evidence for postseismic viscoelastic relaxation following the 1959 m 7 5 hebgen lake montana earthquake a 1983 releveling survey conducted by the national geodetic survey combined with previous surveys in 1923 1960 1967 and 1975 provides evidence for ongoing vertical deformation of a broad region diameter of 150 km surrounding the site of the 1959 hebgen lake earthquake deformation consists of relative uplift centered roughly on the coseismic fault and a smaller amplitude zone of relative subsidence south of the fault maximum observed elevation change during the postseismic period 1960 1983 exceeds 30 cm assuming that the entire uplift i e 1923 1983 occurred following the 1959 earthquake i e uplift measured between 1923 and 1960 was entirely postseismic the rate of vertical deformation appears to have decreased exponentially with a characteristic decay time of about 10 years the spatial pattern and time behavior of the observed movements are consistent with simple models of postseismic deformation following normal faulting in an elastic layer thickness of 30 40 km overlying a viscoelastic half space viscosity of 1019 pa s this model may also account for the anomalously large horizontal strain around the hebgen lake region measured by repeated trilateration surveys during the period 1973 1984 the releveling measurements in the hebgen lake region appear to provide the first observations of viscoelastic relaxation in the asthenosphere following an intraplate earthquake in the united states

seismic and aseismic deformation associated with the 1952 kern county california earthquake and relationship to the quaternary history of the white wolf fault synthesis of geodetic geologic and seismic data from the white wolf fault california indicates that the fault separates an area of late quaternary and continuing rapid uplift in the tehachapi mountains and transverse ranges from even more rapid subsidence in the southern san joaquin valley on july 21 1952 rupture of the white wolf fault produced the ml 7 2 kern county earthquake we used the aftershock zone to delimit the size of the faulted slip surface and applied constraints imposed by the known 1952 1953 horizontal shear strains to model the measured coseismic vertical displacements with an elastic dislocation model a curved fault trace with decreasing fault depth 27 to 10 km from the surface vertically to the base slip 3 to 1 m and dip 75 to 20 from the 1952 epicenter at the southwest end of the fault toward the northeast provides the fit most consistent with the geodetic record the measured seismic moment the fault plane solution and the pattern of surface rupture two short releveled lines near the 1952 epicenter tilted 4 and 17 rad down to the north from 5 10 years before the earthquake the preseismic tilts differ significantly from ten other surveys of these lines left lateral fault crossing shear strain from 0 2 20 years before the quake was two times greater than both preseismic off fault strains and the post seismic fault crossing strains during the first seven years after the earthquake aseismic deformation was negligible from 1959 to 1972 uplift reached 160 mm over an area larger than the aftershock zone rising first in the epicentral region and then at the northeast end of the fault this was unaccompanied by any surface fault slip reconstruction of the vertical separation on the white wolf fault from late quaternary and late miocene stratigraphic marker beds shows that the rate of reverse fault slip increased forty fold from 0 1 0 2 mm yr to 3 9 mm yr between the past 10 15 m y and the most recent 0 6 1 2 m y we estimate a 170 to 450 yr average recurrence interval for earthquakes on the white wolf fault with slip equivalent to that in 1952 the 1952 earthquake appears to be characteristic of the quaternary record of fault displacement in the increase in white wolf slip toward the san andreas fault the ratio of reverse to lateral slip 1 3 1 and the ratio of vertical fault slip to emergence of the hanging wall block 3 1 the 8500 m deep sedimentary basin on the down thrown block cannot be explained by repeated slip of the white wolf fault in an elastic medium

evidence of suppression of the unequal refraction error in geodetic leveling analyses of historic data indicate that procedures in force since the nineteenth century have effectively suppressed the unequal refraction error ure in geodetic leveling although theoretical considerations argue that large refraction errors should accumulate where levelings traverse gentle slopes permitting long sight lengths extensive examination of routinely developed results lends little support to this argument our analyses of the historic record consider 1 height differences based on otherwise similar levelings over the same route but characterized by substantially different sight length 2 modeled refraction error differences and actually measured elevation changes on both a section by section and a line by line basis 3 misclosures produced from levelings identified with significantly different procedural constraints in technically stable areas of comparable variation in terrain and climate and 4 alternatively and sequentially developed heights in areas of tectonic stability and areas of persisting instability all of these analyses indicate that the ure is generally small and unpredictable and hence inconsistent with both theoretical expectations and the results of two conceptually different experimental studies this inconsistency probably is attributable to the inability of the theoretical models and the failure of the experiments to incorporate in their design those procedures especially the rejection criteria at the setup section and circuit level that normally minimize refraction error traditionally invoked procedural specifications may have suppressed the ure through biasing of observations toward less refractive conditions whereas all of the theoretical models assume an averaged sampling of the atmosphere alternatively a variety of real world complexities that are disregarded in the models may take on added importance in normally constrained leveling thus refraction corrections based on simplified models and mean atmospheric and terrain conditions tend to overcompensate substantially for refraction errors associated with routinely constrained surveys

topographic amplification of tectonic displacement implications for geodetic measurement of strain changes correlations of level changes with topography demand an assessment of the effect of an irregular free boundary on surface deformation this is examined through a plane strain elastic model with topography of small slope subjected to a change in the far field horizontal stress to leading order vertical surface displacements due to the topographic perturbation are proportional to the local relief elevationdependent uplift results from a compressional change and downdrop results from a tensional change the model further predicts that the ratio of elevation change to elevation is proportional to and of the same order of magnitude as the regional strain horizontal strains are locally perturbed by topography as well with the magnitude scaling with the local slope the predicted localization of level changes is very small in aseismic regions and cannot contribute significantly to measured correlations a test case in southern california bears this out with strains of order 10 6 accompanied by elevation change to elevation ratios of order 10 4 releveling following the nankaido tonankai earthquakes which induced large coseismic and postseismic strains reveals scattered examples of elevation dependent level changes however when compared to modeled strains the correlations are again at least an order of magnitude larger than the localization effect predicted by the elastic model although the topographic perturbation of vertical displacements appears to be unmeasurably small local variations in horizontal strain or borehole dilatation across steep relief may be discernible with current technology

saugus palmdale california field test for refraction error in historical leveling surveys a field test designed to measure atmospheric refraction error in historical and modern leveling was conducted in may june 1981 on a 50 km long grade from saugus to palmdale california during 1955 1971 the length of sights made between the level instrument and rods systematically decreased from 60 m to 26 m the difference in height near palmdale measured by single run long sight 42 m and short sight 22 m leveling during the test was 6 times larger than expected random error correction for refraction by using either the observed or modeled vertical temperature gradient in kukkamaki s balanced sight equation reduced the height difference to the level of random error uncertainty the observed temperature gradient obeyed a power law relation t a bzc where z is the height and a b and c are constants that depended on atmospheric conditions and the ground surface beneath the line of sight the refraction corrected leveling satisfies the specifications and meets all standards of first order control surveys the six historical surveys of the saugus palmdale grade were corrected for refraction error using the results of the experiment and for rod scale errors and nontectonic subsidence considered in previous investigations the corrected uplift near palmdale reached 56 16 mm with respect to saugus during the period 1955 1965 this amount of uplift is about one third that obtained before removal of refraction error the corrected displacement profiles also reveal previously unrecognized deformation in the epicentral region of the 1971 san fernando ml 6 4 earthquake during the decade before the main shock

groundwater salinization in the azores archipelago portugal groundwater salinization in coastal regions causes severe constraints to water supply and economic losses to society worldwide in the azores archipelago groundwater abstraction in wells drilled in coastal aquifers is very important for water supply and quality problems have been reported therefore a groundwater chemistry dataset from wells was compiled to study groundwater salinization in these aquifers waters are mainly of the na cl type presenting a slightly acidic to slightly alkaline character with a ph between 5 63 and 8 50 median 7 40 electrical conductivity measurements range from 127 to 9 670 s cm median 862 suggesting highly variable mineralization with higher values observed on santa maria sao miguel pico graciosa and sao jorge islands the major ion composition reflects the contribution of seawater to the groundwater compositional evolution which is essentially explained by seawater intrusion into wells in many samples exchange reactions of na k for ca2 mg2 are associated with salinization the seawater fraction in groundwater composition reaches a maximum of 22 5 these results are extremely challenging to water managers in the azores because failure to comply with national water quality regulations and with european union groundwater directive requirements often occurs

uplift across long valley caldera california the results of levelings along u s highway 395 between lee vining and toms place california in 1957 1975 1980 1982 and 1983 define the development of a dome shaped uplift across the long valley caldera these levelings indicate that toms place remained virtually invariant with respect to lee vining during the full interval 1957 1983 implying that the end points of the survey route lie beyond the range of the developing dome no significant uplift occurred before 1975 but by october 1980 the uplift near casa diablo hot springs reached 0 25 m and the half width of the dome was of the order of 25 km the uplift of casa diablo hot springs increased to 0 35 m by august 1982 and to about 0 40 m by august 1983 without any appreciable increase in the lateral extent of the dome the august 1982 to august 1983 uplift apparently occurred before february 1983 with little or no uplift during the period february august 1983 the 1975 1983 uplift is attributed to the injection of 0 19 km3 of magma into a spherical chamber at a depth of 10 km beneath the southern quadrant of the ancient resurgent dome within the caldera examination of the full vertical control record through the long valley area indicates that the 1975 1983 uplift is unique within the period 1905 1983 although comparisons of the results of a 1932 leveling against a 1914 datum disclose a 1914 1932 down to the northwest tilt of about 10 rad over the reach between toms place and lee vining this tilt if real is more reasonably attributed to regional tectonic deformation than it is to the movement of magma at depth

tectonic motions and systematic errors in leveling and trilateration data for california abstract we examined leveling and trilateration data for southern california we used mathematical models that allow for both tectonic motion and systematic errors for both data types we find evidence of systematic errors the leveling data reveal no significant tectonic motion except the direct effects of earthquakes trilateration data show steadily accumulating shear strain but previously reported episodic dilatations probably result from systematic errors

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

hydrogeochemical processes occurring in the hydrothermal systems of the gonghe guide basin northwestern china critical insights from a principal components analysis pca the gonghe guide basin is a geologically complex area located in the northeastern qinghai tibet plateau although it is far away from the himalayan geothermal belt hot springs with high contents of sio2 li b and as are widely distributed there principal components analysis pca was used to identify the geochemical genesis of the major constituents in geothermal waters and cold groundwaters from the study areas as well as the related hydrogeochemical processes the results indicate that these constituents can be represented by six factors factor 1 f li k and sio2 factor 2 ec cl and na factor 3 ph text hco 3 mg2 and ca2 factor 4 b as fe and al factor 5 text so 4 2 and sr and factor 6 text no 3 generally the dissolution of silicate and carbonate minerals is the predominant geochemical processes responsible for the occurrence of the constituents that constitute factors 1 and 3 respectively in contrast although halite is not a primary mineral in the aquifer matrix its leaching results in the enrichment of chloride and sodium in the groundwaters which make significant contributions to the high ec values of some water samples although arsenic and boron are associated with factor 4 elevated levels of these elements in groundwater may be derived from the leaching of crystalline rocks like granite and gneiss rather than the input of potential magmatic fluids moreover anthropogenic activity has an impact on the hydrochemistry of the groundwaters as well as indicated by the elevated concentrations of nitrate the sole component of factor 6 in some samples it is also worth noting that the pca results may not match well with the hydrogeochemical analyses factor 5 is composed of sulfate and strontium whereas celestite is unlikely to be the primary source of sulfate in groundwater

an assessment of the accuracy of the geodetic measurements that define the southern california uplift examination of the charge that the geodetic measurements which define the southern california uplift are seriously flawed by height dependent systematic errors indicates that this charge is unfounded our review of those factors designed to minimize the effects of rod error shows that systematic errors attributable to rod miscalibration are trivial and would tend to cancel during the particularly pertinent period 1955 1965 comparisons between the results of measurements in which the correlation between topography and signal is generally poor reveal large aseismic tilts in a number of places within and around the margins of the uplift especially significant in this context are the results of preuplift and postuplift levelings over routes characterized by diverse length topography and atmospheric conditions that produce closely matching temporally equivalent heights for a representative bench mark within the uplift statistical analyses of the short wavelength components of uplift signal and elevation along a frequently repeated survey line indicate variable correlations between the two however the spatial and temporal patterns of these correlations are inconsistent with their attribution to height dependent systematic errors statistically significant short wavelength correlations along this survey line are reasonably explained in part as due to real movement associated with differentially subsiding bench marks and there is a strong likelihood that this movement tends to dominate many of the correlations

brines in the carboniferous sydney coalfield atlantic canada abstract formation waters within upper carboniferous sandstones in the sub sea prince and phalen coal mines nova scotia originated as residual evaporative fluids probably during the precipitation of windsor group lower carboniferous salts which underlie the coal measures salinity varies from 7800 to 176 000 mg l and the waters are na ca cl brines enriched in ca sr and br and depleted in na k mg and so4 relative to the seawater evaporation curve br cl and na cl ratios suggest that the brine composition corresponds to an evaporation ratio of as much as 30 the brines lie close to the meteoric line on h o isotopic plots but with a compositional range of 18o from 4 18 to 6 99 and of d from 42 4 to 23 5 distant from modern meteoric or ocean water mine water composition contrasts with that of nearby salt spring brines which are inferred to have originated through dissolution of windsor group evaporites by modern meteoric waters however a contribution to the mine waters from halite dissolution and from br in organic matter cannot be ruled out present concentrations of several elements in the brines can be explained by water rock interaction the original windsor brines probably moved up into the overlying coal measure sandstones along faults prior to the late triassic the high salinity and irregular salinity distribution in the phalen sandstones suggests that the brines have undergone only modest dilution and are virtually immobile in contrast prince waters show a progressive increase in salinity with depth and are inferred to have mixed with surface waters basinal brines from which these modern formation fluids were derived may have been important agents in base metal and ba mineralisation from the mid carboniferous onwards as saline fluid inclusions are common in zn pb sulphide deposits in the region

hydrologic and geologic factors controlling surface and groundwater chemistry in indian wells owens valley area southeastern california usa the indian wells owens valley area is located in the semi arid basin and range province which is characterized by alternating mountains and alluvial basins surface water resources are limited in this arid region and water demand is mainly met by groundwater pumpage in a classic basin and range groundwater system water flows from recharge areas in the mountains to discharge areas in adjacent valleys discharge areas are generally occupied by playas where large amounts of salt deposition occur due to evaporating groundwater hydrochemical data from a total of 1368 spring surface and well water samples collected over an 80 year period were used to evaluate water quality and to determine processes that control water chemistry q mode hierarchical cluster analysis hca was employed for partitioning the water samples into hydrochemical facies also known as water groups or water types five major water groups resulted from the hca analysis the samples from the area were classified as recharge area waters ca na hco3 water and na ca hco3 water transition zone waters na hco3 cl water and discharge area waters na cl water and more concentrated na cl water spatial plots of the major statistical groups show that the samples that belong to the same group are located in close proximity to one another suggesting the same processes and or flowpaths inverse geochemical models of the statistical groups were developed using phreeqc to elucidate the chemical reactions controlling water chemistry the inverse geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area in a broad sense the reactions responsible for the hydrochemical evolution in the area fall into four categories 1 silicate weathering reactions 2 dissolution of salts 3 precipitation of calcite amorphous silica and clay minerals and 4 ion exchange

geodetic evidence for subsidence due to groundwater withdrawal in many parts of the united states of america abstract analysis of repeated levelings conducted by the national geodetic survey indicates many locations of relative subsidence in the u s a specific criteria are used to identify those subsidence features which most likely result from sediment compaction due to lowering of water levels in underground aquifer systems previously reported areas of such subsidence that seem to be confirmed by this study include south central arizona savannah georgia pecos and houston galveston texas denver colorado san joaquin valley santa clara valley saugus basin los angeles basin and bunker hill san timoteo california milford utah raft river valley idaho baton rouge and new orleans louisiana and las vegas nevada in addition our analysis indicates that such subsidence is more widespread than previously reported occurring in a number of locations within the atlantic and gulf of mexico coastal plains and along the mississippi valley as well as in many other unconsolidated sedimentary basins from which groundwater has been extracted and for which repeated leveling measurements are available more than 30 new locations of subsidence possibly due to water withdrawal have been identified the best documented of these include ventura ontario and san pedro santa monica california monroe and alexandria louisiana and jackson mississippi subsidence in newly identified locations ranges from several tens of millimeters to a few hundred millimeters over distances of 10 60 km and times of 2 48 yr subsidence may also have occurred in other groundwater basins where water levels have been drawn down and remained undetected because of a lack of repeated levelings it is important to be aware of and to continue to monitor such effects because of increasing rates of utilization of groundwater resources and the potential for significant engineering problems due to surface movements in addition identifying cases of subsidence due to water withdrawal is essential in order to use effectively releveling observations for investigating tectonic deformation along these lines our analysis suggests that some of the releveling observations used to define a region of tectonic uplift in southern california more likely reflect subsidence due to water level declines within sedimentary basins around the periphery of the presumed zone of uplift

contemporary movements and tectonics on canada s west coast a discussion abstract evidence from published tidal records and geodetic relevelling data in british columbia indicates that there is a consistent pattern of contemporary uplift on the outer coast 2 mm yr and subsidence on the inner coast 1 2 mm yr the zero uplift contour or hinge line runs through hecate strait georgia strait and victoria this pattern continues southwards into washington state but is interrupted to the north by considerable uplift in southeastern alaska although glacio isostatic recovery has dominated vertical movements in the region over the last 10 000 years the distribution and trend of the observed contemporary movements are not compatible with the pattern to be expected from this source and are most probably tectonic in origin there is however no clear distinction between the movements seen opposite the queen charlotte transform margin and the vancouver island convergent margin comparison with movements observed at other active plate margins show that the pattern is essentially similar to that seen in association with subduction and convergence the paradox that the vertical movement rates are much too great to explain observed geology and topography may be soluble by assuming that discontinuous lateral shifts of the movement pattern occur on a scale of hundreds of thousands of years

geochemistry and origin of formation brines from the paris basin france 2 saline solutions associated with oil fields abstract oil fields from the paris basin are located in three geological levels dogger middle jurassic rhaetian and keuper upper triassic the origin of water and dissolved salts in saline solutions associated with oil is investigated using the hypothesis that cl and br are conservative in solution in a diagram of cl br ratios vs cl the points of the dogger and the keuper aquifers lie in the zone of primary brines whereas those of the rhaetian are located in the zone of secondary brines the na cl ratio is very high in all of the saline solutions suggesting either a relatively poorly evolved brine at the beginning of halite deposition or some halite dissolution all of the saline solutions especially those from the dogger aquifer are clearly diluted dilution by meteoric waters would not alter the cl br ratio high concentrations of lithium rubidium and boron are attributed to the presence of an extremely evolved brine of marine origin in mixtures of secondary brines formed by dissolution of halite and small amounts of sylvite and ca sulphate mass balance calculations of the excess of cl with respect to na k allows the fraction x of water derived from the primary brine to be calculated assumptions are that all na and k is derived from the secondary brine and that the cl content of the primary brine is constrained by bischofite saturation at 11 000 mmol kg 1 the typical proportion of water from the primary brine waters is 0 7 in the dogger formation and 2 4 in the keuper values of the concentration factor cf expressed as the ratio of the molal concentration of a conservative ion in the evolved brine to its concentration in seawater have been calculated for lithium solutions from the dogger and keuper aquifers have cfli values of 1 8 103 and of 7 7 103 respectively in the rhaetian aquifer the linear relationship between heavy isotope contents of the brine 2h and 18o and the cl content indicates a mixture of two water sources the first one is meteoric water as defined by the intersection of the formation water line with the global meteoric water line 2 h 65 18 o 9 3 the other end member is enriched in heavy isotopes and in cl and is attributed to seawater that has dissolved evaporites mainly halite however the presence of small amounts of an extremely evolved brine is required to account for the bromide lithium rubidium and boron contents of the formation brine from the rhaetian aquifer as this contribution is very limited in amount it cannot affect the heavy isotope content of the formation water mass balance equations are solved for ternary mixtures of meteoric water seawater and brine the same constraints as above no na and k supplied by the primary brine and clbrine 11 000 mmol kg 1 are applied it is also assumed that the seawater component has the same ionic contents as modern seawater and that the salt content of the meteoric component is negligible the fraction of primary brines is x 1 4 according to the cl balance this estimate agrees with that obtained from the lithium balance assuming that the primary brine component was the same as that of the keuper formation water mass balance calculations also indicate that the so42 content of the rhaetian formation water is exclusively due to the secondary brine component in the three saline solutions the very high ca2 contents and high ca 2 mg 2 ratios may be attributed to reaction of the very evolved brine free of so2 4 with gypsum or anhydrite the result is an exchange of mg2 for ca2 which causes a release of ca2 to the solution and a precipitation of secondary mg sulphate this process can also account for the high strontium contents of the analysed samples values of the ratio 87 sr 86 sr are very high in the keuper formation water due to close contact of the solutions with the granitic basement or with granite derived detrital deposits values in the rhaetian and dogger aquifers equal those of upper triassic marine deposits the stable isotope 34s and 18o content of the dissolved aqueous so2 4 indicates a triassic origin for the bulk of sulphate involved in the evolution of formation waters from the rhaetian and from the dogger all geochemical indicators thus show a vertical migration of triassic brines however aqueous so2 4 from the keuper has a permian isotopic signature suggesting a reworking in solution of salts from this period

the sea slope problem revisited discrepancies in sea surface topography based on comparisons between the results of steric leveling and repeated geodetic levelings have identified what is known as the sea slope problem this problem is actually twofold 1 the sea surface relief based on steric leveling differs significantly from that based on geodetic leveling along several generally north south coasts and 2 successively propagated levelings between several widely separated tide stations indicate that the stationary sea slope seemingly has been changing with time whereas differenced sea level means between these stations indicate that the sea surface relief has remained virtually invariant during the same intervals reexamination of the three reported discrepancies between geodetically and sterically determined sea slopes indicates that the australian example is based on leveling of a quality inappropriate to the comparison the discrepancy developed along the atlantic coast of the united states is limited to the reach between portsmouth hampton roads virginia and key west florida where the accuracy of steric leveling may be especially vulnerable owing to the dynamic effects of the gulf stream reconsideration of the example along the pacific coast of the united states indicates that the various discrepancies are due chiefly to intrasurvey movement and resultant distortion of geodetically defined height differences between tide stations agreement between the results of steric and geodetic leveling along tectonically inactive north south coasts devoid of strong boundary currents is generally good this observation supports the conclusions 1 that any directionally dependent systematic error in geodetic leveling is measurably insignificant and 2 that where allowance is made for the possible effects of major boundary currents or intrasurvey movement during levelings between tide stations the sea slope problem tends to vanish

hydrogeochemical evolution of groundwater in a mediterranean coastal aquifer mersin erdemli basin turkey in this study hydrogeologic and hydrochemical information from the mersin erdemli groundwater system were integrated and used to determine the main factors and mechanisms controlling the chemistry of groundwaters in the area and anthropogenic factors presently affecting them the phreeqc geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area in a broad sense the reactions responsible for the hydrochemical evolution in the area fall into four categories 1 silicate weathering reactions 2 dissolution of salts 3 precipitation of calcite amorphous silica and kaolinite 4 ion exchange as determined by multivariate statistical analysis anthropogenic factors show seasonality in the area where most contaminated waters related to fertilizer and fungicide applications that occur during early summer season

contemporary tilting in the central atlantic coastal plain geodetic leveling across the cape hatteras arch between norfolk va and new bern nc 240 km suggests an unusually large northward tilting new bern appears to have risen relative to norfolk as much as 18 pm 3 cm between 1932 and 1963 and 26 6 pm 3 cm between 1963 and 1979 although on the basis of geomorphic evidence this area has been interpreted by some as having undergone significant holocene tilting the rates indicated by leveling seem unrealistically large not only with respect to the longer term geologic estimates but also in comparison with contemporary tide gauge estimates of crustal movement a detailed analysis of the leveling results was carried out to evaluate to the extent possible their validity as estimates of neotectonic movement the apparent consistency of repeated resurveys the low topographic relief and the large magnitude of observed tilting argue against certain types of systematic error accumulation loop misclosure analysis is inconclusive however comparison of

identification of the origin of salinization in groundwater using multivariate statistical analysis and geochemical modeling a case study of kaohsiung southwest taiwan the study of brine aquifers in southern taiwan is highly complicated by hybrid geochemical reactions which obscure important geochemical information using multivariate analysis on major and minor ion compositions normalized by cl content chemical constituents were combined into two principal components representing brine mixing and mineral precipitation comparing to multivariate analysis on the original data this procedure reveals more geochemical information it demonstrates that the brine groundwater of the region is primarily composed of highly evaporated seawater the evaporation ratio is 70 a point at which calcite dolomite and gypsum precipitate oxygen and hydrogen isotopic compositions confirm this inference and further geochemical modeling quantitatively determined the evaporation ratio to be about 85 natural boron contamination is a consequence of brine groundwater two evolutionary trends in the plotting of the cl b ratio versus cl can be identified 1 cl b ratio decreases with boron being released from clay minerals when brine aquifers are flushed with freshwater and 2 cl b ratio increases when seawater of a high cl b ratio infiltrates coastal aquifers

preconsolidation stress of aquifer systems in areas of induced land subsidence aquifer systems in the eloy picacho area arizona the houston galveston area texas and the tulare wasco area and santa clara valley california appear to have been overconsolidated by an amount that ranged approximately from 1 6 to 6 2 bars 16 to 63 m of water before man began to withdraw groundwater from them the relation between land subsidence and water level decline in these areas consists of two linear segments in these areas subsidence per unit water level decline was approximately constant until water levels had declined an amount that ranged from 16 to 63 m when water levels declined past these values subsidence per unit water level decline increased to larger constant values although slow drainage from aquitards may have contributed to this response it is interpreted here to be caused primarily by natural overconsolidation of the compacting part of the aquifer system the water level decline at which the ratio of subsidence to unit water level decline changed indicates approximately the amount by which the preconsolidation stress exceeded the overburden stress on the aquifer system that existed before groundwater withdrawals began

on kalgoorlie australia timmins porcupine canada and factors in intense gold mineralisation abstract the golden mile gold deposits of kalgoorlie eastern goldfields province yilgarn craton australia 46 moz au and the gold deposits in the timmins porcupine camp southern abitibi province superior craton canada 63 7 moz au are earth s two biggest archaean lode gold camps while similarities at the camp scale are dominant they differ in that the golden mile is a compact camp of one major deposit with two nearby subordinate deposits separated by less than 10 km along strike whereas timmins porcupine consists of a relatively large camp with 30 important mines distributed over 20 km strike length seismic data show a detachment fault at the base of the supracrustal rocks at kalgoorlie at between 5 and 9 km but none is identified in the timmins porcupine camp map scale patterns ages and lithologies are superficially similar the gabbros in kalgoorlie and conglomerates in timmins porcupine are distinctive rock types but served similar competence contrast functions late orogenic sediments are an important host at timmins porcupine for competence contrast reasons but are apparently absent in the golden mile area gold deposit formation in both camps is of the same age 2 67 ga with a long duration of mineralisation porphyries albitites and lamprophyres are characteristic features but played no major genetic role both camps have early elements of mineralisation that have an epithermal character in cu au w v 3 and f o 2 and both camps lie in belts locally characterised by the abundance of telluride minerals however none of these characteristics seem to be necessary or sufficient for intense gold mineralisation syn mineralisation transpressive deformation in both camps involved the imbrication of thrust slices followed by strike slip movement along a major crust scale fault with a dilatational curve in its trend in the centre of both camps the various deposits in each of the two camps were formed from immediately before to just after strike slip deformation and opening of late orogenic sedimentary basins both areas are characterised by an early episode of intense thrust faulting extensive intersecting fracture arrays likely developed as thrusting gave way to strike slip faulting these arrays may have enabled access to fertile source rock and also served as fluid conduits throughout deformation moreover both terranes are characterised by a relatively short pre mineralisation crustal history thin ned subcontinental lithospheric mantle and input of juvenile mantle derived material the pre mineralisation crustal history and evolution of the host terranes thus may have been the most important single factor in the formation of giant orogenic gold deposits at kalgoorlie and timmins porcupine

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

strainmeters and tiltmeters despite steady effort over the last century continuously recording tiltmeters and strainmeters have not yet been successful except for earth tide measurements this article reviews the techniques and instrument designs that have been developed in this field the continuous measurement of true tectonic motions which have rates of 10 14 s 1 requires extremely high instrument stability but more rapid motions tides and seismic waves apart are even smaller and not much more easily detectable much past effort has been spent improving the transducers used in these instruments which usually measure small displacements the commonest choices are optical the most accurate capacitive the most sensitive and inductive the most rugged nowadays building a transducer is the easiest part a much harder task equally important to a good design is attaching the instrument to the ground so that it can detect the signal wanted this part of the design includes choosing a location a large underground opening is thermally stable but distorting a surface installation is easy to build but noisy because of soil weathering and a borehole is inaccessible to weather but also to the operator all such installations and indeed the whole field of strain and tilt measurement of course rely on the assumption that the deformations of interest can be measured over baselengths of a few hundred meters or less this is true for tides and seismic waves but unproven for tectonic motions appropriate attachment techniques differ for each location and many mundane details such as cementing techniques for borehole instruments remain to be worked out the goal of measuring tectonic and tidal tilt has created many tiltmeter designs most are relatively small instruments that use some form of pendulum or bubble level a few use a liquid surface to measure tilts over a long baseline repeated experience has shown the latter type when well built to be superior to the former proving end monument motions to be a dominant source of noise the same appears to hold true for strainmeters the best results coming from long base laser instruments though strainmeters using rigid or flexible material length standards are useful for special purposes and borehole instruments show promise because achieving a good design has been so difficult it is important to select the goals an instrument must meet and be prepared to compromise on others the difficulty of validating results from this type of instrument makes comparison tests essential such tests as have been made so far show that good results cannot be gotten at low cost or without careful attention to details