eolian dune interdune sand sheet and siliciclastic sabkha sediments of an offshore prograding sand sea dhahran area saudi arabia an offshore prograding sand sea exists along portions of the arabian gulf coastline near dhahran saudi arabia in this region sediments of eolian dune interdune sand sheet and siliciclastic sabkha intercalate with marine deposits this depositional setting is characterized by strong offshore winds which supply abundant sand to the coastline and cause at present time the outbuilding of the dune system this quartz detrital dominant setting contrasts markedly with the carbonate dominant setting resulting from onshore winds in the trucial coast area to the south the broad intercalation of eolian and marine deposits which results creates ideal potential for subregional stratigraphic petroleum traps due to pinch out of porous and permeable dune sands into impermeable m rine mudstones within the eolian system itself are potential reservoir rocks dunes sources organic rich sabkha and interdune deposits and seals zones of early cementation in all deposits early cementation is very common in all facies of the eolian sand sea the early cementation occurs owing to 1 soil formation 2 deposition of pore filling gypsiferous cements from saturated solutions near water table and 3 addition of sand size windblown evaporitic material to sands downwind of sabkhas

new relationships between vs thickness of sediments and resonance frequency calculated by the h v ratio of seismic noise for the cologne area germany noise measurements were carried out in the cologne area germany and the resonance frequency of each site was estimated from the main peak in the spectral ratio between the horizontal and vertical component for 32 of these sites the thickness of the sedimentary cover was known from boreholes and a clear correlation between resonance frequency and sediment thickness was observed a formula that correlates cover thickness with frequency of the main peak in the horizontal to vertical spectral ratio was derived in addition a best fitting shear wave velocity distribution with depth vs z as well as a relationship between average shear wave velocity vs and thickness of the sedimentary cover was calculated by using all of the noise measurements and applying the derived relationships we obtained a subsoil classification for the cologne area

predicting regolith thickness in the complex weathering setting of the central mt lofty ranges south australia abstract we describe a model to predict regolith thickness in a 128 000 ha study area in the central mt lofty ranges in south australia the term regolith encompasses soil a and b horizons and highly weathered bedrock c horizon the thickness of the regolith has a major control on water holding capacity for plant growth and movement of water through the landscape and as such is important in hydropedological modelling and in evaluating land suitability e g for forestry and agriculture thickness estimates also have direct application in mineral exploration and seismic risk assessment geology and landscape evolution within the study area is complex reflecting the variable nature of bedrock materials and the partial preservation of deeply weathered profiles as a consequence of weathering processes dating to the cenozoic or possibly older these characteristics together with strong climatic gradients make the study area an ideal location to understand environmental and landscape evolution controls on weathering depth the area also features weathered landscape analogues to many parts of southern australia we use a digital soil mapping rules based approach to develop a model to predict regolith thickness this model uses statistically based relationships established between 714 regolith thickness measurements and 29 geographic environmental covariates including geology geochemistry terrain and climate themes and with a ground resolution of 10 m accuracy testing based on a 75 25 training test data split on the resulting map established a correlation r 2 of 0 64 this result is encouraging and is a significant advance over regolith depth mapping by traditionally based regolith landscape mapping methods finally it leads the way towards a nationally consistent regolith thickness map for landscape scale environmental simulation modelling and decision support

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

estimating bedrock depth in the case of regolith sites using ambient noise analysis abstract subsurface geometry particularly the depth of bedrock is crucial in seismic hazard studies because the basin geometry has been shown to play an important role in the altering of seismic waves estimating the bedrock surface using ambient seismic noise analysis has been undertaken by many researchers with most studies focusing on sites with a strong impedance contrast between the bedrock and the overlying materials the application of this technique at regolith sites which is subjected to impedance contrasts in the low to high range is underdeveloped and requires further attention this study seeks to address this need and is focused on the city of adelaide in south australia which exhibits site amplification and is associated with various impedance contrasts analyses of ambient noise data are carried out using the generic function gf of the classic horizontal vertical spectral ratio hvsr method and the spatial autocorrelation spac technique to estimate the depth to bedrock comparison of the bedrock depth predictions from the seismic methods with boreholes drilled in close proximity to the measured sites demonstrate that the spac method provides superior estimates especially to those obtained from the other approach this work demonstrates that the microtremor spac method is an effective tool for estimating bedrock structure at regolith sites

microtremors as a geophysical exploration tool applications and limitations the usefulness of microtremors as a geophysical exploration tool has been analyzed this application is possible due to the relationship between the main resonance frequency of a given soil obtained from the h v spectral ratios of microtremors its thickness and average shear velocity we first measured the ambient noise at 33 sites and determined their main resonance frequency detailed geotechnical information was available for 23 of the sites thereby allowing us to establish a quantitative relationship between the resonance frequency and the thickness of the soil and indirectly between either of them and the shear velocity of the soil the practical application of this relationship has revealed its usefulness in determining the surface structure of a valley with excellent accuracy with an error of only 15 in the depths calculated these errors are due to the simplification of the problem that this method implies it requires that the shear velocity vary constantly with depth throughout the study region which is evidently not always so and that the input data themselves intrinsically have a certain degree of uncertainty this method is therefore not valid when there is no mechanical contrast between the study soil and the underlying layer or when the shear velocity varies irregularly with depth in the study area

landscape responses to intraplate tectonism quantitative constraints from be 10 nuclide abundances cosmogenic 10 be concentrations in bedrock and alluvium combined with structural studies provide a novel approach for identifying neotectonic forcing of landscape evolution in mildly deforming continental interiors measured 10 be concentrations in the flinders ranges indicate rapid and spatially variable rates of bedrock erosion in a catchment that has incurred at least three large surface rupturing earthquakes since 67 ka 10 be derived erosion rates are lower where late quaternary neotectonic activity is reduced or absent implying that 10 be concentration may act as a tracer for disequilibrium landscapes responding to recent tectonism mechanisms for elevated erosion rates include 1 headward migration of fault generated bedrock knickpoints and resultant oversteepening of stream profiles and catchment hillslopes and 2 liberation of bedrock material from catchment hillslopes via co seismic shaking despite climatic influences on sediment production and transport this study shows that tectonism can provide a dominant control on bedrock erosion rate and relief production in unglaciated mountain belts even in intraplate settings where rates of crustal deformation are mild and earthquake activity is episodic 2007 elsevier b v all rights reserved

comment on microtremor observations of deep sediment resonance in metropolitan memphis tennessee by paul bodin kevin smith steve horton and howard hwang abstract bodin et al eng geol 62 2001 159 reported three sets of maxima in observed h v particle motion spectra where the longest period set of peaks provided clear mapping information on the thickness of post cretaceous sediments in the mississippi embayment but the remaining peaks remained largely unexplained a review of microtremor array studies for similar sites and similar frequencies suggests that the microtremor field is best interpreted in terms of rayleigh wave energy use of this approach with modeling of particle motion h v ratios for realistic models of the mississippi embayment shows that the eng geol 62 2001 159 second set of spectral maxima can be associated with higher mode rayleigh wave energy and may contain information on a possible velocity inversion in the shear velocity profile of the site a third spectral maximum appears to be associated with soft soils loess and may be able to be used for mapping the near surface thickness order 15 m of this unit

influence of orbital parameters on pleistocene loess deposition in central alaska few long proxy climatic records are available from terrestrial locations the isotope records of pleistocene climate change found in marine cores reflect worldwide ice volume and temperature changes forced by variations in the earth s orbital geometry comparable terrestrial records are rare loess wind deposited silt is perhaps the closest terrestrial analogue to marine sediments in that both result from more or less continuous deposition of fine grained sediment here we examine the hypothesis that mag netic susceptibility variations through loess sections reflect climate forcing we statistically tested cross correlations between high precision orbitally tuned marine oxygen isotope curves recording the past 250 000 yr bp and magnetic susceptibility profiles through a thick loess section in central alaska highly significant p 0 0001 correlations indicate strong thick palaeosols formed in arctic loess during early parts of interglacial periods correspond ing to isotope stages 7 and 5 thinner soils formed during interstadial events corresponding to early stage 7 and stage 3 autocorrelation and time series analysis of the loess data show spectral peaks at 125 000 41 000 and 23 000 yr bp showing for the first time that terrestrial orbital periodicities influenced and are recorded in proxy climatic data from terrestrial aeolian deposits at high latitudes

modes of active intraplate deformation flinders ranges australia 1 the flinders ranges form one of the most seismically active zones within the australian continent with seismogenic strain rates over the last 30 years of 10 16 s 1 active deformation in the region reflects late neogene increases in stress levels in the indo australian plate as a response to increased plate boundary forcing from collision zones with the neighboring asian and pacific plates geological and geophysical observations suggest two modes of active deformation in operation in the flinders ranges over the last several million years 1 low amplitude 200 500 m long wavelength 200 km lithospheric flexure and 2 active reverse faulting along the range front with fault slip rates of up to 50 m myr 1 numerical models are developed to explore the contribution of each of these deformation modes to the observed geophysical signals an elastic mode of deformation is suggested by a distinctive long wavelength positive correlation between gravity and topography in which the flinders ranges are bordered by anomalous topographic and gravity lows now occupied by playa lake systems centered some 50 km outboard of range bounding faults numerical models show that flexural instabilities localized by vertical loads arising from older tectonic structuring produce a first order match with observed topography and gravity numerical models are also used to illustrate how the localized failure evident in the contemporary seismicity and quaternary faulting record within the flinders ranges reflects thermal weakening associated with extraordinary concentrations of heat producing elements in the crust as reflected in modern day heat flows of 90 mw m 2

microtremor recordings in northern mississippi abstract this paper presents the results of 305 single point microtremor recordings covering northern mississippi that is situated within the upper mississippi embayment area both long and short term recordings were obtained by a le 3d 20s seismometer over a large network of points where the unconsolidated sediment thickness ust varies from zero to 1400 m applying the nakamura method the recordings were processed to determine predominant frequency f0 and its relation to ust initial results of wind influence on the frequency spectra particularly in low frequency band 0 05 0 2 hz and dominant vibration direction are also presented it is shown that analysis of systematic microtremor recordings can provide a stable and reliable estimation of the predominant frequency from which estimates of average shear wave velocity of overall sediment profile can be derived predominant frequency and average shear wave velocity is reasonably well correlated with ust wind and human activities are found to produce peaks over the low frequency band

vs30 estimates using constrained h v measurements abstract most seismic codes adopt the average shear wave velocity as a key parameter in the first 30 m of subsoil v s 30 estimates of v s 30 are therefore required for both large and small scale seismic microzonation we propose a technique to measure the v s 30 based on the horizontal to vertical spectral ratio h v of microtremor recorded at a single station the h v is fitted with a synthetic curve using the independently known thickness of a superficial layer of the subsoil as a constraint the proposed procedure consists of three steps 1 identify the depth of a shallow stratigraphic horizon from independent geotechnical data 2 identify its corresponding h v marker and 3 use it as a constraint to fit the experimental h v curve with the theoretical one the synthetic h v curve is calculated by assuming a stratified one dimensional 1d soil model and a tremor wave field from distant random sources that are composed of rayleigh and love waves this technique has been validated on different geological settings following a triple check procedure 1 the theoretical rayleigh wave phase velocity dispersion curves calculated for the model derived from the h v fit were compared to the experimental curves measured with the 2d extended spatial autocorrelation esac method and the 1d refraction microtremor remi array surveys 2 the v s profiles and 3 the v s 30 estimates obtained by the proposed technique were compared to those obtained by using the latter array techniques finally the inferred stratigraphy was compared to the geological model the proposed technique is not meant to provide accurate v s profiles but has the potential to provide v s 30 estimates that are coherent with those measured through esac and remi and to satisfy law requirements furthermore the h v is found to be capable in detecting deviations from 1d subsoil geometry over the length of a few meters the correctness of which was confirmed by direct drilling

ground motion amplification in the santa monica area effects of shallow basin edge structure abstract the 1994 northridge earthquake produced ground motions in the northwest portion of the los angeles basin that were significantly larger than rock site motions observed at locations just north of the basin the santa monica area was hit particularly hard with numerous structures being damaged or destroyed by the strong ground shaking in this region the basin edge geology is controlled by the active strand of the east west striking santa monica fault and virtually all of the structural damage occurred at or south of the fault location we have used 2d finite difference ground motion simulations to investigate the effect of the basin edge structure in amplifying ground response constraints on the basin edge structure come from geologic cross sections geophysical data and seismological observations our simulations indicate that the shallow basin edge structure 1 km deep formed by the active strand of the santa monica fault creates a large amplification in motions immediately south of the fault scarp in very good agreement with mainshock damage patterns recorded ground motions and locations of elevated site response this large amplification results from constructive interference of direct waves with the basin edge generated surface waves and is quite similar to the basin edge effect associated with the 1995 kobe earthquake in addition we find that focusing effects created by the deeper basin structure 3 to 4 km deep cannot explain the large motions observed immediately south of the fault scarp this strongly suggests that the deep basin focusing models proposed by gao et al 1996 and alex and olsen 1998 are not likely explanations of the observed pattern of ground motion amplification in the santa monica area

late pleistocene variability of arabian sea summer monsoon winds and continental aridity eolian records from the lithogenic component of deep sea sediments the modern indian ocean summer monsoon is driven by differential heating between the asian continent and the indian ocean to the south this differential heating produces a strong pressure gradient which drives southwest monsoon winds during june july and august satellite and meteorological observations aerosol measurements sediment trap studies and mineralogical studies indicate an atmospheric mode of transport for modern lithogenic sediments in the northwest arabian sea analyses of lithogenic grain size and mass accumulation rate mar records from the owen ridge indicate that eolian transport has been the primary mode of transport for the past 370 kyr visual inspection shows that the mar record is positively correlated with global ice volume as indicated by the marine 18o record in contrast the grain size record varies at a much higher frequency showing little correlation to either the mar or the 18o records spectral analyses confirm these relationships indicating that the lithogenic grain size and mar records are coherent only over the precession band whereby the grain size leads the mar by 124 8 kyr we conclude that an eolian transport mechanism is the only mechanism that allows for this phase difference and at the same time is supported by comparison of the grain size and mar with independent eolian records we use lithogenic grain size as a paleoclimatic indicator of summer monsoon wind strength and lithogenic mar as a paleoclimatic indicator of source area aridity these interpretations are supported by comparison of the lithogenic records to independent indicators of wind strength globigerina bulloides upwelling record and aridity a loess record from central china such comparisons indicate high coherence and zero phase relationships our work supports the findings of previous studies which have documented the link between monsoon strength and the earth s axial precession cycles both the lithogenic mar and the grain size records have high coherency with precessional insolation maximum lithogenic mar source area aridity is in phase with 18o global ice volume and leads maximum precessional insolation by 88 6 kyr we attribute this lead to the influence of glacial conditions on the aridity and therefore the deflation potential of the source areas maximum lithogenic grain size summer monsoon wind strength lags maximum precession by 148 9 kyr we attribute this lag both to the influence of global and or local ice volume and to the availability of latent heat from the southern hemisphere indian ocean the two of which combine to determine the strength of the indian ocean monsoon

bedrock erosion and relief production in the northern flinders ranges australia cosmogenic 10be concentrations in exposed bedrock surfaces and alluvial sediment in the northern flinders ranges reveal surprisingly high erosion rates for a supposedly ancient and stable landscape bedrock erosion rates increase with decreasing elevation in the yudnamutana catchment from summit surfaces 13 96 1 29 and 14 38 1 40 m myr 1 to hillslopes 17 61 2 21 to 29 24 4 38 m myr 1 to valley bottoms 53 19 7 26 to 227 95 21 39 m myr 1 indicating late quaternary increases to topographic relief minimum cliff retreat rates 9 30 3 60 to 24 54 8 53 m myr 1 indicate that even the most resistant parts of cliff faces have undergone significant late quaternary erosion however erosion rates from visibly weathered and varnished tors protruding from steep bedrock hillslopes 4 17 0 42 to 14 00 1 97 m myr 1 indicate that bedrock may locally weather at rates equivalent to or even slower than summit surfaces 10be concentrations in contemporary alluvial sediment indicate catchment averaged erosion at a rate dominated by more rapid erosion 22 79 2 78 m myr 1 consistent with an average rate from individual hillslope point measurements late cenozoic relief production in the yudnamutana catchment resulted from 1 tectonic uplift at rates of 30 160 m myr 1 due to range front reverse faulting which maintained steep river gradients and uplifted summit surfaces and 2 climate change which episodically increased both in situ bedrock weathering rates and frequency magnitude distributions of large magnitude floods leading to increased incision rates these results provide quantitative evidence that the australian landscape is in places considerably more dynamic than commonly perceived copyright 2006 john wiley sons ltd

a simplified analysis of the total seismic hazard in italy abstract total seismic hazard assessment i e the base hazard modified by local site conditions plays a key role in seismic risk prevention and mitigation this is an important topic due to the impact of a reliable hazard assessment on the resilience of local communities in the case of an earthquake this paper presents a study that evaluates the total seismic hazard for the entire italy excluding the island of sardinia the results are expressed in terms of amplification factors and total hazard parameters to this end soil characterisation was performed firstly using italian seismic network data for 259 sites uniformly distributed across italy and secondly using the mean value of the shear wave velocity available from a global dataset produced by the united states geological survey the amplification effects were quantified according to i an approach consistent with the italian building code and ii one dimensional site response analyses these two procedures are referred to as parsimonious and rigorous here respectively the results indicate a generally satisfactory match between the estimates obtained by means of these two procedures for periods lower than 0 5 s while parsimonious procedures at periods longer than 0 5 s provide an upper limit on the total seismic hazard finally a seismic classification in terms of the classes of total hazard parameters is proposed for the italian peninsula area

pleistocene climates in china dated by magnetic susceptibility the magnetic susceptibility of loess and interbedded soils in central china varies with the degree of pedogenesis and serves as a proxy measure of climate the concentration of magnetic minerals in the sediment is inversely proportional to sedimentation rates throughout the brunhes epoch susceptibility measurements combined with the reversal stratigraphy provide a time scale that is independent of astronomic chronology on this scale the susceptibility record closely parallels the oxygen isotope fluctuations in deep sea sediments suggesting a close interdependence of the chinese dust falls the volume of land based ice and global climate

microtremor observations of deep sediment resonance in metropolitan memphis tennessee we measured site resonance periods throughout metropolitan memphis tennessee the site resonance was derived from recordings of ambient microtremor and is a direct measurement of seismic ground shaking in the memphis metropolitan area the period t0 in s is predicted by the empirical relation t0 0 39899 7 8922 10 3h 3 0634 10 6h2 350 h 1100 m where h is the thickness in m of the unconsolidated sediments that overly hard paleozoic rocks assuming that a quarter wavelength relationship governs the relationship between resonant period sediment thickness and average shear wave speed we estimate the average shear wave speed of unconsolidated sediments as a function of sediment thicknesses vs 521 15 0 37459h 350 h 1100 m the scatter in the observations and discordance with earlier work suggests that caution is warranted in applying these values of wave speed indiscriminately to sites in the absence of further detailed work

comprehensive ambient noise analyses for seismic microzonation of sarpol e zahab after the mw 7 3 2017 iran earthquake abstract this study is intended to investigate ambient noise recordings in form of array and single station measurements at sarpol e zahab city after the destructive mw 7 3 earthquake of 12 november 2017 in kermanshah province iran the espac f k hvtfa and hvsr methods are applied to analyze the ambient noise and obtain useful information on three key factors of site seismic properties i e the geometry of ground layers their mechanical characteristics and site resonance frequencies the results of this study are presented as maps of the fundamental frequency of the ground depth of bedrock the thickness of top cover materials as well as the average shear wave velocity vs 700 and vs 30 for sarpol e zahab the analyses show that the single value of vs 30 does not represent seismic ground response and the depth of competent bedrock which dominates the low frequency seismic response amplifications is located far beyond 30 m in this city the most effective grade ii seismic microzonation of sarpol e zahab is provided by combining the results of these analyses

clay mineral accumulation rates in the arabian sea during the late quaternary abstract the regional variations in clay mineral concentrations in 39 turbidite free and undisturbed deep sea sediment cores from the arabian sea are compared with distribution patterns of clay mineral accumulation rates during the holocene and the last glaciation dust plumes from the red sea area arabia mesopotamia iran and pakistan can be traced by accumulation rates of mineral specific dust loads during the late quaternary the major proportions of aeolo marine sediments in the western arabian sea were derived from arabia during the summer season the clay mineral assemblage in these dust plumes consists of illite smectite kaolinite chlorite and palygorskite in decreasing order of abundance the distribution pattern of palygorskite in particular reveals that dust transport from southern arabia occurs mainly with northwesterly to westerly winds in the mid troposphere dust plumes from iran and pakistan which are characterized by high chlorite content are dispersed by northwesterly winds over the northwestern arabian sea dust contributions from the red sea area which are rich in smectite and characterized by the occurrence of amphiboles are transported to the gulf of aden the amount of dust related to northeast monsoon winds during the winter season appears to be negligible when compared to the proportions borne on other dust bearing winds in addition to aeolian contributions we distinguish two fluvial contributions a chlorite illite kaolinite and quartz rich assemblage from oman and pakistan into the gulf of oman and a smectite rich assemblage which is dominant off southern india originating from rivers that drain the indian subcontinent the significant difference between the holocene and glacial accumulation rates of wind transported clay minerals consist in the higher abundance of quartz illite and chlorite in the northwestern arabian sea during the last glaciation this pattern indicates intensified dust contributions by northwesterly winds from the persian gulf area which was dry during glacial times

seismic moment assessment of earthquakes in stable continental regions iii new madrid 1811 1812 charleston 1886 and lisbon 1755 summary the sizes of three major or great historical earthquakes are reassessed using the isoseismal area regression tools developed in parts i and ii of this study of stable continental region scr seismicity the earthquakes are 1811 new madrid central united states and its following sequence 1886 charleston coastal south carolina and 1755 lisbon oceanic intraplate off the continental shelf of portugal the analysis confirms the large size of these events and for the first time places constraints on the uncertainty of their seismic moment release because of the exceptionally low seismic wave attenuation of eastern north america ena a separate north american regression of seismic moment on isoseismal area was developed additionally the unknown western extents of the new madrid isoseismal areas were calibrated with the patterns of the m 6 3 6 6 1843 and 1895 earthquakes application of part ii analysis procedures with these corrections yields new madrid size estimates expressed as moment magnitude of m 8 1 0 31 for the 1811 december 16 m 7 8 0 33 for the 1812 january 23 and m 8 0 0 33 for the 1812 february 7 principal events the charleston earthquake s magnitude decreases from m 7 4 to m 7 3 0 26 after compensation for the effect of coastal plain sediments on its inner isoseismals intensity regressions for lisbon are calibrated against the isoseismal pattern of the nearly co located m 7 8 1969 st vincent earthquake which in this case increases the predicted size of lisbon from m 8 4 to m 8 7 0 39 these size estimates are supported by data from independent phenomena extent and severity of liquefaction the maximum distance of induced landslides and for lisbon tsunami wave amplitudes estimated source parameters are controlled by crustal or lithospheric temperature which governs the depth extent of brittle faulting using estimated continental and oceanic geotherms viable fault lengths are 30 80 km for charleston 120 180 km for 1811 new madrid and 180 280 km for lisbon for average displacements of 2 4 m 8 11 m and 10 14 m respectively and for average static stress and strain drops at the estimated seismic moments of this study the 1811 new madrid and the 1755 lisbon events are respectively the largest known scr and oceanic lithosphere earthquakes

study of basin edge effects on the ground motion characteristics using 2 5 d modelling this paper presents the role of basin edge geometry in the generation of surface waves using 2 5 d modelling the simulated responses of various basin edge models revealed surface wave generation near the basin edge and their propagation normal to the edge seismic responses of basin edge models using different fundamental frequency of soil along with spectral analysis of differential ground motion confirmed that surface waves start generating near the basin edge when body wave frequency exceeds the fundamental frequency of soil spectral analysis of differential ground motion also confirmed the generation of high frequency surface wave an increase of surface wave amplitude with soil thickness was obtained large ground displacement observed near the basin edge may be due to the interference of surface diffracted waves with the direct waves and their multiples the effect of edge roughness on the surface wave characteristics was found to be negligible as compared with the edge geometry simulated results revealed a decrease of surface wave amplitude with edge slope particularly in the case of surface waves caused by s waves surface wave generation near the basin edge was obtained for all four considered angles of incidence at the same time it was also inferred that the characteristics of these surface waves depend on the angle of incidence to some extent the findings of this paper reveal that basin edge effects deserve a particular attention for the purpose of earthquake resistant design and seismic microzonation

complexities in eolian and marine interactions processes and eustatic controls on erg development abstract the interplay between eolian and marine realms includes process interactions cycles of transgression and regression and possible inland effects of marine coastal events process interactions are geologically common and most obvious where eolian and marine environments are adjacent these interactions include sediment exchange between the two environments the supply of marine ions to the erg for surface and near surface cementation and the control directly or indirectly of marine events on the sediment budget of an erg regression accompanied by erg progradation over marine deposits occurs with both onshore and offshore winds marine transgression of ergs varies from producing a planar marine scoured surface to a planar deflation surface that precedes the transgression to varying degrees of paleotopographic dune preservation and a variety of transitional facies the extent of paleotopographic dune preservation is largely a function of the energy level of the transgressing marine realm the rate of the transgression and potential for early dune cementation general correlations between ergs and global eustatic sea level and coastal onlap curves occur for coastal and near coastal cyclic erg sequences eustatic control of inland ergs exists to the extent that sea level controls in large measure the extent of the basin exposed to subaerial processes i e regional base level and probably to a lesser extent the sediment supply to the erg direct correlation of inland erg events to coastal onlap curves is dubious at present but an indirect relationship may exist

atmospheric summer circulation and coastal upwelling in the arabian sea during the holocene and the last glaciation accumulation rates of biogenic and lithogenic components were studied in 39 turbidite free well dated sediment cores from the northern indian ocean to define the proportions of fluvial and eolian input and to reconstruct quaternary patterns of coastal upwelling the majority of dust deposited in the western arabian sea during the holocene about 100 106 t yr 1 is advected from arabia by northwesterly winds which overlie the low level southwest monsoon the glacial increase in dust flux to 160 106 t yr 1 culminated in the northern arabian sea most probably due to i entrainment of dust rich in chlorite dolomite and lithogenic carbonate in the then dry persian gulf and ii a southward shift of the mean position of the southwest monsoon during glacial summer this shift is recorded in reduced accumulation rates of biogenic opal and increased rates of marine carbonate off somalia and oman both the terrigenous and biogenic sediment records show that the northwesterly winds and the southwest monsoon persisted over the last 27 000 yr as well as the asian continental summer heat low however the glacial seasonal time span of the southwest monsoon season was much reduced most likely because of a delay in the seasonal onset of the southwest monsoon

two and half dimensional simulation of ridge effects on the ground motion characteristics seismic responses of weathered and non weathered ridge models were simulated to study the ridge effects on the ground motion characteristics the range of ridge slope from 19 98 to 45 was considered to produce a possible set of generalized results 2 5 d modeling based on parsimonious staggered grid approximation of elastodynamic wave equations was adopted in simulations computed results reveal an increase of amplitude of incoming waves with both elevation and the slope of the ridge further the characteristics of surface waves are highly ridge slope dependent the analysis of responses of weathered and non weathered ridge models reveals that ridge has caused a strong generation of surface waves near its top the surface waves are not dominating on the top of the ridge but at some lower elevation the increase of weathering of ridge further intensified the ridge effect analysis in frequency domain based on spectral ratio method does not indicate a ny pattern in the spectral amplification factor and is very much sensitive to slope source focal mechanism and location however on an average there is a continuous decrease of amplification with slope in the vertical component and increase in the transverse component and it is increasing in the radial component up to slope 38 0 and thereafter decreasing

deriving wavefield characteristics and shear velocity profiles from two dimensional small aperture arrays analysis of ambient vibrations in a small size alluvial basin colfiorito italy we analyze the dispersion characteristics of ambient noise vibrations for this purpose two dimensional 2d seismic array data were acquired in four different sites in the colfiorito plain an alluvial intramountain basin that exhibits strong site effects assuming seismic noise being mainly composed of surface waves we derive one dimensional 1d shallow shear velocity profiles through the inversion of dispersion curves measured by frequency wavenumber f k methods the inverted shear wave velocity profiles are consistent with a priori information for those sites that can be approximated by 1d simple models in these cases the use of passive records of seismic vibrations can be a valuable tool for determining the shallow velocity profile if a detailed depiction of velocity structure is not required the theoretical dispersion curves for rayleigh and love waves were compared with the measured dispersion curves for vertical and horizontal components respectively this allows us to discuss qualitatively the composition of ambient vibrations outlining a large proportion of love waves in the noise wave field and the effects of higher modes we also use the single station method for investigating the origin of the horizontal to vertical h v peak in the plain of colfiorito in terms of ellipticity of the fundamental rayleigh mode

late pleistocene and holocene aeolian dust deposition in north china and the northwest pacific ocean abstract rates of dust deposition in the north pacific and the central loess plateau of china show a poor correlation during the last 30 000 yr although in both cases the dust was derived from deserts in northern china loess accumulation rates were high at the time of the last glacial maximum while dust flux to the north pacific was low at this time maximum dust flux to the north pacific is recorded in the mid holocene but holocene rates of loess accumulation have been low these differences are shown to reflect the different nature of the wind conditions responsible for dust transport to the loess plateau and the north pacific dust transport responsible for formation of the loess occurred mainly in the lower 1 5 km of the atmosphere and was accomplished by cold low level northwesterly winds associated with cold waves emanating from the mongolian anticyclone at present such conditions occur quite frequently in winter but during the coldest phases of the pleistocene they probably also occurred in the spring and summer long range dust transport from northern china to the north pacific requires that the dust is lifted to high levels above 3 km where it can be incorporated into the strong mid latitude westerlies strong vertical motions of the atmosphere occur most frequently in the spring when the mongolian anticyclone begins to weaken and frontal depressions move across the deserts of northern china such frontal depressions were probably more frequent during the climatic optimum of the mid holocene and during previous interglacials changes in continental aridity have probably played a minor role in controlling the magnitude of the dust flux to the north pacific

nehrp soil classifications for estimating site dependent seismic coefficients in the upper mississippi embayment abstract local soil conditions have a profound influence on the characteristics of ground shaking during an earthquake exceptionally deep soil deposits on the order of 100 1000 m deep are found in the upper mississippi embayment of the central united states shear waves sh from earthquakes in the new madrid seismic zone are expected to be strongly affected by the sharp impedance contrasts at the bedrock sediment interface attenuation of seismic waves in the soil column and the sh wave velocities of the more poorly consolidated near surface 50 m soils sh wave velocities of the near surface soils at nearly 400 sites in the upper mississippi embayment were determined using conventional seismic sh wave refraction and reflection techniques based on the average sh wave velocities of the upper 30 m of the soils sites in the mississippi river floodplain portion of the study area are predominantly classified as site class d 180 360 m s in accordance with the 1997 nehrp provisions sites away from the active floodplains in western kentucky and western tennessee the sh wave velocities of the upper 30 m of soils typically ranged from mid 200 to mid 300 m s several sites in western kentucky had averaged sh wave velocities greater than 360 m s thereby qualifying them as site class c 360 760 m s in accordance with the 1997 nehrp provisions one dimensional site effects including amplification and dynamic site period were calculated for a representative suite of sites across the upper mississippi embayment at latitude 38 5 although seismic attenuation is greater in the mississippi river floodplain i e thicker lower velocity material the site effects tend to be greater than in the uplands of western tennessee because of larger impedance contrasts within the near surface soils

seismic moment assessment of earthquakes in stable continental regions ii historical seismicity summary this part i study in conjunction with part 11 develops a method to determine within specified uncertainty bounds the seismic moment and thus moment magnitude of all earthquakes of stable continental regions scr for which instrumental or intensity data exist its basis is polynomial regression analysis using a database of scr earthquakes with direct seismic moment determination the independent variables include modern teleseismic magnitudes and regional magnitudes part i and isoseismal areas or number of recording stations part 11 part i11 is an application of the methodology of parts i and i1 to several major historical earthquakes all data used in the regressions are assigned individual uncertainties estimated from the literature or from experience formal confidence limits 68 per cent or 95 per cent on both the regression formulas and the predicted seismic moment values are then possible via error propagation analysis the most complete development is for the teleseismic magnitudes m and mb for both the final regression for log m is a quadratic formula that closely emulates the relationship between amplitude magnitudes and log m expected from dislocation theory and source scaling arguments regressions are also derived for the regional magnitudes mlg and m because there are many scr events mainly pre 1964 that have no teleseismic magnitudes prediction uncertainties from teleseismic magnitudes in moment magnitude units are in the ao 18 0 28 range and from regional magnitudes in the ko 23 0 38 range over a wide magnitude band finally the methodology developed here is generic even though the database is specific application to plate boundary oceanic intraplate or active continental intraplate regions should be straightforward

physical model study of beach profile evolution by sea level rise in the presence of seawalls abstract persistent and accelerating sea level rise slr may have a significant impact on the evolution of sandy coastlines this century the response of natural sandy beaches to slr has been much discussed in the literature however there is a lack of knowledge about the impact of slr on engineered coasts laboratory experiments comprising over 320 h of testing were conducted in a 44 m l x 1 2 m w x 1 6 m d wave flume to investigate the influence of coastal armouring in the form of seawalls on coastal response to slr the study was designed to investigate the effects of contrasting types of seawalls reflective impermeable versus dissipative permeable on beach profile response to increased water levels in the presence of both erosive and accretionary wave conditions the results obtained showed that seawalls alter the evolution of the equilibrium profile with rising water level causing increased lowering of the profile adjacent to the structure under erosive wave conditions modelled profiles both with and without seawall structures in place were observed to translate landward in response to slr and erode the upper profile it was found that the erosion demand at the upper beach due to a rise in water level remains similar whether a structure is present or not but that a seawall concentrates the erosion in the area adjacent to the seawall resulting in enhanced and localised profile lowering the type of structure present dissipative permeable versus reflective impermeable was not observed to have a significant influence on this response under accretive conditions the preservation of a large shoreface and berm resulted in no wave structure interaction occurring with the result that the presence of a seawall had no impact on profile evolution a potential two step method for estimating the observed profile response to water level rise in the presence of seawalls is proposed whereby a simple profile translation model is used to provide a first estimate of the erosion demand and then this eroded volume is redistributed in front of the seawall out to the position of the offshore bar

asian aridity and the zonal westerlies late pleistocene and holocene record of eolian deposition in the northwest pacific ocean rea d k and leinen m 1988 asian aridity and the zonal westerlies late pleistocene and holocene record of eolian deposition in the northwest pacific ocean palaeogeogr palaeoclimatol palaeoecol 66 1 8 a 30 000 year record of eolian deposition in the northwestern pacific ocean provides a history of the aridity of the asian source region and information on the changing latitude and intensity of the zonal westerlies the position of the maximum in eolian flux to the deep sea remained unchanged at 38 to 40 n during this entire time period but the dust flux record of aridity is greatest 6000 years ago at the holocene climatic optimum eolian grainsize data indicate that the northern margin of the westerly jet stream retreated northward during the holocene to a poleward extreme at about 6000 years ago and then moved back toward the equator the change in wind intensity across this margin was continually reduced throughout the holocene these sorts of data enhance our understanding of the behavior of the atmosphere during times of climate change and can be used to test computer generated models of past climatic conditions

microtremor measurements used to map thickness of soft sediments the observations about the behavior of microtremor spectra presented here show that noise measurements can be used as a powerful tool to determine the thickness of soft cover layers the most suitable method for this determination is nakamura s technique which is the ratio of the horizontal component noise spectrum and that of the vertical component i i v spectrum the frequency of the main peak in these spectral ratios correlates well with the sediment thickness at the site using an extensive database of microtremor measurements carried out in the western lower rhine embayment germany it was possible to show that this correlation is clearly valid for a wide range of thickness namely from tens of meters to more than 1000 m a simple formula was derived that for the sediments to be found in the area investigated directly calculates the cover thickness from the frequency of the main peak in the h v spectrum a comparison with calculated resonant frequencies sug gests the relation derived from the noise measurements depending on the velocity depth function of the shear wave classical spectral ratios are shown to be strongly influenced by the noise level and are therefore less reliable in determining the res onant frequency of the subsoil the practical relevance of the investigation is illus trated by means of cross sections constructed from results of the microtremor anal yses which provide a convincing image of the surficial structure of the areas investigated

australia s large earthquakes and recent fault scarps abstract nineteen large earthquakes up to magnitude ms 6 8 have occurred within continental australia this century and at least seven recent prehistoric fault scarps have been discovered the magnitude of the earthquake causing each of these prehistoric fault scarps has been estimated from the observed fault length and maximum scarp height and none exeeds magnitude 7 0 their occurrence demonstrates that the australian plate is undergoing significant internal deformation but as yet there is no model to explain their cause nor the likely site of the next large earthquake the absence of earthquake epicentres on the current tectonic map of australia is a regrettable omission

microtremor hvsr study for assessing site effects in the bovec basin nw slovenia related to 1998 mw5 6 and 2004 mw5 2 earthquakes abstract the bovec basin which is filled with glacial and fluvial sediments has recently been struck by two strong earthquakes 1998 and 2004 which caused extensive damage vii viii ems 98 strong site effects resulted in large variations in damage to buildings in the area which could not be explained by the surface variations in quaternary sediments the microtremor horizontal to vertical spectral ratio hvrs method was therefore applied to a 200 m dense grid of free field measurements to assess the fundamental frequency of the sediments large variations in the sediment frequency 3 22 hz were obtained with most of the observed values in the range 6 12 hz the observed frequencies cannot be related to the total thickness of quaternary sediments sand gravel but can be explained by the presence of conglomerate or lithified moraine at shallow depths the results were compared also with the velocity structure derived from seismic refraction data microtremor measurements performed in several two and some three and four storey houses masonry with rc floors which prevail in the bovec basin have shown that the main building frequencies in the area are in the range 7 11 hz this indicates that damage to houses in both earthquakes in some parts of the basin was enhanced by site amplification and soil structure resonance areas of possible soil structure resonance were identified in the settlements bovec brdo bovec mala vas cezsoca and kal koritnica considerable changes in fundamental frequencies within short distances were established in the town of bovec their values are as high as 22 hz in the central part of the town but diminish to 6 11 hz in the adjacent brdo and mala vas districts this is in agreement with the distribution of damage in both earthquakes which was considerably higher in brdo and mala vas although the houses in the central part of the town are older microtremor investigations have proved an effective tool for assessment of site effects in cases of complex geological structure commonly encountered in young alpine basins filled with glaciofluvial sediments which are partly cemented lithified layers can considerably change the fundamental frequency and consequently the site effects by taking additional measurements in buildings possible soil structure resonance can be identified