a new automatic subsurface gas monitoring system for seismogeochemical studies installed in haruno borehole shizuoka prefecture central japan the results of subsurface gas monitoring by application of gas chromatography gc to the gas composition of bubbles associated with groundwater for seismogeochemical studies are reported an automated gas monitoring system was used to determine gas compositions in a 500 m borehole at the haruno crustal movement observation site hos central japan during period 1 from december 1999 to december 2000 the average two standard deviation 2sd compositions of gases in this period were he 82 29 ppmv h2 170 62 ppmv ar 0 05 0 07 n2 50 8 and ch4 45 6 a new automated gas monitoring system equipped with a micro gc was installed in the borehole at the hos and gas bubbles from the borehole were monitored during period 2 from december 2006 to march 2007 the average two standard deviation 2sd compositions of gases in this period were he 8 7 ppmv h2 13 15 ppmv ar 0 6 0 3 n2 66 7 and ch4 14 14 the gas concentration ratios he ar h2 ar n2 ar and ch4 ar fluctuated significantly over time and repeatedly showed abrupt spike like increases during period 2 the gas compositions obtained in period 1 and 2 were markedly different over the period from 2006 to 2007 the gas bubbles were depleted in he h2 and ch4 of deep origin but enriched in ar and n2 of atmospheric origin this difference can be interpreted as being due to an irreversible change of the aquifer gas system the present deep component in the hos gas is estimated to have composition he 63 ppmv h2 37 ppmv ar 0 17 n2 63 and ch4 37 the new monitoring system is able to analyze the gas composition using a smaller volume of sample gas and with greater precision than the previous system during the 3 month monitoring period 2 the separation capacity of the capillary column of the micro gc was sufficiently maintained to determine gas chromatographic peak areas for the five gaseous species examined this study confirms that the new monitoring system with micro gc is promising for continuous subsurface gas monitoring for earthquake prediction studies

mixing processes in modern estuarine sediments from the gulf of khambhat western india abstract sandy and muddy detritus from two distinctive end member provenance terrains basaltic and granitic are transported to the estuaries of the gulf of khambhat by fluvial discharge and opposing tidal currents making this embayment ideal for investigating the effects of mineralogical and geochemical mixing on sediment composition in estuarine depositional systems rivers flowing predominantly from the north over precambrian metasediments and granites supply a felsic plutoniclastic sand to the gulf whilst a mafic volcaniclastic sand sourced by deccan basalts is transported by rivers draining the western ghats and from the local coastal erosion in the southern part of the gulf sediments from the tapti estuary are rich in basaltic rock fragments 50 and are characterised by a distinctly basaltic source composition la sc 0 25 0 86 th sc 0 12 0 40 cr th 13 121 eu eu 0 93 1 68 and lree hree 2 96 6 57 by contrast the sediments of the sabarmati inner estuary are rich in quartz grains 80 as evident from the major and trace element compositions la sc 1 38 6 63 th sc 0 58 2 98 cr th 0 58 19 39 eu eu 0 46 0 86 and lree hree 2 90 11 40 the detrital compositions of the remaining major estuaries the narmada dhadhar and mahi scatter across a broad range in a qfr diagram and contain varying amounts of quartz feldspar and rock fragments in the narmada estuary the mixed signature characterised by ree values including eu eu 0 42 2 28 and lree hree 4 37 14 80 is caused by the presence of diverse rock types that crop out in the source area in the mahi estuary which largely flows across felsic source terrains the compositional signature is controlled by mixing of felsic detritus from riverine input with mafic sediments from seaward side in the estuary the two end member detrital compositions plutoniclastic and volcaniclastic are mixed in the macro tidal estuaries mixing of sediment takes place where fluvial currents and tidal flows interact and the proportion of mixing varies systematically from outer to central to inner estuary a high degree of mixing of felsic sediments with deccan basalt derived sediments takes place in the outer estuary resulting in felsic mafic ratios of 40 60 sediments in the central estuaries 65 35 and in the fluvial dominated inner estuaries 90 10 are characterised by moderate to minor degrees of mixing the mixing in estuaries is systematic and is reflected in both the mineralogy and geochemistry of the sediments provenances of ancient estuarine successions should therefore be interpreted with great care incorporating awareness of the mixing processes which influence sediment compositions to different degrees in estuaries especially those characterised by strong tidal currents

delineating alteration footprints from field and aster swir spectra geochemistry and gamma ray spectrometry above regolith covered base metal deposits an example from abra western australia

seismic scale saturation relations in turbidite reservoirs undergoing waterflood estimates of the effective fluid modulus from seismic cannot be directly converted to the true pore volume weighted mean saturation s w determined from fluid flow principles by using the saturation laws currently in use one of the reasons is that seismic waves sample the reservoir geology and production induced saturation heterogeneity in a different way from the fluids this mismatch prevents accurate quantitative evaluation of saturation changes from 4d seismic analysis to tackle this problem a reservoir related saturation law is developed for a turbidite reservoir this geology being chosen because the architecture for a single sand package can be modelled as a stack of horizontal beds an effective medium and perturbation theory are applied to the determination of the seismic properties of this model this calculation provides a relationship that connects the true saturation s w to the effective fluid modulus from seismic via statistical measures of the vertical spread of the porosity and saturation variations in the reservoir these statistics can be extracted from the simulation model and if known enable the new saturation law to deliver a significant improvement in accuracy when estimating s w compared to other well known laws the relationship that has been developed also captures the effect of inter bedded shales and can therefore be used to estimate true saturation in regions of the reservoir with moderate to low net to gross provided the fraction of the shale component is known in practice the final choice of saturation law depends upon the reservoir information available the assumptions that can be tolerated and the accuracy required in any particular reservoir characterization study

frequency dependence of the groundwater discharge at an artesian well as recognized from tidal fluctuation records groundwater discharge temperature and electrical conductivity of an artesian well were measured at nishiawakura okayama prefecture southwest japan the discharge ranged from 2 10 4 to 5 10 4 m3 s and showed tidal fluctuations of about 5 10 5 m3 s induced by strain although the groundwater temperature reflected the same tidal fluctuations as the discharge the electrical conductivity did not manifest tidal fluctuations the discharge slightly leads the theoretical tidal strain and its response to the strain of the diurnal constituents is different from that of the semidiurnal constituents the discharge fluctuations induced by atmospheric loading also have some frequency dependence these can be explained by the vertical or horizontal groundwater flow leakage from the aquifer which has been used in the explanation of the well water level fluctuations induced by tidal strain and atmospheric loading

mudstone petrology of the mesoproterozoic unkar group grand canyon u s a provenance weathering and sediment transport on intracratonic rodinia abstract the synthesis of mudstone petrology and interbedded sandstone detrital zircon geochronology provides insights into the provenance weathering regime hydrodynamic effects and diagenesis of the mesoproterozoic unkar group unkar mudstones were derived largely from the grenville orogen go of southwest texas and the adjacent yavapai mazatzal ym and southern granite rhyolite sgr terranes detrital zircon data indicate distinct pulses of go derived sediment during hakatai and dox formation deposition whereas shinumo sediment contains a larger component of ym and sgr material an increase in plagioclase and biotite abundances in the dox further suggest an orogenic pulse bulk chemistry including elevated cr and ni abundances and ree systematics implicate a heterogeneous provenance for unkar sediment best approximated by a mix of granite or granodiorite with some basalt weathering of unkar sediment as determined from mudstone and crystalline source bulk chemical trends is characterized as moderate cia values between 55 and 70 indicative of a temperate climate in an orogenic setting small less than 10 wt amounts of detrital kaolinite and chlorite are consistent with a moderate temperate weathering regime illite the dominant clay mineral in the unkar group is largely the 2m1 polytype and detrital in origin however it is estimated that 7 of the k in the escalante creek member results from k metasomatism and may form up to 15 wt authigenic 1m or 1md illite the clay size fraction and zircon are the chief contributors to the ree budget in unkar mudstones lithostratigraphic variations in the hree distributions can be attributed partially to variable zircon abundance in the silt size fraction a likely function of hydrodynamic sorting age constraints on the duration of unkar group sedimentation range from 30 to 100 my for the 1100 m conformable shinumo dox succession and result in compacted sedimentation rates of between 1 0 and 3 6 cm 103 yr these rates are comparable to mesozoic foreland basin settings

linear poroelasticity of groundwater levels from observational records at wells in hokkaido japan abstract the natural fluctuation of groundwater level depends not only on the stress applied to an aquifer but also on the type of rock that comprises it poroelastic parameters such as strain sensitivity loading efficiency and poroelastic bulk moduli are used to analyze the hydrologic attributes of aquifers in this study we use records of groundwater levels from 19 wells to calculate coefficients of poroelastic characteristics the records allow a comprehensive description of how groundwater levels vary with fluctuations of volumetric strain in the crust s interior we estimate strain sensitivities in two ways a using the wells response to tidal strain and b using coseismic changes in groundwater level based on historical data the strain sensitivities estimated by the two different methods have good linear correlation we also estimate loading efficiency using observational records and calculate bulk moduli from the loading efficiencies and strain sensitivities the bulk moduli obtained in this manner are roughly consistent with laboratory values

the composition and evolution of the continental crust rare earth element evidence from sedimentary rocks the composition of the present day upper crust inferred from the uniformity of sedimentary rock r e e rare earth element patterns is close to that of granodiorite a revised andesite model is used to obtain total crustal composition the lower crust is the composition remaining assuming that the upper crust one third of the total is derived from intracrustal partial melting the upper crustal r e e pattern has pronounced eu depletion eu eu 0 64 the lower crustal pattern has eu enrichment eu eu 1 17 and the total crust has no eu anomaly relative to chondritic abundances the eu depletion in the upper crust is attributed to retention of eu in plagioclase in the lower crust because plagioclase is not stable below 40 km 10 kbar the anomaly is intracrustal in origin the archaean upper crust has a different r e e pattern to that of the present day upper crust being lower in total r e e and la yb ratios and lacking an eu anomaly these data are used to infer the archaean upper crustal composition which resembles that of the present day total crust except that ni and cr contents are higher the archaean crustal composition can be modelled by a mixture of tholeiites and tonalite trondhjemites the latter have steep light r e e enriched heavy r e e depleted patterns consistent with equilibration with garnet and hence probable mantle derivation there is little reason to suppose that the archaean lower crust was different in composition from the upper crust except locally where partial melting episodes occurred the r e e evidence is consistent with isotopic and geological evidence for a low continental growth rate in the early archaean a massive increase to about 70 of the total crust between about 3000 and 2500 ma b p and a slow increase until the present day the change from archaean to post archaean r e e patterns in the upper crust is not isochronous but is reflected in the sedimentary rock r e e patterns at differing times in different continents on the basis of a model composition for the mantle 36 of the potassium 30 of uranium 15 of lanthanum and 3 of ytterbium are concentrated in the present continental crust this enrichment is related to ionic size and valency differences from common mantle cations e g mg fe pre 3 9 ga b p crusts were obliterated by meteorite bombardment no geochemical evidence exists for primordial anorthositic sialic or mafic crusts

volcanic components in pelitic sediments the origin of the clay minerals present in pelitic sediments has been widely debated weaver1 suggests that illite and interstratified illite smectite i s dominate the association of illite with marine sediments2 and the proposal3 4 that illite forms from smectite an expandable clay mineral sometimes referred to as montmorillonite in the marine environment has also been discussed weaver5 argues for a continental origin of illite produced by weathering of k feldspar others6 9 have shown that smectite and i s 20 50 illite are converted to i s of higher illite content 60 80 in pelitic sediments by low grade metamorphism per cent illite will always refer to the per cent illite in i s the designation should not be confused with the content of discrete illite or mica commonly present in these sediments here we present clay mineral and k ar data for cretaceous marine shales from the western interior of north america demonstrating a volcanic origin for much of these sediments this observation is correlated with eustatic sea level rise increased volcanic activity sedimentary preservation of organic matter and incorporated into a petrogenetic tectonic model for pelitic sediments

chemical weathering of a marine terrace chronosequence santa cruz california i interpreting rates and controls based on soil concentration depth profiles abstract the spatial and temporal changes in element and mineral concentrations in regolith profiles in a chronosequence developed on marine terraces along coastal california are interpreted in terms of chemical weathering rates and processes in regoliths up to 15 m deep and 226 kyrs old quartz normalized mass transfer coefficients indicate non stoichiometric preferential release of sr ca na from plagioclase along with lesser amounts of k rb and ba derived from k feldspar smectite weathering results in the loss of mg and concurrent incorporation of al and fe into secondary kaolinite and fe oxides in shallow argillic horizons elemental losses from weathering of the santa cruz terraces fall within the range of those for other marine terraces along the pacific coast of north america residual amounts of plagioclase and k feldspar decrease with terrace depth and increasing age the gradient of the weathering profile bs is defined by the ratio of the weathering rate r to the velocity at which the profile penetrates into the protolith a spreadsheet calculator further refines profile geometries demonstrating that the non linear regions at low residual feldspar concentrations at shallow depth are dominated by exponential changes in mineral surface to volume ratios and at high residual feldspar concentrations at greater depth by the approach to thermodynamic saturation these parameters are of secondary importance to the fluid flux qh which in thermodynamically saturated pore water controls the weathering velocity and mineral losses from the profiles long term fluid fluxes required to reproduce the feldspar weathering profiles are in agreement with contemporary values based on solute cl balances qh 0 025 0 17 m yr 1 during saturation controlled and solute limited weathering the greater loss of plagioclase relative to k feldspar is dependent on the large difference in their respective solubilities instead of the small difference between their respective reaction kinetics the steady state weathering rate under such conditions is defined as r q h m sol m total 1 s v b s the product of qh and the ratio of solubilized to solid state feldspar msat mtotal define the weathering velocity the weathering gradient bs reflects the kinetic rate of reaction where sv is the volumetric surface area of the residual feldspar both this rate expression and the spreadsheet calculations produce similar plagioclase weathering rates r 5 14 10 16 mol m 2 s 1 which agree with those reported for other environments of comparable climate and age weathering dependent concentration profiles are commonly described in literature the present paper provides methods by which these data can yield a more fundamental understanding of the weathering processes involved

chemical overprinting of magmatism by weathering a practical method for evaluating the degree of chemical weathering of granitoids abstract quantitative determination of the degree of chemical weathering of rocks is a fundamental task in environmental and engineering geology and many weathering indices based on whole rock chemistry have been proposed however most classical indices are of limited application to granitoids in a wide area because these lithotypes generally exhibit wide chemical variation arising from their petrogenesis the chemical evolution produced during rock weathering therefore overprints pre existing magmatic chemical variation this problem can cause many classical weathering indices to yield misleading results this study proposes a method that compensates for the influence of petrogenesis on calculation of the weathering index the method is based on a bivariate plot of the magmatic chemical variation mcv in granitoids and the degree of chemical weathering dcw the mcv axis must be based on an element that reflects magmatic processes and is also relatively immobile during rock weathering in this study tio 2 contents are utilized for the mcv the dcw axis is fundamentally defined by the ratios of more mobile to less mobile elements during weathering and hence many classical indices can be applied the improved value of the degree of chemical weathering dcw i for a weathered rock is derived by dcw i s mcv cv mcv 1 dcw 1 where mcv 1 is the measured composition e g tio 2 content of the weathered rock dcw 1 denotes the ratios of more mobile to less mobile elements of the weathered rock the s parameter is the slope of the least square linear regression for fresh granitoids in the mcv dcw relationship mcv cv is a correction factor which is given by the average point on the mcv axis e g average tio 2 of the fresh rocks this method is useful for evaluating the degree of weathering of various granitoids and enhances the practical application of many weathering indices

submarine hot springs and the origin of life the discovery of hydrothermal vents at oceanic ridge crests and the appreciation of their importance in the element balance of the oceans is one of the main recent advances in marine geochemistry1 it is likely that vents were present in the oceans of the primitive earth because the process of hydrothermal circulation probably began early in the earth s history2 here we examine the popular hypothesis3 7 that life arose in these vents this proposal however is based on a number of misunderstandings concerning the organic chemistry involved an example is the suggestion that organic compounds were destroyed on the surface of the early earth by the impact of asteroids and comets but at the same time assuming that organic syntheses can occur in hydrothermal vents7 the high temperatures in the vents would not allow synthesis of organic compounds but would decompose them unless the exposure time at vent temperatures was short8 11 even if the essential organic molecules were available in the hot hydrothermal waters the subsequent steps of polymerization and the conversion of these polymers into the first organisms would not occur as the vent waters were quenched to the colder temperatures of the primitive oceans

precursory and coseismic groundwater temperature perturbation an example from taiwan abstract we have conducted taiwan s first groundwater temperature earthquake precursory and coseismic signal study using totally 8 month time series of groundwater temperature from two monitoring wells in eastern taiwan we applied hilbert huang transform hht analysis to identify possible precursory signals with periods ranging from one to ten minutes and duration of tens of hours that occurred one to three days before mw 4 7 earthquakes these signals are not correlated with atmospheric and pumping processes the precursors are sensitive to an earthquake within an epicentral distance that is about 20 to 25 time of the earthquake rupture length with this limited dataset we found the rates of false positives and false negatives are 16 7 and 28 6 respectively exact physical processes that generate such signals are unclear and additional data are needed but we propose that real time groundwater temperature monitoring has potentials to become a low cost but beneficial way to complement other earthquake precursory projects for more robust short term earthquake forecasting

geochemistry of archean shales from the pilbara supergroup western australia archean clastic sedimentary rocks are well exposed in the pilbara block of western australia shales from turbidites in the gorge creek group ca 3 4 ae and shales from the whim creek group ca 2 7 ae have been examined the gorge creek group samples characterized by muscovite quartzchlorite mineralogy are enriched in incompatible elements k th u lree by factors of about two when compared to younger archean shales from the yilgarn block alkali and alkaline earth elements are depleted in a systematic fashion according to size when compared with an estimate of archean upper crust abundances this depletion is less notable in the whim creek group such a pattern indicates the source of these rocks underwent a rather severe episode of weathering the gorge creek group also has fairly high b content 85 29 ppm which may indicate normal marine conditions during deposition rare earth element ree patterns for the pilbara samples are characterized by light ree enrichment lanybn 7 5 and no or very slight eu depletion eueu 0 82 0 99 a source comprised of about 80 felsic igneous rocks without large negative eu anomalies felsic volcanics tonalites trondhjemites and 20 mafic ultramafic volcanics is indicated by the trace element data very high abundances of cr and ni cannot be explained by any reasonable provenance model and a secondary enrichment process is called for

metasaprolite in the mcgrath gneiss minnesota usa viewing paleoproterozoic weathering through a veil of metamorphism and metasomatism abstract a 2100 ma 420 cm thick metasaprolite which is devoid of plagioclase but contains abundant microcline occurs in the archean mcgrath gneiss beneath the overlying paleoproterozoic denham formation despite being recrystallized under amphibolite facies conditions and chemically modified by potassium metasomatism mass fluxes related to weathering and metasomatism of the mcgrath metasaprolite can be estimated by judicious application of several geochemical parameters and the a c n k plot fedo et al 1995 the metasaprolite yields values of 67 94 for the plagioclase index of alteration 62 72 for the chemical index of alteration and 47 for the feldspar index of weathering and the total mass flux removed by weathering is a minimum of 2 4 moles cm 2 such values correspond to an intermediate degree or intensity of weathering compared to other more intensely weathered paleosols in the region such as those beneath the baraboo and sioux quartzites potassium metasomatism occurred at 1742 ma during the geon 17 yavapai tectonothermal event when a minimum of 0 33 moles cm 2 k 2 o was added to the metasaprolite although the absence of pedogenic textures precludes interpretation of climatic conditions during weathering of the mcgrath gneiss the level of atmospheric p co 2 can be estimated by application of sheldon s 2006 method which yields a minimum of 3 7 pal for a weathering duration of 100 000 years

scale effects on modelling the seismic signature of gas results from an outcrop analogue numerous examples of reservoir fields from continental and marine environments involve thin bedded geology yet the inter relationship between thin bedded geology fluid flow and seismic wave propagation is poorly understood in this paper we explore the 4d seismic signature due to saturation changes of gas within thin layers and address the challenge of identifying the relevant scales and properties which correctly define the geology fluid flow and seismic wave propagation in the field based on the study of an outcrop analogue for a thin bedded turbidite we model the time lapse seismic response to fluid saturation changes for different levels of model scale and explore discrepancies in quantitative seismic attributes caused by upscaling our model reflects the geological complexity associated with thin bedded turbidites and its coupling to fluid flow which in turn affects the gas saturation distribution in space and its time lapse seismic imprint rock matrix and fluid properties are modelled after selected fields to reproduce representative field models with realistic impedance contrasts in addition seismic modelling includes multiples in order to assess their contribution in seismic propagation through thin gas layers our results show that multiples could contribute significantly to the measured amplitudes in the case of thin bedded geology this suggests that forward inverse modelling involving the flow simulation and seismic domains used in time lapse seismic interpretation should account for thin layers when these are present in the geological setting

volcanic strain change prior to an earthquake swarm observed by groundwater level sensors in meakan dake hokkaido japan abstract we installed and operated a low cost groundwater level observation system at intermittent hot spring wells in order to monitor volcanic strain signals from the active meakan dake volcano in eastern hokkaido japan data are sampled at 1 hz and are transmitted to the data center in real time evaluation of the water level time series with theoretical predictive tidal strain and coseismic static strain changes has suggested that the wells penetrate to the artesian aquifer and act as a volumetric strain sensor an active earthquake swarm with more than 400 events occurred at the shallower part of the volcano from january 9 to 11 2008 three independent wells recorded pre to co swarm groundwater drops simultaneously which represented a decrease in volumetric strain the total volumetric strain change during the three active days was estimated to be from 6 to 7 10 7 the observed data including changes in volumetric strain absence of deformation in the gps coordinates and activation of deep low frequency earthquakes might imply possible deflation of a source deeper than 10 km and these preceding deeper activities might induce an earthquake swarm in a shallower part of the meakan dake volcano

assesment of the response of the meteorological hydrological parameters on the soil gas radon emission at hsinchu northern taiwan a prerequisite to identify earthquake precursors abstract the present study is an attempt to assess and quantify the influence of the meteorological atmospheric temperature and pressure and hydrological rainfall and ground water head gwh parameters on the soil gas radon emission at hsinchu northern taiwan the quasi periodic variations corresponding to diurnal and semi diurnal periods were estimated and eliminated by decomposing the time series for the period of september 16 2009 to march 5 2010 to singular spectrum analysis the reconstructed non periodic variations which reproduce the salient feature of recorded time series were searched for meteorological hydrological influences in radon emission the combined response of barometric pressure and atmosphere temperature are found to be small when compared to the total variability in radon the influence of rainfall on radon is found to be strongest at the onset of rainfall radon shows a step jump that attains peak with a time lag of 12 15 h this enhancement is attributed to entrapment of soil gas in the top soil cover as increased soil moisture prevents escape of radon into the atmosphere capping effect the decay of radon after the recession of rainfall is approximated by double exponential decay terms one corresponding to the natural decay of radon with half life of 3 84 days and second representing slow weakening of capping effect the third effect related to internal loading due to rise and fall of groundwater modulates the propagation of radon in overlying strata accounting for the long term variations in radon the rainfall inflicted changes in radon look strikingly similar to earthquake related precursory or co seismic perturbations inferred by long term synotopic observations it is surmised that unless radon variations are corrected for meteorological hydrological contamination some precursory signals are masked on one hand while on the other hand some anomalies are falsely viewed as earthquake precursors

discrimination between pressure and fluid saturation changes from time lapse seismic data explicit expressions for computing saturation and pressure related changes from time lapse seismic data have been derived and tested on a real time lapse seismic data set necessary input is near and far offset stacks for the baseline seismic survey and the repeat survey the method has been tested successfully in a segment where pressure measurements in two wells verify a pore pressure increase of 5 to 6 mpa between the baseline survey and the monitor survey estimated pressure changes using the proposed relationships fit very well with observations between the baseline and monitor seismic surveys 27 of the estimated recoverable hydrocarbon reserves were produced from this segment the estimated saturation changes also agree well with observed changes apart from some areas in the water zone that are mapped as being exposed to saturation changes which is unlikely saturation changes in other segments close to the original oil water contact and the top reservoir interface are also estimated and conf

identification of earthquake signals from groundwater level records using the hht method summary coseismic signals of groundwater levels are generally obtained by subtracting the responses of atmospheric pressure earth tides and precipitation from the observed data however if the observations are conducted without nearby barometers pluviometers or earth tide data for correction coseismic signals are often difficult to extract in this case the hilbert huang transform hht is used to obtain the instantaneous frequencies and amplitudes for every point of the decomposed intrinsic mode functions imfs from groundwater level data for differentiating the related frequency dependent responses without a further auxiliary input the extracted coseismic signals show intense amplitude pulses that are clearly seen in the third imf in addition two types of coseismic signals can be readily distinguished in the results from the hht transform one is an instantaneous short time signal induced by the passing of seismic waves another coseismic signal is a sustained signal induced by the nearfield earthquake occurring near the hualien station taiwan and shows a positive correlation between the earthquake distance and magnitude our results generally show that using the hht transform improves our understanding of automatic detection of the coseismic signals from the groundwater level

hydrological response to earthquakes in the haibara well central japan ii possible mechanism inferred from time varying hydraulic properties summary 28 coseismic groundwater level decreases have been observed at the haibara well shizuoka prefecture central japan from 1981 to 1997 these groundwater level changes cannot be explained as the poroelastic response to coseismic static strain we use the atmospheric pressure and tidal responses of the well rock properties measured on core samples from the same formation and pumping test results to characterize the hydraulic and mechanical properties of the aquifer the responses of the haibara well to the m2 earth tide constituent and to atmospheric pressure have varied over time in particular increasing amplitude and decreasing phase lags were observed after the 1993 pumping test as well as after earthquakes that caused coseismic water level changes the tidal response together with the surface load efficiency derived from the atmospheric pressure response is used to estimate the mechanical properties of the aquifer the largest amplitude of the m2 constituent 2 2 mm is small enough to imply that pore fluid in this system is approximately twice as compressible as water possibly due to the presence of a small amount of exsolved gas diffusion of a coseismic pressure drop near the well could account for the observed time histories of the water level changes the time histories of the water level drops are well matched by the decay of a coseismic pressure drop at least 80 m away from the well removal of a small amount of gas from the formation in that location might in turn explain the coseismic pressure drops

effects of chemical weathering and sorting on the petrogenesis of siliciclastic sediments with implications for provenance studies the bulk chemical compositions mineralogy and mineral proportions of sands and muds of the mallacoota basin in southeastern australia reflect the composition of weathering profiles mantling source rocks rather than bedrock muds contain abundant clay minerals that are virtually absent from the source rocks but abundant in the weathering profiles sands are strongly enriched in quartz relative to source rocks even in the headwaters of the fluvial system demonstrating that feldspar destruction occurs by in situ chemical weathering within profiles and before detritus enters the fluvial system k feldspar is proportionally more abundant in fluvial sands than in source rocks because plagioclase is more rapidly destroyed than either quartz or k feldspar in weathering profiles subsequent erosion and sorting produce sands enriched in quartz with high k feldspar plagioclase ratios relative to source rocks the composition of plagioclase incorporated into the fluvial sands is also controlled by chemical weat

hydrological responses induced by the tokachi oki earthquake in 2003 at hot spring wells in hokkaido japan 1 thirty hydrological responses induced by the m8 0 tokachi oki earthquake in 2003 were observed at hot spring wells and an undersea coal mine in hokkaido japan most of the decreases and increases in groundwater levels or discharge rates can be explained as a poroelastic response to earthquake induced volumetric strain inferred from a fault model determined by dense static gps observation in five wells observed groundwater level changes and inferred volumetric strain steps induced by the tokachi oki earthquake are consistent with groundwater level changes that are proportional to the inferred volumetric strain steps induced by four large earthquakes in 1993 1994

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

modal and geochemical compositions of the lower silurian clastic rocks in north qilian nw china implications for provenance chemical weathering and tectonic setting abstract the north qilian orogenic belt records the transition from ordovician marine back arc basin to early devonian terrestrial molasse basin as the central qilian block was sutured to the north china craton the detrital framework and geochemical composition of lower silurian sedimentary rocks within the north qilian belt record the provenance tectonic setting and a variety of sedimentary processes that operated during transport from source to sink the petrological and geochemical characteristics of sandstones siltstones and shales in the western segment of the north qilian belt indicate a generally low degree of chemical weathering of source area s and limited sorting prior to deposition these characteristics suggest an active tectonic setting in contrast samples studied from the eastern part of the north qilian belt indicate low to moderate chemical weathering and low to moderate hydraulic sorting such characteristics imply a more stable tectonic setting geochemical data including eu eu ti nb th sc and co th ratios suggest contrasting source regions for the western and eastern segments of the north qilian belt sources in the west included basement rocks of the central qilian block and the north china craton in addition western sources may have included mafic rocks located within the north qilian arc in contrast data derived from eastern samples suggest a felsic provenance that probably formed part of the basement complex in the central qilian block and the north china craton overall detrital and geochemical data combined with the regional geology suggest a foreland basin setting that formed during collision of the central qilian block with the north china craton

paleovalley morphology and fluvial system evolution of eocene oligocene sediments auriferous gravels northern sierra nevada california implications for climate tectonics and topography in the northern sierra nevada california eocene oligocene fluvial sediments the auriferous gravels rest unconformably in well defined basement incised paleovalleys providing a record of paleolandscape geomorphology and drainage system evolution paleovalley surface mapping shows that local topography and bedrock lithology controlled the location of broad terraced paleovalley segments which formed in the central and eastern metamorphic bedrock belts and subsequently became areas of significant fluvial deposition high gradient high energy deposits are present near the edges of these areas suggesting that tributaries and outlets resided in steeper narrow paleovalleys multiple strath terraces are common in broad paleovalleys indicating that incision events occurred both before deposition and during paleovalley widening followed by periods of aggradation broad paleovalley deposits contain predominantly braided stream facies deposited in an energetically variable system multiple upward fining cycles bounded by erosional surfaces are composed of alternating coarse grained channel belt and fine grained floodplain packages an overall upward fining succession suggests that the locus of fluvial deposition shifted and depositional energy waned over time as the system backfilled successive broad paleovalleys paleochannel slope estimates of 0 004 0 055 were obtained based on average grain sizes of coarse channel fills anomalously thick up to 11 m laterally continuous 1 3 km floodplain units containing kaolinite rich clay and oxisol intervals record high fine grained sediment supply driven by high rates of chemical weathering in the warm eocene climate based on sedimentary characteristics combined with floral and detrital zircon data braided stream deposition within the basin occurred from the late early eocene through late eocene and aggradation primarily occurred in broad lower gradient reaches behind a major bedrock knickpoint created in the late mesozoic early cenozoic possibly due to asymmetric batholith unroofing the diachronous localized nature of paleovalley incision and braided stream aggradation within the northern sierra nevada invalidates previous estimates of the timing and amount of range uplift based on paleochannel reconstructions and gradients both internal and external drivers influenced the evolution of the fluvial system through 1 the pattern of basin filling as the locus of deposition migrated east to west 2 the warm eocene climate which increased chemical weathering and contributed a high sediment supply and 3 changes in base level due to eustasy and or laramide tectonism this record of laramide tectonics in the sierra nevada and basin and range is important for the timing of sierra nevada uplift for tectonic reconstructions of western north america and for studies of landscape evolution in tectonically active orogens

weathering and global denudation a negative correlation between sediment yield and weathering history as measured by the chemical alteration cia of the suspended sediment is observed for many of the world s major rivers and other regions of denudation the weathering history is a first order control on the sediment yield of such areas termed equilibrium denudation regions for other areas data scatter with either apparent increases or decreases of sediment yield for given cia values these areas are termed nonequilibrium denudation regions low sediment yields can be attributed to moderated erosion either natural or human induced and or the incorporation of unweathered glacial debris accelerated erosion resulting in high sediment yield is primarily human induced and results from cultivation and other land use each of these effects has a profound influence on global sediment discharge from the continents pre human suspended sediment discharge from the continents is estimated to be 12 6 times 10 15 g yr or about 0 6 the

correlated transient fluid pulsing and seismic tremor in the costa rica subduction zone continuous measurements of fluid flow were made over a six month period across the nicoya peninsula costa rica pacific convergent margin utilizing osmotically driven fluid flow meters designed to quantify both inflow and outflow rates on the order of 10 5 to 3 cm d significant transience in flow was observed through the surface of the forearc three periods of correlated flow signals were seen on the subduction forearc among three instruments located in the out of sequence thrust oost zone over along margin strike distances of 30 km amplitudes of ground velocity recorded on collocated ocean bottom seismometers obs increase during the three correlated flow events the seismic signal has frequency characteristics that resemble volcanic and non volcanic tremor we hypothesize that repeated plate boundary slow slip events potentially originating at the up dip limit of the seismogenic zone generate the observed signals within the toe of the forearc we propose a model in which the poro elastic stress strain field around a series of creep dislocations simultaneously forces flow through fracture networks in the forearc and oceanic basement rocks and induces diffuse flow through the shallow sediments the former generates the seismic tremor like noise recorded by the obss and the latter generates the flow transients recorded by the fluid flow meters we suggest that high sensitivity fluid flow meters can be utilized to detect transient tectonic strain events in offshore environments where traditional geodetic techniques lack resolution or are not possible d 2005 elsevier b v all rights reserved

geochemical records of qionghai lake sediments in southwestern china linked to late quaternary climate changes abstract knowledge of the chemical weathering history under the subtropical monsoonal climate will help to resolve the discrepancies regarding how climate conditions constrain chemical weathering major element and rare earth element ree compositions of the qionghai lake sediments in sichuan province southwestern china were analyzed aiming to provide information on sediment source discrimination and history of chemical weathering intensities and its responses to variations of indian summer monsoon ism and paleoclimate conditions as revealed by the a cn k diagram and other provenance proxies including tio2 zr ratio th sc vs zr sc and la th vs hf diagrams as well as the ree characteristics the source of qionghai lake sediments was felsic rocks additionally these sediments were subjected to small changes in provenance sedimentary sorting and recycling and weak diagenesis after deposition and or metasomatism indicating original signals were maintained on the intensity of chemical weathering of source area the chemical weathering intensities inferred from cia chemical index of alteration values have significantly fluctuated over the past 28 kyr reflecting three stages of paleoclimate evolution which is consistent with grain size characteristics carbonate contents low frequency magnetic susceptibilities toc and biomarker proxy paq the cia values changed significantly during the typical warm and cold climate events including the last glacial maximum heinrich 1 cold event younger dryas and holocene climatic optimum and generally exhibited an increasing trend in amplitude correspondingly in concert with the climate shifting from cold and dry to warm and humid conditions generally warm and humid climate conditions suggest enhanced chemical weathering intensity whereas weak chemical weathering denotes cold and dry climate in the ism region in addition sequential variations of the cia values during the past 28 kyr may reflect changing chemical weathering processes in responses to the varying intensities of indian summer monsoon and the climate conditions forced by the northern hemisphere solar insolation

late paleozoic sedex deposits in south china formed in a carbonate platform at the northern margin of gondwana abstract sedex sulfide deposits hosted in black shale and carbonate are common in the south china block the dajiangping pyrite deposit is the largest of these deposits and is made up of stratiform orebodies hosted in black shales sandstone interlayered with stratiform orebodies contains detrital zircon grains with the youngest ages of 429 ma pyrite from the orebodies has a re os isochron age of 389 62 ma indicative of formation of the hosting strata and syngenetic pyrite ores in the mid late devonian the hosting strata is a transgression sequence in a passive margin and composed of carbonaceous limestone in the lower part and black shales in the upper part the ore hosting black shales have high toc total organic carbon mo as pb zn and cd indicating an anoxic euxinic deep basin origin the high redox proxies v v ni 0 6 and v cr 1 and the positive correlations of toc with mo and v in black shales are also consistent with an anoxic depositional environment the dajiangping deposit is located close to the ne trending wuchuan sihui fault which was active during the devonian the mid late devonian mineralization age and the anoxic euxinic deep basinal condition of this deposit thus imply that the formation of this deposit was causally linked to hydrothermal fluid exhalation in an anoxic fault bounded basin that developed in a carbonate platform of the south china block the regional distribution of many devonian stratiform carbonaceous sediment hosted sulfide deposits along the ne trending fault bounded basins in south china similar to the dajiangping deposit indicates that these deposits formed at a basin developed in the passive margin setting of the south china block during the devonian this environment was caused by the break up and northward migration of the south china block from gandwana

paleoclimatic control on the composition of the paleoproterozoic serpent formation huronian supergroup canada a greenhouse to icehouse transition unlike other feldspathic arenites in the 12 km thick huronian supergroup strata of the 250 350 m thick serpent formation contain abundant plagioclase deposited in a distal alluvial setting the serpent formation consists of arenites with minor shale and siltstone the plagioclase abundance could reflect unroofing of a unique source relative to other huronian units or could be due to less intense chemical weathering major trace and rare earth element ree geochemistry of the serpent formation are used to evaluate these two possibilities serpent formation source rocks form part of the archean superior province which mainly consists of tonalitic granitic and supracrustal assemblages and their metamorphosed equivalents in al2o3cao na2ok2o acnk space shales define a linear array which indicates that the unweathered source contained plagioclase and k feldspar in the ratio of 5 1 this particular array indicates that serpent fluvial systems tapped a variably weathered carapace developed on the superior province rather than purely fresh bedrock a modelled mixture of 80 tonalite and 20 granite group rocks reproduces ree and trace element characteristics of the serpent formation sandstones and shales average eu eu 0 87 lan smn 4 4 gdnybn 1 8 and th sc 1 65 mass balance considerations indicate that less than 5 supracrustal group rocks can be added at the expense of the granite group a unique source for serpent detritus is rejected because underlying and overlying units have approximately the same provenance composition plagioclase k feldspar ratios in serpent sandstones range from 2 1 to 1 2 which achieves mass balance among source mudstone and sandstone compositions when plotted in acnk space achievement of mass balance implies that sandstones and mudstones were derived from the same weathering profiles these findings indicate that plagioclase preservation in the serpent formation is related to less intense compared with other huronian arenites paleoweathering conditions probably a harbinger of the widespread continental glaciation recorded in the overlying gowganda formation

rupture preparation process controlled by surface roughness on meter scale laboratory fault abstract we investigate the effect of fault surface roughness on rupture preparation characteristics using meter scale metagabbro specimens we repeatedly conducted the experiments with the same pair of rock specimens to make the fault surface rough we obtained three experimental results under the same experimental conditions 6 7 mpa of normal stress and 0 01 mm s of loading rate but at different roughness conditions smooth moderately roughened and heavily roughened during each experiment we observed many stick slip events preceded by precursory slow slip we investigated when and where slow slip initiated by using the strain gauge data processed by the kalman filter algorithm the observed rupture preparation processes on the smooth fault i e the first experiment among the three showed high repeatability of the spatiotemporal distributions of slow slip initiation local stress measurements revealed that slow slip initiated around the region where the ratio of shear to normal stress was the highest as expected from finite element method fem modeling however the exact location of slow slip initiation was where became locally minimum probably due to the frictional heterogeneity in the experiment on the moderately roughened fault some irregular events were observed though the basic characteristics of other regular events were similar to those on the smooth fault local stress data revealed that the spatiotemporal characteristics of slow slip initiation and the resulting drop for irregular events were different from those for regular ones even under similar stress conditions on the heavily roughened fault the location of slow slip initiation was not consistent with anymore because of the highly heterogeneous static friction on the fault which also decreased the repeatability of spatiotemporal distributions of slow slip initiation these results suggest that fault surface roughness strongly controls the rupture preparation process and generally increases its complexity with the degree of roughness

zircon u pb ages and hf isotopes of paleozoic metasedimentary rocks from the habahe group in the qinghe area chinese altai and their tectonic implications abstract as one of the largest accretionary orogens in earth s history the central asian orogenic belt has attracted much attention in the past two decades but there are still many unresolved issues regarding its tectonic nature and evolution this is the case with the chinese altai whose tectonic provenance remains controversial especially for the paleozoic era as the most widely exposed meta sedimentary rocks in the chinese altai the habahe group was previously considered as representing a component of precambrian micro continent forming at a passive continental margin our new u pb data for detrital zircons from the habahe group in the qinghe region of the eastern chinese altai indicate that the strata were deposited from the late silurian to early devonian 427 405 ma and experienced regional metamorphism in the middle devonian 383 9 ma as constrained by the age of youngest detrital zircons 427 13 ma the age 405 3 ma of the tonalite that intrudes the habahe group and the metamorphic age of 383 9 ma additionally the majority of zircons from the habahe group have positive ehf t values 0 22 15 02 these data combined with geochemical features and maturity of the sedimentary rocks indicate an immature provenance for the habahe group with the source materials mainly derived from a juvenile crust with some old continental components the juvenile crust was most likely formed in a subduction zone developing in the chinese altai during early middle paleozoic time new geochemical data presented in this study suggest that the chinese altai was a transitional arc during early paleozoic time similar to the japan type arc with involvements of old continental components therefore it is proposed that the chinese altai was likely rifted from the south margin of the siberia craton probably related to the break up of the rodinia supercontinent and then experienced accretion and reworking with the subduction of the paleo asian ocean during early paleozoic time

saturation scale effect on time lapse seismic signatures quantitative interpretation of time lapse seismic signatures aims at assisting reservoir engineering and management operations time lapse signatures are thought to be primarily induced by saturation and pressure changes core flooding and reservoir flow simulations indicate that a change of the driving forces during dynamic fluid injection gives rise to a varying saturation scale this saturation scale is yet another variable controlling the time lapse seismic signal in this work we investigate the saturation scale effect on time lapse seismic signatures by analysing simple modelling scenarios we consider three characteristic saturation scales ranging from few millimetres to metres which may form during gas injection in an unconsolidated water saturated reservoir using the random patchy saturation model we compare the corresponding acoustic signatures i e attenuation reflectivity and seismic gather associated with each saturation scale the results show that the millimetre saturation scale produces minimum attenuation and the same seismic signatures with those obtained from the elastic modelling the centimetre saturation scale produces maximum attenuation whereas the metre saturation scale causes highest velocity dispersion the analyses of the time shift and amplitude change indicate that ignoring a time dependent saturation scale can result in biased estimation discrimination of the saturation and the fluid pressure in particular the 4d signal can be strongly affected by the saturationscale change when the reservoir gas saturation is low and the effective pressure is high in the presence of an increasing decreasing saturation scale during injection interpreting an observed time shift and amplitude change using the gassmann model will lead to underestimation overestimation of the change in gas saturation and fluid pressure we show that including the effects of capillarity and residual saturation into the rock physics modelling can potentially reduce the interpretation uncertainty due to the saturation scale change

reconstructing a high paleolatitude mesozoic paleoenvironment from a truncated and deeply buried regolith norwegian north sea abstract the paleoregolith in this study was unconformably overlain by lower cretaceous valanginian marine deposits of the asgard formation and buried below two kilometers of sediments on the utsira high norwegian north sea the upwards intensification of chemical alteration manifested in the replacement of feldspars by clays leaching of base cations and reduced mechanical rock strength in addition to the presence of terrestrial biotitic features suggested weathering during subaerial exposure of the utsira high during the mesozoic the paleoregolith can be divided into three weathering facies altered coherent rock saprock and saprolite whereas the absence of true soil horizons suggested erosional truncation of the regolith before burial possible remnants of the eroded soil were identified as pedogenic mud aggregates in the overlying asgard formation bearing similar compositional characteristics as the saprolite clay mineralogy bulk geochemical composition micromorphology and depth of biotic features were used to reconstruct the paleoenvironmental conditions that prevailed during the formation of the regolith in the mesozoic north sea our results point to a regolith formation under periodically water restricted conditions promoting the co existence of interstratified illite smectite beidellite and kaolinite deep presence of endomycorrhizae the fungal extension of the root structure and precipitation of iron oxide nodules application of recently developed geochemical climofunctions indicated that the regolith formed in a mesic 10 12 c and subhumid 1157 1406 mm yr environment and under strongly acidic soil conditions ph 5 2 5 6

detrital zircon u pb hf isotopes and whole rock geochemistry of neoproterozoic cambrian successions in the cathaysia block of south china implications on paleogeographic reconstruction in supercontinent abstract paleogeographic reconstruction of the cathaysia block of south china and its link with orogeny associated with rodinia and gondwana remain enigmatic leading to controversial models proposed for supercontinental configuration this study presents detailed provenance analysis of late neoproterozoic to early paleozoic sedimentary successions from the cathaysia block to trace the sedimentary provenance that was essentially linked to previously adjacent continents blocks zircon u pb dating combined with published paleontological evidence suggests an ediacaran depositional age range 633 542 ma for the lechangxia group while deposition of the bacun group most likely commenced during early cambrian the older strata were sourced mainly from recycling of quartz rich sedimentary rocks while the younger one received sediments dominantly from felsic igneous rocks high sio2 contents 54 6 79 3 wt and k2o na2o ratios 0 69 35 7 detrital zircon age distribution and abundant monocrystalline quartz indicate a passive setting for ediacaran and early cambrian successions in great contrast the middle cambrian strata was likely deposited in collisional setting considering relatively lower sio2 contents 67 9 74 5 wt and k2o na2o ratios 0 97 1 63 plus absence of old zircons this tectonic transition is consistent with the change from quartz arenite to arkose that could be related to a disconformity between early and middle cambrian strata dominant late mesoproterozoic detritus 1250 1050 ma in the lechangxia group was possibly sourced from older grenville orogens 1300 1050 ma in western australia and east antarctica because rocks of these ages are rare in the cathaysia block similarly abundant early neoproterozoic clastic 1000 950 ma in the late ediacaran and early cambrian successions imply an increasing input from younger grenville orogens 990 950 ma in east antarctica and eastern india thus the cathaysia block was a part of the east gondwana assembly and was linked to eastern india east antarctica and western australia during ediacaran and cambrian the source change was coeval with the pinjarra orogeny 550 520 ma and the early stage of the kuunga orogeny 570 550 ma in middle cambrian strata the middle neoproterozoic sediments 850 700 ma were mainly derived from intrinsic sources likely to be the wuyishan terrane this provenance variation can be linked to the middle cambrian uplift of the cathaysia block in synchronous with the later phase of the kuunga orogeny 530 480 ma

bounds on low frequency seismic velocities in partially saturated rocks the most common technique for estimating seismic velocities in rocks with mixed pore fluid saturations is to use gassmann s relations with an effective fluid whose density and compressibility are averages of the individual pore fluid properties this approach is applicable only if the gas oil and brine phases are mixed uniformly at a very small scale so the different wave induced increments of pore pressure in each phase have time to diffuse and equilibrate during a seismic period in contrast saturations that are heterogeneous over scales larger than the characteristic diffusion length i e patchy saturation will always lead to higher seismic velocities than if the same fluids are mixed uniformly at a fine scale critical saturation scales separating uniform from patchy behavior are typically of the order 0 1 1 cm for laboratory measurements and tens of centimeters for field seismic frequencies for low seismic frequencies velocities corresponding to patchy and homogeneous saturations represent a

an early soda ocean in analogy to modern soda lakes commonly associated with volcanic regions it is postulated that the ancient sea had a high alkalinity a high ph and low ca and mg concentrations the change towards nacl dominance as observed in the present day ocean can best be explained by a series of mineral equilibria crustal differentiation and life processes in principle hydrothermal leaching of chlorine from the oceanic crust caused this ion to accumulate in the sea while at the same time dissolved carbonates became gradually removed by organisms and carbonates the switch from a soda to a halite ocean was accomplished 1 ga ago critical biochemical events marking the chemical evolution of the precambrian sea and their implications for the pco2 in air will be discussed

the 4d seismic signature of oil water contact movement due to natural production in a stacked turbidite reservoir combined time lapse reservoir simulation and seismic modelling has been performed on both 1d and 3d models of a channelized turbidite reservoir the models have been built using core log laboratory and seismic data from the nelson field central north sea as a template oil and water movement in the main channels channel margins and interchannel regions is investigated with a particular focus being the effect of poor net to gross the analysis confirms that saturation effects dominate the response whilst stress sensitivity effects play a minor role the trough peak signature in the seismic difference volumes formed by the sweep of the water can be continued and mapped slightly further than the channel margins this characteristic 4d signature remains roughly intact despite the complicated depositional architecture and accurately delineates the area of moved fluid but it needs additional calibration to combat the detrimental influence of the low net to gross signal strength is largely dependent on reservoir quality but is also compromised by the net to gross fluid distribution and more critically by the exact timing of the seismic survey for example a region of bypassed oil zone remains undetected as it forms early during the production this work demonstrates that to understand fully the 4d signature at a quantitative level requires adequate knowledge of the fluid properties but also more critically the geology

acoustic signatures of partial saturation the relationship between elastic wave velocities and water saturation in a water gas reservoir depends strongly on whether saturation is heterogeneous patchy or homogeneous heterogeneity in saturation may result from lithologic heterogeneity because under conditions of capillary equilibrium different lithologies within a reservoir can have different saturations depending on their porosities and permeabilities we investigate this phenomenon by generating models of a reservoir in which we control the distribution of lithologic units and theoretically determine the corresponding velocity saturation relationship we assume a state of capillary equilibrium in the reservoir and determine the saturation level of each region within the reservoir from the corresponding capillary pressure curve for the lithologic unit at that location the velocities we calculate for these models show that saturation heterogeneity caused by lithologic variation can lead to a distinct dependence of velocity on saturation in a water gas saturated reservoir a patchy distribution of the different lithologic units is found to cause p wave velocity to exhibit a noticeable and almost continuous velocity variation across the entire saturation range this is in distinct contrast to the response of a homogeneous reservoir where there is only a large change in velocity at water saturations close to 100

thermal stability of amino acids in siliceous ooze under alkaline hydrothermal conditions abstract hydrothermal systems have been suggested as being favourable environments for the origin and evolution of life on the primitive earth to test this hypothesis it is necessary to investigate under hydrothermal conditions the behaviour of biomolecules such as amino acids aas a major component of organisms in contrast to submarine hydrothermal systems hot springs in the rift valley in eastern africa on the thick continental crust often have a high ph alkaline conditions as a result of enrichment via na 2 co 3 and volatile gases we reacted siliceous ooze with an aqueous solution of nacl and na 2 co 3 at elevated temperature 100 300 c to evaluate the thermal stability of the aas under alkaline hydrothermal conditions the aas in the sediment in peptide form were released to the liquid phase and decomposed through hydrolysis of peptide bonds comparison of the results with those from similar experiments using the same sediment sample under neutral conditions reveals that the rates of decomposition of the aas are significantly inhibited under alkaline conditions moreover aas remained in both the solid and liquid phases even after heating at 300 c for 240 h our results indicate that aas are more thermally stable in alkaline solution indicating that these hydrothermal conditions are more favourable for the evolution of primitive life on the thick continental crust they also imply that alkaline hydrothermal systems on other planets might be plausible places for extraterrestrial life

groundwater responses to the 2011 tohoku earthquake on jeju island korea groundwater responses at 15 monitoring wells on jeju island were observed in relation to the magnitude 9 0 tohoku earthquake off the pacific coast of honshu japan on 11 march 2011 at 14 46 23 h local time 05 46 24 h utc time in coastal areas the groundwater level responses to the earthquake were oscillatory at 12 wells and the range of the maximum groundwater level changes was 3 192 4 cm the response durations were approximately 1 62 min the relationship between the maximum groundwater level changes and the response durations displayed a high correlation coefficient r 0 81 groundwater temperature changes were also observed at 7 of 12 wells 3 10 min after the seismic wave arrived and the range was from 0 01 c to 1 20 c in mid elevation areas the groundwater level changes appeared in three different forms oscillatory spiky and persistent the groundwater temperature changes were also observed at two wells one indicated decreasing and recovering temperatures and the other exhibited rising and persistent temperatures the primary temperature changes occurred 5 6 min after the earthquake and 2 3 min after the seismic wave arrived in addition the electrical conductivities at the depth of the transition zone were monitored and the responses to the earthquake appeared at all three wells although the electrical conductivity and temperature changes were not well understood groundwater inflow and mixing were likely caused by the earthquake and the responses were various and site specific the responses to the earthquake were closely related to the hydrogeological characteristics at each monitoring well and a more detailed hydrogeological characterization is needed to understand the mechanisms related to earthquakes in general copyright 2012 john wiley sons ltd

origin of the wunugetushan porphyry cu mo deposit inner mongolia ne china constraints from geology geochronology geochemistry and isotopic compositions abstract the wunugetushan porphyry cu mo deposit is located in the southeastern margin of the mongol okhotsk orogenic belt and in the northwestern segment of the great xing an range ne china the orebodies of this deposit are mainly hosted in the monzogranitic porphyry stock and in contact with the granitic porphyry dyke and biotite granite batholith the shrimp zircon u pb dating of the granitic porphyry dyke yielded ages of 201 4 3 1 ma 2 mswd 1 5 these results indicate that the magmatism in the wunugetushan area might have occurred at ca 201 ma in the early jurassic and that the mineralization age ca 181 ma of this deposit is later than the age of intrusive granitic porphyry in the area geochemically the wunugetushan granitoids belong to high k calc alkaline and shoshonitic series enriched in k rb nd and pb and depleted in sr nb ti and p with negative eu anomalies in situ hf isotopic analyses of zircons using la mc icp ms indicate that the ehf t values for zircons from a granitic porphyry sample vary from 2 4 to 11 8 and that the corresponding crustal model ages tdmc vary from 483 to 1088 ma the least altered monzogranitic porphyry granitic porphyry and biotite granite yielded relatively uniform end t values from 1 0 to 0 6 and low 87sr 86sr i ratios ranging from 0 704387 to 0 708385 the geochemical and sr nd hf isotopic data for the granitoids indicate that the source magma for these rocks could be derived from a juvenile lower crust the 34s values of sulfides show a narrow range 0 76 to 3 20 similar to those of magmatic sulfur further implying a lower crust origin based on the results of this study and the regional geodynamic evolution it is proposed that the formation of the wunugetushan deposit and associated granitoids should be linked to the southeastward subduction of the mongol okhotsk oceanic plate beneath the erguna massif during the early jurassic and that the monzogranitic porphyry intrusions in wunugetushan area probably provided important ore metals responsible for the large scale cu mo mineralization

determination of fluid flow properties from the response of water levels in wells to atmospheric loading the water level in a well that taps a partially confined aquifer is often sensitive to atmospheric loading the magnitude and character of this response is partly governed by the well radius the lateral hydraulic diffusivity of the aquifer the thickness and vertical pneumatic diffusivity of the unsaturated zone and the thickness and vertical hydraulic diffusivity of the saturated zone overlying the aquifer these key elements can be combined into five dimensionless parameters that partly govern the phase and attenuation of the response in many cases the response of a well to atmospheric loading can be broken up into a high intermediate and low frequency response the high frequency response is governed largely by the well radius and lateral diffusivity of the aquifer the intermediate frequency response is governed by the loading efficiency of the aquifer the low frequency response is governed by the vertical pneumatic diffusivity and thickness of the unsaturated zone and the vertical hydraulic diffusivity and thickness of the saturated material above the aquifer cross spectral estimation is used to fit the response to atmospheric loading of three water wells to the theoretical curves in order to yield estimates of three of the key dimensionless parameters these estimates then are used to make estimates or place bounds on the vertical pneumatic diffusivity of the unsaturated zone the lateral permeability of the aquifer and the composite vertical hydraulic diffusivity of the overlying saturated materials

impact of flow simulation parameters on saturation scales and seismic velocity scales of fluid saturation below seismic resolution introduce uncertainties in the interpretation of seismic velocity a coarse scale or patchy distribution always has a higher effective seismic velocity than a fine scale or uniform distribution we present a multidisciplinary study which links rock physics and seismic modeling with reservoir engineering and provides strategies to reduce uncertainties in saturation scales in our study we performed fine scale flow simulations that helped us to understand which reservoir parameters control the subseismic resolution fluid distribution our studies show that when gas is injected into oil reservoirs gravitational forces induce the formation of subresolution gas caps which lead to patchy saturation at seismic scales we also learned that the uniform saturation model is appropriate for most waterflooding into oil and for primary production scenarios where gas comes out of solution fluid density contrasts mobility ratios and residual oil saturatio

mixing relationships in the martian regolith and the composition of globally homogeneous dust abstract comparison of the chemical compositions of martian soils reveals distinct mixing trends resulting from admixture of variable amounts of sulfate chloride cement at viking landing sites and of the local andesitic rock fragments at the mars pathfinder site these trends most easily visualized in plots of oxides versus so 3 intersect approximately at a common composition thought to represent a global dust that has been homogenized by pervasive aeolian activity the source rocks that were weathered to produce the global dust are inferred to have been basalts rather than felsic rocks based on the observation that the dust lies along well established chemical weathering trends for terrestrial basalts the basaltic protolith was chemically similar e g high fe mg low al 2 o 3 to basaltic shergottite meteorites chemical changes during the weathering of martian basaltic rocks are apparently not as drastic as in terrestrial weathering perhaps because of evaporation of hydrous fluids that leave soluble components behind in the residue comparison with chemical trends for previously proposed martian soil formation mechanisms suggests that palagonitization of basalts more readily explains the dust composition than do hydrothermal alteration at higher temperatures or reactions of rocks with an acid fog produced by volcanic exhalations local or temporal processing of dust into soil involves not only cementation by salts and mixing with rock fragments but also chemical fractionations of fe 2 o 3 tio 2 presumably resulting from aeolian sorting by grain size and density if the global dust represents a broad average of the martian surficial or upper crustal composition the planet s surface geology is dominated by basaltic volcanic rocks and evaporitic salts

the metamorphic characteristics of metapelites of the mashan group in mashan area eastern heilongjiang province china constraint on the crustal evolution of the jiamusi massif abstract mashan complex in the southeastern margin of the jiamusi massif has traditionally been interpreted to be the oldest stratigraphic sequence in eastern ne china here we investigated the mashan complex in the ximashan area and present lots of new la icp ms zircon u pb petrological and mineralogical chemical data in addition with phase equilibria modeling to constrain the timing of metamorphism p t conditions and the p t path of the mashan complex and furthermore to deduce the crustal evolution of the jiamusi massif the protoliths of the metapelites from the mashan complex in the ximashan area are clay rocks and sandstones whose provenance is dominantly felsic rocks which formed from a continental island arc three metamorphic generation assemblages m2 m4 are recognized in the studied samples a peak granulite facies stage a post peak near isothermal decompression stage and a late near isobaric cooling stage which together define a clockwise p t path it reveals important information related to the collision orogeny subsequent uplift and post collision process zircon u pb dating of two metapelitic samples yielded metamorphic ages of the older group varying from 535 6 to 480 5 ma which can be perfectly correlated with the age range 501 6 to 498 6 ma of magmatic activities recorded by the gneissic granite sample the data presented here together with those published allow us to preliminarily infer that the peak of the granulite facies metamorphism in the ximashan area of the jiamusi massif might have occurred at 530 500 ma the younger of the metamorphic ages 476 453 ma should be regarded as the age of late stage therefore a collision orogeny regime is favored to interpret the metamorphic evolution of metapelites of the mashan group in the mashan area

deep weathering of granitic rocks a case of tunnelling in nw spain abstract this paper highlights a case of extensive development of saprolith from granitic bedrock in nw spain the weathering front at the study area extends to more than 250 m in depth the drilling of a railway tunnel madrid galicia high speed line through the bedrock and saprolith resulted in significant technical issues and economic losses cross sections revealing the 3d complexity of saprolith development are mainly based on fieldwork boreholes laboratory tests and the excavation works saprock is always observed overlying unweathered igneous bedrock two saprolite facies one clay rich and the other clay poor overlie the saprock the recognition is based on several criteria these deposits gradually thicken from the boundaries between the granitoid and metasedimentary roof pendants factors controlling saprolith development are discussed and the chemical and mineralogical changes and trends that occur are described variations in some geotechnical properties and the loss of quality of the rock masses from an engineering perspective are also quantified

late eocene clay boron derived paleosalinity in the qaidam basin and its implications for regional tectonics and climate abstract the qaidam basin located on the northeastern tibetan plateau and containing cenozoic sediments with a maximum thickness of 12 000 m is an ideal place to study the phased uplift of the ne tibetan plateau and regional climate change the estimation of the paleosalinity of sedimentary environments not only helps to evaluate the evolution of lakes in this region but offers insights into contemporaneous climate change we present detailed geochemical and mineralogical investigations from the lacustrine interval of the hongliugou section in the northern qaidam basin to reconstruct salinity fluctuations in the paleolake during the late eocene era 42 0 35 5 ma the clay mineral assemblages mainly contain smectite illite chlorite kaolinite and irregular illite smectite mixed layers clay boron derived paleosalinity estimates equivalent boron content couch s paleosalimeter and b ga ratios along with other proxies sensitive to salinity changes e g rb k ratios and ostracod assemblages collectively indicate an overall brackish sedimentary environment with a higher salinity period at approximately 40 0 39 2 ma this higher salinity period indicates a more arid environment and is probably related to global cooling however the global cooling in late eocene cannot explain the overall stable long term salinity pattern implying that other factors exist we propose that the migration of the yiliping depression depocenter in the northern qaidam and increased orographic rainfall induced by late eocene tectonic activity at the northern margin of the basin might have partly offset the increase in salinity driven by global cooling

mid holocene extreme hydrological events in the eastern great rann of kachchh western india abstract the present study is an attempt to reconstruct the paleohydrological conditions during the mid holocene in the hyper arid terrain of the northern great rann of kachchh remote sensing detailed field geomorphology sedimentology geochemistry and optical chronology suggests that the fluvial sediments fringing the khadir island were transported locally and deposited during the extreme hydrological events corresponding to the mid to late holocene indian summer monsoon ism variability overall five extreme hydrological events are deciphered during the last 5 ka which broadly correlates with periods of strengthened ism our data indicate that the emergence and decline of the harappan civilization was unrelated to any major fluvial system in the region

tropical chemical weathering of hillslope deposits and bedrock source in the aburra valley northern colombian andes abstract tropical chemical weathering produces extensive lateritization and formation of deep weathering profiles both processes are fundamental to landscape evolution and slope instability the aburra valley of the northern colombian andes is characterized by tropical conditions the valley slopes are mostly covered by hillslope deposits originating from four basement rock suites which comprise contrasting granitoid volcanic sedimentary ophiolitic and metamorphic sources respectively tropical chemical weathering of the aburra hillslope deposits and their respective bedrock were examined using x ray fluorescence and x ray diffraction analysis to document and quantify their chemical weathering profiles compositions and mineralogical properties the chemical index of alteration cia loss on ignition loi and the mobiles index imob were used to quantify the degree of weathering of hillslope deposits and bedrock source weathering trends were analyzed using a cn k and a cnk fm diagrams the material mantling the slopes in the aburra valley records an intense weathering history chemical weathering is characterized by increased development of clay minerals kaolinite halloysite and iron and aluminum sesquioxides lateritization characterizes the final stage of the weathering profiles concentrations of cao na2o k2o decrease markedly in the weathering products compared to the fresh bedrock source whereas concentrations of al2o3 fe2o3 and mgo increase significantly cia ratios of matrix slope deposits derived from all four sources near 100 whereas those of boulder slope deposits and saprolites are lower but exceed source rock values different a cn k weathering paths are evident for each lithotype validating the correlation established between the hillslope deposits and their various parents chemical weathering indices in some samples are strongly influenced by the presence of sesquioxides as reflected by high loi anomalously low cia and varying enrichment trends on the a cnk fm diagrams consequently different chemical indices based on different criteria need to be combined to obtain best results as illustrated here by the combination of loi cia and imob the overall results suggest that tropical conditions have dominated for a long time in the northern colombian andes leading to uniformly high weathering indices in matrix slope deposits irrespective of parent lithotype prolonged warm and humid conditions could thus be responsible for the weathering and remobilization of extensive old hillslope deposits during the quaternary however in addition to the influence of climatic factors tectonism has also undoubtedly influenced slope evolution in the aburra valley

revisiting borehole strain typhoons and slow earthquakes using quantitative estimates of precipitation induced strain changes taiwan experiences high deformation rates particularly along its eastern margin where a shortening rate of about 30 mm yr is experienced in the longitudinal valley and the coastal range four sacks evertson borehole strainmeters have been installed in this area since 2003 liu et al 2009 proposed that a number of strain transient events primarily coincident with low barometric pressure during passages of typhoons were due to deep triggered slow slip here we extend that investigation with a quantitative analysis of the strain responses to precipitation as well as barometric pressure and the earth tides in order to isolate tectonic source effects estimates of the strain responses to barometric pressure and groundwater level changes for the different stations vary over the ranges 1 to 3 nanostrain millibar hpa and 0 3 to 1 0 nanostrain hpa respectively consistent with theoretical values derived using hooke s law liu et al 2009 noted that during some typhoons including at least one with very heavy rainfall the observed strain changes were consistent with only barometric forcing by considering a more extensive data set we now find that the strain response to rainfall is about 5 1 nanostrain hpa a larger strain response to rainfall compared to that to air pressure and water level may be associated with an additional strain from fluid pressure changes that take place due to infiltration of precipitation using a state space model we remove the strain response to rainfall in addition to those due to air pressure changes and the earth tides and investigate whether corrected strain changes are related to environmental disturbances or tectonic original motions the majority of strain changes attributed to slow earthquakes seem rather to be associated with environmental factors however some events show remaining strain changes after all corrections these events include strain polarity changes during passages of typhoons a characteristic that is not anticipated from our estimates of the precipitation transfer function that are more readily explained in terms of tectonic origin motions but clearly the triggering argument is now weaker than that presented in liu et al 2009 additional on site water level sensors and rain gauges will provide data critical for a more complete understanding including the currently unresolved issue of why for some typhoons there appears to be a much smaller transfer function for precipitation induced strain changes

the lower crust of the dharwar craton southern india patchwork of archean granulitic domains u pb geochronological major and trace element and isotope geochemical data identify crustal domains of contrasted petrological origins and histories in the lower crust of the dharwar craton all affected by granulite facies metamorphism and deformation in the neoarchean four lower crustal domains have been identified and investigated across the neoarchean amphibolite to granulite facies transition zone 1 in the southern part of the western dharwar craton wdc high grade metamorphism affects rocks formed before 3 0 ga high grade metamorphism is recorded at ca 2 51 ga followed by possible complex cooling and resetting until 2 2 ga 2 the br hills mm hills domain represents the lower crust of the central dharwar province cdp which is here defined as a transitional crust between the old 3 ga wdc and the eastern dharwar province edp not older than 2 7 ga this granulitic domain contains the oldest rocks of the dharwar craton with ttg suites formed at ca 3 4 ga and ca 2 6 ga suites of probable crustal recycling origin both suites are involved in 2513 5ma granulite facies metamorphism 3 the nilgiri granulitic domain is tectonically juxtaposed with the deepest level of the wdc as a consequence of neoarchean dextral slip along the moyar shear zone the massif consists of rocks of orogenic affinities formed between 2 70 and 2 56 ga and overprinted by granulite facies metamorphism at 2518 10 ma 4 the krishnagiri domain exposes the deepest levels of the eastern dharwar craton it is composed of ttg and calc alkaline igneous protoliths formed between 2 55 and 2 53 ga migmatization in the upper part of the domain took place at 2507 6ma and granulite facies overprint in the deepest parts of the domain is constrained at 2516 5 ma the krishnagiri domain was magmatically accreted to the lower crust of both the cdp and edp by interaction with mafic magmatism inducing reworking of the 2 7 2 6 ga or older overlying crust the nilgiri granulites share several temporal and petrological properties with the madras granulites that make the easternmost outcrop of the dharwar craton we tentatively suggest that the nilgiri and madras granulites evolved as parts of a common madras domain in the lower crust of the edp before activation of the moyar shear zone in this sense the nilgiri massif may be considered as an allochtonous unit in a context of neoarchean ultra hot orogeny in south india

deepwater turbidite system analysis west africa sedimentary model and implications for reservoir model construction the complex sedimentary architecture of various offshore turbidite systems within the tertiary formations of gulf of guinea offshore west africa can be explained by using 3d seismic interpretation to define sedimentary and stratigraphically units which then become input for reservoir models and simulations the geologic model is composed of sedimentary units of different scales whose width thickness and lateral continuity composition facies partitions and lateral vertical succession are determined from analysis of 3d seismic and well data

comparative geochemistry of pleistocene and paleoproterozoic huronian glaciogenic laminated deposits relevance to crustal and atmospheric composition in the last 2 3 ga abstract comparison of the major and trace element geochemistry of glaciogenic laminated deposits of pleistocene and paleoproterozoic age from an area north of lake huron ontario has revealed differences and similarities that may provide insight into the erosional history of part of the archean superior province of the canadian shield during the last 2 ga and some aspects of the evolution of the earth s atmosphere both the major element and trace element compositions of the ancient and recent glacial deposits are very similar the paleoproterozoic mudstones are however enriched in fe and u characteristics that may reflect the oxygen content of the archean early paleoproterozoic atmosphere hydrosphere system strong ca depletion is exhibited by the paleoproterozoic glaciogenic argillites but is absent from the pleistocene samples the proterozoic argillites have slightly higher values for a chemical index of alteration than those of pleistocene muds these characteristics may reflect the acid natur

cryptic climatic signatures and tectonic controls on cryogenian diamictites in the nw tarim craton china unravelling the origins of cryogenian diamictites is vital in determining their significance in a snowball earth context and their relationship to environmental processes here we present new sedimentological and geochemical data for the cryogenian sedimentary rocks from the tarim craton nw china the diamictite member of the east qiaoenbrak formation contains 1 granitic pebbles with high sphericity 2 well developed stratification and 3 bed scale grain size changes suggesting cyclicity also 4 ice rafted debris is conspicuously absent rather than deposits of direct glacial origin the succession is instead interpreted as a subaqueous fan complex the major and trace element ratios and ree patterns are consistent throughout 22 sampled intervals in the qiaoenbrak group suggesting a uniformly felsic source area probably from an island arc chemical index of alteration cia analysis indicates low cia values 49 5 54 3 average 51 6 throughout the qiaoenbrak group we suggest that both the qiaoenbrak group and yuermeinak formation were deposited during the marinoan glaciation in a long lasting cold and dry interval it is likely that the qiaoenbrak group was deposited in a fault controlled basin adjacent to an active continental margin although the material may ultimately have derived from a glacial source e g outwash

a polygenetic palaeosol from the silurian wenlock of southwest ireland a problematic palaeosol unit caps a thick basalt at the top of the clogher head formation dunquin group late wenlock silurian in the dingle peninsula southwest ireland the main part of the unit consists of an altered calc alkaline basalt with a fine clay assemblage of chlorite corrensite and smectite probably resulting from weathering during wenlock times the uppermost part of the unit consists of detrital silicates which were admixed by bioturbation and well defined burrow fills are present the underlying weathered basalt was possibly truncated before the detrital horizon was deposited and finally the whole unit underwent a phase of surface water gleying a catenary relationship existed locally with the pseudo gley developed lower in the landscape while contemporaneous basalts in topographically higher better drained areas largely escaped the effects of gleying these now exhibit reddened tops the complex history and the possiblity of the incompleteness of the profile makes accurate assessment of the soil climate function difficult however the occurrence of calcrete bearing palaeosols in the overlying mill cove formation supports the view that the basalt was weathered under a sub humid or semi arid climate considering the alteration of the dunquin group to actinolite prehnite grade the preservation of the smectite is highly unusual there is no evidence for its origin due to more recent weathering or interstratal neoformation it is thus interpreted as a relict product of the original weathering phase

tidal responses and earthquake related changes in the water level of deep wells monitoring of the water level has been continued in 100 m deep and 500 m deep wells in the southern kanto district japan to examine the relationship between changes in the well water level and earthquake occurrence by using a bayesian approach the observed data were decomposed into four components tidal response barometric response trend drift and irregular noise components loading effects of the ocean tide on aquifer dilatation were evaluated by using schwiderski s ocean tide models and the harmonic constants compiled by the international hydrographic bureau well aquifer properties were examined based on the tidal and barometric responses of the water level coseismic water level steps were detected in both wells for two earthquakes during the observation period from april 1985 to december 1989 by calibrating the strain sensitivity of the well water levels based on the tidal responses strain changes equivalent to the coseismic steps in the water levels were estimated the coseismic strain changes obtained for the deeper well can be explained reasonably by earthquake fault models in a viscoelastic half space however those observed in the shallower well were too large and in the wrong direction to be explained by the earthquake fault models

focal zone of a future tokai earthquake inferred from the seismicity pattern around the plate interface abstract a future large tokai earthquake has been considered to be the most urgent problem of impending disasters in the central part of the japanese islands since the first warning was announced in 1976 recent progress in observations has provided a great amount of data thus making a detailed investigation possible in this study based on the seismicity and the focal mechanism patterns of microearthquake data the mechanical situation that governs plate interactions around the tokai district was investigated it was found that the seismicity in the subducting philippine sea slab is composed of three characteristic groups of activities intense activity beneath lake hamana a linear cluster extending from lake hamana toward the northwest and a broad cluster expanding over the inland area in the west of suruga bay we propose that these activities occur inside the subducting oceanic crust and reflect the present stress state acting there the mechanism inducing these activities is assumed to come from two stress sources the lateral stretching of the slab and the partial locking between both plates this interpretation leads to the hypothesis that the broad cluster in the west of suruga bay represents a stress concentration due to locking the activity beneath lake hamana is proposed to represent shearing motion induced there and is interpreted to form the boundary between the rupture zones of the 1944 tonankai earthquake and a future large tokai earthquake these analyses resulted in identifying the wide inland area extending from the west coast of suruga bay to lake hamana to be a focal zone of a future tokai earthquake the zone proposed in this study indicates a significant deviation in its strike from the original model proposed by ishibashi in that the former parallels the nankai trough while the latter parallels the suruga trough

deep sea smokers windows to a subsurface biosphere since the discovery of hyperthermophilic microbial activity in hydrothermal fluids recovered from smoker vents on the east pacific rise the widely accepted upper temperature limit for life based on pure culture data has risen from below the boiling point of water at atmospheric pressure to approximately 115 degrees c many microbiologists seem willing to speculate that the maximum may be closer to 150 degrees c we have postulated not only higher temperatures than these under deep sea hydrostatic pressures but also the existence of a biosphere subsurface to accessible seafloor vents new geochemical information from the endeavour segment of the juan de fuca ridge indicative of subsurface organic material caused us to re examine both the literature on hyperthermophilic microorganisms cultured from deep sea smoker environments and recent results of microbial sampling efforts at actively discharging smokers on the endeavour segment here we offer the case for a subsurface biosphere based on an interdisciplinary view of microbial and geochemical analyses of endeavour smoker fluids a case in keeping with rapidly evolving geophysical understanding of organic stability under deep sea hydrothermal conditions

hydrological response to earthquakes in the haibara well central japan i groundwater level changes revealed using state space decomposition of atmospheric pressure rainfall and tidal responses summary for the groundwater level observed at the haibara well shizuoka prefecture central japan time series analysis using state space modelling is applied to extract hydrological anomalies related to earthquakes this method can decompose observed groundwater level time series into five components atmospheric pressure tidal and precipitation responses observation noise and residual water level the decomposed responses to atmospheric pressure and precipitation are independently determined and are consistent with the expected response to surface loading in the groundwater level at the haibara well 28 coseismic changes can be discerned during the period from 1981 april to 1997 december there is a threshold in the relationship between earthquake magnitude and the well hypocentre distance above which earthquakes cause coseismic changes in the residual water level all of the coseismic water level changes at the haibara well are decreases although 33 per cent of the estimated coseismic volumetric strain steps are contraction which would be expected to cause water level increases the coseismic changes in groundwater level are more closely proportional to the estimated ground motion than to coseismic volumetric strain steps suggesting that ground motion due to earthquakes is the major cause of the coseismic water level drops and that the contribution from static strain is rather small possible pre or inter earthquake water level changes have occurred at the haibara well and may have been caused by local aseismic crustal deformation

groundwater level anomalies associated with a hypothetical preslip prior to the anticipated tokai earthquake detectability using the groundwater observation network of the geological survey of japan aist we infer the groundwater level anomalies associated with a hypothetical preslip prior to the anticipated m 8 tokai earthquake and evaluate the detectability of the anomalies using data from seven groundwater wells we evaluate the detectability of the anomalies under the following assumptions 1 an mw 5 5 6 5 aseismic preslip event occurs at the plate boundary in and around the hypothetical focal zone of the tokai earthquake 2 the total amount of the strain step at each observation associated with the preslip can be calculated by tensile and shear faulting based on the dislocation model 3 a normalized strain history associated with the preslip is defined from the results of numerical simulations based on rate and state dependent friction laws and 4 the groundwater level anomaly prior to the earthquake is proportional to the estimated history of the strain change associated with the preslip we investigate the detection time of the anomaly at seven wells given an mw 5 5 6 0 or 6 5 aseismic preslip at one of the 272 grid points in and around the area of the hypothetical focal zone of the tokai earthquake as a result over the time interval between 1 and 48 hours prior to the hypothetical tokai earthquake we are able to detect at each of the seven wells a hypothetical mw 6 5 preslip at 10 86 of the 272 grid points an mw 6 preslip at 0 19 grid points and an mw 5 5 preslip at 0 5 grid points

geochemistry of the eocene clastic sediments suonahu formation in the north qiangtang basin tibet implications for paleoclimate conditions provenance and tectonic setting the geochemistry of the clastic sedimentary units of the suonahu formation from the qd17 well in the northern qiangtang basin tibet was studied using various chemical analyses sio2 al2o3 ratios