serial ruptures of the san andreas fault carrizo plain california revealed by three dimensional excavations 1 it is poorly known if fault slip repeats regularly through many earthquake cycles well documented measurements of successive slips rarely span more than three earthquake cycles in this paper we present evidence of six sequential offsets across the san andreas fault at a site in the carrizo plain using stream channels as piercing lines we opened a latticework of trenches across the offset channels on both sides of the fault to expose their subsurface stratigraphy we can correlate the channels across the fault on the basis of their elevations shapes stratigraphy and ages the three dimensional excavations allow us to locate accurately the offset channel pairs and to determine the amounts of motion for each pair we find that the dextral slips associated with the six events in the last millennium are from oldest to youngest 5 4 0 6 8 0 0 5 1 4 0 5 5 2 0 6 7 6 0 4 and 7 9 0 1 m in this series three and possibly four of the six offset values are between 7 and 8 m the common occurrence of 7 8 m offsets suggests remarkably regular but not strictly uniform slip behavior age constraints for these events at our site combined with previous paleoseismic investigations within a few kilometers allow a construction of offset history and a preliminary evaluation of slip and time predictable models the average slip rate over the span of the past five events between a d 1210 and a d 1857 has been 34 mm yr not resolvably different from the previously determined late holocene slip rate and the modern geodetic strain accumulation rate we find that the slip predictable model is a better fit than the time predictable model in general earthquake slip is positively correlated with the time interval preceding the event smaller offsets coincide with shorter prior intervals and larger offset with longer prior intervals

geomorphic and biological indicators of paleoseismicity and holocene uplift rate at a coastal normal fault footwall western corinth gulf greece abstract the westernmost part of the gulf of corinth greece is an area of very fast extension and active normal faulting accompanied by intense coastal uplift and high seismicity this study presents geomorphic and biological evidence of holocene coastal uplift at the western extremity of the gulf where such evidence was previously unknown narrow shore platforms benches and rare notches occur mainly on holocene littoral conglomerates of uplifting small fan deltas they are perhaps the only primary paleoseismic evidence likely to provide information on earthquake recurrence on coastal faults in the specific part of the rift whereas dated marine fauna can provide constraints on the average holocene coastal uplift rate the types of geomorphic and biological evidence identified are not ideal and there are limitations and pitfalls involved in their evaluation in a first approach 5 uplifted paleoshorelines may be identified at 0 4 0 7 1 0 1 3 1 4 1 7 2 0 2 3 and 2 8 3 4 m a m s l probably forming after 1728 or 2250 cal b p a most conservative estimate for the average coastal uplift rate during the late holocene is 1 6 or 1 9 mm yr minimum with different amounts of reservoir correction some of the obtained radiocarbon ages of lithophaga sp allow for much higher holocene uplift rates of the order of 3 4 mm yr which cannot be discarded but require further research that the identified paleoshoreline record corresponds to episodes of coastal uplift only cannot be demonstrated beyond all doubt yet it appears the most likely interpretation given the geological and active tectonic context and present knowledge on eustatic sea level fluctuations in the mediterranean proving that the documented uplifts were abrupt i e arguably coseismic is equally difficult but rather probable five earthquakes in the last ca 2000 yr on the coastal fault zone that is responsible for the uplift compare well with historical seismicity and the results of recent on fault paleoseismological studies at the nearby eliki fault zone exact amounts of coseismic uplift cannot be determined precisely unless the rate of non seismic uplift of northern peloponnesus at the specific part of the corinth rift is somehow constrained

tsunami history of an oregon coastal lake reveals a 4600 yr record of great earthquakes on the cascadia subduction zone bradley lake on the southern oregon coastal plain records local tsunamis and seismic shaking on the cascadia subduction zone over the last 7000 yr thirteen marine incursions delivered landward thinning sheets of sand to the lake from nearshore beach and dune environments to the west following each incursion a slug of marine water near the bottom of the freshwater lake instigated a few year to several decade period of a brackish 4 salinity lake four additional disturbances without marine incursions destabilized sideslopes and bottom sediment producing a suspension deposit that blanketed the lake bottom considering the magnitude and duration of the disturbances necessary to produce bradley lake s marine incursions a local tsunami generated by a great earthquake on the cascadia subduction zone is the only accountable mechanism extreme ocean levels must have been at least 5 8 m above sea level and the cumulative duration of each marine incursion must have been at least 10 min disturbances without marine incursions require seismic shaking as well over the 4600 yr period when bradley lake was an optimum tsunami recorder tsunamis from cascadia plate boundary earthquakes came in clusters between 4600 and 2800 cal yr b p tsunamis occurred at the average frequency of 3 4 every 1000 yr then starting 2800 cal yr b p there was a 930 1260 yr interval with no tsunamis that gap was followed by a 1000 yr period with 4 tsunamis in the last millennium a 670 750 yr gap preceded the a d 1700 earthquake and tsunami the a d 1700 earthquake may be the fi rst of a new cluster of plate boundary earthquakes and accompanying tsunamis local tsunamis entered bradley lake an average of every 390 yr whereas the portion of the cascadia plate boundary that underlies bradley lake ruptured in a great earthquake less frequently about once every 500 yr therefore the entire length of the subduction zone does not rupture in every earthquake and bradley lake has recorded earthquakes caused by rupture along the entire length of the cascadia plate boundary as well as earthquakes caused by rupture of shorter segments of the boundary the tsunami record from bradley lake indicates that at times most recently 1700 yr b p overlapping or adjoining segments of the cascadia plate boundary ruptured within decades of each other

the deglacial evolution of north atlantic deep convection deepwater formation in the north atlantic by open ocean convection is an essential component of the overturning circulation of the atlantic ocean which helps regulate global climate we use water column radiocarbon reconstructions to examine changes in northeast atlantic convection since the last glacial maximum during cold intervals we infer a reduction in open ocean convection and an associated incursion of an extremely radiocarbon 14c depleted water mass interpreted to be antarctic intermediate water comparing the timing of deep convection changes in the northeast and northwest atlantic we suggest that despite a strong control on greenland temperature by northeast atlantic convection reduced open ocean convection in both the northwest and northeast atlantic is necessary to account for contemporaneous perturbations in atmospheric circulation

coseismic uplift of holocene marine terraces in the pakarae river area eastern north island new zealand abstract holocene marine terraces along 15 km of the northeastern coast of north island record episodic tectonic uplift a maximum of seven terraces are arranged in staircase fashion and lie about 20 km above the subduction interface between the pacific and australian plates the highest t1 corresponds with the maximum of the holocene marine transgression about 6700 14 c yr b p younger terraces are marine abrasion platforms overlain by thin beach deposits radiocarbon ages of marine shells from beach deposits indicate that uplift above marine conditions occurred ca 6700 t1 5500 t2 3900 t3 2500 4 1600 t5 1000 t6 and slightly younger than 600 t7 yr b p uplift probably occurred coseismically the maximum late holocene uplift rate in the study area is 8 mm yr altitudinal distribution of terraces suggests deformation exists as a ca 20 km elongate dome broken at the southern end by the pakarae fault which trends across the dome rupture on this fault has accompanied the growth of the dome but is not responsible for it bathymetric profiling suggests that an active fault parallel to and about 5 km offshore is probably responsible for the episodic coastal uplift

late pleistocene and halocene sea level changes in japan implications for tectonic histories and mantle rheology abstract it is very important to separate the tectonic and glacial isostatic components in the observed holocene and late pleistocene sea level changes in tectonically active areas such as japan for studying tectonic processes and for constraining mantle rheology the separation can be achieved by considering the spatial dependence of the relative sea level on the geometry of the coastline around the site where sea level is evaluated in fact the relative sea level caused by the last deglaciation at sites in the embayment such as tokyo and osaka has a sea level curve with a high stand at mid holocene and that site situated on the tip of peninsula has a sea level curve culminating towards the present the geometric effect also causes the regional difference of the sea level variations in the late glacial phase in the japanese islands the regional difference of the predicted relative sea level is about 5 m at 6000 years ago 20 m at 10 000 years ago and 30 m at 18 000 years ago comparison between observations and predictions indicates that the observations at several sites in japan are consistent with the predicted sea level variations more systematic data is required for the period 18 000 years ago to the present in order to examine tectonic processes and mantle rheology

the melting history of the late pleistocene antarctic ice sheet spatial and temporal variations in the sea levels of the past 20 000 years around the globe place constraints on the melting history of the major late pleistocene ice sheets the antarctic ice sheets provided a significant contribution to the sea level rise at a rate that was approximately synchronous with the melting of the laurentide ice sheet except for the interval 9 000 6 000 years ago when it may have lagged behind minor melting of the antarctic ice sheet continued throughout the holocene

use of electrical conductivity to analyze depositional environments example of a holocene delta sequence on the nobi plain central japan abstract the usefulness of electrical conductivity ec of stirred holocene deltaic sediments from three cores from the nobi plain japan was assessed as a proxy for marine transgression and regression lack of correlation of ec with mud content for the sediments with 20 mud suggested that permeability was a negligible factor marine deposits showed high ec 0 9 ms cm terrestrial deposits low ec

evidence for large earthquakes in metropolitan los angeles the sierra madre fault along the southern flank of the san gabriel mountains in the los angeles region has failed in magnitude 7 2 to 7 6 events at least twice in the past 15 000 years restoration of slip on the fault indicated a minimum of about 4 0 meters of slip from the most recent earthquake and suggests a total cumulative slip of about 10 5 meters for the past two prehistoric earthquakes large surface displacements and strong ground motions resulting from greater than magnitude 7 earthquakes within the los angeles region are not yet considered in most seismic hazard and risk assessments

lagoon subsidence and tsunami on the west coast of new zealand abstract sediment core and trench data from a coastal lagoon on the west coast of the south island new zealand are used to investigate evidence for co seismic subsidence and associated tsunami inundation physical data are used to document a salt marsh soil buried 80 cm below the modern sediment surface that is locally covered by a gravelly sand bed the sediment record also contains geochemical and biological diatom and foram evidence for abrupt changes in salinity of lagoon waters that link to subsidence tsunami flooding and to the open versus closed state of the lagoon tidal entrance at the local scale these relationships allow for separation of tsunami evidence from other agents of environmental change in the lagoon we also propose a conceptual connection between these local changes and regional drivers of landscape development most notably major earthquakes and resultant pulses in sediment supply to the coast

crustal bright spots and anisotropy from multi component p and s wave measurements in southern germany abstract controlled shear wave experiments have focussed on deep crustal targets that were earlier recognized by dekorp p wave surveys in southern germany black forest upper palatinate a prominent p wave reflection bright spot at 8 km depth at the ktb deep drilling site is not seen on a comparable s wave reflection section in contrast to deeper reflections this behaviour can be explained either by purely compositional effects layer with anomalously high quartz content or by fluid accumulation reservoir in a fracture zone a 20 km deep 10 km long prominent p wave reflection in the southwestern black forest is only partially accompanied by corresponding s wave reflections the influence of the physical state of the rock e g stress related cracking in addition to possible compositional variations is suggested to explain the contrasting p and s wave reflection strength seismic anisotropy of 10 magnitude revealed by s wave splitting in vertical seismic profiling data at the ktb to more than 4 km depth is attributed to sub vertically dipping and nw striking foliation

great earthquakes and tsunamis of the past 2000 years at the salmon river estuary central oregon coast usa four buried tidal marsh soils at a protected inlet near the mouth of the salmon river yield definitive to equivocal evidence for coseismic subsidence and burial by tsunami deposited sand during great earthquakes at the cascadia subduction zone an extensive landward tapering sheet of sand overlies a peaty tidal marsh soil over much of the lower estuary limited pollen and macrofossil data suggest that the soil suddenly subsided 0 3 1 0 m shortly before burial regional correlation of similar soils at tens of estuaries to the north and south and precise 14c ages from one salmon river site imply that the youngest soil subsided during the great earthquake of 26 january a d 1700 evidence for sudden subsidence of three older soils during great earthquakes is more equivocal because older soil stratigraphy can be explained by local hydrographic changes in the estuary regional 14c correlation of two of the three older soils with soils at sites that better meet criteria for a great earthquake origin is consistent with the older soils recording subsidence and tsunamis during at least two great earthquakes pollen evidence of sudden coseismic subsidence from the older soils is inconclusive probably because the amount of subsidence was small 0 5 m the shallow depths of the older soils yield rates of relative sea level rise substantially less than rates previously calculated for oregon estuaries manuscript received 10 october 2003

great earthquake paleogeodesy and tsunamis of the past 2000 years at alsea bay central oregon coast usa the width of plate boundary fault rupture at the cascadia subduction zone a dimension related to earthquake magnitude remains uncertain because of the lack of quantitative information about land level movements during past great earthquake deformation cycles beneath a marsh at alsea bay on the central oregon coast four sheets of tsunami deposited sand blanket contacts between tidal mud and peat radiocarbon ages for the sheets match ages for similar evidence of regional coseismic subsidence and tsunamis during four of cascadia s great earthquakes barring rapid unrecorded postseismic uplift reconstruction of changes in land level from core samples using diatom and foraminiferal transfer functions includes modest coseismic subsidence 0 470 2 m during the four earthquakes interpretation is complicated however by the 30 38 of potentially unreliable transfer function values from samples with poor analogs in modern diatom and foraminiferal assemblages reconstructions of coseismic subsidence using good analog samples range from 0 4670 12 to 0 0970 20 m showing greater variability than implied by sample specific errors from apparent high rates of land uplift following subsidence and tsunamis we infer that postseismic rebound caused by slip on deep parts of the plate boundary and or viscoelastic stress relaxation in the upper plate may be almost as large as coseismic subsidence modest coseismic subsidence 100 km landward of the deformation front implies that plate boundary ruptures in central oregon were largely offshore ruptures may have been long and narrow during earthquakes near magnitude 9 as suggested for the ad 1700 earthquake or of smaller and more variable dimensions and magnitudes r 2008 elsevier ltd all rights reserved

fragmentary evidence of great earthquake subsidence during holocene emergence valdivia estuary south central chile a reconnaissance of holocene stratigraphy beneath fringing marshes of the valdivia estuary where an m 9 5 earthquake caused 1 2 m of regional coseismic subsidence in 1960 shows only fragmentary evidence of prehistoric coseismic sub sidence in most of the 150 hand driven cores that were examined a distinct uncon formity separates 0 5 1 5 m of late holocene tidal and floodplain mud peat and sand from underlying middle holocene subtidal mud and sand at the las coloradas site where stratigraphy is best preserved two a horizons of marsh and meadow soils abruptly overlain by sand and mud probably record coseismic subsidence shortly fol lowed by tsunamis the amount of subsidence during the earthquakes proved difficult to reconstruct with a diatom transfer function because of differences between modern and fossil diatom assemblages maximum 14 c ages on macrofossils from the two a horizons at the las coloradas site of 1 7 1 3 ka and 2 7 1 7 ka allow correlation of the younger horizon with either of two of six 14 c dated a horizons buried by tsunami sand or post tsunami tidal sand 200 km to the south at maullin and with a lake wide mass wasting event in lago puyehue 100 km to the southeast tidal records of prehistoric coseismic subsidence at valdivia are scarce because of a sea level fall of 3 8 m over the past 6000 years erosion of marsh and meadow soils during subsidence induced flooding of the estuary and largely complete land level recovery during cycles of coseismic subsidence and postseismic uplift online material diatom species data from the las coloradas site valdivia estuary

stratigraphic and microfossil evidence for late holocene tsunamis at swantown marsh whidbey island washington abstract four muddy sand sheets occur within a tidal marsh peat at swantown on the west coast of whidbey island washington the two largest sand sheets pinch out about 100 m inland and became thinner and finer grained landward all four sand sheets contain marine microfossils and have internal stratification they record repeated inundation of the marsh over a short time period by distinct pulses of sediment laden ocean water consistent with deposition by a tsunami wave train the layers have been radiocarbon dated to 1160 1350 1400 1700 1810 2060 and 1830 2120 cal yr b p the overlap in age between the two youngest layers and inferred great earthquake events at the cascadia plate boundary some 250 km to the west suggests they were emplaced by tsunamis from this source area the two older layers do not correlate with plate boundary events they may be products of tsunamis caused by earthquakes on local faults in the strait of juan de fuca or by submarine landslides in this area

geologic evidence for earthquakes during the past 2000 years along the copalis river southern coastal washington evidence for several prehistoric earthquakes is present in deposits less than 2000 years old that crop out at the copalis river estuary 47 07 2 n 124 09 7 w the deposits show that land subsided decimeters into the intertidal zone on as many as three occasions and that sand vented while the land underwent little or no subsidence on another occasion the evidence for earthquake induced subsidence consists of buried marsh and forest soils that evince sudden estuarine submergence attended on at least one occasion by a landward directed surge of sandy water this combination of submergence and surge implies subsidence and tsunami exposed evidence for subsidence and tsunami along the copalis river is strong for a time within a few decades of 300 years ago moderate for a time 1400 1900 years ago and weak subsidence or lacking tsunami for an intermediate time also about 1400 1900 years ago the history of sudden submergence and tsunami in the past 2000 years at the copalis river estuary resembles that shown by buried soils farther south in coastal washington at grays harbor and willapa bay the history can be explained most simply by great mw of 8 or 9 thrust earthquakes at the boundary between the juan de fuca and north america plates with one or two earthquakes occurring 1400 1900 years ago and another close to 300 years ago the evidence for earthquake induced venting along the copalis river consists of sand intrusions and vented sand volcanoes the sand rose through muddy estuarine deposits at least 3 m thick entraining these deposits in fragments as much as 0 3 m long intrusion occurred at one or more times in the past 2000 years and at least some of the venting occurred 900 1300 years ago the sand bodies do not imply artesian flow of flood pressured groundwater because the sand vented forcefully and infrequently through a lowland that probably lacked natural levees the earthquake implied by the venting of sand 900 1300 years ago could have come from a source below above or at the boundary between the juan de fuca and north america plates if from the subducted juan de fuca plate the implied earthquake was farther west or larger than the largest earthquakes within that plate during the past 100 years evidence permitting a source within the north america plate includes a fault scarp an uplifted tideflat and landslides near puget sound dating from the interval 700 1700 years ago a plate boundary source would explain buried soils whose estuarine submergence and burial imply coseismic subsidence for parts of coastal washington in the interval 600 1300 years ago however stratigraphy shows that little or no coseismic subsidence occurred along the copalis river during the venting 900 1300 years ago if a plate boundary earthquake struck coastal washington 900 1300 years ago the earthquake produced a different distribution of land level change than did the plate boundary earthquakes inferred for 1400 1900 and 300 years ago

coseismic fault related fold model growth structure and the historic multisegment blind thrust earthquake on the basement involved yoro thrust central japan 1 we use high resolution seismic reflection profiles boring transects and mapping of fold scarps that deform late quaternary and holocene sediments to define the kinematic evolution subsurface geometry coseismic behavior and fault slip rates for an active basement involved blind thrust system in central japan coseismic fold scarps on the yoro basement involved fold are defined by narrow fold limbs and angular hinges on seismic profiles suggesting that at least 3 9 km of fault slip is consumed by wedge thrust folding in the upper 10 km of the crust the close coincidence and kinematic link between folded horizons and the underlying thrust geometry indicate that the yoro basement involved fold has accommodated slip at an average rate of 3 2 0 1 mm yr on a shallowly west dipping thrust fault since early pleistocene time past large magnitude earthquakes including an historic m 7 7 event in a d 1586 that occurred on the yoro blind thrust are shown to have produced discrete folding by curved hinge kink band migration above the eastward propagating tip of the wedge thrust coseismic fold scarps formed during the a d 1586 earthquake can be traced along the en echelon active folds that extend for at least 60 km in spite of different styles of folding along the apparently hard linked nobi ise blind thrust system we thus emphasize the importance of this multisegment earthquake rupture across these structures and the potential risk for similar future events in en echelon active fold and thrust belts

identifying coseismic subsidence in tidal wetland stratigraphic sequences at the cascadia subduction zone of western north america tidal wetland stratigraphy reveals that great plate boundary earthquakes have caused hundreds of kilometers of coast to subside at the cascadia subduction zone however determining earthquake recurrence intervals and mapping the coastal extent of past great earthquake ruptures in this region are complicated by the effects of many sedimentologic hydrographic and oceanographic processes that occur on the coasts of tectonically passive as well as active continental margins tidal wetland stratigraphy at many cascadia estuaries differs little from that at similar sites on passive margin coasts where stratigraphic sequences form through nonseismic processes unrelated to coseismic land level changes methods developed through study of similar stratigraphic sequences in europe provide a framework for investigating the cascadia estuarine record five kinds of criteria must be evaluated when inferring regional coastal subsidence due to great plate boundary earthquakes the suddenness and amount of submergence the lateral extent of submerged tidal wetland soils the coincidence of submergence with tsunami deposits and the degree of synchroneity of submergence events at widely spaced sites evaluation of such criteria at the cascadia subduction zone indicates regional coastal subsidence during at least two great earthquakes evidence for a coseismic origin remains equivocal however for the many peat mud contacts in cascadia stratigraphic sequences that lack 1 contrasts in lithology or fossils indicative of more than half a meter of submergence 2 well studied tsunami deposits or 3 precise ages needed for regional correlation paleoecologic studies of fossil assemblages are particularly important in estimating the size of sudden sea level changes recorded by abrupt peat mud contacts and in helping to distinguish erosional and gradually formed contacts from coseismic contacts reconstruction of a history of great earthquakes for the cascadia subduction zone will require rigorous application of the above criteria and many detailed investigations

past earthquake induced rapid subsidence along the northern san andreas fault a paleoseismological method for investigating strike slip faults evidence of rapid relative sea level changes preserved in sediment of coastal estuaries along the north coast segment of the san andreas fault provides information on the dates of past earthquakes this approach although successfully used to document large subduction zone earthquakes has not been used previously to constrain the dates of san andreas fault or other strike slip fault earthquakes data on prehistoric san andreas fault earthquakes is needed for development of robust probabilistic hazard assessments in northern california and the san francisco bay area evidence of earthquake induced subsidence is preserved in marshes at the northern margin of bolinas lagoon and the southeastern margin of bodega harbor these sites occupy structural basins or troughs along the northern san andreas fault radiocarbon dating and identification of the first occurrence of nonnative pollen near abrupt sedimentological changes in cores are used to constrain the dates of san andreas fault earthquakes over about the last 800 years estuarine sediment from northern bolinas lagoon preserves evidence of an earthquake that occurred about 750 years ago evidence for this earthquake includes a marsh soil that was abruptly buried by tidal flat mud or coarse poorly sorted deltaic deposits containing a mixture of terrestrial sediment and marine mud evaluation of diatom assemblages from above and below the buried soil horizon provides evidence of at least several decimeters of sustained relative sea level rise three buried soils in a marsh at the southern end of bodega harbor are likely a result of coseismic subsidence all three buried marsh soils have abrupt upper contacts although diatom evidence for decimeters of sustained subsidence is not as strong as it is for the buried soil in bolinas lagoon existing paleoseismic data on the northern san andreas fault is compared with results of this study in order to evaluate the dates of prehistoric large earthquakes and length of past ruptures these data indicate that an earthquake occurred about 400 years ago and another earthquake occurred about 700 years ago the data allow for 1906 type ruptures of the fault from the santa cruz mountains to at least point arena however a sequence of closely timed smaller earthquakes would produce a similar set of paleoseismic data

evidence for earthquake induced subsidence about 1100 yr ago in coastal marshes of southern puget sound washington buried forest and high marsh soils indicate abrupt changes in relative sea level at four coastal localities in southern puget sound at little skookum inlet and red salmon creek douglas fir stumps in growth position are buried by salt marsh peat at localities along mcallister creek and the nisqually river high marsh soils are buried by tidal flat mud localized liquefaction coincided with submergence of the high marsh soil at mcallister creek dramatic changes in seed and diatom assemblages across these contacts confirm rapid submergence at little skookum inlet and red salmon creek salt marsh peat immediately above a buried forest soil contains diatoms indicative of low marsh and tidal flat environments at mcallister creek and nisqually river low marsh and tidal flat diatoms are abundant in laminated mud directly over high marsh peat inferences from modern analogs indicate at least 1 m of subsidence at each site and possibly up to 3 m at skookum inlet abrupt burial of lowland soils in southern puget sound is best explained by coseismic subsidence some of the submergence may be the result of coseismic compaction and postearthquake settlement widespread buried soils large amounts of subsidence coeval submergence across a wide area and ground shaking at the time of subsidence all point to a large earthquake between 1150 and 1010 cal yr b p in southern puget sound as the most likely cause of subsidence

detecting vertical faulting event horizons from holocene synfaulting in shallow marine sediments on the western margin of the nobi plain central japan abstract holocene activity of the kuwana fault was reconstructed on the basis of 82 accelerator mass spectrometry ams dates and stepwise changes in the depositional rates of shallow marine sediments in four cores drilled to examine the regularity of the recurrence interval of ruptures of this active intraplate fault in our model depositional rates on the footwall and hanging wall are nearly equal during interseismic periods but depositional rates on the footwall become markedly larger than those on the hanging wall just after vertical displacement of the fault to detect the timing of each faulting event more precisely we compared changes in the depositional rates in cores from both the downthrown footwall and uplifted hanging wall sides of the fault as a result six probable and one possible paleoseismic events including the last two historical earthquakes were inferred to have occurred during the last 7000 yr on the basis of stepwise changes in the depositional rate on the two sides of the fault the timing of the faulting events was estimated from depositional rate curves of four cores probable ages of seismic events were approximately 6200 5700 4000 3600 and 2100 calendar years before present and a d 745 and 1586 the average earthquake recurrence interval on the kuwana fault calculated from these data is about 1000 yr the average vertical slip rate of the fault has been at least 1 mm yr during the last 7000 yr

high accuracy synchronism for seismic reflectors and 14c ages holocene prodelta succession of the kiso river central japan abstract horizons at 500 yr intervals for the past 6000 years can be inferred in two cores drilled along a high resolution seismic line in the prodelta of the kiso river ise bay central japan these horizon ages clearly indicate that a given seismic reflection line in the profile is isochronous synchronism between ages and reflectors in the succession is especially distinct for the interval from 5000 to 2500 yr bp despite the reflectors having inclined planes and having the same ages at different depths these data indicate that the kiso river delta prograded to form a downlap surface before the maximum flooding stage of the post glacial relative sea level rise at about 6000 yr bp delta progradation beginning late in the transgressive stage was caused by the flow of large amounts of sediment into this steep river that is part of the active japanese volcanic arc

the earthquake potential of the new madrid seismic zone the fault system responsible for new madrid seismicity has generated temporally clustered very large earthquakes in a d 900 100 years and a d 1450 150 years as well as in 1811 1812 given the uncertainties in dating liquefaction features the time between the past three new madrid events may be as short as 200 years and as long as 800 years with an average of 500 years this advance in understanding the late holocene history of the new madrid seismic zone and thus the contemporary tectonic behavior of the associated fault system was made through studies of hundreds of earthquake induced liquefaction features at more than 250 sites across the new madrid region we have found evidence that prehistoric sand blows like those that formed during the 1811 1812 earthquakes are probably com pound structures resulting from multiple earthquakes closely clustered in time or earthquake sequences from the spatial distribution and size of sand blows and their sedimentary units we infer the source zones and estimate the magnitudes of earth quakes within each sequence and thereby characterize the detailed behavior of the fault system it appears that fault rupture was complex and that the central branch of the seismic zone produced very large earthquakes during the a d 900 and a d 1450 events as well as in 1811 1812 on the basis of a minimum recurrence rate of 200 years we are now entering the period during which the next 1811 1812 type event could occur

evidence for coseismic and aseismic uplift in the last 1000 years in the focal area of a shallow thrust earthquake on the noto peninsula west central japan 1 raised shorelines on the noto peninsula on the western coast of central japan suggest a millennial history of recurrent uplift emergence of the coastline by up to 50 cm was recently recorded in association with a moderate earthquake m w 6 7 on 25 march 2007 the shoreline uplift is indicated by the displacement of sessile organisms such as calcareous tubeworms which can also be examined as indicators of past shifts in shoreline level three levels of pre 2007 paleoshorelines are thus identified on this stretch of the japan sea coast the lowest of these dated at ad 1720 1950 tilts northward away from the likely source of a pair of ca m 6 4 earthquakes in 1892 which occurred in a different area to the 2007 earthquake the middle paleo shoreline dated at ad 1430 1655 records a 30 40 cm emergence that may be aseismic the high paleo shoreline dated at ad 1025 1235 records a coseismic uplift of 50 cm and is limited to the area raised coseismically in 2007 the most recent event preceding the 2007 earthquake thus appears to have occurred approximately 1000 years ago

reconstruction of holocene environmental changes in the kiso ibi nagara compound river delta nobi plain central japan by diatom analyses of drilling cores abstract holocene environmental changes were reconstructed by analyzing diatom assemblages from sediment cores ym kzn nk and mc from the nobi plain central japan five diatom assemblage zones were identified 1 at the beginning of the holocene freshwater species were dominant 2 then marine and brackish marine species increased indicating transgression 3 in the middle holocene proportions of marine and brackish marine species became almost constant with marine species dominant 4 marine species began to be replaced by freshwater species indicating marine regression as a result of delta progradation and 5 freshwater species again became dominant these diatom assemblages correlate with previously defined lithological units zones 1 and 2 with unit b fluvial to coastal plain zone 3 with unit c inner bay or prodelta zone 4 mainly with unit d1 delta front slope and zone 5 with units d2 delta front platform and e delta plain and flood plain although the shoreline migrated landward transgression faster than it migrated seaward regression transgressive diatom assemblage changes decrease in marine brackish water species took up to 1000 years whereas regressive changes required only a few hundred years diatom analysis is useful for reconstructing not only holocene sea level changes and sedimentary environments but also local geographic effects

six similar sequential ruptures of the san andreas fault carrizo plain california we document the precise sizes but not the dates of the six latest offsets across the san andreas fault at wallace creek california three and perhaps four of these including the latest in 1857 show dextral offset of 7 5 8 m the third and fourth offsets however are just 1 4 and 5 2 m the predominance of similar offsets for the latest six events suggests that the fundamental properties of the fault system that control slip size do not vary greatly from event to event the large offsets imply that ruptures involving this site are typically more than 200 km long

late holocene coseismic uplift on the hua tung coast eastern taiwan evidence from mass mortality of intertidal organisms abstract the evidence of coseismic uplift on the dynamic wave dominated hua tung coast fringing the active coastal range eastern taiwan has been equivocal due to complex controls by wave and terrestrial sediment over morphological and ecological systems of the coast this study by applying radiocarbon dating methods demonstrates coseismic uplift nature of the coast by finding synchronously killed intertidal organisms mostly boring shell jouannetia sp stranded at different sites of the coast with distinct physiographic characters based on these data together with evidence from wave cut notch sequences two coseismic uplift systems are recognized one centers around the northern middle part of the coast and yields events with uplift amounts of maximal 3 6 m and an average recurrence interval of at least several hundred years the most recent activity of this system influencing at least 70 km of coast occurred at 0 9 ka the earthquake generating this event also triggered extensive landslides debris flows in the region another system exemplified by the uplift associated with the 2003 cheng kung earthquake centers on the southern part of the coast and yields uplift of likely

evidence for liquefaction identified in peeled slices of holocene deposits along the lower columbia river washington peels made from 10 geoslices beneath a riverbank at washington9s hunting island 45 km inland from the pacific coast aid in identifying sand that liquefied during prehistoric earthquakes of estimated magnitude 8 9 at the cascadia subduction zone each slice was obtained by driving sheetpile and a shutter plate to depths of 6 8 m the resulting sample as long as 8 m had a trapezoidal cross section 42 55 cm by 8 cm the slicing created few artifacts other than bending and smearing at slice edges each slice is dominated by well stratified sand and mud deposited by the tidal columbia river nearly 90 of the sand is distinctly laminated the sand contains mud beds as thick as 0 5 m and at least 20 m long and it is capped by a mud bed that contains a buried soil that marks the 1700 cascadia earthquake of estimated magnitude 9 every slice intersected sills and dikes of fluidized sand and many slices show folds and faults as well sills which outnumber dikes mostly follow and locally invade the undersides of mud beds the mud beds probably impeded diffuse upward flow of water expelled from liquefied sand trapped beneath mud beds this water flowed laterally destroyed bedding by entraining fluidizing sand and locally scoured the overlying mud horizontal zones of folded sand extend at least 10 or 20 m and some contain low angle faults many of the folds probably formed while sand was weakened by liquefaction the low angle faults may mark the soles of river bottom slumps or lateral spreads as many as four great cascadia earthquakes in the past 2000 yr contributed to the intrusions folds and faults this subsurface evidence for fluid escape and deformation casts doubt on maximum accelerations that were previously inferred from local absence of liquefaction features at the ground surface along the columbia river the geosliced evidence for liquefaction abounds not only beneath banks riddled with dikes but also beneath banks in which dikes are absent such dike free banks of the columbia river if interpreted without study of postdepositional structures in deposits beneath them provide insufficient basis for setting upper bounds on the strength of shaking from great cascadia earthquakes online material data from outcrop surveys vibracores and penetrometer tests tabular summary of depositional and postdepositional features in geoslices

new evidence for a large earthquake in the new madrid seismic zone between a d 1400 and 1670 in an integrated geological archaeological and geophysical study in the new madrid seismic zone of the southeastern united states we documented a prehistoric sand blow and related feeder dikes at an archaeological site near steele missouri archaeological analysis combined with radiocarbon dating suggest that the earthquake induced features formed between a d 1400 and 1670 this paleoseismic study provides the best evidence to date for a large earthquake occurring in the zone within 400 yr prior to the 1811 1812 new madrid earthquake sequence to determine an optimal location for excavating at the study site we mapped surficial artifact density and conducted geophysical surveys in doing so we were able to reveal critical relationships for constraining the age of the prehistoric earthquake with minimal impact to the archaeological site

activity of the yoro fault system determined from coseismic subsidence events recorded in the holocene delta sequence of the nobi plain central japan the holocene delta sequence of the nobi plain central japan records coseismic subsidence in the western part of the plain caused during the past 6000 years by movement on the yoro fault we identified four episodes of upward fining deposition and increasing electrical conductivity in delta front deposits that occurred 600 200 1300 900 4200 3800 and 5600 4700 years ago suggesting that episodes of sea level rise interrupted progradation of the kiso river delta considering the general trend of relative sea level fall during the middle to late holocene under the influence of eustasy and hydroisostasy the temporal correspondence of rises of relative sea level with activity on the yoro fault suggests they reflect coseismic subsidence due to yoro fault activity the timing of the coseismic subsidence events identified in this study also corresponds with that of previously reported faulting events at the kuwana fault to the south of the yoro fault these results are consistent with the previous interpretation that the yoro and kuwana faults comprise a behavioral segment within the yoro fault system our off fault paleoseismic study shows that coseismic subsidence events detected in holocene delta sequences can provide further evidence of faulting events inferred from the on fault paleoseismic studies