palaeoenvironment of the eocene eckfeld maar lake germany implications from geochemical analysis of the oil shale sequence abstract drill core samples from the depth interval between 19 4 and 32 0 m of the laminated central lake facies of the eocene eckfeld maar were investigated for biomarker and stable isotope composition bulk organic geochemical parameters c n hi and the molecular composition of the soluble organic matter indicate a dominance of particulate organic matter from land plants and microbially derived lipids in the lower part of the sedimentary succession an angiosperm dominated vegetation is indicated from the terpenoid biomarker composition abundant 4 methylsteroids in the 25 6 30 8 m section of the oil shale sequence reflect a contribution of algal derived biomass samples with high concentrations of methylsteroids are characterized by low amounts of triterpenoids related to the arborane skeleton and vice versa this pattern is interpreted as reflecting differences in autochthonous organic matter production vs microbial activity in the lowermost section 32 0 30 6 m a trend towards heavier 18 o and 13 c values indicates the evolution of permanently meromictic conditions in the lake and an increase in methanogenesis high 13 c values of siderites 10 throughout most of the sequence are consistent with permanently anoxic conditions at the sediment water interface the lighter 18 o values of siderites from turbidites relative to siderites from biogenic laminites are postulated to have been caused by temporary phases of increased precipitation followed by landslides and improved circulation within the lake depletion of the organic matter in 13 c average 13 c 29 4 in comparison with the fossil wood ranging from 23 1 to 26 6 is explained by the dominance of waxy lipid rich land plant material e g leaf waxes resins bark over wood supplied to the lake carbon cycling during anoxic decomposition of organic matter is assumed to further affect the 13 c values through the activity of anaerobic e g methanogenic bacteria resulting in a depletion of the biomass in 13 c the overall trend in the isotopic composition of organic carbon towards heavier values in the depth interval between 26 0 and 3 2 m is accompanied by decreasing c n ratios indicating an increase in aquatic organic matter production the geochemistry of the oil shale succession points towards a highly productive eutrophic ecosystem with intense microbial activity under meromictic conditions in the maar lake beside the high input of land plants to the biomass major contributions from bacteria and phytoplankton are indicated by the biomarker composition

five thousand years of surface ruptures on the wellington fault new zealand implications for recurrence and fault segmentation new paleoseismic studies have been undertaken on the wellington hutt valley w hv segment of the wellington fault to characterize its late holocene record of surface rupturing earthquakes trenches and radiocarbon dates from te kopahou and te marua have provided evidence and improved timing for the four most recent earthquake ruptures these events have been recognized on the basis of upward terminating faults coseismic deposition progressive displacement and faulting of colluviums at te kopahou colluvial and scree deposition resulting from surface rupture and strong earthquake shaking buries old ground surfaces associated with peat and or soil development at te marua the timing of the two youngest events has been refined by bracketing the ages of the youngest faulted and unfaulted alluvial terraces of the hutt river assuming that the w hv segment acts as a rupture segment along its length the approximate timings of these faulting events is as follows the most recent faulting event event i occurred between 110 and 310 cal yr b p a d 1640 1840 the penultimate faulting event event ii between 790 and 930 cal yr b p event iii occurred between 1835 and 2340 cal yr b p and event iv between 2460 and 4900 yr b p the minimum and maximum earthquake recurrence intervals derived from the four youngest events are 715 and 1575 yr respectively with a median value of 1145 yr revisions of the earthquake timing recurrence interval data and recently the single event displacement and slip rate collectively reduce the seismic hazard for the w hv segment of the wellington fault a four event paleoearthquake record from the pahiatua section of the wellington fault is statistically similar to that from the w hv segment this has significant implications with respect to the rupture length and magnitude or clustering of future surface rupturing earthquakes on the wellington fault

prolonged impact of earthquake induced landslides on sediment yield in a mountain watershed the tanzawa region japan abstract to determine for how long a landslide affects sediment discharge the sediment yields of 15 check dam basins were compared with the time series of landslide distributions in a mountain basin in the tanzawa region central japan the distribution of sediment yield was quantitatively estimated from deposition in the sediment pools of check dams the relationship between the landslide history and sediment discharge in the nakagawa river basin was examined for an approximately 80 year period two major landslide events occurred during this period the 1923 kanto earthquake and the 1972 disaster caused by heavy rainfall the resulting trend in sediment discharge of the whole basin estimated using reservoir sedimentation in the miho dam at its base was nearly constant with high sediment discharge 2897 m 3 km 2 yr 1 in the intervening quarter century despite the recovery of vegetation on landslide areas in this period comparisons of the landslide distributions resulting from the two disasters the sediment yields of check dam basins and the sediment discharge of the whole basin indicate that recent sediment discharge contains landslide debris that was originated by the kanto earthquake that occurred over 80 years ago thus to understand high sediment discharge it is essential to investigate not only the current basin condition and recent events but also the landslide history of the basin for at least the previous 100 years

sediment generation and delivery from large historic landslides in the southern alps new zealand abstract there is much variability of sediment yield in mountain river systems because it is influenced by both periodic e g snowmelt monsoonal circulation and episodic high intensity rainstorms earthquakes controls in the southern alps of new zealand landslides are dominant mechanisms of conveying large amounts of debris to river channels this paper attempts to quantify catastrophic modes of sediment delivery by presenting three recent examples of large landslides on the western slopes of the southern alps a combination of ground surveys dem based volume calculations and air photo interpretation attributes immediate postfailure sediment yields in excess of 70 000 t km 2 a 1 in the short term such landslide derived sediment pulses pose significant hazards to downstream settlements and infrastructure on alluvial fans where they cause massive aggradation increased flooding frequency and large scale channel avulsion in addition to intramontane valley floor obliteration or channel metamorphosis these geomorphic impacts may thus occur far beyond the initial locations of slope failure these catastrophic off site effects involve apparent net sediment delivery rates in the order of 10 5 10 6 m 3 a 1 the accurate quantification of the relative contribution of debris from the disturbing landslide to overall sediment flux is extremely difficult nonetheless are quantitative estimates of landslide derived sediment production and delivery important data to develop a more comprehensive understanding of the variability in alpine sediment flux such data are essential not only for use in hydraulic engineering or catchment management but also in gauging potential future impacts from rainstorm and earthquake induced landsliding in the southern alps

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

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

storm frequency and magnitude in response to holocene climate variability lake tutira north eastern new zealand abstract a mid to late holocene record of storm events is preserved in the sediments of lake tutira located on the eastern north island of new zealand previous studies of a 6 m sediment core established a storm chronology for the last 2250 years eden d n page m j 1998 palaeoclimatic implications of a storm erosion record from late holocene lake sediments north island new zealand palaeogeogr palaeoclimatol palaeoecol 139 37 58 here we extend the record using a 27 m sediment core to lake formation 7200 cal yr ago outside the last 500 yr of human influence the core records landscape response to natural climate variability and to tectonism volcanism associated with the active collisional plate boundary setting based on sedimentological and biogeochemical analyses 1400 layers of dominantly terrigenous storm derived sediment have been identified a storm event chronology supported by twelve tephra and three 14c ages indicates that storm magnitude and frequency has varied over the last 7200 yr twenty five periods with an increased frequency of large storms occur typically of decadal to centennial duration periods of major storm activity occur at about 500 700 1100 1250 1850 2100 2850 3200 3600 4000 4300 4500 4700 4900 5700 5900 and 6850 6900 cal yr bp several other local and regional climate proxies record conditions that are consistent with the timing and periodicity of major storms in the tutira record a period centred on 2000 yr ago has the highest incidence of storms with a recurrence of 1 storm 2 9 yr this is identified as a time of major environmental change by several other records by comparison average storm frequency throughout the record is 1 storm 5 yr and while this is consistent with modern el nino southern oscillation enso periodicity the record shows no increase in frequency around 4000 years at the time of enso intensification this likely reflects new zealand s location between tropical and polar latitudes where climate shifts are driven by the interplay between enso interdecadal pacific oscillation ipo and the southern annular mode sam the lake tutira record provides support for the growing evidence that climate variability during the holocene has involved periods of rapid change correlation of this detailed storm event and sediment flux record with other geomorphic and sedimentary records in the nearby waipaoa source to sink sedimentary system improves understanding of the timing and rates of climatically induced landscape change and its downstream effects

the importance of earthquake induced landslides to long term slope erosion and slope failure hazards in seismically active regions abstract this paper describes a general method for determining the amount of earthquake induced landsliding that occurs in a seismically active region over time this determination can be used as a quantitative measure of the long term hazard from seismically triggered landslides as well as a measure of the importance of this process to regional slope erosion rates and landscape evolution the method uses data from historical earthquakes to relate total volume of landslide material dislodged by an earthquake to the magnitude m and seismic moment m0 of the earthquake from worldwide data a linear regression relation between landslide volume v and m0 is determined as v m0 1018 9 0 13 where v is measured in m3 and m0 is in dyn cm to determine the amount of earthquake generated landsliding over time this relation is combined with data on seismic moment release for a particular region which may be derived from either earthquake history or fault slip data the form of the m0 v relation allows the rate of production of earthquake induced landslides over time to be determined from total rate of seismic moment release without regard to the distribution of individual events thus simplifying and generalizing the determination application of the method to twelve seismically active regions with areas ranging from 13 275 to 2 308 000 km2 shows that erosion rates from earthquake induced landslides vary significantly from region to region of the regions studied the highest rates were determined for the island of hawaii new zealand western new guinea and the san francisco bay region of california significantly lower rates were determined for iran tibet the sierra nevada great basin region of california and central japan for the time period from 715 ad to the present intermediate rates were determined for peru southern california onshore california turkey and central japan for the time period from 1586 ad to the present to determine the relative long term importance of seismically triggered landslides these erosion rates are compared to erosion rates calculated for other slope processes and to rates calculated from fluvial sediment discharge comparisons with other slope processes indicate that earthquake induced landslides are the predominant agents of slope erosion on the island of hawaii in the san francisco bay region and in western new guinea for hawaii the san francisco bay region and sierra nevada great basin region of california the erosion rates calculated for earthquake induced landslides also exceed the regional erosion rates calculated from fluvial sediment discharge

holocene vegetation and climate change in southern new zealand linkages between forest composition and quantitative surface moisture reconstructions from an ombrogenous bog this paper presents a holocene pollen record from an ombrotrophic bog in southland new zealand together with multiproxy data testate amoebae peat humification and plant macrofossils from the same core to establish an independent semiquantitative record of peatland surface moisture linkages between reconstructed peatland surface moisture and regional forest composition are investigated using redundancy analysis of the forest pollen data constrained with predicted bog water table depths over 32 of the pollen data variance can be explained by surface moisture changes in the bog suggesting a common cause of water table and regional vegetation change water tables were higher during the early to mid holocene when the forest was dominated by podocarp taxa water tables lowered after about 3300 cal yr bp coevally with the expansion of nothofagus species culminating with the dominance of nothofagus subgenus fuscospora in the past 1200 cal yr bp this is in apparent opposition to the warm dry to cool wet trend suggested by subjective interpretation of pollen data alone from this and other studies we suggest that during the late holocene drier summers associated with shifts in solar insolation caused reduced surface wetness and summer humidity which together with a trend to cooler winters apparently favoured the regeneration of nothofagus species copyright 2002 john wiley sons ltd

effects of peat compaction on delta evolution a review on processes responses measuring and modeling abstract peat is most compressible of all natural soils compaction of peat layers potentially leads to substantial amounts of land subsidence peat is common in many distal parts of holocene deltas which are often densely populated it is known that land subsidence due to peat compaction may have serious societal implications in such areas as it may cause damage to construction works and lead to land inundation effects of peat compaction on the natural evolution of deltas are however poorly understood whereas this might be an important control on delta evolution at both local and regional scales the main objective of this paper is to review current knowledge concerning the peat compaction process and its effect on delta evolution in holocene settings and to identify gaps in this knowledge an overview is given regarding 1 the compaction process 2 presumed and potential effects of peat compaction on delta evolution 3 field methods to quantify peat compaction and 4 numerical models to calculate the amount and rate of peat compaction peat compaction and formation influence channel belt elevation channel belt geometry and channel belt configuration last mentioned aspect mostly concerns the influence of peat compaction on avulsion which is one of the most important processes controlling delta evolution interactions between peat compaction peat formation and avulsion have seldom been studied and remain unclear partly because factors such as peat type organic matter content sediment sequence composition and groundwater table fluctuation are so far not taken into account peat compaction and formation potentially influence avulsion as 1 a decrease in accommodation space created by peat compaction underneath a channel causes superelevation and or an increase in lateral migration 2 the high cohesiveness of peat banks inhibits lateral migration which increases bed aggradation decreases sediment transport capacity and hence increases crevassing frequencies which possibly evolve into an avulsion although the low regional gradient in peatlands will hinder this and 3 peat compaction and oxidation in flood basins following groundwater table lowering leads to relief amplification of channel belts at delta scale variations in compaction rates might stimulate the occurrence of nodal avulsions to quantify effects of peat compaction on delta evolution and to determine the relative importance of different factors involved field research should be combined with numerical models describing peat compaction and formation the model should be validated and calibrated with field data

driving mechanisms of coastal change peat compaction and the destruction of late holocene coastal wetlands abstract this paper examines the role of peat compaction as a driving mechanism behind the widespread inundation of a late holocene coastal wetland in southeast england uk detailed stratigraphic and dating evidence lithology grain size foraminifera pollen and radiocarbon dates from a sample site in romney marsh documents the gradual inundation of a coastal wetland after 1263 1085 cal yr bp c 700 850 ad and the establishment of a saltmarsh shortly thereafter there was a rapid increase in water depth that was associated with the deposition of nearly 4 m of laminated intertidal mudflat and tidal channel sediments prior to site reclamation from the sea by ad 1460 grain size data and statistical analysis of sand and mud laminae thicknesses suggest the laminated sediments accumulated rapidly c 0 2 m per year as heterolithic tidal rhythmites rapid compaction of the thick peat bed that underlies the study site provided the accommodation space for their deposition this process began with the gradual tidal inundation of the site but accelerated following the widening of a breach in a coastal barrier in the 13th century compaction lowered the peat surface by at least 3 m and was associated with widespread landscape change the study demonstrates the powerful influence that compaction had on the evolution of the late holocene landscape at this site and we believe at many other coastal lowlands in northwest europe this process is likely to have been a key driving mechanism behind rapid late holocene coastal change far exceeding the longer term effects of either eustatic change or crustal uplift subsidence

high frequency holocene glacier fluctuations in new zealand differ from the northern signature understanding the timings of interhemispheric climate changes during the holocene along with their causes remains a major problem of climate science here we present a high resolution 10be chronology of glacier fluctuations in new zealand s southern alps over the past 7000 years including at least five events during the last millennium the extents of glacier advances decreased from the middle to the late holocene in contrast with the northern hemisphere pattern several glacier advances occurred in new zealand during classic northern warm periods these findings point to the importance of regional driving and or amplifying mechanisms we suggest that atmospheric circulation changes in the southwest pacific were one important factor in forcing high frequency holocene glacier fluctuations in new zealand

a relationship between alluvial backswamps and avulsion cycles an example from the willwood formation of the bighorn basin wyoming abstract stratigraphically limited intervals from the lower eocene willwood formation contain laterally extensive carbonaceous shales and ribbon sandstone networks associated with channel avulsion we present data from one such interval that documents the avulsion sequence vertical sections measured along the outcrop of this interval are similar and comprise a basal carbonaceous shale overlain by fine grained deposits on which weakly developed hydromorphic paleosols formed the paleosols enclose and are locally incised by ribbon sandstones some of which cut down to and partly through the carbonaceous shale the ribbons have width thickness ratios between 3 and 13 some ribbons cluster at a particular stratigraphic level which together with paleocurrent trends suggests that they formed channel networks sections are capped by yellow brown paleosols showing moderate pedogenic development we suggest that the carbonaceous shales developed in low lying topogeneous swamps in distal portions of the floodplain far from the trunk channel such a location set limits on the sediment that they received the mudrocks with weakly developed paleosols and associated ribbon sandstones are interpreted as crevasse splay complexes resulting from avulsion of the trunk river the ribbon sandstones represent ancient feeder channels of the avulsion complex the rapid influx of avulsion deposits appears to have been crucial to preserving the organic material and this study reveals an important and as yet uncharacterized link between trunk channel processes and the accumulation of organic rich deposits in distal alluvial swamps similar deposits are found in other stratigraphic units in the rocky mountain region and the development of these and other organic rich deposits should be reassessed in terms of channel avulsion

holocene sedimentary record from lake tutira a template for upland watershed erosion proximal to the waipaoa sedimentary system northeastern new zealand abstract a holocene lake record from northeastern new zealand provides a detailed record of environmental controls on upper watershed sedimentation and is proximal to the waipaoa margins source to sink focus site in that context lake tutira in hawke s bay was cored in 2003 to recover a complete sedimentary record since the lake s formation ca 7 2 ka the 27 14 m long core contains alternating lithotypes that are sedimentary responses to lacustrine organic accumulation normal to severe rainfalls earthquakes and volcanism a diatom allochthonous ranking scheme pollen counts and c and n percentages were used to identify intra lake and watershed derived storm deposits and modes of lithotype deposition the lithotypes and depositional modes are tephras volcanic airfall organic rich mud algal rich lake sedimentation massive to weakly graded brown silty clay beds homogenites and redeposited lake sediments grey graded sandy mud beds intense storm delivered sediment and thin yellow clay layers run off from small storms using 12 tephras and 3 radiocarbon ages to provide a chronology the long term sedimentation rate is ca 3 3 mm year which increases to 10 mm year following european colonisation storm beds occur in response to rainfall events with no obvious correlation to el nino southern oscillation polarity or strength moreover no single climate index appears to correlate strongly with the historic rainfall event record having characterised and identified storm beds over the lake s history a hindcast relationship implies that around 53 pre historic storms occurred with a magnitude similar to the severe cyclone bola event of 1988 plus 7 potentially larger storm events despite the prominence of storm beds a summation of the total percent thickness as an indication of the relative modes of emplacement for each lithotype shows that proportionally the balance of intra lake versus storm sources preserved in the lake bed is 69 and 26 respectively as well as storms lake sedimentation is strongly influenced by earthquakes that destabilize the terrigenous sediment laden lake margins to generate homogenites represented by the brown silty clay beds these deposits tend to be thicker after a hiatus in seismic activity and after sustained periods of lake margin loading as inferred from the occurrence of thick graded storm beds comparison with marine records on the adjacent continental margin suggests that more terrestrial events are captured in the lake record due to i close hillslope lake connectivity with little intervening storage of sediment compared with the waipaoa sedimentary system and ii the preservation of event stratigraphy at tutira compared to its reduced preservation in the dynamic marine environment only major storms such as cyclone bola leave an imprint traceable to the ocean whereas identifiable sedimentary responses to individual earthquakes are localized although through landscape preconditioning and sediment production they contribute to the overall high terrigenous input to the ocean in contrast low frequency high magnitude perturbations volcanic eruptions european deforestation are preserved through the source to sink sedimentary system consistent with earlier hypotheses

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

geological controls of copper gold and silver in the serra geral group realeza region parana brazil abstract the serra geral group has high cu concentrations in southern brazil including the realeza parana region where au and ag also occur the basalts 46 7 50 8 wt sio 2 have breccias at the top of 10 out of 31 studied flows in the realeza section and at the top of 5 out of 7 analyzed flows in the capanema section sand injectites occur at the top of basalts in 18 out of 23 flows from the realeza section the average content of cu in three samples of mineralized breccias is 3788 ppm one sample from a silicified sandstone sill intruded at the top of a basalt flow has up to 0 66 ppm au k 2 o was not leached during basalt alteration the hydrothermal breccias particularly when sand is present show enrichment in u which leads to higher values of scintillometry rate of emission of k u and th in the basalts breccias and sandstones pd 17 5 8 4 ppb is higher than pt 12 5 5 ppb suggesting a hydrothermal remobilization of the metals the serra geral group is thus shown to have high potential for precious and base metal deposits

quaternary slip rate and geomorphology of the alpine fault implications for kinematics and seismic hazard in southwest new zealand glacial landforms at 12 localities in 9 river valleys are offset by the southern end of the onshore alpine fault offsets cluster at 435 1240 and 1850 m consistent with evidence for glacial retreat at 18 58 and 79 calendar ka the peak of an offset fluvial aggradation surface is correlated with the last glacial maximum at 22 ka displacement rates derived from features aged 18 22 58 and 79 cal ka are 24 2 2 2 23 2 4 9 21 4 2 6 and 23 5 2 7 mm yr respectively with uncertainties at the 95 confidence level the joint probability weighted mean and arithmetic mean of all observations pooled by rank are 23 1 1 5 23 2 1 4 and 23 1 1 7 mm yr respectively we conclude that the mean surface displacement rate for this section of the alpine fault is 23 1 mm yr with standard error in the range of 0 7 0 9 mm yr the reduction in estimated long term slip rate from 26 6 mm yr to 23 2 mm yr results in an increase in estimated hazard associated with faulting distributed across the rest of the plate boundary model dependent probabilities of alpine fault rupture within the next 50 yr are in the range 14 29 the 36 3 mm yr of total plate motion nuvel 1a is partitioned into 23 2 mm yr of alpine fault dextral strike slip 12 4 mm yr of horizontal motion by clockwise block rotations and oblique dextral reverse faulting up to 80 km southeast of the alpine fault and 5 3 mm yr of heave on reverse faults at the peripheries of the plate boundary

major earthquakes occur regularly on an isolated plate boundary fault the scarcity of long geological records of major earthquakes on different types of faults makes testing hypotheses of regular versus random or clustered earthquake recurrence behavior difficult we provide a fault proximal major earthquake record spanning 8000 years on the strike slip alpine fault in new zealand cyclic stratigraphy at hokuri creek suggests that the fault ruptured to the surface 24 times and event ages yield a 0 33 coefficient of variation in recurrence interval we associate this near regular earthquake recurrence with a geometrically simple strike slip fault with high slip rate accommodating a high proportion of plate boundary motion that works in isolation from other faults we propose that it is valid to apply time dependent earthquake recurrence models for seismic hazard estimation to similar faults worldwide

middle holocene avulsion belt deposits in the central rhine meuse delta the netherlands abstract the schoonrewoerd fluvial system in the central rhine meuse delta was active as a rhine distributary between 3900 and 3800 14c years bp based on planform patterns cross sectional facies architecture reconstructed paleodischarge and its short period of activity the schoonrewoerd fluvial system is interpreted to represent a failed avulsion the schoonrewoerd system consists of a complex of ribbon channel sand bodies encased in a lens of clayey deposits and it can be traced for more than 35 km in a downstream direction prominent features of the system are longitudinal facies architecture change with channel sand body width thickness ratio decreasing downstream from 40 to 5 and high lateral facies variability multiple anastomosing sand bodies occur in its upper and middle reaches paleodischarge reconstruction indicates that the schoonrewoerd system was only a minor distributary within the rhine meuse deltaic system specific stream power in the lower reach is estimated to have been low 0 5 to 1 8 w m2 the short period of activity of the schoonrewoerd system suggests that very high floodplain sedimentation rates were associated with the avulsion process with the formation of meters thick fine grained sedimentary successions in 100 years the facies architecture of the short lived schoonrewoerd system is interpreted to reflect the first stages of avulsion broadly analogous to the modern saskatchewan river avulsion in canada smith et al 1989 sedimentology v 36 p 1 23 having escaped from later erosion by a more mature channel belt many other systems often partly eroded with similar facies architecture exist in the west central rhine meuse delta suggesting that avulsion belt deposits are a major component of the holocene delta deposits the facies architecture model of the schoonrewoerd avulsion belt deposits presented in this paper may provide clues for the interpretation of fine grained sedimentary successions in ancient fluviodeltaic deposits

episodic behavior of the jordan valley section of the dead sea fault inferred from a 14 ka long integrated catalog of large earthquakes the continuous record of large surface rupturing earthquakes along the dead sea fault brings unprecedented insights for paleoseismic and archaeoseismic research in most recent studies paleoseismic trenching documents the late holocene faulting activity while tectonic geomorphology addresses the long term behavior 10 ka with a tendency to smooth the effect of individual earthquake rupture events m w 7 here we combine historical archaeological and paleoseismic investigations to build a consolidated catalog of destructive surface rupturing earthquakes for the last 14 ka along the left lateral jordan valley fault segment the 120 km long fault segment limited to the north and the south by major pull apart basins the hula and the dead sea respectively is mapped in detail and shows five subsegments with narrow stepovers width 3 km we conducted quantitative geomorphology along the fault measured more than 20 offset drainages excavated four trenches at two sites and investigated archaeological sites with seismic damage in the jordan valley our results in paleoseismic trenching with 28 radiocarbon datings and the archaeoseismology at tell saydiyeh supplemented with a rich historical seismic record document 12 surface rupturing events along the fault segment with a mean interval of 1160 yr and an average 5 mm yr slip rate for the last 25 ka the most complete part of the catalog indicates recurrence intervals that vary from 280 yr to 1500 yr with a median value of 790 yr and suggests an episodic behavior for the jordan valley fault our study allows a better constraint of the seismic cycle and related short term variations late holocene versus long term behavior holocene and late pleistocene of a major continental transform fault

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

origin of small scale segmentation and transpressional thrusting along the alpine fault new zealand the alpine fault is the major structural feature of the australian pacific plate boundary in the south island of new zealand geologic evidence suggests that half to three quarters of the plate boundary displacement is accommodated by movement on the fault detailed investigation of the central section of the alpine fault has revealed that it consists of oblique thrust sections striking 020 050 that are linked by subvertical right lateral faults striking between 065 and 090 the segmentation is on a scale of 1 10 km similarly oriented right lateral faults are abundant southeast of the alpine fault and are consistent with stresses induced in an elastic layer by an oblique slip ductile fault zone below propagation of the fault to the surface is predicted to result in an en echelon arrangement of strike slip and thrust segments it is suggested that the spatial distribution of segments is affected by the existence of deeply incised valleys in the hanging wall that disturb the stress field to depths of 1 4 km the segmentation is near surface and does not appear to act as a barrier to the propagation of large earthquakes

sediment production and delivery from recent large landslides and earthquake induced rock falls in the upper soca river valley slovenia abstract landsliding not only changes the morphology of the terrain but is also an effective factor in sediment production extreme events such as earthquake induced large rock falls or rainfall induced landslides may during the event itself or in a period after it greatly increase the sediment delivery and river sediment transport the effects of strong earthquakes and large landslides on sedimentation are evident in the upper soca river basin nw slovenia the annual sediment production in the headwaters of this typical alpine valley in western slovenia is estimated to average 1000 m 3 km 2 a 1 in the last few years two large landslides triggered there were of comparable volume but differed regarding sediment delivery to the fluvial network the 2000 sto e landslide at 1 5 million m 3 was a debris flow that delivered more than 1 million m 3 to the koritnica river the strug complex landslide was initiated in 2001 by a rock slide and soon amounted to an estimated volume of 310 000 m 3 in 2002 it released over 20 rainfall induced debris flows on the order of 100 to 1000 m 3 to the fluvial system in mountainous terrain in the headwaters of the upper soca river slope failures may occur during strong earthquakes depending on the event magnitude the earthquake of april 12 1998 m s 5 6 caused more than 100 failures among them 50 rock falls about 260 000 m 3 of rock fall material will remain on hill slopes with no potential of reaching the river network while an estimated volume of 480 000 m 3 may be released to watercourses in a longer period during extreme events about 200 000 m 3 of rock fall debris was deposited in areas from where the material was released to watercourses during rainfall events as a consequence of the 1998 earthquake hyperconcentrated flows were observed during floods in some torrential tributary channels of the upper soca river after the earthquake of july 12 2004 m s 4 9 50 rather superficial slope failures including 38 rock falls were registered from 2000 until 2004 more than 150 000 m 3 sediments were dredged from the upper soca river channel

late holocene rupture history of the alpine fault in south westland new zealand abstract strata and fault relationships revealed in five trenches excavated across the recent trace of the alpine fault at the haast okuru and turnbull rivers south westland new zealand record the three most recent surface faulting events using back stripping techniques to remove the three faulting events and the sedimentary units associated with the faulting restores the cross sections to gravel bed floodplains at the haast and okuru rivers at about a d 750 horizontal and vertical offsets of stream channels and terrace risers reveal characteristic displacements of about 8 9 m dextral and up to 1 m vertical per event cumulative dextral displacement is 25 3 m in the past three events the most recent surface rupture event was probably in a d 1717 and the next prior events were about a d 1230 50 and about a d 750 50 the timing of these events is consistent with past large great earthquakes on the southern section of the alpine fault inferred from off fault data but there are fewer events identified in trenches our three event dataset indicates the average surface rupture recurrence interval for the south westland section of the fault is about 480 years much longer than the current elapsed time of 295 years therefore the alpine fault in south westland may not be close to rupture as is often speculated

late quaternary slip rates and slip partitioning on the alpine fault new zealand abstract published geological data on late quaternary offsets on the alpine fault new zealand have been assembled into a common format and analysed with respect to uncertainties uncertainties arise mainly from measurement of offset features relating apparent offsets to actual fault slip and dating the offset features despite the considerable uncertainties the data form a coherent set consistent with a relatively constant rate of strike slip of 27 5 mm year between milford sound and hokitika this rate represents 70 75 of the fault parallel interplate motion north of the confluence with the hope fault the rate drops substantially dip slip rates on the other hand show considerable variation along strike rising to a maximum of more than 10 mm year in the central section and decreasing to zero at the southern end partitioning of c 25 of the interplate slip on to structures east of the alpine fault occurs in the central section consistent with predictions from critical wedge models the partitioning of all the fault normal component of displacement on to other structures in the south may be related in part to a doubling in width of the deforming wedge to the east most probably however the fault normal displacement is mainly accommodated by underthrusting of the australian plate offshore due to a change in the nature of the crust from continental to oceanic

mississippi delta subsidence primarily caused by compaction of holocene strata coastal subsidence causes sea level rise shoreline erosion and wetland loss which poses a threat to coastal populations this is especially evident in the mississippi delta in the southern united states which was devastated by hurricane katrina in 2005 the loss of protective wetlands is considered a critical factor in the extensive flood damage the causes of subsidence in coastal louisiana attributed to factors as diverse as shallow compaction and deep crustal processes remain controversial current estimates of subsidence rates vary by several orders of magnitude here we use a series of radiocarbon dated sediment cores from the mississippi delta to analyse late holocene deposits and assess compaction rates we find that millennial scale compaction rates primarily associated with peat can reach 5mm per year values that exceed recent model predictions locally and on timescales of decades to centuries rates are likely to be 10 mm or more per year we conclude that compaction of holocene strata contributes significantly to the exceptionally high rates of relative sea level rise and coastal wetland loss in the mississippi delta and is likely to cause subsidence in other organic rich and often densely populated coastal plains

long term earthquake clustering summary we analyse statistically the long term properties of several instrumental earthquake catalogues complete catalogues exhibit both short and long term clustering for earthquakes of all depth ranges after accounting for the effect of short term clustering we find that in residual declustered catalogues long term clustering not periodicity characterizes the occurrence of all earthquakes shallow intermediate and deep the degree of clustering in residual catalogues is the same for earthquakes in different depth ranges circumstantial evidence indicates that the long term v ariation of seismicity is governed by a power law temporal distribution as in short term clustering it is scale invariant the fractal dimension of an earthquake set on the time axis is of the order of 0 8 0 9 therefore mainshock occurrence is closer to a stationary poisson process than standard aftershock sequences of shallow earthquakes

geological impacts on coastal wetland landscapes some general effects of sediment autocompaction in the holocene of northwest europe a simulation model is described providing general insights into autocompaction effects in stratigraphic sequences formed on coastal mudflats and marshes over uneven basements lithological units and buried landscapes are progressively displaced and distorted the synthetic sequences resembling bedding geometries described from the northwest european holocene autocompaction also promotes local deposition rates that may greatly exceed the rates at which accommodation space is created transgressive silts are associated with especially large deposition rates because of the high compressibility of underlying peats the experimental relationships between apparent rates of sea level rise and bed thickness resemble empirical trends for the holocene the latter are however reinforced by an intrinsic lithology related effect not included in the model

prolonged seismically induced erosion and the mass balance of a large earthquake large earthquakes deform the earth s surface and drive topographic growth in the frontal zones of mountain belts they also induce widespread mass wasting reducing relief the sum of these two opposing effects is unknown using a time series of landslide maps and suspended sediment transport data we show that the mw7 6 chi chi earthquake in taiwan was followed by a period of enhanced mass wasting and fluvial sediment evacuation peaking at more than five times the background rate and returning progressively to pre earthquake levels in about six years therefore it is now possible to calculate the mass balance and topographic effect of the earthquake the choshui river has removed sediment representing more than 30 of the added rock mass from the epicentral area this has resulted in a reduction of surface uplift by up to 0 25 m or 35 of local elevation change and a reduction of the area where the chi chi earthquake has built topography for other large earthquakes erosion may evolve in similar predictable ways reducing the efficiency of mountain building in fold and thrust belts and the topographic expression of seismogenic faults prolonging the risk of triggered processes and impeding economic regeneration of epicentral areas

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

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

re examining southern hemisphere westerly wind behavior insights from a late holocene precipitation reconstruction using new zealand fjord sediments abstract the behavior of the southern hemisphere westerly winds sww is inherently linked with climate variability understanding past sww climate feedbacks is key to predicting future climate change however we are limited by a lack of sww reconstructions particularly from the southwest pacific here we examine fjord sediments from fiordland new zealand 44 5 46 5 s to determine how the sww have fluctuated in position and strength in response to regional late holocene climate change and we compare our record to patagonia climate reconstructions in order to evaluate large scale sww behavior sww flow over the southern alps of new zealand drives orographic rainfall that is recorded within fjord sediments as changes in the relative contributions of terrestrial to marine organic matter which can be measured by bulk sediment 13 c and organic c n ratios using these proxies cores from three new zealand fjords show that precipitation decreased between 1400 1100 and 750 150 cal yr bp with short duration shifts toward drier conditions at 1900 and 900 cal yr bp precipitation increased 2100 1400 and 1100 700 cal yr bp with a short interval of wetter conditions around 400 cal yr bp these results indicate that westerly airflow over new zealand was stronger weaker during intervals of relatively warm cool climate our comparison of precipitation reconstructions from fiordland and patagonia shows dissimilarities in sww flow between regions while to date most mechanisms for changing the sww have invoked purely zonal shifts our results suggest that meridional changes in sww flow occurred in addition to zonal shifts in fiordland the meridional airflow associated with sam and or el nino like climate phenomena may be responsible for wet intervals while sam and or la nina like phenomena may promote dry conditions

fine grained splay deposition in the avulsion belt of the lower saskatchewan river canada abstract in or about 1883 a northward avulsion of the meandering lower saskatchewan river at the cumberland marshes initiated a broad belt of alluvial sedimentation that has continued to evolve to the present and now covers some 500 km2 the avulsion belt comprises a complex alluvial terrain dominated by individual and coalesced splays and associated wetlands connected by networks of active and abandoned channels of various sizes the windy lake splay a predominantly fine grained feature typical of large parts of the avulsion belt was examined to investigate the relationships between splay evolution and facies development the splay now largely inactive mostly formed over a 35 year period depositing nearly 2 m of sediment over a 7 2 km2 area the splay surface is ch racterized by stable well defined anastomosed distributary channels that separate interchannel wetland basins heights of channel levees diminish downstream and the levees merge with channel mouth bars whose progradation forms the locus of lakeward channel extension and the base for subsequent subaerial levee deposition the anastomosed channel pattern was created when the mouth bars of separate distributary channels merged during progradation vibracore and soil probe profiles show the splay to be dominated by upward coarsening lacustrine prodeltaic mouth bar facies sequences capped by levees and organic rich interchannel wetland deposits channels now containing sand only sporadically in narrowed or slightly migrated reaches will eventually fill with fine sediment when abandonment s complete the windy lake splay is typical of stage iii splays smith et al 1989 whose deposits and associated lacustrine fills form at least half of the avulsion belt thin widespread predominantly upward coarsening sequences capped by either nondepositional horizons or true overbank fines may be characteristic of many avulsive suites in the ancient alluvial record

speleothem stable isotope records interpreted within a multi proxy framework and implications for new zealand palaeoclimate reconstruction a primary step in the interpretation of speleothem stable isotope records 18o 16o and 13c 12c is to conduct a comparison with other local palaeoclimate proxies here two new master speleothem 18o and 13c records one from eastern north island and the other from western southern south island new zealand are evaluated against independent precipitation and temperature proxy information to assess their palaeoclimate reconstruction potential this comparison also resulted in a serendipitous opportunity to reconstruct past circulation using climate regime classification lorrey a m fowler a m salinger j 2007a regional climate regime classification as a qualitative tool for interpreting multi proxy palaeoclimate data spatial patterns a new zealand case study palaeo 3 in press specifically because these two regional climate districts are hyper sensitive to westerly circulation changes and in many cases exhibit contrasting climate character in response to circulation anomalies for both the western south island and the eastern north island master speleothem 13c records variations tracked changes in relative regional precipitation the 18o master speleothem record for both regions varied with temperature change both records contain strong regional climate signals that suggest they have good value for palaeoclimate reconstruction the ensuing attempt at a multi proxy reconstruction of regional climate regimes from the compiled proxies indicates past circulation in the new zealand sector has varied considerably during the past four millennia centennial scale circulation changes for the past 4000 years are evident and are analogous to modern blocking zonal and trough regime types kidson j w 2000 an analysis of new zealand synoptic types and their use in defining weather regimes international journal of climatology 20 299 316 that characterise changes in present day prevailing westerly circulation this palaeoclimate reconstruction indicates modern regional climate regime classification can be extended at least as far back as the temporal coverage of the records presented here and it can likely be improved on with better dating control and the addition of new records with higher resolution it is also anticipated that future work will expand to include more proxy data from across new zealand to improve the clarity of past climate regime occurrence for the late holocene

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

coastal dunes in westland new zealand provide a record of paleoseismic activity on the alpine fault regional episodes of coastal progradation and dune formation in south westland new zealand have quickly followed all known alpine fault earthquakes since a d 1200 this reflects rapid transport of large postseismic sediment pulses from mountain catchments to the coast and accumulation of this material as a dune ridge this study provides the first demonstration of this link for multiple events over a region the dune sequences also provide evidence of another previously unrecognized regional aggradation event which may be earthquake related and which occurred just 50 yr after a large alpine fault earthquake coastal dunes have great potential for paleoseismic application because the spatial separation of earthquake induced sediment pulses on a prograding coast allows identification of events closely spaced in time coastal dune systems have the potential to improve paleoseismic understanding over the holocene for many plate boundary faults near coastal areas

large rock avalanches triggered by the m 7 9 denali fault alaska earthquake of 3 november 2002 the moment magnitude m 7 9 denali fault alaska earthquake of 3 november 2002 triggered thousands of landslides primarily rock falls and rock slides that ranged in volume from rock falls of a few cubic meters to rock avalanches having volumes as great as 20 10 6 m 3 the pattern of landsliding was unusual the number and concentration of triggered slides was much less than expected for an earthquake of this magnitude and the landslides were concentrated in a narrow zone about 30 km wide that straddled the fault rupture zone over its entire 300 km length despite the overall sparse landslide concentration the earthquake triggered several large rock avalanches that clustered along the western third of the rupture zone where acceleration levels and ground shaking frequencies are thought to have been the highest inferences about near field strong shaking characteristics drawn from interpretation of the landslide distribution are strikingly consistent with results of recent inversion modeling that indicate that high frequency energy generation was greatest in the western part of the fault rupture zone and decreased markedly to the east d 2005 elsevier b v all rights reserved

erosional control on the structural evolution of a transpressional thrust complex on the alpine fault new zealand abstract the waikukupa thrust is a 4 km long oblique thrust segment of the new zealand alpine fault that has developed over the last 65 000 years emplacing mylonite and cataclasite over fluvioglacial gravel during the last 20 000 years or so a 2 km long out of sequence imbricate the hare mare thrust has formed on the east side of the waikukupa river valley the average rate of slip on the two thrusts is estimated at 22 30 mm year analysis of the fault structure in terms of critical wedge theory is consistent with imbrication resulting from a reduction in wedge taper below the critical value due to rapid river erosion the internal structure of the waikukupa thrust sheet consists of reverse faults and angular folds forming duplex like systems associated with minor strike slip faults within the limits of uncertainty the structures are consistent with strain accumulating during internal transpressional shear of the thrust sheet while the taper of the latter was subcritical prior to the transfer of fault displacement to the hare mare imbricate the thrust complex forms part of a serrated range front fault system consisting of oblique thrust sections linked by strike slip faults we introduce the term serial partitioning for this type of partitioned transpressional fault system its development is linked to the erosional processes at the range front an alternative system consisting of parallel thrust and strike slip faults we here term parallel partitioning while angle of obliquity is an important parameter in determining which partitioning model develops we suggest that erosion rate is also an influential factor

how rivers react to large earthquakes evidence from central taiwan earthquakes and bedrock river incision are fundamental processes in the evolution of tectonically active landscapes yet little work has focused on understanding how a bedrock river responds to a single large earthquake data from the 1999 m w 7 6 chi chi earthquake in central taiwan show dramatic differences in river response that depend on the proximity to the rupture zone near the fault scarp vertical ground deformation intensifi es river incision on a time scale of years to decades while distal to the fault landslides induced by the earthquake mantle bedrock on the river bed with sediment impeding incision for decades to centuries as the material is evacuated this surprising spatial and temporal variability in bedrock incision caused by earthquakes has implications for the paleoseismic interpretation of bedrock terraces and for the evolution of tectonically active landscapes

quasi periodic recurrence of large earthquakes on the southern san andreas fault it has been 153 yr since the last large earthquake on the southern san andreas fault california united states but the average interseismic interval is only 100 yr if the recurrence of large earthquakes is periodic rather than random or clustered the length of this period is notable and would generally increase the risk estimated in probabilistic seismic hazard analyses unfortunately robust characterization of a distribution describing earthquake recurrence on a single fault is limited by the brevity of most earthquake records here we use statistical tests on a 3000 yr combined record of 29 ground rupturing earthquakes from wrightwood california we show that earthquake recurrence there is more regular than expected from a poisson distribution and is not clustered leading us to conclude that recurrence is quasi periodic the observation of unimodal time dependence is persistent across an observationally based sensitivity analysis that critically examines alternative interpretations of the geologic record the results support formal forecast efforts that use renewal models to estimate probabilities of future earthquakes on the southern san andreas fault only four intervals 15 from the record are longer than the present open interval highlighting the current hazard posed by this fault

landslide induced river channel avulsions in mountain catchments of southwest new zealand pulsed or chronic supply of landslide debris to valley floors has historically caused substantial aggradation and channel instability in several alpine catchments of sw new zealand in this regional investigation of landslide impacts on river morphology three types of landslide induced channel avulsion are discerned i upstream backwater avulsions ii contact avulsions and iii downstream loading avulsions the basis for this qualitative geomorphic process response framework is the principal direction of fluvial response with respect to its position relative to the causative landslide emplacement site downstream avulsions have the highest damage potential to land use and infrastructure on unconfined mountain fringe alluvial fans in the wake of such events catastrophic aggradation may obliterate up to several km2 of mature floodplain forests by burial under several metres within a few decades estimates of mean aggradation rates are high 220 mm year 1 and exceed long term 103 year trends of fluvial degradation by an order of magnitude future potential avulsion routeways may be detected by geomorphic mapping of abandoned channels which are preferentially reactivated in the wake of landslide induced sediment waves

stream response to repeated coseismic folding tiptonville dome new madrid seismic zone abstract fluvial response to tectonic deformation is dependent on the amount and style of surface deformation and the relative size of the stream active folding in the new madrid seismic zone nmsz forms the tiptonville dome a 15 km long and 5 km wide surface fold with up to 11 m of late holocene structural relief the fold is crossed by streams of varying size from the mississippi river to small flood plain streams fluvial response of these streams to repeated coseismic folding has only been preserved for the past 2 3 ka since the tiptonville meander of the mississippi river migrated across the area forming the present flood plain this surface comprises a sandy point bar deposit locally overlain by clayey overbank and silty sand crevasse splay deposits an abandoned chute channel infilled with laminated sandy silt and silty clay and an abandoned neck cutoff filled with a sandy cutoff bar and silty clay oxbow lake deposits dating various stream responses to coseismic folding has more tightly constrained the timing of earthquake events in the central nmsz and provides a means of partitioning the deformation amount into individual seismic events three earthquakes have been dated in the reelfoot lake area ca a d 900 1470 and 1812 the latter two earthquakes had large local coseismic deformation both of these events were responsible for numerous stream responses such as shifting depocenters modification of mississippi river channel geometry and derangement of small streams overbank sedimentation ceased on the dome as it was uplifted above the normal flood stage and sedimentation of crevasse splay deposits from the mississippi river colluvium from the scarp and lacustrine sediment accumulated in the adjacent reelfoot basin the much larger mississippi river channel responded to uplift by increasing its sinuosity across the uplift relative to both upstream and downstream increasing its width depth ratio across and downstream of the uplift and decreasing the width depth ratio upstream of the uplift despite the size of the mississippi river it has not yet attained equilibrium since the latest uplift 190 years ago small channels that could not downcut through the uplift were filled locally reversed flow direction or formed a lake where they were dammed uplift and stream response to folding along the tiptonville dome is less dramatic between 2 3 and 0 53 ka during this interval abandoned channel fill and overbank deposition across the dome suggests that it was not a high relief feature one earthquake event occurred during this interval ca a d 900 but coseismic stream response was probably limited to a slight aggradation of a small flood plain stream