flow directions in dikes from anisotropy of magnetic susceptibility data the bootstrap way one of the first applications of anisotropy of magnetic susceptibility ams was an attempt to determine flow directions from mafic dikes khan 1962 since the seminal work of knight and walker 1988 defining the expected behavior of ams in response to magma flow there has been increasing interest in using ams for this purpose here we present a quantitative method for interpretation of ams data from dikes using a parametric bootstrap first dikes must be sampled with at least five and preferrably more samples from within 10 cm of the dike margin the distributions of the eigenvalues and eigenvectors of the ams tensor are delineated by calculating eigenparameters of many bootstrapped paradata sets we generate paradata sets by first selecting a sample at random then calculating a replacement set of data by drawing tensor elements from normal distributions with the mean and standard deviation of the entire site the bounds containing 95 of the eigenparameters of the bootstrapped data serve as confidence limits for the parameter of interest classification of dikes proceeds as follows sites whose maximum and intermediate eigenvalues could not be distinguished are deemed uninterpretable in addition sites with principal eigenvectors with angles 45 away from the dike margin inverse or with markedly different directions on either side of the dike scissored are excluded the remaining dikes are classified as having unique flow direction information if the principal eigenvectors from at least one side are distinct from the dike plane based on the distribution of the bootstrapped principal eigenvectors if neither side has principal eigenvectors distinct from the dike plane the dikes are classified as having lineation information only a study comprising 251 dikes from the troodos ophiolite has 151 sites with directional data 38 sites with lineations only 7 inverse sites 5 scissored sites and 55 sites not fitting into any other category the flow directions interpreted from the data were generally southerly toward a fossil transform zone

multiple tectonic rotations and transform tectonism in an intraoceanic suture zone sw cyprus abstract new palaeomagnetic data from the late cretaceous neotethyan troodos ophiolite and related units in sw cyprus provide compelling evidence that transform tectonism is recorded outside the main outcrop of the fossil southern troodos transform fault zone sttfz high level intrusive and extrusive sequences were sampled along the sw margin of the troodos massif and in ophiolitic slivers preserved along arcuate fault lineaments further to the south and west these units show cross cutting relationships with corresponding differences in remanent magnetisation directions characteristic of syn magmatic rotation in an active transform setting net tectonic rotation analyses allow decomposition of the total rotation at these sites into early and late components early transform related rotations are consistently clockwise in agreement with all other studies of rotations associated with the sttfz further to the east late rotations and the net rotations derived at localities where cross cutting relationships were not present are regarded as composite in origin the composite rotation axes closely relate to the orientation of observed regional structures in these circumstances additional constraints are used to attempt geologically viable interpretations the overall distribution of transform related rotations steeply and shallowly plunging rotation axes and spreading axis related rotations sub horizontal rotation axes is comparable with that along the sttfz and adjacent parts of the troodos massif this is most readily explained by simple along strike extension of the primary spreading axis and transform fabrics into sw cyprus with minor late disruption by high angle dextral shear zones and neotectonic graben systems

spreading structure of the troodos ophiolite cyprus some paleomagnetic constraints it has been suggested that grabens on the northern flank of the troodos ophiolite formed by listric faulting in an oceanic environment and represent axial valleys fossilized by ridge jumping this paleomagnetic survey of the solea graben was carried out to constrain the structural interpretation an analysis was devised which restores both the dikes sampled to vertical and the primary remanent magnetizations to a previously derived structurally corrected remanent magnetization direction typically two solutions for the original dike orientation and the pole and angle of net rotation are obtained for each dike sampled these solutions can be separated if a locally consistent original dike strike is assumed reasons are discussed for the selection of the solution that gives an original northwesterly dike strike results are consistent with a graben rotations are up to 78 at the sites studied rotation vectors are subhorizontal and subparallel to the original dike strike suggestive of an axial process for the development of the structure however on the basis of field observations an alternative mode of origin is proposed invoking ephemeral extreme upper crustal extension by listric faulting on the west flank of an intermediate to fast spreading axis the grabens being formed by antithetic faulting

spreading structure of the troodos ophiolite cyprus orientations of dikes within the sheeted dike complex of the troodos ophiolite reveal primary spreading structure produced at a complex ridge transform intersection three structural grabens are defined by listric and planar normal faults and rotated dikes that dip symmetrically toward graben axes faults flatten at depth into a detachment within the upper parts of the plutonic complex large exhalative massive sulfide deposits occur within the pillow sections of two of the grabens and appear to be associated with underlying altered and mineralized normal fault zones that channeled hydrothermal fluids we suggest that the grabens are fossil axial valleys produced by successive eastward jumps of an approximately north trending present coordinates slow spreading ridge crest a simple model for ridge migration indicates eastward jumps of 8 13 km changes in ridge orientation are suggested by changes in trends of dikes and graben axes comparison of the pattern of dikes near the arakapas fault zone with the structure of active ridge transform intersections suggests that the fault is a right offset sinistral transform in contrast to earlier models in which a ridge to the west of the exposed troodos complex was proposed

comments on a revisit of drawdown behavior during pumping in unconfined aquifers by d mao l wan t c j yeh c h lee k c hsu j c wen and w lu

paleomagnetism carried by crystal inclusions the effect of preferred crystallographic orientation abstract randomly oriented phlogopite crystals from a pegmatite contain submicroscopic inclusions of magnetite the inclusions have oblate magnetic fabrics subparallel to the ab crystal plane alternating field demagnetization of individual crystals shows that the remanence is influenced by the crystal symmetry of the phlogopite host the magnetizations isolated by alternating field demagnetization either cluster close to the a axis or scatter in the ab plane coarse grained igneous and metamorphic rocks can only record a paleofield direction accurately if there is a suitable orientation distribution of the rock forming minerals that host the ferromagnets an isotropic distribution of rock forming minerals is preferable but it is not obligatory rock forming minerals that have l fabrics or s fabrics with a strong l component are also suitable if they contain oblate inclusion fabrics of ferromagnets

time dependent onshore tsunami response abstract while bulk measures of the onshore impact of a tsunami including the maximum run up elevation and inundation distance are important for hazard planning the temporal evolution of the onshore flow dynamics likely controls the extent of the onshore destruction and the erosion and deposition of sediment that occurs however the time varying dynamics of actual tsunamis are even more difficult to measure in situ than the bulk parameters here a numerical model based on the non linear shallow water equations is used to examine the effects variations in the wave characteristics bed slope and bottom roughness have on the temporal evolution of the onshore flow model results indicate that the onshore flow dynamics vary significantly over the parameter space examined for example the flow dynamics over steep smooth morphologies tend to be temporally symmetric with similar magnitude velocities generated during the run up and run down phases of inundation conversely on shallow rough onshore topographies the flow dynamics tend to be temporally skewed toward the run down phase of inundation with the magnitude of the flow velocities during run up and run down being significantly different furthermore for near breaking tsunami waves inundating over steep topography the flow velocity tends to accelerate almost instantaneously to a maximum and then decrease monotonically conversely when very long waves inundate over shallow topography the flow accelerates more slowly and can remain steady for a period of time before beginning to decelerate these results indicate that a single set of assumptions concerning the onshore flow dynamics cannot be applied to all tsunamis and site specific analyses may be required

numerical study of vegetation damping effects on solitary wave run up using the nonlinear shallow water equations abstract vegetation damping effects on propagating water waves have been investigated by many researchers this paper investigates the effects of damping due to vegetation on solitary water wave run up via numerical simulation the numerical model is based on an implementation of morison s formulation for vegetation induced inertia and drag stresses in the nonlinear shallow water equations the numerical model is solved via a finite volume method on a cartesian cut cell mesh the accuracy of the numerical scheme and the effects of the vegetation terms in the present model are validated by comparison with experiment results the model is then applied to simulate a solitary wave propagating on a plane slope with vegetation the sensitivity of solitary wave run up to plant height diameter and stem density is investigated by comparison of the numerical results for different patterns of vegetation the numerical results show that vegetation can effectively reduce solitary wave propagation velocity and that solitary wave run up is decreased with increase of plant height in water and also diameter and stem density

separating multidomain and single domain like remanences in pseudo single domain magnetites 215 540 nm by low temperature demagnetization it has long been hypothesized that the pseudo single domain properties of submicron magnetites are a result of coexisting multidomain and single domain like remanences we have separated these two types of remanence by low temperature demagnetization ltd in which samples are cooled through the low temperature magnetite isotropic point and rewarmed to room temperature all in zero field at the isotropic point the first crystalline anisotropy constant vanishes and multidomain remanence due to displaced domain walls will be unpinned we measured stepwise alternating field af and thermal demagnetization curves of weak field thermoremanent magnetization trm and anhysteretic remanent magnetization and of saturation isothermal remanent magnetization irms both with and without prior ltd for magnetites with mean particle sizes of 215 390 and 540 nm the memory fraction of remanence recovered after ltd which represents the single domain like component decreased from 44 for 215 nm grains to 23 for 540 nm grains in the case of irms memory of trm was approximately twice as large af decay curves were soft and multidomain like before ltd but became harder and single domain like in shape after ltd ltd removed most low unblocking temperature trm and irms distributed low unblocking temperatures are therefore a multidomain phenomenon probably resulting from successive adjustments of domain walls to changing internal fields and pinning strengths during heating

dike surface lineations as magma flow indicators within the sheeted dike complex of the troodos ophiolite cyprus mesoscopic flow lineations and anisotropy of magnetic susceptibility ams have been measured for dikes within the cretaceous age troodos ophiolite with the goal of comparing the direction of initial magma flow through dike conduits immediately following crack propagation with that of flow of subsequent magma emplaced during later stages of dike growth dike margin indicators of flow include cusp axes and elongate vesicles found high in the ophiolite pseudostratigraphy and ridge and groove structures termed hot slickenlines found throughout the complex a unique flow direction is determined where elongate vesicles near dike margins display imbrication with respect to the margin significant changes in vesicle elongation directions across dikes likely indicate either changes in magma flow direction after dike propagation or back flow of magma during the waning stages of intrusion surface lineations generally lie subparallel to the direction of flow inferred from ams determinations on cores within 5 cm of dike margins surface lineations also lie subparallel to the long axis e1 of the orientation ellipsoid defined by long axes of groundmass plagioclase phenocrysts measured in sections from ams cores correlation of surface lineations with interior indicators of flow ams plagioclase trachytic texture indicate that the surface features are good proxies for grain scale magma flow directions during dike propagation in troodos dikes orientations of surface flow features in the dikes of the troodos ophiolite indicate an approximately equal mix of subhorizontal to near vertical magma flow contradicting the paradigm of primarily vertical flow of magma beneath continuous axial magma chambers at oceanic spreading centers our data are consistent with a model of magma emplacement both vertically and horizontally away from isolated magma chambers beneath axial volcanoes spaced along a ridge crest

shallow intrusive directions of sheeted dikes in the troodos ophiolite anisotropy of magnetic susceptibility and structural data sheeted dikes play a central role in the formation of oceanic crust it is commonly assumed that sheeted dikes intrude vertically upward from elongated mid ocean ridge mor magma chambers but there are no direct observational data bearing on this hypothesis this assumption contrasts with the intrusive behavior of subaerial volcanoes where magmas rise into shallow central magma chambers that laterally feed vertically oriented dikes the authors have studied intrusive directions of sheeted dikes in a structural analogue to oceanic crust the troodos ophiolite structural and magnetic fabric data of 65 dikes provide consistent results and suggest a broad distribution of shallow 20 degree to nearly vertical upward magma transport directions these data suggest that horizontal emplacement has to be considered for sheeted dikes at mors implying more centralized mor plumbing systems than previously thought such plumbing systems provide ample opportunity for complex mixing fractionation and contamination of mor lavas in magma chambers and tabular magma storage volumes whether the mor magma supply is linear or centralized also has a fundamental effect on crustal accretion processes and the geometry of hydrothermal convection systems

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

magnetic studies of magma supply and sea floor metamorphism troodos ophiolite dikes abstract dikes of the eastern troodos ophiolite of cyprus intruded at slow ocean spreading axes with dips ranging up to 15 from vertical and with bimodal strikes now ne sw and n s due to post 88 ma sinistral microplate rotation varied dike orientations may represent local stress fields during dike crack propagation but do not influence the spatial distributions or orientation distributions of dikes magnetic fabrics nor of their palaeomagnetic signals anisotropy of magnetic susceptibility ams integrates mineral orientation distributions from each of 1289 specimens sampled from dikes at 356 sites over 400 km2 in the eastern troodos ophiolite of cyprus in 90 of dikes ams fabrics define a foliation kmax kint parallel to dike walls and a lineation kmax that varies regionally and systematically magma flow alignment of accessory magnetite controls the ams with a subordinate contribution from the mafic silicate matrix that is reduced in anisotropy by sea floor metamorphism titanomagnetite has less influence on anisotropy occasionally intermediate and minimum susceptibility axes are switched so as to be incompatible with the kinematically reasonable flow plane but maximum susceptibility kmax still defines the magmatic flow axis such blended subfabrics of kinematically compatible mafic silicate and misaligned multidomain magnetite subfabrics are rare areas of steep magma flow kmax plunge 70 and of shallow magma flow alternate in a systematic and gradual spatial pattern foci of steep flow were spaced 4 km parallel to the spreading axes and 6 km perpendicular to the spreading axes ridge parallel separation of steep flow suggest the spacing of magma feeders to the dikes whereas ridge perpendicular spacing of 6 km at a spreading rate of 50 mm a implies the magma sources may have been active for 240 ka the magma feeders feeding dikes may have been 2 km in diameter stable paleomagnetic vectors in some cases verified by reversal tests are retained by magnetite and titanomagnetite in all specimens the stable components were isolated by three cycles of low temperature demagnetization ltd followed by 10 steps of incremental thermal demagnetization td 47 of primary a components 338 2 57 2 n 207 95 3 9 mean tub 397 8 c are overprinted by a b component 341 4 63 5 n 96 95 8 7 mean tub 182 11 c a and b components are ubiquitous and shared equally by the n s and ne sw striking dikes a component unblocking temperatures tub are zoned subparallel to the fossil spreading axis their spatial pattern is consistent with chemical remagnetization at some certain off axis distance determined by sea floor spreading a components indicate less microplate rotation and more northerly palaeolatitudes that are consistent with metamorphic remagnetization after some spreading from the ridge axis thus their magnetizations are younger than those of the overlying volcanic sequence for which chrms are commonly reported as 274 33 88 ma

numerical study of periodic long wave run up on a rigid vegetation sloping beach abstract coastal vegetation can reduce long wave run up on beaches and inland propagation distances and thus mitigate these hazards this paper investigates periodic long wave run up on coastal rigid vegetation sloping beaches via a numerical study rigid vegetation is approximated as rigid sticks and the numerical model is based on an implementation of morison s formulation 21 for rigid structures induced inertia and drag stresses in the nonlinear shallow water equations the numerical model is solved via a finite volume method on a cartesian cut cell mesh the accuracy of the numerical model is validated by comparison with experimental results the model is then applied to simulate various hypothetical cases of long periodic wave run up on a sloping vegetated beach with different plant diameters and densities and incident long waves with different periods the sensitivity of long wave run up to plant diameter stem density and wave period is investigated by comparison of the numerical results for different vegetation characteristics and different wave periods the numerical results show that rigid vegetation can effectively reduce long wave run up and that wave run up is decreased with increase of plant diameter and stem density moreover the attenuation of long periodic wave run up due to vegetation is sensitive to the variation of the incident wave period and the attenuation of wave run up is not increased or decreased monotonically with incident wave period

paleomagnetic arguments for block rotations along the arakapas fault cyprus paleomagnetic data from the sheeted dike complex north of the arakapas fault reveal significant internal rotations the north south trending dikes have remanent magnetization directions close to the well known westerly paleomagnetic direction of the troodos massif whereas the east west trending dikes near the arakapas fault have northerly remanent magnetization directions the paleomagnetic data are in agreement with the apparent clockwise rotation of the dikes contrary to recent geological analyses which postulate that the pattern of dike trends is due to dike injection into a sigmoidal stress field along a sinistral transform fault the paleomagnetic results indicate clockwise rotations about vertical axes in response to a dextral shear in addition to the rotations around vertical axes small rotations around subhorizontal axes are inferred from the paleomagnetic data for tilted dikes thus these data reinforce the vertical intrusion hypothesis

vertical distribution and alteration of dikes in a profile through the troodos ophiolite in situ oceanic crust at intermediate depths of from one to five km is presently largely inaccessible to continuous examination and sampling except in the possibly special circumstances of major transform faults the study of ophiolites over this interval where thin sub vertical dikes are usually important may provide guidance to the nature of in situ oceanic crust at these depths the likelihood that similarities exist between in situ and ophiolitic oceanic crust has recently been strengthened by the possible identification of a dike complex below 0 8 km depth in dsdp hole 504b1 sub vertical basic dikes occur over a 4 6 km depth interval from 0 2 to 4 8 km crustal depth in a profile through the troodos cyprus ophiolite exponential growth and arctangent decay in dike density occur over 2 3 km and 1 0 km intervals respectively secondary magnetite is the dominant dike magnetic material of the dikes and associated screens these results have implications for the construction alteration history and magnetization of in situ oceanic crust at intermediate depths

paleomagnetic constraints on the formation of the solea graben troodos ophiolite cyprus abstract the solea graben on the northern flank of the troodos ophiolite cyprus is a 15 20 km wide asymmetric structure primarily defined by dike attitudes in the sheeted dike complex the wider western portion of the graben consists mainly of gently dipping dikes while the eastern portion is narrow and consists of blocks of dikes with widely varying attitudes using a method which restores the sampled dikes to vertical and the primary remanent magnetizations to a previously known stable remanent magnetization direction for the troodos complex we have calculated rotation axes and amounts of rotation for the dikes the rotation axes for dikes in the western portion of the solea graben are subhorizontal and subparallel to the original strikes of the dikes in the eastern portion the rotation axes have varying attitudes including some which are very steep our results are consistent with field observations that suggest that the western solea graben formed by listric normal faulting near the axis of a spreading center with rotation of the dikes above a detachment surface across the graben axis on the eastern portion more intense intrusive activity and minor normal faulting resulted in less rotation about subhorizontal axes and some rotations about vertical axes

surface water waves over a shallow canopy the dynamics of water waves passing over a vegetation canopy is modelled theoretically to simplify the geometry we examine a periodic array of vertical cylinders fixed on a slowly varying seabed the macroscale behaviour of wave attenuation is predicted based on microscale dynamics between plants interstitial turbulence is modelled by reynolds equations with a locally constant eddy viscosity determined by energy considerations using the asymptotic method of multiple scale expansions the slow evolution of waves is derived by considering the coupling with the small scale motion in the canopy after numerical solution of the canonical boundary value problem in a few unit cells predictions of macroscale effects such as wave attenuation are made and compared with laboratory experiments the counteracting effects of shoaling and dissipation are discussed for different vegetation densities

efficient computation of surf zone waves using the nonlinear shallow water equations with non hydrostatic pressure abstract a numerical method for non hydrostatic free surface irrotational flow governed by the nonlinear shallow water equations including the effects of vertical acceleration is presented at the aim of studying surf zone phenomena a vertical boundary fitted grid is used with the water depth divided into a number of layers a compact finite difference scheme is employed for accurate computation of frequency dispersion requiring a limited vertical resolution and hence capable of predicting the onset of wave breaking a novel wet dry algorithm is applied for a proper handling of moving shoreline mass and momentum are strictly conserved at discrete level while the method only dissipates energy in the case of wave breaking the numerical results are verified with a number of tests and show that the proposed model using two layers without ad hoc assumptions enables to resolve propagating nonlinear shoaling breaking waves and wave run up within the surf and swash zones in an efficient manner

tectonics of the akamas and mamonia ophiolites western cyprus magnetic petrofabrics and paleomagnetism abstract the akamas ophiolite is shown to be a distal off axis extension of the main outcrop of cretaceous ophiolite in the troodos complex of cyprus mantle sequence harzburgites of both ophiolites share similarly oriented mantle flow fabrics and the same tertiary magnetizations acquired during exhumation however compared with the troodos mantle sequence rocks the akamas ferromagnetic mineralogy is more oxidized and remanences with lower blocking temperatures were acquired chemically paleopoles calculated from published vectors and our own new data define an apparent polar wander path apwp for the troodos microplate the apwp shows that between 88 and 50 ma the troodos microplate was equatorial and the vertical axis for its 60 anticlockwise rotation was located within the microplate subsequently the microplate drifted northward to 34 n with minor anticlockwise rotation at a reduced rate that requires microplate rotation about a vertical axis located to the west of cyprus in the last 50 ma the allochthonous triassic mamonia terrane docked with the cretaceous troodos terrane in sw cyprus within it disrupted tectonized ophiolite has been regarded as part of a triassic ocean floor or as sheared fragments of cretaceous troodos ophiolite incorporated into the mamonia terrane when it docked with the troodos terrane whatever their provenance their paleomagnetic signals postdate their penetrative deformation and metamorphism and their paleopoles may still be used to track their post strain motion our calculations of paleopoles from published vectors for the mamonia terrane smear along an extension of the apwp for the troodos microplate that is moreover concentric with the troodos microplate this suggests that the paleopole dispersion of the triassic mamonia rocks and their post magnetization disruption occurred during their accretion onto the anticlockwise spinning troodos microplate

anisotropy of magnetic remanence a brief review of mineralogical sources physical origins and geological applications and comparison with susceptibility anisotropy the magnetic fabric of rocks and sediments is most commonly characterized in terms of the anisotropy of low field magnetic susceptibility ams however alternative methods based on remanent magnetization measured in the absence of a magnetic field rather than induced magnetization measured in the applied field have distinct advantages for certain geological applications this is particularly true for 1 adjunct studies in paleomagnetism in order to assess the fidelity with which a natural remanence records the paleofield orientation 2 studies of weakly magnetic or weakly deformed rocks for which susceptibility anisotropy is very difficult to measure precisely and 3 quantitative applications such as strain estimation the fundamental differences between susceptibility and remanence and their respective anisotropies are due to several factors 1 susceptibility arises from all of the minerals present in a sample whereas remanence is carried exclusively by a relatively small number of ferromagnetic minerals 2 ferromagnetic minerals are generally more anisotropic than para and diamagnetic minerals 3 for ferromagnetic minerals remanence is inevitably more anisotropic than susceptibility and 4 a number of common minerals including single domain magnetites possess an inverse anisotropy of susceptibility i e they tend to have minimum susceptibility parallel to the long axis of an individual particle remanence is immune to this phenomenon as a consequence of all these factors remanence anisotropy may generally provide a better quantitative estimate of the actual distribution of particle orientations in a rock sample

the run up of nonbreaking and breaking solitary waves abstract the run up of nonbreaking and breaking solitary waves on plane impermeable beaches is investigated with a lagrangian finite element boussinesq wave model wave breaking is parameterized with an artificial viscosity diffusion term in the momentum equation and bottom friction is modelled with a term quadratic in the horizontal fluid velocity comparisons are presented with laboratory data of maximum run up shoreline motion and spatial profiles of near shore free surface elevation for both steep 20 and gradual 2 88 slopes for the steep slope only waves which do not break on run up are considered and excellent agreement is obtained with the laboratory data for the gradual slope wave shoaling breaking bore formation and subsequent collapse at the shoreline are predicted well by the model although the breaking algorithm does not attempt to model the details of the turbulent flow in the breaking region the backwash bore is also modelled reasonably well although it persists longer in the numerical computations than in the laboratory data it is shown that the inclusion of nonhydrostatic effects reduces the tendency of waves to break and improves the agreement of the numerical results with the laboratory run up data this allows higher amplitude waves to be modelled and larger propagation distances to be treated without the need to limit the wave steepness with artificial dissipation

numerical model for coastal wave propagation through mild slope zone in the presence of rigid vegetation abstract the study of wave propagation on coastal vegetation field is fundamental to assessing the effectiveness and limitations of vegetation in coastal protection this paper presents a refraction diffraction wave model for the investigation of wave propagation through a coastal mild slope zone in the presence of rigid vegetation via numerical simulation the model is based on the implementation of a module for vegetation induced wave energy dissipation in the parabolic mild slope equation the model is capable of simulating both wave refraction and diffraction and economical in computation and may bridge the gap between the wave energy spectrum and the phase resolved models for wave propagation through coastal vegetation fields the model is validated through by comparison with experimental results the model is subsequently applied to a simulation of a wave propagating on a plane in the presence of different patterns of rigid vegetation the sensitivity of the wave height to the plant height the diameter and the stem density is investigated by comparison of the numerical results for wave height attenuation that results from different patterns of rigid vegetation the numerical results show that wave height attenuation due to rigid vegetation has a higher variability for the different rigid plant conditions and that the attenuation of the wave height due to the rigid vegetation increases alongside the plant height under water as well as the diameter and plant stem density the results further indicate that for wave propagates through coastal rigid vegetation zones with a high plant height under water large diameter and high stem density the wave height along the propagating direction is decreased nonlinearly with the increase of the wave propagating distance and nonlinearity is more obvious for the plant with a higher height under water as well as a larger diameter and higher stem density

tsunami run up and draw down on a plane beach tsunami run up and draw down motions on a uniformly sloping beach are evaluated based on fully nonlinear shallow water wave theory the nonlinear equations of mass conservation and linear momentum are first transformed to a single linear hyperbolic equation to solve the problem with arbitrary initial conditions we apply the fourier bessel transform and inversion of the transform leads to the green function representation the solutions in the physical time and space domains are then obtained by numerical integration with this semi analytic solution technique several examples of tsunami run up and draw down motions are presented in particular detailed shoreline motion velocity field and inundation depth on the shore are closely examined it was found that the maximum flow velocity occurs at the moving shoreline and the maximum momentum flux occurs in the vicinity of the extreme draw down location the direction of both the maximum flow velocity and the maximum momentum flux depend on the initial waveform it is in the inshore direction when the initial waveform is predominantly depression and in the offshore direction when the initial waves have a dominant elevation characteristic

structure of a fossil ridge transform intersection in the troodos ophiolite recent palaeomagnetic studies of sheeted dykes adjacent to the east west trending southern troodos transform fault of cyprus have demonstrated significant clockwise block rotations which are most easily interpreted as being due to drag induced by dextral strike slip faulting along the transform1 6 we show here that such rotations have not occurred along the entire length of the transform instead to the west of the areas previously studied the sheeted dykes have been subjected to simple tilting only indicating normal faulting but no strike slip the changeover between these two domains of differing structural styles near the village of mandria is approximately in line with the centre of the solea graben a north south trending structure within the troodos massif which has previously been interpreted as a fossil ridge axis7 we suggest that the mandria area represents a fossilized ridge transform intersection and present the results of a detailed field investigation of the area together with preliminary palaeomagnetic data to determine the relationship between tectonism and magmatism at such plate boundary zones we use our findings to test a recent theoretical model8 of deformation processes at ridge transform intersections and show that distributed deformation due to block rotation is largely confined to the ridge transform corner itself

magnetic anisotropy of some phyllosilicates magnetic susceptibility anisotropy of susceptibility and hysteresis of single microcrystals of chlorite biotite phlogopite muscovite zinnwaldite and fuchsite were measured in low and high magnetic fields with an alternating gradient force magnetometer micromag their properties are sufficient to account for the low field susceptibility ams of most micaceous rocks nearly all samples show some ferromagnetic contribution at low fields due to inclusions of pseudosingle domain and multidomain magnetite the paramagnetic contribution isolated at high fields usually exceeds the ferromagnetic contribution the paramagnetic susceptibility is intrinsic to the silicate lattice and agrees with values predicted from chemical composition within the limits of error the minimum susceptibility is nearly parallel to c another axis is parallel to b and the third susceptibility usually the maximum is close to a the paramagnetic susceptibility has a disk shaped magnitude ellipsoid with strong anisotropy p 2 the ferromagnetic contributions at low fields have more variably shaped ellipsoids with greater eccentricity p 5 the silicate lattice does not constrain their orientation our technique cannot determine the principal axes of the ferromagnetic component however its principal values usually correspond with the paramagnetic principal susceptibilities in order of magnitude thus the combined paramagnetic ferromagnetic anisotropy recognised in routine studies of ams should faithfully represent the petrofabric of most micaceous rocks nevertheless nearly 10 of our samples have incompatible anisotropy ellipsoids for the silicate host and magnetite inclusions these yield a net inverse ams that does not correctly represent the orientation of the silicate lattice therefore some caution is necessary in petrofabric ams studies of micaceous rocks

shoreline motion in nonlinear shallow water coastal models abstract different shoreline boundary conditions for numerical models of the non linear shallow water equations based on godunov type schemes are compared the study focuses on the peregrine and williams peregrine d h williams s m 2001 swash overtopping a truncated plane beach journal of fluid mechanics 440 391 399 problem of a single bore collapsing on a slope this is considered the best test to assess performances of the shoreline boundary treatments in terms of all the parameters of interest in swash zone modelling emphasis is given to the shoreline trajectory and flow velocity modelling a mismatch of the velocity at the early stage of the motion is highlighted most of the tested techniques perform similarly in terms of maximum run up the backwash phase is critical in all cases starting from the brocchini et al brocchini m bernetti r mancinelli a albertini g 2001 an efficient solver for nearshore flows based on the waf method coastal engineering 43 2 105 129 shoreline boundary treatment a simple technique that improves the accuracy of velocity predictions is also developed a sensitivity analysis of the domain resolution and the threshold value of the water depth that defines a wet cell is also presented

seismic evidence for a magma chamber beneath the slow spreading mid atlantic ridge seismic reflections from magma chambers have been observed along the fast spreading east pacific rise1 2 and the intermediate spreading valu fa ridge3 4 sub axial reflections also exist beneath the intermediate spreading juan de fuca ridge5 but no magma chambers have been identified beneath the slow spreading mid atlantic ridge suggesting that here magma chambers lie unusually deep or are transient features6 11 seismic reflection profiles acquired in 1989 over the snake pit hydrothermal area in the rift valley of the mid atlantic ridge 25 km south of the kane fracture zone showed no evidence of magmatic activity12 although geochemical analyses of hydrothermal vent fluids suggest the existence of magma at depths as shallow as 1a 2 km13 14 by suppressing in these data high amplitude coherent noise generated at the sea floor i have obtained images in an otherwise non reflective crust of seismic reflections beneath and just south of the snake pit hydrothermal area these reflections define a small 4 km wide dome whose apex is 1 200 m beneath the sea floor as bright reflections from the upper flanks of this dome occur in the depth range suggested by the vent fluid geochemistry i interpret the dome to be the seismic expression of a small magma chamber

distribution of alteration zones in the upper oceanic crust aging of the upper oceanic crust produces alteration zones that have distinct mineralogical and geochemical characteristics five zones are recognized in the troodos ophiolite and in situ oceanic crust 1 a sea floor weathering zone swz 2 a low temperature zone ltz 3 a transition zone tz 4 an upper dike zone udz and 5 a mineralized zone mz the mz may be overlain by the swz ltz or tz but in the known examples it is always underlain by the udz the development of the swz is dependent upon the duration of cold seawater circulation which is dependent upon seafloor topography and the rate and nature of sedimentation the boundary between the low and high temperature zones is largely controlled by permeability contrasts lateral variation in the depth of this boundary indicates that the thermal gradient is not uniform within the crust this along with the evidence for disequilibrium assemblages implies that regional metamorphic zones are not appropriate to describe the distribution of alteration effects

viscous magnetization at 300 k in a profile through troodos type oceanic crust abstract this study examines the question of the relative importance of viscous magnetism vm at 300 k to the total magnetization of older oceanic crust a section through the troodos cyprus ophiolite now recognized as a good proxy for in situ oceanic crust has been used as the source of samples the section extends downwards continuously from little altered submarine extrusives through greenschist facies sheeted dikes to mafic and variously serpentinized ultramafic cumulate intrusives the principal result of the investigation is that vm is not expected to be the dominant magnetization and is often relatively negligible at all crustal levels vm acquisition varies irregularly with depth with predicted maximum values equivalent to about one third of the total magnetization in the extrusives and sheeted dikes the contribution of vm in two samples of serpentinized ultramafics is insignificant vm acquisition does not show any simple relationships with primary lithology alteration history or magnetic properties or history the occurrence of two stage vm growth mechanisms is widespread the second stage typically has an onset time of about 103 min and an acquisition rate three times that of the initial growth mechanism the physical origin of this two stage mechanism and its significance in predicting vm growth over geologic time intervals are considered to be important problems for future work

interpreting anomalous magnetic fabrics in ophiolite dikes abstract anisotropy of magnetic susceptibility ams may reveal mineral orientation distributions defining magmatic flow axes in igneous dikes the mafic silicates are the best indication of magmatic flow but fe ti accessories may contribute more to the bulk susceptibility if the orientation distributions of the two subfabrics are incongruent anomalous fabrics will occur that do not reflect magma flow axes for ophiolite dikes ocean floor metamorphism changes the mineralogy producing new fe oxides by retrogression and exsolution from mafic silicates and by the oxidation of primary oxides incompatibly oriented ferro magnetic subfabrics may be isolated by anisotropy of anhysteretic remanence aarm anomalous ams fabrics in ophiolites elsewhere have been attributed to inverse fabric contributions from single domain magnetite in varying combinations however in ophiolite dikes from the troodos ophiolite of cyprus anomalous fabrics arise from ocean floor metamorphism extensively or completely replacing the original magnetite and titanomagnetite accessory phases with titanomagnetite fe 2 4 ti 0 6 o 4 tm60 and its oxidised versions titanomaghemite to varying degrees according to depth beneath the ocean floor distance from spreading axis and proximity to transform faults at best the oxide orientation distribution defined by aarm could only be indirectly related to magma flow if its nucleation orientation controlled by a host lattice however more commonly the topotactic lattice reorganization produces weaker arm fabric anisotropies although recrystallized oxidised tm60 dominates the bulk low field susceptibility its anisotropy is generally too feeble to compete with the flow fabric defined by the ams contribution from paramagnetic mafic silicates

long waves through emergent coastal vegetation we study the effects of emergent coastal forests on the propagation of long surface waves of small amplitude the forest is idealized by an array of vertical cylinders simple models are employed to represent bed friction and to simulate turbulence generated by flow through the tree trunks a multi scale homogenization analysis similar to that for seepage flows is carried out to deduce the effective equations on the macro scale the effective coefficients are calculated by numerically solving the micro scale problem in a unit cell surrounding one or several cylinders analytical and numerical solutions for wave attenuation on the macro scale for different bathymetries and coastal forest configurations are presented for a transient incident wave analytical results are discussed for the damping of a leading tsunami for comparison series of laboratory data for periodic and transient incident waves are also presented good agreement is found even though some of the measured waves are short or nonlinear

ams detection of inverse fabrics without aarm in ophiolite dikes inverse fabric contributions from single domain sd magnetite complicate interpretation of magmatic flow from anisotropy of magnetic susceptibility ams in the s troodos ophiolite dike swarm flow directions and magma chamber dimensions may only be inferred correctly if magnetic fabrics correspond to the orientation distribution od of minerals magnetite shape fabrics were isolated by anisotropy of anhysteretic remanence aarm but ams ambiguously merges magnetite and silicate fabrics however with the retrospective benefit of aarm in this area we recommend avoiding sd complications by excluding magnetite rich samples for which the bulk low field susceptibility 27 500 si magma flow was steeply upwards to the sw proximal to an axial magma chamber

anisotropy of magnetic susceptibility measurement schemes the precision of ams determination is enhanced by measuring susceptibility in directions with a uniform orientation distribution that include the four body diagonals some standard 10 5 cm samples with mean susceptibility 100 si possess too few magnetic grains for reliable petrofabric interpretation whatever the measurement strategy we should only interpret their ams if they pass fabric homogeneity tests

the runup of solitary waves this is a study of the runup of solitary waves on plane beaches an approximate theory is presented for non breaking waves and an asymptotic result is derived for the maximum runup of solitary waves a series of laboratory experiments is described to support the theory it is shown that the linear theory predicts the maximum runup satisfactorily and that the nonlinear theory describes the climb of solitary waves equally well different runup regimes are found to exist for the runup of breaking and non breaking waves a breaking criterion is derived for determining whether a solitary wave will break as it climbs up a sloping beach and a different criterion is shown to apply for determining whether a wave will break during rundown these results are used to explain some of the existing empirical runup relationships

a 2d numerical model of wave run up and overtopping a two dimensional 2d numerical model of wave run up and overtopping is presented the model called ott 2d is based on the 2d nonlinear shallow water nlsw equations on a sloping bed including bed shear stress these equations are solved using an upwind finite volume technique and a hierarchical cartesian adaptive mesh refinement amr algorithm the 2d nature of the model means that it can be used to simulate wave transformation run up overtopping and regeneration by obliquely incident and multi directional waves over alongshore inhomogeneous sea walls and complex submerged or surface piercing features the numerical technique used includes accurate shock modeling and uses no special shoreline tracking algorithm or shoreline coordinate transformation which means that noncontiguous flows and multiple shorelines can easily be simulated the adaptivity of the model ensures that only those parts of the flow that require higher resolution such as the region of the moving shoreline receive it resulting in a model with a high level of efficiency the model is shown to accurately reproduce analytical and benchmark numerical solutions existing wave flume and wave basin datasets are used to test the ability of the model to approximate 1d and 2d wave transformation run up and overtopping finally we study a 2d dataset of overtopping of random waves at off normal incidence to investigate overtopping of a sea wall by long crested waves the data set is interesting as it has not been studied in detail before and suggests that in some instances overtopping at an angle can lead to more flooding than at normal incidence

magnetic fabrics reveal upper mantle flow fabrics in the troodos ophiolite complex cyprus abstract the foliations and lineations recognized in outcrops of the troodos mantle sequence provide relatively few and imprecise observations of the mineral fabric thus their kinematic interpretation and any inferences about the metamorphic flow patterns are tenuous however every outcrop yields the anisotropy of magnetic susceptibility ams from which we may infer the combined orientation distribution response of silicates pyroxene serpentine and magnetite furthermore in many outcrops the anisotropy of anhysteretic remanence aarm isolates the contribution of magnetite to the orientation distribution ams and aarm each provide a magnitude ellipsoid whose principal directions define the orientation distribution of several hundred minerals in each sample and thus their flow fabric within the troodos mantle sequence high temperature semi cataclastic silicate flow directions were uniform through volumes of 1 km3 but differ between adjacent subareas this reflects the scale of the heterogeneity of solid state flow however averaged over the entire area of 100 km2 the global orientation distribution of silicate alignments were consistent indicating early silicate flow up to the west away from a spreading axis that lay east of the troodos range on the same regional scale later magnetite alignments indicate flow up to the north west the non horizontal and non coaxial flow stages suggest that the mantle sequence was affected by diapiric rise in the solid state radiating from centres which may originally have been magma chambers the one responsible for the recorded flow patterns may have been approximately 30 km in diameter and located se of mount troodos

tectonic rotations in extensional regimes and their paleomagnetic consequences for oceanic basalts paleomagnetic samples of many deep sea drilling project dsdp basalts have shallower inclinations than would be inferred from the paleolatitude at which the basalts were extruded at mid ocean ridges rather than arising from peculiarities of the geomagnetic field the anomalous magnetic directions may result from tectonic rotations along the listric normal faults which often characterize extensional tectonic regimes several lines of evidence support this conclusion observations of the basin and range province an extensional tectonic regime occurring in continental crust observations of the troodos complex cyprus an oceanic extensional tectonic regime now exposed on land and analysis of possible fault patterns associated with the magma chambers postulated to occur at some mid oceanic ridges the tectonic rotations resulting from movement along the listric normal faults occur about a horizontal axis generally perpendicular to the extension direction and typically amount to 30 to 50 although rotations as large as 70 to 90 are not uncommon the paleomagnetic consequences of these rotations can be calculated for dsdp basalts if the original strike and latitude of a ridge are known at four dsdp sites for which adequate data are available namely sites 319 332 410 and 417 rotations ranging from 50 to 70 are required to explain the paleomagnetic results if the original strike and location of the ridge are not known as is the case for most of the older parts of the pacific ocean the paleomagnetic data and the inferred rotation determine a relationship between possible ridge strikes and locations this information combined with a similar but independent relationship derived from the marine magnetic anomalies puts severe constraints on the original strike and location of the ridge

magnetic fabric interpretation complicated by inclusions in mafic silicates abstract the expected relationships between anisotropy of low field magnetic susceptibility ams and crystal symmetry of mafic silicates are disturbed by the presence of magnetite inclusions measurements of ams anisotropy of anhysteretic remanence aarm and theoretically predicted bulk susceptibilities from chemical composition all favour the exercise of great caution in the interpretation of preferred orientation distributions of silicates from a rock s ams these results pertain mainly to the mafic silicates of lower crustal rocks pyroxene orthopyroxene amphibole and some of their low grade metamorphic alterations serpentine epidote

magnetic fabrics and petrofabrics their orientation distributions and anisotropies abstract magnetic fabric and other petrofabric anisotropies may be described by second rank tensors represented by ellipsoids for a homogeneous petrofabric that is adequately sampled a stereoplot of the orientation distribution of the tensors principal axes maximum intermediate and minimum should show three orthogonal concentrations the concentrations form some combination of shapes from circular clusters through partial girdles to full girdles the concentrations elliptical eccentricities are constrained by the symmetry of the sample orientation distribution i e l l s l s etc as well as the individual sample anisotropies the mean orientations of principal axes must be orthogonal just as with individual sample tensors this requires tensor statistics for their calculation jelinek 1978 furthermore elliptical confidence cones for the means should parallel principal planes preserving overall orthorhombic symmetry however in practice sub orthorhombic symmetry may arise from unrepresentative sampling but it may also be a useful indicator of multiple or heterogeneous petrofabrics in the case of magnetic fabrics the wide range in average susceptibility values and variation in magnetic mineralogy permit small numbers of high susceptibility samples to deflect the orientation of the tensor mean away from the majority of samples normalizing the samples by their bulk susceptibility overcomes this but the orientation of high susceptibility outliers may signify an event or subfabric of importance that we should not discard therefore stereoplots of both normalized and non normalized orientation distributions should be compared preferably also identifying the outliers it is important to distinguish the shape of the orientation distribution ellipsoid from the shape of the individual magnetic fabric ellipsoids the qualitative l s nomenclature is best replaced by tj where tj 1 oblate tj 1 prolate jelinek 1981 invariably the orientation distribution is described by an ellipsoid whose shape is more spherical than that of the individual sample anisotropy ellipsoids because the latter have scattered orientations furthermore the shape of the orientation distribution ellipsoid need bear no relation to the shape of individual sample ellipsoid anisotropies the concepts are illustrated with 1119 measurements of anisotropy of magnetic susceptibility ams from seven areas and with 188 measurements of anisotropy of anhysteretic remanence aarm from two areas

paleomagnetic vectors and tilted dikes abstract where tectonic deformation reorients rocks without penetrative strain their paleomagnetic vectors may be restored to their original attitudes by untilting for strata paleomagnetic inclination is readily restored but the tilt axis must be precisely known if paleodeclination is required for dikes without the knowledge of the rotation s neither declination nor inclination of the paleomagnetic vector can be uniquely defined furthermore back rotating dike orientations to an upright attitude assumes primary verticality whereas primary dike dips are bimodal across the spreading axes e g troodos ophiolite cyprus in the cyprus ophiolite the dikes of the limassol forest transform zone are tilted due to uplift of the mantle sequence rocks and deflected against the arakapas fault their paleomagnetic vectors may be restored rotating about the two axes defined by the strike and the vertical or about a net axis that is possibly the actual tectonic rotation axis this net axis is determined from the tectonic regional dispersion of the dike orientations in this test case the results of the restorations differ slightly but underline the difficulty in selecting the best restoration procedure and the greater difficulty of restoring the paleomagnetic data from dikes vis a vis strata for dikes it is recommended that the paleomagnetic vectors are restored using average dike orientations to minimize the inaccuracies due to the large primary variation in dike orientation