assessment of post storm recovery of beaches using video imaging techniques a case study at gold coast australia ever expanding networks of surf cameras offer a unique opportunity to monitor the coastline over large expanses at very little cost compared to traditional in situ survey methods here we describe and test a new coastal monitoring system maintained by coastalcoms pty ltd at their test site at gold coast australia the two camera system monitors two highly sensitive 4 km stretches of sandy coastline adjacent to high value assets the traditional static multi camera setup has been replaced by a single rotational camera a 14 month data set encompassing one major storm a recovery period and a seasonal cycle was analyzed positive shoreline detections using the new camera system were available 64 of the time roughly 145 days of the available 226 where daily offshore significant wave heights hs 1 m comparison of the coastalcoms derived shorelines and in situ survey data showed a mean shoreward bias of 25 5 m daily shoreline estimates were used to calculate weekly and five week running mean beach widths at both sites analysis showed that both sites eroded between 15 22 m during the may 2009 storm and then recovered during the proceeding five month calm period distinct intersite variability was observed between the more exposed northern beaches that displayed an annual shoreline cycle and very little intrasite variability and the more sheltered southern palm beach site that displayed large intrasite spatial variability and sensitivity to changes to both wave direction and wave height

objective beach state classification from optical sensing of cross shore dissipation profiles remote sensing using terrestrial optical charge coupled device cameras is a useful data collection method for geophysical measurement in the nearshore zone where in situ measurement is difficult and time consuming in particular optical video sensing of the variability in human visible surface refraction due to the nearshore incident wave field is becoming an established method for distal measurement of nearshore subtidal morphology we report on the use of a low mounted shore normal camera for gathering data on cross shore dissipative characteristics of a dynamic open beach data are analyzed for the purposes of classifying three of wright and shorts intermediate classes of morphological beach state as determined by expert raters although these beach states are usually thought of as being distinctive in terms of their longshore bar variability theory predicts that differences should also be observed in cross shore dissipative characteristics three methods of generating features from statistical features from the archived optical data are described and compared in terms of their ability to discriminate between the beach states principal component scores of the percentile distributions were found to provide slightly better classification performance i e 85 while approximating the data using relatively fewer features whereas classification using intensity distributions alone resulted in the worst performance classifying 78 of beach states correctly class center moment profiles for each beach state were constructed and results indicate that cross shore wave dissipation becomes more disorganized as linear bars devolve into more complex transverse structures

paleomagnetism of rocks from burin peninsula newfoundland hypothesis of late paleozoic displacement of acadia criticized the posttectonic st lawrence granite 360 5 ma and associated subvertical dikes have two magnetizations n and h n points north with an intermediate upward inclination declination 005 inclination 50 alpha 95 10 paleopole 12 n 120 e we consider n to have been acquired close to the time of initial cooling the h magnetization points south with low inclination h is also the dominant magnetization in the nearby permo carboniferous spanish room formation h is considered to be an overprint acquired chemically during the kiaman reversed superchron late carboniferous and permian the n magnetization corresponds to a paleolatitude of 31 7 s very different from the near equatorial values expected from the commonly accepted late devonian and earliest carboniferous tournaisian reference paleofields for cratonic north america this is generally consistent with the hypothesis of a southerly displaced acadia proposed by kent and opdyke although the displacement is much greater 30 rather than 15 however we show that all inclinations observed from middle to upper devonian and tournaisian rocks from the craton are not significantly different either from the kiaman paleofield or from the h overprints observed from newfoundland some of these cratonic studies are not very detailed but it is noteworthy that the declination observed in the most comprehensive of them catskill red beds also agrees with the kiaman paleofield and with the h overprints from newfoundland declinations in some other cratonic studies show small departures of only a few degrees with one exception based on limited sampling and two from the colorado plateau which may have been rotated which could be caused by experimental inaccuracies moreover the directions obtained from cratonic studies are 97 reversed as they are in rocks with kiaman magnetizations we suggest therefore that the commonly accepted late devonian to earliest carboniferous reference paleofield for north america is either entirely kiaman in age or has been seriously affected by kiaman overprinting consequently the 30 of southerly displacement which the n magnetization of the st lawrence granite apears to indicate and the 15 invoked by kent and opdyke we consider to be illusory three late precambrian rock units 623 to 606 ma have scattered declinations but similar inclinations yielding paleolatitudes of about 35 the scattered declinations presumable were caused by local pre carboniferous relative rotations there is little or no evidence of kiaman overprinting in precambrian rocks indicating that overprinting is comparatively superficial and is probably related to late paleozoic groundwater circulation

weathering effects on the magnetic properties of the milledgeville granite georgia abstract one of the major problems in paleomagnetic sampling of granites in the southeastern united states is finding fresh outcrop since most outcrops are weathered to some extent it is important to quantify the effect of weathering on the magnetic properties of individual samples the lake sinclair dam site near milledgeville georgia was chosen for this study where a very fresh stable granite outcrops in the excavated spillway lying immediately above is the weathered equivalent drilled samples were obtained from fresh and weathered portions at one outcrop and the remanent and induced magnetizations measured with af demagnetization it was possible to obtain the stable remanent directions exhibited by fresh samples from all weathered samples the induced and remanent magnetic behavior can be explained by maghemitization during weathering and the development of a secondary low oxidation magnetic phase and the reduction in domain size of primary magnetite

paleomagnetic evidence for the continuity and independent movement of a distinct major crustal block in the southern appalachians the magnetization of 22 granitic and gneissic southern appalachian rock units with estimated cooling ages of 415 250 m y has been determined included are 842 samples from 114 sites within 19 granites 100 sites and 3 gneisses 14 sites located in north carolina south carolina and georgia data for units which cooled to temperatures 20 000 km sup 2 in size a mean paleopole for this group with corrections for maximum tilt estimates exhibits good precision but has a paleosite latitude of approx 10 sup 0 n without tilt correction the paleopole for group b still exhibits an anomalous paleositemore latitude of approx 4 sup 0 n these data indicate that the group b block elberton sparta crustal block lying to the se has an apparent paleosite latitude corresponding to magnetization at a location to the north of the zone containing group a units less

magnetization of the austell gneiss northwest georgia piedmont the austell gneiss is located in the piedmont 16 km west of atlanta georgia and 8 km northwest of the brevard fault zone this metamorphosed granite gneiss lies refolded in the nose of the austell frolona antiform a doubly plunging structure of regional extent subsequent to intrusion the unit has undergone four episodes of deformation the first and second generation folds f1 and f2 are coaxial but not coplanar the two later fold events were less intense and have little effect on local outcrop patterns in the study area the age of the unit has been estimated to be greater than 325 m y but less than 365 m y the induced and remanent magnetic properties for at least six cores drilled at each of 10 sites within the austell gneiss have been determined the magnetic foliation for the unit is approximately parallel with field estimates for s1 foliation planes exhibited by mineral orientations within the body indicating post emplacement magnetic grain mobility the stable remanent magnetization exhibited by the body was therefore probably acquired during or slightly after the f1 or f2 deformational events as a result of cooling from metamorphic temperatures 600 c or alternatively from secondary magnetite grain nucleation and growth a paleopole position calculated for these data without structural correction 126 2 34 4 dp 6 6 dm 13 2 can be explained by magnetic acquisition in at least three possible geologic settings from simple to complex these are the following first since a large oval of confidence is observed for the unit and minor tilting can not be resolved the data may be explained by magnetization of the austell at its present site during cooling from metamorphic temperatures second a northwestward thrust event may have resulted in bringing the austell to its present location third the data can be explained by two major translational events the austell may have initially been magnetized and then moved to the northeast by transcurrent strike slip faulting 1000 km into juxtaposition with the southern appalachians followed by thrusting of the unit to the northwest to its present location in support of this last interpretation is the similarity between the paleopole for the austell and paleopoles determined for the maritime provinces of north america which were suggested to have moved 1500 km to the northeast during the mid to late paleozoic against such an interpretation is the lack of geologic evidence in support of large scale left lateral strike slip faulting in the southern appalachians

a review of paleomagnetic results from the carboniferous of north america the concept of carboniferous geomagnetic field horizon markers results from the east coast carboniferous basin contain an important time stratigraphic horizon of possible global significance late carboniferous units are found to have mostly reversed magnetizations while older carboniferous units may have normal reverse or most frequently dual polarity magnetizations this feature records the change in geomagnetic field from a period of common polarity changes to a period of mainly reversed polarity the kiaman magnetic interval recognition of the stratigraphic position of this polarity feature provides a time line for correlation of units within and among carboniferous basins in the east coast carboniferous basin of atlantic canada this horizon has now been located at the riversdale group level early pennsylvanian namurian westphalian boundary since remanence acquisition of red sediments is often a lengthy process possibly spanning field reversal time scales red bed units pre dating and post dating this time line can in most instances be readily distinguished the former generally recording both polarities and the latter just one reverse polarity a polar displacement of at least 16 is recorded in the results from the east coast carboniferous basin paleolatitude maps show that the area was located near the equator and was displaced northwards by about 8 during the pennsylvanian it cannot be ascertained if those observations are representative of the whole of north america or merely the atlantic seaboard poles derived from other areas of north america do not all fit the regular pattern observed on the atlantic coast using the horizon marker as a tool it is suggested that those poles are post time line in age so that none of them is representative of the position of north america prior to the time line

anisotropy of magnetic susceptibility data indicating remagnetization in diabase dikes induced and remanent magnetic analyses have been performed on drilled samples from 2 generations of unweathered diabase dikes a breccia dike and the host tonalite which make up the basement on which the russell dam foundation was poured the maximum magnetic foliation plane for most samples defined by anisotropy of magnetic susceptibility ams data is vertical and is oriented perpendicular to maximum stresses developed in the region during mid late paleozoic time the excellent ams data consistency between units of different ages is interpreted to be indicative of stress controlled magnetite recrystallization at the site it is inferred that this recrystallization is responsible for the multicomponent remanent magnetization rm in these samples which was probably acquired over long periods of time

stratigraphy paleomagnetism and magnetic fabric of the toba tuffs constraints on the sources and eruptive styles the toba depression in north central sumatra is a complex of several overlapping calderas resulting from three major ignimbrite forming eruptions within the depression the upland masses of samosir and northern uluan consist of welded ignimbrite capped by coarse breccia and lacustrine sediment hitherto interpreted to be two parts of a single resurgent dome this study has demonstrated that the welded tuffs of samosir and uluan have different magnetic polarities and therefore at least two different ignimbrites are present the samosir uluan massif may consist of parts of two resurgent domes the first ignimbrite eruption occurred at 0 84 ma and produced a very thick 400 m densely welded unit having a reversed polarity anisotropy of magnetic susceptibility ams flow direction and lithic size data indicate that the source lies in the southern part of the toba depression and the thick deposit of uluan is thought to have ponded in a 40 km wide caldera the second ignimbrite is normally magnetized ams flow direction data indicate two separate source vents one to the north in the haranggaol caldera and another to the south the thick deposit at samosir is thought to have ponded in the southern caldera coarse sediments then accumulated over samosir and northern uluan and were capped by lacustrine deposits a renewed episode of resurgence then uplifted samosir island and possibly the northern part of uluan at approximately 0 075 ma the last and apparently largest ignimbrite eruption occurred from calderas in the north and south parts of the toba depression this ignimbrite is mostly nonwelded and normally magnetized part of the uluan dome was destroyed by collapse of the sibandung caldera and latung graben and concomitant with renewed subsidence of the haranggaol and porsea calderas

quantification of sand bar morphology a video technique based on wave dissipation a technique is presented to remotely measure the scales and morphology of natural sand bars based on the preferential dissipation of wind waves and swell over the crests of the bar photographic or video images are recorded and statistical uncertainties associated with incident wave height modulations removed by averaging time exposures ground truth testing of the technique was carried out as part of the superduck experiment in october 1986 the time exposures generally provided a good mapping of underlying morphology allowing detection of the bar and determination of cross shore and longshore length scales however during high waves persistent surface foam obscures the relationship of image intensity to local dissipation modeled theoretically by dissipation of a random wave field and an enhancement technique of image differencing must be done to remove the bias errors in the estimate of bar crest distance from the shoreline are generally less than 35 but this value depends on the geometry of the particular bar logistic simplicity and quantitative capabilities make this technique very attractive

the morphodynamic effects of incident wave groupiness and tide range on an energetic beach abstract the roles played by daily tide range and incident wave groupiness in affecting the short term morphodynamic responses of an energetic beach are examined demodulation of original tide and wave time series from the moderate energy narrabeen beach australia resulted in new time series of daily tide range and a daily grouping factor which expresses the relative amplitude of the alternation between groups of high and low waves using these new time series together with time series of daily beach state and changing breaker conditions statistical analyses were performed aimed at determining the contributions made by tide and groupiness in explaining time varying beach state additional to those made by time varying wave conditions eigenvector analyses of monthly surveyed beach and surf zone profiles provided a set of time series on modes of profile configuration change which were also analyzed to determine the relative effects of waves and tide range on profile shape both tide range and groupiness are significant determinants of beach state the six beach states are reflective low tide terrace transverse bar and rip rhythmic bar and beach longshore bar trough and dissipative wright and short 1984 provided that wave conditions are within the appropriate range to favor beach states at the reflective end of the sequence spring tides will tend to favor the low tide terrace over the transverse bar and rip state higher tide ranges are also associated with more subdued bar trough topography the more accentuated bar trough profiles are developed when tide range is minimal overall higher relative incident wave groupiness favors the more dissipative states incident wave groupiness is the dominant factor determining whether the low tide terrace state or transverse bar and rip state prevails provided incident wave steepnesses permit one or the other of these states groupiness is also important in discriminating between the transverse bar and rip and rhythmic bar and beach states

timescales for the evolution of seismic anisotropy in mantle flow 1 we study systematically the relationship between olivine lattice preferred orientation and the mantle flow field that produces it using the plastic flow recrystallization model of kaminski and ribe 2001 in this model a polycrystal responds to an imposed deformation rate tensor by simultaneous intracrystalline slip and dynamic recrystallization by nucleation and grain boundary migration numerical solutions for the mean orientation of the a axes of an initially isotropic aggregate deformed uniformly with a characteristic strain rate show that the lattice preferred orientation evolves in three stages 1 for small times recrystallization is not yet active and the average a axis follows the long axis of the finite strain ellipsoid 2 for intermediate times the fabric is controlled by grain boundary migration and the average a axis rotates toward the orientation corresponding to the maximum resolved shear stress on the softest slip system 3 for the fabric is controlled by plastic deformation and average a axis rotates toward the orientation of the long axis of the finite strain ellipsoid corresponding to an infinite deformation the infinite strain axis in more realistic nonuniform flows lattice preferred orientation evolution depends on a dimensionless grain orientation lag parameter x defined locally as the ratio of the intrinsic lattice preferred orientation adjustment timescale to the timescale for changes of the infinite strain axis along path lines in the flow explicit numerical calculation of the lattice preferred orientation evolution in simple fluid dynamical models for ridges and for plume ridge interaction shows that the average a axis aligns with the flow direction only in those parts of the flow field where 1 calculation of provides a simple way to evaluate the likely distribution of lattice preferred orientation in a candidate flow field at low numerical cost

oxygen isotopic compositions of the late orogenic granites in the southern piedmont of the appalachian mountains u s a and their relationship to subcrustal structures and lithologies abstract data were acquired from 143 whole rock samples from 20 late orogenic post metamorphic hercynian age granitic plutons from the piedmont of the southern appalachians principally in georgia and south carolina these plutons exhibit a regional gradient in oxygen isotopic compositions in which the granites confined to the inner piedmont to the northwest are 18 o enriched 11 4 to 7 9 whereas those toward the southeast within the charlotte slate and portions of the kiokee belts have distinctly lower 18 o 16 o compositions 8 2 to 5 5 one body that lies along the southeastern edge of the piedmont in south carolina however appears to be anomalously 18 o enriched 8 9 most plutons display 18 o 16 o variations of 18 o enriched plutons occupy areas characterized by negative anomalies whereas low 18 o bodies are invariably restricted to regions of positive anomalies 2 87 sr 86 sr data where granites with 18 o values 18 o enriched plutons 9 have ratios 0 710 3 contrasting chemical and accessory mineral compositions in which many 18 o depleted granites have a number of i type characteristics whereas several of the most 18 o enriched plutons exhibit a number of s type features it can be inferred from these data that the 18 o enriched granites were formed from continental crustal protoliths that underlie much of the inner piedmont and portions of the kiokee belt whereas the low 18 o plutons were derived from more mafic sources beneath the charlotte slate and portions of the kiokee belt the overall correspondence between the regional 18 o 16 o patterns exhibited by the granites and gravity data implies that these grantes may be essentially rooted to their protoliths in turn suggesting that the large scale translational movement recently proposed for the southern piedmont may have occurred prior to intrusion of these granites 320 m y ago

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

video observations and model predictions of depth induced wave dissipation time averaged video observations of the nearshore zone show the process of wave breaking as one or more white alongshore bands of high intensity corresponding to the preferential location of breaking wave dissipation on one or more sandbars across a known depth profile similar bands of dissipation can be predicted with existing wave transformation models based on the wave energy balance this opens up possibilities for estimating bathymetry from video observations by processing observed intensities into a model predicted proxy of wave dissipation and the inverse modeling of this dissipation proxy into depth the objectives of this paper are 1 to present a technique for processing time averaged cross shore image intensity profiles into profiles that solely contain the contribution due to wave breaking and 2 to empirically determine which modeled wave dissipation proxy relates best to the cross shore shape of the obtained breaking induced intensity the processing technique involves the removal of background illumination and noise and most importantly a correction for white foam that after being generated in the breaking process remains floating at the water surface this foam thus contributes to high image intensities but is not predicted by wave transformation models based on video and bathymetric data collected at the double barred beach at egmond aan zee the netherlands and a standard wave transformation model containing the wave and roller energy balances we find that the modeled cross shore distribution of the dissipation of the energy of the surface roller the white aerated mass of water at the breaking wave front matches the observed cross shore shape of breaking induced intensity well other hypothesized dissipation proxies result in a larger 10 m seaward bias in the locations of maximum breaking induced intensity and model predicted dissipation or do not predict the cross shore change in the area below the breaking induced intensity bands correctly

long term automated monitoring of nearshore wave height from digital video this paper presents a new method for estimating nearshore wave height from a digital video sequence the method identifies main wave breaking zones in the video records and estimates the height of breaking waves inside the detected breaking zones a geometric rectification is applied to the resulting estimation to convert the height measurement from image pixels to meters the validation of the algorithm was undertaken over three months at surfers paradise australia the performance of the algorithm was demonstrated to be comparable with that of buoy measured wave height as well as manual estimates of the onshore wave height by a surf reporter the results indicate that the method can be used as a cost effective tool for long term monitoring of nearshore wave conditions

the spatial and temporal variability of sand bar morphology the spatial and temporal variability of nearshore sand bar morphology is quantified using a unique data set spanning 2 years the data consist of daily time exposure images of incident wave breaking on an open coast sandy beach which may be used to infer bar morphology lippmann and holman 1989 the morphology in each image is classified into an eight state morphologic scheme in which bars are uniquely defined by four independent criteria the most frequently observed morphologies are the longshore periodic rhythmic bars observed in 68 of the data linear bars occur under highest wave conditions h s 1 78 m and are unstable mean residence time 2 days shore attached rhythmic bars are the most stable mean residence time 11 days and generally form 5 16 days following peak wave events non rhythmic three dimensional bars are very transient mean residence time 3 days eighty seven percent of transitions to lower bar types defined in text occurred one state at a time supporting our selection of the ordering of states and suggesting the suitability of a sequential morphology model transitions to higher states occurred under rising wave energy and were evenly spread among the possible higher states with more substantial changes in morphology resulting from larger wave increases this suggests that up state erosional transitions based on offshore bar migration are better described by an equilibrium model where response is better correlated with incident wave energy than with preceding morphological state time exposure images were also digitized to yield quantitative estimates of bar crest location as a function of longshore distance principal component analysis was used to decompose bar position into two dimensional linear and three dimensional longshore variable components cross shore linear bar position ranges 50 m about the 2 year mean 27 m standard deviation and dominates bar variability 74 6 three dimensional bar structure accounts for 14 of the variance 12 m standard deviation changes in incident wave height precede cross shore bar migration by less than 1 day changes in longshore variability are inversely correlated to changing wave conditions with bar morphology becoming linear rapidly during storms on time scales of less than 1 day evolution to significantly three dimensional structure typically occurs over 5 7 days following peak wave events

paleomagnetism of certain constituents of the bay st george sub basin western newfoundland abstract paleomagnetic studies have been made of certain constituents of the bay st george sub basin specifically results are reported from the spout falls formation tournaisian the jeffreys village member of the robinsons river formation visean and the searston formation namurian westphalian the following magnetizations have been isolated spout falls a tournaisian with d 343 5 i 22 7 k 61 2 95 7 1 and the corresponding pole at 28 6 n 139 5 e 4 5 8 5 spout falls b kiaman with d 166 7 i 12 2 k 51 7 95 10 7 and the corresponding pole at 34 5 s 42 7 w 5 5 10 9 jeffreys village a visean with d 351 2 i 27 3 k 54 0 95 7 6 and the corresponding pole at 26 5 n 130 7 e 4 5 8 3 searston a namurian with d 161 7 i 11 7 k 107 95 7 4 and the corresponding pole at 33 9 s 37 2 w 3 8 7 5 and searston c with d 111 6 i 13 8 k 28 8 95 14 5 and the corresponding pole at 19 6 s 19 0 e 7 6 14 8 after comparison with paleopoles of similar ages derived from eastern and western newfoundland rocks from constituents of the east coast basin and for interior north america it is concluded that 1 it is unlikely that any large scale relative motion took place since the early carboniferous between eastern and western newfoundland 2 it is unlikely that any north south relative motion took place between the east coast basin and the bay st george sub basin and 3 the bay st george sub basin results do not support the earlier proposed displaced terrane hypothesis of the northern appalachians in as much as the motions during the carboniferous are not supported there is evidence of the northward motion of the appalachians and north america as a whole during the carboniferous the magnetostratigraphic horizon marker in the carboniferous separating a dominant normal and reversed magnetization on the older side and an entirely reversed kiaman magnetization on the younger side may be placed in the bay st george sub basin at the base of the searston formation

artificial neural network correction of remotely sensed sandbar location abstract this contribution details an accurate method for the remote sensing of submerged sandbar location through the application of an artificial neural network to video data lippmann and holman lippmann t c holman r a 1989 quantification of sandbar morphology a video technique based on wave dissipation j geophys res 94 c1 995 1011 have shown that the intensity maxima seen in time averaged video images of the nearshore zone provide a reasonable proxy for sandbar location however recent studies have indicated that there may be a large deviation up to 30 40 m between the measured bar position and predictions based on the intensity maximum in the cross shore direction these deviations occur largely due to modulations of the breakpoint by the tide and variations in the incident wave energy this paper utilises an artificial neural network to model the cross shore movement in the intensity maximum due to tides and waves the resulting signal is then removed from the video estimates to provide an accurate estimation of the sand bar location unique field data sets collected as part of the coast3d experiment are used to train and test the neural network model these data consist of simultaneous measurements of the nearshore bathymetry and video imagery of the double bar system at egmond aan zee the netherlands the resulting model yields accurate estimates of sandbar location with residual errors of less than 5 m for the outer bar and less than 10 m for the inner bar the artificial neural network model is utilised to extend the bathymetric data set for egmond aan zee for times when wave conditions were too large to allow physical measurement

magnetic anisotropy in the trenton limestone results of a new technique anisotropy of anhysteretic susceptibility a new method for determining magnetic anisotropy using anhysteric remanence susceptibility is described the magnetic fabric of a collection of trenton limestone specimens has been determined using this method as well as by conventional anisotropy of magnetic susceptibility the results demonstrate the usefulness of the new method for finding the magnetic fabric of rock units such as the trenton in which the bulk magnetic susceptibilities are low a model is proposed to explain the observed foliated and lineated fabric as a consequence of overburden compaction and regional horizontal stresses the original fabric is inferred to have been isotropic the anisotropy resides in secondary magnetite of late paleozoic age it is argued that the observed magnetic fabric must therefore be alleghenian or younger in age our method has the potential to determine paleostress directions in carbonates elsewhere provided our assumptions are correct

correlation of magnetitic susceptibility with18o 16o data in late orogenic granites of the southern appalachian piedmont initial magnetic susceptibility generally indicative of magnetite content has been determined for 445 samples from 17 granites located in the southern appalachian piedmont of georgia and south carolina these values have been correlated with whole rock 18o data from the same plutons yielding a pronounced inverse relationship it has previously been shown for the southern piedmont that low oxygen isotopic 18o enriched values usually occur in s type granites wenner 1 this issue it follows then that i type granites are characterized by high susceptibilities 1 10 4 g oe and s type granites by low susceptibilities 1 10 4 g oe an interesting result of this work has been the observation that some s type granites exhibit good within site clusters of remanent magnetic directions while i type granites generally do not

morphodynamics of intermediate beaches a video imaging and numerical modelling study four years of time exposure images of palm beach sydney australia are used to a develop a phenomenological scheme based on surf zone properties for the classification of the four intermediate beach states low tide terrace ltt transverse bar rip tbr rhythmic bar beach rbb and longshore bar trough lbt identified by wright l d short a d 1984 morphodynamic variability of surf zones and beaches marine geology 56 93 118 and b determine environmental conditions associated with the different beach states the overall agreement between beach state classifications obtained by visual classifications of images and those predicted by the phenomenological scheme exceeds 90 analysis of time series of intermediate beach states and wave data indicates that the nearshore morphology continuously cycles through the four beach states in response to variations in the incident wave energy the results also indicate that lbt morphology is produced by high energy wave conditions erosive while the progression towards ltt occurs under lower waves accretive a depth averaged morphodynamic model is employed to determine the morphodynamic processes governing the rbb to tbr and tbr to ltt transitions model results indicate that the rbb to tbr transition is governed by the erosion of the original longshore bars in the initial rbb morphology and the formation and subsequent welding of shoals in the lee of the original longshore bars model results also indicate that rbb to tbr transitions can occur under shore normal and oblique wave conditions the tbr to ltt model simulations indicate that under obliquely incident waves progressive erosion of the transverse shoals and deposition of the eroded sediment in rip channels gradually diminishes the longshore variability in morphology resulting in an ltt morphology

anisotropy of magnetic susceptibility sedimentological igneous and structural tectonic applications as was noted by graham 1954 anisotropy of magnetic susceptibility ams data has many applications to the study of geological processes this type of anisotropy expresses directional variation in the magnetization induced in a rock most notably in its iron oxides and especially in its magnetite and hematite the ams is commonly expressed by an ellipsoid of which the principal axes are k1 k2 and k3 from greatest to least this ellipsoid is generally interpreted in terms of the distribution and shape of grains of magnetic minerals in a rock although the ellipsoid determined depends also on magnetocrystalline anisotropy and on factors of instrumental technique ellwood et al in press 1987 the challenge for the geoscientist in analyzing ams data is first to identify the origin of the ams geometry then second to relate that geometry to the natural processes which produced the inferred or measured distribution of magnetic materials

modeling olivine cpo evolution with complex deformation histories implications for the interpretation of seismic anisotropy in the mantle relating seismic anisotropy to mantle flow requires detailed understanding of the development and evolution of olivine crystallographic preferred orientation cpo recent experimental and field studies have shown that olivine cpo evolution depends strongly on the integrated deformation history which may lead to differences in how the corresponding seismic anisotropy should be interpreted in this study two widely used numerical models for cpo evolution d rex and vpsc are evaluated to further examine the effect of deformation history on olivine texture and seismic anisotropy building on previous experimental work models are initiated with several different cpos to simulate unique deformation histories significantly models initiated with a preexisting cpo evolve differently than the cpos generated without preexisting texture moreover the cpo in each model evolves differently as a function of strain numerical simulations are compared to laboratory experiments by boneh and skemer 2014 in general the d rex and vpsc models are able to reproduce the experimentally observed cpos although the models significantly over estimate the strength of the cpo and in some instances produce different cpo from what is observed experimentally based on comparison with experiments recommended parameters for d rex are m 10 5 and 0 3 and for vpsc 10 100 numerical modeling confirms that cpo evolution in olivine is highly sensitive to the details of the initial cpo even at strains greater than 2 these observations imply that there is a long transient interval of cpo realignment which must be considered carefully in the modeling or interpretation of seismic anisotropy in complex tectonic settings

estimates of flow direction for calc alkaline welded tuffs and paleomagnetic data reliability from anisotropy of magnetic susceptibility measurements central san juan mountains southwest colorado abstract flow directions are estimated from the measurement of the magnetic fabric of 106 samples collected at 18 sites in four welded tuff units in the central san juan mountains of southern colorado the estimates assume that the tuffs generally flowed directly away from the extrusive vents and that the lineations of magnetic grains within the tuffs represent the flow direction at individual sites errors in the estimation may arise from topographic variation rheomorphism post emplacement mass flow within the tuff and other factors magnetic lineation is defined as the site mean anisotropy of magnetic susceptibility maximum azimuth a test on the flow directions for individual units is based on the projection of lineation azimuths and their intersection within or near the known source caldera for the tuff this test is positive for the four units examined paleomagnetic results for these tuffs are probably reliable indicators of the geomagnetic field direction in southwest colorado during the time 28 2 26 5 ma of emplacement

estimation of wave phase speed and nearshore bathymetry from video imagery a new remote sensing technique based on video image processing has been developed for the estimation of nearshore bathymetry the shoreward propagation of waves is measured using pixel intensity time series collected at a cross shore array of locations using remotely operated video cameras the incident band is identified and the cross spectral matrix is calculated for this band the cross shore component of wavenumber is found as the gradient in phase of the first complex empirical orthogonal function of this matrix water depth is then inferred from linear wave theory s dispersion relationship full bathymetry maps may be measured by collecting data in a large array composed of both cross shore and longshore lines data are collected hourly throughout the day and a stable daily estimate of bathymetry is calculated from the median of the hourly estimates the technique was tested using 30 days of hourly data collected at the sandyduck experiment in duck north carolina in october 1997 errors calculated as the difference between estimated depth and ground truth data show a mean bias of 35 cm rms error 91 cm expressed as a fraction of the true water depth the mean percent error was 13 rms error 34 excluding the region of known wave nonlinearities over the bar crest the accuracy of the technique improved and the mean rms error was 20 cm 75 cm additionally under low amplitude swells wave height h 1 m the performance of the technique across the entire profile improved to 6 29 of the true water depth with a mean rms error of 12 cm 71 cm

non linear principal component analysis of nearshore bathymetry spatially and temporally extensive nearshore bathymetric datasets have recently been analyzed with complex principal component analysis cpca to extract propagating spatial patterns that constitute most to the dominant lower dimensional structure in the datasets cpca assumes this structure to be linear which may be an oversimplification of the true structure as the nearshore is a strongly non linear system here we investigate whether a neural network based circular non linear principal component analysis nlpca cir provides a more representative approximation of the underlying lower dimensional structure of nearshore depth data than possible with cpca to that end nlpca cir was applied to three datasets characterized by interannual offshore directed sandbar behavior coming from egmond the netherlands hasaki coast japan and duck north carolina usa the main difference between these datasets is the temporal variation in sandbar amplitude which is smallest at egmond and largest at duck we find that the first nlpca cir mode 1 at egmond and hasaki leads to a more complete characterization of the lower dimensional data structure than possible with cpca i e the underlying low dimensional structure of bathymetric data at egmond and hasaki is indeed non linear this is not the case at duck where the temporal variations in sandbar amplitude are so large that the non linear lower dimensional structure in the data should it exist is no longer visually apparent and can no longer be detected by nlpca cir this suggests that a simple visual check of the data suffices to decide whether one should resort to nlpca cir or to the more simple and computationally quicker cpca

short term changes in the morphodynamic states of beaches and surf zones an empirical predictive model a time series of 6 5 years of daily observations of beach states and wave characteristics from southeastern australia was analyzed with the aim of determining the degree to which time varying beach state can be explained and predicted the six commonly occurring beach states dissipative longshore bar trough rhythmic bar and beach transverse bar and rip low tide terrace and reflective discussed earlier were related by means of discrete discriminant analyses to the parameter hb wst where hb is breaker height ws is the fall velocity of the beach sand and t is peak breaker period using a total of 1545 cases two values were used in the analyses the immediate value occurring on the day the particular state was observed and a weighted mean value expressing recently antecedent conditions the immediate value made a negligible contribution to explaining day to day beach state observations however the antecedent conditions showed a strong relationship and provide a successful means of prediction by examining cases where the time derivatives of both state and were near zero it was possible to define the equilibrium conditions associated with each state directions of change erosional or accretionary are predicted in terms of departures of from the equilibrium value appropriate to the beach state prevailing at the time change begins