nonlinear soil response of a borehole station based on one dimensional inversion during the 2005 fukuoka prefecture western offshore earthquake the objective of this article is to present the nonlinear response of a soft sedimentary site based on a one dimensional inversion by a genetic algorithm of the shear wave velocity structure and damping factors of a borehole soil column during the 2005 fukuoka prefecture western offshore earthquake first we confirm that according to the source rupture mechanism the major and minor axes in the horizontal plane at the borehole station are the transverse and radial directions respectively then in order to corroborate in the linear domain the s wave transfer function of the borehole s logging we perform time dependent spectral ratios analyses on small aftershocks finally we show qualitative evidence of nonlinearity during the main shock associated with a significant shift toward low frequencies of several resonant modes and we evaluate the degree of nonlinearity by inverting the shear wave veloc ity structure and damping factors because of a directional effect present only in the major axis around 8 hz which prevents the use of the conventional objective function that minimizes the integrated residuals between observed and theoretical ratios we introduce a simple objective function that depends only on peaks frequency and amplitude the efficiency of the objective function and the robustness of the inversion are shown by performing eight independent inversions converging to very similar minima

a comparison and test of various site response estimation techniques including three that are not reference site dependent abstract we compare various site response estimation techniques using after shock data of the 1989 loma prieta earthquake collected in oakland california because of recent interest in comparing results from weak and strong motion to infer any nonlinearity and between direct s and coda waves we pay particular attention to the uncertainties first sediment to bedrock spectral ratio estimates between pairs of sites are compared with those obtained from various generalized inversion approaches where the source and site effects of multiply recorded events are solved for simultaneously we find that the site amplification factors are very similar among these approaches but that the uncertainties can be significantly different depending on how the data are weighted we also examine and test three site response estimation techniques that do not rely on a reference site to estimate source and path effects the first involves a parameterized source and path effects inversion even when the bedrock data are excluded from consideration this approach is found to reveal the frequency dependence of site response at each of the sediment sites the second technique involves taking horizontal to vertical component spectral ratios receiver function type estimates of shear wave aftershock data these are also found to reveal the frequency dependence of site response at the sediment sites and the results for the bedrock site are relatively flat and near unity the third estimate is formed by taking horizontal to vertical component ratios of ambient seismic noise and these are shown to reveal the fundamental resonant frequency of the sediment sites unfortunately discrepancies exist among all of the site response estimates and with one dimensional predictions with respect to a frequency independent scaling factor nevertheless the highly frequency dependent character of site response is well constrained and the fact that non reference site dependent methods are capable of revealing this is promising for site specific hazard assessments in regions that lack adequate reference sites

nonlinear ground motion amplification by sediments during the 1994 northridge earthquake it has been known since at least 1898 ref 1 that sediments can amplify earthquake ground motion relative to bedrock for the weak ground motion accompanying small earthquakes the amplification due to sediments is well understood in terms of linear elasticity hooke s law 2 but there has been a long standing debate regarding the amplification associated with the strong ground motion produced by large earthquakes the view of geotechnical engineers based largely on laboratory studies is that hooke s law breaks down at larger strains causing a reduced nonlinear amplification seismologists on the other hand have tended to remain sceptical of this nonlinear effect mainly because the relatively few strong motion observations seemed to be consistent with linear elasticity although some recent earthquake studies have demonstrated nonlinear behaviour under certain circumstances3 4 the significance of nonlinearity for the type of stiff soil sites found in the greater los angeles region remains unresolved5 here we report that ground motion amplification due to sediments for the main shock of the 1994 northridge earthquake was up to a factor of two less than the amplification observed for its aftershocks these observations imply significant nonlinearity in such amplification and bring into question the use of measurements of weak ground motion to predict the strong ground motion at sedimentary sites

seasonal variations in the southern hemisphere storm tracks and jet streams as revealed in a reanalysis dataset abstract regional characteristics of the climatological seasonal variations in southern hemisphere sh storm tracks are examined based on a reanalysis dataset when differences in vertical structure between the subpolar and subtropical jet streams spj and stj respectively are considered the regional characteristics can be interpreted reasonably well from a potential vorticity perspective of baroclinic eddy growth and downstream development of a baroclinic wave packet eddy activity in the upper and lower tropospheres is strongest in the core region of the spj over the eastern south atlantic and indian ocean throughout the year even in austral winter when the intense stj forms over the indian ocean and south pacific showing its eddy driven nature the spj accompanies the strong surface westerlies along a well defined baroclinic zone above an intense oceanic frontal zone in this core region of the storm track low level eddy activity is strongly correlated with the local near surface baroclinicity

atmospheric circulations induced by a midlatitude sst front a gcm study the atmospheric effects of sea surface temperature sst anomalies over and near western boundary currents are a matter of renewed interest the general circulation model gcm of the laboratoire de meteorologie dynamique lmd z has a zooming capability that allows a regionally increased resolution this gcm is used to analyze the impact of a sharp sst front in the north atlantic ocean two simulations are compared one with climatological ssts and the other with an enhanced gulf stream front the results corroborate the theory developed previously by the present team to explain the impact of oceanic fronts in this theory the vertical velocity at the top of the atmospheric boundary layer has two components mechanical and thermal it is the latter that is dominant in the tropics while in midlatitudes both play a role in determining the wind convergence above the boundary layer the strengthened sst front does generate the previously predicted stronger ascent above the warmer water south of the front and stronger descent above the colder waters to the north in the gcm simulations the ascent over the warm anomalies is deeper and more intense than the descent

influence of a sedimentary basin infilling description on the 2 d p sv wave propagation using linear and non linear constitutive models numerical modelling is a useful tool to understand the role of different parameters site geometry impedance contrast material properties constitutive model input motion governing site effects we focus here on the 2 d p sv seismic wave propagation in a simple shaped asymmetric model we consider two ways of describing the sedimentary infilling properties the basin is either composed of distinct homogeneous geological layers or is described through properties progressively changing as a function of depth smooth model in order to study the wave propagation in the two basins with similar soil properties p and s velocities of the layered basin are deduced from the smooth basin ones making both models compatible in a kinematic point of view p and s velocities globally increase with depth following epri non linear properties are considered as constant in layers for the two basins we assess the influence of the model choice on the wave propagation while taking into account linear and non linear constitutive models we test the influence of the input motion by propagating two different input motions the first being a simple impulsive one and the second a real complex accelerogram we find that transfer functions computed in each basin are quite similar irrespective of the soil constitutive behaviour and the input motion moreover we show that the maximum shear strain spatial distribution depends on the input motion frequency content and maximum values depend on the input motion strength and complexity maximum shear strains are generally higher for superficial layers than for deeper ones we show that the highest shear strain values are located above discontinuities where velocities are lower and the soil is more non linear than in the underlying layer regardless of the input motion indeed in a layered basin the shear strain is higher above interfaces for all the soil constitutive models that were used in the smooth visco elastoplastic model a kind of layering appears absent in a viscoelastic model due to the different non linear properties in each layer moreover no matter what the model structure and the input motion used maximum shear strain levels are higher in the visco elastoplastic soil than in the viscoelastic one such a numerical study helps to understand the non linearity location and therefore the consequences of a model choice when performing a site specific study

types of elastic nonlinearity of sedimentary soils 1 vertical array records of the 1995 kobe earthquake showed clearly nonlinearity of soil behavior although there have been few observational validations earlier scientific publications on soil nonlinearity appeared since 1970 s in theoretical studies nonlinearity has been introduced in constitutive relations as the quadratic correction to hooke s law but the question of the types of soil nonlinearity was not investigated here we show on the basis of data processing and nonlinear system identification technique that sediments represent physical systems possessing mostly odd types of nonlinearity even order nonlinearities become comparable with odd order ones only in special cases like liquefied soils though the even and odd nonlinearities have much in common the frequencies of combination harmonics shapes of seismic solitary waves and other nonlinear phenomena are different in these two cases on the whole the nonlinearity in soils leads to changes in spectra of propagating seismic signals the spectra tending to take the form of e f f n

molluscan faunas and paleobathymetry of holocene sequences in the northeastern nile delta egypt abstract the fossil molluscan component serves as a valuable indicator of the paleobathymetric variations which occurred in the nile delta egypt during the past 7500 years paleobiocoenoses have been identified on the basis of molluscan faunas in three radiocarbon dated cores as part of a long term study to help interpret the holocene evolution of the northeastern delta one of these smithsonian boring s 21 near port said has been selected as a type core because it includes a near complete holocene coarsening upward sequence of distinct open marine to coastal lithofacies typical of this depocenter the fossil molluscan faunas comprising 59 species all of which are presently living in the mediterranean serve to determine approximate changes in paleodepth at this site with time in particular the recognized paleocommunities show a good correspondence with several infralittoral biocoenoses of unconsolidated mud and sand rich substrates of the present mediterranean terrigenous mud fine well sorted sands fine sands in very shallow water and superficial muddy sands in sheltered areas the methodology was applied to two other cores of near comparable age in this region smithsonian core s 31 and boring fadda 1 earlier studied by others these two were also selected because they are characterized by a holocene sequence of marine to coastal lithologies similar to core s 21 the approach used serves to determine temporal and spatial differences in paleobathymetry at the three sites this investigation shows that analysis of the faunas in subsurface sections serves to refine paleoenvironmental interpretations of the nile delta moreover the molluscan paleobiocoenoses are best evaluated in conjunction with the lithofacies in which they occur

in situ assessment of the g γ curve for characterizing the nonlinear response of soil application to the garner valley downhole array and the wildlife liquefaction array abstract we analyze the nonlinear and near surface geological effects of two network for earthquake engineering simulation at university of california santa barbara nees ucsb instrumented sites the garner valley downhole array gvda and the wildlife liquefaction array wla the seismic interferometry by deconvolution method is applied to earthquake data recorded by the multisensor vertical array between january 2005 and september 2013 along the cross section local shear wave velocity is extracted by estimating travel time between sensors the s wave velocity profiles are constructed and compared with classical in situ geophysical surveys we show that velocity values change according to the amplitude of the ground motion and we find anisotropy between east west and north south directions at the gvda site the ratio between average peak particle velocity v and local s wave velocity between two boreholes is tested as a deformation proxy using average peak particle acceleration a the a versus curve is used to represent the stress strain curve for observing the site s nonlinear responses under different levels of excitation nonlinearity is observed from quite low shear strain levels 1 10 5 and a classic hyperbolic model is derived proves to be a good deformation proxy finally the shear modulus degradation curves are constructed for each depth and test site and they are similar to previous laboratory measurements or in situ geophysical surveys a simple comparison regarding nonlinear behavior between gvda and wla is performed

simulation of ground motion from strong earthquakes of kamchatka region 1992 1993 at rock and soil sites to estimate the parameters of ground motion in future strong earthquakes characteristics of radiation and propagation of seismic waves in the kamchatka region were studied regional parameters of radiation and propagation of seismic waves were estimated by comparing simulations of earthquake records with data recorded by stations of the kamchatka strong motion network acceleration time histories of strong earthquakes mw 6 8 7 5 depths 45 55 km that occurred near the eastern coast of kamchatka in 1992 1993 were simulated at rock and soil stations located at epicentral distances of 67 195 km in these calculations the source spectra and the estimates of frequency dependent attenuation and geometrical spreading obtained earlier for kamchatka were used the local seismic wave amplification was estimated based on shallow geophysical site investigations and deep crustal seismic explorations and parameters defining the shapes of the waveforms the duration etc were selected showing the best fit to the observations the estimated parameters of radiation and propagation of seismic waves describe all the studied earthquakes well based on the waveforms of the acceleration time histories models of slip distribution over the fault planes were constructed for the studied earthquakes station pet can be considered as a reference rock station having the minimum site effects the intensity of ground motion at the other studied stations was higher than at pet due to the soil response or other effects primarily topographic ones at soil stations ins aer and dch the parameters of soil profiles homogeneous pyroclastic deposits were estimated and nonlinear models of their behavior in the strong motion were constructed the obtained parameters of radiation and propagation of seismic waves and models of soil behavior can be used for forecasting ground motion in future strong earthquakes in kamchatka

sedimentology faunal content and pollen record of middle pleistocene palustrine and lagoonal sediments from the peri adriatic basin abruzzi eastern central italy abstract a 25 m thick outcrop section exposed at torre mucchia on the sea cliff north of ortona eastern central italy comprises a rare middle pleistocene succession of shallow water and paralic sediments along the western adriatic sea an integrated study of the section including facies and microfacies analyses and characterization of paleobiological associations mollusks fishes ostracods foraminifers and pollen enable a detailed reconstruction of the paleoenvironmental and paleoclimatic conditions during deposition the shallow water deposits include a transgressive deepening and fining upward shoreface to offshore transition facies succession overlain by a regressive shoreface foreshore sandstone body with an erosive base and a rooted and pedogenically altered horizon at the top that imply deposition during sea level fall this forced regressive unit is overlain by paralic strata forming a transgressive succession comprising palustrine carbonates and back barrier lagoonal mudstones the palustrine carbonates exhibit some of the typical features encountered in palustrine limestones deposited within seasonal freshwater wetlands marl prairies following the sea level rising trend the freshwater marshes were abruptly replaced by a barrier lagoon system that allowed deposition of the overlying mud rich unit within these deposits the faunal assemblages are consistent with a low energy brackish environment characterized by a relatively high degree of confinement the pollen record documents the development of open forest vegetation dominated by pinus and accompanied by a number of mesophilous and thermophilous tree taxa whose composition supports a tentative correlation with marine oxygen isotope stage 17 the new pollen record from torre mucchia improves our understanding of the vegetation development in the italian peninsula during the middle pleistocene and sheds new light on the role played by the most marked glacial periods in determining the history of tree taxa

site response estimation for the 2003 miyagi oki earthquake sequence considering nonlinear site response the m w 7 0 miyagi oki earthquake which occurred on 26 may 2003 was well recorded by the kik net and k net networks a large number of stations recorded very high peak ground accelerations above 0 5g and large peak ground velocities above 0 5 m sec these high ground motion values are thought to come from a combination of the effect of shallow sediment layers of the upper couple of meters and the enhanced high frequency ground motion content associated with this intraslab earthquake the objective of this study is to examine the effect of sediment amplification at network stations with peak ground acceleration 0 3g linear site response is first estimated from observed weak motion aftershock records in this case we use a spectral inversion method without reference stations to separate the source path and site response effects the resulting weak motion analysis for the source path and site response agree with other previous studies the mainshock site response is obtained separately using the same spectral inversion technique with the addition of a frequency dependent radiation pattern the comparison of the site am plification from aftershocks with the mainshock indicates the possibility of nonlinear site response at many stations during the mw 7 0 event the results also suggest a correlation between lownear surface materialvelocity and thedegreeofnonlinearity

coseismic and postseismic velocity changes measured by repeating earthquakes 1 repeating earthquakes that rupture approximately the same fault patch and have nearly identical waveforms are a useful tool for measuring temporal changes in wave propagation in the earth s crust since source and path effects are common to all earthquakes in a repeating earthquake sequence multiplet differences in their waveforms can be attributed to changes in the characteristics of the medium we have identified over 20 multiplets containing between 5 and 40 repeating events in the aftershock zones of the 1989 loma prieta and 1984 morgan hill california earthquakes postmain shock events reveal delays of phases in the early s wave coda of as much as 0 2 s relative to premain shock events the delay amounts to a path averaged coseismic velocity decrease of about 1 5 for p waves and 3 5 for s waves since most of the multiplets are aftershocks and follow omori s law we have excellent temporal sampling in the immediate postmain shock period we find that the amplitude of the velocity decrease decays logarithmically in time following the main shock in some cases it returns to the premain shock values while in others it does not similar results are obtained for the morgan hill main shock because the fractional change in s wave velocity is greater than the fractional change in p wave velocity it suggests that the opening or connection of fluid filled fractures is the underlying cause the magnitude of the velocity change implies that low effective pressures are present in the source region of the velocity change our results suggest that the changes are predominantly near the stations and shallow but we cannot exclude the possibility that changes occur at greater depth as well if the variations are shallow we may be detecting the lingering effects of nonlinearity during main shock strong ground motion if the variations are deep it suggests that pore pressures at seismogenic depths are high which would likely play a key role in the earthquake process

urban seismology northridge aftershocks recorded by multi scale arrays of portable digital seismographs we deployed portable digital seismographs in the san fernando valley sfv the los angeles basin lab and surrounding hills to record aftershocks of the 17 january 1994 northridge california earthquake the purpose of the deployment was to investigate factors relevant to seismic zonation in urban areas such as site amplification sedimentary basin effects and the variability of ground motion over short baselines we placed seismographs at 47 sites not all concurrently and recorded about 290 earthquakes with magnitudes up to 5 1 at five stations or more we deployed widely spaced stations for profiles across the san fernando valley as well as five dense arrays apertures of 200 to 500 m in areas of high damage such as the collapsed interstate 10 overpass sherman oaks and the collapsed parking garage at calstate northridge aftershock data analysis indicates a correlation of site amplification with mainshock damage we found several cases where the site amplification depended on the azimuth of the aftershock possibly indicating focusing from basin structures for the parking garage array we found large ground motion variabilities a factor of 2 over 200 m distances for sites on the same mapped soil unit array analysis of the aftershock seismograms demonstrates that sizable arrivals after the direct s waves consist of surface waves traveling from the same azimuth as that of the epicenter these surface waves increase the duration of motions and can have frequencies as high as about 4 hz for the events studied here we do not observe large arrivals reflected from the southern edge of the san fernando valley

evidence for and implications of self healing pulses of slip in earthquake rupture dislocation time histories of models derived from waveforms of seven earthquakes are discussed in each model dislocation rise times the duration of slip for a given point on the fault are found to be short compared to the overall duration of the earthquake 10 however in many crack like numerical models of dynamic rupture the slip duration at a given point is comparable to the overall duration of the rupture i e slip at a given point continues until information is received that the rupture has stopped propagating alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are 1 the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes 2 earthquakes are composed of a sequence of small dimension short duration events that are separated by locked regions barriers 3 rupture occurs in a narrow self healing pulse of slip that travels along the fault surface evidence is discussed that suggests that slip durations are indeed short and that the self healing slip pulse model is the most appropriate explanation a qualitative model is presented that produces self healing slip pulses the key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity the model has the following features high static strength of materials kilobar range low static stress drops in the range of tens of bars and relatively low frictional stress during slip less than several hundreds of bars it is suggested that the reason that the average dislocation scales with fault length is because large amplitude slip pulses are difficult to stop and hence tend to propagate large distances this model may explain why seismicity and ambient stress are low along fault segments that have experienced large earthquakes it also qualitatively explains why the recurrence time for large earthquakes may be irregular

expected seismic shaking in los angeles reduced by san andreas fault zone plasticity computer simulations of large m 7 8 earthquakes rupturing the southern san andreas fault from se to nw e g shakeout widely used for earthquake drills have predicted strong long period ground motions in the densely populated los angeles basin due to channeling of waves through a series of interconnected sedimentary basins recently the importance of this waveguide amplification effect for seismic shaking in the los angeles basin has also been confirmed from observations of the ambient seismic field by simulating the shakeout earthquake scenario based on a kinematic source description for a medium governed by drucker prager plasticity we show that nonlinear material behavior could reduce the earlier predictions of large long period ground motions in the los angeles basin by up to 70 as compared to viscoelastic solutions these reductions are primarily due to yielding near the fault although yielding may also occur in the shallow low velocity deposits of the los angeles basin if cohesions are close to zero fault zone plasticity remains important even for conservative values of cohesions suggesting that current simulations assuming a linear response of rocks are overpredicting ground motions during future large earthquakes on the southern san andreas fault

predicting nonlinear site response using spectral acceleration vs pgv vs30 a case history using the volvi test site in this study we analyze the efficiency of the ratio between particle velocity and shear wave velocity as a strain proxy for evaluating the nonlinear seismic response of sediments the in situ stress strain relationships are derived from accelerometric vertical array recordings at the tst site in volvi thessaloniki greece first the shear wave velocity between two successive sensors was computed by seismic interferometry and strain was computed as the velocity ratio or the relative displacement between sensors the shear wave velocity profile and in situ shear modulus degradation curve with strain were compared with previous studies performed at the tst site finally the stress strain relationships were derived from data recorded at the surface by extending the strain proxy and stress values to the ratio between peak ground velocity and the vs30 parameter used for site classification i e without requiring the accelerometric vertical array our model captures the in situ nonlinear response of the site without consideration of azimuth or distance of the earthquakes in conclusion the acceleration stress values based on the accelerometric response spectra instead of peak ground acceleration compared with the deformation strain proxy provide an effective model of the in situ nonlinear response providing information that can be integrated into ground motion prediction equations

stochastic finite fault modeling of ground motions from the 1994 northridge california earthquake ii widespread nonlinear response at soil sites on average soil sites behaved nonlinearly during the m 6 7 1994 north ridge california earthquake this conclusion follows from an analysis that combines elements of two independent lines of investigation first we apply the stochastic finite fault simulation method calibrated with 28 rock site recordings of the north ridge mainshock to the simulation of the input motions to the soil sites that recorded this event the calibrated model has a near zero average bias in reproducing ground motions at rock sites in the frequency range from 0 1 to 12 5 hz the soil sites selected are those where there is colocation of strong motion acce lerographs and temporary instruments from the northridge aftershock observation network at these sites weak motion amplification functions based on numerous aftershock records have been empirically determined in three separate investigations reported in the literature these empirical weak motion amplification factors can be applied to the simulated input rock motions at each soil site to determine the ex pected motions during the mainshock i e neglecting nonlinearity these expected motions can then be compared to the actual recordings during the mainshock this analysis shows that the recorded strong motion spectra are significantly over estimated if weak motion amplifications are used the null hypothesis stating that the inferred differences between weak and strong motion amplifications are statis tically insignificant is rejected with 95 confidence in the frequency range from approximately 2 2 to 10 hz on average the difference between weak and strong motion amplifications is a factor of 2 nonlinear response at those soil stations for which the input peak acceleration exceeded 150 to 200 cm sec 2 contributes most to this observed average difference these findings suggest a significant nonlinear re sponse at soil stations in the los angeles urban area during the northridge main shock the effect is consistent with the increase in damping of shear waves at high levels of strain which is well known from geotechnical studies of soil properties

changes in shear moduli of liquefied and nonliquefied soils during the 1995 kobe earthquake and its aftershocks at three vertical array sites acceleration records of the 1995 kobe earthquake and its first after shocks provided by vertical arrays at port island pi sgk and tks sites were used to estimate changes in the shear moduli of subsurface soils caused by strong ground motion shear moduli estimates are based on stress strain relations deter mined for consecutive time intervals during the mainshock and aftershocks we found that in the upper 0 13 m at pi reclaimed fill above the groundwater level the shear modulus decreased by 80 90 of its initial value owing to liquefaction signs of its recovery appeared 3 5 min after the decrease in the intensity of strong motion at depths of 13 18 m reclaimed fill below the water level and 27 32 5 m water saturated sand at pi 0 11 m at sgk and 0 14 m at tks water saturated alluvium the shear modulus decrease was estimated at about 80 50 60 60 70 and 50 respectively recovery began immediately after the decrease in the intensity of strong motion and was completed within a few minutes the results show that the behavior of the upper layers at sites pi and sgk where the highest accelerations were recorded was dynamically unstable so far as the method can be applied to any site where vertical array records and profiling data are available ac cumulation of representative data on nonlinear soil behavior during strong motion for various soil conditions is desirable summarizing and generalizing these data we may be able to predict soil behavior in future earthquakes

storm track response to sst fronts in the northwestern pacific region in an agcm abstractthe storm track response to sea surface temperature sst fronts in the northwestern pacific region is investigated using an atmospheric general circulation model with a 50 km horizontal resolution the following two experiments are conducted one with 0 25 daily sst data cntl and the other with smoothed ssts over an area covering sst fronts associated with the kuroshio the kuroshio extension the oyashio and the subpolar front smthk the storm track estimated from the local deepening rate of surface pressure ldr exhibits a prominent peak in this region in cntl in january whereas the storm track peak weakens and moves eastward in smthk storm track differences between cntl and smthk are only found in explosive deepening events with ldr larger than 1 hpa h 1 a diagnostic equation of ldr suggests that latent heat release associated with large scale condensation contributes to the storm track enhancement the sst fronts also affect the large scale atmospheric circulation over the northeast

nonlinear behavior of soils revealed from the records of the 2000 tottori japan earthquake at stations of the digital strong motion network kik net acceleration records of the tottori earthquake 6 october 2000 pro vided by stations of the digital strong motion network kik net show clear evidence of the nonlinearity of soil response at sites located in near fault zones in this study records of the mainshock of the tottori earthquake are analyzed and stresses and strains induced by the strong motion in the upper 100 or 200 m of soil are recon structed at sites located within 80 km from the fault plane for reconstructing stresses and strains the method is applied which we developed and used previously for studying the response of soils during the 1995 kobe earthquake nonlinear time dependent stress strain relations in the soil layers are estimated based on vertical array records a good agreement between the observed and simulated accelerograms of the tottori earthquake testifies to the validity of the obtained vertical distributions of stresses and strains in the soil layers we also evaluated variations of the shear moduli of the soil layers caused by the strong motion at stations located at different distances from the fault plane changes in the rheological properties of the upper soil layers were found at the stations closest to the fault plane a similarity in stress strain relations describing the behavior of similar soils during the 1995 kobe earth quake and the 2000 tottori earthquake was obtained indicating the possibility of precasting soil behavior in future earthquakes at sites where profiling data are available

surface sediments and macrofaunas of the crati submarine fan ionian sea italy abstract five dredge samples 8 grab samples and 18 light gravity cores from the fan delta fed crati submarine fan indicate that the surface cover of the fan is mud dominated comprising muddy turbidites thin bedded silty sandy turbidites and prodelta muds this high mud content does not reflect an abandonment phase of the fan but is the product both of the composition of the sediment load discharged by the crati river and of the littoral processes affecting the constline of the crati fan delta a predominantly northward longshore drift catches most of the coarse bed load and redistributes it along the actively prograding beaches of the fan delta the whole mud reaches the submarine basin via turbidity currents and surficial turbid plumes the biogenic fraction represented by mollusca and benthic foraminifera is scarce because of the high terrigenous input in situ mollusc assemblages which occur only outside the channellized areas vary significantly in composition between the different depositional environments of the fan there is a much higher proportion of filter feeding species in depositional areas more affected by the flow of turbidity currents lobes levees

finite difference modeling of two aftershocks of the 1994 northridge california earthquake recent evidence for nonlinear behavior of strong motions generated by the northridge california earthquake relies explicitly on the analysis of aftershock data thus correcting these observations for propagational and source effects becomes a crucial step in these studies here we demonstrate that the dipping structure near the edges of the san fernando valley can strongly alter the local site responses especially for shallow events we model two aftershocks with similar epicenters but with shallow 4 km and deep 16 km hypocentral depths waveforms from 12 portable instruments deployed across the basin and recording these events were processed and studied in the 0 3 4 hz bandpass for the shallow event distinctive features are a broad direct s phase and large amplitude surface waves at the basin stations and high frequency s phases at stations in the santa monica mountains the deep event is less strongly affected by the basin but displays strong evidence of the source radiation pattern an array analysis indicates 2d propagation for most of the strong arrivals some of these features are explained by a simple 2d basin model containing a strong shallow contrast a factor of 2 jump in seismic velocity at a depth of 1 km within the basin and a moderate deeper gradient

storm track response to ocean fronts in a global high resolution climate model synoptic atmospheric eddies are affected by lower tropospheric air temperature gradients and by turbulent heat fluxes from the surface in this study we examine how ocean fronts affect these quantities and hence the storm tracks we focus on two midlatitude regions where ocean fronts lie close to the storm tracks the north west atlantic and the southern ocean an atmospheric climate model of reasonably high resolution 50 km is applied in a climate length 60 year simulation in order to obtain stable statistics simulations with frontal structure in the sea surface temperature sst in one of the regions are compared against simulations with globally smoothed sst we show that in both regions the ocean fronts have a strong influence on the transient eddy heat and moisture fluxes not just in the boundary layer but also in the free troposphere local differences in these quantities between the simulations reach 20 40 of the maximum values in the simulation with smoothed sst averaged over the entire region of the storm track over the ocean the corresponding differences are 10 20 the effect on the transient eddy meridional wind variance is strong in the boundary layer but relatively weak above that the potential mechanisms by which the ocean fronts influence the storm tracks are discussed and our results are compared against previous studies with regional models aquaplanet models and coarse resolution coupled models

interdecadal variability of the pacific ocean model response to observed heat flux and wind stress anomalies variability of the pacific ocean is examined in numerical simulations with an ocean general circulation model forced by observed anomalies of surface heat flux wind stress and turbulent kinetic energy tke over the period 1970 88 the model captures the 1976 77 winter time climate shift in sea surface temperature as well as its monthly seasonal and longer term variability as evidenced in regional time series and empirical orthogonal function analyses examination of the surface mixed layer heat budget reveals that the 1976 77 shift was caused by a unique concurrance of sustained heat flux input anomalies and very strong horizontal advection anomalies during a multi month period preceding the shift in both the central pacific region where cooling occurred and the california coastal region where warming occurred in the central pacific the warm conditions preceding and the cold conditions following the shift tend to be maintained by anomalous vertical mixing due to increases in the atmospheric momentum flux tke input into the mixed layer which deepens in the model after the shift from the early 1970s to the late 1970s and 1980s since the ocean model does not contain feedback to the atmosphere and it succeeds in capturing the major features of the 1976 77 shift it appears that the midlatitude part of the shift was driven by the atmosphere although effects of midlatitude ocean atmosphere feedback are still possible the surface mixed layer heat budget also reveals that in the central pacific the effects of heat flux input and vertical mixing anomalies are comparable in amplitude while horizontal advection anomalies are roughly half that size in the california coastal region in contrast where wind variability is much weaker than in the central pacific horizontal advection and vertical mixing effects on the mixed layer heat budget are only one quarter the size of typical heat flux input anomalies

a modeling study of the relative roles of tropical and extratropical sst anomalies in the variability of the global atmosphere ocean system abstract in three parallel experiments an atmospheric general circulation model has been subjected to observed monthly varying sea surface temperature ssi conditions in each of the following domains near global ocean goga run tropical pacific toga run and midlatitude north pacific moga run four independent realizations were obtained for the model response to the sequence of sst anomalies during the 1946 88 period in each of the above regions the principal modes of coupling between the imposed sst forcing and the simulated northern hemisphere wintertime 5 1 5 mb height field in various experiments have been identified using a singular value decomposition svd procedure the leading svd mode for the goga experiment is qualitatively similar to that based on observational data although the amplitudes of the simulated height anomalies are notably lower than the observed value the sst pattern of this mode resembles that associated with el nino events the accompanying 5 1 5 mb height anomaly i

replication of apparent nonlinear seismic response with linear wave propagation models it is necessary to understand ground motion amplification by sediment defined as the ratio of ground motions at sediment sites to those at rock sites to predict seismic loadings for earthquake engineering at sediment sites observed weak motion amplifications from magnitude 3 to 4 aftershocks of the 1994 northridge earthquake were twice as large as magnitude 6 7 mainshock amplifications amplitude dependent nonlinear amplification by sediment is one explanation however earthquake simulations with empirical impulse responses and elastic finite difference calculations with weakly heterogeneous random three dimensional 3d crustal velocity variations show that linear wave propagation can explain observed apparently nonlinear sediment responses random 3d velocity variations also reproduce the observed log normal dispersion of peak ground motions deterministic wave propagation models are not adequate to quantify the scaling and dispersion of near source ground motions

benthic biofacies to interpret holocene environmental changes and human impact in alexandria s eastern harbour egypt holocene molluscan and foraminiferal faunas sensitive ecological markers are statistically treated to define their temporal and spatial distributions in radiocarbon dated cores in alexandria s eastern harbour up core variations of these benthic biofacies record the evolution of depositional environments during the past 8000 years in this long occupied eastern mediterranean port the most important change occurred in the mid holocene between 6300 and 4300 yr ago a time of lower sea level and minimal human activity this faunal change indicating a transition from a somewhat protected to a more open and higher energy marine environment resulted primarily from rise of sea level lowering of the harbour floor and diminished shielding by pleistocene coastal ridges and reefs near the bay mouth and within the harbour since that time faunal assemblages have remained generally constant except during the period from 2100 to 1800 yr ago when greeks and romans built the heptastadion that connected alexandria to pharos island this construction effectively separated the eastern from the western harbour absence of a well marked faunal change during the past 18 centuries is unexpected particularly in light of the much increased population and associated human effects the harbour s overall large size rise in relative sea level and continued exchange of marine water between the open shelf and port have maintained an active circulation pattern the strong current regime and reworking of bottom sediments have generally masked short term human effects and altered the harbour s late holocene sediment stratigraphy these factors help explain why benthic biofacies primarily record influences of natural processes that prevailed in this relatively unconfined high energy marine setting rather than those of a more constricted and anthropogenically impacted port

scenario shakemaps for ottawa canada ottawa ranks third among canadian urban areas in terms of seismic risk scenario shakemaps are generated for the ottawa region to study the expected ground shaking intensity distribution patterns for input to damage and risk studies variability in near surface geology plays an important role in earthquake ground shaking in the region the quarter wavelength method is used to generate frequency dependent amplification functions for typical generic soil profiles across the city using shear wave velocity and depth to bedrock data from 17 250 compiled soil profiles the methodology is validated using the ground motion and did you feel it records from the 2010 m 5 val des bois earthquake which occurred 60 km from ottawa it is noted that the calculated amplifications for typical ottawa soil profiles are often greater than generic national earthquake hazards reduction program factors as applied in building code applications for a scenario earthquake corresponding to the national building code of canada probability level of graphic 1 expected modified mercalli intensity values in soft soil areas of ottawa would be near 7 on average the impact of event location on expected ground motions and intensities was tested by considering the occurrence of a scenario earthquake a given magnitude event at various locations in the region the results of this study may be used as input to seismic risk studies for ottawa 1 embed inline graphic 1 gif

nonlinearity liquefaction and velocity variation of soft soil layers in port island kobe during the hyogo ken nanbu earthquake clear nonlinear behavior is analyzed from the acceleration records of the 1995 hyogo ken nanbu earthquake at port island kobe from four triaxial in struments placed at four different depths the surficial effects during strong ground motions were compared with those during weak motions before and after the main shock we used a spectral ratio technique and a nonlinear inversion for velocity structure to analyze the data from the spectral analysis we observed a large variation of the spectral ratios between the surface and different depths during the strong ground motions and during the liquefied state the spectral ratios after the mainshock i e after the liquefied state are different from those before the mainshock the peak frequencies in the spectral ratios after the mainshock are shifted to lower fre quencies with respect to those in the spectral ratios before the mainshock we in verted the s wave velocities using a genetic algorithm technique to determine the velocity structure before during and after the mainshock the s wave velocity struc ture before and after the mainshock was found to be different specifically the s wave velocity of the second layer 5 m to 16 m depth after the mainshock was 20 lower than before our analysis shows that the liquefied state remains at least 3 hr after the mainshock but no more than 24 hr the rigidity of the soil decreased close to zero when liquefaction happened and later increases gradually following a trend that resembles a consolidation curve the strong influence of nonlinearity during the mainshock yielded a big reduction of the horizontal surface ground motions so that the observed horizontal peak acceleration was only about 25 of the peak acceler ation expected from the linear theory however the nonlinear effects in the vertical peak acceleration were not significant

kuroshio extension variability and forcing of the pacific decadal oscillations responses and potential feedback abstract a forcing mechanism is sought for the large scale circulation changes in the kuroshio extension region of the western north pacific ocean as inferred by topex poseidon sea surface height ssh data the low frequency signal of the kuroshio extension over the last decade was characterized by a modulation in its zonal mean flow intensity the mean kuroshio extension jet weakened progressively from 1993 to 1996 and this trend reversed after 1997 the ability to simulate the major trends in the observed ssh signals with linear vorticity dynamics leads the authors to conclude that the modulation in the zonal mean jet was remotely forced by wind stress curl anomalies in the eastern north pacific ocean related to the pacific decadal oscillations pdos to be specific the weakening strengthening trend in 1993 96 1997 2001 was caused by westward expansions of negative positive ssh anomalies south of the kuroshio extension and positive negative ssh anomalies north of the kuroshio extension emerg

role of ocean mesoscale structures in shaping the angola low pressure system and the southern africa rainfall southern african climate is under the influence of both tropical and subtropical systems which result in a complex region where important interactions co exist over a large spectrum of spatiotemporal scales the angola low al situated on boundary between tropical and subtropical southern africa has been diagnosed as a key driver of moisture distribution in the region on daily to seasonal time scales it has been demonstrated that the al pressure system is sensitive to the dynamics of the neighbouring oceans but to date no study has considered the model resolution of air sea interactions required to simulate this sensitivity using sensitivity experiments with a regional atmospheric model which differ only in the mesoscale sea surface temperature sst forcing characteristics either the full spectrum of sst variability or only its large scale components are included we first quantify the importance of sst gradients on the al strength and variability the results suggest that the mesoscale sst variability of the angola benguela frontal zone abfz plays a key role in al activity particularly during the late summer synoptic scale tropical lows which form the al are automatically detected and the results suggest more extreme events occur when the model is forced by mesoscale ssts everywhere and in the abfz area only the rainfall resulting from those events suggests that tropical low episodes are associated with nearly 15 of the total rain in angola and namibia the link between al dynamics and wet spells is also discussed with the former showing a different spatial pattern as well as frequency when the ocean is fully resolved

marine and nonmarine deposition in a long term low accommodation setting an example from the middle pleistocene qm2 unit eastern central italy abstract facies anatomy and large scale stratigraphic organization of mid pleistocene strata qm2 unit exposed near the town of ortona eastern central italy have been defined through an integrated outcrop and subsurface dataset and record sedimentation within a long term low accommodation setting the studied interval can be subdivided into nine facies associations reflecting a range of continental marginal marine nearshore and innermost shelf environments and contains a well preserved record of high frequency relative sea level changes in the form of a stack of three unconformity bounded sequences each of the three sequences designated qm23 qm22 and qm21 from oldest to youngest consists of a specific subset of the nine identified facies associations as a function of preserved depositional systems and systems tracts typically the following architectural elements occur in ascending stratigraphic order i a basal unconformity molded by fluvial incision and subaerial exposure during sea level fall and shoreface erosion during subsequent rise ii a maximum regressive surface which is coincident with the sequence boundary iii a transgressive systems tract including braided river conglomerates and floodplain fines within the confines of an incised valley palustrine carbonates and back barrier lagoon mudstones and a deepening and fining upward shoreface to offshore transition facies succession bounded at the base by a wave ravinement surface iv a sharp regressive surface of marine erosion produced by shoreface incision during relative sea level fall and v a prograding downstepping and offlapping sharp based lithofacies assemblage of either beach conglomerates or sandstones ascribed to the falling stage systems tract overlain by a rooted paleosol marking subaerial exposure sequences were deposited on the uplifting palaeo adriatic shelf in response to repeated high frequency and high amplitude eustatic changes in sea level that would promote the creation of accommodation space by subtracting space to deposition the contemporaneous regional uplift of the basin margin may be accounted for the shingled downstepping configuration of individual sequences to form a falling stage sequence set of a larger composite sequence in dip view the erosional contact at the base of the qm2 falling stage sequence set is a composite regressive surface resulting from the downdip convergence and amalgamation of multiple erosional surfaces produced by the progressive basinward translation of successive sequences results from this study have direct implications for the oil and gas field development and exploration when making predictions of reservoir and seal geometries within shallow marine marginal marine and nonmarine sediments emplaced in similar long term limited accommodation settings

nature of the differences in the intraseasonal variability of the pacific and atlantic storm tracks a diagnostic study abstract on the basis of an intraseasonal variability index of storm track evaluated for 40 winters 1963 64 through 2003 04 of ncep ncar reanalysis data it is found that well defined midwinter minimum mwmin midwinter maximum mwmax occurs in 21 8 winters over the north pacific in contrast mwmin mwmax occurs in 4 25 of the 40 winters over the north atlantic the power spectrum of such an index for the pacific has a broad peak between 5 and 10 yr whereas the spectrum of the index for the atlantic has comparable power in two spectral bands 2 2 8 and 3 5 8 yr over the north pacific the increase in the zonal asymmetry of the background baroclinicity as well as in the corresponding horizontal deformation of the time mean jet from early late winter to midwinter is distinctly larger in an mwmin winter associated with these changes there is a distinctly stronger barotropic damping rate in the january of an mwmin winter the increase in the net conversion rate of eddy kinetic energy from early

northern winter stationary waves theory and modeling a review is provided of stationary wave theory the theory for the deviations from zonal symmetry of the climate to help focus the discussion the authors concentrate exclusively on northern winter several theoretical issues including the external rossby wave dispersion relation and vertical structure critical latitude absorption the nonlinear response to orography and the interaction of forced wave trains with preexisting zonal asymmetries are chosen for discussion while simultaneously presenting a decomposition of the wintertime stationary wave field using a nonlinear steady state model

model projections of the changes in atmospheric circulation and surface climate over north america the north atlantic and europe in the twenty first century abstractthe impacts of climate change on the north america north atlantic europe sector are studied using a coupled general circulation model the climate model version 3 cm3 and a high resolution atmosphere only model the high resolution atmospheric model hiram both developed at the geophysical fluid dynamics laboratory the cm3 experiment is conducted under two climate change scenarios for the 1860 2100 period the sea surface temperature sst forcing prescribed in the time slice integrations with hiram is derived from observations for the 1979 2008 period and projection by cm3 for the 2086 95 period the wintertime response in the late twenty first century is characterized by an enhancement of the positive phase of the north atlantic oscillation in sea level pressure slp and poleward and eastward displacements of the atlantic jet stream and storm track the forcing pattern due to eddy vorticity fluxes in the perturbed storm track matches well with the response pattern of the slp field in the

nonlinear soil response a reality geotechnical models consistently indicate that the stress strain relationship of soils is nonlinear and hysteretic especially at shear strains larger than 10 5 to 10 4 nonlinear effects such as an increase in damping and reduction in shear wave velocity as excitation strength increases are commonly recognized in the dynamic loading of soils on the other hand these effects are usually ignored in seismological models of ground motion prediction because of the lack of compelling corroborative evidence from strong motion observations the situation is being changed by recently obtained data explicit evidence of strong motion deamplification accompanied by changes in resonant frequencies are found in the data from the 1985 michoacan mexico and the 1989 loma prieta california earthquakes the events recorded by the vertical and surface accelerograph arrays in taiwan as well as a number of other events throughout the world evidence of nonlinear behavior becomes apparent beyond a threshold acceleration of 100 to 200 gal nonlinearity is considerable in cohesionless soil but may be negligible in stiff soils the findings of recent years indicate that nonlinear site effects are more common than previously recognized in strong motion seismology

site amplification in the san fernando valley california variability of site effect estimation using the s wave coda and h v methods during the months that followed the 17 january 1994 m 6 7 northridge california earthquake portable digital seismic stations were deployed in the san fernando basin to record aftershock data and estimate site amplification factors this study analyzes data recorded on 31 three component stations from 38 aftershocks ranging from m 3 0 to m 5 1 and depths from 0 2 to 19 km site responses from the 31 stations are estimated from coda waves s waves and ratios of horizontal to vertical h v recordings for the coda and the s waves site response is estimated using both direct spectral ratios and a generalized inversion scheme results from the inversions indicate that the effect of qs can be significant especially at high frequencies site amplifications estimated from the coda of the vertical and horizontal components can be significantly different from each other depending on the choice of the reference site the difference is reduced when an average of six rock sites is used as a reference site in addition when using this multi reference site the coda amplification from rock sites is usually within a factor of 2 of the amplification determined from the direct spectral ratios and the inversion of the s waves however for nonrock sites the coda amplification can be larger by a factor of 2 or more when compared with the amplification estimated from the direct spectral ratios and the inversion of the s waves the h v method for estimating site response is found to extract the same predominant peaks as the direct spectral ratio and the inversion methods the amplifications determined from the hiv method are however different from the amplifications determined from the other methods finally the stations were grouped into classes based on two different classifications general geology and a more detailed classification using a quaternary geology map for the los angeles and san fernando areas average site response estimates using the site characterization based on the detailed geology show better correlation between amplification and surface geology than the general geology classification

pliocene pleistocene sequences bounded by subaerial unconformities within foramol ramp calcarenites and mixed deposits salento se italy nine discrete metre scale sequences of early pliocene to middle pleistocene age were deposited in the small novoli graben salento peninsula puglia s italy they consist of carbonate and mixed carbonate siliciclastic sediments deposited on a slowly subsiding foreland ramp skeletal concentrations and intervening less fossiliferous intervals have been examined to provide information on major environmental parameters and infer the dynamics of their changes taphonomic and palaeoecological analyses indicate that storm induced waves and currents reduced sediment input and settling behaviour of components were the main factors controlling the features of the various shellbed types the concentrations were formed below fair weather wave base in low stress inner to outer shelf environments and are often associated with surfaces or intervals that are characterized by sedimentary condensation vertical change in the fossil content within individual cycles indicates water depth changes that were parallel to climatic fluctuations hence may result from glacio eustatic sea level changes most sequences are bounded by subaerial karstic unconformities because of the regional setting of low subsidence rate the record of the relative sea level fluctuations is incomplete episodes of subaerial exposure and concomitant effects of vadose diagenesis are documented by i diagenetic changes leading to hardening of unconformity horizons ii local subvertical solution pits developed in the vadose zone below unconformity surfaces iii networks of polygonal cracks below unconformities and iv infilling of solution pits and polygonal cracks with vadose silt and marine sediment inwashed during transgressions following the subaerial stages lower sequences are characterized by tighter cementation and significant increase in moldic and vuggy porosity due to superimposition of the diagenetic effects of repeated high amplitude sea level fluctuations

characteristics of soil response in near fault zones during the 1999 chi chi taiwan earthquake distribution of parameters characterizing soil response during the 1999 chi chi taiwan earthquake mw 7 6 around the fault plane is studied the results of stochastic finite fault simulations performed in pavlenko and wen 2008 and constructed models of soil behavior at 31 soil sites were used for the estimation of amplification of seismic waves in soil layers average stresses strains and shear moduli reduction in the upper 30 m of soil as well as nonlinear components of soil response during the chi chi earthquake amplification factors were found to increase with increasing distance from the fault or with decreasing the level of input motion to soil layers whereas average stresses and strains shear moduli reduction and nonlinear components of soil response decrease with distance as r 1 the area of strong nonlinearity where soil behavior is substantially nonlinear the content of nonlinear components in soil response is more than 40 50 of the intensity of the response and spectra of oscillations on the surface take the smoothed form close to e f f n is located within 20 25 km from the fault plane 1 4 of its length nonlinearity decreases with increasing distance from the fault and at 40 50 km from the fault 1 2 of the fault length soil response becomes virtually linear comparing soil behavior in near fault zones during the 1999 chi chi the 1995 kobe mw 6 8 and the 2000 tottori japan mw 6 7 earthquakes we found similarity in the behavior of similar soils and predominance of the hard type of soil behavior resonant phenomena in upper soil layers were observed at many studied sites however during the chi chi earthquake they involved deeper layers down to 40 60 m than during lesser magnitude kobe and tottori earthquakes

late pleistocene and holocene sedimentary facies on the ebro continental shelf abstract late pleistocene holocene history of the ebro continental shelf of northeastern spain is recorded in two main sedimentary units 1 a lower transgressive unit that covers the shelf and is exposed on the outer shelf south of 40 40 n and 2 an upper progradational prodeltaic unit that borders the ebro delta and extends southward along the inner shelf the lower transgressive unit includes a large linear shoal found at a water depth of 90 m and hardground mounds at water depths of 70 80 m some patches of earlier pleistocene prodelta mud remain also exposed or covered by a thin veneer of transgressive sand on the northern outer shelf this relict sand sheet is 2 3 m thick and contains 9000 12 500 yr old oyster and other shells at water depths of 78 88 m the upper prodelta unit covers most of the inner shelf from water depths of 20 80 m and extends from the present ebro river delta to an area to the southwest where the unit progressively thins and narrows interpretation of high resolution seismic reflection data shows the following facies occurring progressively offshore 1 a thick stratified facies with thin progradational foresets beds 2 a faintly laminated facies with sparse reflectors of low continuity and 3 a thin transparent bottomset facies underlain by a prominent flat lying reflector deposition in the northern half of the prodelta began as soon as the shoreline transgressed over the mid shelf but progradation of the southern half did not begin until about 1000 3000 yrs after the transgression a classic deltaic progradational sequence is shown in the ebro prodelta mud by 1 gradation of seismic facies away from the delta 2 coarsening upward sequences near the delta and fining upward sequences in the distal mud belt deposits and 3 thin storm sand layers and shell lags in the nearshore stratified facies the boundaries of the prodeltaic unit are controlled by increased current speeds on the outer shelf where the shelf narrows and by development of the shoreface sand body resulting from shoaling waves on the inner shelf

storm track dynamics this paper reviews the current state of observational theoretical and modeling knowledge of the midlatitude storm tracks of the northern hemisphere cool season observed storm track structures and variations form the first part of the review the climatological storm track structure is described and the seasonal interannual and interdecadal storm track variations are discussed in particular the observation that the pacific storm track exhibits a marked minimum during midwinter when the background baroclinicity is strongest and a new finding that storm tracks exhibit notable variations in their intensity on decadal timescales are highlighted as challenges that any comprehensive storm track theory or model has to be able to address physical processes important to storm track dynamics make up the second part of the review the roles played by baroclinic processes linear instability downstream development barotropic modulation and diabatic heating are discussed understanding of these processes forms the core of our current theoretical knowledge of storm track dynamics and provides a context within which both observational and modeling results can be interpreted the eddy energy budget is presented to show that all of these processes are important in the maintenance of the storm tracks the final part of the review deals with the ability to model storm tracks the success as well as remaining problems in idealized storm track modeling which is based on a linearized dynamical system are discussed perhaps on a more pragmatic side it is pointed out that while the current generation of atmospheric general circulation models faithfully reproduce the climatological storm track structure and to a certain extent the seasonal and enso related interannual variations of storm tracks in depth comparisons between observed and modeled storm track variations are still lacking

identification of the non linear behaviour of liquefied and non liquefied soils during the 1995 kobe earthquake summary a method based on the non linear system identification technique is suggested for estimating the contents of the non linear components which are the result of quadratic cubic and higherorder non linearities in the ground response during the strong motion the method is applied to data from the near fault zone of the 1995 kobe earthquake and the contents of linear and non linear components in the ground response changing with time during the strong motion are estimated for port island pi sgk and tks sites located at 2 6 and 15 km from the fault plane respectively at pi the non linear part of the response increased with developing liquefaction it was as high as 40 60 per cent of the intensity of the response at sgk and tks sites the non linear components of the response did not exceed 40 and 13 per cent of the intensity of the response respectively odd order non linear components predominated in the soil response whereas even order non linear components increased and became comparable with odd order ones in liquefied soils and in cases of high intensity of the strong motion when the loading parts of the stress strain relations of the upper layers gained noticeable even components as a whole the contents of odd order and even order components in the soil response are determined by the shapes of the stress strain relations in the upper most non linear soil layers at the three sites changes in spectra of earthquake signals in subsurface soil layers were substantial as a result of the high non linearity of the soil behaviour and spectra of signals on the surface tend to take the form of e f f k the limiting spectral shape was achieved during the kobe earthquake at pi and sgk sites the proposed methods for processing vertical array records allow understanding of seismic wave transformations in subsurface soils and are useful for predicting the soil behaviour during future earthquakes

influence of small scale north atlantic sea surface temperature patterns on the marine boundary layer and free troposphere a study using the atmospheric arpege model a high resolution global atmospheric model is used to investigate the influence of the representation of small scale north atlantic sea surface temperature sst patterns on the atmosphere during boreal winter two ensembles of forced simulations are performed and compared in the first ensemble hres the full spatial resolution of the sst is maintained while small scale features are smoothed out in the gulf stream region for the second ensemble smth the model shows a reasonable climatology in term of large scale circulation and air sea interaction coefficient when compared to reanalyses and satellite observations respectively the impact of small scale sst patterns as depicted by differences between hres and smth shows a strong meso scale local mean response in terms of surface heat fluxes convective precipitation and to a lesser extent cloudiness the main mechanism behind these statistical differences is that of a simple hydrostatic pressure adjustment related to increased sst and marine atmospheric boundary layer temperature gradient along the north atlantic sst front the model response to small scale sst patterns also includes remote large scale effects upper tropospheric winds show a decrease downstream of the eddy driven jet maxima over the central north atlantic while the subtropical jet exhibits a significant northward shift in particular over the eastern mediterranean region significant changes are simulated in regard to the north atlantic storm track such as a southward shift of the storm density off the coast of north america towards the maximum sst gradient a storm density decrease is also depicted over greenland and the nordic seas while a significant increase is seen over the northern part of the mediterranean basin changes in rossby wave breaking frequencies and weather regimes spatial patterns are shown to be associated to the jets and storm track changes

upper miocene molluscs of monti livornesi tuscany italy biotic changes across environmental gradients abstract the upper miocene mollusc assemblages of monti livornesi used as a means to study the nature of mediterranean benthic communities at the edge of the messinian salinity crisis are framed in a high resolution stratigraphic scheme and quantitatively approached by the study of historical museum collections and modern samples instead of a single assemblage from either tortonian or messinian age as previously thought this fauna comes from three consecutive shallowing upward depositional sequences bounded by regional unconformities the luppiano upper tortonian lowermost messinian rosignano and raquese units early messinian facies analysis taphonomy and quantitative paleoecology show that the luppiano assemblage is characterised by aragonitic species from a eutrophic brackish water shallow marine muddy bottom the rosignano assemblage by calcitic species from an oligotrophic coarse grained seafloor close to a coral reef and the raquese assemblage from an open marine muddy bottom published comparisons between miocene and pliocene faunal lists should be considered only crude estimates of faunal change until more is known about the distribution of species along paleoenvironmental gradients the analysis of miocene and pliocene abundance data allows us to frame the monti livornesi molluscs along carbonate siliciclastic and water depth gradients and to reach a better understanding of the effects of salinity crisis on the mediterranean biota

inducing in situ nonlinear soil response applying an active source 1 it is well known that soil sites have a profound effect on ground motion during large earthquakes the complex structure of soil deposits and the highly nonlinear constitutive behavior of soils largely control nonlinear site response at soil sites measurements of nonlinear soil response under natural conditions are critical to advancing our understanding of soil behavior during earthquakes many factors limit the use of earthquake observations to estimate nonlinear site response such that quantitative characterization of nonlinear behavior relies almost exclusively on laboratory experiments and modeling of wave propagation here we introduce a new method for in situ characterization of the nonlinear behavior of a natural soil formation using measurements obtained immediately adjacent to a large vibrator source to our knowledge we are the first group to propose and test such an approach employing a large surface vibrator as a source we measure the nonlinear behavior of the soil by incrementally increasing the source amplitude over a range of frequencies and monitoring changes in the output spectra we apply a homodyne algorithm for measuring spectral amplitudes which provides robust signal to noise ratios at the frequencies of interest spectral ratios are computed between the receivers and the source as well as receiver pairs located in an array adjacent to the source providing the means to separate source and near source nonlinearity from pervasive nonlinearity in the soil column we find clear evidence of nonlinearity in significant decreases in the frequency of peak spectral ratios corresponding to material softening with amplitude observed across the array as the source amplitude is increased the observed peak shifts are consistent with laboratory measurements of soil nonlinearity our results provide constraints for future numerical modeling studies of strong ground motion during earthquakes

wind driven shifts in the latitude of the kuroshio oyashio extension and generation of sst anomalies on decadal timescales abstract the causes of decadal variations of north pacific sea surface temperatures ssts are examined using a hindcast performed with an ocean general circulation model thermodynamically coupled to an atmospheric mixed layer model ogcm aml model and forced by the time history of observed surface winds the shift in north pacific ocean climate that occurred around 1976 77 is focused on since this is the best observed example available after the 1976 77 shift the aleutian low deepened and moved to the southeast of its previous position this placed anomalous cyclonic flow over the north pacific the sst response as simulated by the ocean model consisted of two components a fast and local part and a delayed and remote part in the central pacific stronger westerlies cool the ocean by increased equatorward ekman drift here the dynamical cooling is sufficiently large that the surface fluxes damp the sst anomaly this ekman response is fast and local and cools the ssts beginning in 1977 and persistin

molluscan palaeoecology and sedimentological features an integrated approach from the miocene meduna section northern italy molluscs were studied to reconstruct the palaeoenvironmental conditions of the miocene sequence of the torrente meduna area friuli northern italy and to compare palaeobiological results with those of an earlier sedimentological analysis the study identifies six fossil communities and relevant individual assemblages and ascribes them to palaeobiocoenoses comparable to modern mediterranean ones introduced by french marine ecologists 1 chlamys praescabriuscula community 2 pecten burdigalensis community 3 loripes dentatus assemblage 4 protoma rotifera community 5 benus ancilla assemblage and 6 venus conus community the palaeobiological analysis demonstrates that the entire miocene sequence up to the late tortonian or very early messinian was deposited within the infralittoral zone at shallow to very shallow depths onto wave influenced bottoms the greatest water depth occurred during early tortonian and was of approximately 25 m palaeobiological and sedimentological methods provide different sets of information which complement each other efficiently general environmental conditions in this case a delta influenced environment can best be reconstructed on the basis of sedimentological data however specific aspects of the environment primarily palaeobathymetry may only be interpreted by means of through palaeobiological analysis

what is a reference site many methods for estimating site response compare ground motions at sites of interest to a nearby rock site that is considered a reference motion the critical assumption in these methods is that the surface rock site record reference is equivalent to the input motion at the base of the soil layers data collected in this study show that surface rock sites can have a site response of their own which could lead to an underestimation of the seismic hazard when these sites are used as reference sites data were collected from local and regional earthquakes on digital recorders both at the surface and in boreholes at two rock sites and one basin site in the san jacinto mountains southern california the two rock sites keenwild and pinon flat are located on granitic bedrock of the southern california peninsular ranges batholith the basin site garner valley is an ancestral lake bed with watersaturated sediments on top of a section of decomposed granite which overlies the competent bedrock ground motion is recorded simultaneously at the surface and in the bedrock at all three sites when the surface rock sites are used as the reference site i e the surface rock motion is used as the input to the basin the computed amplification underestimates the actual amplification at the basin site for frequencies above 2 to 5 hz this underestimation by a factor of 2 to 4 depending on frequency and site results from the rock sites having a site response of their own above the 2 to 5 hz frequencies the near surface weathering and cracking of the bedrock affects the recorded ground motions at frequencies of engineering interest even at sites that appear to be located on competent crystalline rock the bedrock borehole ground motion can be used as the reference motion but the effect of the downgoing wave field and the resulting destructive interference must be considered this destructive interference may produce pseudo resonances in the spectral amplification estimates if one is careful the bedrock borehole ground motion can be considered a good reference site for seismic hazard analysis even at distances as large as 20 km from the soil site

seismic ground motion hazard mapping incorporating site effects for los angeles orange and ventura counties california a geographical information system application abstract the seismic ground motion hazard with site conditions incorporated is mapped for a 10 probability of exceedance in 50 years for the three counties affected by the 1994 northridge earthquake mw 6 7 the source model of petersen et al 1996 was used to calculate peak horizontal acceleration pga and 5 damped spectral acceleration sa levels at 0 3 and 1 sec periods for alluvium soft rock and hard rock site conditions a geologic map that differentiates the three site conditions was produced using shear wave velocity maps of tinsley and fumal 1985 and extended into other areas that were not mapped by tinsley and fumal using 1 250 000 scale geologic maps ground motion maps for each site condition were overlaid with the geologic map to produce the resulting hazard maps the effect of geology on the hazard is observed only slightly in the peak ground acceleration map more in the 0 3 sec sa map and significantly more in the 1 sec sa map the uncertainties for ground motions represented on these three maps ranges from 0 1 to 0 3 g for pga and 0 2 to 1 0 for sa in general 95 confidence limits are about 50 of the mean ground motion value

the slip history of the 1994 northridge california earthquake determined from strong motion teleseismic gps and leveling data we present a rupture model of the northridge earthquake determined from the joint inversion of near source strong ground motion recordings p and sh teleseismic body waves global positioning system gps displacement vectors and permanent uplift measured along leveling lines the fault is defined to strike 122 and dip 40 to the south southwest the average rake vector is determined to be 101 and average slip is 1 3 m the peak slip reaches about 3 m our estimate of the seismic moment is 1 3 0 2 10 26 dyne cm potency of 0 4 km3 the rupture area is small relative to the overall aftershock dimensions and is approximately 15 km along strike nearly 20 km in the dip direction and there is no indication of slip shallower than about 5 to 6 km the up dip strong motion velocity waveforms are dominated by large s wave pulses attributed to source directivity and are comprised of at least 2 to 3 distinct arrivals a few seconds apart stations at southern azimuths indicate two main s wave arrivals separated longer in time about 4 to 5 sec these observations are best modeled with a complex distribution of subevents the initial s wave arrival comes from an asperity that begins at the hypocenter and extends up dip and to the north where a second larger subevent is centered about 12 km away the secondary s arrivals at southern azimuths are best fit with additional energy radiation from another high slip region at a depth of 19 km 8 km west of the hypocenter the resolving power of the individual data sets is examined by predicting the geodetic gps and leveling displacements with the dislocation model determined from the waveform data and vice versa and also by analyzing how well the teleseismic solution predicts the recorded strong motions the general features of the geodetic displacements are not well predicted from the model determined independently from the strong motion data likewise the slip model determined from geodetic data does not adequately reproduce the strong motion characteristics whereas a particularly smooth slip pattern is sufficient to satisfy the geodetic data the strong motion and teleseismic data require a more heterogeneous slip distribution in order to reproduce the velocity amplitudes and frequency content although the teleseismic model can adequately reproduce the overall amplitude and frequency content of the strong motion velocity recordings it does a poor job of predicting the geodetic data consequently a robust representation of the slip history and heterogeneity requires a combined analysis of these data sets

the signature of the midlatitude tropospheric storm tracks in the surface winds abstract storm track analysis is applied to the meridional winds at 10 m and 850 hpa for the winters of 1999 2006 the analysis is focused on the north atlantic and north pacific ocean basins and the southern ocean spanning the region south of the indian ocean the spatial patterns that emerge from the analysis of the 850 hpa winds are the typical free tropospheric storm tracks the spatial patterns that emerge from the analysis of the surface winds differ from the free tropospheric storm tracks the spatial differences between the surface and free tropospheric storm tracks can be explained by the influence of the spatial variability in the instability of the atmospheric boundary layer strongly unstable boundary layers allow greater downward mixing of free tropospheric momentum momentum mixing and this may be the cause of the stronger surface storm tracks in regions with greater instability in the time mean principal component analysis suggests that the basin scale variability that is reflected in th

seasonal evolutions of atmospheric response to decadal sst anomalies in the north pacific subarctic frontal zone observations and a coupled model simulation abstractpotential impacts of pronounced decadal scale variations in the north pacific sea surface temperature sst that tend to be confined to the subarctic frontal zone safz upon seasonally varying atmospheric states are investigated by using 48 yr observational data and a 120 yr simulation with an ocean atmosphere coupled general circulation model cgcm sst fields based on in situ observations and the ocean component of the cgcm have horizontal resolutions of 2 0 and 0 5 respectively which can reasonably resolve frontal sst gradient across the safz both the observations and cgcm simulation provide a consistent picture between sst anomalies in the safz yielded by its decadal scale meridional displacement and their association with atmospheric anomalies correlated with sst anomalies persistent in the safz from fall to winter a coherent decadal scale signal in the wintertime atmospheric circulation over the north pacific starts emerging in november and develops into an equivalent barotropic an

temporal changes of shallow seismic velocity around the karadere duzce branch of the north anatolian fault and strong ground motion we analyze temporal variations of seismic velocity along the karadere duzce branch of the north anatolian fault using seismograms generated by repeating earthquake clusters in the aftershock zones of the 1999 mw7 4 izmit and mw7 1 duzce earthquakes the analysis employs 36 sets of highly repeating earthquakes each containing 4 18 events the events in each cluster are relocated by detailed multi step analysis and are likely to rupture approximately the same fault patch at different times the decay rates of the repeating events in individual clusters are compatible with the omori s law for the decay rate of regional aftershocks a sliding window waveform cross correlation technique is used to measure travel time differences and evolving decorrelation in waveforms generated by each set of the repeating events we find clear step like delays in the direct s and early s coda waves sharp seismic velocity reduction immediately after the duzce main shock followed by gradual logarithmic type recoveries a gradual increase of seismic velocities is also observed before the duzce main shock probably reflecting post seismic recovery from the earlier izmit main shock the temporal behavior is similar at each station for clusters at various source locations indicating that the temporal changes of material properties occur in the top most portion of the crust the effects are most prominent at stations situated in the immediate vicinity of the recently ruptured fault zones and generally decrease with normal distance from the fault a strong correlation between the co seismic delays and intensities of the strong ground motion generated by the duzce main shock implies that the radiated seismic waves produced the velocity reductions in the shallow material

substrate related changes in pectinid fossil assemblages quantitative analysis of pectinid bivalvia assemblages in the lower pliocene deposits of the almeria nijar and poniente basins in southeastern spain reveals changes in the taphonomical attributes taxonomical composition and shell morphology of these assemblages in relation to the sediments in which they occur the lower pliocene deposits in both basins consist of outer platform clays silts and fine sands which laterally and vertically pass into innerplatform and deltaic sands and conglomerates proximal and distal tempestite beds are intercalated in the sands and silts calcirudites accumulated in shallow water settings with no influx of terrigenous sediments the variations of pectinid assemblages according to the embedding sediments represent changes in the assemblages in proximal distal depth gradients pecten and chlamys species predominate in shallow water conglomerates and calcirudites chlamys seniensis lamarck and flabellipecten bosniasckii stefani and pantanelli are the most abundant pectinids in coarseto medium sands and in intercalated proximal tempestites from the inner platform and delta front amusium cristatum bronn is the most common component in the assemblages from outer platform fine sands silts clays and distal tempestites assemblages from shallow water coarse grained deposits comprise strongly ribbed inflated shells while those from deep water fine grained lithofacies are mainly composed of smooth flat shelled species

multivariate hierarchical analyses of miocene mollusk assemblages of europe paleogeographic paleoecological and biostratigraphic implications mollusk dominated fossil assemblages from the marine miocene bioprovinces of europe the boreal province and the paratethys were analyzed by using bulk samples collected hierarchically across several spatiotemporal scales the study explores quantitative patterns recorded by benthic mollusk assemblages including implications for paleogeographic biostratigraphic and paleoenvironmental patterns and the relationship between spatiotemporal scale of analysis and levels of variability in paleontological data a total of 8455 specimens from 23 samples were collected from siliciclastic sediments clay and sand at 12 localities from france belgium the netherlands germany poland austria and hungary with the exception of one sample of serravallian age from the southeastern north atlantic all samples came from burdigalian and langhian deposits of the paratethys and the boreal province all specimens were identified to species level 297 species total classified in terms of ecology and analyzed by using multivariate and computer intensive methods the analyses focused on 1 bivalve gastropod ratios 2 diversity levels 3 multivariate taxonomic and ecological patterns and 4 multivariate euclidean distances between samples compared at five different scales within sites within localities within facies among facies among provinces the bivalve gastropod ratio is a highly volatile parameter thus its informative value is highly limited the estimates of alpha diversity sample species richness standardized by rarefaction indicate that fossil assemblages of the boreal province display higher diversity levels than those of the paratethys this result is consistent with the general tendency of isolated epicontinental basins to display impoverished fauna and may be due to geographic barriers limiting larval dispersal and to environmental instabilities inherent to marginal environments of epicontinental seaways rarefactions of pooled data indicate that for both provinces the taxonomic turnover among sites beta diversity accounts for 30 40 of species diversity multivariate analyses indicate that biogeographic variation between the provinces is the most important factor controlling differences among samples whereas facies type and stratigraphic position of samples play a secondary role the strong biogeographic signature is consistent with recent paleogeographic reconstructions that suggest a lack of a direct marine connection between the two provinces at that time the relatively poorer discrimination of mollusk assemblages across facies and biostratigraphic stages reflects the overriding role of the middle miocene biogeography in controlling the composition of mollusk assemblages the hierarchical multivariate analysis shows that with the increase in the scale of observation within sites within localities within facies among facies among provinces the average multivariate distance between samples increases continuously new heterogeneities that add notable amounts of new variation exist at each scale of observation the highest increase is observed for the among provinces comparison level again indicating the major role of geographic sources of variation in the data the hierarchical approach provides a rigorous way to quantify the effects of scale dependent sources of variability on paleontological patterns

quasigeostrophic transient wave activity flux updated climatology and its role in polar vortex anomalies abstract the climatology of transient wave activity flux defined by plumb has been calculated for each calendar month for high frequency hf and low frequency lf waves using the ncar ncep reanalyses for both hemispheres wave activity flux of both hf and lf waves shows upward propagation of waves from the lower troposphere into the upper troposphere then into the lower stratosphere during the summer and at least up to the midstratosphere during other seasons while the upward flux emanating from the lower troposphere is particularly large in the two storm tracks in the northern hemisphere nh it is large in most of the extratropics in the southern hemisphere sh the hf waves radiate equatorward most noticeably in the upper troposphere whereas the lf waves do not show visible signs of equatorward radiation the total horizontal flux is generally dominated by the advective flux that represents the eddy enstrophy advection by the mean flow and appears predominantly pseudoeastward divergence of th

the structure and energetics of midlatitude disturbances accompanying cold air outbreaks over east asia abstract the onset dates for 11 individual cold air outbreaks over the east asian seaboard during the winter monsoon experiment 1 december 1978 28 february 1979 are used for constructing composite synoptic charts the three dimensional structure and energetics of disturbances with time males shorter than 5 days are distinguished from the corresponding properties of more slowly varying fluctuations by using time filtering techniques it is seen that the high frequency disturbances accompanying the cold surges experience systematic structural changes as they migrate along a well defined storm track from east asia to the gulf of alaska the typical life cycle of such extratropical storms is characterized by a barolinic growth phase coinciding with the polar outbreaks and a decay phase in which barotropic processes play an active role the propagation of low frequency fluctuations is oriented toward lower latitudes with new vorticity centers developing downstream and equatorward of the primary disturbanc

on the observed relationships between wintertime variability in kuroshio oyashio extension sea surface temperatures and the atmospheric circulation over the north pacific abstractobservational analyses reveal that wintertime variations in sea surface temperatures sst in the kuroshio oyashio extension koe region of the north pacific are associated with two distinct and robust patterns of atmospheric variability 1 a pattern that peaks in amplitude approximately 2 3 weeks prior to large koe sst anomalies and is consistent with atmospheric forcing of the sst field and 2 a very different pattern that lags sst anomalies in the koe region by approximately a month the latter pattern is dominated by low sea level pressure anomalies and turbulent heat fluxes directed into the atmosphere over warm sst anomalies and is interpreted as the transient atmospheric response to sst anomalies over the koe region the results contribute to a growing body of evidence that suggests variations in ssts in the midlatitude oceans are capable of significantly influencing the large scale atmospheric circulation especially near western boundary currents

nonlinear barotropic response to a localized topographic forcing formation of a tropical surf zone and its effect on interhemispheric propagation abstract the nonlinear response of a barotropic nondivergent spherical flow representative of the upper troposphere but without a tropical hadley cell to localized extratropical topographic forcing is examined using high resolution contour surgery calculations the response is shown to vary greatly with forcing amplitude and can be significantly different from the linear response at large amplitude rossby wave breaking occurs in the tropics irrespective of the direction of the equatorial winds and leads to small scale stirring and the formation of a tropical surf zone which inhibits the meridional propagation of the disturbance

variability of the observed midlatitude storm tracks in relation to low frequency changes in the circulation pattern abstract the principal modes of month to month variability of the wintertime storm tracks over the north pacific and north atlantic are identified by empirical orthogonal function analysis of the root mean square statistics of bandpass 2 5 6 day filtered geopotential height data for 19 yr one of the two leading modes depicts fluctuations in the level of synoptic scale activity without any noticeable spatial displacement of the storm track axes whereas the other mode is associated with meridional shifts of the storm tracks from their time averaged positions higher order modes are indicative of diversion or truncation of cyclone tracks in particular geographical regions it is demonstrated that the leading storm track modes are linked to some of the best known monthly averaged teleconnection patterns the dipolar western pacific and western atlantic patterns for the monthly mean flow are seen to be accompanied by marked changes in the intensity of the storm tracks over the western oceans whereas the m

dominant anomaly patterns in the near surface baroclinicity and accompanying anomalies in the atmosphere and oceans part i north atlantic basin abstract variability in the monthly mean flow and storm track in the north atlantic basin is examined with a focus on the near surface baroclinicity b bxi byj dominant patterns of anomalous b found from empirical orthogonal function eof analyses generally show patterns of shift and changes in the strength of b composited anomalies in the monthly mean wind at various pressure levels based on the signals in the eofs display robust accompanying anomalies in the mean flow up to 50 hpa in the winter and up to 100 hpa in other seasons anomalous eddy fields accompanying the anomalous bx patterns exhibit broadly speaking structures anticipated from linear theories of baroclinic instabilities and suggest a tendency for anomalous wave fluxes to accelerate decelerate the surface westerly accordingly atmospheric anomalies accompanying by anomalies have patterns different from those that accompany bx anomalies but are as large as those found for bx anomalies in the sea surface temperature sst found for

estimation of nonlinear time dependent soil behavior in strong ground motion based on vertical array data to improve our understanding of nonlinear elastic properties of soils a method is proposed of estimation of stress strain relations of soils in situ in strong ground motion based on vertical array data strong motion records provided by seismic vertical arrays allow estimation of nonlinear stress strain relations in soil layers at different depths from the surface down to the location of the deepest device as an example records obtained during the main shock of the 1995 kobe earthquake at port island sgk and tks sites were used to estimate the stress strain relations in the soil profiles for different layers different types of nonlinear stress strain relations were selected according to the profiling data to account for temporal changes in the soil behavior consecutive parts of records were examined and for successive time intervals the relations were found showing the best fit approximation to the observed data at port island and sgk sites where the strongest accelerations were recorded the obtained stress strain relations showed systematic changes in the upper layers 0 14 m such as a progressive reduction of the slopes of the stress strain curves due to liquefaction at port island and reduction and recovery of the slopes at sgk and tks sites at the three sites the stress strain relations remained stable in layers below 11 14 m thus the proposed approach gives us a representation of the soil behavior in layers at different depths in strong ground motion it allows calculation of the propagation of arbitrary seismic signals in the studied profiles and estimation of nonlinear components in the ground response by the nonlinear system identification technique the method can also be applied to evaluate the ground response at sites where profiling data are available and an imposed motion can be estimated

midwinter suppression of baroclinic wave activity in the pacific abstract seasonal variations in baroclinic wave activity and jet stream structure in the northern hemisphere are investigated based upon over 20 years of daily data baroclinic wave activity at each grid point is represented for each day by an envelope function the lowpass filtered time series of the squared highpass filtered geopotential height baroclinic wave activity over the atlantic exhibits a single maximum in january whereas in the pacific it exhibits peaks in late autumn and in early spring and a significant weakening in midwinter which is more evident at the tropopause level than near the surface this suppression occurs despite the fact that the low level baroclinity and the intensity of the jet stream are strongest in midwinter based on the analysis of 31 day running mean fields for individual winters it is shown that over both the oceans baroclinic wave activity is positively correlated with the strength of the upper tropospheric jet for wind speeds up to 45 m s 1 when the strength of t

nonlinear soil behavior at the kashiwazaki kariwa nuclear power plant during the niigata chuetsu oki earthquake july 16 2007 records of the niigata chuetsu oki earthquake july 16 2007 mw 6 6 depth 17 km and its aftershocks from seismic vertical arrays deployed at the territory of the kashiwazaki kariwa nuclear power plant 15 km from the fault are used to study the soil behavior down to 250 m during strong ground motion nonlinear models of soil behavior during the main shock and six aftershocks are constructed and stresses and strains induced by the strong motion in the soil layers at various depths are estimated the data are processed using the method developed by pavlenko and irikura bull seismol soc am 96 6 2131 2145 2003 and previously applied for studying the soil behavior in near fault zones during the 1995 kobe and 2000 tottori earthquakes a rather good agreement between the recorded and simulated acceleration time histories testifies to the validity of the obtained vertical distributions of stresses and strains in soil layers in the upper softer layers 45 m at the territory of the plant the shear moduli were reduced by 30 35 during the main shock and by 1 5 3 during the aftershocks the constructed models of soil behavior can be used in scenario earthquake shaking maps of japan where based on source modeling parameters the level of strong motion can be evaluated for the territory of the power plant in future earthquakes with various magnitudes and fault planes using methods of stochastic finite fault modeling of ground motions from the chuetsu oki earthquake we estimated input motion to the soil layers during the main shock and found that it differs from the imposed motion recorded by the deepest sensor of the vertical array by slightly decreased by a factor of 1 2 low frequency f 10 hz spectral components

the information content of high frequency seismograms and the near surface geologic structure of hard rock recording sites due to hardware developments in the last decade the high frequency end of the frequency band of seismic waves analyzed for source mechanisms has been extended into the audio frequency range 20 hz in principle the short wavelengths corresponding to these frequencies can provide information about the details of seismic sources but in fact much of the signal is the site response of the nearsurface several examples of waveform data recorded at hard rock sites which are generally assumed to have a flat transfer function are presented to demonstrate the severe signal distortions includingfmax produced by near surface structures analysis of the geology of a number of sites indicates that the overall attenuation of high frequency 1 hz seismic waves is controlled by the whole path q between source and receiver but the presence of distinctfmax site resonance peaks is controlled by the nature of the surface layer and the underlying near surface structure models of vertical decoupling of the surface and nearsurface and horizontal decoupling of adjacent sites on hard rock outcrops are proposed and their behaviour is compared to the observations of hard rock site response the upper bound to the frequency band of the seismic waves that contain significant source information which can be deconvolved from a site response or an array response is discussed in terms offmax and the correlation of waveform distortion with the outcrop scale geologic structure of hard rock sites it is concluded that although the velocity structures of hard rock sites unlike those of alluvium sites allow some audio frequency seismic energy to propagate to the surface the resulting signals are a highly distorted limited subset of the source spectra

a wavelet based seismogram inversion algorithm for the in situ characterization of nonlinear soil behavior we present a full waveform inversion algorithm of downhole array seismogram recordings that can be used to estimate the inelastic soil behavior in situ during earthquake ground motion for this purpose we first develop a new hysteretic scheme that improves upon existing nonlinear site response models by allowing adjustment of the width and length of the hysteresis loop for a relatively small number of soil parameters the constitutive law is formulated to approximate the response of saturated cohesive materials and does not account for volumetric changes due to shear leading to pore pressure development and potential liquefaction we implement the soil model in the forward operator of the inversion and evaluate the constitutive parameters that maximize the cross correlation between site response predictions and observations on ground surface the objective function is defined in the wavelet domain which allows equal weight to be assigned across all frequency bands of the non stationary signal we evaluate the convergence rate and robustness of the proposed scheme for noise free and noise contaminated data and illustrate good performance of the inversion for signal to noise ratios as low as 3 we finally employ the proposed scheme to downhole array data and show that results compare very well with published data on generic soil conditions and previous geotechnical investigation studies at the array site by assuming a realistic hysteretic model and estimating the constitutive soil parameters the proposed inversion accounts for the instantaneous adjustment of soil response to the level and strain and load path during transient loading and allows results to be used in predictions of nonlinear site effects during future events

impacts of sst anomalies in the agulhas current system on the regional climate variability abstractthe potential impact of the variability in the agulhas current system on the large scale atmospheric state in the southern hemisphere is examined using the monthly near surface baroclinicity as the key parameter for the period between september 1980 and august 2002 dominant patterns of anomalous near surface baroclinicity found from empirical orthogonal function eof analyses in the region that includes most of the agulhas current system show a wide variety of anomaly patterns some of which indicate spatial shifts in the position of the agulhas retroflection and or agulhas return current composited anomalies in various atmospheric fields sea surface temperature and the net surface heat flux at the air sea boundary based on the signals in the eofs suggest that sea surface temperature anomalies in the agulhas current system thermally force the atmosphere on the synoptic scale via modification of the near surface baroclinicity in march and april and possibly in january and february as well

site response for urban los angeles using aftershocks of the northridge earthquake ground motion records from aftershocks of the 1994 northridge earthquake are used to estimate site response in the urban los angeles area over 1300 shear wave records from 61 sources and 90 sites are used in a linear inversion for source and site response spectra the methodology makes no assumptions about the shape of the source spectrum to obtain a stable unique inverse a q model and geometrical spreading factor are assumed in addition the site response at a hard rock site is constrained to be approximately 1 0 with a kappa of 0 02 the site response spectra compare favorably with the results of previous and on going investigations in los angeles a couple of first order effects are lower site response in the surrounding mountains dominated by mesozoic and tertiary rocks and higher values in the san fernando and los angeles basins containing surficial pleistocene and holocene alluvial deposits results show good correlation of high site response spectral values with localized areas of severe damage interstate 10 collapse sherman oaks northridge interstate 5 14 collapse however widespread trends in site response across the sedimentary basins are not obvious the data suggest that site responses are lower near the southern margin of the san fernando valley for sources to the north due to north dipping sedimentary structures but the general pattern of site response is characterized by high variability on length scales less than a kilometer variations of a factor of 2 in site response are observed over the length scale of 200 m and for the same surficial geologic unit for some of the alluvial basin sites surface wave generation is a significant contributor to elevated site response at lower frequencies below 2 hz the total damage pattern for the northridge earthquake is influenced by strong source directivity to the north and strong local site effects the correlation of weak motion site response estimates with areas of significant damage demonstrates the value of these field measurements in future urban planning and in the reduction of seismic risk in urban areas

feedbacks of sea surface temperature to wintertime storm tracks in the north atlantic abstractin this study the lagged maximum covariance analysis is performed on winter storm track anomalies represented by the meridional heat flux by synoptic scale 2 8 days transient eddies and sea surface temperature sst anomalies in the north atlantic which are both derived from reanalysis datasets spanning the twentieth century the analysis shows significant seasonal and interannual coupling between storm track and sst variations on seasonal time scales it is found that sst anomalies in the preceding early winter november december which are expected to change the lower tropospheric baroclinicity can significantly influence storm tracks in early spring march that is an intensification and slight northward shift of storm tracks in response to a midlatitude sst dipole with a cold pole centered to the southeast of newfoundland and a warm pole in the western subtropical atlantic this storm track response pattern is similar to the storm track forcing pattern in early spring which resembl

determination of geomechanical site effects in france from macroseismic intensities and reliability of macroseismic magnitude of historical events results from a detailed analysis of the french macroseismic database sirene96 show that geomechanical site effects i e site effects due to superficial geology can be statistically detected and quantified from macroseismic data our results are used to derive a predictive map of potential site effects in france and to check if site effects induce a significant overestimation of macroseismic magnitude of historical events the key hypothesis of our work is that geological formations of similar age produce similar site effects because one expects the younger sediments to be less compacted and therefore more prone to cause site effects a geological formation is associated with each intensity using a geographic information system gis and the digital geological map of france two approaches are developed in order to characterise the intensity increase associated with geological formations having the same age the first approach is based on the intensities that differ significantly from the average pattern intensities which are labelled as anomalies in the second approach a theoretical intensity attenuation law is computed for each selected event only from observations located on formations older than 2 my according to the results of the first approach these formations are unlikely to cause site effects and for the sake of simplicity they are labelled as rocks younger formations are defined as sediments the derived attenuation laws are then used to compute the residuals for each observation residuals are classified as a function of the age of the formations on which they are located the results of the two approaches are in good agreement no intensity amplification is detected for formations older than 1 my for younger formations the younger the formations the larger the average intensity increase the average intensity increase reaches 0 6 0 2 degree on the msk scale for 0 my sediments the results are better expressed in terms of probability for 0 my sediments there is an estimated 83 probability of observing an intensity increase for 0 01 my and 0 75 my sediments this probability is about 52 the magnitude of the intensity increase is variable but it is generally small it has a 26 probability to reach 1 degree or above on the msk scale for 0 my sediments and this probability falls to about 5 for 0 01 and 0 75 my formations a predictive map of geomechanical site effects is produced by extrapolating the characteristics of intensity increases to all geologic formations of similar age in france glacial and fluvial valleys already known as being subject to site effects clearly appear on this map as well as less expected areas such as the south atlantic coast lastly new estimations of macroseismic magnitude that exclude intensities potentially affected by geomechanical site effects are realised a magnitude overestimation due to site effects can possibly exist but it remains limited 0 2 this result tends to demonstrate that geomechanical site effects in france do not significantly distort our knowledge of historical seismicity

trapping of synoptic scale disturbances into the north pacific subtropical jet core in midwinter 1 over the northwestern nw pacific a subtropical jet stream develops at 30 n in midwinter as the east asian winter monsoon intensifies eddies with subweekly periods propagating through the midlatitude tropopause into the nw pacific storm track tend to be trapped into the jet core 1000 km away from a surface baroclinic zone at 40 n while lifted up by 3 km the trapping appears to weaken the interaction of the upper level eddies with the baroclinic zone thus acting against eddy amplification and thereby contributing to the midwinter minimum in the eddy activity as observed before the late 1980s since then under the reduced trapping effect by the weakened jet upper level eddies tended to propagate right above the surface baroclinic zone while strongly interacting it even in midwinter as in fall and spring this midwinter tendency acted to enhance the eddy amplification that led to the recent disappearance of the activity minimum

stratigraphic paleoecology of the valle di manche section crotone basin italy a candidate gssp of the middle pleistocene abstract macro benthic assemblages from the lower to middle pleistocene of the valle di manche vdm section crotone basin southern italy were used to assess the value of merging paleoecological quantitative patterns into a sequence stratigraphic framework two way cluster and detrended correspondence dca analyses were applied to the macrofossil data matrix comprising 22 samples 157 species and 5761 specimens specifically two way cluster analysis allowed for the characterization of five shelf related biofacies and four sub biofacies along section biofacies change along the vdm generally supported previous sequence stratigraphic interpretations and suggests that faunal turnover is the result of habitat tracking dca stratigraphic curves dc1 sample scores calibrated to the depth preferences of extant species provided quantitative estimates of bathymetry and the assessment of related parameters e g grain size sedimentation turbidity when plotted stratigraphically calibrated dc1 scores highlight the magnitude of relative sea level fluctuations at the scale of the section as well as individual sequences and systems tracts additionally dca derived paleobathymetric trends track the oscillations of the 18 o record indicative of global sea level change based on this comparison it is held that macro benthic assemblages once supported by a robust statistical interpretation can be employed successfully as a proxy for 18 o depicting the variability in local water depths the potential of this approach is especially high for studies in shallow water depositional settings where dependable 18 o data are typically difficult to obtain

numerical experiments of the storm track sensitivity to oceanic frontal strength within the kuroshio oyashio extensions the sensitivity of the north pacific storm track to midlatitude oceanic frontal strength within the kuroshio oyashio extensions is investigated by applying artificially changed meridional sea surface temperature sst gradients in the weather research forecasting model version 3 4 the result of sensitivity experiments further confirms the close relationship between the storm track activity and meridional sst gradient i e the storm track activity can be intensified as a response to increases in the oceanic frontal strength in order to better understand the mechanism for the storm track intensification due to increased sst gradient velocity temperature correlation and local energetics are analyzed the result indicates that the enhancement of the meridional sst gradient leads to amplitude magnification of eddy meridional velocity and temperature and their phase consistency suggesting that synoptic scale eddies tend to approach the optimum structure for the baroclinic energy conversion which is mainly responsible for the sst front induced enhancement of storm track activity in order to estimate the impact of the oceanic front on the maintenance of the near surface baroclinicity further investigation is made by the composite analysis with the increase in oceanic frontal strength the near surface baroclinicity experiences a slow but strong restoration the increase in the meridional sst gradient results in the intensification in the cross frontal differential sensible heat flux which can more effectively offset the relaxing effect of the transient eddy poleward heat transport

spatial patterns and intensity of the surface storm tracks in cmip5 models abstractto improve the understanding of storm tracks and western boundary current wbc interactions surface storm tracks in 12 cmip5 models are examined against era interim all models capture an equatorward displacement toward the wbcs in the locations of the surface storm tracks maxima relative to those at 850 hpa an estimated storm track metric is developed to analyze the location of the surface storm track it shows that the equatorward shift is influenced by both the lower tropospheric instability and the baroclinicity basin scale spatial correlations between models and era interim for the storm tracks near surface stability sst gradient and baroclinicity are calculated to test the ability of the gcms match reanalysis an intermodel comparison of the spatial correlations suggests that differences relative to era interim in the position of the storm track aloft have the strongest influence on differences in the surface storm track position however in the north atlantic biases in the surf

estimation of nonlinear soil behavior during the 1999 chi chi taiwan earthquake the 1999 chi chi taiwan earthquake mw 7 6 was one of the strongest earthquakes in recent years recorded by a large number of strong motion devices though only surface records are available the obtained strong motion database indicates the variety of ground responses in the near fault zones in this study accelerograms of the chi chi earthquake were simulated at rock and soil sites and models of soil behavior were constructed at seven soil sites tcu065 tcu072 tcu138 chy026 chy104 chy074 and chy015 for which parameters of the soil profiles are known down to depths of at least 70 m and at 24 other soil sites for which parameters of the soil profiles are known down to 30 40 m all the sites were located within 50 km from the fault for reconstructing stresses and strains in the soil layers we used a method similar to that developed for the estimation of soil behavior based on vertical array records as input for the soil layers acceleration time histories simulated by stochastic finite fault modelling with a prescribed slip distribution over the fault plane were taken in spite of the largeness of the earthquake s magnitude and the proximity of the studied soil sites to the fault plane the soil behavior at these sites was relatively simple i e a fairly good agreement between the spectra of the observed and simulated accelerograms and between their waveforms was obtained even in cases where a single stress strain relation was used to describe the behavior of whole soil thickness down to 70 80 m during strong motion obviously this is due to homogeneity in the characteristics of soil layers in depth at all the studied sites resonant phenomena in soil layers down to 40 60 m and nonlinearity of soil response were the main factors defining soil behavior at tcu065 tcu110 tcu115 chy101 chy036 and chy039 liquefaction phenomena occurred in the upper soil layers estimated strains achieved 0 6 0 8 at other stations maximum strains in the soil layers were as high as 0 1 0 4 according to our estimates thus valuable data on the in situ soil behavior during the chi chi earthquake was obtained similarity in the behavior of similar soils during the 1995 kobe 2000 tottori japan and chi chi taiwan earthquakes was found indicating the possibility of forecasting soil behavior in future earthquakes in the near fault zones of the three earthquakes hard type soil behavior and resonant phenomena in the upper surface layers prevail both leading to high acceleration amplitudes on the surface

north pacific decadal variability in the community climate system model version 2 abstract north pacific decadal oceanic and atmospheric variability is examined from a 650 yr control integration of the community climate system model version 2 the dominant pattern of winter sea surface temperature sst variability is similar to the observed pacific decadal oscillation with maximum amplitude along the kuroshio extension sst anomalies in this region exhibit significant spectral peaks at approximately 16 and 40 yr lateral geostrophic heat flux divergence caused by a meridional shift of the kuroshio extension forced by basin scale wind stress curl anomalies 3 5 yr earlier is responsible for the decadal sst variability local surface heat flux and ekman heat flux divergence act as a damping and positive feedback respectively a simple linear rossby wave model is invoked to explicitly demonstrate the link between the wind stress curl forcing and decadal variability in the kuroshio extension the rossby wave model not only successfully reproduces the two decadal spectral peaks but a

on the existence of storm tracks abstract given that middle latitude weather systems transport heat in a manner such as to weaken the baroclinicity that is thought to be crucial to their growth it is perhaps surprising that concentrated regions of such eddy activity i e storm tracks are found in the northern hemisphere winter the existence and possible self maintenance of storm tracks is investigated using a linear stationary wave model with storm track region forcings taken from data averaged over a number of winters it is found that the direct thermal effect of the eddies does indeed act against the existence of the storm track their vorticity fluxes lead to some reduction of this effect it is argued that the mean diabatic heating in the storm track region is an indirect eddy effect this heating is found to maintain the mean maximum in baroclinicity in the region further the mean low level flow induced by the eddy effects is such as to enhance the warm western oceanic boundary currents that are crucial to the existence of t

response of the baiu rainband to northwest pacific sst anomalies and its impact on atmospheric circulation abstractthe pacific japan pj teleconnection pattern leads to a meridional precipitation dipole between the subtropics and east asia in the summer of el nino decaying years however observational analysis and model experiments indicate that increased sea surface temperature sst in the kuroshio oyashio extension koe region where a strong northward decreasing sst gradient occurs induces a northward shift of baiu rainfall with the subtropical jet forming a tripolar precipitation anomaly pattern over the northwest pacific in july the leading empirical orthogonal function eof mode for precipitation represents the meridional dipole between subtropical and baiu rainfalls while eof 2 features the northward shifted baiu rainband the pj atmospheric forcing increases koe sst which enhances northward shifts in the subtropical jet and baiu rainband resulting in oceanic forcing over the koe in experiments using a regional climate model the subtropical jet response to koe sst forcing explains about 20