changing views of the san andreas fault the magnitude 7 0 earthquake that struck haiti on 12 january 2010 is a reminder of the devastation caused by large earthquakes because recurrence of large m 7 8 earthquakes is rare on the order of centuries studying the past behavior of a fault guides future expectations paleoseismologists examine the stratigraphic and geomorphic history of deposits and landforms along a fault for evidence of past ruptures such observations provide information on when earthquakes happened what parts of the fault failed and the size of the earthquakes the collected geologic data form the backbone of probabilistic seismic hazard analyses 1 used by the insurance and engineering industries and are increasingly used to explore models of lithosphere rheology and fault interaction 2 3 because of sparse data however inferences about patterns of strain accumulation and release are a common occurrence on pages 1119 and 1117 of this issue zielke et al 4 and grant ludwig et al 5 present data and interpretations providing an exciting new view that questions fault behavior models that have been applied to the south central san andreas fault for decades highlighting the value of revisiting old problems with new techniques

temporal slip rate stability and variations on the hope fault new zealand during the late quaternary abstract the hope fault transfers slip from hikurangi subduction to the alpine fault in the northern south island of new zealand it accommodates mainly dextral strike slip and currently carries the highest slip rate in the marlborough fault system displacements displacement rates and earthquake recurrence intervals have been determined using a combination of high resolution lidar for 59 dextral displacements 2 5 200 m together with calibrated radiocarbon ages 130 yr to 13 000 yr for abandoned stream channels terrace risers and alluvial fans mean single event displacement sed of 3 0 6 m 2 2 to 4 6 m for 21 measurements and mean recurrence interval of 266 100 yr range 128 to 560 yr have been determined for the five most recent surface rupturing earthquakes on time scales 2300 yr the dextral slip rate is uniform at 12 2 2 4 mm yr however when averaged over time intervals of 230 to 1700 yr slip rates range from 4 to 46 4 mm yr this order of magnitude variability in slip rate over shorter timescales cannot be fully attributed to errors in displacement and age data and is at least partly due to variations in earthquake recurrence interval and inferred sed short term non characteristic earthquake behaviour may be due to changes in fault loading arising from stress interactions between different segments of the hope fault and nearby faults

flow of variably fluidized granular masses across three dimensional terrain 2 numerical predictions and experimental tests numerical solutions of the equations describing flow of variably fluidized coulomb mixtures predict key features of dry granular avalanches and water saturated debris flows measured in physical experiments these features include time dependent speeds depths and widths of flows as well as the geometry of resulting deposits three dimensional 3 d boundary surfaces strongly influence flow dynamics because transverse shearing and cross stream momentum transport occur where topography obstructs or redirects motion consequent energy dissipation can cause local deceleration and deposition even on steep slopes velocities of surge fronts and other discontinuities that develop as flows cross 3 d terrain are predicted accurately by using a riemann solution algorithm the algorithm employs a gravity wave speed that accounts for different intensities of lateral stress transfer in regions of extending and compressing flow and in regions with different degrees of fluidization field observations and experiments indicate that flows in which fluid plays a significant role typically have high friction margins with weaker interiors partly fluidized by pore pressure interaction of the strong perimeter and weak interior produces relatively steep sided flat topped deposits to simulate these effects we compute pore pressure distributions using an advection diffusion model with enhanced diffusivity near flow margins although challenges remain in evaluating pore pressure distributions in diverse geophysical flows riemann solutions of the depth averaged 3 d coulomb mixture equations provide a powerful tool for interpreting and predicting flow behavior they provide a means of modeling debris flows rock avalanches pyroclastic flows and related phenomena without invoking and calibrating rheological parameters that have questionable physical significance

past and future earthquakes on the san andreas fault the san andreas fault in calfornia is one of the best studied earthquake generating faults in the world in their perspective weldon et al discuss recent efforts to construct rupture scenarios that is possible histories of the date location and length of fault rupture of past earthquakes on the fault existing knowledge of the locations and dates of past earthquakes can be explained by different scenarios but the authors argue that the evidence favors the hypothesis that the fault breaks in relatively infrequent large earthquakes they caution that the current 148 year hiatus since the last big earthquake is likely to end within the next 50 years with a large rupture or sequence of ruptures spanning a substantial part of the fault

insight into zircon ree oxy barometers a lattice strain model perspective abstract zircon rare earth element ree oxy barometers have been widely used to calculate magma oxygen fugacity however sometimes confusing results are obtained such as extremely reduced oxygen fugacity in hadean magmas e g fmq 8 extremely oxidized oxygen fugacity in post hadean magmas e g fmq 10 and contradictory oxygen fugacities recorded in ore related porphyry magmas nno 5 vs nno 1 to address these issues this work reviews the underlying assumption of zircon ree oxy barometers the lattice strain model by introducing a geochemical filter to identify clean inclusion free zircon and a new parameter k to constrain the d zircon whole rock deviation from the lattice strain model we systematically re evaluate the common zircon ree oxy barometers address the issues noted in hadean post hadean and ore related magmas and provide an alternate approach to using zircon ree in studies of magmatic processes

faulting associated with historical and recent earthquakes in the eastern mediterranean region summary this paper summarizes evidence for surface faulting in historical and recent earthquakes in the eastern mediterranean region and in the middle east such information is particularly important for studies of active tectonics and for palaeoseismology we have found 78 cases of faulting pre 1900 and 72 post 1900 some of which show that faults that have apparently been inactive this century had already ruptured before 1900 for some cases faulting could not have been predicted from 20th century activity and in others it could have been expected but has not been observed during the instrumental period the data are suycient to allow the derivation of relationships between magnitude and rupture length

holocene earthquake records from the cascadia subduction zone and northern san andreas fault based on precise dating of offshore turbidites abstract we present preliminary evidence for a 10 000 year earthquake record from two major fault systems based on sediment cores collected along the continental margins of western north america new stratigraphic evidence from cascadia demonstrates that 13 earthquakes ruptured the entire margin from vancouver island to at least the california border since the eruption of the mazama ash 7700 years ago the 13 events above this prominent stratigraphic marker have an average repeat time of 600 years and the youngest event 300 years ago coincides with the coastal record we also extend the record of past earthquakes to the base of the holocene at least 9800 years ago during which 18 events correlate along the same region the sequence of holocene events in cascadia appears to contain a repeating pattern of events a tantalizing first look at what may be the long term behavior of a major fault system the northern california margin cores show a cyclic record of turbidite beds that may represent holoce

visibility of fault strands in exploratory trenches and timing of rupture events many estimates of seismic risk depend crucially on how well the date of faulting events can be determined from the stratigraphic position of fault strands exposed in exploratory trenches however fault strands cut by trenches may seem to die out where they are in fact only poorly expressed or they may actually die out such ambiguity can lead to misinterpretation of the time of the most recent displacement and also of the recurrence interval between faulting events to investigate the frequency of occurrence and other characteristics of strands that falsely appear to die out or that actually do die out more than 1200 fault strands were analyzed for strands associated with individual faulting events 45 could not be visibly traced in the trench walls to the ground surface that existed at the time of faulting for reverse and strike slip faults the number exceeds 70 thus any apparent upward termination of a fault strand that is thought to indicate the date of a faulting event requires critical examination and corroboration from other evidence nonvisibility i e dieout upward obscure segments and dieout downward is more common on strike slip and reverse faults than on normal faults and is more common in soil horizonsmore than in clay and gravel nonvisibility occurs on strands that have had large 1m as well as small displacements less

great cascadia earthquakes and tsunamis of the past 6700 years coquille river estuary southern coastal oregon cascadia subduction zone earthquakes dropped tidal marshes and low lying forests to tidal flat elevations 12 times in the last 6700 cal yr b p at the coquille river estuary in southwestern oregon the youngest buried soil preserved in tidal marsh deposits near the estuary mouth records the a d 1700 earthquake that ruptured the entire cascadia margin eleven other buried marsh and upland soils found in tributary valleys of the estuary provide repeated evidence for rapid lasting relative sea level rise interpreted as coseismic subsidence additional stratigraphic criteria supporting a coseismic origin for soil burial include lateral soil correlation over hundreds of meters fossil diatom assemblages that indicate a maximum of 1 2 3 0 m of submergence and sand deposits overlying buried soils consistent with earthquakeinduced tsunamis that traveled 10 km up the estuary twelve earthquakes occurred in the last 6500 6720 cal yr b p recurring on average every 570 590 yr intervals between earthquakes varied from a few hundred years to over 1000 comparisons of the coquille record to earthquake histories from adjacent sites in oregon southwestern washington and northwestern california suggest that at least two earthquakes in the last 4000 yr did not rupture the entire length of the subduction zone an earthquake 760 1140 cal yr b p in southwestern washington may have ruptured as far south as coos bay but probably stopped before it reached the coquille estuary because no buried soil records the event and tidal marsh conditions were set to record an earthquake an earthquake limited to a southern segment of the cascadia margin 1940 2130 cal yr b p probably did not rupture north of the coquille estuary an analysis of relative sea level histories from either side of the coquille fault failed to find conclusive evidence for late holocene vertical deformation however we cannot preclude recent upper plate faulting if the fault is active as geomorphic features suggest then constraints on the highest possible elevation of mean tide level allow a maximum vertical slip rate of 0 2 0 4 mm yr in the past 6200 6310 cal yr b p

quantitative refinement of calibrated 14c distributions abstract a new method is presented for using known ordering or other relationships between 14c samples to reduce 14c dating uncertainty the order of sample formation is often known from for example stratigraphic superposition dendrochronology or crosscutting field relations constraints such as a minimum time between dates and limits from historical information are also readily included dendrochronologically calibrated calendric date histograms initially represent each date the method uses bayes theorem and the relational constraints to upweight date ranges in each date distribution consistent with the other date distributions and the constraints and downweight unlikely portions the reweighted date distributions retain all dating possibilities present in the initial calibrated date distributions but each date in the result now reflects the extra information such as ordering supplied through the constraints in addition one may add information incrementally and thus analyze systematically its effect on all the date distributions thus the method can be used to assess the consistency of the quantitative data at hand the bayesian approach also uses the empirical calibrated date distributions directly so information is not lost prematurely by summarized dates to a mean and variance or confidence intervals the approach is illustrated with data from two densely sampled paleoseismic sites on the san andreas fault in southern california an average reduction in 14 c date distribution variance of 59 is achieved using ordering information alone and 85 is achieved by also applying sedimentation rate constraints and historical information

variation in 14c age of macrofossils and different fractions of minute peat samples dated by ams accurate 14c dating of peat samples is crucial if peat stratigraphies are to be used as historical archives to analyse the variation in 14c age within small peat samples the 14c age of different mire plant remains and peat fractions n 39 from 2 cm thick peat slices was determined using accelerator mass spectrometry the 14c ages of mosses were assumed to be the most accurate to verify this we also tested the possibility that uncertainties could be introduced by mosses at the mire surface reassimilating co2 produced during the decomposition of old peat the average 14c content of living mosses 110 5 110 9 absolute modern pm did not differ between threesphagnum species representing hummock carpet and lawn growing species their 14c contents were also identical within experimental limits to the current 14c content of the atmosphere depending on sampled depth and peat type the differences in calibrated 14c age between different fragments or fractions within specific 2 cm thick peat samples

discordant 14c ages from buried tidal marsh soils in the cascadia subduction zone southern oregon coast peaty tidal marsh soils interbedded with estuarine mud in late holocene stratigraphic sequences near coos bay oregon may have been submerged and buried during great m 8 subduction earthquakes smaller localized earthquakes or by nontectonic processes radiocarbon dating might help distinguish among these alternatives by showing that soils at different sites were submerged at different times along this part of the cascadia subduction zone but comparison of conventional 14c ages for different materials from the same buried soils shows that they contain materials that differ in age by many hundreds of years errors in calibrated soil ages represent about the same length of time as recurrence times for submergence events 150 500 yr this similarity precludes using conventional 14c ages to distinguish buried soils along the southern oregon coast accelerator mass spectrometer 14c ages of carefully selected macrofossils from the tops of peaty soils should provide more precise estimates of the times of submergence events

evidence for large earthquakes on the san andreas fault at the wrightwood california paleoseismic site a d 500 to present we present structural and stratigraphic evidence from a paleoseismic site near wrightwood california for 14 large earthquakes that occurred on the southern san andreas fault during the past 1500 years in a network of 38 trenches and creek bank exposures we have exposed a composite section of interbedded debris flow deposits and thin peat layers more than 24 m thick fluvial deposits occur along the northern margin of the site the site is a 150 m wide zone of deformation bounded on the surface by a main fault zone along the northwest margin and a secondary fault zone to the southwest evidence for most of the 14 earthquakes occurs along structures within both zones we identify paleoearthquake horizons using in filled fissures scarps multiple rupture terminations and widespread folding and tilting of beds ages of stratigraphic units and earthquakes are constrained by historic data and 72 14c ages mostly from samples of peat and some from plant fibers wood pine cones and charcoal comparison of the long well resolved paleoseimic record at wrightwood with records at other sites along the fault indicates that rupture lengths of past earthquakes were at least 100 km long paleoseismic records at sites in the coachella valley suggest that each of the past five large earthquakes recorded there ruptured the fault at least as far northwest as wrightwood comparisons with event chronologies at pallett creek and sites to the northwest suggests that approximately the same part of the fault that ruptured in 1857 may also have failed in the early to mid sixteenth century and several other times during the past 1200 years records at pallett creek and pitman canyon suggest that in addition to the 14 earthquakes we document one and possibly two other large earthquakes ruptured the part of the fault including wrightwood since about a d 500 these observations and elapsed times that are significantly longer than mean recurrence intervals at wrightwood and sites to the southeast suggest that at least the southermost 200 km of the san andreas fault is near failure

accurate surface exposure dating with lichens lichenometry accurately dates exposure times of glacial moraines and landslides when measuring the longest axis of the largest crustose lichen on many blocks as demonstrated by numerous examples in sweden the sizes of rhizocarpon subgenus rhizocarpon describe five pulses of glacial moraine creation in 120 yr six historic california earthquakes between ad 1800 and 1906 caused many landslides that constrain lichen growth as linear with a dating accuracy of 0 5 yr crustose lichen sizes date earthquake created additions to sierra nevada talus with an accuracy of 5 yr the oldest lichen ages are 400 yr for lecanora sierrae 800 yr for lecidea atrobrunnea and 1100 yr for acarospora chlorophana and rhizocarpon subgenus rhizocarpon lichen sizes also record differing spatial attenuation of ground shaking from the magnitude m w 7 9 san andreas earthquake of ad 1857 and the more distant smaller san jacinto ad 1800 earthquake which both caused sierra nevada rockfalls ad 1800 seismic shaking was relatively stronger than that of ad 1857 farther north perhaps expressing stronger love and rayleigh styles of surface waves from the north trending ad 1800 surface rupture that were particularly efficient in causing rockfalls at greater distances

a more precise chronology of earthquakes produced by the san andreas fault in southern california improved methods of radiocarbon analysis have enabled us to date more precisely the earthquake ruptures of the san andreas fault that are recorded in the sediments at pallett creek previous dates of these events had 95 confidence errors of 50 100 calendar years new error limits are less than 23 calendar years for all but two of the dated events this greater precision is due to larger sample size longer counting time lower background noise levels more precise conversion of radiocarbon ages to calendric dates and better stratigraphic constraints and statistical techniques the new date ranges with one exception fall within the broader ranges estimated previously but our estimate of the average interval between the latest 10 episodes of faulting is now about 132 years variability about the mean interval is much greater than was suspected previously five of the nine intervals are shorter than a century three of the remaining four intervals are about two to three centuries long despite the wide range of these intervals a pattern in the occurrence of large earthquakes at pallett creek is apparent in the new data the past 10 earthquakes occur in four clusters each of which consists of two or three events earthquakes within the clusters are separated by periods of several decades but the clusters are separated by dormant periods of two to three centuries this pattern may reflect important mechanical aspects of the fault s behavior if this pattern continues into the future the current period of dormancy will probably be greater than two centuries this would mean that the section of the fault represented by the pallett creek site is currently in the middle of one of its longer periods of repose between clusters and sections of the fault farther to the southeast are much more likely to produce the next great earthquake in california the greater precision of dates now available for large earthquakes recorded at the pallett creek site enables speculative correlation of events between paleoseismic sites along the southern half of the san andreas fault a history of great earthquakes with overlapping rupture zones along the mojave section of the fault remains one of the more attractive possibilities

paleoearthquakes on the southern san andreas fault wrightwood california 3000 to 1500 b c a new method for evaluating paleoseismic evidence and earthquake horizons we present evidence of 11 14 earthquakes that occurred between 3000 and 1500 b c on the san andreas fault at the wrightwood paleoseismic site earthquake evidence is presented in a novel form in which we rank high moderate poor or low the quality of all evidence of ground deformation which are called event indicators event indicator quality reflects our confidence that the morphologic and sedimentologic evidence can be attributable to a ground deforming earthquake and that the earthquake horizon is accurately identified by the morphology of the feature in four vertical meters of section exposed in ten trenches we document 316 event indicators attributable to 32 separate stratigraphic horizons each stratigraphic horizon is evaluated based on the sum of rank rs maximum rank rm average rank ra number of observations obs and sum of higher quality event indicators rs 1 of the 32 stratigraphic horizons 14 contain 83 of the event indicators and are qualified based on the number and quality of event indicators the remaining 18 do not have satisfactory evidence for further consideration eleven of the 14 stratigraphic horizons have sufficient number and quality of event indicators to be qualified as probable to very likely earthquakes the remaining three stratigraphic horizons are associated with somewhat ambiguous features and are qualified as possible earthquakes although no single measurement defines an obvious threshold for designation as an earthquake horizon rs rm and rs 1 correlate best with the interpreted earthquake quality earthquake age distributions are determined from radiocarbon ages of peat samples using a bayesian approach to layer dating the average recurrence interval for the 10 consecutive and highest quality earthquakes is 111 93 131 years and individual intervals are 50 of the average with comparison with the previously published 14 15 earthquake record between a d 500 and present we find no evidence to suggest significant variations in the average recurrence rate at wrightwood during the past 5000 years

2300 yr history of seismicity from silting events in lake tadoussac charlevoix quebec silt layers in organic rich lake sediments are interpreted to represent the historic earthquakes of 1638 1663 1791 1870 and 1925 of the charlevoix region of eastern canada this interpretation is based on the relative spacing of the layers and the accelerator mass spectrometer sup 14 c dating of a twig in one of the cores the silt layers were presumably caused by landslides on tributary streams and by resuspension of the sediment the cores contain up to 22 layers 1 to 45 mm thick over a depth equivalent to about 2300 yr if there is a correlation between thickness and magnitude there would have been four events of richter magnitude 7 5 or greater in a d 1663 1320 60 and 320 b c the 18 other layers could correspond to earthquakes of magnitude 6 to 7 the recurrence interval from 300 b c to a d 800 is 120 yr followed until a d 1500 by a quiet period when there was a single large event the recurrence interval from a d 1500 to the present is 75 yr

long term earthquake clustering a 50 000 year paleoseismic record in the dead sea graben the temporal distribution of earthquakes in the dead sea graben is studied through a 50 000 year paleoseismic record recovered in laminated sediments of the late pleistocene lake lisan paleo dead sea the lisan represents more than 10 times the 4000 years of historical earthquake records it is the longest and most complete paleoseismic record along the dead sea transform and possibly the longest continuous record on earth it includes unique exposures of seismite beds earthquake induced structures associated with slip events on syndepositional faults the seismites are layers consisting of mixtures of fragmented and pulverized laminae the places where the seismites abut syndepositional faults are interpreted as evidence for their formation at the sediment water interface during slip events on these faults thicker sediment accumulation above the seismites in the downthrown blocks indicates that a seismite formed at the water sediment interface on both sides of the fault scarps modern analogs and the association with surface ruptures suggest that each seismite formed during a m l 5 5 earthquake the 230 th 234 u ages of a columnar section obtained by thermal ionization mass spectrometry give a mean recurrence time of 1600 years of m l 5 5 earthquakes in the dead sea graben the earthquakes cluster in 10 000 year periods separated by quiet periods of similar length this distribution implies that a long term behavior of the dead sea transform should be represented by a mean recurrence of at least 20 000 year record this observation has ramifications for seismic hazard assessment based on shorter records

a 100 year average recurrence interval for the san andreas fault at wrightwood california evidence for five large earthquakes during the past five centuries along the san andreas fault zone 70 kilometers northeast of los angeles california indicates that the average recurrence interval and the temporal variability are significantly smaller than previously thought rapid sedimentation during the past 5000 years in a 150 meter wide structural depression has produced a greater than 21 meter thick sequence of debris flow and stream deposits interbedded with more than 50 datable peat layers fault scarps colluvial wedges fissure infills upward termination of ruptures and tilted and folded deposits above listric faults provide evidence for large earthquakes that occurred in a d 1857 1812 and about 1700 1610 and 1470

earthquake triggered increase in sediment delivery from an active mountain belt in tectonically active mountain belts earthquake triggered landslides deliver large amounts of sediment to rivers we quantify the geomorphic impact of the 1999 mw 7 6 chi chi earthquake in taiwan which triggered 20 000 landslides coseismic weakening of substrate material caused increased landsliding during subsequent typhoons most coseismic landslides remained confined to hillslopes downslope transport of sediment into the channel network occurred during later storms the sequential processes have led to a factor of four increase in unit sediment concentration in rivers draining the epicentral area and increased the magnitude and frequency of hyperpycnal sediment delivery to the ocean four years after the earthquake rates of hillslope mass wasting remain elevated in the epicentral area

paleoseismic event dating and the conditional probability of large earthquakes on the southern san andreas fault california we introduce a quantitative approach to paleoearthquake dating and apply it to paleoseismic data from the wrightwood and pallett creek sites on the southern san andreas fault we illustrate how stratigraphic ordering sedimentolog ical and historical data can be used quantitatively in the process of estimating earth quake ages calibrated radiocarbon age distributions are used directly from layer dating through recurrence intervals and recurrence probability estimation the method does not eliminate subjective judgements in event dating but it does provide a means of systematically and objectively approaching the dating process date dis tributions for the most recent 14 events at wrightwood are based on sample and contextual evidence in fumal et al 2002 and site context and slip history in weldon et al 2002 pallett creek event and dating descriptions are from published sources for the five most recent events at wrightwood our results are consistent with pre viously published estimates with generally comparable or narrower uncertainties for pallett creek our earthquake date estimates generally overlap with previous results but typically have broader uncertainties some event date estimates are very sensitive to details of data interpretation the historical earthquake in 1857 ruptured the ground at both sites but is not constrained by radiocarbon data radiocarbon ages peat accumulation rates and historical constraints at pallett creek for event x yield a date estimate in the earliest 1800s and preclude a date in the late 1600s this event is almost certainly the historical 1812 earthquake as previously concluded by sieh et al 1989 this earthquake also produced ground deformation at wrightwood all events at pallett creek except for event t about a d 1360 and possibly event i about a d 960 have corresponding events at wrightwood with some overlap in age ranges event t falls during a period of low sedimentation at wrightwood when conditions were not favorable for recording earthquake evidence previously pro posed correlations of pallett creek x with wrightwood w3 in the 1690s and pallett creek event v with w5 around 1480 fumal et al 1993 appear unlikely after our dating reevaluation apparent internal inconsistencies among event layer and dating relationships around events r and v identify them as candidates for further inves tigation at the site conditional probabilities of earthquake recurrence were estimated using poisson lognormal and empirical models the presence of 12 or 13 events at wrightwood during the same interval that 10 events are reported at pallett creek is reflected in mean recurrence intervals of 105 and 135 years respectively average poisson model 30 year conditional probabilities are about 20 at pallett creek and 25 at wrightwood the lognormal model conditional probabilities are somewhat higher about 25 for pallett creek and 34 for wrightwood lognormal variance rln estimates of 0 76 and 0 70 respectively imply only weak time predictability conditional probabilities of 29 and 46 respectively were estimated for an em pirical distribution derived from the data alone conditional probability uncertainties are dominated by the brevity of the event series dating uncertainty contributes only secondarily wrightwood and pallett creek event chronologies both suggest varia tions in recurrence interval with time hinting that some form of recurrence rate modulation may be at work but formal testing shows that neither series is more ordered than might be produced by a poisson process

problems encountered with the 14c dating of peat abstract pairs of neighbouring short columns of peat from two sites in northern england were divided into contiguous 1 cm thick slices that were sub sampled for pollen and plant macro fossil analysis for each slice the remaining peat was then split into humic acid humin and fulvic acid fractions and radiocarbon dated this research demonstrates that significant variations can occur in the radiocarbon content of discrete chemically defined fractions of peat a total of 127 radiocarbon dates was obtained the results from the four columns of peat are highly variable and mutually inconsistent the fulvic acid fraction although normally younger than the corresponding humic acid and humin fractions has very little effect on a combined date in these samples however it is removed from all samples prior to dating in order to remove any carbonates which could contaminate samples the variations in the ages obtained for the humic acid and corresponding humin fractions range from the humin fraction being 630 years older than the humic acid srr 4029 to the humic acid being 1210 years older than the humin fraction srr 4007 even when a two sigma confidence is allowed no correlation was apparent between pollen concentration 13 c enrichment degree of humification and the conventional radiocarbon ages

depositional processes in large scale debris flow experiments this study examines the depositional process and characteristics of deposits of large scale experimental debris flows to 15 m3 composed of mixtures of gravel to 32 mm sand and mud the experiments were performed using a 95 m long 2 m wide debris flow flume that slopes 31 following release experimental debris flows invariably developed numerous shallow 10 cm deep surges sediment transported by surges accumulated abruptly on a 3 runout slope at the mouth of the flume deposits developed in a complex manner through a combination of shoving forward and shouldering aside previously deposited debris and through progressive vertical accretion progressive accretion by the experimental flows is contrary to commonly assumed en masse sedimentation by debris flows despite progressive sediment emplacement deposits were composed of unstratified accumulations of generally unsorted debris hence massively textured poorly sorted debris flow deposits are not emplaced uniquely en masse the depositional

the seismic activity of the marmara sea region over the last 2000 years we examined the seismicity of the region of the sea of marmara in northwest turkey over the last 2000 yr using the historical record of the region we found no evidence for truly large earthquakes of a size comparable to those in the north anatolian fault zone in the marmara basin events are smaller in keeping with the known fault segmentation of the basin over the last 2000 yr seismic mo ment release accounted for the known right lateral shear velocity across the marmara region observed by global positioning system measurements its average rate is relatively constant and varies between 1 6 and 2 4 cm yr the long term seismicity in the marmara sea region shows that large earthquakes are less frequent than pre dicted from the 100 yr long instrumental period

late holocene rupture behavior and earthquake chronology on the hope fault new zealand the hope fault is the most active and southernmost splay of the marlborough fault system in the northern south island of new zealand the fault consists of five geometrically defined segments we used trenching to acquire paleoseismic data and radiocarbon dating of faulted late holocene sediments on the hurunui segment of the hope fault to derive an earthquake chronology that extends from the historic 1888 mw 7 1 amuri earthquake to ca 300 c e thereby providing the longest chronologic record of earthquakes on the hope fault to date earthquake event horizons were identified by upward fault terminations colluvial wedges unconformities and or progressive folding of shutter basin deposits six earthquakes identified at c e 1888 1740 1840 1479 1623 819 1092 439 551 and 373 419 indicate a mean recurrence interval of 298 88 yr with successive median interevent times ranging from 98 to 595 yr the large variance in interevent times with respect to mean recurrence interval is explained by 1 possible coalescence of rupture overlap from the adjacent hope river segment onto the hurunui segment at our study site including the 1888 mw 7 1 amuri earthquake sourced primarily from the hope river segment which results in apparently shorter interevent times at the study site compared to mean recurrence intervals from adjacent fault segments 2 possible earthquake temporal clustering on the hurunui segment which could result in interevent times that are significantly shorter or longer than interevent times and mean recurrence intervals predicted by a periodic earthquake rupture model and or 3 missing events which could result in interevent times and mean recurrence intervals at the study site that are longer than the actual mean recurrence interval while we cannot exclude option 3 as a possibility we prefer options 1 and 2 to explain earthquake chronologies and rupture behavior on the hurunui segment of the hope fault given the detailed nature of our geologic and chronologic investigations by demonstrating that the 1888 amuri earthquake propagated through a proposed segment boundary we provide the first evidence for coseismic multisegment ruptures on the hope fault in contrast the penultimate earthquake ruptured the hurunui segment at 1740 1840 c e with no known rupture of the hope river segment paleoearthquake records near geometrically complex segment structural boundaries on major strike slip faults may show temporal recurrence distributions resulting from earthquake ruptures that variably arrest or propagate through proposed segment boundaries we note that earthquake recurrence along major strike slip plate boundary faults may vary between more periodic and more episodic end members even on adjacent geometrically defined segments

the effect of forearc mantle serpentinization on ground motions from megathrust and intraslab events in the cascadia subduction zone we re examine large scale structural controls on ground motions from megathrust and intraslab events in the cascadia subduction zone in light of recent evidence pointing to a highly hydrated and serpentinized forearc mantle we employ 2d p sv pseudospectral synthetic seismograms double couple line sources and a structural model for cascadia based on the study of bostock et al 2002 that includes both serpentinized forearc mantle and eclogitized oceanic crust as in a previous study cohee et al 1991 we note that ground motions at greater epicentral distances are dominated by postcritical reflections from the moho however in our modeling of megathrust earthquakes we find that the presence or absence of serpentinized forearc mantle dictates whether maximum ground motions in the pacific northwest urban corridor portland seattle vancouver victoria result from postcritical reflection at the oceanic moho or continental moho respectively as well as their range dependence moreover serpentinization reduces the efficacy of the subducting oceanic crust as a wave guide by allowing energy to escape through the overlying wedge this effect is particularly important for intraslab wadati benioff events as it allows focusing of upward propagating energy toward the surface that would otherwise be redirected downward consequently ground motions from intraslab sources at lower frequencies 0 2 hz can be up to 5 times greater than those modeled in the absence of a serpentinized forearc mantle at higher frequencies the lower q of serpentine may act to reduce this amplification

structure and earthquake offsets on the san andreas fault at the wrightwood california paleoseismic site thirty eight trenches and natural exposures across the san andreas fault zone four km northwest of wrightwood california reveal the structure and stratigraphy of this paleoseismic site a 25 m thick stratigraphic section of late holocene peat debris flows and fluvial sediments have accumulated syntectonically and are deformed in a complicated flower or flake structure within the fault zone whereas slip is everywhere parallel to the trend of the san andreas fault layering within the fan shaped section guides the surface faulting and transtensive portions of the structure are connected to transpressive portions by bedding parallel detachment faults the structure has grown through time widely distributing the evidence for individual earthquakes the broad zone of deformation and rapid sedimentation permit the characterization of an unusually large number of prehistoric earthquakes the presence of at least four geomorphically similar sites within 10 km along the fault zone suggests that this kind of site is common and other sites should be exploited to date the upper 12 m of section deposited during the past 1600 yr has been completely characterized and dated to show evidence of 14 prehistoric earthquakes the a d 1857 earthquake produced only 1 2 m of slip here commensurate with the site9s proximity to the southern end of the rupture six to 10 m of slip accumulated during the past three earthquakes and 30 60 m of cumulative slip occurred during the past 14 events suggesting a mean displacement of 2 4 m per event at the site coupled with the mean recurrence interval of slightly more than 100 yr this implies a slip rate of 2 4 cm yr for the san andreas fault north of its junction with the san jacinto fault