geologist controlled trends versus computer controlled trends introducing a high resolution approach to subsurface structural mapping using well log data trend surface analysis and geospatial analysisa companion paper to mei s 2009 new insights on faults in the peace river arch region northwest alberta based on existing well log data and refined trend surface analysis canadian journal of earth sciences 46 1 41 65 this paper introduces a refined trend surface analysis tsa for detecting faults with small metre scale offsets 5 20 m conventional tsa uses a global polynomial method to model the trend the power of the polynomial e g first second or third order is the only parameter for input the refined approach is different in that it uses local fit techniques to generate the trend the refined approach provides greater flexibility for inputting geological knowledge in the trend surface modelling process this results in a trend surface with the maximum amount of unwanted information which is removed from the residual surface after removal of the trend from the data leaving features of interest optimally highlighted in the residuals such a trend is referred to as a geologist controlled trend to differentiate it from the trend surface modelled by conventional tsa which is primarily a computer controlled global polynomial surface the refined approach goes one step beyond conventional tsa by incorporati

the roles of elevation and salinity as primary controls on living foraminiferal distributions cowpen marsh tees estuary uk abstract benthic foraminiferal assemblages in subrecent deposits are commonly used to reconstruct past sea level interpretations are generally made by comparison with either modern dead or total live plus dead assemblages in both cases there will have been post mortem changes that have differentially affected preservation it is therefore important to establish the primary ecological controls by analysis of the living assemblages we have determined the spatial and temporal variability of intertidal benthic foraminifera in the surface 0 1 cm sediments from a time series survey of 31 sampling stations at cowpen marsh for a period of 12 months we counted 112 067 live foraminifera assigned to 28 species the fauna was dominated by two agglutinated species jadammina macrescens and trochammina inflata on the high and middle marshes and three calcareous species elphidium williamsoni haynesina germanica and quinqueloculina spp on the low marsh and tidal flat the standing crop of the whole intertidal zone including the high middle low marsh and tidal flat habitats and the individual species varied both temporally and spatially the standing crop of the intertidal zone as a whole was greatest in the summer months and showed a positive correlation with elevation the standing crops of the high and middle marshes showed similar temporal variation with peaks in summer and autumn and a trough in winter the low marsh showed numerous peaks and troughs of standing crop during the year whereas the tidal flat showed a single peak in summer the standing crops of jadammina macrescens and trochammina inflata on the high and middle marshes peaked from april to may and august to october with troughs in winter these agglutinated species showed a strong correlation with elevation haynesina germanica peaked in may to august and november to january on the low marsh whereas on the tidal flat there was a single peak in july the standing crops of e williamsoni on the low marsh and tidal flat were relatively high in june and may and july respectively quinqueloculina spp peaked in may to july on the low marsh and july on the tidal flat the species was also found in the middle marsh from july to may and high marsh from september to november haynesina germanica showed a strong negative correlation with elevation whereas the other two dominant calcareous species demonstrated weak negative correlations with both elevation and salinity reconstructing former sea level depends primarily on the recognition of high and middle marsh assemblages and in this study these are shown to be strongly controlled by elevation rather than salinity caution may be needed in interpreting low marsh and tidal flat data as salinity plays a more important role here

distribution of aseismic slip rate on the hayward fault inferred from seismic and geodetic data 1 we solve for the slip rate distribution on the hayward fault by performing a least squares inversion of geodetic and seismic data sets our analysis focuses on the northern 60 km of the fault interferometric synthetic aperture radar insar data from 13 independent ers interferograms are stacked to obtain range change rates from 1992 to 2000 horizontal surface displacement rates at 141 bench marks are measured using gps from 1994 to 2003 surface creep observations and estimates of deep slip rates determined from characteristic repeating earthquake sequences are also incorporated in the inversion the fault is discretized into 283 triangular dislocation elements that approximate the nonplanar attributes of the fault surface south of the city of hayward a steeply east dipping fault geometry accommodates the divergence of the surface trace and the microseismicity at depth the inferred slip rate distribution is consistent with a fault that creeps aseismically at a rate of 5 mm yr to a depth of 4 6 km the interferometric synthetic aperture radar insar data require an aseismic slip rate that approaches the geologic slip rate on the northernmost fault segment beneath point pinole although the insar data might be complicated by a small dip slip component at this location a low slip rate patch of 1 mm yr is inferred beneath san leandro consistent with the source location of the 1868 earthquake we calculate that the entire fault is accumulating a slip rate deficit equivalent to a mw 6 77 0 05 per century however this estimate of potential coseismic moment represents an upper bound because we do not know how much of the accumulated strain will be released through aseismic processes such as afterslip

monitoring aseismic surface creep along the north anatolian fault turkey using ground based lidar abstract we studied the surface creep along the north anatolian fault naf one of the most seismically active structures of the eastern mediterranean by using a ground based light detection and ranging lidar system at the ismetpasa and destek sections aseismic surface creep has been known to exist at ismetpasa since the 1970s but it has not been previously reported for the destek site three manmade walls across the fault were monitored for 3 yrs between june 2007 and november 2009 using lidar the surveys revealed that a significant amount of aseismic strain is being continuously released along these sections of the naf 6 8 10 0 4 0 mm yr and 9 1 10 1 4 0 mm yr at two sites near ismetpasa and 6 0 7 2 4 0 mm yr at destek despite this these fault segments are still capable of generating large earthquakes since 50 70 of the yearly slip i e 20 25 mm yr still accumulates on the fault as was demonstrated by the well known 20th century earthquake sequence of 1939 1999

estuaries of the past and present a biofacies perspective abstract estuaries are complex sedimentary and ecological systems where controlling factors are variable largely depending on wave vs tidal dominance and fluvial processes paleoenvironmental reconstruction of their ancient counterparts in the form of coastal valley deposits in the subsurface or outcrop requires a multidisciplinary approach microfossils can play an integral part in identifying estuarine subenvironments foraminifera can be abundant in modern estuaries and resemble characteristics of brackish ichnofaunal communities in featuring low species diversity but high abundances of opportunistic species different feeding strategies and common infaunal species whereas sediment distribution is highly controlled by energy regimes foraminifera seem to respond to salinities and tidal exposure whereas individual taxa can widely range bathymetrically the combination of certain taxa becomes diagnostic for estuarine environments fossil marginal marine assemblages are dominated by agglutinated species due to taphonomic loss of the calcareous component that is often dominant in modern estuaries when comparisons between fossil and modern assemblages are undertaken it is advisable to compare with recent subsurface or remnant assemblages for a more accurate basis of paleoenvironmental interpretation more integrated research with detailed taphonomic observations is needed on ancient coastal valley deposits to find the paleoecological requirements of extinct taxa and their link to sedimentary facies and ichnofacies

living stained benthic foraminifera within surficial sediments of the skagerrak abstract an analysis of living stained benthic foraminifera within four box cores raised from water depths of 74 to 621 m in the skagerrak shows that faunal patterns at different water depths are strikingly different within this relatively shallow organicrich marginal sea environment although some genera show vertical stratification within the sediments a number of taxa are found over wide intervals or have different patterns between cores the vertical distributional data are compared with deep sea data from the eastern margin of north america benthic foraminifera from a deep core at 530 m in the skagerrak have similar faunal patterns within the surficial sediments as found in the deep sea but shallow cores at 74 and 212 m have more complex patterns this difference between shallow and deep cores within the skagerrak and the north atlantic is attributed to higher biological activity in the shallow environments which creates a greater amount of heterogeneity within the shallow water sediments than is found in deeper environments the faunal data suggest that the use of benthic foraminifera for paleoenvironmental reconstructions in shallow organicrich regions will be complicated in future studies the ecology of individual species is difficult to assess because of the complex faunal patterns observed within the surficial sediments geochemical studies for estimating bottom water oxygen or organic carbon flux will also be difficult since these studies assume that taxa occupy particular microhabitats within the surficial sediments

the most recent large earthquake on the rodgers creek fault san francisco bay area the rodgers creek fault rcf is a principal component of the san andreas fault system north of san francisco no evidence appears in the historical record of a large earthquake on the rcf implying that the most recent earthquake mre occurred before 1824 when a franciscan mission was built near the fault at sonoma and probably before 1776 when a mission and presidio were built in san francisco the first appearance of nonnative pollen in the stratigraphic record at the triangle g ranch study site on the south central reach of the rcf confirms that the mre occurred before local settlement and the beginning of livestock grazing chronological modeling of earthquake age using radiocarbon dated charcoal from near the top of a faulted alluvial sequence at the site indicates that the mre occurred no earlier than a d 1690 and most likely occurred after a d 1715 with these age constraints we know that the elapsed time since the mre on the rcf is more than 181 years and less than 315 years and is probably between 229 and 290 years this elapsed time is similar to published recurrence interval estimates of 131 to 370 years preferred value of 230 years and 136 to 345 years mean of 205 years calculated from geologic data and a regional earthquake model respectively importantly then the elapsed time may have reached or exceeded the average recurrence time for the fault the age of the mre on the rcf is similar to the age of prehistoric surface rupture on the northern and southern sections of the hayward fault to the south this suggests possible rupture scenarios that involve simultaneous rupture of the rodgers creek and hayward faults a buried channel is offset 2 2 1 2 0 8 m along one side of a pressure ridge at the triangle g ranch site this provides a minimum estimate of right lateral slip during the mre at this location total slip at the site may be similar to but is probably greater than the 2 0 3 0 2 m measured previously at the nearby beebe ranch site

historic surface slip along the san andreas fault near parkfield california the parkfield earthquake prediction experiment is focusing close attention on the 44 km long section of the san andreas fault that last ruptured seismically in 1966 ms 6 0 the 20 km long central segment of the 1966 parkfield rupture extending from the mainshock epicenter at middle mountain southeastward to gold hill forms a 1 to 2 km salient northeastward away from the dominant n40 w strike following the 1966 earthquake afterslip aseismic slip has been nearly constant moderate parkfield earthquakes have recurred on average every 21 years since 1857 when a great earthquake m 8 ruptured at least as far north as the southern parkfield segment many measurements of slip have been made near parkfield since 1966 nevertheless much of the history of surface slip remained uncertain especially the total amount associated with the 1966 event in 1985 we measured accumulated slip on the four oldest cultural features offset by the fault along the 1966 parkfield rupture segment we interpret net slip on each feature as a sum of event slip sum of coseismic and rapid preseismic and postseismic slip from parkfield earthquakes and steady interseismic slip as measured over the last 20 years on nearby alinement arrays creep meters and trilateration lines we assumed for each site that event slip was identical for the 1922 1934 and 1966 parkfield events and that long term average rate of interseismic slip was constant between all events two fences on the southern segment southeast of gold hill indicate event slip of 13 and 15 cm and interseismic slip rate of 0 36 and 0 30 cm yr since 1959 and 1908 respectively at these sites redundant independent data support our assumption that both event and interseismic slip occur uniformly on the central segment near parkfield both the 1934 and the 1966 ruptures offset a bridge built in 1932 interseismic slip rate near the bridge has been about 1 1 cm yr since 1966 thus we deduce an average event slip of 31 cm for the 1934 and 1966 earthquakes on a parallel fault trace 1 km to the southwest slip was about 8 cm in 1966 thus total event slip summed across the entire fault zone near parkfield was nearly 40 cm on middle mountain 4 km north of the 1966 mainshock epicenter an offset fence indicates 17 cm of slip in 1966 and a 2 26 cm yr interseismic slip rate since circa 1946 thus the central segment of the 1966 rupture is characterized by much larger event slip 40 cm than both distal segments 15 cm this amount of surface slip per event is about twice what had been previously assumed larger 1966 surface slip in the central part of the rupture is geodetically compatible with a coseismic slip of 65 10 cm slip on a narrow buried asperity between middle mountain and gold hill that has been inferred from the depth distribution of early aftershocks assuming our characteristic surface slip model one can further deduce a deficit in slip since the great 1857 earthquake taking the long term slip rate as 3 3 cm yr the surface slip deficit is 3 0 2 m south of gold hill but only 0 3 0 3 m northward from parkfield

microhabitats of salt marsh foraminifera st catherines island georgia usa abstract salt marsh foraminifera of st catherines island georgia occupy a range of epibenthic to deep infaunal to 30 cm micro habitats freshly collected specimens of arenoparrella mexicana from 27 to 30 cm below the marsh surface extruded pseudopodial nets and actively collected foreign material about the aperture salt marsh foraminifera may be primarily epibenthic 0 1 cm epibenthic to intermediate infaunal 0 10 cm or deep infaunal 0 30 cm most of the twelve commonly occurring species in st catherines island marshes are epibenthic to intermediate infaunal species distributional patterns differ with regard to maximum depth of infaunal occurrences infaunal microhabitat utilization in different marsh zones and environments and the presence or absence of subsurface population maxima selective preservation impacts both calcareous and agglutinated foraminifera intense bioturbation primarily by halophytes and decapod crustaceans may contribute to the deep infaunal occurrences of foraminifera in these environments

the off fault deformation on the north anatolian fault zone and assessment of slip rate from carbonate veins abstract discrepancies in earthquake characteristics between geodetically determined and geologically observed slip rates are prominent for the eastern part of the north anatolian fault naf zone we investigated the spatial distribution of deformation across a naf fault segment near erzincan ne turkey through field observations of physiographic features along the principle fault and a carbonate filled fissure system we propose that distributed deformation across the principal fault in a stretching zone caused sigmoidal simple shear rotation of the carbonate filled fissure system displacement data of that sigmoidal fissure using isotopic age data of the carbonate fill indicates an off fault deformation rate of 15 90 3 19 mm per year for the holocene which corresponds to at least 50 of the geodetically estimated annual slip across the fault it is critical to take the distributed deformation into account for determining earthquake characteristics of active fault systems

reconstructing relative sea level change using uk salt marsh foraminifera abstract the position of past sea levels can be reconstructed using a series of sea level index points that possess information on age location altitude and a quantified vertical relationship with a former tidal frame the indicative meaning whilst these points fix the altitude of relative sea level at one instant in time they provide no information on its variation between them here a foraminiferal transfer function is used to reconstruct changes in water depth from fossil assemblages preserved within salt marsh sediments the transfer function performs reliably in the high marsh zone where agglutinated foraminiferal species are dominant in lower marsh environments where calcareous species are prevalent postmortem test dissolution alters the fossil assemblages and leaves them without modern analogues to circumvent this problem a new transfer function based on agglutinated foraminifera and utilising preserved test linings is developed this new transfer function significantly reduces the number of samples without modern analogues but at the expense of diminished sensitivity in the low marsh environment additionally the transfer function is used to establish a series of sea level index points that place observed lateral shifts in depositional environment into a vertical and temporal context the combination of age altitude and high resolution water level reconstructions offers the potential to obtain more detailed and reliable records of relative sea level change from salt marsh sediments

recent salt marsh development and natural regeneration of reclaimed areas in the plentzia estuary n spain the distribution of benthic foraminifera a range of elements and 137cs and 210pb were studied in surface sediments and 0 5 m cores from the plentzia estuarine marshes northern spain to determine the recent development of these previously reclaimed coastal areas these marshes receive abundant calcium carbonate from regional rocks and this allows calcareous foraminifera to colonize all marsh subenvironments good preservation of the original foraminiferal assemblages in the buried sediments is also favoured by high regional background carbonate benthic foraminifera are shown to be sensitive to both elevation above mean sea level exposure and salinity results from the chemical analyses indicate moderate anthropogenic pollution in the estuary and maximum input seems to have occurred in the 1960s recent marsh foraminiferal assemblages are good analogues for the palaeoenvironmental interpretation of historical and holocene cores and the combined micropalaeontological geochemical approach is demonstrated to be successful for the identification of short term anthropogenic impacts on this coastal region

re evaluation of the 1836 hayward fault and the 1838 san andreas fault earthquakes abstract current seismic hazard models include two major earthquakes m 7 in the san francisco bay area that are close in space and time an 1836 event on the northern hayward fault and an 1838 event on the peninsula section of the san andreas fault analysis and interpretation of the available historical accounts indicate that the 1836 event occurred east of monterey bay far from the hayward fault and was of m 6 also the 1838 event was not confined to the 60 km peninsula san andreas as current models indicate instead faulting probably extended from san francisco to san juan bautista 140 km indicating a significantly larger earthquake m 7 than previously thought damaging effects of the 1836 earthquake were reported only from santa clara to carmel and no contemporary effects were reported to the north of santa clara or near the hayward fault the illusion of an 1836 hayward earthquake evolved from a newspaper reminiscence published following the 1868 hayward earthquake stating that the 1868 effects in the east bay were similar to those of an 1836 event the article describes various strong effects in the east bay that differ completely from the effects recorded for the 1836 earthquake but are very similar to those documented for the major 1838 san andreas earthquake that caused extensive damage on both sides of san francisco bay based on this and other evidence we conclude that the reminiscence describes the destructive june 1838 effects but it erroneously indicates the date as june 1836 there is no evidence for any major historical earthquakes in the san francisco bay area before the 1838 earthquake back to the founding of mission san francisco dolores in 1776 during the 1838 san andreas fault earthquake the shaking intensity in monterey was as strong as or stronger than during the great 1906 san andreas fault earthquake this suggests that the 1838 san andreas fault rupture may have extended to san juan bautista as it did in 1906 numerous probable aftershocks were felt in the area south of san juan bautista these damaged carmel and santa cruz in 1840 and alisal 16 km west of the san andreas fault in 1841 the northern end of the 1838 faulting was previously assumed to be 25 km south of san francisco however mission san francisco dolores was damaged in 1838 but not in 1906 suggesting that the 1838 faulting extended to san francisco also the 1838 aftershocks were felt in oakland as frequently and violently as those following the major 1868 hayward earthquake suggesting that the 1838 faulting on the san andreas extended to the latitude of oakland the 1838 fault segment ruptured again 68 years later as part of the overlapping 1906 san andreas fault rupture this and similar evidence from southern california indicates that m 7 san andreas fault earthquakes can recur at intervals of 68 years or less when they are followed by m 8 earthquakes on overlapping segments of the fault

creeping along the ismetpasa section of the north anatolian fault western turkey rate and extent from insar creeping along the north anatolian fault naf at ismetpasa turkey was discovered some thirty years ago about a decade after the first observations of the phenomenon along the san andreas fault in california however little is known about its lateral extent and rate in order to study its three dimensional nature and rupture characteristics we use synthetic aperture radar interferometry insar and elastic dislocation models compared also with field observations interferograms with temporal baselines ranging between 1 25 and 5 years show that the creeping section starts at the western termination of the 1943 m 7 6 earthquake rupture it continues about 70 km to the west overlapping with the eastern part of the 1944 m 7 3 earthquake rupture offsets along strike indicate a maximum creep rate of 11f3 mm year near the mid point of the creeping section decreasing gradually towards the edges near ismetpasa insar data yield 8f3 mm year of creep rate consistent with recent instrumental triangulation and creepmeter measurements modeling of the insar and gps data suggests that the faultcreep occurs most probably at a shallow depth 0 7 km our analysis combined with previous studies suggests that creeping might have commenced following the 1944 earthquake and thus may be a long lasting but transient slip episode d 2005 elsevier b v all rights reserved

evidence for surface rupture in 1868 on the hayward fault in north oakland and major rupturing in prehistoric earthquakes wgcep90 estimated the hayward fault to have a high probability 0 45 in 30 yr of producing a future m7 bay area earthquake this was based on a generic recurrence time and an unverified segmentation model because there were few direct observations for the southern fault and none for the northern hayward fault to better constrain recurrence and segmentation of the northern hayward fault we trenched in north oakland unexpectedly we observed evidence of surface rupture probably from the m7 1868 earthquake this extends the limit of that surface rupture 13 km north of the segmentation boundary used in the wgcep90 model and forces serious re evaluation of the current two segment paradigm although we found that major prehistoric ruptures have occurred here we could not radiocarbon date them however the last major prehistoric event appears correlative with a recently recognized event 13 km to the north dated ad 1640 1776

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

seismic velocity structure and seismotectonics of the eastern san francisco bay region california the hayward fault system is considered the most likely fault system in the san francisco bay area california to produce a major earthquake in the next 30 years to better understand this fault system we use microseismicity to study its structure and kinematics we present a new 3d seismic velocity model for the eastern san francisco bay region using microseismicity and controlled sources which reveals a 10 velocity contrast across the hayward fault in the upper 10 km with higher velocity in the franciscan complex to the west relative to the great valley sequence to the east this contrast is imaged more sharply in our localized model than in previous regional scale models thick cenozoic sedimentary basins such as the livermore basin which may experience particularly strong shaking during an earthquake are imaged in the model the accurate earthquake locations and focal mechanisms obtained by using the 3d model allow us to study fault complexity and its implications for seismic hazard the relocated hypocenters along the hayward fault in general are consistent with a near vertical or steeply east dipping fault zone the southern hayward fault merges smoothly with the calaveras fault at depth suggesting that large earthquakes may rupture across both faults the use of the 3d velocity model reveals that most earthquakes along the hayward fault have near vertical strike slip focal mechanisms consistent with the large scale orientation and sense of slip of the fault with no evidence for zones of complex fracturing acting as barriers to earthquake rupture online material velocity model validation experiments and additional seismicity plots

historic creep rate and potential for seismic slip along the hayward fault california the hayward fault is considered the most likely source of one or more major earthquakes in the san francisco bay area in the next few decades historically at least one and probably two major earthquakes about m 6 8 occurred along the hayward fault one in 1836 and another in 1868 little is known about the 1836 event but the 1868 earthquake was accompanied by a surface rupture that extended as much as 41 km along the southern part of the fault although the amount of surface slip in 1868 is uncertain right slip including afterslip reached at least several centimeters and possibly several decimeters in places this paper documents the spatial variation of creep rate along the hayward fault since the 1868 earthquake creep aseismic fault slip occurs over at least 66 km and may extend over the fault s entire 82 km length of which about 13 km lies underwater creep rate seems nearly constant over decades but short term variations occur we derive creep rate mainly from our own systematic surveying of offset cultural features curbs fences and buildings on each feature we solve directly for accumulated creep by using multiple linear regression creep rate mostly falls in the range of 3 5 6 5 mm yr but systematic variation occurs along strike fault segments with distinctly higher and lower rates generally correspond to parts of the fault most salient from the overall average alinement of the fault most distinctive is a 4 km long section near the south end of the fault that creeps at about 9 mm yr such a high rate has occurred there at least since the 1920s and probably since the 1868 earthquake as indicated by an offset railroad track built in 1869 we suggest that this 9 mm yr slip rate may approach the long term or deep slip rate that controls average recurrence interval between major earthquakes if so assuming an elastic rebound model the potential for slip in large earthquakes below the surficial creeping zone is now 1 1 m in the southern 1868 segment of the fault and 1 4 m in the northern 1836 segment subtracting surface creep rates from a long term slip rate of 9 mm yr gives present potential for surface slip in large earthquakes of up to 0 8 m with an average of 0 6 m in the northern segment and 0 4 m in the southern segment we present a simple hypothesis for rupture potential that is compatible with historic creep rate microseismicity distribution and geodetic data if seismic rupture occurs on segments 41 km long by 10 km deep 7 km fully locked 3 km creeping today s potential for seismic moment release is 1 4 1019 and 1 1 1019 n m for both 1836 and 1868 segments respectively and 2 5 1019 n m for both segments jointly converting moment to magnitude gives ml 6 8 in the northern segment ml 6 7 in the southern segment and ml 7 0 for simultaneous rupture of both

microseismicity and creeping faults hints from modeling the hayward fault california usa abstract creeping segments of strike slip faults are often characterized by high rates of microseismicity on or near the fault this microseismicity releases only a small fraction of the slip occurring on the fault and the majority of the accumulating elastic strain is released either through aseismic creep or in rare large events distinguishing between creeping or non creeping patches on faults and determining the resulting accumulated slip deficit is important in assessing the seismic hazard associated with a fault unfortunately surface creep data alone are insufficient to constrain the creep at depth on the fault here we analyze the possibility of using microseismicity as a further constraint an analysis of the accumulation of coulomb stress associated with the fault creep indicates that the transition from creeping regions to locked patches has the potential to affect the local seismicity pattern precise relative relocations of the microseismicity of the hayward fault 1 f waldhauser w l ellsworth fault structure and mechanics of the hayward fault california from double difference earthquake locations j geophys res 107 3 doi 10 1029 2000jb000084 2002 indicate that a fraction of the events repeat indicating recurrent ruptures of the same small patch a comparison of the creeping pattern resulting from a finite element deformation model with this precisely relocated microseismicity indicates that the non repeating earthquakes mainly occur in the transitional zones from creeping to locked patches while recurrent repeating earthquakes cluster in high creep rate regions building from this observation we have developed an analysis approach to better define patterns of creep and thus the slip deficit on the hayward fault additionally this creep rate and its spatial pattern on the fault vary as a function of time after the system is loaded by earthquakes on the locked patches

using foraminiferal transfer functions to produce high resolution sea level records from salt marsh deposits maine usa quantitative analyses of foraminiferal distributions along the coast of maine are used to provide transfer functions for reconstruction of sea level changes from fossil foraminiferal assemblages the indicative meaning of fossil assemblages is most accurately predicted by a training set that incorporates live and dead foraminifera and that uses flooding duration not height as the predictor variable sea level records are produced for two sites in maine usa a middle marsh site in scarboro and a high marsh site in machiasport these records offer temporal resolution of five to seven years and span the past century they are compared with instrumental data from a nearby tidal station to assess their accuracy strong correlations are found between the geologic records and the observational data in particular between the foraminiferal record from machiasport and the tide gauge record from eastport r2 0 83 p 0 005 thus a foraminifera based transfer function approach offers great potential for reso

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

empirical constraints on magnitude distance relationships for seismically induced submarine tsunamigenic landslides abstract seismically induced submarine landslide tsunamis here called silts attract growing attention due to their unique setting damage potential and short warning time a question of key importance especially for tsunami early warning is how far can an earthquake trigger a tsunamigenic slump here we investigate the relationships between earthquake magnitude and the maximal distance between the seismogenic fault and the tsunamigenic slumps rf and between the earthquake epicenter and the slump re and propose empirical constraints on these magnitude distance m d relations the 49 identified silts are spread in various seismotectonic and bathymetric settings in different seas around the globe we found that the maximal distance of the tsunamigenic submarine landslide from the parent earthquake grows with the magnitude and is bounded by an envelope constrained by mw as low as 4 9 for several kilometers the 1968 liguria coast italy and as far as 250 km for mw 7 7 the 1819 rann of kachchh india higher earthquake magnitudes also produce silts seemingly distances lower than 250 km however it is suspected that the available data is limited and unable to reflect the true nature of silt s generation generalized empirical relations between the earthquake magnitude mw and the maximal distance from the seismogenic fault to its generated silt rf in km are log rf 1 17 0 49 mw r2 0 78 the empirical distance between the earthquake epicenter and the corresponding tsunamigenic slump re in km is log re 0 87 0 45 mw r2 0 83 although many earthquakes within the m d bounding envelope did not produce tsunamis the successful events still enable the delineation of the m d zone vulnerable to tsunami generation which in turn can be applied to tsunami early warning procedures this is particularly important for near coast inland earthquakes as their tsunamigenic potential might be overlooked

variability of intertidal foraminiferal assemblages in a salt marsh oregon usa we studied 18 sampling stations along a transect to investigate the similarity between live rose bengal stained foraminiferal populations and dead assemblages their small scale spatial variations and the distribution of infaunal foraminifera in a salt marsh toms creek marsh at the upper end of the south slough arm of the coos bay estuary oregon usa we aimed to test to what extent taphonomic processes small scale variability and infaunal distribution influence the accuracy of sea level reconstructions based on intertidal foraminifera cluster analyses have shown that dead assemblages occur in distinct zones with respect to elevation a prerequisite for using foraminifera as sea level indicators our nonparametric multivariate analysis of variance showed that small scale spatial variability has only a small influence on live rose bengal stained populations and dead assemblages the dissimilarity was higher however between live rose bengal stained populations in the middle marsh we observed early diagenetic dissolution of calcareous tests in the dead assemblages if comparable post depositional processes and similar minor spatial variability also characterize fossil assemblages then dead assemblage are the best modern analogs for paleoenvironmental reconstructions the toms creek tidal flat and low marsh vascular plant zones are dominated by miliammina fusca the middle marsh is dominated by balticammina pseudomacrescens and trochammina inflata and the high marsh and upland marsh transition zone are dominated by trochamminita irregularis analysis of infaunal foraminifera showed that most living specimens are found in the surface sediments and the majority of live rose bengal stained infaunal specimens are restricted to the upper 10 cm but living individuals are found to depths of 50 cm the dominant infaunal specimens are similar to those in the corresponding surface samples and no species have been found living solely infaunally the total numbers of infaunal foraminifera are small compared to the total numbers of dead specimens in the surface samples this suggests that surface samples adequately represent the modern intertidal environment in toms creek

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