18o exchange between steam and carbon dioxide in volcanic and hydrothermal gases implications for the source of water abstract the oxygen isotopic compositions of h 2 o and co 2 from 31 fumaroles from different volcanoes vesuvio campi flegrei vulcano and etna in italy soufriere of guadeloupe in lesser antilles prove that 18 o exchange between co 2 and steam is fast enough in natural gas phases to allow rapid isotopic reequilibration within a wide temperature range 100 1000 c the isotopic composition of h 2 o discharged by volcanic hydrothermal fumaroles is affected by isotopic reequilibration along with cooling of the gas phase and this secondary process must be taken into account when interpreting the origin of the water from isotopic data the use of corrected 18 o values computed considering the overall oxygen isotopic composition of the h 2 o co 2 system is therefore compulsory to overcome interpretative biases as an example we apply this method to 100 600 c fumaroles at vulcano crater whose isotopic composition is reinterpreted considering the effects of 18 o exchange between co 2 and h 2 o in contrast to most previous interpretations the corrected isotopic values for h 2 o clearly show that the vulcano system is fed by a two component mixture of magmatic water with a typical andesitic composition and either 18 o shifted seawater or magmatic steam partly condensed within the volcanic ground with minor contribution of local meteoric water the possible additional effects of isotopic reequilibration involving other o and h bearing gas species in volcanic fluids such as so 2 h 2 s hcl hf and h 2 have been also considered the influence of so 2 upon the isotopic composition of h 2 o is subordinate with respect to that of co 2 whereas significant shifts in deuterium composition are expected from hydrogen isotopic exchanges in the h 2 o h 2 s hcl hf h 2 gas system

magnitude scale and quantification of earthquakes despite various shortcomings the earthquake magnitude scale is one of the most fundamental earthquake source parameters to be used for catalogs although use of a uniform scale is desirable it is not always possible because of changes in instrumentation the data reduction method and the magnitude formula the station distribution etc as a result various magnitude scales have been developed and are currently in use recent developments in seismometry and earthquake source theories provide more quantitative source parameters than the magnitude in order to maintain continuity and uniformity of the data it is important to relate these magnitude scales and the new parameters in view of this importance relations between different magnitude scales are examined with an emphasis on the difference in the period of the waves used for the magnitude determination use of several magnitude scales determined at different periods provides a convenient method for characterizing earthquakes the moment magnitude can be used to quantify both shallow and deep earthquakes on the basis of wave energy radiated and provides a uniform scheme

a tsunami deposit at the cretaceous tertiary boundary in texas at sites near the brazos river texas an iridium anomaly and the paleontologic cretaceous tertiary boundary directly overlie a sandstone bed in which coarse grained sandstone with large clasts of mudstone and reworked carbonate nodules grades upward to wave ripple laminated very fine grained sandstone this bed is the only sandstone bed in a sequence of uppermost cretaceous to lowermost paleocene mudstone that records about 1 million years of quiet water deposition in midshelf to outer shelf depths conditions for depositing such a sandstone layer at these depths are most consistent with the occurrence of a tsunami about 50 to 100 meters high the most likely source for such a tsunami at the cretaceous tertiary boundary is a bolidewater impact

qlg tomography in colombia the crustal attenuation of lg waves in colombia was estimated and analyzed using local seismological data from the national seismological network of colombia rsnc the selected dataset comprises 510 crustal earthquakes with a total of 2928 ray paths this large dataset allowed us to invert for a regional average of qlg tomographic images for colombia and simultaneously source size for each event and site term at the seismological stations the computed regional average for qlg in the frequency band 0 5 5 0 hz was found to agree with the previously reported values in neighboring regions in order to resolve the lateral variation in the attenuation of lg waves in the crust independent tomographic inversions for 26 frequencies between 0 5 and 5 0 hz were conducted the resulting maps confirm that heterogeneities in the crust exist and that they are related to the large scale tectonic features in the country the highest attenuation in the region is linked to the presence of active volcanic arcs where the crust is weakened by partial melting relatively high attenuation is also found in zones where the crust is composed of accreted oceanic rocks and in regions with near surface low velocity sedimentary layers 2002 elsevier science b v all rights reserved

geochemistry of thermal waters in the southern volcanic zone chile implications for structural controls on geothermal fluid composition abstract thermal waters in the southern volcanic zone svz of chile between 36 41 s were studied using major and selected trace element relationships to characterize their geochemistry formation mechanisms and to explore the influence of regional structural controls on fluid composition three sets of waters were identified based on physicochemical characteristics i nacl waters ii acid sulfate waters and iii bicarbonate hco3 waters nacl waters are the most abundant type in the studied region and their chemistry is controlled by significant water rock interaction they are characterized by an alkaline ph 7 2 9 3 generally lower temperatures avg 55 c and relatively high concentrations of cl na b as li and cs acid sulfate waters are typically associated with volcanoes and have a strong magmatic volcanic component due to the absorption of magmatic vapors they are acidic ph 892 ppm in the region and are similar in temperature 6 2 to nacl waters they have elevated concentrations of most cations ca k na mg ba sr as a result of intense shallow cation leaching due to the absorption of co2 rich volcanic vapors on the peripheries of geothermal systems the thermal waters were also characterized according to their spatial relation with the dominant fault systems of the region the nne striking intra arc liquine ofqui fault system lofs and the wnw striking andean transverse faults atf the inherent differences in fault nature between these fault systems constitutes the primary structural control influencing geothermal fluid development in the svz the chemistry of waters spatially associated with the lofs as a whole is defined by high vertical permeability networks and lack magmatic reservoir development therefore these waters tend to have higher cl b ratios and strong correlations between trace alkali metals and cl due to rapid efficient upflow pathways in contrast waters spatially associated with the atf have lower cl b ratios and show no correlation between trace alkali metals and cl due to degassing magma chambers and decreased vertical permeability the relationship between water type and structural domain in cl b ratios and trace metal behavior provides evidence that fault geometry and kinematics exert a fundamental control on geothermal fluid development in the svz of chile

anelasticity and thermal structure of the oceanic upper mantle temperature calibration with heat flow data the thermal structure of the oceanic upper mantle is examined on the basis of seismic attenuation surface heat flow and mid ocean ridge basalt morb composition the comparison of seismic q with laboratory q determined at sufficiently high pressure and temperature allows us to constrain temperature in the earth since the inferred absolute temperature relies on knowledge of the frequency dependence of q if any we calibrate an unknown frequency effect on q by comparing the derived temperatures with geotherms calculated from surface heat flow and morb composition this comparison yields a correction factor found to be small for the geotherm derived from laboratory ultrasonic q examples of thermal structure are presented for the iceland plateau and the pacific ocean under the iceland plateau we expect partial melt for the asthenosphere only in the vicinity of the spreading ridge in asthenosphere older than 5 m y of the iceland plateau and older than 40 m y of the pacific ocean temperatures are below the dry peridotite solidus and no partial melt is expected these results are consistent with the thermal structure derived from a comparison of seismic and laboratory velocities it is shown that there is a good agreement between temperatures determined from seismic attenuation heat flow and morb chemistry since the laboratory measurements were made on a dry peridotite and we employ a dry peridotite solidus for determining the geotherm the consistency in temperatures derived from three independent data strongly suggests that the upper mantle remote from subduction zones is essentially dry it appears that the spreading process in mid ocean ridge causes asthenosphere material to ascend from greater depths where it was at higher temperature this gives rise to pressure release melting

geochemistry of champagne hot springs shallow hydrothermal vent field and associated sediments dominica lesser antilles the champagne hot springs chs shallow submarine hydrothermal system is located along the submerged flank of the plat pays volcanic system on the southwest section of the island of dominica lesser antilles we have conducted a detailed geochemical study of the hydrothermal system with the objectives to investigate the source of the hydrothermal fluids and gases their effect on sediment and precipitate chemistry as well as comparing the submarine vent chemistry with nearby on land hydrothermal vents finally we compare our findings to previous preliminary data from chs and compare sediment chemistry to that of average caribbean sediments we also report on a newly discovered area of submarine hydrothermal venting located approximately 40 m to the north of chs this area consists of hydrothermally altered areas of sand that contain abundant coatings of hydrous ferric oxides hfo on sediment grains geochemical and mineralogical analyses of vent waters pore waters gases sediments and precipitates reveal that the vent fluids consist of a mixture of entrained seawater and meteorically derived hydrothermal fluid in varying proportions vent fluids are depleted in br s o4 c l n a k and sr 2 relative to ambient seawater these species are all positively correlated with mg 2 which is also depleted relative to seawater boron fe as sb mn si and li are all enriched relative to ambient seawater pore waters in the hydrothermally altered sand patches have essentially the same chemistry mixing between fe 2 rich vent fluids and seawater causes rapid oxidation of fe 2 to insoluble fe 3 and leads to precipitation of hfo at the vent site and subsequent formation of hydrothermally altered sand patches the elevated concentrations of as and sb in the precipitates and sediments relative to average caribbean seafloor sediments reflect adsorption by hfo gas samples from the vent site are typical arc type gases and have both meteoric and magmatic signatures d 2005 elsevier b v all rights reserved

major and trace element geochemistry of neutral and acidic thermal springs at el chichon volcano mexico implications for monitoring of the volcanic activity abstract four groups of thermal springs with temperatures from 50 to 80 c are located on the s sw w slopes of el chichon volcano a composite dome tephra edifice which exploded in 1982 with a 1 km wide 160 m deep crater left very dynamic thermal activity inside the crater variations in chemistry and migration of pools and fumaroles drastic changes in the crater lake volume and chemistry contrasts with the stable behavior of the flank hot springs during the time of observations 1974 2005 all known groups of hot springs are located on the contact of the basement and volcanic edifice and only on the w sw s slopes of the volcano at almost same elevations 600 650 m asl and less than 3 km of direct distance from the crater three groups of near neutral ph 6 springs at sw s slopes have the total thermal water outflow rate higher than 300 l s and are similar in composition the fourth and farthest group on the western slope discharges acidic ph 2 saline 10 g kg of cl water with a much lower outflow rate water rock interaction modeling of main types of the el chichon thermal waters using regular log q k graphs saturation indices vs temperature showed maximum equilibrium temperature slightly higher than 200 c acidic waters are equilibrated with some clay minerals at about 120 c three main sources of the salinity of thermal water are suggested on the basis of mixing plots and isotopic data a magmatic source for co2 boron sulfur and a limited part of cl volcanic rock source for the major cations and trace elements the oil bearing evaporitic basement source oil field brine for nacl br a part of ca and some trace elements all flank thermal springs end up in the river rio magdalena that has a variable seasonal flow rates from 4 to 20 m3 s any changes in the chemistry of springs must notably change the composition of the streams draining hot springs and eventually rio magdalena a monthly geochemical monitoring of rio magdalena and streams draining main hot springs would be a useful tool for surveying the activity of the volcano

hydrogeochemistry of the thermal waters from the sciacca geothermal field sicily southern italy summary the sciacca basin southern sicily italy well known since the roman times for the importance of its thermo mineral waters is characterized by a large occurrence of thermal fluid discharges whose main thermal aquifer is located within the triassic carbonate rocks this reservoir represents the deepest formation cropping out in the area shallower and cooler thermal aquifers are located within the tertiary limestone and quaternary sand and gravel deposits in this work new geochemical and isotopic data of thermal waters and dissolved gases from springs and wells were investigated to assess the origin of thermal fluids and the structure of the hydrothermal system the main thermal aquifer at about 60 c and located at 43 m a s l is fed by an 18 o enriched 18 o 4 d 0 thermal marine end member affected by cooling and dilution 1 2 caused by mixing with inland originated meteoric waters 18 o 8 d 58 this meteoric recharge is likely related to the area of ficuzza and san genuardo mts located 12 and 23 km n of sciacca respectively at an altitude comprised between 900 and 1180 m a s l after this primary dilution the deep thermal aquifer emerging at the antiche terme selinuntine discharging site is not apparently affected by further dilution processes in the sciacca area where the sedimentary cover does not allow infiltration of local meteoric waters down to the triassic reservoir conversely the shallower thermal aquifers hosted within the tertiary quaternary sedimentary horizons are locally supplied by direct infiltration of meteoric water occurring at variable altitudes up to about 400 m a s l san calogero mt with the only exception of the molinelli thermal spring direct contribution from the deep thermal end member to thermal springs fed by the shallower aquifers can be considered negligible

chemical and isotopic composition of waters and dissolved gases in some thermal springs of sicily and adjacent volcanic islands italy hydrochemical major and some minor constituents stable isotope open image in new window and open image in new window 13ctdic total dissolved inorganic carbon and dissolved gas composition have been determined on 33 thermal discharges located throughout sicily italy and its adjacent islands on the basis of major ion contents four main water types have been distinguished 1 a na cl type 2 a ca mg na so4 cl type 3 a ca mg hco3 type and 4 a na hco3 type water most waters are meteoric in origin or resulting from mixing between meteoric water and heavy isotope end members in some samples 18o values reflect the effects of equilibrium processes between thermal waters and rocks positive 18o shift or thermal waters and co2 negative 18o shift dissolved gas composition indicates the occurrence of gas water interaction processes in thermal aquifers n2 o2 ratios higher than air saturated water asw suggest the presence of geochemical processes responsible for dissolved oxygen consumption high co2 contents more than 3000 cc litre stp dissolved in the thermal waters indicate the presence of an external source of carbon dioxide rich gas tdic content and 13ctdic show very large ranges from 4 6 to 145 3 mmol kg and from 10 0 and 2 8 respectively calculated values indicate the significant contribution from a deep source of carbon dioxide inorganic in origin interaction with mediterranean magmatic co2 characterized by heavier carbon isotope ratios open image in new window value from 3 to 0 vs v pdb capasso et al 1997 giammanco et al 1998 inguaggiato et al 2000 with respect to morb value and or input of co2 derived from thermal decomposition of marine carbonates have been inferred

geological effects and implications of the 2010 tsunami along the central coast of chile abstract geological effects of the 2010 chilean tsunami were quantified at five near field sites along a 200 km segment of coast located between the two zones of predominant fault slip field measurements including topography flow depths flow directions scour depths and deposit thicknesses provide insights into the processes and morphological changes associated with tsunami inundation and return flow the superposition of downed trees recorded multiple strong onshore and alongshore flows that arrived at different times and from different directions the most likely explanation for the diverse directions and timing of coastal inundation combines 1 variable fault rupture and asymmetrical slip displacement of the seafloor away from the epicenter with 2 resonant amplification of coastal edge waves other possible contributing factors include local interaction of incoming flow and return flow and delayed wave reflection by the southern coast of peru coastal embayments amplified the maximum inundation distances at two sites 2 4 and 2 6 km respectively tsunami vertical erosion included scour and planation of the land surface inundation scour around the bases of trees and channel incision from return flow sheets and wedges of sand and gravel were deposited at all of the sites locally derived boulders up to 1 m in diameter were transported as much as 400 m inland and deposited as fields of dispersed clasts the presence of lobate bedforms at one site indicates that at least some of the late stage sediment transport was as bed load and not as suspended load most of the tsunami deposits were less than 25 cm thick exceptions were thick deposits near open ocean river mouths where sediment supply was abundant human alterations of the land surface at most of the sites provided opportunities to examine some tsunami effects that otherwise would not have been possible including flow histories boulder dispersion and vegetation controls on deposit thickness

fluid geochemistry and geothermometry in the unexploited geothermal field of the vicano cimino volcanic district central italy abstract the vicano cimino volcanic district vcvd is related to the post orogenic magmatic activity of the peri tyrrhenian sector of central italy the chemical and isotopic compositions of 333 water discharges and 25 gas emissions indicate the occurrence of two main sources 1 cold ca hco 3 to ca na k hco 3 type waters from relatively shallow aquifers hosted in volcanic and sedimentary formations and 2 thermal ca so 4 hco 3 type waters located in a deep co 2 pressurized reservoir hosted in carbonate evaporite rocks and separated from the shallow aquifers by thick sequences of low permeability formations carbon dioxide is mainly produced by thermal metamorphic decarbonation within the deepest and hottest parts of the carbonate evaporite reservoir 13 c co 2 from 3 1 to 2 2 vs vpdb likely affected by a mantle rooted co 2 release of co 2 rich gases from the deep aquifer into the overlying shallow aquifers produces high co 2 springs and bubbling pools the spatial distribution of thermal waters and co 2 rich cold discharges is strongly controlled by fractures and faults located in correspondence with buried structural highs stable isotopes d and 18 o suggest that meteoric water feeds both the shallow and deep reservoirs the relatively low r r a values 0 27 1 19 indicate that he is mainly deriving from a crustal source with minor component from the mantle affected by crustal contamination related to the subduction of the adriatic plate consistently relatively high n 2 ar and n 2 3 he ratios and positive 15 n n 2 values from 0 91 to 5 7 vs air characterize the vcvd gas discharges suggesting the occurrence of a significant excess nitrogen isotopic compositions of ch 4 13 c ch 4 and d ch 4 values from 28 9 to 22 1 vs vpdb and from 176 to 138 vs vsmow respectively and composition of light alkanes are indicative of prevalent thermogenic ch 4 although the occurrence of abiogenic ch 4 production cannot be excluded the 34 s h 2 s values from 9 3 to 11 4 vs vcdt are consistent with the hypothesis of h 2 s production from thermogenic reduction of triassic anhydrites gas geothermometry in the h 2 o h 2 ar h 2 s system suggests that the vcvd gases equilibrated in a liquid phase at redox conditions controlled by interactions of fluids with the local mineral assemblage at temperatures lower 2000 m geothermal wells this confirms that secondary processes i e steam condensation gas dissolution in shallow aquifers re equilibration at lower temperature and microbial activity significantly affect the chemistry of the uprising fluids thermal water chemistry supports the occurrence in this area of an anomalous heat flow that coupled with the recent demographic growth makes this site suitable for direct and indirect exploitation of the geothermal resource in agreement with the preliminary surveys carried out in the 1970 s 1990 s for geothermal exploration purposes

time dependent onshore tsunami response abstract while bulk measures of the onshore impact of a tsunami including the maximum run up elevation and inundation distance are important for hazard planning the temporal evolution of the onshore flow dynamics likely controls the extent of the onshore destruction and the erosion and deposition of sediment that occurs however the time varying dynamics of actual tsunamis are even more difficult to measure in situ than the bulk parameters here a numerical model based on the non linear shallow water equations is used to examine the effects variations in the wave characteristics bed slope and bottom roughness have on the temporal evolution of the onshore flow model results indicate that the onshore flow dynamics vary significantly over the parameter space examined for example the flow dynamics over steep smooth morphologies tend to be temporally symmetric with similar magnitude velocities generated during the run up and run down phases of inundation conversely on shallow rough onshore topographies the flow dynamics tend to be temporally skewed toward the run down phase of inundation with the magnitude of the flow velocities during run up and run down being significantly different furthermore for near breaking tsunami waves inundating over steep topography the flow velocity tends to accelerate almost instantaneously to a maximum and then decrease monotonically conversely when very long waves inundate over shallow topography the flow accelerates more slowly and can remain steady for a period of time before beginning to decelerate these results indicate that a single set of assumptions concerning the onshore flow dynamics cannot be applied to all tsunamis and site specific analyses may be required

tsunamigenic incisions produced by the december 2004 earthquake along the coasts of thailand indonesia and sri lanka field observations and satellite images indicate that tsunami waves exhibit specific patterns during flooding and recession forming characteristic incisions in the coastal landscape to study these incisions we analyze high resolution remote sensing images of the coastline of indonesia thailand and sri lanka impacted by the tsunami of december 26th 2004 the analysis sheds light on the different mechanisms by which currents scour incisions during the flooding and receding phases of a tsunami during flooding the high velocity flow indents the levees of existing tidal channels and bays leaving short flood scours the receding water then dissects the coastline with equally spaced return channels widening toward the coast

horizontal and vertical variation of 2004 indian tsunami deposits an example of two transects along the western coast of thailand abstract we investigated horizontal and vertical variations in modern tsunami deposits along two transects at nam khem and khao lak western coast of thailand deposited by the large tsunami associated with the earthquake magnitude 9 0 of 26 december 2004 off sumatra indonesia tsunami waves 6 10 m high struck the area approximately 2 h after the earthquake tsunami deposits cover the low lying coastal plains and extend more than 1 km inland from the shoreline no landward decrease in sediment thicknesses was found clearly at either transect terrace scarps and a steep slope behind the coastal plain probably stopped tsunami deposition further inland causing substantial sediments to be deposited in front of these features very clear vertical variations in grain size and multiple layers are found in the deposits to about 600 m inland at nam khem fine grained sediments overlie the coarse grained sediments of the basal layer of the tsunami deposits at some sites the fine grained sediments are overlain by another layer of coarse grained sediments suggesting deposits laid down in succession by multiple waves the basal coarse grained sediments at nam khem fine landward the up flow waned inland based on the assumption that the grain size of the basal deposits relates to the strength of the up flow these results are potentially useful in disaster prevention and coastal environmental change management as well as for interpreting paleotsunami deposits in geological records

the ml scale in southern california measurements 9 941 of peak amplitudes on wood anderson instruments or simulated wood anderson instruments in the southern california seismographic network for 972 earthquakes primarily located in southern california were studied with the aim of determining a new distance correction curve for use in determining the local magnitude m l events in the mammoth lakes area were found to give an unusual attenuation pattern and were excluded from the analysis as were readings from any one earthquake at distances beyond the first occurrence of amplitudes less than 0 3 mm the remaining 7 355 amplitudes from 814 earthquakes yielded the following equation for m l distance correction log a 0 log a 0 1 110log r 100 0 00189 r 100 3 0 where r is hypocentral distance in kilometers a new set of station corrections was also determined from the analysis the standard deviation of the m l residuals obtained by using this curve and the station corrections was 0 21 the data used to derive the equation came from earthquakes with hypocentral distances ranging from about 10 to 700 km and focal depths down to 20 km with most depths less than 10 km the log a 0 values from this equation are similar to the standard values listed in richter 1958 for 50 200 km the effect at close distances is consistent with that found in several other studies and is simply due to a difference in the observed 1 r geometrical spreading for body waves and the 1 r 2 spreading assumed by gutenberg and richter in the construction of the log a 0 table m l s computed from our curve and those reported in the caltech catalog show a systematic dependence on magnitude small earthquakes have larger magnitudes than in the catalog and large earthquakes have smaller magnitudes by as much as 0 6 units to a large extent these systematic differences are due to the nonuniform distribution of data in magnitude distance space small earthquakes are preferentially recorded at close distances relative to large earthquakes for large earthquakes however the difference in the two magnitudes is not solely due to the new correction for attenuation magnitudes computed using richter s log a 0 curve are also low relative to the catalog values the differences in that case may be due to subjective judgment on the part of those determining the catalog magnitudes the use of data other than the caltech wood anderson seismographs the use of different station corrections or the use of teleseismic magnitude determinations whatever their cause the departures at large magnitude may explain a 1 0 0 7 proportionality found by luco 1982 between m l s determined from real wood anderson records and those from records synthesized from strong motion instruments if it were not for the biases in reported magnitudes luco s finding would imply a magnitude dependent shape in the attenuation curves we studied residuals in three magnitude classes 2 0 m l 3 5 3 5 m l 5 5 and 5 5 m l 7 0 and found no support for such a magnitude dependence based on our results we propose that local magnitude scales be defined such that m l 3 correspond to 10 mm of motion on a wood anderson instrument at 17 km hypocentral distance rather than 1 mm of motion at 100 km this is consistent with the original definition of magnitude in southern california and will allow more meaningful comparison of earthquakes in regions having very different attenuation of waves within the first 100 km

local magnitude scale and seismicity rate for tanzania east africa abstract a local magnitude scale is developed for tanzania east africa using data collected by the 1994 1995 tanzania broadband seismic experiment the waveform data from 1189 local and regional earthquakes located within east africa were corrected for instrument response and convolved with the nominal wood anderson torsion seismograph response appropriate for the original definition of local magnitude a total of 24 710 maximum s wave amplitudes were incorporated into an iterative regression for individual event local magnitudes 38 horizontal component station factors and 2 linear distance dependent factors in the log a 0 term of the equation for m l the resulting distance correction log a 0 is given by log a 0 0 776 log r 17 0 000902 r 17 2 0 where r is hypocentral distance in kilometers this distance correction yields much less ground motion attenuation than observed for southern california and is similar to that observed for local s waves and regional lg waves propagating in eastern north america normalizing the distance correction using the standard constraint of 1 mm ground motion at 100 km for a magnitude 3 0 earthquake results in a bias of nearly half of a magnitude unit between m b and m l with m l being larger normalizing using the constraint of 10 mm of motion at 17 km for m l 3 0 removes the bias in magnitude measures and indicates that structure within tanzania is relatively high q the seismicity rate of tanzania for 1994 1995 was examined using the gutenberg richter seismicity distribution and is seen to follow the relation log n 4 63 0 84 m l where n is the number of earthquakes per year of local magnitude m l or greater the catalog of events used in this study is seen to be complete to magnitude 2 to 2 5

boron and magnesium isotopic composition of seawater the isotopic systems of boron and magnesium are increasingly being used as proxies for a number of environmental variables and processes the isotopic composition of seawater for both systems plays a central role in these studies and is an important interlaboratory standard given the long residence times of both elements 10 7 years it is commonly assumed that seawater is isotopically homogenous for these systems yet no systematic studies currently exist here we present the b and mg isotopic composition of 26 28 seawater samples from a number of ocean basins that encompass a significant range in salinity 32 to 38 psu temperature 0 3 to 25 9c and water depth 0 to 1240 m we find no significant or systematic variation for either system in accordance with their long residence times we recommend that the mean values we report 11 b 39 61 0 04 2 s e n 28 25 mg 0 43 0 01 2 s e n 26 26 mg 0 82 0 01 2 s e n 26 be used in future studies involving mg and b isotopes copyright 2010 by the american geophysical union

beach recovery after 2004 indian ocean tsunami from phang nga thailand the 2004 indian ocean tsunami devastated the coastal areas along the andaman western coast of thailand and left unique physical evidence of its impact including the erosional landforms of the pre tsunami topography here we show the results from monitoring the natural recovery of beach areas at khuk khak and bang niang tidal channels of khao lak area phang nga thailand a series of satellite images before and after the tsunami event was employed for calculating the beach area and locating the position of the changed shoreline field surveys to follow up the development of the post tsunami beach area were conducted from 2005 to 2007 and the yearly beach profile was measured in 2006 as a result the scoured beach areas where the tidal channel inlets were located underwent continuous recovery the return of post tsunami sediments within the beach zone was either achieved by normal wind and wave processes or during the storm surges in the rainy season post 2004 beach sediments were derived mainly from near offshore sources the present situation of the beach zone has almost completed reversion back to the equilibrium stage and this has occurred within 2 years after the tsunami event we suggest these results provide a better understanding of the geomorphological process involved in beach recovery after severe erosion such as by tsunami events

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

sedimentological and geomorphological imprints of holocene tsunamis in southwestern spain an approach to establish the recurrence period this paper reviews the sedimentological and geomorphological imprints of prehistoric and historical tsunamis in the four main estuaries of sw spain these imprints include beach erosion filling of intertidal channels deposition of bioclastic layers washover fans and reworked aeolian sheets and the breaching of spits and tombolos most of these imprints were caused by the 218 209 bc and ad 1755 tsunamis although evidence of other tsunamis has been identified in these two events effects on human populations were severe and diverse such as human loss of life changes in coastal settlements and international borders damage to port infrastructure or flooding of marsh and inhabited areas new radiocarbon reservoir data were included in order to obtain an approach to the recurrence period of these high energy events 700 1000 years in this area 2013 elsevier b v

geochemistry of fluids discharged over the seismic area of the southern apennines calabria region southern italy implications for fluid fault relationships abstract the first comprehensive geochemical data set of the fluids circulating over a 14 000 km2 wide seismic prone area of the southern apennines calabria region italy is presented here the geochemical investigations were carried out with the twofold aim of constraining the origin and interactions of the circulating fluids and to investigate possible relationships with local faults sixty samples of both thermal and cold waters were collected from which the dissolved gases were extracted the geochemical features of the water samples display different types and degrees of water rock interactions irrespective of the outlet temperature the calculated equilibrium temperatures of the thermal waters 60 160 c and the low heat flow of the whole study area are consistent with a heating process due to deep water circulation and rapid upflow through lithospheric structures the composition of the dissolved gases reveals that crustal originating gases n2 and co2 dominated feed all the groundwaters the 3he 4he ratios of the dissolved he in the range of 0 03 0 22rac for the thermal waters and 0 05 0 63rac for the cold waters rac he isotope ratio corrected for atmospheric contamination are mainly the result of a two component radiogenic and atmospheric mixing although indications of mantle derived he are found in some cold waters as the study area had been hit by 18 of the most destructive earthquakes magnitude ranging from 5 9 to 7 2 occurring over a 280 a time span 1626 1908 in the southern apennines the reported results on the circulating fluids may represent the reference for a better inside knowledge of the fault fluid relationships and for the development of long term geochemical monitoring strategies for the area

tropical glaciers g kaser and h osmaston eds publisher cambridge university press cambridge 2001 206 pp isbn 0 521 63333 8

source inversion of w phase speeding up seismic tsunami warning w phase is a long period phase arriving before s wave it can be interpreted as superposition of the fundamental first second and third overtones of spheroidal modes or rayleigh waves and has a group velocity from 4 5 to 9 km s 1 over a period range of 100 1000 s the amplitude of long period waves better represents the tsunami potential of an earthquake because of the fast group velocity of w phase most of w phase energy is contained within a short time window after the arrival of the p wave at a distance of 50 w phase energy is contained within 23 min after the origin time which is the distinct advantage of using w phase for rapid tsunami warning purposes we use a time domain deconvolution method to extract w phases from the broad band records of global seismic networks the bandwidth of w phase is approximately from 0 001 to 0 01 hz and we bandpass filter the data from 0 001 to 0 005 hz in most cases having extracted w phase from the vertical component records we perform a linear inversion using a point source to determine mw and the source mechanism for several large earthquakes including the 2004 sumatra andaman earthquake the 2005 nias earthquake the 2006 kuril is earthquake and the 2007 sumatra earthquake w phase inversion yields reliable solutions and holds promise of the use of w phase for rapid assessment of tsunami potential

carbonate assimilation at merapi volcano java indonesia insights from crystal isotope stratigraphy recent basaltic andesite lavas from merapi volcano contain abundant complexly zoned plagioclase phenocrysts analysed here for their petrographic textures major element composition and sr isotope composition anorthite an content in individual crystals can vary by as much as 55 mol an

potassium rich volcanic rocks of the muriah complex java indonesia products of multiple magma sources abstract the extinct pleistocene volcano muriah situated behind the main pleistocene recent sunda magmatic arc in north central java has erupted at least two contrasted groups of lavas one group forms a well defined compositional series anhydrous series from leucite basanite to tephritic phonolite with olivine and tschermakitic clinopyroxene the main phenocrysts the other group the hydrous series includes compositionally variable tephrites and high k andesites with common plagioclase biotite and amphibole lavas of the anhydrous series are much richer in lil trace elements than the most potassic lavas of neighbouring active volcanoes but relative hfs element enrichment is less pronounced ree patterns have almost constant slopes from la 250 600 times chondrites to yb 5 10 times chondrites while those of lavas of active centres are less light enriched and show flattening in the heavy ree anhydrous series initial 87sr 86sr ratios 0 7043 0 7046 are lower than those of active centres 0 7047 0 7053 hydrous series lavas are intermediate in all these geochemical characteristics the most mafic a series leucite basanite with mg mg fe 2 0 69 140 ppm ni and 620 ppm cr was probably derived from the primary magma for the series by fractionation of only 5 wt olivine its ree pattern suggests derivation from a garnet bearing source experiments on this basanite with up to 10 olivine and 20 orthopyroxene added and in the presence of h2o and h2o co2 mixtures have shown that for all but very high magma water contents the olivine and garnet liquidus fields are widely separated by fields of phlogopite and clinopyroxene there is no liquidus field of orthopyroxene hence if magma production involved an equilibrium melting process alone the most probable sources are of garnet bearing phlogopite clinopyroxenite type alternatively this magma may represent the end product of interaction between a low k basanite magma from a garnet lherzolite source in the asthenosphere and a phlogopite bearing lherzolite zone in the lower lithosphere its production was probably related to crustal doming and extension superimposed on the dominant subduction regime hydrous series magmas may have resulted from mixing between anhydrous series magmas and high k calc alkaline basaltic to andesitic magmas more directly related to subduction processes

stable and radiogenic isotopes as tracers for the origin mixing and subsurface history of fluids in submarine shallow water hydrothermal systems the shallow water hydrothermal system in tutum bay on the west side of ambitle island papua new guinea provides us with an exceptional opportunity to study isotope systematics in a near shore setting compared to seawater the hydrothermal fluids in tutum bay have lower values for dd d 18 o d 13 c and 87 sr and higher values for 3 h d 34 s so4 and d 18 o so4 the d 18 o and dd records for vents 1 and 4 indicate that fluid compositions remained stable over an extended period interpretation of isotope data clearly demonstrates the predominantly meteoric origin of tutum bay hydrothermal fluids despite their location in a marine environment d 18 o and dd values are identical to mean average annual precipitation in eastern papua new guinea the hypothesis that these fluids are a simple product of mixing between seawater and onshore hydrothermal fluids from the waramung w 1 and kapkai w 2 thermal areas has been rejected because the observed d 37 cl 3 h d 34 s so4 and d 18 o so4 values cannot be explained by a simple mixing model the application of d 18 o so4 and d 13 c thermometers in combination with 3 h values corroborates the three step model of pichler et al pichler t veizer j hall g e m 1999 the chemical composition of shallow water hydrothermal fluids in tutum bay ambitle island papua new guinea and their effect on ambient seawater marine chemistry 64 3 229 252 where 1 phase separation in the deep reservoir beneath ambitle island produces a high temperature vapor that rises upward and subsequently reacts with cooler ground water to form a low ph co2 rich water of approximately 150 160 8c 2 caused by the steep topography this co2 rich fluid moves laterally towards the margin of the hydrothermal system where it mixes with the marginal upflow of the deep reservoir fluid this produces a dilute chloride water of approximately 165 8c and 3 possibly the entrainment of minor amounts of ground or seawater during its final ascent d 2004 elsevier b v all rights reserved

precursory inflation of shallow magma reservoirs at west sunda volcanoes detected by insar 1 we use 2006 2009 alos interferometric synthetic aperture radar data over the entire west sunda arc indonesia home of 13 of the world s active volcanoes to derive arc wide time dependent ground deformation data we present unambiguous evidence of inflation at six volcanoes three of which erupted after the observation period we show that these volcanoes have shallow magma reservoirs at 1 3 km depth below the average regional elevation a global comparison of reservoir depths at arc volcanoes suggests that volcanoes in extensional and strike slip settings west sunda can develop shallow reservoirs whereas volcanoes in compressional settings may lack them thus magma ascend through the upper crust could be influenced by intra arc tectonic settings

the chemistry of trace elements in surface geothermal waters and steam iceland abstract the geochemistry of trace elements in surface geothermal fluids in iceland was studied the sampled fluids included hot springs mud pots steam vents and soil solutions with temperatures ranging from 4 to 100 c ph between 2 01 and 9 10 and total dissolved solids between 86 and 4375 ppm the surface geothermal waters may be categorized into three groups based on their chemical composition namely nacl waters steam heated acid sulfate waters and mixed waters nacl waters with ph 8 are considered to represent aquifer geothermal fluids that have undergone boiling in the upflow they contained only low concentrations of most metals

d h and 18 o 16 o ratios of water in the crater lake at kusatsu shirane volcano japan abstract the d h and 18o 16o ratios of water in the active crater lake situated on the kusatsu shirane volcano japan are about 20 and 6 respectively higher than local meteoric water the ratios show seasonal variations superimposed on a gradual change over nine years the isotopic ratios started to increase in early 1990 and decrease in the spring of 1995 the seasonal variation which is high in winter and low in summer correlates with the temperature difference between lake water and ambient air the large temperature difference in winter enhances the evaporation of lake water and produces the enriched isotopic ratios relative to the ratios in summer the accumulation of snow and the decrease in the flux of meteoric water into the lake strengthens the winter time isotopic enrichment the enriched isotopic ratios of the lake water over a long time result from the addition of an end member with heavy isotopic ratios contained in a thermal fluid supplied to the lake considering the water balance in the lake the isotopic ratios of the thermal fluid were found to be close to the lake water itself suggesting the circulation of the lake water seeping through lake floor based on the correlation between cl concentration and the isotopic ratios the contribution by the heavy end member was estimated to be 25 36 relative to the enrichment by evaporation the heavy end member could be a liquid phase evolved from a parental fluid which is a mixture of local meteoric water and a magmatic fluid as found in high temperature volcanic gases

fluid geochemistry and geothermometry in the western sector of the sabatini volcanic district and the tolfa mountains central italy abstract a geochemical survey of 197 fluid discharges cold and thermal waters and bubbling pools and 15 gas emissions from the western sector of the sabatini volcanic district and the tolfa mountains latium central italy was carried out in 2007 2008 the chemical and isotopic compositions of the fluid discharges indicate the occurrence of two main sources 1 relatively shallow aquifers with ca na k hco 3 and ca mg hco 3 compositions when trapped in volcanic and sedimentary formations respectively and 2 a deep reservoir which is hosted in the mesozoic carbonate sequence rich in co 2 and having a ca so 4 hco 3 composition dissolution of a co 2 rich gas phase into the shallow aquifers produces high tds and high pco 2 cold waters while oxidation of deep derived h 2 s to so 4 2 generates low ph the 13 c co 2 values for gas emissions from 2 8 to 2 7 vs vpdb suggest that the origin of co 2 associated with the deep fluids is mainly related to thermo metamorphic reactions within the carbonate reservoir although significant mantle contribution may also occur however r r a values 0 37 0 62 indicate that he is mainly produced by a crustal source with a minor component from a crust contaminated mantle on the basis of the 13 c ch 4 and d ch 4 values from 25 7 to 19 5 vs vpdb and from 152 to 93 4 vs vsmow respectively ch 4 production is associated with thermogenic processes possibly related to abiogenic co 2 reduction within the carbonate reservoir the 34 s h 2 s values from 9 3 to 10 4 vs vcdt are consistent with the hypothesis of a sedimentary source of sulfur from thermogenic reduction of triassic sulfates geothermometric evaluations based on chemical equilibria co 2 ch 4 and separately h 2 s suggest that the reservoir equilibrium temperature is up to 300 c the d and 18 o data indicate that water recharging both the shallow and deep aquifers has a meteoric origin fluid geochemistry coupled with gravimetric data and tectonic lineaments supports the idea that significant contributions from a deep seated geothermal brine are present in the stigliano thermal fluid discharges exploration surveys investigated this area during 70 s 90 s for geothermal purposes nevertheless presently the area is still under exploited the presence of thermal waters and anomalous heat flow together with the demographic growth of the last years makes this site a suitable location for direct applications of the geothermal resource

hydrochemistry of the cesme geothermal area in western turkey abstract hydrochemical characterization of thermal waters discharged from springs and wells in the cesme geothermal area show that there are two groups one is of thermal waters from a lower aquifer composed of triassic karst limestones which are the main potential reservoir of the area they are of na cl type and between 37 and 62 c and have total dissolved solids tds with around 35 000 mg l the other group are thermal waters derived from an upper aquifer formed by neogene terrestrial sediments these have lower discharge temperatures 37 40 c and lower tds values due to their having mixed with local groundwater before emerging the isotopic and chemical data shows that the initial aqueous solution is a mixture of modern seawater and meteoric water in various proportions enrichment in 18o and d values and tritium contents 8 1 tu of thermal waters reflect a rapid circulation and the contribution of modern seawater the thermal waters are undersaturated with respect to gypsum but oversaturated or around equilibrium with respect to dolomite and calcite several chemical geothermometry techniques applied to cesme geothermal waters gave estimated reservoir temperatures of around 85 100 c

erosion deposition and landscape change on the sendai coastal plain japan resulting from the march 11 2011 tohoku oki tsunami case studies of recent tsunami impacts have proven to be extremely useful in understanding the geologic processes involved during inundation and return flow and refining the criteria used to identify paleotsunami deposits in the geologic record here we report on erosion deposition and associated landscape change resulting from the march 11 2011 tohoku oki tsunami along a nearly 4 5 km shore normal transect on the coastal plain near sendai japan the study area on the broad low relief prograding coastal sendai plain comprised a sand beach backed by 3 m high sand dunes and a forest a wetland the teizan canal agricultural rice fields buildings and roads field observations focused on measurements of tsunami flow characteristics height and direction mapping of erosion features and assessing sediment deposition based on shallow trenches at 50 100 m spacing recorded tsunami inundation heights reached up to about 11 m above mean sea level within the first 500 m from the shoreline and then ranged between 3 and 5 m for the next 2 km gradually decreasing to about 3 m close to the inundation limit the tsunami deposit generally thinned landward from an average maximum 30 cm thick sand deposit in the coastal forest to a thin mud drape several mm thick near the inundation limit a discontinuous sand dominated sheet was prevalent to about 2800 m from the shoreline where mud content then gradually increased further landward eventually resulting in a mud dominated deposit ranging from 3 5 cm to a few mm thickness the overall thinning and fining of the deposit was often interrupted by localized features that led to complex sedimentological relationships over short distances satellite imagery taken on 14 march 2011 3 days after the tohoku oki tsunami shows prominent foreshore incisions with 100 s meters spacing alongshore a foredune ridge that underwent severe erosion and development of a prominent shore parallel elongated scour depression our field survey in early may 2011 revealed that the foreshore recovered quickly with rapid post tsunami sediment deposition from incident waves whereas the dune ridge complex had undergone only minor re working from eolian processes

limestone assimilation and the origin of co2 emissions at the alban hills central italy constraints from experimental petrology abstract the alban hills volcanic region 20 km south of rome in the roman province emitted a large volume of potassic magmas 280 km 3 during the quaternary chemical interactions between ascending magmas and the 7000 8000 m thick sedimentary carbonate basement are documented by abundant high temperature skarn xenoliths in the eruptive products and have been frequently corroborated by geochemical surveys in this paper we characterize the effect of carbonate assimilation on phase relationships at 200 mpa and 1150 1050 c by experimental petrology calcite and dolomite addition promotes the crystallization of ca rich pyroxene and mg rich olivine respectively and addition of both carbonates results in the desilication of the melt furthermore carbonate assimilation liberates a large quantity of co 2 rich fluid a comparison of experimental versus natural mineral glass and bulk rock compositions suggests large variations in the degree of carbonate assimilation for the different alban hills eruptions a maximum of 15 wt assimilation is suggested by some melt inclusion and clinopyroxene compositions however most of the natural data indicate assimilation of between 3 and 12 wt carbonate current high co 2 emissions in this area most likely indicate that such an assimilation process still occurs at depth we calculate that a magma intruding into the carbonate basement with a rate of 1 2 10 6 m 3 year estimated by geophysical studies and assimilating 3 12 wt of host rocks would release an amount of co 2 matching the current yearly emissions at the alban hills our results strongly suggest that current co 2 emissions in this region are the shallow manifestation of hot mafic magma intrusion in the carbonate hosted reservoir at 5 6 km depth with important consequences for the present day volcanic hazard evaluation in this densely populated and historical area

sedimentological and geomorphological effects of the sumatra andaman tsunami in the area of khao lak southern thailand the sumatra andaman tsunami left distinctive sedimentological and geomorphological signatures in the area of khao lak fine grained sediments predominantly layers of cohesive carbonate rich fine sandy silt with thicknesses of 1 10 cm erosionally overlying pre tsunami sandy soils and sediments represent the most common tsunami deposits in the study area petrographically they differ significantly from other coastal sediments and affiliated soils due to their grain size and corresponding clay mineral content muddy shelf sediments sub wave base are indicated as a main source the present results suggest that indications of shelf influence although varying regionally might contribute to the identification of fine grained tsunami sediments and their differentiation from storm sediments however the observed differences of tsunami sediments to soils and other coastal sediments especially with respect to carbonate mineralogy might disappear in short geological time under conditions of intensive weathering and bioturbation at cape pakarang hundreds of boulders with up to 24 tons were deposited on the foreshore and upper shoreface applying nott s earth planet sci lett 210 269 276 2003 formulas minimum flow velocities of 3 9 m s are required to transport the largest boulders the devastating tsunami effect of both onshore flow and backflow is documented by damaged human constructions geomorphological effects include intensive widening of estuary mouths and the development of erosional channels now estuary mouths are reduced and erosional channels cut off from the sea due to the formation of a post tsunami beach ridge

geochemistry of the magmatic hydrothermal system of kawah ijen volcano east java indonesia samples from kawah ijen crater lake spring and fumarole discharges were collected between 1990 and 1996 for chemical and isotopic analysis an extremely low ph 0 3 lake contains so 4 cl waters produced during absorption of magmatic volatiles into shallow ground water the acidic waters dissolve the rock isochemically to produce immature solutions the strong d and 18 o enrichment of the lake is mainly due to enhanced evaporation at elevated temperature but involvement of a magmatic component with heavy isotopic ratios also modifies the lake d and 18 o content the large so4 s d 23 8 26 4 measured in the lake suggest that dissolved so 4 forms during disproportionation of magmatic so 2 in the hydrothermal conduit at temperatures of 250 280 c the lake 18 o so4 and 18 o h2o values may reflect equilibration during subsurface circulation of the water at temperatures near 150 c significant variations in the lake s bulk composition from 1990 to 1996 were not detected however we interpret a change in the distribution and concentration of polythionate species in 1996 as a result of increased so 2 rich gas input to the lake system thermal springs at kawah ijen consist of acidic so 4 cl waters on the lakeshore and neutral ph hco 3 so 4 cl na waters in blawan village 17 km from the crater the cation contents of these discharges are diluted compared to the crater lake but still do not represent equilibrium with the rock the so 4 cl ratios and water and sulfur isotopic compositions support the idea that these springs are mixtures of summit acidic so 4 cl water and ground water the lakeshore fumarole discharges t 170 245 c have both a magmatic and a hydrothermal component and are supersaturated with respect to elemental sulfur the apparent equilibrium temperature of the gas is 260 c the proportions of the oxidized so 2 dominated magmatic vapor anti of the reduced h 2 s dominated hydrothermal vapor in the fumaroles varied between 1979 and 1996 this may be the result of interaction of so 2 bearing magmatic vapors with the summit acidic hydrothermal reservoir this idea is supported by the lower h 2 s so 2 ratio deduced for the gas producing the so 4 cl reservoir feeding the lake compared with that observed in the subaerial gas discharges the condensing gas may have equilibrated in a liquid vapor zone at about 350 c elemental sulfur occurs in the crater lake environment as banded sediments exposed on the lakeshore and as a subaqueous molten body on the crater floor the sediments were precipitated in the past during inorganic oxidation of h 2 s in the lake water this process was not continuous but was interrupted by periods of massive silica poorly crystallized precipitation similar to the present day lake conditions we suggest that the factor controlling the type of deposition is related to whether h 2 s or silica rich volcanic discharges enter the lake this could depend on the efficiency with which the lake water circulates in the hydrothermal cell beneath the crater quenched liquid sulfur products show 34 s values similar to those found in the banded deposits suggesting that the subaqueous molten body simply consists of melted sediments previously accumulated at the lake bottom

magnetotelluric and geomagnetic modelling reveals zones of very high electrical conductivity in the upper crust of central java abstract we present results of two and three dimensional modelling of magnetotelluric and geomagnetic data from central java indonesia we adopt a hypothesis testing approach where we examine the influence of individual structural elements of competing models on the total model responses the models show that ocean anomalies do not overwhelm the signal due to strong electrical conductivity anomalies within java these highly conducting regions with resistivities of below 1 m are located in the central and northern parts of the island fitting of the geomagnetic data requires that the innermost parts of both regions consist of material with extremely low resistivity 0 2 m young sediments tephra and their alteration products can be responsible for some of the low resistivity regions at shallow depths the two zones of extremely high conductivity however are best explained as consequences of geothermal activity in the vicinity of active volcanism mt merapi in central java and by fluid or graphite enrichment along shear zones in northern java subduction zone related processes in a depth range of 70 400 km cannot be resolved because the highly conductive regions at shallow depths effectively screen deeper structures

unusually large tsunamis frequent a currently creeping part of the aleutian megathrust current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust here we report geological evidence for large tsunamis occurring on average every 300 340 years near the source areas of the 1946 and 1957 aleutian tsunamis these areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate that the megathrust is currently creeping at sedanka island evidence for large tsunamis includes six sand sheets that blanket a lowland facing the pacific ocean rise to 15 m above mean sea level contain marine diatoms cap terraces adjoin evidence for scour and date from the past 1700 years the youngest sheet and modern drift logs found as far as 800 m inland and 18 m elevation likely record the 1957 tsunami previously unrecognized tsunami sources coexist with a presently creeping megathrust along this part of the aleutian subduction zone

geochemistry of the acid kawah putih lake patuha volcano west java indonesia abstract kawah putih is a summit crater of patuha volcano west java indonesia which contains a shallow 300 m wide lake with strongly mineralized acid sulfate chloride water the lake water has a temperature of 26 34 c ph s tot 2500 4600 ppm and cl 5300 12 600 ppm and floating sulfur globules with sulfide inclusions are common sulfur oxyanion concentrations are unusually high with s 4 o 6 2 s 5 o 6 2 s 6 o 6 2 2400 4200 ppm subaerial fumaroles thermodynamic modeling of the lake fluids indicates that the lake water is saturated with silica phases barite pyrite and various pb sb cu as bi bearing sulfides when sulfur saturation is assumed precipitating phases predicted by the model calculations are consistent with the bulk chemistry of the sulfur rich bottom sediments and their identified mineral phases much of the lake water chemistry can be explained by congruent rock dissolution in combination with preferential enrichments from entering fumarolic gases or brines and element removal by precipitating mineral phases as indicated by a comparison of the fluids volcanic rocks and lake bed sediment flank springs on the mountain at different elevations vary in composition and are consistent with local rock dissolution as a dominant factor and ph dependent element mobility discharges of warm sulfate and chloride rich water at the highest elevation and a near neutral spring at lower level may contain a small contribution of crater lake water the acid fluid induced processes at patuha have led to the accumulation of elements that are commonly associated with volcano hosted epithermal ore deposits the dispersal of heavy metals and other potentially toxic elements from the volcano via the local drainage system is a matter of serious environmental concern

genesis of dacitic magmatism at batur volcano bali indonesia implications for the origins of stratovolcano calderas abstract batur is an active stratovolcano on the island of bali indonesia with a large well formed caldera whose formation is correlated with the eruption about 23 700 years ago of a thick ignimbrite sheet our study of the volcanic stratigraphy and geochemistry of batur shows the formation of the caldera was signalled by a change in the composition of the erupting material from basaltic and andesitic to dacitic the dacitic rocks are glassy possess equilibrium phenocryst assemblages and display compositional characteristics consistent with an origin by crystal liquid fractionation from more mafic parent magmas in a shallow chamber possibly at 1 5 km depth and 1000 1070 c however although separated by a gap of 6 wt sio 2 the dacitic rocks are clearly related in their minor and trace element geochemistry to those basalts and basaltic andesites erupted after the caldera was formed rather than to the andesites erupted immediately before the dacites first appeared we infer from this and published experimental modelling of the possible crystallization behaviour of basaltic magma chambers that a magmatic cycle involving caldera formation began independently of the previous activity of batur by formation of a new closed system magma chamber beneath the volcano fractional crystallization possibly at the walls of the chamber led to the early production of derivative siliceous magmas and consequently to caldera formation while most of the magma retained its original composition the postcaldera batur basalts represent the largely undifferentiated core liquids of this chamber this model contrasts with the traditional evolutionary model for stratovolcano calderas but may be applicable to the origins of calderas similar to that of batur particularly those in volcanic island arcs

geomarkers of the 218 209 bc atlantic tsunami in the roman lacus ligustinus sw spain a palaeogeographical approach between 218 and 209 bc the western coasts of iberia suffered the impact of a historical tsunami with an epicentre probably located in the atlantic ocean near the cape st vincent area sw portugal palaeogeographical changes in the river guadalquivir estuary the ancient roman lacus ligustinus have been recorded in erosional and depositional landforms both stratigraphically and as landscape relicts the tsunamigenic waves run up of w5 m and their subsequent backwash eroded the previous littoral spits transversally generating rectilinear cliffs and incisions the littoral foredunes were also eroded and reactivated as transgressive dunes over the edge of the marshes former coastal sediments w520e100 bc generated overwash deposits ebb tide deltas and sand sheets within the estuary as well as a subsequent bioclastic beach on the lagoon shore defining the post tsunami 130 bce80 ad estuarine shoreline roman lagoon some coastal pre roman 7th to 3rd centuries bc human settlements were abandoned and later in the roman period 1st century ad saltworks were installed morphological and sedimentological changes in the coast triggered by this event were similar or greater than the changes in coastal features related to the ad 1755 lisbon tsunami

styles of early diagenesis and the preservation potential of onshore tsunami deposits a re survey of isla mocha central chile 2 years after the february 27 2010 maule tsunami abstract the style of early diagenesis and preservation of onshore tsunami deposits are poorly constrained only tsunami surveys and subsequent re surveys can fill this information gap here we present the results of a first re survey in 2012 on isla mocha following the original survey in 2010 in the wake of the february 27 2010 maule earthquake and tsunami in central chile as a result of this tsunami a large number of boulders consisting of clay rich fine sandstones representing the miocene age bedrock of the island had been transferred from the tidal to shallow subtidal zone onto the coastal plain coarse clastic sediment mixtures of pebbles granules and sand entrained at coastal plain terraces and transported up to the maximum runup position c 600 m from the coast by the inflow had been left behind as extensive backflow blankets on the lower coastal plain in 2012 vegetation had covered the 2010 tsunami deposits sediment beyond 200 m from the coast had been removed by a combination of surface processes and grazing cattle grain size distributions of the preserved sediment show an increase of the sand fraction at the expense of the coarser grain sizes boulders show patterns resembling mud cracks on the surface and evidence of disintegration into smaller fragments and sand veneers of dried algae documenting the derivation of the boulders from the tidal zones had flaked off partly or completely from most rock surfaces at the northern wind facing coast of the island a c 130 m long and 1 2 m high beach ridge had accumulated most likely from reworked tsunami sediment boulders deposited by tsunamis are commonly assigned a high preservation potential we demonstrate for the first time that such boulders may in fact disintegrate rapidly and disappear from the record over short geological time scales given a lithology susceptible to weathering the degree of modification to the lsla mocha tsunami boulders and deposits strongly questions the applicability of inverse models using paleotsunami deposit thickness and grain size distributions to infer parameters and magnitudes of the causative tsunamis inverse models would consequently underestimate tsunami flow parameters and may result in the inference of erroneous transport modes and event magnitudes our study gives strong evidence in support of re survey studies following the deposition of tsunami sediments by tracing and quantifying the changes affecting them

preservation potential of tsunami deposits on arid siliciclastic coasts abstract numerous post tsunami surveys have been conducted in the last two decades especially since the 2004 indian ocean tsunami these studies have documented a variety of characteristic sedimentary and erosional features that can be ascribed to known events nevertheless the question arises whether these structures are just ephemeral or have a potential to be preserved in the geological record this review describes the changes that have affected muddy to sandy siliciclastic tsunami deposits in peru each of these was surveyed in the first months after the tsunami chimbote 1996 camana 2001 and pisco paracas 2007 here we describe the changes we observed during re surveys in 2007 and 2008 it has long been recognized that onshore tsunami deposits may suffer from surficial processes tectonic movements and anthropogenic alteration earthquake induced uplift or subsidence may subject a tsunami deposit to erosion or burial respectively quick burial in rapidly subsiding coastal areas may enhance preservation deposits of the last or most landward reaching wave may be preferentially preserved if they escape erosion by subsequent tsunami waves however inland areas are also vulnerable to subaerial reworking including by wind and by humans the peruvian examples reviewed here show that the preservation of arid coast tsunami deposits depends on interactions that are more complex that hitherto perceived these involve sediment type grain size depositional setting co seismic movement bioturbation winds and anthropogenic modification in one example all traces of the tsunami have been removed or reworked by flash floods and ocean waves in another example clasts on a coastal plain from tsunami backwash began to be rounded and abraded by eolian sands immediately after the event eolian processes also smoothed and filled tsunami scours by contrast muddy tsunami deposits in certain areas escaped erosion by wind probably because of their greater cohesion in still another example 0 5 m of co seismic uplift was not enough to prevent ocean waves from removing a tsunami sand sheet that had mantled a coastal marsh the buried record of tsunami deposits on modern coasts may therefore not fully represent the vulnerability of these regions to tsunamigenic hazards

geomorphological effects of tsunami run up and backwash abstract geomorphological processes associated with tsunami run up and backwash are highly complex to date most studies have considered the sedimentology of palaeo tsunamis while almost no detailed studies have been undertaken in areas known to have been affected by tsunamis in recent times research on contemporary tsunamis show that coastal landscapes may be greatly altered not only by direct tsunami run up orthogonal to the shoreline but also by episodes of vigorous backwash and by water flow sub parallel to the coastline the combined effect of these processes produces hitherto unrecognised coastal landforms that are dominated by the effects of high magnitude erosion and deposition deposition of large boulders is also associated with severe tsunamis while in adjacent areas run up processes often result in the deposition of continuous and discontinuous sediment sheets in many instances the upper limit of sediment deposition lies well below the upper limit of wave run up which is frequently marked by a well defined zone of stripped vegetation and soil the processes described have considerable implications for models of coastal evolution it may even be the case that the evolution of particular stretches of coastline are dominated by such high magnitude low frequency events

synthesis of wood anderson seismograms from broadband digital records abstract wood anderson torsion seismograms are synthesized by convolution with cosited broadband digital seismograph recordings and compared with the photographically recorded wood anderson seismograms at berkeley and mt hamilton the objective is to use routinely the synthesized seismograms to determine local magnitude comparison of local magnitude values calculated from both synthesized and photographic seismograms shows that the variation in local magnitude between the two types of seismograms is less than the variation among the photographic seismograms consequently broadband digital recordings can provide reliable local magnitude estimates without introducing significant bias it is shown that the static magnification of standard t s 0 8 sec wood anderson torsion seismographs determined from measurement of the free period and tilt sensitivity is 2080 60 and not 2800 as often reported this discrepancy is due to the erroneous assumption that the taught wire suspension in a wood anderson seismograph does not distort significantly thus leading to an incorrect estimate of the radius of gyration and consequently to a theoretical geometrical magnification of 2800

fracturing of the panamanian isthmus during initial collision with south america tectonic collision between south america and panama began at 23 25 ma the collision is significant because it ultimately led to development of the panamanian isthmus which in turn had wide ranging oceanic climatic biologic and tectonic implications within the panama canal zone volcanic activity transitioned from hydrous mantle wedge derived arc magmatism to localized extensional arc magmatism at 24 ma and overall marks a permanent change in arc evolution we interpret the arc geochemical change to result from fracturing of the panama block during initial collision with south america fracturing of the panama block led to localized crustal extension normal faulting sedimentary basin formation and extensional magmatism in the canal basin and bocas del toro synchronous with this change both panama and inboard south america experienced a broad episode of exhumation indicated by u th he and fission track thermochronology coupled with changing geographic patterns of sedimentary deposition in the colombian eastern cordillera and llanos basin such observations allow for construction of a new tectonic model of the south america panama collision northern andes uplift and panama orocline formation finally synchroneity of panama arc chemical changes and linked uplift indicates that onset of collision and isthmus formation began earlier than commonly assumed

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

geothermal systems on the island of java indonesia abstract this paper presents an overview of the geothermal systems on the island of bali indonesia physicochemical data of hot springs and shallow geothermal wells were collected from four geothermal locations penebel batur banjar and banyuwedang the concentrations for the three main anions varied significantly indicating a different geothermal history the values for cl ranged from 0 1 to 1000 mg l for hco3 from 20 to 2200 mg l and for so42 from 0 1 to 500 mg l although the island of bali is underlain by carbonate rocks a carbonate host rock for the geothermal reservoirs could not be confirmed because the ca2 mg2 hco3 molar ratios were approximately 0 4 well below 1 0 and the k mg ratios were approaching those of a calc alkaline rock reservoir the hco3 of the thermal waters correlated with ca2 mg2 sr2 and k indicating water rock interaction in the presence of carbonic acid phase separation was inferred for the bedugul and banjar geothermal systems because of relatively high b cl ratios boron isotopes were determined for selected samples with values ranging from 11b of 1 3 to 22 5 nbs 951 the heavy 11b of 22 5 together with a low b cl ratio indicated seawater input in the banyuwedang geothermal system the hydrogen and oxygen isotopic composition of the thermal water plotted along the global meteoric water line gmwl and close to the mean annual value for precipitation in jakarta indicating a meteoric origin of the geothermal water comparison of the si na k na k ca and na li geothermometers with actual reservoir temperature measurements and physicochemical considerations led to the conclusion that the na li thermometer provided most reliable results for the determination of geothermal reservoir temperatures on bali using this thermometer the following reservoir temperatures were calculated 1 penebel bedugul from 235 to 254 c 2 batur 240 c and 3 banjar 255 c due to seawater input this thermometer could not be applied to the banyuwedang geothermal system there application of a sio2 thermometer indicated a reservoir temperature below 100 c

the first ml scale for north of vietnam abstract the first local magnitude scale ml for northern vietnam has been derived using a portable broadband seismic network in northern vietnam as part of the cooperation between the vietnam institute of geophysics and the institute of earth sciences at academia sinica taiwan the composite horizontal peak amplitude data used in this study is comprised a total of 202 amplitude records from 14 broadband stations which measure 36 shallow earthquakes with focal depths less than 36 km occurred in and around north western vietnam during 01 2006 10 2007 the new distance correction function obtained in this study is log a 0 1 74 log r 0 00048 r 0 522 where a0 and r are the empirically determined distance correction and hypocentral distance respectively this distance correction relation for northern vietnam is quite similar to one for southern california implying relative efficient attenuation with distances the correlation between the new ml and duration magnitudes md which is still being used for making the official earthquake bulletin in vietnam is expressed as m l 0 955 m d 0 17

magmatic evolution at batur volcanic field bali indonesia petrological evidence for polybaric fractional crystallization and implications for caldera forming eruptions abstract batur volcanic field bvf in bali indonesia underwent a complex evolution that comprised three periods of building and two major caldera forming eruptions the magmas erupted show a broad range of compositions from basaltic to rhyolitic 50 71 wt sio2 and variable phenocryst assemblages based on their mineralogy and geochemistry these magmas may be assigned to four distinct suites 1 plagioclase olivine suite that comprises basalts only 2 plagioclase orthopyroxene clinopyroxene amphibole suite that includes andesites 3 plagioclase clinopyroxene orthopyroxene suite that consists of basalts to andesites and 4 plagioclase olivine clinopyroxene suite with basaltic andesite to dacite magmas modelling indicates that the compositional variations within the various suites were produced by fractional crystallization of observed phenocryst assemblages it also suggests that the four suites were produced by fractionation from basaltic parental magmas with similar major element compositions incompatible trace element ratios however indicate that there were significant differences in trace element contents between the parental melts likely to reflect variable degrees of depletion of a morb like mantle wedge and variable degrees of metasomatism by a slab derived component enriched in large ion lithophile elements lile and light rare earth elements lree additional variations in h2o 1 3 wt within the parental melts are necessary to account for the range of phenocryst assemblages that produced the four suites initial variations in h2o content combined with variable pressure of crystallization possibly

the stable isotope geochemistry of volcanic lakes with examples from indonesia abstract stable isotope compositions d 18o and 34s of volcanic lake waters gas condensates and spring waters from indonesia italy japan and russia were measured the spring fluids and gas samples plot in a broad array between meteoric waters and local high temperature volcanic gas compositions the d and 18o data from volcanic lakes in east indonesia plot in a concave band ranging from local meteoric waters to evaporated fluids to waters heavier than local high temperature volcanic gases we investigated isotopic fractionation processes in volcanic lakes at elevated temperatures with simultaneous mixing of meteoric waters and volcanic gases an elevated lake water temperature gives enhanced kinetic isotope fractionation and changes in equilibrium fractionation factors providing relatively flat isotope evolution curves in 18o d diagrams a numerical simulation model is used to derive the timescales of isotopic evolution of crater lakes as a function of atmospheric parameters lake water temperature and fluxes of meteoric water volcanic gas input evaporation and seepage losses the same model is used to derive the flux magnitude of the keli mutu lakes in indonesia the calculated volcanic gas fluxes are of the same order as those derived from energy budget models or direct gas flux measurements in open craters several 100 m3 volcanic water day and indicate a water residence time of 1 2 decades the 34s data from the keli mutu lakes show a much wider range than those from gases and springs which is probably related to the precipitation of sulfur in these acid brine lakes the isotopic mass balance and s cl values suggest that about half of the sulfur input in the hottest keli mutu lake is converted into native sulfur

thermal modeling of the southern alps new zealand finite element modeling of the thermal regime across the southern alps of new zealand has been carried out along two profiles situated near the franz josef and haast valleys the modeling involves viscous deformation beneath the southern alps including both uplift and erosion and crustal lithospheric thickening as a result of crustal shortening extending to 20 mm y of a 25 km thick crust published uplift rates and crustal thickness variations along the two profiles are used to constrain the modeled advection of crustal material and results are compared with the recent heat flow determinations 190 50 mw m2 in the franz josef valley and 90 25 mw m2 in the haast valley comparisons of the model with published k ar and fission track ages show that the observed heat flow in the franz josef valley is consistent with observed zircon fission track ages of around 1 ma if the present day uplift rate is close to 10 mm y major thermal differences between the franz josef and haast profiles appear to be due to different uplift and erosion rates there is weak evidence that frictional heating close to the alpine fault zone is not significant the modeling provides explanations for the distribution of seismicity beneath the southern alps and predicts a low surface heat flow over the eastern foothills due to the dominant thermal effect of crustal thickening beneath this region predicted temperatures at mid crustal depth beneath the zone of maximum uplift rate are 50 100 c cooler than those indicated in previously published models which implies that thermal weakening of the crust may not be the main factor causing the aseismicity of the central southern alps the results of the modeling demonstrate that the different types of reset age data in the region within 25 km of the alpine fault are critical for constraining models of the deformation and the thermal regime beneath the southern alps

process based modeling of tsunami inundation and sediment transport 1 the infrequent and unpredictable nature of tsunamis precludes the use of field experiments to measure the hydrodynamic and sediment transport processes that occur instead these processes are often approximated from laboratory numerical and theoretical studies or inferred from observations of the resultant sediment deposits here delft3d a three dimensional numerical model is used to simulate the inundation and sediment transport of a tsunami similar in magnitude to the 26 december 2004 indian ocean tsunami over one measured and three idealized morphologies the model is first shown to match well the observations taken at kuala meurisi sumatra and then used to examine in detail the processes that occur during the tsunami the model predicts that at a given cross shore location the onshore flow accelerates rapidly to a maximum as the wavefront passes and then gradually decelerates before reversing direction and flowing offshore the onshore flow does not tend to zero everywhere at maximum inundation but instead flow reversal occurs near the shoreline even as the wavefront continues to inundate landward while some sediment is eroded by the passing wavefront the suspension of sandy sediment is dominated by the long duration high velocity backwash that occurs along the beach face and offshore of the shoreline some of the sediment suspended during backwash is advected shoreward by the subsequent wave creating large spatial gradients in the suspended sediment concentrations which may not be in equilibrium with the local hydrodynamics the inundation and transport of sediment during a tsunami can be affected by complexities in the morphological profile and interactions between multiple waves and many of the hydrodynamic and sediment transport processes predicted here are similar to analogous processes previously observed in the swash zone

attenuation of coda waves at the tres virgenes volcanic area baja california sur mexico we estimated the coda wave attenuation quality factor q c at the tres virgenes volcanic area from 26 local seismic events recorded by a portable network of seven digital stations the quality factor q c was estimated using the single scattering attenuation model of sato 1977 in the frequency range from 6 to 24 hz the magnitudes of the analyzed events range from 1 to 3 these events occurred at hypocentral depths ranging from 3 to 6 km and were recorded at epicentral distances of up to 30 km within the variation of q c six out of seven stations analyzed showed quite similar values at all frequencies data from these six stations led to an average q c given by q c f 50 3 f 0 65 0 20 in the indicated frequency range for the seventh station which is located near a steam production well anomalous low q c values were obtained for this particular site we found q c f 4 3 0 6 f 1 33 0 05 in this zone we observed an abnormally strong reduction of q c leading to attenuation values that are three to four times larger than for the whole area of study results from other geophysical studies suggest the presence of a highly conductive body below this particular area a correlation of the observed coda attenuation with a geothermal anomaly is suggested manuscript received 27 february 2000

coastal changes in the sendai area from the impact of the 2011 tōhoku oki tsunami interpretations of time series satellite images helicopter borne video footage and field observations a combination of time series satellite imagery helicopter borne video footage and field observation is used to identify the impact of a major tsunami on a low lying coastal zone located in eastern japan a comparison is made between the coast protected by armoured engineered sea walls and the coast without changes are mapped from before and after imagery and sedimentary processes identified from the video footage the results are validated by field observations the impact along a natural coast with minimal defences is erosion focussed on the back beach along coasts with hard engineered protection constructed to defend against erosion the presence of three to six metre high concrete faced embankments results in severe erosion on their landward faces the erosion is due to the tsunami wave accelerating through a hydraulic jump as it passes over the embankment resulting in the formation of a ditch into which the foundations collapse engineered coastal defences are thus found to be small defence against highly energetic tsunami waves that overtop them there is little erosion or sedimentation of the whole beach and where active it mainly forms v shaped channels these channels are probably initiated during tsunami inflow and then further developed during tsunami backflow tsunami backflow on such a low lying area takes place energetically as sheet flow immediately after tsunami flooding has ceased subsequently when the water level landward of the coastal dune ridges falls below their elevation flow becomes confined to rivers and breaches in the coast formed during tsunami inflow enigmatic short lived strand lines are attributed to the slow fall of sea level after such a major tsunami immediately after the tsunami coastal reconstruction begins sourced from the sediment recently flushed into the sea by tsunami backflow

lg coda q variations across south america and their relation to crustal evolution nine broadband seismograph stations in south america have provided 389 recordings of lg coda with paths that cover most of the continent lg coda q q0v and frequency dependence values at 1 hz obtained from these records were inverted using back projection tomography to obtain regionalized maps of q0 and the entire western margin of the continent the active andean mountain belt is typified by low q0 250 450 whereas broad regions of high q0 700 1100 span the central brazilian shield and contiguous regions to the north and south intermediate q0 450 700 characterizes the northern patagonia platform and most of the atlantic shield reduced q0 in the atlantic shield may be related to tectonic or igneous activity that occurred during the breakup of gondwanaland during the jurassic period this q distribution is generally consistent with earlier studies where q0 was found to be directly proportional to the time that has elapsed since the most recent episode of major tectonic or orogenic activity in any region reduced q0 in the patagonian platform may however be due to young sediments there

how did the ad 1755 tsunami impact on sand barriers across the southern coast of portugal idl pest oe cte la0019 2013 plani2c ed481b 2014 132 0 post doc eu fp7 research project risc kit ga 2013 603458 e fct investigator program ref if 01047 2014

geochemistry mineralogy and chemical modeling of the acid crater lake of kawah ijen volcano indonesia the kawah ijen volcano with a record of phreatic eruptions has its 1000 m wide crater filled with a lake that has existed for at least one century at present the lake waters are hot t 37 c strongly mineralized tds 105 g l and extremely acidic ph 0 4 by its volume the javanese lake is probably the largest accumulation in the world of such acidic waters mineralogy of the suspended solids within the lake waters suggests that concentrations of si ca ti and ba are controlled by precipitation of silica gypsum anatase and barite lake sediment is composed of chemical precipitates with composition similar to the suspended solids thermodynamic calculations predict that the lake waters have reached equilibrium with respect to cristobalite barite gypsum anglesite celestite and amorphous silica in agreement with the analytical observations significant concentrations of ferric iron suggest that the current lake waters are fairly oxidized sulfides are absent in the water column but are always present in the native s spherules that form porous aggregates which float on the lake the presence of native s provides direct evidence of more reduced conditions at the lake floor where h 2 s is probably being injected into the lake with progressive addition of h 2 s to the acid waters native s pyrite and enargite are theoretically predicted to be saturated reactions between upward streaming h 2 s bearing gases discharged by subaqueous fumaroles and metals dissolved in the acidic waters could initiate precipitation of these sulfides a model of direct absorption of hot magmatic gases into cool water accounts for the extreme acidity of the crater lake results show that strongly acidic sulfate rich solutions are formed under oxidizing conditions at high gas water ratios reactions between the acidic fluids and the ijen andesite were modeled to account for elevated cation concentrations in lake water current concentrations of conservative rockforming elements are produced by dissolution of approximately 60 g of andesite per kg of acid solution complete neutralization of the acid lake waters by reaction with the wallrock produces a theoretical alteration assemblage equivalent to that observed in volcano hosted acid sulfate epithermal ore deposits

coda q in the eastern caribbean west indies summary coda q q has been estimated from seismograms of local earthquakes recorded on short period seismographs on some of the eastern caribbean islands of the lesser antilles arc west indies using the s s single scattering model the region was subdivided into four distinct subregions in order to investigate lateral variations in q the qc values exhibit a strong frequency dependence in the frequency band 1 5 to 16 hz with calculated coda q at 1 hz qo ranging from a minimum of 97 in the dominica area to a maximum of 145 in the leewards the degree of frequency dependence is also largest in the dominica area n 1 09 and smallest in the leewards n 0 82 although there appears to be some lateral and depth variation of both q and n in the region this variation does not seem to be very significant

processes controlling the distribution of boron and chlorine in natural waters in iceland abstract the concentrations of b and cl in natural waters in iceland lie in the range 0 001 10 and 1 20 000 ppm respectively lowest concentrations occur in surface and groundwaters in the central highlands highest cl concentrations are found in high temperature waters on the reykjanes peninsula and highest b concentrations in well waters from high temperature geothermal systems in the axial zones of the active volcanic belts the b and cl contents of icelandic basalts are 0 1 6 6 and 75 750 ppm respectively these large variations are considered to result from variable degassing during consolidation as well as concentration variations in the initial magma tholeftes are lowest in both elements av 1 2 ppm b and 170 ppm ci transitional basalts intermediate av 2 1 ppm b and 240 ppm ci and alkali basalts highest av 3 8 ppm b and 340 ppm cl cl b ratios in tholeiites are most often within 25 50 but somewhat lower in alkali basalts most geothermal waters contain b and cl within 0 05 1 and 10 100 ppm respectively these rather low values are attributed to the low content of b and cl in the basaltic rock the b and cl distribution in the icelandic natural waters indicate that these elements act as essentially incompatible their sources of supply include 1 the atmosphere seawater spray and aerosols 2 the rock with which the water interacts 3 seawater groundwater and 4 magma intrusions in surface water and nonthermal groundwater the dominant source of supply of cl is seawater spray and aerosols but the soil and rock contribute often significantly to the b in these waters their cl b ratio is similar to that of seawater 1330 or somewhat lower boron and cl concentrations generally increase with water temperature warm waters cl b ratios intermediate between those of seawater and basalt with increasing temperature this ratio decreases and gradually approaches that of the rock some high temperature geothermal waters have as low cl b ratios as 1 and b concentrations as high as 10 ppm the cause is either b degassing of the magmatic intrusive heat source or phase separation in the producing aquifer some low temperature waters

the boron isotope systematics of icelandic geothermal waters 1 meteoric water charged systems we have measured the boron isotope composition and boron and chloride concentrations of 27 icelandic geothermal fluids from both high and low temperature systems the 11b values range from 6 7 in the krafla system to 25 0 in a warm spring from the southern lowlands in addition we have also determined the 11b values of basaltic glass from nesjavellir 5 3 1 4 and travertine from snaefellsnes 22 0 5 the b isotope and cl b systematics of the high temperature systems are dominated by the composition of the local basalts the lower temperature systems show evidence for mixing with b and cl of a marine origin together with some uptake of b into secondary mineral phases the data from the snaefellsnes geothermal system indicate that the fluids have undergone interaction with basalts that have undergone significant low temperature alteration by seawater

the effect of hydrate content on seismic attenuation a case study for mallik 2l 38 well data mackenzie delta canada 1 observations of velocities in sediments containing gas hydrates show that the strength of sediments increases with hydrate saturation hence it is expected that the attenuation of these sediments will decrease with increasing hydrate saturation however sonic log measurements in the mallik 2l 38 well and cross hole tomography measurements in the mallik field have shown that attenuation increases with hydrate saturation we studied a range of mechanisms by which increasing hydrate saturation could cause increased attenuation we found that a difference in permeability between the host sediment and the newly formed hydrate can produce the observed effect we modelled attenuation in terms of biot and squirt flow mechanisms in composite media we have used our model to predict observed attenuations in the mallik 2l 38 well mackenzie delta canada