determination of spectral properties of earthquakes from their magnitudes abstract following the recommendation of the iaspei commission on magnitudes from 1967 p wave magnitudes of distant earthquakes are being computed with the aid of the calibration functions of gutenberg and richter 1956 with the development of the instrumental seismology especially in view of the availability of broad band recordings the question arises whether the functions are still adequate in this investigation new calibration functions for p and s waves are presented which are not only dependent on epicentral distance and focal depth but also on the period of the spectral component of the wave the determination of calibration functions is based on the currently most plausible global models for the velocity and anelasticity distribution taking into account the effective bandwidth of the instruments employed eventually leads to the so called spectral magnitudes from the spectral magnitudes m t the energy density spectrum e t of the respective wave can readily be computed the corresponding formula is e t 10 2m t 1 4 with e t in joules per hertz

gravel ripples on the inner scotian shelf abstract sidescan sonar and photo video surveys have revealed the presence of symmetrical gravel bedforms interpreted as wave generated ripples with wavelengths of 1 3 to 3 0 m occurring in patches and narrow ribbons in depths of 15 to 65 m on the inner scotian shelf direct observations and sediment sampling from the pisces iv submersible have been used to ground truth surface based survey dam and to quantify relationships between the bedforms and the processes responsible for their formation the ripples are formed in polymodal sandy gravels with modal sizes ranging from 0 1 to 45 mm evaluation of threshold criteria for coarse sediments together with an 11 year record from a nearby wave rider buoy suggests that existing models for wave entrainment of gravel on rippled surfaces ove estimate the critical velocity by a factor of approximately 2 and that conditions suitable for transport of the coarsest 45 mm size mode sampled in the ripple crests occur on average 43 hr yr analysis of gravel ripples on the inner scotian shelf and of other examples noted in the recent literature extends the range of empirical data for oscillation ripple wavelengths by a factor of 3 and for ripple grain size by a factor of 5 the gravel ripples display a linear scaling to wave orbital diameter similar to that reported for orbital ripples in sand use of such relations for paleoenvironmental interpretation of gravel ripples preserved in the rock record is complicated by the difficulty of selecting appropriate grain size and wave parameters conditions suitable for potential formatio of large scale symmetrical ripples in coarse sediments extend from the outer continental shelf to shallow shore face settings with possible fetch lengths as short as 20 km under intense storms

implications for sea level research of salt marsh and mudflat accretionary processes along paraglacial barrier coasts abstract paraglacial coastlines with dynamic coarse clastic barrier beaches are common in mid to high latitudes today and have been during the holocene sediments that have been deposited along these coastlines often in back barrier locations have been used to reconstruct relative sea level rsl movements and tendencies usually through the use of sea level index points derived frequently from salt marsh and mudflat deposits however the asymptotic relationship between minerogenic marsh mudflat accretion rates and time will produce regressive stratigraphies with a negative sea level tendency signature even within regimes of rising rsl the influence of gravel barriers on sedimentation will also tend to encourage regressive stratigraphies furthermore organogenic sediment production may release marsh accretion rates from the control of tidal inundation and result in succession to reed swamp despite rsl rise episodic minerogenic sediment supply to the marsh can trigger switches between marsh emergence and submergence which may result in stratigraphic sequences corresponding to negative and positive tendencies of rsl respectively although submergence may be prevented by organogenic sediment supply forcing by rsl rise may result in marsh emergence following initial submergence as a result of renewed accretion on the submerged marsh

the amplitude spectra of p and s waves and the body wave magnitude of earthquakes abstract synthetic calibration functions for body wave magnitudes are presented they have been obtained from computations made under the assumption that the variation of amplitude spectra along the earth s surface is due to radial velocity heterogeneity and radial changes of the dissipation factor q inside the earth only the new calibration functions depend on the epicentral distance and the focal depth of the earthquake as well as on the period of the body wave under consideration no single calibration function exists which would produce magnitude figures identical for all fourier components of a body wave observations on several hundreds of strong earthquakes in recent years show that the p wave magnitudes vary systematically with the period of the wave with the application of the synthetic calibration function a general increase of the teleseismically determined p wave magnitudes with frequency is observed this fact reconciles acceleration response spectra from narrowband strong motion analyzers in the near field of an earthquake and spectral magnitudes determined from far field observations by sensitive narrow band seismographs the strength of high frequent spectral components generally exceeds the strength of low frequent components determined in both cases

on the importance of continuity of magnitude scales abstract to describe an individual earthquake or the seismicity of a region simple parameters such as magnitudes are necessary in seismicity studies observations for as long as possible time intervals should be at disposal and subsequently the continuity of the parameters quality should be guaranteed m gr or m s can be such parameters m b sp of usgs and isc is another one but it has been accumulated only since the 1960s an international proposal to introduce or revive classical m b asks to change the traditional procedure of measuring the p maximum within a few seconds from the p onset some confusion appears to exist for recent m b data in edr of usgs it is strongly hoped that the traditional procedure of usgs for m b sp determination will not be discontinued and that the new m b will be introduced only as an additional parameter

the role of relative sea level rise and changing sediment supply on holocene gravel barrier development the example of porlock somerset uk the holocene development of the coastal system at porlock has been driven by variations in the rate of relative sea level rise providing a long term control on longshore sediment supply which in t

observations of morphological change and sediment transport on a steep gravel beach abstract observations of morphological change and swash sediment loads concurrent with measurements of water level waves and currents were obtained during a spring to spring tidal cycle on a steep macrotidal gravel beach in southwest england the wave conditions experienced during the field experiment were relatively calm and the significant inshore wave height and period averaged 0 4 m and 6 s respectively incident frequency water motions dominated the hydrodynamics and the phasing between water surface elevation and cross shore and alongshore currents was inconsistent with standing edge wave motion morphological change was directly related to maxima in shoreline elevation and four modes of berm adjustment identified regression and rollover in response to falling and rising water levels respectively and removal and reformation during and after storms respectively swash processes transported substantial amounts of sediment at rates comparable to sand beaches and the net transport under modal wave conditions was estimated to be 1 kg per swash onshore per unit metre beach width steep hydrodynamic gradients induced by the abrupt slope breaks of the step and berm are one of the main causes of the large morphological variability characteristic of gravel beaches

hydrodynamics and morphological adjustment of a mixed sand and gravel beach torere bay of plenty new zealand detailed measurements of cross shore wave energy transformation swash sediment transport and beach profile change under low energy conditions are reported from a mixed sand and gravel beach at torere bay bay of plenty new zealand measurements were undertaken during a 10 day period following a storm event and document post storm recovery of the beach nearshore wave spectra identify periods in which incident wave energy is dominated by swell and wind wave energy results show that wind wave energy observed in the nearshore is effectively removed from beachface spectra at the break point step under lower tidal stages swash is driven by longer period swell energy although dissipation of short period wave energy is critical in entraining sediments on the lower beach at higher tidal stages wind wave energy is able to propagate across the break point step shoal and break on the lower beachface tidal modulation of wave processes across the lower beachface under low incident wave conditions is found to stimulate active sediment reworking migration of the break point step and shoreward sediment flux to promote beach accretion

sediment and particulate organic carbon budgets of a subarctic estuarine fjard lake melville labrador abstract sediment and particulate organic carbon poc budgets constructed for oceanic regions provide a means to quantify the burial of poc providing a baseline against which future change can be measured here we developed the first mass balance budgets of sediment and poc terrestrial and marine for the lake melville system lms goose bay and lake melville in central labrador using previously published data 210pb based mass accumulation rates river discharge and total suspended solids together with measurements of oc and 13c signatures within dated sediment cores collected from the lms basins and water from main tributaries and groswater bay a two end member mixing model was used to establish fractions of terrigenous and marine poc overall our mass balance budgets show that the churchill river is the major supply of sediment 16 7 7 8 108 kg y 1 and pocterr 18 4 6 6 106 kg y 1 to the lms accounting for 47 and 56 of the total input to the system respectively although the churchill river drains directly into goose bay along with the smaller goose river the majority of sediment 12 9 7 8 108 kg y 1 and pocterr 11 8 7 0 106 kg y 1 is transported eastward through the surface water plume into lake melville inputs of pocmar from autochthonous primary production estimated by applying an empirical relationship between sediment surface flux of pocmar and water depth to goose bay 1 8 106 kg y 1 and lake melville 98 3 4 7 106 kg y 1 increase with increasing distance from the churchill river to investigate the potential changes to the sediment load of the churchill river to the lms following impoundment at muskrat falls we calculated the sediment increase using the median reservoir shoreline erosion potential this approach showed that the delivery of sediment and pocterr to the lms by the churchill river may double during the two years following impoundment of the lower churchill river

spectral magnitudes magnitude spectra and earthquake quantification the stability issue of the corner period and of the maximum magnitude for a given earthquake abstract p wave magnitude spectra of a foreshock mainshock aftershock sequence on 7 and 8 may 1986 in the aleutian islands are determined using broad band seismograms recorded at the grf array the magnitude spectra are compared for different stations of the array the maximum magnitude is stable with a standard deviation below 1 the reliability of other source parameters fault length seismic moment and stress drop derived from the magnitude spectrum m f depends on the determination of the corner period different methods to derive the corner period are compared best suited and most stable is the one based on the formula t c 0 e s f df 0 e s f f df where es f 102mf 14 is the energy density spectrum of the p wave and mf the spectral p wave magnitude of the earthquake at the respective period

zoned calcites in jurassic ammonite chambers trace elements isotopes and neomorphic origin zoned calcites were found in the phragmacone chambers of three sonniniid ammonites from marine middle jurassic sandstones isle of skye u k each ammonite has a unique sequence of up to nine zones of calcite which fill or partially fill the chambers zones are defined by changes in the density of minute opaque inclusions and variation in trace element composition proximal early calcites have undulose extinction and some exhibit the specific fabrics of fascicular optic and radiaxial fibrous calcites microdolomite inclusions are found in one specimen early calcites interpreted as replacements after a single isopachous fringe of acicular carbonate probably high magnesium calcite are succeeded by blocky ferroan calcite cement in one specimen there are two distinct generations of calcite in the others there is a continuous mosaic incorporating both early calcites and late cement isotopic composition of the early calcite zones demonstrates the initial importance of organic derived carbon 13c 26 18o o further cementation and mineralogical stabilization took place at increased temperatures and probably after modification of the pore water isotopic composition calcites with 13c o 18o 10 the distinctive fabrics and zonal patterns probably developed during the replacement of the precursor cement and are not primary growth features reversals in isotopic and trace element trends are believed to be related to the rate of neomorphic crystal growth and hence to the degree of exchange with external pore waters further increase in temperature probably during tertiary igneous activity gave rise to the extremely light 18o values of the late cements in the ammonite which had previously had least contact with external waters cements with 13c o 18o 20

examination of mesoscale forcing of a swash aligned gravel barrier from nova scotia abstract the possibility by which the retreat of a swash aligned gravel barrier on nova scotia s atlantic coast may be influenced by varying mesoscale time domains of differential process conditions is examined tide gauge data are used to generate definition of mesoscale process domains regarded as influential in barrier behaviour semi diurnal high water tidal residuals from halifax nova scotia tide gauge 1920 1990 are characterised for both surge magnitude and frequency on an annual basis these two variables are combined to define three event types of annual surge histories first order n th step markov analyses show that significant memory exists in 6 year and 22 year transitions between surge event types the longer transition sequence mirrors a major decadal mesoscale domain change in surge generation which is suggested to be associated with phases of barrier crest reworking that enhance barrier retreat when the domain change occurs the shorter transition sequence may reflect cyclonic activity cycles on the scotian shelf superimposed on the longer term transition

normal blue and red earthquakes a new way of earthquake classification on the basis of body wave magnitudes abstract monochromatic magnitudes based on p and on s waves provide a means to recognize differences in the spectral contents of body waves radiated from earthquake foci new synthetic magnitude calibration functions taking into account periods of waves recorded improve the consistency of magnitude figures assigned routinely to earthquakes first results of a world wide regionalization of earthquakes according to their spectral character are presented preponderance of short period radiation in one class of earthquakes and of long period radiation in another is seen if the radiation is compared with that of normal earthquakes

the anelasticity of the earth s mantle in the european area frequency dependence of q abstract the frequency dependence of q is estimated for the earth s mantle beneath the atlantic ocean and the european continent employing an absorption band model a minimum q of 106 and 324 for the western and eastern part of europe is found resp for both regions the upper cut off frequency of the absorption band is estimated at 1 6 hz

verification of magnitudes of himalayan region earthquakes of 1903 1985 from gottingen observatory abstract from the microfilms of gottingen observatory seismograms magnitudes are verified for thirty seven major and great earthquakes magnitude 7 in the himalayan region for the period 1903 1985 duda 1992 had earlier determined magnitudes of these earthquakes from gottingen records there were three other major earthquakes for which magnitudes could not be determined as their records from gottingen were not found the magnitude values were determined using p s and surface waves from long and medium period instruments the magnitudes from short period p and s waves were not redetermined to avoid uncertainties of such measurements from the microfilms as compared to duda 1992 the present values of the surface wave magnitudes corresponding to 20 3 s period from horizontal components are found to be higher for nine earthquakes by 0 2 0 5 units the body wave magnitudes are similarly changed these changes bring the magnitudes closer to the values given in earlier catalogs the relative quiescence after 1950 is striking the seismogram portions of earthquakes magnitude 7 5 are reproduced

barrier island arcs along abandoned mississippi river deltas abstract generation of transgressive barrier island arcs along the mississippi river delta plain and preservation of barrier shoreline facies in their retreat paths on the inner shelf is controlled by 1 shoreface translation 2 age of the transgression and 3 the thickness of the barrier island arc sediment package barrier island arcs experience an average relative sea level rise of 0 50 1 00 cm yr 1 and shoreface retreat rates range from 5 15 m yr 1 young barrier island arc sediment packages isles dernieres are thin and have experienced limited landward retreat of the shoreface older barrier island arcs chandeleur islands are thicker and have experienced significant landward movement of the shoreface because of the greater time available for retreat if the transgressed barrier shoreline sediment package lies above the advancing ravinement surface the entire sequence is truncated a thin reworked sand sheet marks the shoreface retreat path the base of the transgressive sediment package can lie below the ravinement surface in older barrier shorelines in this setting the superstructure of the barrier shoreline is truncated leaving the basal portion of the transgressive sequence preserved on the inner shelf a variety of transgressive stratigraphic sequences from sand sheets to truncated barrier islands to sand filled tidal inlet scars have been identified by high resolution seismic profiling across the shoreface retreat paths of mississippi delta barrier island arcs one of these examples the isles dernieres represents a recently detached barrier island arc in the early stages of transgression an older example the chandeleur islands represents a barrier island arc experiencing long term shoreface retreat this paper describes the stratigraphic character and preserved transgressive facies for the isles dernieres and chandeleur islands

gravelly shoreface deposits a comparison of modern and ancient facies sequences the morphology and dynamics of modern gravel shorefaces are poorly documented this hinders the interpretation of possible ancient counterparts a comparative study of a modern chesil beach england and an ancient baytree member of the cardium formation alberta gravel shoreface shows that the two systems are very similar close to and above sea level with a high about 1 m gravel plunge step lying below plane bedded sands and gravels of the beachface the shoreface at chesil beach is dominated by asymmetrical gravel wave ripples these are oriented offshore near the toe of the shoreface and onshore in shallower depths this may reflect offshore movement during storms and landward reworking during fair weather the baytree member is over 12 m thick and comprises over 80 conglomerate conglomerate is decimetre bedded massive or cross bedded with sets over 60 cm thick produced by gravel bedforms migrating alongshore it is interbedded with discontinuous cm to dm bedded sandstones which may be cross bedded pebble fabric and cross bed orientation both indicate strong alongshore sediment transport near the base of the section pebble orientations suggest that gravel wave ripples developed below the zone of strong longshore flows differences between these two examples may be attributed to different directions of wave approach

magnitudes of large shallow earthquakes from 1904 to 1980 abstract in order to obtain a uniform magnitude catalogue surface wave magnitudes ms and broad band body wave magnitudes mb have been determined for large shallow earthquakes from 1904 to 1980 in making the catalogue homogeneous the author consistently adheres to the original definitions of ms and mb given by gutenberg 1945 and gutenberg and richter 1956 the determinations of ms and mb are all based on the amplitude and period data listed in gutenberg and richter s unpublished notes bulletins from stations worldwide and other basic information mb is measured on broad band instruments in periods of 8 s consistency of the magnitude determinations from these different sources is carefully checked in detail more than 900 shallow shocks of magnitude 7 and over are catalogued the meaning of the magnitude scales in various catalogues is examined in terms of ms and mb most of the magnitudes listed by gutenberg and richter 1954 in their seismicity of the earth are basically ms for large shocks shallower than 40 km but are basically mb for large shocks at depths of 40 60 km the surface wave magnitudes given by earthquake data reports are higher than ms by 0 2 unit whether the combined horizontal amplitude or the vertical amplitude is used mb and the currently used 1 s body wave magnitude are measured at different periods and should not be directly compared

geological hazards and disasters in newfoundland and labrador a geological disaster occurs when natural geological processes impact on our activities either through loss of life or injury or through economic loss a geological hazard is a potential disaster geological hazard in the province of newfoundland and labrador was studied by archival research using a variety of sources to document the historical record of disaster this record although undoubtedly incomplete and selective demonstrates that the province was affected by numerous geological disasters that inflicted a major economic and social cost at least 80 people have been killed in newfoundland and labrador since 1863 in such incidents including debris flows rockfalls avalanches and tsunamis many newfoundland communities have developed at the base of steep slopes and are therefore prone to landslides and avalanches or are built adjacent to the coast and are susceptible to storm damage the economic cost is difficult to estimate but remedial measures for individual events range from can 20 000 f

description and dating of a submerged beach in the northern north sea abstract an assumed submerged beach bordering the northern part of the north sea plateau towards the norwegian trench at 130 to 160 m waterdepth has previously been described based on interpretation of seismic profiling the seismic unit is parallel to the edge of the plateau for at least 50 km with an eastward dipping bedding soil borings and vibrocorer samples reveal that a stiff to hard clay is overlain by a thin lag deposit of coarse material on the plateau by an up to 40 m thick coarsening upwards sequence of sand and gravel on the upper part of the slope and by gradually finer material further eastwards in deeper water a low sea level is also indicated by the foraminiferal faunas and abundant littoral and aeolian textures on quartz sand grains nine radiocarbon datings of shell material found in sand and gravel from about 1 to 23 m below the sea bed gave ages from 10 800 to 12 500 yrs b p we thus consider the interpretation of the edge of the plateau and the top of the slope as a submerged beach built out in late weichselian time to be confirmed by the sample evidence

barrier and lagoon coast evolution under differing relative sea level regimes examples from ireland and nova scotia abstract although the coasts of southern ireland and eastern nova scotia possess many basic similarities especially in terms of geology glacial history sediment character resistance to erosion and wave and tide regimes there is a fundamental contrast in holocene sea level history in ireland recent the past 4000 years sea level rise has been limited to less than 1 mm year by contrast the atlantic coast of nova scotia has been experiencing sea level rises up to three to five times greater over the same period under these markedly differing relative sea level rise regimes barrier and lagoon evolution has varied considerably in ireland barrier lagoon form is controlled by local basement expression particularly through the emergence of headlands creating largely closed sediment systems and the requirement to maintain cross shore drainage it is this latter factor that leads to a simple four fold categorization of the irish barriers and lagoons from freshwater seepage to open tidal environments the nova scotian examples are associated with rapidly moving erosional fronts with local basement control relegated to a subordinate role at the expense of rapid changes in sediment supply barriers can both grow and decay under these conditions subject to certain critical but as yet ill defined thresholds simultaneously forcing development and destruction of adjoining lagoons these major differences also find expression in sedimentary sequences

coarse clastic barrier beaches a discussion of the distinctive dynamic and morphosedimentary characteristics abstract coarse clastic barriers are common on mid and high latitude coasts they possess a morphosedimentary and dynamic distinctiveness which sets them apart from sandy fineclastic barrier forms the reflective nature of the seaward barrier favors the development of zero mode sub harmonic edge waves particularly during long period swells 10 20 s manifest in the formation of high level cusps in some circumstances the pattern of recent overwashing of the barrier is related to cusps lack of distinct tidal passes due partly to the high seepage potential of coarse barriers means that very little sediment is transported seaward thus the barriers roll steadily onshore and sections show a variety of washover facies related to the volume of overwash surges

a drowned holocene barrier spit off cape ann massachusetts seismic profiles and bathymetric contours reveal a drowned barrier spit on jeffreys ledge off cape ann massachusetts seaward dipping internal reflectors indicate that a regressive barrier formed during the early holocene low sea level stillstand preservation of the barrier spit may have been favored by its large size as much as 20 m thick by an ample sediment supply from unconsolidated glacial drift and by the subsequent rapid sea level rise the barrier spit is present in water depths of 50 to 70 m and indicates a low relative sea level stand of 50 m this value confirms the low relative sea level stand of 47 m postulated by oldale et al 1983 for northeast massachusetts and new hampshire on the basis of the submerged delta of the merrimack river and it indicates that the barrier and delta were contemporaneous oldale et al 1983

morphosedimentary development of drumlin flank barriers with rapidly rising sea level story head nova scotia abstract the morphodynamic and morphosedimentary development of drift aligned and swash aligned coarse clastic barriers plays an important role in the evolution of paraglacial coasts this paper discusses the development of two contrasting barriers attached to a drumlin headland at story head on the atlantic coast of nova scotia southeastern canada a 3 4 mm a 1 sea level rise is forcing rapid barrier changes including landward migration rollover of the swash aligned barrier at 5 8 m a 1 and barrier thinning elongation and breaching morphological development reflects the highly variable longshore distribution of wave power imposed initially by the topography of the drumlin and its position in the incident wave field and later by morphosedimentary feedback resulting from such gradients gradual reduction of an inherently intermittent sediment supply leads to reworking cannibalization of the barrier ultimately finding expression in a series of distinct wave formed sediment cells further diminution of the sediment supply coupled to cell development results in the drift aligned system decaying into a series of high water residuals separated by breach depressions with splayed spit recurves at the margins although the swash aligned barrier is stretched within the predominant overwash regime and may eventually separate from the headland it has remained intact until very recently when an initial breach occurred the evolutionary sequence of the headland barrier system has an important effect on adjacent sedimentary environments

storm induced damages along the catalan coast nw mediterranean during the period 1958 2008 abstract the temporal and spatial patterns of storm induced damage along the catalan coast nw mediterranean during the last 50 years have been analyzed to identify main climatic and non climatic forcings in the absence of systematic data a storm induced damage database compiled from press news has been built which together with an intensity scale has allowed us to characterize the frequency and intensity of damage although no temporal trend has been detected in storm induced hazards coastal damage has increased at a rate of about 40 per decade during the last 50 years along the catalan coast the main non climatic factors identified controlling this trend were the urban growth along the coastal fringe and the generalized erosive behavior of beaches the first one increased values at risk and the second one increased their exposure to storm induced hazards in spite of the importance of non climatic factors to modulate coastal damage an exponential dependence of damages on storm induced inundation and erosion was detected in addition to this storm induced geomorphic changes along the ebro delta coast have also been analyzed during the period analyzed harmful storms seem to be clustered with most of the events being present in the late 1990s and especially from 2001 to 2004 resulting in frequent events of intense beach barrier breaching massive overwash and flooding they are mainly expressed in sensitive areas which are subject to long term erosional processes and comprise a low lying profile and a narrow beach this reflects the role of coastal morphology in controlling the intensity of storm induced hazards along the deltaic coast shoreline evolution rates calculated during this period were significantly larger than the previously recorded ones reflecting a pulsating erosion behavior where large pulses occur during stormy periods and are reduced during post storm periods under the present scenario of maximum coastal development storm induced damage has been reported almost every year which could indicate that the present overall beach configuration status along the catalan coast has reached its limit for protecting the hinterland against storms

barrier dynamics and landward migration with holocene sea level rise barrier beaches islands and spits have become the subject of mounting interest1 2 due to human development on these land forms it is commonly thought that barrier beaches continuously migrate landward in response to sea level rise often by over wash processes maintain mass through time and that these processes are occurring at a rate commensurate with human 100 yr time frames while some barriers are naturally migrating quite rapidly3 4 other barriers decidedly are not here i present data which illustrate that many us atlantic coast barriers are not evolving over the short term in accordance with generally accepted hypotheses and argue that the presumed norm may actually be the exception

storm and tide dominated shorelines in cretaceous moosebar lower gates interval outcrop equivalents of deep basin gas trap in western canada the moosebar and gates formations crop out in the deformed foothills belt south of fort st john british columbia they permit examination of the depositional environments of sandstones and conglomerates that are gas bearing in the equivalent wilrich falher interval of the deep basin of alberta and british columbia the moosebar gates interval consists of several upward coarsening and marine to nonmarine sequences moosebar bioturbated shales pass upward into turbidites and offshore storm deposits flow directions indicate a north dipping paleoslope a second coarsening upward sequence at the top of the moosebar and base of the gates terminates in a lenticular fluvial conglomerate up to 30 m thick which is overlain by coals carbonaceous mudstones and sandstones above the carbonaceous zone a major lateral facies change is observed fluvial conglomerates in the south grade into beach conglomerates northward the upper part of the beach conglomerate consists of exposed three dimensional storm berms at least 500 m long up to 1 5 m high with wavelengths of 12 to 24 m the berms trend east west seaward of the conglomerate beach are herringbone cross bedded tidal sandstones with a marine trace fauna graded sharp based conglomerates also are present probably washed out to sea by storms farther north at the same stratigraphic level is a series of partly overlapping conglomerate bars up to 5 m thick and 40 to 50 m across the tops of these bars are covered with storm formed symmetric conglomeratic dunes details of the orientation and geometry of these conglomerate bodies along with their internal structure and pebble fabrics suggest that four major environments fluvial beach offshore conglomerate bars and offshore graded storm conglomerates should be identifiable and predictable in the subsurface

coastal changes in the arctic the arctic s climate system is changing air temperatures major river discharges and open water season length have increased and storm intensities and tracks are changing thirteen quantitative studies of the rates of coastline position change throughout the arctic show that recently observed changes have not increased coastal erosion rates which currently range between 0 and 2 m yr when averaged for the arctic shelf seas current data is probably insufficient both spatially and temporally however to capture change at decadal to sub decadal time scales in this context we describe the current understanding of arctic coastal geomorphodynamics with an emphasis on erosional regimes of coasts with ice rich sedimentary deposits in the laptev east siberian and beaufort seas where local coastal erosion can reach 30 m yr we also examine coasts with lithified rocky substrates where geomorphodynamics are intensified by rapid glacial retreat coastlines of svalbard greenland and the canadian archipelago are less frequently studied than ice rich continental coasts of north america and siberia and studies often focus on coastal sections composed of unlithified material as air temperature and sea ice duration and extent change longer thaw and wave seasons will intensify coastal dynamics in the arctic

morphostratigraphy and facies architecture of sandy barriers along the eastern shore of nova scotia abstract linear southeast trending valleys along the eastern shore of nova scotia were initially formed by fluvial incision and subsequently scoured during pleistocene glaciations estuarine and barrier sedimentation was initiated when the valleys were drowned during the marine transgression of the early to mid holocene this coast continues to experience transgression due to relative sea level rise of 35 40 cm per century eastern shore barriers have formed under a wave dominated regime the modal wave is highly energetic with a height of 1 5 2 m and a 9 10 s period tidal range is low mesotidal with maximum spring range of 2 1 m fluvial sediment supply to eastern shore estuaries is negligible four sandy barriers from the eastern shore exhibit erosional and progradational morphologies that result from differences in the balance between relative sea level rise sediment supply and depositional processes within coastal compartments morphological contrasts represent the cyclic nature of barrier and estuarine evolution along the eastern shore during transgression sedimentation commences with a unit of fine grained central basin deposits overlain by a bed of fine to medium massive and cross bedded flood tidal delta sands an erosional surface lies at the contact between the flood tidal delta facies and the overlying nearshore facies of tabular and cross bedded gravelly sands in some cases the nearshore unit may grade upward into a second younger flood tidal delta deposit that is in turn incised and then filled by sandy channel fill facies the tidal delta facies is overlain by beach sands at the seaward side and washover deposits on the landward side of the barrier the uppermost facies in the sequence includes a composite unit of upper beach and dune sands where sediment supply is sufficient a beach ridge plain will form producing a composite barrier stratigraphy with transgressive and regressive elements

morphology and stratigraphy of small barrier lagoon systems in maine abstract the coast of maine contains over 200 individual barrier lagoon systems most quite small with an aggregate length of nearly 100 km although they represent less than 5 of the tidally influenced coastline of maine they are widely distributed and occur in a variety of dynamic regimes and physiographic regions their morphology and backbarrier stratigraphy are different from better studied coastal plain systems and provide important clues to the holocene evolution of the maine coast in a study of geomorphic form and backbarrier stratigraphy inlet processes and holocene sea level rise have been identified as the principal controls on coarse grained barrier stratigraphy barriers in maine are found in five distinct geomorphic forms identified herein as barrier spits pocket barriers double tombolos cuspate barriers and looped barriers the few long sandy beaches in southwestern maine are mostly barrier spits the remainder of the barrier types is composed primarily of gravel or mixed sand and gravel the barriers protect a variety of backbarrier environments fresh and brackish ponds lagoons and fresh and saltwater marshes the barriers may or may not have inlets normal wave action coarse grain size and a deeply embayed coast result in barriers with steep reflective profiles several meters above mhw occasional storm events completely wash over the barriers building steep lobate gravel fans along their landward margin few if any extensive storm layers are recognized as extending into the distal backbarrier environments however during sea level rise and landward barrier retreat this abrupt storm generated transition zone inters the backbarrier sediments statistical comparisons of barrier morphology location and backbarrier environment type with backbarrier stratigraphy show that holocene backbarrier stratigraphy is best predicted by the modern backbarrier environment type this in turn is influenced most by the absence or presence and long term stability or instability of a tidal inlet geomorphic barrier form and location in coastal geomorphic compartments show little or no correlation with backbarrier stratigraphy in contrast to previous classifications of barrier lagoon systems based primarily on sandy coastal plain examples in maine the shape or origin of the backbarrier system is relatively unimportant the presence or absence of a tidal inlet is of paramount importance in shaping the holocene stratigraphy of the backbarrier region

spectral p wave magnitudes aki s ω square model and source parameters of earthquakes abstract the earthquake magnitude is a quantity sampling the spectrum of the far field radiation with a suit of properly defined magnitudes in a sufficiently broad range of frequencies the radiated spectrum can be restored and analyzed a method is proposed for the extraction of stress drop fault length and seismic moment from magnitudes on a routine basis thereby the theoretical spectrum as predicted by the square model of aki is utilized in applying the method to earthquakes which occurred in several parts of asia over a time span of 3 years it is shown that in most cases earthquakes in a given region are characterized by the same stress drop varying however from region to region in one region a change of the stress drop with time is found eventually indicating a change in the state of stress in the particular region during the time interval investigated

a submerged beach between norway and ekofisk in the north sea abstract on a recent geophysical pipeline route survey between the sw coast of norway and the ekofisk oil field in the north sea a submerged beach deposit was discovered the beach is located on the shoulder of the sw slope of the norwegian trench at a water depth of 90 m the beach is similar in structure to a submerged beach previously described for a deposit located 380 km further nnw in the same type of regional environment the shoulder of the western slope this beach is however located 40 70 m deeper suggesting a possible post glacial dipping of the north sea plateau

overwash occurrence consequent on morphodynamic changes following lagoon outlet closure on a coarse clastic barrier the reduction in sediment volume of an ebb tide delta as a consequence of lagoon outlet closure on a coarse clastic barrier in southeast ireland initiated a sequence of beachface and barrier changes downdrift elimination of sediment supply to the ebb delta caused a cessation of downdrift longshore swash bar welding and led to beach volume reductions which in turn allowed a temporal sequence of beach and nearshore morphodynamic domains to develop these domains then controlled the sedimentation regime of the barrier adjacent to the old outlet a temporal sequence of a dissipative barrier b reflective barrier and c inner reflective barrier face outer dissipative subtidal wave regimes match respectively periods of a barrier crest build up by crestal dune development b barrier crest instability barrier width increasing barrier height decreasing due to rhythmic overwash and c a return to barrier crest stability with limited aeolian accretion two barriers at different stages in this sequence are discussed

moment magnitude determination for local and regional earthquakes based on source spectra we investigated the use of an automated routine to determine moment magnitudes from the displacement spectra of local and regional earthquakes two algorithms a genetic algorithm and a converging grid search were developed and tested with earthquake data from mexico norway and deception island antarctica it was found that compared with manual analysis the algorithms give reliable automatic moment magnitude m w estimates in the range 1 m 8 the converging grid search appeared to be more cost effective than the genetic algorithm m w at local and regional distances seems superior to amplitude based magnitudes that saturate for large earthquakes the application of the automated algorithm in near real time may help to obtain a nonsaturated magnitude estimate in the case of a large earthquake immediately after the earthquake has occurred also the method can be useful for processing large amounts of data manuscript received 27 july 2001

the anelasticity of the earth s mantle in the european area abstract the anelastic attenuation of seismic waves as expressed by the q factor is compared for two regions between the mid atlantic ridge and the seismic station hamburg f r g and the hindu kush and the same station eight earthquakes in the distance range 44 7 to 59 1 were chosen the spectral ratios of short period scs and scp as well as pcs and pcp phases were computed and used to estimate the differential effect of attenuation on p and s waves assuming the ratio of q factors for p and for s waves to be q q 1 75 q values of 161 for the western part and of 324 for the eastern part of europe are found the pronounced difference of the average q values for the earth s mantle is interpreted as being related to a regional variation of the anelasticity in the lowermost mantle below 2200 km in the frequency band 0 1 to 0 6 hz the q factors are likely to be frequency independent

modelling gravel barrier response to storms and sudden relative sea level change using xbeach g abstract this paper investigates the response of a mixed sand and gravel msg barrier coastline to storms and sudden relative sea level change using the numerical model xbeach g the barrier beaches of southern hawke s bay new zealand provide a natural laboratory for the work owing to spatial variability in instantaneous land deformation that occurred during the 1931 hawke s bay earthquake historic 1931 and contemporary 2017 morphodynamics of one tectonically uplifted 1 5 m and one subsided 0 78 m barrier were modelled under energetic waves hs 1 6 m xbeach g was designed to simulate pure gravel beach morphodynamics but despite this the model demonstrated high quantitative skill when calibrated for the msg coast results reveal the storm impact regimes of each profile and potential linkages to decadal scale barrier development observed in historical beach profile data storm swash processes at the uplifted profile indicate long term barrier stability due to a lack of change at the barrier crest and ridge building observed in model simulations provides a potential formative mechanism for decadal scale beach progradation at the subsided barrier modelled historic crest build up up to 0 3 m and narrowing over 5 m indicate an overtopping mode of response to sudden relative sea level rise simulation results are consistent with historical beach profile observations that also show chronic narrowing of the subsided barrier through time simulations of the modern barrier draw attention to the possibility that it may be on a trajectory toward catastrophic breakdown under extreme conditions but further work is needed to distinguish the relative importance of historical sudden sea level rise versus deficits in sediment supply to this shoreline

gravel barrier migration and overstepping abstract despite the widespread occurrence of gravel barriers on mid to high latitude coasts understanding of their stability and relationship to gravel deposits on the inner continental shelf remains rudimentary on sand dominated coasts subject to rising relative sea level barrier overstepping has been postulated as a mechanism for preservation of beach deposits on the shelf but direct observation of overstepping events has been lacking observations at a site on the atlantic coast of canada reveal migration of a gravel barrier at 8 m a 1 landward over back barrier mud following abandonment of part of the barrier volume on the shoreface this provides clear evidence for overstepping and suggests that it may play a role in the formation of inner shelf gravel deposits integrity of the migrating stretching barrier depends on continued sediment supply from the headland source to a connecting ridge which must become progressively longer as the landward displacement of the barrier increases

barrier island evolution middle atlantic shelf u s a part ii evidence from the shelf floor where the atlantic coastal gradient is low and the substrate is unconsolidated shoreface processes lead to an equilibrium shoreface surface characterized by a straightened plan view and a concave up profile maintenance of this surface during the post glacial sea level rise may lead to barrier formation by mainland beach detachment where the outer oceanic shoreface is maintained by wave and current processes downwelling storm currents sweep sand from the shoreface of the middle atlantic bight transport it downcoast and seaward and deposit it on the adjacent inner shelf some of this sand is returned by the action of asymmetrical wave orbital currents during fair weather however there is a net loss in most areas the loss is not made good by river sand input since on the atlantic coast all river sand is trapped by estuaries as a result the shoreface in these areas is undergoing erosional retreat mean horizontal retreat rates are on the order of 1 3 m yr 1 but most movement occurs in brief episodes with recurrence rates on the order of several events per century erosional shoreface retreat coupled with aeolian overshoot storm washover and the movement of sand through inlets into the lagoons has lead to landward migration of the atlantic barriers through the holocene period of sea level rise the landward retreat of the barrier as a whole is as dependent on inlet formation as it is on erosional shoreface retreat repeated inlet breaching and the downdrift migration of inlets yields coalescing flood tidal deltas within the lagoon the resulting surface forms a platform on which the subaerial barrier deposits can advance under the impetus of storm washover and aeolian action the backbarrier deposits eventually re emerge at the shoreface where their upper beds are eroded and recycled the barrier thus migrates over a pavement of its own flood tidal deltas and washover fans sand is added to the system partly through the erosion of updrift headlands but mainly by means of scour in inlets which reaches down to the underlying pleistocene the modern shelf sand sheet is the debris blanket resulting from the retreat process the leading edge occurs as a thin veneer of rip current fallout on the shoreface this is periodically stripped off by winter storms to expose the underlying backbarrier strata further seaward shelf sands eroded from the shoreface rest disconformably on backbarrier deposits shoreface beach and dune strata are always missing every grain of sand in this shelf sand sheet has occupied a position on the beach or upper shoreface within the recent past however the sheet as a whole has been reconstituted its primary structures are those of the inner shelf floor backbarrier sand and mud deposits characterized by channeling and landward dipping reflectors can be traced for over 100 km seaward across the middle atlantic shelf beneath the modern sand sheet the backbarrier stratum together with the overlying shelf sand layer constitutes the record of barrier retreat across the atlantic shelf surface during holocene time the sheet like nature of this record indicates that viewed at the appropriate time scale barrier migration is a continuous process

preliminary reference calibrating functions for body wave magnitudes refracted p waves abstract body wave magnitudes are being routinely determined and published at observatories and data centers for a large number of earthquakes using the calibrating functions of gutenberg and richter these functions were obtained on the basis of amplitude measurements from seismographs with variable and generally unknown periods and bandwidths it may be surmised that the calibrating functions degrade the new data obtained largely from modern standardized instruments new calibrating functions appear to be overdue in seismological practice in this study amplitude variation curves for p waves are presented the functions form the basis for the respective new calibrating functions employing the ray theoretical approximation the amplitude variation along the earth s surface is computed for the prem model of velocity and anelasticity of the earth the calibrating functions depend on the epicentral distance and the focal depth as well as on the period of the wave due to multibranching of ray paths in the epicentral distance range up to 25 the synthetic amplitude distance curves show an oscillatory behavior at epicentral distances up to about 20 the oscillations are most pronounced for small focal depths the computed curves are suitable to explain the oscillations observed earlier from high precision amplitude observations for southeastern europe and asia minor vanek and stelzner 1960

evolution of the barrier islands of southern long island new york three lines of evidence based on data from more than 400 boreholes and vibrocores have been used to reconstruct the evolution of the barrier islands during the holocene transgression in southern long island new york 1 the holocene transgressive stratigraphic sequence behind the present barriers 2 the stratigraphic patterns of the inner shelf and 3 the morphology of the now buried late pleistocene coastal features the extensive preservation of backbarrier sediments radiocarbon dated between 7000 and 8000 yr bp on the inner shelf of southern long island suggests that the barriers have not retreated by continuous shoreface erosion alone but have also undergone discontinuous retreat by in place drowning of barriers and stepwise retreat of the surf zone such stepwise retreat of the surf zone has prevented the backbarrier sediments from being reworked based on the presence of submerged barrier sand bodies in seismic records it is inferred that about 9000 years ago when the sea stood about 24 m below the present sea level a chain of barriers developed on the present shelf about 7 km offshore of the present barriers with continued sea level rise the 24 m barrier built upward until the sea reached about 15 m msl just prior to 7000 yr bp the barriers were then submerged by the rapidly rising sea and the surf zone shifted rapidly landward to a position about 2 km from the present shoreline the surf zone overstepped to the landward margin of the old lagoon which had become fixed at the steep seaward face of mid wisconsinan or sangamonian coastal barriers during the past 5000 or 6000 years the shoreface has retreated continuously by about 2 km evidence from southern long island and elsewhere in regions of coastal submergence indicates that rapid sea level rise and low sand supply seem to favour the stepwise retreat of barriers whereas slow rates of submergence and a greater supply of sand generally favour continuous shoreface retreat stationary upbuilding or seaward progradation of barriers may occur when supply of sand is great and or submergence is slowed or reversed morphologic highs on the pretransgression surface such as old barrier ridges tend to fix the migrating barrier shoreline during either continuous retreat or stepwise retreat of barriers

magnitude spectra and other source parameters for some major 1985 and 1986 earthquakes abstract broad band seismograms are used to determine the magnitude spectrum of an earthquake the spectrum represents the velocity amplitude density spectrum at the earthquake source scaled in magnitude units a method is presented to routinely utilize the magnitude spectrum for the independent determination of the seismic energy released the seismic moment the fault length and the stress drop the method is applied to six earthquakes in three different regions it is found that the stress drop is higher for the intraplate earthquake than for the interplate earthquakes also it is observed that the largest foreshock of an interplate earthquake has a clearly higher stress drop than the largest aftershock the results indicate that there are measurable regional differences in source parameters and that there are time variations in the parameters within each region

spectral amplitude distance curves for p waves effects of velocity and q distribution abstract earthquake magnitude calibrating functions are based on amplitude distance curves the curves can be obtained either empirically or theoretically in the latter case from standard velocity and q models of the earth theoretical amplitude variation curves for p waves are presented for the prem and iasp91 velocity models a comparison with the empirical hms curve available for a particular period 8 s shows better agreement with the iasp91 model a further improvement is achieved by adjusting the q model as well as the ratio of radiation intensity of s to p waves at the source broadband observations of seismic waves require the amplitude distance curves to be computed in the period range of up to 10 octaves a strong dependence of the curves on the q model is found at periods shorter than about 4 s it is concluded that the standard q model for the magnitude calibrating functions can be ultimately selected only on the basis of amplitude measurements at possibly short periods and from the comparison of the resulting amplitude variation curves with theoretical ones

the importance of sea level fluctuations in the formation of linear conglomerate bodies carrot creek member of cardium formation cretaceous western interior seaway alberta canada abstract the raven river member of the cardium formation turonian upper cretaceous in the carrot creek area of alberta contains two coarsening upward sequences of marine mudstones and sandstones the lower sequence coarsens from black mudstones into bioturbated fine grained sandstones and is capped by a gritty siderite horizon which probably indicates a pause in deposition the sandstones of the upper sequence contain hummocky cross stratification suggesting open marine deposition below fairweather wave base the two sequences are scoured to variable depths by a major erosion surface which has a relative relief of up to 20 m a structure map and three dimensional mesh diagrams of this surface suggest four topographic elements a relatively high terrace a bevel at which und rlying beds are truncated and a series of bumps and hollows these are interpreted to represent a remnant erosional topography which gradually fades away into the final topographic element the smooth basin plain the erosion surface is covered with conglomerate assigned to the carrot creek member of the cardium the conglomerate thickness reaches about 20 m against the bevel and in some of the hollows but usually thins to a veneer on the terrace on top of the bumps and on the distal basin floor the conglomerate bodies are relatively long and narrow and trend northwest southeast they are overlain by marine mudstones of the dismal rat member the elongate conglomerate bodies appear at first sight to be another case of western interior seaway offshore bars encased in marine mudstones many tens of kilometers seaward of time equivalent shoreline deposits however the erosion surface indicates that the conglomerates are not genetically part of the underlying coarsening upward sequence we propose a rapid relative lowering of sea level following deposition of the hummocky cross stratified sandstones the shoreline advanced many kilometers northeastward into the basin and during stillstand wave erosion cut a new shoreface profile the bevel during this lowstand incised rivers supplied gravel to the shoreface waves worked the gravel alongshore against the bevel and into the erosional hollows subsequent transgres ion spread some gravel southwestward back across the terrace storms transported gravel stringers into the transgressive muds accumulating in the hollows other erosional surfaces of this type exist in alberta at the cardium viking and bad heart horizons and in new mexico at the gallup tocito horizon suggesting that sea level changes and shoreface incision may be an alternative explanation for other long narrow offshore bars encased in marine shales