deterministic approach for the seismic microzonation of bucharest the mapping of the seismic ground motion in bucharest due to the strong vrancea earthquakes is carried out using a complex hybrid waveform modeling method which combines the modal summation technique valid for laterally homogeneous anelastic media with finite differences technique and optimizes the advantages of both methods for recent earthquakes it is possible to validate the modeling by comparing the synthetic seismograms with the records we consider for our computations the frequency range from 0 05 to 1 0 hz and control the synthetic signals against the accelerograms of the magurele station low pass filtered with a cut off frequency of 1 0 hz of the 3 last major strong m w 6 vrancea earthquakes using the hybrid method with a double couple seismic source approximation scaled for the source dimensions and relatively simple regional bedrock and local structure models we succeeded in reproducing the recorded ground motion in bucharest at a satisfactory level for seismic engineering extending the modeling to the entire territory of the bucharest area we construct a new seismic microzonation map where five different zones are identified by their characteristic response spectra

strong shaking in los angeles expected from southern san andreas earthquake 1 the southernmost san andreas fault has a high probability of rupturing in a large greater than magnitude 7 5 earthquake sometime during the next few decades new simulations show that the chain of sedimentary basins between san bernardino and downtown los angeles form an effective waveguide that channels love waves along the southern edge of the san bernardino and san gabriel mountains earthquake scenarios with northward rupture in which the guided wave is efficiently excited produce unusually high long period ground motions over much of the greater los angeles region including intense localized amplitude modulations arising from variations in waveguide cross section

heterogeneity spectrum and scale anisotropy in the upper crust revealed by the german continental deep drilling ktb holes crustal heterogeneities and their statistical characteristics bear important information about the dynamic processes and evolution of the crust the velocity well log data from the german continental deep drilling project ktb offer a rare opportunity to measure directly the properties of crustal heterogeneities in this study we first estimated the power spectrum of crustal heterogeneities from the p velocity well logs of the two holes for the first time a power law spectrum of crustal heterogeneities was directly observed in the spatial wavelength range from a few meters to a few kilometers the slope of the vertical 1d power spectrum of the random velocity perturbations is about 1 1 corresponding to a flicker noise random medium the scale anisotropy ratio aspect ratio and the horizontal spectral slope of crustal heterogeneities were also estimated by cross correlation analysis between these two holes to be about 1 8 and 2 0 respectively

site to bedrock over 1d transfer function ratio an indicator of the proportion of edge generated surface waves 1 we study multi dimensional site effects in the smallsize deep sediment filled basin of grenoble french alps avery dense array composed of 3 component seismometers over a 1 km aperture is used to investigate propagation parameters of waves propagating across the array we present results for 6 teleseismic events for which we had a reference rock site for the frequency range 0 1 to 1 hz records are clearly dominated by edge generated surface waves quantification of energy carried by each identified wave train allows interpreting the difference between siteto bedrock and 1d transfer function estimates in terms of laterally propagating basin edge induced waves only above the fundamental resonance frequency of the basin a simple ratio between site to bedrock and 1d transfer function curves should thus provide an estimation of the relative contribution of 1d and 2d 3d effects in ground motion on the condition that all the time signal length is taken into account index terms 7212 seismology earthquake ground motions and engineering 7223 seismology seismic hazard assessment and prediction 7294 seismology instruments and techniques citation cornou c and p y bard site tobedrock over 1d transfer function ratio an indicator of the proportion of edge generated surface waves geophys res lett 30 9 1453 doi 10 1029 2002gl016593 2003

vrancea source influence on local seismic response in bucharest the mapping of the seismic ground motion in bucharest due to the strong vrancea earthquakes is carried out using a complex hybrid waveform modeling method that allows easy parametric tests starting from the actually available strong motion database we can make realistic predictions for the possible ground motion the basic information necessary for the modeling consists of a the representative mechanisms for the strong subcrustal events b the average regional structural model and c the local structure for bucharest two scenario earthquakes are considered and the source influence on the local response is analyzed in order to define generally valid ground motion parameters to be used in the seismic hazard estimations the source has its own detectable contribution on the ground motion and its effects on the local response in bucharest are quite stable on the transversal component t while the radial r and vertical v components are sensitive to the scenario earthquake although the strongest local effects affect the t component both observed and synthetic a complete determination of the seismic input for the built environment requires the knowledge of all three components of motion r v t the damage observed in bucharest for the march 4 1977 vrancea event the strongest earthquake to strike the city in modern times is in agreement with the synthetic signals and local response

estimating geophysical bedrock depth using single station analysis and geophysical data in the extra carpathian area of romania local site evaluation is an essential step in understanding the amplification of seismic motion induced by the complex geological structure and their estimation for future strong earthquakes in urban regions one of the critical parameters on evaluating amplification effects is the depth of the geophysical bedrock whose interface to soft sediments is responsible for the development of destructive resonance phenomena the present study is focused on the estimation of the geophysical bedrock depth along the extra carpathian area of romania moesian platform and surroundings by correlating and interpolating the results obtained from single station measurements with the available geological geophysical data each site was investigated through the computation of horizontal to vertical h v spectral ratios from three component single station measurements of ambient vibrations the geophysical bedrock depth was computed using a two step inversion scheme based on the retrieval of the rayleigh wave ellipticity peak at each seismic station using a regional generic velocity profile the fundamental frequency of resonance reaches the lowest value in the deepest side 0 07 hz and is rising to 13 hz in the south of the moesian platform where a shallow bedrock is present the computed bedrock depths from 30 to 3100 m show a dipping tendency towards the southern carpathians and complex features such as local outcrops and lateral depth variations superpose this gradually dipping trend in the carpathian foreland the bedrock is interpreted as the transition between different sediment layers of neogene while outside this area as the neogene cretaceous transition

the shear wave velocity underneath bucharest city romania from the analysis of love waves summary from the dispersion of love waves we infer models of shear wave velocity structure underneath bucharest romania at depths down to 2 km that can contribute to seismic hazard estimation waves from eight regional events recorded during 10 months with a network of 34 seismic broad band stations of the urban seismology urs experiment are used although these events provide poor azimuthal coverage the data reliably constrain a shear wave velocity model with an interface between the neogene and the cretaceous sediments that is dipping northwards towards the carpathian mountains array processing techniques that account for non uniform wave propagation are used to estimate the dispersion of structural phase velocity from this we infer subsurface structure at three different latitudes the neogene sediments are represented by a gradient layer with no significant lateral variation shear wave velocity increases from approximately 400 m s 1 near the surface to 1 km s 1 at 1 km depth and 5 km in the south and to 1 35 km s 1 at 1 5 km depth and 5 km in the north from the centre of bucharest respectively for the half space representing the cretaceous sediments we obtain shear wave velocities of 2 7 2 9 km s 1 the results are consistent with results from boreholes and shallow seismics for the near surface structure and results from receiver function studies and crustal refraction seismic studies for the deeper structure the details of the neogene layer comprising a vertical gradient fill a gap in existing models of the subsurface structure of bucharest and can contribute to modelling of seismic hazard for the city since the signalto noise ratio restricted useful data to the frequency range from 90 to 290 mhz the inversion could not constrain the near surface velocity independently due to strong trade off between near surface velocity and depth of half space the latter had to be introduced as ap rioridata from previous studies

a hybrid method for the estimation of ground motion in sedimentary basins quantitative modeling for mexico city to estimate the ground motion in two dimensional 2d laterally heterogeneous anelastic media a hybrid technique has been developed that combines modal summation and the finite difference method in the calculation of the local wave field owing to a seismic event both for small and large epicentral distances it is possible to take into account the source path and local soil effects as a practical application we have simulated the ground motion in mexico city caused by the michoacan earthquake of september 19 1985 by studying the one dimensional 1d response of the two sedimentary layers present in mexico city it is possible to explain the difference in amplitudes observed between records for receivers inside and outside the lake bed zone these simple models show that the sedimentary cover produces the concentration of high frequency waves 0 2 to 0 5 hz on the horizontal components of motion the large amplitude coda of ground motion observed inside the lake bed zone and the spectral ratios between signals observed inside and outside the lake bed zone can only be explained by 2d models of the sedimentary basin in such models the ground motion is mainly controlled by the response of the uppermost clay layer the synthetic signals explain the major characteristics relative amplitudes spectral ratios and frequency content of the observed ground motion the large amplitude coda of the ground motion observed in the lake bed zone can be explained as resonance effects and the excitation of local surface waves in the laterally heterogeneous clay layer also for the 1985 michoacan event the energy contributions of the three subevents are important to explain the observed durations

characterization of seismogenic zones of romania although the time and magnitude range covered by available seismological data is limited several significant regional trends are outlined in the seismogenic zones of romania vrancea region which is by far the most seismically active area has a persistent rate of occurrence of intermediate depth earthquakes clustered in a very confined focal volume and a clear compressive stress regime the deformation field as deduced from the available fault plane solutions is drastically reduced in the crust where the maximum magnitude is below 6 5 except shabla zone in bulgaria the system of major faults developed in a nw se direction in the carpathians foredeep area is certainly linked to the subduction process in vrancea although they seem not to play a significantly active role as could be expected for an active subduction process the existing data indicate an extensional deformation regime over the foredeep area and southern carpathians while a predominant compressive regime is outlined at the contact between the eastern margin of the pannonian depression and carpathians orogen in agreement with the bending tendency of the maximum horizontal compression orientation of the crustal stress field from ne sw in western and central europe to e w in the intra carpathian region grunthal and strohmeyer 1992

introduction to special section the ktb deep drill hole when we pose the question what do we want to know about the earth the answer is everything we are demanding we must be demanding our life and the very survival of our species depends on our understanding of the earth as long as we do not know when earthquakes will happen when volcanoes will erupt and how water circulates or energy is stored or minerals are concentrated our life is a matter of chance fortunately we are curious creatures and our curiousity leads us to observe measure and interpret our surroundings

fractal variability in superdeep borehole implications for the signature of crustal heterogeneities abstract the deep and superdeep boreholes of the german continental deep drilling program ktb provide probably the most extensive data archive on in situ properties of metamorphic crustal rock from a single site analysis of the variability of several geophysical parameters point out fractal features and a degree of correlation between data values comparable to 1 f noise accordingly the earth s crust at the ktb site can be statistically described as an inhomogeneous medium whose properties are basically invariant from metre to kilometre scale piecewise homogeneous models appear to be inadequate to represent petrophysical properties at least in the vertical dimension and 1 f noise offers a far more suitable concept to simulate heterogeneities in the earth s crust

lateral propagation effects observed at parkway new zealand a case history to compare 1d versus 2d site effects abstract the importance of 2d or 3d site effects has been shown by theoretical studies however there is a lack of observational evidence of site effects due to lateral heterogeneities we have evaluated 1d and 2d site effects in the data obtained by a dense seismograph array that operated for more than 2 months in the alluvial basin of parkway new zealand 1d site effects were evaluated using three independent techniques spectral ratios relative to a reference station spectral ratios of horizontal relative to vertical ground motion and a generalized inversion scheme site effects due to lateral heterogeneity were investigated in detail for two events using frequency wavenumber analysis our results show that it is not possible to separate 1d from 2d site effects using frequency domain techniques this explains the scatter obtained from standard 1d data analysis the 1d resonance peaks will be more or less contaminated with laterally propagating waves for different events

structural model for the saxothuringian moldanubian suture in the variscan basement of the oberpfalz northeastern bavaria f r g interpreted from geophysical data abstract the moldanubian saxothuringian boundary marks a prominent subduction zone in the internal parts of the european variscides in the oberpfalz area deep reflection seismic profiles show a high density of various reflectors mainly in the upper crust indicating a complex polyphase deformation during the collision process seismic structures and related data from surface geology suggest that the moldanubian saxothuringian collision consisted of two main phases the first phase is marked by extensive nw directed overthrusting of moldanubian onto saxothuringian crust along se dipping master decollements some of which can be traced down to the moho during an advanced stage progressive overthrusting led to the development of wedge structures associated with se directed backthrusting and backfolding in the upper structural levels subsequently some of these wedges and their related decollements were folded to form the main ne striking anticlines the first phase of crustal imbrication correlates with a regional low pressure high temperature metamorphism at about 320 ma decreasing in grade northwestward the second phase is characterized by a reorientation of the main direction of crustal shortening from nw se to sw ne which is interpreted as the result of the n directed indentation of the vindelician terrane into the moldanubian this event is recorded by conjugate systems of overthrusting and subsequent strike slip faulting in the oberpfalz and the bavarian forest and the black forest vosges area in the area of the southern german block between these basement outcrops the indentation front is marked by the arc shaped axes of gravimetric and magnetic anomalies and permo carboniferous troughs

broad band power law spectra of well log data in japan summary for the purpose of revealing the statistical characteristics of p wave velocity s wave velocity and density in the uppermost part of the crust we analysed well log data obtained from five deep wells in different tectonic regions in japan three wells through the mainly sedimentary rocks in the kanto plain and two wells in the kuju volcano group in kyushu island in the kanto plain the power spectral density of fractional fluctuation of p wave velocity and that of density are proportional to a power of the spatial wavelength from a few metres to 100 m where the power index slope of the power spectral density at double logarithmic scale is 1 1 1 3 at the kuju volcano group that of p and s wave velocity and density also obey a power law with a power index of 1 3 1 6 for wavelengths from a few metres to few hundred metres correcting the effect of the moving box car observation window which corresponds to the separation of two receivers of the logging tool we find that the power law characteristics hold for wavelengths down to a few tens of centimetres the 1 d sections of the elastic inhomogeneities follow a kind of band limited self affine random process comparing the power spectral densities we find smaller values of the power index in stable areas and larger values in tectonically active areas the difference in the power index arises from long wavelength components

site effect study in urban area experimental results in grenoble france three methods are used to determine the site effect in the town of grenoble located in the western alps first we use the classical spectral ratio method in 14 sites to calculate the transfer function of the basin we find an amplification of 10 in the frequency range of 0 25 to 10 hz second we compare these results with the h over v spectral ratio method and propose a map of resonance frequency of the basin we find a lower resonance frequency in the center of the basin than on the edge that is consistent with the structure deduced from a gravity bouguer anomaly map finally we use the empirical green s function method to simulate a m w 5 5 earthquake at a distance of 20 km from the town the simulated acceleration reaches the level of 2 m s2 in the center of the basin compared to 0 2 m s2 on the edges the simulated ground motion we compute is smaller than the french seismic codes on the edge of the valley but significantly larger in the center

subsidence analysis and tectonic evolution of the external carpathian moesian platform region during neogene times abstract the miocene pliocene subsidence of the tectonic platforms in the romanian carpathians foreland is analysed using standard 1d backstripping techniques for individual wells combined in two regional sections and six contour maps the subsidence patterns were integrated together with previous paleostress and kinematic studies in order to derive the tertiary kinematics of the buried faults in the carpathians lower plate the study revealed accelerated subsidence during the early miocene in the western part of the moesian platform getic depression in direct relationship with the opening of a wsw ene trending extensional basin the largest subsidence recorded in the front of the carpathians took place during the late miocene due to final e ward emplacement of the thrust sheets the late miocene subsidence showed anomalous high values between the intramoesian and trotus faults as a result of the orogenic collision with the east european platform northward and acceleration of the subduction process in the se carpathians corner further pliocene subsidence continued only in the latter region the depocenter being shifted southward near the junction with the south carpathians foreland

analysis of three component ambient vibration array measurements summary both synthetic and observed ambient vibration array data are analysed using high resolution beam forming in addition to a classical analysis of the vertical component this paper presents results derived from processing horizontal components we analyse phase velocities of fundamental and higher mode rayleigh and love waves and particle motions ellipticity retrieved from h v spectral ratios a combined inversion with a genetic algorithm and a strategy for selecting possible model parameters allow us to define structural models explaining the data the results from synthetic data for simple models with one or two layers of sediments suggest that in most cases the number of layers has to be reduced to a few sediment strata to find the original structure generally reducing the number of soft sediment layers in the inversion process with genetic algorithms leads to a class of models that are less smooth they have a stronger impedance contrast between sediments and bedrock combining love and rayleigh wave dispersion curves with the ellipticity of the fundamental mode rayleigh waves has some advantages scatter is reduced when compared to using structural models obtained only from rayleigh wave phase velocity curves by adding information from love waves some structures can be excluded another possibility for constraining inversion results is to include supplementary geological or borehole information analysing radial components also can provide segments of rayleigh wave dispersion curves for modes not seen on the vertical component finally using ellipticity information allows us to confine the total depth of the soft sediments for real sites considerable variability in the measured phase velocity curves is observed this comes from lateral changes in the structure or seismic sources within the array constraining the inversion by combining love and rayleigh wave information can help reduce such problems frequency bands in which the rayleigh wave dispersion curves show considerable scatter are often better resolved by love waves information from the horizontal component can be used to correctly assign the mode number to the different phase velocity curve segments especially when two modes seem to merge at osculation points such merging of modes is usually observed for rayleigh waves and thus can be partly solved if additional information from the love waves and the horizontal component of rayleigh waves is considered whenever a site presents a velocity inversion below the top layer love wave data clearly helps to better constrain the solution

strong motion from surface waves in deep sedimentary basins it is widely recognized that long period surface waves generated by conversion of body waves at the boundaries of deep sedimentary basins make an important contribution to strong ground motion the factors controlling the amplitude of such motion however are not widely understood a study of pseudovelocity response spectra of strong motion records from the los angeles basin shows that late arriving surface waves with group velocities of about 1 km sec dominate the ground motion for periods of 3 sec and longer the rate of amplitude decay for these waves is less than for the body waves and depends significantly on period with smaller decay for longer periods the amplitude can be modeled by the equation batchmode documentclass fleqn 10pt legalpaper article usepackage amssymb usepackage amsfonts usepackage amsmath pagestyle empty begin document mathrm log y f mathbf m r mathrm e c br mathrm b end document where y is the pseudovelocity response f m r e is an attenuation relation based on a general strong motion data set m is moment magnitude r e is the distance from the source to the edge of the basin r b is the distance from the edge of the basin to the recording site and b and c are parameters fit to the data the equation gives values larger by as much as a factor of 3 than given by the attenuation relationships based on general strong motion data sets for the same source site distance it is clear that surface waves need to be taken into account in the design of long period structures in deep sedimentary basins the ground motion levels specified by the earthquake provisions of current building codes in california at least accommodate the long period ground motions from basin edge generated surface waves for periods of 5 sec and less and earthquakes with moment magnitudes of 7 5 or less located more than 20 km outside the basin there may be problems at longer periods and for earthquakes located closer to the basin edge the results of this study suggest that anelastic attenuation may need to be included in attempts to model long period motion in deep sedimentary basins to obtain better data on surface waves in the future operators of strong motion networks should take special care for the faithful recording of the long period components of ground motion it will also be necessary to insure that at least some selected recorders once triggered continue to operate for a time sufficient for the surface waves to traverse the basin with velocities of about 1 km sec that time will be as long as 100 sec for a basin the size of the los angeles basin

estimation of site effects in bucharest caused by the may 30 31 1990 vrancea seismic events the vrancea region seismicity characterized by focal depths larger than 60 km and major events with magnitudes m w 6 9 is responsible for the most destructive effects experienced in the romanian territory and may seriously affect high risk construction located on a wide area from central to eastern europe this seismogenic volume must be taken into account both for seismic hazard analysis at the regional level southeastern europe and national level romania and bulgaria as well as for microzonation studies of the highly populated cities located in the range of influence of this source since about four destructive earthquakes occur every century in vrancea the microzonation of bucharest the main city exposed to the potential damages due to these strong intermediate depth shocks represents an essential step towards the mitigation of the local seismic risk two main approaches can be considered for the evaluation of the local seismic hazard a collection and extended use for engineering purposes of the recorded strong motion data and b advanced modelling techniques that allow us the computation of a realistic seismic input which can compensate for the lack of strong motion records actually available only for a few events that occurred in the last 20 30 years

a comparison of observed and simulated site response in the rhone valley summary site effects in the city of sion in the rhone valley are analysed from weak motion signals recorded on a dense temporary array we simulate the recorded events with a 3 d finite differ ence method for frequencies up to 4 hz using a recently developed velocity model of the sion basin site to reference fourier spectral ratios are computed from 16 local and regional events all sites exhibit amplification factors of up to 12 between 0 5 and 0 6 hz which can be reproduced by the numerical simulations by rotating the weak motion to directions parallel and perpendicular to the valley axis we show that this low frequency amplification is caused by the sh00 and sv0 fundamental modes of 2 d resonance additional peaks of amplification can be observed at higher frequencies with amplification factors of up to 20 at some sites application of the high resolution frequency wavenumber and the multiple signal char acterization method to the vertical component of recorded and simulated signals show that edge generated surface waves arriving from almost all directions dominate the wavefield at 1 25 and 2 50 hz peak ground velocities computed from the simulated ground motion show interference patterns that depend strongly on the incidence direction and the computed amplification of peak ground velocities are generally in agreement with the observations we conclude that the complex 3 d geometry of the basin needs to be considered to evaluate site effects up to at least 2 5 hz

spectral amplification in a sediment filled valley exhibiting clear basin edge induced waves various site response estimates are presented for a linear array deployed in the coachella valley california during the 1992 landers big bear aftershock sequence this systematic comparison is unique in that the response of the site is clearly dominated by basin edge induced waves average sediment to bedrock spectral ratios for long s wave windows which include the basin edge induced waves exhibit amplification factors as high as 18 below 7 hz the deep basin structure which gives rise to the obvious multi dimensional effects produces a fundamental resonant peak that shifts between basin sites from 0 23 to 0 48 hz as the depth to bedrock changes above 0 6 hz where the largest amplifications occur the response is remarkably similar between sites and appears to be dominated by a near surface layer that is relatively uniform across the valley the apparent fundamental resonant frequency of this layer is between 0 8 and 1 hz sediment to bedrock spectral ratios computed using shorter windows that exclude the basin edge induced waves imply that the multi dimensional effects are significant only below 4 hz where they increase amplifications by an approximate factor of 2 spectral ratios computed using coda windows taken at twice the s wave travel time exhibit amplifications that are an average factor of 1 7 greater between 1 and 4 hz than those of the s wave estimates this discrepancy does not improve by taking coda windows later at four times the s wave travel time horizontal to vertical component s wave spectral ratios do not agree with the sediment to bedrock ratios however they do exhibit a clear peak at the fundamental resonant frequency of the deep basin structure sediment to bedrock spectral ratios of ambient seismic noise are also inconsistent with the s wave estimates however horizontal to vertical noise ratios exhibit clear peaks near the fundamental resonant frequencies of both the deep basin structure below 0 6 hz and the suspected near surface layer between 0 8 and 1 hz therefore ambient noise data appear to provide valuable constraints on the basin structure ongoing efforts involve multi dimensional modeling of the observed basin edge induced phases and resonant frequencies

upper crustal seismic velocity heterogeneity as derived from a variety of p wave sonic logs sonic log measurements provide detailed 1 d information on the distribution of elastic properties within the upper crystalline crust at scales from about one metre to several kilometres 10 p wave sonic logs from six upper crustal drill sites in europe and north america have been analysed for their second order statistics the penetrated lithological sequences comprise archean volcanic sequences proterozoic mafic layered intrusions and precambrian to phanerozoic gneisses and granites despite this variability in geological setting tectonic history and petrological composition there are notable similarities between the various data sets after removing a large scale deterministic component from the observed velocity depth function the residual velocity fluctuations of all data sets can be described by autocovariance functions corresponding to band limited self affine stochastic processes with quasi gaussian probability density functions depending on the maximum spatial wavelength present in the stochastic part of the data the deterministic trend can be approximated either by a low order polynomial best fit or by a moving average of the original sonic log data the choice of the trend has a significant impact on the correlation length and on the standard deviation of the residual stochastic component but does not affect the hurst number for trends defined by low order polynomial best fits correlation lengths were found to range from 60 to 160 m whereas for trends defined by a moving average the correlation lengths are dominated by the upper cut off wavenumber of the corresponding filter regardless of the trend removed the autocovariance functions of all data sets are characterised by low hurst numbers of around 0 1 0 2 or equivalently by power spectra decaying as 1 k a possible explanation of this statistical uniformity is that sonic log fluctuations are more sensitive to the physical state in particular to the distribution of cracks than to the petrological composition of the probed rocks

an investigation on how inner core structures obtained through radar data assimilation affect track forecasting of typhoon jangmi 2008 near taiwan island the impacts of radar data assimilation da on the westward track deflection of typhoon jangmi 2008 near taiwan island and the deflection mechanism are investigated initial conditions from two data assimilation experiments with significant track forecast differences are analyzed and compared the environmental axisymmetric wavenumber 1 to 3 asymmetric fields of the typhoon are decomposed using vortex separation and fourier decomposition methods the components are selectively recomposed into new initial conditions that include different vortex scale components to examine the impact of individual components on the track prediction the wavenumber 1 asymmetric structure is found to play a dominant role in the westward deflection of typhoon jangmi and the accurate analysis of this component with radar da helps to improve the track forecast the wavenumber 1 asymmetric circulation is manifested as a pair of cyclonic and anticyclonic gyres with well defined ventilation flows through the inner core region which provides additional steering of the typhoon vortex the layer mean environmental steering flow and ventilation flow associated with the wavenumber 1 gyres are further calculated to quantitatively evaluate the impact of ventilation flow the ventilation flow is shown to be responsible for most of the westward motion component suggesting again its role in causing the westward track deflection of typhoon jangmi the results also suggest the importance of analyzing vortex scale asymmetric structures for accurate tropical cyclone track forecasting especially when there is a significant track deflection

observations of basin ground motions from a dense seismic array in san jose california we installed a dense array of 41 digital seismographs in san jose california to evaluate in detail the effects of a deep sedimentary basin and shallow sedimentary deposits on earthquake ground motions this urban array is located near the eastern edge of the santa clara valley and spans the evergreen sedimentary basin identified by gravity data average station spacing is 1 km with three stations initially spaced 110 m apart despite the high noise urban environment the stations of the array successfully triggered on and recorded small local earthquakes m 2 5 2 8 at 10 25 km distance and larger regional events such as the m 5 0 bolinas earthquake 90 km distance m 4 6 5 6 earthquakes near mammoth lakes 270 km distance m 4 9 5 6 events in western nevada 420 km distance and the m 7 1 hector mine earthquake 590 km distance maps of spectral ratios across the array show that the highest amplitudes in all frequency bands studied 0 125 8 hz are generally observed at stations farther from the eastern edge of the santa clara valley larger spectral amplitudes are often observed above the western edge of the evergreen basin snapshots of the recorded wavefield crossing the array for regional events to the east reveal that large low frequency 0 125 0 5 hz arrivals after the s wave travel from south to north across the array a moving window cross correlation analysis finds that these later arrivals are surface waves traveling from the south the timing and propagation direction of these arrivals indicates that they were likely produced by scattering of incident s waves at the border of the santa clara valley to the south of the array it is remarkable that the largest low frequency phases at many of the valley sites for regional events to the east are basin surface waves coming from a direction about 70 degrees different from that of the epicenters basin surface waves emanating from the eastern edge of the valley are also identified by the cross correlation analysis

scaling behaviour of vertical magnetic susceptibility and its fractal characterization an example from the german continental deep drilling project ktb the variations of rock magnetism reflect the geological inhomogeneities of the earth s crust i e its petrological mineralogical and structural organization the present state of the crust bears meaningful information of its past dynamic processes and evolution we analysed magnetic susceptibility data series from the boreholes of the german continental deep drilling project ktb by means of spectral and rescaled range r s analyses we could detect a scaling behaviour of magnetic data series and quantify it in fractal terms in particular the r s method yields more precise results than the fourier analysis and leads to hurst coefficients h 0 5 which means that the magnetic variations exhibit some persistence with depth because of the relation between rock magnetism and crustal features we suggest that the magnetic vertical inhomogeneities in the ktb area can be described by a self affine model with h 0 8 corresponding to a fractal dimension d 1 2