the 2007 m5 4 alum rock california earthquake implications for future earthquakes on the central and southern calaveras fault 1 the similarity of seismograms recorded by two seismic stations demonstrate that the 31 october 2007 moment magnitude m5 4 alum rock earthquake is a repeat of a 1955 ml5 5 earthquake both occurred on oppenheimer et al s 1990 zone v stuck patch on the central calaveras fault providing new support for their model of calaveras fault earthquake activity we suggest that zone v fails only in a family of recurring m 5 4 5 5 earthquakes the 1955 and 2007 earthquakes are the penultimate and ultimate zone v events earthquakes in 1891 and 1864 are possible earlier zone v events the next zone v event is not expected in the next few decades assuming a time dependent recurrence model the mean forecast date is 2064 2035 2104 95 confidence range we further suggest that zones i ii iii and iv fail in recurring m 5 1 5 3 m 5 6 5 8 m 6 1 6 3 and m 4 9 5 0 earthquakes respectively if our earthquake recurrence model is correct the next zone i event is overdue and could occur anytime and m5 6 earthquakes should not occur on zones ii iii and iv before 2014 2012 and 2026 respectively we cannot rule out the possibility that zone vi which lies at the southern end of the mission seismic trend where the southern hayward and central calaveras faults appear to connect at depth fails aseismically or in large events on the southern hayward fault such as last occurred in 1868 or in large events on the adjoining northern calaveras fault segment

systematic survey of high resolution b value imaging along californian faults inference on asperities understanding and forecasting earthquake occurrences is presumably linked to understanding the stress distribution in the earth s crust this cannot be measured instrumentally with useful coverage however the size distribution of earthquakes quantified by the gutenberg richter b value is possibly a proxy to differential stress conditions and could therewith act as a crude stress meter wherever seismicity is observed in this study we improve the methodology of b value imaging for application to a high resolution 3 d analysis of a complex fault network in particular we develop a distance dependent sampling algorithm and introduce a linearity measure to restrict our output to those regions where the magnitude distribution strictly follows a power law we assess the catalog completeness along the fault traces using the bayesian magnitude of completeness method and systematically image b values for 243 major fault segments in california we identify and report b value structures revisiting previously published features e g the parkfield asperity and documenting additional anomalies e g along the san andreas and northridge faults combining local b values with local earthquake productivity rates we derive probability maps for the annual potential of one or more m6 events as indicated by the microseismicity of the last three decades we present a physical concept of how different stressing conditions along a fault surface may lead to b value variation and explain nonlinear frequency magnitude distributions detailed spatial b value information and its physical interpretation can advance our understanding of earthquake occurrence and ideally lead to improved forecasting ability

the earthquake cycle in the san francisco bay region a d 1600 2012 abstract stress changes produced by the 1906 san francisco earthquake had a profound effect on the seismicity of the san francisco bay region sfbr dramatically reducing it in the twentieth century whether the sfbr is still within or has emerged from this seismic quiescence is an issue of debate with implications for earthquake mechanics and seismic hazards historically the sfbr has not experienced one complete earthquake cycle i e the accumulation of stress its release primarily as coseismic slip during surface faulting earthquakes its re accumulation in the interval following and its subsequent rerelease the historical record of earthquake occurrence in the sfbr appears to be complete at about m 5 5 back to 1850 bakun 1999 for large events the record may be complete back to 1776 which represents about half a cycle paleoseismic data provide a more complete view of the most recent pre 1906 sfbr earthquake cycle extending it back to about 1600 using these we have developed estimates of magnitude and seismic moment for alternative sequences of surface faulting paleoearthquakes occurring between 1600 and 1776 on the region s major faults from these we calculate seismic moment and moment release rates for different time intervals between 1600 and 2012 these show the variability in moment release and suggest that in the sfbr regional plate boundary stress can be released on a single fault in great earthquakes such as that in 1906 and in multiple ruptures distributed on the regional plate boundary fault system on a decadal time scale

lead 210 sediment geochronology in a changing coastal environment abstract sediment accumulation rate studies utilizing excess 210 pb and 137 cs were conducted as part of recent investigations of biogeochemical cycling at a single site in cape lookout bight a rapidly changing coastal basin on the outer banks of north carolina u s a cores three meters in length reveal a depositional history for the bight interior characterized by a gradual transition in texture from coarse grained to fine grained material over the period 1946 1979 this transition is controlled by progressive enclosure of the bight by an active northerly migrating recurved spit the textural gradation is periodically interrupted by layers of well sorted sand associated with major storm events lead 210 data indicate that the upper meter of the sediment has accumulated at a rate of 3 35 to 4 71 g cm 2 yr 1 or approximately 8 4 to 11 8 cm yr 1 at o 0 84 below 120 cm depth dilution of clay and silt by low activity sand necessitates correction of the 210 pb profile in order to establish a geochronology grain size 210 pb distribution measurements at three depths reveal that the specific activity dpm g 1 of clay is 3 2 times that of silt and 24 7 times that of sand corrections of bulk sediment excess 210 pb activities based on these measurements lead to dates for textural changes which are consistent with charted changes in basin morphology and major storm events sixteen 137 cs measurements between 33 241 cm depth reveal a peak activity at 105 115 cm and indicate a minimum sedimentation rate of approximately 2 7 g cm 2 yr 1

determining the times and distances of particle transit in a mountain stream using fallout radionuclides abstract targeting of erosion and pollution control programs is much more effective if the time for fine particles to be transported through a watershed the travel distance the proportions of old and new sediment in suspension and the rate of erosion of the landscape can be estimated in this paper we present a novel technique for tracing suspended sediment in a mountain stream using fallout radionuclides sorbed to sediment atmospherically delivered 7 be 210 pb and 137 cs accumulate in the snowpack are released with its melting and sorb to fine particulates a portion of which are carried downslope into stream channels the half life of cosmogenic 7 be is short 53 4 days thus sediment residing on the stream bed should contain little of the radionuclide the different signatures of newly delivered sediment from the landscape with its 7 be tag and older untagged sediment from the channel is the basis for the tracing the total flux of such radionuclides compared to the inventory in the soil permits estimates of the rates of erosion of the landscape fine suspended particulates in the gold fork river id are transported downstream through the drainage in one or more steps having lengths of tens of kilometers length of the step decreases from about 60 km near the peak of the hydrograph to about 12 km near baseflow the percent of sediment in suspension that is new i e recently delivered from the landscape ranges from 96 to 12 the remaining sediment is resuspended older channel sediment residence times for particulates range from 1 6 days early in the hydrograph at the upper site to 103 days late in the hydrograph at the lowest elevation location rates of erosion of fine sediment calculated from the flux of radionuclides average 0 0023 cm year the long distance transport of fine particles suggests that delivery through the gold fork drainage to the basin outlet is fairly rapid once particles reach the channel and perhaps is also rapid in similar and smaller basins

the removal rates of234th and228th from waters of the new york bight abstract the mean residence time of thorium with respect to non radioactive removal from water was determined as a function of location in three traverses of the new york bight using both 234 th 238 u and 228 th 228 ra correlates well with salinity increasing from about ten days near shore to 70 days at the shelf break it shows a much weaker correlation with suspended matter concentrations both because suspended matter varies in its scavenging efficiency and because salinity is a longer term integrator of scavenging potential s computed from 228 th 228 ra were often higher than those computed from 234 th 238 u either because of the detrital matter present as reflected in the 232 th concentrations or because the water parcels had recently arrived from environments of lower scavenging efficiency anomalous isotopic concentrations found in three adjacent samples can best be explained as the result of an episodic release of 228 ra from bottom sediments at a rate 200 times the normal one

long term monitoring of creep rate along the hayward fault and evidence for a lasting creep response to 1989 loma prieta earthquake we present results from over 30 yr of precise surveys of creep along the hayward fault along most of the fault spatial variability in long term creep rates is well determined by these data and can help constrain 3d models of the depth of the creeping zone however creep at the south end of the fault stopped completely for more than 6 years after the m7 1989 loma prieta earthquake lpeq perhaps delayed by stress drop imposed by this event with a decade of detailed data before lpeq and a decade after it we report that creep response to that event does indeed indicate the expected deficit in creep

supply and dispersal of flood sediment from a steep tropical watershed hanalei bay kaua i hawai i usa in contrast to many small mountainous watersheds in temperate coastal regions where fl uvial discharge and wave energy commonly coincide deposition and reworking of tropical fl ood sediment can be seasonally decoupled and this has important implications for coral reef ecosystems an understanding of the interaction between tropical fl ood sedimentation and wave climate is essential to identifying and mitigating effects of watershed changes on coral reefs as urbanization and climate change proceed sedimentary facies and isotopic properties of sediment in hanalei bay on the island of kaua i hawai i usa were used to assess deposition and reworking of fldeposits from the hanalei river in a case study demonstrating the potential ecosystem effects of runoff from a steep tropical watershed in hanalei bay the youngest and thickest terrigenous sediment was consistently present near the river mouth and in a bathymetric depression that acted as at least a temporary sediment sink during this 2 yr study the largest fl ood events occurred in late winter and spring 2006 substantial terrestrial sediment delivered by those fl oods still remained in the bay as of june 2006 because oceanic conditions were not suffi ciently energetic to transport all of the sediment offshore additional sediment was deposited in the bay by a summer 2006 fl ood that coincided with seasonal low wave energy in most years fl ood sediment accumulating in the bay and on its fringing reefs would be remobilized and advected out of the bay during winter when the wave climate is energetic turbidity and sedimentation on corals resulting from late spring and summer fl oods during low wave energy could have a greater impact on coral reef ecosystems than fl oods in other seasons an effect that could be exacerbated if the incidence and sediment load of tropical summer fl oods increase due to urbanization and climate change

transport of the environmental radionuclides in an alpine watershed abstract the radionuclides137cs 210pb and7be have been examined in the alpine rho ne watershed switzerland during a period of two years in order to evaluate their usefulness as tracers of the removal and transport rate of top soil particles and particle reactive contaminants of atmospheric origin the specific activities of the radionuclides in fluvial suspension show a distinct seasonal pattern which depends on the hydrologic regime of the stream and the sources of the suspended matter input output budgets based on the atmospheric deposition and fluvial removal of three radionuclides in the alpine rho ne watershed are used to estimate their erosional residence times the simplest one box model yields mean residence times of about 800 and 1400 years for137cs and210pb respectively the removal rate of short lived7be suggests that a part of the watershed 0 6 2 3 of the total surface is exposed to a rapid erosion in which the mean residence time of the radionuclides is in the range of 1 220 days this has little influence on the calculated residence time of137cs but increases the estimated residence time of210pb in soil to over 1800 years the use of210pb 7be pair in fluvial output may be very helpful in the assessment of the impact of atmospheric pollutants on the water quality in rivers and lakes

seismic activity of the san francisco bay region moment magnitude m with objective confidence level uncertainties are estimated for felt san francisco bay region earthquakes using bakun and went worth s 1997 analysis strategy for seismic intensity observations the frequency magnitude distribution is well described for m 5 5 events since 1850 by a gutenberg richter relation with a b value of 0 90 the seismic moment rate m yr since 1836 is 2 68 1018 n m yr 95 confidence range 1 29 1018 n m yr to 4 07 1018 n m yr the seismic moment rate since 1850 is nearly the same m yr in the 56 years before 1906 is about 10 times that in the 70 years after 1906 in contrast m yr since 1977 is about equal that in the 56 years before 1906 80 1 14 of the plate motion moment accumulation rate is available for release in earthquakes the historical m yr and the portion of the plate motion moment accumulation rate available for release in earthquakes are used in a seismic cycle model to estimate the rate of seismic activity in the twenty first century high and low rates of future seismic activity are both permissible given the range of possible seismic cycle recurrence times t and the uncertainties in the historical m and in the percentage of plate motion available for release in earthquakes if the historical seismic moment rate is not greater than the estimated 2 68 1018 n m yr and the percentage of the plate motion moment accumulation available for release in earthquakes is not less than the estimated 80 then for all t the rate of seismic moment release from now until the next 1906 sized shock will be comparable to the rate from 1836 to 1905 when m 6 1 2 shocks occurred every 15 to 20 years

a 21 event 4 000 year history of surface ruptures in the anza seismic gap san jacinto fault and implications for long term earthquake production on a major plate boundary fault paleoseismic work completed at hog lake on the san jacinto fault sjf near anza california indicates that at least 21 surface ruptures have occurred in the anza seismic gap over the past 4 000 years the ages of the ruptures are constrained by 111 radiocarbon dates 97 of which fall in stratigraphic order the average recurrence interval for all ruptures for this period is about 185 105 years although some ruptures such as occurred in the april 1918 earthquake caused only minor displacement we rate the expression of each interpreted event in each of the twelve developed field exposures presented in this work by assigning numeric values for the presence of different criteria that indicate rupture to a paleo ground surface weakly expressed ruptures for example the deformation we interpret to be the result of the historical 1918 earthquake received low scores and are interpreted as smaller earthquakes from this analysis we infer that at least fifteen of the identified ruptures are indicative of large earthquakes similar to the penultimate earthquake inferred to be the m w 7 3 22 november 1800 earthquake the adjusted recurrence interval for large earthquakes lengthens to approximately 254 years comparison with the rupture history at the mystic lake paleoseismic site on the claremont strand indicates that it is plausible that several of the large ruptures identified at hog lake could have jumped the hemet step over at mystic lake and continued on the claremont strand or vice versa but most of the event ages do not match between the two sites indicating that most ruptures do not jump the step finally comparison with san andreas fault ruptures both to the north and south of its juncture with the sjf suggest that some northern sjf ruptures identified at mystic lake may correlate with events identified at wrightwood but that these northern ruptures have no match at hog lake and can not indicate rupture of the entire sjf onto the saf

beryllium 7 wet deposition variation with storm height synoptic classification and tree canopy state in the mid atlantic usa short lived fallout isotopes such as beryllium 7 7be are increasingly used as erosion and sediment tracers in watersheds 7be is produced in the atmosphere and delivered to the earth s surface primarily in precipitation however relatively little has been published about the variation in 7be wet deposition caused by storm type and vegetation cover our analysis of precipitation throughfall and sediments in two forested headwater catchments in the mid atlantic usa indicates significant variation in isotope deposition with storm type and storm height individual summer convective thunderstorms were associated with 7be activity concentrations up to 5 0 bq l 1 in precipitation and 4 7 bq l 1 in throughfall while single event wet depositional fluxes reached 168 bq m 2 in precipitation and 103 bq m 2 in throughfall storms originating from the continental usa were associated with lower 7be activity concentrations and single event wet depositional fluxes for precipitation 0 7 1 2 bq l 1 and 15 8 65 0 bq m 2 and throughfall 0 1 0 3 bq l 1 and 13 5 98 9 bq m 2 tropical systems had relatively low activity concentrations 0 2 0 5 bq l 1 in precipitation and 0 2 1 0 bq l 1 in throughfall but relatively high single event depositional fluxes due to large rainfall volumes 32 8 67 6 bq m 2 in precipitation and 25 7 134 bq m 2 in throughfall the largest sources of 7be depositional variation were attributed to storm characteristics including precipitation amount and maximum storm height 7be activity associated with fluvial suspended sediments also exhibited the highest concentration and variability in summer 175 1450 bq kg 1 we conclude the dominant source of variation on event level 7be deposition is storm type our results illustrate the complex relationships between 7be deposition in precipitation and throughfall and demonstrate event scale relationships between the 7be in precipitation and on suspended sediment copyright 2015 john wiley sons ltd

integration of paleoseismic data from multiple sites to develop an objective earthquake chronology application to the weber segment of the wasatch fault zone utah we present a method to evaluate and integrate paleoseismic data from multiple sites into a single objective measure of earthquake timing and recurrence on discrete segments of active faults we apply this method to the weber segment ws of the wasatch fault zone using data from four fault trench studies completed between 1981 and 2009 after systematically reevaluating the stratigraphic and chro nologic data from each trench site we constructed time stratigraphic oxcal models that yield site probability density functions pdfs of the times of individual earth quakes we next qualitatively correlated the site pdfs into a segment wide earthquake chronology which is supported by overlapping site pdfs large per event displace ments and prominent segment boundaries for each segment wide earthquake we computed the product of the site pdf probabilities in common time bins which emphasizes the overlap in the site earthquake times and gives more weight to the narrowest best defined pdfs the product method yields smaller earthquake timing uncertainties compared to taking the mean of the site pdfs but is best suited to earth quakes constrained by broad overlapping site pdfs we calculated segment wide earthquake recurrence intervals and uncertainties using a monte carlo model five surface faulting earthquakes occurred on the ws at about 5 9 4 5 3 1 1 1 and 0 6 ka with the exception of the 1 1 ka event we used the product method to define the earthquake times the revised ws chronology yields a mean recurrence interval of 1 3 kyr 0 7 1 9 kyr estimated two sigma 2 range based on interevent recurrence these data help clarify the paleoearthquake history of the ws including the important question of the timing and rupture extent of the most recent earthquake and are essential to the improvement of earthquake probability assessments for the wasatch front region

hydraulic tomography analog outcrop study combining travel time and steady shape inversion summary travel time and steady shape inversions are complementary methods for tomographic aquifer characterization in this work a combined procedure is presented that facilitates determination of spatial hydraulic conductivity and specific storage distributions in heterogeneous groundwater systems the procedure is applied to a highly heterogeneous sedimentary aquifer analog that is implemented as a two and three dimensional case study in a numerical flow model by interpreting the observations from multiple simulated short term pumping tests the main hydraulic features of the analog are successfully reconstructed the final results demonstrate the encouraging potential of the combined procedure for identifying the dominant structural elements and composition of sedimentary aquifers however limits derived from the test design of hydraulic travel time tomography in our synthetic case study prevented us from resolving small scale 10 cm in size variability of hydraulic conductivity with high discrepancies up to 5 orders of magnitude a better reconstruction of the aquifer hydraulic parameters is expected by utilizing a larger amount of measurements which involve more test and observation intervals although such a test design would be less feasible for field applications still this newly combined scheme is very attractive for an up scaled reconstruction on the sub meter scale for the present case study representative parameter values could be estimated in a computationally efficient way

comment on a natural gradient experiment on solute transport in a sand aquifer 2 spatial moments and the advection and dispersion of nonreactive tracers by d l freyberg

a note on the recent natural gradient tracer test at the borden site the variance in particle position a measure of dispersion is reviewed in the context of certain models of flow in random porous media asymptotic results for a highly stratified medium and an isotropic medium are particularly highlighted results of the natural gradient tracer test at the borden site are reviewed in light of these models this review suggests that the moments obtained for the conservative tracers at the borden site could as well be explained by a model that more explicitly represents the three dimensional nature of the flow field

radioisotopic evidence of perturbations of recent sedimentary record in lakes a word of caution for climate studies the rate of climatic change estimated from the gradient of signals recorded in lake sediments may be erroneous if post depositional perturbations are overlooked a smear out of a pulse signal over a variable thickness of core section due to physical or biological mixing is a well known phenomena much less attention is paid to a possible overestimation of the rate of change when a part of record is missing due to an erosion event in this paper we show a few examples of recent lake sediment perturbations and the resulting distortions in the time scale as documented by short lived radionuclides

natural 210pb 7be and fallout 137cs 239 240pu 90sr radionuclides as geochemical tracers of sedimentation in greifensee switzerland the average sedimentation rate of greifensee has been evaluated by using varve counting and 210pb and fallout radionuclide dating from 4 different sites in the lake to amount to 0 14 0 02 g cm 2 yr 1 the geochronology of greifensee agrees with previous dating attempts based on varve counting of sediments from the deepest part of the lake emerson and widmer 1978 a simple erosion model for substances derived predominantly from the drainage basin can explain the inventories of the natural and fallout radionuclides in the lake sediments

geochemistry and deposition of 7be in river estuarine and coastal waters the atmospheric flux of cosmogenic 7be 53 3 day half life and the mode of 7be deposition in river estuarine and coastal environments have been examined the atmospheric flux of 7be commonly supports inventories ranging from 1 0 to 2 0 pci cm2 1 pci 0 037 bq beryllium 7 concentrations in water phase samples collected across salinity gradients in several estuaries along the eastern coastline of the united states range from 0 03 to 0 53 pci l and primarily reflect variations in 7be supply and sorption kinetics the major process controlling the concentration of 7be on estuarine suspended particles appears to be the length of time that these particles remain in the water column field particle to water distribution coefficients for 7be have a median value of about 4 104 but range over an order of magnitude reflecting short term variations in 7be input particle dynamics and particulate iron content rather than equilibrium sorption desorption responses to changes in water salinity or particle type residence times of 7be in the water column range from a few days in estuarine areas of rapid fine particle deposition to several weeks in high energy environments where pronounced sediment resuspension reintroduces deposited 7be back into the water column inventories of 7be in sediments range from nondetectable to 3 3 pci cm2 with the highest inventories in areas where fine particles are accumulating rapidly such sites are also major repositories for other particle reactive substances a 7be budget for the james estuary indicates that less than 5 of the expected 7be input is in the water column and that the short term estuarine trapping efficiency for atmospherically derived 7be is somewhere between 50 and 100

estimating surface subsurface sediment mixing in karst settings using 7be isotopes this study shows that the cosmogenic radionuclide beryllium 7 can be used to track sediment movement through caves the activities of beryllium 7 and cesium 137 were measured in two different karst settings at both surface and subsurface sites before and after storm runoff events at one site 7be enriched sediment was detected up to 1 5 km along a stream conduit after a moderate storm event however the activity of 137cs was too variable to show a meaningful pattern the percentages of surface sediment that was found ranged from 0 to 52 along the entire 3 km cave stream and from 33 to 52 along the upper 1 5 km at the other site as much as 96 of the sediment initially discharged at the spring during a storm event was fresh surface material that had traveled into and through the cave stream moreover during the 4 day runoff event approximately 23 of the total suspended sediment flux was estimated to originate from surface erosion with 78 being reworked sediment from within the cave the data in this study shows that cosmogenic radionuclides with multi year half lives are too long lived to track sediment origins in the caves whereas 7be with a 53 2 day half life can be used to track movement of sediment along cave streams

probabilistic seismic hazard in the san francisco bay area based on a simplified viscoelastic cycle model of fault interactions 1 we construct a viscoelastic cycle model of plate boundary deformation that includes the effect of time dependent interseismic strain accumulation coseismic strain release and viscoelastic relaxation of the substrate beneath the seismogenic crust for a given fault system time averaged stress changes at any point not on a fault are constrained to zero that is kinematic consistency is enforced for the fault system the dates of last rupture mean recurrence times and the slip distributions of the assumed repeating ruptures are key inputs into the viscoelastic cycle model this simple formulation allows construction of stress evolution at all points in the plate boundary zone for purposes of probabilistic seismic hazard analysis psha stress evolution is combined with a coulomb failure stress threshold at representative points on the fault segments to estimate the times of their respective future ruptures in our psha we consider uncertainties in a four dimensional parameter space the rupture peridocities slip distributions time of last earthquake for prehistoric ruptures and coulomb failure stress thresholds we apply this methodology to the san francisco bay region using a recently determined fault chronology of area faults assuming single segment rupture scenarios we find that future rupture probabilities of area faults in the coming decades are the highest for the southern hayward rodgers creek and northern calaveras faults this conclusion is qualitatively similar to that of working group on california earthquake probabilities but the probabilities derived here are significantly higher given that fault rupture probabilities are highly model dependent no single model should be used to assess to time dependent rupture probabilities we suggest that several models including the present one be used in a comprehensive psha methodology as was done by working group on california earthquake probabilities

a record of large earthquakes on the southern hayward fault for the past 500 years the hayward fault a major branch of the right lateral san andreas fault system traverses the densely populated eastern san francisco bay region california we conducted a paleoseismic investigation to better understand the hayward fault9s past earthquake behavior the site is near the south end of tyson9s lagoon a sag pond formed in a right step of the fault in fremont because the hayward fault creeps at the surface we identified paleoseismic events using features that we judge to be unique to ground ruptures or the result of strong ground motion such as the presence of fault scarp colluvial deposits and liquefaction we correlate the most recent event evidence e1 to the historical 1868 m 6 9 earthquake that caused liquefaction in the pond and recognize three additional paleoruptures since a d 1470 110 yr event ages were estimated by chronological modeling which incorporated historical and stratigraphic information and radiocarbon and pollen data modeled mean age and 95 percentile ranges of the three earlier events are a d 1730 1650 1790 yr e2 a d 1630 1530 1740 yr e3 and a d 1470 1360 1580 e4 the ages of these paleoearthquakes yield a mean recurrence of 130 40 yr although the mean recurrence is well determined for the period a d 1470 1868 individual intervals are less well determined e1 e2 140 80 70 yr e2 e3 100 90 100 yr and e3 e4 150 130 110 yr

timing of large earthquakes during the past 500 years along the santa cruz mountains segment of the san andreas fault at mill canyon near watsonville california a paleoseismic investigation across the santa cruz mountains section of the san andreas fault at mill canyon indicates that four surface rupturing earthquakes have occurred there during the past 500 years at this site right lateral fault slip has moved a low shutter ridge across the mouth of the canyon ponding latest holocene sediments these alluvial deposits are deformed along a narrow zone of faulting there is excellent evidence for a 1906 m 7 8 and three earlier earthquakes consisting of well developed fissures scarps and colluvial wedges deformation resulting from the earlier earthquakes is comparable to that from 1906 suggesting they also were large magnitude events the earthquake prior to 1906 occurred either about a d 1750 1711 1770 or a d 1855 1789 1904 depending on assumptions incorporated into two alternative oxcal models if the later age range is correct then the earthquake may have been a historical early to mid nineteenth century earthquake possibly the a d 1838 earthquake both models are viable and there is no way to select one over the other with the available data two earlier earthquakes occurred about a d 1690 1660 1720 and a d 1522 1454 1605 using oxcal recalculation of the age of the reported penultimate earthquake reported from the grizzly flat site located about 10 km northwest of mill canyon indicates it occurred about a d 1105 1545 earlier than any of the past three earthquakes and possibly correlates to the fourth earthquake at mill canyon

chronologies of sedimentary processes in sediments of the foam site long island sound connecticut a detailed study of the sedimentation and diagenetic history of diver taken sediment cores from the foam site in long island sound was made by determining the distribution with depth of the following properties sup 234 th sub xs sup 7 be sup 210 pb sub xs sup 239 240 pu selected trace elements sup 14 c in both shells and organic fraction pore water sulfate and the diagenetic reaction products solid phase organic carbon and sulfur the sup 234 th sub xs and sup 7 be data indicate that the upper 4 cm are well mixed on the time scale of about a year the distributions of sup 210 pb sub xs sup 239 240 pu and anthropogenic trace metal excesses in the 4 15 cm section are controlled by the mixing of the surface 0 4 cm sediment into this layer the net sediment accumulation rate in the 0 15 cm layer is about 0 03 cm yr the average sediment accumulation rate in the approx 18 100 cm layer as determined from sup 14 c ages of shell layers is 0 094 0 021 cm yr perhaps a factor of approx 2 lower than that estimated from diagenetic modelling of solid phase sulfur and organic carbon depth profiles the sediment structure indicates that the sediment accumulation in this depth zone has beenmore episodic with the possibility of erosion as well as deposition having occurred their study shows that in high energy and dynamic sedimentary environments such as the foam site the results of steady state diagenetic modelling should be accepted only over time and depth scales permitted by the physical evidence less

beryllium 7 as a tracer to study mechanisms and rates of metal scavenging from lake surface waters the removal of be 7 from lake surface waters lake lugano switzerland italy was studied from september 1995 to may 1996 during this period the atmospheric input and sedimentary flux of be 7 as well as concentrations of dissolved 1 m be 7 in the epilimnion were measured the separation of dissolved colloidal and particulate fractions of be 7 was carried out using continuous flow centrifugation cfc and tangential flow filtration tff techniques lacustrine colloids log kc 6 were shown to be much more efficient sorbents for be 7 than the suspended particles log kp 4 5 particle concentrations cp ranged from 0 5 to 2 mg l the ratio of colloid 10 kd to particle concentration cc cp was close to 0 09 during winter months when detrital inputs are dominant but was higher 0 16 in summer and in spring after an algal bloom the be 7 data were used to estimate coagulation rates of colloids the highest coagulation rates coag 0 4 d 1 along with the lowest kc log kc 5 2 were found after an algal bloom in spring

evidence for a twelfth large earthquake on the southern hayward fault in the past 1900 years we present age and stratigraphic evidence for an additional paleoearth quake at the tyson lagoon site the acquisition of 19 additional radiocarbon dates and the inclusion of this additional event has resolved a large age discrepancy in our earlier earthquake chronology the age of event e10 was previously poorly con strained thus increasing the uncertainty in the mean recurrence interval ri a critical factor in seismic hazard evaluation reinspection of many trench logs revealed sub stantial evidence suggesting that an additional earthquake occurred between e10 and e9 within unit u45 strata in older u45 are faulted in the main fault zone and overlain by scarp colluviums in two locations we conclude that an additional surface rupturing event e9 5 occurred between e9 and e10 since 91 a d 40 yr 1 11 paleoearthquakes preceded the m 6 8 earthquake in 1868 yielding a mean ri of 161 65 yr 1 standard deviation of recurrence intervals however the standard error of the mean sem is well determined at 10 yr since 1300 a d the mean rate has increased slightly but is indistinguishable from the overall rate within the uncertainties recurrence for the 12 event sequence seems fairly regular the coeffi cient of variation is 0 40 and it yields a 30 yr earthquake probability of 29 the apparent regularity in timing implied by this earthquake chronology lends support for the use of time dependent renewal models rather than assuming a random process to forecast earthquakes at least for the southern hayward fault online material twelve event oxcal model for paleoearthquakes of the hayward fault

accumulation of fine grained sediments in a periodically energetic clastic environment cape lookout bight north carolina abstract soft highly reduced fluid like muds are accumulating at an average rate of 10 cm yr on a seabed at cape lookout bight that is neither below wave base during frequent winter storms nor subjected only to negligible fairweather tidal currents much of the sediment settling to the bottom is in the form of enormous up to 1 cm long aggregates of marine snow that are generally believed to occur only in quiet oceanic environments field measurements show that near bottom currents are typically 25 50 cm sec with directions that appear to be decoupled from the well defined rise and fall of tide a tendency toward extended ebb flows missed floods suggests that sediments may be transported into the bight from barden inlet for prolonged periods of time the lack of correlation between susp nded sediment concentration and near bottom current speed or direction indicates that little or no resuspension occurs during tidal flows or during 1 2 hr storms with winds in the 15 20 m sec 30 40 kt speed range high vertical flux of marine snow together with an apparent resistance of bottom sediments to resuspension offer an explanation for this and other backbarrier mud deposits that are impossible to explain by the settling of individual particles and difficult to explain by the settling of salt floc sized aggregates

a multitracer study of radionuclides in lake zurich switzerland 2 residence times removal processes and sediment focusing residence and settling times of particles and particle reactive nuclides evaluated from in situ tracer studies can be used as diagnostic indicators of trace element pathways in lakes natural e g 210pb 7be and 10be and artificial i e chernobyl 137cs radionuclide fluxes through lake zurich at 50 and 130 m depth from 1983 to 1987 atmospheric fluxes of the same nuclides and fluxes of 10be during 1987 allowed the calculation of nuclide residence times as well as particle settling and transit velocities in lake zurich the residence time of 210pb in the lake is approximately 1 month and hence of the same order as the residence times of particles and stable pb steady state residence times for 7be were calculated as 150 170 days while non steady state instantaneous removal residence times ranged from 50 to 800 days polonium 210 was removed from lake zurich with removal times of 10 26 months indicating slow removal processes or efficient recycling in the lake water transit velocities of particles calculated from the attenuation of chernobyl 137cs fluxes at 50 m and 130 m depth during early may 1986 were 17 m d 1 while 2 4 5 m d 1 was calculated as an effective settling velocity from the attenuation of 7be fluxes at 130 m depth as compared to 50 m depth model calculations reveal that the overall removal process of atmospherically deposited 7be from the water column to the sediments is mainly controlled by the adsorption coagulation step and not by the rate of particle settling extra inputs of 10be 210pb or 137cs into the lower trap i e rebound flux originating from episodic lateral inputs of fine particles with a high content of 210pb 10be and 137s were observed during the lake stratification period i e summer this novel observation of summertime radionuclide and sediment focusing is different from previously described wind generated resuspension and focusing effects caused by river plumes and lake sediments during the stagnation period boundary and focusing effects for radionuclide bearing particles are proposed to explain observed summertime enhancements of longer lived nuclide fluxes at 130 m depth as well as the decrease in calculated effective settling velocities

migration of contaminants in groundwater at a landfill a case study 4 a natural gradient dispersion test abstract a natural gradient tracer test using a chloride solution with an initial injection volume of 0 7 m 3 was performed in the sandy aquifer at the borden site the solution was injected into five well points set 1 m below the water table in an uncontaminated zone situated above the contaminant plume at a location 450 m downflow from the landfill under conditions of natural groundwater flow the tracer slug was monitored for a period of 4 months by withdrawing small volume samples from points in a three dimensional array of bundle type multilevel samplers measurements of hydraulic head were obtained from a network of miniature piezometers soon after injection the tracer slug gradually split into two halves one half moving horizontally at an average velocity of 2 9 10 6 ms 1 and the other horizontally at 8 2 10 7 ms 1 although the split has been attributed to local lateral heterogeneity the nature of the heterogeneity and its influence on the hydraulic head distribution were not clearly distinguishable in the field data obtained before during or after the test the chloride patterns for each of the two halves of the tracer slug evolved into gaussian forms although the patterns demonstrated some irregularity at early time the relatively smooth gaussian forms were unexpected because the aquifer has numerous small scale heterogeneities observed in vertical cores obtained from the tracer zone and because the glaciofluvial origin of the aquifer suggests that heterogeneities are not laterally continuous simulated chloride distributions from a three dimensional analytical solution to the advection dispersion equation were fitted to the field data to obtain best fit estimates of the values of longitudinal transverse horizontal and transverse vertical dispersivity at various travel distances for each of the two halves of the tracer zone this is the first known field test that has permitted the estimation of three principal dispersion coefficients in layered media the longitudinal dispersivity was found to increase from 0 01 m at a distance of 0 75 m from the source to 0 08 m at 11 0 m the transverse horizontal dispersivity increased also to a value of 0 03 m at 11 0 m transverse vertical dispersion was very weak and was accounted for by molecular diffusion the relative lack of vertical dispersion is consistent with the shape of the plume of leachate contamination from the landfill it was concluded that the observed increase in dispersivity along the path of migration is likely caused by heterogeneities information on the dispersion controlling heterogeneities is not yet available as practical field methodologies for their identification and description have not yet been developed until such information is incorporated into mass transport models a realistic solution of the dispersion problem in heterogeneous media will remain elusive

interseismic coupling and refined earthquake potential on the hayward calaveras fault zone interseismic strain accumulation and fault creep is usually estimated from gps and alignment arrays data which provide precise but spatially sparse measurements here we use interferometric synthetic aperture radar to resolve the interseismic deformation associated with the hayward and calaveras faults hf and cf in the east san francisco bay area the large 1992 2011 sar data set permits evaluation of short and long wavelength deformation larger than 2 mm yr without alignment of the velocity field to a gps based model our time series approach in which the interferogram selection is based on the spatial coherence enables deformation mapping in vegetated areas and leads to refined estimates of along fault surface creep rates creep rates vary from 0 2 mm yr on the northern cf to 14 2 mm yr on the central cf south of the hf surface junction we estimate the long term slip rates by inverting the long wavelength deformation and the distribution of shallow slip due to creep by inverting the remaining velocity field this distribution of slip reveals the locations of locked and slowly creeping patches with potential for a m6 8 0 3 on the hf near san leandro a m6 6 0 2 on the northern cf near dublin a m6 5 0 1 on the hf south of fremont and a m6 2 0 2 on the central cf near morgan hill with cascading multisegment ruptures the hf rupturing from berkeley to the cf junction could produce a m6 9 0 1 the northern cf a m6 6 0 1 the central cf a m6 9 0 2 from the junction to gilroy and a joint rupture of the hf and central cf could produce a m7 1 0 1

deriving a long paleoseismic record from a shallow water holocene basin next to the alpine fault new zealand a sedimentary sequence that was highly sensitive to fault rupture driven changes in water level and sediment supply has been used to extract a continuous record of 22 large earthquakes on the alpine fault the fastest slipping fault in new zealand at hokuri creek in south westland an 18 m thickness of holocene sediments accumulated against the alpine fault scarp from ca a d 800 to 6000 b c we used geomorphological mapping sedimentology and paleoenvironmental reconstruction to investigate the relationship between these sediments and alpine fault rupture we found that repeated fault rupture is the most convincing mechanism for explaining all the features of the alternating peat and silt sedimentary sequence climate has contributed to sedimentation but is unlikely to be the driver of these cyclical changes in sediment type and paleoenvironment other nontectonic causes for the sedimentary alternations do not produce the incremental increase in basin accommodation space necessary to maintain the shallow water environment for 6800 yr our detailed documentation of this near fault sedimentary basin sequence highlights the advantages of extracting paleoearthquake records from such sites the continuity of sedimentation abundance of dateable material and pristine preservation of older events

paleoseismology and tectonic geomorphology of the pallatanga fault central ecuador a major structure of the south american crust the pallatanga fault pf is a prominent nne ssw strike slip fault crossing central ecuador this structure is suspected to have hosted large earthquakes including the 1797 riobamba event which caused severe destructions to buildings and a heavy death toll more than 12 000 people as well as widespread secondary effects like landsliding liquefaction and surface cracking the scope of this study is to evaluate the seismic history of the fault through a paleoseismological approach this work also aims at improving the seismotectonic map of this part of the andes through a new mapping campaign and finally aims at improving the seismic hazard assessment we show that the pf continues to the north of the previously mapped fault portion in the western cordillera rumipamba pallatanga portion into the inter andean valley riobamba basin field evidences of faulting are numerous ranging from a clear geomorphological signature to fault plane outcrops along the western side of the riobamba basin the strike slip component seems predominant along several fault portions with a typical landscape assemblage dextral offsets of valleys fluvial terrace risers and generation of linear pressure ridges in the core of the inter andean valley the main fault portion exhibits a vertical component along the c 100 m high cumulative scarp the presence of such an active fault bounding the western suburbs of riobamba drastically increases the seismic risk for this densely inhabited and vulnerable city to the east peltetec massif cordillera real the continuation of the pallatanga fault is suspected but not definitely proved yet based on the analysis of three trenches we state that the rumipamba pallatanga section of the pf experienced 4 maybe 5 holocene to historical strong events mw 7 the coseismic behavior of the fault is deduced from the occurrence of several colluvial wedges and layers associated with the fault activity and interbedded within the organic black soil sequence according to a series of 14c datings we document that these events occurred during the last 6500 years the clear deformation of the shallowest layer 14c 1633 ad is most likely associated with the 1797 riobamba earthquake after retrodeforming one of the 3 trenches we estimate coseismic vertical throws 0 70 to 0 90 m because of bad outcrop conditions we could not determine the horizontal component of slip and we used the slip vector determined in a previous work with a tectonic geomorphology study assuming this slip vector we obtain total coseismic offsets between 3 5 and 4 5 m indicative of earthquake magnitudes around c mw 7 5 the estimated recurrence time intervals range between 1300 and 3000 years indicating an average slip rate of c 2 5 mm a for the rumipamba pallatanga section of the fault

7be in sargasso sea and long island sound waters 7be was measured in surface waters of the western sargasso sea and long island sound the calculated standing crop in the sargasso sea is equal to that predicted from precipitation collectors long island sound is deficient in 7be virtually none exists in the water column and less than half of the expected standing crop has been reported for the sediments a possible sink for the missing 7be may be the salt marshes or tidal mud flats ringing long island sound

observations of event scale sedimentary dynamics with an instrumented bottom boundary layer tripod abstract a new approach to examine event scale sedimentation is described that establishes a direct connection between water column signals and changes in the seabed the po river italy shelf is a good case study due to the dominant impact of winter storm events on sediment transport and the availability of coincident measurements necessary for the analysis repeated deployments of an instrumented bottom boundary layer tripod at this site have produced a nearly continuous record of sediment transport over 2 5 y sediment cores were collected every 3 mo during this time and seabed inventories of 7 be half life 53 3 d were used to determine net sediment deposition or erosion during each deployment comparison of these values with the net elevation change obtained from the tripod altimeter shows good agreement varying from 2 cm deposition to 1 cm erosion the altimeter s use is extended to quantify the net seabed change that results from individual storm induced sediment resuspension events lasting from days to weeks within each event analysis of the altimeter record has proved challenging likely due to changes in sediment porosity that occur during a storm event however net erosion and deposition that occurs over an event can be evaluated and was found to be

holocene paleoearthquakes on the tianqiaogou huangyangchuan fault in the northeastern boundary fault system of the tibetan plateau abstract rupture behavior one of the quantitative features of active fault is fundamental for understanding crustal deformation mechanisms and assessing regional seismic risk the 120 km long tianqiaogou huangyangchuan fault thf is an important branch fault of the qilian haiyuan fault system qhfs the main boundary fault zone at the emerging northeastern margin of the tibetan plateau mismatching with the fast strike slip rate there is no m 5 earthquake recorded along the thf to obtain more precise information of the rupture behaviors along the boundary structure we conducted a 1 50 000 active fault mapping and paleoearthquake trenching on the thf two trenches respectively illustrates at least 3 rupture events combining the radiocarbon dating and the oxcal modeling according to the overlap of their age ranges and the analysis on completeness of the sedimentary records it is determined at least 5 paleoearthquakes occurred along the thf in the holocene with respective age ranges of 485 675 bce 2085 295 bce 5590 1090 bce 7910 970 bce and 9975 955 bce and moment magnitudes estimated to be 7 3 7 4 meanwhile the detailed investigations on paleoseismology and tectonic geomorphology show the thf was not involved into the seismogenic structure of the nearby 1927 gulang m8 earthquake the monte carlo statistical analysis of these paleoearthquakes yields a mean recurrence interval of 2 4 0 3 ka illustrating a strong activity of the thf that accords with its slip rates and an important role as a tectonic boundary accommodating the eastward extruding of the northeastern tibet relative to the gobi alashan block moreover based on its strong activity and long elapsed time of at least 1 7 ka we propose the thf is another seismic gap with a potential of m 7 earthquakes similar to the tianzhu gap near the triple junction in the qhfs showing a high seismic risk along the thf and in this region

measurement of 7be in soils and sediments by gamma spectroscopy abstract measurement of cosmogenic 7 be in soils and sediments by gamma spectroscopy has been routine for three decades however the analytical constraints of this method have yet to be adequately described natural abundance of 7 be in bulk soils and sediments is typically low 10 6 to 10 8 atoms kg 1 resulting in very low signal to noise ratio in the gamma spectrum 7 be quantification is further complicated by numerous interferences from ubiquitous 238 u and 232 th series radionuclides we investigated the environmental gamma spectrum in the region of 7 be emission using spectra obtained from hundreds of natural stream sediment samples one well characterized sediment naturally enriched in 7 be and pure standard materials enriched in both 238 u series and 232 th series decay chains in typical samples no fewer than three discrete photopeaks directly interfere with 7 be measurement one of which the 228 ac 478 3 kev photon yields significant positive bias risks of 7 be false positives due to this overlapping photopeak approach 50 for typical soils or sediments detection limits for 7 be in these materials using conventional high purity germanium instruments are as low as 0 1 bq but increase by up to a factor of four in the presence of modest activities of 238 u and 232 th series nuclides here we demonstrate a methodology for the measurement of low 7 be abundances in soils and sediments that is unbiased and that optimizes precision

environmental chemistry of beryllium 7 in addition to the stable isotope 9be be is also formed as two cosmogenic isotopes of interest to earth scientists cosmogenic be is formed primarily in the stratosphere from cosmic ray spallation of oxygen and nitrogen but some is produced in the troposphere and in situ on the surface of the earth production of cosmogenic be was hypothesized by peters 1955 soon after naturally occurring 7be was identified in precipitation by arnold and al salih 1955 and essentially concurrently and independently by goel et al 1956 10be t1 2 1 5 106 yr was first detected by arnold 1956 in marine sediment cores the 10be 7be production ratio is approximately 0 5 lal and peters 1967 after its formation in the atmosphere cosmogenic be adsorbs electrostatically to aerosols that may be washed out by precipitation and delivered to ecosystems the amount of cosmogenic be that reaches the surface of the earth is a function of production rate cosmic ray intensity stratosphere troposphere mixing circulation and advection within the troposphere and efficiency of removal from the troposphere wet and dry deposition feely et al 1989 since the discovery of cosmic ray produced be numerous researchers have gathered data on its 1 production 2 fluxes to the oceans and terrestrial ecosystems 3 distribution and inventory in soils snow sediments and vegetation and 4 geochemical behavior in 1955 peters suggested that the relatively long half life of 10be could make it useful for quantifying tertiary sedimentation rates and other surficial processes the focus of this chapter is the short lived radionuclide 7be t1 2 53 12 0 07 days jaeger et al 1996 due to its short half life relative ease of measurement and well defined source term 7be serves as a useful tool for tracing and quantifying environmental processes on the

seasonal controls on meteoric 7be in coarse grained river channels cosmogenic 7be is a natural tracer of short term hydrological processes but its distribution in upland fluvial environments over different temporal and spatial scales has not been well described we measured 7be in 450 sediment samples collected from perennial channels draining the middle of the connecticut river basin an environment that is predominantly well sorted sand by sampling tributaries that have natural and managed fluctuations in discharge we find that the 7be activity in thalweg sediments is not necessarily limited by the supply of new or fine grained sediment but is controlled seasonally by atmospheric flux variations and the magnitude and frequency of bed mobilizing events in late winter 7be concentrations in transitional bedload are lowest typically 1 to 3 bq kg 1 as 7be is lost from watersheds via radioactive decay in the snowpack in mid summer however 7be concentrations are at least twice as high because of increased convective storm activity which delivers high 7be fluxes directly to the fluvial system a mixed layer of sediment at least 8 cm thick is maintained for months in channels during persistent low rainfall and flow conditions indicating that stationary sediments can be recharged with 7be however bed mobilizing rain on snowmelt events in late spring can reset 7be amounts and concentrations in the channel as previously buried old sediment with low 7be is mixed into the thalweg we conclude that given proper temporal and spatial sampling 7be is a valuable tracer of seasonal timescale mass transport and exchange in coarse grained fluvial systems copyright 2013 john wiley sons ltd

seasonal variations in 7be activity in the sediments of cape lookout bight north carolina abstract short term sediment accumulation rates were determined using activity distributions of 7be in the surficial sediments of a station a 1 in cape lookout bight north carolina usa this semienclosed coastal marine basin is characterized by high annual accumulation rates protected from high energy conditions by its geomorphology the relatively quiescent waters of the bight s interior cause it to act as an efficient settling trap for fine grained sediment lack of bioturbation in the surface sediments allowed for variations in depth integrated activity profiles of 7be to be interpreted as short term accumulation events beryllium 7 inventories exhibited seasonal cyclicity with inaxima occurring during spring february through june the inventory of 7be ranged from 5 8 to 32 6 dpm cin 2 and was always well in excess of the atmospherically supported value x 3 8 dpm cm 2 n 15 accumulation rates calculated froin 7be activity profiles indicate that the delivery of particulate matter to the sediments of cape lookout bight is not constant throughout an annual cycle the highest monthly accumulation rates appeared to be associated with north northeast storm activity inputs were generally highest during late winter early spring when storm frequency is greatest short term accumulation rates derived from this study agree with 210pb rates calculated for a ten year period of accumulation the annual sediment accumulation rates for each of the two years over which the study was conducted was found to be 4 8 0 8 g cm 2y 1 and 3 7 1 2g cm 2y 1

beryllium 7 the cinderella of fallout radionuclide sediment tracers current concern for the sustainable management of soil resources and the many adverse effects of increased sediment loads on streams and river systems has generated a need for more information on rates and patterns of soil loss and an improved understanding of catchment sediment budgets traditional measurement techniques are frequently unable to meet the requirements and fallout radionuclides have been shown to offer considerable potential for tracing the mobilization transfer redistribution and storage of soil and sediment within catchments and river systems caesium 137 and lead 210 have been the most widely used fallout radionuclide sediment tracers but their half lives mean that the information that they provide is in most instances limited to the medium term e g 25 120 years the need for information on shorter timescales has directed attention to the potential for using beryllium 7 which has a considerable shorter half life for tracing soil and sediment redistribution over short timescales e g days weeks to date however there have been relatively few attempts to exploit this potential this situation is likely to be in part a reflection of the emphasis of early work on 137cs and 210pb and the more recent nature of work using 7be however it may also reflect the limitations and constraints imposed by the nature of 7be fallout and the short half life of this radionuclide this contribution explores recent work in using 7be as a sediment tracer and the constraints imposed by its origin and behaviour attention is directed to fallout inputs the application of 7be to tracing soil and sediment redistribution on slopes and on river floodplains its use as a source fingerprint and other related applications the likely future potential of 7be as a sediment tracer is assessed copyright 2012 john wiley sons ltd

probabilistic estimates of surface coseismic slip and afterslip for hayward fault earthquakes we examine the partition of long term geologic slip on the hayward fault into interseismic creep coseismic slip and afterslip using monte carlo simulations we compute expected coseismic slip and afterslip at three alinement array sites for hayward fault earthquakes with nominal moment magnitudes ranging from about 6 5 to 7 1 we consider how interseismic creep might affect the coseismic slip distribution as well as the variability in locations of large and small slip patches and the magnitude of an earthquake for a given rupture area we calibrate the estimates to be consistent with the ratio of interseismic creep rate at the alinement array sites to the geologic slip rate for the hayward fault we find that the coseismic slip at the surface is expected to comprise only a small fraction of the long term geologic slip the median values of coseismic slip are less than 0 2 m in nearly all cases as a result of the influence of interseismic creep and afterslip however afterslip makes a substantial contribution to the long term geologic slip and may be responsible for up to 0 5 1 5 m median plus one standard deviation s d of additional slip following an earthquake rupture thus utility and transportation infrastructure could be severely impacted by afterslip in the hours and days following a large earthquake on the hayward fault that generated little coseismic slip inherent spatial variability in earthquake slip combined with the uncertainty in how interseismic creep affects coseismic slip results in large uncertainties in these slip estimates

uncertainty in strain rate from field measurements of the geometry rates and kinematics of active normal faults implications for seismic hazard assessment abstract multiple measurements of the geometry kinematics and rates of slip across the auletta fault campania italy are presented and we use these to determine 1 the spatial resolution of field measurements needed to accurately calculate a representative strain rate 2 what aspects of the geometry and kinematics would introduce uncertainty with regard to the strain rate if not measured in the field we find that the magnitude of the post last glacial maximum throw across the fault varies along strike if such variations are unnoticed different values for a representative strain rate hence different results in seismic hazard calculations would be produced to demonstrate this we progressively degrade our dataset calculating the implied strain rate at each step excluding measurements can alter strain rate results beyond 1 uncertainty thus we urge caution when using only one measurement of slip rate for calculating hazard we investigate the effect of approximating the throw profile along the fault with boxcar and triangular distributions and show that this can underestimate or overestimate the strain rate with results in the range of 72 237 of our most detailed strain rate calculation we discuss how improved understanding of the potential implied errors in strain rate calculations from field structural data should be implemented in seismic hazard calculations

a record of large earthquakes on the southern hayward fault for the past 1800 yearsa record of large earthquakes on the southern hayward fault for the past 1800 years

ground motion modeling of hayward fault scenario earthquakes part i construction of the suite of scenarios abstract we construct kinematic earthquake rupture models for a suite of 39 m w 6 6 7 2 scenario earthquakes involving the hayward calaveras and rodgers creek faults we use these rupture models in 3d ground motion simulations as discussed in part ii aagaard et al 2010 to provide detailed estimates of the shaking for each scenario we employ both geophysical constraints and empirical relations to provide realistic variation in the rupture dimensions slip heterogeneity hypocenters rupture speeds and rise times the five rupture lengths include portions of the hayward fault as well as combined rupture of the hayward and rodgers creek faults and the hayward and calaveras faults we vary rupture directivity using multiple hypocenters typically three per rupture length yielding north to south rupture bilateral rupture and south to north rupture for each rupture length and hypocenter we consider multiple random distributions of slip we use two approaches to account for how aseismic creep might reduce coseismic slip for one subset of scenarios we follow the slip predictable approach and reduce the nominal slip in creeping regions according to the creep rate and time since the most recent earthquake whereas for another subset of scenarios we apply a vertical gradient to the nominal slip in creeping regions the rupture models include local variations in rupture speed and use a ray tracing algorithm to propagate the rupture front although we are not attempting to simulate the 1868 hayward fault earthquake in detail a few of the scenarios are designed to have source parameters that might be similar to this historical event

earthquake recurrence on the south hayward fault is most consistent with a time dependent renewal process 1 elastic rebound and stress renewal are important components of earthquake forecasting because if large earthquakes can be shown to be periodic then rupture probability is time dependent while renewal models are used in formal forecasts it has not been possible to exclude the alternate view that repeated large earthquakes can happen in rapid succession without requiring time for stress regeneration here a consistency test between time dependent and time independent recurrence distributions is made using a monte carlo method to replicate the paleoseismic series on the south hayward fault time dependent distributions with recurrence interval of 210 years and coefficient of variation of 0 6 reproduce the event series on the south hayward 5 times more often than any exponential distribution a highly significant difference as determined using a two tailed z test for relative proportions therefore large hayward fault earthquakes are quasi periodic and are most consistent with a stress renewal process

seasonal patterns in permeable sediment and water column biogeochemical properties on the inner shelf of the middle atlantic bight abstract this study examines the responsiveness of permeable shelf sediments to seasonal factors affecting cycles of organic matter deposition and erosion at a site on the inner continental shelf within the middle atlantic bight 39 27 n 74 14 w water depth 13 m sediment inventories of chlorophyll phaeopigments and fine particles enriched in organic matter are reported from scuba diver collected cores retrieved during six cruises conducted over 2 years these measurements provide little evidence for substantial seasonal variation in rates of organic matter accumulation in spite of the potential for the sinking of large phytoplankton blooms associated with summer upwelling downwelling events or for wave orbital motion to cause both phytodetritus and benthic algae to be trapped in sand ripples sediment permeability porosity grain size and extracellular proteolytic activity in both coarse and fine fractions showed little seasonality instead a negative correlation between chlorophyll in surface sediments and bottom water pools r 2 0 56 was observed furthermore overlays of other water column properties with results of a principal component analysis of sediment variables suggest benthic pelagic biogeochemical cycling is forced primarily by sediment resuspension events wave and current observations made during this study and during previous long term experiments in the study area show that sediment resuspension stems from bottom stresses produced by both persistent irregular wind waves and by very intense storm waves that occur in all seasons

reply to comment on a natural gradient experiment on solute transport in a sand aquifer 2 spatial moments and the advection and dispersion of nonreactive tracers by d l freyberg

the use of 7be to identify event and seasonal sedimentation near the po river delta adriatic sea in october 2000 a major flood event of the po river occurred the resulting seabed deposit was initially sampled in december 2000 and most sites were reoccupied on subsequent cruises over a 3 yr period using the maximum penetration depth of the short lived radioisotope 7be half life 53 3 d the flood deposit was found to be up to 15 cm thick individual depocenters of thick strata were located immediately adjacent to the distributaries at the river mouth in relatively shallow water 30 m these flood deposit thicknesses are minimum estimates because the depth of 234th half life 24 1 d exceeds that of 7be in physically stratified flood sediment indicating that the first sediment deposited during the flood event likely originated from the river channel 30 55 of the estimated sediment load delivered to the shelf during the flood event can be accounted for using 7be penetration depths seasonal deposition also can be quantified using 7be after removing the effects of biological mixing seasonal deposition rates are a maximum of 6 cm yr 1 near the pila distributary decreasing to 2 cm yr 1 in the southern portions of the dispersal system

residence times of234th and7be in lake geneva the activities of two short lived natural radionuclides 234th and7be were measured in lake geneva water suspended solids and sediments in order to obtain their removal residence times in the lake four independent methods of estimation are presented and compared the calcuated residence times of234th and7be vary from 60 to 280 days and from 60 to 1100 days respectively depending on season and the method used in general 7be residence times are significantly longer than those of234th for both nuclides the removal residence times are significantly longer than their respective radioactive mean lives as a consequence the estimates based on their water column inventories are not as reliable as the estimates obtained from the measured fluxes of these nuclides into sediment traps estimates based on the bottom sediment inventories are similar in magnitude to those obtained from flux into sediment traps but occasionally are erroneous because of small scale sediment heterogeneity

time and depth scales of fine sediment delivery into gravel stream beds constraints from fallout radionuclides on fine sediment residence time and delivery abstract particles of fine sediment can clog interstitial pore spaces of coarser grained sediment in river beds and thereby impede the exchange of water dissolved constituents and particulate matter with consequent ecological impacts the extent to which fine sediment reduces connectivity between the stream bed and overlying channel is a function in part of sediment residence time short residence times imply frequent exchange of matter and reduced impact of fine sediment on stream bed habitat while long residence times indicate that with respect to fine sediment delivery the stream bed is more isolated from the overlying channel here we present a novel technique to quantify the residence time of river bed sediment at various depths over annual and decadal timescales using the fallout radionuclides frns 7be t1 2 53 days and 210pbex t1 2 22 3 years we placed mesh cylinders filled with 7be free sediment into a stream bed to quantify the capture of 7be tagged particles in the absence of scour and fill we also took cores to the depth of refusal in alluvial sediment in unregulated and regulated rivers in vermont and new hampshire sampled watershed areas ranged from 29 to 410 km2 and core depths ranged from 19 to 77 cm the 210pbex activity profiles of cores show that bed sediment is exchanged to the depth of refusal at decadal timescales in contrast 7be activity profiles indicate that fine sediment infiltrating into the bed had residence times ranging from 4 to 300 days in unregulated rivers cores from a regulated river are notably different subsurface sediment residence times were always longer than in unregulated rivers at comparable depths likely owing to restriction of bed mobilization and clogging of bed material by fine sediment these results suggest that filtration can be an important component of bed material delivery to stream beds but filtration does not deliver material as deeply into the bed as scour and fill we find that fallout radionuclides provide direct measurements of time and depth scales of active exchange of particulate matter which are key controls on hyporheic function

the utility of estuarine settling basins for constructing multi decadal high resolution records of sedimentation abstract obtaining long term records of sediment flux and sources to estuaries is a major challenge in coastal and estuarine research due to the dynamic processes that actively work to remove the high resolution long term sediment record examining cores from sediment settling basins directly adjacent to or within estuarine systems provides a potential alternative means of establishing a history of estuarine sedimentation as a recently established settling basin with high rates of sedimentation cape lookout bight nc presents an ideal coastal environment to capture a long term record of sedimentation in 2010 a 4 6 m long core was extracted from the deepest portion of the basin through lithologic description grain size water content and radioisotope analysis excess 210 pb a high resolution geochronology of sedimentation has been established for the basin the record begins with spit accretion that captured part of the marine shelf and formed the basin a transition in sediment type from dominantly marine through storm induced overwash to dominantly estuarine was identified in the basin this transition reflects the increased trapping efficiency of fine estuarine mud due to the changing geomorphology of the settling basin an abrupt increase in the rate of estuarine sedimentation occurred 1983 1985 after careful reconstruction of basin geomorphology this increased rate of sedimentation is not attributed to internal dynamics within the basin but instead is interpreted to be the result of increased estuarine sediment flux through barden s inlet from the upper estuary this work underscores the importance of considering changing basin physiography and sediment dynamics before interpreting the paleo record as those mechanisms can hide or eliminate allogenic signatures from the sediment profile

paleoseismic and postseismic observations of surface slip along the parkfield segment of the san andreas fault parkfield is considered a transitional segment along the san andreas fault saf between continuous fault creep to the northwest and segments to the southeast that last slipped in the great 1857 fort tejon earthquake historically creep and recurring m 6 0 earthquakes have been observed at parkfield california but the segment s relevance in great saf earthquakes has remained uncertain this paleoseismic study of the central parkfield segment provides a 2000 year record of tectonically deformed fluvial and sag stratigraphy two fault perpendicular excavations across a pressure ridge and a sag pond 200 m north of carr hill exposed five primary fault zones displaying apparent vertical offsets upward splaying clay shear bands and warped stratigraphy four of five fault zones extended into the uppermost stratigraphy suggesting recent surface offset and fault creep several antithetic fault splays and one primary fault zone displayed upward terminations but strong indicators of large magnitude earthquakes with meter scale surface offset and rupture such as filled fissures and colluvial scarp deposits were not observed the absence of evidence for large magnitude earthquakes does not preclude the possibility of 1857 style earthquakes extending into the parkfield segment however all deformation exposed within these trenches is consistent with repeated small ground rupture and fault creep the 2004 m 6 0 parkfield earthquake ruptured through the site and activated at least three of the five fault zones exposed in our excavations comparison between 2004 vertical offset and vertical offsets within the exposed stratigraphy suggests a recurrence interval between 8 and 188 years for m 6 0 earthquakes at parkfield online material supplemental unit descriptions unanalyzed radiocarbon samples and trench logs and photos

slip in the 1868 hayward earthquake from the analysis of historical triangulation data despite the importance of the hayward fault for earthquake hazards in the san francisco bay area neither the rupture length nor the average coseismic slip in the most recent major earthquake which occurred in 1868 is well known we estimate slip in the 1868 earthquake by analyzing triangulation data collected between 1853 1860 and 1876 1891 we apply a denuisancing procedure that projects out the dependence of that data on station coordinates allowing their displacements to be estimated directly the best fit to the data is obtained with a 52 km long by 10 km deep rupture that extends from warm springs to near berkeley considerably longer than the 30 km of reported surface breakage the estimated slip for an earthquake of this length is 1 9 0 4 m and the seismic moment is m0 3 0 0 7 1019 n m corresponding to mw 7 0 the data are inconsistent with regionally high strain rate prior to the 1906 earthquake as had been previously suggested the triangulation data record northeastward displacement of station loma prieta presumably as a result of the 1865 earthquake the fault normal displacement is not easily explained by slip on either the san andreas fault or the 1989 loma prieta rupture surface this observation is however consistent with an mw 6 3 4 thrust event northeast of the san andreas fault in the southern santa cruz mountains thrust belt

direct determination of7be in sediments cosmic ray produced7be 53 days half life is directly measurable in freshly collected samples of river and coastal zone sediments using a lithium drifted germanium detector calibration of the detector is discussed and an assessment of overall accuracy and sensitivity presented the detection limit for a 250 g dry weight sediment sample contained in a marinelli beaker and counted for 200 minutes is approximately 0 4 pci g applications toward locating zones of rapid sedimentation as well as in understanding shallow water sedimentation dynamics are suggested

beryllium in river baseflow shallow groundwaters and major aquifers of the u k abstract beryllium is potentially a highly toxic element which may be mobilised especially under acidic conditions in natural waters results from major aquifers the unsaturated zone from shallow groundwaters and river baseflow were used to establish the naturally occurring baseline concentrations in u k waters out of 924 samples from 13 aquifer units be was detected in only 12 samples in carbonate aquifers no be was found above the detection limit of 0 05 g l the occurrence of be 0 05 g l was restricted to arenaceous aquifers where concentrations up to 1 g l be were found mainly in the carboniferous millstone grit and lower cretaceous lower greensand aquifers interstitial water profiles from the unsaturated zones of the lower greensand surrey and triassic sandstone west midlands contain be concentrations in excess of 10 g l within the top 10 m which may persist to the water table at concentrations near to 1 g l be the only major anomaly to be found in river baseflow was from the mourne mountains of northern ireland where be concentrations of up to 4 7 g l were found associated with the outcrop of the tertiary granite intrusion elsewhere be 0 22 g l was found in neutral groundwaters derived from granite feeding the acid loch fleet southern scotland in which concentrations of 0 09 g l were maintained beryllium occurrence therefore depends strongly on geology the predominant aqueous species below ph 5 5 is be 2 and above this be oh dominates the presence of high al in most waters sampled greatly suppresses the formation of bef complex ions beryllium shows close geochemical behaviour with mg across a range of ph which may have environmental consequences if be substitution for mg takes place

meteoric cosmogenic beryllium 10 adsorbed to river sediment and soil applications for earth surface dynamics abstract rainfall scavenges meteoric cosmogenic 10be from the atmosphere 10be falls to the earth s surface where it binds tightly to sediment particles in non acidic soils over the life span of those soils as such meteoric 10be has the potential to be an excellent geochemical tracer of erosion and stability of surfaces in a diverse range of natural settings meteoric 10be has great potential as a recorder of first order erosion rates and soil residence times even though this tracer was first developed in the late 1980s and showed great promise as a geomorphic tool it was sidelined in the past two decades with the rise of the sister nuclide in situ 10be which is produced at a known rate inside quartz minerals since these early days substantial progress has been made in several areas that now shed new light on the applicability of the meteoric variety of this cosmogenic nuclide here we revisit the potential of this tracer and we summarize the progress 1 the atmospheric production and fallout is now described by numeric models and agrees with present day measurements and paleo archives such as from rain and ice cores 2 short term fluctuations in solar modulation of cosmic rays or in the delivery of 10be are averaged out over the time scale soils accumulate 3 in many cases the delivery of 10be is not dependent on the amount of precipitation 4 we explore where 10be is retained in soils and sediment 5 we suggest a law to account for the strong grain size dependence that controls adsorption and the measured nuclide concentrations and 6 we present a set of algebraic expressions that allows calculation of both soil or sediment ages and erosion rates from the inventory of meteoric 10be distributed through a vertical soil column the mathematical description is greatly simplified if the accumulation of 10be is at a steady state with its export through erosion in this case a surface sample allows for the calculation of an erosion rate explored further this approach allows calculation of catchment wide erosion rates from river sediment similar to the approach using 10be produced in situ in contrast to the in situ 10be approach however these analyses can be performed on any sample of fine grained material even where no quartz minerals are present therefore this technique may serve as a tool to date sediment where no other chronometer is available to track particle sources and to measure earth surface process rates in soil suspended river sediment and fine grained sedimentary deposits

the 1978 borden tracer experiment analysis of the spatial moments a reanalysis of the 1978 tracer experiment at borden ontario is performed using spatial moments the tracer experiment involved the uniform injection of chloride ions into an aquifer and the resulting plume was allowed to migrate under natural gradient conditions detailed monitoring of the evolving plume was then performed in three dimensions the work of sudicky et al 1983 showed that the solute cloud evolved as two plumes owing to variations in hydraulic conductivity at the site in this paper we compute the zeroth through the fourth spatial moments of the plume in the lower hydraulic conductivity zone from these moments the solute mass of the plume the velocity of the center of mass the dispersion the skew and the kurtosis of the plume are calculated these results are compared with the results of sudicky et al as well as with the theoretical results of gelhar et al 1979 and naff 1990 our computed plume velocity and apparent horizontal transverse macrodispersivity are in agreement with the estimates of sudicky et al however our apparent longitudinal macrodispersivity estimate exceeds that of sudicky et al by a factor of 2 the apparent horizontal transverse macrodispersivity obtained is also quite similar to that of freyberg 1986 at early times the plume is found to be positively skewed as well as platykurtic this supports the findings of gelhar et al and contradicts those of naff

210pb and210po during the destruction of stratification in the dead sea abstract the progressive weakening and final disappearance in 1979 of the long term meromictic structure of the dead sea are clearly reflected in the depth profiles of 210 pb and 210 po in 1977 78 prior to overturn dissolved 210 pb 35 50 dpm kg 1 predominated over particulate 210 pb 1 2 dpm kg 1 in the oxic upper waters whereas the reverse was true in the anoxic deep waters 16 20 dpm kg 1 particulate vs 2 5 dpm kg 1 dissolved the exact extent of the disequilibrium between 210 pb and 226 ra is hard to evaluate in the upper oxic layers because the progressive deepenings resulted in mixing with deep waters by contrast one can estimate the residence time of dissolved 210 pb in the unperturbed anoxic deepest layers because these remained isolated at about 3 years following the overturn of 1979 dissolved 210 pb exceeded particulate 210 pb at all depths the 210 po profiles of the stratified lake resembled in shape those of its grandparent 210 pb but with distinct characteristics of their own in the oxic upper waters where particulate 210 po 8 12 dpm kg 1 was greatly in excess over particulate 210 pb while dissolved 210 po 25 40 dpm kg 1 was slightly deficient immediately following the overturn dissolved and particulate 210 po were similar about 15 dpm kg 1 at all depths the destruction of the lake s meromictic structure was accompanied by a reduction of its 210 pb inventory while that of 210 po was almost unaffected thus at overturn a transient state was created with the inventory of 210 po exceeding that of 210 pb

constraining the timescales of sediment sequestration associated with large woody debris using cosmogenic 7be 1 the beneficial ecogeomorphic functions associated with large woody debris lwd in fluvial environments are well documented and include positive sediment impacts such as channel margin sequestration increased substrate heterogeneity and decreased channel embeddedness as well as numerous secondary benefits such as nutrient retention and increased habitat heterogeneity despite an extensive literature documenting such positive sediment attributes of lwd in forested channels a quantitative analysis of in channel sediment storage times associated with channel obstructions has traditionally been difficult to assess in this study along a 9 km stretch of the ducktrap river in coastal maine we present a novel application of fallout cosmogenic 7be t1 2 53 days coupled with a constant initial activity cia sediment aging model to quantitatively assess transitional bed load storage times in bars associated with in channel obstructions lwd and boulders we find that reach scale variability in unit stream power and lwd frequency affect sediment storage times with transport limited reaches providing longer term sediment sequestration generally 100 days associated with in channel obstructions than supply limited ones 100 days estimates of sediment baraccumulation rates also varied between reaches from 0 2 g cm 2 d 1 in the supply limited reach to 0 7 g cm 2 d 1 in the transport limited reach last greater frequency of sites increased sediment volumes and storage times and naturally viable recruitment mechanisms for lwd in forested channels document its superior ecogeomorphic function when compared to boulders in this study even in the ducktrap river where twentieth century logging has greatly reduced the size frequency and geomorphic efficacy of in channel wood this study has implications for channel restoration efforts and documents a novel application of 7be and cia methodology to constraining transitional bed load storage times in the fluvial environment

holocene slip rate of the hayward fault at union city california measured offsets of well dated alluvial fan deposits near the masonic home in union city constrain holocene slip rate of the hayward fault between 7 and 9 mm yr our best minimum geologic slip rate over the past 8 27 0 08 kyr i e 8270 years is 8 0 0 7 mm yr a steep stream its channel cut into bedrock flows southwest out of the east bay hills crosses the fault and deposits its load on an alluvial fan we cut two 5 m deep fault parallel trenches 20 30 m southwest of the main fault through the crest of the fan walls of the trenches reveal a series of nested distributary channel fills these channels had cut into old surfaces that are indicated by paleosols developed on flood silts we distinguished many channel fills by their shape clast size flow direction elevation and relation to paleosols enabling us to correlate them between both trenches two distinct episodes of fan deposition occurred during the holocene reconstructing the apex positions of these fan units indicates that about 42 6 m and 66 6 m of fault slip has occurred since their inceptions at about 4 58 0 05 ka and 8 27 0 05 ka respectively we lowered the age and age uncertainty of the younger unit from earlier reports based on new multiple radiocarbon dates the 4 58 ka slip rate of 9 2 1 3 mm yr is not significantly different at 95 confidence from the 8 27 ka slip rate of 8 0 0 7 mm yr because current regional strain rates are fully consistent with neogene plate tectonic rates lisowski et al 1991 and the historic surface rate of creep in union city is only 4 7 0 1 mm yr galehouse 1994 the larger 8 mm yr holocene slip rate implies that strain is now accumulating on a locked zone at depth the 8 mm yr rate is probably minimal because earlier trenching evidence nearby implies that some unknown additional amount of fault deformation occurs outside of the narrow fault zone assumed in measuring slip lienkaemper et al 1991 suggest that the fast creep rate of 9 mm yr measured near the southern end of the hayward fault may underestimate the deep slip rate because 1868 surface slip occurred there in addition to the continuing fast creep if the historic deep slip rate equals the long term rate then the 9 mm yr creep rate reflects the minimum seismic loading rate of the hayward fault better than the 8 mm yr holocene rates do