active tectonics of the seattle fault and central puget sound washington implications for earthquake hazards we use an extensive network of marine high resolution and conventional industry seismic reflection data to constrain the location shallow structure and displacement rates of the seattle fault zone and crosscutting high angle faults in the puget lowland of western washington analysis of seismic profiles extending 50 km across the puget lowland from lake washington to hood canal indicates that the west trending seattle fault comprises a broad 4 6 km zone of three or more south dipping reverse faults quaternary sediment has been folded and faulted along all faults in the zone but is clearly most pronounced along fault a the northernmost fault which forms the boundary between the seattle uplift and seattle basin analysis of growth strata deposited across fault a indicate minimum quaternary slip rates of about 0 6 mm yr slip rates across the entire zone are estimated to be 0 7 1 1 mm yr the seattle fault is cut into two main segments by an active north trending high angle strike slip fault zone with cumulative dextral displacement of about 2 4 km faults in this zone truncate and warp reflections in tertiary and quaternary strata and locally coincide with bathymetric lineaments cumulative slip rates on these faults may exceed 0 2 mm yr assuming no other crosscutting faults this north trending fault zone divides the seattle fault into 30 40 km long western and eastern segments although this geometry could limit the area ruptured in some seattle fault earthquakes a large event ca a d 900 appears to have involved both segments regional seismic hazard assessments must 1 incorporate new information on fault length geometry and displacement rates on the seattle fault and 2 consider the hazard presented by the previously unrecognized north trending fault zone

holocene subaqueous paleoseismology of lake tahoe gravity flow deposits recovered in a suite of sediment cores in lake tahoe were examined to determine if the event deposits were triggered by strong shaking from earthquakes on active faults within and in close proximity to the lake tahoe basin the acoustic character and distribution of individual lacustrine deposits as well as potential source regions were constrained by high resolution seismic chirp reflection and multibeam bathymetric data between 14 and 17 holocene event deposits have been identified in lake tahoe and examination of their source areas suggests they originated from different initiation points along the steep margin with some being synchronous around the basin as opposed to flood related deposits lithologic characteristics magnetic susceptibility carbon and nitrogen isotopic signatures opal content and 14 c dating indicate that these event deposits are reworked lacustrine material radiocarbon dates indicate that the emplacement of these event deposit sediments correlates well with the late holocene paleoseismic earthquake record developed for the tahoe basin when taken alone the causality of these events may appear ambiguous but when the evidence is examined comprehensively it suggests that strong shaking may likely have been the primary trigger for many of the event deposits observed in the lake throughout the holocene for example four event deposits are assigned to tahoe basin faults the most recent earthquakes occurred on the incline village fault between 630 and 120 cal yr b p the southern segment of the west tahoe fault between 4510 and 4070 cal yr b p on the central and northern segments of the west tahoe fault 5600 5330 cal yr b p and on the west tahoe fault between 7890 and 7190 cal yr b p the oldest of the four associated tahoe basin events coincides with the beginning of an extended period when lake tahoe was likely not spilling or spilling intermittently and this suggests that active faulting and footwall uplift cut off the outlet at this time exaggerating drought conditions downstream likewise the event between 5600 and 5330 cal yr b p on the west tahoe fault may have exaggerated a smaller drought reflected downstream in pyramid lake this event may also be the most recent event mre on the largest segment of the west tahoe fault if correct the period since the last rupture is approximately twice the estimated average recurrence interval for the rubicon segment of the west tahoe fault a more complete holocene record of strong shaking greatly extends the paleoseismic record in the region and indicates a combined recurrence interval of between 750 and 800 yr for all faults in the region

pollen and lignin records of late quaternary vegetation lake washington analyses of lignin oxidation products and pollen for an 11 meter core from lake washington provide independent but similar reconstructions of the late quaternary vegetation in the puget lowland an exception is in sediments of the late pleistocene where pollen percentages and influx values suggest conifer forest whereas lignin compositions suggest a treeless source region this dissimilarity appears to result from different major provenances eolian transport of pollen to the lake from adjacent or downstream drainage basins as opposed to fluvial transport of lignified plant debris only from the lake washington drainage basin

subtropical anticyclones and summer monsoons the summer subtropical circulation in the lower troposphere is characterized by continental monsoon rains and anticyclones over the oceans in winter the subtropical circulation is more strongly dominated by the zonally averaged flow and its interactions with orography here the mechanics of the summer and winter lowertropospheric subtropical circulation are explored through the use of a primitive equation model and comparison with observations by prescribing in the model the heatings associated with several of the world s monsoons it is confirmed that the equatorward portion of each subtropical anticyclone may be viewed as the kelvin wave response to the monsoon heating over the continent to the west a poleward flowing low level jet into a monsoon such as the great plains jet is required for sverdrup vorticity balance this jet effectively closes off the subtropical anticyclone to the east and also transports moisture into the monsoon region the low level jet into north america induced by its monsoon heating is augmented by a remote response to the asian monsoon heating the rossby wave response to the west of subtropical monsoon heating interacting with the midlatitude westerlies produces a region of adiabatic descent it is demonstrated here that a local diabatic enhancement can lead to a strengthening of the descent longitudinal mountain chains act to block the westerly flow and also tend to produce descent in this region below the descent sverdrup vorticity balance implies equatorward flow that closes off the subtropical anticyclone to the west and induces cool upwelling in the ocean through ekman transport feedbacks involving for example sea surface temperatures may further enhance the descent in these regions the conclusion is that the mediterranean type climates of regions such as california and chile may be induced remotely by the monsoon to the east hence it can be argued that the subtropical circulation in summer comprises a set of weakly interacting monsoon systems each involving monsoon rains a low level poleward jet a subtropical anticyclone to the east and descent and equatorward flow to the west in winter it is demonstrated how the nonlinear interaction between the strong zonal mean circulation associated with the winter hadley cell and the mountains can define many of the large scale features of the subtropical circulation the blocking effect of the longitudinal mountain chains is shown to be very important subsequent diabatic effects such as a local diabatic enhancement would appear to be essential for producing the observed amplitude of these features

sediment dynamics and hydrologic events affecting small lacustrine systems on the southern central tibetan plateau the example of tt lake a sedimentological geochemical micropaleontological and palynological study of a lacustrine sediment record from the small tt lake southern central tibetan plateau shows that the background sedimentation was frequently interrupted by event related deposits these event related deposits are interpreted as the result of hydrologic events that are triggered by above average precipitation events in total 11 events were recorded in the tt lake sequence two types can be differentiated fluvial runoff events caused by precipitation that carried sediment in suspension into the lake and a sediment mass transport caused by torrential precipitation the hydrologic events appear to be decoupled from long term climate and environmental variations but there is evidence that anthropogenic impact in terms of pastoralism might have favored the runoff events the multi proxy approach proved to be valuable and allowed for a detailed study of sedimentary processes within the lake and its watershed in order to asse

evidence of a strong paleoearthquake in 9 1 ka cal bp interpreted from mass transport deposits western quebec northeastern ontario canada this paper reviews and expands upon stratigraphic and chronologic evidence supporting the interpretation of a strong early postglacial paleoearthquake in western quebec northeastern ontario canada event horizon mapping at dasserat dufresnoy and duparquet lakes quebec coring at chassignolle and malartic lakes quebec analysis of varve exposures near both the twin falls and frederick house dams ontario and review of published and unpublished logs of varve exposures reveal that mass transport deposits formed in or are inferred to have formed in varve year vyr 1483 relative to the timiskaming varve series and about 9 1 ka cal bp are present at numerous locations within the study area the spatial extent of the vyr 1483 mass transport deposit signature covers at least 14 600 km2 and is best explained by shaking from a paleoearthquake the magnitude of the event is estimated to be a minimum of m 7 3 which is indicative of a strong paleoearthquake the vyr 1483 paleoearthquake is one of 11 events of m 5 occurring within a 425 varve year period between 9 4 and 8 95 ka cal bp and is likely part of a period of elevated early postglacial seismicity associated with rapid crustal unloading the absence of an equivalent signature within the younger portion of the glaciolacustrine or lacustrine deposits in local lakes implies that this paleoearthquake is the strongest to occur within the study area since about 9 1 ka cal bp the highly precise correlation of widely spaced mass transport and disturbed deposits provided by varves is essential to the paleoearthquake interpretation

the preservation potential of coastal coseismic and tsunami evidence observed following the 2012 mw 7 8 haida gwaii thrust earthquake abstract we describe near field coseismic and tsunami evidence collected following the 28 october 2012 m w 7 8 thrust earthquake that occurred offshore western haida gwaii british columbia and discuss factors that influence its extent and preservation potential observations indicate minor geomorphic and sedimentological impacts on the rugged and unpopulated west coast of the islands despite widespread coastal coseismic subsidence 0 5 m triggered landslides and tsunami waves exceeding 3 m in runup maximum 13 m along 230 km of coastline evidence left by the tsunami was minimal likely because it occurred during a low tide that restricted its onshore reach its flow depth and its capacity to entrain and transport significant amounts of clastic sediment sources of which are minimal or absent on the dominantly steep rocky coastline it is unlikely that subaerial evidence of coseismic subsidence and tsunami inundation will be recognizably recorded in the coastal stratigraphy of western haida gwaii due to the relatively small magnitude of subsidence a lack of suitable coastal environments such as tidal marshes to record paleoelevation differences sedimentation rates that are too low to bury a paleoseismic or paleotsunami record and long term relative sea level fall leading to erosion and bioturbation a higher preservation potential is likely for tsunami deposits in coastal lakes ponds and bogs as well as coseismic slope failure deposits offshore in lakes and in sheltered fjords our findings imply that large tsunamigenic earthquakes are likely undersampled in the paleoseismic record of haida gwaii and of other plate margins with similar characteristics

interdecadal changes in summertime typhoon tracks abstract the present work examines interdecadal variations of typhoon tracks in the western north pacific wnp during the boreal summer june september for the period 1951 2001 typhoon tracks are expressed as percentage values of the total number of typhoon passages into a 5 5 latitude longitude grid box with respect to the total number of typhoons formed in the wnp the analysis period is divided into two interdecadal periods id1 1951 79 and id2 1980 2001 from id1 to id2 typhoon passage frequency decreased significantly in the east china sea and philippine sea but increased slightly in the south china sea the time series of typhoon passage frequency over the east china sea and south china sea further reveal a regime shift in the late 1970s while those over the philippine sea indicate a continuous downward trend of 9 decade 1 the interdecadal changes in typhoon tracks are associated with the westward expansion of the subtropical northwestern pacific high snph in the late 1970s the e

location structure and seismicity of the seattle fault zone washington evidence from aeromagnetic anomalies geologic mapping and seismic reflection data a high resolution aeromagnetic survey of the puget lowland shows details of the seattle fault zone an active but largely concealed east trending zone of reverse faulting at the southern margin of the seattle basin three elongate east trending magnetic anomalies are associated with north dipping tertiary strata exposed in the hanging wall the magnetic anomalies indicate where these strata continue beneath glacial deposits the northernmost anomaly a narrow elongate magnetic high precisely correlates with magnetic miocene volcanic conglomerate the middle anomaly a broad magnetic low correlates with thick nonmagnetic eocene and oligocene marine and fluvial strata the southern anomaly a broad complex magnetic high correlates with eocene volcanic and sedimentary rocks this tripartite package of anomalies is especially clear over bainbridge island west of seattle and over the region east of lake washington although attenuated in the intervening region the pattern can be correlated with the mapped strike of beds following a northwest striking anticline beneath seattle the aeromagnetic and geologic data define three main strands of the seattle fault zone identified in marine seismic reflection profiles to be subparallel to mapped bedrock trends over a distance of 50 km the locus of faulting coincides with a diffuse zone of shallow crustal seismicity and the region of uplift produced by the m 7 seattle earthquake of a d 900 930

evidence of late glacial paleoseismicity from submarine landslide deposits within lac dasserat northwestern quebec canada abstract an integrated seismo and chronostratigraphic investigation at lac dasserat northwestern quebec identified 74 separate failures within eight event horizons horizons e and b and h and g have strong or moderately strong multi landslide signatures respectively composed of 11 23 failures while horizons f d c and a have minor landslide signatures consisting of a single or pair of deposit s cores collected at six sites recovered glacial lake ojibway varve deposits that are interbedded with the event horizons the correlation of the varves to the regional timiskaming varve series allowed varve ages or ranges of varve ages to be determined for the event horizons horizons h g e and b are interpreted to be evidence of paleoearthquakes with differing levels of interpretative confidence based on the relative strength of the multi landslide signatures the correlation to other disturbed deposits of similar age in the region and the lack or possibility of alternative aseismic mechanisms the four interpreted paleoearthquakes occurred between 9770 200 and 8470 200 cal yr bp when glacial lake ojibway was impounded behind the laurentide ice sheet during deglaciation they probably represent an elevated period of seismicity at deglaciation that was driven by crustal unloading

seismic reflection images beneath puget sound western washington state the puget lowland thrust sheet hypothesis seismic reflection data show that the densely populated puget lowland of western washington state is underlain by subhorizontal paleogene and neogene sedimentary rocks deformed by west and northwest trending faults and folds from south to north beneath the lowland features seen on the seismic data include the horizontally stratified 3 5 km thick tacoma sedimentary basin the seattle uplift with south dipping 20 strata on its south flank and steeply 50 to 90 north dipping strata and the west trending seattle fault on its north flank the 7 5 km thick northward thinning seattle sedimentary basin the antiformal kingston arch and the northwest trending transpressional southern whidbey island fault zone swif interpreting the uplifts as fault bend and fault propagation folds leads to the hypothesis that the puget lowland lies on a north directed thrust sheet the base of the thrust sheet may lie at 14 to 20 km depth within or at the base of a thick block of basaltic crescent formation its edges may be right lateral strike slip faults along the base of the cascade range on the east and the olympic mountains on the west our model suggests that the seattle fault has a long term slip rate of about 0 25 mm year and is large enough to generate a m7 6 to 7 7 earthquake

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

tree ring correlation between prehistoric landslides and abrupt tectonic events in seattle washington radiocarbon ages of submerged trees on landslide deposits in lake washington seattle indicate that the most recent slides in three separate areas may have occurred simultaneously about 1000 years ago tree ring crossdating shows that seven bark bearing trees from one of these recent slides and a tree 23 kilometers to the northwest in a probable tsunami deposit on the shore of puget sound died in the same season of the same year the close coincidence among the most recent lake landslides a probable tsunami abrupt subsidence and other possible seismic events gives evidence for a strong prehistoric earthquake in the seattle region

response of tropical cyclone tracks to sea surface temperature in the western north pacific abstracta set of short term experiments using a regional atmospheric model ram were carried out to investigate the response of tropical cyclone tc tracks to sea surface temperature sst in the western north pacific for 10 selected tc cases occurring during 2002 07 a warm and a cold run are performed with 2 and 2 k added to the ssts uniformly over the model domain respectively the cases can be classified into three groups in terms of recurvature recurved tracks in the warm and cold runs a recurved track in the warm run and a nonrecurved track in the cold run and nonrecurved tracks in both runs commonly the warm run produced northward movement of the tc faster than the cold run the rapid northward migration can be mainly explained by the result that cyclonic circulation to the west of the tc is found in the steering flow in the warm run and it is not in the cold run the beta effect is also activated under the warm sst environment for the typical tc cases a linear baroclinic model experimen

atmosphere ocean thermal coupling in the north atlantic a positive feedback in this article it is examined whether a positive atmosphere ocean feedback is found over the north atlantic through a series of general circulation model gcm experiments a 60 year integration of an atmospheric gcm agcm coupled with a 50 m deep motionless ocean was conducted the coupled run was compared with two uncoupled runs one with prescribed mid latitude climato logical sea surface temperatures ssts and the other with daily ssts derived from the coupled experiment the uncoupled atmosphere forces the slab ocean to obtain sst responses in these runs consistent with previous studies the coupled atmosphere ocean fields show interannual variances larger than those in the uncoupled runs due to reduction in the local thermal damping patterns of maximum atmosphere ocean covariability show the north atlantic oscillation nao and tripole sst anomalies both in the coupled and uncoupled fields indicating a dominant role of the atmosphere in generating the sst anomalies on the other hand analyses of the temporal variability in the three runs suggest an active role of sst anomalies in determining the polarity of the air sea coupled variability longer than the interannual time scale a combined analysis of forcing sst upper air height and the response sst anomalies in the uncoupled run identified that a patch of positive sst anomalies in the mid latitude band around 40 n effectively excite the positive phase of the nao which in turn reinforces the tripole sst anomalies this relationship was further confirmed by a nine member ensemble agcm experiment forced by the relevant sst anomalies since the forcing and response sst anomaly patterns bear some resemblance these results manifest positive feedback at work in the coupled atmosphere ocean patterns the processes responsible for this positive feedback were elaborated by a series of linear model experiments the local thermal adjustment of the atmosphere to the sst anomalies results in increased precipitation over the gulf stream region associated diabatic heating applied to a linear baroclinic model yields a positive height response to the east which highly influences the southern part of the nao this stationary response in turn induces a northward deflection in the storm track activity leading to an eddy vorticity feedback that tends to force the positive phase of the nao

origin and evolution of the seattle fault and seattle basin washington analysis of seismic reflection data reveals that the seattle basin washington is markedly asymmetric and consists of 9 10 km of eocene and younger deposits the basin began as a discrete geologic element in the late eocene 40 ma the result of a reorganization in regional fault geometry and kinematics in this reorganization dextral offset on the puget fault south east of seattle stepped eastward and the seattle fault began as a restraining transfer zone north vergent reverse or thrust faulting on the seattle fault forced flexural subsidence in the seattle basin to the north offset on the seattle fault and subsidence of the seattle basin have continued to the present

scale interaction between typhoons and the north pacific subtropical high and associated remote effects during the baiu meiyu season the interaction between typhoons and the north pacific subtropical high and the associated remote impact on east asian and north pacific anomalous weather during the baiu meiyu season have been investigated using the japanese long term reanalysis project data aided by the japan meteorological agency climate data assimilation system the typhoons that appeared in july have been categorized into two primary tracks the hainan island course hc and the okinawa island course oc a typhoon gives rise to negative absolute vorticity advection along its eastern periphery which locally reinforces the western ridge of the north pacific subtropical high whereas the resultant anomalous high stimulates the westward northward migration of the hc oc typhoon through its combination with the background flow a combined effect of the typhoon and its induced anomalous anticyclonic circulation increases the transportation of moisture into the baiu meiyu frontal zone in the vicinity of japan over the east china sea and the sea of japan northward or northeastward moisture flux is pronounced along the western periphery of the typhoon induced anticyclonic circulation anomaly in the hc category triggering heavy rainfall on central japan s sea of japan coast similar remote effects also operate in the oc category which is responsible for the occurrence of extremely heavy rainfall along the pacific coast of western japan when an oc typhoon approaches the asian jet it is capable of giving rise to anticyclonic vorticity within the jet leading to the downstream development of stationary rossby wave packets via the north pacific waveguide

sensitivity of simulated tropical cyclone structure and intensity to horizontal resolution abstract the weather research and forecasting wrf model is used to test the sensitivity of simulations of hurricane ivan 2004 to changes in horizontal grid spacing for grid lengths from 8 to 1 km as resolution is increased minimum central pressure decreases significantly by 30 hpa from 8 to 1 km grid spacing although this increase in intensity is not uniform across similar reductions in grid spacing even when pressure fields are interpolated to a common grid this implies that the additional strengthening of the simulated tropical cyclone tc at higher resolution is not attributable to sampling but is due to changes in the representation of physical processes important to tc intensity the most apparent changes in simulated tc structure with resolution occur near a grid length of 4 km at 4 km grid spacing and below polygonal eyewall segments appear suggestive of breaking vortex rossby waves with sub 4 km grid lengths localized intense updraft cores within the eyewall are numerous and bo

a tsunami about 1000 years ago in puget sound washington water surged from puget sound sometime between 1000 and 1100 years ago overrunning tidal marshes and mantling them with centimeters of sand one overrun site is 10 kilometers northwest of downtown seattle another is on whidbey island some 30 kilometers farther north neither site has been widely mantled with sand at any other time in the past 2000 years deposition of the sand coincided to the year or less with abrupt probably tectonic subsidence at the seattle site and with landsliding into nearby lake washington these findings show that a tsunami was generated in puget sound and they tend to confirm that a large shallow earthquake occurred in the seattle area about 1000 years ago

structure and dynamics of the summertime pacific japan teleconnection pattern convective activity over the tropical western pacific is known to influence the extratropical circulation over east asia in the boreal summer in the form of teleconnection called the pacific japan pj pattern but its structure and dynamics have not yet been studied in depth in this study a composite analysis is performed for 32 monthly events of enhanced convection observed to the east of the philippines the composited monthly mean vorticity anomalies associated with the pj pattern are elongated zonally with a distinct poleward tilt with height this structure differs fundamentally from a combination of the first baroclinic mode in the tropics and the barotropic structure in midlatitudes as has widely been accepted as a conceptual model of the pj pattern a wave activity flux points polewards only in the lower troposphere indicating that rossby wave teleconnection occurs primarily through a low level south westerly jet those tilted anomalies over the western pacific can effectively gain kinetic energy in the exits of the mean jet streams in the upper and lower troposphere and available potential energy ape in the presence of the vertically sheared jets the enhanced convection can generate ape effectively and the associated low level anomalous circulation acts to increase moisture supply into the convective region while enhancing evaporation from the pre warmed ocean surface it is thus hypothesized that the pj pattern may be regarded as a dynamical mode that can be effectively excited in the zonally asymmetric baroclinic mean flow associated with the asian summer monsoon with an efficient self sustaining mechanism through moist processes copyright 2006 royal meteorological society

structure and formation mechanisms of the northern hemisphere summertime subtropical highs abstract three dimensional structure and dynamics of the climatological mean summertime subtropical highs over the north pacific and atlantic i e the azores high are investigated each of the observed surface highs is accompanied by a meridional vorticity dipole aloft exhibiting barotropic and baroclinic structures in its northern and southern portions respectively in a manner dynamically consistent with the observed midtropospheric subsidence each of the highs develops over the relatively cool eastern ocean where a pronounced near surface thermal contrast exists with a heated landmass to the east the authors demonstrate through numerical experiments that those highs can be reproduced in response to a local shallow cooling heating couplet associated with this thermal contrast although the upper level response is somewhat underestimated the model experiments suggest that the near surface thermal contrasts associated with those surface subtropical highs over the pacific and atlantic can act as s

hemispheric asymmetry of subauroral ion drifts statistical results a large database of more than 18 000 subauroral ion drift said events from dmsp observations from 1987 to 2012 is used to systematically investigate the features of said said occurs mostly at 62 60 magnetic latitude mlat and 22 15 22 45 magnetic local time mlt for geomagnetically quiet conditions and at 58 56 mlat and 22 15 22 45 mlt for geomagnetically disturbed conditions in the north hemisphere nh south hemisphere sh respectively significant north south asymmetries in said occurrence shape and geomagnetic activity variations are found in this statistical study the latitudinal width of a said is larger in the nh than in the sh an interesting finding of this work is that the said occurrence probability peaks have an 180 difference in longitude between the two hemispheres in the geographic coordinates for both geomagnetically quiet and disturbed conditions the said width peaks in almost the same geomagnetic meridian zone with a geomagnetic longitude of 80 120 in both hemispheres significant hemispheric asymmetries and spike signatures with sharp dips are found in all the latitudinal profiles of the horizontal velocities of saids the said is highly correlated to geomagnetic activity indicating that the location and evolution of the said might be influenced by global geomagnetic activity auroral dynamics and the dynamics of ring currents

attribution of projected future changes in tropical cyclone passage frequency over the western north pacific abstractthis paper performs an attribution analysis of future changes in the frequency of tropical cyclone tc passages over the western north pacific basin projected by seven general circulation models the models project increases in the passage frequency over the tropical central north pacific and decreases in regions to the west and northwest including east asian countries the attribution analysis reveals that while changes of the basinwide tc count would decrease the frequency of passages throughout the basin the gross horizontal contrast in the passage frequency changes is caused by a projected eastward shift of main tc development regions probably caused by el nino like sea surface temperature changes the change in the frequency of passages is also caused by changes of tc translation vectors and preferable tracks in particular the translation vector would rotate clockwise to point in a more easterly direction over oceanic regions south of japan decreasing the passage frequency over the kor

high temperature memory in calcic amphiboles and constraints on compositional control of their 40ar 39ar ages well characterized calcic amphiboles from an incompletely mixed magmatic rock association of mainly intermediate dioritic composition were studied by incremental heating experiments of 40 ar 39 ar the rocks in question were thermally overprinted by late hercynian granites microprobe and scanning electron microscopy analyses show that the amphibole grains consist of two different calcic hornblende varieties 1 a si and mg rich variety and 2 a variety enriched in al ti fe k and na the mg si rich hornblende can be further characterized by its higher cao k 2 o ratios 30 50 compared to the al ti fe k na rich hornblende 12 15 three hornblende separates that previously had yielded conventional k ar ages of 320 317 and 302 ma have been dated by the 40 ar 39 ar step heating technique the low and medium temperature parts of the 40 ar 39 ar age spectrum show discordant ar systematics with single step ages generally younger than 325 ma the gas released at the highest temperature steps preserves an exceptional record of old and remarkably similar integrated ages 342 346 and 344 ma the high temperature ages correspond to phases with higher apparent cao k 2 o ratios 30 45 and are interpreted to result from ar release from mg si hornblende domains that are assumed to have been very resistent to ar loss during the late hercynian thermal events the results of this study suggest that ar retentivity differs among calcic amphiboles and mg si rich hornblendes are more ar retentive than their al ti fe k na rich counterparts

paleoearthquakes in the puget sound region recorded in sediments from lake washington u s a holocene sediments in lake washington contain a series of turbidites that were episodically deposited throughout the lake the magnetic signatures of these terrigenous layers are temporally and areally correlatable large earthquakes appear to have triggered slumping on the steep basin walls and landslides in the drainage area resulting in turbidite deposition one prominent turbidite appears to have been deposited about 1100 years ago as the result of a large earthquake downcore susceptibility patterns suggest that near simultaneous slumping occurred in at least three separate locations two of which now contain submerged forests several other large earthquakes may have occurred in the last 3000 years

tree ring evidence for an a d 1700 cascadia earthquake in washington and northern oregon geologic evidence and radiocarbon dating indicate that a subduction earthquake or series of earthquakes occurred about 300 yr ago along the pacific northwest coast of the united states some radiocarbon dates come from remnants of the myriad trees drowned by coincident subsidence at several coastal lowland locations in washington and northern oregon we located two or more trees that survived partial submergence and lived to the 1990s many of them were damaged by shaking and or inundation some survivors recorded the event s by anomalous changes in ring width or anatomy of their annual rings the disturbance initiating the changes can be dated to between the growing seasons of a d 1699 and 1700 one killed tree has a last ring of a d 1699 tree ring dated evidence of disturbance extends along about 100 km of coastal washington and northern oregon these results support the inference that a great m w 8 earthquake or larger at the cascadia subduction zone generated the historical tsunami that struck japan in january 1700

crustal earthquake triggering by pre historic great earthquakes on subduction zone thrusts triggering of earthquakes on upper plate faults during and shortly after recent great m 8 0 subduction thrust earthquakes raises concerns about earthquake triggering following cascadia subduction zone earthquakes of particular regard to cascadia was the previously noted but only qualitatively identified clustering of m 6 5 crustal earthquakes in the puget sound region between about 1200 900 cal years b p and the possibility that this was triggered by a great cascadia thrust subduction thrust earthquake and therefore portends future such clusters we confirm quantitatively the extraordinary nature of the puget sound region crustal earthquake clustering between 1200 900 cal years b p at least over the last 16 000 we conclude that this cluster was not triggered by the penultimate and possibly full margin great cascadia subduction thrust earthquake however we also show that the paleoseismic record for cascadia is consistent with conclusions of our companion study of the global modern record outside cascadia that m 8 6 subduction thrust events have a high probability of triggering at least one or more m 6 5 crustal earthquakes

optical dating of tsunami laid sands abstract the ages of some tsunami deposits can be determined by optical dating a key requirement being that the deposits are derived from sediment that was reworked and exposed to daylight by tidal currents waves wind or bioturbation during the last years before the tsunami measurements have been made using 1 4 ev infrared excitation of k feldspar grains separated from samples of prehistoric tsunami sand sheets and modern analogs of tsunami source sediments at four sites in washington state and british columbia source sands gave equivalent doses indicative of recent exposure to daylight tsunami sand at cultus bay washington yielded an optical age of 1285 95 yr calendric years before a d 1995 1 at 2 this age overlaps the range of from 1030 to 1100 yr determined through a combination of high precision radiocarbon dating and stratigraphic correlation tsunami sands at three sites near tofino and port alberni on vancouver island british columbia have optical ages of 260 20 325 25 and 335 45 yr historical records and radiocarbon dating show that the sand at each of the three sites is between 150 and 400 yr old these optical ages support the hypothesis that the vancouver island sands were deposited by a tsunami generated by a large earthquake on the cascadia subduction zone about 300 yr ago

attribution of decadal variability in tropical cyclone passage frequency over the western north pacific a new approach emphasizing the genesis location of cyclones abstractvariability in tropical cyclone tc activity is a matter of direct concern for affected populations on interannual and longer time scales variability in tc passage frequency can be associated with total tc frequency over the concerned ocean basin basinwide frequency bf the spatial distribution of tc genesis in the basin genesis distribution gd and the preferable track pt that can be considered as a function of genesis locations to facilitate investigation of mechanisms responsible for the variability the authors propose an approach of decomposing anomalies in the passage frequency into contributions of variability in bf gd and pt which is named the integration of statistics on tc activity by genesis location istagl analysis application of this approach to tc best track data in the western north pacific wnp basin reveals that overall distribution of the passage frequency trends over the 1961 2010 period is mainly due to the pt trends on decadal time scales passage frequen

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

an estimation of water origins in the vicinity of a tropical cyclone s center and associated dynamic processes to clarify the time evolution of water origins in the vicinity of a tropical cyclone tc s center we have simulated typhoon man yi july 2007 in our case study using an isotopic regional spectral model the model results confirm that the replacement of water origins occurs successively as the tc develops and migrates northward over the western north pacific it is confirmed that in this case a significant proportion of total precipitable water around the cyclone center comes from external regions rather than the underlying ocean during the mature stage of a tc similar features can also be seen in the proportion of each oceanic origin to total condensation indian ocean south china sea and maritime continent water vapors begin to increase gradually at the developing stage and reach their peak at the decay stage when the tc approaches southwestern japan these remote ocean vapors are transported to the east of the cyclone via the moisture conveyor belt a zone characterized by distinct low level moisture flux that stretches from the indian ocean to the tc and are further supplied into the inner region of the tc by inflow within the boundary layer associated with its secondary circulation since it takes time to undergo these two dynamic processes the delayed influence of remote ocean vapors on the tc appears to become evident during the mature stage

glaciofluvial infilling and scour of the puget lowland washington during ice sheet glaciation the puget lobe the southwesternmost extension of the cordilleran ice sheet last advanced into the puget lowland of western washington at about 15 ka the advancing ice sheet deposited voluminous sediment on a prograding proglacial outwash plain that extended from the olympic mountains to the cascade range herein recognized as the great lowland fill subsequent overrunning by the ice sheet excavated deep linear troughs now occupied by the large lakes and marine waters of puget sound excavation of these troughs and valleys of the puget lowland required the net transport of about 1000 km3 of sediment almost entirely during ice occupation and primarily by subglacial water these landforms of glaciofluvial deposition and erosion define the modern landscape here emphasizing the importance of these processes in the region s geomorphology

abrupt uplift within the past 1700 years at southern puget sound washington shorelines rose as much as 7 meters along southern puget sound and hood canal between 500 and 1700 years ago evidence for this uplift consists of elevated wave cut shore platforms near seattle and emerged peat covered tidal flats as much as 60 kilometers to the southwest the uplift was too rapid for waves to leave intermediate shorelines on even the best preserved platform the tidal flats also emerged abruptly they changed into freshwater swamps and meadows without first becoming tidal marshes where uplift was greatest it adjoined an inferred fault that crosses puget sound at seattle and it probably accompanied reverse slip on that fault 1000 to 1100 years ago the uplift and probable fault slip show that the crust of the north america plate contains potential sources of damaging earthquakes in the puget sound region

the southern whidbey island fault an active structure in the puget lowland washington information from seismic reflection profiles outcrops boreholes and potential field surveys is used to interpret the structure and history of the southern whidbey island fault in the puget lowland of western washington this northwest trending fault comprises a broad as wide as 6 11 km steep northeast dipping zone that includes several splays with inferred strike slip reverse and thrust displacement transpressional deformation along the southern whidbey island fault is indicated by along strike variations in structural style and geometry positive flower structure local unconformities out of plane displacements and juxtaposition of correlative sedimentary units with different histories the southern whidbey island fault represents a segment of a boundary between two major crustal blocks the cascade block to the northeast is floored by diverse assemblages of pre tertiary rocks the coast range block to the southwest is floored by lower eocene marine basaltic rocks of the crescent formation the fault probably originated during the early eocene as a dextral strike slip fault along the eastern side of a continental margin rift bending of the fault and transpressional deformation began during the late middle eocene and continues to the present oblique convergence and clockwise rotation along the continental margin are the inferred driving forces for ongoing deformation evidence for quaternary movement on the southern whidbey island fault includes 1 offset and disrupted upper quaternary strata imaged on seismic reflection profiles 2 borehole data that suggests as much as 420 m of structural relief on the tertiary quaternary boundary in the fault zone 3 several meters of displacement along exposed faults in upper quaternary sediments 4 late quaternary folds with limb dips of as much as 9 5 large scale liquefaction features in upper quaternary sediments within the fault zone and 6 minor historical seismicity the southern whidbey island fault should be considered capable of generating large earthquakes m s 7 and represents a potential seismic hazard to residents of the puget lowland

holocene landslides and a 3500 year record of pacific northwest earthquakes from sediments in lake washington lake washington which forms the eastern boundary of seattle is located in a tectonically active area containing several strands of the seattle fault high resolution seismic reflection profiling sidescan swath imagery and sediment coring were used to define deformation of holocene lake sediments and the distribution geometry age and causes of submarine landslides numerous large block slides sediment slumps and debris flows are present throughout the lake and large landslides obscure the surficial structure of seattle fault strands as they pass through the lake in addition most bays along the lake margin are the headwalls of large submarine slides submerged forests show evidence of deep seated block failures that have exposed glacial sediments and tertiary rocks the massive submarine block slides and retrogressive submarine slope failures were triggered most likely by large m b 7 earthquakes on the seattle fault and or large to great m b 8 temblors occurring elsewhere in cascadia buried landslides suggest that submarine slope failures and mass wasting occurred more than once in the last 11 000 yr sediments in lake washington preserve a record of episodic deposition of turbidites possibly caused by seismically induced submarine landslides magnetic susceptibility profiles on 36 gravity cores show a characteristic series of magnetic peaks that can be traced throughout the lake x radiography and grain size analyses suggest that the magnetic peaks represent anomalous detrital layers that in some cases are turbidites the areal extent and magnetic signatures of many of the deposits suggest multiple sources which is consistent with numerous local landslides caused by large earthquakes radiocarbon dating and correlation of the downcore magnetic profiles establish a sediment record in which episodic sedimentary disturbances occurred seven times in the last 3500 yr if these deposits are seismically induced turbidites seismites then large earthquakes have occurred about every 300 500 yr in the puget sound region

geologic evidence of earthquakes at the snohomish delta washington in the past 1200 yr exposed channel banks along distributaries of the lower snohomish delta in the puget lowland of washington reveal evidence of at least three episodes of liquefaction at least one event of abrupt subsidence and at least one tsunami since ca a d 800 the 45 measured stratigraphic sections consist mostly of 2 4 m of olivegray intertidal mud containing abundant marsh plant rhizomes the most distinctive stratigraphic unit is a couplet comprising a 0 523 cm thick laminated fining upward tsunami laid sand bed overlain by 2210 cm of gray clay we correlated the couplet which is generally 2 m below the modern marsh surface across an 20 km2 area sand dikes and sand filled cracks to 1 m wide which terminate upward at the couplet and sand volcanoes preserved at the level of the sand bed record liquefaction at the same time as couplet deposition differences in the type and abundance of marsh plant rhizomes across the couplet horizon as well as the gray clay layer suggest that compaction during this liquefaction led to abrupt local lowering of the marsh surface by as much as 50 75 cm radiocarbon ages show that the tsunami and liquefaction date from ca a d 800 to 980 similar to the age of a large earthquake on the seattle fault 50 km to the south we have found evidence for at least two and possibly as many as five other earthquakes in the measured sections at two or more stratigraphic levels above the couplet sand dikes locally feed sand volcanoes radiocarbon ages and stratigraphic position gov suggest that one set of these dikes formed ca a d 910 990 radiocarbon ages on a younger set indicate a limiting maximum age of a d 1400 1640 we also interpret a sharp lithologic change from olive gray rhizome rich mud to grayer rhizome poor mud 1 m above the couplet to indicate a second abrupt lowering of the marsh surface during an earthquake ca a d 1040 1400 but no conclusive liquefaction structures have been identified at this horizon two distinctive coarse sand laminae 30 80 cm below the couplet may record tsunamis older than a d 800 thus study shows that in the past 1200 yr this part of washington s puget lowland has been subjected to stronger ground shaking than in historic times since ca 1870

the importance of site selection sediment supply and hydrodynamics a case study of submarine paleoseismology on the northern cascadia margin washington usa abstract the washington continental margin presents both a classic test of submarine paleoseismology and an opportunity to explore advancement of the field through analysis of sediment dispersal in a heterogeneous system new and archive core bathymetric backscatter and seismic reflection data from the washington cascadia margin show that during high stand conditions the northernmost canyons barkley nitinat juan de fuca jdf and to some extent quillayute are relict systems with little holocene recharge the remaining canyons quinault grays guide and willapa are recharged to a varying degrees by northward transport of columbia river derived sediment all systems are nonetheless active conduits for turbidity currents during the holocene which are weaker and more restricted than their pleistocene counterparts sedimentologic and ct analysis supported by radiocarbon ages micropaleontology and the mazama ash datum show that the holocene sedimentary sequence consists of a series of sand to mud turbidites in the active portions of all systems interbedded with hemipelagic sediment however the pleistocene astoria and nitinat fans are largely inactive in the holocene with turbidity current activity limited to the proximal parts of the main channels within active systems the turbidite record is modulated by local landsliding and growth of active folds and faults in the relict systems the turbidite record begins in the middle canyon reaches as opposed to the actively recharged systems which have a turbidite record in the more proximal canyon reaches deposits in the relict systems increase in thickness and modal grain size downstream suggesting multiple sources and or entrainment of material along the canyon walls hydrodynamic models using monte carlo model searches for best fitting flow parameters show the most likely pathways by which holocene and pleistocene currents flowed through the complex accretionary wedge to the abyssal plain model results supported by heavy mineral distributions show that the northern canyon systems barkley nitinat jdf quillayute are independent of the southern systems quinault guide grays willapa during the holocene supporting the classic confluence test balancing of sediment volumes required suggests sediment supplied to the slope canyons and abyssal channels in turbidity current events is 2 5 times greater than that supplied by recharge to the canyon heads by external sources this implies a process that is independent of recharge that scavenges the plentiful relict and hemipelagic sediment supply on the continental slope lithostratigraphic correlation and age models suggest similar sequences were deposited in most systems independently and likely synchronously the correlated turbidite sequence suggests deposition of 23 holocene and 16 post mazama turbidites in most parts of the canyon systems with only modest variation mostly attributable to evidence of bypassing and erosion the best candidate for triggering of these sequences remains great earthquakes and the sequence correlates well to onshore and other offshore paleoseismologic evidence the new data including new cores in northern oregon suggest revisions to segmented rupture boundaries several partial ruptures segment b likely extended further north to juan de fuca canyon one event was resolved into two and one washington only event was added most segment c ruptures were found to extend further northward to the latitude of astoria canyon mean recurrence times are therefore revised to 434 years for the washington coast and 340 years for the central and northern oregon coast conditional probabilities in the next 50 years also are revised to 10 17 for the washington coast and 16 22 for the central and northern oregon coast in cascadia sumatra and other locales globally core siting spatial sample density high resolution analysis of core and regional geophysics and understanding of flow dynamics are critical to capturing a paleoseismic record sedimentary records vary across turbidity current systems of varying sediment supply physiography and sediment sources variations in the record will reflect these factors yet may still present a consistent paleoseismic history this analysis highlights the importance of a thorough understanding of flow paths hydrodynamics and the interplay of sedimentation and local tectonics when testing for evidence of earthquakes in the sedimentary record of active margins

a history of pacific northwest earthquakes recorded in holocene sediments from lake washington large earthquakes can trigger slumping of the steep walls of lake basins and landslides in the drainage area resulting in turbidite deposition in the lake and increased detrital flux from inlets holocene sediments in piston cores from lake washington contain a series of terrigenous layers that were episodically deposited in the lake sedimentological geochemical and paleomagnetic analyses on nine piston cores show that the detrital layers are temporally and areally correlatable indicating basinwide disruptions these layers are opaque on x radiographs are coincident with magnetic susceptibility peaks have abundant aluminosilicate minerals are relatively coarse grained and have low organic carbon and biogenic silica contents the thicknesses and geographic distributions of the layers suggest that they are not due to floods or delta destabilization side scan swath imagery and subbottom profiling show that large slumps subaqueous landslides and debris flows are common along the margins of the lake a detailed chronology established from 21 radiocarbon ages on five cores show that a prominent turbidite was deposited about 1000 1100 years ago this turbidite apparently was triggered by a large earthquake that probably occurred on the seattle fault other depositional events in the sediment record at 1500 1700 2400 2500 and 2800 3200 years ago coincide with periods of landsliding that have been previously inferred from the dating of drowned trees in the lake more than 30 depositional events have occurred in the last 12 000 years and 21 disturbances have occurred since the deposition of the mazama ash about 7 600 years ago if all the events are due to earthquakes the puget sound region has been subject to major shaking every 300 to 400 years the strong intensities needed to trigger subaqueous slides may not be generated by just local sources such as the seattle fault but could also be caused by great subduction earthquakes occurring along the coast

late holocene rupture of the northern san andreas fault and possible stress linkage to the cascadia subduction zone we relate the late holocene northern san andreas fault nsaf paleo seismic history developed using marine sediment cores along the northern california continental margin to a similar dataset of cores collected along the cascadia margin including channels from barclay canyon off vancouver island to just north of mon terey bay stratigraphic correlation and evidence of synchronous triggering imply earthquake origin and both temporal records are compatible with onshore paleoseis mic data in order to make comparisons between the temporal earthquake records from the nsaf and cascadia we refine correlations of southern cascadia great earth quakes including the land paleoseismic record along the nsaf during the last 2800 yr 15 turbidites including one likely from the great 1906 earthquake establish an average repeat time of 200 yr similar to the onshore value of 240 yr the combined land and marine paleoseismic record from the southern cascadia subduction zone includes a similar number of events during the same period while the average recurrence interval for full margin cascadia events is 520 yr the southern cascadia margin has a repeat time of 220 yr similar to that of the nsaf thirteen of the 15 nsaf events were preceded by cascadia events by 0 80 yr averaging 25 45 yr as compared to 80 400 yr by which cascadia events follow the nsaf based on the temporal association we model the coseismic and cumulative post seismic deformation from great cascadia megathrust events and compute related stress changes along the nsaf in order to test the possibility that cascadia earth quakes triggered the penultimate and perhaps other nsaf events the coulomb fail ure stress cfs resulting from viscous deformation related to a cascadia earthquake over 60 yr does not contribute significantly to the total cfs on the nsaf however the coseismic deformation increases cfs on the northern san andreas fault nsaf b y up to about 9 bars offshore of point delgada most likely enough to trigger that fault to fail in north to south propagating ruptures

1500 years of lake sedimentation due to fire earthquakes floods and land clearance in the oregon coast range geomorphic sensitivity to floods during timber harvest period

atmospheric sensitivity to sst near the kuroshio extension during the extratropical transition of typhoon tokage abstract it is hypothesized that the tropical to extratropical transition of a cyclone in the western north pacific can be sensitive to the underlying sea surface temperature sst distribution this hypothesis was tested through a case study of typhoon tokage using a series of high resolution simulations by the weather research forecast wrf numerical weather prediction model simulations were carried out for a control sst distribution and for sst distributions with imposed warm and cold perturbations of 1 5 c maximum amplitude in the vicinity of the kuroshio extension the simulations with the warm sst perturbation yielded a cyclone slightly weaker than in the control sst case about 2 days after transition in contrast the cold sst perturbation case yielded a cyclone with a central pressure 10 hpa lower than in the control case at the same point in the storm s life cycle apparently due to its more northward track and hence closer proximity to an approaching upper level trough and perhaps in associati

giant earthquakes in south central chile revealed by holocene mass wasting events in lake puyehue abstract very high resolution reflection seismic profiling 3 5 khz revealed nine holocene mass wasting events in lake puyehue south central chile these events are made up of numerous coeval mass wasting deposits and some homogenites which are radiocarbon dated the two youngest mass wasting events could be attributed to the giant ad 1960 and ad 1575 valdivia earthquakes the most extensive event took place around 1660 cal yr bp evaluation of all possible slope failure processes led us to infer that giant earthquakes roughly comparable to the ad 1960 valdivia earthquake mw 9 5 are the most likely trigger mechanisms of all mass wasting events in lake puyehue these occurred with a mean recurrence rate of 1000 yr although relatively aperiodically ranging between 500 and 2000 yr quantitative comparison of mass wasting events related to historically reported earthquakes ad 1960 and ad 1575 showed significant differences although these earthquakes are assumed to have had a comparable strength a lowered background sedimentation rate could be responsible for this variable earthquake recording which highlights the importance of a thorough assessment of the depositional history before using lacustrine records for quantitative paleoseismic analysis

large scale vapor transport of remotely evaporated seawater by a rossby wave response to typhoon forcing during the baiu meiyu season as revealed by the jra 55 reanalysis the modulation of large scale moisture transport from the tropics into east asia in response to typhoon induced heating during the mature stage of the baiu meiyu season is investigated using the japanese 55 year reanalysis jra 55 aided by a rayleigh type global isotope circulation model icm we highlighted the typhoons that migrate northward along the western periphery of the north pacific subtropical high and approach the vicinity of japan anomalous anticyclonic circulations to the northeast and southeast of typhoons and cyclonic circulation to their west become evident as they migrate toward japan which could be interpreted as a rossby wave response to typhoon heating these resultant anomalous circulation patterns form moisture conveyor belt mcb stretching from the south asian monsoon region to east asia via the confluence region between the monsoon westerlies and central pacific easterlies the icm results confirm that the well defined nature of the mcb leads to penetration of the indian ocean south china sea philippine sea and pacific ocean water vapors into western japan the typhoons have the potential to accumulate large amounts of moisture from distant tropical oceans through the interaction of their rossby wave response with the background flow in the case of a typical typhoon the total precipitable water around the typhoon center as it approaches japan is maintained by the moisture supply from distant oceans rather than from the underlying ocean which indirectly leads to the occurrence of heavy rainfall over western japan

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

time dependent recurrence of strong earthquake shaking near plate boundaries a lake sediment perspective abstract accurate probabilistic seismic hazard analysis requires a good knowledge of the recurrence parameters of the strongest earthquakes in a region due to the typical short temporal span of instrumental and historical data it is often unclear whether one should adopt a time dependent or time independent poissonian recurrence model the choice of which has large repercussions on the probability estimates for new strong events the rapidly growing discipline of lacustrine paleoseismology aims at producing long continuous records of strong seismic shaking which integrate the activity of all significant seismic sources in a region and allow a reliable determination of recurrence patterns the typical continuous sedimentation regime in lakes can lead to complete sensitive paleoseismic records and a reduced temporal uncertainty in recurrence intervals here i present a worldwide compilation of published long lacustrine paleoseismic records grouped per tectonic domain and statistically explore the variability of their recurrence intervals expressed by the coefficient of variation cov a cov 1 indicates a time independent process whereas cov 1 may be related to changes in the sensitivity of the lacustrine paleoseismograph or to real earthquake clustering due to e g stress transfer between neighboring faults the most useful lacustrine paleoseismic records can be retrieved in high seismicity settings where many paleoseismic events can be recorded in a relatively short time span i e

a modelling and observational study of the relationship between sea surface temperature in the north west atlantic and the atmospheric general circulation results from four pairs of 50 day wintertime integrations of the meteorological office s 5 level general circulation model with warm and cold sea surface temperature s s t anomalies of about 3 k in the northwest atlantic are described difference fields between the warm and cold integrations are statistically significant at the 1 level with positive geopotential height over the central north atlantic and weaker negative height over europe the storm track over the atlantic is displaced from its normal position results from four further pairs of integrations with halved s s t anomalies are also described the response is approximately linear with systematic differences in 500 mb geopotential height over the atlantic parts of which are just significant at the 10 level with half the full s s t anomaly overall however the model s response is weaker than could be obtained with tropical s s t anomalies of the same magnitude results from the model integrations are compared with results from an observational study of the relationship between wintertime s s t in the north west atlantic and mean sea level pressure and 500mb height two independent 30 year periods were chosen for study thus minimizing the influence of long term trends in s s t over the atlantic and europe the model results compared well with the observations with s s t data lagging the atmosphere by one month the observational study appears to show that the s s t anomalies are initially forced by perturbations in the atmospheric circulation with s s t data leading the atmosphere by one month results show that atmospheric and s s t anomalies are most persistent in the period october to december throughout the winter these lagged relationships are much weaker and not statistically significant diagnostics of e vector divergence from the gcm experiments are used to suggest that anomalous baroclinic wave activity over the atlantic is important as a momentum forcing for the anomalous time mean flow pattern on the other hand the role of thermal forcing provided by anomalous diabatic heating and transient eddy heat flux convergence may be important to substantiate this statement a simple linear steadystate two layer model of the response to extratropical thermal forcing is described with a suitable basic state flow and a mid tropospheric heat source given mainly by the transient eddy heat flux convergence the response is shown to be equivalent barotropic with a downstream ridge and ascent over the thermal source conversely results from an ocean mixed layer model are discussed which suggest that warm s s t anomalies could be maintained by a positive surface pressure perturbation positioned downstream of the anomaly through anomalous northward advection of warm ocean water by ekman drift currents this northward advection would balance the sensible and latent heat loss into the atmosphere over the s s t anomaly hence it is possible that some positive ocean atmosphere feedback may account for the persistence of such atmospheric and oceanic anomalies