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

relationships between gas geochemistry and release rates and the geomechanical state of igneous rock massifs in contrast to sedimentary sequences the relationships between the stressed state of igneous rocks and the chemistry and physical properties of gases contained within them are not well known here we attempt to fill this gap by using as an example the apatite nepheline and rare metal ore deposits hosted within the khibiny and lovozero alkaline nepheline syenite complexes of the kola peninsula nw russia these massifs are characterized by unusually high for igneous rocks contents of multi component essentially hydrogen hydrocarbon gases and also by high hardness elasticity and unevenly distributed subhorizontal tectonic stresses relationships between the chemical and dynamic characteristics of the gases and the geomechanical properties of the host rocks have been examined using field observations and laboratory experiments patterns of gas release variations in time and space gas emissions from rock pillars during artificial loading variations of gas pressure in sealed shot holes and changes in liberation rates of gaseous components during experimental rock loading are suggested to result from changes in rock stress and deformation state gas compositions in sealed shot holes in stressed rocks change with time partly this is due to belated release of gases held in fluid inclusions and isolated voids and their subsequent mixing with gases held in interconnected fracture systems as the included gases are preferentially released as fluid inclusion arrays are opened during later stages of stress build up partly it may also be because released gases may react with new fracture surfaces to generate enhanced levels of reduced h2 gases

coseismic changes of subsurface gas compositions disclosed by an improved seismo geochemical system an automatic system for seismo geochemical observation has been improved to monitor small changes in subsurface gas composition this system is computer based and consists of an on site monitoring unit for gas analyses and a telemetry unit for transmitting the observation data to our laboratory the analytical data with this system showed three coseismic anomalies in spring gas compositions at a monitoring station for these 11 months these anomalies were associated with a far and large earthquake or two small and near ones respectively the gas anomaly as a spike like signal appears only for a short period and can be detected on the basis of temporally dense data provided by the new system the result shows that the behavior of subsurface gases is sensitive to crustal movements

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

iceberg trajectory modeling and meltwater injection in the southern ocean this is the first large scale modeling study of iceberg trajectories and melt rates in the southern ocean an iceberg model was seeded with climatological iceberg calving rates based on a calculation of the net surface accumulation from each snow catchment area on the antarctic continent in most areas modeled trajectories show good agreement with observed patterns of iceberg motion though discrepencies in the weddell sea have highlighted problems in the ocean general circulation model output used to force the iceberg model the coriolis force is found to be important in keeping bergs entrained in the coastal current around antarctica and topographic features are important in causing bergs to depart from the coastal regions the modeled geographic distribution of iceberg meltwater joining the ocean has been calculated and is found in many near coastal regions to be comparable in magnitude to the excess of precipitation over evaporation p e

earthquakes produce carbon dioxide in crustal faults abstract fourier transform infrared ftir microanalysis of pseudotachylytes i e friction induced melts produced by seismic slip from the nojima fault japan reveals that earthquakes almost instantaneously expel 99 wt of the wall rock co 2 content carbon is exsolved because it is supersaturated in the friction melts by extrapolation to a crustal scale fault rupture large events such as the m7 2 kobe earthquake 1995 may yield a total production of 1 8 to 3 4 10 3 tons co 2 within a few seconds this extraordinary release of co 2 can cause a flash fluid pressure increase in the fault plane and therefore enhance earthquake slip or trigger aftershocks it may also explain the anomalous discharge of carbon monitored in nearby fault springs after large earthquakes because carbon saturation in silicate melts is pressure dependent ftir can be used as a new tool to constrain the maximum depth of pseudotachylyte formation in exhumed faults

rising social complexity agricultural intensification and the earliest rice paddies on the loess plateau of northern china geoarchaeological studies of landscapes immediately adjacent to archaeological sites can contribute information on the direct impact of small scale societies on their associated landscapes this direct connection allows us to understand aspects of the motivations economic decision making and agricultural strategies and how they affected local site catchments the origin and spreading of farming communities onto the loess plateau of northern china provides a good example of this we recorded sediment profiles that were immediately adjacent to the site of huizui in the yiluo river basin here we identified evidence for human land use beginning with the early mid holocene deposits which are consistent with stable hillslope soils indicating that the first mixed forager millet farmers of the peiligang neolithic had a very light ecological footprint on the landscape this is in contrast to the later middle neolithic yangshao period farmers sediments from the yangshao period revealed paleolandscape and phytolith evidence for the earliest neolithic paddy farming well outside of the natural habitat of wild rice in addition to evidence for massive deforestation and soil erosion a 15 m deep sediment sequence containing sets of gravels beginning ca 7200 cal bp and gleyed soils dating from ca 6600 cal bp contained rice phytoliths archaeological waste suggesting manuring and micromorphological data indicating trampling these signs of intensive landscape management go hand in hand with rapidly increasing social complexity

the impact of environmental change and human land use on alluvial valleys in the loess plateau of china during the middle holocene abstract in recent years a growing number of studies have reported proxy evidence for holocene climatic and environmental change on the loess plateau of north central china pollen from lake cores and sediment analyses from loess sections firmly point to a warm moist mid holocene climatic optimum archaeological evidence indicates that at the same time human agricultural settlements expanded into this area during the middle neolithic period a geoarchaeological study of sediment sections from several valleys within the catchment of the yiluo river henan province indicates a sequence beginning with a stable landscape soil development and high water tables in the early mid holocene which was exploited by early neolithic millet farmers in the peiligang period subsequently there was a rapid shift to episodes of hillslope erosion and increased valley alluviation in the later mid holocene the resulting alluvial sediments dating from 5300 5010 cal bc through 2130 1870 cal bc represent clay rich water logged deposits that contain sediment and phytolith evidence for the first rice paddy farming in this region this coincides with the first migration of neolithic rice farmers to the area in the yangshao period ca 5500 cal bc these fills temporally and stratigraphically linked to archaeological sites and human land use practices suggest that they originated as a direct result of human impact on the landscape after ca 2000 cal bc holocene valley incision in this catchment led to narrowing floodplains the disappearance of the valley wetland deposits and a reduction in land available for paddy farming

seismic measurements reveal a saturated porous layer beneath an active antarctic ice stream seismic reflection studies recently conducted on ice stream b part of the marine ice sheet of west antarctica show a metres thick layer immediately beneath the ice in which both compressional p and shear s wave speeds are very low these low wave speeds imply that the material in the layer is highly porous and is saturated with water at a high pore pressure from this and from arguments presented in an accompanying paper1 to the effect that the layer would be too weak to support the shear stress exerted by the overlying ice we conclude that the layer is deforming and that the ice stream probably moves principally by such deformation

origin and coseismic behavior of mineral spring gas at byakko japan studied by automated gas chromatographic analyses abstract the origin and coseismic behavior of mineral spring gas were examined on the basis of continual monitoring data for several gas species the automatic monitoring system used in this study consists of two gas chromatographs and a personal computer several gas species can simultaneously be analyzed with these analyzers the system was so stable and sensitive that minute coseismic anomalies in these species could be detected a positive correlation between n 2 ar and ch 4 ar implies that the mineral spring gas is a mixture of atmospheric air and lithospheric gas the lithospheric gas is mainly composed of n 2 and ch 4 and also contains trace amounts of he it is inferred from isotopic data that lithospheric n 2 and ch 4 are thermogenic and he is mostly radiogenic in contrast o 2 and h 2 in trace amounts show large diurnal fluctuations suggesting that these species should be mostly biogenic ten earthquakes felt around the station occurred during the monitoring period and four of them coincided with coseismic anomalies in the he ar ratio the anomalies may be interpreted as follows by the ground motion at these felt quakes he accumulated in the ground was additionally released into the spring water the continual monitoring of these gas species enables us to discuss in detail the origin and behavior of the spring gas and to evaluate background noise of the data

prediction of iceberg trajectories for the north atlantic and arctic oceans icebergs are a well known hazard for shipping their study also provides information about diverse geophysical processes as varied as ocean circulation air sea fluxes calving rates of glaciers or the mass balance of ice sheets as a first step to obtaining this information from iceberg data we have developed a model of iceberg drift driven by ocean and atmospheric forcing derived from general circulation models we have applied the drift model to a distribution of typical icebergs released from the main tidewater glaciers of the north atlantic and arctic oceans we demonstrate that the main driving force of iceberg motion is rooted in the unsteady component of oceanic advection from simulated trajectories we are able to reproduce the observed southwards limit of iceberg penetration and demonstrate sometimes surprising geographical links between iceberg origin and ultimate melting zones

early middle holocene ecological change and its influence on human subsistence strategies in the luoyang basin north central china in north central china subsistence practices transitioned from hunting and gathering to millet based agriculture between the early and middle holocene to better understand how ancient environmental changes influenced this shift in subsistence strategies and human activities at regional to local levels we conducted palynological and lithologic analyses on radiocarbon dated sediment cores from the luoyang basin western henan province our palynological results suggest that vegetation shifted from broad leaved deciduous forest 9230 8850 cal yr bp to steppe meadow vegetation 8850 7550 cal yr bp and then to steppe with sparse trees 7550 6920 cal yr bp lithologic analyses also indicate that the stabilization of the luoyang basin s floodplain after similar to 8370 cal yr bp might have attracted people to move into the basin promoting the emergence of millet based agriculture during the peiligang culture period 8500 7000 cal yr bp once agricultural practices emerged the climatic optimum after similar to 7550 cal yr bp likely facilitated the expansion of the yangshao culture 7000 5000 cal yr bp in north central china as agriculture intensified pollen taxa related to human disturbance such as urtica increased in abundance

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

precursors and fluid flows in the case of the 1996 ml 5 2 saint paul de fenouillet earthquake pyrenees france a complete pre co and post seismic scenario abstract earthquake precursors are now regularly described but often detected only after a major or moderate seismic event presence and influence of fluids in the seismogenic processes are often observed at the time of earthquake studies even today the understanding of the physical processes involved in the source region is a real challenge for seismic hazard assessment here the aftershock sequence of the m l 5 2 1996 saint paul de fenouillet eastern pyrenees france earthquake is first re examined with p wave cross correlations resulting in extracting three multiplets and in determining new locations multiplets and spatio temporal distribution analysis of the aftershocks allow for quantifying the hydraulic diffusivity d at a maximum value of 5 m 2 s and the permeability k at 10 15 m 2 in the upper pyrenean crust second a model is established in order to explain the hydrogeochemical transient anomalies which occurred during the 15 day period preceding the 1996 earthquake these anomalies consist on a temporal and spatial sequence of gas emissions in the epicentral area and on chloride and lead concentration variations in a bottled mineral water 25 km north to the main shock epicenter the proposed model processed in a standard elastic half space consists of creep on a low angle crustal normal fault generating volumetric strain field changes over a distance of 25 km from the epicentral area this model is able to constrain not only the mechanisms and the locations of the geochemical anomalies but also their timing and probable casual links to the triggering of the impending major event also the active extension proposed here is compatible with seismological observations in the pyrenees thus the possibility of such creep which can be considered as a slow slip event is discussed in the pyrenean tectonic and geological context the model is discussed and compared to previous proposed models on precursor processes of earthquakes especially concerning the preparation zone concept finally a complete seismic scenario over the period beginning 15 days before the quake and ending 5 days after is proposed and discussed

precursory diffuse carbon dioxide degassing signature related to a 5 1 magnitude earthquake in el salvador central america abstract anomalous changes in the diffuse emission of carbon dioxide have been observed before some of the aftershocks of the 13 february 2001 el salvador earthquake magnitude 6 6 a significant increase in soil co 2 efflux was detected 8 days before a 5 1 magnitude earthquake on 8 may 2001 25 km away from the observation site in addition pre and co seismic co 2 efflux variations have also been observed related to the onset of a seismic swarm beneath san vicente volcano on may 2001 strain changes and or fluid pressure fluctuations prior to earthquakes in the crust are hypothesized to be responsible for the observed variations in gas efflux at the surface environment of san vicente volcano

sediment deformation beneath glaciers rheology and geological consequences experiments beneath breidamerkurjokull in iceland have led to development of flow laws for the subglacial till relating strain rate to shear stress and effective pressure and assuming either bingham fluid or nonlinearly viscous fluid behavior water pressures in the till are less than ice pressures and it is suggested that this may lead to infiltration of ice into the sediment which inhibits sliding at the ice sediment interface where water pressures are equal or near to ice pressures infiltration does not occur and sliding may result a one dimensional theory of subglacial deformation is developed in which the empirical flow law is coupled with a model of subglacial hydrology and consolidation this predicts stable states in which subglacial sediment either does not deform or a dilatant deforming horizon forms with positive effective pressures at the ice bed interface or unstable states where zero or negative effective pressures are predicted time dependent analyses show that response times following perturbations of the system may be of the order of 103 years and thus that unsteady behavior may be normal on glaciers flowing over unlithified sediment beds it is suggested that the natural variability of material properties in subglacial sediment beds leads to the development of drumlins on the glacier bed it is suggested that unstable deformation at zero or negative effective stress leads to piping in subglacial sediments at the glacier terminus and the growth of sediment floored subglacial tunnels their frequency is that which is sufficient to draw down subglacial water pressures so as to prevent unstable deformation where they discharge large water volumes subglacial sediments flow laterally toward them producing tunnel valleys this sediment is then removed by water flowing along the axial tunnel tunnel valleys can be regarded as the equivalent in soft sediment areas of eskers in bedrock areas

the 1995 kobe earthquake seismic image of the source zone and its implications for the rupture nucleation in order to understand what may have triggered the 1995 kobe japan earthquake and how the rupture proceeded after initiation we determined high resolution three dimensional 3 d p and s wave velocity and poisson s ratio structures in the kobe epicentral area and relocated the aftershocks with the obtained 3 d velocity model we used 64 337 p and 49 200 s wave high quality arrival times from 3634 kobe aftershocks and local microearthquakes recorded by both permanent seismic networks and portable stations that were set up following the kobe mainshock significant velocity variations of up to 6 are revealed in the aftershock area we found that areas with high aftershock activity are generally associated with low poisson s ratio which may be the strong and competent parts of the fault zone and were apt to generate aftershocks the kobe mainshock hypocenter is located in a distinctive zone characterized by low p and s wave velocities and a high poisson s ratio this anomaly exists in the depth range of 16 to 21 km and extends 15 to 20 km laterally this anomaly may be due to a fluid filled fractured rock matrix that contributed to the initiation of the kobe earthquake our interpretation has been supported by many pieces of evidence from hydrological geochemical seismological and geophysical investigations conducted at the kobe earthquake region

relationship between seismicity and subsurface fluids central coast ranges california seismicity is irregularly distributed in the central coast ranges of california with several large areas having virtually no seismic activity since 1968 aseismic areas correlate with zones of abnormally high pore fluid pressures ahps 130 of hydrostatic level line surveys suggest that aseismic areas have experienced significant historical uplift moreover these aseismic areas show a remarkable correlation with perennial saline springs that represent technically expelled formation fluid as indicated by their perennial flow 18o and d enrichment to 6 3 and 13 respectively elevated b to 331 ppm and chemistry dominated by na and cl aseismic areas are dominantly located at the center of structural blocks that are under compression and are bounded by major faults and seismicity belts volumetric strain within these blocks creates pockets of overpressured formation fluid that greatly reduce seismic activity while promoting aseismic uplift seismic cross sections reveal three dimensional pockets of aseismicity that are floored and surrounded by scattered hypocenters we suggest that overpressured formation fluids originate at depths of 1 to 7 km within these pockets on the basis of na k ca geothermometry estimates that are consistent with stratigraphic information and available drill hole data these overpressured fluid pockets may also influence seismicity on major faults such as the upper 3 km of the active greenville fault which is relatively aseismic where it separates two overpressured pockets decreasing flow rates observed at some saline springs may represent a local transition to a period of increased seismic activity while many studies have linked generation of earthquakes to man made fluid overpressures our data show that the dominant long term effect of ahps is to reduce seismicity and promote uplift

dry or humid mid holocene humidity changes in arid and semi arid china abstract spatial changes of effective moisture during the mid holocene have been reconstructed based on the compilation of recently published paleoclimate records including ice core lake level pollen assemblage and loess paleosol records both geological data and the spatial pattern indicate that it was dry in deserts during the mid holocene but the timing of the beginning and end of dry intervals differs from place to place deserts having higher aridity index values remain dry longer dry intervals during the mid holocene are more possibly asynchronous than synchronous in arid and semi arid china in the xinjiang region except in sites located in deserts the climate is generally wet during 7000 5000 a bp in the northern qinghai tibetan plateau effective moisture in most sites began to decrease after 5000 a bp the climate became dry after 4000 a bp except in the deserts in the loess plateau and the inner mongolia plateau

geochemical precursors to seismic activity studies of earthquake precursory phenomena during the last several decades have found that significant geophysical and geochemical changes can occur prior to intermediate and large earthquakes among the more intensely investigated geochemical phenomena have been 1 changes in the concentrations of dissolved ions and gases in groundwaters and 2 variations in the concentrations of crustal and mantle volatiles in ground gases the concentration changes have typically showed no conanomalies trend either increasing or decreasing and the spatial and temporal distribution of the observed anomalies have been highly variable as a result there is little agreement on the physical or chemical processes responsible for the observed anomalies mechanisms proposed to account for precursory groundwater anomalies include ultrasonic vibration pressure sensitive solubility pore volume collapse fracture induced increases in reactive surfaces and aquifer breaching fluid mixing precursory changes in soil gas composition have been suggested to result from pore volume collapse micro fracture induced exposure of fresh reactive silicate surfaces and breaching of buried gas rich horizons an analysis of the available field and laboratory data suggests that the aquifer breaching fluid mixing ab fm model can best account for many of the reported changes in temperature dissolved ion and dissolved gas concentrations in groundwater ultrasonic vibration and pressure sensitive solubility models cannot reasonably account for the geochemical variations observed and although the pore collapse model could explain some of the observed chemical changes in groundwater and ground gas uncertainties remain regarding its ability to generate anomalies of the magnitude observed other geochemical anomalies in particular those associated with hydrogen and radon seem best accounted for by increases in reactive surface areas irsa model that may accompany precursory deformation around the epicenter of an impending earthquake analysis of the probable response of these models to the earthquake preparation process as well as to other environmental factors suggests that geochemical monitoring programs can provide information that may be valuable in forecasting the probability of an earthquake however because of the complexity of the earthquake preparation process the absolute prediction of seismic events using geochemical methods alone does not presently appear to be feasible

positive mass balance during the late 20th century on austfonna svalbard revealed using satellite radar interferometry determining whether increasing temperature or precipitation will dominate the cryo spheric response to climate change is key to forecasting future sea level rise the volume of ice contained in the ice caps and glaciers of the arctic archipelago of svalbard is small compared with that of the greenland or antarctic ice sheets but is likely to be affected much more rapidly in the short term by climate change this study investigates the mass balance of austfonna svalbard s largest ice cap equilibrium line fluxes for the whole ice cap and for individual drainage basins were estimated by combining surface velocities measured using satellite radar interferometry with ice thicknesses derived from radio echo sounding these fluxes were compared with balance fluxes to reveal that during the 1990s the total mass balance of the accumulation zone was 5 6 2 0 10 8 m 3 a 1 three basins in the quiescent phase of their surge cycles contributed 75 of this accumulation the remaining volume may be attributable either to as yet unidentified surge type glaciers or to increased precipitation this result emphasizes the importance of considering the surge dynamics of glaciers when attempting to draw any conclusions on climate change based on snapshot observations of the cryosphere

the variation of summer monsoon precipitation in central china since the last deglaciation abstract two stalagmites c996 1 and c996 2 collected from the jiuxian cave in the shaanxi province in central china have been studied with u series dating and stable isotope analysis thirty eight 230 th dating results showed that the stalagmite c996 1 was continuously deposited through the last 8 5 ka bp thousand years before present present 1950 ad and c996 2 was deposited through the last 19 ka bp excluding two growth hiatuses between 8 3 and 5 7 ka bp and 15 4 and 11 9 ka bp with a relatively stable boundary condition we interpret the 18 o of speleothem calcite as most indicative of the amount of summer monsoon precipitation although temperature and other factors might have some minor impact the 18 o records show notable changes within the last glacial maximum lgm resembling other east asian monsoon records such as those from the hulu and sanbao caves suggesting that significant monsoonal climate changes occurred in eastern asia as far north as the qinling mountains during the lgm interval a comparison of our records to precisely dated contemporaneous speleothem records from other caves shows that the increasing trend of 18 o during the holocene commenced as early as 7 5 ka bp in the low latitude monsoonal area i e the hoti cave while at higher latitudes this shift occurred later such as 7 0 ka bp in the dongge cave 5 3 ka bp in the heshang cave 4 7 ka bp in the sanbao cave and 4 5 ka bp in the jiuxian cave these results imply an asynchronous change of the summer monsoon precipitation occurred in east asia during the holocene the asynchrony may be related to the responses of a coupled tropical and subtropical monsoon system to changes of the insolation and the differences in thermal forcing which result from the complex geographical configuration the variation of sea surface temperature sst in the western tropical pacific may also have important impacts on the summer monsoon precipitation changes in central and northern china because it affects the northwestern pacific subtropical high a monsoon front regulator more robust tests are needed to confirm this phenomenon and to evaluate the contribution of different factors in detail

origin of hydrogen and carbon dioxide in fault gases and its relation to fault activity gases occluded in fracture zones of active faults are characterized by a high concentration of h 2 and or co 2 a predominant gas species h 2 or co 2 is related to the lithofacies which the fault cuts carbon dioxide concentration in sediments fluctuates with temperature this evidence and sigma 13 c of co 2 about 20 suggests that co 2 originates from organic materials carbon dioxide with sigma 13 c of 5 to 17 in brecciated gneiss containing marble may have been produced by interaction between organically derived co 2 and the marble or alternatively may have been magmatically derived hydrogen usually occurs in sheared silicate rocks and its concentration fluctuates a great deal the concentration of h 2 from active faults associated with historical earthquakes usually amounts to as high as several percent in maximum whereas the concentration of h 2 from quaternary faults not associated with historical earthquakes is at most 1

helium systematics of cold seep fluids at monterey bay california usa temporal variations and mantle contributions 1 we report helium isotope ratios 3he 4he as well as helium and neon abundance results for submarine cold seep fluids from extrovert cliff in monterey bay california samples were collected in copper tubing attached to submarine flux meters operating in continuous pumping mode following instrumentation recovery the tubing was sectioned to produce for the first time a high resolution time series of dissolved he and ne variations over a time span of several days noble gas concentrations are variable and appear affected by interaction with a hydrocarbon phase within the aquifer however it is still possible to resolve the he signal into components associated with air equilibration excess air entrainment and terrigenic fluxes both crustal and mantle derived the mantle he contribution reaches 25 30 in some samples up to 2 3 ra where ra air 3he 4he our quasi continuous he ne record shows remarkable fluctuations over time scales of only a few hours and reflects the combined effects of gas stripping by hydrocarbons and an episodic input of mantle derived fluids

anomalies in geophysical and geochemical parameters revealed on the occasion of the paravani m 5 6 and spitak m 6 9 earthquakes caucasus abstract on the occasion of the paravani may 13 1986 and spitak december 7 1988 earthquakes which occurred in the caucasus irregularities in several geophysical and geochemical parameters were revealed in this paper data on anomalies in the water level in deep wells in the helium content in thermal waters in electromagnetic signals revealed by surface and underground antennae and in an f gt function based on traveltimes of p and s waves are presented data were collected from sites located in the georgian s s r in the case of the spitak earthquake the anomalies in all the presented parameters can be attributed to the processes that preceded and accompanied the earthquake for the paravani earthquake no significant precursory phase seems to have been reflected in the helium content in thermal waters though this phase can be observed in the other parameters in general it would appear that the magnitude of the earthquake and the distance from the epicentre exert a significant control on the appearance of the anomalies

behavior and origin of helium neon argon and nitrogen from active faults compositional variations of gas species occluded in fracture zones type i within active faults are essentially the same as those in bubble gases type ii separating from mineral springs along faults the variation in type ii is hydrogeochemically interpreted as a result of dissolving and degassing of atmospheric air in groundwater at various temperatures the comparison of these variations in both types of gases suggests that ne ar and n2 in the type i gases are of atmospheric origin and their fluctuation is strongly controlled by the circulation of groundwater which recharges and discharges atmospheric air at various temperatures further hydrogeochemical evaluation shows that a part of he observed in fault zones is of radiogenic origin but its proportion is very small in active faults in these zones juvenile he emission related to the tectonic stresses causing earthquake may be substantially modified by the compositional fluctuation of gases controlled by the water circulation within the fault system accordingly monitoring of rare gases except for h2 from historically active faults may be less effective for earthquake prediction in contrast gas bubbles of high he content issuing from mineral springs which usually occur along prehistorically active faults are less contaminated by air and may provide some general precursory information concerning regional stresses at depth prior to an earthquake

anomalous diffuse co2 emissions at the masaya volcano nicaragua related to seismic volcanic unrest anomalous changes in the diffuse emission of carbon dioxide within the masaya caldera have been observed before two seismic events that occurred at 10 and 30 km from the observation site their epicenters are located respectively south of managua in las colinas 4 3 magnitude and the xiloa caldera 3 6 magnitude in 2002 and 2003 recorded by the geochemical station located at el comalito masaya volcano nicaragua anomalous increases were observed which occurred around 50 and 8 days before the main seismic event that took place in las colinas and 4 days before the seismic swarm at the xiloa caldera with a maximum co2 efflux of 9 3 and 10 7 kg m 2 day 1 respectively the anomalous co2 efflux increases remained after filtering with multiple regression analysis was applied to the co2 efflux time series which indicated that atmospheric variables during the first 4 months explained 23 co2 variability whereas during the rest of the time series co2 efflux values are poorly controlled with only 6 the observed anomalies of the diffuse co2 emission rate might be related to pressure changes within the volcanic hydrothermal system and or to geostructural changes in the crust due to stress strain changes caused before and during the earthquakes formation and seem not to be related to the activity of the main crater of masaya volcano

bio climatic imprints on a holocene loess palaeosol from china micromorphology heavy minerals pollen and soil properties were examined in a typical holocene loess profile in the north of the loess plateau consisting of a palaeosol locally known as the ansai palaeosol underlain by the malan loess and overlain by modern loess the palaeosol consists of an upper humus rich ab horizon over a clay rich bt horizon the humus rich horizon is intensely weathered contains precipitated calcitic material derived from the overlying modern loess and has both high pollen content and diversity clay coatings in the clay rich horizon indicate formation by eluviation illuviation of clay pedogenetic characteristics and pollen analysis imply that the vegetation during the time of most intensive soil development is likely to have been a warm temperate forest a complex interpretation of the loess palaeosol sequence recognizes several development stages the phase of soil development maximum and minimum limiting ages for which are ca 8800 and 4400 c 14 years bp involved continuing but reduced loess deposition and successive holocene bio climatic environment overprinted new features on the palaeosol c 2003 elsevier ltd all rights reserved

holocene monsoon climate documented by oxygen and carbon isotopes from lake sediments and peat bogs in china a review and synthesis there has been much recent debate about holocene climate variation in the monsoon region of china especially the temporal pattern of variations in precipitation the time transgressive nature of the holocene precipitation maximum and the extent to which variations in regions influenced by the indian summer monsoon ism and the east asian summer monsoon easm have been synchronous we summarize and compare carbonate oxygen isotope records delta o 18 carb from ten lakes within the present day ism region we discuss their paleoclimate significance considering the present day moisture source isotopic composition of precipitation and the hydrological setting the delta o 18 carb records are controlled mainly by the isotopic composition of lake water which in turn is a function of regional precipitation evaporation p e balance and the proportion of precipitation that is monsoon derived we normalized the delta o 18 carb data and used these records to generate an integrated moisture index this index along with oxygen isotope records from speleothems and carbon isotope records delta c 13 org from peats within the monsoon region suggests that holocene climate was broadly synchronous across the monsoon region and within the limits of accuracy of the existing age models provides no strong evidence for previously proposed anti phasing of the ism and the easm stable isotope records from lake sediments and peat bogs have excellent potential for providing high quality paleoclimate data for monsoon asia and complement high resolution speleothem sequences which are only found in certain localities c 2011 elsevier ltd all rights reserved

springwater chloride ion anomaly prior to a ml 5 2 pyrenean earthquake abstract we performed over a 598 day sampling period chemical analyses of commercially bottled spring water namely alet water rising in the vicinity of saint paul de fenouillet french eastern pyrenees where a ml 5 2 earthquake occurred these data display a chloride ion anomaly starting 5 days prior to the quake and lasting 10 13 days the anomaly is characterized by cl concentrations 36 above background values this precursory chemical change is attributed to a pre seismic strain change which induced mixing of geochemically different aquifers chloride rich groundwaters are known to rise close 10 km to the alet spring and mixing calculations suggest that a limited inflow of similar waters within the alet hydrologic system is a viable explanation for the chloride ion anomaly this result confirms that mineral springs are promising sites for the search of earthquake geochemical precursors

in situ thermal profiles and laboratory impact experiments on iceberg ice a series of 40 impact tests was conducted on large right circular cylinders 68 5 cm diameter and 25 7 cm thickness of iceberg ice collected from an iceberg in labrador temperature profiles were also obtained for the iceberg and the profiles exhibited differences associated with the probe location temperatures as low as 15 c were measured at penetration depths of about 8 m the impact specimens were confined at the perimeter and base by a rigid metallic ring and plate a spherically terminated impactor with center mounted pressure transducer was dropped on to the flat top surface of specimens from various heights and with various added masses impact velocity varied from 1 8 to 3 9 m s 1 impactor mass varied from 155 to 510 kg and the ice specimen temperature varied from 0 5 to 14 5 c peak center pressures averaged from about 25 mpa at the highest temperature to about 41 mpa at the lowest temperature with the highest recorded pressure being 50 mpa crater volume increased with increasing impact energy as expected however the specific energy of the ejected material was found to decrease as the energy of impact and crater volume increased a mechanism for this observed behaviour is proposed

radon concentrations in soil gas considering radioactive equilibrium conditions with application to estimating fault zone geometry a calculation method for determining the amount of rn isotopes and daughter products at the start of measurement cras is proposed as a more accurate means of estimating the initial rn concentration in soil gas the cras utilizes the decay law between 222rn and 220rn isotopes and the daughter products 218po and 216po and is applicable to scintillation counter measurements as rn is both inert and chemically stable it is useful for fault investigation based on the soil gas geochemistry however the total number of particles emitted by the decay of rn has generally been considered to be proportional to the initial rn concentration without considering the gas condition with respect to radioactive equilibrium the cras method is shown to be effective to derive rn concentration for soil gases under both nonequilibrium conditions in which the total number of decays increases with time and equilibrium conditions which are typical of normal soil under low gas flux the cras method in conjunction with finite difference method simulation is applied to the analysis of two active fault areas in japan and it is demonstrated that this combination could detect the sharp rises in 222rn concentrations associated with faults the method also allows the determination of fault geometry near the surface based on the asymmetry variation of the rn concentration distribution when coupled with a numerical simulation of 222rn transport the results for the new method as applied to the two case studies are consistent with the data collected from the geological survey it implies that the cras method is suitable for investigating the fault system and interstitial gas mobility through fractures the present analyses have also demonstrated that high rn concentrations require the recent and repeated accumulation of 222rn parents 230th and 226ra in fault gouges through deep gas release during fault movement

thermal energy conservation in icebergs and tracking by temperature calculations using a two dimensional numerical model which simulates the heat balance and temperature distribution of icebergs show that the temperature in the central region of an iceberg is almost unaffected by the thermal conditions imposed on its boundary hence the original temperature of the iceberg at the time of calving is retained in its core owing to the insulating quality of the ice when correlated with glacioclimatic conditions this temperature conservation may be used to backtrack an iceberg to its parent ice cliff nine different icebergs were manually temperature profiled in the barents sea during late winter 1988 1990 a scenario is considered wherein one of these icebergs under the forces of winds and currents is assumed to set off from franz josef land in late autumn 1987 the numerical heat balance model is used to compute the temperature distribution heat balance and ablation of this iceberg as it drifts through the barents sea the calculations show that the heat balance of the part of the iceberg exposed to air has marginal influence on the ablation and thus on the expected lifetime of the iceberg ablation of the submerged body also occurs during winter when the water temperature is well below the melting point of glacial ice this is caused by freezing point depression leading to an ablation of about 0 5 m per month of the underside and sidewalls of the submerged body for water temperatures above 0 6 c the ablation results in a steep temperature gradient reaching the core temperature 3 m into the ice with a tolerance of 0 4 c the temperature is virtually free of any thermal boundary influence 12 m into the ice the simulated and measured temperature profiles of the iceberg are compared with measurements of the thermal regime of austfonna nordaustlandet and the churlenis ice dome on franz josef land the model calculations indicate that the ice cliffs on svalbard can be excluded as parent ice cliffs for these icebergs and that the core temperature of the bergs appears to be a conservative tracer

ground water radon anomaly before the kobe earthquake in japan radon concentration in ground water increased for several months before the 1995 southern hyogo prefecture kobe earthquake on 17 january 1995 from late october 1994 the beginning of the observation to the end of december 1994 radon concentration increased about fourfold on 8 january 9 days before the earthquake the radon concentration reached a peak of more than 10 times that at the beginning of the observation before starting to decrease these radon changes are likely to be precursory phenomena of the disastrous earthquake

co2 and radon measurements in the vogtland area germany a contribution to earthquake prediction research the interpretation of long term radon measure ments in a spring located in vogtland shows a significant relationship to the seismicity of a region close to the sampling point a statistical check was performed in order to identify the anomaly generating area the cause for this relation is emission of mantle originated gases including co2 influenced by tectonic processes in the crust

a systematic compilation of earthquake precursors article a survey of published scientific literature was undertaken to identify and catalog observed earthquake pre cursors the earthquake precursors selected for analysis included electric and magnetic fields gas emissions groundwater level changes temperature changes surface deformations and seismicity for each of these precursors the published scientific literature was searched to document the statistics of each reported earth quake precursor spatial extent time duration amplitude signal noise ratio to analyze dependence of the observable for each precursor on earthquake magnitude and to explore proposed physical models to explain eachearthquakeprecursor somegeneralcharacteristics wereobservedfortheseprecursoryphenomena first the largest amplitude precursory anomalies tend to occur before the largest magnitude earthquakes also the number of precursory anomalies tends to increase the closer in time to the occurrence of the earthquake finally theprecursoryanomaliestendtooccurclosetotheeventualepicenterof theearthquake ingeneral the physical models indicate that all of the precursory phenomena are related to deformation that occurs near the fault prior to the main earthquake while the models provide plausible physical explanations for the pre cursors there are many free parameters in the models that are poorly resolved

the dynamics of ice sheet outlets a comparison of data from aircraft altimetry landsat imagery and radia echo sounding has shown characteristic surface topographies associated with sheet and stream flow the transition between the two is abrupt and occurs at a step in the subglacial topography this marks the onset of basal sliding and high velocities caused by subglacial water it results in crevassed amphitheatre like basins round the head of outlet glaciers it is also the zone of maximum driving stress beyond which values decline rapidly as velocities increase this abrupt transition appears to be topographically controlled since basal temperatures are at the pressure melting point well inland of the change in regime the marie byrd land ice streams exhibit qualitative differences from other ice sheet outlets however the change to lower driving stresses is much more gradual and occurs several hundred kilometres inland such ice streams have particularly low surface slopes and appear in form and flow regime to resemble confined ice shelves rather than grounded ice the repeated association of the transition to rapid sliding with a distinct subglacial feature implies a stabilizing effect on discharge through outlet glaciers acceleration of the ice is pinned to a subglacial step and propagation of high velocities inland of this feature seems improbable rapid ice flow through subglacial trenches may also ensure a relatively permanent trough through accentuation of the feature by erosion this is concentrated towards the heads of outlet glaciers up stream of the region where significant basal decoupling occurs this may be a mechanism for the overdeepening of fjords at their inland ends and the development of very steep fjord headwalls

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

gas anomalies at three mineral springs and a fumarole before an inland earthquake central japan conspicuous anomalies in gas compositions were observed at a fumarole and three mineral springs about 1 3 months prior to an inland earthquake of 6 8 magnitude in central japan on september 14 1984 the epicentral distances are 9 km for the fumarole and 50 71 and 95 km for the springs the anomalies in he ar n2 ar and ch4 ar ratios of bubble gases from the springs can be attributed to fluctuations in the emission rate of some deep seated gas due to change in pore pressure which is subjected to crustal stress resulting in the earthquake the anomaly at the fumarole showed an increase in discharge rate of deep volcanic gas under a compressional stress near the focal region since the behavior of subsurface fluids represented by he ar and other ratios is presumably controlled by the change of pore pressure temporal variations in the fluids can be used as a strain gauge for the crust on the other hand the precursory emissions of h2 which were observed after changes in he ar and other ratios had occurred may have resulted from a reaction between groundwater and the surface of newly formed cracks the timing and amplitude of the geochemical anomalies are compatible with the result predicted by a dilatancy model without fluid diffusion although h2 emission may be related to groundwater permeation into newly formed cracks monitoring of several gases with automatic gas chromatographs at several stations may be useful for unraveling earthquake mechanisms and for predicting earthquakes

holocene east asian monsoonal precipitation pattern revealed by grain size distribution of core sediments of daihai lake in inner mongolia of north central china abstract two sediment cores recovered in the central part of daihai lake in north central china were analysed at 2 to 4 cm intervals for grain size distribution grain size distributions of the lake sediments are inferred to be a proxy for past changes in east asian monsoon precipitation such that greater silt size percentage and higher median grain size reflect increased monsoonal precipitation rates the grain size record of daihai lake sediments spanning the last ca 10 000 yr indicates that the monsoonal precipitation in the lake region can be divided into three stages the early middle and late holocene during the early holocene before ca 7900 cal yr bp the median grain size md and the silt fraction content were relatively low and constant suggesting relatively low precipitation over the lake region the middle holocene between ca 7900 and 3100 cal yr bp was marked by intensified and highly variable monsoonal precipitation as indicated by high and variable md values and silt contents of the lake sediments during this period average precipitation rate gradually increased from ca 7900 to 6900 cal yr bp displayed intense oscillations between ca 6900 and 4400 cal yr bp and exhibited a decreasing trend while fluctuating from ca 4400 to 3100 cal yr bp although generally high during the middle holocene both the md and the silt content assumed distinctly low values at the short intervals of ca 6500 6400 6000 5900 5700 5600 4400 4200 cal yr bp implying that monsoonal precipitation might have been significantly reduced during these intervals during the late holocene since ca 3100 cal yr bp grain size values suggest that precipitation decreased however during the late holocene relatively higher md values and silt contents occurring between ca 1700 to 1000 cal yr bp may denote an intensification of hydrological cycles in the lake area changes in the east asian monsoonal precipitation were not only directly linked with the changing seasonality of solar insolation resulting from progressive changes in the earth s orbital parameters but also may have been closely related to variations in the temperature and size of the western pacific warm pool in the intensity of the el nino southern oscillation and in the path and strength of the north equatorial current in the western pacific

modeling iceberg rafted sedimentation in high latitude fjord environments 1 an iceberg model sedberg has been developed to simulate sedimentation in high latitude glaciated fjords sediments deposited in fjords provide an important record of glaciological response to changing climatic conditions the model simulates the formation drift and melt of a population of icebergs utilizing monte carlo based techniques with a number of underlying parametric probability distributions to describe the stochastic behavior of iceberg formation and dynamics the model captures iceberg dynamics and melt in fjord environments and has been applied to kangerdlugssuaq fjord in east greenland as an example of an iceberg dominated sedimentary environment sedimentation has been simulated over the past 1500 years encompassing the climatic intervals of the medieval warm period mwp and the little ice age lia model results have been compared with the observed sedimentary record the model demonstrates that the glaciological regime e g basal debris thickness mean annual calving rate mean iceberg size plays a more important role than the direct influence of climate ocean and air temperatures on iceberg sedimentation rate although often changes in climate result in changes to the glaciological regime

the surface topography of large ice masses from landsat imagery les images de landsat mss de l antarctique et du svalbard ont ete comparees a des mesures altimetriques effectuees a partir d avion

anthropogenic origins of a late holocene basin wide unconformity in the middle reaches of the yellow river the luoyang basin henan province china we evaluate the relative importance of climate change fluvial dynamics and anthropogenic environmental modification in forming the holocene sedimentary record of the luoyang basin a tributary drainage basin of the yellow river located in western henan province china our 2011 fieldwork south of the erlitou site in the luoyang basin indicates that an unconformity dating to ca ad 1100 is roughly coincident with a major southward shift in the lower course of the yellow river in ad 1128 the governor of kaifeng breached the dikes of the yellow river to impede an advancing army causing the yellow river to flow south out to the yellow sea we argue that the dike breach not only changed the fluvial dynamics of the yellow river but also switched the rivers in the luoyang basin from an aggrading to an incising system the resumption of sedimentation in the luoyang basin is roughly coincident with the next major shift of the yellow river s main course northward to the bohai sea in ad 1855 the unconformity found in the luoyang basin may be a legacy of historically contingent human agency rather than climatic shifts or gradual environmental modification

geochemical monitoring of geothermal waters 2002 2004 along the north anatolian fault zone turkey spatial and temporal variations and relationship to seismic activity a total of nine geothermal fields located along an 800 km long e w transect of the north anatolian fault zone nafz turkey were monitored for three years 2002 2004 inclusive 3 sampling periods per year to investigate any possible relationship between seismic activity and temporal variations in the chemistry and isotope characteristics of waters in the fields the geothermal fields monitored in the study were from west to east yalova efteni bolu mudurnu seben kursunlu cankiri hamamozu gozlek and resadiye the chemical major anion cation contents and isotopic 18o 16o d h 3h compositions of hot and cold waters of the geothermal sites were determined in order to both characterize the chemical nature of the individual fields and identify possible temporal variations associated with localized seismic activity the geothermal waters associated with the nafz are dominantly na hco3 whereas the cold waters are of the ca hco3 type the oxygen and hydrogen isotope compositions reveal that the hot waters are meteoric in origin as are their cold water counterparts however the lower 18o d and 3h contents of the hot waters point to the fact that they are older than the cold waters and that their host aquifers are recharged from higher altitudes with virtually no input from recent post bomb precipitation although no major earthquakes e g with m 5 were recorded along the nafz during the course of the monitoring period variations in the chemical and isotopic compositions of some waters were observed indeed the timing of the chemical isotopic changes seems to correlate with the occurrence of seismic activity of moderate magnitude 3 m 5 close to the sampling sites in this respect cl 3h and ca seem to be the most sensitive tracers of seismically induced crustal perturbations and the yalova and efteni fields appear to be the key localities where the effects of seismic activity on the geothermal fluids are most pronounced over the monitoring period the present study has produced a baseline database for future studies directed at characterizing the effects of moderate major earthquakes on the composition of geothermal waters along the nafz future work involving longer monitoring periods with more frequent sampling intervals should lead to a better understanding of the underlying mechanism s producing the observed chemical and isotopic variations

the huanghe yellow river and changjiang yangtze river deltas a review on their characteristics evolution and sediment discharge during the holocene abstract today asian rivers play an important role in delivering sediment from the land to the oceans however past sediment discharge before human activities modified the landscape is not well known and is estimated to have been roughly one third to one half of the present level chinese rivers have been strongly influenced by human activities and their sediment discharge has changed over the last 6000 years for the study of the long term human impact on rivers and catchment basins chinese rivers provide excellent examples because continuous historical records are available here the characteristics evolution and sediment discharge during the holocene of the deltas of two large chinese rivers huanghe yellow river and changjiang yangtze river are summarized the huanghe and changjiang deltas are different with respect to coastal environments water and sediment discharge the pattern of development of the delta lobe thickness of holocene sediments and basal topography of the incised valleys formed during the last glacial period the huanghe delta is characterized by a high concentration of sediment huge sediment discharge thin holocene deltaic sediments a lateral delta lobe shift and a steep longitudinal profile in its lower reaches the changjiang delta is characterized by a large water discharge a large interseasonal water level change a tide dominated coastal environment continuous seaward progradation with isolated river mouth sand bodies thick holocene sediments and a deep incised valley formed during the last glacial period based on the sediment volume of prograding deltaic sediments over the last 6000 years the sediment discharge of huanghe 1000 years ago is estimated to have been 1 10 8 tons year 1 10 of the present level an abrupt increase occurred at ca 1000 years ago as a consequence of human activities on the loess plateau especially involving cultivation and deforestation moreover the estimated sediment load of huanghe at sanmenxia station prior to 1000 years was 2 7 4 0 10 8 tons year or about 20 15 25 of the present level our recent study estimated that the sediment discharge of changjiang before 2000 years bp was ca 2 4 10 8 tons year total sediment discharge of both rivers before 2000 years bp is estimated to have been 3 4 10 8 tons year or only about 20 of the present level moreover the total sediment load to the lower reaches is estimated to have been 5 6 10 8 tons year or one fourth the present level

a high resolution stalagmite record of the holocene east asian monsoon from mt shennongjia central china high resolution oxygen isotope 18o profiles of six stalagmites from sanbao cave in hubei province central china established with 1413 oxygen isotope data and 65 230th ages provide a continuous history of east asian summer monsoon easm intensity for the period from 13 0 2 thousand years before present ky bp relative to ad 1950 the 18o record includes four distinct stages in the evolution of the easm 1 an abrupt transition 11 5 ky bp into the holocene 2 a period of gradual increase in monsoon intensity 11 5 9 5 ky bp 3 the maximum humid period 9 5 6 5 ky bp and 4 a period of gradual decline in monsoon intensity 6 5 0 2 ky bp comparison of sanbao with regional records of comparable resolution reveals that the timing of the beginning and end of the holocene optimum as defined by the minimum in 18 o was similar in the indian and east asian monsoon systems this supports the idea that shifts in the monsoon tied to shifts in the mean position of the inter tropical convergen

subglacial till a physical framework for its properties and processes the continuum theory of mixtures provides a framework around which present knowledge of subglacial till can be organized the proposed framework is provisional in two senses the constitutive description of till will require improvement and not all potentially significant processes have been included till is treated as a three component mixture of water clasts coarse grained solids and fine grained matrix solids these components obey mass balance equations and their behavior is subject to constitutive relations that describe such processes as darcian water transport fine grained sediment transport consolidation shear deformation dilatancy and comminution five state variables uniquely determine the compressibility permeability shear strength and other physical properties numerical solutions of the state evolutions equations illustrate that the properties of till are highly responsive to changes in the subglacial environment

gas geochemical changes at mineral springs associated with the 1995 southern hyogo earthquake m 7 2 japan abstract gas concentrations monitored at a mineral spring in central japan over the past 15 years showed similar changes before and after two large earthquakes september 1984 m 6 9 50 km distant and january 1995 m 7 2 220 km distant namely a concurrent and abrupt drop in all three gas ratios he ar n 2 ar and ch 4 ar several months before the events improved measurements of gas compositions since 1991 and the addition of gas discharge rate monitoring since 1993 disclosed the following features for anomalies in response to small earthquakes as well as the large 1995 event 1 the gas ratios increased for both large and small earthquakes but they did not return to the preseismic values for the large event as they did within a few hours for the small events 2 at the 1995 event the gas discharge rate decreased remarkably 3 h before the event and then increased to higher than preseismic level for several months in contrast coseismic rates at small events generally increased for less than 15 min 3 during a seismically quiet period from january 1993 to december 1994 the variation in the he ar ratio was well correlated with that of gas discharge rate such correlation disappeared in august and september 1994 when the three gas ratios dropped before the large event 4 gas compositions at an auxiliary monitoring site revealed a coseismic change similar to that described above for the 1995 event these lines of evidence show that subsurface fluids may habitually respond to changes in physical conditions relating to earthquake occurrences and thus suggest the usefulness of monitoring subsurface fluids for earthquake prediction

wetland geomorphology and paleoecology near akab muclil rio bravo floodplain of the belize coastal plain abstract to understand wetland geomorphology and paleoecology we collected a 2 6 m sediment core from a flooded swamp adjacent to the maya archaeological site of akab muclil in the maya lowlands of northwestern belize the site of akab muclil has a known occupation that persisted from early maya classic 1700 1350 bp through the terminal maya classic 1180 1050 bp and into the postclassic 1050 450 bp and lies near a vast network of ancient maya canal and field systems we analyzed this core using a combination of paleoecological and geochemical techniques to determine the history of land use and natural change over time within this wetland accelerator mass spectrometry dating pollen charcoal analysis micropaleontology geochemical analysis and magnetic susceptibility provide a suite of methods from which we interpret the geomorphic and ecological history of this wetland system four ams dates from the length of the core provide us with an age model that runs from 1675 cal bp through the maya classic onward to the present at the base of this system soil composition and chemistry provide evidence that the system changed from a seasonally wet terrestrial soil to a perennially wet swamp as the basal mollisol soil lies buried by peats and calcareous sediments this shift to a perennial wetland could be related to ancient maya water management or a natural geomorphic change though we suspect the former because of nearby ancient maya large scale geomorphic and hydrological manipulation in the form of intensive canalization and agriculture evidence of ancient maya uses and impacts including sedimentation zea mays pollen and high charcoal counts occur from the lowest levels of the sequence through the classic and into the postclassic period above this level the strata change to stable peats laminated deposits of light gray dark gray gypsum authigenic carbonate and layers of fibrist peat with little evidence of human impact until recent increases in charcoal and phosphorous this study compared with other regional studies indicates a later transition from terrestrial to wetland later human impacts in the postclassic and a geomorphic impact record closely tied to the history of the adjacent site rather than broader land use trends