the 23 19 aftershock of the 15 october 1979 imperial valley earthquake more evidence for an asperity the well recorded strong ground motion data for the 23 19 aftershock of the 15 october 1979 imperial valley earthquake provide a good opportunity to study the high frequency source characteristics and the path effects at near source distances the best fitting point source model has a strike slip mechanism n40 w which is nearly identical to the main event the estimated stress drop is extremely high roughly 500 bars with a triangular time history 0 1 0 1 sec but with a moment of 1 0 10 24 dyne cm a double source model found by inversion fits the high frequency data better but indicates complex faulting the first source with strike n319 e dip 42 ne and slip angle 165 has a moment of 0 7 10 24 dyne cm the second source with strike n324 e dip 82 sw and slip angle 181 lies about 0 5 km to the north and has a seismic moment twice that of the first source source dimensions appear very small for this amount of energy release many of the anomalous behaviors observed at certain stations for the main event are also present in the aftershock data these features are examined in terms of path effects

local site effects in atakoy istanbul turkey due to a future large earthquake in the marmara sea summary since the 1999 izmit and duzce earthquakes in northwest turkey many seismic hazard studies have focused on the city of istanbul an important issue in this respect is local site effects strong amplifications are expected at a number of locations due to the local geological conditions in this study we estimate the local site effects in the atakoy area southwestern istanbul by applying several techniques using synthetic data hybrid 3 d modelling and 1 d modelling and comparing to empirical data we apply a hybrid 3 d finite difference method that combines a complex source and wave propagation for a regional 1 d velocity model with site effects calculated for a local 3 d velocity structure the local velocity model is built from geological geotechnical and geomorphological data the results indicate that strongest spectral amplifi cations sa in the atakoy area occur around 1 hz and that amplification levels are largest for alluvial sites where sa reaching a factor of 1 5 2 can be expected in the case of a large earth quake we also compare our results to h v horizontal to vertical component of the recorded signal spectral ratios calculated for microtremor data recorded at 30 sites as well as to ambient noise synthetics simulated using a 1 d approach because the applied methods complement each other they provide comprehensive and reliable information about the local site effects in atakoy added to that our results have significant implications for the southwestern parts of istanbul built on similar geological formations for which therefore similar sa levels are expected

relationship between cyclone tracks anticyclone tracks and baroclinic waveguides abstract this study presents observational results concerning the structure and evolution of high frequency fluctuations with periods shorter than 6 days in the geopotential height field the results are based on a statistical analysis of 1000 500 and 250 mb height fields derived from twice daily nmc final analyses over the northern hemisphere for the 20 winters 1964 65 through 1983 84 the disturbances assume the form of waves elongated in the meridional direction with a mean wavelength of 4000 km a westward tilt with height and a mean eastward phase propagation of 12 1 5 m s 1 these results support an interpretation in terms of finite amplitude baroclinic waves whose structure and evolution varies with geographical location over the continents and especially along the eastern slopes of the rockies and the tibetan plateau the waves show marked departures in structure and evolution from those over the oceans in particular we find evidence of a systematic influence of the terrain in steering the

sensitivity of ground motion simulations to earthquake source parameters a case study for istanbul turkey following the disastrous earthquakes in izmit and duzce along the north anatolian fault in 1999 the earthquake hazard in the istanbul area became a great concern in this study we simulate strong ground motions caused by a scenario earthquake m 7 5 in the marmara sea and investigate the effect of varying the input parameters on the broadband frequency ground motion simulations are based on a multiasperity source model that involves the combined rupture of the north anatolian fault segments beneath the marmara sea we use a hybrid model combin ing a deterministic simulation of the low frequencies 0 1 1 0 hz with a semisto chastic simulation of the high frequencies 1 0 10 0 hz computation at each fre quency range is performed separately and the total ground motion is combined in the time domain computations are linear and are performed at bedrock level thereby not taking any effect of local geological conditions into account we calculate a total of 17 earthquake scenarios corresponding to different source and attenuation param eters to study their effect on the ground motion the most significant parameters in terms of ground shaking level are the rise time rupture velocity rupture initiation point and stress drop the largest variability of strong ground motions is observed in regions adjacent to asperities and is associated with frequencies higher than 5 hz for lower frequencies our simulated velocity spectra within the istanbul area are fairly stable among scenarios the average standard deviations of all ground motion measures are less than 35 of the mean online material figures of peak ground acceleration and peak ground velocity and their differences to the reference scenario values

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

a new perspective on southern hemisphere storm tracks abstract a detailed view of southern hemisphere storm tracks is obtained based on the application of filtered variance and modern feature tracking techniques to a wide range of 45 yr european centre for medium range weather forecasts ecmwf re analysis era 40 data it has been checked that the conclusions drawn in this study are valid even if data from only the satellite era are used the emphasis of the paper is on the winter season but results for the four seasons are also discussed both upper and lower tropospheric fields are used the tracking analysis focuses on systems that last longer than 2 days and are mobile move more than 1000 km many of the results support previous ideas about the storm tracks but some new insights are also obtained in the summer there is a rather circular strong deep high latitude storm track in winter the high latitude storm track is more asymmetric with a spiral from the atlantic and indian oceans in toward antarctica and a subtropical jet related lower latitu

air sea interaction effects in the lower troposphere across the north wall of the gulf stream abstract significant atmospheric and oceanographic differences have often been observed in the regions lying on either side of the north wall of the gulf stream satellite visible range sensors have revealed changes in reflectivity across the gulf stream believed to be due to changes in sea state that are related to these atmospheric and oceanic differences in addition lines of low level cloud paralleling the edge of the gulf stream have been observed to persist in satellite imagery for several days at a time anomalous radar propagation also has been noted to occur in these same regions in an attempt to document the interrelation of these phenomena the lower atmosphere over the north wall of the gulf stream was studied on two separate occasions sea state photography and measurements of sea surface temperature air temperature dew point temperature and atmospheric pressure were made by an instrumented rp 3a aircraft flying at various altitudes from the gulf stream across the north wall and onto

evaluating the compatibility of dynamic rupture based synthetic ground motion with empirical ground motion prediction equation we performed an assessment of a database of synthetic ground motion generated by a suite of dynamic rupture simulations to verify compatibility of the peak ground amplitudes with respect to empirical ground motion prediction equations gmpes the dynamic rupture model database developed by dalguer and mai 2011 is composed of 360 earthquake scenarios with moment magnitudes in the range of 5 5 7 for three mechanisms of faulting reverse normal and strike slip and for both buried faults and surface rupturing faults having depth and non depth dependent normal stresses initial shear stress distribution follows a von karman stochastic distribution overall we show quantitatively that the upper frequency limit of the suite of simulations is 1 0 hz up to this frequency the synthetic data are compatible with the empirical model which means that the residuals defined as the differences between observed and predicted ground motions fall in the range of of the empirical gmpe characteristics of the mean values along distance 10 45 km and period t 1 0 s including standard deviation of the synthetic response spectra and peak ground velocity are comparable to their counterpart empirical gmpe at very near source 1 2 km synthetics show supersaturation of the mean peak values which is different from the saturation features predicted by the gmpes the effect of source parameters such as stress drop peak slip velocity and rupture speed and of surface and buried rupture as well as hanging wall and footwall are highly sensitive to ground motion suggesting that these effects contribute to the variability of ground motion near the source and that inclusion of them in the source terms may contribute to reducing uncertainties in gmpes

broadband wavelength slip model of the 1906 ecuador colombia megathrust earthquake based on seismic intensity and tsunami data abstract the 1906 01 31 ecuador colombia earthquake mw8 4 8 6 is one of the largest megathrust earthquakes that have occurred at the interface of the nazca and south american plates recently the source process of the earthquake has been re examined using historical tsunami waveforms yielding a slip distribution mainly near to the trench and a smaller moment magnitude than previous estimations previous studies have shown that tsunami data can sufficiently constrain the long wavelength characteristics of slip during an earthquake however to fully understand strong ground motion generation process during earthquakes in a broadband frequency range the study of shorter wavelength slip responsible for high frequency ground motion generation is also necessary in this study we use the tsunami slip model of the 1906 earthquake as well as comprehensive macro seismic intensity estimations of the earthquake to elaborate a broadband wavelength bb source model appropriate for the generation of broadband frequency strong ground motions as well as tsunami modeling our results show that a bb slip model of the earthquake is able to satisfactorily reproduce observed intensity values as well as tsunami waveforms our bb slip model implies an increase in total moment magnitude to a value up to 8 6 respect to the estimation from tsunami data which represent the contribution of short wavelength slips to seismic radiation the methodology developed in this study is suitable to study the generation process of high frequency ground motions during large earthquakes

stochastic strong motion simulation in borehole and on surface for the 2011 mw 9 0 tohoku oki megathrust earthquake considering p sv and sh amplification transfer functionsstochastic strong motion simulation in borehole and on surface for the tohoku oki megathrust earthquake

streamer depth versus vessel and seismic interference noise abstractfor marine seismic surveying it is commonly assumed that the noise level decreases with depth in addition recent advances in broadband seismic have shown that a greater receiver depth is beneficial in preserving low frequency data however in a heavily trafficked ocean noise from other ships including seismic interference is a counteractive process in which the noise actually varies with depth normal modes can be used to explain and predict the ship noise and seismic interference noise level we find that weather noise is dominant below the first mode s cutoff frequency approximately 6 hz ship noise is dominant from that frequency to the upper end of the useful seismic frequency band 80 hz we have used a data set in which the streamer was towed at 8 45 and 60 m depths in three passes over the same area in the north sea the water depth is 135 m on average we observe that the noise level at 45 and 60 m depth is approximately 1 6 times stronger than that at 8 m we find that the air

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

complexity of the mw 6 3 2009 l aquila central italy earthquake 2 broadband strong motion modeling 1 near fault strong ground motions 0 1 10 hz recorded during the mw 6 3 2009 l aquila earthquake exhibit great spatial variability modeling the observed seismograms allows linking distinct features of the observed wavefield to particular source and propagation effects and provides insights on strong motion complexity from this moderate magnitude event we utilize a hybrid integral composite approach based on a k square kinematic rupture model combining low frequency coherent and high frequency incoherent source radiation and providing omega squared source spectral decay several source model features proven to be stable by means of an uncertainty analysis in the preceding low frequency 2 hz

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

scenario source models and strong ground motion for future mega earthquakes application to lima central peru the 2011 moment magnitude m w 9 0 tohoku oki japan earthquake occurred in a region where giant megathrust earthquakes were not expected this earthquake proved the difficulty in assessing seismic hazard by relying mainly on information from historical and instrumental seismicity to help improve the seismic hazard assessment for such rare events we propose a methodology to estimate the slip distribution of future megathrust earthquakes based on a model of interseismic coupling distribution in subduction margins as well as information of historical earthquakes and apply the method to the central peru region lima the slip model obtained from geodetic data represents the large scale features of asperities within the megathrust which is appropriate for simulation of long period waves and tsunami modeling for the simulation of a broadband strong ground motion we add small scale heterogeneities to the source slip to be able to simulate high frequencies to achieve this purpose we propose broadband source models constructed by adding short wavelength slip distributions obtained from a von karman power spectral density function to the slip model inferred from interseismic geodetic data using these slip models and assuming several hypocenter locations we calculate a set of strong ground motions for lima and incorporate site effects obtained from microtremors surveys and geotechnical data our simulated average pseudospectral accelerations period 0 3 s are above graphic 1 for wide areas in lima which may be critical in terms of damage of low to midrise masonry and reinforced concrete buildings which characterize the majority of buildings in lima 1 embed inline graphic 1 gif

satellite measurements reveal persistent small scale features in ocean winds four year averages of 25 kilometer resolution measurements of near surface wind speed and direction over the global ocean from the quikscat satellite radar scatterometer reveal the existence of surprisingly persistent small scale features in the dynamically and thermodynamically important curl and divergence of the wind stress air sea interaction over sea surface temperature fronts throughout the world ocean is evident in both the curl and divergence fields as are the influences of islands and coastal mountains ocean currents such as the gulf stream generate distinctive patterns in the curl field these previously unresolved features have important implications for oceanographic and air sea interaction research

repeatability issues of 3 d vsp data increased repeatability is recognized as one major issue for improving the time lapse seismic technology as a reservoir management tool a 3 d vertical seismic profiling vsp data set acquired over a period of two days is used to analyze how repeatable a permanent installed geophone array can be and how repeatability changes with inaccuracies in source positioning it is found that for a frequency range between 3 5 and 50 hz the difference root mean square rms level between two recorded traces belonging to two different shots is about 8 this fact shows that there is a potential for acquiring very accurate time lapse seismic data by using a permanently installed downhole geophone array repeatability variation with increasing shot separation distances is analyzed showing a rapid decrease in repeatability as the accuracy of the positioning of the repeat survey decreases horizontal geophone components show approximately the same degree of repeatability compared to the vertical component but horizontal geophone data is slightly more sensitive to positioning errors the results show that repeated 3 d vsp surveys preferably using permanently installed geophone arrays might be an efficient tool for detailed and precise monitoring of fluid and pressure changes within a hydrocarbon reservoir

midlatitude wind stress sea surface temperature coupling in the vicinity of oceanic fronts the influences of strong gradients in sea surface temperature on near surface cross front winds are explored in a series of idealized numerical modeling experiments the atmospheric model is the naval research laboratory coupled ocean atmosphere mesoscale prediction system coamps model which is fully coupled to the regional ocean modeling system roms ocean model a series of idealized two dimensional model calculations is carried out in which the wind blows from the warm to cold side or the cold to warm side of an initially prescribed ocean front the evolution of the near surface winds boundary layer and thermal structure is described and the balances in the momentum equation are diagnosed the changes in surface winds across the front are consistent with previous models and observations showing a strong positive correlation with the sea surface temperature and boundary layer thickness the coupling arises mainly as a result of changes in the flux richardson number across the front and the strength of the coupling coefficient grows quadratically with the strength of the cross front geostrophic wind the acceleration of the winds over warm water results primarily from the rapid change in turbulent mixing and the resulting unbalanced coriolis force in the vicinity of the front much of the loss gain of momentum perpendicular to the front in the upper and lower boundary layer results from acceleration deceleration of the flow parallel to the front via the coriolis term this mechanism is different from the previously suggested processes of downward mixing of momentum and adjustment to the horizontal pressure gradient and is active for flows off the equator with sufficiently strong winds although the main focus of this work is on the midlatitude strong wind regime calculations at low latitudes and with weak winds show that the pressure gradient and turbulent mixing terms dominate the cross front momentum budget consistent with previous work

validation of teleseismic inversion of the 2004 mw 6 3 les saintes lesser antilles earthquake by 3d finite difference forward modeling we study the 21 november 2004 mw 6 3 les saintes earthquake that occurred south of the island of guadeloupe at a shallow depth damaging some buildings on the island the objective of this work is to assess the potential of a teleseismic source study to reproduce local ground motion the velocity model of this area is not currently well known and the near field seismograms are affected by paths and site effects we first analyze this earthquake as a point source and then as an extended fault using teleseismic broadband waveform inversion approach from the p and sh waveforms at stations well distributed in azimuth we obtain two stable and reliable solutions of the spatiotemporal history of the earthquake rupture on each nodal plane the models show a rupture duration of 6 sec and a maximum slip of about 1 m but have different locations of the main asperity we then carry out the forward modeling of the seismic wave propagation at the regional scale coupled with the obtained kinematic source models taking into account the topography the bathymetry and the sea layer we investigate if one of the fault models could produce synthetics that match the local observed ground motions the simulation results provide a better understanding of the uncertainty of source path and site effects even if our knowledge of the underground geological structure is limited to the 1d stratified model it is inferred that the 1d model does not seem to be appropriate in the northern direction middle of guadeloupe island due to the unknown basin structure while it is relatively sufficient in the eastern and the northwestern directions from the source by careful comparison of the synthetic and observed displacement seismograms in terms of main phase forms and arrival times at low frequency especially at the closest station gbga the fault model with northeast faulting is estimated to be the more relevant to the measured local ground motions

estimation of strong ground motion from the great 1964 mw 9 2 prince william sound alaska earthquake we are generating physically plausible near field synthetic ground motions for the great 1964 prince william sound alaska earthquake compatible with available seismological data tectonic information and eyewitness accounts the first objective of this study is the simulation of the low frequency i e f 0 03 hz strong ground motions on selected locations and on a dense grid of observation points extending over the shallow dipping causative fault of the 1964 alaska earthquake in order to accomplish this task we are utilizing the slip model proposed by johnson et al 1996 based on a joint inversion of tsunami waveforms and geodetic data the calculations are carried out using the discrete wavenumber representation method bouchon and aki 1977 bouchon 1979 and the generalized transmission and reflection coefficient technique luco and apsel 1983 the second objective of this study is the reconstruction of the strong ground motion time histories and response spectra that the city of anchorage experienced during the 1964 alaska earthquake the low frequency i e f 0 03 hz ground motions are generated using the methodology described previously the intermediate frequency i e 0 03 f 0 50 hz ground motions are simulated by convolving green s functions generated by the discrete wavenumber representation method with far field radiation pulses of circular cracks sato and hirasawa 1973 dong and papageorgiou 2002a the high frequency i e 0 5 f 8 0 hz ground motions are simulated using the stochastic modeling approach the three independently derived ground motion components are then properly combined to generate synthetic broadband ground motion time histories and response spectra for the city of anchorage due to the 1964 prince william sound earthquake the third objective of this study is the validation of the synthetic strong ground motions for the 1964 alaska earthquake against observed tectonic deformation ground motion estimates inferred from descriptions of structural damage and eyewitness accounts in summary the analysis presented in this study contributes to a better understanding of the seismological aspects of the 1964 alaska earthquake and provides synthetic time histories and response spectra for engineering applications compatible with all available information i e seismological tectonic and eyewitness accounts it should be noted however that the generated strong ground motions are not necessarily unique nor do they reflect the entire uncertainty that characterizes the problem under investigation

deep atmospheric response to the spring kuroshio over the east china sea abstractthe atmospheric response to the spring kuroshio front over the east china sea is investigated using a suite of high resolution satellite data and a regional atmospheric model the atmospheric response appears to extend beyond the marine atmospheric boundary layer with frequent occurrence of cumulus convection in spring quick scatterometer quikscat wind speed shows a clear effect of sea surface temperature sst with high low wind speed observed over the warm cold tongue this in phase relationship between sst and surface wind speed is indicative of sst influence on the atmosphere wind convergence is found on the warmer flank of the kuroshio front accompanied by a narrow rainband the analysis of satellite borne radar measurements indicates that deep convection appears over the kuroshio warm tongue in the spring season with enhanced convective precipitation frequent occurrence of cumulus convection and increased precipitation cloud tops in altitude these deep convective activities

north atlantic barotropic vorticity balances in numerical models abstractnumerical simulations are conducted across model platforms and resolutions with a focus on the north atlantic barotropic vorticity diagnostics confirm that the subtropical gyre is characterized by an inviscid balance primarily between the applied wind stress curl and bottom pressure torque in an area integrated budget over the gulf stream the northward return flow is balanced by bottom pressure torque these integrated budgets are shown to be consistent across model platforms and resolution suggesting that these balances are robust two of the simulations at 100 and 10 km resolutions produce a more northerly separating gulf stream but obtain the correct integrated vorticity balances in these simulations viscous torque is nonnegligible on smaller scales indicating that the separation is linked to the details of the local dynamics these results are shown to be consistent with a scale analysis argument that suggests that the biharmonic viscous torque in particular is upsetting the inviscid

investigation of flow and flow noise around a seismic streamer cable in marine seismic explorations flow noise from the turbulent boundary layer that forms around a streamer cable due to its relative motion through water significantly affects the quality of collected data understanding this noise generation mechanism is valuable for the development of future seismic streamer cables we qualitatively characterize the area of turbulent flow surrounding a seismic streamer cable and relate this characteristic to the statistics of the measured noise signal the main finding is that the boundary layer thickness around a seismic streamer appears to be about 25 cm in an ocean environment this is significantly larger than the thickness of 2 5 to 5 cm that has been reported in the literature from laboratory experiments we attribute this discrepancy to the unsteadiness of the ocean environment estimations of the spatial extent of the recorded boundary layer noise indicate that the optimal hydrophone separation needs to be about 0 5 m for the noise to be uncorrelated the sign

role of the gulf stream and kuroshio oyashio systems in large scale atmosphere ocean interaction a review abstract ocean atmosphere interaction over the northern hemisphere western boundary current wbc regions i e the gulf stream kuroshio oyashio and their extensions is reviewed with an emphasis on their role in basin scale climate variability sst anomalies exhibit considerable variance on interannual to decadal time scales in these regions low frequency sst variability is primarily driven by basin scale wind stress curl variability via the oceanic rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the wbc related oceanic fronts rectification of the variability by mesoscale eddies reemergence of the anomalies from the preceding winter and tropical remote forcing also play important roles in driving and maintaining the low frequency variability in these regions in the gulf stream region interaction with the deep western boundary current also likely influences the low frequency variability surface heat fluxes damp the low frequency sst anomalies ove

near fault strong motion complexity of the 2000 tottori earthquake japan from a broadband source asperity model abstract the october 6 2000 tottori earthquake that occurred in central japan was an intermediate size strike slip event that produced a very large number of near field strong motion recordings the large amount of recorded data provides a unique opportunity for investigating a source asperity model of the tottori earthquake that combined with a hybrid strong motion simulation technique is able to reproduce the observed broadband frequency near fault ground motion we investigated the optimum source asperity parameters of the tottori earthquake by applying a genetic algorithm ga inversion scheme to optimise the fitting between simulated and observed response spectra and peak ground acceleration pga values we constrained the initial model of our inversion by using the heterogeneous slip distribution obtained from a kinematic inversion of the source of previous studies we used all the observed near fault ground motions 100 m from the borehole strong motion network of japan kik net which are little affected by surficial geology site effects the calculation of broadband frequency strong ground motion 0 1 10 hz is achieved by applying a hybrid technique that combines a deterministic simulation of the wave propagation for the low frequencies and a semi stochastic modelling approach for the high frequencies for the simulation of the high frequencies we introduce a frequency dependent radiation pattern model that efficiently removes the dependence of the pattern coefficient on the azimuth and take off angle as the frequency increases the good agreement between the observed and simulated broadband ground motions shows that our inversion procedure is successful in estimating the optimum asperity parameters of the tottori earthquake and provides a good test for the strong ground motion simulation technique the ratio of background stress drop to average asperity stress drop from our inversion is nearly 50 in agreement with the theoretical asperity model of das and kostrov das s kostrov b v 1986 fracture of a single asperity on a finite fault a model for weak earthquakes earthquake source mechanics agu pp 91 96 and an empirical ratio of asperities to rupture area seismol res lett 70 1999 59 80 the simulated radiation pattern is very complex for epicentral distances within half the fault length but it approaches the radiation of a double couple point source for larger distances the rupture velocity and rise time have a significant influence on the peak ground velocity pgv distribution around the fault an increase in rupture velocity produces a similar effect on the ground motion as a reduction in rise time

the basic ingredients of the north atlantic storm track part i land sea contrast and orography understanding and predicting changes in storm tracks over longer time scales is a challenging problem particularly in the north atlantic this is due in part to the complex range of forcings land sea contrast orography sea surface temperatures etc that combine to produce the structure of the storm track the impact of land sea contrast and midlatitude orography on the north atlantic storm track is investigated through a hierarchy of gcm simulations using idealized and semirealistic boundary conditions in a highresolution version of the hadley centre atmosphere model hadam3 this framework captures the largescale essence of features such as the north and south american continents eurasia and the rocky mountains enabling the results to be applied more directly to realistic modeling situations than was possible with previous idealized studies the physical processes by which the forcing mechanisms impact the large scale flow and the midlatitude storm tracks are discussed the characteristics of the north american continent are found to be very important in generating the structure of the north atlantic storm track in particular the southwest northeast tilt in the upper tropospheric jet produced by southward deflection of the westerly flow incident on the rocky mountains leads to enhanced storm development along an axis close to that of the continent s eastern coastline the approximately triangular shape of north america also enables a cold pool of air to develop in the northeast intensifying the surface temperature contrast across the eastern coastline consistent with further enhancements of baroclinicity and storm growth along the same axis

simulated strong ground motions for the great m 9 3 sumatra andaman earthquake of 26 december 2004 on 26 december 2004 a devastating earthquake of m 9 3 occurred offshore northern sumatra due to the size of this earthquake and the accompanying tsunami wave disastrous consequences have been observed in several countries around the indian ocean the tectonics in the region are characterized by the oblique north northeast oriented subduction of the indian australian plate under the sunda microplate with a rate of 6 6 5 cm yr this oblique convergence results in strain partitioning where the trench perpendicular thrust faulting along the subducting slab accommodates the east west component of the motion whereas the north south component of the motion is probably accommodated by the right lateral strike slip faulting along the great sumatran fault and the mentawi fault source parameters of the 26 december 2004 event have been used for modeling the resulting ground motions in the nearby affected regions results give an insight on the importance of ground shaking in the total destruction of places like banda aceh northern sumatra indonesia the modeling is performed for a multiasperity finite fault using a hybrid procedure combining deterministic modeling at low frequencies and semistochastic modeling at high frequencies results show that strong shaking was distributed over a large area including northwestern sumatra and its offshore islands in banda aceh which experienced significant damage bedrock velocities reached 60 cm sec with duration of the shaking of ca 150 sec the largest ground motions occurred near the strongest asperities of the fault plane where velocities of 200 cm sec are modeled for bedrock conditions

northern hemisphere winter atmospheric transient eddy heat fluxes and the gulf stream and kuroshio oyashio extension variability abstractspatial and temporal covariability between the atmospheric transient eddy heat fluxes i e t and q in the northern hemisphere winter january march and the paths of the gulf stream gs kuroshio extension ke and oyashio extension oe are examined based on an atmospheric reanalyses and ocean observations for 1979 2009 for the climatological winter mean the northward heat fluxes by the synoptic 2 8 days transient eddies exhibit canonical storm tracks with their maxima collocated with the gs and ke oe the intraseasonal 8 days 3 months counterpart while having overall similar amplitude shows a spatial pattern with more localized maxima near the major orography and blocking regions lateral heat flux divergence by transient eddies as the sum of the two frequency bands exhibits very close coupling with the exact locations of the ocean fronts linear regression is used to examine the lead lag relationship between interannual changes in the northward heat fluxes by the transient

western boundary currents and frontal air sea interaction gulf stream and kuroshio extension abstract in the northern hemisphere midlatitude western boundary current wbc systems there is a complex interaction between dynamics and thermodynamics and between atmosphere and ocean their potential contribution to the climate system motivated major parallel field programs in both the north pacific kuroshio extension system study kess and the north atlantic climate variability and predictability clivar mode water dynamics experiment climode and preliminary observations and analyses from these programs highlight that complexity the gulf stream gs in the north atlantic and the kuroshio extension ke in the north pacific have broad similarities as subtropical gyre wbcs but they also have significant differences which affect the regional air sea exchange processes and their larger scale interactions the 15 yr satellite altimeter data record which provides a rich source of information is combined here with the longer historical record from in situ data to describe and compare the curr

how strong are the southern hemisphere storm tracks 1 the real strength of the southern hemisphere sh storm tracks is poorly known as the ncep ncar and ecmwf reanalyses differ significantly in this measure in this work the cosmic gps radio occultation dataset is used to investigate this issue the ratio of the strength of the sh storm tracks to that in the northern hemisphere nh based on the cosmic dataset can be regarded as close to the true inter hemisphere ratio since the dataset has similar biases and errors in both hemispheres comparing this ratio with that based on the reanalysis it is found that the strength of the sh storm tracks in the ncep ncar reanalysis is significantly biased low by at least 25 at 300 hpa while those in the ecmwf reanalyses are much closer to that inferred from cosmic observations but era40 may be biased low by 5 10

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

dissipative intraplate faulting during the 2016 mw 6 2 tottori japan earthquake the 2016 m w 6 2 tottori earthquake occurred on 21 october 2016 and produced thousands of aftershocks here we analyze high resolution relocated seismicity together with source properties of the mainshock to better understand the rupture process and energy budget we use a matched filter algorithm to detect and precisely locate 10 000 previously unidentified aftershocks which delineate a network of sharp subparallel lineations exhibiting significant branching and segmentation seismicity below 8 km depth forms highly localized fault structures subparallel to the mainshock strike shallow seismicity near the main rupture plane forms more diffuse clusters and lineations that often are at a high angle in map view to the mainshock strike an empirical green s function technique is used to derive apparent source time functions for the mainshock which show a large amplitude pulse 2 4 s long we invert the apparent source time functions for a slip distribution and observe a 16 km 2 patch with average slip 3 2 m 93 of the seismic moment is below 8 km depth which is approximately the depth below which the seismicity becomes very localized these observations suggest that the mainshock rupture area was entirely within the lower half of the seismogenic zone the radiated seismic energy is estimated to be 5 7 10 13 j while the static stress drop is estimated to be 18 27 mpa these values yield a radiation efficiency of 5 7 which indicates that the tottori mainshock was extremely dissipative we conclude that this inefficiency in energy radiation is likely a product of the immature intraplate environment and the underlying geometric complexity

ocean frontal effects on the vertical development of clouds over the western north pacific in situ and satellite observations abstract a suite of shipboard and satellite observations are analyzed and synthesized to investigate the three dimensional structure of clouds and influences from sea surface temperature fronts over the western north pacific sharp transitions are observed across the kuroshio extension ke front in the marine atmospheric boundary layer mabl and its clouds the ocean s influence appears to extend beyond the mabl with higher cloud tops in altitude along the ke front than the surroundings in winter intense turbulent heat release from the ocean takes place on the southern flank of the ke front where the cloud top penetrates above the mabl and reaches the midtroposphere in this band of high cloud tops frequent lightning activity is observed the results of this study suggest a sea level pressure mechanism for which the temperature gradient in the mabl induces strong surface wind convergence on the southern flank of the ke front deepening the clouds there in early summer sea fog frequently occurs on

separation of climatological imprints of the kuroshio extension and oyashio fronts on the wintertime atmospheric boundary layer their sensitivity to sst resolution prescribed for atmospheric reanalysis abstractmesoscale structures of the wintertime marine atmospheric boundary layer mabl as climatological imprints of oceanic fronts within the kuroshio oyashio extension koe region east of japan are investigated by taking advantage of high horizontal resolution of the era interim global atmospheric reanalysis data for which the resolution of sea surface temperature sst data has been improved these imprints including locally enhanced sensible and latent heat fluxes and local maxima in cloudiness and precipitation in association with locally strengthened surface wind convergence in the vicinities of sst fronts along the warm kuroshio extension and cool oyashio to its north are also identified in high resolution satellite data in addition to these mesoscale mabl features meridionally confined near surface baroclinic zones and zonally oriented sea level pressure slp minima associated with the dual sst fronts are represented in era interim only in the period of high resolution sst but those impri

influence of the meridional shifts of the kuroshio and the oyashio extensions on the atmospheric circulation abstract the meridional shifts of the oyashio extension oe and of the kuroshio extension ke as derived from high resolution monthly sea surface temperature sst anomalies in 1982 2008 and historical temperature profiles in 1979 2007 respectively are shown based on lagged regression analysis to significantly influence the large scale atmospheric circulation the signals are independent from the enso teleconnections which were removed by seasonally varying asymmetric regression onto the first three principal components of the tropical pacific sst anomalies the response to the meridional shifts of the oe front is equivalent barotropic and broadly resembles the north pacific oscillation western pacific pattern in a positive phase for a northward frontal displacement the response may reach 35 m at 250 hpa for a typical oe shift a strong sensitivity since the associated sst anomaly is 0 5 k however the amplitude but not the pattern or statistical significance strongly depends on the lag and an

estimation of the high frequency radiation of the 2000 tottori japan earthquake based on a dynamic model of fault rupture application to the strong ground motion simulation abstract in the present study we investigate the high frequency hf radiation mechanism of the 2000 tottori earthquake in japan based on a 3d spontaneous fault rupture dynamic model we generalize the model of hf radiation of a suddenly stopping circular crack madariaga 1977 boatwright 1982 to the radiation from a general 3d rupture in a planar fault where hf is radiated during gradual changes of rupture velocity at the rupture front local rupture velocity changes are expressed as the divergence of local rupture velocity vectors that are derived from gradients of rupture times from the dynamic model our numerical model of the tottori earthquake indicates that rupture velocity changes are largely induced by barriers locally stronger fault sections across the fault plane and that hf radiation mainly originates within asperities large stress drop regions in areas where the product of dynamic stress drop and rupture velocity changes is maximum we develop a strong ground motion simulation methodology that incorporates hf radiation inferred from a dynamic fault rupture model using this methodology we investigate the hf radiation of the tottori earthquake by inverting observed near source acceleration envelopes of the earthquake our inversion results corroborate that hf radiation originates within asperities and show that significant hf radiation represents no more than a 20 of the total asperity area our results show that the incorporation of a directivity factor on the basis of a well defined physical rupture model to the radiation pattern leads to a significant improvement in fitting of observed ground motions our simulated near source strong ground motions of the tottori earthquake are also able to reproduce the 2 radiation theoretically predicted in 2d dynamic fault rupture models

the atmospheric response to weak sea surface temperature fronts abstractthe response of the atmospheric boundary layer to fronts of sea surface temperature sst is characterized by correlations between wind stress divergence and the downwind component of the sst gradient and between the wind stress curl and the crosswind component of the sst gradient the associated regression or coupling coefficients for the wind stress divergence are consistently larger than those for the wind stress curl to explore the underlying physics the authors introduce a linearized model of the atmospheric boundary layer response to sst induced modulations of boundary layer hydrostatic pressure and vertical mixing in the presence of advection by a background ekman spiral model solutions are a strong function of the sst scale and background advection and recover observed characteristics the coupling coefficients for wind stress divergence and curl are governed by distinct physics wind stress divergence results from either large scale winds crossing the front or from a thermally direct

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

the influence of sea surface temperature on surface wind in the eastern equatorial pacific seasonal and interannual variability abstract the climate of the eastern pacific exhibits a pronounced equatorial asymmetry boundary layer air originating in the southern hemisphere trades crosses the equator and flows into the intertropical convergence zone itcz whose southern limit is nearly always located at least 4 to the north of the equator the sea surface temperature sst distribution is characterized by a prominent cold tongue centered 1 s a strong frontal zone centered 2 n and a warm eastward current centered near 5 n the surface wind field exhibits a pronounced horizontal divergence as the air flows northward across the oceanic frontal zone these features vary in strength in response to the annual cycle and the el nino southern oscillation phenomenon the northward cross equatorial surface winds the cold tongue and the frontal zone all tend to be strongest during the cold season july through november during the cold season of the coldest years when the cold tongue is most prominent the cross equatorial flow t

strong ground motion estimation in the sea of marmara region turkey based on a scenario earthquake we perform a broadband frequency bedrock strong ground motion simulation in the marmara sea region turkey based on several fault rupture scenarios and a source asperity model the technique combines a deterministic simulation of seismic wave propagation at low frequencies with a semi stochastic procedure for the high frequencies to model the high frequencies we applied a frequency dependent radiation pattern model which efficiently removes the effective dependence of the pattern coefficient on the azimuth and take off angle as the frequency increases the earthquake scenarios considered consist of the rupture of the closest segments of the north anatolian fault system to the city of istanbul our scenario earthquakes involve the rupture of the entire north anatolian fault beneath the sea of marmara namely the combined rupture of the central marmara fault and north boundary fault segments we defined three fault rupture scenarios based on the location of the hypocenter selecting a preferred hypocentral location near a fault bend for each case we analysed the effect of location of the asperity within the central marmara fault on the subsequent ground motion as well as the influence of anelasticity on the highfrequency attenuation characteristics the fault and asperity parameters for each scenario were determined from empirical scalings and from results of kinematic and dynamic models of fault rupture we calculated the resulting time series and spectra for ground motion at istanbul and evaluated the sensitivity of the predictions to choice of model parameters the location of the hypocenter is thus shown to be a critical parameter for determining the worst scenario earthquake at istanbul we also found that anelasticity has a significant effect on the regional attenuation of peak ground accelerations our simulated ground motions result in large values of acceleration response spectra at long periods which could be critical for building damage at istanbul during an actual earthquake d 2004 elsevier b v all rights reserved

the response of the pacific storm track and atmospheric circulation to kuroshio extension variability an index of the kuroshio extension front strength is produced using a maximum covariance analysis between sea surface temperature sst and sea surface height ssh gradient observations and composites of the atmospheric state are presented during its positive and negative phases using reanalysis data 1992 2011 it is found that when the kuroshio extension is less more meandering with a stronger weaker sst front the atmospheric heat transport by transient eddies is increased in the western eastern pacific region consistent with an increase decrease in low level baroclinicity analysis of the eddy mean flow interaction shows that this zonal shift in heat transport forces anomalous barotropic flow in the eastern pacific where blocking frequency is strongly influenced the above relationships cannot be reconciled with the known response of the north pacific storm track to remote forcing from the tropical pacific nor can they be explained by the response of the ocean to atmospheric forcing via surface heat fluxes or winds rather the zonal shift in the storm track highlighted here and the associated changes in the large scale circulation are interpreted as a response to the interannual variability of the kuroshio extension front

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

near fault broadband ground motion simulations of the 2016 meinong taiwan earthquakenear fault broadband ground motion simulations of the 2016 meinong taiwan earthquake

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

dynamic inversion of the 2000 tottori earthquake based on elliptical subfault approximations 1 we propose a simplified nonlinear method for the kinematic and dynamic inversion of near field strong motion data at low frequencies using a few elliptical patches we reduce the number of independent parameters of the inverse problem we apply this method to the dynamic inversion of the western tottori japan earthquake mw 6 6 6 8 of 6 october 2000 using unfiltered records we relocated the hypocenter close to 14 km in depth fifteen records obtained by the kik net and k net accelerometer networks were then filtered to the 0 1 0 5 hz frequency range and integrated to displacement we compare observed and synthetic records using the 2 norm a nonlinear kinematic inversion for the elliptical subfaults is first computed using the neighborhood algorithm na inversion converges to a slip distribution modeled by just two elliptical patches we then propose a dynamic inversion method based on the same simple geometrical ideas dynamic rupture propagation is computed by finite differences on a coarse numerical grid rupture propagation is controlled by a classical slip weakening friction law inversion is implemented with the na for a barrier model in this model prestress is uniform and rupture propagation is arrested by a simple distribution of barriers inversion converges to a model with two elliptical barriers synthetics computed for the dynamic inversion fit the observed data reducing the variance by nearly 60 by making different assumptions about the rupture process we illustrate the nonuniqueness of the solution to dynamic inversion

near fault strong motion complexity of the 2003 bam earthquake iran and low frequency ground motion simulation summary the 2003 december 26 bam earthquake was an intermediate size strike slip event that occurred beneath the bam city causing more than 26000 fatalities the record of the only near fault station bam station shows a clear long period pulse in almost fault normal direction suggesting a near fault forward directivity effect contributing to the heavy damage observed in bam city in this study the long period 0 1 1 5hz strong ground motions were simulated to answer some ambiguities in source parameters for fully description of the observed motion in different components at bam station to this end the hisada s kinematic model accounting for both heterogeneous source characteristics and underground geology is applied to simulate the long period ground motion different source scenarios suggested by previous studies are examined and the optimum scenario that could provide the best fitting between the simulated and observed motions for different components was introduced the slip model and asperities as well as velocity structure parameters are optimized in order to have the best possible fit between the simulated and observed velocity time histories and spectra the good agreements between the simulated and observed low frequency motions indicate a successful identification of source and slip parameters of the bam earthquake and provide a good test for the simulation technique furthermore the uniqueness of the identified source parameters and the slip model is further checked against the observed near and far field recordings of the bam earthquake a good agreement between the simulated and the observed waveforms provides a base for model verification and results confirmation

new approach for coupling k 2 and empirical green s functions application to the blind prediction of broad band ground motion in the grenoble basin summary we present a new approach for performing broad band ground motion time histories 0 1 30 hz of a future earthquake in a sedimentary basin synthetics are computed with an hybrid scheme combining reciprocity based 3 d spectral element method simulations at low frequencies and empirical green s functions egf at high frequencies the combination between both deterministic and empirical parts results in a set of hybrid green s functions summed according to a new k 2 kinematic model algorithm the summation technique enables to remove the high frequency artefacts that appear above the egf corner frequency the ground motion variability is assessed by generating a variety of source parameter sets selected from ap rioriprobability density functions this leads to a population of response spectra from which the median spectral acceleration and standard deviation values are derived the method is applied to simulate a m w 5 5 event in the deep grenoble basin french alps the comparison with ec8 regulations suggests the need of specific design spectra in the grenoble valley

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

three dimensional simulation of the near fault ground motion for the 1995 hyogo ken nanbu kobe japan earthquake abstract the 17 january 1995 hyogo ken nanbu earthquake is a typical example showing that the ground motions along basin edge faults can be very destructive in this study we simulate the near fault ground motion from this earthquake based on a kinematic fault model and a simplified 3d velocity structure of the kobe area the kinematic earthquake rupture and the wave propagation are modeled using a 3d finite difference method fdm our simulation identifies the basin edge effect as an important factor that influenced the ground motion amplification pattern in the kobe area we found that the coupling of the source directivity and basin edge effects causes impulsive ground motions with extremely high amplitude at periods greater than 1 sec and in a narrow zone offset less than 1 km from the basin edge the combination of these effects acted to create a fairly continuous band of amplification that extends about 30 km in an elongated zone parallel to the basin edge boundary in some areas localized site effects might have been as important as the abovementioned effects but they cannot explain the continuity of the extended east west zone of damage

is it optimal to tow air guns shallow to enhance low frequencies abstractin marine seismic acquisition it used to be commonly accepted that it is optimal to tow the source deep to enhance the low frequency content in the seismic data however mayne and quay found in 1971 that the low frequency response of air guns actually improves as the source depth decreases we evaluated a simple ad hoc theory that demonstrates that two effects are counteracting each other the free surface effect favors deep towed sources whereas the bubble time period increasing with decreasing source depth favors shallower tow depths from a fjord test we found that combining several source depths in an air gun array might flatten and improve the low frequency part of the source spectrum the experiment confirms that various source depths result in local characteristic maxima in the low frequency spectrum corresponding to the bubble time period of the air gun

dependence of the climatological axial latitudes of the tropospheric westerlies and storm tracks on the latitude of an extratropical oceanic front 1 major storm tracks where migratory cyclones and anticyclones recurrently develop are observed around midlatitude oceanic frontal zones with strong meridional gradient of sea surface temperature sst a set of atmospheric general circulation model experiments is performed with zonally uniform sst prescribed at the model lower boundary the latitudinal sst profile for each hemisphere is characterized by a single front the frontal latitude is varied systematically from one experiment to another while the intensity of the frontal gradient is kept unchanged though idealized the experiments reveal a climatological tendency for a low level storm track to be organized along or slightly poleward of the sst front if located in the subtropics or midlatitudes as a surface manifestation of an eddy driven polar front jet pfj surface westerly axis tends to form on the poleward flank of the front this anchoring effect of the sst front is also hinted at upper levels but the climatological positions of the storm track and pfj are less sensitive to the frontal latitude for the sst front at subpolar latitude the joint primary axes of the upper level storm track and pfj form in midlatitudes away from the sst front their positions correspond to their counterpart simulated with a particular sst profile from which frontal gradient has been removed suggesting that the anchoring effect of a subpolar sst front on the storm track and pfj is overshadowed by atmospheric internal dynamics namely the self maintenance mechanism of a midlatitude storm track and pfj through their interactions

the effect of gulf stream induced baroclinicity on u s east coast winter cyclones abstract midlatitude cyclones develop off the carolinas during winters and move north producing gale force winds ice and heavy snow it is believed that boundary layer and air sea interaction processes are very important during the development stages of these east coast storms the marine boundary layer mbl off the mid atlantic coastline is highly baroclinic due to the proximity of the gulf stream just offshore typical horizontal distances between the wilmington coastline and the western edge of the gulf stream vary between 90 and 250 km annually and this distance can deviate by over 30 km within a single week while similar weekly gulf stream position standard deviations also exist at cape hatteras the average annual distance to the gulf stream frontal zone is much smaller off cape hatteras normally ranging between 30 and 100 km this research investigates the low level baroclinic conditions present prior to observed storm events the examination of nine years of data on the gulf stream position

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

two types of surface wind response to the east china sea kuroshio front abstracteffects of the sea surface temperature sst front along the east china sea kuroshio on sea surface winds at different time scales are investigated in winter and spring the climatological vector wind is strongest on the sst front while the scalar wind speed reaches a maximum on the warm flank of the front and is collocated with the maximum difference between sea surface temperature and surface air temperature sst sat the distinction is due to the change in relative importance of two physical processes of sst wind interaction at different time scales the sst front induced sea surface level pressure slp adjustment sf slp contributes to a strong vector wind above the front on long time scales consistent with the collocation of baroclinicity in the marine boundary layer and corroborated by the similarity between the thermal wind and observed wind shear between 1000 and 850 hpa in contrast the sst modulation of synoptic winds is more evident on the warm flank of the sst front large ther

strong ground motion simulation of the 12 may 2008 mw 7 9 wenchuan earthquake using various slip models abstract on 12 may 2008 a devastating earthquake of m w 7 9 occurred in the sichuan province of china the earthquake had disastrous consequences and cost more than 69 000 lives the rupture occurred along a 300 km long fault dipping northwest along the longmen shan fold thrust belt which separates the longmen shan of the tibetan plateau in the northwest from the sichuan basin in the southeast and is associated with a significant change in the crustal thickness we simulate the ground shaking due to the wenchuan earthquake by applying a hybrid broadband frequency strong ground motion simulation technique that combines deterministic simulation of low frequencies 0 1 1 0 hz with semistochastic modeling of high frequencies 1 0 10 hz we use three available finite fault slip models obtained from waveform inversion as input models for the earthquake scenarios the resulting simulations reveal large variations in ground shaking due to the rupture complexity in terms of a variety of factors including the location of asperities and the width of the fault plane the applied methodology successfully reproduces the strong ground motion distribution and frequency content of the seismic waves the simulated ground motions when calibrated with the recorded data can also be used to verify the finite fault slip models based on different teleseismic data and inversion schemes comparison with the damage distribution from reconnaissance field observations confirms the fault rupture complexity the applied simulation methodology provides a promising platform for predictive studies