dynamic triggering and earthquake swarms on east pacific rise transform faults while dynamic earthquake triggering has been reported in several continental settings offshore observations are rare oceanic transform faults share properties with continental geothermal areas known for dynamic triggering high geothermal gradients high seismicity rates and frequent swarms we study dynamic triggering along the east pacific rise by analyzing 1 year of seismicity recorded by ocean bottom seismographs by comparing the response to teleseismic waves from global earthquakes we find triggering to be most sensitive to changes in normal stress and to preferentially occur above 0 25 kpa the clearest example of triggering occurs on the quebrada and gofar faults after the mw8 0 wenchuan earthquake on gofar triggered seismicity occurs between the rupture areas of large earthquakes within a zone characterized by aseismic slip abundant microseismicity frequent swarms and low vp we infer that lithological properties inhibiting rupture propagation such as high porosity and fluid content also favor dynamic triggering

exploration of remote triggering a survey of multiple fault structures in haiti triggering studies provide an important tool for understanding the fundamental physics of how faults slip and interact and they also provide clues about the stress states of faults in this study we explore how seismic waves from the 27 february 2010 mw8 8 maule chile mainshock interact with the left lateral strike slip enriquillo plantain garden fault epgf and surrounding reverse faults in the southern haiti peninsula the chile mainshock occurred 6 000 km away and just 46 days after the 12 january 2010 mw7 0 haiti earthquake a tragic event which activated multiple faults in the southern haiti peninsula during the surface waves of the chile mainshock several tectonic tremor signals were observed originating from south of the epgf trace cross correlation of the triggered tremor and transient stresses resolved onto to the epgf indicates that the love wave of the chile mainshock was the primary driving mechanism of the triggered deep shear slip and tremor signals as opposed to dilatational stress changes generated by the rayleigh wave we also searched for any influence of transient stresses on haiti aftershock activity by applying the matched filter technique to multiple days of seismic data around the time of the chile mainshock while we identified a slight increase in haiti aftershock activity rate the rate changes were significant only when small magnitude events were included in the significance tests these observations are generally consistent with recent inferences that deep tectonic tremor is more sensitive than shallow earthquakes to external stress perturbations

assessing impact of irrigation water on groundwater recharge and quality in arid environment using cfcs tritium and stable isotopes in the zhangye basin northwest china summary environmental tracers cfcs 18o 2h and tritium were used to determine the natural groundwater recharge and the impact of irrigation activity on the groundwater system in the semi arid zhangye basin of china groundwaters in the irrigated areas have been identified as mixtures containing fractions recharged in different periods of time the cfc and 3h data show that the oldest fraction in the groundwater was recharged before 1950 whereas the younger fractions were recharged in different periods of time since 1950 stable isotope 18o 2h cfc and electrical conductivity data show that most of the samples can be regarded as binary mixtures with the river irrigation water presents the younger fraction and the regional groundwater presents the older fraction binary mixing model is used to estimate the age and fraction of the younger component most of the younger fraction was recharged after 1980s in response to the increasing irrigation activities compared to local precipitation surface water plays a major role in recharging the aquifer in the irrigated area the irrigation activity had more impact on the aquifer under thin unsaturated zone no 3 concentration in groundwater combined with a proper mixing model however they can provide evidences that the cfcs found in groundwater were introduced by infiltrating irrigation return flow and therefore reveal that human activities can produce a much localized water circulation and influence groundwater vulnerability

chemical characteristics of groundwater in parts of the gambhir river basin bharatpur district rajasthan india twenty nine dug well samples have been collected from the gambhir river basin in the bharatpur district of rajasthan state in india for hydrogeochemical study to understand the sources of dissolved ions and assess the chemical quality of the water broadly speaking the groundwaters have a chemical composition within the permissible limits suggested for drinking water nitrate is higher than the acceptable limit in some samples due to the use of fertilizers graphical treatment of the major ion chemistry helps in deciphering the chemical characteristics of groundwaters which may then be used for grouping the samples to identify the trends of the chemical alteration of the meteoric water four groups have been identified in the gambhir river basin groundwater system 1 hco3 enriched 2 mixed type 3 alkali rich high tds type and 4 hco3 deficient possible aqueous species have been identified for these four groups of samples in groups i and ii the species are ca hco3 2 mg hco3 2 nacl na2so4 and nahco3 group iii in addition to these species has abundance of kcl group iv has ca hco3 2 nacl caso4 and rather rare species such as cacl2 mgcl2 and mgso4 interpretation of the data reveals that feldspar and pyrite weathering reactions do not play a significant role in giving groundwaters their observed chemical characteristics groups i and ii samples have evidently been derived by dissolution of surface salts whereas groups iii and iv groundwaters suggest dissolution of a marine evaporite sequence similar to the one known to exist to the west of the study area unconformably overlying the rocks of the delhi super group there are indications that joints play an important role in segregating groundwaters with different chemical characteristics

oxygen and hydrogen isotopes in the hydrologic cycle changes of the isotopic composition of water within the water cycle provide a recognizable signature relating such water to the different phases of the cycle the isotope fractionations that accompany the evaporation from the ocean and other surface waters and the reverse process of rain formation account for the most notable changes as a result meteoric waters are depleted in the heavy isotopic species of h and o relative to ocean waters whereas waters in evaporative systems such as lakes plants and soilwaters are relatively enriched during the passage through the aquifers the isotope composition of water is essentially a conservative property at ambient temperatures but at elevated temperatures interaction with the rock matrix may perturb the isotope composition these changes of the isotope composition in atmospheric waters surface water soil and groundwaters as well as in the biosphere are applied in the characterization of hydrological system as well as indicators of paleo climatological conditions in proxy materials in climatic archives such as ice lake sediments or organic materials

on the sensitivity of transtensional versus transpressional tectonic regimes to remote dynamic triggering by coulomb failure abstract accumulating evidence although still strongly spatially aliased indicates that although remote dynamic triggering of small to moderate m w

hydrochemical processes governing groundwater quality of sedimentary aquifers in central saudi arabia and its environmental implications the present study deals with the interpretation of the major processes governing the groundwater chemistry in parts of qassim and riyadh province of saudi arabia the study area that is dominated by agricultural activities is represented by a multi layered aquifer system with sedimentary formations ranging from cambrian to the quaternary present as outcrops groundwater samples from 97 agricultural bore wells in the area were collected and analyzed for 16 physio chemical parameters the evaluation of the main hydrochemical processes affecting the groundwater quality was carried out by interpreting the ionic relationships and hydrochemical facies analysis the interpretation pointed toward evaporation gypsum dissolution and ion exchange as main factors controlling the major ion groundwater chemistry the piper plot showed so4 cl type of groundwater with majority of the samples falling in the zone of permanent hardness due to the formation of non carbonate salts principal component analysis that helps to understand the underlying natural and anthropogenic factors controlling the groundwater chemistry in an area was used in the present study based on which four principal components pcs were extracted the first pc as expected was dominated by the major ions and was attributed to natural processes whereas the extracted components mainly heavy metals in pc 2 3 and 4 pointed toward anthropogenic activities playing an active role in affecting the trace element hydrochemistry

assessment of geochemistry and hydrogeochemical processes in groundwater of the tefenni plain burdur turkey the tefenni burdur plain is located in the southwest of turkey and is semi closed basin groundwater is densely used as drinking irrigation and domestic water in the tefenni plain hydrogeochemical processes controlling groundwater chemistry and geochemical assessment of groundwater were investigated in the tefenni burdur turkey plain the conceptual hydrogeological model of the plain was prepared for qualitative description of the underground geology and interpretation of hydrogeochemical processes of the study area in this study groundwater samples for two seasons were analyzed and major ion chemistry of groundwater was researched to understand the groundwater geochemistry two major hydrochemical facies ca2 mg2 hco3 and mg2 ca2 hco3 were determined in the area mg2 na so42 and cl concentrations of water samples increased seasonally related to ion exchange of minerals in rocks by rainwater in wet season various graphical plots and multivariate statistical analysis pearson correlation analysis were used for identifying the occurrence of different geochemical processes carbonate weathering in dry season and silicate weathering in wet season were the major hydrogeochemical processes in the study area in addition ion exchange and reverse ion exchange were two possible processes of water rock interaction in the basin the mechanism controlling groundwater chemistry at the tefenni plain is originally regulated by the geogenic process rather than antropogenic activities

quantifying sulfate components and their variations in soils of the mcmurdo dry valleys antarctica 1 many soils of the mcmurdo dry valleys mdv antarctica being old hyperarid and frigid have accumulated abundant atmospheric salts over the last several million years this salt repository offers an opportunity to study atmospheric chemistry past and present the origin and transport of ions in soils the weathering activity of soils and postdepositional soil leaching processes within this unique environment in particular soil sulfate in the mdv is known to have multiple origins but the precise proportions of different sulfate components remain elusive here we test a hypothesis that soil sulfate in the mdv is a predictable mixture of three major components sea salt sulfate non sea salt sulfate and background sulfate derived from weathering and volcanic sources that to a large extent varies as a function of elevation and distance from the coast by measuring sulfate s three stable isotope parameters i e 17o 18o and 34s plus estimating independently the end member stable isotope parameters for the three components on the basis of published reports and our measured data we solve explicitly the mixing proportion for each component using a set of three simultaneous linear equations the results from four spatially representative soil profiles show that the sum of such calculated proportions for the three components is very close to unity in most samples suggesting that a simple three component mixing model is a good representation of the soil sulfate budget while significant uncertainties still exist in the isotope compositions of different sulfate end members these data provide important initial constraints on sulfate diversity as well as its spatial and vertical distribution in the mdv

delineation of groundwater provenance in arctic environment using isotopic compositions of water and sulphate abstract little is known about water rock interaction related to deeper groundwater flows along tectonic discontinuities in the arctic glacial catchments therefore we analyzed oxygen and sulfur isotope compositions 18o 34s of dissolved sulfate so42 to better understand this process in groundwater from mineral and thermal springs and subglacial outflows of southern spitsbergen our results show that coupled 18o 34s of so42 is a useful measure of groundwater provenance and its relation to water rock interaction along flow paths in different lithologies in the studied area groundwater rock interaction with carbonate and crystalline rocks contributes two different sources of sulfide derived so42 with distinctive isotope compositions and leaves similar isotopic signature as in shallow surface environment e g proglacial lakes and streams the sulfide derived so42 from paleozoic carbonates has lower 34s 5 and higher 18o 5 compared to higher 34s 10 to 15 and more negative 18o 10 in the precambrian crystalline rocks minor contributions of so42 are from sea spray conversely direct inflows of seawater appear to be negligible if any moreover the more negative 2h and 18o values 85 to 70 and 12 to 9 respectively suggest that majority of the studied groundwater and surface water is from melting of snow ice formed in fall winter months compared to lower contributions from spring summer precipitation with higher 2h and 18o 65 to 55 and 8 to 6 interestingly the water soluble so42 from the antarctic soils with high 34s 12 to 16 and negative 18o 15 to 5 is remarkably similar to the sulfide derived so42 from the precambrian crystalline rocks analyzed by us in southern spitsbergen this implies that sulfide oxidation might be a widespread process in polar environments even under extremely dry conditions as in antarctica

global ubiquity of dynamic earthquake triggering surface waves that were generated by 12 out of 15 earthquakes with magnitudes greater than 7 since 1990 led to a global increase in the number of small earthquakes this suggests that dynamic triggering of earthquakes is common and is independent of the tectonic environment earthquakes can be triggered by local changes in the stress field static triggering1 2 3 4 5 6 7 due to nearby earthquakes or by stresses caused by the passage of surface rayleigh and love waves from a remote large earthquake dynamic triggering8 9 10 11 12 13 14 15 16 17 18 however the mechanism frequency controlling factors and the global extent of dynamic triggering are yet to be fully understood because rayleigh waves involve compressional and dilatational particle motion volumetric changes as well as shearing whereas love waves only involve shearing triggering by either wave type implies fundamentally different physical mechanisms here we analyse broadband seismograms from over 500 globally distributed stations and use an automated approach to systematically identify small triggered earthquakes the low amplitude signals of such earthquakes would normally be masked by high amplitude surface waves our analysis reveals that out of 15 earthquakes studied of magnitude m greater than 7 0 that occurred after 1990 12 are associated with significant increases in the detection of smaller earthquakes during the passage of both the love and rayleigh waves we conclude that dynamic triggering is a ubiquitous phenomenon that is independent of the tectonic environment of the main earthquake or the triggered event

sensitivity to long term climate change of subpermafrost groundwater systems in svalbard deep subpermafrost aquifers are highly climate dependent with the permafrost as an aquitard preventing groundwater recharge and discharge a study from the high arctic island of spitsbergen svalbard shows that during a glacial to interglacial phase both the permafrost and the glacier regime will respond to climatic changes and a glacier fed groundwater flow system will vary accordingly a full glaciation results in the melting of permafrost and groundwater can flow through pores and fracture systems in the rocks and sediments below the temperate zones of glaciers these groundwater flow systems will mainly be localized to fjords and valleys and form low lying terrestrial springs when the relative sea level drops during deglaciation due to glacio isostatic rise during an interglaciation permafrost develops and thickens and the groundwater recharge and discharge areas will thereby be gradually reduced to a minimum reached at the warmest part of an interglaciation an already frozen spring system cannot reopen before the permafrost melts only groundwater springs related to permanently warm based glacial ice will persist into the next glaciation during a new glaciation flow systems that terminated during the previous interglaciation may become revitalized if overridden by warm based ice causing permafrost thawing

the hydrochemistry of meltwaters draining a polythermal based high arctic glacier south svalbard i the ablation season solute and runoff time series at finsterwalderbreen svalbard provide evidence for considerable basal routing of water and the existence of at least two contrasting subglacial chemical weathering environments the hydrochemistry of a subglacial upwelling provides evidence for a snowmelt fed subglacial reservoir that dominates bulk runoff during recession flow high concentrations of cl and crustal ions high pco2 and ratios of so2 4 so2 4 hco 3 close to 0 5 indicate the passage of snowmelt through a subglacial weathering environment characterized by high rock water ratios prolonged residence times and restricted access to the atmosphere at higher discharges bulk runoff becomes dominated by icemelt from the lower part of the glacier that is conveyed through a chemical weathering environment characterized by low rock water ratios short residence times and free contact with atmospheric gases these observations suggest that icemelt is routed via a hydrological system composed of basal ice marginal englacial and supraglacial components and is directed to the glacier margins by the ice surface slope upwelling water flows relatively independently of icemelt to the terminus via a subglacial drainage system possibly constituting flow through a sediment layer cold basal ice at the terminus forces it to take a subterranean routing in its latter stages the existence of spatially discrete flow paths conveying icemelt and subglacial snowmelt to the terminus may be the norm for polythermal based glaciers on svalbard proglacial mixing of these components to form the bulk meltwaters gives rise to hydrochemical trends that resemble those of warm based glaciers these hydrochemical characteristics of bulk runoff have not been documented on any other glacier on svalbard to date and have significance for understanding interactions between thermal regime and glacier hydrology 1998 john wiley sons ltd

stable isotope evidence for microbial sulphate reduction at the bed of a polythermal high arctic glacier glacier beds may be host to a range of microbial communities which drive oxic waters towards anoxia along certain hydrological flowpaths chemical and isotopic signatures in meltwaters from finsterwalderbreen a polythermal glacier on sedimentary bedrock in svalbard show clear evidence for anoxia at the glacier bed increases in 34s and 18o of sulphate indicate that microbial sulphate reduction has resulted in significant decreases in sulphate concentration the 13c of the dissolved inorganic carbon dic is isotopically light 13c 8 which is consistent with the use of bedrock kerogen and or the necromass of sulphide oxidising bacteria as organic substrates for the sulphate reducing bacteria calculated rates of organic carbon mineralisation correspond to 10 of the total annual dic flux of the glacial meltwaters this microbial ecosystem is chemoautotrophically based ultimately being sustained by the kerogen and or bacterial necromass and sulphides in the bedrock this work suggests that glacier beds can be refugia for life when climatic and or atmospheric conditions are otherwise inclement and also supports the contention that microbial life is present in subglacial lake vostok

global glacier mass changes and their contributions to sea level rise from 1961 to 2016 glaciers distinct from the greenland and antarctic ice sheets cover an area of approximately 706 000 square kilometres globally1 with an estimated total volume of 170 000 cubic kilometres or 0 4 metres of potential sea level rise equivalent2 retreating and thinning glaciers are icons of climate change3 and affect regional runoff4 as well as global sea level5 6 in past reports from the intergovernmental panel on climate change estimates of changes in glacier mass were based on the multiplication of averaged or interpolated results from available observations of a few hundred glaciers by defined regional glacier areas7 10 for data scarce regions these results had to be complemented with estimates based on satellite altimetry and gravimetry11 these past approaches were challenged by the small number and heterogeneous spatiotemporal distribution of in situ measurement series and their often unknown ability to represent their respective mountain ranges as well as by the spatial limitations of satellite altimetry for which only point data are available and gravimetry with its coarse resolution here we use an extrapolation of glaciological and geodetic observations to show that glaciers contributed 27 22 millimetres to global mean sea level rise from 1961 to 2016 regional specific mass change rates for 2006 2016 range from 0 1 metres to 1 2 metres of water equivalent per year resulting in a global sea level contribution of 335 144 gigatonnes or 0 92 0 39 millimetres per year although statistical uncertainty ranges overlap our conclusions suggest that glacier mass loss may be larger than previously reported11 the present glacier mass loss is equivalent to the sea level contribution of the greenland ice sheet12 clearly exceeds the loss from the antarctic ice sheet13 and accounts for 25 to 30 per cent of the total observed sea level rise14 present mass loss rates indicate that glaciers could almost disappear in some mountain ranges in this century while heavily glacierized regions will continue to contribute to sea level rise beyond 2100 the largest collection so far of glaciological and geodetic observations suggests that glaciers contributed about 27 millimetres to sea level rise from 1961 to 2016 at rates of ice loss that could see the disappearance of many glaciers this century

enhancement of glacial solute fluxes in the proglacial zone of a polythermal glacier annual proglacial solute fluxes and chemical weathering rates at a polythermal high arctic glacier are presented bulk meltwater chemistry and discharge were monitored continuously at gauging stations located at the eastern and western margins of the glacier terminus and at the outlet 2 5 km downstream where meltwaters discharge into the fjord fluxes of non snowpack hco 3 so 4 2 ca 2 and mg 2 increase by 30 47 between the glacier terminus and the outlet indicating that meltwaters are able to access and chemically weather efflorescent sulphates carbonates and sulphides in the proglacial zone smaller increases in the fluxes of non snowpack derived na k and si indicate that proglacial chemical weathering of silicates is less significant en3hanced solute fluxes in the proglacial zone are mainly due to the chemical weathering of active layer sediments the pco 2 of active layer ground waters is above atmospheric pressure this implies that solute acquisition in the active layer involves no drawdown of co 2 the annual proglacial chemical weathering rate in 1999 is calculated to be 2600 meq m 2 this exceeds the chemical weathering rate for the glaciated part of the catchment 790 meq m 2 by a factor of 3 3 hence the proglacial zone at finster walderbreen is identified as an area of high geochemical reactivity and a source of co 2

application of multivariate statistical procedures on major ions and trace elements in a multilayered coastal aquifer the case of the south rhodope coastal aquifer multivariate statistical techniques including cluster analysis and principal components analysis were applied on 22 variables consisted of 3 physicochemical parameters 8 major ions and 11 trace elements samples were collected from the south rhodope multilayered coastal aquifer in north greece which is facing saltwater intrusion and anthropogenic contamination over the last 35 years cluster analysis grouped the variables into five main groups while principal components analysis revealed four distinct hydrochemical processes in the aquifer system explaining 84 5 of the total variance between the variables the identified processes correspond to saltwater intrusion and subsequent reverse cation exchange the presence of deep connate groundwater masses application of fertilizers in shallow wells and anthropogenic contamination with heavy metals nearby an improperly constructed landfill the wells categorized with the above techniques were grouped and five constituent ratios na cl mg ca cl ca hco3 so4 ca so4 and ca mg were utilized to identify the ones which enable the more accurate distinction between the group cases the results of stepwise discriminant analysis showed that the calculated classification function can distinguish almost 80 of groundwater samples with the na cl ratio being the most statistically significant grouping variable all the aforementioned statistical models managed to successfully identify numerous hydrochemical processes in a complex multilayered aquifer system and to explicitly attribute them for every investigated well allowing a deeper insight into groundwater chemical characteristics with the use of an optimized smaller number of variables

changes in water chemistry along the newly formed high arctic fluvial lacustrine system of the brattegg valley sw spitsbergen svalbard changes in water chemistry along the high arctic fluvial lacustrine system located in wedel jarlsberg land in the sw spitsbergen svalbard were investigated during the summer season of 2010 and 2011 the newly formed river lake system consists of three lakes connected with the brattegg river the first bathymetric measurements of these lakes were made by the authors in 2010 the brattegg river catchment represents a partly glaciered arctic water system the studied lakes are characterized by low mineralization and temperature of water the value of the electrolytic conductivity ec ranges from 30 2 to 50 5 s cm 1 and the temperature of surface water from 1 5 to 7 8 c the temperature increase takes place downstream starting from upper lake to the outflow from myrktjorna lake the waters of lakes have higher temperatures than the stream the predominant ions are hco3 up to 16 5 mg l 1 cl 6 66 8 53 mg l 1 ca2 2 40 4 45 mg l 1 and na 2 65 3 36 mg l 1 the highest values of ammonium and doc found in the lowest myrktjorna lake seem to be related to the presence of aquatic organisms and also birds from the group of 10 analyzed microelements increased concentrations of aluminum up to almost 500 g l 1 are present in the lakes water water isotopic composition ranges for 18o and 2h from 10 6 to 10 9 and from 70 8 to 72 3 respectively the vertical zonality of lake waters is manifested in a decrease in the temperature and increase in ec and chemical elements concentrations

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

hydrochemical assessment of groundwater in mesozoic sedimentary aquifers in an arid region a case study from wadi nisah in central saudi arabia wadi nisah which lies to the south of riyadh city is an important source of groundwater supply and agricultural production in the central region of saudi arabia twenty nine groundwater samples were collected from wells tapping the shallow alluvial aquifer as well as the mesozoic manjur and dhruma aquifer in western wadi nisah the interpretation of the results of the major ion analysis reveals that geogenic factors mainly rock water interaction and mineral dissolution control the groundwater chemistry the samples are characterized by high tds and ec values saturation indices of the groundwater show that minerals dissolution is the primary factor affecting the groundwater composition piper plot reveals groundwater mixing as ca mg cl so4 facies mixed ca mg cl so4 facies and na k cl so4 facies is present in the study area gypsum and dolomite weathering coupled with reverse ion exchange are responsible for the dominance of alkaline earth elements over alkali elements principal component analysis helped in the extraction of three principal components accounting for approximately 78 of the total data variability the extracted components point mainly towards geogenic influences however the third principal component shows the influence of anthropogenic pollution mainly nitrate pollution from agricultural activity in the area

evidence for widespread anoxia in the proglacial zone of an arctic glacier the major ion so42 hco3 no3 and stable isotope composition 18o h2o 18o so42 34s so42 and dic 13c of ground and surface water samples collected from the proglacial zone of a retreating high arctic glacier finsterwalderbreen svalbard indicate the widespread occurrence of microbially mediated processes under anoxic conditions the 18o so42 of active layer groundwaters lake and stream waters is strongly depleted in 18o compared to the 18o h2o and stable isotope mass balance arguments indicate that 75 95 of so42 in these waters is produced by the oxidation of sulphide minerals using fe iii and no3 under anoxic conditions consistent with this is the frequent loss or depletion of no3 from ground and surface waters so42 concentrations and 18o so42 and 18o h2o data suggest that much of the so42 is generated anoxically early in the melt season in 18o depleted snowmelt and is immobilized as sulphate salts in near surface moraine due to evaporative concentration these salts are remobilized later in the season by rainfall and glacial flood events and cause the 18o so42 of proglacial meltwaters to be 18o h2o the latter become isotopically heavy through the melt season due to evaporation the lack of any relationship between 34s so42 and 18o so42 and relatively heavy dic 13c values in proglacial waters suggests that sulphate reduction is not a significant process acidity produced during anoxic oxidation of sulphides appears to drive chemical weathering in the proglacial zone enabling high chemical weathering rates to be maintained despite the absence of dissolved oxygen similar findings have been reported from subglacial environments where anoxic sulphide oxidation is widely observed the absence of evidence for sulphate reduction in the proglacial groundwaters however suggests that the degree of anoxia in deglaciated settings may not be widespread as in subglacial environments where significant sulphate reduction has been observed

identification and evolution of hydrogeochemical processes in the groundwater environment in an area of the palar and cheyyar river basins southern india the palar and cheyyar river basins in tamil nadu state of southern india are characterised by different geological formations and groundwater is the major source for domestic agricultural and other water related activities hydrogeochemical studies were carried out in this area with the objective of identifying the geochemical processes and their relation to groundwater quality groundwater samples were collected once a month from 43 groundwater wells in this area from january 1998 to july 1999 sampling procedures and chemical analysis were carried out as per the standard methods chemical data are used for mathematical calculations and graphical plots to understand the chemical process and its relation to the groundwater quality the chemical composition of groundwater in the central part of the study area mainly depends on the recharge from lakes and the river which is explained by a mixing mechanism in addition weathering of silicate minerals controls the concentration of major ions such as sodium calcium magnesium and potassium in the groundwater of this area further the activity ratios indicate that the groundwater is in equilibrium with kaolinite smectite and montmorrillonite the reverse ion exchange process controls the concentration of calcium magnesium and sodium in hard rock formations and dissolution of carbonate minerals and accessory minerals is the source of ca and mg in addition to cation exchange in the sedimentary formations in general the chemical composition of the groundwater in this area is influenced by rock water interaction dissolution and deposition of carbonate and silicate minerals ion exchange and surface water interactions

transient stresses at parkfield california produced by the m 7 4 landers earthquake of june 28 1992 observations from the upsar dense seismograph array the m 7 4 landers earthquake triggered widespread seismicity in the western united states because the transient dynamic stresses induced at regional distances by the landers surface waves are much larger than the expected static stresses the magnitude and the characteristics of the dynamic stresses may bear upon the earthquake triggering mechanism the landers earthquake was recorded on the upsar u s geological survey parkfield small aperture array array a group of 14 triaxial accelerometers located within a 1 square km region 10 km southwest of the town of parkfield california 412 km northwest of the landers epicenter no triggered earthquakes were observed at parkfield multiple filter analysis shows that the displacements obtained by double integration are dominated by the fundamental mode love and rayleigh modes with some higher mode contributions for periods shorter than 10 s most of the surface waves propagated along the great circle path from landers but a late arriving surface wave appears to have been scattered from the sierra nevada mountains we used a standard geodetic inversion procedure to determine the surface strain and stress tensors as functions of time from the observed displacements peak dynamic strains and stresses at earth s surface are about 7 strain and 0 035 mpa respectively and they have a flat amplitude spectrum between 2 s and 15 s period these stresses agree well with stresses predicted from a simple equation using the ground velocity spectrum observed at a single station peak stresses ranged from about 0 035 mpa at the surface to about 0 12 mpa between 2 and 14 km depth with the sharp increase of stress away from the surface resulting from the rapid increase of rigidity with depth and from the influence of mode shapes because of the free surface boundary conditions the horizontal components of the stress tensor tend to dominate in the top 5 6 km of the crust which might cause triggered seismicity to have strike slip or normal mechanisms comparison of dynamic stresses induced by the landers loma prieta and petrolia earthquakes at a variety of sites indicates that the landers stresses were not spectacularly larger than those induced by the other sources landers dynamic stresses were comparable to coalinga static stresses at parkfield the effective strain caused by landers at parkfield where no earthquakes were triggered are the same amplitude as those at some sites in nevada where earthquakes were triggered comparing various authors observations of dynamic stresses there is no obvious characteristic of these stresses that correlates with the triggered seismicity

dynamic strains at regional and teleseismic distances abstract we develop formulas for the size of dynamic strains caused by seismic waves from an earthquake of given magnitude and distance these formulas include peak strain peak dissipated power and total dissipated energy and they are applicable at regional and teleseismic distances the formulas are fits to data from 89 large 6 5 m w 9 0 shallow earthquakes with source distances between 500 and 16 000 km recorded between 1977 and 2013 by three long base laser strainmeters at pinon flat observatory in southern california these strainmeters provide uniquely well calibrated measurements of tensor strain the residuals to the fits suggest that strain values can usually be predicted to within a factor of 2 these data also show that the strain tensor can be substantially different from that expected for plane waves in particular the extension perpendicular to the back azimuth which should be zero is always 20 or more of the extension along that azimuth how much the strains resemble those for plane waves depends on their path perhaps because inhomogeneities along different paths produce different amounts of multipathing the observed strains are systematically 10 30 larger at nearby laser strainmeter sites in the salton trough suggesting local amplification from inhomogeneous crustal structure online material tables of earthquake catalogs and dynamic strain analysis and figures of earthquake magnitude distance distributions and time delays of maximum strain

assessment of groundwater quality for irrigation purposes and identification of hydrogeochemical evolution mechanisms in pengyang county china groundwater is an important water source for agricultural irrigation in penyang county some traditional methods such as irrigation coefficient sodium adsorption ratio total alkalinity total salinity and total dissolved solids were employed to assess groundwater quality in this area in addition an improved technique for order preference by similarity to ideal solution model was applied for comprehensive assessment the origin of major ions and groundwater hydrogeochemical evolution was also discussed groundwater in penyang county contains relative concentrations of dominant constituents in the following order na ca2 mg2 k for cations and hco3 so42 cl co32 for anions groundwater quality is largely excellent and or good suggesting general suitability for agricultural use calcite and dolomite are found saturated in groundwater and thus tend to precipitate out while halite fluorite and gypsum are unsaturated and will dissolve into groundwater during flow groundwater in the study area is weathering dominated and mineral weathering carbonate and silicate minerals and ion exchange are the most important factors controlling groundwater chemistry

enrichment of fluoride in groundwater under the impact of saline water intrusion at the salt lake area of yuncheng basin northern china long term intake of high fluoride groundwater causes endemic fluorosis this study for the first time discovered that the salt lake water intrusion into neighboring shallow aquifers might result in elevation of fluoride content of the groundwater two cross sections along the groundwater flow paths were selected to study the geochemical processes controlling fluoride concentration in yuncheng basin northern china there are two major reasons for the observed elevation of fluoride content one is the direct contribution of the saline water the other is the undersaturation of the groundwater with respect to fluorite due to salt water intrusion which appears to be more important reason the processes of the fluorine activity reduction and the change of na ca ratio in groundwater induced by the intrusion of saline water favor further dissolution of fluorine bearing mineral and it was modeled using phreeqc with the increase in na concentration by adding nacl or na2so4 as na source calcium content kept invariable the increase of naf concentration was rapid at first and then became slower and the concentrations of hf hf2 caf and mgf were continuously decreasing the geochemical conditions in the study area are advantageous to the complexation of f with na and the decline of saturation index of caf2 regardless of the water type cl na or so4 na type water

the 11 april 2012 east indian ocean earthquake triggered large aftershocks worldwide although strong remote aftershocks are exceedingly rare their rate increased fivefold during the six days following the 2012 east indian ocean earthquake perhaps as a result of the strike slip nature of the 2012 event or a build up of close to failure nucleation sites

geochemical evolution and quality assessment of water resources in the sarcheshmeh copper mine area iran using multivariate statistical techniques hydrochemical data were gathered throughout the last 12 years from 57 sampling stations in the drainage basin of the sarcheshmeh copper mine kerman province iran the mean values of these data for each sampling station were used to evaluate water quality and to determine processes that control water chemistry principal component analyses specified the oxidation of sulfide minerals dissolution of carbonate and sulfate minerals and weathering of silicate minerals as the principal processes responsible for the chemical composition of water in the study area q mode cluster analysis revealed three main water groups the first group had a ca hco3 so4 composition whereas the second and third groups had ca so4 and ca mg so4 composition respectively the results of this study clearly indicated the role of sulfide minerals oxidation and the buffering processes in the geochemical evolution of water in the sarcheshmeh area due to these processes extensive changes occurred in the chemical composition of water by passage through the mining area or waste and low grade dumps so that the fresh water of the peripheral area of the pit evolved to an acid water rich in sulfate and heavy metals at the outlet of the pit and in the seepages of waste and low grade dumps

glacial weathering sulfide oxidation and global carbon cycle feedbacks connections between glaciation chemical weathering and the global carbon cycle could steer the evolution of global climate over geologic time but even the directionality of feedbacks in this system remain to be resolved here we assemble a compilation of hydrochemical data from glacierized catchments use this data to evaluate the dominant chemical reactions associated with glacial weathering and explore the implications for long term geochemical cycles weathering yields from catchments in our compilation are higher than the global average which results in part from higher runoff in glaciated catchments our analysis supports the theory that glacial weathering is characterized predominantly by weathering of trace sulfide and carbonate minerals to evaluate the effects of glacial weathering on atmospheric pco 2 we use a solute mixing model to predict the ratio of alkalinity to dissolved inorganic carbon dic generated by weathering reactions compared with nonglacial weathering glacial weathering is more likely to yield alkalinity dic ratios less than 1 suggesting that enhanced sulfide oxidation as a result of glaciation may act as a source of co 2 to the atmosphere back of the envelope calculations indicate that oxidative fluxes could change ocean atmosphere co 2 equilibrium by 25 ppm or more over 10 ky over longer timescales co 2 release could act as a negative feedback limiting progress of glaciation dependent on lithology and the concentration of atmospheric o 2 future work on glaciation weathering carbon cycle feedbacks should consider weathering of trace sulfide minerals in addition to silicate minerals

remote dynamic triggering of earthquakes in three unconventional canadian hydrocarbon regions based on a multiple station matched filter approachremote dynamic triggering of earthquakes in three unconventional canadian hydrocarbon regions

geochemical weathering at the bed of haut glacier d arolla switzerland a new model waters were sampled from 17 boreholes at haut glacier d arolla during the 1993 and 1994 ablation seasons three types of concentrated subglacial water were identified based on the relative proportions of ca 2c h co 3 and so4 2 to si type a waters are the most solute rich and have the lowest relative proportion of si they are believed to form in hydrologically inefficient areas of a distributed drainage system most solute is obtained from coupled sulphide oxidation and carbonate dissolution so cd it is possible that there is a subglacial source of o2 perhaps from gas bubbles released during regelation because the high so4 2 levels found up to 1200 eq l are greater than could be achieved if sulphides are oxidized by oxygen in saturated water at 0 c c 414 eq l a more likely alternative is that sulphide is oxidized by fe 3c in anoxic environments if this is the case exchange reactions involving fe iii and fe ii from silicates are possible these have the potential to generate relatively high concentrations of hco3 with respect to so4 2 formation of secondary weathering products such as clays may explain the low si concentrations of type a waters type b waters were the most frequently sampled subglacial water they are believed to be representative of waters flowing in more efficient parts of a distributed drainage system residence time and reaction kinetics help determine the solute composition of these waters the initial water rock reactions are carbonate and silicate hydrolysis and there is exchange of divalent cations from solution for monovalent cations held on surface exchange sites hydrolysis is followed by so cd the so4 2 concentrations usually are 414 eq l although some range up to 580 eq l which suggests that elements of the distributed drainage system may become anoxic type c waters were the most dilute yet they were very turbid their chemical composition is characterized by low so4 2 h co3 ratios and high ph type c waters were usually artefacts of the borehole chemical weathering environment true type c waters are believed to flow through sulphide poor basal debris particularly in the channel marginal zone the composition of bulk runoff was most similar to diluted type b waters at high discharge and was similar to a mixture of type b and c waters at lower discharge these observations suggest that some supraglacial meltwaters input to the bed are stored temporarily in the channel marginal zone during rising discharge and are released during declining flow little of the subglacial chemical weathering we infer is associated with the sequestration of atmospheric co2 t he progression of reactions is from carbonate and silicate hydrolysis through sulphide oxidation by first oxygen and then fe iii which drives further carbonate and silicate weathering a crude estimate of the ratio of carbonate to silicate weathering following hydrolysis is 4 1 we speculate that microbial oxidation of organic carbon also may occur both sulphide oxidation and microbial oxidation of organic carbon are likely to drive the bed towards suboxic conditions hence we believe that subglacial chemical weathering does not sequester significant quantities of atmospheric co2 and that one of the key controls on the rate and magnitude of solute acquisition is microbial activity which catalyses the reduction of fe iii and the oxidation of fes2 copyright 2002 john wiley sons ltd

strong tremor near parkfield ca excited by the 2002 denali fault earthquake 1 we show clear evidence of non volcanic tremor triggered by 2002 mw7 8 denali fault earthquake near parkfield triggered tremor is identified as bursts of high frequency 2 8 hz non impulsive seismic energy whose envelope is coherent among many stations and has the same periodicity as the passing surface waves the tremor originates from at least three hypocenters near the san andreas fault with differing frictional regimes two in the creeping section and the other where the san andreas is transitional between creeping and locked all the sources originate below the seismogenic zone suggesting that transitional frictional properties are necessary conditions for tremor generation tremor is excited by the love waves when the san andreas is sheared in a right lateral sense encouraging slip and is absent when the san andreas is sheared in a left lateral sense consistent with a simple frictional response to the driving stress

dip range for intracontinental reverse fault ruptures truth not stranger than friction abstract histograms of fault dips have been compiled for moderate to large m 5 5 reverse slip intracontinental earthquakes with the slip vector raking 90 30 in the fault plane the principal data set is restricted to earthquakes where the fault plane in the focal mechanism can be unambiguously distinguished from the auxilliary plane the reverse fault dips are bracketed within the range 12 1 the observed dip range is consistent with reactivation of faults possessing rock friction coefficients within byerlee9s 1978 range 0 85 s 0 6 undergoing frictional lockup at dips approaching 60 the broad 25 to 35 peak may arise from progressive domino steepening of imbricate reverse faults above the optimal dip for reactivation in regions undergoing bulk shortening paucity of very low angle thrusts implies that it is generally the steeper ramps within ramp flat assemblages that fail in moderate to large earthquakes the subsidiary peak at 45 to 55 likely results from compressional reactivation of former normal faults in areas undergoing tectonic inversion requiring some degree of fluid overpressuring the results are consistent with previous studies on the dip range for active normal faults that again demonstrate frictional lockup at reactivation angles approaching 60 together these analyses suggest that byerlee friction coefficients apply to faults with displacements of up to a few kilometers

groundwater hydrochemistry in the active layer of the proglacial zone finsterwalderbreen svalbard abstract glacial bulk meltwaters and active layer groundwaters were sampled from the proglacial zone of finsterwalderbreen during a single melt season in 1999 in order to determine the geochemical processes that maintain high chemical weathering rates in the proglacial zone of this glacier results demonstrate that the principle means of solute acquisition is the weathering of highly reactive moraine and fluvial active layer sediments by supra permafrost groundwaters active layer groundwater derives from the thaw of the proglacial snowpack buried ice and glacial bulk meltwaters groundwater evolves by sulphide oxidation and carbonate dissolution evaporation and freeze concentration of groundwater in summer and winter respectively produce mg ca sulphate salts on the proglacial surface re dissolution of these salts in early summer produces groundwaters that are supersaturated with respect to calcite there is a pronounced spatial pattern to the geochemical evolution of groundwater close to the main proglacial channel active layer sediments are flushed diurnally by bulk meltwaters here mg ca sulphate deposits become exhausted in the early season and geochemical evolution proceeds by a combination of sulphide oxidation and carbonate dissolution at greater distances from the channel the dissolution of mg ca sulphate salts is a major influence and dilution by the bulk meltwaters is relatively minor the influence of sulphate salt dissolution decreases during the sampling season as these salts are exhausted and waters become increasingly routed by subsurface flowpaths

dynamic stresses coulomb failure and remote triggering corrected abstract dynamic stresses associated with crustal surface waves with 15 30 s periods and peak amplitudes

influence of glaciation on mechanisms of mineral weathering in two high arctic catchments in order to investigate the effect of glaciation on mineral weathering the stream water chemistry and the bacterial community composition were analysed in two catchments containing nominally identical sedimentary formations but which differed in the extent of glaciation the stream waters were analysed for major ions 34s 18oso4 and 18oh2o and associated stream sediments were analysed by 16s rrna gene tagged sequencing sulphate comprised 72 86 and 35 45 of the summer anion budget in meq in the unglaciated and glaciated catchments respectively this indicates that sulfuric acid generated from pyrite weathering is a significant weathering agent in both catchments based on the relative proportions of cations sulphate and bicarbonate the stream water chemistry of the unglaciated catchment was found to be consistent with a sulphide oxidation coupled to silicate dissolution weathering process whereas in the glaciated catchment both carbonates and silicates weathered via both sulfuric and carbonic acids stable isotope measurements of sulphate together with inferences of metabolic processes catalysed by resident microbial communities revealed that the pyrite oxidation reaction differed between the two catchments no 34s fractionation relative to pyrite was observed in the unglaciated catchment and this was interpreted to reflect pyrite oxidation under oxic conditions in contrast 34s and 18oso4 values were positively correlated in the glaciated catchment and were positively offset from pyrite this was interpreted to reflect pyrite oxidation under anoxic conditions with loss of s intermediates this study suggests that glaciation may alter stream water chemistry and the mechanism of pyrite oxidation through an interplay of biological physical and chemical factors

fault mechanics and the kinematics of block rotations in many strike slip tectonic settings large rotations up to 100 of crustal blocks have been inferred from paleomagnetic data these blocks are bounded by sets of parallel faults which accommodate the relative motion between the blocks as regional deformation progresses simple geometrical considerations require that the faults must also rotate in this paper we show that on the basis of mechanical considerations the amount of fault rotation permissible under a stationary stress field is limited to 20 to 45 consequently block rotations that are larger than 40 or 45 require more than one set of accompanying faults to accommodate the block rotation examples of such multiple sets with 40 to 45 between them as predicted by the model were recognized in sistan iran in yerington the lake mead area nevada and in southern california

a note on fault reactivation reactivation of existing faults whose normal lies in the 1 3 plane of a stress field with effective principal compressive stresses 1 2 3 is considered for the simplest frictional failure criterion n n p where and n are respectively the shear and normal stresses to the existing fault p is the fluid pressure and is the static friction for a plane oriented at to 1 the stress ratio for reactivation is 1 3 1 cot 1 tan this ratio has a minimum positive value at the optimum angle for reactivation given by 12tan 1 1 but reaches infinity when 2 beyond which 3 0 is a necessary condition for reactivation an important consequence is that for typical rock friction coefficients it is unlikely that normal faults will be reactivated as high angle reverse faults or thrusts as low angle normal faults unless the effective least principal stress is tensile

hydrochemistry of meltwaters draining a polythermal based high arctic glacier south svalbard ii winter and early spring the hydrochemistry of naled and upwelling water sampled from the forefields of finsterwalderbreen svalbard during spring are used for the first time to infer the hydrology of overwinter meltwaters at a polythermal based glacier hydrochemical variations in naled are explained in terms of different water sources and their chemical alteration during freezing two water sources to naled are identified surficially routed snowmelt and subglacial water naled that results from the freezing of the former is enriched in atmospherically derived ions such as na and cl and is believed to be formed during winter warm periods naled of subglacial origin contains relatively high proportions of crustally derived solute it reflects the freezing of subglacial meltwaters that continue to issue from a subterranean upwellling during winter an increasing dominance of so2 4 mg2 na and cl in subglacial naled with increasing distance from the upwelling reflects the progressive freezing of this water body and the associated removal of ca2 and hco by calcite precipitation these spatial trends are accentuated by the leaching of soluble ions from the naled close to its source by subsequent upwelling waters the chemistry of spring upwelling waters also of subglacial origin strongly reflects this process meltwater produced by geothermal heating of glacier basal ice is believed to be the principal source of water to the subglacial drainage system during winter solute acquisition by this meltwater is limited by a scarcity of proton suppliers evolution of this dilute meltwater carries an imprint of ion exchange processes some stored subglacial water from the end of the previous ablation season may supplement the basal meltwater component in early winter copyright 2000 john wiley sons ltd

s wave triggering of tremor beneath the parkfield california section of the san andreas fault by the 2011 tohoku japan earthquake observations and theory the dynamic stresses that are associated with the energetic seismic waves generated by the m w 9 0 tohoku earthquake off the northeast coast of japan triggered bursts of tectonic tremor beneath the parkfield section of the san andreas fault saf at an epicentral distance of 8200 km the onset of tremor begins midway through the 100 s period s wave arrival with a minor burst coinciding with the shsh arrival as recorded on the nearby broadband seismic station pkd a more pronounced burst coincides with the love arrival followed by a series of impulsive tremor bursts apparently modulated by the 20 to 30 s period rayleigh wave the triggered tremor was located at depths between 20 and 30 km beneath the surface trace of the fault with the burst coincident with the s wave centered beneath the fault 30 km northwest of parkfield most of the subsequent activity including the tremor coincident with the shsh arrival was concentrated beneath a stretch of the fault extending from 10 to 40 km southeast of parkfield the seismic waves from the tohoku epicenter form a horizontal incidence angle of 14 with respect to the local strike of the saf computed peak dynamic coulomb stresses on the fault at tremor depths are in the 0 7 10 kpa range the apparent modulation of tremor bursts by the small strike parallel rayleigh wave stresses 0 7 kpa is likely enabled by pore pressure variations driven by the rayleigh wave dilatational stress these results are consistent with the strike parallel dynamic stresses s associated with the s shsh and surface wave phases triggering small increments of dextral slip on the fault with a low friction 0 2 the vertical dynamic stresses d do not trigger tremor with vertical or oblique slip under this simple coulomb failure model