a new attenuation relation for strong ground motion in japan based on recorded data following the 1995 hyogo ken nanbu kobe earthquake the japanese government in an effort to prevent future earthquake disasters installed networks consisting of a large number of strong motion observation stations further national seismic hazard maps were made available to the public on an internet website in march 2005 by the headquarters for earthquake research promotion however these maps indicate only the local seismic intensity for japan as empirically con verted from predicted peak velocity in consolidated soils for various applications other strong motion indexes such as the response spectral acceleration are required in this study a database of whole japanese strong ground motion records between 1963 and 2003 is established in order to identify a new standard attenuation relation for japan for response acceleration as well as peak value it is usually very difficult to determine a suitable model form due to the large variability of strong motion data and correlation among the model variables because the strong coupling of variables in an attenuation model and the statistical power of the data is often not large enough to determine the necessity of these parameters therefore in this study our model has only three variables earthquake magnitude shortest distance to the seismic fault plane and focal depth to improve predictions given by the model site correction terms are adopted and additional terms for correcting regional anomalous seismic intensity with respect to the base model are determined the good fit between the model and observed strong motion records suggests that the new model is reasonably robust

empirical spectral acceleration amplification in the iwate miyagi and niigata regions japan inferred by a spectral ratio method using ground motion prediction equations abstract using the strong ground motion dataset of m w 4 0 6 0 earthquakes in japan from k net and kik net we studied empirically the 5 damped spectral acceleration amplification for periods from 0 05 to 5 s at 75 seismic stations located in the iwate miyagi and niigata regions the method of study is based on estimating the empirical site effect from the spectral ratio of observed and predicted ground motions based on the ground motion prediction equations gmpes our results show a large amplification at most analyzed stations at periods of 0 1 s and shorter at periods of 0 3 s and longer large amplifications generally dominate at basin stations but deamplifications generally dominate at mountain stations empirical amplification factors of spectral acceleration were used to correct the observed strong ground motion data of two crustal earthquakes the 2008 iwate miyagi nairiku earthquake m w 6 9 and the 2004 chuetsu earthquake m w 6 6 the site corrected data fit better with gmpes inferred by less standard error we took advantage of a large body of empirical data to develop a mean empirical site response model for each region these empirical models are superior to models predicted from gmpes using only v s 30 site corrections those relations have shown a low correlation at short periods such as 0 1 s we also found the relations are different for the mountain and basin stations the method is efficient for calculating site effects at observation stations where insufficient velocity structure information and a history of earthquake recordings are available

long period site response in northeastern japan from ground motion prediction equations we evaluated the long period site response of peak ground velocities pgvs and peak ground displacements pgds in the 5 30 s period range at 198 k net kik net and japan meteorological agency strong motion stations in northeastern japan long period site responses were estimated empirically based on the ratio of observed ground motions on free surfaces to the values predicted by ground motion prediction equations gmpes on bedrock in which the shear wave velocity is 2000 m s our results show large site amplifications generally dominate at basin stations whereas site deamplifications generally dominate at mountain stations the long period site response factors of pgvs and pgds have ranges of 0 6 3 6 and 0 4 3 1 respectively for which the factors of pgvs are larger than those of pgds by an average factor of 1 3 long period site responses were used to correct the observed strong ground motions of eight earthquakes the long period site corrected data fit better with gmpes that were inferred from smaller standard errors and show a better correlation with sediment thickness and thus may contribute to reducing the variability of seismic hazard assessment

particle size related mineral magnetic source sediment linkages in the rhode river catchment maryland usa characterization of both the source materials and the bottom sediments of an estuary by magnetic characters on a particle size basis allows the source of the bottom sediments to be determined and indicates a shift in sediment sources corresponding to changing land use patterns the major source of the sediments in the lower part of cores from the middle of the estuary is eroding shorelines soil derived particulates from the uplands dominate the upper part of the cores this change in source occurred in the early part of the 19th century the magnetic character of the most recent sediments suggests a progressive depletion through time of the upland soils in the finest fractions

sediment sources and transport pathways in a rural catchment herefordshire uk the relative significance of primary and secondary suspended sediment sources has been identified in a small 15 km2 agricultural catchment through the application of a linear unmixing model using mineral magnetic geochemical and radionuclide signatures of fine sediments roads appear to be important as a secondary source of suspended sediment and in the conveyance of topsoils to the river channel roads also alter the source signatures of sediment in transport especially that derived from agricultural topsoils modelling suggests that c 30 of the suspended sediment collected from suspended sediment traps in the river leadon were derived from or transported via roads relative contributions from primary sources of c 43 and c 27 were estimated from a combined subsoil and channel bank subsurface source and a combined arable and grassland topsoil source respectively

a new method in mineral magnetism for the separation of weak antiferromagnetic signal from a strong ferrimagnetic background 1 this paper describes a new magnetic method for determining the contribution of weakly magnetic hematite against a strongly magnetic e g magnetite background the method involves measurements of mfr a residual or final remanence after hysteretic demagnetization of saturated isothermal remanent magnetization in terms of sensitivity and precision our proposed method is superior to the currently popular approach known as the hirm method compared to the latter mfr has no error amplification caused by subtraction of terms the method utilizes the available software for hysteretic demagnetization function on an automated vibrating sample magnetometer vsm this in turn automatically decreases some of the disturbing effects of the strong magnetic background e g magnetic viscosity initially non zero offset of hirm for partially oxidized magnetite etc

sediment provenance in a tropical fluvial and marine context by magnetic fingerprinting of transportable sand fractions the sources and fluxes of sediment to the great barrier reef lagoon from northeastern australian rivers have been the subject of much concern and study with the large catchments of the burdekin and fitzroy rivers thought to be the key sources at present here the utility of newly developed magnetic fingerprinting methods for identifying sediment provenance both onshore and offshore and in association with individual large flood events is investigated within the burdekin catchment sediments are mobilized from different subcatchments by runoff generated by intense localized rainfall events magnetic measurements were made on untreated and acid treated samples of river channel sediments within the burdekin river subcatchments and from the estuarine and inner shelf depocentres of burdekin river sediments the acid treatment removes all discrete magnetic particles and coatings and leaves magnetic inclusions protected within host silicate grains as the basis of the measured magnetic signature of a sample the magnetic properties of the acid treated samples display statistically distinct sediment provenance groupings sand samples from the upper burdekin river appear magnetically distinct from samples from tributaries of the burdekin e g hann creek fanning river and also from nearby coastal rivers including the haughton suspended sand samples from a burdekin flood event in 2000 appear to have a different source compared with those from floods in 1998 and 1999 comparisons of the terrestrial acid treated sand fractions with the same acid treated sand size fractions from transects taken offshore suggest that the surface sediments in upstart bay and bowling green bay have different sources some of these sources are as yet unidentified but may represent the unsampled lower discharge south western burdekin subcatchments and or along shore drift of sand from the south perhaps even from the fitzroy river over millennial timescales of cyclone pumping the magnetic inclusion method precludes any obfuscation or confounding of sediment source which might arise from hydraulic sorting and or post depositional magnetic diagenesis or authigenesis

fingerprinting upland sediment sources particle size specific magnetic linkages between soils lake sediments and suspended sediments accelerated erosion of fine grained sediment is an environmental problem of international dimensions erosion control strategies and targeting of mitigation measures require robust and quantitative identification of sediment sources here we use magnetic fingerprinting to characterize soils and examine their affinity with and contribution to suspended sediments transported within two subcatchments feeding bassenthwaite lake northwest england a high resolution soil magnetic susceptibility survey was made using a field susceptometer zh instruments sm400 probe combining the spatial and vertical down profile soil magnetic data a subset of soil profiles was selected for detailed laboratory based magnetic remanence analyses the magnetic properties of the catchment soils are highly particle size dependent magnetic analyses were performed on the 31 63 m fraction for particle size specific comparison both with the suspended sediments and lake sediments fuzzy cluster analysis groups the soil magnetic data into six clusters apparently reflecting variations in parent material and horizon type with three magnetically hard soils as unclassified outliers examination of the cluster affinity of the soils suspended sediments and lake sediments indicates that topsoils of the upper newlands valley and subsoils around keskadale beck are a major source of the newlands beck suspended load and the recent post nineteenth century sediments in the deep lake basin older lake sediments show strong affinity with a small number of the derwent suspended sediments and one of the glenderamackin soils a large number of derwent suspended sediments show no affinity with any of the soils or lake sediments instead forming a coherent discrete and statistically unclassified group possibly resulting from mixing between the magnetically hard subsoils of the medium to high altitude glenderamackin and troutbeck areas and softer lower altitude glenderamackin soils the lack of any affinity of these suspended sediments with the lake sediments may indicate deposition along the derwent flood plain and or in the shallow delta of lake bassenthwaite particle size specific magnetic fingerprinting is thus shown to be both highly discriminatory and quantitatively robust even within the homogeneous geological units of this catchment area such a methodological approach has important implications for small large scale catchment management where sources of sediment arising from areas with uniform geology have been difficult to determine using other approaches such as geochemical or radionuclide analyses

fission track evidence for late oligocene and mid miocene activity along the north anatolian fault in south western thrace apatite fission track ft analyses of sandstone samples collected across the trace of the ganos segment of the north anatolian fault naf in south western thrace turkey indicate that a significant structural discontinuity was in existence at least by the latest oligocene such discontinuity had a complex kinematic history as exhumation south of it occurred during the latest oligocene and north of it during the mid miocene our data imply that early pliocene westward propagation of the naf in the marmara region followed a pre existing structural discontinuity such discontinuity could be related to the development of the intra pontide suture marking the terminal closure of the intra pontide ocean during the oligocene

characterisation of soils by mineral magnetic measurements processes of iron mineral authigenesis diagenesis and dissolution in interaction with primary inputs of iron minerals act to produce vertical differentiation of soil magnetic properties thus magnetic iron oxides in common with other iron forms may both respond to and reflect soil forming processes investigation of the degree of detectable and persistent magnetic differentiation within different soil materials can provide insights into the nature and direction of distinct sets of soil processes evidence of clear association between magnetic variation and discrete types of soil environment also has applied significance in several areas of environmental study for example the observed magnetic variation can be used to discriminate between individual soils and soil horizons for the purposes of soil surveying sediment tagging and tracing and empirical modelling of source sediment linkages this paper reports the use of mineral magnetic techniques to characterise the iron oxide assemblages within soils of varying type and provenance the effect of different pedogenic regimes have been investigated through measurement of a range of magnetic parameters including magnetic susceptibility frequency dependent susceptibility and anhysteretic and saturation remanences contrary to current pedological thought but in accord with other magnetically based studies e g mullins the presence of magnetite maghemite typically of superparamagnetic single domain grain size within soils has been found to be an extremely widespread phenomenon its contemporary neoformation within the soil environment is inferred however the input of artificially generated ferrimagnetic material is indicated for one of the magnetically enhanced soils examined here and the possibility of extraneous sources of magnetite in topsoils should be considered before pedogenic processes of magnetic enhancement are inferred from the data presented discrimination of industrially derived magnetic particles appears possible on the basis of their very low levels of frequency dependent susceptibility fd low anhysteretic remanence arm and dissociation from the finer clay sized not the formation but the active dissolution of ferrimagnetic minerals is indicated for soils affected by the processes of gleying and podsolisation eluvial horizons of podsolised profiles demonstrate almost total loss of detectable magnetic content variations in the form of the iron reprecipitated in the underlying illuvial layers may reflect differences in the pedological characteristics of these horizons within gleyed waterlogged soils processes of magnetite dissolution appear to be grain size specific preferential reduction of those grains of ultrafine superparamagnetic and fine single domain magnetic grain size is indicated where soil forms a major contributor to catchment sediment loads this has significance in the area of source sediment modelling soil derived from permanently wet or highly leached catchment areas is unlikely to contribute to peaks in the magnetic content of deposited sediments further only those erosional processes that operate at a faster rate than those of magnetic depletion will have the capacity to produce peaks in sediment ferrimagnetic concentrations such as have been observed within the historical magnetic record

modelling magnetization data using simplex two new approaches to modelling magnetization data are described the first approach models the magnetic properties of natural materials in terms of mixtures of possible source materials the second approach models the magnetic properties of natural materials in terms of mixtures of magnetite and haematite crystals of varying concentrations and grain sizes in the second approach the magnetic characteristics of magnetite and haematite and their variation with grain size are described by bicubic spline functions the methods are applied to remanence and susceptibility measurements on a suite of lake sediment particle size fractions and on a set of samples from a soil profile

use of composite fingerprints to determine the provenance of the contemporary suspended sediment load transported by rivers sediment fingerprinting appears to offer a valuable alternative to direct monitoring for elucidating the provenance of suspended sediment and the relative importance of spatial zones or subcatchments comprising larger 500 km 2 drainage basins against this background a quantitative composite fingerprinting technique incorporating both statistically verified multicomponent signatures and a multivariate sediment mixing model has been employed to determine the spatial origin of contemporary suspended sediment transported from the upper and middle reaches of the river exe 601km 2 and river severn 4325 km 2 basins uk spatial origin is addressed in terms of the relative contribution from three distinct geological subareas constituting each study basin the consistency of the composite fingerprinting approach is examined using the estimates for mean and seasonal variations in source area contributions and also a comparison between the results obtained for individual flood events and alternative lines of evidence provided by flood travel times and the spatial distribution of precipitation it is argued that fingerprinting estimates for sediment provenance are consistent with existing information on suspended sediment yields from different subcatchments within the study basins although in the severn the role of storage and remobilization in producing signature averaging may complicate comparison of the fingerprinting data with typical floodwater routing times validation represents the greatest problem for the cost benefit of fingerprinting and scope still exists for further refinement of the procedures involved 1998 john wiley sons ltd

rupture processes of the 2004 chuetsu mid niigata prefecture earthquake japan a series of events in a complex fault system 1 we relocated the hypocenters of the 2004 chuetsu earthquake sequence niigata japan using the double difference method the distribution of aftershocks reveals a complex fault system consisting of five different fault planes inversions of strong motion records for the five major events within the sequence indicate that the mainshock mw 6 6 and the largest aftershock mw 6 3 occurred on parallel wnw dipping fault planes the zones of large slip asperities of these two events are located near the hypocenters in contrast the three other large earthquakes mw 5 9 5 7 and 5 9 occurred on east dipping fault planes oriented perpendicular to the fault plane of the mainshock we used slip distributions deduced from waveform inversions to estimate the coulomb failure stress changes that occurred immediately prior to each event cff values were positive at the hypocenters and within the asperities of the major aftershocks these results suggest that stress changes resulting from individual earthquakes led directly to the occurrence of subsequent earthquakes within the complex fault system

the late holocene history of gormire lake ne england and its catchment a multiproxy reconstruction of past human impact sedimentary evidence spanning the last 3500 years from cores taken from the centre of gormire lake cleveland northeast england points to two periods of deforestation and catchment erosion the first mainly late iron age romano british phase began c 200 bc and ended c ad 600 the second began c ad 1200 the time of early monastic activity and continued into the nineteenth century the chronology for the core rests on 137cs 210pb and 14c measurements and on the history of lead accumulation in the sediments the majority of the ams 14c dates are shown to be too old to varying degrees depending on the source of the organic matter in the sediments the record of vegetation change is derived from pollen analysis evidence for changes in sediment composition and source and for catchment erosion comes from magnetic measurements element analyses using xrf and organic biogeochemical analyses there is a high degree of coherence between all these lines of evidence interpretation of the magnetic record

accounting for site effects in probabilistic seismic hazard analyses of southern california overview of the scec phase iii report this article presents an overview of the southern california earthquake center scec phase iii effort to determine the extent to which probabilistic seismic hazard analysis psha can be improved by accounting for site effects the contri butions made in this endeavor are represented in the various articles that compose this special issue of bssa given the somewhat arbitrary nature of the site effect distinction it must be care fully defined in any given context with respect to psha we define the site effect as the response relative to an attenuation relationship averaged over all damaging earthquakes in the region a diligent effort has been made to identify any attributes that predispose a site to greater or lower levels of shaking the most detailed maps of quaternary geology are not found to be helpful either they are overly detailed in terms of distinguishing different amplification factors or present southern california strong motion observations are inadequate to reveal their superiority a map based on the average shear wave velocity in the upper 30 m however is found to delineate significantly different amplification factors a correlation of amplification with basin depth is also found to be significant implying up to a factor of two difference between the shallowest and deepest parts of the los angeles basin in fact for peak accel eration the basin depth correction is more influential than the 30 m shear wave ve locity questions remain however as to whether basin depth is a proxy for some other site attribute in spite of these significant and important site effects the standard deviation of an attenuation relationship the prediction error is not significantly reduced by making such corrections that is given the influence of basin edge induced waves subsur face focusing and scattering in general any model that attempts to predict ground motion with only a few parameters will have a substantial intrinsic variability our best hope for reducing such uncertainties is via waveform modeling based on first principals of physics finally questions remain with respect to the overall reliability of attenuation re lationships at large magnitudes and short distances current discrepancies between viable models produce up to a factor of 3 difference among predicted 10 in 50 yr exceedance levels part of which results from the uncertain influence of sediment nonlinearity

using magnetic susceptibility to facilitate more rapid reproducible and precise delineation of hydric soils in the midwestern usa abstract standard field indicators currently used for hydric soil delineations usda nrcs 1998 field indicators of hydric soils in the united states version 4 0 in g w hurt et al ed united states department of agriculture nrcs fort worth tx are useful but in some cases they can be subjective difficult to recognize or time consuming to assess magnetic susceptibility ms measurements acquired rapidly in the field with a portable meter have great potential to help soil scientists delineate and map areas of hydric soils more precisely and objectively at five sites in illinois from 5 to 15 ha in area with contrasting soil types and glacial histories the ms values of surface soils were measured along transects and afterwards mapped and contoured the ms values were found to be consistently higher in well drained soils and lower in hydric soils reflecting anaerobic deterioration of both detrital magnetite and soil formed ferrimagnetics at each site volumetric ms values were statistically compared to field indicators to determine a critical ms value for hydric soil delineation such critical values range between 22 10 5 and 33 10 5 si in silty loessal or alluvial soils in illinois but are as high as 61 10 5 si at a site with fine sandy soil a higher magnetite content and slower dissolution rate in sandy soils may explain the difference among sites with silty parent material the lowest critical value 22 10 5 si occurs in soil with low ph 4 5 5 5 since acidic conditions are less favorable to ferrimagnetic mineral neoformation and enhance magnetite dissolution because of their sensitivity to parent material properties and soil ph critical ms values must be determined on a site specific basis the ms of studied soil samples 0 5 cm depth is mainly controlled by neoformed ultrafine ferrimagnetics and detrital magnetite concentrations with a minor contribution from anthropogenic fly ash neoformed ferrimagnetics are present in all samples but based on high fd 5 to 10 are most prevalent in high ph mollisols of northeastern illinois scanning electron microscope images display significantly more detrital magnetite alteration in hydric soils substantiating that reductive dissolution of magnetite aided by microorganisms is a primary cause for lower ms fly ash comprises 8 50 of the 5 m strongly magnetic particles and typically accounts for 5 15 of the total ms signal the proportion of fly ash in 5 m strongly magnetic fractions is greater in hydric soils because of lower natural magnetite contents possibly combined with historical topsoil accumulation in lower landscapes magnetic fly ash particles are also more altered in low ms soils implying that significant magnetite dissolution can occur in less than 150 years

fingerprinting suspended sediment sources in the catchment of the river ouse yorkshire uk statistically verified composite fingerprints and a multivariate mixing model have been employed to establish the main sources of the suspended sediment transported through the lower non tidal reaches of the river ouse and one of its main tributaries the river wharfe during the period 1994 1997 in the case of the suspended sediment samples collected from the river ouse the load weighted mean contributions from uncultivated topsoil cultivated topsoil and channel bank sources were estimated to be c 25 38 and 37 respectively while for the river wharfe these sources contributed c 70 4 and 23 respectively c 4 was derived from woodland topsoil suspended sediment samples collected during higher flows evidenced a greater contribution from channel banks than samples collected during lower flows source materials were also differentiated according to the three main geological source areas carboniferous permian and triassic and jurassic and their load weighted mean contributions were estimated to be c 24 41 and 35 for the river ouse and c 91 9 and 0 there are no jurassic rocks in this catchment for the river wharfe respectively when suspended sediment samples from tributary streams were used to characterize each geological source area the equivalent results for the river ouse were c 30 46 and 24 considering the three main tributaries that contribute to the river ouse the load weighted mean contributions from the rivers swale ure and nidd were estimated to be 82 15 and 3 respectively these values have been compared with estimates of the relative magnitude of the annual suspended sediment loads of these three rivers for the years 1995 and 1996 derived from continuous monitoring of discharge and turbidity differences between the two sets of results are ascribed to the different periods of record involved and to the timing of suspended sediment sampling relative to the overall storm hydrograph and thus the degree to which the available samples are representative of the overall suspended sediment flux although a number of limitations must be recognized the fingerprinting approach to source ascription is seen as providing valuable information regarding suspended sediment sources in the study catchments copyright 1999 john wiley sons ltd

variability in earthquake stress drop and apparent stress 1 we apply empirical green s function coda based analysis to four earthquake sequences in japan that span a magnitude range of 1 8 to 6 9 to measure radiated energy corner frequency and stress drop we find no systematic dependence of apparent stress or stress drop on seismic moment for these sequences and find they both are log normally distributed however we identify several anomalous events both energetic and enervated that show sharply different spectral signatures from the rest of the population these events indicate that much of the variation in apparent stress and stress drop is statistically significant which may have important implications for seismic hazard analysis

rupture process of the 2008 iwate miyagi nairiku japan earthquake derived from near source strong motion records abstract we derive the rupture process of the 2008 iwate miyagi nairiku japan earthquake m jma 7 2 during which the largest ground acceleration to date namely 4022 cm sec 2 was recorded at a hanging wall station iwth25 station of kik net just above the hypocenter velocity waveform data 0 1 1 hz at 14 strong motion stations of k net and kik net including the borehole records of iwth25 are inverted using the multi time window linear waveform inversion method we assume a horizontally layered velocity structure model having low velocity subsurface layers for each station in order to calculate the green s functions the waveform inversion indicates that there are two major slip patches one patch extends from the hypocenter to the southern shallower part of the fault a particularly large slip area in this patch is centered approximately 8 km to the south of the hypocenter with a maximum slip of 6 2 m the area ruptured between 4 and 9 sec after the initial break the other patch with smaller slip is located in the northern part which broke after the rupture of the southern slip patch the initial 0 4 sec rupture occurred beneath iwth25 contributing to the synthesis of a distinctive upward velocity pulse at this station examination of the slip contribution to the synthetic velocity waveforms and comparison of the isochrones with the slip distribution suggest that a peak acceleration greater than 4000 cm sec 2 observed at iwth25 was generated from the area that is closest to the hypocenter in the southern particularly large slip area

holocene sediment dynamics in an upland temperate lake catchment climatic and land use impacts in the english lake district accelerated erosion and transport of fine sediment from upland temperate catchments can reflect increased erosivity and or erodibility due in turn to climatic and or human forcing identification of sediment fluxes and sources over holocene timescales can both enable understanding of the relative impacts of these forcings and provide perspective on recent sediment fluxes here we present a 5500 yr record of sediment fluxes and sources from lake bassenthwaite in the english lake district utilizing magnetic measurements and fuzzy clustering coupled with independent pollen and archaeological records to identify the timing and impact of catchment disturbance this record shows that recent sediment flux increases ie within the last 150 years are unprecedented in scale throughout the mid late holocene and appear to be in response to specific human changes occurring within the catchment earlier episodes of human activity from the mid holocene onwards show no link with increased lake sediment fluxes

mineral magnetic characterization of sediment sources from an analysis of lake and floodplain sediments in the catchments of the old mill reservoir and slapton ley south devon uk research on suspended sediment transport in the catchments of the old mill reservoir and slapton lower ley south devon has attempted to discriminate changing catchment sources on the basis of downcore variations in the mineral magnetic properties of lake reservoir and floodplain sediments here we examine these downcore variations and also explore the variability in catchment sources and the influence of topographic controls on mineral magnetic signatures of topsoils and subsoils particle size controls on the mineral magnetic signatures are explored by an analysis of a fractionated sediment sample whilst the possible impact of diagenesis is assessed by an examination of the mn profiles in the lake and reservoir sediments from this analysis it is evident that the mineral magnetic signatures of well sorted floodplain deposits are more likely to reflect the particle size composition of the transported material by contrast the mineral magnetic record in the sediment of slapton ley appears to be most strongly influenced by dissolution of magnetic minerals the sediment of the old mill reservoir provides the only suitable record for the application of a simple mixing model which is developed in order to quantify changes in the relative contribution of topsoil and subsoil through time the research has important implications for attempting to reconstruct sediment sources in highly eutrophic lakes and emphasizes the uncertainty in the application of simple mixing models 1998 john wiley sons ltd

ground motion simulations within shakemap methodology application to the 2008 iwate miyagi nairiku japan and 1980 irpinia italy earthquakes

source storage and mobilisation of fine sediment in a chalk stream system concern for sediment problems in the upper river piddle dorset including accumulation of fine sediment on the channel bed and elevated turbidity levels during periods of stable flow provided the stimulus for a detailed field investigation of the sediment dynamics of this chalk stream system undertaken during the period november 1991 to april 1993 two monitoring stations were established at south farm piddletrenthide and lawrence mede piddlehinton and estimates of suspended sediment load were obtained for these two sites in addition suspended sediment concentrations and bed sediment loadings were regularly sampled at several other sites sediment traps were deployed at ten representative sites along the river channel field observations of sediment sources and pathways were made during storm events and a sediment source fingerprinting study was undertaken estimates of annual suspended sediment yield provided values of 9 12 t km 2 year 1 which must be seen as low by uk standards elevated suspended sediment concentrations were not restricted to storm events but occurred throughout the monitoring period in response to remobilisation of sediment stored in the channel the evidence provided by the sediment loads recorded at the two monitoring stations by the sediment traps and by the measurements of bed sediment loading indicated that substantial amounts of sediment accumulated in the channel of the upper and middle reaches of the river during the winter months and that this slug of sediment was slowly transmitted downstream during the following summer fingerprinting of the transported sediment and of potential sources indicated that the dominant source of suspended sediment was likely to be surface soil from cultivated areas field reconnaissance surveys undertaken during storm events indicated that substantial inputs of surface runoff and suspended sediment entered the stream much of this sediment is however stored within the channel system and slowly transmitted downstream copyright 1999 john wiley sons ltd

sediment source tracing using environmental magnetism a new approach with examples from australia environmental magnetism can be used for sediment source tracing in situations such as stream junctions where two catchments deliver magnetically distinguishable well combined average source mixes to a trunk stream consistent mineral magnetic parameter relationships show that spatially and temporally constant magnetic mineral assemblages occur along reaches of natural streams for most of the confluence mixing situations examined it is possible to distinguish between tributaries using magnetic parameter relationships using these relationships relative tributary contributions to the resultant downstream mix can be quantified the method can be used for tracing suspended and bedload sediments so that the principal source catchments can be determined by a sequence of measurements at stream junctions along a drainage network there is considerable potential for using this new and easily applied method for studies of sediment delivery processes and sediment movement in fluvial environments

high attenuation rate for shallow small earthquakes in japan we compared the attenuation characteristics of peak ground accelerations pgas and velocities pgvs of strong motion from shallow small earthquakes that occurred in japan with those predicted by the equations of si and midorikawa j struct constr eng 523 63 70 1999 the observed pgas and pgvs at stations far from the seismic source decayed more rapidly than the predicted ones the same tendencies have been reported for deep moderate and large earthquakes but not for shallow moderate and large earthquakes this indicates that the peak values of ground motion from shallow small earthquakes attenuate more steeply than those from shallow moderate or large earthquakes to investigate the reason for this difference we numerically simulated strong ground motion for point sources of mw 4 and 6 earthquakes using a 2d finite difference method the analyses of the synthetic waveforms suggested that the above differences are caused by surface waves which are predominant at stations far from the seismic source for shallow moderate earthquakes but not for shallow small earthquakes thus although loss due to reflection at the boundaries of the discontinuous earth structure occurs in all shallow earthquakes the apparent attenuation rate for a moderate or large earthquake is essentially the same as that of body waves propagating in a homogeneous medium due to the dominance of surface waves