origin of the catalina eddy abstract during late springs through early fall the normal regime of low level westerly and northwesterly flow within the bight of southern california is occasionally interrupted by periods of southerly flow elevated marine layers and increased low level cloudiness this transition often termed the catalina eddy is limited to narrow zone of 100 km from the coastal mountains and brings cooler temperatures and improved air quality this paper describes the initiation and evolution of catalina eddy events using both composite and case study approaches it is found that this phenomenon is produced by the interaction between the synoptic scale flow and the formidable topography of the region as a result of synoptic scale pressure falls along the central california coast and or mesoscale lee troughing southeast of point conception an alongshore pressure gradient with lower pressure to the north becomes established the result of such a pressure gradient in a coastal zone with an adjacent topographic barr

high 3he emanations from the source regions of recent large earthquakes central japan 1 recently two shallow mw 6 6 inland earthquakes the 2004 mid niigata prefecture earthquake and the 2007 niigataken chuetsu oki earthquake occurred in the niigata sedimentary basin near the boundary between the eurasian and the north american plates in order to elucidate the geographic distribution of the 3he 4he ratios in and around the seismic source regions new helium isotope data from hot spring gases and water samples from much denser sampling than in previous studies were determined although temporal changes in the 3he 4he ratios obtained from each well were unknown before and after the earthquakes higher 3he 4he ratios were observed in the earthquake source regions compared to other regions geochemical evidence for the presence of hot spring gases and natural gases with anomalously high 3he 4he ratios 3 8 ra indicates infiltration of mantle fluids derived from the subcrustal lithosphere a plausible source of mantle helium can be attributed to upward mobilization of aqueous fluids generated by dehydration of the subducting pacific plate slab resulting in the acquisition of primordial helium from a mantle wedge as the fluids into the crust in addition aqueous fluids may raise the earth s surface along permeable conduits leading to the reactivation of high angle inverted normal faults and the triggering of recent earthquakes

helium isotopes as geochemical indicators of a serpentinized fore arc mantle wedge new helium isotope data from hot springs on eastern kyushu island were obtained in order to elucidate the geographic distribution of 3 he 4 he ratios in the fore arc regions of southwest japan systematic regional variations in 3 he 4 he ratios are clearly distinguished across the fore arc from kyushu island 0 093 0 79 r a where r a denotes the atmospheric 3 he 4 he ratio of 1 4 x 10 6 to shikoku island 0 17 3 6 r a and to the kii peninsula 0 24 7 4 r a the distribution of mantle helium relative to total helium reveals a close association with the geophysical evidence of a serpentinized fore arc mantle wedge including the occurrence of deep nonvolcanic low frequency tremors lfts believed to be caused by upwardly mobile aqueous fluids derived from slab dehydration flux of mantle helium carried by aqueous fluids via a non serpentinized fore arc mantle wedge is very low on kyushu island where lfts have not been detected and 3 he 4 he ratios are lower than the atmospheric ratio on the other hand hot springs above the regions where lfts occur in the kii peninsula and northern shikoku island have high 3 he 4 he ratios indicating a significant contribution of mantle helium carried by aqueous fluids via a serpentinized fore arc mantle wedge the helium isotopes in hot and natural spring gases may be a useful geochemical indicator of a serpentinized fore arc mantle wedge especially in areas with sparse seismic station coverage

gps tec technique for observation of the evolution of substorm particle precipitation 1 one of the signatures of magnetospheric substorms is the precipitation of high energy particles into the high latitude ionosphere in this paper we introduce a new method of tracking substorm particle precipitation using gps total electron content tec and provide some preliminary observations of precipitation signatures from application of this method using tec measurements from several gps receivers we examined particle precipitation signatures associated with two separate substorm events 4 october 2008 and 29 october 2008 and monitored the expansion of the high energy precipitation regions with a higher temporal and spatial resolution than previously available for each event we have observed tec signatures associated with substorm particle precipitation along 20 to 25 separate gps raypaths from up to 7 gps receivers located in the canadian arctic this is in addition to particle injection signatures found in cluster satellite data and precipitation signatures in ground based riometer data signature timing on different raypaths from different stations indicates a mainly northward tailward expansion of the precipitation injection region with a smaller westward azimuthal component for the events studied by applying a triangulation method we also calculated propagation velocity of the precipitation boundary in regions covered by our gps receivers for each substorm expansion velocity ranged from 0 3 2 km s northward and 0 1 km s westward and tended to decrease in magnitude at higher latitudes

gas geochemistry of the hot spring in the litang fault zone southeast tibetan plateau abstract the southeast tibetan plateau is a region with high level seismic activity and strong hydrothermal activity several large 7 5 m 7 historical earthquakes have occurred in the litang fault zone lfz eastern tibetan plateau since 1700 litang ms 5 1 earthquake occurred on sept 23 2016 indicating the reactivation of the lfz this study was undertaken to elucidate spatial temporal variations of the hot spring gas geochemistry along the lfz from jun 2010 to april 2016 the chemical components he ne and c isotropic ratios of bubbling gas samples taken from 18 hot springs along lfz were investigated helium isotope ratios 3he 4he measured in hot springs varied from 0 06 to 0 93 ra ra air 3he 4he 1 39 10 6 with mantle derivd he up to 11 1 in the lfz assuming r ra 8 for mantle indicated the fault was a crustal scale feature that acts as a conduit for deep fluid from the mantle co2 concentrations of the majority of hot spring gas samples were 80 vol co2 3he ratios varied from 1 4 to 929 5 1010 and 13cco2 values varied from 19 2 to 2 3 vs pdb the proportions of mantle derived co2 varied from 0 to 1 8 crustal marine limestone was the major contributor 75 to the carbon inventory of the majority of hot spring gas samples before litang ms 5 1 earthquake the 3he 4he ratios obviously increased in the heni spring from may 2013 to apr 2016 the geographical distribution of the mantle derivd he decreased from east to west along 30 n in the southeast tibetan plateau relative to a corresponding increase in the radiogenic component the gas geochemical data suggested that the upwelling mantle fluids into the crust play an important role in seismic activity in the strike slip faults along 30 n in the southeast tibetan plateau

dipping san andreas and hayward faults revealed beneath san francisco bay california the san francisco bay area is crossed by several right lateral strike slip faults of the san andreas fault zone fault plane reflections reveal that two of these faults the san andreas and hayward dip toward each other below seismogenic depths at 60 and 70 respectively and persist to the base of the crust previously a horizontal detachment linking the two faults in the lower crust beneath san francisco bay was proposed the only near vertical incidence reflection data available prior to the most recent experiment in 1997 were recorded parallel to the major fault structures when the new reflection data recorded orthogonal to the faults are compared with the older data the highest amplitude reflections show clear variations in moveout with recording azimuth in addition reflection times consistently increase with distance from the faults if the reflectors were horizontal reflection moveout would be independent of azimuth and reflection times would be independent of distance from the faults the best fit solution from three dimensional traveltime modeling is a pair of high angle dipping surfaces the close correspondence of these dipping structures with the san andreas and hayward faults leads us to conclude that they are the faults beneath seismogenic depths if the faults retain their observed dips they would converge into a single zone in the upper mantle 45 km beneath the surface although we can only observe them in the crust

helium and carbon isotopic signatures of thermal spring gases in southeast yunnan china abstract late palaeozoic and cenozoic magmatism including pingbian quaternary basaltic volcanoes occurs in southeast yunnan china where seismic tomography evidence indicates magma activity in the uppermost mantle however the characteristics of mantle fluid release remain poorly understood here we report the chemical compositions of hot spring gases in se yunnan and measure the 3he 4he ratios 4he 20ne ratios and 13c values co2 ch4 to determine their origins and the factors influencing their migration except for five samples contaminated by the atmosphere 4he 20ne ratios 0 39 2 39 the rc ra ratios rc is the air corrected 3he 4he ratio ra is the air ratio with 1 4 10 6 range from 0 042 ra to 0 470 ra indicating that the helium is mostly of crustal origin with minor addition of mantle derived helium the calculated maximum proportion of mantle helium was 5 of total helium indicating that mantle 3he leakage correlates with the ductile lower crust the hot spring gases are fractionated by the partial dissolution of co2 in groundwater and the initial 13cco2 values are modelled by rayleigh fractionation within a range of 26 5 to 6 14 the modelled co2 in samples estimated by the he c isotope coupling model originates from the mixing of limestone and organic sediment end members the isotopic signature of ch4 69 2 to 35 9 suggests a thermogenic source and microbial oxidation in some samples furthermore the apparent isotopic temperatures are estimated using fractionation factors for ch4 and co2 suggesting a lack of magmatism in the crust beneath the red river fault zone 188 318 c but partial melting under the bozhushan granitoid plutons 572 688 c the low emission of mantle derived helium is attributed to the low fault permeability and minor active crustal deformation in present day se yunnan which restrain the upward migration of mantle fluids

noble gas isotopic compositions and water gas chemistry of soda springs from the islands of bioko sao tome and annobon along with cameroon volcanic line west africa abstract chemical and isotopic compositions are reported for water and co 2 and noble gases in groundwater and soda springs from bioko principe sao tome and annobon all islands located in the off shore part of the cameroon volcanic line in west africa the soda spring waters are of ca mg hco 3 type with d and 18 o values that range from 20 to 8 and 5 4 to 2 7 respectively indicative of a meteoric origin co 2 is the main gas species in the springs 13 c co 2 values vary from 2 8 to 5 0 overlapping the observed mantle c range 3 to 8 co 2 3 he ratios 3 9 10 9 suggest that most c 90 in the samples is derived from the mantle neon has atmospheric isotopic compositions while ar is slightly enriched in radiogenic 40 ar 3 he 4 he ratios 3 0 to 10 1 10 6 or 2 1 to 7 2 r a where r a is the atmospheric ratio of 1 4 10 6 are much higher than those for typical crustal fluids 10 8 but lower than those expected for fluids derived from high 3 he 4 he hotspots like loihi and iceland this precludes significant contributions of such fluids in the source regions of the gases and by inference in the magmatism of these oceanic islands alternatively approximately 90 of the he in sao tome gases is inferred to be derived from a source similar to the morb source the 3 he 4 he ratio for the bioko gas 6 6 10 6 may be derived from a source with a higher time integrated u th 3 he ratio than the morb source

carbon isotope geochemistry of natural gases from the green tuff basin japan carbon isotopic analyses of c1 c4 hydrocarbons were carried out to investigate the origin and formation mechanism of natural gases commercially produced from volcanic rocks as well as sedimentary rocks in the green tuff basin of northeast japan whose high 3he 4he ratios have suggested a possible magmatic origin 13c pdb values of methane ethane propane and n butane range from 54 4 to 33 3 from 32 5 to 20 9v from 27 7 to 20 6 and from 25 3 to 20 5 respectively all of which fall within the ranges of published data of worldwide gases of biogenie origin most samples show the isotope distribution pattern wherein the 13c values become less negative with increasing molecular weight of the hydrocarbons suggesting that the c2 hydrocarbons were not derived by methane polymerization the 13c values of c2 c4 hydrocarbons are explained by thermogenic breakdown of organic matter whereas the 13c values of methane are more or less lower than those expected from the same origin these results indicate that the gases from the green tuff basin consist of thermogenic hydrocarbons plus variable amounts of isotopically lighter microbial methane significant contributions of abiogenic methane which would be isotopically heavier than the thermogenic methane are not plausible for the gases

analysis of a california catalina eddy event abstract during the period 26 29 may 1968 a shallow cyclonic circulation known 1ocally as a catalina eddy developed in the offshore waters of southern california a synoptic and mesoscale analysis of the event establishes the following 1 the incipient circulation forms on the coast near santa barbara downwind of the coastal mountains 2 cyclonic shear vorticity appears offshore in response to lee troughing downstream of the coastal mountains between vandenberg and pt mugu california 3 mountain wave activity may be aiding incipient eddy formation in association with synoptic scale subsidence and the generation of a stable layer new the crest of the coastal mountains 4 a southeastward displacement and offshore expansion of the circulation occurs following the passage of the synoptic scale ridge line and 5 dissipation of the eddy occurs with the onset of a broad onshore flow

detailed fault structure of the 2000 western tottori japan earthquake sequence we investigate the faulting process of the aftershock region of the 2000 western tottori earthquake m w 6 6 by combining aftershock hypocenters and moment tensor solutions aftershock locations were precisely determined by the double difference method using p and s phase arrival data of the japan meteorological agency unified catalog by combining the relocated hypocenters and moment tensor solutions of aftershocks by broadband waveform inversion of freesia f net we successfully resolved very detailed fault structures activated by the mainshock the estimated fault model resolves 15 individual fault segments that are consistent with both aftershock distribution and focal mechanism solutions rupture in the mainshock was principally confined to the three fault elements in the southern half of the zone which is also where the earliest aftershocks concentrate with time the northern part of the zone becomes activated which is also reflected in the postseismic deformation field from the stress tensor analysis of aftershock focal mechanisms we found a rather uniform stress field in the aftershock region although fault strikes were scattered the maximum stress direction is n107 e which is consistent with the tectonic stress field in this region in the northern part of the fault where no slip occurred during the mainshock but postseismic slip was observed the maximum stress direction of n130 e was possible as an alternative solution of stress tensor inversion

the catalina eddy and its effect on pollution over southern california abstract a case study of a catalina eddy during project basin is presented there appears to he a topographic influence in the generation of this eddy detailed surface and upper air data over los angeles illustrate the effect of the eddy on the boundary layer and on the transport of ozone out of the basin isentropic analyses are consistent with visual satellite images of the phenomena the catalina eddy was shown to extend throughout the entire depth of the strong temperature inversion that exist over los angeles with maximum wind speeds within the inversion surface ozone levels downwind of the eddy are shown to vary depending on the local circulations

release of mantle and crustal helium from a fault following an inland earthquake abstract static stress changes caused by megathrust slip of the 2011 mw 9 0 tohoku oki earthquake considerably affected the seismicity patterns in inland areas resulting in the occurrence of numerous earthquakes along several active faults in japan on june 30 2011 the mj 5 4 central nagano earthquake occurred at a shallow depth of 5 km indicating the reactivation of the gofukuji fault in central japan this study was undertaken to elucidate spatial and temporal changes of 3he 4he ratios around a source region before and after an inland earthquake using both existing and new and helium isotope data from hot spring and drinking water wells gas samples near the gofukuji fault and its surrounding active faults are characterized by an increase in postseismic 3he 4he ratios in contrast the postseismic ratios decreased by up to about 30 away from the mainshock epicenter episodic faulting could either release stored crustal radiogenic helium from host rocks or enhance the transfer of mantle volatiles through permeable fault zones such that subsequent fluid flow near to the source region could then explain the spatio temporal variations in 3he 4he ratios

helium isotopes as a tool for detecting concealed active faults 1 a magnitude mj 7 3 crustal earthquake occurred in the western tottori area southwest japan on 6 october 2000 however there was no obvious prefaulting indication at surface of a fault corresponding to the western tottori earthquake in 2000 this study was undertaken to elucidate the geographic distribution of 3he 4he ratios around the seismic source region using helium isotope data obtained from groundwater samples from drinking water wells the maximum 3he 4he ratio observed was from the water well nearest to the epicenter of the main shock in addition there appears to be a clear trend of decreasing 3he 4he ratios with distance away from the main trace of the probable fault segments the observations provide significant evidence that the source fault of the earthquake in 2000 is associated with leakage of mantle volatiles through the crust to the earth s surface we suggest that helium isotopes can be regarded as a tool for investigating and or mapping concealed active faults with no surface expression

a numerical modeling study of the catalina eddy abstract a numerical modeling study of the catalina eddy was performed to investigate the causes of his occasional vortex over the bight of california the eddy was successfully simulated by imposing over the mesoscale domain a strong northwesterly flow resembling one that was associated with a june 1988 occurrence in the simulation a low pressure center form in the ice of the san rafael mountains that is over the northern bight the low forms because of leeside subsidence warning daytime diabatic heating of the flow that traverses the mountains is insignificant in response to the leeside low the large scale northwesterly flow turns cyclonically around point conception strengthening the westerly component of the flow over the bight the coastal mountains south of los angeles are a barrier to the large scale northwesterlies and to the westerly flow over the bight causing marine air to pool below the mountains mean height the pooled marine air replaces much warmer air in the strongly inverted lay

radon variations at arrowhead and murrieta springs continuous and discrete measurements two continuous radon monitors crms have been deployed at arrowhead hot springs along the san andreas fault near san bernardino and at murrieta hot springs along the elsinore fault the recorded hourly and daily radon variations during 1983 are within 5 of the mean values the radon levels increased however by about 10 20 above their normal baseline levels in midyear several small magnitude earthquakes m 3 0 3 5 occurred within 20 km of the arrowhead site near the end of the period of the radon increase

origin of methane rich natural gas in japan formation of gas fields due to large scale submarine volcanism eighty seven samples of ch4 rich natural gas were collected from commercial gas and oil wells in japan the3he 4he and4he 20ne ratios chemical composition of major minor and trace components ch4 c2h6 c3h8 co2 n2 o2 ar he ne and h2 and the c isotope composition of ch4 are reported most3he 4he ratios of natural gases in the forearc regions are as low as 1 4 10 7 and are comparable to those from large gas reservoirs in other parts of the world suggesting that the ch4 has a biogenic origin in contrast the3he 4he ratios of samples from gas reservoirs in the green tuff region along the japan sea vary considerably high ratios are observed for gases from volcaniclastic reservoirs in the deeper zone and low ratios are found in shallow reservoirs of sedimentary rocks the highest3he 4he ratio 9 37 0 34 10 6 is equivalent to the highest value in the subduction zone the high4he 20ne ratios observed in most samples suggest that there is no significant atmospheric contamination an overall regularity between3he 4he ratios and 13cch4 values is observed for japanese natural gases the 13cch4 value of gas with a high3he 4he ratio reaches about 35 and that of gas with a low ratio is about 75 total c to3he ratios c 3he vary over a wide range 6 108 9 1012 but those of gases in volcaniclastic reservoirs are in a rather narrow range with a value of 2 109 coinciding with that of a mantle reservoir the relation between the observed3he 4he ratios and 13cch4 values of gases together with their c 3he ratios suggests that ch4 rich gases in volcaniclastic reservoirs are a mixture of gases from two sources magmatic and biogenic the formation of gas reservoirs with high3he 4he ratios may be attributed to large scale submarine volcanism that occurred in the middle miocene gas separation from volcaniclastic rocks is expected to have occurred during the process of sea water rock interaction at a high temperature over a long period in a submarine environment the middle miocene volcanic episode which occurred under extensional stress was quite different from the present arc volcanism and is thought to have been closely related to the opening of the japan sea

helium isotope systematics at nevado del ruiz volcano colombia implications for the volcanic hydrothermal system abstract we have collected 14 water and gas samples from 9 thermal springs and gas vents near nevado del ruiz volcano colombia the 3 he 4 he and 4 he 20 ne ratios vary significantly from 0 98 r atm where r atm is the atmospheric 3 he 4 he ratio of 1 4 10 6 to 6 30 r atm and from 0 37 to 7 0 respectively the 3 he 4 he ratio corrected for air contamination decreases with increasing distance from the central crater of the volcano to the sampling site the trend is very similar to that observed at ontake volcano japan a hydrodynamic porous media dispersion model can explain the 3 he 4 he trend the temporal variations in the 3 he 4 he ratio at four sites provide useful information on the apparent velocity of the magmatic fluid flow brought on by a volcanic eruption the estimated value of several tens m day 1 agrees well with the inferred velocity of flow in oshima volcano japan and is comparable to the largest rate of groundwater movement in a deep sedimentary basin

the isotopic composition of radiogenic helium and its use to study groundwater movement in confined aquifers abstract the 3 he 4 he ratio for radiogenic he is shown to be primarily determined by the abundance of li and neutron absorbing elements in the host formations and is almost independent of the radioelement abundance the 3 he 4 he ratios have been computed for various li contents in rock matrices with average abundances of other elements the 3 he 4 he ratio is specific for each formation and may therefore be used to study crustal diffusion of he it is shown however that both the 3he and 4he contents of continental basements are likely to exceed those of the mantle so that diffusion of mantle he through continental crust is not likely to occur changes in the 3 he 4 he ratio for dissolved he have potential for studying groundwater movement and mixing processes atmospheric he which was dissolved at recharge is progressively diluted by radiogenic he with an isotopic ratio characteristic of the aquifer as the groundwater migrates down dip mixing proportions for formation he and atmospheric he in aquifers for which there is admixture of fracture borne water and interstitially stored water can also be estimated from isotopic measurements these processes are discussed in relation to two aquifers in eastern england

helium and carbon isotope variations in liaodong peninsula ne china chemical and c he isotopic compositions have been measured for n2 rich hydrothermal gases from the liaodong abbreviation of east liaoning province peninsula from which the oldest crustal rocks in china with 3 8 ga outcrop with the exception of one sample containing tritogenic 3he and atmospheric 4he in liaoyang the observed 3he 4he ratios from 0 1 ra to 0 7 ra indicate 1 8 helium from mantle 92 98 from crust and 0 1 0 8 from atmosphere despite the lack of quaternary volcanism such 3he 4he ratios suggest together with geophysical evidences the existence of intrusive magmas that contain mantle helium and heat within the liaodong middle lower crust the 3he 4he ratios are high along the ne trending jinzhou faults and gradually decrease with the increase of distance from the faults such a spatial distribution suggests that the mantle helium exsolves from magmatic reservoir in the middle lower crust becomes focused into the root zones of jinzhou faults and subsequently traverses the crust via permeable fault zones when transversely migrated by groundwater circulation in near surface mantle helium with high 3he 4he ratio may have been further diluted to the observed values by addition of radiogenic helium produced in the crust this pattern shows strong evidence that the major faults played an important role on mantle derived components transport from mantle upwards

fluid participation in deep fault zones evidence from geological geochemical and 18o 16o relations fluid incursion into fault zones and their deeper level counterparts brittle ductile shear zones is examined in a number of different crustal environments at the grenville front translation was accommodated along two mylonite zones and an associated boundary fault the high mz ii and low temperature mz i mylonite zones formed at 580 to 640 c and 430 to 490 c respectively in the presence of fluids of metamorphic orgin indigenous to the immediate rocks a population of posttectonic quartz veins occupying brittle fractures were precipitated from fluids with extremely negative 18o at 200 to 300 c the water may have been derived from downwards penetration into fault zones of low 18o precipitation on a mountain range induced by continental collision with uplift accommodated at deep levels by the mylonite zones coupled with rebound on the boundary faults at lagoa real brazil archaean gneisses overlie proterozoic sediments along thrust surfaces and contain brittle ductile shear zones locally occupied by uranium deposits following deformation at 500 to 540 c in the presence of metamorphic fluids and under conditions of low water to rock ratio shear zones underwent local intense oxidation and desilicification all minerals undergo a shift of 10 indicating discharge of meteoric water recharged formation brines in the underlying proterozoic sediments up through the archaean gneisses during overthrusting about 1000 km3 of solutions passed through these structures at yellow knife a series of large scale shear zones developed by brittle ductile mechanisms involving volume dilation with migration of 5 wt volatiles into the shear zone from surrounding metabasalts this early deformation involved no departures in redox state or whole rock 18o from background states of fe2 fe 0 72 and 7 to 7 5 respectively attesting to conditions of low water rock shear zones subsequently acted as high permeability conduits for pulsed discharge of 9 km3 of reduced metamorphic hydrothermal fluids at 360 450 c the west bay fault a late major transcurrent structure contains massive bull quartz that grew at 200 300 c from fluids of 2 to 6 possibly formation brines in general flow regimes in these fault and shear zones follow a sequence from conditions of high temperature and pressure with locally derived fluids at low water to rock ratios during initiation of the structures to high fluxes of reduced formation or metamorphic fluids along conduits as the structures propagate and intersect hydrothermal reservoirs later in the tectonic evolution and at shallower crustal levels there was incursion of oxidizing fluids from near surface reservoirs into the faults

summit outgassing as indicated by radon mercury and ph mapping kilauea volcano hawaii abstract surface geochemical mapping of rn hg and ph on the summit of kilauea volcano hawaii has shown some of the characteristics of outgassing rn concentrations measured in shallow ground gas are highest 10 to 155 units i e up to 0 016 nci l222rn over deep structures associated with the summit caldera low 1 to 5 units over the upper rift zones which are underlain by shallow intrusions and low to negative 1 to 3 units over most of the volcanically inactive peripheral areas high rn concentrations were measured over peripheral well developed structures such as the kaoiki and koae fault systems 45 and 12 units respectively the pattern of rn values broadly suggests the existence of a summit wide convection system interrupted locally by specific permeable structures the low ph 3 5 to 5 6 of soils over the caldera is suggested to be largely due to the sulfurous component of the ground gas the low concentrations of hg 5 to 80 ppb in these soils are postulated as being partly a function of subsurface complexing of hg with the abundant sulfur the shallow intrusions below the upper rift zones appear to have outgassed much of their sulfur content so soils in these areas are only slightly acid 5 6 to 6 2 allowing the accumulation of hg to concentrations of several thousands of ppb these conditions change during extrusive and intrusive events with the increases in shallow subsurface temperatures and volatiles in ground gas producing an increase in rn concentration and a decrease in soil hg due to volatilization after such events rn concentration decreases and soil hg increases significantly

magmatic fluids play a role in the development of active gas chimneys and massive gas hydrates in the japan sea abstract the earth s marine continental margins hold significant amount of carbon in the form of gas hydrate which can interact dynamically with seawater and the atmosphere and potentially influence global climate it is generally assumed that degradation of organic matter through either biogenic or thermogenic processes is responsible for the majority of the gas hydrate presently found in these deposits we present stable isotope and noble gas results from gas hydrates in the eastern margin of the japan sea and compare them with previously published data regarding gases which are found nearby in deep hydrocarbon wells associated with early miocene igneous and sedimentary rocks our results show that most of the gases which accumulate in the hydrate can be described as a mixture between a deeply sourced methane rich thermogenic crustal source tc a methane rich admixture of biogenic gases with relatively shallow air saturated seawater basw and a methane poor magmatic mantle source mm the presence of hydrate with a mantle 3he 4he signatures indicates that fluids enriched in mantle gases are responsible for the mobilization of thermogenic gas within active japan sea chimney structures the growth of primary hydrate at shallow marine sediment depths is ongoing as is the cycling of gas to hydrate which is eventually buried and dissociated at the base of the gas hydrate stability zone leading to large pockmark structures

mantle fluids in the karakoram fault helium isotope evidence abstract the karakoram fault kkf is the 1000 km long strike slip fault separating the western himalaya from the tibetan plateau from geologic and geodetic data the kkf is argued either to be a lithospheric scale fault with hundreds of km of offset at several cm a or to be almost inactive with cumulative offset of only a few tens of kilometers and to be just the upper crustal localization of distributed deformation at depth here we show 3he 4he ratios in geothermal springs along a 500 km segment of the kkf are 3 100 times the normal ratio in continental crust providing unequivocal evidence that a component of these hydrologic systems is derived from tectonically active mantle mantle enrichment is absent along the indus yarlung suture zone isz just 35 km southwest of the kkf suggesting that the mantle fluids flow only within the kkf within the last few ma the kkf must have accessed tectonically active tibetan mantle northeast of the mantle suture which we therefore locate vertically beneath the kkf very close to the surface trace of the isz hence in southwestern tibet indian crust may not now be underthrusting substantially north of the isz even though miocene underthrusting may have placed indian crust north of the isz in the lower half of the tibetan plateau crust this is in significant contrast to central and eastern tibet where underthrust indian material not only forms the lower half of the tibetan crust but is also currently underthrusting for 200 km north of the isz our new constraint on kkf penetration to the mantle allows an improved description of the continuously evolving karakoram fault as a tectonically significant yet perhaps geologically ephemeral lithospheric structure

research on groundwater radon as a fluid phase precursor to earthquakes groundwater radon monitoring work carried out in southern california by the university of southern california since 1974 is summarized here this effort began with a sampling network over a locked segment of the san andreas fault from tejon to cajon and was later expanded to cover part of the southern transverse mountain ranges groundwater samples were brought back weekly to the laboratory for high precision scintillation counting needs for more frequent sampling and less labor prompted the development of an economical and field worthy instrument known as the continuous radon monitor about 10 have been installed in the network since early 1980 the groundwater radon content was found to show anomalous increases mostly at a single station before a number of moderate and nearby earthquakes our work is hampered by a lack of large earthquakes that may have a regional impact on radon anomalies and by the complexity of the underground hydrological regime to circumvent this difficulty we have chosen to monitor only deep artesian wells or hot spring wells

transport of radon from fractured rock the transport of 222rn from fractured rock has been studied in an abandoned mine pressure induced flow both natural and artificial is quite important and can easily cause an order of magnitude increase in the instantaneous transport of radon into the tunnel airspace compared to that due to flowfree diffusion permeability studies indicate that large scale cracks of surface density of the order of several cracks per square meter dominate flow in first order effective flux due to natural pressure variation follows an approximate dp dt dependence in higher order there exists an enhancement of time averaged flux by typically a factor of 2 due to natural pressure variation mathematical modeling indicates that the relation between pressure and the strength and time dependence of the radon transport is difficult to explain solely with conventional models for semi infinite homogeneous porous media a model of cul de sac chambers is proposed to account for some of this dependence

geographical distribution of 3he 4he ratios in japan implications for arc tectonics and incipient magmatism the 3he 4he and 4he 20ne ratios of 115 natural gas samples including various types of gases from volcanoes hot springs mineral springs water wells petroleum fields and natural gas fields were measured using a mass spectrometer the observed 3he 4he and 4he 20ne ratios range from 7 47 10 8 to 9 65 10 6 and from 0 26 to 1100 respectively the 3he 4he ratios reflect well the geotectonic structure of the japanese islands in northeastern ne japan there is a clear geographical difference in the 3he 4he ratios between the frontal arc forearc and volcanic arc back arc regions lower ratios were found in the trench side region and higher ratios in the back arc side this result suggests that the mantle derived helium in the volcanic arc region is associated with the diapiric uprise of a magma lower 3he 4he ratios in the frontal arc region may be due to radiogenic he produced by radioactive decay of u and th in the crustal and sedimentary rocks in southwestern sw japan there is no clear geographical contrast in the 3he 4he ratios some samples in the frontal arc region show quite high 3he 4he ratios the tendency of the 3he 4he ratios agrees with the distribution of terrestrial heat flow data and reflects geotectonic structures different from ne japan the high 3he 4he ratios observed in the frontal arc region in sw japan may be indicative of renewed or incipient magmatism due to a descending young and warm slab

simulation of tensile crack generation by three dimensional dynamic shear rupture propagation during an earthquake 1 as there is no evidence that cracks are created directly in modes ii and iii shear cracks probably occur only along a weakness plane as in a preexisting fault mode i fracture therefore may be an important factor in crack formation during shallow earthquakes a three dimensional shear dynamic rupture process was simulated on the assumption that shear slip occurs only in a preexisting fault and the possibility of introducing new internal cracks that propagate under tensile stress as a consequence of the dynamic process of shear slip propagation the discrete element method dem was used to solve this problem because it can introduce internal tensile cracks the simple slip weakening model was used as the friction law on the preexisting fault for shear rupture propagation for new tensile cracks fracture follows classical griffith theory when the critical value for tensile fracture surface energy is reached the proposed model was used to simulate the rupture process of a strike slip shallow fault results show that the generation of new cracks is affected by rupture directivity in terms of the hypocenter and asperity location as well as by fault geometry with respect to the free surface cracks develop a flower like structure that surrounds the preexisting fault when the asperity is located at less than a certain depth the flower like structure that originates from the top of the fault reaches the free surface we consider that this is the mechanism for forming the flower structure near surface during a strike slip shallow earthquake

a monochromatic earthquake suggesting deep seated magmatic activity beneath the izu ooshima volcano japan after a quiescence of 12 years the izu ooshima volcano located about 30 km east of the izu peninsula in central japan erupted on november 15 1986 on august 27 1985 about 1 year before the eruption a peculiar earthquake of magnitude 2 7 took place near the moho boundary just beneath the izu ooshima volcano where seismic activity is otherwise absent analysis of digital data obtained by the telemetered seismic network of the national research center for disaster prevention reveals the following distinctive features of the seismic waves 1 the main part of the wave train is composed of s waves and a small p phase precedes it 2 the spectral density has a sharp peak at 1 0 hz which is independent of the epicentral distance azimuth and time indicating a monochromatic spectrum at the source 3 ground motion for the initial part of the s wave is polarized in the n s direction at almost all the stations the amplitude ratios of s to p waves and the polarization pattern of s waves suggest that a traction force caused by magma flow is a more probable source than a double couple mechanism free oscillation of the magma reservoir or opening of a tensile crack we propose a traction force model for this earthquake in which magma flow through a conduit produces unidirectional viscous force on the conduit walls the observations imply a n s force direction and a maximum force of about 2 8 1010 n the pressure difference between the ends of the conduit is estimated as 6 1 107 pa 610 bar under the assumption of conduit dimensions of 2 km 1 km the monochromatic nature of the source spectrum is difficult to account for by the free oscillation of a magma reservoir we tentatively suggest the intermittent opening of a barrier in the conduit as a plausible mechanism of the periodic oscillation

the role of kelvin waves in evolution of the catalina eddy abstract the response to pressure falls near a coastline is studied with a linear shallow water representation of the inversion capped marine layer the aim is to examine catalina eddy development in the southern california bight region of particular interest is response sensitivity to background flow parallel to the coastline as quantified by a froude number fr a conceptual model of eddy evolution is formulated that focuses on a pair of kelvin waves triggered by the pressure falls for subcritical fr fr 1 the waves move out of the regions of most favored growth located to the immediate north and south of the pressure fall center only a weak residual circulation remains in the bight region and an eddy does not form for supercritical fr the waves tend to be held in place by the background flow they thus undergo considerable amplification before dissipation eventually halts growth a vigorous eddy circulation results in the bight region that resembles observed structures

large amplitude gps tec variations associated with pc5 6 magnetic field variations observed on the ground and at geosynchronous orbit large amplitude variations in gps total electron content tec at pc5 6 6 67 mhz frequencies have been observed using a high data rate global positioning system gps receiver of the canadian high arctic ionospheric network tec variations with peak to peak amplitudes of 2 7 tec units 1 tecu 1016 el m 2 were observed over a 2 5 h period in the postnoon sector on 9 september 2011 during a period of high auroral activity within a moderate geomagnetic storm tec observations were from the sanikiluaq nunavut 56 54 n 280 77 e gps receiver located in the auroral region over this same time period compressional pc5 6 magnetic field variations were observed by the geosynchronous goes 13 magnetometer and the ground based sanikiluaq magnetometer goes 13 has a northern magnetic footprint in close proximity to sanikiluaq cross correlation analysis indicates that magnetic field and tec variations were possibly linked no natural hazards or nuclear explosions capable of exciting tec perturbations were reported on this day using a triangulation technique involving tec measurements of multiple gps satellites the propagation velocity of tec variations in the ionosphere was also calculated this calculation revealed two distinct events lower frequency 0 9 mhz tec variations that propagated westward consistent with the westward propagation of compressional pc5 waves observed by goes 13 and 15 satellites and higher frequency 3 3 mhz tec variations that propagated southward this is the first report of variations in ionospheric tec linked to satellite observations of pc5 6 ulf waves

evidence of kelvin waves in california s marine layer and related eddy generation abstract evidence suggests that an internal solitary kelvin wave exists in the marine layer along california the marine layer is lifted over the central coast by a weak cyclonic circulation this bump initially 850 m high moves to the north along the coast at 6 m s 1 the undisturbed layer depth is 100 200 m thick the crest height of the wave decreases to 500 m farther north winds under the raised marine layer are southerly the leading edge of the wave is easily followed by satellite as the thickened marine layer is marked by overcast stratus a greatly curved offshore leading edge indicates that nonlinear effects are important offshore scale in the overcast is about 300 km in the south and 50 km in the north surface pressure gradient alongshore is closely related to the marine layer depth the surface wind shifts when the leading and trailing edge of the wave passes northerly wave progression ceases at the sharp bend formed by cape mendocino at this time a vortex is formed in the marine laye

rare gas isotopic compositions in natural gases of japan isotopic and elemental compositions of rare gases in various types of gas samples collected in the japanese islands were investigated excess3he was found in most samples many samples showed a regionally uniform high3he 4he ratio of about 7 times the atmospheric ratio the he concentrations varied from 0 6 to 1800 ppm and they were low in co2 rich gases and high in n2 rich gases ne isotopic deviations from the atmospheric ne were detected in most volcanic gases the deviations and the elemental abundance patterns in volcanic gases can be explained by a mixing between two components one is mass fractionated rare gases and the other is isotopically atmospheric and is enriched in heavy rare gas elements ar was a mixture of mass fractionated ar atmospheric ar and radiogenic ar and the contribution of radiogenic40ar was small in all samples except for he elemental abundance patterns were progressively enriched in the heavier rare gases relative to the atmosphere several samples were highly enriched in kr and xe relative to the abundance pattern of dissolution equilibrium of atmospheric rare gases in water the component which is highly enriched in heavy rare gases may be released from sedimentary materials in the crust

relationship between 3he 4he ratios and subduction of the philippine sea plate beneath southwest japan 1 regional and local variations in mantle helium provide insight into the coupling of mantle crust tectonics and heat and or mass transfer from the earth s interior in order to further elucidate the geographic distribution of3he 4he ratios in southwest japan the data from a total of 924 sites were compiled and synthesized these include data from 48 additional hot spring and drinking water well sites on the northern kyushu island and in the northern chugoku region there appears to be good correlation between variations in helium isotope ratios and the geophysical evidence used to determine the configuration of the subducting philippine sea plate phs seismological studies reveal that the leading edge of the aseismic slab does not extend to the northern chugoku region nor to the osaka bay area where gas samples with significantly elevated 3he 4he ratios occur this is consistent with a mantle derived helium in these areas from melts and or mantle fluids ascribed to upwelling asthenosphere without being hindered by the descending phs slab in contrast gas samples in the regions where the overriding crust comes into direct contact with the subducting phs are dominated by radiogenic helium derived from the crust because of the absence of a mantle wedge the most plausible source of mantle helium owing to the abrupt changes in the seismicity and focal mechanisms of intraplate earthquakes the phs is considered to have slab tears beneath the kii channel and or the eastern kii peninsula oriented in a nw se direction however the lenear alignment of anomalously high3he 4he ratios does not appear to be nw se trending along the assumed slab tears but rather forms an broad ene wsw trending zone between the tears where low frequency events occur the emanation of gas with elevated3he 4he ratios in the central peninsula can be explained by the upward mobilization of mantle volatiles derived from the mantle wedge above the phs and or transferred from the hydrated slab mantle through the n s trending fractured medium within the phs accordingly the helium isotopes observed on the earth s surface may be efficient geochemical indicators of the configuration of a relatively younger warm aseismic slab and be especially useful in seismically inactive areas

constraints on fluid origins and migration velocities along the marmara main fault sea of marmara turkey using helium isotopes abstract fluids venting from the submarine portion of the marmara main fault part of the north anatolian fault system turkey were sampled in ti bottles deployed by submersible the fluids consist of mixtures of fault derived gases fault related cold seep fluids and ambient seawater these components can readily be distinguished using the isotopes of he and the he ne ratios 3he 4he ratios range between 0 03 0 1 and 4 9 0 4 ra indicating that both crustal and mantle derived sources of helium are sampled by the fault the dominant gas in all the samples analyzed is methane with the abundance of co2 below detection 2 in the mantle rich high 3he 4he fluids this is in contrast to nearly all mantle derived fluids where the c species are dominated by co2 while high ch4 co2 ratios may reflect organic or inorganic reactions within the crust which reduce mantle derived co2 to methane this is not a priori necessary we show that simple dilution of mantle fluids with methane produced within local sediments could result in the high 3he 4he methane rich gases currently emanating from the fault this observation is supported by an anticorrelation between 3he 4he and c 3he which is consistent with addition of c and 4he simultaneously to the fluids the highest 3he 4he ratios were found in the tekirdag basin at the foot of the escarpment bordering the western sea of marmara where seismic data are consistent with the presence of a fault network at depth which could provide conduits permitting deep seated fluids to rise to the surface the lack of recent volcanism or any evidence of underlying magmatism in the area along with low temperature fluids strongly suggests that the 3he rich helium in these fluids was derived from the mantle itself with the marmara main fault providing a high permeability conduit from the mantle to the surface assuming that the mantle source to the fluids originally had a 3he 4he ratio of 6 ra the minimum fluid velocities considering only vertical transport and no mixing with parentless 4he implied by the high 3he 4he ratios are of the order of 1 100 mm yr 1

preliminary results of seismogeochemical research in china several kinds of geochemical anomaly before strong earthquakes have been observed in china since 1966 they include changes in groundwater radon levels ion content of water ca 2 mg 2 cl so4 2 f dissolved gases h2 co2 and gases escaping from the aeration zone through abandoned dry wells ar n2 co2 the radon anomalies may be grouped as long term and short term anomalies most of the geochemical anomalies observed are characterized by a pattern of increase the largest amplitude recorded was 37 times the base level preliminary study indicates that the types of seismogeochemical anomaly observed prior to strong earthquakes depend on tectonic geologic lithologic and hydrogeological conditions at the monitoring station results obtained from modelling experiments on the mechanisms of some anomalies are given

tomographic evidence for the mantle upwelling beneath southwestern japan and its implications for arc magmatism abstract the seismotectonics and volcanotectonics of southwestern sw japan have been affected by the subduction of the old pacific and the young philippine sea slabs we have attempted to determine the three dimensional p and s wave velocity structures of the upper mantle in sw japan by using a large amount of high quality arrival time data recorded by the dense seismograph network on the japanese islands to understand the tectonic framework of sw japan our results show the existence of a large low velocity anomaly below the philippine sea slab in the chugoku and shikoku districts at least down to depths of 300 km we infer that the low velocity zone is an upwelling flow from depth two shallower low velocity zones derived from this low velocity zone are detected one is toward the quaternary volcanoes in the chugoku district and the other is toward the uppermost mantle beneath the kii peninsula the former suggests that the magma for the quaternary volcanoes in the chugoku district is attributable to the upwelling flow in the upper mantle this idea supports the geochemical and petrological observations that the erupted alkalic basalt in the chugoku district should have originated from a more primitive or enriched mantle the latter is responsible for the absence of a high velocity anomaly corresponding to the subducted philippine sea slab beneath the kii peninsula the philippine sea slab could have been more hydrated locally beneath the kii peninsula than that in the surrounding regions by the interaction with the mantle upwelling consequently dehydration reactions could be involved during the progressive metamorphism accompanied by intensive intraslab seismicity lowering the seismic velocity in the slab aqueous fluids thus released to the overriding plate might be a possible source of mantle type helium and trigger a long term swarm activity in the crust of the overriding plate our results indicate the importance of the heterogeneous structure below the philippine sea slab with regard to the tectonics of sw japan

quikscat reveals the surface circulation of the catalina eddy 1 the catalina eddy a small recurring cyclonic vortex in the ocean off los angeles is of keen interest to local weather forecasters because of the moderating oceanic effect it brings to the city its small size and shallow vertical extent have made it difficult to monitor and predict using conventional data the microwave scatterometer on the quikscat spacecraft has generated high resolution surface wind vectors that provide the first visualization of the complete cyclonic flow of the eddy moreover the superior performance of the quikscat scatterometer demonstrates the relative inaccuracy and inconsistency of predictions of the eddy based upon numerical weather prediction models

high latitude gps tec changes associated with a sudden magnetospheric compression 1 using ionospheric total electron content tec measured by global positioning system gps receivers of the canadian high arctic ionospheric network chain we provide clear evidence for a systematic and propagating temporary tec enhancement produced by compression of the magnetosphere due to a sudden increase in solar wind dynamic pressure the magnetospheric compression is evident in themis goes satellite data application of a gps triangulation technique revealed that the tec changes propagated with a speed of 3 6 km s in the antisunward direction near noon and 8 km s in the sunward direction in the pre noon lower latitude sector characteristics of these tec changes along with riometer absorption measurements seems to indicate that the tec change is due to electron density enhancement in the f region and is possibly due to particle precipitation associated with sudden magnetospheric compression

seismic moment assessment of earthquakes in stable continental regions iii new madrid 1811 1812 charleston 1886 and lisbon 1755 summary the sizes of three major or great historical earthquakes are reassessed using the isoseismal area regression tools developed in parts i and ii of this study of stable continental region scr seismicity the earthquakes are 1811 new madrid central united states and its following sequence 1886 charleston coastal south carolina and 1755 lisbon oceanic intraplate off the continental shelf of portugal the analysis confirms the large size of these events and for the first time places constraints on the uncertainty of their seismic moment release because of the exceptionally low seismic wave attenuation of eastern north america ena a separate north american regression of seismic moment on isoseismal area was developed additionally the unknown western extents of the new madrid isoseismal areas were calibrated with the patterns of the m 6 3 6 6 1843 and 1895 earthquakes application of part ii analysis procedures with these corrections yields new madrid size estimates expressed as moment magnitude of m 8 1 0 31 for the 1811 december 16 m 7 8 0 33 for the 1812 january 23 and m 8 0 0 33 for the 1812 february 7 principal events the charleston earthquake s magnitude decreases from m 7 4 to m 7 3 0 26 after compensation for the effect of coastal plain sediments on its inner isoseismals intensity regressions for lisbon are calibrated against the isoseismal pattern of the nearly co located m 7 8 1969 st vincent earthquake which in this case increases the predicted size of lisbon from m 8 4 to m 8 7 0 39 these size estimates are supported by data from independent phenomena extent and severity of liquefaction the maximum distance of induced landslides and for lisbon tsunami wave amplitudes estimated source parameters are controlled by crustal or lithospheric temperature which governs the depth extent of brittle faulting using estimated continental and oceanic geotherms viable fault lengths are 30 80 km for charleston 120 180 km for 1811 new madrid and 180 280 km for lisbon for average displacements of 2 4 m 8 11 m and 10 14 m respectively and for average static stress and strain drops at the estimated seismic moments of this study the 1811 new madrid and the 1755 lisbon events are respectively the largest known scr and oceanic lithosphere earthquakes

the 0 125 degree finite volume general circulation model on the nasa columbia supercomputer preliminary simulations of mesoscale vortices 1 the nasa columbia supercomputer was ranked second on the top500 list in november 2004 such a quantum jump in computing power provides unprecedented opportunities to conduct ultra high resolution simulations with the finite volume general circulation model fvgcm during 2004 the model was run in realtime experimentally at 0 25 degree resolution producing remarkable hurricane forecasts atlas et al 2005 in 2005 the horizontal resolution was further doubled which makes the fvgcm comparable to the first mesoscale resolving general circulation model at the earth simulator center ohfuchi et al 2004 nine 5 day 0 125 degree simulations of three hurricanes in 2004 are presented first for model validation then it is shown how the model can simulate the formation of the catalina eddies and hawaiian lee vortices which are generated by the interaction of the synoptic scale flow with surface forcing and have never been reproduced in a gcm before

simulation and prediction of the catalina eddy abstract observational studies generally suggest that the formation of the catalina eddy in the bight of southern california results from interaction between the synoptic scale northerly flow and the topographic barrier along the southern california coast in an attempt to better understand the eddy generation mechanisms a high resolution mesoscale model is initialized and forced on the lateral boundaries by nmc s large scale objective analysis and a detailed numerical study of the 26 30 june 1988 catalina eddy event is presented the model results compare favorably with the observations and generally support the aforementioned mechanism of the eddy formation it appears that a warm air mass over the bight resulting from adiabatic heating of low level downslope flow deflected by the mountain barrier significantly helps create the alongshore and offshore pressure gradients favorable for the generation of a cyclonic vorticity although current operational forecast models are capable of often accurately pr

gas geochemistry of hot springs at the tengchong field southwest china controlled by the spatial distribution of magmatic chamber abstract the tengchong volcanic field located at the collision zone between the indian and eurasian plates is well known for its large scale holocene volcanic eruptions and extensive hydrothermal activities bubbling gases from eight geothermal springs at the tengchong field were collected and analyzed for their chemical and isotopic compositions 3he 4he 20ne n2 ar 13cch4 and 13cco2 the results show that the gas samples could be categorized into a group i dominated by n2 and a group ii with co2 as major component the air corrected 3he 4he ratios ranged from 0 17 ra to 4 76 ra and the calculated mantle contributions dramatically varied from 1 9 to 77 9 for group ii by contrast an invariant air corrected 3he 4he ratio of about 0 30 ra and a relatively constant mantle contribution of 4 0 to 5 0 was obtained for group i the sampling sites just on top of the magma chamber received significant mantle derived helium and magmatic gas components at the proximal site of the magma chamber 95 magmatic gas contributions the calculated n2 ar ratio of the hydrothermal endmember for group ii sample sites close to the magma chamber was 61 7 66 2 suggesting that the reaction zone temperature is between 223 c and 252 c the influence of the magma chamber decreases with increasing distance of the sampling sites from the chamber apex the sampling sites group i at the marginal area discharge gases with relatively low 3he 4he ratios and magmatic contributions 19 24 the temperature of the reaction zone for this group was estimated to be 74 c based on the n2 ar ratio of 42 this study provided important constraints to relate hydrothermal gas geochemistry directly with the spatial distribution of the underlying magma chamber plain language summary geochemical characteristics of gases discharged from hydrothermal systems are usually affected by deep magmatic processes shallow hot fluids circulation and water rock interactions in the reaction zone in this study we analyzed the gas abundances and isotopic compositions of hydrothermal gas discharged from the yunnan tibet geothermal belt we used a gas mixing model to quantify the contributions of mantle derived magmatic endmember and hydrothermal endmember the 3he 4he ratios magmatic contribution and temperature of the reaction zone decreased significantly with increasing distance from the magma chamber underneath the tengchong field highlighting the intimate relationships between gas transport hydrothermal circulation and the extent of the magma chamber

flow of mantle fluids through the ductile lower crust helium isotope trends heat and mass are injected into the shallow crust when mantle fluids are able to flow through the ductile lower crust minimum 3he 4he ratios in surface fluids from the northern basin and range province western north america increase systematically from low crustal values in the east to high mantle values in the west a regional trend that correlates with the rates of active crustal deformation the highest ratios occur where the extension and shear strain rates are greatest the correspondence of helium isotope ratios and active transtensional deformation indicates a deformation enhanced permeability and that mantle fluids can penetrate the ductile lithosphere even in regions where there is no substantial magmatism superimposed on the regional trend are local high 3he 4he anomalies indicating hidden magmatic activity and or deep fluid production with locally enhanced permeability identifying zones with high resource potential particularly for geothermal energy development

crustal heterogeneity in the 2000 western tottori earthquake region effect of fluids from slab dehydration abstract in order to understand the generating mechanism of the western tottori earthquake m 7 3 that occurred on 6 october 2000 in southwest japan we determined high resolution 3d p and s wave velocity and poisson s ratio structures in the epicentral area we used 17 542 p and 13 831 s wave high quality arrival times from 721 tottori aftershocks and other local microearthquakes recorded by the dense high sensitivity seismic network hi net installed recently on the japan islands significant variations of up to 4 for seismic velocity and 9 for poisson s ratio are revealed in the aftershock area areas with large coseismic slips and high aftershock activity are associated with high p wave velocity v p high poisson s ratio and high electrical conductivity which may represent strong and competent parts of the fault zone containing fluids the western tottori mainshock hypocenter is located in a boundary zone where both velocity and poisson s ratio change drastically both p and s wave velocities are slower in the lower crust under the mainshock hypocenter and low frequency microearthquakes were detected within the slow anomalies around the moho discontinuity before and after the occurrence of the 2000 western tottori earthquake these results and other related evidence suggest that the strong crustal heterogeneity in the western tottori source area is associated with fluids and arc magma under nearby the daisen volcano which may have influenced the nucleation and rupture process of the western tottori earthquake the arc magma and fluids are thought to result from the dehydration reactions of the subducting philippine sea slab in this region these results suggest that the nucleation of shallow earthquakes could be controlled by a deep structure and regime and so it is important to study the deeper crust and upper mantle structure and processes for clarifying the generating mechanism of large crustal earthquakes

the chemical compositions and abundances of volatiles in the siberian large igneous province constraints on magmatic co2 and so2 emissions into the atmosphere abstract the siberian large igneous province slip is known to be synchronous with the most severe mass extinction on the earth at the end of permian the viability of the slip as a trigger for the mass extinction depends crucially on the total amounts of important volatiles such as co 2 and so 2 emitted from the slip into the atmosphere the chemical compositions and abundances of volatiles in picrite and gabbroic rocks of the slip have been determined by a vacuum stepwise heating mass spectrometer system the volatiles released at temperatures 2 o with high contents of co 2 so 2 and h 2 plus detectable he the total amounts of primary volatiles in the picrite are 19 991 mm 3 stp g stp standard temperature and pressure h 2 o 331 co 2 202 h 2 28 co 13 so 2 and 2 h 2 s the total amounts of primary volatiles in the gabbroic rocks are 2869 mm 3 stp g h 2 o 131 so 2 120 h 2 85 co 2 79 h 2 s and 16 co these data together with other important constraints from literatures are used to calculate the total amounts of volatiles emitted from the slip into the atmosphere in our mass balance calculations we used the abundances of co 2 and so 2 in melt inclusions in olivine phenocrysts from the slip determined previously by other researchers to represent their initial concentrations in magma before degassing and our new data for the slip picrite to represent the volatile compositions of magma basalt after eruption our results for the gabbroic rocks are used to estimate the proportions of volatiles that are still retained in the subvolcanic intrusions of the slip the results reveal that the total amounts of important volatiles emitted from the slip are 8 5 10 7 tg co 2 4 4 10 6 tg co 7 0 10 6 tg h 2 s and 6 8 10 7 tg so 2 tg trillion grams these values are similar to the previous estimates using different methods by other researchers our data support a popular notion that the end permian mass extinction on the earth was caused by the emission of enormous amounts of volatiles from the slip into the atmosphere

complete miscibility between silicate melts and hydrous fluids in the upper mantle experimental evidence and geochemical implications the phase relationships between silicate melts and hydrous fluids were studied by direct visual observation in an externally heated diamond anvil cell complete miscibility of silicate melt and water was observed for a wide range of melt compositions including nepheline jadeite dacite haplogranite and ca bearing granite some evidence for complete miscibility was also observed in the system basalt h2o the critical temperatures in all systems decrease rapidly with pressure at 15 kbar the critical temperature for nepheline is around 550 c for jadeite around 800 c and for granitic compositions it is close to 900 c in general the critical temperatures appear to increase with silica content in the system our results suggest that there is complete miscibility between silicate melts and water in most of the upper mantle except at very shallow depths this means that a water saturated solidus cannot be defined any more in the deeper parts of the upper mantle very silica rich melt inclusions found in spinel lherzolites associated with fluid inclusion are probably the result of the unmixing of a supercritical fluid containing comparable amounts of water and silicate components the decomposition of amphibole in a subducted slab occurs at conditions where the miscibility gap between fluid and silicate melt is not yet closed while the decomposition of phengite and lawsonite occurs far beyond the critical curve accordingly the fluids released by the breakdown of these minerals should have very different properties highly mobile hydrous fluids containing little dissolved silicate should be produced by amphibole breakdown while the decomposition of lawsonite and phengite will lead to much more silicate rich and less mobile fluid phases

three dimensional distributions of s wave reflectors in the source region of the 2000 western tottori earthquake 1 we conducted a reflection analysis of the aftershock waveforms in the source region of the 2000 western tottori earthquake we obtained three dimensional distributions of s wave reflectors in the source region by using 9000 waveform traces in the cross section projected along the mainshock fault plane we found three major reflection zones at depths of 15 25 km 30 40 km and 50 60 km the first and second are thought to correspond to the conrad and the moho discontinuities the depth of these reflective zones seems to change along the fault direction also cross sections perpendicular to the fault plane show that the strengths of the reflected waves are different between the two sides of the fault plane this result suggests that the mainshock fault plane is located at the boundary of medium properties and its near vertical downward extension in the lower crust

nonvolcanic tremors deep beneath the san andreas fault we have discovered nonvolcanic tremor activity i e long duration seismic signals with no clear p or s waves within a transform plate boundary zone along the san andreas fault near cholame california the inferred epicentral region of the 1857 fort tejon earthquake moment magnitude 7 8 the tremors occur between 20 to 40 kilometers depth below the seismogenic zone the upper 15 kilometers of earth s crust where earthquakes occur and their activity rates may correlate with variations in local earthquake activity

imaging the seismic structure and stress field in the source region of the 2004 mid niigata prefecture earthquake structural zones of weakness and seismogenic stress concentration by ductile flow 1 we deployed a dense temporal seismic network in the source region of the 2004 mid niigata prefecture earthquake thrust fault japan a detailed velocity structure and accurate aftershock distributions were elucidated by inverting aftershock arrival times using double difference tomography a stress tensor inversion using the first motion data was also conducted in order to investigate the stress field the seismic velocities in the hanging wall above the main shock fault are lower than those in the footwall with the velocity contrast extending to a depth of approximately 10 km the aftershocks along the main shock rupture zone are distributed around the sharp boundary between the low and high velocity bodies furthermore aftershocks associated with the largest aftershock appear to be aligned on a boundary between low and high velocity zones in the footwall the orientation of maximum principal stress 1 is consistent with the regional compressional strain rate axis inferred from gps data except in the southwestern side of the main shock hypocenter where the azimuth of 1 rotates approximately 20 counterclockwise the main shock hypocenter was located roughly at the transition zone where the structure of the hanging wall changes laterally and the azimuth of 1 rotates heterogeneous structures of the seismic velocity and the stress field combined with the ductile deformation of the upper crust may have concentrated seismogenic stress around the hypocenter area to cause the complex distributions of aftershock sequence on structural boundaries

active degassing of mantle derived fluid a geochemical study along the vulture line southern apennines italy abstract we report the results of a geochemical study of gas emissions along a ne sw transect in southern italy in order to test the hypothesis that the region around monte vulture is affected by degassing of mantle derived fluids through a lithospheric discontinuity we also investigated lavas from the monte vulture volcano displaying 3 he 4 he up to 6 0 ra and sr isotopes that are consistent with an origin in mantle that has had minimal pollution from subducted adriatic slab similar 3 he 4 he in fluids from around mt vulture indicate that the deep volcanic system is still degassing mantle derived he occurs in fluids along the length of the vulture line reinforcing the hypothesis that it is a deep tectonic discontinuity along which mantle fluids and or melts advect to the surface the co 2 3 he ratios are highly variable 2 7 10 8 2 15 10 11 in response to processes such as gas dissolution into aquifers addition of crustal gases and degassing fractionation

mantle derived helium in foreland basins in xinjiang northwest china abstract hydrocarbon rich natural gases from the tarim junggar turpan hami and santanghu basins in xinjiang northwest china have measured 3he 4he ratios from 0 01 to 0 6 times higher than the atmospheric value indicating 0 7 helium derived from the mantle the mantle derived helium is high in foreland basins associated with the tianshan kunlun and zhayier halalate orogenic mountains but low towards the center of basins this spatial distribution suggests that the mantle derived helium originates either from fluids or small scale melts in the upper asthenospheric or lithospheric mantle which have found pathways into the root zones of the major faults defining these mountains but do not significantly move into the basins themselves during upward transport to near the surface the mantle derived helium is significantly diluted by radiogenic helium produced in the crust despite the lack of recent magmatic activity or extensional tectonics within the basins this pattern shows strong evidence that the major faults play an important role in mantle derived components degassing from the mantle to the surface

3 he 4 he ratios in ch 4 rich natural gases suggest magmatic origin natural gas and oil fields commercially exploited since the 1950s are distributed in the zonal area facing the sea of japan in north east japan we report here measurements of the 3he 4he ratios in 27 ch4 rich natural gases obtained from commercial oil and gas wells in the area we observed extraordinarily high 3he 4he ratios up to 8 65 10 6 in gases from wells drilled into deep reservoirs in volcaniclastic rock formations the so called green tuff fig 1 these values are almost identical to those of volcanic fumaroles in the japanese islands in contrast gases in shallower sedimentary rock reservoirs have low 3he 4he ratios with a minimum value of 0 3 10 6 these low values are similar to those of natural gases originating from biological materials this suggests that the formation of natural gas reservoirs in the volcaniclastic rock may be attributed to large scale magmatic activities which occurred in the middle miocene

the relationship between late cenozoic tectonic events and stress field and basin development in northeast japan the regional tectonic stress field basin development and crustal deformation of the ne japan arc in the interval between 32 ma to the quaternary can be synthesized based on dike vein and fault orientation data as well as on the compilation of the regional geology an extensional stress field became prevalent from 32 ma and major normal faulting started at 25 20 ma which resulted from back arc rifting normal faulting trending nearly parallel to the arc propagated from the present japan sea coast to the forearc side following the trenchward migration of the main volcanic field from 20 to 15 ma normal faults with an oblique trend to the arc developed due to the counterclockwise rotation of ne japan the rapid clockwise rotation of sw japan since 16 ma produced a nw se directed transtensional stress regime in the ne japan arc due to crustal stretching associated with this pull apart movement the back arc side of the ne japan arc subsided rapidly to middle bathyal environments after the termination of the opening of the japan sea at about 14 ma a neutral stress regime prevailed which included phases of both weak extension and compression lithospheric cooling eventually led to thermal subsidence of the back arc region and igneous underplating caused uplift of the axial zone of the volcanic arc the increase in velocity of the westward motion of the pacific plate at around 4 ma produced strong compression across the arc reactivating most of the miocene normal faults and uplifting the volcanic arc the greatest crustal shortening occurred in areas that were stretched the most in the miocene within the volcanic arc which implies tectonic inversion

heat source for an amagmatic hydrothermal system noto peninsula central japan 1 although there is no evidence of volcanism in the noto peninsula since the late miocene the peninsula has long been known to be unusual and atypical of non volcanic regions as indicated by high temperature hot springs and a geothermal gradient greater than 50 k km in order to provide geochemical constraints on the heat source for amagmatic hydrothermal activity the chemical and isotopic compositions of 14 gas and water samples from hot springs were measured the observed 3he 4he ratios of most hot spring gases range from 0 03 to 1 2 ra ra denotes the atmospheric 3he 4he ratio of 1 4 10 6 in these samples mantle helium composes less than 10 of the total helium indicating an insignificant contribution of mantle derived volatiles from for example newly ascending magma and or aqueous fluid generated by dehydration of the subducting slab the noto peninsula mainly consists of neogene volcaniclastic and sedimentary rocks overlying paleozoic to mesozoic basement rocks associated with uranium bearing granite pegmatite containing elevated concentrations of heat generating elements such as uranium thorium and potassium a plausible heat source for the amagmatic hydrothermal activity can be attributed to this distinctive geological environment where high heat producing granitic rocks are buried under neogene sedimentary rocks with low thermal conductivities that act as thermal blankets most noto peninsula hot springs are found in areas of active faulting where stress concentrations since the late miocene could open an existing fault pathway because the fluid pressure is close to the lithostatic pressure meteoric waters circulating through hot basement rock come to the surface along these permeable conduits with minimal mixing with shallow groundwater resulting in emanation of high temperature hot springs with low 3he 4he ratio gases along active fault zones

dynamics of the pacific north american plate boundary in the western united states the vertically averaged deviatoric stress tensor field within the western united states was determined with topographic data geoid data recent global positioning system observations and strain rate magnitudes and styles from quaternary faults gravitational potential energy differences control the large fault normal compression on the california coast deformation in the basin and range is driven in part by gravitational potential energy differences but extension directions there are modified by plate interaction stresses the california shear zone has relatively low vertically averaged viscosity of about 1021 pascal seconds whereas the basin and range has a higher vertically averaged viscosity of 1022pascal seconds

high strain rate zone in central honshu resulting from the viscosity heterogeneities in the crust and mantle abstract a linear zone with high strain rates along the backarc side of central honshu the so called niigata kobe tectonic zone has been revealed by the dense gps array geonet operated by the geographical survey institute of japan in order to explore the origin of this zone we examine rheological heterogeneities in the crust or mantle above a subducting slab which possibly contribute to the high strain rates we calculate velocity profiles at the surface of the upper plate due to loading and unloading of the subducting philippine sea plate using a 2 dimensional finite element method from the numerical experiments we find that the high strain rates can be reproduced by viscosity heterogeneities either in the crust or the mantle if viscosity heterogeneity in the crust is an origin the conditions to be satisfied are i an effective elastic thickness of 5 km for short term loading 10 2 10 3 yr ii a low viscosity 19 pa s in the lower crust beneath the zone with a normal viscosity 10 21 pa s in the ambient lower crust and iii a uniform viscosity of 10 19 pa s in the upper mantle on the other hand if viscosity heterogeneity in the mantle is an origin the conditions to be satisfied are i an effective elastic thickness of 30 km for short term loading ii a low viscosity 10 18 pa s at least down to a depth of 60 km in the zone and to a depth of 10 km further seaward below the moho depth and iii a viscosity of 10 20 pa s in the ambient mantle the crust heterogeneity model contradicts the 15 km cut off depth of intraplate seismicity and the 20 km effective elastic thickness previously inferred from gravity and topography in central honshu the fact that quaternary active faults and intraplate earthquakes are not particularly concentrated in the zone also favours the mantle viscosity heterogeneity model thus we prefer the mantle heterogeneity model we suggest that upward movement of water dehydrated from the subducting philippine sea and pacific plates partial melting of the mantle above the pacific plate and serpentinization in the wedge mantle above the philippine sea plate are possible origins of the low viscous upper mantle possible low viscosities in the upper mantle wedge presented in this study seem to provide important constraints for subduction processes of oceanic plates and strain accumulation processes in the upper plate

gas geochemistry applied to earthquake prediction an overview terrestrial gases in groundwater and soil air have been extensively studied in recent years in seismically active areas especially in ussr china japan and united states in search of premonitory changes that might be useful for earthquake prediction concentrations of radon helium hydrogen mercury carbon dioxide and several other volatiles have been found generally to be anomalously high along active faults suggesting that the faults may be paths of least resistance for the terrestrial gases generated or stored in the earth to escape to the atmosphere temporal gas concentration changes with durations of a few hours to many months have been observed before many large earthquakes at a relatively small number of favorably situated stations at epicentral distances of up to several hundreds of kilometers these sensitive stations are generally located along active faults especially at intersections or bends of faults or some other structurally weak zones possibly because of tectonic strain concentration at such places however gas concentrations especially those measured at or near the ground surface may also be significantly affected by meteorological hydrological and other nontectonic changes in the environment the nontectonically induced variations must be carefully eliminated or recognized in the search of true earthquake related anomalies

origin and interactions of fluids circulating over the amik basin hatay turkey and relationships with the hydrologic geologic and tectonic settings abstract we investigated the geochemical features of the fluids circulating over the amik basin se turkey syria border which is crossed by the northern extension of the dsf dead sea fault and represents the boundary area of three tectonic plates anatolian arabian and african plates we collected 34 water samples thermal and cold from natural springs and boreholes as well as 8 gas samples bubbling and gas seepage besides the gases dissolved in the sampled waters the results show that the dissolved gas phase is a mixture of shallow atmospheric and deep components either of mantle and crustal origin coherently the sampled waters are variable mixtures of shallow and deep ground waters the latter being characterised by higher salinity and longer residence times the deep groundwaters from boreholes deeper than 1000 m have a ch 4 dominated dissolved gas phase related to the presence of hydrocarbon reservoirs the very unique tectonic setting of the area includes the presence of an ophiolitic block outcropping in the westernmost area on the african plate as well as basalts located to the north and east on the arabic plate the diffuse presence of co 2 enriched gases although diluted by the huge groundwater circulation testifies a regional degassing activity fluids circulating over the ophiolitic block are marked by h 2 dominated gases with abiogenic methane and high ph waters the measured 3 he 4 he isotopic ratios display contributions from both crustal and mantle derived sources over both sides of the dsf although the serpentinization process is generally independent from mantle type contribution the recorded helium isotopic ratios highlight variable contents of mantle derived fluids due to the absence of recent volcanism over the western side of the basin african plate we argue that co 2 rich volatiles carrying mantle type helium and enriched in heavy carbon are degassed by deep rooted regional faults rather than from volcanic sources

crustal structure across the san andreas fault southern california from teleseismic converted waves crustal structure along a 140 km long profile across the san andreas fault saf in southern california was imaged by stacking teleseismic p s converted phases recorded by a dense short period seismic array the crust mantle discontinuity moho is visible as a continuous feature at a depth around 30 km but is offset 6 to 8 km beneath the saf a small moho disruption can also be seen under the eastern california shear zone ecsz these results suggest that the saf and ecsz extend through the entire crust the moho upwarp under the san gabriel mountains indicates that the mountain ranges were lifted en masse as a result of crustal buckling under horizontal compression

continuous gps array and present day crustal deformation of japan a gps array with about 1 000 permanent stations is under operation in japan the gps array revealed coseismic deformations associated with large earthquakes and ongoing secular deformation in the japanese islands based on daily coordinate data of the gps stations strain rate distribution is estimated most regions with a large strain rate are related to plate boundaries and active volcanoes in addition the niigata kobe tectonic zone nktz is recognized as a region of large strain rate along the japan sea coast and in the northern chubu and kinki districts this newly found tectonic zone may be related to a hypothetical boundary between the eurasian or amurian and the okhotsk or north america plates precise observation of crustal deformation provides important boundary conditions on numerical modeling of earthquakes and other crustal activities appropriate computation methods of continuous deformation field are directly applicable to data assimilation for such numerical simulations

multiple lines of evidence for crustal magma storage beneath the mesozoic crystalline iide mountains northeast japan 1 it has been recognized that the iide mountains consisting of mesozoic sedimentary rocks and late cretaceous to paleogene granitic rocks northeast japan are unique although they occur in a nonvolcanic region hot springs in the iide mountains have anomalously high heat discharge values similar to those from hot springs in volcanic regions in order to provide geochemical constraints on the heat source for the hydrothermal activity the chemical and isotopic compositions of 10 gas and water samples were determined the 3he 4he ratios determined range from 0 22 to 7 9 ra and the highest ratio is similar to morb type helium indicating a significant contribution of primordial mantle helium considering the relationship between the magnitude of the 3he 4he ratios and the distance of the sample locations from the kitamata dake the peak in the iide mountains where the largest ratio occurs it is apparent that there is a sharp decrease in 3he 4he ratios laterally away from the peak furthermore the peak is also the location where geophysical anomalies such as an anomalous conductive body and zones with low vp and low vs have been detected in the middle lower crust these high helium ratios are considered to indicate the likelihood of mantle derived materials supplying morb type helium beneath the kitamata dake and the possibility that mantle derived helium has been diluted by atmospheric and or crustal components with lower helium ratios away from the peak in order to examine whether or not ancient magma of middle miocene age is a possible source of the high 3he 4he ratios of the hot spring gases we calculated the evolution in 3he 4he ratios of the ancient magma with time as a result it is concluded that the anomaly beneath the iide mountains is due to newly ascending magmas in the present day subduction system rather than hydrothermal fluids related to late remnant magmatism of middle miocene age

how ductile are ductile shear zones three premises of ductile deformation in the middle and lower crust are widely accepted 1 rocks flow with power law viscous rheology 2 localization in ductile shear zones involves strain softening and 3 fluid flows into and is channelized within ductile shear zones ductile viscous shear zones should therefore initially develop along planes of maximum shear stress strain soften and rotate as material planes into the field of progressive extension however the mean stress or pressure within a weak elongate viscous band being stretched is higher than the surrounding matrix and this is difficult to reconcile with premise 3 in contrast mohr coulomb brittle faults always have lower pressure within the fault zone flow of fluid and melt into high temperature shear zones therefore implies that ductile shear zones are not perfectly viscous but have a pressure dependent viscoplastic rheology the continued pressure dependence may reflect significant microcracking on the grain scale even when localized deformation does not produce larger scale discrete fractures

helium isotope variations in turkey relationship to tectonics volcanism and recent seismic activities the distribution of helium isotope ratios in the various tectonic provinces of turkey is examined through a synthesis of previously published data and the results of a recent survey along the north anatolian fault zone nafz following the catastrophic 1999 earthquakes the r ra values where r sample 3he 4he and ra air 3he 4he cover a wide range from 0 05 to 7 87 and the mantle derived helium is clearly identified in most locations the mantle derived component is high 50 of total he in a regions of central and eastern anatolia both of which are associated with historically active volcanoes and b the seismically active west to central segment of nafz while the mantle contribution reaches a maximum at nemrut volcano in eastern anatolia a region of dominantly compressional tectonics and with moderate enthalpy geothermal fields it is relatively low 50 in the western anatolian extensional province even though this region has the highest geothermal potential the average 3he enthalpy ratios estimated for the different provinces suggest lithospheric stretching and rise of the geotherm as the major mechanism of high heat flow yet limited intrusive activity in western anatolia is suggested as the reason for the comparatively low he additions and consequently low 1 7 106 atoms j 3he enthalpy ratios a more extensive magmatic activity appears to be responsible for the greater input of both heat and helium in eastern and central anatolia with intra province 3he enthalpy variations from 3 1 106 atoms j in eastern to 0 25 106 atoms j in central anatolia reflecting the ageing of hydro magmatic systems the relatively high 3he concentrations in low enthalpy waters of northern anatolia 2 8 106 atoms j are particularly significant since there is no evidence of volcanic activity associated with the strike slip motion along the seismically active segment of nafz continuous monitoring of he isotope compositions along nafz should lead to a better understanding of this apparent anomaly as well as the relationship if any between he isotope variations and seismic activities in this region

earthquake doublet in an active shear zone southwest japan constraints from geophysical and geochemical findings abstract in 1997 the kagoshima earthquake doublet consisting of two closely associated mw 6 strike slip events five km and 48 days apart has occurred in southwest japan the location is where an e w trending discontinuity along 32 n latitude on southern kyushu island is clearly defined in gps velocities indicating the presence of a highly active left lateral shear zone however there have not been any obvious indications of active faulting at the surface prior to the earthquake doublet which could be associated with this shear zone three dimensional inversion of magnetotelluric sounding data obtained in the source region of the earthquake doublet reveals a near vertical conductive zone with a width of 20 km extending down to the base of the crust and perhaps into the upper mantle toward the okinawa trough the prominent conductor corresponds to the western part of the active shear zone elevated 3 he 4 he ratios in groundwaters sampled from hot spring and drinking water wells suggest the emission of mantle derived helium from the seismic source region the geophysical and geochemical observations are significant indications that the invasion of mantle fluids into the crust driven by upwelling asthenosphere from the okinawa trough triggers the notable left lateral shearing in the zone in the present day subduction system in addition the existence of aqueous fluids in and below the seismogenic layer could change the strength of the zones and alter the local stress regime resulting in the occurrence of the 1997 earthquake doublet

computerized x ray tomography analysis of three dimensional fault geometries in basement induced wrench faulting abstract computerized x ray tomography applied to sandbox experiments makes it possible to analyze the kinematic evolution as well as the three dimensional geometry of faults in basement controlled wrench faulting with increasing basement displacement the evolution of shear bands developed in the model sand bed is observed as follows 1 the right stepping shears that have a cirque or shell or ship body shape develop on both sides of the basement fault 2 the shears on the one side of the basement fault join those on the other side and therefore each shear surface forms a helicoidal shape shears reach the surface of the sand near or above the basement fault thereby en echelon riedel shears are observed at the surface of the sand 3 lower angle shears and p shears lying within the zone defined by the first riedels have steeper dips and a less pronounced helicoidal aspect than the riedels such three dimensional shape and kinematic evolution of shears in the fault experiments agree well with the similar faults which propagate up through the unconsolidated sediments from a wrench fault in bedrock as observed in the excavated trenches at some active faults in the fault experiments the strike of the riedel shear to the basement fault in dense sand is larger than that in loose sand in reasonable agreement with the directions predicted by the coulomb criterion in terms of the angle of internal friction likewise the geometries of the riedel shears are considered to depend on the overburden materials in natural cases of wrench faulting

spatial variations in 3he 4he ratios along a high strain rate zone central japan abstract a linear zone with high strain rates along the japan sea coast the niigata kobe tectonic zone nktz is considered to be associated with rheological heterogeneities in the lower crust and or upper mantle helium isotope variations along the nktz reveal a close association with the geophysical evidence for rheological heterogeneities in the crust and mantle in the southern nktz the 3 he 4 he ratios lower than 3 4 ra ra denotes the atmospheric 3 he 4 he ratio of 1 4 10 6 could be interpreted as a two component mixture of helium stored in aqueous fluids driven off the subducting oceanic crust and radiogenic crustal helium higher 3 he 4 he ratios are observed in the central nktz where quaternary volcanoes and high temperature hot springs are concentrated suggesting that the 3 he emanation manifest in the central nktz results from the effective transfer of mantle helium by intrusion and degassing of mantle derived magma in the crust in the northern nktz where two large inland earthquakes occurred recently there appears to be many samples with 3 he 4 he ratios significantly higher than those observed in the fore arc side of northeast japan a plausible source of mantle helium could be attributed to upward mobilization of aqueous fluids generated by dehydration of the subducting pacific plate slab

superposed epoch analysis of the ionospheric convection evolution during substorms imf by dependence we present superposed epoch analyses of the average ionospheric convection response in the northern and southern hemispheres to magnetospheric substorms occurring under different orientations of the interplanetary magnetic field imf observations of the ionospheric convection were provided by the super dual auroral radar network superdarn and substorms were identified using the far ultraviolet fuv instrument on board the imager for magnetopause to aurora global exploration image spacecraft we find that during the substorm growth phase the expected imf by dependent dawn dusk asymmetry is observed over the entire convection pattern but that during the expansion phase this asymmetry is retained only in the polar cap and dayside auroral zone in the nightside auroral zone the convection is reordered according to the local substorm electrodynamics with any remaining dusk dawn asymmetry being more closely related to the magnetic local time of substorm onset itself only weakly governed by imf by owing to the preponderance of substorms occurring just prior to magnetic midnight the substorm asymmetry tends to be an azimuthal extension of the dusk convection cell across the midnight sector a manifestation of the so called harang discontinuity this results in the northern southern hemisphere nightside auroral convection during substorms generally resembling the expected pattern for negative positive imf by when the preexisting convection pattern in the northern southern hemisphere is driven by positive negative imf by the nightside auroral convection changes markedly over the course of the substorm to establish this same harang configuration

helium and carbon isotopic compositions of thermal springs in the earthquake zone of sichuan southwestern china abstract the origins of gases from hot springs and earthquake activity in the western part of sichuan province southwestern china are discussed in terms of helium and carbon isotopes and energy released by earthquakes 13 c values of co 2 in free and dissolved gases range from 3 34 to 17 09 and 3 he 4 he ratios vary from 1 5 10 8 to 3 63 10 6 the isotopic compositions indicate that carbon dioxide from the hot springs is a mixture of crustal and mantle co 2 and helium is derived from the crust mantle and atmosphere the thermal springs in different earthquake and or fault zones as well as in different parts of the same zone have different values of 13 c and 3 he 4 he the more tectonically active the district is the larger the 13 c and 3 he 4 he values and the greater the frequency of earthquakes this means that more heat energy is derived from the deep earth with upward migration of anatectic fluids in the active tectonic district such as in the kangding district therefore hot spring gases he co 2 etc may be important geochemical markers for determination of seismological and tectonic activity

association of subsurface radon changes in alaska and the northeastern united states with earthquakes abstract changes of radon concentration in the ground have been reported to correlate with seismic activity in many places over widely varying distances from the earthquake epicenters sometimes over 100 s and occasionally over 1000 s of km depending on the magnitude m of the earthquakes for proper use of such correlations in forecasting the location and size of impending earthquakes it would be useful to establish a relation between m and the maximum distance x m at which radon can be significantly altered by preseismic effects we have monitored radon in the ground continuously at blue mountain lake ny starting dec 3 1975 and at three locations in alaska icy bay yakataga and sand point starting nov 12 1979 march 5 1980 and june 29 1980 respectively sample correlations from visual examination of the recent radon record and tentative use of a proposed scaling relation show a number of possible earthquake related signals at these locations the data are compatible with scaling relations that were derived from two separate models of premonitory elastic strains in this work x m 10 0 48 m where x m is in units of km and m 3 since tilt and strain signals correlate similarly with magnitude and distance it is likely that most earthquake related radon signals are mechanically induced

a large intraplate earthquake triggered by latent magmatism 1 a magnitude mj 7 3 intraplate earthquake occurred in the western tottori area southwest japan on 6 october 2000 where there was no apparent prefaulting subsurface indication of the source fault of the 2000 earthquake magnetotelluric soundings were taken in and around where the aftershocks occurred in order to image three dimensional electrical resistivity structure at depths of up to 40 km which could indicate an anomalously conductive body in the middle crust to the upper mantle on the southwestern side of the source fault free gas and dissolved gases collected from groundwater wells around the seismic source region are characterized by 3he 4he ratios several times higher than the atmospheric value the highest value of 5 1ra is similar to those of typical arc related volcanic gases although alkali basalts of early pleistocene age are sparsely distributed in the western tottori area the observed 3he 4he ratios are higher than the calculated 3he 4he ratio derived from the ancient magmatism considering postextrusive radiogenic ingrowth of 4he by decay of u and th included in the magma therefore it is concluded that the geophysical anomaly imaged to the southwest of the source fault is attributed to latent magmatism in the present day subduction system aqueous fluids separated from the cooling crustal magma could cause deep low frequency earthquakes around the moho discontinuity and migrate into the brittle upper crust in addition the presence of aqueous fluid is expected to weaken the crustal materials locally anelastic deformation implying notable compressive deformation in the e w direction was observed in the region where aftershocks were distributed under overpressure conditions the existing fault could serve as a pathway for aqueous fluids expelled from magma with high 3he 4he ratios so the upwelling of overpressurized fluids toward the earth s surface results in the emanation of groundwaters with high 3he 4he ratios along the trace of the source fault segments

geochemistry of fluid inclusions in travertines from western and northern turkey inferences on the role of active faults in fluids circulation the understanding of the relationship between the geochemistry of fluids circulating during travertine deposition and the presence of active faults is crucial for evaluating the seismogenetic potential of an area here we investigate travertines from pamukkale and resadiye turkey sited in seismic regions and next to thermal springs these travertines formed 24 500 50 000 pamukkale and 240 14 600 years resadiye bp we characterize fluid inclusions fis and studied concentration of ho co o n and he he ne and ar and bulk composition trace elements and c o fis from both localities are mainly primary with low salinity and homogenization temperature around 136 140 c ho is the major component followed by co with the highest gas content measured in pamukkale travertines concentrations of ne ar together with o n indicate that travertines from both areas precipitated from atmosphere derived fluids the he he is 0 5 1 3 ra in pamukkale and 0 9 4 4 ra in resadiye samples with r ra 1 are modified by cosmogenic he addition during exposure to cosmic rays excluding these data fis of resadiye are mostly atmosphere derived this implies a shallow formation where the circulation was dominated by meteoric waters which is consistent with their young age instead fis of pamukkale show mixing of mantle crustal and atmosphere derived he indicating that these travertines formed in lithospheric fractures based on the c and o of bulk rocks we infer that travertines formed involving crustal mechanochemical rather than organic and mantle derived co trace elements of pamukkale and resadiye show comparable rare earth element patterns we conclude that travertines formed in response of seismogenetic activity

dynamics of a catalina eddy revealed by numerical simulation abstract through numerical simulations with the pennsylvania state university ncar mesoscale model the dynamics of a catalina eddy event that formed during the period 26 30 june 1988 off the coast of southern california is examined a strengthening and veering of the low level synoptic scale winds from climatological northwesterlies to northerlies results in a more pronounced effect of the coastal orography around the california bight region in particular relative vorticity formed by flow over the coastal terrain remains offshore prior to the formation of a quasi steady eddy within the bight the northerlies are strong enough to advect anomalously high vorticity out of the region the formation of a mature catalina eddy relies on a rapid deceleration of the synoptic scale northerlies on 30 june such that vorticity once formed remains in the bight the eddy is also strongly modulated by the diurnal cycle northwesterly flow around 500 m above mean sea level impinging on the mountains north of the b

seismic images of the source area of the 2004 mid niigata prefecture earthquake in northeast japan to better understand the generation mechanism of the 23 october 2004 mid niigata prefecture earthquake m 6 8 we used 120 352 p wave and 95 391 s wave high quality arrival times from 5013 earthquakes to determine the three dimensional seismic velocity vp vs and poisson s ratio structures in and around the source area the hypocenter locations of the aftershocks are relocated accurately by using absolute and relative travel time double difference data our results demonstrate that the seismic velocity and poisson s ratio vary markedly around the source area most active faults are located along the margins of low velocity and high velocity zones an obvious change in seismic velocity and poisson s ratio occurs between the northwest and southeast parts of the study area and this boundary zone reflects the spatial distribution of active faults being well consistent with the surface geological features most of the large historic crustal earthquakes are located in or around the low seismic velocity zones the mainshock hypocenter is located near the margin of low velocity high poisson s ratio and high velocity low poisson s ratio anomalies along the active fault zone a zone with pronounced low velocity and high poisson s ratio is clearly imaged in the lower crust under the source area reflecting the existence of fluids that are released due to the dehydration of the subducting pacific slab such fluids might have reduced the mechanical strength of the fault zone and thus initiated the mid niigata prefecture earthquake