detailed tephrochronology and composition of major holocene eruptions from avachinsky kozelsky and koryaksky volcanoes in kamchatka abstract avachinsky kozelsky and koryaksky volcanoes form one of the most volcanically active clusters in the kamchatka volcanic arc and are located in close proximity of the cities of petropavlovsk kamchatsky and elizovo the most populated area in kamchatka in this paper we report a compilation of new and revised previously published data on the eruptive history of these volcanoes during the past 13 5 kyrs we identify 217 explosive eruptions of these volcanoes determine their ages using 207 radiocarbon dates and bayesian statistical modeling and characterize their tephra geochemically using major and trace element compositions of bulk samples 40 samples and volcanic glass 75 samples avachinsky has been the most active during the holocene time and had 150 explosive eruptions koryaksky produced 60 eruptions and kozelsky had only two eruptions in the early holocene our new data confirm the onset of the avachinsky postglacial activity at 11 3 cal ka bp and previously distinguished two major stages of avachinsky holocene eruptive history stage i 8 3 8 cal ka bp and stage ii 3 8 cal ka bp present during stage i eruptions were relatively rare but they included at least six large pumice eruptions with tephra volumes exceeding 0 5 km3 stage i tephras had low k andesitic bulk compositions and low k rhyolitic matrix glasses the andesites likely sampled volatile rich crystal mush from a long lived magma chamber under avachinsky volcano the stage ii started at 3 8 cal ka bp with a powerful eruption and was related to the construction of the young cone inside the avachinsky somma the subsequent late holocene eruptions were frequent but most of them did not exceed the volume of 0 3 km3 the stage ii tephras are mostly cindery basaltic andesites containing well crystallized groundmasses of andesitic composition these tephras originate from smaller perhaps more shallow magmatic reservoirs and their matrix glasses are likely products of in situ crystallization of relatively mafic magmas on their ascent to the surface koryaksky volcano was mostly active in the early holocene when avachinsky was quiet koryaksky tephras had a relatively constant bulk medium k andesitic composition during the holocene thanks to characteristic compositions high frequency and well constrained ages tephras of avachinsky and koryaksky volcanoes can be used for high resolution dating of local sediments some eruptions of avachinsky volcano reached volcanic explosivity index vei 5 and produced widely dispersed tephras these eruptions could have had global environmental effects and their tephras can be used for the correlation of disparate sedimentary archives some avachinsky and koryaksky eruptions were closely spaced in time however their tephras are easily distinguished by respective low k and medium k compositions and by different trace element patterns which imply compositionally different sources in the mantle wedge we interpret these differences to reflect the increasing slab surface temperature and transition of slab component from a relatively low temperature fluid like phase under avachinsky to more high temperature and solute rich supercritical fluid or melt under koryaksky the transition appears to be very sharp in kamchatka causing a large compositional shift in magmas just behind the volcanic front

rupture area and displacement of past cascadia great earthquakes from coastal coseismic subsidence coastal marshes record a 6500 yr history of coseismic displacements in great earthquakes at the cascadia subduction zone we compiled estimates of coseismic displacement for past megathrust events based on correlations with megathrust triggered turbidites and estimated megathrust slip based on comparisons of marsh displacements with dislocation model predictions age correlated marsh data are compatible with event rupture extents defi ned by the published turbidite record and a 6500 yr mean recurrence interval that increases northward from 230 to 480 yr within the constraints of the marsh data the width of the coseismic rupture zone generally agrees with the downdip width of the interseismic locked zone inferred from geodetic and thermal data in southernmost cascadia where the model does not include the complex deformation near the mendocino triple junction the coastal data may be better fi t by a model with an 25 narrower rupture than that inferred from regional geophysical data at each coastal marsh site coseismic displacements are roughly similar from event to event independent of the time since the previous event slip in the a d 1700 earthquake was consistent with the preceding interval of strain accumulation 200 yr only at the northern and southern ends of the margin but it was apparently much higher in southern washington and northern oregon possibly indicating postseismic contamination and or catch up coseismic slip to make up for a defi cit in the preceding event overall agreement between the dislocation models and the marsh data for most of the margin implies that such models can be usefully applied to rupture and ground shaking predictions

the 2006 2007 kuril islands great earthquake sequence the southwestern half of a 500 km long seismic gap in the central kuril island arc subduction zone experienced two great earthquakes with extensive preshock and aftershock sequences in late 2006 to early 2007 the nature of seismic coupling in the gap had been uncertain due to the limited historical record of prior large events and the presence of distinctive upper plate trench and outer rise structures relative to adjacent regions along the arc that have experienced repeated great interplate earthquakes in the last few centuries the intraplate region seaward of the seismic gap had several shallow compressional events during the preceding decades notably an m s 7 2 event on 16 march 1963 leading to speculation that the interplate fault was seismically coupled this issue was partly resolved by failure of the shallow portion of the interplate megathrust in an m w 8 3 thrust event on 15 november 2006 this event ruptured 250 km along the seismic gap just northeast of the great 1963 kuril island m w 8 5 earthquake rupture zone within minutes of the thrust event intense earthquake activity commenced beneath the outer wall of the trench seaward of the interplate rupture with the larger events having normal faulting mechanisms an unusual double band of interplate and intraplate aftershocks developed on 13 january 2007 an m w 8 1 extensional earthquake ruptured within the pacific plate beneath the seaward edge of the kuril trench this event is the third largest normal faulting earthquake seaward of a subduction zone on record and its rupture zone extended to at least 33 km depth and paralleled most of the length of the 2006 rupture the 13 january 2007 event produced stronger shaking in japan than the larger thrust event as a consequence of higher short period energy radiation from the source the great event aftershock sequences were dominated by the expected faulting geometries thrust faulting for the 2006 rupture zone and normal faulting for the 2007 rupture zone a large intraplate compressional event occurred on 15 january 2009 m w 7 4 near 45 km depth below the rupture zone of the 2007 event and in the vicinity of the 16 march 1963 compressional event the fault geometry rupture process and slip distributions of the two great events are estimated using very broadband teleseismic body and surface wave observations the occurrence of the thrust event in the shallowest portion of the interplate fault in a region with a paucity of large thrust events at greater depths suggests that the event removed most of the slip deficit on this portion of the interplate fault this great earthquake doublet demonstrates the heightened seismic hazard posed by induced intraplate faulting following large interplate thrust events future seismic failure of the remainder of the seismic gap appears viable with the northeastern region that has also experienced compressional activity seaward of the megathrust warranting particular attention

beach ridges and prograded beach deposits as palaeoenvironment records abstract beach ridges are landforms commonly developed on prograded coasts with beach shorelines a sequence of beach ridges coupled with their subsurface deposits can be regarded as a time series of coastal evolution methodological advances in field surveying and chronology applicable to beach ridges have led to detailed palaeoenvironmental reconstructions to be derived from such sequences this paper reconsiders the basic aspects of beach ridges and deposits which need to be properly understood for their comprehensive interpretation in a palaeo environmental context it also reviews case studies in which beach ridge sequences have been used to unveil past sea level history catastrophic events and climate changes proposed formative processes of beach ridges include 1 progradation of sandy beach and berm formations in relation to fairweather waves coupled with aeolian foredune accumulation 2 building of gravel ridges by storm waves 3 welding of longshore bars beach ridge formation through sea level oscillation is thought to be questionable and caution is suggested for this process when undertaking palaeoenvironmental reconstruction beach deposit stratification is known to dip either landwards or seawards but landward dips are uncommon seaward dipping stratification is formed in relation to beachface progradation and is usually dissected in places by erosion surfaces resulting from episodic beach retreat the boundary between the foreshore and the underlying shoreface is well defined only in the case that longshore bars lead to complex bedding structure relative to that of the foreshore reliable chronology of beach ridges can be determined by radiocarbon and optically stimulated luminescence osl dating radiocarbon dating of articulated shells which are considered not to be extensively reworked provides robust results but osl dating is more useful as it enables direct dating of sediment grains it is noted that there are restrictions in chronological resolution and continuity inherent to beach ridge and beach deposits the plan view geomorphic expression of beach ridges typically consists of ridge sets with multi decadal intervals whereas their internal sedimentary structures define shorter time scales records of beach sedimentation and erosion are likely to be reworked by episodic high magnitude beach retreat and the resultant record of the net progradation is likely to be sporadic and discontinuous the height of sandy beach ridges is often variable due to differing degrees of aeolian sand accumulation and they are thus not used as sea level indicators unless purely wave built gravel ridge height is a relatively reliable indicator of sea level but can vary in response to storminess fluctuations subsurface sediment facies boundaries are preferred as sea level indicators and those proposed include boundaries of aeolian beach foreshore shoreface and upper lower shorefaces catastrophic events are expressed in both erosional and depositional records erosion surfaces or scarp imprints revealed in a cross section of beach deposits indicate storm or tsunami events however erosional events are likely to rework previous records of sedimentation and even other erosional events and thus the apparent history decoded from the resultant deposits tends to be biased several attempts for estimating the frequency and intensity of prehistoric cyclones rely on assumed relationships between the level of coarse sand beach ridges and cyclone inundation the formative process of coarse sand ridges remains uncertain and needs to be clarified as it constitutes the fundamental basis of these attempts the growth rates of beach ridge systems are expected to reflect fluctuations in river sediment discharge to the coast and in aeolian sand flux due to onshore winds both of which are affected by climate change assessment of the growth rate is potentially improved by ground penetrating radar survey of subsurface structure and by detailed chronology orientation of beach ridges reflects long term trends in wave direction inferred relationships between beach ridges and cyclic fluctuations of sea level and climate rely on weak assumptions and are not substantiated by rigid chronological evidence and thus remain highly questionable correlation between the inherently decadal signal of beach ridge intervals and possible climate cycles such as sunspot activity is probably coincidental as it lacks causal explanations

heat flow density measurements in the sediments of three lakes in northern sweden abstract heat flow density measurements in the sediments of three lakes 36 m 73 m and 99 m deep were carried out during a period of 3 5 years the gradient measurements were made from ice during the winter season with a bullard type probe with nine thermistors 0 5 m apart the thermal conductivity was measured in situ corrections were made for the disturbing temperature wave in the horizontally stratified sediments caused by seasonal variations in the bottom water temperature it is clearly shown that the differences in bottom water temperatures between different years can be fully corrected for only by very long time series the heat flow density values obtained are compared with measurements in boreholes and they seem to be correct to within 20 30

geological effects and implications of the 2010 tsunami along the central coast of chile abstract geological effects of the 2010 chilean tsunami were quantified at five near field sites along a 200 km segment of coast located between the two zones of predominant fault slip field measurements including topography flow depths flow directions scour depths and deposit thicknesses provide insights into the processes and morphological changes associated with tsunami inundation and return flow the superposition of downed trees recorded multiple strong onshore and alongshore flows that arrived at different times and from different directions the most likely explanation for the diverse directions and timing of coastal inundation combines 1 variable fault rupture and asymmetrical slip displacement of the seafloor away from the epicenter with 2 resonant amplification of coastal edge waves other possible contributing factors include local interaction of incoming flow and return flow and delayed wave reflection by the southern coast of peru coastal embayments amplified the maximum inundation distances at two sites 2 4 and 2 6 km respectively tsunami vertical erosion included scour and planation of the land surface inundation scour around the bases of trees and channel incision from return flow sheets and wedges of sand and gravel were deposited at all of the sites locally derived boulders up to 1 m in diameter were transported as much as 400 m inland and deposited as fields of dispersed clasts the presence of lobate bedforms at one site indicates that at least some of the late stage sediment transport was as bed load and not as suspended load most of the tsunami deposits were less than 25 cm thick exceptions were thick deposits near open ocean river mouths where sediment supply was abundant human alterations of the land surface at most of the sites provided opportunities to examine some tsunami effects that otherwise would not have been possible including flow histories boulder dispersion and vegetation controls on deposit thickness

relationship between the maximum extent of tsunami sand and the inundation limit of the 2011 tohoku oki tsunami on the sendai plain japan abstract this paper focuses on the relationship between the maximum extent of sandy tsunami deposits and inundation distance of the 2011 tohoku oki tsunami inundation limits of the tohoku oki tsunami were assessed over seven shore normal transects along the sendai coastal plain inundation distances were found to range from 0 6 to 4 0 km at the maximum extent of the tsunami deposit the sand unit ranged in thicknesses from 0 1 to 4 0 cm the maximum limit of the 0 5 cm thick sand layer extended to over 90 of the inundation distance where the inundation distance was less than 2 5 km this observation is consistent with previous studies that examined characteristics of recent tsunami events that had inundation distances of at least 2 km the maximum limit of the 0 5 cm thick sand layer extended to 3 km 57 76 of the inundation distance where the inundation distance was more than 2 5 km our results are important for estimating paleo tsunami inundation distances based on the landward extent of sand deposits and valuable for the assessment of future tsunami risks in other coastal areas in the world which have been devastated by huge tsunamis in the past

the 1960 chile earthquake inversion for slip distribution from surface deformation summary a total of 166 observations of sea level change 130 measurements of elevation difference and 16 determinations of horizontal strain provide an excellent view of the quasi static source process of the great 1960 chilean earthquake these surface deformation data were employed in classical uniform slip fault models as well as more recently developed models that allow spatial variability of slip the best uniform slip planar usp model is 850km long 130km wide and dips 20 seventeen metres of fault displacement contributed to a usp moment of 9 4 times 1022 n m the variable slip planar vsp model concentrates slip on a 900 km long 150 km wide band parallel to the coast several peaks of slip with dimensions of 50 100 km appear in this band and are thought to represent major subduction zone asperities important fractures of the oceanic lithosphere bound the 1960 rupture and are offered as a potential source of fault segmentation within the chilean subduction zone the vsp moment for 1960 earthquake totals 9 5 times 1022 n m about one fifth of the value estimated for the foreshock mainshock sequence from seismic methods except for areas out to sea geodetic resolution on the fault is fairly uniform thus it is unlikely that slip missed by the network could increase the vsp moment much beyond 1 8 times 1023 n m several patches of moment isolated from the main body at 80 110 km depth are found down dip in the vsp model and are presumably indicative of aseismic slip one patch at the northern end of the rupture is probably associated with the initiation phase of the mainshock although the time sequence of the relationship is unknown tide gauge records suggest that another patch between 40 and 43 s responsible for the observed strain and uplifts inland at those latitudes is not of coseismic origin but derives from in place post seismic creep over several years apparently great 1960 type events are not typical members of the 128 yr earthquake cycle in south central chile the nazca south america boundary here is characterized by a variable rupture mode in which major asperities are completely broken by great earthquakes only once in four or five earthquake cycles the more frequent large earthquakes that geographically overlap the great events fill in between the locked zones

fault slip and seismic moment of the 1700 cascadia earthquake inferred from japanese tsunami descriptions 1 the 1700 cascadia earthquake attained moment magnitude 9 according to new estimates based on effects of its tsunami in japan computed coseismic seafloor deformation for hypothetical ruptures in cascadia and tsunami modeling in the pacific ocean reports of damage and flooding show that the 1700 cascadia tsunami reached 1 5 m heights at seven shoreline sites in japan three sets of estimated heights express uncertainty about location and depth of reported flooding landward decline in tsunami heights from shorelines and post 1700 land level changes we compare each set with tsunami heights computed from six cascadia sources each source is vertical seafloor displacement calculated with a three dimensional elastic dislocation model for three sources the rupture extends the 1100 km length of the subduction zone and differs in width and shallow dip for the other sources ruptures of ordinary width extend 360 670 km to compute tsunami waveforms we use a linear long wave approximation with a finite difference method and we employ modern bathymetry with nearshore grid spacing as small as 0 4 km the various combinations of japanese tsunami heights and cascadia sources give seismic moment of 1 9 1022 n m equivalent to moment magnitude 8 7 9 2 this range excludes several unquantified uncertainties the most likely earthquake of moment magnitude 9 0 has 19 m of coseismic slip on an offshore full slip zone 1100 km long with linearly decreasing slip on a downdip partial slip zone the shorter rupture models require up to 40 m offshore slip and predict land level changes inconsistent with coastal paleoseismological evidence

earthquake supercycles inferred from sea level changes recorded in the corals of west sumatra records of relative sea level change extracted from corals of the mentawai islands sumatra imply that this 700 kilometer long section of the sunda megathrust has generated broadly similar sequences of great earthquakes about every two centuries for at least the past 700 years the moment magnitude 8 4 earthquake of september 2007 represents the first in a series of large partial failures of the mentawai section that will probably be completed within the next several decades

coseismic subsidence in the 1700 great cascadia earthquake coastal estimates versus elastic dislocation models seismic hazard assessments for a cascadia subduction zone earthquake are largely based on the rupture area predictions of dislocation models constrained by geodetic and geothermal data this paper tests the consistency of the models for the 1700 great cascadia earthquake with compiled coastal coseismic subsidence as estimated from paleoelevation studies coastal estimates have large uncertainties but show a consistent pattern greatest coseismic subsidence 1 2 m occurred in northern oregon southern washington subsidence elsewhere was 0 1 m elastic dislocation models constrained by interseismic geodetic and thermal data are used to predict the coseismic subsidence for two likely strain accumulation periods of i 800 and ii 550 yr of plate convergence and for uniform megathrust slip of 10 20 30 and 50 m the former two models provide a better and equally good fit predicted subsidence is in broad agreement with marsh estimates discrepancies exist however at the ends of the subduction zone in the south misfit may be due to breakup of the gorda plate the discrepancy in the north may be explained if the 1700 event released only part of the accumulated strain there consistent with long term net uplift in excess of eustatic sea level rise the coseismic slip magnitude estimated by comparing uniform slip model predictions with marsh coseismic subsidence estimates is consistent with the m 9 earthquake indicated by japanese tsunami records the coseismic slip was greatest in northern oregon southern washington declining to the north and south

were they all giants perspectives on late holocene plate boundary earthquakes at the northern end of the cascadia subduction zone abstract the relative magnitude of plate boundary earthquakes at the northern end of the cascadia subduction zone was assessed from the temporal concordance between the ages of coseismically buried late holocene soils in southwest washington their counterparts in central and southern cascadia offshore turbidites and paleoseismic deposits on the west coast of vancouver island only three of the seven buried soils in southwest washington that can be reliably traced as buried soils or paleotsunami deposits in the coastal lowlands of south central and southern cascadia have well dated counterparts in northern cascadia the three wide ranging events date from cascadia earthquakes y 250 cal bp u 1260 cal bp and n 2520 cal bp all three likely ruptured the entire plate margin and therefore potentially qualify as giants m w 9 deposits that may derive from tsunamis generated by earthquakes s 1570 cal bp l 2870 cal bp and j 3360 cal bp can also be found in northern cascadia but the ages of these deposits are not yet well enough constrained to determine whether they are coeval with their southern counterparts earthquake w 850 cal bp appears to be present in the northern cascadia paleoseismic record but yields considerably older ages than in central cascadia and may be missing from southernmost cascadia the onshore record of an offshore turbidite t2 displays a similar spatio temporal pattern to that of earthquake w

a 1500 yr record of north atlantic storm activity based on optically dated relict beach scarps understanding of long term dynamics of intense coastal storms is important for determining the frequency and impact of these events on sandy coasts we use optically stimulated luminescence osl dates on relict scarps within a prograded barrier sequence to reconstruct the chronology of large magnitude erosional events in the western gulf of maine osl dates obtained on quartz rich sediments immediately overlying relict scarps indicate severe beach erosion and retreat due to erosional events ca 1550 390 290 and 150 cal yr b p our data provide new evidence of increased storm activity most likely frequency and or intensity of extratropical storms during the past 500 yr which was preceded by a relatively calm period lasting 1000 yr the width of the coastal sequence preserved between successive paleoscarps shows strong correlation with the time interval elapsed between storms our fi ndings indicate that diagnostic geophysical and sedimentological signatures of severe erosional events offer new opportunities for assessing the impact and timing of major storms along sandy coasts

tsunami geomorphology erosion and deposition from the 15 november 2006 kuril island tsunami the 15 november 2006 kuril earthquake mw 8 1 8 4 and tsunami enabled us to collect a compelling data set of coastal geomorphic change in the kuril islands from 3 months before to 9 and 21 months after the tsunami our pre tsunami and post tsunami surveys of the islands including four topographic profi les measured in 2006 and reoccupied in 2007 allow us the confi dence to attribute many changes to the tsunami in spite of an absence of eyewitness accounts in the central islands areas with low runup 15 m underwent massive erosion that dramatically altered the coastline tsunami deposits roughly corresponded with the extent of tsunami runup and inundation the amount of sediment eroded by the tsunami far outweighed the amount deposited on land in all cases studied the tsunami was dominantly erosive in the kuril islands because the high relief topography of the coastline accelerated tsunami outfl ow

dating deep lake sediments by using amino acid racemization in fossil ostracodes the long term rate of racemization for amino acids preserved in fossil ostracode shells was determined by using independently dated sediment cores from five deep lakes the racemization rates for aspartic and glutamic acids in the common ostracode genus candona were calibrated for the past 100 k y providing the basis for an age equation with a realistic age uncertainty of 20 the new age equation can be applied to other hypolimnic settings because the temperature below the thermocline of deep lakes from middle and high latitude regions can reasonably be assumed to remain close to 4 c the sample size required for analysis is an order of magnitude less than for 14c dating and presents new opportunities to date deposits that are organic matter poor or those with large 14c reservoir effects

using uplifted holocene beach berms for paleoseismic analysis on the santa maria island south central chile major earthquakes m 8 have repeatedly ruptured the nazca south america plate interface of south central chile involving meter scale land level changes earthquake recurrence intervals however extending beyond limited historical records are virtually unknown but would provide crucial data on the tectonic behavior of forearcs we analyzed the spatiotemporal pattern of holocene earthquakes on santa maria island smi 37 degrees s located 20 km off the chilean coast and approximately 70 km east of the trench smi hosts a minimum of 21 uplifted beach berms of which a subset were dated to calculate a mean uplift rate of 2 3 0 2 m ky and a tilting rate of 0 022 0 002 degrees ky the inferred recurrence interval of strandline forming earthquakes is similar to 180 years combining coseismic uplift and aseismic subsidence during an earthquake cycle the net gain in strandline elevation in this environment is similar to 0 4 m per event

toward understanding tectonic control on the mw 8 8 2010 maule chile earthquake the maule earthquake of 27th february 2010 m w 8 8 affected similar to 500 km of the nazca south america plate boundary in south central chile producing spectacular crustal deformation here we present a detailed estimate of static coseismic surface offsets as measured by survey and continuous gps both in near and far field regions earthquake slip along the megathrust has been inferred from a joint inversion of our new data together with published gps insar and land level changes data using green s functions generated by a spherical finite element model with realistic subduction zone geometry the combination of the data sets provided a good resolution indicating that most of the slip was well resolved coseismic slip was concentrated north of the epicenter with up to 16 m of slip whereas to the south it reached over 10 m within two minor patches a comparison of coseismic slip with the slip deficit accumulated since the last great earthquake in 1835 suggests that the 2010 event closed a mature seismic gap slip deficit distribution shows an apparent local overshoot that highlight cycle to cycle variability which has to be taken into account when anticipating future events from interseismic observations rupture propagation was obviously not affected by bathymetric features of the incoming plate instead splay faults in the upper plate seem to have limited rupture propagation in the updip and along strike directions additionally we found that along strike gradients in slip are spatially correlated with geometrical inflections of the megathrust our study suggests that persistent tectonic features may control strain accumulation and release along subduction megathrusts c 2012 elsevier b v all rights reserved

a nexus of plate interaction vertical deformation of holocene wave built terraces on the kamchatsky peninsula kamchatka russia kamchatsky peninsula lies within a complex meeting place of tectonic plates in particular the orthogonal interaction of the west moving komandorsky island block with mainland kamchatka examining the holocene history of vertical deformation of marine wave built terraces along the peninsular coast we differentiated tectonic blocks undergoing uplift and tilting separated by zones of stable or subsided shorelines we analyzed 200 excavations along 30 coastal profiles and quantified vertical deformation on single profiles as well as along the coast using paleoshorelines dated with marker tephras for the past 2000 yr the average rates of vertical deformation range from about 1 to 7 mm yr uplift patterns are similar to those detected from historical leveling and from mapping of the stage 5e quaternary marine terrace ca 120 ka average vertical deformation in the holocene is highest for the shortest studied time period from ca a d 250 to 600 and it is several times faster than rates for marine oxygen isotope stage mis 5e terraces vertical displacements observed along the coast are most likely coseismic and probably have included subsidence as well as uplift events because subsidence is generally associated with erosion almost surely more prehistoric large earthquakes occurred than are recorded as topographic steps in these terraces we suggest that the distribution of coastal uplift and subsidence observed along the kamchatsky peninsula coastline is qualitatively explained by the squeezing of the kamchatsky peninsula block between the bering and okhotsk plates and the komandorsky island block

coseismic coastal subsidence associated with unusually wide rupture of prehistoric earthquakes on the kamchatka subduction zone a record in buried erosional scarps and tsunami deposits abstract the prograding strand plain of avachinsky bay kamchatka russia along the highly active kamchatka subduction zone exhibits geological evidence buried erosional scarps for coseismic subsidence only three times in the last four millennia the last event about 1200 years ago this same coast has a historical record since a d 1737 of five subduction zone earthquakes with large tsunami runup 5 m the last of which was the 1952 mw 9 kamchatka earthquake and a geological record of more than 30 large tsunamis in the last 4000 years this rarity of buried scarps relative to large earthquakes contrasts with the cascadia strand plain in sw washington state where most or all large events are represented by buried scarps a strong factor in the amplitude and sign of coseismic deformation is distance from the seaward edge of a subduction zone the trench the avachinsky bay coastline is 180 200 km from the trench with 25 slab dip requiring unusually wide ruptures to generate significant coseismic subsidence this coastal zone is undergoing net subsidence approximately equivalent to the total of the three coseismic subsidence events generating a sequence of beach ridges that increase in elevation seaward each of the three unusual coseismic subsidence events comprises a an earthquake whose deformation field caused b onshore coseismic subsidence thus local sea level rise and c sufficient deformation offshore to produce a large tsunami a b c followed by d a period of coastal erosion and shoreline retreat leaving e an erosional beach scarp that was f subsequently buried once progradation resumed we identified dated and correlated the scarps and tsunami deposits from these events with several field methods including trenching tephrostratigraphy and ground penetrating radar the scarps were correlated over an alongshore distance of 50 70 km the most recent event event 1 occurred 800 cal ad 1100 1250 14 years bp event 2 600 cal bc 2400 2450 14 years bp and event 3 1700 cal bc 3300 3500 14 years bp we developed methods for quantifying subsidence coastal erosion and tsunami size for each of these events all three retain evidence of 0 4 1 2 m of coseismic subsidence coastal erosion in the case of event 1 averaged more than 100 m all three event tsunamis were amongst the largest in the last 4000 years

the application of diatoms to reconstruct the history of subduction zone earthquakes and tsunamis abstract earthquake and tsunami records on centennial and millennial temporal scales are necessary to understanding long term subduction zone behavior and the occurrences of large but infrequent events microfossils such as diatoms incorporated into coastal stratigraphy provide some of the most detailed reconstructions of the history of earthquakes and tsunamis we explore qualitative and quantitative techniques that employ the relation between diatoms and salinity tidal elevation and life form to 1 reconstruct records of vertical land level change associated with large earthquakes and 2 identify anomalous sand and silt beds deposited by tsunamis a global database shows that diatoms have been successfully employed in the reconstruction of earthquake and tsunami histories in chile the indian ocean japan new zealand the north sea the pacific northwest of north america and the south pacific we use case studies from some of these locations to highlight advancements in the field and new capabilities that diatoms have enabled examples from the pacific northwest of north america illustrate the evolution of quantitative diatom based reconstructions of earthquake related land level change in alaska and japan diatoms have documented land level changes throughout the earthquake deformation cycle including possible preseismic land level change signals and postseismic deformation diatoms helped identify coseismic uplift along the central chile subduction zone coast and uplift and subsidence along the alaska aleutian megathrust expanding our knowledge of the variability of slip in megathrust ruptures in tsunami studies diatoms help determine the provenance of anomalous sands and silts found in low energy coastal stratigraphic sequences in japan allochthonous marine and brackish diatoms within sand deposits signaled repeated marine incursions into a coastal lake helping identify a possible predecessor to the 2011 tohoku tsunami in the pacific northwest of north america and chile diatoms were used to estimate tsunami run up beyond the landward limit of tsunami sedimentation examples from the north sea thailand and japan show how the fragmentation and sorting of diatom valves may provide evidence of high energy transport during the rapid turbulent flow of a tsunami to conclude we emphasize the importance of studying the modern diatom response to changes in land level and or tsunami inundation to improve diatom based records of prehistoric earthquakes and tsunamis

geological and historical evidence of irregular recurrent earthquakes in japan great m 8 earthquakes repeatedly occur along the subduction zones around japan and cause fault slip of a few to several metres releasing strains accumulated from decades to centuries of plate motions assuming a simple characteristic earthquake model that similar earthquakes repeat at regular intervals probabilities of future earthquake occurrence have been calculated by a government committee however recent studies on past earthquakes including geological traces from giant m 9 earthquakes indicate a variety of size and recurrence interval of interplate earthquakes along the kuril trench off hokkaido limited historical records indicate that average recurrence interval of great earthquakes is approximately 100 years but the tsunami deposits show that giant earthquakes occurred at a much longer interval of approximately 400 years along the japan trench off northern honshu recurrence of giant earthquakes similar to the 2011 tohoku earthquake with an interval of approximately 600 years is inferred from historical records and tsunami deposits along the sagami trough near tokyo two types of kanto earthquakes with recurrence interval of a few hundred years and a few thousand years had been recognized but studies show that the recent three kanto earthquakes had different source extents along the nankai trough off western japan recurrence of great earthquakes with an interval of approximately 100 years has been identified from historical literature but tsunami deposits indicate that the sizes of the recurrent earthquakes are variable such variability makes it difficult to apply a simple characteristic earthquake model for the long term forecast and several attempts such as use of geological data for the evaluation of future earthquake probabilities or the estimation of maximum earthquake size in each subduction zone are being conducted by government committees

subduction zone slip variability during the last millennium south central chile abstract the arauco peninsula 37 38 s in south central chile has been proposed as a possible barrier to the along strike propagation of megathrust ruptures separating historical earthquakes to the south 1960 ad 1837 1737 and 1575 and north 2010 ad 1835 1751 1657 and 1570 of the peninsula however the 2010 mw 8 8 earthquake propagated into the arauco peninsula re rupturing part of the megathrust that had ruptured only 50 years earlier during the largest subduction zone earthquake in the instrumental record mw 9 5 to better understand long term slip variability in the arauco peninsula region we analyzed four coastal sedimentary sections from two sites tirua 38 3 s and quidico 38 1 s located within the overlap of the 2010 and 1960 ruptures to reconstruct a 600 year record of coseismic land level change and tsunami inundation stratigraphic lithologic and diatom results show variable coseismic land level change coincident with tsunami inundation of the tirua and quidico marshes that is consistent with regional historical accounts of coseismic subsidence during earthquakes along the valdivia portion of the subduction zone 1960 ad and 1575 and coseismic uplift during earthquakes along the maule portion of the subduction zone 2010 ad 1835 1751 in addition we document variable coseismic land level change associated with three new prehistoric earthquakes and accompanying tsunamis in 1470 1570 ad 1425 1455 and 270 410 the mixed record of coseismic subsidence and uplift that we document illustrates the variability of down dip and lateral slip distribution at the overlap of the 2010 and 1960 ruptures showing that ruptures have repeatedly propagated into but not through the arauco peninsula and suggesting the area has persisted as a long term impediment to slip through at least seven of the last megathrust earthquakes 600 years

slip distribution of the 1952 kamchatka great earthquake based on near field tsunami deposits and historical records we explore the magnitude and slip distribution of the 1952 kamchatka earthquake mw 8 8 9 0 using constraints from the 1952 kamchatka tsunami our new field data provide more comprehensive coverage of the near field tsunami than had been available to date we examine the effects of internal slip distribution within complex earthquake ruptures on near field tsunami runup and evaluate some of the limitations of this approach our approach compares tsunami deposit distribution with simulated runup from tsunamis generated by different configurations of seafloor deformation from hypothetical earthquakes resembling that of the 1952 kamchatka earthquake we identify areas of high slip because different distributions of seafloor deformation result in variations in tsunami runup in the near field mapped deposits and local observations of the 1952 kamchatka tsunami indicate that near field runup in central kamchatka was consistently less than 10 m averaging 6 m while south kamchatka to the northern kuril islands had more variability and higher average runup 8 m runup in south kamchatka and 10 m runup in the northern kuril islands our simulations show that in order to produce the distribution of runup indicated by tsunami deposits and historical observations the 1952 earthquake had regions of high slip off the coast of southern kamchatka and the location of high slip is shallower in the subduction zone than previously interpreted online material sedimentary methodology model inputs and simulation results

rapid aseismic moment release following the 5 december 1997 kronotsky kamchatka earthquake model inversions of displacements of continuously operating gps stations in kamchatka show that aseismic afterslip during 2 months following the mw 7 8 5 december 1997 kronotsky subduction earthquake released as much moment as the earthquake itself the rapidly decaying transient slip on the subduction underthrust occurred near the downdip edge of the coseismic rupture and extended laterally away from it including a region of vigorous foreshock activity a logarithmic decay function fit to the cumulative afterslip curve has a relaxation time of about 3 days rapid afterslip can contribute significantly to the moment release of partially coupled subduction zones

seismo turbidites in aysen fjord southern chile reveal a complex pattern of rupture modes along the 1960 megathrust earthquake segment grainsize analysis and end member modeling of a long sediment core from aysen fjord southern chile allows to identify over 25 seismo turbidites in the last 9 000 years considering the shaking intensities required to trigger these turbidites v1 2 vi1 2 the majority can be related to megathrust earthquakes multiple studies in south central chile have aimed at finding traces of giant tsunamigenic megathrust earthquakes leading to the current 5 500 year long paleoseismological record of the valdivia segment however none of these cover the southern third of the segment aysen fjord allows to fill this data gap and presents the first crucial paleoseismic data to demonstrate that the 1960 event was not unique for the valdivia segment yielding a recurrence rate of 321 116 years in the last two millennia moreover the oldest identified events in aysen fjord date back to 9 000 cal years bp and thus also extend the regional paleoseismological record in time we infer a large temporal variability in rupture modes with successions of full segment ruptures alternating with partial and cascading ruptures the latter seems to significantly postpone the occurrence of another full rupture when consecutively occurring in different parts of the segment additionally one outstanding period of seismic quiescence during which no megathrust earthquake evidence has been found at any paleoseismic site occurred after a full rupture in ad similar to 745 that presents an unusual uplift subsidence pattern such variability makes it highly speculative to anticipate the rupture mode of the next megathrust earthquake along the valdivia segment

mixed convection processes below a saline disposal basin abstract saline groundwater and irrigation drainage are commonly diverted and stored in both natural and artificial depressions throughout the murray darling basin of australia the disposal basin brines that are formed are often denser than ambient groundwater under certain conditions these dense brines may become unstable causing them to mix with groundwater over distances several orders of magnitude greater than due to diffusion alone a model is developed to study the mixed convection processes below a saline disposal basin located between a recharge and discharge zone numerical simulations are performed in cross section using the 2 d density dependent model sutra saturated unsaturated transport it is shown that the salt front movement is related to both the ability of the dense saline brines to mix convectively with underlying groundwaters rayleigh convection and the strength of the regional advective velocity both homogeneous and heterogeneous aquifer systems are studied and the effects of anisotropy are considered our numerical results suggest that the behaviour of a dense brine plume overlying less dense groundwater in a homogeneous porous medium depends on the magnitude of at least two non dimensional numbers a rayleigh number and modified peclet number defined in terms of basin scale hydrogeologic parameters including dispersion it is shown that the onset of gravitational instabilities and the formation of free convective cells begins when the magnitude of a non dimensional parameter combining the rayleigh and modified peclet number exceeds a certain critical value 1997 elsevier science b v all rights reserved

hydrological and geochemical processes controlling variations in na mg2 cl so42 groundwater brines south eastern australia abstract evaporative discharge of regional groundwater from more than 50 playa lakes at the 400 km 2 raak plain groundwater discharge complex forms a very large reservoir of hypersaline na mg 2 cl so 4 2 type subsurface brine but very little salt precipitates the main processes controlling the formation and evolution of brine compositions are a evapo concentration of the regional groundwater b mixing between the high and low tds end members and c subsurface gypsum precipitation uniformity in these processes across the entire groundwater discharge complex coupled with the chemical similarity between the regional groundwater and local recharge sources has led to remarkably similar brine chemistries and evaporite compositions across raak plain the similarity between the source waters and the ultimate brine compositions indicates that solutes are generally conserved within the system the greatest variation in groundwater chemistry at raak plain was found to occur within the playa lakes particularly within the top 1 2 m of the subsurface brine body rather than amongst the different lakes this small scale variability is a result of 1 advective and diffusive mixing between the hypersaline shallow 20 kyr

coseismic and pre seismic subsidence associated with great earthquakes in alaska abstract alternating beds of peat and mud in sediment sequences on the south central alaskan coast record coseismic and inter seismic relative land and sea level movements caused by repeated great earthquakes on the alaska aleutian subduction zone during the ad 1964 mw 9 2 earthquake tidal marshes and wetlands around upper cook inlet experienced up to 2 m of subsidence burying peat forming communities with intertidal mud here we use quantitative analyses of fossil diatoms within peat mud couplets to reconstruct land sea level changes for the 1964 and five earlier great earthquakes during the past 3300 years in contrast to geodetic observations that are limited to the present post seismic phase we quantify varying spatial patterns of uplift and subsidence through complete earthquake cycles relative land uplift characterises most of the inter seismic phase of each cycle at our sites whereas each great earthquake was preceded by a short period of pre seismic relative land subsidence

erosion deposition and landscape change on the sendai coastal plain japan resulting from the march 11 2011 tohoku oki tsunami case studies of recent tsunami impacts have proven to be extremely useful in understanding the geologic processes involved during inundation and return flow and refining the criteria used to identify paleotsunami deposits in the geologic record here we report on erosion deposition and associated landscape change resulting from the march 11 2011 tohoku oki tsunami along a nearly 4 5 km shore normal transect on the coastal plain near sendai japan the study area on the broad low relief prograding coastal sendai plain comprised a sand beach backed by 3 m high sand dunes and a forest a wetland the teizan canal agricultural rice fields buildings and roads field observations focused on measurements of tsunami flow characteristics height and direction mapping of erosion features and assessing sediment deposition based on shallow trenches at 50 100 m spacing recorded tsunami inundation heights reached up to about 11 m above mean sea level within the first 500 m from the shoreline and then ranged between 3 and 5 m for the next 2 km gradually decreasing to about 3 m close to the inundation limit the tsunami deposit generally thinned landward from an average maximum 30 cm thick sand deposit in the coastal forest to a thin mud drape several mm thick near the inundation limit a discontinuous sand dominated sheet was prevalent to about 2800 m from the shoreline where mud content then gradually increased further landward eventually resulting in a mud dominated deposit ranging from 3 5 cm to a few mm thickness the overall thinning and fining of the deposit was often interrupted by localized features that led to complex sedimentological relationships over short distances satellite imagery taken on 14 march 2011 3 days after the tohoku oki tsunami shows prominent foreshore incisions with 100 s meters spacing alongshore a foredune ridge that underwent severe erosion and development of a prominent shore parallel elongated scour depression our field survey in early may 2011 revealed that the foreshore recovered quickly with rapid post tsunami sediment deposition from incident waves whereas the dune ridge complex had undergone only minor re working from eolian processes

dating of late holocene beach shoreline positions by regional correlation of coseismic retreat events in the columbia river littoral cell usa abstract beaches and barrier spits of the columbia river littoral cell crlc 160 km in length experienced substantial progradation 0 5 2 5 km in width during the late holocene the accreted beach plains and barriers preserved evidence of episodic catastrophic retreat that was forced by coseismic subsidence the abrupt subsidence events 0 5 1 5 m submergence are associated with slip on the underlying cascadia megathrust with a mean recurrence interval of 500 yr ground penetrating radar gpr profiles taken across the barriers and beach plains show high angle beach retreat scarps 3 15 m vertical relief and foredune ridge slump scarps 5 15 m vertical relief the upper shoreface retreat features are correlated throughout the littoral cell by radiocarbon age position relative to abandoned foredune ridges and distinct sequences of large and small scarps particularly large retreat scarps 10 15 m in height are associated with the first oldest and fourth oldest prehistoric scarps a and d respectively a maximum of 10 retreat scarps in the long beach subcell date from 216 211 calrcybp to 4756 114 calrcybp the youngest seven scarps a g are correlated between all four subcells showing a regional response to the coseismic strain cycles backshore disturbance features 1 3 m vertical relief are observed in the gpr profiles but they are not identified here due to their discontinuities between adjacent profiles at 5 km longshore spacing the seven regional scarps a g are directly correlated to seven coseismic subsidence events reported to date between 0 3 and 3 2 ka the correlation of scarps to earthquake events provides high resolution proxy ages for shoreline positions in late holocene time the proxy shoreline positions are dated at 0 3 1 1 1 3 1 7 2 5 2 8 and 3 2 ka based on buried wetland sequences from adjacent tidal basins the paleoshoreline dating demonstrates that the onset of net shoreface progradation between 4 7 and 0 3 ka was delayed with increasing distance 0 100 km from the columbia river sand source the history of beach progradation reflects the sequential filling of bay and shoreface accommodation spaces located down drift of the columbia river mouth these late holocene shoreline changes portend future redistributions of existing sand within the littoral system as the limited sand reserves continue to migrate away from the columbia river mouth source

beach ridge patterns in west aceh indonesia and their response to large earthquakes along the northern sunda trench abstract the morphology of beach ridge plains along active margins can be used to reconstruct coastal subsidence during large megathrust earthquakes here we use satellite imagery and automatic level surveys to reconstruct the build up of a new beach ridge along a 10 km long stretch of the western acehnese coast after the complete destruction of the beach during the great sumatra andaman earthquake and successive tsunami in december 2004 the western acehnese coast is characterized by ridge and swale topography reflecting the long term progradation of the coastline radiocarbon dates obtained from marshy deposits in between ridges indicate an average progradation rate of 1 3 1 8 m per year over the last 1000 years as a result of coseismic subsidence of 0 5 1 m and tsunami inundation in 2004 the most seaward beach ridge was destroyed and the coastline receded on average 110 m landward representing 65 85 years of average progradation however by 2006 a new 22 m wide ridge had formed in the following years the coast prograded by an additional 30 m but has not yet recovered to its pre december 2004 position in addition to the spatial data topographic surveys conducted in 2009 2012 and 2013 indicate that the crest of the newly formed beach ridge is 0 8 1 3 m higher than the crests of older beach ridges further inland the source material for the new ridge is most likely sand transported seaward by the back flow of the 2004 tsunami and stored on the upper shoreface in the months and years after the tsunami this sediment is reworked by regular coastal processes and transported back to shore leading to the reconstruction of a higher beach ridge in equilibrium with the vertical displacement of the coast and the resulting higher relative sea level the preservation potential of the newly formed ridge depends on sediment availability within the coastal system to balance coastal profile adjustments due to rapid postseismic uplift in aceh the preservation of seismically modified beach ridge morphology seems likely and another prominent ridge can be found in 640 m distance to the shoreline it most likely formed in the aftermath of a previous megathrust earthquake and tsunami about 600 years ago matching sediment and coral records for this region

estimating coseismic coastal uplift with an intertidal mussel calibration for the 2010 maule chile earthquake mw 8 8 abstract coseismic coastal uplift has been quantified using sessile intertidal organisms after several great earthquakes following fitzroy s pioneer measurements in 1835 a dense survey of such markers may complement space geodetic data to obtain an accurate distribution of fault slip and earthquake segmentation however uplift estimates based on diverse intertidal organisms tend to differ because of few methodological and comparative studies here we calibrate and estimate coastal uplift in the southern segment of the 2010 maule chile earthquake m w 8 8 using 1100 post earthquake elevation measurements of the sessile mussel perumytilus purpuratus this mussel is the predominant competitor for rocky shores all along the pacific coast of south america where it forms fringes or belts distinctively in the middle intertidal zone these belts are centered at mean sea level and their width should equal one third of the tidal range we measured belt widths close to this value at 40 of the sites but overall widths are highly variable due to the unevenness in belt tops belt bases in turn are rather regular belt top unevenness apparently results from locally enhanced wave splash whereas belt base evenness is controlled by predation according to our measurements made beyond the earthquake rupture the belt base is at the bottom of the middle intertidal zone and thus we propose to estimate coastal uplift using the belt base mean elevation plus one sixth of the tidal range to reach mean sea level within errors our estimates agree with gps displacements but differ from other methods comparisons of joint inversions for megathrust slip suggest combining space geodetic data with estimates from intertidal organisms may locally increase the detail of slip distributions

evidence for eight great earthquake subsidence events detected with ground penetrating radar willapa barrier washington a new approach to detect holocene subduction zone earthquakes combines the results from ground penetrating radar gpr vibracores and accelerator mass spectrometry ams dates from a barrier spit located west of willapa bay southwest washington gpr data show a 10 m thick facies of beach sand within which we identify and vibracores confirm beach parallel wave eroded buried scarps mantled with multiple beds of magnetite the eight gpr detected buried scarps are interpreted to be eroded by minor transgressions caused by instantaneous barrier subsidence during earthquakes associated with the juan de fuca plate subducting under the north american plate of these scarps four have been ams dated at 300 1110 2540 and 4250 radiocarbon yr b p no datable material has yet been found for the other four radar detected scarps but we interpolate and extrapolate dates of 1800 3400 5000 and 5800 yr b p

hydrological processes in the tyrrell basin southeastern australia abstract the tyrrell basin in semi arid southeastern australia provides an ideal setting where saline acid groundwaters evaporites redbeds syngenetic sulphides and thick groundwater brine bodies are all present and in many instances are actively forming today the relatively flat landscape and the associated regional groundwater systems with their concomitantly low hydraulic gradients create a setting in which is developed a clearer than normal aerial separation of a wide range of complex interwoven physico chemical processes detailed work in the tyrrell basin over a number of years has enabled the establishment of a hydrogeological framework which forms the basis for unravelling otherwise complicated hydrochemical interactions between groundwater systems and salt lakes indeed the interactions between groundwater flow systems and the regional groundwater discharge landscape in general and the spring zones of salt lakes in particular have important implications bearing upon the solution migration deposition and concentration of salts and metals by regional groundwater systems in arid and semi arid areas

coastal deformation and great subduction earthquakes isla santa maria chile 37 s isla santa maria at the active margin of south central chile is the result of earthquake related uplift and deformation in the forearc since at least late pleistocene time field mapping dating of key depositional horizons and analysis of seismic refl ection profi les reveal ongoing deformation in this sector of the chilean forearc the 30 km 2 island is located 12 km above the interplate seismogenic zone and 75 km landward of the trench it is situated near the southern termination of the concepcion earthquake rupture segment where charles darwin measured 3 m of coseismic uplift during a m 8 megathrust earthquake in 1835 permanent postearthquake deformation from this earthquake and an earlier event in 1751 is registered by emerged landward tilted abrasion surfaces uplift at 2 m k y and tilting at 0 025 k y of the island have been fairly constant throughout the late quaternary and have resulted in emergence of the island above sea level 31 k y ago the island is composed of a late pleistocene upper tilted surface with two asymmetric tilt domains and holocene lowlands characterized by uplifted and tilted strandlines industry offshore seismic refl ection profi les covering an area of 1800 km 2 and crustal seismicity reveal active reversefault cored anticlines surrounding isla santa maria the principal fault apparently roots in the plate interface thrust these reverse faults in the upper plate result from inversion of late cretaceous to early pliocene normal faults and rift structure of the arauco forearc basin positive inversion of these inherited structures started between 3 6 and 2 5 ma and resulted in continuous shortening rates of 0 8 mm yr the seismic refl ection profi les show that the asymmetric tilt domains and progressive syntectonic sedimentation are linked to the position of the island in the forelimbs of two converging anticlines whereas their backlimbs have been removed by cliff retreat the 2 m uplift contour of the 1835 earthquake is parallel to the strike of active faults and antiforms in the arauco concepcion region the close relation among the asymmetric uplift and tilt of the island modern deformation patterns and reverse faults rooted in the plate interface suggests that slip on the plate interface thrust infl uences localizes and segments surface deformation during large interplate earthquakes furthermore the link between positive inversion of pre existing structures uplift and tilt patterns in the forearc emphasizes the importance of inherited structural fabrics in guiding plate boundary deformation

coastal erosion and recovery from a cascadia subduction zone earthquake and tsunami abstract tsunamis generated by great earthquakes threaten coastal infrastructure development and human life earlier work has documented the inland extent and frequency of past tsunamis but little is known about the magnitude of material eroded during prehistoric tsunamis and how erosion and coastal recovery are recorded in coastal stratigraphy in this study we use high resolution ground penetrating radar gpr to image and quantify coastal erosion experienced during a late holocene 900 cal bp cascadia subduction zone earthquake and tsunami along the northern california coast the gpr profiles illustrate three stratigraphic signatures created during co seismic subsidence and tsunami erosion and coastal recovery the first is erosional truncation of the underlying seaward dipping reflections created by pre tsunami normal beach progradation the second is a series of landward dipping flat lying and channelized reflections marking the filling of erosional topography and coastal reworking of the irregular shoreline following inundation and erosion the third is an abrupt landward termination of the stratigraphic unit marking coastal straightening and post tsunami rejuvenation of normal coastal progradation erosion from the 900 cal bp earthquake and tsunami extended 110 m inland of the contemporary shoreline and removed reworked 225 000 28 000 m3 of sand from a 1 7 km stretch of the coast far exceeding anything experienced during historical el ninos along the pacific coast of north america this study provides the first quantitative estimate of the amount of coastal erosion from a pre historic earthquake and tsunami and outlines a strategy for estimating erosion during similar events elsewhere

the a d 900 930 seattle fault zone earthquake with a wider coseismic rupture patch and postseismic submergence inferences from new sedimentary evidence stratigraphic evidence for coseismic uplift a tsunami and a sandy debris flow linked to the a d 900 930 seattle fault zone earthquake and subsequent submergence is present at gorst at the terminus of sinclair inlet washington this study indicates that at least 3 m of uplift preceded a tsunami followed by a sandy debris flow though the seattle and tacoma fault zones ruptured within the error of ages of the tsunami deposit model simulations indicate the seattle fault generates an order of magnitude larger tsunami in the vicinity of the field area than the tacoma fault and is the more likely generator of the tsunami simulations indicate amplitude from a seattle fault zone generated wave train was 4 5 m and stratigraphy shows the tsunami left a sandy deposit soft sediment deformation narrows the time window for the debris flow to the hours to months after the tsunami slope failure in unconsolidated glacial sands likely initiated a debris flow that surged at least 2 km down gorst creek valley and left a more than 40 cm thick deposit along the creek and in the wetlands submergence of a thuja plicata western red cedar swamp into the intertidal zone indicates at least 1 5 m of submergence in the last 1100 years this submergence indicates uplift on nearby marine terraces associated with the seattle fault zone was likely higher and the a d 900 930 earthquake was potentially larger than previously recognized

postseismic coastal development in aceh indonesia field observations and numerical modeling we model postseismic changes to the shoreline of west aceh indonesia a region largely affected by the december 2004 sumatra andaman earthquake and ensuing indian ocean tsunami using a cross shore morphodynamic model subsidence of 0 5 1 0 m and tsunami scouring during the 2004 event caused the complete destruction of the beach and the landward displacement of the western coast of aceh by an average of 110 m comparing a series of satellite images and topographic surveys we reconstruct the build up of a new beach ridge along a 6 km long stretch of coastline in the years following the event we then use the cross shore model unibest tc developed for a wave dominated sandy shoreline to determine the controlling factors of shoreline recovery input parameters include bathymetric data measured in 2015 grain size characteristics of offshore sediment samples modeled wave data tidal elevations from a nearby tide gauge station as well as measured and modeled postseismic uplift data after establishing a cross shore profile in equilibrium with the prevailing hydrodynamic conditions we simulate the post tsunami recovery the effect of the monsoon seasons as well as the influence of postseismic land level changes for up to 10 years and compare them to the observed coastal development our modeling results indicate that the recovery of the western acehnese shoreline after the 2004 tsunami was quick with littoral sediment transport normalizing to pre tsunami conditions within two to four years following the event however field data shows that the shoreline stabilized 50 90 m landward of its pre 2004 tsunami position most likely due to the build up of a prominent higher beach ridge in response to coseismic subsidence observed variability in shoreline position in the order of a few tens of meters since 2009 can be attributed to seasonal wave climate variability related to the monsoon cycle the effect of postseismic uplift on shoreline position is small and in the order of only a few meters over 10 years which is 3 to 5 times smaller than long term coastal progradation rates that are driven by abundant sediment supply to the littoral zone this overall progradational trend will promote preservation of seismically modified beach ridges which can serve as paleoseismic indicators

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

a full holocene tephrochronology for the kamchatsky peninsula region applications from kamchatka to north america abstract geochemically fingerprinted widespread tephra layers serve as excellent marker horizons which can directly link and synchronize disparate sedimentary archives and be used for dating various deposits related to climate shifts faulting events tsunami and human occupation in addition tephras represent records of explosive volcanic activity and permit assessment of regional ashfall hazard in this paper we report a detailed holocene tephrochronological model developed for the kamchatsky peninsula region of eastern kamchatka nw pacific based on 2800 new electron microprobe analyses of single glass shards from tephra samples collected in the area as well as on previously published data tephra ages are modeled based on a compilation of 223 14c dates including published dates for shiveluch proximal tephra sequence and regional marker tephras new ams 14c dates and modeled calibrated ages from the krutoberegovo key site the main source volcanoes for tephra in the region are shiveluch and kliuchevskoi located 60 100 km to the west in addition local tephra sequences contain two tephras from the plosky volcanic massif and three regional marker tephras from ksudach and avachinsky volcanoes located in the eastern volcanic front of kamchatka this tephrochronological framework contributes to the combined history of environmental change tectonic events and volcanic impact in the study area and farther afield this study is another step in the construction of the kamchatka wide holocene tephrochronological framework under the same methodological umbrella our dataset provides a research reference for tephra and cryptotephra studies in the northwest pacific the bering sea and north america

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

sub bottom temperature perturbations due to temperature variations at the boundary of inhomogeneous lake or oceanic sediments abstract for many years continental heat flow data were obtained from temperature gradients measured in boreholes and conductivity measurements made on representative cores because of the difficulty of obtaining deep holes in suitable regions increasing use is being made of measurements made in the top few meters of the sediments at the bottom of continental lakes for reliable heat flow results two conditions must be met first an accurate record of the temperature history at the top of the sediment should be available preferably over a time span of 4 or 5 years second if the thermal properties are not constant with depth then the depth dependence should be known errors that may arise if either or both of these conditions cannot be met can be serious using various surface thermal histories we compare results from models assuming constant diffusivity a diffusivity changing exponentially with depth and a layered medium all being structures based upon observed variations near the sediment water interface where conductivity may change by a factor of two over 2 or 3 m in some situations errors as large as several hundred percents may occur but in such cases it should be possible to deduce from the data that something has occurred to make the data unreliable more realistically there are occasions where a temperature depth plot which is linear within normally acceptable limits of accuracy and with a gradient that is within the range of expectations may be as much as 100 in error

combining constraints from tsunami modeling and sedimentology to untangle the 1969 ozernoi and 1971 kamchatskii tsunamis 1 large tsunamigenic earthquakes occurred in 1969 mw 7 7 and 1971 mw 7 8 along the bering sea and northernmost pacific coast of kamchatka both resultant tsunamis were recorded on tide gauges but only the 1969 tsunami has cataloged observations of runup and these observations are limited and questionable we used a combination of field mapping of tsunami deposits and tsunami modeling to augment this historical record we mapped tsunami deposits above a d 1956 and 1964 volcanic ash layers along more than 200 km of shoreline however the 1969 and 1971 tsunami deposits are not distinguishable in the field the distribution of tsunami deposit elevation has two latitudinal peaks from 58 to 57 sediment runup typically ranges from 2 to 4 m decreasing to the south from 57 to 56 sediment runup typically ranges from 3 to 6 m maximum more than 10 m increasing to the south models of local runup for the 1969 and 1971 tsunamis explain most of the sediment distribution differentiate the two tsunamis in some localities and elucidate the earthquakes focal mechanisms and rupture areas

uplift and subsidence associated with the great aceh andaman earthquake of 2004 rupture of the sunda megathrust on 26 december 2004 produced broad regions of uplift and subsidence we define the pivot line separating these regions as a first step in defining the lateral extent and the downdip limit of rupture during that great m w 9 2 earthquake in the region of the andaman and nicobar islands we rely exclusively on the interpretation of satellite imagery and a tidal model at the southern limit of the great rupture we rely principally on field measurements of emerged coral microatolls uplift extends from the middle of simeulue island sumatra at 2 5 n to preparis island myanmar burma at 14 9 n thus the rupture is 1600 km long the distance from the pivot line to the trench varies appreciably the northern and western andaman islands rose whereas the southern and eastern portion of the islands subsided the nicobar islands and the west coast of aceh province sumatra subsided tilt at the southern end of the rupture is steep the distance from 1 5 m of uplift to the pivot line is just 60 km our method of using satellite imagery to recognize changes in elevation relative to sea surface height and of using a tidal model to place quantitative bounds on coseismic uplift or subsidence is a novel approach that can be adapted to other forms of remote sensing and can be applied to other subduction zones in tropical regions

beach ridges as paleoseismic indicators of abrupt coastal subsidence during subduction zone earthquakes and implications for alaska aleutian subduction zone paleoseismology southeast coast of the kenai peninsula alaska abstract the kenai section of the eastern alaska aleutian subduction zone straddles two areas of high slip in the 1964 great alaska earthquake and is the least studied of the three megathrust segments kodiak kenai prince william sound that ruptured in 1964 investigation of two coastal sites in the eastern part of the kenai segment on the southeast coast of the kenai peninsula identified evidence for two subduction zone earthquakes that predate the 1964 earthquake both coastal sites provide paleoseismic data through inferred coseismic subsidence of wetlands and associated subsidence induced erosion of beach ridges at verdant cove paleo beach ridges record the paleoseismic history whereas at quicksand cove buried soils in drowned coastal wetlands are the primary indicators of paleoearthquake occurrence and age the timing of submergence and death of trees mark the oldest earthquake at verdant cove that is consistent with the age of a well documented 900 year ago subduction zone earthquake that ruptured the prince william sound segment of the megathrust to the east and the kodiak segment to the west soils buried within the last 400 450 years mark the penultimate earthquake on the southeast coast of the kenai peninsula the penultimate earthquake probably occurred before ad 1840 from its absence in russian historical accounts the penultimate subduction zone earthquake on the kenai segment did not rupture in conjunction with the prince william sound to the northeast therefore the kenai segment which is presently creeping can rupture independently of the adjacent prince william sound segment that is presently locked

microfossils from coastal environments as indicators of paleo earthquakes tsunamis and storms abstract coastal risk assessment and hazard mitigation require datasets on centennial and millennial temporal scales to capture natural variability and multiple occurrences of the largest but least frequent events coastal sediments from low energy depositional environments archive geologic evidence of paleo earthquakes tsunamis and storms many of the best reconstructions of these events are derived from changes in microfossil diatoms foraminifera and pollen assemblages in this review we explain how microfossils are used to reconstruct records of paleoearthquakes by quantifying the amount of coseismic and interseismic vertical land movements along tectonically active coastlines examples from the united states alaska and the pacific northwest japan and chile show that microfossil based transfer functions may provide continuous records of vertical land movement during earthquake deformation cycles we discuss how microfossil habitat preferences and taphonomic character are used to constrain sediment provenance e g beach nearshore or offshore sources and identify overwash deposits and how this information can be used to reconstruct the recurrence of tsunamis and storms analysis of overwash deposits from thailand and malaysia indicates the ability of microfossils to resolve individual waves within tsunami sediments and an example from the sendai coastal plain in japan uses foraminifera to ascribe a beach to nearshore provenance for the 2011 tohoku tsunami deposit finally we present recent examples from the gulf of mexico on the use of foraminifera to estimate the volume and distance of transport of storm overwash from hurricanes

source model of the great 2011 tohoku earthquake estimated from tsunami waveforms and crustal deformation data the slip distribution of the 11 march 2011 tohoku earthquake is inferred from tsunami waveforms gps data and seafloor crustal deformation data the major slip region extends all the way to the trench and the large slip area extends 300 km long and 160 km wide the largest slip of 44 m is located up dip of the hypocenter the large slip amount about 41 m ruptured the plate interface near the trench the seismic moment calculated from the estimated slip distribution is 5 5 10 22 n m mw 9 1 the large tsunami due to the 2011 tohoku earthquake is generated from those large slip areas near the trench the additional uplift at the sedimentary wedge as suggested for the 1896 sanriku earthquake may have occurred during the 2011 tohoku earthquake too

land level changes produced by the mw 8 8 2010 chilean earthquake we observed vertically displaced coastal and river markers after the 27 february 2010 chilean earthquake moment magnitude mw 8 8 land level changes range between 2 5 and 1 meters evident along an approximately 500 kilometers long segment identified here as the maximum length of coseismic rupture a hinge line located 120 kilometers from the trench separates uplifted areas to the west from subsided regions a simple elastic dislocation model fits these observations well model parameters give a similar seismic moment to seismological estimates and suggest that most of the plate convergence since the 1835 great earthquake was elastically stored and then released during this event

asperity distribution of the 1952 great kamchatka earthquake and its relation to future earthquake potential in kamchatka the 1952 kamchatka earthquake is among the largest earthquakes of this century with an estimated magnitude of m w 9 0 we inverted tide gauge records from japan north america the aleutians and hawaii for the asperity distribution the results show two areas of high slip the average slip is over 3 m giving a seismic moment estimate of 155 x 102onm or m w 8 8 the 20th century seismicity of the 1952 rupture zone shows a strong correlation to the asperity distribution which suggests that the large earthquakes m 7 are controlled by the locations of the asperities and that future large earthquakes will also recur in the asperity regions

a stable isotope investigation of groundwater surface water interactions at lake tyrrell victoria australia herczeg a l barnes c j macumber p g and olley j m 1992 a stable isotope investigation of groundwater surface water interactions at lake tyrrell victoria australia in w b lyons d t long a l herczeg and m e hines guesteditors the geochemistry of acid groundwater systems chem geol 96 19 32 the stable isotope composition of regional groundwaters around lake tyrrell victoria indicates that the groundwaters are derived entirely from meteoric water that has undergone some degree of evaporation during recharge seepage waters at the western margin of lake tyrrell victoria have a characteristic chemical and isotopic signature of regional groundwater flowing from the northeast and east on a transect of shallow groundwaters across the lake the isotopic composition is increasingly enriched in the heavy isotopes toward the centre of the lake but define a steeper slope on a dd djso plot than that of the regional groundwaters the stable isotopic compositions of the shallow groundwaters within the seepage zone are typical of those due to evaporative enrichment currently occurring with a small component of vertical mixing with the deeper reflux brines reflux brines below the lake are relatively more enriched in tso than the brines forming now at the lake surface the reflux brines appear to have undergone several cycles of evaporation and admixture of regional groundwater as have waters within the mixing zone between regional groundwater and reflux brines

holocene key marker tephra layers in kamchatka russia detailed tephrochronological studies in kamchatka peninsula russia permitted documentation of 24 holocene key marker tephra layers related to the largest explosive eruptions from 11 volcanic centers each layer was traced for tens to hundreds of kilometers away from the source volcano its stratigraphic position area of dispersal age characteristic features of grain size distribution and chemical and mineral composition confirmed its identification the most important marker tephra horizons covering a large part of the peninsula are from north to south ages given in14c yr b p sh2 1000 yr b p and sh3 1400 yr b p from shiveluch volcano kz 7500 yr b p from kizimen volcano krm 7900 yr b p from karymsky caldera khg 7000 yr b p from khangar volcano av1 3500 yr b p av2 4000 yr b p av4 5500 yr b p and av5 5600 yr b p from avachinsky volcano op 1500 yr b p from the baraniy amfiteatr crater at opala volcano khd 2800 yr b p from the maar at khodutka volcano ks1 1800 yr b p and ks2 6000 yr b p from the ksudach calderas ksht3 a d 1907 from shtyubel cone in ksudach volcanic massif and ko 7700 yr b p from the kuril lake iliinsky caldera tephra layers sh5 2600 yr b p from shiveluch volcano av3 4500 yr b p from avachinsky volcano optr 4600 yr b p from opala volcano ks3 6100 yr b p and ks4 8800 yr b p from ksudach calderas ksht1 1100 yr b p from shtyubel cone and zlt 4600 yr b p from iliinsky volcano cover smaller areas and have local stratigraphic value as do the ash layers from the historically recorded eruptions of shiveluch sh1964 and bezymianny b1956 volcanoes the dated tephra layers provide a record of the most voluminous explosive events in kamchatka during the holocene and form a tephrochronological timescale for dating and correlating various deposits