reassessment of the 1907 sumatra tsunami earthquake based on macroseismic seismological and tsunami observations and modeling on 4 january 1907 an earthquake occurred off the west coast of sumatra indonesia with an instrumental surface wave magnitude ms in the range of 7 5 8 0 at periods of 40 s the tsunami it generated was destructive on the islands of nias and simeulue where it killed hundreds and gave rise to the legend of the s mong this tsunami was also observed in other parts of the indian ocean basin relative to its instrumented magnitude the size of the tsunami was anomalous qualifying the event as a tsunami earthquake however unusually for a tsunami earthquake the shaking on nias was severe 7 ems we revisit the 1907 earthquake with a multidisciplinary approach by extracting evidence describing shaking effects or the tsunami from written documents and by acquiring new seismograms combining these we discriminate two large earthquakes within an hour of each other with clear differences in seismological character the first we interpret to be a tsunami earthquake with characteristic low levels of shaking an estimated average seismic moment m0 of 2 5 1028 dyn cm mw 8 2 in the frequency band 6 8 mhz and an epicentral location close to the front of the sunda megathrust the seismograms we analyzed also document a regular growth of moment with period approaching mw 8 4 at the longest resolvable period 170 s for the second earthquake that caused damage on nias we estimate ms 7 based on seismograms and phase data we also identify two ms 6 aftershocks within 24 h of the mainshock additionally we present a dataset of 88 locations within the indian ocean basin where the tsunami was observed using a subset of these we forward modeled the tsunami to propose a seismic rupture model extending along the sunda megathrust for about 220 km 94 7 e to 97 e with a maximum modeled slip of 21 m our new rupture model provides an acceptable fit to our new dataset of tsunami runup and inundation values from 88 local and far field locations in the indian ocean basin we also urge caution against an over reliance on the s mong legend for tsunami evacuation as its premise that a tsunami will only follow an earthquake with very severe ground motions is rendered ineffective for tsunami earthquakes

paleoseismic study on active normal faults in the southeastern weihe graben central china abstract field investigations and trench excavations can provide direct and indirect geological evidence for the occurrence of paleo earthquakes in this study we present geological and topographical evidence for the occurrence of great paleo earthquakes produced by active normal faults in the southeastern weihe graben central china field and trench observations in combination with radiocarbon ages reveal that i four surface faulting events occurred in the past 4000 years with an average recurrence interval of 1000 years which is in contrast with the previously estimated interval of 2000 2900 years ii the most recent fault event is correlated to the 1556 m 8 5 huaxian earthquake iii an alluvial terrace riser that formed at 5300 yr b p has been vertically offset by 9 11 m indicating an average vertical slip rate of 1 7 2 1 mm yr in the late holocene our results confirm that normal faults in the southeastern weihe graben have been active in the late holocene as source seismogenic faults and that these faults have the potential to trigger large earthquakes of m 7 in the future therefore it is important to urgently reevaluate the seismic potential and seismic hazard in the densely populated weihe graben region

simulated ground motions for hypothesized mw 8 subduction earthquakes in washington and oregon the amplitude and duration of strong ground motions from hypothesized mw 8 subduction zone thrust earthquakes in the puget sound portland region were estimated using a semi empirical method the simulation procedure assumes the rupture surface may be represented by a grid of fault elements finite difference wave simulation in a detailed 2 d velocity structure identifies direct s and the moho postcritical reflection as the primary components of the s wave field at horizontal distances of 0 to 150 km green s functions containing these two arrivals are computed with generalized ray theory in an equivalent 1 d structure for each source element receiver propagation path scattering and attenuation structure are empirically modeled by the use of corrected accelerograms from mw 7 michoacan mexico and valparaiso chile aftershocks for the fault element source functions different site conditions are empirically included in the simulation procedure by using empirical source functions recorded on rock and soil sites spatial variations in slip on the fault asperities are introduced by weighting the fault elements the technique has been validated for large subduction zone earthquakes by modeling acceleration time histories and response spectra from the 1985 michoacan mw 8 0 and valparaiso mw 8 0 main shocks somerville et al 1991 fault models for the puget sound and portland regions and seismic velocity structure models have been adapted from published regional studies uncertainty in the location of the asperities on the fault surface results in a large degree of uncertainty in the simulated ground motions at a given site if distance is defined as the distance to the closest asperity then the variability in the ground motions is reduced indicating that this uncertainty can be lessened by constraining the depth of the asperity the ground motion estimates are relatively insensitive to the difference in fault dip between the puget sound and portland fault models the attenuation of peak acceleration with distance r from the fault asperity for a mw 8 subduction earthquake is given by in pga 1 5 3 33 in r 128 0 79 s where s is a site term equal to 0 for rock and 1 for soil when distance r is the distance to the fault plane the attenuation relation is in pga 2 8 1 26 in r 0 79 s formal estimates of uncertainty in the calculated ground motions have been obtained by estimating both parametric uncertainty from the range of source models of hypothesized cascadia subduction earthquakes and modeling and random uncertainty from the misfit between recorded and simulated ground motions of the 1985 michoacan and valparaiso earthquakes for periods less than 1 sec the estimated response spectral velocities on soil sites in the seattle olympia region are about twice those recorded during the 1949 olympia and 1965 seattle wadati benioff zone earthquakes and the durations of strong motion on rock sites are significantly longer 45 to 60 sec versus 10 to 15 sec

age and significance of earthquake induced liquefaction near vancouver british columbia canada in late 1994 sand dykes large sand blows and deformed strata were exposed in the walls of an excavation at annacis island on the fraser river delta near vancouver british columbia the features record liquefaction during a large earthquake about 1700 years ago this was perhaps the largest earthquake to affect the vancouver area in the last 3500 years similar less well dated features have been reported from several other sites on the fraser delta and may be products of the same earthquake three radiocarbon ages that closely delimit the time of liquefaction on annacis island are similar to the most precise radiocarbon ages on coseismically subsided marsh soils at estuaries in southern washington and oregon both the liquefaction and the subsidence may have been produced by a single great plate boundary earthquake at the cascadia subduction zone alternatively liquefaction at annacis island may have been caused by a large crustal or subcrustal earthquake of about the same age as a plate boundary earthquake farther west the data from annacis island and other sites on the fraser delta suggest that earthquakes capable of producing extensive liquefaction in this area are rare events further liquefaction analysis using historical seismicity suggests that current assessment procedures may overestimate liquefaction risk

namurian uplift in australia and south america triggered the main gondwanan glaciation the permo carboniferous glacigenic sediment at the base of the gondwanan basins reflects the culmination1 2 of the glacial episode that started in australia and southern south america in the namurian after two local episodes in northern south america and adjacent africa in the visean and latest devonian3 fig 1 here we show that the start of each episode was associated with orogenic uplift of the bordering regions northern south america and adjacent africa in the latest devonian and visean and southern south america and eastern and central australia in the namurian all areas except southern south america in the namurian were at mid and not high latitudes thus we show that whereas the first order control of glaciation was the configuration of the continents and oceans during the closing of palaeo tethys orogenesis provided a second order control by the accumulation of ice about bordering uplifts during the three glacial episodes

probabilistic methodology for the analysis of paleoliquefaction features paleoliquefaction features can be used to estimate lower bounds on the magnitude and ground motion associated with the earthquake that caused the liquefaction feature the engineering back analysis of paleoliquefaction features is usually conducted using state of the practice liquefaction triggering analysis methodologies recent studies have shown that these methodologies are associated with variable probabilities of liquefaction depending on the soil parameters this would imply that estimates of magnitude and ground motion intensity obtained from these methodologies would not be consistent for all soil sites moreover these estimates could be unconservative in this paper the use of a probabilistic methodology for the back analysis of paleoliquefaction features is proposed the proposed methodology permits the incorporation of model and parameter uncertainty into the analysis and results in more robust estimates of past magnitude and a measure of the uncertainty associated with these predictions previously published paleoliquefaction data are used to demonstrate the applicability of the proposed method magnitude estimates obtained with the proposed method do not differ significantly from those obtained using deterministic methodologies but the proposed methodology permits a quantification of the uncertainty associated with magnitude estimates

gnss r nonlocal sea state dependencies model and empirical verification global navigation satellite system reflectometry gnss r is an active bistatic remote sensing technique operating at l band frequencies gnss r signals scattered from a rough ocean surface are known to interact with longer surface waves than traditional scatterometery and altimetry signals a revised forward model for gnss r measurements is presented which assumes an ocean surface wave spectrum that is forced by other sources than just the local near surface winds the model is motivated by recent spaceborne gnss r observations that indicate a strong scattering dependence on significant wave height even after controlling for local wind speed this behavior is not well represented by the most commonly used gnss r scattering model which features a one to one relationship between wind speed and the mean square slope of the ocean surface the revised forward model incorporates a third generation wave model that is skillful at representing long waves an anchored spectral tail model and a gnss r electromagnetic scattering model in comparisons with the spaceborne measurements the new model is much better able to reproduce the empirical behavior

development of magnitude bound relations for paleoliquefaction analyses new zealand case study abstract magnitude bound relations are often used to estimate paleoearthquake magnitudes from paleoliquefaction data this study proposes new zealand based magnitude bound curves that are developed using a liquefaction field observations and b a newly proposed back calculation approach that combines the simplified liquefaction evaluation procedure with a regionally appropriate ground motion prediction equation for b both deterministic and probabilistic frameworks are proposed the magnitude bound curves back calculated using either the deterministic or probabilistic frameworks are advantageous in that they can be used to predict the spatial distribution of liquefaction in regions where historical liquefaction field observations are limited or poorly documented and because soil and site specific conditions can be incorporated into magnitude bound analyses moreover curves developed using the probabilistic framework allow for the range of possible causative earthquake magnitudes to be better understood and quantified to demonstrate the use of the proposed relations paleoliquefaction features discovered in eastern christchurch nz are analyzed the 1869 mw4 8 christchurch earthquake and or 1717 mw8 1 alpine fault earthquake are found to be the most likely candidates amongst known historical and paleoearthquakes for triggering liquefaction over the permissible time range ca 1660 to 1905 a d this study demonstrates the potential of the proposed magnitude bound curves to provide insight in to past present and future hazards proving their utility even in cases of limited evidence the approach of developing and applying magnitude bound curves proposed herein is not limited to parts of new zealand but rather can be applied worldwide

plate boundary earthquakes and tsunamis of the past 5500 yr sixes river estuary southern oregon eleven plate boundary earthquakes over the past 5500 yr have left a stratigraphic signature in coastal wetland sediments at the lower sixes river valley in south coastal oregon within a 1 8 km2 abandoned meander valley 10 buried wetland soils record gradual and abrupt relative sea level changes back in time to 6000 yr ago an additional youngest buried soil at the mouth of the sixes river subsided during the a d 1700 cascadia earthquake multiple lines of evidence indicate that tectonic subsidence caused soil burial including permanent relative sea level rise following burial lateral continuity of buried soil horizons over hundreds of meters diatom assemblages showing that sea level rose abruptly at least 0 5 m and sand deposits on top of buried soils demonstrating coincidence of coseismic subsidence and tsunami inundation for at least two of the buried soils liquefaction of sediment accompanied subsidence the 11 soil burial events took place between 300 and 5400 yr ago yielding an average recurrence interval of plateboundary earthquakes of 510 yr comparing paleoseismic sites in southern washington and south coastal oregon with the sixes river site for the past 3500 yr indicates that the number and timing of recorded plate boundary earthquakes are not the same at all sites in particular a sixes earthquake at 2000 yr ago lacks a likely correlative in southern washington therefore unlike the a d 1700 cascadia earthquake some cascadia plate boundary earthquakes do not rupture the entire subduction zone from southern oregon to southern washington in the lower sixes river valley the upperplate cape blanco anticline deforms sediment of late pleistocene and holocene age directly above the subduction zone differential tectonic subsidence occurred during two of the plate boundary earthquakes when a blind upper plate reverse fault for which the cape blanco anticline is the surface fold slipped coseismically with rupture of the plate boundary during these two earthquakes sites 2 km from the anticline axis subsided 0 5 m more than sites 1 km from the axis

directional wind wave coupling in fully coupled atmosphere wave ocean models results from cblast hurricane abstractthe extreme high winds intense rainfall large ocean waves and copious sea spray in hurricanes push the surface exchange parameters for temperature water vapor and momentum into untested regimes the coupled boundary layer air sea transfer cblast hurricane program is aimed at developing improved coupling parameterizations using the observations collected during the cblast hurricane field program for the next generation hurricane research prediction models hurricane induced surface waves that determine the surface stress are highly asymmetric which can affect storm structure and intensity significantly much of the stress is supported by waves in the wavelength range of 0 1 10 m which is the unresolved spectral tail in present wave models a directional wind wave coupling method is developed to include effects of directionality of the wind and waves in hurricanes the surface stress vector is calculated using the two dimensional wave spectra from a wave model with an added short wave s

intra arc deformations with vertical rotation axes the case of the pre middle miocene terranes of southwest japan abstract various folds bends with vertical or subvertical rotation axes occur in the pre middle miocene terranes of southwest japan they are variable in shape conical folds accordion folds megakink bands and so on and some are accompanied with strike slip faults they range from several kilometers to more than 100 km in width and some of their hinge surfaces are traceable more than a few tens of kilometers their shapes which resemble megakink band or buckle folds indicate that they were produced by horizontal compression with vertical or subvertical 2 axes in a shallow level of the crust they were superimposed on the pre middle miocene fold and thrust structures or nappe melange complexes and are regarded to have been formed mostly during the middle miocene contemporaneous with the clockwise rotation of southwest japan related to the fan shaped opening of the sea of japan geometrical analysis clearly suggests that the drifting southwest japan behaved as a non rigid body and the formation of these structures resulted from the differential rotation of the terranes and the collision of the izu bonin arc with eastern southwest japan

sheltered coastal environments as archives of paleo tsunami deposits observations from the 2004 indian ocean tsunami the 2004 earthquake left several traces of coseismic land deformation and tsunami deposits both on the islands along the plate boundary and distant shores of the indian ocean rim countries researchers are now exploring these sites to develop a chronology of past events where the coastal regions are also inundated by storm surges there is an additional challenge to discriminate between the deposits formed by these two processes paleo tsunami research relies largely on finding deposits where preservation potential is high and storm surge origin can be excluded during the past decade of our work along the andaman and nicobar islands and the east coast of india we have observed that the 2004 tsunami deposits are best preserved in lagoons inland streams and also on elevated terraces chronological evidence for older events obtained from such sites is better correlated with those from thailand sri lanka and indonesia reiterating their usefulness in tsunami geology studies c 2014 elsevier ltd all rights reserved

silurian to mid devonian basin development of the melbourne zone lachlan fold belt southeastern australia abstract the melbourne zone comprises early ordovician to early devonian marine turbidites which pass conformably upward into a mid devonian fluviatile succession there are four pulses of silurian to mid devonian deep marine sandstone dominated sedimentation early silurian late llandovery late silurian ludlow earliest devonian lochkovian and late early devonian emsian two dispersal patterns have been defined using more than 1100 palaeocurrent measurements mainly from sole marks and cross laminations in graded beds together with sandstone compositions the older pattern of silurian to earliest devonian age contains the lowest three sandstone pulses palaeocurrents and provenance define a wedge of southwesterly derived sediment of largely cratonic provenance thinning eastward this older dispersal pattern is part of an early ordovician to earliest devonian east facing passive continental margin succession palaeocurrents and provenance in the emsian sandstone pulse comprise three patterns 1 west to southwesterly directed palaeocurrents associated with fine to coarse grained locally conglomeratic lithic sandstones containing a high proportion of volcanic detritus 2 east to northeasterly directed palaeocurrents associated with fine to medium grained quartz lithic sandstones 3 north to northwesterly and south to southeasterly directed palaeocurrents associated with fine to medium grained sandstones of variable lithic composition the palaeocurrent and provenance pattern defines a nnw elongate basin with a tectonically active eastern margin and is similar to the coeval mathinna basin of northeastern tasmania both basins are part of the same system of wrench basins which developed along the western side of the wagga omeo metamorphic belt during the earliest devonian to middle devonian the change in tectonic setting in the earliest devonian appears to have occurred during an interval of significant dextral translation of the eastern lachlan fold belt towards the sse along the governor and associated fault zones

the significance of e w structural trends for the alice springs orogeny in the charters towers province north queensland e w structural and igneous trends in the charters towers province are highly anomalous within the overall n s trending tasman orogen of eastern australia and resulted from a sequence of n s shortening events a succession of e w trending fias foliation intersection inflexion axis preserved within porphyroblasts dated at 474 7 7 2 413 13 and 381 1 8 1 ma correspond with adjacent granite crystallization ages and e w trending fia ages in the greenvale province to the nw the magnetic anomaly map of australia reveals that this e w trending portion of the tasman orogen links with and truncates several earlier formed orogens the e w trend of the charters towers province resulted from overprinting of early palaeozoic n s trending structures in the tasman orogen by younger e w ones during the alice springs orogeny 450 300 ma resolving the e w pluton shape and distribution of cambrian to devonian magmatic activity plus the truncational nature of aeromagnetic data from central australia to the east coast

tracking basement cross strike discontinuities in the indian crust beneath the himalayan orogen using gravity data relationship to upper crustal faults the himalaya is the result of the on going convergence and collision of india and asia two plates with complex and protracted geological evolutions the internal configuration and processes that govern the rise of the himalaya and tibetan plateau are crucial to understand continental collision zones however knowledge of the prior configuration of the colliding plates is equally important since inherited preorogenic basement structures can undeniably influence the development of the orogenic architecture throughout the orogen s cycle of collision and eventual collapse three northeast trending palaeotopographic ridges of faulted precambrian indian basement underlie the ganga basin south of the himalaya oil and natural gas commission 1968 valdiya 1976 gahalaut kundu 2012 our study godin harris 2014 illustrates a crustal scale fault origin for these ridges and succeeds in determining how far north beneath the himalayan system they extend and how they ultimately govern the location of upper crustal faults in southern tibet spectrally filtered egm2008 bouguer gravity data and edges in its horizontal gradient at different source depths gravity worms over northern peninsular india the himalaya and southern tibet reveal several continuous himalayan cross strike discontinuities interpreted to represent crustal faults fig 1 gravity lineaments in peninsular india coincide with edges of the precambrian basement ridges and megakinks up to 100 km wide develop in foreland cover sequences between the interpreted basement faults the interpreted basement faults project northward beneath the himalayan system and southern tibet our results suggest that several active himalayan cross strike faults such as the ones related to many graben in southern tibet are rooted in the underplated indian lower crust or step en echelon along interpreted basement faults our interpretation thus suggests that south tibet graben are spatially related to deepseated crustal scale faults rooted in the underplated indian crust these major discontinuities partition the himalayan range into distinct zones and could ultimately contribute to lateral variability in tectonic evolution along the orogen s strike

hurricane directional wave spectrum spatial variation in the open ocean abstract the sea surface directional wave spectrum was measured for the first time in all quadrants of a hurricane s inner core over open water the nasa airborne scanning radar altimeter sra carried aboard one of the noaa wp 3d hurricane research aircraft at 1 5 km height acquired the open ocean data on 24 august 1998 when bonnie a large hurricane with 1 min sustained surface winds of nearly 50 m s 1 was about 400 km east of abaco island bahamas the noaa aircraft spent more than five hours within 180 km of the eye and made five eye penetrations grayscale coded images of hurricane bonnie wave topography include individual waves as high as 19 m peak to trough the dominant waves generally propagated at significant angles to the downwind direction at some positions three different wave fields of comparable energy crossed each other partitioning the sra directional wave spectra enabled determination of the characteristics of the various components of the hurricane wave field and mapping of their sp

liquefaction evidence for the strength of ground motions resulting from late holocene cascadia subduction earthquakes with emphasis on the event of 1700 a d during the past decade paleoseismic studies done by many researchers in the coastal regions of the pacific northwest have shown that regional downdropping and subsequent tsunami inundation occurred in response to a major earthquake along the cascadia subduction zone this earthquake occurred almost certainly in 1700 a d and is believed by many to have been of m 8 5 9 or perhaps larger in order to characterize the severity of ground motions from this earthquake we report on a field search and analysis of seismically induced liquefaction features the search was conducted chiefly along the banks of islands in the lowermost columbia river of oregon and washington and in stream banks along smaller rivers throughout southwestern washington to a lesser extent the investigation included rivers in central oregon numerous small to moderate sized liquefaction features from the earthquake of 1700 a d were found in some regions but there was a notable lack of liquefaction features in others the regional distribution of liquefaction features is evaluated as a function of geologic and geotechnical factors in different field settings near the coast our use of widely different field settings each in which we independently assess the strength of shaking and arrive at the same conclusion enhances the credibility of our interpretations our regional inventory of liquefaction features and preliminary geotechnical analysis of liquefaction potential provide substantial evidence for only moderate levels of ground shaking in coastal washington and oregon during the subduction earthquake of 1700 a d additionally it appears that a similar conclusion can be reached for an earlier subduction earthquake that occurred within the past 1100 years which also has been characterized by others as being m 8 or greater on the basis of more limited data for older events collected in our regional study it appears that seismic shaking has been no stronger throughout holocene time our interpreted levels of shaking are considerably lower than current estimates in the technical literature that use theoretical and statistical models to predict ground motions of subduction earthquakes in the cascadia region because of the influence of estimated ground motions from cascadia subduction zone earthquakes on seismic hazard evaluations more paleoliquefaction and geotechnical field studies are needed to definitively bracket the strength of shaking with further work it should be possible to extend the record of seismic shaking through much of holocene time in large portions of washington and oregon

strain measurements and the potential for a great subduction earthquake off the coast of washington geodetic measurements of deformation in northwestern washington indicate that strain is accumulating at a rate close to that predicted by a model of the cascadia subduction zone in which the plate interface underlying the continental slope and outer continental shelf is currently locked but the remainder of the interface slips continuously presumably this locked segment will eventually rupture in a great thrust earthquake with a down dip extent greater than 100 kilometers

paleoseismic features as indicators of earthquake hazards in north coastal san diego county california usa abstract new road cut and mass grading excavations in the north coastal area of san diego county california expose heretofore generally unrecognized probable late holocene tsunami deposits and paleoseismically deformed sediments remnant tsunami deposits occur up to 100 m in elevation around the margins of modern coastal lagoons and estuaries and combined with local mima mounds of possible sand blow origin provide indirect but compelling evidence for the late quaternary activity of onshore and offshore faults in the immediate study area probable paleoliquefaction features are regionally widespread and range from fissures filled with sediments derived from overlying marine terrace sand and soil to the more traditional sand filled injection dikes and sills lateral spreads and filled craterlets the source of most liquefied sediment is underlying tertiary bedrock sand and local quaternary marine terrace deposits a paleoseismic liquefaction origin rather than soft sediment loading is deduced for these features based on morphology internal stratigraphy field setting and near proximity to known seismogenic sources some paleoseismic events impacted late holocene indian middens and burial sites the last seismic event probably occurred within the past 1 to 3 ka and possibly even records the historic earthquakes of either november 22 1800 or may 27 1862 the liquefaction features also affect marine terrace sediments tens of meters above modern regional water levels inferentially recording paleoseismic events in this mediterranean type climatic region during winter rains when high level perched water saturates the several meter thick source sediments based on their regional extent the paleoseismic features were likely caused by m 7 tectonic events inferentially generated by the nearby offshore newport inglewood rose canyon fault system or possibly by smaller recently exposed related and localized faults accordingly the seismic hazard of the north coastal area of san diego county may be substantially higher than previously assumed and hence of concern owing to the rapid ongoing and projected population increase

on the dependence of sea surface roughness on wave development abstract the aerodynamic roughness of the sea surface z0 is investigated using data from lake ontario from the north sea near the dutch coast and from an exposed site in the atlantic ocean off the coast of nova scotia scaling z0 by rms wave height gives consistent results for all three datasets except where wave heights in the atlantic ocean are dominated by swell the normalized roughness depends strongly on wave age younger waves traveling slower than the wind are rougher than mature waves alternatively the roughness may be normalized using the friction velocity u of the wind stress again young waves are rougher than mature waves this contradicts some recent deductions in the literature but the contradiction arises from attempts to describe z0 in laboratory tanks and in the field with a single simple parameterization here it is demonstrated that laboratory waves are inappropriate for direct comparison with field data being much smoother than their field equivalents in the open ocea

strong ground motion from the michoacan mexico earthquake the network of strong motion accelerographs in mexico includes instruments that were installed under an international cooperative research program in sites selected for the high potenial of a large earthquake the 19 september 1985 earthquake magnitude 8 1 occurred in a seismic gap where an earthquake was expected as a result there is an excellent descripton of the ground motions that caused the disaster

modeling waves and wind stress 1 a model for wave and wind stress prediction is constructed the source functions that drive the space time evolution of the energy spectra are developed in form based on theory and laboratory and field experiments the calibration factors proportionality constants of the source functions are determined from a comparison of modeled and observed significant height and mean period the observations are for the month of january 2005 and are derived from an array of laser range finders mounted on a bridge between two platforms in the ekofisk oil field in the north sea the model calculates the form stress on the waves and adds it vectorially to the sheltering modified skin stress the resulting drag coefficient versus wind speed is shown to have the observed structure low in light winds increasing in moderate winds and increasing more slowly in very strong winds modeled spectral shapes in the four quadrants of hurricane bonnie 1998 match the scanning radar altimeter measurements modeled spectral properties in hurricane ike 2008 are compared against ndbc buoy estimates with good results drag coefficients in the mixed seas produced by hurricanes show dependence on wave age of the wind sea swell propagation direction and water depth the need for wave and stress modeling for atmosphere ocean coupling is emphasized the new wave model has all the necessary attributes to be the basis for such a coupler

thermal and structural evolution of the intracratonic arltunga nappe complex central australia the thermal and structural evolution of a paleozoic thrust system in central australia the arltunga nappe complex has been examined through field mapping petrographic microstructural and chemical analyses k ar and 40ar 39ar thermochronology and multi diffusion domain time temperature modeling of k feldspar 40ar 39ar data the arltunga nappe complex contains three distinct tectonic units bounded by regional faults and shear zones that have undergone contrasting deformational and metamorphic histories the cooling history of the three tectonic units has been constrained by k ar and 40ar 39ar isotopic age data from k feldspars micas and amphiboles results are consistent with a piggyback history of crustal imbrication spanning over 100 m y with the hottest rocks uplifted and cooled first and with imbrication acting progressively toward the foreland implications for the intracratonic paleozoic tectonics of central australia are 1 uplift within the structurally highest tectonic unit was initiated before 400 ma 2 continued piggyback imbrication footwall failure and uplift and exhumation of the crust resulted in duplexing in the lowest structural unit at approximately 325 300 ma 3 the contrast in thermal history between the tectonic units indicates that once widely separated crustal segments were juxtaposed during thrusting above a hinterland dipping megathrust resulting in 85 km of crustal shortening

kilometer scale kinking of crystalline rocks in a transpressive convergent setting central sierra nevada california structural analyses in the lake edison area of the central sierra nevada california show that prominent north northeast trending lineaments represent traces of joints and faults that have accommodated slip within a 4 8 km wide right lateral north northwest trending monoclinal kink band the kilometer scale kink band formed in cretaceous granitic rocks and the closely spaced mineralized joints and faults formed at 79 ma joints and faults strike 070 within the kink band and 020 030 outside the kink band a kink band kinematic model indicates that 3 7 2 1 1 9 km of right lateral displacement was accommodated across the kink band and that as much as 148 m of left lateral slip on faults within the kink band occurred a sensitivity study on four model parameters varied the angle made by the inner and outer limbs of the kink band the number of faults within the kink band and the kink band width and length this analysis yields estimates for right lateral displacement across the kink band and left lateral slip on faults within the kink band that fall into the range constrained by geologic relationships kinking may have been the last stage of right lateral deformation which started with development of the rosy finch shear zone the presence of curved lineaments in the southern sierra nevada indicates that kilometer scale kink bands may exist elsewhere in the sierra nevada batholith such arc parallel kinking has been described in several other transpressive settings and kilometer scale kink bands may be a process by which late stage arc parallel deformation is accommodated in convergent margins

winds waves and shorelines from ancient martian seas we consider under what environmental conditions water waves and thus eventually shorelines should be expected to be produced on hypothetical ancient martian seas and lakes for winds and atmospheric pressures that are too small no waves should be expected and thus no shorelines if the winds and atmospheric pressure are above some threshold then waves can be formed and shorelines are possible we establish these criteria separating conditions under which waves will or will not form on an ancient martian open body of water we consider not only atmospheric pressure and wind but also temperature and salinity but find these latter effects to be secondary the normal criterion for the onset of water waves under terrestrial conditions is extended to recognize the greater atmospheric viscous boundary layer depth for low atmospheric pressures we used terrestrial wave models to predict the wave environment expected for reasonable ranges of atmospheric pressure and wind for end member cases of ocean salinity these models were modified only to reflect the different fluids considered at mars the different martian surface gravity and the varying atmospheric pressure wind and fetch the models were favorably validated against one another and also against experiments conducted in a wave tank in a pressure controlled wind tunnel nasa ames marswit we conclude that if wave cut shorelines can be confirmed on mars this can constrain the range of possible atmospheric pressures and wind speeds that could have existed when the open water was present on mars

the geometry and kinematics of a suite of conjugate kink bands southeastern australia abstract a conjugate set of subvertical kink bands is exposed in coastal outcrops of well foliated ordovician turbidites near mystery bay australia all kink bands with widths exceeding 3 cm have complex internal structures including compound and parasitic kinks stepped kink boundaries internal crenulations variable kink angles and prismatic voids the kink bands are interpreted to result from rotation of short foliation segments between fixed kink planes with subsequent widening and modification by layer parallel shear external to the kink band layer parallel shear of both sinistral and dextral sense accompanied kinking and indicates a variable stress system during kink band development conjugate kink bands are abundant and are used to estimate bulk strain orientations in general the dominant kink set of a conjugate pair is inclined at a lower angle to the external foliation than the weaker set and this angular disparity increases with increasing dominance of one set these observations are at variance with relationships described from experimental bulk pure shear deformation of anisotropic materials it is suggested that orthogonal constraints in these experiments restrict layer parallel shear to within a developing kink band and are therefore unlike many natural kink systems simple shear experiments can produce structures geometrically similar to natural kink bands

tsunamigenic earthquakes past and present milestones we review a number of events which taken individually have significantly affected our understanding of the generation of tsunamis by earthquake sources and our efforts at mitigating their hazards notably through the development of warning algorithms starting with the 1700 cascadia earthquake we examine how significant tsunamis have changed our views in fields as diverse as seismotectonics the diversity of earthquake cycles the development of warning algorithms the response of communities at risk to warnings and their education the latter being either formal or rooted in ancestral heritage we discuss in detail lessons from the 2004 sumatra disasters and review the performance of warning centers and the response of affected populations during the nine significant tsunamis which have taken place since 2004

radiocarbon evidence for extensive plate boundary rupture about 300 years ago at the cascadia subduction zone the cascadia subduction zone a region of converging tectonic plates along the pacific coast of north america has a geological history of very large plate boundary earthquakes1 2 but no such earthquakes have struck this region since euro american settlement about 150 years ago geophysical estimates of the moment magnitudes mw of the largest such earthquakes range from 8 ref 3 to 9 1 2 ref 4 radiocarbon dating of earthquake killed vegetation can set upper bounds on earthquake size by constraining the length of plate boundary that ruptured in individual earth quakes such dating has shown that the most recent rupture or series of ruptures extended at least 55 km along the washington coast within a period of a few decades about 300 years ago5 here we report 85 new 14c ages which suggest that this most recent rupture or series extended at least 900 km between southern british columbia and northern california by comparing the 14c ages with written records of the past 150 years we conclude that a single magnitude 9 earthquake or a series of lesser earthquakes ruptured most of the length of the cascadia subduction zone between the late 1600s and early 1800s and probably in the early 1700s

the dependence of sea surface roughness on the height and steepness of the waves it is proposed that the sea surface roughness zo can be predicted from the height and steepness of the waves zo hs a hs lp b where hs and lp are the significant wave height and peak wavelength for the combined sea and swell spectrum best estimates for the coefficients are a 1200 b 4 5 the proposed formula is shown to predict well the magnitude and behavior of the drag coefficient as observed in wave tanks lakes and the open ocean thus reconciling observations that previously had appeared disparate indeed the formula suggests that changes in roughness due to limited duration or fetch are of order 10 or less thus all deep water pure windseas regardless of fetch or duration extract momentum from the air at a rate similar to that predicted for a fully developed sea this is confirmed using published field data for a wide range of conditions over lakes and coastal seas only for field data corresponding to extremely young waves u10 cp 3 were there appreciable differences between the predicted and observed roughness values the latter being larger on average significant changes in roughness may be caused by shoaling or by swell a large increase in roughness is predicted for shoaling waves if the depth is less than about 0 2lp the presence of swell in the open ocean acts on average to significantly decrease the effective wave steepness and hence the mean roughness compared to that for a pure windsea thus the predicted open ocean roughness is at most wind speeds significantly less than is observed for pure wind waves on lakes only at high wind speeds such that the windsea dominates the swell do the mean open ocean values reach those for a fully developed sea

a high resolution hindcast of wind and waves for the north sea the norwegian sea and the barents sea 1 a combined high resolution atmospheric downscaling and wave hindcast based on the era 40 reanalysis covering the norwegian sea the north sea and the barents sea is presented the period covered is from september 1957 to august 2002 the dynamic atmospheric downscaling is performed as a series of short prognostic runs initialized from a blend of era 40 and the previous prognostic run to preserve the fine scale surface features from the high resolution model while maintaining the large scale synoptic field from era 40 the nested wam wave model hindcast consists of a coarse 50 km model covering the north atlantic forced with era 40 winds and a nested 10 11 km resolution model forced with downscaled winds a comparison against in situ and satellite observations of wind and sea state reveals significant improvement in mean values and upper percentiles of wind vectors and the significant wave height over era 40 improvement is also found in the mean wave period era 40 is biased low in wind speed and significant wave height a bias which is not reproduced by the downscaling the atmospheric downscaling also reproduces polar lows which cannot be resolved by era 40 but the lows are too weak and short lived as the downscaling is not capable of capturing their full life cycle

vented sediments and tsunami deposits in the puget lowland washington differentiating sedimentary processes the sandy deposits produced by tsunamis and liquefaction share many sedimentary features and distinctions between the two are important in seismically active coastal zones both types of deposits are present in the wetlands bordering puget sound where one or more earthquakes about 1100 years ago caused both tsunami flooding and sediment venting this co occurrence allows an examination of the resulting deposits and a comparison with tsunami and liquefaction features of modern events vented sediments occur at four of five wetland field localities and tsunami deposits at two in comparison with tsunami deposits vented sediments in this study and from other studies tend to be thicker although they can be thin vented sediments also have more variable thickness at both outcrop and map scale are associated with injected dykes and contain clasts derived from underlying deposits further vented sediments tend to contain a greater variety of sedimentary structures and these structures vary laterally over metres tsunami deposits compared with vented sediments are commonly thinner fine and thin landward more consistently have more uniform thickness on outcrop and map scales and have the potential of containing coarser clasts up to boulders for both tsunami deposits and vented sediments the availability and grain size of source material condition the characteristics of the deposit in the cases presented in this paper both foraminifera and diatom assemblages within tsunami deposits and vented sediments consisted of brackish and marine species and no distinction between processes could be made based on microfossils in summary this study indicates a need for more careful analysis and mapping of coastal sediments associated with earthquakes to avoid misidentification of processes and misevaluation of hazards

case for very low coupling stress on the cascadia ssubduction fault a fundamental problem in plate tectonics is the shear strength of major plate boundary faults this translates to the question whether the generally observed small earthquake stress drops of 3 10 mpa on major faults release most of the accumulated stress or only a small fraction of it there is strong evidence that the san andreas fault a major transform plate boundary is weak 20 mpa shear resistance it is not yet clear whether subduction thrust faults are also weak we present two types of evidence from the northern cascadia subduction zone that indicate very low coupling shear stress on that plate interface and hence very low strength of the subduction thrust fault comparable to that estimated for the san andreas fault first the well defined surface heat flow and heat generation allow negligible frictional heating on the plate interface the average shear stress on the fault must thus be very low over a time scale of a few million years second focal mechanism solutions for small crustal earthquakes in the southern vancouver island area indicate that the horizontal stress in the direction of plate convergence has a similar magnitude to the vertical stress this inferred stress state requires the present tectonic stress coupled across the subduction thrust fault to be very low one explanation for the weakness of the fault is the presence of near lithostatic pore fluid pressure in the region of the fault zone for which there is independent evidence the conclusion of a weak subduction thrust fault does not conflict with geodetic observations of contemporary surface deformation which indicate that the fault is currently locked accumulating strain energy toward a future great earthquake the surface deformation responds to the small 20 mpa temporal changes of the stress field associated with the subduction earthquake cycle this transient stress is superimposed on the larger background regional stress field in which the maximum compression is parallel to the margin the weakness of the cascadia subduction thrust fault and the unusual stress state of the forearc region have important implications for earthquake hazards for example a subduction earthquake may induce large strike slip earthquakes in the forearc that affect a large area

sea state dependence of the wind stress over the ocean under hurricane winds 1 the impact of the surface wave field sea state on the wind stress over the ocean is investigated with fetch dependent seas under uniform wind and with complex seas under idealized tropical cyclone winds two different approaches are employed to calculate the wind stress and the mean wind profile the near peak frequency range of the surface wave field is simulated using the wavewatch iii model the high frequency part of the surface wave field is empirically determined using a range of different tail levels the results suggest that the drag coefficient magnitude is very sensitive to the spectral tail level but is not as sensitive to the drag coefficient calculation methods the drag coefficients at 40 m s vary from 1 10 3 to 4 10 3 depending on the saturation level the misalignment angle between the wind stress vector and the wind vector is sensitive to the stress calculation method used in particular if the cross wind swell is allowed to contribute to the wind stress it tends to increase the misalignment angle our results predict enhanced sea state dependence of the drag coefficient for a fast moving tropical cyclone than for a slow moving storm or for simple fetch dependent seas this may be attributed to swell that is significantly misaligned with local wind

hurricane directional wave spectrum spatial variation at landfall abstract the nasa scanning radar altimeter sra flew aboard one of the noaa wp 3d hurricane research aircraft to document the sea surface directional wave spectrum in the region between charleston south carolina and cape hatteras north carolina as hurricane bonnie was making landfall near wilmington north carolina on 26 august 1998 two days earlier the sra had documented the hurricane wave field spatial variation in open water when bonnie was 400 km east of abaco island bahamas bonnie was similar in size during the two flights the maximum wind speed was lower during the landfall flight 39 m s 1 than it had been during the first flight 46 m s 1 also bonnie was moving faster prior to landfall 9 5 m s 1 than when it was encountered in the open ocean 5 m s 1 the open ocean wave height spatial variation indicated that hurricane bonnie would have produced waves of 10 m height on the shore northeast of wilmington had it not been for the continental shelf the gradual shoaling distributed t

pluton accommodation at high strain rates in the upper continental crust the example of the central extremadura batholith spain abstract emplacement in the tensional bridge of a stepped dextral shear zone system is proposed for the central extremadura batholith spain the country rocks show a pervasive anisotropy that conditioned the style of the structures developed as a consequence of the transference of displacement from the stepped shear zones to the releasing area the kinematic evolution of the resulting megakink fold provided the volume increase necessary for the granite emplacement thermal and kinematic models suggest that the growth of individual plutons took place in periods of no more than several hundred to a few thousand years fast strain rates 10 10 10 11 s 1 must concentrate in local structures e g initiation of kink folds even in zones deforming as a whole under typical strain rates 10 14 1 s 1 granite plutons might be used as strain rate gauges for syn plutonic structures

characterization of turbulent airflow over evolving water waves in a wind wave tank 1 results of an experimental investigation of the turbulent boundary layer in airflow over evolving young wind waves are presented the experiments were conducted in a laboratory wind wave flume consisting of a closed loop wind tunnel capable of generating wind speed that may exceed 15 m s atop of a 5 m long wave tank simultaneous measurements of mean wind velocity and of instantaneous fluctuations of the horizontal and vertical air velocity components were carried out along the test section at different airflow rates and at numerous heights above the highest wave instantaneous surface elevation at the air sensors location was simultaneously recorded the friction velocities at all locations and for all airflow rates were determined by two independent methods by fitting the logarithmic velocity profiles and by extrapolating the measured reynolds shear stresses to mean water surface level the variation with height and along the test section of the fluctuations of two velocity components in the mean flow and in the vertical directions was also studied and the results compared with flow behavior over rough and smooth plates wave induced airflow parameters were then investigated by application of cross spectral analysis results on the vertical extent of wave induced boundary layer on the phase relation between the wave induced velocity fluctuations and the surface elevation as well as on the wave induced reynolds shear stress are reported

multi scale kinking in northeast tasmania crustal shortening at shallow crustal levels abstract analysis of s 1 cleavage trends in the ordovician devonian mathinna group of northeast tasmania has identified mega scale up to 9 km axial surface spacing kink bands and kink folds these formed after the regional steep slaty cleavage and are contemporaneous with but post date small scale cm scale vertical kink bands small scale sinistral kink bands strike approximately 032 and predominate in number over the approximately e w striking dextral kink bands the geometry of the small scale kink bands indicates a 166 10 trending principal shortening during kinking kink bands overprint minerals in the contact aureole of the middle to upper devonian granite granodiorite scottsdale batholith and pre date deposition of the parmeener supergroup of upper carboniferous age megakinking in ne tasmania is correlated with megakinking in the lachlan fold belt new south wales which occurred under the same bulk shortening direction and also during the middle carboniferous prior to kinking the regional slaty cleavage in the mathinna group was near vertical and trended 157 which is subparallel to the principal shortening direction during kinking 166 10 because of this close alignment and the presence of a pre existing planar anisostropy throughout the region megakinks developed despite only 4 5 bulk shortening kinking in ne tasmania occurred at 120 45 mpa approximately 4 2 km depth the brittle and instantaneous nature of kinking is consistent with deformation at such shallow crustal levels megakinking may be a typical expression of crustal tectonics of minor bulk shortening at shallow crustal levels only in the case of regions with a pre existing steep planar structural grain subparallel to the principal shortening direction

attenuation and source parameters of earthquakes in the cascadia region digital ground motion data recorded by the western canada telemetered network wctn are used to examine the attenuation and source parameters of earthquakes in the cascadia region of southwestern british columbia and northwestern washington the data base is comprised of over 1000 vertical component fourier spectra from earthquakes of magnitude 3 to 7 at distances from 10 to 500 km regression analyses determine the shape and coefficients of the regional attenuation curve and source spectra for 68 earthquakes seismic moment and stress drop are inferred from the amplitudes of the source spectra shallow h 10 km earthquakes have an attenuation curve with a complex shape exhibiting significant flattening no apparent geometric spreading in the distance range from 75 to 230 km this shape is probably a result of strong reflected phases from mid crustal discontinuities and the subducting slab events within the subducting slab and the lower crust exhibit a simple r 1 attenuation curve the anelastic attenuation coefficient for the region as a whole is given by q 380 f 0 39 the duration of motion for each wctn record is determined as the value that yields the observed relationship between time domain and spectral domain amplitudes according to random process theory these durations are approximately constant within 50 km of the source then increase with distance as 0 07 r the high frequency ground motions from cascadia earthquakes are relatively weak cascadia source spectra are characterized by an average brune stress drop of about 30 bars this is significantly lower than the average california stress drop of 70 to 100 bars and dramatically lower than the average eastern stress drop of 150 to 200 bars it is concluded that there are significant regional variations in source parameters hazard estimates for the cascadia region based on california groundmotion relations may be overly conservative

paleoliquefaction evidence for a strong holocene earthquake in south central indiana earthquake induced paleoliquefaction features in holocene sediments in south central indiana are evidence for strong shaking in the recent prehistoric past in an area where only infrequent low magnitude earthquakes have occurred during the 200 yr of the historic record distribution of liquefaction features and geotechnical analyses of liquefied sediments are the basis for estimating that an earthquake with a magnitude of 6 9 was centered near vallonia indiana radiometric archaeologic and stratigraphic relations bracket the event to between 3 7 ka and 4 2 ka b p evidence for a local source for strong shaking requires reassessment of earthquakes hazards in the southern indiana northern kentucky southwestern ohio 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

renewal of tidal forests in washington state after a subduction earthquake in a d 1700 abstract with few exceptions today s tidal trees near washington s pacific coast postdate an earthquake that lowered the region by 1 m or more the earthquake which occurred in a d 1700 is the most recent to have ruptured much of the plate boundary at this central part of the cascadia subduction zone because of the coseismic subsidence lowland forests became tidal flats where thousands of trees died most of the trees killed were sitka spruce picea sitchensis in the centuries since the earthquake tidal deposits have built new land that has been colonized by new sitka spruce all but several tens of the region s tidal spruce consequently postdate 1700 as shown by counts of annual rings in 121 of the largest spruce in tidal forests at copalis river grays harbor and willapa bay forests began to return to each of these estuaries in the early 1700s and spread seaward in the late 1700s and 1800s annual rings in the oldest of the trees thus record a large fraction of the earthquake recurrence interval that began with the 1700 earthquake

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

basement control on the deformation of cover basins an example from the cobar district in the lachlan fold belt australia abstract early carboniferous deformation of ensialic early devonian to early carboniferous sedimentary basins in the cobar district was controlled by movement on reactivated basement faults two cover zones each with different structures reflect differences in basement geometry particularly the frequency and orientation of pre existing faults zone 1 a high strain zone on the eastern edge of the deformed basins has a vertical cleavage and down dip lineation characteristic of slate belts zone 2 a low strain zone to the west bears the imprint of wrench tectonics at least in the early part of the history of its deformation the boundary between zones 1 and 2 is a sharply defined cleavage front and is localized along a major fault in zone 2 nw trending f 1 folds developed initially as a response to left lateral movement on wnw trending basement faults later f 1 folds trending west suggest rotation of the direction of local maximum principal stress perhaps as resistance to sliding of basement blocks developed further rotation of this local stress direction led to the formation of ne trending f 2 folds and to left lateral movement on bounding n and nne trending faults in zone 1 deformation was more intense and controlled by high angle reverse movement with some left lateral displacement on n and nw trending basement faults leading to d 1 folding cleavage formation and vertical extension in the cover shortening was both oblique and parallel to the eastern margin of the basin at an early stage of deformation before cleavage formation zone 1 may have been locally coupled to zone 2 subzone boundaries defined by abrupt changes in strike of s 1 and f 1 in zone 1 probably represent reactivated faults which acted as hinge lines separating areas deforming in response to different directions of shortening except for possible folds contributing to abrupt changes in strike of d 1 structures regional d 2 structures are absent from zone 1 this contrasts with the well developed f 2 folds in zone 2

wave follower field measurements of the wind input spectral function part ii parameterization of the wind input abstract nearly all of the momentum transferred from wind to waves comes about through wave induced pressure acting on the slopes of waves known as form drag direct field measurements of the wave induced pressure in airflow over water waves are difficult and consequently rare those that have been reported are for deep water conditions and conditions in which the level of forcing measured by the ratio of wind speed to the speed of the dominant spectral peak waves is quite weak u10 cp 3 the data reported here were obtained over a large shallow lake during the australian shallow water experiment auswex the propagation speeds of the dominant waves were limited by depth and the waves were correspondingly steep this wider range of forcing and concomitant wave steepness revealed some new aspects of the rate of wave amplification by wind the so called wind input source function in the energy balance equation for wind driven water waves it was found that the exponential growth rate parameter fra

physical models of regional fold superposition the role of competence contrast abstract physical models of superposed folds demonstrate that rheologic contrast strongly controls the style of fold interference rheologic contrast affects strain partitioning between layer parallel shortening and buckling and affects the development of structural anisotropies parallel to first generation folds laminates with insignificant competence contrast are characterized by circular to elliptical domes and basins type 1 interference in addition to folding the layers accommodate shortening by layer parallel thickening preferentially in the fold culminations laminates with significant competence contrast are characterized by buckled fold hingelines and axial surfaces type 2 interference the less competent layers thicken in the hinges the more competent layers maintain their initial thickness in plan view the f 1 hingelines are refolded in a lobate cuspate to box style whose axial traces form conjugate pairs the models are dynamically scaled to represent folds with km scale wavelengths the evolution of surface structures map patterns at different depths and equal area projections synthesized from structure contour maps were used for analysis comparable to regional analysis common to field studies gravitational body forces effectively damp the vertical amplitudes of both the first and second generation folds thereby enhancing the formation of type 2 interference

common features of the excitation and propagation of strong ground motion for north american earthquakes the central matter of this investigation is the commonly held belief that eastern north america ena earthquakes are felt to much greater distances at all levels of intensity than their western u s wus counterparts of the same source strength by comparing the areas enclosed by modified mercalli intensities i to iii felt iv v vi and vii for ena and wus earthquakes at the same source strength we find that this proposition is mostly false at damaging levels of ground motion intensities vi to vii and greater for m 7 neither should such differences exist if strong ground motion is confined to r 150 km and arrives principally as body waves and if ena and wus earthquakes share the same average stress drop in fact observable differences in the areas enclosed by intensity vi a vi for ena and wus earthquakes at the same m point to slight but significant differences in stress drop the ena earthquakes having stress drops a factor of about 2 higher only for the largest earthquakes m 7 as the 1811 to 1812 new madrid and 1886 charleston earthquakes seem to be can strong ground motion propagate to much greater distances as low loss higher mode surface waves in ena relative to wus the strong dependence of high frequency strong ground motion on stress drop and its weak dependence on m admit the possibility that the 1811 to 1812 events and the 1886 charleston earthquakes are no larger than m 6 to 7 provided that their stress drops are higher than average by a factor of 2 or so

effect of surface waves on air sea momentum exchange part i effect of mature and growing seas the effect of surface waves on air sea momentum exchange over mature and growing seas is investigated by combining ocean wave models and a wave boundary layer model the combined model estimates the wind stress by explicitly calculating the wave induced stress in the frequency range near the spectral peak the noaa ncep surface wave model wavewatch iii is used to estimate the spectra while the spectra in the equilibrium range are determined by an analytical model this approach allows for the estimation of the drag coefficient and the equivalent surface roughness for any surface wave fields numerical experiments are performed for constant winds from 10 to 45 m s21 to investigate the effect of mature and growing seas on air sea momentum exchange for mature seas the charnock coefficient is estimated to be about 0 01 0 02 and the drag coefficient increases as wind speed increases both of which are within the range of previous observational data with growing seas results for winds less than 30 m s 21 show that the drag coefficient is larger for younger seas which is consistent with earlier studies for winds higher than 30 m s 21 however results show a different trend that is very young waves yield less drag this is because the wave induced stress due to very young waves makes a small contribution to the total wind stress in very high wind conditions

wind and waves in extreme hurricanes waves breaking at the ocean surface are important to the dynamical chemical and biological processes at the air sea interface the traditional view is that the white capping and aero dynamical surface roughness increase with wind speed up to a limiting value this view is fundamental to hurricane forecasting and climate research but it has never been verified at extreme winds here we show with observations that at high wind speeds white caps remain constant and at still higher wind speeds are joined and increasingly dominated by streaks of foam and spray at surface wind speeds of 40 m s the streaks merge into a white out the roughness begins to decrease and a high velocity surface jet begins to develop the roughness reduces to virtually zero by 80 m s wind speed rendering the surface aero dynamically extremely smooth in the most intense part of extreme or major hurricanes wind speed 50 m s a preliminary assessment shows that cross swell dominant in large regions of hurricanes allows the roughness under high wind conditions to increase considerably before it reduces to the same low values

megakinking in the lachlan fold belt australia abstract the regional n s tectonic grain of the easternmost lachlan fold belt is produced by upright tight folds with well developed quasi vertical axial surface foliation and comprises domains in which the early folds and foliation have consistent orientation the domains are up to a few tens of kilometres along trend and are separated by narrow zones across which the tectonic grain swings commonly by 20 to 30 to produce a regional tectonic kink pattern these megakinks have both sinistral 070 10 and dextral 110 10 trends the dextral zones being more common in the megakink bands which may be up to 10 km wide there are commonly second order kink zones a few hundred metres wide in which the pre existing fold trends are rotated 90 or more from their regional n s trend small scale kink bands of metre to millimetre width are much more common in the megakink bands than in the planar domains between outcrop scale kink folds were formed by a subhorizontal principal compression acting parallel to the tectonic grain even where that grain is more than 90 oblique to the regional trend outcrop scale kinks are thus interpreted to have formed first under regional n s compression with the megakink domains rotating later the megakinking event is mid carboniferous c 330 ma being younger than the regional early carboniferous folding and older than the latest carboniferous basal sediment of the sydney basin the megakinks appear to have nucleated along strike of pre existing ese and ene trending lineaments in the lachlan fold belt possibly under continent wide n s compression

the stratigraphy and deformation history of the tumut region implications for the development of the lachlan fold belt abstract the tumut region forms the southern part of the tumut synclinorial zone in the southeastern part of the lachlan fold belt lfb the area contains two major stratigraphie packages ordovician to early silurian quartz rich to quartz intermediate flysch and volcanics package a and overlying fossiliferous early late silurian volcanics and flysch package b rhyolite within the older package a yields a u pb zircon age of 428 6 ma both packages were meridionally folded during the siluro devonian bowning orogeny following intrusion of the gocup granite at 411 5 ma an earlier deformation characterised by thrust faulting e w recumbent folding and later local coaxial upright folding is present only in the older flysch and volcanics package a this earlier deformation is part of the benambran orogeny that affects the ordovician metamorphics of the wagga metamorphic belt and other parts of the lfb and is constrained to about 425 ma fold characteristics of this deformation are indicative of thin skinned intraplate transpressional deformation rather than classical collisional tectonics as envisaged by some workers for the benambran orogeny here and elsewhere in the lfb the composition and deformational history of the older flysch indicates that it is part of the ordovician to early silurian molong volcanic belt consequently the older concept of an early silurian tumut trough incorporating both packages of rocks is rejected instead it is proposed that up to 2500 m of early late silurian rocks formed in a pull apart basin the tumut basin thus the silurian depositional history of the tumut region previously considered unique in the lfb is little different from other basins of similar age throughout the lfb

detection limits of tidal wetland sequences to identify variable rupture modes of megathrust earthquakes abstract recent paleoseismological studies question whether segment boundaries identified for 20th and 21st century great m8 earthquakes persist through multiple earthquake cycles or whether smaller segments with different boundaries rupture and cause significant hazards the smaller segments may include some currently slipping rather than locked in this review we outline general principles regarding indicators of relative sea level change in tidal wetlands and the conditions in which paleoseismic indicators must be distinct from those resulting from non seismic processes we present new evidence from sites across southcentral alaska to illustrate different detection limits of paleoseismic indicators and consider alternative interpretations for marsh submergence and emergence we compare predictions of coseismic uplift and subsidence derived from geophysical models of earthquakes with different rupture modes the spatial patterns of agreement and misfits between model predictions and quantitative reconstructions of coseismic submergence and emergence suggest that no earthquake within the last 4000 years had a pattern of rupture the same as the mw 9 2 alaska earthquake in 1964 from the alaska examples and research from other subduction zones we suggest that if we want to understand whether a megathrust ruptures in segments of variable length in different earthquakes we need to be site specific as to what sort of geological based criteria eliminate the possibility of a particular rupture mode in different earthquakes we conclude that coastal paleoseismological studies benefit from a methodological framework that employs rigorous evaluation of five essential criteria and a sixth which may be very robust but only occur at some sites 1 lateral extent of peat mud or mud peat couplets with sharp contacts 2 suddenness of submergence or emergence and replicated within each site 3 amount of vertical motion quantified with 95 error terms and replicated within each site 4 syncroneity of submergence and emergence based on statistical age modelling 5 spatial pattern of submergence and emergence 6 possible additional evidence such as evidence of a tsunami or liquefaction concurrent with submergence or emergence we suggest that it is possible to consider detection limits as low as 0 1 0 2 m coseismic vertical change

boundary layer turbulence over surface waves in a strongly forced condition les and observation abstractthe impact of sea state on air sea momentum flux or wind stress is a poorly understood component of wind wave interactions particularly in high wind conditions the wind stress and mean

significance of the early foliation at bermagui n s w australia the first generation mesoscopic folds f1 in the ordovician turbidites at bermagui n s w australia are tight to locally isoclinal and have a convergently fanning axial surface foliation s1 which is a differentiated crenulation cleavage s1 overprints an earlier foliation herein called s in psammites s is a strong alignment of mineral grains and rough micaceous folia and in pelites s is a microbanding of quartzose and micaceous layers depending on rock type and position in the f1 fold profile s may be 1 parallel to bedding 2 rotated out of parallelism with bedding by the s1 cleavage and 3 truly cross cutting bedding in many places s cuts across bedding demonstrating that it is a superimposed tectonic foliation and not simply an inherited depositional fabric in outcrops south of bermagui s changes vergence with apparent congruence with f1 folds in other outcrops near bermagui however s maintains a constant vergence around f1 folds the geometry indicating a pre f1 anticline to the east since there is no evidence for large scale pre f1 folds the various relations of s to s1 and f1 are best explained by the rarely described process of late stage hinge nucleation during a single protracted f1 folding sequence other possibilities such as fold hinge migration and pre fold imbricate stacking are discussed but considered less likely

contrasts in morphogenesis and tectonic setting during contemporaneous emplacement of s and i type granitoids in the eastern lachlan fold belt southeastern australia

the tampere schist belt structural style within an early proterozoic volcanic arc system in southern finland abstract the central part of the narrow e w trending tampere schist belt comprises volcanic and sedimentary rocks of low metamorphic grade surrounded by intrusive rocks and migmatites the first folding event with subvertical axial surfaces and originally subhorizontal fold axes dominates the structure of the belt well preserved primary structures indicate a major e w trending syncline in the northern part of the belt with minor upright open to tight synclines and anticlines in the limb areas f 1 fold axes in the limbs have been rotated towards the steeply to vertically plunging stretching lineation dextral f 2 folds with subvertical e w to ne sw striking s 2 crenulation cleavage and steeply plunging fold axes overprint penetrative s 1 schistosity subhorizontal dextral shear is inferred from the d 2 structures d 3 kinking and fracturing is restricted to narrow nw se to n s trending zones the shear zone between the schists and the migmatites to the south is a south dipping thrust or reverse fault with uplift of the higher grade rocks in the northern part of the tampere schist belt another major fault is postulated both shear zones were formed at a late stage of progressive d 1 deformation on the basis of these structures and published sedimentological geochemical and isotopic data the tampere schist belt is interpreted as an upper part of a thrust sheet within a forearc of an ancient volcanic arc system the vergence of structures suggests subduction toward the present south

tectonic affinity of the mathinna group in the lachlan fold belt abstract pre carboniferous rocks of tasmania comprise two disparate terranes which were brought together during the middle palaeozoic the eastern tasmania terrane consists of middle palaeozoic granitoids and the mathinna group a turbidite succession of ordovician to early devonian age the older part of the adjacent western tasmania terrane the only part of the southern tasmanides with exposed precambrian basement is related to the kanmantoo fold belt and older tectonic provinces located northwest of tasmania the younger part of the western tasmania terrane comprises upper cambrian to lower devonian terrestrial to shallow marine siliciclastics and carbonates a marked contrast to the coeval deep water deposits of the mathinna group the contact between the two terranes is concealed by the tamar valley in northern tasmania the main folds in the eastern tasmania terrane verge to the northeast whereas structures in the adjacent western tasmania terrane indicate tectonic transport to the southwest with the break in structural facing coinciding with the tamar valley reinvestigation of the structure of the westernmost eastern tasmania terrane where there is a large recumbent f1 fold 10 km extent in profile view raises the possibility that a second generation of structures previously regarded as of only local importance could have caused rotation of the upright to steeply west dipping axial surfaces of f1 folds to recumbent attitudes during southwesterly directed thrusting in this interpretation recumbent or near recumbent zones could reflect ramps in a sole thrust and the mid devonian imbricate thrust zone near beaconsfield on the west bank of the tamar river would be either the frontal thrust system or a splay off the sole thrust which continues westward beneath the exposed precambrian badger head block the implications of this new interpretation are that docking of the eastern and western tasmania terranes must have occurred after the ordovician but before the middle devonian during the consolidation phase there were two deformations of the mathinna group the first which occurred in the early devonian prior to emplacement of the st marys porphyrite 388 1 ma produced upright to locally overturned folds verging to the northeast the second which took place during the early middle devonian before deposition of givetian cave deposits resulted in the mathinna group being thrust southwestward this sense of thrusting is opposite to the direction of thrusting at the same time in the melbourne zone of victoria where the fold and thrust belt verges eastward away from the craton a concealed devonian transfer fault zone in bass strait could account for this change of polarity

current deformation and the width of the seismogenic zone of the northern cascadia subduction thrust evidence has been obtained for the accumulation of elastic strain across the northern cascadia subduction zone that may be released in a future very large subduction thrust earthquake vertical and horizontal strain rates across the southern vancouver island region have been determined through 1 long term trends in tide gauge data 2 changes in repeated accurate leveling surveys 3 changes in repeated high accuracy gravity profiles and 4 horizontal shortening observed in repeated precise positioning surveys the outer coast is uplifting at a rate of a few millimeters per year decreasing landward and shortening is occurring across the 100 km wide coastal region at a rate of about 0 1 microstrain per year mm km 1yr 1 the results are compared with the distribution of strain accumulation predicted from elastic dislocation and viscoelastic models for a subduction thrust fault the location of the fault as used in the models is well defined by multichannel seismic reflection and other geophysical data most of the observed current deformation can be explained by interseismic strain accumulation associated with the subduction thrust of southern vancouver island and northern washington provided the locked portion is restricted to a 60 km wide band offshore beneath the continental shelf and slope this conclusion also results from modeling the coseismic subsidence on the outer coast of vancouver island about 300 years ago deduced from paleoseismicity data the unusually narrow downdip extent of the subduction thrust seismogenic zone that extends little if at all beneath the coast is a consequence of high temperatures associated with the young age of the subducted oceanic lithosphere and the thick blanket of insulating sediments the high temperatures limit brittle seismogenic behavior downdip to where the thrust fault is at a depth of less than 15 km the distance from the seismic portion of the megathrust limits the estimated ground motion at the major centers of vancouver and victoria from this source the narrow width may also limit the earthquake size however events of magnitude well over 8 are possible

episodic tectonic subsidence of late holocene salt marshes northern oregon central cascadia margin salt marsh subsurface deposits 0 4 m depth in netarts bay a small coastal lagoon of northern oregon record six events of marsh burial in the last several thousand years five of the buried marsh surfaces show sharp nonerosional upper contacts with either anomalous sand layers tsunami deposits or tidal flat mud deposits these sequences indicate episodic abrupt subsidence of the marsh surfaces to low intertidal levels in contrast lower marsh contacts with underlying intertidal muds are gradational indicating gradual uplift and development of the marsh three independent measures of deposit elevation relative to mean tidal level percent organics diatom assemblages and percent eolian sand have been used to estimate vertical displacements of marsh surfaces abrupt subsidence displacements of 1 1 5 m alternate with gradual uplift displacements of the order of 0 5 1 0 m the vertical tectonic movements are interpreted to reflect coseismic strain release abrupt subsidence following interseismic strain accumulation gradual uplift associated with interplate coupling between the juan de fuca plate and the north american plate in the cascadia subduction zone recurrence intervals between subsidence events range from possibly less than 300 years to at least 1000 years with the last dated event likely occurring 300 400 radiocarbon years before present rcybp significant 14c age overlaps of at least four subsidence events recorded at netarts and reported for southern washington and other northern oregon bays at 300 500 1000 1300 1400 1800 and 3000 3300 rcybp suggest the potential for event synchroneity over at least 200 km of the central part of the cascadia subduction zone additional work is needed to test the synchroneity of these episodic events of coseismic subsidence

uncertainty propagation in coupled atmosphere wave ocean prediction system a study of hurricane earl 2010 abstractthis study focuses on understanding the evolution of hurricane earl 2010 with respect to random perturbations in the storm s initial strength size and asymmetry in wind distribution we

field occurrences of liquefaction induced features a primer for engineering geologic analysis of paleoseismic shaking discussed in this paper are the factors that control the typical manifestations of liquefaction that are found in continental field settings the factors are given mainly in terms of the local geologic field situation and the geotechnical properties there a meaningful interpretation of liquefaction based data for quantitative analysis of paleoseismic shaking requires understanding of both geologic and geotechnical roles in the mode of ground failure at a specific site recommendations are made for the size of the field area that must be searched for liquefaction effects in order to develop adequate data for engineering geologic geotechnical analyses of paleoseismicity the areal extent must be based on an appreciation that the tectonic situation can cause seismically induced liquefaction effects to form in some locales but not in others nearby even for a strong earthquake in the region our guidelines for the conduct of the field search and preliminary analysis of the data relate to three issues for which liquefaction features are especially useful in answering has there been strong holocene latest pleistocene shaking in the region where was the tectonic source and what was the strength of shaking understanding of the various factors that control the manifestations of liquefaction effects which we present in this paper is essential for developing credible answers to these questions

fault and kink band relationships at mystery bay australia abstract spectacular conjugate kink bands are exposed in a 400 m wide kink zone of coastal outcrops of ordovician turbidites south of mystery bay on the new south wales south coast within the kink zone upright f 1 and f 2 folds with subhorizontal axial trends exhibit a segmented counterclockwise rotation of approximately 55 about a near vertical axis from trends outside the kink zone the kink zone is cut by numerous conjugate faults with total offsets indicative of compression at high angles to the foliation kink band development is directly controlled by fault location and is commonly concentrated in wedge shaped fault blocks between non parallel faults major faults separate regions of kink bands with distinctly different geometries and do not offset the kinks and hence were initiated prior to kinking the opposing stress orientations inferred from the conjugate faults and kinks permit two models of the deformational history 1 1 regional layer normal compression causing fault movement followed by a single or multiple switch of regional principal stress orientations causing kink development and 2 2 regional layer normal compression causing fault movement with synchronous kink band development resulting from local stresses imparted to the adjacent wedge shaped fault blocks conclusive evidence to discriminate between the two models has not been observed although circumstantial evidence supports the latter the feasibility of a synchronous development is supported by a mohr circle stress analysis under certain conditions reductions of both the shear stress on a fault plane and the normal stress acting parallel to the fault plane during stick slip faulting will induce a transient stress system compatible with kink band development kinking by local reorientation of principal compressive stress to lower angles to the orogen may thus be an important process accompanying late stage faulting under regional compression normal to the orogen

a horizontal buckle model as a dynamic mechanism for back arc spreading of the japan sea a horizontal buckle model is proposed for the geodynamics of neogene clockwise rotation of the sw japan arc and the back arc spreading of the japan sea the model explains the dynamics and kinematics of the formation of megakink bands developed extensively in the shimanto belt of the outer zone of sw japan yanai 1986a 1986b using the megakink bands as indicators of stress orientation and shortening magnitude the regional sigma 1 axial trajectory sigma 1 sigma 2 sigma 3 is longitudinal and almost parallel to the long axis of the sw japan arc and the sigma 2 axis is directed nearly vertical the shortening magnitude increases up to 22 crossing sw japan from japan sea to the philippine sea these data suggest that the rotation mode of sw japan is analogous to buckle folding with vertical rotation axes in which the external compressional force is exerted parallel to the arc trend the sw japan wing was moved with reference to the nearly fixed ryukyu wing forming the inner

prefolding and premegakinking magnetizations from the devonian comerong volcanics new south wales australia and their bearing on the gondwana pole path palaeomagnetic results from the late middle to early late devonian comerong volcanics in the budawang synclinorium lachlan fold belt lfb new south wales australia satisfy a fold test and support the hypothesis that foliated parts of the lfb have been folded by megakinks during the terminal mid carboniferous orogenic phase the preferred pole position is at 76 9 s 330 7 e a95 7 2 allowing calibration of the australian pole path at around 370 ma ago an alterative pole position at 71 3 s 283 1 e same a95 takes into account a possible rotation of the megakinked terrane by 15 clockwise with respect to the australian craton although there are still problems unravelling previously published results from silurian rocks in the lfb both because of unreliability and uncertainty as to where the lfb crustal units lay in relation to the australian craton there is no geological reason to suspect any large relative movement between the lfb and the craton since the middle devonian and thus the comerong volcanics pole position is representative of the late devonian for australia the new pole requires reassessment of many other poles that have previously been accepted as representing the siluro devonian for australia and gondwanaland we present reasons for believing that the magnetization or remagnetization of many rock units e g mereenie sandstone and mulga downs group australia and the gneigura supergroup africa was later than sedimentation probably during widespread early carboniferous deformation another rock unit msissi norite africa could be of early carboniferous rather than late devonian age

terminal fold belt deformation relationship of mid carboniferous megakinks in the tasman fold belt to coeval thrusts in cratonic australia megakinks in the meridional tectonic grain of the tasman fold belt were formed by north south compression in the mid carboniferous and appear to be related to the same stress system that formed intracratonic thrusts in central australia during the alice springs orogeny

numerical simulation of sea surface directional wave spectra under hurricane wind forcing numerical simulation of sea surface directional wave spectra under hurricane wind forcing was carried out using a high resolution wave model the simulation was run for four days as hurricane bonnie 1998 approached the u s east coast the results are compared with buoy observations and nasa scanning radar altimeter sra data which were obtained on 24 august 1998 in the open ocean and on 26 august when the storm was approaching the shore the simulated significant wave height in the open ocean reached 14 m agreeing well with the sra and buoy observations it gradually decreased as the hurricane approached the shore in the open ocean the dominant wavelength and wave direction in all four quadrants relative to the storm center were simulated very accurately for the landfall case however the simulated dominant wavelength displays noticeable overestimation because the wave model cannot properly simulate shoaling processes direct comparison of the model and sra directional spectra in all four quadrants of the hurricane shows excellent agreement in general in some cases the model produces smoother spectra with narrower directional spreading than do the observations the spatial characteristics of the spectra depend on the relative position from the hurricane center the hurricane translation speed and bathymetry attempts are made to provide simple explanations for the misalignment between local wind and wave directions and for the effect of hurricane translation speed on wave spectra

use of liquefaction induced features for paleoseismic analysis an overview of how seismic liquefaction features can be distinguished from other features and how their regional distribution and properties of source sediment can be used to infer the location and strength of holocene paleo earthquakes abstract liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the holocene these features include dikes craters vented sand sills and laterally spreading landslides the relatively high seismic shaking level required for their formation makes them particularly valuable as records of strong paleo earthquakes this state of the art summary for using liquefaction induced features for paleoseismic interpretation and analysis takes into account both geological and geotechnical engineering perspectives the driving mechanism for formation of the features is primarily the increased pore water pressure associated with liquefaction of sand rich sediment the role of this mechanism is often supplemented greatly by the direct action of seismic shaking at the ground surface which strains and breaks the clay rich cap that lies immediately above the sediment that liquefied discussed in the text are the processes involved in formation of the features as well as their morphology and characteristics in field settings whether liquefaction occurs is controlled mainly by sediment grain size sediment packing depth to the water table and strength and duration of seismic shaking formation of recognizable features in the field generally requires a low permeability cap above the sediment that liquefied field manifestations are controlled largely by the severity of liquefaction and the thickness and properties of the low permeability cap criteria are presented for determining whether observed sediment deformation in the field originated by seismically induced liquefaction these criteria have been developed mainly by observing historic effects of liquefaction in varied field settings the most important criterion is that a seismic liquefaction origin requires widespread regional development of features around a core area where the effects are most severe in addition the features must have a morphology that is consistent with a very sudden application of a large hydraulic force this article discusses case studies in widely separated and different geological settings coastal south carolina the new madrid seismic zone the wabash valley seismic zone and coastal washington state these studies encompass most of the range of settings and the types of liquefaction induced features likely to be encountered anywhere the case studies describe the observed features and the logic for assigning a seismic liquefaction origin to them also discussed are some types of sediment deformations that can be misinterpreted as having a seismic origin two independent methods for estimating prehistoric magnitude are discussed briefly one method is based on determination of the maximum distance from the epicenter over which liquefaction induced effects have formed the other method is based on use of geotechnical engineering techniques at sites of marginal liquefaction in order to bracket the peak accelerations as a function of epicentral distance these accelerations can then be compared with predictions from seismological models

time and size of a giant earthquake in cascadia inferred from japanese tsunami records of january 1700 geological evidence shows that great earthquakes have occurred in the recent prehistoric past in the cascadia subduction zone off the pacific coast of north america the most recent event or series of events is dated at about 300 years ago1 4 but the precise date and magnitude have not been determined geological investigations have not been able to distinguish a single giant earthquake from a series of great earthquakes occurring over a timespan of a decade or two4 although this information is important for the assessment of future hazard5 we have found several tsunami records in japan from ad 1700 with no indication of a local cause historical earthquake records and palaeoseismic evidence indicate the absence of a large earthquake in 1700 in south america alaska or kamchatka leaving cascadia as the most likely source of this tsunami the estimated time of the earthquake is the evening about 21 00 local time of 26 january 1700 the magnitude is estimated as 9 from the tsunami heights in which case the earthquake ruptured the entire length of the cascadia subduction zone2 these estimates are consistent with native american legends that an earthquake occurred on a winter night6

geotechnical analysis of paleoseismic shaking using liquefaction features a major updating a new methodology is proposed for the geotechnical analysis of strength of paleoseismic shaking using liquefaction effects the proposed method provides recommendations for selection of both individual and regionally located test sites provides techniques for validation of field data for use in back analysis and presents a recently developed energy based solution to back calculate paleoearthquake magnitude and strength of shaking the proposed method allows investigators to qualitatively assess the influence of post earthquake density change and aging the proposed method also describes how the back calculations from individual sites should be integrated into a regional assessment of paleoseismic parameters

ages and relative sizes of pre 2004 tsunamis in the bay of bengal inferred from geologic evidence in the andaman and nicobar islands 1 geologic evidence along the northern part of the 2004 aceh andaman rupture suggests that this region generated as many as five tsunamis in the prior 2000 years we identify this evidence by drawing analogy with geologic records of land level change and the tsunami in 2004 from the andaman and nicobar islands a n these analogs include subsided mangrove swamps uplifted coral terraces liquefaction and organic soils coated by sand and coral rubble the pre 2004 evidence varies in potency and materials dated provide limiting ages on inferred tsunamis the earliest tsunamis occurred between the second and sixth centuries a d evidenced by coral debris of the southern car nicobar island a subsequent tsunami probably in the range a d 770 1040 is inferred from deposits both in a n and on the indian subcontinent it is the strongest candidate for a 2004 caliber earthquake in the past 2000 years a n also contain tsunami deposits from a d 1250 to 1450 that probably match those previously reported from sumatra and thailand and which likely date to the 1390s or 1450s if correlated with well dated coral uplift offshore sumatra thus age data from a n suggest that within the uncertainties in estimating relative sizes of paleo earthquakes and tsunamis the 1000 year interval can be divided in half by the earthquake or earthquakes of a d 1250 1450 of magnitude 8 0 and consequent tsunamis unlike the transoceanic tsunamis generated by full or partial rupture of the subduction interface the a n geology further provides evidence for the smaller sized historical tsunamis of 1762 and 1881 which may have been damaging locally

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

measurements of the viscous tangential stress in the airflow above wind waves 1 the stress and drag at the surface of the ocean are crucial parameters for both short term forecasting and the modeling of long term global climate trends however the partition between viscous turbulent and wave stresses and in particular the effects of airflow separation are not well understood we present direct measurements of the velocity in the airflow above wind generated waves we observe intermittent separation of the viscous sublayer past the crest of the wind waves leading to dramatic along wave variability in the surface viscous tangential stress these results hold for wind speeds that would normally be considered low to moderate these viscous stress measurements in the airflow above the wavy surface and within the separated region are to the best of the authors knowledge the first of this kind