a scaling law for slow earthquakes with the availability of the global positioning system and other technical advances a growing number of unusual earthquake phenomena occurring at relatively long periods have been recognized they include deep episodic tremor low frequency earthquakes slow slip events and silent earthquakes based on data chiefly from western japan ide et al report that these slow seismic events follow a unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes a diverse array of unusual earthquake phenomena occurring at relatively long periods slow events follow a unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes indicating that they comprise a new earthquake category recently a series of unusual earthquake phenomena have been discovered including deep episodic tremor1 low frequency earthquakes2 very low frequency earthquakes3 slow slip events4 and silent earthquakes5 6 7 8 9 each of these has been demonstrated to arise from shear slip just as do regular earthquakes but with longer characteristic durations and radiating much less seismic energy here we show that these slow events follow a simple unified scaling relationship that clearly differentiates their behaviour from that of regular earthquakes we find that their seismic moment is proportional to the characteristic duration and their moment rate function is constant with a spectral high frequency decay of f 1 this scaling and spectral behaviour demonstrates that they can be thought of as different manifestations of the same phenomena and that they comprise a new earthquake category the observed scale dependence of rupture velocity for these events can be explained by either a constant low stress drop model or a diffusional constant slip model this new scaling law unifies a diverse class of slow seismic events and may lead to a better understanding of the plate subduction process and large earthquake generation

coesite eclogites from the roberts victor kimberlite south africa abstract coesite or pseudomorphic quartz is more common than previously recognized in the eclogite xenolith suite from the roberts victor mine south africa all coesite eclogites in this study 18 samples are classified as group i and have mineral compositions that span virtually the entire compositional range of group i eclogites described from this locality most of the roberts victor group i eclogite suite may be in equilibrium with free silica thus weakening the case for these rocks representing residues of partial melting oxygen isotope compositions of garnets from 15 samples are in the range 5 32 6 95 similar to other roberts victor group i eclogites these observations are consistent with a model in which protoliths of these rocks were oceanic basalts and intrusive rocks that underwent exchange with seawater at relatively low temperatures to variable extents prior to subduction and metamorphism to eclogite facies without suffering significant partial melting during or following subduction

the detection of low magnitude seismic events using array based waveform correlation summary it has long been accepted that occurrences of a known signal are most effectively detected by cross correlating the incoming data stream with a waveform template such matched signal detectors have received very little attention in the field of detection seismology because there are relatively few instances in which the form of an anticipated seismic signal is known a priori repeating events in highly confined geographical regions have been observed to produce very similar waveforms and good signals from events at a given site can be exploited to detect subsequent co located events at lower magnitudes than would be possible using traditional power detectors even greater improvement in signal detectability can be achieved using seismic arrays running correlation coefficients from single sensors can be stacked over an array or network to result in a network correlation coefficient displaying a significant array gain if two events are co located the time separating the corresponding patterns in the wave train as indicated by the cross correlation function is identical for all seismic stations and this property means that the correlation coefficient traces are coherent even when the waveforms are not we illustrate the power of array based waveform correlation using the 1997 august 16 kara sea event the weak event that occurred 4 hr after the main event was barely detected using an sta lta detector on the spits array but is readily detected by signal matching on a single channel the main event was also recorded by the far more distant norsar array but no conventional detection can be made for the second event a clear detection is however made when the correlation coefficient traces are beamformed over all sensors of the array we estimate the reduction in detection threshold of a test signal on a regional seismic array using waveform correlation by scaling down a master signal and immersing it into seismic noise we show that for this case waveform correlation using a single channel detects signals of approximately 0 7 orders of magnitude lower than is possible using an sta lta detector on the array beam waveform matching on the full array provides an additional improvement of approximately 0 4 magnitude units we describe a case study in which small seismic events at the barentsburg coal mine on spitsbergen were detected using the signals from a major rockburst as master waveforms many spurious triggers occurred in this study whereby short sections of signal exhibited coincidental similarity with unrelated incoming wave fronts we demonstrate how such false alarms can almost always be identified and screened out automatically by performing frequency wavenumber analysis upon the set of individual correlation coefficient traces

mechanism of deep low frequency earthquakes further evidence that deep non volcanic tremor is generated by shear slip on the plate interface 1 we study the mechanism of low frequency earthquakes lfes in the nankai trough in western shikoku japan precise locations have previously suggested that they represent shear slip on the plate boundary in this paper we examine the mechanism of these events due to the low signal to noise ratio we analyze stacked lfe waveforms and compare them with the waveforms of nearby earthquakes of known mechanism within the subducting philippine sea plate analysis of both the focal mechanism using p wave first motions and the moment tensor using s waveforms indicates that lfes represent shear slip on a low angle thrust fault dipping to the northwest namely the plate interface together with reports that deep tremor consists of a swarm of lfes our results suggest that deep tremor is generated directly by shear slip on the plate interface and as such represents a seismic signature of the accompanying slow slip events

global seismic event detection using a matched filter on long period seismograms an image derived by stacking long period seismograms is used as an empirical matched filter to detect and locate earthquakes records from 564 events mb 6 recorded at very long periods t 60 s by the 15 to 20 stations of the international deployment of accelerometers ida network are stacked using a method that emphasizes the surface wave arrivals the first 3 hours of this time versus range image are used to construct a matched filter for continuous application to the ida data the output of this filter contains spatial and temporal peaks that define the location and origin time of probable seismic events implementation of this technique to 11 years of ida data from 1981 to 1991 identifies 4061 events these include 65 of cataloged events of mb 5 5 earthquakes which appear anomalously strong relative to their surface wave magnitudes are mainly located on oceanic transform faults and probably represent unusually slow ruptures the method successfully detects two eruptions of the el chichon volcano in southern mexico from the anomalous low frequency energy radiated during the eruptions in addition 32 earthquakes are detected which are not in the standard global catalogs these events appear to be about ms 5 and are mainly located in the southern oceans where there are gaps in the coverage of the high frequency networks although these earthquakes are probably slow since they occur mostly on oceanic transform faults they are not silent as they also can be observed in higher frequency data

the analysis of beach profile changes using dean s method and empirical orthogonal functions abstract sea bottom changes in the cross shore direction have been analysed the cross shore profile as a major factor of beach configuration has been presented schematically as a superposition of a basic curve reflecting the mean layout and slope of the shore given by dean s function y a 2 3 and superimposed various bars troughs berms etc depicting local characteristic features of the profile the local features of the profile have been analysed by use of one 1 d and two dimensional 2 d empirical orthogonal functions on the basis of field observations and measurements the parameter a has been presented as a function of time three time scales have been distinguished short seasonal and long term with respect to which more or less regular changes of the parameter a occur the modified parameter a was applied to two different field sites namly lubiatowo baltic sea poland and gold beach black sea bulgaria it has been found that in extreme cases the parameter a can vary in time by a factor of two or more for the same grain size distribution

two dimensional reduced physics model to describe historic morphodynamic behaviour of an estuary inlet abstract understanding medium to long term morphodynamic change is important for sustainable coastal and estuary management this paper analyses morphodynamic change of a complex estuary inlet which is subjected to multiple environmental drivers and proposes a reduced physics model to explain the historic medium term morphodynamic change of the inlet the analysis shows that even though the estuary inlet undergoes multiscale morphological change the changes that take place over a timescale of several years are more significant and important the reduced physics model suggests that this simplified modelling approach is able to recognise principal historic morphodynamic trends in the estuary however the length and quality of the inlet bathymetry data set limits the applicability of the models and the quality of model outputs

complex evolution of transient slip derived from precise tremor locations in western shikoku japan transient slip events which occur more slowly than traditional earthquakes are increasingly being recognized as important components of strain release on faults and may substantially impact the earthquake cycle surface based geodetic instruments provide estimates of the overall slip distribution in larger transients but are unable to capture the detailed evolution of such slip either in time or in space accompanying some of these slip transients is a relatively weak extended duration seismic signal known as nonvolcanic tremor which has recently been shown to be generated by a sequence of shear failures occurring as part of the slip event by precisely locating the tremor we can track some features of slip evolution with unprecedented resolution here we analyze two weeklong episodes of tremor and slow slip in western shikoku japan we find that these slip transients do not evolve in a smooth and steady fashion but contain numerous subevents of smaller size and shorter duration in addition to along strike migration rates of 10 km d observed previously much faster migration also occurs usually in the slab dip direction at rates of 25 150 km h over distances of up to 20 km we observe such migration episodes in both the updip and downdip directions these episodes may be most common on certain portions of the plate boundary that generate strong tremor in intermittent bursts the surrounding regions of the fault may slip more continuously driving these stronger patches to repeated failures tremor activity has a strong tidal periodicity possibly reflecting the modulation of slow slip velocity by tidal stresses

stable isotope compositions and water contents of boninite series volcanic rocks from chichi jima bonin islands japan measurements of stable isotope compositions and water contents of boninite series volcanic rocks from the island of chichi jima bonin islands japan confirm that a large amount 1 6 2 4 wt of primary water was present in these unusual magmas an enrichment of 0 6 in18o during differentiation is explained by crystallization of18o depleted mafic phases silicic glasses have elevated 18o values and relatively low d values indicating that they were modified by low temperature alteration and hydration processes mafic glasses on the other hand have for the most part retained their primary isotopic signatures since eocene time primary d values of 53 for boninite glasses are higher than those of morb and suggest that the water was derived from subducted oceanic lithosphere

oxygen isotope systematics of eclogite mineral phases from south africa abstract eleven eclogite xenoliths from the bobbejaan and roberts victor mines south africa have been characterized by a variety of geochemical techniques the samples include nine bimineralic eclogites and two grospydites that span the range of mantle eclogite major element compositions primary phase end member compositions range from py 75 al 16 gr 09 jd 18 di 82 caes 0 to py 28 al 21 gr 51 jd 49 di 36 caes 15 oxygen isotope analyses of mineral separates were performed for clinopyroxene and garnet isotopic values 18 o range from 4 0 to 7 8 for clinopyroxene and 3 6 to 7 2 for garnet differences in isotopic values between the primary phases clinopyroxene minus garnet range in value from 0 6 to 0 6 although oxygen isotopes are not expected to fractionate at mantle temperatures the anion electrostatic site potential values determined by smyth 1989 are consistent with small degrees of fractionation in the mantle oxygen isotope fractionation between minerals may be calculated by the equation of smyth and clayton f a 10 6 t 2 where a 0 7911 ev fractionation values at 1300 k range from 0 6 jd pyr to 0 03 cats grs while at 1600 k these values are between 0 39 and 0 02 respectively the re equilibration temperatures of the studied eclogite suite are 1050 to 1250 c at 30 kbar therefore the obtained differences between the mineral phases are consistent with the calculated isotope fractionation values the data obtained for eclogite oxygen isotopes suggest that 18 o may fractionate to a small extent at mantle pt conditions

statistical analysis and forecasts of long term sandbank evolution at great yarmouth uk abstract a data driven model has been developed to analyse the long term evolution of a sandbank system and to make ensemble predictions in a period of 8 years the method uses a combination of empirical orthogonal function eof analysis to define spatial and temporal patterns of variability jack knife resampling to generate an ensemble of eofs a causal auto regression technique to extrapolate the temporal eigenfunctions and straightforward statistical analysis of the resulting ensemble of predictions to determine a forecast and associated uncertainty the methodology has been applied to a very demanding site which includes a curved shoreline and a group of mobile nearshore sandbanks the site is on the eastern coast of the uk and includes the great yarmouth sandbanks and neighbouring shoreline a sequence of 33 high quality historical survey charts reaching back to 1848 have been used to analyse the patterns and to predict morphological evolution of the sandbank system the forecasts demonstrate an improved skill relative to an assumption of persistence but suffer in locations where there are propagating features in the morphology that are not well described by eofs

reproduction of estuarine bathymetry by means of a process based model western scheldt case study the netherlands abstract the current study aims to investigate the processes governing the evolution of major morphological features in alluvial estuaries as well as their morphodynamic interaction with the geometry by means of a 3d morphodynamic process based numerical model delft3d the main hypothesis is that channel shoal patterns evolve through the interaction between tidal movement the available sediments and the tidal basins geometry once such a system is not disturbed too much by extreme events stable morphological patterns will emerge that compare well with observed features starting from a flat bed and imposing the western scheldt geometry model results show two distinct time scales i e channel shoal pattern formation within decades and a slow longitudinal profile development continuing for centuries the developing channel shoal patterns reflect major morphological features observed in the western scheldt estuary using the 1998 bathymetry as a reference we applied different indicators and techniques to evaluate the model performance over time namely visual comparison hypsometries brier skill score bss mean basin depth and longitudinal profiles sensitivity analysis shows that trends in development are similar for different model parameter settings like introducing salt fresh water density differences or variations in sediment grain size and sediment transport formulation varying river discharge and including non erodible layers dredging and dumping activities and 3d hydrodynamics led to occasional improvements the geometry is an important governing factor for pattern development applying an erodible geometry reveals a timescale for geometric adaptation that is much longer than the pattern development timescale within the basin model runs including highly schematized extreme conditions suggest that extreme events play a limited role the main conclusion of the study is that the interaction between tidal forcing and basin geometry plays a major role in the development of morphological features in an alluvial tidal basin such as the western scheldt a process based model taking into account these major forcing mechanisms can predict such features with significant skill the bathymetries generated in this study may form the basis for further studies considering for example the impact of sea level rise on estuarine morphodynamic development or a rapid assessment of estuarine bathymetry in the absence of measured data

graphite and diamond bearing eclogite xenoliths from the bellsbank kimberlites northern cape south africa one diamond bearing and eight graphite bearing eclogite xenoliths are described from the bellsbank kimberlites cape province south africa graphite mostly occurs as discrete grains which are commonly in the form of tabular prisms diamond is octahedral both group i and group ii eclogite varieties are represented by the graphite bearing specimens while the single diamond bearing eclogite is of the group i variety the carbon isotopic composition of the graphite varies from 13c 7 to 13c 2 8 this is within the range of carbon isotopic compositions for inclusion free diamonds in kimberlite from this locality suggesting that the carbon for the eclogites as well as some of the kimberlite diamonds are derived from the same source the present day nd isotopic compositions of clinopyroxene from three graphite bearing xenoliths are slightly higher than the bulk earth estimate sr isotopic compositions of the clinopyroxene in these xenoliths vary from 87sr 86sr 0 703 to 87sr 86sr 0 706 this could be due to derivation of the xenoliths from a protolith with variable 87sr 86sr isotopic composition or could be the result of mixing between a low sr high 87sr 86sr component and a high sr low 87sr 86sr component

the effect of sea breeze on beach morphology surf zone hydrodynamics and sediment resuspension abstract beach morphodynamic processes were investigated over part of a sea breeze cycle on a microtidal low wave energy sandy beach in southwestern australia prior to the onset of the sea breeze offshore winds with speeds less than 5 m s prevailed during the sea breeze alongshore winds with speeds higher than 10 m s were experienced the sea breeze induced pronounced changes to the nearshore morphodynamics which were similar to that of a storm event 1 root mean square wave height increased from 0 3 to 0 5 m 2 zero upcrossing wave period decreased from 8 to 4 s 3 mean cross shore flows reached velocities of 0 2 m s directed offshore and 4 the longshore current increased in strength from 0 05 to 1 0 m s before the sea breeze sediment resuspension typically occurred during isolated high wave events associated with the passage of wave groups flux coupling between the wave oscillatory currents and the suspended sediment jaffe b e sternberg r w sallenger a h 1984 the role of suspended sediment in shore normal beach profile changes proc 19th int conf coastal engineering asce pp 1983 1996 induced net onshore suspended sediment transport resulting in beachface accretion and a steepening of the foreshore profile in contrast during the sea breeze sediment resuspension was almost continuous the suspended sediment load increased six fold and as a consequence the longshore suspended sediment transport rate increased by a factor of 100 during the sea breeze cross shore transport was directed offshore and primarily associated with mean offshore flows this resulted in erosion of the beachface and deposition in the surf zone and consequently a flattening of the beach profile the suspended sediment load was strongly related to the shields parameter defined for the combined action of waves and currents investigation of the suspended sediment profiles indicated that the degree of vertical mixing parameterised by the sediment diffusion coefficient increased with distance from the bed in addition the sediment diffusion coefficient exhibited a large temporal variation ranging between 0 005 and 0 018 m2 s the variability in the sediment diffusion coefficient is possibly due to changes in the sea bed morphology

in situ oxygen isotope major and trace element constraints on the metasomatic modification and crustal origin of a diamondiferous eclogite from roberts victor kaapvaal craton a subducted oceanic crustal origin for most eclogite xenoliths in kimberlites has long been a cornerstone of tectonic models for craton development however eclogite xenoliths often have protracted and complex histories involving multiple metasomatic events that could overprint some of the key geochemical indicators typically taken as evidence of a subducted origin e g garnet 18o values and mineral 87sr 86sr compositions to assess the potential for disturbance of oxygen isotopic compositions in mantle eclogites via diamond forming and other possible metasomatic fluids we have conducted a multi technique in situ study of a diamondiferous eclogite xenolith from the roberts victor kimberlite s africa using sims we provide the first texturally controlled in situ measurements of 18o values in eclogitic garnet in close proximity to diamond garnet and clinopyroxene modal proportions are heterogeneous in the xenolith and garnet compositions vary from mg 75 8 79 2 grossular proportions 8 05 10 14 mol and omphacitic pyroxene has jd13 24 and mg 86 6 90 0 rare earth element patterns of minerals across the xenolith including grains close to diamond are typical lree depleted garnets and markedly lree enriched pyroxenes these silicate minerals also record detectable intra and inter grain lree abundance variations clinopyroxenes of the studied xenoliths show hfse and sr abundance variations that are decoupled from lree contents and major element variations mineralogical constraints and bulk rock reconstructions indicate that the studied sample likely experienced selective incompatible element enrichment during small volume 0 03 wt infiltration of metasomatic fluid s potentially linked to ancient diamond evolution intra grain major element lree and hfse variations in clinopyroxene resulted from late stage metasomatism oxygen isotope compositions in garnet are decoupled from all major and trace element variations with garnet 18o values being uniform across the xenolith in a wide variety of textural settings garnet 18o values of 6 5 0 2 are higher than the mean 5 19 0 26 of the mantle garnet range 4 8 5 5 modelling of the buffering effect of mantle peridotite on co2 rich and h2o rich metasomatic fluids at temperatures within the diamond stability field indicates that the likelihood of a metasomatic fluid with exotic oxygen isotopic composition arriving at a mantle eclogite body with its isotopic composition unmodified after percolative flow through dominantly peridotitic mantle at great depth is very low as we find no evidence of metasomatically induced garnet oxygen isotope variations in the studied diamondiferous eclogite xenolith we conclude that the most likely origin for the elevated garnet 18o values is via inheritance from a crustal protolith altered at relatively low temperatures these results have broader relevance and support the hypothesis of a low pressure protolith for mantle eclogite xenoliths demonstrating the robust nature of garnet oxygen isotope compositions even in diamond bearing eclogites

long term morphodynamic evolution of estuaries an inverse problem abstract a new technique for predicting long term variations in estuary morphology is developed using a morphological evolution equation that isolates diffusive and non diffusive processes in estuaries the contribution from non diffusive processes to the morphological changes of the estuary is incorporated in the governing equation by a source function the source function is derived by solving an inverse problem using historic survey data of the humber estuary uk covering a period of 150 years source functions derived for the consecutive pairs of bathymetry surveys show a significant structure persistent throughout the entire data set large scale features such as tidal channels tidal flats and linear banks in the outer estuary are persistently visible in the source function empirical orthogonal function eof analysis is used to analyse the spatial and temporal variation in the source function the first spatial eigenfunction which corresponds to the time mean value of the source function captures over 92 of the mean square of the data over 65 of the data variance is captured by the first six eigenfunctions the first temporal eigenfunction which corresponds to the mean value of the source function is almost constant as expected

oxygen isotope composition of syngenetic inclusions in diamond from the finsch mine rsa oxygen isotope data have been obtained for silicate inclusions in diamonds and similar associated minerals in peridotitic and eclogitic xenoliths from the finsch kimberlite by laser fluorination oxygen isotope analyses of syngenetic inclusions weighing 20 400 g have been obtained by laser heating in the presence of clf3 18o 16o ratios are determined on oxygen converted to co2 over hot graphite and for samples weighing less than 750 g producing 12 moles o2 enhanced co production in the graphite reactor causes a systematic shift in both 13c and 18o that varies as a function of sample weight a pressure effect correction procedure based on the magnitude of 13c co2 depletion relative to 13c graphite is used to obtain corrected 18o values for inclusions with an accuracy estimated to be 0 3 for samples weighing 40 g syngenetic inclusions in host diamonds with similar 13c values 8 4 to 2 7 have oxygen isotope compositions that vary significantly with a clear distinction between inclusions of peridotitic 4 6 to 5 6 and eclogitic paragenesis 5 7 to 8 0 the mean 18o composition of olivine inclusions is indistinguishable from that of typical peridotitic mantle 5 25 0 22 whereas syngenetic purple garnet inclusions possess relatively low 18o values 5 00 0 33 reversed oxygen isotope fractionation between olivine and garnet in both diamond inclusions and diamondiferous peridotite xenoliths suggests that garnet preserves subtle isotopic disequilibrium related to genesis of cr rich garnet and or exchange with the diamond forming fluid garnet in eclogite xenoliths in kimberlite show a range of 18o values from 2 3 to 7 3 but garnets in diamondiferous eclogites and as inclusions in diamond all have values 4 7

early proterozoic oceanic crust and the evolution of subcontinental mantle eclogites and related rocks from southern africa seven eclogitic nodules from kimberlites in southern africa have been studied in detail for whole rock major and trace element geochemistry petrography and mineral chemistry by electron microprobe high purity mineral separates from six of these samples have been analyzed for trace elements and for the isotopic composition of sr nd and oxygen three eclogite groups are recognized group a eclogites have very high mg fe low na in pyroxene moderate 18o 4 7 to 5 3 and low 87sr 86sr and 143 144nd olivine and enstatite may also be present as accessory phases in this group group b eclogites have moderate to high mg fe ratios high na in pyroxene low 18o 3 0 to 3 4 high 87sr 86sr and 143nd 144nd ratios and extremely lree depleted hree enriched garnets with no eu anomalies group c eclogites have low mg fe ratios high na in pyroxene and variable sr nd and o isotope compositions accessory feldspar is present in one sample that may be of crustal origin mineral separates of garnet and pyroxene have positive eu anomalies the group a eclogites are too refractory to represent magma compositions and must have formed as cumulate dike rocks in the upper mantle that contain a minor trapped liquid component this is supported by the presence of accessory olivine and enstatite and by their ksm and knd which are similar to empirical pyroxene garnet partition coefficients the group b eclogites are extremely depleted in incompatible elements and have ndvalues 10x to 20x morb the high 87sr 86sr of these eclogites is not consistent with their strongly depleted lree and high nd and cannot be primary it must have been imposed on the protolith the low 18o of these eclogites cannot form by mantle fractionation processes and must also be inherited from the protolith both the sr and oxygen isotope data are consistent with high temperature hydrothermal alteration of a basaltic protolith followed by partial melting to form the refractory compositions observed now the hydrothermal fluid may have been sea water but secondary enrichment of the protolith in rb is required to generate the observed high sr ratios the high na content of the pyroxenes supports a spilitic alteration event the major and trace element characteristics of the group c eclogites are consistent with recrystallization of a cumulate gabbro protolith one group c rock is probably a garnet granulite derived from the lower crust the other may represent the plutonic portion of oceanic crust a reconstructed whole rock isochron for the three bellsbank eclogites yields an age of 2 1 0 1 b y this implies that plate tectonic processes involving the generation and subduction of oceanic crust have been active since the early proterozoic the early proterozoic ocean crust consisted of two components a plutonic section of gabbro cumulates group c eclogites and a volcanic section of basalt group b eclogites the volcanic component has undergone substantial hydro thermal alteration and subsequent partial melting to form a refractory residue the plutonic component is less modified

eclogite facies fluid infiltration constraints from δ 18 o zoning in garnet in situ analysis reveals that eclogite facies garnets are zoned in 18o with lower values in the core and rims that are 1 5 to 2 5 higher this pattern is present in 9 out of 12 garnets analyzed by sims from four orogenic eclogite terranes and correlates with an increase in the mole fraction of pyrope and mg fe ratio from core to rim indicating prograde garnet growth at the maximum temperatures and the time scales experienced by these garnets calculated intragranular diffusion distances for oxygen are small 5 from two kimberlites are homogeneous in 18o possibly due to diffusive exchange which is possible for prolonged periods at higher mantle temperatures homogeneity of 18o in garnets outside the normal mantle range 5 6 may be common in kimberlitic samples

extracting decadal morphological behaviour from high resolution long term bathymetric surveys along the holland coast using eigenfunction analysis abstract the understanding and prediction of coastal behaviour over a time span of decades and alongshore stretches of tens of kilometres is important in coastal management the controlling variables for coastal behaviour on these scales are yet unknown it is hypothesised that regions exhibiting different large scale coastal behaviour lscb regions are controlled by different hydrodynamic forcings or by different sedimentological or morphological constraints or by some combination of these factors the objective of this study is to elaborate a method that effectively quantifies large scale morphological changes from a large bathymetric data set large temporal and spatial extent combined with a high resolution such to define lscb regions the method of analysis consists of a combination of the empirical eigenfunction technique and a moving window approach the method has been applied on a data set of over 14 000 nearshore profiles the data set consists of yearly soundings of the nearshore profile along a coastal stretch of 115 km length the holland coast the alongshore profile spacing is generally 250 m all profiles surveyed in the period 1963 1990 are included in the analysis application of the method on the dutch data set reveals that lscb regions indeed can be identified the sizes of the lscb regions are 5 km 15 km 20 km 32 km and 42 km differences in behaviour of the secondary morphology i e morphology other than the mean profile shape e g nearshore bars are most pronounced the change in behaviour between lscb regions generally occurs over distances as short as about 2 km the boundaries between the regions are therefore surprisingly sharp in general no clear long term trends in the development of the shape of the sub aqueous profile have been observed along the holland coast along certain stretches trends in cross shore shifting of the sub aqueous profile occurred the average shape of the sub aqueous profile seems to have no relation with the trend in cross shore shifting of the shoreline the 1 m contour the sub decadal shoreline fluctuations however are possibly related to the largescale dynamics of multiple bar systems

oxygen isotopes in coexisting garnets clinopyroxenes and phlogopites of roberts victor eclogites implications for petrogenesis and mantle metasomatism abstract 18 o values of coexisting garnet clinopyroxene and phlogopite for twelve compositionally and texturally diverse roberts victor eclogite xenoliths range from 3 8 to 7 1 4 0 to 7 4 and 5 9 to 7 4 respectively differences between the 18 o values of coexisting garnets and clinopyroxenes are normally zero however there is some variation in the 18 o values of different fractions of the same mineral in four samples which suggests the presence of isotopic zonation and inhomogeneity possibly resulting from the introduction of a secondary fluid which metasomatized the eclogites and resulted in the formation of phlogopite amphibole and celsian the 18 o value of the metasomatic fluid is generally buffered by the isotopic composition of the primary garnet and clinopyroxene as indicated by a correlation between the isotopic composition of phlogopite and the primary pyroxene and garnet the large range in 18 o values of the eclogites and the similarity in the isotopic composition of coexisting pyroxene and garnet support the interpretation that the roberts victor eclogites represent metamorphosed altered basalts the eclogites were subjected to infiltration metasomatism in the mantle prior to their incorporation in the kimberlite and the source of this fluid was probably unrelated to the eclogite

on the formation of sand banks of finite extent we consider a model where the fluid depth depends on both horizontal coordinates quasi steady depth uniform non divergent fluid flow is governed by inertial pressure and bottom frictional forces sand transport is proportional to the cube of the instantaneous current but augmented by a down slope component and by wind wave action and sand is conserved it is found that low parallel banks grow fastest so that in an extensive spatially uniform sea previous calculations for linear banks are appropriate the inclination of banks to the tidal currents can be interpreted in terms of similarly inclined deposition bands resulting from vorticity generation and advection in flow over a small isolated hump a small bump can evolve to an equilibrium bank typically after an initial rapid extension across the tidal currents provided that sand is sufficiently restricted and particularly if some wind wave action prevents growth up to the sea surface sand banks are likely to be in a late stage of evolution when the main change is a slow lengthening as the net current and transport along the bank side slows and turns around the bank end with net deposition the equilibrium is apparently stable except when there is an overall bed slope in the direction of the tidal currents or when sand is abundant

reply to comments by taylor and neal on trace element crystal chemistry of mantle eclogites in summary there are no existing clinopyroxene liquid ree distribution data obtained under appropriate conditions to permit numerical modeling of trace elements to constitute a critical test of the pyroxene fractionation process there are however numerous clinopyroxeneliquid partitioning data in the literature that give qualitatively similar patterns to those observed in grospydites further the high pressure fractionation model accounts for the major element and exsolution phenomena in a manner directly consistent with experimental petrologic studies and can qualitatively account for the trace element and isotopic characteristics of the rocks in a manner consistent with the crystal chemistry of the phases we therefore continue to prefer the high pressure clinopyroxene fractionation model over a low pressure plagioclase fractionation model for the origin of the grospydites

statistical analysis of coastal morphological data sets over seasonal to decadal time scales statistical analysis of long term morphological data on coastal sedimentary features provides important information on the processes governing these features and their evolution in space and time in this paper seasonal yearly and decadal i e long term behavior of coastal morphological features is derived from field data by using both simple and advanced statistical techniques the sedimentary features which we are especially focusing on are a nearshore bars and b large scale shoreline undulations for example longshore sand waves and nesses high quality bathymetric field data of regularly sampled cross shore profiles and shorelines were the basis of the available data sets at noordwijk beach the netherlands duck north carolina usa sylt germany lubiatowo poland and winterton uk additional data sets from argus video images see holman r a stanley j 2007 the history capabilities and future of argus coastal engineering special issue of the coastview project doi 10 1016 j coastaleng 2007 01 003 and aerial photographs were used to increase the temporal and spatial resolution of the data sets where possible the statistical methods applied include some linear and non linear techniques described by larson et al larson m capobianco m jansen h rozyfiski g southgate h n stive m wijnberg k m hulscher s 2003 analysis and modeling of field data on coastal morphological evolution over yearly and decadal time scales part 1 background and linear techniques journal of coastal research 19 4 760 775 and southgate et al southgate h n wijnberg k m larson m capobianco m jansen h 2003 analysis of field data of coastal morphological evolution over yearly to decadal timescales part 2 non linear techniques journal of coastal research 19 4 776 789 the methods proved to be useful for extracting characteristics of the coastal sedimentary features concerning length scales e g spacing and rhythmicity and temporal scales e g migration rates and evolutionary patterns however the success of the statistical analysis strongly depends on the total size of the data set characterized by the specific spatial coverage spatial resolution temporal resolution and overall length in time recent data sets from remote sensing video systems like argus often meet these requirements and are of major importance for the formulation of conceptual behavior models c 2007 elsevier b v all rights reserved less

thermodynamics and lattice vibrations of minerals 5 applications to phase equilibria isotopic fractionation and high pressure thermodynamic properties in previous papers in this series a model that uses available elastic structural and spectroscopic data on minerals has been used to predict the thermodynamic functions cv heat capacity s entropy e internal energy and f helmholtz free energy in this paper four applications to problems of current geochemical and geophysical interest are presented 1 interpretation of complex trends of calorimetric data 2 calculation of phase equilibria 3 calculation of oxygen isotopic fractionation factors and 4 estimation of the effect of pressure on thermodynamic functions the model demonstrates that trends in high temperature thermodynamic properties of silicates are determined by the position and relative numbers of high frequency modes generally antisymmetric si al o stretching modes the position of these modes varies systematically with degree of polymerization of tetrahedra and therefore high temperature calorimetric behavior is relatively systematic as a function of crystal structure and mineral composition trends at low frequency are much more complex because the low frequency optic modes that most strongly influence the low temperature thermodynamic functions depend in a complex way on the size coordination and mass of cations and various polyhedra in the minerals the heat capacity curves of kyanite andalusite and sillimanite and of quartz coesite and stishovite show crossovers that cannot be explained by debye theory which accounts only for acoustic mode behavior but can be explained by the model spectra proposed because proper account is taken of the changing low and high frequency optic modes upon polymorphic transformations the proposed model is sufficiently accurate that phase equilibrium problems can be addressed the quartz coesite stishovite equilibrium curves the kyanite andalusite sillimanite triple point and the breakdown of albite to jadeite plus quartz are cited as specific examples for each example predicted slopes of equilibrium curves agree moderately well to excellently with slopes determined experimentally the calculated slopes are sensitive to spectroscopic parameters particularly to the distribution of optic modes in the far infrared this sensitivity is discussed in detail for the albite breakdown reaction the model can be used for prediction of isotopic fractionation factors if spectra of the isotopic forms of the mineral are known or postulated a simple set of rules for generating hypothetical spectra of 18o minerals from measured spectra of the 16o forms is given reduced partition functions are calculated for 13 minerals at 298 k the model values of reduced partition function 1000 ln of these minerals decrease in the order quartz calcite albite muscovite clinoenstatite anorthite diopside pyrope grossular zircon forsterite andradite rutile in good agreement with experimental data at 1000 k the first six minerals show small crossovers so that the order becomes calcite muscovite albite quartz anorthite and clinoenstatite the differences in 1000 ln at high temperature for these minerals are so small that the model probably cannot address the deviations from experimental trends the model clearly defines the region in which the fractionation factors do not follow a 1 t trend and should be useful for extrapolation of experimental data to low temperatures finally a modified gruneisen parameter model is proposed for shift of the lattice vibrational frequencies under compression and thermodynamic properties to 1000 kbar 1000 k are given for nine minerals at 1 mbar the predicted decrease in entropy at 298 k ranges from 54 of the 1 bar value for periclase to 25 for stishovite

an autocorrelation method to detect low frequency earthquakes within tremor 1 recent studies have shown that deep tremor in the nankai trough under western shikoku consists of a swarm of low frequency earthquakes lfes that occur as slow shear slip on the down dip extension of the primary seismogenic zone of the plate interface the similarity of tremor in other locations suggests a similar mechanism but the absence of cataloged low frequency earthquakes prevents a similar analysis in this study we develop a method for identifying lfes within tremor the method employs a matched filter algorithm similar to the technique used to infer that tremor in parts of shikoku is comprised of lfes however in this case we do not assume the origin times or locations of any lfes a priori we search for lfes using the running autocorrelation of tremor waveforms for 6 hi net stations in the vicinity of the tremor source time lags showing strong similarity in the autocorrelation represent either repeats or near repeats of lfes within the tremor we test the method on an hour of hi net recordings of tremor and demonstrates that it extracts both known and previously unidentified lfes once identified we cross correlate waveforms to measure relative arrival times and locate the lfes the results are able to explain most of the tremor as a swarm of lfes and the locations of newly identified events appear to fill a gap in the spatial distribution of known lfes this method should allow us to extend the analysis of shelly et al 2007a to parts of the nankai trough in shikoku that have sparse lfe coverage and may also allow us to extend our analysis to other regions that experience deep tremor but where lfes have not yet been identified

long term morphological modeling of a tidal inlet the arcachon basin france abstract the arcachon lagoon on the french atlantic coast is a triangular shaped lagoon of 20 km on a side connected to the ocean by a 3 km wide inlet between the mainland and an elongated sand spit this tidal inlet exhibits a particularly active morphology due to locally strong tidal currents and rough wave conditions during the past 300 years minimum and maximum spatial extents of the cap ferret sand spit have varied by 8 km while one or two channels have alternately allowed circulation between the lagoon and the ocean these impressive morphological changes have never prevented regular flushing of the lagoon eventhough the spit came as close as 300 m from the coast during the 18th century according to bruun s concept of tidal inlet stability theory and engineering 1978 510 pp the balance between longshore littoral transport and the tidal prism ensures the perpetuity of the inlet process modeling was believed to give better insight into the respective roles of tides and waves in driving the long term morphological changes of the inlet a two dimensional horizontal morphodynamic model was therefore developed combining modules for hydrodynamics waves sediment transport and bathymetry updates the use of process models at a scale of decades requires a schematization of the input conditions we defined representative mean annual wave and tide conditions with respect to sediment transport i e conditions that induce the same annual transport as measured in the field driven by these representative conditions simulations run from the 1993 bathymetry show that the tide is responsible for the opening of a new channel at the extremity of the sand spit where tidal currents are the strongest while waves induce a littoral transport responsible for the longshore drift of sand bodies across the inlet one particular simulation consisted in running the model from a hypothetical initial topography where the channels are filled with sand and the entire inlet is set to a constant depth 3 m the results show the reproduction of a channel and bar system comparable to historical observations which supports the idea that the lagoon is unlikely to be disconnected from the ocean provided tide and wave conditions remain fairly constant in the following decades

low frequency continuous tremor around the moho discontinuity away from volcanoes in the southwest japan 1 recent enhancement of seismic networks in the japan islands revealed occurrence of low frequency continuous tremors of a beltlike distribution in the southwest japan where the subducting philippine sea plate reaches depths of 30 40 km source depth of the tremor is estimated by selecting tremor segments with relatively clear p wave onsets the source region of the tremor is assumed to correspond to lowermost parts of crust close to a triple boundary of the crust mantle wedge and the subducting slab the long duration of the phenomenon indicates existence of fluid relating to the generation of the tremor the most probable fluid is considered to be water produced by dehydration process of chlorite and amphibole in the slab on the basis of data from high pressure and temperature experiments the northern border of the beltlike distribution is possibly rimmed by the edge of the mantle wedge because serpentine formation absorbs fluid water

cascadia tremor polarization evidence for plate interface slip 1 new seismic measurements of the repeated phenomenon of episodic tremor and slip in northern cascadia indicate identical source processes of tremor and slow slip predicted polarization directions of upgoing s waves radiated from shear slip on the plate interface align with the relative motion between the juan de fuca and north american plates seismic observations from small aperture array data on the olympic peninsula of the cascadia subduction zone show uncharacteristically stable linear particle motion coincident with the passage of tremor sources beneath the array the azimuth of this horizontal ground motion matches expected polarizations from slip on the plate interface this finding suggests that cascadia tremor is shear slip on the plate interface implying that as in japan geodetically observed slow slip and seismically observed tremor are manifestations of the same phenomenon

morphodynamic behaviour of a mixed sand gravel ebb tidal delta deben estuary suffolk uk the morphodynamics of inlets and ebb tidal deltas reflect the interaction between wave and tidal current driven sediment transport and significantly influence the behaviour of adjacent shorelines studies of inlet morphodynamics have tended to focus on sand dominated coastlines and reference to gravel dominated or gravel rich inlets is rare this work characterises and conceptualises the morphodynamics of a meso tidal sand gravel inlet at the month of the deben estuary southeast england behaviour of the inlet and ebb tidal delta over the last 200 yr is analysed with respect to planform configuration and bathymetry the estuary inlet is historically dynamic with ebb tidal shoals exhibiting broadly cyclic behaviour oil a 10 to 30 yr timescale quantification of inlet parameters for the most recent cycle 1981 2003 indicate an average ebb delta volume of 1 x 10 6 m 3 and inlet cross sectional area of 775 m 2 bypassing volumes provide a direct indicator of annual longshore sediment transport rate over this most recent cycle of 30 40 x 10 3 m 3 yr 1 short term increases in total ebb tidal delta volume are linked to annual variability in the north to northeasterly wind climate the sediment bypassing mechanism operating in the deben inlet is comparable to the ebb delta breaching model of fitzgerald fitzgerald d m 1988 shoreline erosional depositional processes associated with tidal inlets in aubrey d g weishar l ed hydrodynamics and sediment dynamics of tidal inlets springer verlag inc new york pp 186 225 although the scales and rates of change exhibited are notably different to sand dominated systems a systematic review of empirical models of sand dominated inlet and ebb tidal delta morphodynamics e g those of o brien m p 1931 estuary tidal prisms related to entrance areas civil engineering 1 738 739 walton t l and adams w d 1976 capacity of inlet outer bars to store sand proceedings of 15th coastal engineering conference 1919 1937 gaudiano d j kana t w 2001 shoal bypassing in mixed energy inlets geomorphic variables and empirical predictions for nine south carolina inlets j coast res 17 2 280 291 shows the deben system to be significantly smaller yet characterised by a longer bypassing cycle than would be expected for its tidal prism this is attributed to its coarse grained sedimentology and the lower efficiency of sediment transporting processes c 2005 elsevier b v all rights reserved