ambient noise tomography ant to study the near surface geological structures of the metropolitan tehran iran region short period fundamental mode rayleigh wave green s functions were estimated using cross correlations of the vertical component of the ambient noise from 2009 october to 2011 may using a variety of seismic sensors for example accelerometers and seismometers deployed in the tehran area standard common low frequency processing procedures were applied to the cross correlations and shorter time windows comprising 10 min segments were used in the processing step to enhance the time resolution of the signal in the frequency range of interest 1 10 s stacking was also conducted using the rms of the estimated empirical green s functions our results demonstrate that ambient seismic noise tomography is a viable technique at periods of 1 10 s in length even when different sensor types are present analysis of the empirical green s functions indicates that the dominant sources of ambient seismic noise originated from the same origin and no significant seasonal or spatial variations in the ambient noise sources were observed multiple filter analysis was used to extract the group velocities from the estimated empirical green s functions which were then inverted to image the spatially varying dispersion at periods of lengths between 1 and 7 s using tomographic inversion of the traveltimes estimated for each frequency the resulting group velocity maps show high correlations with known geological and tectonic features of the study region in general most of the tehran basin with certain exceptions could be clearly resolved with low group velocities whereas the mountain ranges were found to be correlated with high group velocities in the tehran basin for 2 and 3 s periods the low velocity zone deepens towards the south southwest which reflects thicker sediments in the southern part of the basin than in the north this feature has also been observed in other geological studies the vs models also show that bedrock depth varies between 400 and 1400 m from north to south within the tehran basin at longer periods main faults are associated with abrupt transitions between regions of high to low velocity anomalies in general our results indicate that ant can be a flexible and effective approach for studying near surface heterogeneity using short period surface wave data

hydrogeochemistry of sodium bicarbonate type bedrock groundwater in the pocheon spa area south korea water rock interaction and hydrologic mixing the pocheon spa land area south korea occurs in a topographically steep fault bounded basin and is characterized by a hydraulic upwelling flow zone of thermal water up to 44 c in its central part hydrogeochemical and environmental isotope data for groundwater in the study area suggested the occurrence of two distinct water types a ca hco3 type and a na hco3 type the former water type is characterized by relatively high concentrations of ca so4 and no3 which show significant temporal variation indicating a strong influence by surface processes in contrast the na hco3 type waters have high and temporally constant temperature ph tds na cl hco3 and f indicating the attainment of a chemical steady state with respect to the host rocks granite and gneiss oxygen hydrogen and tritium isotope data also indicate the differences in hydrologic conditions between the two groups the relatively lower 18o d and tritium values for na hco3 type waters suggest that they recharged at higher elevations and have comparatively long mean residence times considering the geologic and hydrogeologic conditions of the study area na hco3 type waters possibly have evolved from ca hco3 type waters mass balance modeling revealed that the chemistry of na hco3 type water was regulated by dissolution of silicates and carbonates and concurrent ion exchange particularly low ca concentrations in na hco3 water was mainly caused by cation exchange multivariate mixing and mass balance modeling m3 modeling was performed to evaluate the hydrologic mixing and mass transfer between discrete water masses occurring in the shallow peripheral part of the central spa land area where hydraulic upwelling occurs based on q mode factor analysis and mixing modeling using phreeqc an ideal mixing among three major water masses surface water shallow groundwater of ca hco3 type deep groundwater of na hco3 type was proposed m3 modeling suggests that all the groundwaters in the spa area can be described as mixtures of these end members after mixing the net mole transfer by geochemical reaction was less than that without mixing therefore it is likely that in the hydraulic mixing zone geochemical reactions are of minor importance and therefore that mixing regulates the groundwater geochemistry

residence time indicators in groundwater the east midlands triassic sandstone aquifer the east midlands triassic sherwood sandstone aquifer which has been the subject of detailed radiometric age studies is used to investigate both inert and reactive constituents of groundwater as indicators of residence time detailed resampling of the aquifer in 1992 has provided a considerable body of new inorganic geochemistry data though without radiocarbon several inert indicators are defined including the isotopic ratios 18o 2h 36cl noble gas ratios as well as the halogen elements cl br f i and their element ratios these form a group of essentially unreactive tracers primarily reflecting changing rainfall inputs and palaeoclimatic conditions except at outcrop where human impacts are also seen clearly the concentrations of cl mainly from atmospheric sources remain below 25 mg l 1 cl over a distance of some 30 km from outcrop reactive indicators the result of time dependent water rock interactions include 13c mg ca sr ca na cl and show diagnostic trends along the flow lines however the concentrations of certain trace elements li rb cs mn and mo which are not limited by solubility constraints show linear trends along the present day flow gradient this water rock interaction is taking place in groundwaters with low total mineralisation and it can be demonstrated that reactions involving these elements and isotopes are occurring entirely within the aquifer since high salinity groundwaters are found below the sherwood sandstone there is good correlation between some of the elements and 14c activities in the 1977 data set and this has been used to derive a concentration age relationship for the 1992 set of data a chemical timescale for the aquifer is then established using a li and b a combination of five trace elements the age of the fresh groundwater is thus shown to be up to 100 ka bp indicating the likelihood of semi continuous recharge during the devensian glacial period preceding the glacial maximum when no recharge occurred 10 20 ka bp this approach may be of value in extending groundwater dating beyond the radiocarbon timescale as well as interpreting sites where no radiocarbon data are available the scatter from the mean age line indicates those groundwaters which are derived from either rapid or slower than average flow zones within the aquifer as well as age stratification this stratification is borne out by a depth profile of groundwater from a new borehole near to outcrop which is shown by a combination of chemical and isotopic tracers to contain holocene overlying late pleistocene water

near fault earthquake ground motion simulation in the grenoble valley by a high performance spectral element code near fault effects are known to produce specific features of earthquake ground motion such as long period velocity pulses and directivity that cannot be predicted by numerical approaches involving vertical plane wave propagation in one dimensional 1d soil models that are used as a standard in engineering applica tions coupling near fault conditions with site effects induced by complex geological structures such as deep alluvial basins or steep topographic irregularities further con tributes to the complexity of earthquake ground motion and to the difficulty to provide reliable predictions without making use of large size 3d numerical simulations in this article we present a parametric study of the seismic response of the grenoble valley france due to an mw 6 seismic source at some 10 km epicentral distance from the urban area that was carried out in the framework of an international benchmark for earthquake ground motion prediction the spectral element code geoelse for seismic wave propagation analyses in 3d heterogeneous media in the linear and non linear range was used for this purpose full advantage was taken of its implementation on parallel computer architectures after introducing geoelse and its parallel per formance and after introducing some of its validation benchmarks the spatial varia bility of the seismic response of the grenoble valley is quantitatively investigated taking into account two effects i the hypocenter location and ii the nonlinear soil behavior through a nonlinear viscoelastic soil model finally numerical results are compared with available data and attenuation relationships of peak values of ground motion in the near fault region based on the results of this work the unfavorable interaction between fault rupture radiation mechanism and complex geological con ditions may give rise to large values of peak ground velocity exceeding 1 m sec even in low to moderate seismicity areas it may therefore considerably increase the level of seismic risk especially in highly populated and industrially active regions such as the alpine valleys

shear wave velocity model of the santiago de chile basin derived from ambient noise measurements a comparison of proxies for seismic site conditions and amplification summary we determined a high resolution 3 d s wave velocity model for a 26 km 12 km area in the northern part of the basin of santiago de chile to reach this goal we used microtremor recordings at 125 sites for deriving the horizontal to vertical h v spectral ratios that we inverted to retrieve local s wave velocity profiles in the inversion procedure we used additional geological and geophysical constraints and values of the thickness of the sedimentary cover already determined by gravimetric measurements which were found to vary substantially over short distances in the investigated area the resulting model was derived by interpolation with a kriging technique between the single s wave velocity profiles and shows locally good agreement with the few existing velocity profile data but allows the entire area as well as deeper parts of the basin to be represented in greater detail the wealth of available data allowed us to check if any correlation between the s wave velocity in the uppermost 30 m v30s and the slope of topography a new technique recently proposed by wald and allen exists on a local scale we observed that while one lithology might provide a greater scatter in the velocity values for the investigated area almost no correlation between topographic gradient and calculated v30s exists whereas a better link is found between v30s and the local geology finally we compared the v30s distribution with the msk intensities for the 1985 valparaiso event pointing out that high intensities are found where the expected v30s values are low and over a thick sedimentary cover although this evidence cannot be generalized for all possible earthquakes it indicates the influence of site effects modifying the ground motion when earthquakes occur well outside of the santiago basin

characterization of shallow geology by high frequency seismic noise tomography summary to study the applicability of the passive seismic interferometry technique to near surface geological studies seismic noise recordings from a small scale 2 d array of seismic stations were performed in the test site of nauen germany rayleigh wave green s functions were estimated for different frequencies a tomographic inversion of the traveltimes estimated for each frequency from the green s functions is then performed allowing the laterally varying 3 d surface wave velocity structure below the array to be retrieved at engineering geotechnical scales furthermore a 2 d s wave velocity cross section is obtained by combining 1 d velocity structures derived from the inversion of the dispersion curves extracted at several points along a profile where other geophysical analyses were performed it is shown that the cross section from passive seismic interferometry provides a clear image of the local structural heterogeneities that are in excellent agreement with georadar and geoelectrical results such findings indicate that the interferometry analysis of seismic noise is potentially of great interest for deriving the shallow 3 d velocity structure in urban areas

effects of topography on seismic wave propagation an example from northern taiwan topography influences ground motion and in general increases the amplitude of shaking at mountain tops and ridges whereas valleys have reduced ground motions as is observed from data recorded during and after real earthquakes and from numerical simulations however recent publications have focused mainly on the implications for ground motion in the mountainous regions themselves whereas the impact on surrounding low lying areas has received less attention here we develop a new spectral element mesh implementation to accommodate realistic topography as well as the complex shape of the taipei sedimentary basin which is located close to the central mountain range in northern taiwan spectral element numerical simulations indicate that high resolution topography can change peak ground velocity pgv values in mountainous areas by 50 compared to a half space response we further demonstrate that large scale topography can affect the propagation of seismic waves in nearby areas for example if a shallow earthquake occurs in the i lan region of taiwan the central mountain range will significantly scatter the surface waves and will in turn reduce the amplitude of ground motion in the taipei basin however as the hypocenter moves deeper topography scatters body waves which subsequently propagate as surface waves into the basin these waves continue to interact with the basin and the surrounding mountains finally resulting in complex amplification patterns in taipei city with an overall pgv increase of more than 50 for realistic subduction zone earthquake scenarios off the northeast coast of taiwan the effects of topography on ground motion in both the mountains and the taipei basin vary and depend on the rupture process the complex interactions that can occur between mountains and surrounding areas especially sedimentary basins illustrate the fact that topography should be taken into account when assessing seismic hazard

three dimensional shallow structure from high frequency ambient noise tomography new results for the mygdonia basin euroseistest area northern greece we examine the use of ambient noise cross correlation tomography for shallow site characterization using a modified two step approach initially we extract rayleigh wave traveltimes from correlation traces of vertical component seismic recordings from a local network installed in mygdonia basin northern greece the obtained rayleigh wave traveltimes show significant spatial variability as well as distance and frequency dependence due to the 3 d structure of the area dispersion and anelastic attenuation effects the traveltime data sets are inverted through a surface wave tomography approach to determine group velocity maps for each frequency the proposed tomographic inversion involves the use of approximate fresnel volumes and interfrequency smoothing constraints to stabilize the results in the last step we determine a final 3 d velocity model using a node based monte carlo 1 d dispersion curve inversion the reliability of the final 3 d velocity model is examined by spatial and depth resolution analysis as well as by inversion for different model parameterizations the obtained results are in very good agreement with previous findings from seismic and other geophysical methods the new 3 d vs model provides additional structural constraints for the shallow sediments and bedrock structure of the northern mygdonia basin up to the depth of 200 250 m present work results suggest that the migration of ambient tomography techniques from large scales tens or hundreds of km to local scales few hundred meters is possible but cannot be used as a black box technique for 3 d modeling and detailed geotechnical site characterization

future acidification of marginal seas a comparative study of the japan east sea and the south china sea the response of marginal peripheral seas to ocean acidification on short and long time scales is not well established through modeling we examine the future acidification of two adjacent marginal seas the south china sea scs and the japan east sea j es our results illustrate the importance of unique features in determining their acidification the j es basin will become completely undersaturated with regard to calcite rapidly in the next few decades while the scs basin will experience relatively slower acidification during its acidification the j es will continually act as a sink for atmospheric co2 whereas the scs will temporarily switch from a source to a sink during the peak pco2 interval only to return slowly to being a source again marginal sea acidification will be determined by multiple factors including their connections with the open ocean and their unique physical and biogeochemical dynamics in addition to the level of atmospheric co2

evidence of deep water inflow in a tectonic window of the northern apennines italy water samples from the river network and from some shallow and brackish springs located in a tectonic window of the northern apennines of italy were studied in the frame of a comprehensive hydrogeological investigation in order to better understand the origin and the mixing processes between the two water types noticed also in previous studies ca hco3 and na cl a sampling campaign covering the drought period during year 2010 was planned to gather electric conductivity temperature and redox potential data along the river network and on groundwater occurrences located inside the tectonic structure additionally eight water samples were collected for hydrochemical major anions and cations na k ca2 mg2 hco3 cl so4 2 and trace ion btot and isotopic 18o 2h 3h analyses and compared with other eighteen samples from shallow and brackish springs collected near the study site during the period 2005 2012 moreover river discharge and water balance estimations were carried out results confirmed the presence of old na cl water with salinity progressively increasing up to 5 5 g l 1 at the northern termination of the tectonic window these values are in agreement with the ions contents of the most mineralized spring macognano spring salinity of 7 6 g l 1 which has been considered as having the deepest and longest flow path stable isotopes and trace ions contents are consistent with rainfall and snowmelt water mixed with brines associated with a hydrocarbon reservoir hosted at depth considering as end member the more mineralized na cl water a cumulate inflow in the range of 12 9 5 9 l s 1 has been estimated this aliquot is released into the river network with different mixing proportions by the groundwater occurrences discharging from the autochthonous flysch unit

three dimensional simulation of a magnitude 7 75 earthquake on the san andreas fault simulation of 2 minutes of long period ground motion in the los angeles area with the use of a three dimensional finite difference method on a parallel supercomputer provides an estimate of the seismic hazard from a magnitude 7 75 earthquake along the 170 kilometer section of the san andreas fault between tejon pass and san bernardino maximum ground velocities are predicted to occur near the fault 2 5 meters per second and in the los angeles basin 1 4 meters per second where large amplitude surface waves prolong shaking for more than 60 seconds simulated spectral amplitudes for some regions within the los angeles basin are up to 10 times larger than those at sites outside the basin at similar distances from the san andreas fault

the influence of preexisting structure and halokinesis on organic matter preservation and thrust system evolution in the ionian basin northwest greece the opening of the ionian basin and its internal differentiation is attested to by lateral facies and thickness variations of the formations deposited during the pliensbachian and tithonian synrift formations the beginning of the synrift sequence is represented by the siniais limestones pliensbachian and their lateral equivalent the louros limestones the geometric characteristics of the extensional basin depend on both extension related to the latest opening of the tethys ocean and halokinesis of the ionian zone evaporitic substratum the orientation of the extensional regime is deduced from the direction of stratigraphic pinch outs of the synrift formations directions of transport of slump features and direction of movement on synsedimentary faults observed in t e base of these formations in the half grabens the postrift period is marked by an unconformity at the base of the vigla limestones which represents the early berriasian breakup during which sedimentation was synchronous in the entire ionian basin the accumulation of organic matter in the lower and upper posidonia beds of the ionian zone during the toarcian and tithonian is directly related to the geometry of the synrift period of the ionian basin restricted subbasins were formed where the geometry of the basin favored stagnation and consequently the locally euxinic conditions of bottom waters anoxic conditions persisted locally to the postrift period in areas where the upper siliceous zone albian cenomanian of the vigla limestones is well developed these areas probably represent subbasins that were preserved by the continuation of halokinetic movements during the postrift period during the early miocene alpine orogeny collision related compressive stresses on the margin induced the reactivation of preexisting fractures which were responsible for the inversion tectonics that affected the mesozoic basin the geometric characteristics of the inverted basin were dependent on lithology evaporites geometry of the extensional structures and direction of the compressional phase the observed geometries do not always correspond to the classical scheme of inversion tectonics the geological evolution in the ionian basin is an example of inversion tectonics of a basin with an evaporitic substratum the opening of the ionian basin and the inversion tectonics influence both the source rocks and the probable hydrocarbon traps of the ionian zone

kinematics of the central hellenides structural analysis along 24 cross sections crosscutting several windows in the central hellenides provides the sense of nappe movements as well as the location of destroyed oceans lying between the apulian and eurasian continents from the mesozoic orogeny took place in two phases the first phase the eo hellenic phase was initiated by convergence of the apulian and pelagonian plates with west directed subduction and closure of the pindos ocean late jurassic obduction of oceanic lithosphere over the western margin of the pelagonian plate was followed by footwall imbrication mylonites and sheath folds during the late cretaceous uplift was associated with ductile normal faulting at depth and tectonic unroofing at shallow crustal levels the second phase the meso hellenic phase comprised the closure of the ambelakia ocean at the eastern margin of the pelagonian plate and continental subduction along the eastern margin of the apulian plate west directed subduction of the ambelakia ocean was associated with eastward directed ductile thrusting folding and blueschist metamorphism blueschist formed within a simple duplex structure at depth and was subsequently overthrusted in the late eocene onto the olympos microcontinent which acted as a major obstacle to the eastward directed nappe movements up to 150 m thick cataclasites kink folds and a spaced cleavage were formed during the late stage of the continental collision a subduction along the eastern margin of the apulian plate caused kink folding and reimbrication of the western parts of the pelagonian basement since the oligocene the overthickened crust collapsed by means of low angle normal faults

three dimensional simulations of seismic wave propagation in the taipei basin with realistic topography based upon the spectral element method we use the spectral element method to simulate strong ground motion throughout the taipei metropolitan area mesh generation for the taipei basin poses two main challenges 1 the basin is surrounded by steep mountains and 2 the city is located on top of a shallow low wave speed sedimentary basin to accommodate the steep and rapidly varying topography we introduce a thin high resolution mesh layer near the surface the mesh for the shallow sedimentary basin is adjusted to honor its complex geometry and sharp lateral wave speed contrasts variations in moho thickness beneath northern taiwan are also incorporated in the mesh spectral element simulations show that ground motion in the taipei metropolitan region is strongly affected by the geometry of the basin and the surrounding mountains the amplification of ground motion is mainly controlled by basin depth and shallow shear wave speeds although surface topography also serves to amplify and prolong seismic shaking

atmospheric carbon dioxide concentration across the mid pleistocene transition the dominant period of pleistocene glacial cycles changed during the mid pleistocene from 40 000 years to 100 000 years for as yet unknown reasons here we present a 2 1 million year record of sea surface partial pressure of co2 pco2 based on boron isotopes in planktic foraminifer shells which suggests that the atmospheric partial pressure of co2 pco2 was relatively stable before the mid pleistocene climate transition glacial pco2 was approximately 31 microatmospheres higher before the transition more than 1 million years ago but interglacial pco2 was similar to that of late pleistocene interglacial cycles 450 000 years ago these estimates are consistent with a close linkage between atmospheric co2 concentration and global climate but the lack of a gradual decrease in interglacial pco2 does not support the suggestion that a long term drawdown of atmospheric co2 was the main cause of the climate transition

surface wave potential for triggering tectonic nonvolcanic tremor corrected abstract source processes commonly posed to explain instances of remote dynamic triggering of tectonic nonvolcanic tremor by surface waves include frictional failure and various modes of fluid activation the relative potential for love and rayleigh wave dynamic stresses to trigger tectonic tremor through failure on critically stressed thrust and vertical strike slip faults under the coulomb griffith failure criteria as a function of incidence angle are anticorrelated over the 15 to 30 km depth range that hosts tectonic tremor love wave potential is high for strike parallel incidence on low angle reverse faults and null for strike normal incidence the opposite holds for rayleigh waves love wave potential is high for both strike parallel and strike normal incidence on vertical strike slip faults and minimal for 45 incidence angles the opposite holds for rayleigh waves this pattern is consistent with documented instances of tremor triggered by love waves incident on the cascadia megathrust and the san andreas fault saf in central california resulting from shear failure on weak faults apparent friction is 0 2 documented instances of tremor triggered by surface waves with strike parallel incidence along the nankai megathrust beneath shikoku japan however are associated primarily with rayleigh waves this is consistent with the tremor bursts resulting from mixed mode failure crack opening and shear failure facilitated by near lithostatic ambient pore pressure low differential stress with a moderate friction coefficient 0 6 on the nankai subduction interface rayleigh wave dilatational stress is relatively weak at tectonic tremor source depths and seems unlikely to contribute significantly to the triggering process except perhaps for an indirect role on the saf in sustaining tremor into the rayleigh wave coda that was initially triggered by love waves

modelling basin effects on earthquake ground motion in the santiago de chile basin by a spectral element code summary simulations of strong ground motion within the santiago de chile metropolitan area were carried out by means of 3 d deterministic wave propagation tool based on the spectral element method the simulated events take into account the pronounced interface between the low velocity sedimentary basin and the bedrock as well as topography of the area to verify our model we simulated a regional earthquake recorded by a dense network installed in the city of santiago for recording aftershock activity after the 2010 february 27 maule main shock the results proof the alluvial basin amplification effects and show a strong dependence of spectral amplification in the basin on the local site conditions moreover we studied the seismic response due to a hypothetical mw 6 0 event occurring along the active san ramon fault which is crossing the eastern edge of the city the scenario earthquakes exhibit that an unfavourable interaction between fault rupture radiation mechanism and complex geological and topographic conditions in the near field region may give rise to large values of peak ground velocity in the basin finally 3 d numerical predictions of ground motion are compared with the one computed according to ground motion prediction equations selected among the next generation attenuation relationships in terms of ground motion peak values and spectral acceleration the comparison underlines that the 3 d scenario simulations predict a significantly higher level of ground motion in the santiago basin especially over deep alluvial deposits moreover also the location of the rupture nucleation largely influences the observed shaking pattern

neotectonic evolution of northwestern continental greece the post miocene sedimentary and structural evolution of nw continental greece changes from west to east

behaviour of major elements and some trace elements li rb cs sr fe mn w f in deep hot waters from granitic areas abstract analyses of selected hot springs in more than sixty areas in granites from europe are presented concentrations of major elements and of some trace elements li rb cs sr fe mn w f in high ph waters are not significantly affected by processes during uprise from the deep reservoir to the surface re equilibrations mixing with surficial waters normalized to k or na concentrations of all other elements are related to the aquifer temperature the knowledge of aquifer temperature and total electric charge of mobile elements cl s possibly f allows us to predict both major elements within 50 and trace elements within a factor 2 or 3 concentrations in alkaline waters from granites

the correlation of microtremors empirical limits and relations between results in frequency and time domains summary the use of the correlation of microtremor records is on its way to develop into a common tool to estimate local shear wave velocity structure for this reason the establishment of the conditions for the correct use of this method and its limitations when applied to real data is becoming increasingly important in addition to the use of frequency domain spatial correlation technique the spatial autocorrelation spac method the use of time domain correlation to obtain the green s function of the medium is rapidly gaining presence we explore the use of microtremor correlation techniques in the time domain to determine local velocity structure and compare with previous results obtained with the same data using spac our data come from three experiments carried out in parkway and wainuiomata valleys in new zealand using broad band portable stations interstation distances range from 5 m to 2 1 km and our results are useful in the frequency band from 0 1 to 7 hz frequency domain correlation requires an isotropic microtremor field a condition that need not be satisfied in the time domain two station correlations provide useful results due to the temporal stationarity and isotropy in average of the microtremor wavefield this manifests itself in the symmetry of the temporal correlation functions with respect to zero time our results show that the local velocity structure and the interstation distance are the key factors conditioning the frequency range where surface wave dispersion can be correctly measured either in frequency or time domains we confirm that when the interstation distance becomes much larger than the dominant wavelengths only the correlation in time domain is useful all our results indicate that the signal obtained in the correlation of vertical component microtremors is due to the fundamental mode of rayleigh waves which appears as the most stable propagation mode without any indication of body waves

aragonite saturation state dynamics in a coastal upwelling zone 1 coastal upwelling zones may be at enhanced risk from ocean acidification as upwelling brings low aragonite saturation state ar waters to the surface that are further suppressed by anthropogenic co2 ar was calculated with ph pco2 and salinity derived alkalinity time series data from autonomous ph and pco2 instruments moored on the oregon shelf and shelf break during different seasons from 2007 to 2011 surface ar values ranged between 0 66 0 04 and 3 9 0 04 compared to an estimated pre industrial range of 1 0 0 1 to 4 7 0 1 upwelling of high co2 water and subsequent removal of co2 by phytoplankton imparts a dynamic range to ar from 1 0 to 4 0 between spring and autumn freshwater input also suppresses saturation states during the spring winter ar is less variable than during other seasons and is controlled primarily by mixing of the water column

early mesozoic oceanic subduction related volcanic rocks pindos basin greece abstract small outcrops of volcanic rocks of mid triassic to early jurassic age in the deep water mesozoic pindos basin have been systematically sampled and analysed geochemically to interpret the tectonic environment in which these rocks formed associated sediments indicate a rifting environment the volcanic rocks include all the main types found in modern back arc basins shoshonites with clinopyroxenes of calc alkaline affinity occur at the basin margin minor enriched type morb contains clinopyroxene typical of morb minor basalts that resemble oib with some subduction related characteristics contain clinopyroxene typical of alkahne rocks thick andesites and pyroclastic rocks with morb like trace elements except for some lile enrichment are associated with cumulate gabbro and oceanic type plagiogranite these thick andesites and pyroclastic rocks formed at an intra backarc ocean ocean subduction zone the supra subduction zone ophiolites of the eastern margin of the pindos basin which are of similar age are probably related to the same subduction zone the overall volcanic assemblage is related to formation of a back arc basin associated with the subduction of paleo tethys the hypothesis that late triassic eariy jurassic rifting formed only small pull apart basins by transtension is inconsistent with the range of volcanic products and the evidence for significant intra back arc subduction

importance of the vertical component of groundwater flow a hydrogeochemical approach in the valley of san luis potosi mexico fractured volcanics exert a control on groundwater flow in the san luis potosi slp valley the chemical composition and temperature of water pumped from boreholes partially penetrating the fractured volcanics indicate that the produced water originates from an upward vertical flow most of the thermal groundwater has been detected in areas related to regional faults and lineaments intensive and uncontrolled pumping from the upper 14 of the aquifer total depth 1500 m causes the rise of water from a deep regional flow system that mixes with the shallower waters the deep waters contain high fluoride concentrations that contaminate the mixture and cause substantial health related effects the recharge controls on the regional flow system require further research however hydrogeochemical evidence supports the view that the origin of this recharge is limited to the western bounding sierra madre occidental higher levels of dissolved na li f and so4 2 derived from tertiary volcanics have been introduced into the exploited region the concentrations indicate lengthy and deep circulation flow li concentration was used as an indicator of groundwater residence time and therefore of the length of the groundwater flow path hydrogeochemical interpretation indicates the presence of three flow systems a shallow local one controlled by a clay layer that subcrops most of the valley floor an intermediate system in which water infiltrates just beyond the boundary of the clay layer and a deep regional system which originates outside the surface catchment the local and intermediate systems circulate through materials with comparatively low hydraulic conductivity low cl concentrations suggest rapid flow in the regional system concentrations of li and f can be used to calculate percentages of waters in mixtures of regional and intermediate flows concentrations of na ca2 and so4 2 appear to be controlled by water rock reactions uncontrolled pumping increases will tend to enhance fluoride concentration and its undesirable effects lack of management of aquifers in basins similar to the slp valley can result in groundwater contamination not only from surface anthropogenic sources but also from natural water rock interactions

geochemical appraisal of fluoride contamination of groundwater in the nayagarh district of orissa india the occurrence of high concentrations of fluoride in groundwater 1 5 mg l in the villages of singhpur and sagaragan in the nayagarh district of orissa and its relation with the fluoride rich hot spring water 10 mg l located nearby have been studied the composition of the hot spring water is very comparable to the other thermal waters of the world thermodynamic considerations show that more than 65 of the groundwater and hot spring water samples are oversaturated with calcite and only four samples are oversaturated with fluorite fluoride concentration shows a positive relation to sodium bicarbonate and ph and a negative relation to calcium and magnesium in fluoride rich groundwater and hot spring water principal component analysis shows that the fluoride rich groundwater was produced due to a mixing of hot spring water with the surrounding groundwater studies of the saturation index of fluorite with log electrical conductivity also indicate mixing of hot spring water with the surrounding groundwater the spatial distribution of fluoride in groundwater follows the topography of the area

ambient seismic noise tomography of a loess high bank at dunaszekcső hungary loess high banks along the right side of the danube in hungary are potential subjects of landslides small scale ambient seismic noise tomography was used at the dunaszekcs high bank the aim of the study was to map near surface velocity anomalies since we assume that the formation of tension cracks which precede landslides are represented by low velocities mapping rayleigh wave group velocity distribution can help to image intact and creviced areas and identify the most vulnerable sections the study area lies at the top of the castle hill of dunaszekcs which was named after castellum lugio a fortress of roman origin the presently active head scarp was formed in april 2011 and our study area was chosen to be at its surroundings cross correlation functions of ambient noise recordings were used to retrieve the dispersion curves which served as the input of the group velocity tomography phase cross correlation and time frequency phase weighted stacking was applied to calculate the cross correlation functions the average rayleigh wave group velocity at the loess high bank was found to be 171 ms 1 the group velocity map at a 0 1 s period revealed a low velocity region whose location coincides with a highly creviced area where slope failure takes place along a several meter wide territory another low velocity region was found which might indicate a previously unknown loosened domain the highest velocities were observed at the supposed remnants of castellum lugio

scholte wave tomography for shallow water marine sediments summary we determine the 3 d in situ shear wave velocities of shallow water marine sediments by extending the method of surface wave tomography to scholte wave records acquired in shallow waters scholte waves are excited by air gun shots in the water column and recorded at the seafloor by ocean bottom seismometers as well as buried geophones our new method comprises three steps 1 we determine local phase slowness values from slowness frequency spectra calculated by a local wavefield transformation of common receiver gathers areal phase slowness maps for each frequency used as reference in the following step are obtained by interpolating the values derived from the local spectra 2 we infer slowness residuals to those reference slowness maps by a tomographic inversion of the phase traveltimes of fundamental scholte wave mode 3 the phase slowness maps together with the residuals at different frequencies define a local dispersion curve at every location of the investigation area from those dispersion curves we determine a model of the depth dependency of shear wave velocities for every location we apply this method to a 1 km2 investigation area in the baltic sea northern germany the phase slowness maps obtained in step 2 show lateral variation of up to 150 per cent the shear wave velocity models derived in the third step typically have very low values 60 80 m s 1 in the top four meters where fine muddy sands can be observed and values exceeding 170 m s 1 for the silts and sands below that level the upper edge of glacial till with shear wave velocities of 300 400 m s 1 is situated approximately 20 m below sea bottom a sensitivity analysis reveals a maximum penetration depth of about 40 m below sea bottom and that density may be an important parameter best resolvable with multimode inversion

the evolution of alkaline groundwaters in the continental intercalaire aquifer of the irhazer plain niger this paper discusses the hydrochemical evolution of groundwaters in the multilayer artesian aquifer of the continental intercalaire the mainly jurassic agadez dabla sandstones aquifer of northern niger isotopic and chemical changes in relation to the geological setting suggest that the increasing hco3 alkalinity of the groundwaters is caused by interaction of deep co2 with the aquifer matrix alteration of feldspars by co2 with a 13c value of 3 0 accounts for the observed alkalinity and isotopic and trends carbon 14 ages have been estimated for recent and holocene groundwaters which have a distinct stable isotopic 2h and 18o signature compared with 14c dead groundwaters from further west on the irhazer plain recharge temperatures estimated by analysis of noble gas contents show that the 14c dead waters were recharged under conditions cooler than present averages in the region possibly at the beginning of deglaciation 16 ka b p or during the period 23 30 ka b p trends in the hydrochemistry of u are related to the deep co2 alteration process radiogenic he contents increase along the flow direction and extremely high values occur in the proximity of u ores denitrification in the paleowaters of the irhazer was assessed by measurements of nitrogen argon ratios

carbonate mineral saturation states along the u s east coast to assess the impact of ocean acidification on the carbonate chemistry of the shelf waters off the southeastern united states south atlantic bight sab we measured carbonate mineral saturation states from january 2005 to may 2006 the findings reveal that aragonite varag 2 6 4 0 and calcite vcal 4 1 6 0 saturation states were considerably higher than those recently reported along the west coast of north america different water mass age between the atlantic and pacific oceans during global ocean circulation is the primary reason for the higher carbonate mineral saturation states in the sab than along the west coast the contrasting water temperatures in the two coasts contribute to such differences both upwelling and freshwater discharge also play important roles in controlling saturation state carbonate mineral saturation in the surface water of the west coast is strongly controlled by the upwelling of high salinity low temperature low oxygen and low ph deep water in comparison saturation states in the surface water of the sab coast are rarely affected by upwelling instead they are strongly influenced by the input of low saturation state water from rivers continued increases of atmospheric co2 under the intergovernmental panel on climate change b1 emission scenario will decrease the carbonate mineral saturation states by up to 40 by the end of this century and aragonite will approach undersaturation near the coast

source processes of the thermal waters from the phlegraean fields naples italy by means of the study of selected minor and trace elements distribution abstract the geochemical characteristics of hydrothermal waters from the phlegraean fields p f naples italy were analysed for minor and trace elements selectively mobilised in hydrothermal systems such as b f hg as pb and tl the water samples collected from a shallow aquifer likely to be fed by deeper fluids showed various geochemical features resulting from the mixing of three components 1 surface waters of meteoric origin 2 hot deep waters deriving from water rock interaction and including deep waters of marine origin 3 magmatic fluids rising from the local magma chamber lying a few kilometres below the town of pozzuoli this setting although very complex provides a reliable means of studying the distribution of the investigated trace elements in particular within the phlegraean area high contents of b 0 1 48 mg l f 0 5 8 mg l as 16 6050 g l and hg 0 7 232 g l were observed the levels of thallium in the springs close to solfatara about 7 g l were in line with those normally recorded in hydrothermal areas whereas high levels of this element up to 23 3 g l were identified in other wells of the study area lead 1 3 to 29 1 g l appears to be anomalous with respect to its normal content in groundwater about 1 g l owing to the presence of high density brines at depth which enhance the solubility of pb in volcanic rocks under hydrothermal conditions the distribution of the investigated trace elements in the phlegraean fields thermal area is probably related to the different ascent pathways of the fluids clearly apart from the influence exerted by anomalous thermal conditions each element shows a different behaviour depending on its geochemical affinity with mineral phases and as a consequence of the different enthalpy values which determine ion partitioning in gaseous phases based on geochemical evidences and on the distribution of minor and trace elements the source processes of the investigated hydrothermal waters were defined five main groups were identified 1 acid sulphate waters resulting from mixing of meteoric water with magmatic gases mainly h 2 s 2 high sulphate chloride waters from a deep reservoir located in the major upflow zone 3 waters associated with significant degassing of magmatic co 2 4 waters from a deep geothermal neutral chloride reservoir resulting from heating of marine water modified by water rock interaction processes 5 cold waters from the inner area influenced by low temperature water rock interaction processes

a comparison of site response techniques using earthquake data and ambient seismic noise analysis in the large urban areas of santiago de chile summary situated in an active tectonic region santiago de chile the country s capital with more than six million inhabitants faces tremendous earthquake risk macroseismic data for the 1985 valparaiso event show large variations in the distribution of damage to buildings within short distances indicating strong effects of local sediments on ground motion therefore a temporary seismic network was installed in the urban area for recording earthquake activity and a study was carried out aiming to estimate site amplification derived from horizontal tovertical h v spectral ratios from earthquake data ehv and ambient noise nhv as well as using the standard spectral ratio ssr technique with a nearby reference station located on igneous rock the results lead to the following conclusions 1 the analysis of earthquake data shows significant dependence on the local geological structure with respect to amplitude and duration 2 an amplification of ground motion at frequencies higher than the fundamental one can be found this amplification would not be found when looking at nhv ratios alone 3 the analysis of nhv spectral ratios shows that they can only provide a lower bound in amplitude for site amplification 4 p wave site responses always show lower amplitudes than those derived by s waves and sometimes even fail to provide some frequencies of amplification 5 no variability in terms of time and amplitude is observed in the analysis of the h v ratio of noise 6 due to the geological conditions in some parts of the investigated area the fundamental resonance frequency of a site is difficult to estimate following standard criteria proposed by the sesame consortium suggesting that these are too restrictive under certain circumstances

the pindos fold and thrust belt greece inversion kinematics of a passive continental margin continuous exposure in the pindos mountain chain greece and the detailed stratigraphic measurements in the area enable us to construct eight balanced cross sections across the pindos fold and thrust belt pftb and to approach quantitatively some parameters which controlled foreland evolution the 160 km wide passive continental margin of the apulian continent in greece was progressively shortened from east to west at rates of 6 mm year between the early oligocene and late eocene from the rear to the frontal part of the wedge fault bend folds duplexes and imbricates were formed while strain was partitioned into faulting 34 layer parallel shortening 23 and buckling 9 foreland subsidence and internal deformation of the orogenic wedge are strongly affected by two parameters of equal importance the thrust load of the overthrusted microcontinents and the rigidity of the underthrusted apulian passive margin changes in the thickness of the pre orogenic sediments and reactivated transform faults induced salients during the lower miocene the orogenic wedge in the peloponnese suffered additional uplift and westward gravitational gliding induced by the intracontinental subduction of the palaeozoic rift zone of the phyllite quartzite series which was reactivated and returned to the earth s surface during the hellenic orogeny

acidification mediated by a river plume and coastal upwelling on a fringing reef at the east coast of hainan island northern south china sea we investigated the dynamics of carbonate system which was greatly modulated by a river plume and coastal upwelling in july 2014 and july 2015 at the east coast of hainan island where a fringing reef distributes inshore by using a three end member mixing model we semi quantitatively estimated the removal of dissolved inorganic carbon dic mediated by biological production in the river plume and upwelled water to be 13 17 mol kg 1 and 15 16 mol kg 1 respectively the enhanced organic production was mainly responsible for these dic consumptions in both two regimes however nearly a half of dic removal was attributed to biocalcification in the plume system while it was negligible in the upwelling system furthermore the modeled results over reefs revealed that river plume and coastal upwelling were two major threats of acidification to coral communities at the east coast of hainan island during cruises in comparison the biological contribution to acidification was limited for balancing between organic production and biocalcification during july 2014 cruise whereas the acidification was greatly intensified by organic degradation during july 2015 cruise it was verified that naturally local acidification physical and biological processes played a major role in great ph decreases on a short term scale leading to coastal waters more vulnerable to anthropogenic ocean acidification uptake of atmospheric co2 by reducing buffering capacity of waters finally effects of acidification associated with other local threats on a fringing reef was further depicted with a conceptual model

near fault peak ground velocity from earthquake and laboratory data we test the hypothesis that peak ground velocity pgv has an upper bound independent of earthquake magnitude and that this bound is controlled primarily by the strength of the seismogenic crust the highest pgvs ranging up to several meters per second have been measured at sites within a few kilometers of the causative faults because the database for near fault pgv is small we use earthquake slip models laboratory experiments and evidence from a mining induced earthquake to investigate the factors influencing near fault pgv and the nature of its scaling for each earthquake slip model we have calculated the peak slip rates for all subfaults and then chosen the maximum of these rates as an estimate of twice the largest near fault pgv nine slip models for eight earthquakes with magnitudes ranging from 6 5 to 7 6 yielded maximum peak slip rates ranging from 2 3 to 12 m sec with a median of 5 9 m sec by making several adjustments pgvs for small earthquakes can be simulated from peak slip rates measured during laboratory stick slip experiments first we adjust the pgv for differences in the state of stress i e the difference between the laboratory loading stresses and those appropriate for faults at seismogenic depths to do this we multiply both the slip and the peak slip rate by the ratio of the effective normal stresses acting on fault planes measured at 6 8 km depth at the ktb site germany deepest available in situ stress measurements to those acting on the laboratory faults we also adjust the seismic moment by replacing the laboratory fault with a buried circular shear crack whose radius is chosen to match the experimental unloading stiffness an additional less important adjustment is needed for experiments run in triaxial loading conditions with these adjustments peak slip rates for 10 stick slip events with scaled moment magnitudes from 2 9 to 1 0 range from 3 3 to 10 3 m sec with a median of 5 4 m sec both the earthquake and laboratory results are consistent with typical maximum peak slip rates averaging between 5 and 6 m sec or corresponding maximum near fault pgvs between 2 5 and 3 m sec at seismogenic depths independent of magnitude our ability to replicate maximum slip rates in the fault zones of earthquakes by adjusting the corresponding laboratory rates using the ratio of effective normal stresses acting on the fault planes suggests that the strength of the seismogenic crust is the important factor limiting the near fault pgv

nonlinear soil response a reality geotechnical models consistently indicate that the stress strain relationship of soils is nonlinear and hysteretic especially at shear strains larger than 10 5 to 10 4 nonlinear effects such as an increase in damping and reduction in shear wave velocity as excitation strength increases are commonly recognized in the dynamic loading of soils on the other hand these effects are usually ignored in seismological models of ground motion prediction because of the lack of compelling corroborative evidence from strong motion observations the situation is being changed by recently obtained data explicit evidence of strong motion deamplification accompanied by changes in resonant frequencies are found in the data from the 1985 michoacan mexico and the 1989 loma prieta california earthquakes the events recorded by the vertical and surface accelerograph arrays in taiwan as well as a number of other events throughout the world evidence of nonlinear behavior becomes apparent beyond a threshold acceleration of 100 to 200 gal nonlinearity is considerable in cohesionless soil but may be negligible in stiff soils the findings of recent years indicate that nonlinear site effects are more common than previously recognized in strong motion seismology

modeling three dimensional site response effects in the marina district basin san francisco california abstract loma prieta aftershock data recorded in the marina district of san francisco clearly show a large amplification in ground motion and a much longer duration of shaking relative to the response recorded at nearby rock sites for frequencies between 1 and 10 hz some of the amplification can be explained by the difference in impedance between the marina sites and the rock sites however 1d models underpredict the amplification in the range 1 to 3 hz and cannot account for the increased durations the available geologic information within the marina district indicates lateral variations in sediment thickness and composition our previous experience with modeling wave propagation in these types of basin environments has shown that these structures can greatly amplify and prolong the duration of the signals observed at sites within the basin in this study the seismic response of the marina basin is modeled with a 3d finite difference wave field simulation technique results from the numerical simulations at the basin sites indicate that the large amplitude arrivals following the direct s wave are surface waves traveling at relatively slow apparent velocities in general the surface waves contain the strongest recorded motions and produce the long duration of shaking observed at these sites in addition spectral ground motions from the 3d basin models do fairly well in reproducing the observed spectral amplification near 1 hz that is characteristic of the basin sites the simulation results suggest that focusing effects due to the geometry of the basin structure itself have a significant impact in determining the resonant periods at these basin sites

non magmatic fracture controlled hydrothermal systems in the idaho batholith south fork payette geothermal system abstract non magmatic fracture controlled hydrothermal systems located within and near the idaho batholith have been examined and evaluated for potential application as natural analogues to high level nuclear waste repositories detailed geochemical petrologic and structural studies of hot springs along the south fork of the payette river sfpr in central idaho usa have been combined to assess the nature of a hydrothermal aquifer system along a major brittle shear zone geochemical modeling of thermal spring water chemistry with solveq reed m h 1992 solveq users manual unpublished report dept of geological sciences university of oregon eugene or indicates reservoir temperatures of 85 c to 160 c and an alteration assemblage consisting of several clays chlorite serpentinites quartz albite microcline and micas geothermometry calculations coupled with independent estimates of geothermal gradients based on heat flow and regional geology allow estimation of reservoir depths ranging from 2 4 to 6 7 km comparison of trace element rare earth element and solveq alteration assemblages supports the hypothesis that waters equilibrated with granitic rocks at depth and ascended to the surface in a short time span stable isotope data d 138 4 to 148 4 and 18 o 17 5 to 19 4 indicate that thermal waters of meteoric origin have interacted with country rocks at a very high water rock w r ratio systematic variations in d values and the amount of 18 o shift for thermal waters suggest that recharge probably occurs at much higher elevations than discharge fracture orientations petrologic relations and geochemical differences between adjacent springs delineate separate hydrothermal systems along the major structure defining the course of the sfpr hydrothermal systems along the sfpr exist primarily as small circulation cells which are probably influenced by minor changes in geothermal gradients associated with different rock types these subsystems are dependent on periodic seismic or microseismic activity to maintain flowpaths a working model of deep fracture controlled hydrothermal convection systems based on the sfpr geothermal system may be used to evaluate the long term behavior of artificial hydrothermal systems associated with high level nuclear waste repositories

inversion of an oligocene volcano tectonic basin and uplifting of its superimposed miocene magmatic arc in the chilean central andes first seismic and gravity evidences abstract a new structural model is presented for the cenozoic part of the main range east of santiago a chain made up of thick miocene ignimbrites and andesitic lavas overlying primitive oligocene volcanoclastics deposited on a thin continental crust because the latter coya machali formation locally show tight folding close to the margins of the miocene volcanics they had previously been described as deformed prior to construction of the arc our field observations analysed along two profiles at 33 and 34 15 s however support the conclusion hinted at by ongoing geochronological and geochemical studies deformation of both formations is synchronous and related to late miocene inversion of the coya machali intra arc basin uplift of the rigid arc rocks and part of its volcanoclastic basement took place mainly along two northward shallowing boundary structures that seem to share a lower decollement the eastern fierro out of sequence thrust and a series of western back thrusts that resemble triangle zones seismic data obtained from el teniente porphyry copper mine 34 s rockbursts and two gravimetric profiles at the western end of the southern profile are compatible with a decollement located at that locality 2 3 km under the surface

distribution of antarctic intermediate water over the blake plateau during a cruise in september 1980 over the blake plateau we observed a northward spread of antarctic intermediate water aaiw in the main axis of the gulf stream the aaiw appeared as a lobe less than 60 km wide extending to at least 31 n the lobe was characterized by negative salinity anomalies of 0 15 10 3 elevated nutrient concentrations and lowered oxygen concentrations tentative evidence suggests that a parcel of aaiw was located over the central blake plateau and geostrophic calculations indicate it may have been attached to the main gulf stream deep flow

characterizing transport between the surface mixed layer and the ocean interior with a forward and adjoint global ocean transport model the theory of first passage time distribution functions and its extension to last passage time distribution functions are applied to the problem of tracking the movement of water masses to and from the surface mixed layer in a global ocean general circulation model the first passage time distribution function is used to determine in a probabilistic sense when and where a fluid element will make its first contact with the surface as a function of its position in the ocean interior the last passage time distribution is used to determine when and where a fluid element made its last contact with the surface a computationally efficient method is presented for recursively computing the first few moments of the first and last passage time distributions by directly inverting the forward and adjoint transport operator this approach allows integrated transport information to be obtained directly from the differential form of the transport operator without the need to perform lengthy multitracer time integration of the transport equations the method which relies on the stationarity of the transport operator is applied to the time averaged transport operator obtained from a three dimensional global ocean simulation performed with an ogcm with this approach the author i computes surface maps showing the fraction of the total ocean volume per unit area that ventilates at each point on the surface of the ocean ii partitions interior water masses based on their formation region at the surface and iii computes the three dimensional spatial distribution of the mean and standard deviation of the age distribution of water

spectral amplification in a sediment filled valley exhibiting clear basin edge induced waves various site response estimates are presented for a linear array deployed in the coachella valley california during the 1992 landers big bear aftershock sequence this systematic comparison is unique in that the response of the site is clearly dominated by basin edge induced waves average sediment to bedrock spectral ratios for long s wave windows which include the basin edge induced waves exhibit amplification factors as high as 18 below 7 hz the deep basin structure which gives rise to the obvious multi dimensional effects produces a fundamental resonant peak that shifts between basin sites from 0 23 to 0 48 hz as the depth to bedrock changes above 0 6 hz where the largest amplifications occur the response is remarkably similar between sites and appears to be dominated by a near surface layer that is relatively uniform across the valley the apparent fundamental resonant frequency of this layer is between 0 8 and 1 hz sediment to bedrock spectral ratios computed using shorter windows that exclude the basin edge induced waves imply that the multi dimensional effects are significant only below 4 hz where they increase amplifications by an approximate factor of 2 spectral ratios computed using coda windows taken at twice the s wave travel time exhibit amplifications that are an average factor of 1 7 greater between 1 and 4 hz than those of the s wave estimates this discrepancy does not improve by taking coda windows later at four times the s wave travel time horizontal to vertical component s wave spectral ratios do not agree with the sediment to bedrock ratios however they do exhibit a clear peak at the fundamental resonant frequency of the deep basin structure sediment to bedrock spectral ratios of ambient seismic noise are also inconsistent with the s wave estimates however horizontal to vertical noise ratios exhibit clear peaks near the fundamental resonant frequencies of both the deep basin structure below 0 6 hz and the suspected near surface layer between 0 8 and 1 hz therefore ambient noise data appear to provide valuable constraints on the basin structure ongoing efforts involve multi dimensional modeling of the observed basin edge induced phases and resonant frequencies

structural controls on basin evolution neogene to quaternary of the ionian zone western greece turbidite deposition of oligocene to early miocene age occurred in the foreland basin to the pindus mountains which formed the nnw trending hellenide thrust front deposition was interrupted by the migration of the deformation front westwards through the foreland basin itself the kalamitsi thrust exposed in west levkas became active in late early miocene times a miocene to pliocene piggy back basin developed fed both from the thrust front to the west and the mountain belt to the east during the mid late miocene deformation remained confined to the ionian and gavrovo zones possibly related to the presence of lubricating evaporites which terminate in the pre apulian zone to the west during the late plio quaternary inner arc extension trenchward of the hellenic arc caused a system of ene and wnw basins to open under the n s tensional regime these were linked by nnw and ne transtensional faults and the system is still active in the lake trikhonis and gulf of corinth areas today in the west of the study area however post pliocene nw se compressional faults dissected the piggy back basin this compressional phase must have been either contemporaneous with or interrupted the extension active in the east from late pliocene times

geochemical characteristics of greek thermal springs abstract a systematic sampling of all known thermal springs and gas emissions of continental greece has been carried out the main gas and water composition and some trace elements in liquid phase sio 2 h 3 bo 3 nh 4 and li have been determined the chemical composition of most thermal springs analyzed is typical of deep na hco 3 rising hot waters which circulate in co 2 rich silicic formations and which acquire progressively a na cl composition by admixing of colder shallower saline connate waters housed in the rock matrix of marine post orogenic tertiary quaternary sediments on the whole the thermal manifestations of continental greece can be fitted in a tectonic framework where high hydraulic gradients enable waters in hot deep aquifers to reach the surface rapidly along fault systems at the boundary of n s and e w trending tertiary basins equilibration temperatures of 80 120 c in the main storage zone 130 150 c max in the nestos xanthi basin have been assessed for most of the study area high n 2 and low h 2 and h 2 s content in gas emissions associated to water samples are consistent with temperatures assessed by using geothermometers in liquid phase

observations of basin ground motions from a dense seismic array in san jose california we installed a dense array of 41 digital seismographs in san jose california to evaluate in detail the effects of a deep sedimentary basin and shallow sedimentary deposits on earthquake ground motions this urban array is located near the eastern edge of the santa clara valley and spans the evergreen sedimentary basin identified by gravity data average station spacing is 1 km with three stations initially spaced 110 m apart despite the high noise urban environment the stations of the array successfully triggered on and recorded small local earthquakes m 2 5 2 8 at 10 25 km distance and larger regional events such as the m 5 0 bolinas earthquake 90 km distance m 4 6 5 6 earthquakes near mammoth lakes 270 km distance m 4 9 5 6 events in western nevada 420 km distance and the m 7 1 hector mine earthquake 590 km distance maps of spectral ratios across the array show that the highest amplitudes in all frequency bands studied 0 125 8 hz are generally observed at stations farther from the eastern edge of the santa clara valley larger spectral amplitudes are often observed above the western edge of the evergreen basin snapshots of the recorded wavefield crossing the array for regional events to the east reveal that large low frequency 0 125 0 5 hz arrivals after the s wave travel from south to north across the array a moving window cross correlation analysis finds that these later arrivals are surface waves traveling from the south the timing and propagation direction of these arrivals indicates that they were likely produced by scattering of incident s waves at the border of the santa clara valley to the south of the array it is remarkable that the largest low frequency phases at many of the valley sites for regional events to the east are basin surface waves coming from a direction about 70 degrees different from that of the epicenters basin surface waves emanating from the eastern edge of the valley are also identified by the cross correlation analysis

three dimensional simulation of the near fault ground motion for the 1995 hyogo ken nanbu kobe japan earthquake abstract the 17 january 1995 hyogo ken nanbu earthquake is a typical example showing that the ground motions along basin edge faults can be very destructive in this study we simulate the near fault ground motion from this earthquake based on a kinematic fault model and a simplified 3d velocity structure of the kobe area the kinematic earthquake rupture and the wave propagation are modeled using a 3d finite difference method fdm our simulation identifies the basin edge effect as an important factor that influenced the ground motion amplification pattern in the kobe area we found that the coupling of the source directivity and basin edge effects causes impulsive ground motions with extremely high amplitude at periods greater than 1 sec and in a narrow zone offset less than 1 km from the basin edge the combination of these effects acted to create a fairly continuous band of amplification that extends about 30 km in an elongated zone parallel to the basin edge boundary in some areas localized site effects might have been as important as the abovementioned effects but they cannot explain the continuity of the extended east west zone of damage

an analysis of simulated and observed blast records in the salt lake basin we have simulated 0 2 to 1 2 hz 3d elastic wave propagation in the salt lake basin from a blast at a nearby open pit mine a fourth order staggered grid finite difference method was used to simulate the blast in a two layer basin model 58 43 9 km consisting of semiconsolidated sediments up to 1 3 km thick surrounded by bedrock data from four blasts in the mine pit recorded by a network of 10 digital three component instruments were compared to the results of the simulation the simulation reproduces the overall pattern of ground motion amplification at basin sites relative to a rock site as measured by ratios of peak particle velocities cumulative kinetic energies and spectral magnitudes considering the simple two layer basin model used in the 3d simulation this finding suggests that the deep 3d basin structure significantly contributes to low frequency ground motion amplification in the salt lake basin 1 1 effects of a near surface layer of low velocity unconsolidated sediments p and s wave velocities of 1 65 and 0 41 km sec respectively that at soil sites along the profile increase the peak particle velocities by up to a factor of 3 and significantly increase the ground motion durations 2 2 attenuation in the sediments which greatly diminishes the ground motion durations on the synthetic seismograms when parameterized by realistic values of the quality factor q 20 for soil sites and 35 for bedrock sites 3 3 2d topographic scattering which increases the peak particle velocities by up to a factor of 2 and increases the signal durations for sites along the profile compared to the records from the simple two layer 3d simulation the records from a 2d p sv wave simulation that includes processes 1 through 3 provide a better match to the blast data especially the observed durations of shaking at five of the six stations along the profile the 2d simulation reproduces the normalized radial and vertical peak particle velocities to within a factor of 2 and the normalized cumulative kinetic energies and spectral amplitudes on these components to within generally a factor of 3 our results suggest that deep basin resonance reverberations in the near surface low velocity layer attenuation and topographic scattering significantly influence site amplification in the salt lake basin future studies of site amplification in the salt lake basin should include the effects of all of these mechanisms

seismic amplification within the seattle basin washington state insights from ships seismic tomography experiments recent observations indicate that the seattle sedimentary basin under lying seattle and other urban centers in the puget lowland washington amplifies long period 1 5 sec weak ground motions by factors of 10 or more we computed east trending p and s wave velocity models across the seattle basin from seismic hazard investigations of puget sound ships experiments to better characterize the seismic hazard the basin poses the 3d tomographic models which resolve features to a depth of 10 km for the first time define the p and s wave velocity structure of the eastern end of the basin the basin which contains sedimentary rocks of eocene to holocene is broadly symmetric in east west section and reaches a maximum thickness of 6 km along our profile beneath north seattle a comparison of our velocity model with coincident amplification curves for weak ground motions pro duced by the 1999 chi chi earthquake suggests that the distribution of quaternary deposits and reduced velocity gradients in the upper part of the basement east of seattle have significance in forecasting variations in seismic wave amplification across the basin specifically eastward increases in the amplification of 0 2 to 5 hz energy correlate with locally thicker unconsolidated deposits and a change from crescent formation basement to pre tertiary cascadia basement these models de fine the extent of the seattle basin the seattle fault and the geometry of the basement contact giving insight into the tectonic evolution of the seattle basin and its influence on ground shaking

three dimensional shear wave velocity imaging by ambient seismic noise tomography summary 3 d shear wave velocity images are of particular interest for engineering seismology to obtain information about the local subsoil structure we present a one step inversion procedure based on the computation of high frequency correlation functions between stations of a small scale array deployed for recording ambient seismic noise the calculation of rayleigh wave phase velocities is based on the frequency domain spatial autocorrelation technique constitutively a tomographic inversion of the traveltimes estimated for each frequency is performed allowing the laterally varying 3 d surface wave velocity structure below the array to be retrieved we test our technique by using simulations of seismic noise for a simple realistic site and by using real world recordings from a small scale array performed at the nauen test site germany the results imply that the cross sections from passive seismic interferometry provide a clear image of the local structural heterogeneities and the shear wave velocities are satisfactorily reproduced the velocity structure is also found to be in good agreement with the results of geoelectrical measurements indicating the potential of the method to be easily applied for deriving the shallow 3 d velocity structure in urban areas and for monitoring purposes

observed and simulated ground motions in the san bernardino basin region for the hector mine california earthquake during the m w 7 1 hector mine earthquake peak ground velocities recorded at sites in the central san bernardino basin region were up to 2 times larger and had significantly longer durations of strong shaking than sites just outside the basin to better understand the effects of 3d structure on the long period ground motion response in this region we have performed finite difference simulations for this earthquake the simulations are numerically accurate for periods of 2 sec and longer and incorporate the detailed spatial and temporal heterogeneity of source rupture as well as complex 3d basin structure here we analyze three models of the san bernardino basin model a with structural constraints from gravity and seismic reflection data model f water well and seismic refraction data and the southern california earthquake center version 3 model hydrologic and seismic refraction data models a and f are characterized by a gradual increase in sediment thickness toward the south with an abrupt step up in the basement surface across the san jacinto fault the basin structure in the scec version 3 model has a nearly uniform sediment thickness of 1 km with little basement topography along the san jacinto fault in models a and f we impose a layered velocity structure within the sediments based on the seismic refraction data and an assumed depth dependent v p v s ratio sediment velocities within the scec version 3 model are given by a smoothly varying rule based function that is calibrated to the seismic refraction measurements due to computational limitations the minimum shear wave velocity is fixed at 600 m sec in all of the models ground motion simulations for both models a and f provide a reasonably good match to the amplitude and waveform characteristics of the recorded motions in these models surface waves are generated as energy enters the basin through the gradually sloping northern margin due to the basement step along the san jacinto fault the surface wave energy is confined to the region north of this structure consistent with the observations the scec version 3 model lacking the basin geometry complexity present in the other two models fails to provide a satisfactory match to the characteristics of the observed motions our study demonstrates the importance of using detailed and accurate basin geometry for predicting ground motions and also highlights the utility of integrating geological geophysical and seismological observations in the development and validation of 3d velocity models

reconciling opposing views on carbon cycling in the coastal ocean continental shelves as sinks and near shore ecosystems as sources of atmospheric co2 despite their moderately sized surface area continental marginal seas play a significant role in the biogeochemical cycles of carbon as they receive huge amounts of upwelled and riverine inputs of carbon and nutrients sustaining a disproportionate large biological activity compared to their relative surface area a synthesis of worldwide measurements of the partial pressure of co2 pco2 indicates that most open shelves in the temperate and high latitude regions are under saturated with respect to atmospheric co2 during all seasons although the low latitude shelves seem to be over saturated most inner estuaries and near shore coastal areas on the other hand are over saturated with respect to atmospheric co2 the scaling of air sea co2 fluxes based on pco2 measurements and carbon massbalance calculations indicate that the continental shelves absorb atmospheric co2 ranging between 0 33 and 0 36 pg c yr 1 that corresponds to an additional sink of 27 to 30 of the co2 uptake by the open oceans based on the most recent pco2 climatology takahashi t sutherland s c wanninkhof r

investigation of the chemical processes controlling the groundwater quality of ilia prefecture neogene formations display complex structure and host confined aquifers that are alternated and very often interrupted by impermeable clay layers in many cases the lack of hydrogeological information and data on those aquifers hinders research and planning of exploitation projects this study attempts to exploit the available information that can be derived from a sampling and the corresponding chemical analyses to reconstruct the hydrogeological image of such areas thus the chemical composition is used as a tool for natural tracing of the groundwater origin and movement in a previously unknown environment such as that of ilia region which was selected as the application area the distribution maps of certain hydrochemical parameters combined with the appropriate hydrochemical and isotopic data contributed to the classification of the groundwater samples by linking the hydrochemical processes with the samples locations as well as the origin of the aquifers recharge water at the same time the effectiveness of the used methodology was evaluated the use of r mode factor analysis led to the determination of the basic hydrochemical processes that shape the groundwater quality the analysis showed that the reducing environment is the defining factor that regulates the presence of the various chemical compounds finally the conceptual model of the aquifers emerged from the analysis of all the data this analysis also pointed out that the recharge of the local aquifers takes place mainly through the river beds and laterally from their contact with the carbonate rocks