holocene river development and environmental change in upper wharfedale yorkshire dales england this paper provides the first radiometrically dated evidence of holocene alluvial landform development in upper wharfedale yorkshire dales four river terraces are identified terraces 1 and 2 are closely linked to late devensian and early holocene environmental change with gravel reworked from local glacial and periglacial sources prior to cementation by carbonate rich waters u series dating of cement provides age estimates for cementation of between ca 5 1 7 4 kyr bp for terrace 1 and ca 3 6 8 0 kyr bp for terrace 2 u series dating of tufas overlying terraces 1 and 2 produced ages of ca 4 2 4 5 kyr bp and ca 2 1 2 2 kyr bp respectively and provide upper age limits for terrace formation terrace 3 marks a change in sediment calibre supply and sedimentation style and 14c dating suggests that the principal source of fine grained material may be agricultural expansion in the yorkshire dales from ca ad 600 1350 cal yr bp radiocarbon dates indicate that terrace 4 was deposited from the eleventh century with initiation of the contemporary floodplain between the fifteenth and seventeenth centuries ad both these lowest units contain sediments contaminated with heavy metals as a result of mining activities within the catchment the evidence presented in this study is comparable to that of research undertaken in upland environments elsewhere in northern and western britain thereby adding to the corpus of information currently available for evaluating the fluvial geomorphological response to climate and vegetation change during the holocene copyright 2000 john wiley sons ltd

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

interferometric daylight seismic imaging summary claerbout s daylight imaging concept is generalized to a theory of interferometric seismic imaging ii interferometric seismic imaging is defined to be any algorithm that inverts correlated seismic data for the reflectivity or source distribution as examples we show that ii can image reflectivity distributions by migrating ghost reflections in passive seismic data and generalizes the receiver function imaging method used by seismologists interferometric seismic imaging can also migrate free surface multiples in common depth point cdp data and image source distributions from passive seismic data both synthetic and field data examples are used to illustrate the different possibilities of ii the key advantage of ii is that it can image source locations or reflectivity distributions from passive seismic data where the source position or wavelet is unknown in some cases it can mitigate defocusing errors as a result of statics or an incorrect migration velocity the main drawback with ii is that severe migration artefacts can be created by partial focusing of virtual multiples

past and recent changes in the large scale tropospheric cycles of lead and other heavy metals as documented in antarctic and greenland snow and ice a review abstract the investigation of the occurrence of lead and other heavy metals in antarctic and greenland ancient ice and recent snow is of great interest in reconstructing the past natural tropospheric cycles of these metals and determining to what extent these cycles have now been altered by man because concentrations to be measured are exceedingly low down to the sub pg g level reliable data can however be obtained only if full control of contamination is achieved from field sampling to laboratory analysis the available data show that the past natural concentrations of pb cd zn cu and hg in antarctic ancient ice are highly dependent upon climatic conditions the highest values occurring during the coldest periods of the ice ages especially during the last glacial maximum about 18 000 years ago human activity has led to an increase in lead concentrations during recent centuries both in antarctica tenfold increase and in greenland two hundredfold increase this last increase was followed by a 7 5 fold decrease during the past two decades mainly as a consequence of the rapid fall in the use of lead alkyl additives in the usa as confirmed by recent isotopic data

three dimensional simulations of ground motions in the san bernardino valley california for hypothetical earthquakes on the san andreas fault three dimensional finite difference simulations of elastic waves in the san bernardino valley were performed for two hypothetical earthquakes on the san andreas fault a point source with moment magnitude m5 and an extended rupture with m6 5 a method is presented for incorporating a source with arbitrary focal mechanism in the grid synthetics from the 3 d simulations are compared with those derived from 2 d vertical cross section and 1 d flat layered models the synthetic seismograms from the 3 d and 2 d simulations exhibit large surface waves produced by conversion of incident s waves at the edge of the basin seismograms from the flat layered model do not contain these converted surface waves and underestimate the duration of shaking the seismograms from the 3 d simulations have larger amplitude coda than do the seismograms from the 2 d case because of the presence of off azimuth surface wave arrivals in the 3 d simulations that are not included in the 2 d simulations snapshots of the wavefield of the 3 d simulation show that these off azimuth arrivals represent surface waves reflected from the edges of the basin the anelastic attenuation of the sediments is a key parameter controlling the overall duration of motion some of the coda energy at rock sites near the basin edges represents leakage of surface wave energy out of the basin for the m6 5 earthquake simulation the largest ground velocities occur where surface waves reflected from the edge of the basin interfere constructively with the trapped waves that follow the direct s wave maps of maximum ground velocity are produced for two directions of rupture propagation the largest velocities occur in localized portions of the basin the location of the largest velocities changes with the rupture propagation direction contours of maximum shaking are also dependent on asperity positions and radiation pattern

geochemical records in holocene lake sediments of northern china implication for natural and anthropogenic inputs daihai lake is located in a hydrologically closed basin within the transitional zone of the east asian monsoon which has experienced significant lake level fluctuations the sedimentary sequence of a 12 08 m core was analyzed for mobile ca mg and sr and immobile elements al and fe and trace metals e g co ni cu zn and pb in order to study the changes of natural chemical compositions and the potential influences of the historical mining and use of metals during the holocene period climate changes have a significant influence on the concentrations of mobile elements in the holocene lake sediment high concentrations occurred during the times with high lake level resulting from enhanced catchment weathering due to strong monsoon effects different from these mobile elements the variation of immobile elements and trace metals in daihai lake sediment shows clear anthropogenic impact of the mining and use of metals in the last several millenniums a gradual increase in the concentrations and fluxes of metals from 5000 cal a b p is correlated well with the emergence of chinese civilization the concentrations and fluxes of these metals and immobile elements in the sediments increased rapidly between 2100 and 1250 cal a b p indicating the extensive use of metals during the warring states period 475 221 b c and the early han dynasty 206 b c 220 a d further increase of trace metals such as cu ni co and pb after the medieval warm period 1200 800 a b p likely reflects the increased metal emissions associated with extensive mining and utilization activities similar patterns of sedimentary metals between daihai lake in northern china and liangzhi lake in central china further indicate significant environmental impacts of the mining and utilization of metals in the progress of chinese civilization in the past several thousand years

deterministic seismic hazard in egypt summary the regional seismic hazard in egypt is assessed using a deterministic approach based on the computation of synthetic seismograms at a set of gridpoints located at distances of 0 2u from each other the main input for this computation are earthquake sources and structural models the earthquake sources are parametrized using focal mechanisms seismogenic areas and regional seismicity a number of deep seismic profiles have been used to define the crustal structures similar sets of gravity profiles have been used to define the density of the layers the peak displacement dmax peak velocity vmax and design ground acceleration dga are chosen and plotted to construct the seismic hazard maps there are similarities between computed and observed amplitudes of ground motion in terms of their values and spatial distributions the results obtained from the deterministic and probabilistic approaches are comparable the areas of high seismic hazard level are of great socio economic importance

geochemistry of daihai lake sediments inner mongolia north china implications for provenance sedimentary sorting and catchment weathering abstract to advance the understanding of sediment distribution catchment weathering hydraulic sorting and sediment provenance in a tectonically stable basin the geochemistry of surface sediment samples from daihai lake in north china is presented mud bulk sediments were analyzed for 10 major and 30 trace elements organic carbon and nitrogen and for 87sr 86sr ratios in silicate fraction acid insoluble ai and carbonates acid soluble as enrichment in fe2o3 cao mno mgo k2o and p2o5 and their positive correlation with al2o3 rb sr ratios and bivariate discrimination diagrams of k vs rb and th u vs th suggest low chemical weathering intensity under semiarid conditions in the daihai catchment accumulation of clays in deeper water sites by sedimentary sorting results in an evident distribution of sediment composition with the lake water depth although similar chondrite normalized ree rare earth element patterns of lake sediment samples with lree light rare earth element enrichment negative eu anomalies and an almost flat hree heavy rare earth element pattern may suggest similar sedimentary source rocks original sediment provenance can be recognized on the basis of their distinctive 87sr 86sr ai ratios and immobile th zr ti and nb trace element signature separating from weathering and sedimentary processes as well as from grain size effect

joint deconvolution of building and downhole strong motion recordings evidence for the seismic wavefield being radiated back into the shallow geological layers in this study the strong motion recordings collected by a vertical array of borehole sensors and a network of accelerometers installed in a nearby building distance between borehole and building 10 m are innovatively jointly analyzed through wavefield deconvolution analysis the analysis shows complicated patterns in the deconvolved wavefield of the borehole sensors that are interpreted by taking advantage of synthetic seismograms generated considering vertically propagating plane waves in the soil and building using a constrained deconvolution approach we show that it is possible to separate the different components of the wavefield and in particular to retrieve the input ground motion and the wavefield radiated back by the building at different levels in the borehole without a priori information about the attenuation structure and velocity of the building and soil this therefore allows the energy radiated back by the structure at different depth to be estimated which in the case of the bottom of the borehole at 145 m is of the order of 10 of the energy of the input wavefield in the 1 10 hz frequency band

2d finite difference viscoelastic wave modelling including surface topography we have pursued two dimensional 2d finite difference fd modelling of seismic scattering from free surface topography exact free surface boundary conditions for the particle velocities have been derived for arbitrary 2d topographies the boundary conditions are combined with a velocity stress formulation of the full viscoelastic wave equations a curved grid represents the physical medium and its upper boundary represents the free surface topography the wave equations are numerically discretized by an eighth order fd method on a staggered grid in space and a leap frog technique and the crank nicholson method in time in order to demonstrate the capabilities of the surface topography modelling technique we simulate incident point sources with a sinusoidal topography in seismic media of increasing complexities we present results using parameters typical of exploration surveys with topography and heterogeneous media topography on homogeneous media is shown to generate significant scattering we show additional effects of layering in the medium with and without randomization using a von karman realization of apparent anisotropy synthetic snapshots and seismograms indicate that prominent surface topography can cause back scattering wave conversions and complex wave patterns which are usually discussed in terms of inter crust heterogeneities

revising the 1759 kattegat earthquake questionnaires using synthetic wavefield analysis abstract in aseismic regions the lack of large earthquakes in modern times makes the study of historical earthquakes essential as such events often serve as the yardstick for estimating seismic hazards since the largest earthquakes with few exceptions took place hundreds of years ago we may claim that their recurrence times are very large or alternatively their magnitudes are biased upwards scandinavia is no exception in this regard and one interesting event in particular is the kattegat earthquake of 22 december 1759 it is unique in the sense that a macroseismic questionnaire was circulated in zealand within days of its occurrence the puzzling feature here is that intensity ranges from vii to i across zealand but then given i iii for hamburg and other north german cities we have chosen two avenues in reassessing the magnitude of the kattegat earthquake namely 1 2d finite difference fd waveform modelling to evaluate possible amplitude amplifications due to sub surface basin structures and 2 re assessing the intensity reports of the 1759 kattegat earthquake in light of the new european macroseismic scale ems 98 our 2d fd results show that the presence of the danish and the north german basins led to shear wave amplitude amplification by factors of 10 and 5 respectively this is equivalent to a significant increase or overestimation of the area of perception tied to i iii the re assessment of the macroseismic observations in light of the above results and the ems 98 downgrade the kattegat earthquake ms magnitude from 5 6 to 5 1

2d surface topography boundary conditions in seismic wave modelling new formulations of boundary conditions at an arbitrary two dimensional 2d free surface topography are derived the top of a curved grid represents the free surface topography while the grid s interior represents the physical medium the velocity stress version of the viscoelastic wave equations is assumed to be valid in this grid however the rectangular grid version attained by grid transformation is used to model wave propagation in this work in order to achieve the numerical discretization we show the detailed solution of the particle velocities at the free surface resulting from discretizing the boundary conditions by second order finite differences fds the resulting system of equations is spatially unconditionally stable the fd order is gradually increased with depth up to eighth order inside the medium staggered grids are used in both space and time and the second order leap frog and crank nicholson methods are used for time stepping we simulate point sources at the surface of a homogeneous medium with a plane free surface containing a hill and a trench applying parameters representing exploration surveys we present examples with a randomly realized surface topography generated by a 1d von karman function of order 1 viscoelastic simulations are presented using this surface with a homogeneous medium and with a layered randomized medium realization all generating significant scattering

monitoring a building using deconvolution interferometry i earthquake data analysis abstract for health monitoring of a building we need to separate the response of the building to an earthquake from the imprint of soil structure coupling and from wave propagation below the base of the building seismic interferometry based on deconvolution where we deconvolve the wave fields recorded at different floors is a technique to extract this building response and thus estimate velocity of the wave that propagates inside the building deconvolution interferometry also allows us to estimate the damping factor of the building compared with other interferometry techniques such as cross correlation and cross coherence interferometry deconvolution interferometry is the most suitable technique to monitor a building using earthquake records for deconvolution interferometry we deconvolve the wave fields recorded at all levels with the waves recorded at a target receiver inside the building this receiver behaves as a virtual source and we retrieve the response of a cut off building a short building that is cut off at the virtual source because the cut off building is independent from the structure below the virtual source the technique might be useful for estimating local structure and local damage we apply deconvolution interferometry to 17 earthquakes recorded during two weeks at a building in fukushima japan and estimate time lapse changes in velocity and normal mode frequency as shown in a previous study the change in velocity correlates with the change in normal mode frequency we compute the velocities from both traveling waves and the fundamental mode using coda wave interferometry these velocities have a negative correlation with the maximum acceleration of the observed earthquake records

inversion of borehole weak motion records observed in istanbul turkey summary the estimation of shear wave velocity and attenuation in near surface geology is of primary importance in engineering seismology in fact such knowledge is essential for site response studies when preparing improved seismic hazard scenarios in this study we propose a linear inversion of the spectra of a deconvolved wavefield collected by a borehole array in istanbul turkey the spectra are calculated using as a reference the recordings collected by a sensor at the surface this allows us to minimize the effect of the deconvolution filter on the peaks amplitudes the feasibility of the proposed inversion scheme and the parametrization of the velocity and attenuation models were tested and assessed using synthetic data the real data inversion is carried out using observation from three weak motion events several starting models are used for each event changing the values of the quality factor qs whereas the starting vs profiles are fixed to what was obtained by the analysis of the deconvolved wavefield in the time domain our results showed that fairly well constrained vs models can be obtained while the variability of the qs profile both between different inversions of the same data set and between the inversions of different data sets might be large this indicates that qs variations observed in models derived by strong motion data inversions should be considered with care however the high agreement of the estimated soil profiles in the uppermost layer both when using different events and different starting models suggests that any variation in the s wave velocity that might be estimated when using strong motion data should be reliable

the north sea lg blockage puzzle summary the north sea lg blockage for wave paths across crustal graben structures is a well established observational fact analysis of such observations implies that lg blockage takes place in graben areas associated with sedimentary basin formation and crustal thinning these intriguing observations have triggered many theoretical studies aimed at highlighting specific lg loss mechanisms albeit so far with only moderate success our approach to this problem is to simulate seismic wavefield propagation through the crustal waveguide using 2 d finite difference techniques the graben structures are known in detail from oil exploration works in the north sea which has enabled us to use realistic crustal models in our lg synthetics in the most extreme model tested the crystalline crust thickness beneath the graben amounted to only 5 km while the overlying sedimentary pile is nearly 10 km thick at the base of the crust in the graben area the moho is elevated nearly 10 km this model has similarities to the oceanic crustal waveguide where total lg blockage is claimed for path lengths exceeding 100 km the synthetic wavefields are displayed in terms of snapshots semblance velocity analysis and time space rms amplitudes the dominant structural lg loss mechanisms are the delay of the lg waves in the thick sediments lg to rg conversions scattering by lateral heterogeneities in the sediments and s wave leakage out of the crustal wave guide and into the upper mantle a fraction of these upper mantle s waves return to the crust and appear as sn coda observationally strong sn phases of long duration are often associated with weak lg phases and vice versa our synthetics produced lg amplitude decay amounting at most to 6 10 db while observational data imply blockage amounting to 15 20 db the latter is equivalent to a pn lg magnitude difference of nearly one magnitude unit the main outcome of this study is therefore that lg wave propagation is very robust and that a dominant blockage effect associated with intrinsic attenuation that is q values of the order of 100 at 2 hz for a path length of minimum 100 km is necessary to conform to observations

the atakoy vertical array turkey insights into seismic wave propagation in the shallow most crustal layers by waveform deconvolution summary a vertical array of accelerometers was installed in atak oy western istanbul with the longterm aim of improving our understanding of in situ soil behaviour to assess the modelling and parametric uncertainties associated with the employed methodologies for strong motion site response analysis and for shallow geological investigations geotechnical and geophysical investigations were carried out to define the subsoil structure at the selected site data associated with 10 earthquakes 2 7 m 4 3 collected during the first months of operation of the array were used to image the upgoing and downgoing waves by deconvolution of waveforms recorded at different depths results have shown that the velocity of propagation of the imaged upgoing and downgoing waves in the borehole is consistent with that of s or p waves depending on the component of ground acceleration analysed but independent of the chosen signal window in particular an excellent agreement was found between the observed upgoing and downgoing wave traveltimes and the ones calculated using a model derived by seismic noise analysis of array data the presence of a smaller pulse on the waveforms obtained by deconvolution of the horizontal components suggests both internal s wave reflection and s to p mode conversion as well as a not normal incidence of the wavefield the presence of a pulse propagating with s wave velocity in the uppermost 25 m in the waveforms obtained by the deconvolution of the vertical components suggests p to s mode conversion these evidences imply that even when site amplification is mainly related to 1 d effects the standard practice in engineering seismology of deconvolving the surface recording down to the bedrock using an approximate s wave transfer function generally valid for vertical incidence of sh waves might lead to errors in the estimation of the input ground motion required in engineering calculations finally downgoing waves with significant amplitudes were found down to 70 m and even to 140 m depth this result provides a warning about the use of shallow borehole recordings as input for the numerical simulation of ground motion and for the derivation of ground motion prediction relationships

damage detection of a building caused by the 2011 tohoku oki earthquake with seismic interferometry we apply seismic interferometry based on deconvolution to earthquake data observed in a building at tokyo metropolitan university to extract building response and estimate velocities and frequencies of traveling waves inside the building the building is a 10 story reinforced concrete structure in tokyo japan the earthquake data were recorded 2 months before 6 months after and 16 months after the m w 9 0 tohoku oki earthquake 11 march 2011 the observation period of each acquisition was 20 30 days we analyze more than 300 earthquakes recorded in these time periods and we find significant reduction 20 in wave velocities and fundamental mode frequencies after the tohoku oki earthquake because deconvolution interferometry separates the response of the building from the effect of complicated wave propagation outside the building we interpret that this reduction is mostly related to the building we can also estimate frequencies of the fundamental mode from observed data and these frequencies contain the responses of building and the ray paths from hypocenters therefore as we find from the data the frequencies estimated from observed data are generally lower than those from deconvolved waveforms due to the effects of wave propagation although the velocities in the building decrease 20 after the tohoku oki earthquake we cannot find significant reduction in the s wave velocities at the near surface depth shallower than 100 m this fact indicates the decrease in velocities is mainly related to the building and hence with deconvolution interferometry we can detect damages to the building caused by the tohoku oki earthquake

lake surface fluctuations since the late glaciation at lake daihai north central china a direct indicator of hydrological process response to east asian monsoon climate abstract sediment retrieved by coring from the center of enclosed lake daihai in north central china and lacustrine sediments obtained from lake terrace outcrops were employed to reconstruct the lake surface fluctuations and the relationships with monsoon climate since the late glaciation based on accelerator mass spectrometry ams radiocarbon chronology before ca 13 ka bp the surface of the lake was lower indicating a deficiency of effective precipitation and dry climate the result of relatively decreased monsoon precipitation during ca 13 11 ka bp the lake surface ascended to a relatively higher level marking a significant increase of effective precipitation the climate became humid indicating strengthened monsoon rainfall then the lake surface experienced a sharp decline ca 11 10 ka bp this could suggest a severe reduction of effective monsoon precipitation and drier climate ca 10 9 0 ka bp the lake surface area expanded temporarily as the level rose denoting the amelioration of monsoon related effective precipitation and a relatively humid climate subsequently the lake surface declined at ca 9 0 7 3 ka bp reflecting the prevalence of dry climate and relatively decreased monsoon precipitation higher lake level and larger lake depth indicated large scale expansion of the lake surface at ca 7 3 3 2 ka bp despite some secondary fluctuations this implied plentiful monsoon related effective precipitation and more humid climate in the lake basin since ca 3 2 ka bp the lake surface has experienced a severe fall except for a minor rise around 2 0 ka bp indicating dry climate as a whole from waning monsoon precipitation and relatively increased evaporation the effective precipitation variations revealed by lake surface fluctuations in lake daihai since the late glaciation are not only related to forcing factors such as insolation and temperature driven air masses from the continent and the ocean but are also influenced by regional feedback from topography vegetation coverage and hydrological status

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

3d viscoelastic wave propagation in the upper borrego valley california constrained by borehole and surface data we have simulated 2 hz wave propagation in a three dimensional model of the upper borrego valley southern california for a m 4 9 earthquake with epicenter 5 km north of the valley a 4th order staggered grid finite difference method was used to calculate viscoelastic ground motion in a basin model 9 km by 5 km by 0 4 km consisting of heterogeneous sediments surrounded by bedrock we simulated the earthquake as a double couple point source and computed the ground motions in the valley separately for the parts of the source incident from below and from the north the earthquake was recorded by a surface array as well as a deep downhole array 0 238 m depth in the center of the valley all equipped with digital three component seismic instruments the simulation reproduces the overall pattern of ground motions at basin and borehole sites and shows a good correlation of observed to synthetic waveforms in particular the 3d simulation reproduces the recorded peak motions cumulative kinetic energies and fourier spectral amplitudes within a factor of 2 for most components at the individual sites the correlation between data and simulation allows us to identify the secondary arrivals in the records as love and rayleigh waves generated at the edges of the valley and the troughs of the basin the peak velocities for the waves incident into the valley from below are generally more than an order of magnitude larger than those for the waves incident from the north the success of the prediction requires the inclusion of anelastic attenuation in the simulation with q values for p and s waves in the alluvium of about 30 we also used a profile of the 3d model and the soil parameters at the deep borehole to examine the ability of 2 5d and 1d model approximations to predict the data the maximum peak velocities and total cumulative kinetic energies are reproduced at the recording sites within a factor of 2 for both 2 5d and 1d model approximations but are underpredicted by up to an order of magnitude at some depths for individual components in particular the 2 5d and 1d simulations tend to underpredict the duration

a finite difference approach for simulating ground responses in sedimentary basins quantitative modelling of the nile valley egypt summary on 1992 october 12 egypt was struck by an earthquake with m b 5 9 or equivalently m s 5 2 it occurred southwest of greater cairo cairo and giza and was widely felt from alexandria in the north to aswan in the south this earthquake also caused widespread destruction and damage mostly concentrated in greater cairo along the nile valley and in the nile delta area the extent of damage caused by this earthquake motivated this study we computed a 2 d finite difference fd synthetic wavefield for a prototype model of the nile valley with a maximum sedimentary basin thickness of 5 km and assumed uniform crustal thickness of 35 km a variant of the latter model tested is a thin crust moho bump beneath the basin we used a 2 5 hz ricker wavelet source that excites both p and or s waves initiated as point sources focal depths vary from 5 to 20 km to simulate different scenarios we investigated how various model features such as source location focal depth and epicentral distance deep sedimentary basin near surface attenuation and crustal thinning beneath the sedimentary basin may influence the wavefield across the nile valley the outstanding result of the wavefield simulations is that the nile valley sedimentary basin and the associated strong impedance contrast produce significant focusing and amplification effects it was found that the peak amplitudes might vary by one order of magnitude in the 3 8 hz frequency band across the nile valley the high vulnerability of the buildings in greater cairo in combination with focusing amplification in the nile valley explain qualitatively the extensive damage in the city itself even for moderate size earthquakes in fact the predicted area of high amplification coincides closely with that of greatest housing damage the effects of near surface attenuation in the uppermost 500 m within the basin and or crustal thinning beneath the basin is less significant these results are interesting on two accounts 1 the extent of variation in the synthetic wavefield will always be less than that observed but unfortunately there are no egyptian records to corroborate these results and 2 wavefield variations are significantly larger than those deduced from ranges of q variations and seismotectonic modelling as used in most seismic risk analysis these results imply that the wavefield simulations can be very informative and provide realistic results in particular when accurate structural model information is available and even more so if the synthetics can be corroborated with dense seismic network recordings

modeling the seismic response of basin edge structure by a sequential waveform method a sequential waveform method is developed to simulate the seismic response of basin edge structure excited by a plane incident p wave the full procedure involves a a previous parameterization of the investigated model using the seismic wave velocities and depths of the sedimentary stratifications b an input motion determined from the records at stations installed on hard rock c forward computation of the p sv elastic wave field by means of a two dimensional finite difference fd method d the optimization of the model vector using simulated annealing technique and comparing the simulated seismic response of the tested structure with the observed wave field e the correction of the initial model by trial and error by testing the differences between synthetics and observed data and f the final solution obtained by iteration using the conjugate gradient algorithm the search of an optimal basin edge model has been parallel processed by varying the shapes and velocities of strata on the basis of the fitting of relative timing amplitude and phase between the output and the observed data the input motion and sensitivity have been checked and the validity of the method has been demonstrated by numeric analysis using the teleseismic records generated by 7 earthquakes recorded at 26 broadband seismic stations we have studied the seismic velocity structure of the southern edge of the jiyang depression located in the bohai bay basin northern china two cross sections show an agreement between the velocity results and the geological sections available in the region in addition we obtain evidence of three hidden faults under the sections and features that suggest major extensions at the paleogene

evaluation of soil building resonance effect in the urban area of the city of matera italy abstract this study discusses the effect of buildings vibrations in the urban field in the context of local seismic response studies in order to evaluate the possible occurrence of double resonance effects during strong motions the aim is to recognise the interaction effect between near surface geology and all overlying buildings in the urban area of the city of matera southern italy single station seismic ambient noise measurements 230 were performed on the main lythologies 134 and on the principal building typologies 96 soil and building measurements allowed estimating the main frequencies and relative amplitudes of the soil fundamental peaks as well as the first vibrational frequency of buildings the period height linear relationship derived by experimental results made it possible estimating the fundamental frequency for all the matera s buildings having also estimated the frequencies at each point of the urban soil it was thus possible to obtain a soil building resonance map in the linear elastic domain matera represents an important case study because the first vibration frequency for most of the buildings is quite close to those of the foundation soils about 21 of buildings show high probability of occurrence of soil building resonance effect about 63 of the buildings are characterised by a medium resonance level while about 16 are at zero or very low level the proposed approach makes it also possible to identify the areas of the city characterised by these different probabilities of resonance levels

archaeology of the anthropocene in the yellow river region china 8000 2000 cal bp although archaeological analysis emphasizes the importance of climatic events as a driver of historical processes we use a variety of environmental and archaeological data to show that human modif

seismic site city interaction main governing phenomena through simplified numerical models this work focuses on the analysis of the multiple interactions between soil layers and civil engineering structures in dense urban areas submitted to a seismic wave to investigate such phenomena called site city interaction sci herein two simplified site city configurations are considered a homogeneous periodically spaced city and a heterogeneous nonperiodically spaced city both on a constant depth basin model these 2d boundary element method models are subjected to a vertically incident plane sh ricker wavelet a parametric study of the city parameters density of buildings and their natural frequencies and the thickness of the basin is carried out to characterize the sci and to investigate its sensitivity to some governing parameters the following parameters are analyzed building vibrations induced ground motion ground motion perturbations inside and outside the city spatial coherency and kinetic energy of the urban wave field a so called site city resonance is reached when the soil fundamental frequency and structure eigenfrequencies coincide building vibrations and ground motion are then significantly decreased and the spatial coherency of the urban field is also strongly modified building density and city configuration play a crucial role in the energy distribution inside the city

a rb sr record of catchment weathering response to holocene climate change in inner mongolia variation in the rubidium to strontium rb sr ratio of the loess palaeosol sequences has been proposed to reflect the degree of pedogenesis and weathering in the northwestern region of china to characterize the rb sr ratio of the dissolved loads of a single catchment we analysed a 12 08 m sediment core from daihai lake in inner mongolia north china dating control was provided by 210pb 137cs and ams 14c sequential extraction experiments were conducted to investigate the concentrations of rb and sr on various chemical fractions in the lake sediments down core variation in the rb sr ratios provides a record of holocene weathering history from 9 to 3 5 ka bp accelerated chemical weathering was experienced throughout the daihai catchment under mainly warm and humid conditions and this reached a maximum at c 5 ka bp however weathering was reduced between c 8 25 and 7 90 ka bp which may reflect the global 8 2 ka cooling event after c 2 5 ka bp increased rb sr ratios with higher frequency of fluctuations indicate reduced weathering within the daihai catchment the highest rb sr ratios in the little ice age lake sediments indicate the weakest phase of holocene chemical weathering resulting from a marked reduction in sr flux into the basin the rb sr record also shows an enhancement of chemical weathering under today s climate but its intensity is less than that of the medieval warm period increased rb sr in lake sediment corresponding to reduced catchment weathering is in striking contrast to rb sr decrease in the glacial loess layers in the loess palaeosol sequence copyright 2005 john wiley sons ltd

attenuation and velocity structure for site response analyses via downhole seismogram inversion a seismic waveform inversion algorithm is proposed for the estimation of elastic soil properties using low amplitude downhole array recordings based on a global optimization scheme in the wavelet domain complemented by a local least square s fit operator in the frequency domain the hybrid scheme can efficiently identify the optimal solution vicinity in the stochastic search space whereas the best fit model detection is substantially accelerated through the local deterministic inversion results presented for selected aftershocks of the mw 7 0 sanriku minami earthquake in japan recorded by the kik net strong motion network illustrate robustness of the impedance structure estimation by contrast the attenuation structure is shown to be sensitive to the frequency content of seismic input data attributed to the deterministic description of the continuum in the forward model that cannot simulate late arrivals of multiple scattered energy sensitivity analyses illustrate that for the same forward model results can be substantially different based on the definition of the objective function it is concluded that even for engineering purposes inversion should aim to decouple intrinsic and scattering attenuation mechanisms

a three dimensional simulation of seismic waves in the santa clara valley california from a loma prieta aftershock abstract the finite difference method is used to propagate elastic waves through a 3 d model of the santa clara valley an alluvium filled basin that underlies the city of san jose california the model was based on depth to bedrock information from water wells in the area the simulation corresponded to a region 30 east west by 22 north south by 6 depth km and contained about 4 million grid points synthetic seismograms from the simulation are accurate at frequencies up to 1 hz motions from a magnitude 4 4 aftershock of the loma prieta earthquake were modeled snapshots of ground motion and synthetic seismograms from the simulation are presented the simulation illustrates s to surface wave conversion at the edges of the basin and the large amplitude and long duration of ground motion in the basin compared to the surrounding rock love waves produced at the edge of the basin are the largest arrivals in the transverse synthetics because of the slow group velocity of the love waves sites near the center of the basin have longer durations of significant motions than basin sites near the valley edges sites near the center of the basin also show larger peak amplitudes on the transverse component array analysis of the synthetic seismograms indicates that love waves tend to propagate parallel to the eastern and western edges of the valley rayleigh waves are produced along the southern margin of the basin from incident s waves large radial motions occur where a rayleigh wave impinges on the northeast margin of the valley some rayleigh waves travel westward across the basin after being scattered from the eastern edge of the valley synthetic seismograms from the simulation have similar peak amplitudes as seismograms recorded by the sunnyvale dense array for this aftershock although the duration of the tranverse component is not matched by the synthetic seismogram using this basin model the simulation indicates that the love waves observed on the actual seismograms were produced by conversion of incident s waves at the southern margin of the santa clara valley 2 d simulations show how the s to love wave conversion is affected by the angle of incidence of the s wave and the sharpness of the velocity transition between the alluvium and bedrock as more accurate basin models are developed 3 d simulations should become valuable for predicting ground motions in sedimentary basins for future large earthquakes

3 d finite difference elastic wave modeling including surface topography three dimensional finite difference fd modeling of seismic scattering from free surface topography has been pursued we have developed exact 3 d free surface topography boundary conditions for the particle velocities a velocity stress formulation of the full elastic wave equations together with the boundary conditions has been numerically modeled by an eighth order fd method on a staggered grid we give a numerical stability criterion for combining the boundary conditions with curved grid wave equations where a curved grid represents the physical medium with topography implementation of this stability criterion stops instabilities from arising in areas of steep and rough topographies we have simulated scattering from teleseismic p waves using a plane vertically incident wavefront and real topography from a 40 40 km area centered at the noress array of seismic receiver stations in southeastern norway synthetic snapshots and seismograms of the wavefield show clear conversion from p waves to rg sh

holocene east asian monsoonal precipitation pattern revealed by grain size distribution of core sediments of daihai lake in inner mongolia of north central china abstract two sediment cores recovered in the central part of daihai lake in north central china were analysed at 2 to 4 cm intervals for grain size distribution grain size distributions of the lake sediments are inferred to be a proxy for past changes in east asian monsoon precipitation such that greater silt size percentage and higher median grain size reflect increased monsoonal precipitation rates the grain size record of daihai lake sediments spanning the last ca 10 000 yr indicates that the monsoonal precipitation in the lake region can be divided into three stages the early middle and late holocene during the early holocene before ca 7900 cal yr bp the median grain size md and the silt fraction content were relatively low and constant suggesting relatively low precipitation over the lake region the middle holocene between ca 7900 and 3100 cal yr bp was marked by intensified and highly variable monsoonal precipitation as indicated by high and variable md values and silt contents of the lake sediments during this period average precipitation rate gradually increased from ca 7900 to 6900 cal yr bp displayed intense oscillations between ca 6900 and 4400 cal yr bp and exhibited a decreasing trend while fluctuating from ca 4400 to 3100 cal yr bp although generally high during the middle holocene both the md and the silt content assumed distinctly low values at the short intervals of ca 6500 6400 6000 5900 5700 5600 4400 4200 cal yr bp implying that monsoonal precipitation might have been significantly reduced during these intervals during the late holocene since ca 3100 cal yr bp grain size values suggest that precipitation decreased however during the late holocene relatively higher md values and silt contents occurring between ca 1700 to 1000 cal yr bp may denote an intensification of hydrological cycles in the lake area changes in the east asian monsoonal precipitation were not only directly linked with the changing seasonality of solar insolation resulting from progressive changes in the earth s orbital parameters but also may have been closely related to variations in the temperature and size of the western pacific warm pool in the intensity of the el nino southern oscillation and in the path and strength of the north equatorial current in the western pacific

status of the crustal stress in egypt as inferred from earthquake focal mechanisms and borehole breakouts abstract the recent stress field has been investigated by the analysis of the directions of maximum horizontal stress h as derived from earthquake focal mechanisms and borehole breakouts in egypt the results indicate that in the southern part of the gulf of suez the shallow borehole breakouts stress directions are not consistent with the deep earthquakes focal mechanisms stress directions analysis of 30 borehole breakouts measurements indicate wnw ese alignment of the maximum horizontal stress with a vector mean of 110 14 p e however the earthquake studies including orientation of p axes reflect ene wsw alignment of h with a vector mean of 66 30 thus the stress directions are not constant throughout the crust along the gulf of aqaba the southern part of the dead sea fault the focal mechanism solutions indicate that the maximum horizontal stress is presently nw se oriented corresponding to strike slip mechanism in concert with the geological evidence in northern egypt the nine earthquake focal mechanisms for the nile delta cairo bitter lakes region scatter in orientation varying from ne sw to nw se for h about 45 from these mechanisms indicate nw se 22 wnw ese 22 ene wsw and 11 ne sw alignment of the maximum horizontal stress while in southern egypt it is relatively uniform and aligned to nearly e w direction with a vector mean of 95 3

joint inversion of h v ratios and dispersion curves from seismic noise estimating the s wave velocity of bedrock 1 a joint inversion of phase velocity and h v ratio curves both obtained from seismic noise recordings permits the retrieval of the shear wave velocity structure of local sedimentary cover our inversion scheme uses a genetic algorithm and considers the influence of higher modes on the data sets encouraged by the results published previously on joint inversion parolai et al 2005 we went one step further we found using a synthetic data set that the impedance contrast at the sediment bedrock interface has a strong influence on the shape of the h v ratio curve which therefore allows the bedrock s wave velocity to be well constrained in the joint inversion procedure our observations were further confirmed using a real data set

pb isotope record over one century in snow from victoria land antarctica pb and ba concentrations and pb isotopic compositions are reported for firn core and snow pit samples from victoria land antarctica dating from 1872 ad to 1994 ad from variations in pb ba ratios and pb isotopic compositions two periods of major pb enhancements were identified from 1891 to 1908 ad and from 1948 to 1994 ad the earlier pollution event is attributed to pb emissions from non ferrous metal production and coal combustion in the southern hemisphere and is in excellent agreement with coincident pollution inputs reported in firn ice cores from two other regions of antarctica at coats land and law dome using pb isotopic systematics it was calculated that 50 of pb deposited in victoria land in 1897 originated from anthropogenic emission sources the more recent period of pb enhancements from 1948 to 1994 ad corresponds to the introduction and widespread use of gasoline alkyl pb additives in automobiles in the southern hemisphere with anthropogenic pb inputs averaging 60 of total pb but with large uncertainty intra and inter annual variations in pb concentrations and isotopic compositions were evaluated in snow pits samples corresponding to the period 1991 1994 substantial variations in pb ba and 206pb 207pb ratios were detected but the absence of a regular seasonal pattern for these parameters suggests that the transport and deposition of aerosols to the antarctic ice sheet are complex and vary from year to year

downhole receiver function a case study receiver function is defined as the spectral ratio of the radial component and the vertical component of the ground motion it is used to characterize converted waves we extend the use of the receiver function to downhole data using waves recorded in a borehole excited by an earthquake of magnitude 4 0 near san fran cisco california on 26 june 1994 the focal depth of the event was 6 6 km and the epicenter was located at a distance of 12 6 km from the borehole array six three component sensors were located at different depths in a borehole to extract a co herent response of the near surface from the incoherent earthquake waves we de convolve the waves recorded by the sensors at different depths with the waves recorded by the sensor on the surface deconvolution applied to the waves in the s time window recorded by the radial component result in an upgoing and adowngoing wave propagating with s wave velocity for the waves in the p time window re corded by the radial component deconvolution also gives an upgoing and a down going wave propagating with s wave velocity this interesting result suggests a p to s conversion at a depth below the deepest sensor to diagnose this we compute the receiverfunction forthe borehole recording of the earthquakewaves thereceiver function shows an upgoing wave with an arrival close to time t 0 for the deepest sensor the agreement of the upgoing wave in the receiver function with the travel time curve for the p to s converted wave calculated using the p and the s wave velocity profile supports the hypothesis of a pronounced p to s conversion we present a synthetic example to illustrate that the first arrival of the receiver function applied to borehole data gives the upward propagating p to s converted wave to corroborate the observation of the mode conversion we apply receiver function to a different earthquake data recorded by the same borehole array in 1998 the focal depth of the event was 6 9 km and the epicenter was located at a distance of 13 km from the borehole array the receiver function for these data also show an upgoing wave with a pulse close to time t 0 at the deepest sensor the moveout of the upgoing wave agrees with the travel time curve for the p to s converted wave hence supporting our observation of the mode conversion

determination of shallow s wave attenuation by down hole waveform deconvolution a case study in istanbul turkey summary the estimation of shear wave velocity and attenuation in near surface geology is of primary importance in engineering seismology in fact their knowledge is essential for site response studies when preparing improved seismic hazard scenarios in this study we propose two approaches for estimating the average shear wave quality factor qs by using recordings of a vertical array of accelerometers the methods are mainly based on the deconvolution of the wavefield recorded in a borehole with that recorded at the surface the first method requires the fourier transform of the deconvolved wavefield to be fitted with a theoretical transfer function valid for the vertical or nearly vertical in the case at hand up to 30 incidence angle propagation of s waves the second method is based on the spectral fitting of the fourier transform of only the acausal part of the deconvolved wavefield with a theoretical transfer function both methods can be applied without any prior knowledge of the subsoil structure since they are based on empirical data analysis and do not require a precise knowledge of the azimuthal orientation of the sensors in the boreholes which is seldom available first we describe the theoretical framework of the proposed methodologies for qs estimation which are based on the assumption that the structure in the borehole is weakly heterogeneous in the vertical direction i e no large impedance contrast exists between the borehole sensor and the surface second by using synthetic accelerograms we verify that in a realistic subsoil structure the assumption of vertical homogeneity can hold and we investigate the robustness and the suitability of the proposed methods finally only the method that was shown to provide the more stable results based on fitting the borehole to surface spectral ratio with a theoretical function is applied to earthquakes signals recorded by a vertical array of accelerometers installed in atak oy western istanbul results show that using borehole data provides a fair and robust estimate of an average qs of about 30 46 and 99 for the 0 50 0 70 0 140 m depth ranges respectively that can be used for numerical simulations of ground motion