semi numerical simulation of groundwater flow induced by periodic forcing with a case study at an island aquifer summary this paper presents an efficient method to analyze the aquifer response to periodic forcing a complex transformation is used to change the time dependent linear aquifer model into an equivalent time independent problem of a complex function referred to as the complex amplitude hereafter the magnitude of the complex amplitude represents the amplitude of the sinusoidal fluctuation of the groundwater level and the argument of the complex amplitude the phase shift of the fluctuation different iterative methods can be used to obtain the numerical solution a semi analytical numerical solution of the groundwater level which is numerical for the spatial variables and analytical for the time variable can be obtained by implementing a simple inverse complex transform to the complex amplitude the advantages of the time independent method include ruling out of initial conditions direct outputs of the amplitude and phase shift of different sinusoidal components of the water level fluctuations on the contrary the numerical solutions of the time dependent model need further computational efforts for the analyses of the amplitudes and phase shifts of different sinusoidal components and have to consider an initial condition whose impacts on the periodicity have to be eliminated by running sufficiently great number of tidal circles a case study at an unconfined aquifer formed by fill materials near lam chau island hong kong sar pr china shows the applicability of the semi numerical solution to analyze tide induced watertable fluctuations the aquifer parameters were estimated by minimizing a least squares objective function to fit the complex amplitude of semidiurnal and diurnal components of the observed water level fluctuations compared with the parameter estimations of some of the previous analytical solutions the numerical method gives not only better fitting to the water level observations but also more aquifer parameters

structure of the california coast ranges and san andreas fault at safod from seismic waveform inversion and reflection imaging 1 a seismic reflection and refraction survey across the san andreas fault saf near parkfield provides a detailed characterization of crustal structure across the location of the san andreas fault observatory at depth safod steep dip prestack migration and frequency domain acoustic waveform tomography were applied to obtain highly resolved images of the upper 5 km of the crust for 15 km on either side of the saf the resulting velocity model constrains the top of the salinian granite with great detail steep dip reflection seismic images show several strong amplitude vertical reflectors in the uppermost crust near safod that define an 2 km wide zone comprising the main saf and two or more local faults another prominent subvertical reflector at 2 4 km depth 9 km to the northeast of the saf marks the boundary between the franciscan terrane and the great valley sequence a deep seismic section of low resolution shows several reflectors in the salinian crust west of the saf two horizontal reflectors around 10 km depth correlate with strains of seismicity observed along strike of the saf they represent midcrustal shear zones partially decoupling the ductile lower crust from the brittle upper crust the deepest reflections from 25 km depth are interpreted as crust mantle boundary

lithology and internal structure of the san andreas fault at depth based on characterization of phase 3 whole rock core in the san andreas fault observatory at depth safod borehole abstract we characterize the lithology and structure of the spot core obtained in 2007 during phase 3 drilling of the san andreas fault observatory at depth safod in order to determine the composition structure and deformation processes of the fault zone at 3 km depth where creep and microseismicity occur a total of approximately 41 m of spot core was taken from three separate sections of the borehole the core samples consist of fractured arkosic sandstones and shale west of the saf zone pacific plate and sheared fine grained sedimentary rocks ultrafine black fault related rocks and phyllosilicate rich fault gouge within the fault zone north american plate the fault zone at safod consists of a broad zone of variably damaged rock containing localized zones of highly concentrated shear that often juxtapose distinct protoliths two zones of serpentinite bearing clay gouge each meters thick occur at the two locations of aseismic creep identified in the borehole on the basis of casing deformation the gouge primarily is comprised of mg rich clays serpentinite lizardite chrysotile with notable increases in magnetite and ni cr oxides hydroxides relative to the surrounding host rock the rocks surrounding the two creeping gouge zones display a range of deformation including fractured protolith block in matrix and foliated cataclasite structure the blocks and clasts predominately consist of sandstone and siltstone embedded in a clay rich matrix that displays a penetrative scaly fabric mineral alteration veins and fracture surface coatings are present throughout the core and reflect a long history of syn deformation fluid rock reaction that contributes to the low strength and creep in the meters thick gouge zones

internal structure of the san jacinto fault zone in the trifurcation area southeast of anza california from data of dense seismic arrays we image the internal structure of the san jacinto fault zone sjfz in the trifurcation area southeast of anza california with seismic records from dense linear and rectangular arrays the examined data include recordings from more than 20 000 local earthquakes and nine teleseismic events automatic detection algorithms and visual inspection are used to identify p and s body waves along with p and s types fault zone trapped waves fztw the location at depth of the main branch of the sjfz the clark fault is identified from systematic waveform changes across lines of sensors within the dense rectangular array delay times of p arrivals from teleseismic and local events indicate damage asymmetry across the fault with higher damage to the ne producing a local reversal of the velocity contrast in the shallow crust with respect to the large scale structure a portion of the damage zone between the main fault and a second mapped surface trace to the ne generates p and s types fztw inversions of high quality s type fztw indicate that the most likely parameters of the trapping structure are width of 70 m s wave velocity reduction of 60 per cent q value of 60 and depth of 2 km the local reversal of the shallow velocity contrast across the fault with respect to large scale structure is consistent with preferred propagation of earthquake ruptures in the area to the nw

tide induced head fluctuations in a confined aquifer with sediment covering its outlet at the sea floor 1 a confined coastal aquifer usually extends under the sea for some distance with its submarine outlet covered by a thin layer of sediment with properties dissimilar from the aquifer previous theoretical studies neglected this outlet capping in this paper an analytical solution is derived for a confined aquifer subject to tidal fluctuations with a leaky boundary condition at the outlet capping for the cases that offshore length of the aquifer and or the leakance of the outlet capping are either zero or infinity existing solutions in literature are obtained it is shown that our analytical solution can also be used to describe the tidal wave propagation in a confined aquifer extending infinitely under a tidal river the full solution agreed well with the observations in a piezometer in the jahe river basin in china 200 m inland from the coastline where the tide induced head fluctuations without delay were observed but cannot be explained using previous analytical and numerical solutions ignoring the effect of the outlet capping the sensitivity analysis showed that the combined actions of the tidal loading and outlet capping lead to complex dependency of the head fluctuation on the outlet capping s leakance when the offshore confined aquifer is short the inland head fluctuation increases with the outlet capping s leakance in this case significant negative phase shift occurs if the leakance is small for offshore aquifer length greater than a threshold value the inland head fluctuations are independent of this length and the outlet capping s leakance

a delineation of regional hydraulic conductivity based on water table fluctuation summary the estimation of regional hydraulic conductivity is essential for the sustainable development and efficient management of groundwater this paper presents a new physical method of estimating hydraulic conductivity based on the water level fluctuation model developed by park and parker park e parker j c 2008 a simple model for water table fluctuations in response to precipitation j hydrol 356 344 349 the developed procedure was validated by comparison with the hypothetical numerical model for a variety of hydraulic conductivities aquifer inclinations and the heterogeneities the model was found to be highly reliable when using water level data far from the hydraulic boundaries the results show that the monitoring data obtained over a range of relative distances of an observation location x to the flow domain w x w 0 2 avoided the boundary effects a correction factor was also proposed based on the deviation analysis of the calibrated k and f n ratio of recharge to precipitation divided by porosity the results from the basal inclinations and the heterogeneities cases suggest that the estimated hydraulic conductivity is representing regional property rather than the local one to confirm the validity of the proposed procedure it was applied to the coastal aquifer of jeju island korea the calibrated hydraulic conductivities were consistent with the results from previous studies these results show that the proposed method is an effective and economical means to estimate hydraulic conductivity of large supporting volumes of subsurface aquifers with the convenient use of recharge and groundwater level data

petrographic and isotopic evidence for holocene long term climate change and shorter term environmental shifts from a stalagmite from the serra do courel of northwestern spain and implications for climatic history across europe and the mediterranean abstract a small stalagmite from cova da arcoia in the serra do courel of northwestern spain provides a record both of general climate change across the holocene and of shorter term shifts between wetter and drier conditions nineteen u series dates from 9 3 ka to the present provide a chronology of the stalagmite with uncertainties of commonly only decades and at the most only 200 years these dates constrain the age of 18 petrographic surfaces that are of two types one type e inferred to result from dissolution during enhanced flow of water and the other type l inferred to result from lesser flow aragonite is more abundant in the earlier parts of the stalagmite and calcite is more abundant in the later part values of 13 c range from 5 6 to 1 3 relative to vpdb but are greatest beneath type l surfaces values of 18 o range from 5 4 to 4 4 relative to vpdb and have a weak but statistically significant correlation with 13 c greater abundance of aragonite greater values of 13 c and lesser frequency of type e surfaces early in the stalagmite suggest a drier and perhaps warmer early to middle holocene whereas greater abundance of calcite and frequent type e surfaces higher in the stalagmite suggest wetter conditions later in the holocene 18 o data are most compatible with this general conclusion however a prominent type e surface records the 8 2 ka event as an isolated wetter episode in the otherwise dry early holocene much of the stalagmite s aragonite and calcite suggests normal stalagmite growth in moderate climatic conditions however the near or complete cessation of growth at type l surfaces and greater 13 c greater 18 o and lesser fluorescence of aragonite beneath those surfaces combine to suggest at least six century scale episodes of strikingly dry conditions on the other hand evidence of dissolutional erosion at type e surfaces suggests at least ten distinct episodes of much wetter conditions these combine to suggest highly variable climate across the holocene at the scale of decades to a few centuries the record from this stalagmite is similar to records from greenland ice cores and from pollen and or stalagmite records from france northernmost spain and more broadly from northern or atlantic facing europe in contrast it suggests trends nearly opposite those in records from eastern and southern spain suggesting that the serra do courel is north of but perhaps not far from the boundary between atlantic and mediterranean regions of holocene climate trends in the iberian peninsula that general antiphasal relationship between northwestern spain and regions to the south and east extends to the specific observation that four of the most pronounced wetter events in the stalagmite s record coincide with periods of widespread drought and or cultural collapse in the mediterranean and middle east

tidal groundwater level fluctuations in l shaped leaky coastal aquifer system this paper presents an analytical solution to describe tidal groundwater level fluctuations in a coastal leaky aquifer system bounded by water land boundaries that form a right angle referred to as l shaped coastlines the system consists of an unconfined aquifer a confined aquifer and a leaky layer between them previously published analytical solutions that discuss only single aquifer constitute a special case of the new solution when the permeability of leaky layer approaches zero a simple approximate solution without integral is presented error analysis and hypothetical example show that the approximate solution has adequate accuracy for both groundwater level prediction and parameter estimation for an l shaped leaky aquifer system q 2002 elsevier science b v all rights reserved

strike slip duplexes abstract strike slip fault systems often contain zones of steep imbricate faults geometrically similar to imbricate fans and duplexes in dip slip thrust and normal fault systems they are evident in map view rather than in vertical sections examples of duplexes are cited from both active and ancient systems and from theoretical and physical models duplexes may form at bends on strike slip faults by a process kinematically analogous to the sequential imbrication of ramps on dip slip faults however some may form and many may initiate as non sequential riedel fractures at fault offsets or on straight fault segments this process is more marked than in dip slip systems where primary anisotropy such as bedding exerts more control on fault geometry strike slip duplexes may be shunted along the fault system parallel to the regional slip vector however duplexes or individual horses will usually also move up or down perpendicular to the slip vector because of the unconstrained upper surface to the fault system these factors mean that no section through a strike slip system should be expected to area balance the faults of strike slip duplexes and imbricate fans may root in kinematically necessary low dip faults or may converge downwards and appear in vertical sections as flower structures

role of hydraulic diffusivity in the decrease of weathering rates over time summary springs emerging within massifs of crystalline rocks were monitored for discharge rate q and the q values combined with geomorphic and hydrographic parameters in a hydrologic model to calculate hydraulic conductivity k and effective porosity n e of the spring watersheds the spring waters several borehole waters and rain water were analyzed for major dissolved compounds strontium and isotopes 18 o 2 h 13 c and 87 sr 86 sr with a shift to less negative values 18 o and 2 h were fitted by a line approximately parallel to the gmwl but no significant dependence on altitude was found the 18 o and 2h values correlate better with those of precipitation amount the 87 sr 86 sr ratios in drilled well waters correlate positively with the depth of water circulation reported in the borehole logs the corresponding regression equations were used to extrapolate the depth of hydraulic circuits within the spring watersheds the previous data together with groundwater travel times calculated by a water balance model and with reactions of granite metassediment plagioclase and biotite precipitating halloysite gibbsite and vermiculite were assembled in a mass balance model to calculate solute flux weathering rates of plagioclase w pl the w pl s were described as a function of d k n e where d is the hydraulic diffusivity the discrepancies between the w pl values and solid state rates based on the differences between elemental isotopic and mineral compositions measured in present day regoliths and in the assumed protolith were assigned to a decrease in d over time from values in the protolith to values in the weathered aquifer

the enhancing effect of the elastic storage of the seabed aquitard on the tide induced groundwater head fluctuation in confined submarine aquifer systems summary this paper investigated the tide induced head fluctuation in a coastal confined aquifer with an infinitely extending semipermeable roof the roof is overlain by an unconfined aquifer terminating at the coastline previous analytical studies ignored the effect of the elastic storage of the semipermeable roof our model incorporated this effect the analytical solution indicated that the increase of the elastic storage of the offshore semipermeable roof may significantly enhance the tidal head fluctuation in the confined aquifer at the coastline a threshold leakance exists in the sense that when the leakance is less than the threshold the head fluctuation at the coastline will become insensitive to leakance and the roof can be regarded as impermeable the threshold strongly depends on the roof s elastic storage and decreases as the roof s elastic storage increases indicating that the roof s leakage effect is significantly enhanced by the increase of the roof s elastic storage

joint inversion for vp vs and vp vs at safod parkfield california we refined the three dimensional 3 d vp vs and vp vs models around the san andreas fault observatory at depth safod site using a new double difference dd seismic tomography code tomoddps that simultaneously solves for earthquake locations and all three velocity models using both absolute and differential p s and s p times this new method is able to provide a more robust vp vs model than that from the original dd tomography code tomodd obtained simply by dividing vp by vs for the new inversion waveform cross correlation times for earthquakes from 2001 to 2002 were also used in addition to arrival times from earthquakes and explosions in the region the vp values extracted from the model along the safod trajectory match well with the borehole log data providing in situ confirmation of our results similar to previous tomographic studies the 3 d structure around parkfield is dominated by the velocity contrast across the san andreas fault saf in both the vp and vs models there is a clear low velocity zone as deep as 7 km along the saf trace compatible with the findings from fault zone guided waves there is a high vp vs anomaly zone on the southwest side of the saf trace that is about 1 2 km wide and extends as deep as 4 km which is interpreted to be due to fluids and fractures in the package of sedimentary rocks abutting the salinian basement rock to the southwest the relocated earthquakes align beneath the northeast edge of this high vp vs zone we carried out a 2 d correlation analysis for an existing resistivity model and the corresponding profiles through our model yielding a classification that distinguishes several major lithologies

mineralogical characterization of protolith and fault rocks from the safod main hole 1 washed cuttings provide a continuous record of the rocks encountered during drilling of the main hole of the san andreas fault observatory at depth safod both protolith and fault rocks exhibit a wide variety of mineral assemblages that reflect variations in some combination of lithology p t conditions deformation mechanisms and fluid composition and abundance regions of distinct neomineralization bounded by faults may record alteration associated with fluid reservoirs confined by faults in addition both smectites occurring as mixed layer phases and serpentine minerals are found in association with active strands of the san andreas fault that were intersected during drilling although their rheological influence is not yet fully known faults containing these mineralogical phases are prime candidates for continuous coring during phase 3 of safod drilling in the summer of 2007

loading effect of water table variation and density effect on tidal head fluctuations in a coastal aquifer system 1 water table variation will result in considerable variation of the weight of the pore water which has loading effects on the groundwater flow in the underlying confined aquifer here we present an analytical solution on such a loading effect in a coastal aquifer system consisting of an unconfined aquifer a confined aquifer and an impermeable layer between them with the two lower layers extending under the sea the solution generalizes several existing ones in the literature the water table variation s loading effects tend to enhance the amplitude and to reduce the phase shift of the tide induced head fluctuation these effects become considerable when the tidal loading coefficient is large the aquifer s offshore extending length is long and the unconfined aquifer has large values of hydraulic conductivity and specific yield numerical examination indicated that the assumption of ignoring the density variation causes an error not greater than 2 5 of the tidal amplitude

hydraulic head response of a confined aquifer influenced by river stage fluctuations and mechanical loading summary the response to river stage fluctuation of a drilled well penetrating a confined aquifer was simulated using a stream aquifer interaction algorithm because the confined aquifer is overlaid by a water table aquifer the algorithm was coupled with formulae used to correct the heads for mechanical loading the coupling of stream aquifer interaction and mechanical loading models was tried for the first time in this study the test site was a drilled well installed on the montalto uffugo aquifer located at the calabria university groundwater test field calabria region south of italy this aquifer comprises a 44 m thick sand bank bounded on bottom and top by clay layers and covered by a 7 m thick sandy conglomerate being adjacent to the mavigliano river overall the head changes caused by a river stage raise represented a contribution of 49 3 57 8 to the total head while mechanical loading accounted for the remaining 50 7 32 2 the loading was triggered by a sequence of short spaced rainfall events lasting for a total of 167 days which caused recharge to the unconfined aquifer thickening the water column by some 3 1 m

evidence for shifting environmental conditions in southwestern france from 33 000 to 15 000 years ago derived from carbon 13 and nitrogen 15 natural abundances in collagen of large herbivores a paleoenvironmental reconstruction of terrestrial environments in southwestern france between 33 and 15 cal kyr bp is provided using 13c and 15n variations in collagen of three herbivorous mammals altogether 161 analyses have been carried out on collagen extracted from skeletal fragments of reindeer horse and bos bison from four successive chronological phases covering the end of mois 3 and mois 2 the 13c values of ungulate collagen are clearly separated between the studied species they are interpreted as reflecting a stable dietary adaptation in a changing environment the variations of 15n values of ungulate collagen are significant especially between specimens from mois 3 and specimens from mois 2 with a minimum during the last glacial maximum this phenomenon seems to reflect changes in the activity of nitrogen cycling processes associated with permafrost development carbon and nitrogen isotopic composition of fossil herbivore collagen are worth investigating as paleoecological and paleoenvironmental tracers in upper pleistocene periglacial continental contexts

a rainfall loading response recorded at 300 meters depth implications for geological weighing lysimeters abstract static pore water pressures in confined aquifers vary in response to ground surface loading changes including precipitation and evaporation under certain hydrogeological conditions such aquifers can function as giant natural weighing lysimeters referenced here as geological weighing lysimeters the extent of the land area weighed increases with aquifer depth and it is of interest to establish at what depth it is still possible to monitor surface water budgets an 86 mm rainfall event produced a clear loading signal in a well in western kansas at 300 m depth the loading effect is quantitatively consistent with elastic deformation induced by the rainfall mass and suggests that geological weighing lysimeters could operate at considerably greater depths thereby monitoring water budgets over a significant land area

joint inversion of gravity and arrival time data from parkfield new constraints on structure and hypocenter locations near the safod drill site 1 taking advantage of large datasets of both gravity and elastic wave arrival time observations available for the parkfield california region we generated an image consistent with both types of data among a variety of strategies the best result was obtained from a simultaneous inversion with a stability requirement that encouraged the perturbed model to remain close to a starting model consisting of a best fit to the arrival time data the preferred model looks essentially the same as the best fit arrival time model in areas where ray coverage is dense with differences being greatest at shallow depths and near the edges of the model where ray paths are few earthquake locations change by no more than about 100 m the general effect being migration of the seismic zone to the northeast closer to the surface trace of the san andreas fault

seismic radiation from an sh line source in a laterally heterogeneous planar fault zone a solution to the class of problems in which an sh line source is operating in a medium consisting of two quarter spaces with an arbitrary number of semi infinite vertical layers in between is given in a frequency wavenumber domain the general result is applied to a model with a single vertical layer and synthetic seismograms are calculated for a source specified as an sh line dislocation at the interface between the vertical layer and the faster quarter space the numerical examples demonstrate that moderate fault normal material heterogeneity can have significant effects on the seismic response of a medium the overall distribution of travel times amplitudes and motion polarities in the presence of fault zone material heterogeneity is different from a corresponding distribution in a homogeneous half space the effects are most prominent near the fault zone where head waves surface waves and trapped modes result in waveform complexities large amplifications over an order of magnitude in the fault zone itself and first motion polarities which are reversed from homogeneous medium predictions the results imply that material heterogeneity should be included in fault zone models which are used for the interpretation of observed seismic data and theoretical calculations of near fault responses such models can be utilized to obtain important fault zone and earthquake source parameters

shallow seismic trapping structure in the san jacinto fault zone near anza california summary we analyse fault zone trapped waves generated by 500 small earthquakes for high resolution imaging of the subsurface structure of the coyote creek clark valley and buck ridge branches of the san jacinto fault zone near anza california based on a small number of selected trapped waves within this data set a previous study concluded on the existence of a lowvelocity waveguide that is continuous to a depth of 15 20 km in contrast our systematic analysis of the larger data set indicates a shallow trapping structure that extends only to a depth of 3 5 km this is based on the following lines of evidence 1 earthquakes clearly outside these fault branches generate fault zone trapped waves that are recorded by stations within the fault zones 2 a traveltime analysis of the difference between the direct s arrivals and trapped wave groups shows no systematic increase moveout with increasing hypocentral distance or event depth estimates based on the observed average moveout values indicate that the propagation distances within the low velocity fault zone layers are 3 5 km 3 quantitative waveform inversions of trapped wave data indicate similar short propagation distances within the low velocity fault zone layers the results are compatible with recent inferences on shallow trapping structures along several other faults and rupture zones the waveform inversions also indicate that the shallow trapping structures are offset to the northeast from the surface trace of each fault branch this may result from a preferred propagation direction of large earthquake ruptures on the san jacinto fault

present day and past last 25000 years marine pollen signal off western iberia abstract the comparison between modern terrestrial and marine pollen signals in and off western iberia shows that marine pollen assemblages give an integrated image of the regional vegetation colonising the adjacent continent present day mediterranean and atlantic forest communities of iberia are well discriminated by south and north marine pollen spectra respectively results from total pollen concentration together with recognized conceptual models of fine particle dynamics in the iberian margin have allowed us to establish the present day pattern of pollen dispersion in this region the 25 000 year long record of continental pollen and marine 18 o of globigerina bulloides ice rafted detritus ird and neogloboquadrina pachyderma s proxies from the galician margin composite core md99 2331 and md03 2697 show that vegetation cover in north western iberia has responded contemporaneously to the climate variability of the north atlantic the vegetation response to the well known north atlantic heinrich events 2 and 1 h2 and h1 is however complex and characterised by two vegetation phases at low and mid altitudes of north western iberia the beginning of each heinrich event is marked on land by an important pine forest reduction and the expansion of heathers which are synchronous with the heaviest planktic 18 o values and the maxima of n pachyderma s suggesting that these first phases were cold and wet pinus forest expansion characterising the second phase of each heinrich event indicates a less cold episode associated during h1 with an increase of dryness as suggested by the development of semi desert associations the comparison of our galician margin multi proxy record with several pollen sequences from in and off iberia allows us to demonstrate that h1 event is the marine equivalent of the oldest dryas on the continent the occurrence of temperate trees during the last glacial maximum lgm and the rapid expansion of deciduous quercus during the bolling allerod period in our galician margin composite sequence show that not only the southern but also north western iberia was a refugium zone for deciduous trees during the last glacial period especially at low and mid altitude zones furthermore the comparison between southern and northern marine and terrestrial sequences allows us to confirm that vegetation responded to the bolling allerod warming the younger dryas cold event and the holocene more quickly in low and mid altitudes of north western iberia and in the south than in the high altitude northern region most likely as the result of the higher density of refugia for temperate trees in these zones during the lgm

a look inside the san andreas fault at parkfield through vertical seismic profiling the san andreas fault observatory at depth pilot hole is located on the southwestern side of the parkfield san andreas fault this observatory includes a vertical seismic profiling vsp array vsp seismograms from nearby microearthquakes contain signals between the p and s waves these signals may be p and s waves scattered by the local geologic structure the collected scattering points form planar surfaces that we interpret as the san andreas fault and four other secondary faults the scattering process includes conversions between p and s waves the strengths of which suggest large contrasts in material properties possibly indicating the presence of cracks or fluids

recurrence models and parkfield california earthquakes main shocks of the earthquake sequences that occurred on the parkfield section of the san andreas fault in central california in 1922 1934 and 1966 are characterized by southeast rupture expansion over the same 20 to 30 km long section of the fault whereas the seismic moments for the 1922 and 1934 events are identical to within a precision of 10 the seismic moment for 1966 is 20 greater than for the earlier events to within a precision of 20 the parkfield area seismicity in general seems well described by a recurring moderate size characteristic earthquake repeating the same epicenter magnitude seismic moment rupture area and southeast direction of rupture expansion an unexplained 10 year advance of the 1934 event is the only discrepancy in the hypothesis that the parkfield earthquakes in 1857 1881 1901 1922 1934 and 1966 represent a strictly periodic process assuming the strictly periodic model and the absence since 1966 of the perturbations hypothesized for the 1922 to 1934 period the next characteristic parkfield earthquake should occur between 1983 and 1993

monitoring of total soil moisture on a scale of hectares using groundwater piezometers a method has been developed for continuous measurement of total soil moisture on a scale of hectares the method is based on accurate measurement of groundwater pressures in thick clay formations and depends on the principle that changes of mechanical load result in changes of groundwater pressure the resulting data are similar to those obtained by conventional weighing lysimeters but on a much larger scale and with no significant hydrologic disturbance of the site several years of field testing show the method to be practicable

carbon isotope constraints on the deglacial co2 rise from ice cores the stable carbon isotope ratio of atmospheric co2 13catm is a key parameter in deciphering past carbon cycle changes here we present 13catm data for the past 24 000 years derived from three independent records from two antarctic ice cores we conclude that a pronounced 0 3 per mil decrease in 13catm during the early deglaciation can be best explained by upwelling of old carbon enriched waters in the southern ocean later in the deglaciation regrowth of the terrestrial biosphere changes in sea surface temperature and ocean circulation governed the 13catm evolution during the last glacial maximum 13catm and atmospheric co2 concentration were essentially constant which suggests that the carbon cycle was in dynamic equilibrium and that the net transfer of carbon to the deep ocean had occurred before then

annual fluctuations of groundwater levels as a result of loading by surface moisture abstract long term hydrographs for deep confined aquifers in southern saskatchewan canada show annual fluctuations characterized by a gradual rise in head from october to may june and a rapid drop from may june to october these fluctuations are distinctly different from the seasonal fluctuations observed in surficial and shallow semi confined aquifers which reflect the response of these aquifers to recharge derived from snow melt and early spring rains on the basis of field data and theoretical considerations it is demonstrated that seasonal fluctuations of the water table are not transmitted down to the deep aquifers provided the confining layers are thick and have sufficiently low hydraulic diffusivity the annual fluctuations in the deep aquifers thus do not reflect seasonal recharge to these aquifers plots of moisture accumulation i e precipitation minus calculated areal evapotranspiration are strikingly similar to the observed hydrographs for the deep aquifers in timing and magnitude of the annual fluctuations it is postulated that the annual head fluctuations in the deep confined aquifers reflect changes of the mechanical load on the formations caused by seasonal changes of the soil moisture snow and storage at the water table the deep confined aquifers thus act as large scale inexact weighing lysimeters

water table response to a tidal agitation in a coastal aquifer the meyer polubarinova kochina theory revisited summary the linear potential model of meyer and polubarinova kochina mpk solves laplace s equation in a quadrant the vertical face of which is subject to a harmonic variation of hydraulic head induced by a tide on the horizontal face of the quadrant a linear combination of the partial derivatives of the head with respect to time and with respect to the vertical cartesian coordinate are linearly related the fields of pore pressure head and darcian velocity trajectories of marked particles the oscillating phreatic surface and its upper envelope are obtained hydrograph in a piezometer located 60 m from the shore line in a thick unconfined coastal aquifer oman is interpreted by the analytical results of the model using the detected groundwater amplitude attenuated as compared with the tide amplitude mpk method provides a potentially superior description to the dupuit forchheimer method for tidally driven phreatic systems

carbon and nitrogen isotopic composition of red deer cervus elaphus collagen as a tool for tracking palaeoenvironmental change during the late glacial and early holocene in the northern jura france abstract red deer bone collagen from rochedane in the jura france was analysed for carbon and nitrogen isotopic composition the specimens range in 14c age from about 13 000 to 8000 yr bp uncalibrated and cover the late glacial and early holocene a time period during which climatic conditions shifted from periglacial to temperate the carbon isotopic compositions of red deer collagen suggest changes in the vegetation cover around the site that are consistent with other palaeoenvironmental indicators such as the palynological record in the jura the nitrogen isotopic compositions exhibit a large range of around 6 interpreted as reflecting changes in the intensity of n cycling coeval to vegetation changes red deer bone collagen appears thus as a valuable proxy for reconstructing palaeoenvironmental changes in continental western europe during the late glacial and holocene

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

seismic trapped modes in the oroville and san andreas fault zones three component borehole seismic profiling of the recently active oroville california normal fault and microearthquake event recording with a near fault three component borehole seismometer on the san andreas fault at parkfield california have shown numerous instances of pronounced dispersive wave trains following the shear wave arrivals these wave trains are interpreted as fault zone trapped seismic modes parkfield earthquakes exciting trapped modes have been located as deep as 10 kilometers as shallow as 4 kilometers and extend 12 kilometers along the fault on either side of the recording station selected oroville and parkfield wave forms are modeled as the fundamental and first higher trapped sh modes of a narrow low velocity layer at the fault modeling results suggest that the oroville fault zone is 18 meters wide at depth and has a shear wave velocity of 1 kilometer per second whereas at parkfield the fault gouge is 100 to 150 meters wide and has a shear wave velocity of 1 1 to 1 8 kilometers per second these low velocity layers are probably the rupture planes on which earthquakes occur

the impact of climate change human interference scale and modeling uncertainties on the estimation of aquifer properties and river flow components summary within the period 1978 2006 climate change and human interferences produced noticeable impacts on the hydrology of a small watershed known as the beca river basin climate change was characterized by a persistent raise in temperature 0 78 c decade 1 and a drop in the annual rainfall 300 mm decade 1 human interferences included the construction of a dam for electric power generation in 1998 and since then the transference of beca river flows from the dam lake to the adjacent t mega river the impacts on catchment hydrology comprised a decline of aquifer hydraulic conductivity and effective porosity by approximately one order of magnitude related to a water table lowering of about 17 m within the bedrock aquifer composed of weathered and fractured hercynian granites and paleozoic metassediments and of saprolite layers derived therefrom aquifer property estimates were compared across spatial scales namely the beca river and the nested sub basins scale sub basin aquifers are more porous and permeable than the basin aquifer because corresponding hydraulic circuits are shallower comparisons were also made between aquifer properties derived from measured and simulated stream flows which revealed effects of modeling uncertainties on the results river flows also suffered a substantial decrease in the course of climate change and human interference especially the overland flows 4 5 decrease and the base flows 2 3 decrease the inter flows were less affected 1 3 decrease because they were partly fed with water from the aquifer storage which in turn underwent depletion the hydrologic changes in the beca river basin anticipate important impacts on the local use of natural water in this context the aforementioned water table lowering may have caused limited access to shallow groundwater for activities such as crop irrigation from dug wells whereas the severe decline in overland flows and base flows had certainly reduced the availability of surface water for the refilling of dam lakes and of groundwater for the supply of public and private boreholes

isotopic reconstruction of past continental environments abstract vertebrate fossils and continental sediments provide a rich record of variations in the isotopic composition of surface environments to interpret these records a greater understanding of isotopic sources as well as fractionations associated with animal physiology soil geochemistry and diagenesis has been essential tooth enamel and fish otoliths yield subannual records of surface environments whereas soil minerals may integrate signals over many thousands of years carbon isotope variations in fossil vertebrates and soils record changes in the structure of vegetation and the isotope composition and concentration of atmospheric co2 oxygen isotope variations may be indirectly related to climate through reconstruction of the oxygen isotope composition of meteoric water or directly related to temperature through application of oxygen isotope paleothermometry to soil minerals or otoliths in africa nitrogen isotope variations show promise as a proxy for rainfall abundance though the gen

modeling rock weathering in small watersheds summary many mountainous watersheds are conceived as aquifer media where multiple groundwater flow systems have developed toth 1963 and as bimodal landscapes where differential weathering of bare and soil mantled rock has occurred wahrhaftig 1965 the results of a weathering algorithm pacheco and van der weijden 2012a 2014 which integrates topographic hydrologic rock structure and chemical data to calculate weathering rates at the watershed scale validated the conceptual models in the river sordo basin a small watershed located in the marao cordillera north of portugal the coupling of weathering groundwater flow and landscape evolution analyses as accomplished in this study is innovative and represents a remarkable achievement towards regionalization of rock weathering at the watershed scale the river sordo basin occupies an area of approximately 51 2 km 2 and was shaped on granite and metassediment terrains between the altitudes 185 1300 m the groundwater flow system is composed of recharge areas located at elevations 700 m identified on the basis of 18 o data discharge cells comprehend terminations of local intermediate and regional flow systems identified on the basis of spring density patterns infiltration depth estimates based on 87 sr 86 sr data and spatial distributions of groundwater ph and natural mineralization intermediate and regional flow systems defined where infiltration depths 125 m develop solely along the contact zone between granites and metassediments because fractures in this region are profound and their density is very large weathering is accelerated where rocks are covered by thick soils being five times faster relative to sectors of the basin where rocks are covered by thin soils differential weathering of bare and soil mantled rock is also revealed by the spatial distribution of calculated aquifer hydraulic diffusivities and groundwater travel times

an expression for land surface water storage monitoring using a two formation geological weighing lysimeter summary field studies have demonstrated that ground surface rainfall accumulation can be detected at depth by synchronous increases in static confined groundwater pore pressures this opens the way for geological weighing lysimeters providing disturbance free water storage monitoring of the surface environment in effect by weighing a significant land area in real time such systems require specific hydrogeological conditions which are not easily verified by field observations and replicated observations from multiple geological formations are a prerequisite for quality control given replication over two monitored formations we introduce an expression which utilises the respective formation piezometric water levels to give an improved combined estimate of the ground surface water budget the expression utilises raw piezometric levels and has the advantage of direct correction for earth tide noise which may sometimes be influenced by local effects in addition to the pure solar lunar tidal potential the expression is particularly simple if the two formations have similar but possibly unknown undrained poisson ratios and porosities surface water budgets can then be estimated using only the respective formation barometric coefficients and piezometric levels an example application to two vertically separated confined aquifers at a new zealand site indicate an improved accuracy over single formation observations the two formation expression for surface storage could find use as an accurate water budget tool with particular application to monitoring diffuse hydrological systems such as wetlands arid regions and heavily forested localities

anatomy of the high frequency ambient seismic wave field at the tcdp borehole 1 the taiwan chelungpu fault drilling project tcdp installed a vertical seismic array between 950 and 1270 m depth in an active thrust fault environment in this paper we analyze continuous noise records of the tcdp array between 1 and 16 hz we apply multiple array processing and noise correlation techniques to study the noise source process properties of the propagation medium and the ambient seismic wave field diurnal amplitude and slowness patterns suggest that noise is generated by cultural activity the vicinity of the recording site to the excitation region indicated by a narrow azimuthal distribution of propagation directions leads to a predominant ballistic propagation regime this is evident from the compatibility of the data with an incident plane wave model polarized direct arrivals of noise correlation functions and the asymmetric arrival shape evidence for contributions from scattering comes from equilibrated earthquake coda energy ratios the frequency dependent randomization of propagation directions and the existence of correlation coda waves we conclude that the ballistic and scattered propagation regime coexist where the first regime dominates the records but the second is weaker yet not negligible consequently the wave field is not equipartitioned correlation signal to noise ratios indicate a frequency dependent noise intensity iterations of the correlation procedure enhance the signature of the scattered regime discrepancies between phase velocities estimated from correlation functions and in situ measurements are associated with the array geometry and its relative orientation to the predominant energy flux the stability of correlation functions suggests their applicability in future monitoring efforts

can carbon 13 in large herbivores reflect the canopy effect in temperate and boreal ecosystems evidence from modern and ancient ungulates abstract local environmental conditions under dense canopy are known to result in depletion in 13c abundance in plants compared to an open land context this canopy effect has been observed in tropical as well as in mid latitude forest ecosystems however the impact of the canopy effect on tissue 13c abundance of temperate and boreal forest dwelling herbivores has not been thoroughly explored nevertheless the canopy effect has been suggested to explain a decrease of about 3 in collagen 13c values in ancient large herbivores from western europe during the forest expansion of the late glacial early holocene period ca 15 000 6000 cal bp some papers have considered the 13c decrease in large herbivore as the main result of global change in atmospheric co2 content a detailed review of 13c values of large herbivores reindeer red deer roe deer and bison from open and closed environments from high and mid latitudes confirm that the canopy effect observed in plants is passed on to their consumers in the paris basin the decline in 13c values of large herbivores at the late glacial early holocene transition around 10 000 years bp appears to be different according to the considered species namely red deer roe deer and large bovines bison and aurochs moreover differences in the pattern of decrease in 13c values are observed in red deer between french northern alps and french jura these differences among species in their isotopic response through time for a given geographical location and within species from different locations suggest variance in ecological responses of species that are associated with the relative use of forested habitat as a result 13c abundances in collagen can be considered as a direct tracker of the degree of closure of the habitat of ancient herbivores

seismic evidence for rock damage and healing on the san andreas fault associated with the 2004 m 6 0 parkfield earthquake we deployed a dense linear array of 45 seismometers across and along the san andreas fault near parkfield a week after the m 6 0 parkfield earthquake on 28 september 2004 to record fault zone seismic waves generated by aftershocks and explosions seismic stations and explosions were co sited with our previous exper iment conducted in 2002 the data from repeated shots detonated in the fall of 2002 and 3 months after the 2004 m 6 0 mainshock show 1 0 1 5 decreases in seismic wave velocity within an 200 m wide zone along the fault strike and smaller changes 0 2 0 5 beyond this zone most likely due to the coseismic damage of rocks during dynamic rupture in the 2004 m 6 0 earthquake the width of the damage zone characterized by larger velocity changes is consistent with the low velocity waveguide model on the san andreas fault near parkfield that we derived from fault zone trapped waves li et al 2004 the damage zone is not symmetric but extends farther on the southwest side of the main fault trace waveform cross correlations for repeated aftershocks in 21 clusters with a total of 130 events located at different depths and distances from the array site show 0 7 1 1 increases in s wave velocity within the fault zone in 3 months starting a week after the earthquake the velocity recovery indicates that the damaged rock has been healing and regaining the strength through rigidity recovery with time most likely due to the closure of cracks opened during the mainshock we estimate that the net decrease in seismic velocities within the fault zone was at least 2 5 caused by the 2004 m 6 0 parkfield earthquake the healing rate was largest in the earlier stage of the postmainshock healing process the magnitude of fault healing varies along the rupture zone being slightly larger for the healing beneath middle mountain correlating well with an area of large mapped slip the fault healing is most promi nent at depths above 7 km

evolution of the stable carbon isotope composition of atmospheric co2 over the last glacial cycle we present new c measurements of atmospheric co covering the last glacial interglacial cycle complementing previous records covering terminations i and ii most prominent in the new record is a significant depletion in c atm of 0 5 occurring during marine isotope stage mis 4 followed by an enrichment of the same magnitude at the beginning of mis 3 such a significant excursion in the record is otherwise only observed at glacial terminations suggesting that similar processes were at play such as changing sea surface temperatures changes in marine biological export in the southern ocean so due to variations in aeolian iron fluxes changes in the atlantic meridional overturning circulation upwelling of deep water in the so and long term trends in terrestrial carbon storage based on previous modeling studies we propose constraints on some of these processes during specific time intervals the decrease in c atm at the end of mis 4 starting approximately 64 kyr b p was accompanied by increasing co this period is also marked by a decrease in aeolian iron flux to the so followed by an increase in so upwelling during heinrich event 6 indicating that it is likely that a large amount of c depleted carbon was transferred to the deep oceans previously i e at the onset of mis 4 apart from the upwelling event at the end of mis 4 and potentially smaller events during heinrich events in mis 3 upwelling of deep water in the so remained reduced until the last glacial termination whereupon a second pulse of isotopically light carbon was released into the atmosphere

continuity of the west napa franklin fault zone inferred from guided waves generated by earthquakes following the 24 august 2014 mw 6 0 south napa earthquake we measure peak ground velocities from fault zone guided waves fzgws generated by on fault earthquakes associated with the 24 august 2014 m w 6 0 south napa earthquake the data were recorded on three arrays deployed across north and south of the 2014 surface rupture the observed fzgws indicate that the west napa fault zone wnfz and the franklin fault ff are continuous in the subsurface for at least 75 km previously published potential field data indicate that the wnfz extends northward to the maacama fault mf and previous geologic mapping indicates that the ff extends southward to the calaveras fault cf this suggests a total length of at least 110 km for the wnfz ff because the wnfz ff appears contiguous with the mf and cf these faults apparently form a continuous calaveras franklin wnfz maacama cfwm fault that is second only in length 300 km to the san andreas fault in the san francisco bay area the long distances over which we observe fzgws coupled with their high amplitudes 2 10 times the s waves suggest that strong shaking from large earthquakes on any part of the cfwm fault may cause far field amplified fault zone shaking we interpret guided waves and seismicity cross sections to indicate multiple upper crustal splays of the wnfz ff including a northward extension of the southhampton fault which may cause strong shaking in the napa valley and the vallejo area based on travel times from each earthquake to each recording array we estimate average p s and guided wave velocities within the wnfz ff 4 8 5 7 2 2 3 2 and 1 1 2 8 km s respectively with fzgw velocities ranging from 58 to 93 of the average s wave velocities

water table fluctuation owing to time varying recharge pumping and leakage this paper presents an analytical solution of a 2 d linearized boussinesq equation to predict water table variation in a horizontal aquifer induced by time varying recharge and or withdrawal from any number of recharge basins pumping wells and leakage sites of different dimensions the rate of time varying recharge or withdrawal is approximated by series of line elements of different lengths and slopes depending on the nature of variation of recharge or withdrawal rate advantage of this approximation scheme is that any complex nature of recharge and or withdrawal rates for any number of recharge basins pumping wells and leakage sites and for any number of these operations can be approximated with more accuracy application of the solution in the prediction of water table variation in the presence of time varying recharging pumping and leakage is demonstrated with the help of an example problem the present analytical solution is validated by comparing its results with the corresponding numerical results obtained from modflow for the same example problem

integrating topography hydrology and rock structure in weathering rate models of spring watersheds weathering rate models designed for watersheds combine chemical data of discharging waters with morphologic and hydrologic parameters of the catchments at the spring watershed scale evaluation of morphologic parameters is subjective due to difficulties in conceiving the catchment geometry besides when springs emerge from crystalline massifs rock structure must be accounted in formulas describing the area of minerals exposed to the percolating fluids for a realistic evaluation of the rates these particular features are not included in the available approaches and for that reason a new model was developed coined throw model this is a lumped approach that integrates t opography h ydrology ro ck structure and w eathering in a single algorithm the study area comprises several stream watersheds and spring sites of the vouga river basin northern portugal shaped on granites firstly the throw model couples a terrain modeling analysis with hydrologic models based on discharge rates to determine hydraulic conductivities k effective porosities ne and annual recharges vr at the stream watershed scale subsequently these parameters are used in a water balance model to estimate concomitant groundwater travel times t the mean k 4 7 3 2 10 7 m s 1 and ne 2 0 1 3 10 2 values are adopted as proxies for the spring watersheds and a firm regression equation is defined between time and stream watershed area a secondly two more runs of terrain modeling analysis are executed to extrapolate morphologic parameters for the spring watersheds the first run hinges on scaling properties of the drainage networks known as horton laws and is used to scale watershed areas across stream orders i the scaling function is described by another regression equation the second run evaluates the order of a spring watershed defined as equivalent order ieq and equated to the mean order of the surrounding stream watersheds having calculated the ieq spring watershed areas and travel times were downscaled using the regression equations a 10 km2 and t 1 4 2 8 year standing on the physical and hydrologic parameters of the spring watersheds the throw model finally calculates plagioclase weathering rates in the vicinity of the spring sites the sib model pacheco and van der weijden 1996 was used before to estimate the contribution of plagioclase dissolution to the chemical composition of these springs van der weijden and pacheco 2006 the chemical data were now coupled with k ne and t in a rate equation to estimate chemical weathering rates of plagioclase in the basin in the throw model the rate equation describes the exposed surface area as a function of fracture spacings openings and porosities pacheco and alencoao 2006 the calculated rates wpl 2 5 1 2 10 14 mol m 2 s 1 are consistent with previous reports and with results of experimental kinetic models the sib results predict formation of halloysite and gibbsite along the flow path which were indeed close to equilibrium with the dissolved al and si activities o develop a weathering model that incorporates rock structure in the rate equation o conceive a weathering model especially designed for fracture artesian springs o create a model that integrates topography hydrology rock structure and weathering

groundwater response to tidal fluctuation in a two zone aquifer summary a coastal aquifer may consist of two zones of distinctly different hydraulic properties with the coastal zone of limited width and the inland zone of infinite width the analytical solutions for groundwater level response to tidal fluctuation in such a two zone aquifer are derived and the underlying physical meanings are discussed a dimensionless zone contrast parameter r is introduced which is controlled by ratio between the product of the transmissivity and storativity of the inland zone and that of the coastal zone in the coastal zone the amplitude of groundwater head fluctuation attenuates more quickly when r becomes greater the amplitude declines exponentially with distance from the coastline and the phase lag increases linearly only when r 1 in the inland zone however the head fluctuation always exhibits an exponential attenuation of the amplitude and a linear increase of the phase lag for any value of r thus the diffusivity of the inland zone can be readily assessed with measurements of fluctuation amplitudes or lags as are frequently used when estimating aquifer parameters in homogeneous aquifers compared with jacob 1950 solution for a semi infinite homogeneous aquifer the existence of the coastal zone reduces the amplitude in the inland zone by a spatially constant coefficient and increases the phase lag by a spatially constant shift inverse estimation of aquifer parameters are discussed based on the analytical solutions the analytical solutions are used to estimate the aquifer parameters in a coastal two zone aquifer located in the west part of dongzhai harbor hainan province china

preparation and characterization of bone and tooth collagen for isotopic analysis abstract criteria are presented for the identification of diagenetic alteration of carbon and nitrogen isotope ratios of bone and tooth collagen prepared by a widely used method measurements of collagen concentrations in tooth and bone atomic c n ratios and carbon and nitrogen concentrations in collagen of 359 historic and prehistoric african humans and modern and prehistoric east african non human mammals are described carbon isotope ratios of collagen lipids from four bones are also presented compared to bone whole teeth have significantly lower collagen concentrations lower carbon and nitrogen concentrations in collagen and similar c n ratios carbon and nitrogen concentrations and c n ratios are relatively constant over a wide range of collagen concentrations however prehistoric specimens with very low collagen concentrations have highly variable c n ratios very low carbon and nitrogen concentrations in collagen and stable carbon and nitrogen isotope ratios unlike collagen at the transition from well preserved to poorly preserved collagen the most reliable indicator of collagen preservation is the concentration of carbon and nitrogen in collagen concentrations of c and n drop abruptly by an order of magnitude at this transition point these attributes provide simple criteria for assessing sample quality since collagen preservation can vary greatly within prehistoric sites these attributes should be reported for each specimen use of purification procedures that remove acid and base soluble contaminants and particulate matter carbonates fulvic acids lipids humic acids sediments and rootlets are recommended wider adoption of these procedures would insure comparability of results between laboratories and permit independent and objective evaluation of sample preservation and more precise dietary climatic and habitat interpretations of collagen isotopic analyses

brown bear ursus arctos l palaeoecology and diet in the late pleistocene and holocene of the nw of the iberian peninsula a study on stable isotopes abstract in this paper we performed stable isotope analysis on bone collagen of 81 samples from at least 39 brown bears ursus arctos dating from late pleistocene to nowadays that lived in the western of the cantabrian mountains to interpret the data obtained we compared brown bear stable isotope signatures with those of cave bears ursus spelaeus red deer cervus elaphus and humans homo sapiens from the same area we observed that the diet of cave bears and brown bears in the cantabrian mountains was based on vegetable matter although their different isotopic signatures suggest different ecological niches wooded lowlands for the cave bear and steep highlands with scarce tree cover for the brown bear in the holocene brown bear maintains isotopic signatures similar to the pleistocene ones in spite of the climatic tempering which seems to be related to an even greater displacement toward the uplands due to a greater anthropic pressure in the ecosystem

seimological studies at parkfield v characteristic microearthquake sequences as fault zone drilling targets studies at very high resolution of microearthquakes at parkfield california since 1987 reveal a systematic organization in space and time dominated by clustering of nearly identical regularly occurring microearthquakes characteristic events on 10 to 20 m wide patches within the fault zone more than half of the 4000 events in our 1987 to 1996 catalog exhibit this trait in general recurrence intervals 0 5 to 2 yr scale with the magnitude of the repeating events for the on scale range mw 0 2 to 1 3 in this study the similar waveforms superimposed locations quasi periodic recurrence and uniform size of these characteristic events permit relative hypocenter location accuracy of meters and predictable occurrence times within windows of a few months clustered characteristic events occur at depths as shallow as about 3 km and these are feasible targets for deep scientific drilling and observation at the focus of a subsequent small earthquake within an active plate boundary fault zone at parkfield the achievable location accuracy to which a hypocenter can be specified as well as the predictability of its occurrence time appear to be uniquely favorable for in situ fault zone measurements

low velocity damaged structure of the san andreas fault at parkfield from fault zone trapped waves 1 we used dense linear seismic arrays across and along the san andreas fault saf at parkfield california to record fault zone trapped waves generated by explosions and microearthquakes in 2002 prominent trapped waves appeared at stations close to the saf main fault trace while some energy was trapped in the north strand at the array site observations and 3 d finite difference simulations of trapped waves at 2 5 hz show evidence of a damaged core zone on the main saf the zone from the surface to seismogenic depths is marked by a low velocity waveguide 150 m wide in which q is 10 50 and shear velocities are reduced by 30 40 from wall rock velocities with the greatest velocity reduction at shallow depth we interpret that this distinct low velocity zone on the main saf is a remanent of damage due to past large earthquakes on the principal fault plane at parkfield a less developed low velocity zone may be evident on the north strand that experienced minor breaks in the 1966 m6 event

sequential aquifer tests at a well field montalto uffugo scalo italy 1 this paper investigates our ability to characterize an aquifer using a sequential aquifer test in a well field that consists of six wells during the test we pumped water out from the aquifer at one well and monitored the water level changes at the rest of the wells to obtain a set of five well hydrographs by pumping at another of the six wells we obtained another set of five hydrographs this procedure was repeated until each of the six wells was pumped we then analyzed the six sets of hydrographs using the classical drawdown time the drawdown distance and the drawdown distance time methods results of the analysis confirm recent findings that the transmissivity estimates vary significantly at early time and stabilize at late time at late time the estimated values from all hydrographs are similar overall but vary slightly according to the locations of the pumping and observation wells in contrast storage coefficient estimates stabilized rapidly to distinct values associated with the well locations we subsequently used a hydraulic tomography approach to include all hydrographs from the sequential aquifer test to estimate the spatially varying transmissivity and storage coefficient fields the estimated fields appear to be realistic they reflect the geologic setting and the behaviors of the well hydrographs although more definitive confirmation is needed

estimating hydraulic properties of coastal aquifers using wave setup summary wave setup is the elevated mean water table at the coast associated with the momentum transfer of wave breaking which occurs generally over several days groundwater responses to wave setup were observed as far as 5 km inland in central maui hawaii the analysis showed that at times of energetic swell events wave driven water table overheights dominate low frequency groundwater fluctuations associated with barometric pressure effects matching peak frequencies at 1 7 10 6 hz and 3 7 10 6 hz were identified in setup and observed head using spectral decomposition similar to tides the setup propagation through the aquifer shows exponentially decreasing amplitudes and linearly increasing time lags due to the longer periods of setup oscillations the signal propagates deeper into the aquifer 10 km in central maui than diurnal tides 5 km and can therefore provide information on greater length scales hydraulic diffusivity was estimated based on the setup propagation an effective diffusivity of 2 3 107 m2 d is consistent with aquifer parameters based on aquifer tests and tides a one dimensional numerical model supports the results of the analytical solution and strengthens the suitability to estimate hydraulic parameters from setup propagation the methodology is expected to be beneficial to high permeability coastal environments such as on volcanic islands and atolls

palaeoenvironmental studies in nw iberia cantabrian range vegetation history and synthetic approach of the last deglaciation phases in the western mediterranean abstract at the north western limit of the mediterranean basin in the mediterranean oceanic transition zone the multidisciplinary study of two palaeolakes villaseca and la mata province of leon provides data on the last deglaciation the juxtaglacial lakes were formed during a deglaciation phase of the last cold stage weichselian wurm estimated from the regional and pyrenean chronological data between circa 48 ka and 32 ka ka 1000 years ago their drainage occurred circa 17 ka and 15 ka respectively during the definitive glacial retreat phases these results provide evidence for a glacial maximum extension preceding the global last glacial maximum lgm and an early deglaciation comparisons with the pyrenean data show that in the most important glacial basins of the pyrenean cantabrian range glaciers were still present at middle elevation circa 18 20 ka the final deglaciation did not happen until around 16 ka during the period 48 13 3 ka along the pyrenean cantabrian range three stages can be distinguished in the deglacial processes between circa 48 and 32 ka the deglacial retreats were contemporaneous with d o events 12 to 6 between circa 32 ka and 18 ka major sedimentary modifications were rare two of them are synchronous with d o 4 and 3 a glacial readvance also occurred during this period along the pyrenean cantabrian range between 18 and 17 ka major sedimentary changes and an increase in the 18o records of the ngrip ice core record are synchronous between 15 and 13 3 ka glacial retreats and sedimentary changes are synchronous with the climatic improvement observed from the end of the oldest dryas to the end of the bolling allerod period these correspondencies suggest relationships between the deglacial processes in the western mediterranean and the palaeoenvironmental events in the north atlantic region during the last glacial interglacial transition during the full glacial period the pollen data indicates dominant steppic environments the oldest dryas was not a constant cooling phase and from around 15 5 ka the pollen data indicates a slight warming during the holocene until circa 2040 cal bp mixed oak forests developed and pine was a prominent component of the cantabrian landscape then the forests were destroyed due to mining agriculture and fire and this favoured the extension of heathland

conodont apatite δ18o values from a platform margin setting oklahoma usa implications for initiation of late ordovician icehouse conditions abstract the uppermost sandbian lower katian stratigraphic record documents a critical time period in earth history lithological evidence and geochemical proxy records suggest that the uppermost sandbian lower katian interval could represent a transitional phase from a long cambrian ordovician greenhouse world to the late ordovician icehouse world to examine this interval of earth s history oxygen isotopes of conodont apatite from the bromide and viola springs formations in southern oklahoma were analyzed in order to provide sea surface temperature estimates at a location that had little influence by terrigenous sedimentation our results are inconsistent with 1 previous suggestions that global cooling occurred across a prominent sequence boundary close to the sandbian katian boundary across north america and 2 the hypothesis that there is a direct connection between volcanic mega eruption s and a significant long term impact on climate during the sandbian katian of laurentia furthermore 18 o values spanning the guttenberg carbon isotope excursion gice an interval that has been interpreted as evidence for an early onset of the late ordovician glaciation are variable a 1 5 18 o shift is observed in the lower gice that is followed by a return to 18 o values that fluctuate around a mean of 19 0 in the upper gice together these observations suggest a short lived cooling event within the lower gice this cooling event may represent enhanced carbon burial and drawdown of atmospheric p co 2 followed by a return to more stable low latitude temperatures in the upper gice

investigation of late pleistocene and early holocene palaeoenvironmental change at el miron cave cantabria spain insights from carbon and nitrogen isotope analyses of red deer abstract el miron cave was occupied by humans for over 40 000 years evidence of late mousterian gravettian solutrean magdalenian azilian mesolithic neolithic chalcolithic bronze age and mediaeval occupations has been found in the cave understanding the local environmental conditions during the occupations is crucial for gaining an insight into the lifeways of el miron s inhabitants as they relied on the surrounding region and its natural resources for their subsistence 170 bones of hunted red deer recovered from the cave were sampled for carbon and nitrogen stable isotope analyses with the aim of reconstructing the palaeoenvironment and palaeoclimate during the human occupation the results show that the surrounding landscape underwent considerable environmental change during the late pleistocene and early to mid holocene shifts in 13c values between the last glacial maximum heinrich stadial 1 heinrich event 1 the late glacial interstadial and the onset of the holocene are likely to reflect changes in water availability and temperature deer 15n generally increased over time indicating the regeneration of soil biological activity and nitrogen cycling which was temporarily halted during the younger dryas comparison of the el miron results with those of 300 deer from other regions of europe shows geographical variations in the timing and magnitude of the variation in 13c and 15n values this variation tracks local climate temperature and water availability and environmental vegetation and forest development changes

guided waves from sources outside faults an indication for shallow fault zone structure using 3 d numerical modeling of seismic wave propagation we investigate the possibility of generating fault zone fz trapped wave energy from sources well outside a fault the fz is represented by a o 200 m wide vertical low velocity layer in a half space we find that fz trapped waves can be excited from sources well outside the fault if 1 the low velocity structure extemds only to shallow depth and the source is located at greater depth or 2 the structure of the low velocity zone is such that only the shallow part of the fz traps energy fz trapped waves are not excited from sources well outside a fz continuous with depth the results support in conjunction with recent observational evidence a model for natural faults with shallow trapping structures rather than ones that span the entire seismogenic zone this may have implications for fault mechanics as well as for aspects of shaking hazard near faults

a seismic sequence from northern apennines italy provides new insight on the role of fluids in the active tectonics of accretionary wedges abstract we analyze a seismic sequence which occurred in 2000 along the northern apennines accretionary wedge italy the sequence developed within the cretaceous triassic limestones of the tectonic wedge where methane rich and oil reservoirs are stored ruptures mainly developed on wnw ese striking thrusts the compressive stress field is consistent with that acting at regional scale in northern apennines seismic parameters indicate that fluids are involved in the seismogenic process the amplitudes of the p and s phases and data from some stations evidence a p to s conversion within v p v s 2 1 layer the attenuation properties of crust show a higher attenuation zone located west of the epicentral cloud eight hundred aftershocks delineate a sub vertical cloud of events between 7 and 14 km depth the space time evolution of the aftershocks is consistent with a diffusive spreading diffusivity 1 9 m 2 s along vertically superimposed thrusts diffusion also controls the time evolution of the sequence fluid pressure is estimated to be roughly equal to the vertical lithostatic stress the overpressure within reservoirs develops by tectonic compaction processes the fluids upraise along sub vertical fractures related to the shortening of the wedge the 2000 sequence occurred in an area that separates a thermal and deeper petroleum system from a shallower biogenic system the divider of these systems controls the attenuation properties of the crust the fluid rock interaction at seismogenetic depth is related to hydrothermal processes more than to compaction in accretionary wedges seismicity activating superimposed thrusts may drive methane and oil upraising from the upper crust

structure of the san andreas fault at safod from p wave tomography and fault guided wave mapping 1 fault guided waves reveal a low velocity fault segment a few hundred meters southwest of the main strand of the san andreas fault saf system in 2004 the san andreas fault observatory at depth safod main hole was drilled 2 5 km underground and 0 7 km west of the saf surface trace a 3 component 4 5 hz seismograph was installed near the bottom of this hole this instrument recorded fault zone guided fg waves originating from earthquakes along the main saf 2 km north and 3 km south of the safod site this 5 km length corresponds to a distinctive low velocity structure imaged in 2003 using microearthquakes recorded on the pilot hole array because this structure transmits fg waves from the main fault it is probably connected to the main saf and is most likely a major unmapped fault

shallow high resolution geophysical investigation along the western segment of the victoria lines fault island of malta abstract the victoria lines fault island of malta is a 15 km long and n260 striking segmented normal fault system which is probably inactive since the late pliocene in the westernmost part the fomm ir rih segment displays comparable geologic throw and escarpment height 150 170 m moreover its hangingwall hosts thin patches of middle pleistocene clastic continental deposits red beds which are poorly preserved elsewhere we acquired two seismic transects by collecting ambient vibration recordings processed by using horizontal to vertical spectral ratios complemented by one high resolution 2 d refraction tomography survey crossing this fault where it is locally covered by red beds and recent colluvial deposits we found a resonance peak at 1 0 hz in the hangingwall block whereas clear peaks in the range 5 0 10 0 hz appear when approaching the subsurface fault and we relate them to the fractured bedrock within the fault zone the best fit tomographic model shows a relatively high vp shallow body vp 2200 2400 m s that we relate to the weathered top of the miocene upper coralline limestone fm bounded on both sides by low vp regions 230 m s above the weathered top bedrock our results depict a clear seismic signature of the victoria lines fault characterized by low seismic velocity and high amplification of ground motion we hypothesize that during the middle pleistocene faulting may have affected the basal part of the red beds so that this part of the investigated complex fault system may be considered inactive since 0 6 myr ago

two dimensional modelling of water table fluctuation in response to localised transient recharge abstract an analytical solution of the linearised boussinesq equation is presented and used to predict the spatio temporal variation of the water table in a finite aquifer system in response to a transient recharge from an overlying rectangular basin the boundary conditions of the finite aquifer are taken as fixed heads which would apply when the aquifer system is surrounded by open water bodies application of the solution is illustrated with the help of a numerical example the results would also have applications in studying stream aquifer interaction in the presence of transient recharge

tide induced groundwater fluctuation in a coastal leaky confined aquifer system extending under the sea this paper presents the analytical solution of groundwater response to tidal fluctuation in a coastal multilayer aquifer system consisting of a leaky confined aquifer a semipermeable layer and an unconfined aquifer the semipermeable layer or the roof of the leaky confined aquifer extends under the sea comparisons are made with solutions derived previously which considered only a single aquifer zero extension of the roof or infinite roof length and demonstrate that the previous solutions are special cases of the solution presented here a hypothetical example is used to discuss the impact of the dimensionless roof length dimensionless leakage and tidal efficiency on the groundwater level fluctuations in the inland part of the confined aquifer the fluctuation decreases significantly with the roof length when the roof length is small but is insensitive to the change of roof length when the roof length is greater than a threshold the impacts of leakage from the offshore and inland portions of the confining unit are different leakage from the offshore portion tends to increase the fluctuation of the groundwater level while leakage from the inland portion tends to decrease the fluctuation the fluctuation increases as the tidal efficiency increases this fact is significant only when the roof length is great and leakage is small

water table fluctuations due to canal seepage and time varying recharge transient water table variation in an unconfined horizontal aquifer lying between two canals located at different elevations above the impermeable barrier and receiving time varying recharge is predicted by obtaining an analytical solution to the linearized boussinesq equation the proposed solution is for the generalized form of time varying recharge and has been obtained by applying an indigenously devised transformation to the flow governing equation the solution for constant rate of recharge a special case of the proposed solution is compared with the existing analytical solution and almost identical values of water table rise are obtained the effect of constant recharge exponentially decreasing recharge and a combination of constant and exponentially decreasing recharge on the water table rise is analyzed with the help of a numerical example

groundwater recharge in a hard rock aquifer a conceptual model including surface loading effects knowledge about the groundwater recharge is essential for the prediction of impacts of groundwater withdrawal and underground construction recharge in the bedrock is however difficult to estimate the objectives of this thesis were to increase the understanding of groundwater recharge in crystalline bedrock to investigate how the recharge could be estimated and to develop new models to describe the recharge the study was based on three approaches groundwater dating using chlorofluorocarbons cfcs geohydraulic field measurements and mathematical modelling low concentrations of cfc 11 and cfc 113 were found in the bedrock groundwater which in combination with low dissolved oxygen levels indicated anaerobe degradation the cfc 12 and tritium concentrations agreed fairly well which means that apparent ages could be true ages the results suggest that cfc dating may not be reliable at forested humid sites covered by fine grained soil a quick response in hydraulic head to precipitation was observed in the studied bedrock despite the 10 m thick till cover a substantial portion of observed head variations was found to be loading effects involving no storage changes or water flow the loading efficiency of the bedrock was estimated from the air pressure response to be 0 95 the surface loading was calculated from measurements of air pressure water in the soil and snow about 20 of the seasonal variation of the hydraulic head was estimated to be related to loading changes only a simple conceptual model could be used to simulate the observed hydraulic heads the loading effect had to be included to properly describe individual recharge events numerical experiments were performed with a soil bedrock profile when the rock was modelled as a heterogeneous continuum unsaturated zones developed at high hydraulic gradients the phenomenon appeared in areas where low conductive zones were located upstream of high conductive zones decreasing the effective hydraulic conductivity of the material

tidal fluctuations in a leaky confined aquifer localised effects of an overlying phreatic aquifer damping of tidal head fluctuations in a leaky confined coastal aquifer is enhanced by leakage into an overlying phreatic aquifer we show that the phreatic aquifer is however resistant to the leakage flow and in particular a deep phreatic aquifer can reduce the leakage effects significantly an analytical solution based on a vertical flow model for the phreatic aquifer is derived for quantifying the role of this upper free water body in tidal propagation in the lower semi confined aquifer

carbon and nitrogen stable isotopes of bone collagen of large herbivores from the late pleistocene kiputz ix cave site gipuzkoa north iberian peninsula for palaeoenvironmental reconstruction abstract the kiputz ix site records climatic variations during the late pleistocene since it represents a continuous time interval record ca 25 13 ka cal bp carbon and nitrogen stable isotopes from the bone collagen of herbivores rangifer tarandus cervus elaphus and bison priscus were analysed to establish environmental and climatic conditions in the northern iberian peninsula faunal distribution over time represents a response to climatic variations showing inverse patterns with reindeer and bison profusion during cold periods and red deer abundance during warmer times the increase in reindeer 15 n values during stadial gs 2 appears to be greater in magnitude than in continental europe and reflects drier warmer climatic conditions the 13 c values of red deer suggest more humid environmental conditions south of the pyrenees during interstadial gs 1 the climatic conditions of southern pyrenees appear to be analogous to that of northern pyrenees regions

the safod pilot hole seismic array wave propagation effects as a function of sensor depth and source location 1 in july 2002 we installed a vertical array of seismometers in the san andreas fault observatory at depth safod pilot hole ph the bottom of this 32 level 1240 m long array of 3 components is located at a depth of 2100 m below ground surface explosion and microearthquake seismograms recorded by the array give valuable insights into the structure of the safod site the ratios of p and s wave velocities vp vs along the array suggest the presence of two faults intersecting the ph the vp vs ratios also depend on source location with high values to the nw and lower ones to the se correlating with high and low creep rates along the saf respectively since higher ratios can be produced by increasing fluid saturation we suggest that this effect might account for both our observations and their correlation with the creep distribution

seismological studies at parkfield i simultaneous inversion for velocity structure and hypocenters using cubic b splines parameterization a model for the 3d p and s wave velocity structure at parkfield has been developed by the systematic inversion of arrival times for microearthquakes and surface vibroseis sources recorded by nearby calnet stations and by the local borehole installed 10 station high resolution seismic network there a modification of the linear b splines model parameterization method of thurber 1983 to a cubic b splines formulation through tests inverting synthetic data sets for the parkfield configuration is found to produce smooth velocity distributions that still retain some small scale features application of the method to 953 p wave and 288 s wave arrivals from 111 microearthquakes and 8 vibroseis locations throughout the study area yields a velocity structure having variable resolution a low velocity zone appears to coincide with the creeping segment of the san andreas fault zone northwest of the 1966 parkfield earthquake epicenter an increase of about 15 per cent in seismic velocities is seen from the northeast to southwest across this segment of the fault zone the higher velocities to the southwest apparently correspond to the granitic basement the contrast across the fault is subdued to the southeast along the 1966 rupture zone a high vp vs ratio of 1 9 is seen in a 2 km wide volume near the location of the 1966 main shock hypocenter presumably the nucleation zone for the expected m 6 parkfield earthquake

tidal wave propagation in a coastal aquifer effects of leakages through its submarine outlet capping and offshore roof summary this paper considers a leaky aquifer system comprising an unconfined aquifer a confined aquifer and a confining layer the aquifer s roof the unconfined aquifer terminates at the coastline the confined aquifer and its roof extend under the sea for a certain distance the aquifer s submarine outlet is covered by a thin layer of sediment referred to as the outlet capping hereafter with properties dissimilar to the aquifer previous studies either neglected the leakage through the aquifer s roof or the outlet capping this paper considers both effects and gives an analytical solution to describe the tide induced head fluctuation in the aquifer system for aquifers with zero or infinite offshore length or with impermeable roof or outlet capping or without the outlet capping existing solutions in the literature are obtained we defined the threshold value for the offshore aquifer length which was found to be less than 5 km for typical coastal aquifer systems for an aquifer with its offshore length greater than the threshold the inland head fluctuation becomes insensitive to variations of this length and the outlet capping s leakance the leakage through the offshore roof decreases the threshold value when the offshore confined aquifer is short the inland head fluctuation increases with the outletcapping s leakance in this case negative phase shift occurs near the coastline only for aquifers with small leakages through the offshore roof and the outlet capping in general