inversion of seismic surface wave data to resolve complex profiles for a complex layered site development of a shear wave velocity profile from inversion of seismic surface wave data can yield nonunique results one class of solutions provides depth averaged profiles that are useful but do not detail the local velocity anomalies simulated annealing inversion can be used to establish whether nonuniqueness is a concern for a particular case and if so focus results to allow a solution that is expected based on independent knowledge of site conditions a two step process is recommended whereby the model parameters are first optimized using simulated annealing and then fine tuned by unconstrained linearized inversion the process also yields useful confidence measures one example of a complex layered site where the proposed procedure is helpful is a desert profile with high velocity cemented layers interspersed among uncemented sediments

evidence for widespread nonlinear strong ground motion in the mw 6 9 loma prieta earthquake we exploit 55 repeating microearthquake sequences on the san andreas fault just south of the rupture zone of the 1989 m w 6 9 loma prieta earthquake to search for time dependent properties of the earth s crust using moving window waveform cross correlation we identify clear and systematic delays as large as 20 msec for the direct s wave and exceeding 50 msec in the early s wave coda following the loma prieta mainshock others have also identified phase delays velocity reductions associated with damaging earthquakes and they have suggested a myriad of possible causal mechanisms here we present new evidence for a mechanism to produce velocity reductions correlated in time and space with an earthquake a strong correlation between the spatial patterns of s delays and the intensity of strong ground motion in the loma prieta earthquake suggests that physical damage the formation or growth of cracks during strong ground motion to the earth s shallow crust is responsible for the observed velocity reductions the strong spatial variability in s delays over short distances and the strong correlation of the magnitude of delays with surface geology indicate that the phase delays accumulate primarily near the receiver the effect is stronger at stations on young soft rocks than at stations on old hard rock disproportionately larger s coda delays than p coda delays suggest that the cracks formed by the strong shaking are fluid filled in the 10 years after loma prieta the initial increase in travel times reduces logarithmically with respect to time often back to the premainshock levels we attribute this behavior to the same slow dynamic healing observed in laboratory studies of the recovery of materials from transient nonlinear strain manuscript received 14 january 2004

borehole response studies at the garner valley downhole array southern california the garner valley downhole array gvda consists of a set of seven downhole strong motion instruments ranging from 0 to 500 m depth one of the objectives of this experiment is to estimate site response and study wave propagation as the energy travels from the bedrock underneath the site up through the soil column the gvda velocity structure is studied by computing synthetic accelerograms for a small event located at an epicentral distance of 10 km these synthetics simulate well the data recorded at the borehole stations in addition theoretical transfer functions are calculated using the obtained velocity model and compare well with the empirical transfer functions from 54 recorded events it is also observed that the downgoing wave effect is predominant in the first 87 m and is strongly reduced at depth using the velocity structure at gvda and the transfer function results it has also been possible to develop a simple method to compute the incident wave field which is needed in nonlinear site response for instance recently there have been many comparative studies between horizontal to vertical h v spectral ratios and traditional spectral ratios although many of these studies show that h v spectral ratios can reproduce the shape of the site response curve most show differences in the amplitude level in the case of garner valley where we have both surface and multiple borehole instruments we find that this discrepancy in amplitude of the site response estimates is because the vertical component has significant site response associated with it due to s to p conversions that begin in the weathered granite boundary at 87 m depth manuscript received 27 august 2001

mound development as an interaction of individual plants with soil water erosion and sedimentation processes on slopes in the mediterranean region semi natural shrubland communities named matorral often present a discontinuous cover where isolated perennial plants alternate with bare inter plant areas in such ecosystems the patchy distribution of the vegetation is usually associated with microtopographic sequences of mounds that develop under isolated plants and break the overall slope continuity in this study the influence of three representative species of the mediterranean matorral rosmarinus officinalis stipa tenacissima and anthyllis cytisoides on slope microtopography is determined and the processes that take part in the development of microtopographic structures beneath the plant canopy are identified the influence of slope gradient plant species and plant parameters on the shape and height of microtopographic structures is also studied the shape of the microtopographic structures is described by using a two dimensional microprofilemeter and mound height is determined by measuring in the field a mound height index defined as the distance from the top to the bottom of the mound the results obtained show that plant species play a major role in the shape and height of the microtopographic structures whereas terrace type structures generally develop under anthyllis shrubs microtopographic forms associated with rosmarinus and stipa plants vary with slope gradient the almost symmetric mound type structures that develop under these two species on gentle slopes change into terrace type structures as slope gradient increases moreover statistically significant differences exist between the three species with regard to mound height mean values of mound height are 19 4 14 6 and 4 3 cm under the canopy of stipa rosmarinus and anthyllis respectively plant parameters essentially roughness and slope gradient have a significant influence on mound height index four main processes were identified as affecting mound development in the studied field site sedimentation differential interrill erosion differential splash erosion and bioturbation plant species interact in different ways with these processes according to their morphologies since stipa and rosmarinus plants are more efficient than anthyllis shrubs in controlling water erosion in retaining sediments and in modifying soil properties under their respective canopies they give rise to higher microtopographic structures that facilitate water and nutrient storage by plants on slopes copyright 2000 john wiley sons ltd

assessing the reliability of the modified three component spatial autocorrelation technique summary analysis of seismic ambient vibrations is becoming a widespread approach to estimate subsurface shear wave velocity profiles however the common restriction to vertical component wavefield data does not allow investigations of love wave dispersion and the partitioning between rayleigh and love waves in this study we extend the modified spatial autocorrelation technique mspac to three component analysis 3c mspac by determination of love wave dispersion curves this technique provides additional information for the determination of shear wave velocity depth profiles furthermore the relative fraction of rayleigh waves in the total portion of surface waves on the horizontal components is estimated tests of the 3c mspac method are presented using synthetic ambient vibration waveform data different types of surface waves are simulated as well as different modes in addition different spatial distributions of sources are used we obtain rayleigh and love wave dispersion curves for broad frequency bands in agreement with the models used for waveform simulation the same applies for the relative fraction of rayleigh waves dispersion curves are observed at lower frequencies for love waves than for rayleigh waves while 3c mspac has clear advantages for determination of love waves velocities 3c mspac and conventional vertical frequency wavenumber analysis complement each other in estimating the rayleigh wave dispersion characteristics inversions of the dispersion curves for the shear wave velocity depth profile show that the use of love wave velocities confirms the results derived from rayleigh wave velocities in the presence of higher mode surface waves love waves even can improve results application of 3c mspac to ambient vibration data recorded during field measurements pulheim germany show dominance of love waves in the wavefield existing shear wave profiles for this site are consistent with models obtained from inversion of rayleigh and love wave dispersion curves

biogeomorphology revisited looking towards the future although biogeomorphological research is well established with many studies on a range of two way interrelations between organisms and geomorphology in different environments there is little consensus over what constitutes biogeomorphology why it might be useful and where it is heading starting with definitions of core biogeomorphic processes we consider the need for future biogeomorphological studies to evaluate the crucial links between bioprocesses biological community dynamics and inorganic earth surface processes five key applications of biogeomorphological research are identified the roles of organisms in environmental reconstruction trace fossil analysis extraterrestrial geomorphology environmental engineering and the built environment some key research directions and methodological challenges for future biogeomorphological research include expanding the spatial and temporal coverage of datasets investigating the role of bioprocesses in landform development tackling scale issues investigating the relevance of nonlinear dynamical ideas to biogeomorphology and developing better sampling and monitoring techniques for bioprocesses

quantitative assessment of in situ salt karstification using shear wave velocity dead sea abstract the dead sea ds coastal areas have been dramatically affected by sinkhole formation since around 1990 such sinkholes along both israeli and jordanian shores are linked to karst cavities that form through slow salt dissolution a quantitative estimate of such in situ salt karstification would be an important indicator of sinkhole hazard one of the indications of salt karstification is its increased hydraulic conductivity caused by the development of dissolution cavities forming conducting channels within the salt layer we measured the hydraulic conductivity k versus shear wave velocity vs of ds salt in situ for estimating the actual salt karstification in areas of sinkhole development these parameters were measured with the magnetic resonance sounding mrs and multichannel analysis of surface waves masw methods respectively understanding of the field relationships was augmented by similar inter relations obtained in the laboratory on samples of ds salt in situ salt velocities vs vary from 750 m s to over 1650 m s while hydraulic conductivity k in the same zones varies between about 10 4 m s to slightly over 10 8 m s both field and laboratory k and vs values fit the exponential function ln k 0 0045 vs 5 416 with a determination coefficient r2 of 0 88 a classification based on vs and k was generated for salt conditions and the corresponding degrees of sinkhole hazard which was verified in the mineral beach sinkhole development area the mapping of sinkhole sites shows that they form within highly conductive zones with k 5 5 10 5 it is suggested that this methodology with some modification can be used for evaluating the conductive properties of karstified rock and associated sinkhole hazards

the importance of surface waves in vibration study and the use of rayleigh waves for estimating the dynamic characteristics of soils vibrations generated during civil engineering work are often dominated by prominent surface waves the propagation of which is strongly influenced by site conditions the effects of soil properties on the shape amplitude and duration of rayleigh waves are shown from synthetic seismograms surface waves are dispersive and may be processed to retrieve the shear characteristics shear wave velocityvs and shear quality factorqs of soil layers a seismic survey was conducted on a site limelette belgium to determine the dynamic characteristics of the ground layers from different seismic methods various refraction profiles and one cross hole test were performed to obtain shear wave velocity profiles the comparison of surface wave inversion method with other techniques shows that the former leads to slightly underestimatedvs values

comparisons of shear wave slowness in the santa clara valley california using blind interpretations of data from invasive and noninvasive methods many groups contributed to a blind interpretation exercise for the deter mination of shear wave slowness beneath the santa clara valley the methods in cluded invasive methods in deep boreholes as well as noninvasive methods using active and passive sources at six sites within the valley with most investigations being conducted at a pair of closely spaced sites near the center of the valley although significant variability exists between the models the slownesses from the various methods are similar enough that linear site amplifications estimated in several ways are generally within 20 of one another the methods were able to de rive slownesses that increase systematically with distance from the valley edge cor responding to a tendency for the sites to be underlain by finer grained materials away from the valley edge this variation is in agreement with measurements made in the boreholes at the sites

euro seistest determination of the geological structure of the volvi basin and validation of the basin response the volvi basin northern greece is a 5 km wide graben of neogene age it has been chosen by european union directorate general xii for science research and development in climatology and natural hazards as a test site euro seistest for studying site effects in one of europe s most seismic active areas the site is located in the epicentral area of the 1978 ms 6 5 earthquake that struck the city of thessaloniki the geometry velocity and stratigraphy of the basin were not well known consequently a number of geophysical and geotechnical studies were performed to determine the 2d geometry and the dynamic characteristics vp vs qs of the valley investigations included 78 refraction tests 20 surface wave inversions and 8 borehole seismic tests as well as geotechnical tests this article presents the methodology used for the geophysical investigation and the results in its center the graben depth reaches 190 m and at least four normal faults have been located along the section the overall graben structure and the fault locations have been confirmed by the records of a shot generated at one edge of the valley and by the measurements of a local earthquake wave propagation appears to be strongly influenced by the thickness of the sediments which in turn is controlled by fault displacements simple 2d modeling of the basin response was performed and the results are in good agreement with weak motion data confirming the validity of the seismic structure inferred from seismic prospecting

shearing of partially consolidated sediments in a lower trench slope setting shimanto belt sw japan abstract detailed mapping of a coastal platform in shikoku sw japan provides evidence for progressive deformation in partially lithified sediments the eocene sediments involved are interpreted as lower slope basin deposits an assemblage of listric normal faults sheath folds broken formations and late stage faulting has developed during the sediments burial and uplift history these structures are typical of many other areas in the shimanto belt of shikoku despite the soft sediment style of deformation the consistency of the fold orientations relative to the regional foliation suggests that they are valid kinematic indicators a sequence of extensional faulting overprinted by synchronous folding and shearing is recognized this is interpreted as the response of the sediments to shape changes in the accretionary basement induced by shortening a general model has been constructed for the evolution of the structures it is proposed that early listric normal faults are subsequently deformed either by shearing along planar surfaces or by motion over frontal and lateral ramps back rotation of sediments during progressive shortening near the front of the prism tightens the fold hinges and rotates the fold axes towards the local shear direction alternative sequences which could account for the observed geometries are also discussed

time lapse changes of seismic velocity in the shallow ground caused by strong ground motion shock of the 2000 western tottori earthquake japan as revealed from coda deconvolution analysis abstract a large earthquake shock often drops the seismic velocity of the shallow ground however it is not clear whether the dropped velocity recovers shortly after the earthquake shock or not the purpose of this article is to report the time lapse changes of seismic velocity in the shallow ground after the 2000 western tottori earthquake japan we deconvolve the coda record of small earthquakes registered on the ground surface by that registered at the 100 m depth in a borehole at a station that experienced a strong shock from the mainshock because coda waves are mostly composed of randomly scattered s waves deconvolution of the two coda records enables us to obtain a robust image of the ground structure assuming that the shear modulus was reduced at the depth of 0 11 m we estimate the shear modulus change in each time period after the mainshock by fitting synthetic coda deconvolution to the observed one from 1 to 16 hz as a result the shear modulus dropped to 52 of the value obtained before the mainshock a few minutes after the strong earthquake shock this caused a decrease in the s wave velocity of 30 and an increase in s wave travel time of 17 msec the shear modulus continued to recover for over 1 yr following the logarithm of the lapse time it recovered to 69 83 87 and 97 of the value obtained before the mainshock in the periods of 0 to 1 week 1 week to 1 month 1 month to 1 yr and 1 to 4 yr after the mainshock respectively

shrub mound formation and stability on semi arid slopes in the northern negev desert of israel a field and simulation study in semi arid areas vegetation is scarce and often dominated by individual shrubs on raised mounds the processes of formation of these mounds are diverse and still debated often shrub mound formation is directly related to the formation of vegetation patterns thereby assuming that shrub mound formation is driven by biological interactions we hypothesize that water related erosion and sedimentation are also important drivers of shrub mound formation in the northern negev desert of israel we test this hypothesis by combining field observations with model simulations we studied shrub mounds in the semi arid catchment of sayeret shaked in the northern negev desert 200 mm annual precipitation height and diameter of shrub canopy and shrub mounds were measured and micro morphological techniques were used to reconstruct the formation of the shrub mounds we used landscape evolution model lapsus to simulate shrub mound formation at short single precipitation event and longer 100 years timescales at different slope angles both field and model results indicate that shrub mounds in sayeret shaked are at least partly formed by redeposition of eroded material below the shrubs and by erosion and lowering of the surrounding crust additional model simulations suggest that mounds are formed most under low shrub density and large shrub canopy diameter shrub mound formation increases with slope in dryer and wetter climates than the studied 200 mm rainfall semi arid climate zone shrub mound formation is less likely

interactions of plant growth and sediment movement on slopes in a semi arid environment abstract the morphology and architecture of the tussocks of alpha grass stipa tenacissima as well as its associated micro topography have been described in several sites on the south versant of the filabres range in southern spain the annual rainfall of this area is between 225 and 275 mm and plant cover ranges from 20 to 45 the results show the formation of micro topographic mounds upslope of the tussocks which are interpreted as deposition bodies originating from the interception of downslope sediment movement by the vegetated patches the tussock architecture shows an outer growing zone a middle mature zone and a central senescent zone the outward expansion of the tussock is performed by tillers in the growing zone which bend at the nodes and root when they come into contact with the soil surface the mat of dead leaves inside the tussock may prevent the stems from bending and this factor plays a significant role in controlling tussock growth a similar effect on slopes is produced by the mound of sediments which accumulate upslope of the tussock and press upon the growing stems a simple simulation model has been built from the above field observations the model is able to reproduce the tussock shapes found in nature and predicts that at low plant rates the tussocks become unstable and collapse while at higher levels of plant vigour and sediment movement rates sedimentation occurs upslope of the tussock and erosion downslope these foci of sedimentation and erosion are crescent shaped and their relative importance depends on the splash factor

modified topsoil islands within patchy mediterranean vegetation in se spain the spatial distribution of some chemical and physical soil properties was determined in the microenvironment of individual plants of three matorral species rosmarinus officinalis l stipa tenacissima l anthyllis cytisoides l in an area of patchy vegetation in south east spain the influence of isolated plants on the chemical and physical status of the topsoil decreased significantly from the plant axis to the bare inter plant area giving rise to islands of improved topsoil properties beneath each plant i e increased organic matter content and aggregate stability and decreased bulk density penetration resistance shear strength and rock fragment content and cover the degree and lateral extent of topsoil modification was significantly more pronounced under rosmarinus and stipa plants than under anthyllis shrubs mainly because of the differential influences of species morphology i e above ground structure and components i e canopy and litter covers on soil properties and erosion sedimentation processes

geophysical investigation of a large landslide in glaciolacustrine clays in the trieves area french alps abstract slope movements in clay deposits are spread all over the world and result from complex deformation processes including internal strains in the landslide body and slipping along rupture surfaces such mass movements are likely to generate changes in the geophysical parameters characterizing the ground which can be used to map the landslide body in the last decade geophysical techniques have been increasingly used for landslide investigation purposes however the success of any geophysical technique is overall controlled by the existence of a geophysical contrast differentiating the body to be mapped for landslides affecting thick clay materials from soft clay to shale or marl electrical and seismic techniques have been mainly applied in the past in this study we attempt to physically characterize the deformation within a large slide avignonet affecting laminated clays which were deposited in a glacially dammed lake during the wurm period clay deposits which cover an area of 300 km2 south of grenoble french alps and have a maximum thickness of 200 m overlay compact alluvial layers and marly limestone of mesozoic age piezometric data at avignonet show that the water table is very shallow implying that the slide developed in saturated clay several seismic and electrical profiles were performed in order to tentatively correlate the variations of p wave vp velocity s wave velocity vs and electrical resistivity with geotechnical data and morphological observations in such saturated and fine material it turned out that only the s wave velocity exhibits significant variations with the displacement rates and the morphological features vs values at shallow depth were found to be inversely correlated with displacement rates measured by gps with a division by at least a factor of 2 between the zones unaffected and strongly deformed by the landslide these results suggest that vs mapping could provide valuable information on the deformation state of the clay material and that the evolution of vs with time could be used as an indicator for characterizing the landslide activity in the subsurface including the evolution into a flow

extrapolation of irregular subsurface structures using the horizontal to vertical spectral ratio of long period microtremors one of the key problems in modeling the 3d subsurface structure of sedimentary basins is extrapolation and or interpolation from 2d models constructed from reflection and refraction surveys the use of microtremor horizontal to vertical h v spectral ratios allowing simple and quick microtremor measurements may be suitable for this purpose the validity and usefulness of long period microtremor h v spectral ratios are investigated as a possible tool for extrapolation in 3d basin structure modeling three component microtremor observations were conducted at 51 stations in the northern section of the osaka basin which encompasses the most complex geological structures in the basin the microtremor h v spectral ratios were measured in the range 1 to 5 sec to reproduce these observations three 2d finite element models have been developed that account for the irregular shape of subsurface structures deduced from seismic reflection studies microtremor array studies and deep drilling data the 3d model obtained by combining the 2d models is consistent with geological information for the area such as surface geology and the location of active faults furthermore compared with the basement structure derived from the gravity prospecting this 3d model is more detailed and offers higher resolution than the gravitational method therefore the microtremor h v spectral ratio represents a useful technique of extrapolation and interpolation for modeling 3d basin structures

deep characterization of the santiago basin using hvsr and cross correlation of ambient seismic noise abstract continuously recorded seismic ambient noise is used to investigate the intermediate and deep structure of the santiago basin for seismic site response evaluation single station h v spectral ratios hvsr were used as a proxy to identify zones with high stiffness soils and low impedance contrast with the underlying bedrock as a complement of available surface geology information frequency domain cross correlation of the vertical components of ambient noise were calculated and used to estimate phase velocity dispersion curves associated to station pairs over different soil deposits in addition noise correlation functions ncfs calculated from time domain cross correlation of the vertical seismic noise records were used to estimate group velocity dispersion curves and to verify results from the spectral method data processing from both methods resolves a frequency band between 0 1 and 8 0 hz a critical band for civil infrastructure that is difficult to determine with traditional local scale passive surface wave methods station pairs with high signal correlation over stiff soils in the center south and east part of the basin mainly associated to flat hvsr response yielded robust phase velocity dispersion curves that vary approximately from 3 5 km s at 0 1 hz to 1 km s at 4 hz shear wave velocity profiles inverted from the dispersion curves show high average shear wave velocities that also have a pronounced increase rate with depth and a lack of clear soil bedrock interface at depths predicted by available gravimetric data

seismic imaging of the shallow subsurface shear wave case histories obtaining high resolution images of the geology and hydrogeology of the subsurface in the depth range from ground level to 50 m is one of the major challenges of modern geophysics the methods which are commonly used such as compressional wave surveys and ground penetrating radar often suffer from adverse effects caused by the near surface conditions changes in water saturation and various sources of noise this paper demonstrates some of the advantages offered by the use of shear wave seismology and by the combination of shear and compressional wave seismic methods in shallow subsurface investigations multicomponent shallow seismic tests were carried out at four different sites to examine the effectiveness of different acquisition geometries under a variety of near surface geological conditions near surface conditions encountered at the sites included thick clays clay sand sequences overlying chalk mudstone overlying granodiorite bedrock and landfill material under all conditions shear wave data acquisition was found to have advantages over compressional wave acquisition for the investigation of the shallow subsurface shear head waves being unaffected by water saturation achieved penetration to greater depths at a site in crewkerne dorset where compressional head wave penetration was limited to the near surface layers better vertical resolution was achieved at shallow depths using shear wave reflection energy at a landfill site shear wave reflections from shallow interfaces were in some cases less affected by noise compared with the equivalent compressional wave reflections combinations of shear and compressional wave data recording allowed the measurement of a poisson s ratio log and gave indications of seismic anisotropy at two sites where dipping clay layers were present

geotechnical properties of lower trench inner slope sediments abstract geotechnical property analyses on sediments recovered by dsdp drilling within select convergent margins were integrated to determine the variability in these properties along the trench inner slope and to delineate the effects of convergence on these properties consolidation states range from very underconsolidated to highly overconsolidated with preconsolidation pressures exceeding 46 000 kpa in quaternary sediments underconsolidated sediments are attributed to 1 1 high sedimentation rates 2 2 low sediment permeability relative to the length of the drainage path 3 laterally applied stresses and 4 induced pore water pressures resulting from the subduction of pelagic sediments with high water content factors contributing to the state of overconsolidation include 1 tectonically induced overpressures 2 removal of overburden by mass movement processes 3 3 low sediment accumulation rates 4 4 age vertical gradients of index properties also vary greatly with the maximum gradient associated with overconsolidated sediments values of porosity generally exceed 30 at all margins studied suggesting this porosity represents the minimum attainable solely by the effects of convergence geotechnical property results and site specific parameters suggest two end members should be considered in the general geotechnical property model for convergent margin sediments clastic dominated margins form the basis for the initial geotechnical property model these margins are characterized by thick trench sediment sequences which are folded and faulted and become progressively more deformed upslope convergence rates are low and no well developed faults or hrst and graben structures are evident on the downbending oceanic plate highly overconsolidated sediments and index property values which change rapidly with depth result from the slow progressive deformation of trench and lower slope sediments examples of clastic dominated margins include the nankai trough aleutian trench and washington continental margin pelagic dominated margins have significantly different geotechnical properties and site specific parameters these margins are characterized by thin clastic trench sediment sequences overlying pelagic sediments on a rapidly converging oceanic plate well developed faults and or hrst and graben structures are evident on the downbending oceanic plate sediment deformation along the trench and lower slope appears limited these sediments are underconsolidated and index property values change gradually but often irregularly with depth japan trench and middle america trench guatemala margins are considered pelagic dominated middle america trench mexico appears to represent an intermediate case having characteristics of both margin types

continental margin tectonics submarine accretionary prisms submarine accretionary prisms are sites of incipient mountain building where sediments and rocks of the deep ocean are uplifted deformed and ultimately transformed to continental crust accretionary prisms develop at sites of lithospheric convergence that is subduction zones commonly accretionary prisms form along continental margins although accretionary prisms may also occur adjacent to island arcs which are ultimately coalesced into continental landmasses here we review the studies of submarine accretionary prisms during the past four years with primary focus on the contributions of geoscientists from the united states

evidence of two dimensional amplification effects in an alluvial valley valnerina italy from velocimetric records and numerical models abstract the results of field surveys velocimetric records and numerical models are reported with the goal of analyzing the local seismic response in a section of the nera river alluvial valley in central italy alluvial deposit geometry and dynamic properties were defined by geological and geophysical investigations 2d amplification effects were pointed out by horizontal to vertical spectral ratios hvsrs as well as by horizontal to horizontal spectral ratios hhsrs to a reference station hvsrs were derived from both noise and weak motion records while hhsrs were only computed from weak motions where travertine deposits are interlayered within the alluvia 2d amplification effects are shown only by hhsrs the observed amplifications 1 consist of peaks of the amplification functions a f in the range 1 10 hz 2 generally correspond to two frequency ranges whose values mainly depend on the valley shaped ratio and on the local heterogenities of the alluvial deposits and 3 can be regarded as due to a 1d resonance combined with lateral wave propagation numerical models via the finite difference method were performed by the italian national institute for geophysics and volcanology web interface for seismological application and by the fast lagrangian analysis of continua codes the obtained results 1 show a good agreement with hhsrs 2 prove that some 2d amplification effects are constrained by both the shape ratio of the valley and the heterogeneity of the alluvial deposits 3 reveal focalization effects within the alluvial deposits strictly related to the shape of the valley and 4 allow the comparison of the a f functions in both linear and nonlinear dynamic behavior and the computation of the shear strains due to ground motion within the alluvial deposits

the impact of a buried high velocity layer in the seismic site amplification of the city of llolleo chile programa de riesgo sismico prs at the university of chile comision nacional de investigacion cientifica y tecnologica conicyt 2017 21171480 fondo nacional de desarrollo cientifico y tecnologico fondecyt 1170430 advanced mining technology center amtc fb0809 pia conicyt

mounds associated with shrubs in aridic soils of northeastern patagonia characteristics and probable genesis abstract studies of mounds associated with shrub clumps in northeastern patagonia indicate that these forms have an average major diameter of 355 cm and an average height of 41 cm mound cover and density are 40 and 450 mounds ha respectively mound and intermound soils present a similar textural composition as well as a similar coarse fragment content 10 20 root and organic matter contents are significantly higher whereas calcium carbonate is significantly lower in the mound than in the intermound soils mounds may represent a relict land surface level lowered in the intermound area mainly by wash erosion mound development is related to discrete shrub clumps that shelter the underlying soil once established the shrub clump and the underlying mound remain as a stable and self maintained system

inversion of surface wave data for subsurface shear wave velocity profiles characterized by a thick buried low velocity layer the study formed part of the simit project integrated italy malta cross border system of civil protection b1 2 19 11 part financed by the european union under the italiamalta cross border cooperation programme 2007 2013

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

volume changes during diagenesis abstract the literature pertaining to volume change during diagenesis of clastic sediments is reviewed with respect to the problem of calculating pre and syn compaction thicknesses of sediments for basin reconstruction and stragraphic correlation studies four major mechanisms for volume change are identified mechanical compaction mechanical dissolution chemical dissolution and phase change the first two of these are found to be strongly dependent on the effective stress whilst the latter two show at least a pressure dependence quantification of the relationships between porosity and depth of burial of a sediment seems to be possible only for specific examples of the first of these processes at present this quantification is dealt with in the accompanying related publication

impediments to predicting site response seismic property estimation and modeling simplifications abstract we compare estimates of the empirical transfer function etf to the plane sh wave theoretical transfer function ttf within a laterally constant medium for invasive and noninvasive estimates of the seismic shear wave slownesses at 13 kiban kyoshin network stations throughout japan the difference between the etf and either of the ttfs is substantially larger than the difference between the two ttfs computed from different estimates of the seismic properties we show that the plane sh wave ttf through a laterally homogeneous medium at vertical incidence inadequately models observed amplifications at most sites for both slowness estimates obtained via downhole measurements and the spectral analysis of surface waves strategies to improve the predictions can be separated into two broad categories improving the measurement of soil properties and improving the theory that maps the 1d soil profile onto spectral amplification using an example site where the 1d plane sh wave formulation poorly predicts the etf we find a more satisfactory fit to the etf by modeling the full wavefield and incorporating spatially correlated variability of the seismic properties we conclude that our ability to model the observed site response transfer function is limited largely by the assumptions of the theoretical formulation rather than the uncertainty of the soil property estimates

generation of high pore pressures in accretionary prisms inferences from the barbados subduction complex recent geological and geophysical exploration of several accretionary complexes reveals that pore pressures inside them are much higher than the hydrostatic values indirect inferences further suggest that such high pore pressures may be present inside most accretionary complexes in this study the mechanisms for generating excess pore pressures is investigated by focusing on the barbados ridge complex which is an end member of sediment rich accretionary prisms modeling is carried out using a two dimensional finite element procedure with constraints provided by the following data deep sea drilling project results on stratigraphy and lithology seismic results on sediment structure and thickness regional geology on tectonic history and laboratory measurements on mechanical properties of sediments coupling among the equations for fluid flow heat transfer and sediment deformation is made throughout the computation the results of the modeling predict that the principal decollement beneath the barbados ridge complex is a zone of high pore pressure high porosity and reversal in seismic velocity these characteristics may be responsible for the mechanical weakness of the decollement which allows continuous subduction of sediments below it and for its seismic signatures results of the modeling further suggest that tectonic overburden may be the most important mechanism for the generation of high pore pressures inside accretionary prisms the direct effect of tectonic compression is of secondary importance and the effect due to temperature increase with subduction is of little significance thrust faulting near the toe of accretionary prisms can disturb pore pressure patterns and produce localized highs rich sediment supply low permeability high subduction angle and high subduction velocity are all favorable factors in creating high pore pressures inside accretionary prisms

pore pressure generation in sedimentary basins overloading versus aquathermal the principal mechanism for abnormally high pore pressure generation has been an important matter of debate for more than a decade among the various mechanisms proposed mechanical overloading and aquathermal pressuring have probably received the greatest attention most previous discussions however have been based upon qualitative conceptual models here we propose a quantitative analysis by first examining the basic principles of porous flow and the fundamental properties of sediments and second by comparing the relative importance of the overloading versus the aquathermal mechanisms the coupling between pore pressure and compaction as well as the nonlinear and path dependent material properties are found to be critical in the present analysis we find that although changes in stress and temperature both contribute to pressure generation mechanical overloading is the main mechanism under normal geological conditions and is capable of producing the observed pore pressure profiles

estimation of s wave velocity structures in and around the sendai basin japan using array records of microtremors we conducted array measurements of microtremors at six sites in and around the sendai basin to estimate deep s wave velocity structures above the seismological bedrock pre tertiary bedrock after estimating phase velocities of microtremors in the frequency range from about 0 5 to 3 hz we succeeded to estimate the deep structures above the pre tertiary bedrock at four soil sites kata okin arah and myg15 and only the upper part just beneath the pliocene layer at the other soil site trma using a rayleigh wave inversion technique at trma and a rock site tama we roughly estimate the deep s wave velocity structures using empirical site amplification factors derived from strong motion records the deepest bedrock depth is 1 km and the shallowest depth is 200 m among these six sites the difference of the bedrock depth between the eastern side and the western side of an active thrust fault the nagamachi rifu line is only 120 m the difference of the bedrock depth between two sites in the east of the basin reaches about 500 m although any geological boundaries or buried faults have not been mapped since the deep s wave velocity structure of the sendai basin had been basically unknown we delineate it for the first time in this article using array measurement of microtremors

effectiveness of vegetation barriers for marly sediment trapping vegetation barriers can be effective in trapping eroded sediment but little knowledge exists on the characteristics of vegetation barriers efficient in trapping all sediments from an eroded zone upslope the objective of this study is to quantify the effectiveness of vegetation barriers for marly sediment trapping relationships between eroded zones and vegetation barriers composed of low vegetation that is to say herbaceous and under shrub layers located downslope and sufficient to stop all the sediments eroded above have been studied in the brusquet experimental marly catchment in the french southern alps 40 plots with surface areas less than 500 m were studied the eroded zones and the vegetation barriers were characterised by their surface areas between which an average linear relationship exists results also showed that for a marly plot with a given surface area a downslope vegetation barrier covering only 20 of this plot can be sufficient to trap all the sediments eroded above it

influence of parameterization on inversion of surface wave dispersion curves and definition of an inversion strategy for sites with a strong vs contrast inversion of the fundamental mode of the rayleigh wave dispersion curve does not provide a unique solution and the choice of the parameterization number of layers range of velocity and thickness values for the layers is of prime importance for obtaining reliable results we analyzed shear wave velocity profiles derived from borehole tests at 10 sites where soil layers overlay bedrock in various geologic contexts one to three seismic layers with linear velocity laws could model all of them three synthetic models defined from this preliminary study were used to understand the influence of parameterization on the dispersion curve inversion this analysis resulted in the definition of a two step inversion procedure for sites exhibiting a strong impedance con trast in the first step the dispersion curve is inverted with an increasing number of layers over half space the evolution of the minimum misfit and bedrock depth with number of layers allows the estimation of the true bedrock depth range in the

love and rayleigh phase velocity maps 5 40 s of the western and central usa from usarray data abstract continuous data recorded on more than 1600 usarray seismic stations operating in the western and central us between 2006 and 2012 are used to map phase velocities of love and rayleigh waves at short periods 5 40 s using a noise correlation technique vertical and transverse records for all station pairs separated by less than 600 km are cross correlated in 4 h long segments and the resulting spectra are stacked for the time period of station operation dispersion curves are determined from the locations of zeros in the real component of the correlation spectra using a method based on that of aki 1957 phase velocity maps expanded on a 0 25 by 0 25 pixel grid are estimated by inversion of the phase velocity measurements comparison with predicted phase velocity maps based on the crustal model crust2 0 combined with the mantle model nd08 shows good agreement at the longer periods strong slow anomalies 25 in the short period maps are geographically correlated with basins and regions of thick sedimentary cover the strength of these anomalies is not well predicted by existing crustal velocity models

s wave velocity profiling by joint inversion of microtremor dispersion curve and horizontal to vertical h v spectrum a joint inverse analysis using both microtremor dispersion curve and horizontal to vertical h v spectrum is proposed for estimating the s wave velocity vs profiles of subsurface soils in the inversion both microtremor dispersion and h v data are assumed to be the rayleigh wave dispersion curve and the surface both rayleigh and love wave h v spectrum that have been theoretically derived by taking into account the effects of their fundamental and higher modes the proposed joint inversion as well as the conventional one using dispersion data alone is per formed at four sites where shallow vs profiles down to engineering bedrock are available the vs profiles estimated by the proposed joint inversion are more con sistent with available down hole velocity logs than those by the conventional method in particular the proposed inversion shows significant improvement in estimating bedrock vs structures compared to the conventional inversion sensitivity analyses indicate that the surface wave h v ratio is sensitive to the bedrock vs structure more than the rayleigh wave phase velocity confirming that the proposed joint inversion including h v spectrum is promising

relative efficiency of three representative matorral species in reducing water erosion at the microscale in a semi arid climate valencia spain abstract in the mediterranean region where rainfall is scarce but often of high intensity the matorral vegetation cover provides essential protection to the soil against the erosivity of rainfall and reduces considerably the water erosion rate three representative species of the mediterranean matorral displaying different morphologies rosmarinus officinalis l stipa tenacissima l anthyllis cytisoides l were selected for study at the microscale plant scale for their relative efficiency in reducing water erosion on slopes the mechanical protection of the soil against raindrop detachment and the improvement of the soil properties by the biological influence of an isolated plant were compared for the three species the quantification of interrill erosion and splash erosion rates under natural rainfall conditions was obtained using erosion microplots of individual plants and splash cups placed at different distances from the plant axis respectively soil samples were also taken in the microenvironment of the plants in order to evaluate possible differential influences of the three species on soil properties relevant to water erosion the results show that the three selected species reduced runoff and soil loss in different ways the screen effect arising from the very dense canopy of stipa tussocks represents an effective way to counteract rainfall erosivity and reducing splash erosion however in the case of rosmarinus in addition to the mechanical protection offered by its canopy and litter covers the latter which lies permanently at the soil surface under the plant canopy improves moreover the topsoil structure because of the important incorporation of organic matter below the canopy cover the role of litter cover in controlling erosion seems therefore to be predominant under rosmarinus as for anthyllis these deciduous shrubs provide little physical protection against the energetic impact of rain at the soil surface as compared to a bare surface nevertheless the three plant species have a positive influence on their microenvironment through the improvement of soil properties under their canopy thus in open matorral patchy vegetation fertile soil islands developed below the plant canopy these differ considerably from the bare soil inter plant areas that give rise to higher soil loss rates

are microtremors useful in site response evaluation we have reviewed the applicability of microtremor measurements to evaluate site response of soft soils to this end we evaluated three different techniques commonly used to estimate site effects from microtremor measurements interpretation of fourier amplitude spectra computation of spectral ratios relative to a firm reference station and finally computation of spectral ratios of horizontal components relative to the vertical component of ground motion nakamura s technique these techniques are applied to microtremor records obtained in three cities in mexico mexico city oaxaca and acapulco these cities differ in their local geological conditions and in their seismotectonic environment in order to evaluate the results obtained from microtremor measurements we compare them with standard spectral ratios of the intense s wave part of weak or strong motion records obtained at the same sites our results showed that microtremor measurements can be used to estimate the dominant period of a site with very acceptable reliability in the range 0 3 to 5 hz the best results were obtained with nakamura s technique which also gives a rough estimate of amplification of seismic waves when the local geology is relatively simple simple numerical simulations indicate that the underlying assumptions of nakamura s technique are consistent with the propagation of rayleigh waves these simple numerical simulations also explain why different researchers have been able to successfully characterize 1d site effects using microtremor records regardless of whether they consider microtremors to consist of surface or body waves our results strongly suggest that the technique by nakamura effectively compensates for source effects in microtremor measurements which eliminates a major limitation to their application in earthquake engineering

characterization of earthquake strong ground motion some underwater landslides are triggered by strong ground motions caused by earthquakes this paper reviews current concepts and trends in the characterization of strong ground motion improved empirical ground motion models have been derived from a strong motion data set that has grown markedly over the past decade however these empirical models have a large degree of uncertainty because the magnitude distance soil category parameterization of these models often oversimplifies reality this reflects the fact that other conditions that are known to have an important influence on strong ground motions such as near fault rupture directivity effects crustal waveguide effects and basin response effects are not treated as parameters of these simple models numerical ground motion models based on seismological theory that include these additional effects have been developed and extensively validated against recorded ground motions and used to estimate the ground motions of past earthquakes and predict the ground motions of future scenario earthquakes

determination of shallow shear wave velocity profiles in the cologne germany area using ambient vibrations summary we have used both single station and array methods to determine shallow shear velocity site profiles in the vicinity of the city of cologne germany from ambient vibration records based on fk analysis we assume that fundamental mode rayleigh waves dominate the analysed wavefield in the frequency range of 0 7 2 2 hz according to this view a close relation exists between h v spectral ratios and the ellipticity of the contributing rayleigh waves the inversion of the shape of h v spectral ratios then provides quantitative information concerning the local shear wave velocity structure however based on tests with synthetic data believed to represent a typical situation in the lower rhine embayment dispersion curves were found to provide stronger constraints on the absolute values of the velocity depth model than the ellipticities the shape of the ellipticities was found to be subject to a strong trade off between the layer thickness and the average layer velocity we have made use of this observation by combining the inversion schemes for dispersion curves and ellipticities such that the velocity depth dependence is essentially constrained by the dispersion curves while the layer thickness is constrained by the ellipticities in order to test this method in practice we have used array recordings of ambient vibrations from three sites where the subsurface geology is fairly well known and geotechnical information is at least partially available in order to keep the parameter space as simple as possible we attempted to fit only a single layer over a half space model however owing to earlier studies from the region we assume a power law depth dependence for sediment velocities for all three sites investigated the inversion resulted in models for which the shear wave velocity within the sediment layer both in absolute value at the surface and in depth dependence are found to be remarkably similar to the results obtained by budny from downhole measurements this is strong support for the interpretation of h v spectral ratios as rayleigh wave ellipticities for all three sites the predicted sh wave site amplification factors at the fundamental frequency are of the order of 5 6 with a slightly smaller value south of cologne

phytogenic mounds of four typical shoot architecture species at different slope gradients on the loess plateau of china abstract in semi arid regions the spatial pattern of vegetation usually appears as a mosaic of plants surrounded by bare soil phytogenic mounds often develop under these plants and create microenvironments that promote plant establishment this study examined the effects of ground slope and plant shoot architecture on mound formation four species representing different shoot architectures artemisia gmelinii with dense shoot architecture artemisia giraldii with expanding shoot architecture tussock forming bothriochloa ischaemum and sophora viciifolia with a main stem shoot architecture and four classes of slope were selected a two dimensional microprofilemeter was used to measure mound shape and height and mound area was measured using the image pro plus software with a planer mound picture phytogenic mound shapes changed from symmetrical mound type to asymmetrical terrace type as slope increased with increasing slope mound height increased for all species the mound area of s viciifolia decreased and that of a giraldii increased a gmelinii and b ischaemum had a relatively constant mound area irrespective of slope among the plant shoot architecture parameters the basal diameter along the slope d ba significantly correlated with mound height while the plant basal diameter perpendicular to the slope d bp and the total cross sectional area of the stem at the base s n were related to mound area the results indicate that phytogenic mounds on gentler slopes are formed due to the difference in rain splash erosion beneath the plant canopy and surrounding bare surfaces on steeper slopes mounds are formed due to water erosion on bare soil and the prevention of erosion and sediment accumulation under plants plant shoot architecture also influences mound formation species with expanding shoot architecture such as a giraldii that spread laterally to create high density stems and occupy a large area can create relatively large mounds species with main stem shoot architecture such as s viciifolia have a mound area that shrinks rapidly with increasing slope

source characteristics of hypothetical subduction earthquakes in the northwestern united states historic earthquake sequences on subduction zones that are similar to the cascadia subduction zone are used to hypothesize the nature of shallow subduction earthquakes that might occur in the northwestern united states based on systematic comparisons of several physical characteristics including physiography and seismicity subduction zones that are deemed most similar to the cascadia subduction zone are those in southern chile southwestern japan and colombia these zones have all experienced very large earthquake sequences and if the cascadia subduction zone is also capable of storing elastic strain energy along its greater than 1000 km length then earthquakes of very large size m w 8 1 2 must be considered circumstantial evidence is presented that suggests but does not prove that large subduction earthquakes along the cascadia subduction zone may have an average repeat time of 400 to 500 yr

amplification phenomena observed in downhole array records generated on a subductive environment abstract the damage caused by earthquakes is strongly dependent on the local site conditions and as a result site characterization and amplification phenomenon have become a subject of considerable interest to engineers and seismologists a vertical array in a soil deposit in llolleo city near the coast of chile has been installed being somewhat unique in that it is located in a subduction zone environment because the coast of chile is one of the most seismically active areas of the world this array is expected to be particularly valuable because it may produce recordings of very strong and very long duration motions the characteristics of this borehole array are presented first which include pore water pressure measurements in clayey soils also some interesting aspects of the earthquakes recorded to date are described which open a question about the suitability of one dimensional analysis in addition the h v spectral ratio proposed by nakamura to estimate natural periods is analyzed microtremor measurements at the surface and the seismic events recorded by the seismic borehole array of llolleo are used looking both at the h v spectral ratio of the motion recorded on the free surface and at the ratio of the response spectra of the motions at the surface and at bedrock on the other hand it is observed that the recorded dynamic pore pressures are controlled by the vertical accelerations or compressional waves

influence of alpine plants growing on steep slopes on sediment trapping and transport by runoff abstract understanding the interactions between soil and the organisms that are conducive to decreasing sediment runoff is a great concern on high elevation ski trails intense rainfalls on steep slopes combined with soil formed on gypsum result in recurrent erosion this study was conducted in the northern french alps to determine the abilities of species 1 to make mounds and 2 to trap sediment and thereby to control erosion at the slope scale we also investigated relevant above ground plant characteristics related to those abilities sediment runoff or deposition was investigated at small and large spatial scales we assessed whether hoof prints in soil reflect sediment runoff at the slope scale by trapping sediment populations of plants growing on two slope angles 25 and 35 and three vegetation cover densities 15 35 60 were surveyed an experiment was also conducted to measure the sediment deposit upslope of target species and over three months during the autumn small mounds were found upslope of the plant and sediment deposit measurements showed that they resulted from a sedimentation process nevertheless the species differed in their capacity to make mounds sesleria caerulea and festuca alpina had the highest amount of sediment deposition over the experimental period among the plant characteristics plant length was positively correlated with mound area while the roundness index of the canopy was negatively correlated with mound height mound formation was also positively related to the number of tillers or shoots sediment accumulation in cow hoof prints was linked to runoff that occurred at the slope scale low deposition in hoof prints means low sediment runoff or a large deposition on mounds due to the increase in vegetation cover all the findings stressed that understanding the processes in action at larger scales requires studying processes at smaller scales

long duration asynchronous ground motions in the colfiorito plain central italy observed on a two dimensional dense array 1 in winter 1998 a small aperture 200 m four station array was operating in the middle of the colfiorito plain waveforms of seven small magnitude 2 1 m 3 7 local earthquakes are analyzed in this study the peculiarity of the array seismograms is a 2 min long duration of the horizontal ground motion the predominant frequency in the plain is around 1 hz in this frequency band earthquake induced ground shaking is synchronous for a few seconds during direct s waves after this time window wave trains show an increasingly chaotic behavior within the array the energy variation of the horizontal ground shaking between the array and a nearby rock outcrop exceeds a factor of 500 at 1 hz in order to help understanding of observations and construct models for future numerical simulations the buried structure of the colfiorito plain has been investigated through seismic refraction profiles and geoelectric measurements a three dimensional reconstruction of the basin structure reveals an extremely complex bedrock topography which is probably a recurrent feature for intermontane basins in tectonically active regions apparent velocities and backazimuths in the frequency band 0 5 1 5 hz indicate that a 180 m deep depression nw of the array is responsible for the generation of edge diffracted surface love waves their arrival to the array breaks the synchronism of vertically reverberating waves which predominate in the first seconds of the s wave window