variations in the discharge and organic matter content of stalagmite drip waters in lower cave bristol six drip waters which were actively depositing stalagmites in lower cave bristol were analysed both for discharge and luminescence properties drip discharges were determined for two different years and show a complex response to surface precipitation variations inter annual variability in drip discharge is demonstrated to be significantly higher than intra annual variability and discharge was demonstrated both to increase and decrease non linearly with increased precipitation drip waters demonstrate a correlation between their luminescence intensity and drip discharge with increased luminescence in winter as more organic matter is flushed through the aquifer the strength of the relationship between luminescence intensity and discharge increases with increased discharge the results presented here have implications for the palaeoenvironmental interpretation of annual growth laminae and the growth rates of stalagmite samples 1997 john wiley sons ltd

on the dimensions of passive ripple marks in the nearshore zone abstract it has been proven on the basis of field observations that the length and height of passive ripple marks in the nearshore zone depend primarily on the sediment grain size d as it turns out the relationships d and d may be approximated with a high degree of accuracy by the equation 17 3 d 1 22 83 5 d 1 08 in which and are expressed in centimeters and d in millimeters it follows that passive ripple dimensions together with grain size distribution of bedload can present only a minimum shear stress at a moment preceding storm damping they will never indicate the storm strength in its maximal development and it is therefore impossible to completely reconstruct the ancient conditions of wave generation by passive ripple mark parameters

predicting the morphodynamic response of silt laden rivers to water and sediment release from reservoirs lower yellow river china the high sediment load of the yellow river results in rapid infilling of its reservoirs when sediment is not regularly flushed simultaneously the downstream reaches of the yellow river experience extremely high siltation rates which are reduced when sediment is retained in its reservoirs to minimize siltation in the reservoirs and the downstream river bed water and sediment are released from the reservoir in a controlled way through flushing experiments in this paper we analyze the effect of such a flushing event on the downstream river bed through data analysis and numerical modeling sedimentation may be minimized by relating the amount of sediment released from the reservoir to the sediment available for release through operational monitoring and by releasing relatively clear water after turbid water despite this flushing of sediment the reservoir will eventually fill up and more sediment released again into the lower yellow river the change in discharge magnitude and frequency brought about by the reservoir will then probably result in increased siltation rates in the lower yellow river compared to the predam situation

recent flowstone growth rates field measurements in comparison to theoretical predictions abstract the model of calcite precipitation kinetics of d buhmann and w dreybrodt based on the rate laws of l n plummer et al is used to predict cave flowstone growth rates these theoretically modelled growth rates are compared to actual growth rates of recent samples found in cave and mine sites in southwest england a good agreement is found between modelled and actual growth rates within the 95 confidence level of the determinations although in general modelled growth rates overestimate actual growth rate by between 2 4 and 4 7 times several reasons for this overestimation are discussed including uncertainties arising from the experimental data of l n plummer et al seasonal shut off of water flow onto the flowstones and significant variations in the growth rate determining parameters during the period of flowstone growth for one flowstone an underestimation of growth rate is observed and is explained by the presence of rimstone pools which pond water on the sample surface

slip distribution of the 2003 boumerdes zemmouri earthquake algeria from teleseismic gps and coastal uplift data 1 using a joint inversion of seismological waveforms and ground displacement observations we estimate several parameters of the fault geometry and rupture process of the mw 6 9 may 21 2003 boumerdes zemmouri earthquake the relocated epicenter is considered as a known parameter total rupture length rupture duration and maximum slip are 55 km from 3 4 e to 4 0 e 12 s and 3 m the modeled south dipping reverse fault oriented ene wsw outcrops a few km offshore which is consistent with the absence of observed surface rupture inland two shallow and relatively localized slip zones are found on both sides of the hypocenter to the sw between boumerdes and zemmouri slip is concentrated between 11 and 2 km depth to the ne between zemmouri and dellys slip is concentrated between 6 km depth and the sea floor various resolution tests indicate that our model is well constrained by the available data and help understanding which data constrains each parameter of the model

nearshore tsunami inundation model validation toward sediment transport applications model predictions from a numerical model delft3d based on the nonlinear shallow water equations are compared with analytical results and laboratory observations from seven tsunami like benchmark experiments and with field observations from the 26 december 2004 indian ocean tsunami the model accurately predicts the magnitude and timing of the measured water levels and flow velocities as well as the magnitude of the maximum inundation distance and run up for both breaking and non breaking waves the shock capturing numerical scheme employed describes well the total decrease in wave height due to breaking but does not reproduce the observed shoaling near the break point the maximum water levels observed onshore near kuala meurisi sumatra following the 26 december 2004 tsunami are well predicted given the uncertainty in the model setup the good agreement between the model predictions and the analytical results and observations demonstrates that the numerical solution and wetting and drying methods employed are appropriate for modeling tsunami inundation for breaking and non breaking long waves extension of the model to include sediment transport may be appropriate for long non breaking tsunami waves using available sediment transport formulations the sediment deposit thickness at kuala meurisi is predicted generally within a factor of 2

a simple general expression for longshore transport of sand gravel and shingle abstract longshore transport of sand gravel and shingle has been studied using field and laboratory data over a wide range of conditions a detailed model crosmor for cross shore and longshore sediment transport has been used to determine the effects of wave period grain size beach surf zone slope and type of waves wind waves or swell waves the longshore transport was found to be proportional to wave height to the power 3 1 h3 1 to grain size to the power 0 6 d50 0 6 and to beach slope to the power 0 4 tan 0 4 regular swell waves yield much larger factor 1 5 longshore transport rates than irregular wind waves of the same height it is proposed to take this effect into account by a swell correction factor based on all results a new simple and general dimensionally correct expression for longshore transport of sand gravel and shingle beaches with grain sizes between 0 1 and 100 mm has been derived short term and long term field data of sand gravel and shingle have been used for verification in most cases the predicted longshore transport rates are within a factor of 2 of the measured values the cerc and kamphuis formulas have also been tested

large earthquakes at the ibero maghrebian region basis for an eews large earthquakes mw 6 imax viii occur at the ibero maghrebian region extending from a point 12ow southwest of cape st vincent to tunisia with different characteristics depending on their location which cause considerable damage and casualties seismic activity at this region is associated with the boundary between the lithospheric plates of eurasia and africa which extends from the azores islands to tunisia the boundary at cape st vincent which has a clear oceanic nature in the westernmost part experiences a transition from an oceanic to a continental boundary with the interaction of the southern border of the iberian peninsula the northern border of africa and the alboran basin between them corresponding to a wide area of deformation further to the east the plate boundary recovers its oceanic nature following the northern coast of algeria and tunisia the region has been divided into four zones with different seismic characteristics from west to east large earthquake occurrence focal depth total seismic moment tensor and average seismic slip velocities for each zone along the region show the differences in seismic release of deformation this must be taken into account in developing an eews for the region

prediction of dune erosion due to storms abstract this paper presents results of experimental and mathematical modelling of beach and dune erosion under storm events re analysis of the experimental results on dune erosion in small scale and large scale flumes shows that the dune erosion for extreme conditions is somewhat smaller than that based on earlier analysis results dune erosion caused by wave impact has been modelled by a cross shore profile model crosmor model which is based on a wave by wave modelling approach solving the wave energy equation for each individual wave the model has been applied to the recent deltaflume experiments on dune erosion the three main processes affecting dune erosion have been taken into account the generation of low frequency effects the production of extra turbulence due to wave breaking and wave collision and the sliding of the dune face due to wave impact the calibrated model can very well simulate the observed dune erosion above the storm surge level during storm events in small scale facilities large scale facilities and in the protoype 1953 storm in the netherlands using the same model settings the mathematical model results have been used to develop a new simplified dune erosion rule

the impact of waves and tides on residual sand transport on a sediment poor energetic and macrotidal continental shelf 2019 the authors the energetic macrotidal shelf off south west england was used to investigate the influence of different tide and wave conditions and their interactions on regional sand transport patterns using a coupled hydrodynamic wave and sediment transport model residual currents and sediment transport patterns are important for the transport and distribution of littoral and shelf sea sediments morphological evolution of the coastal and inner continental shelf zones and coastal planning waves heavily influence sand transport across this macrotidal environment median 50 exceedance waves enhance transport in the tidal direction extreme 1 exceedance waves can reverse the dominant transport path shift the dominant transport phase from flood to ebb and activate sand transport below 120 m depth wave tide interactions encompassing radiation stresses stoke s drift enhanced bottom friction and bed shear stress refraction current induced doppler shift and wave blocking significantly and nonlinearly enhance sand transport determined by differencing transport between coupled wave only and tide only simulations a new continental shelf classification scheme is presented based on sand transport magnitude due to wave forcing tide forcing and nonlinear wave tide interactions classification changes between different wave tide conditions have implications for sand transport direction and distribution across the shelf nonlinear interactions dominate sand transport during extreme waves at springs across most of this macrotidal shelf at neaps nonlinear interactions drive a significant proportion of sand transport under median and extreme waves despite negligible tide induced transport this emphasizes the critical need to consider wave tide interactions when considering sand transport in energetic environments globally where previously tides alone or uncoupled waves have been considered

moment tensor inversion for iberia maghreb earthquakes 2005 2008 abstract we present and discuss a set of 77 moment tensor solutions for earthquakes in the iberia maghreb region from mid 2005 to the end of 2008 with moment magnitudes ranging from 3 2 to 6 0 inversion is based upon full three component intermediate period waveforms recorded at regional seismic broadband stations following the recent densification of permanent broadband networks and large scale temporary deployments at present more than 150 stations are recording in spain portugal and morocco this unprecedented station density allows analysis of small events from available short distance recordings and in general leads to more reliable source estimates due to data redundancies that permit elimination of waveforms affected by noise or complicated propagation effects the solutions for 2005 2008 constitute an important upgrade of the iberia maghreb moment tensor inventory to 225 solutions to date enhancing the image of seismotectonics at the compressive n algerian margin in the betic alboran shear zone and at the transpressive sw iberian margin as well as providing valuable constraints on seismic deformation in the western betics and the iberian foreland where little information has been previously available new solutions for the foreland and three recent seismic series in the western betics show strike slip and reverse faulting style contrasting with the dominance of normal faulting in the adjacent areas towards east in these areas as well as at the sw iberian margin faulting orientations are heterogeneous including solutions with opposite kinematics this indicates control by local stress conditions and points to fault interaction along the n algerian margin a counterclockwise rotation of slip vectors of thrust events from east to west becomes apparent several solutions for the area offshore cape st vincent are located at sub moho depths between 40 and 60 km supporting a large brittle layer thickness in the oceanic lithosphere

amplitude spectra moment tensor inversion of shallow earthquakes in spain summary the study of focal mechanisms for shallow earthquakes of low to moderate magnitude at regional distances requires a proper inversion technique one of the major problems is the correct separation of path effects from source effects the method used should take into account problems arising from errors in the definition of crustal structure and inclusion of the high frequency content of the waveforms in this study a method of frequency domain moment tensor inversion to determine deviatoric moment tensor solutions from body wave amplitude spectra is described the method has been tested with synthetic data to define instabilities that are due to mismodelling of several parameters the inversion technique is applied to broadband seismic data of shallow 10 km depth earthquakes in spain solutions are obtained for a range of depths and compared with solutions obtained with different methods such as first motion polarities and moment tensor inversion in the time domain a combined fit of amplitude spectra first motion polarities and double couple component is introduced as a method which resolves better the non uniqueness of solution the proposed method can be implemented in fast moment tensor inversion when a green functions database has been created in advance for the studied area

practical sand transport formula for non breaking waves and currents many existing practical sand transport formulae for the coastal marine environment are restricted to a limited range of hydrodynamic and sand conditions this paper presents a new practical formula for net sand transport induced by non breaking waves and currents the formula is especially developed for cross shore sand transport under wave dominated conditions and is based on the semi unsteady half wave cycle concept with bed shear stress as the main forcing parameter unsteady phase lag effects between velocities and concentrations which are especially important for rippled bed and fine sand sheet flow conditions are accounted for through parameterisations recently recognised effects on the net transport rate related to flow acceleration skewness and progressive surface waves are also included to account for the latter the formula includes the effects of boundary layer streaming and advection effects which occur under real waves but not in oscillatory tunnel flows the formula is developed using a database of 226 net transport rate measurements from large scale oscillatory flow tunnels and a large wave flume covering a wide range of full scale flow conditions and uniform and graded sands with median diameter ranging from 0 13 mm to 0 54 mm good overall agreement is obtained between observed and predicted net transport rates with 78 of the predictions falling within a factor 2 of the measurements for several distinctly different conditions the behaviour of the net transport with increasing flow strength agrees well with observations indicating that the most important transport processes in both the rippled bed and sheet flow regime are well captured by the formula however for some flow conditions good quantitative agreement could only be obtained by introducing separate calibration parameters the new formula has been validated against independent net transport rate data for oscillatory flow conditions and steady flow conditions

simulations of strong ground motion in sw iberia for the 1969 february 28 ms 8 0 and the 1755 november 1 m 8 5 earthquakes i velocity model summary this is the first paper of a series of two concerning strong ground motion in sw iberia due to earthquakes originating from the adjacent atlantic area the aim of this paper is to build and calibrate a velocity model that will be used in the companion paper for seismic intensity modelling of the 1969 m s 8 0 and 1755 m 8 5 8 7 earthquakes taking into account the geological evolution of the region since the palaeozoic we build a 3 d velocity model down to the moho discontinuity substantially different from a simple 1 d layered model the velocity model presented in this paper is built a priori using information originating from a variety of geological and geophysical studies its resolution is sufficient to simulate realistically seismic wave propagation in the low frequency f 0 5 hz range which is the most significant for the study of the destructive effects of large earthquakes at a regional scale to validate the model we compute synthetic seismograms for three recent earthquakes of moderate magnitudes 4 6 m w 5 3 located offshore in the most seismically active area in the region synthetics are generated using a wave propagation code based on the finite difference method which was chosen for its simplicity and accuracy in the frequency range considered in this study 0 1 0 5 hz we compare simulated waveforms with threecomponent seismograms for 9 different stations traveltimes of the direct p waves and the amplitude of ground motion are accurately reproduced at all stations the frequency content of the seismograms fits the observations especially for the lowest frequencies investigated 0 1 0 3 hz for each earthquake the estimated seismic moment is in good agreement with values obtained by other authors using different methods we conclude that the velocity model provides encouraging results for the computation of low frequency seismograms in the region and can be used for the study of larger earthquakes for which the radiated wavefield has a predominant low frequency spectrum

the earthquakes of 29 july 2003 12 february 2007 and 17 december 2009 in the region of cape saint vincent sw iberia and their relation with the 1755 lisbon earthquake abstract the cape saint vincent region is of major seismological interest for its tectonic complexity and for the occurrence of the great 1755 lisbon earthquake no structure capable of generating such a large earthquake has yet been convincingly identified but all authors agree that there is a possibility of a similar earthquake occurring offshore of the cape sometime in the future to shed some light on the region s dynamics we here examine the mechanism of the three largest earthquakes to have occurred in the last 40 years west of the cape 29 july 2003 m w 5 3 12 february 2007 m w 6 1 and 17 december 2009 m w 5 5 by inversion of the body waves and the kinematic slip distribution we estimated the three earthquakes to have had similar characteristics dimensions maximum slip stress drop source time function focal depth and rupture velocity although there were differences in the geometry of the rupture that reflect the great seismotectonic complexity of the zone the focal mechanisms of the 2003 and 2007 earthquakes were similar corresponding to thrusting motion but the 2009 earthquake had a dip slip motion in a vertical plane as deduced from the slip distributions the three shocks show ne sw rupture planes with the energy released propagating to the ne compatible with the regional nw se horizontal compression produced by the convergence of the eurasian and african plates applied to the generation of the 1755 lisbon earthquake this direction of faulting would correspond to a complex rupture along ne sw trending thrust faults at the gorringe bank the horseshoe scarp and the marquis de pombal fault with the rupture propagating to the ne towards the portuguese coast such a model could explain that unusually large and tsunami generating earthquake

speleothem palynology an undervalued tool in quaternary studies palynological analysis of cave sediments in particular the analysis of pollen from speleothems is not a widely adopted approach to palaeoenvironmental studies in the british isles this disregard of speleopalynology may be due to the lack of understanding of the cave pollen taphonomy and uncertainty and suspicion as to what cave pollen spectra actually represent however a number of studies of pollen from caves have been carried out particularly in belgium france and spain which have demonstrated speleothem pollen spectra to be representative of contemporary vegetation above the cave with pollen generally well preserved speleothems have the distinct advantage over other pollen sources that they can be dated by high precision tims u th dating up to an order of magnitude further back in time than 14c dating of organic sediments would allow this potentially allows previously unconstrained middle pleistocene palynological records to be precisely and accurately dated thus providing a geochronologically controlled terrestrial record of palaeoenvironmental change this paper presents a timely review of speleothem palynology aiming to eliminate biases and misconceptions and illustrate the enormous potential this unique source of palaeoenvironmental data holds particularly in providing accurately dated pollen records from previously understudied environments and time periods

a cromerian complex stalagmite from the mendip hills england in order to provide a better chronological constraint on a british middle pleistocene interglacial a large stalagmite boss from the mendip hills was selected for palaeoclimate data using pollen analysis dating analyses by thermal ionisation mass spectrometry tims of uranium thorium ratios and by magnetostratigraphy constrain the age of the sample to 450 780 ka the isotopic consistency of the tims analyses plus the presence of luminescence laminations suggest that the sample has been preserved under closed system conditions pollen assemblages have been recovered from the speleothems despite the fact that the ph of calcite deposition is usually greater than 7 furthermore the evidence presented here indicates that the pollen was probably transported by the speleothem feedwater rather than entering the cave aerially the pollen record contained within the stalagmite is interpreted as early mid interglacial but does not have clear cromerian affinity 1997 john wiley sons ltd

geometry prediction for wave generated bedforms published data on wave generated bedform geometry from field and laboratory measurements are re evaluated in terms of relative fluid orbit diameter at the bed and a wave period parameter d 8t2 laboratory bedform data shows a strong dependence on these parameters however for very small values of the period parameter typically field data there is evidence that bedform length depends only on sediment grain size the disappearance of sediment bedforms at high fluid velocities apparently occurs through a decrease in bedform height improved methods for the prediction of bedform geometry under waves are provided in graphical form and computer code

late quaternary speleothem pollen in the british isles as with many terrestrial areas the british quaternary sequence is characterised by incomplete fragmentary records whose correlation is based on stratigraphic or biostratigraphic techniques due to the lack of radiometric ages beyond the 40 kyr limit of 14c dating speleothems secondary cave calcite deposits offer a significant advantage over many sources of palaeoenvironmental information they can be dated to a high precision and accuracy by uranium thorium 238u 230th thermal ionisation and inductively coupled plasma icp mass spectrometry in the time period back to 500 kyr they may also contain sufficient well preserved pollen representative of contemporary vegetation above the cave to allow palaeoenvironmental reconstruction this study adopts the novel approach of combining pollen and thermal ionisation mass spectrometric tims u th dating of british speleothems to produce well constrained palaeoenvironmental records we report for the first time precisely dated records of pollen assemblages from speleothems suggesting the presence of thermophilous arboreal species in phases previously considered to have been consistently cool or cold and devoid of trees copyright 2007 john wiley sons ltd

a geomagnetic polarity time scale for the period 0 17 ma based on 40ar 39ar plateau ages for selected field reversals utilizing 40ar 39ar plateau ages for selected field reversals at 1 2 10 16 and 34 ma a geomagnetic polarity time scale gpts is constructed following the technique of cande and kent 1992 this differs markedly from previous gpts especially in middle late miocene time the ages for the chrons in post miocene time are in agreement with values derived by the astrochronological technique refinements in this gpts await acquisition of 40ar 39ar plateau ages for field reversals in the time frames 3 8 ma and 11 15 ma

an analysis of eemian climate in western and central europe on the basis of 31 pollen diagrams and additional data for botanical macrofossils an analysis is made of the last interglacial eemian climatic history in western and central europe the main tool for this analysis is the climatic indicator species method only selected woody species are used for the quantification of data partial climatic range diagrams are presented for abies alba acer monspessulanum acer tataricum buxus sempervirens tilia tomentosa the problem of time correlation and pollen zonation of the eemian is discussed the climatic analysis itself is based on an improved version of the indicator species method in this version not every site is analysed for its climatic values instead maps and tables on the migrational history of hedera ilex buxus abies and species of acer tilia and abies are the basis for climatic maps showing respectively january and july isotherms for the periods of the corylus zone e4a and the carpinus zone e5 it is concluded that mean january temperatures were as much as 3 c higher at amsterdam the netherlands than at present and mean temperatures in july were 2 c higher however the thermal maximum in winter was later zone e5 than the summer thermal maximum zone e4a winter temperatures changed parallel to rise and fall of global sea level precipitation changes are more difficult to estimate in the first part of the eemian precipitation must have been relatively low but from zone e4b onward it increased to higher values reaching 800 mm and probably substantially more in zones e5 and e6 hence the eemian climate was in its beginning relatively more contintental and later from e4b onward more oceanic however as compared with the holocene the eemian climate was generally speaking more oceanic

earthquake early warning for southern iberia a p wave threshold based approach 1 the south of the iberian peninsula is a region in which large damaging earthquakes occur separated by long time intervals an example was the great 1755 lisbon earthquake intensity imax x which occurred sw of san vicente cape sw iberian peninsula due to this risk of damaging earthquakes the implementation of earthquake early warning system eews technologies is of considerable interest with the aim of investigating the feasibility of an eews in this region of the iberian peninsula empirical scaling relationships have been derived between the early warning parameters and the earthquake size and or its potential damaging effects for this region an appropriate and suitable strategy is proposed for an eews in the sw iberian peninsula which takes into account the limitations of the existing seismological networks

mobile bed friction at high shear stress analysis demonstrates and experiments confirm that the frictional behavior of mobile beds at high shear stress is inherently different from either of the two classical cases smooth wall and rough wall for those two cases the characteristic lengths for friction are based on viscosity and grain size respectively for the new mobile bed friction relation this length varies with the thickness of the shear layer occupied by the moving bed load particles this thickness is itself directly related to shear stress giving rise to the prediction that at high shear stress shields ordinate greater than unity the effective roughness ratio effective roughness particle diameter should be approximately five times the shields ordinate the high shear stress experimental results show a variation in accord with the prediction

seismic sources on the iberia african plate boundary and their tectonic implications the plate boundary between iberia and africa has been studied using data on seismicity and focal mechanisms the region has been divided into three areas a the gulf of cadiz b the betics alboran sea and northern morocco and c algeria seismicity shows a complex behavior large shallow earthquakes h 30 km occur in areas a and c and moderate shocks in area b intermediate depth activity 30 h 150 km is located in area b the depth earthquakes h 650 km are located to the south of granada moment rate slip velocity andhvalues have been estimated for shallow shocks and show similar characteristics for the gulf of cadiz and algeria and quite different ones for the central region focal mechanisms of 80 selected shallow earthquakes 8 mb 4 show thrust faulting in the gulf of cadiz and algeria with horizontal nnw sse compression and normal faulting in the alboran sea with e w extension focal mechanisms of 26 intermediate depth earthquakes in the alboran sea display vertical motions with a predominant plane trending e w solutions for very deep shocks correspond to vertical dip slip along n s trends frohlich diagrams and seismic moment tensors show different behavior in the gulf of cadiz betic alboran sea and northern morocco and northern algeria for shallow events the stress pattern of intermediate depth and very deep earthquakes has different directions vertical extension in the nw se direction for intermediate depth earthquakes and tension and pressure axes dipping about 45 o for very deep earthquakes regional stress pattern may result from the collision between the african plate and iberia with extension and subduction of lithospheric material in the alboran sea at intermediate depth the very deep seismicity may be correlated with older subduction processes

the paleomagnetism and u th dating of mexican stalagmite das2 a 72 cm high stalagmite from mexico das2 has been analyzed for its paleomagnetism and has provided a record of secular variation beginning about 1200 years ago to present the stalagmite did not grow uniformly and a low content of magnetic material has rendered the record less precise in some parts a topographic test involving the magnetic measurement of coeval specimens from the sides of the stalagmite has shown that the record is detectably free from depositional errors age data were provided by the u th method and concordancy checked by14c and226ra methods shallow inclinations at the base of the record are followed by a partial anticlockwise loop in the declination inclination plot there is good agreement between the das2 data and the southwest u s a archeomagnetic record and with a lacustrine record from oregon from 750 to 1400 ad comparison of the record with the present field at the site latitude shows that westward drift of the field has persisted for at least 1200 years at a drift rate of about 0 30 yr 1 a close match in declinations with the present field at the site latitude suggests that the stalagmite may have recorded the passing of the northern edge of the gulf of guinea negative anomaly about 1000 years ago though the corresponding inclination feature is not present in the record an archeomagnetic synthesis by merrill and mcelhinny of worldwide data to estimate positions of the main dipole shows that it was tilted away from mexico from 500 to 1250 ad and this may account for the shallow inclinations seen at the start of the record

determination of earthquake early warning parameters τ c and pd for southern california summary we explore a practical approach to earthquake early warning in southern california by determining a ground motion period parameter c and a high pass filtered displacement amplitude parameter pd from the initial 3 s of the p waveforms recorded at the southern california seismic network stations for earthquakes with m 4 0 at a given site we estimate the magnitude of an event from c and the peak ground motion velocity pgv from pd the incoming threecomponent signals are recursively converted to ground acceleration velocity and displacement the displacements are recursively filtered with a one way butterworth high pass filter with a cut off frequency of 0 075 hz and a p wave trigger is constantly monitored when a trigger occurs c and pd are computed we found the relationship between c and magnitude m for southern california and between pd and pgv for both southern california and taiwan these two relationships can be used to detect the occurrence of a major earthquake and provide onsite warning in the area around the station where onset of strong ground motion is expected within seconds after the arrival of the p wave when the station density is high the methods can be applied to multistation data to increase the robustness of onsite early warning and to add the regional warning approach in an ideal situation such warnings would be available within 10 s of the origin time of a large earthquake whose subsequent ground motion may last for tens of seconds

the predictability of cross shore bed evolution of sandy beaches at the time scale of storms and seasons using process based profile models deterministic and probabilistic profile models have been compared with hydrodynamic and morphodynamic data of laboratory and field experiments on the time scale of storms and seasons the large scale laboratory experiment is a pure 2d case and offers and ideal test case for cross shore profile models as disturbing alongshore non uniformities are absent the field experiments are performed at the egmond site the netherlands during the eu coast3d project and represent storm time scale oct nov 1998 as well as seasonal time scale conditions may 1998 sep 1999 the objective of the paper is to present information of coastal processes on these time scales and to assess the predictive capabilities coastal process based profile models with respect to hydrodynamics and morphodynamics at sandy beaches on the time scales of storms and seasons profile models can quite accurately errors smaller than 10 represent the cross shore significant wave height distribution in the surf zone if the wave breaking model is properly calibrated the wave breaking coefficient should be a function of local wave steepness and bottom slope for most accurate results profile models can reasonably represent the cross shore and longshore currents undertow in a pure 2d case and in 3d field conditions profile models including cross shore mixing effects and breaker delay effects do not produce better predictions of the longshore and cross shore current velocities profile models using default settings can quite reasonably simulate the behaviour of the outer and inner bars on the storm time scale the behaviour of the beach cannot be modelled with sufficient accuracy on the storm time scale profile models can reasonably simulate the post storm onshore bar migration provided that the near bed orbital velocities and wave asymmetry related sand transport are represented in a sufficiently accurate way using non linear wave theories profile models cannot simulate the beach recovery processes on the post storm time scale because these essentially 3d processes are not sufficiently known to be included in the models profile models using default settings cannot simulate the behaviour of the outer and inner bars and the beach on the seasonal time scale the behaviour of the outer bar on the seasonal time scale can only be represented properly after tuning using measured bed profiles the simulation of the inner bar and beach morphology on the seasonal time scale could not be improved by tuning

oscillatory ripple geometry ripple geometry provides a bed roughness which governs the bed shear stress and the profile of eddy viscosity or diffusion coefficient required for the description of the sediment concentration profile or rate of sediment transport an analysis is made of ripple geometries using known tabulated laboratory and field data as well as water tunnel data obtained by the writer three different types of ripples can be identified sand light sediment and oscillating bed ripples they reflect different effects of the fluid shear stress and fluid acceleration on bed sediments it is also shown that when the bed shear stress or the amplitude of the water particle motion relative to the sediment size is small the resulting vortices are more regular with low turbulence intensity and the generated ripples are two dimensional they are called growing or vortex ripples which are strongly influenced by the amplitude of the water particle motion at the other extreme when the bed shear stress or the amplitude of the

stratification effects by cohesive and noncohesive sediment this study focuses on stratification effects induced by the interaction between suspensions of fine grained cohesive and noncohesive sediment and the turbulent flow in estuarine and coastal environments a concise literature review reveals that this interaction may cause an appreciable modification of the vertical profiles of velocity vertical eddy viscosity diffusivity and reynolds stresses this interaction is further studied with a one dimensional vertical 1dv numerical model which includes the standard k turbulence model with buoyancy destruction terms application of this model to the experimental results by coleman 1981 shows that the measured changes in the velocity profile can be explained entirely by sediment induced buoyancy effects it is argued that capacity for cohesive sediment is cc e a fluid mud layer is formed upon the deposition of the cohesive sediment flocs contrary to the case with noncohesive sediment where the depositing grains immediately form a rigid bed thus a two layer fluid system develops causing significant damping of the vertical mixing processes decreasing the carrying capacity further this positive feed back results in a catastrophic collapse of the turbulence field and the concentration profile a scaling law for this saturation behavior is derived from classical stratified flow theory this law is sustained with a series of numerical experiments with the 1dv model it also predicts the suspended sediment concentrations observed in the yellow river to the right order of magnitude it is concluded that sediment induced buoyancy yields appreciable stratification effects at already moderate suspended sediment concentrations in the case of cohesive sediment these stratification effects can result in a catastrophic collapse of the turbulent flow field and the vertical profile of suspended sediment concentration

movable bed roughness in the flow of irregular waves and currents over movable beds the bed roughness ks in the flow of irregular waves and currents over a movable bed is studied on the basis of measured current profiles and the model of you 1994 it is found that the movable bed roughness kt is affected by both waves and currents and that the existing formulae derived in purely oscillatory flow generally fail to predict ks in the flow of waves and currents a new formula is proposed to calculate k in the flow of irregular waves and currents over a movable bed the present bed roughness formula together with you s 1994 model gives better prediction of current shear velocity u and especially apparent roughness z than the existing formulae derived in purely oscillatory flow

annual growth banding in a cave stalagmite the presence of microscopic luminescence banding in cave calcite deposits speleothems has recently been reported1 3 the luminescence seems to be caused by excitation of humic and fulvic acids derived from the overlying soil and subsequently incorporated into the calcite3 4 we have tested whether such luminescence corresponds to annual growth layers using high precision thermal ionization mass spectrometric 238u 234u 230 th ages from banded sections of a holocene stalagmite we report here that the timespans yielded by counting bands on the assumption that they are annual agree within error limits with those obtained by our uranium thorium dating this demonstration that the banding is annual should make banded speleothems valuable resources for providing high resolution records of past climate in which precipitation can be estimated from growth rates5 6 and temperatures from stable isotope measurements7 and solar terrestrial correlations as the luminescence intensity can be related to the solar sunspot cycle1 3

a threshold based earthquake early warning using dense accelerometer networks most earthquake early warning systems eews developed so far are conceived as either regional network based or on site stand alone systems the recent implementation of nationwide high dynamic range dense accelerometer arrays makes now available potentially in real time unsaturated waveforms of moderate to large magnitude earthquakes recorded at very short epicentral distances 10 20 km this would allow for a drastic increase of the early warning lead time for example the time between the alert notification and the arrival time of potentially destructive waves at a given target site by analysing strong motion data from modern accelerograph networks in japan taiwan and italy we propose an integrated regional on site early warning method which can be used in the very first seconds after a moderate to large earthquake to map the most probable damaged zones the method is based on the real time measurement of the period c and peak displacement pd parameters at stations located at increasing distances from the earthquake epicentre the recorded values of early warning parameters are compared to threshold values which are set for a minimum magnitude 6 and instrumental intensity vii according to the empirical regression analyses of strong motion data at each recording site the alert level is assigned based on a decisional table with four alert levels defined upon critical values of the parameters pd and c which are set according to the error bounds estimated on the derived prediction equations given a real time evolutionary estimation of earthquake location from first p arrivals the method furnishes an estimation of the extent of potential damage zone as inferred from continuously updated averages of the period parameter and from mapping of the alert levels determined at the near source accelerometer stations the off line application of the method to strong motion records of the m w 6 3 2009 central italy earthquake shows a very consistent match between the rapidly predicted within a few seconds from the first recorded p wave and observed damage zone the latter being mapped from detailed macroseismic surveys a few days after the event the proposed approach is suitable for italy where during the last two decades a dense network of wide dynamic range accelerometer arrays has been deployed by the department of civil protection dpc the istituto nazionale di geofisica e vulcanologia ingv and other regional research agencies

magnitude estimation using the first three seconds p wave amplitude in earthquake early warning 1 pd is the peak amplitude of displacement in the first three seconds after the arrival of the p wave we investigated the attenuation of pd with the hypocentral distance r in southern california as a function of magnitude m and obtained the following relationship log pd 3 463 0 729 m 1 374 log r 0 305 given an earthquake location determined by the p wave arrival times at stations close to the epicenter this relationship can be used to define a so called pd magnitude of earthquakes our result shows that for earthquakes in southern california the pd magnitudes agree with the catalog magnitudes with a standard deviation of 0 18 for events less than magnitude 6 5 therefore pd is a robust measurement for estimating the magnitudes of earthquakes and has practical application in earthquake early warning systems citation wu y m and l zhao 2006 magnitude estimation using the first three seconds p wave amplitude in earthquake early warning geophys res lett 33 l16312 doi 10 1029 2006gl026871

sediment transport part iii bed forms and alluvial roughness a method is presented that makes the classification of bed forms the prediction of the bed form dimensions and the effective hydraulic roughness of the bed forms feasible the proposed relationships are based on the analysis of reliable flume and field data a verification analysis using about 1 500 alternative reliable flume and field data shows good results in predicting the hydraulic roughness friction factor for field conditions the proposed method yields considerably better results than previously proposed methods which are reviewed here the proposed method has also been used to predict the flow depth and the total bed material load

fault identification for buried strike slip earthquakes using insar the 1994 and 2004 al hoceima morocco earthquakes summary the 1994 m w 6 0 and 2004 m w 6 5 al hoceima earthquakes are the largest to have occurred in morocco for 100 yr and give valuable insight into the poorly understood tectonics of the area bodywave modelling indicates the earthquakes occurred on near vertical strike slip faults with the nodal planes oriented nw se and ne sw distinguishing between the primary fault plane and auxiliary planes using either geodetic or seismic data is difficult due to the spatial symmetry in deformation fields and radiation pattern of moderately sized buried strikeslip earthquakes preliminary studies using aftershock locations and surface observations have been unable to identify the orientation of the primary fault plane for either earthquake conclusively we use radar interferometry and aftershock relocation of the earthquake sequence to resolve the ambiguity for the 2004 earthquake inverting the interferograms for a uniform slip model based either of the two potential nodal planes results in similar misfits to the data however the ne sw best fit fault plane has an unrealistically high fault slip to length ratio and we conclude the nw se striking nodal plane is the primary fault plane and slip was right lateral we carry out tests on synthetic data for a buried strike slip earthquake in which the orientation of the fault plane is known a priori independent of geometry missing data and correlated noise models produced assuming the auxiliary plane to be the fault plane have very high fault slip to length ratios the 1994 earthquake had a smaller magnitude and comparisons of model misfits and slip to length ratios do not conclusively indicate which of the nodal planes is the primary fault plane nonetheless the insar data provides valuable information by improving the accuracy of the earthquake location by an order of magnitude we carry out a multiple event relocation of the entire earthquake sequence including aftershocks making use of the absolute locations for the 1994 and 2004 main shocks from our insar study the aftershock locations are consistent with a nw se orientated fault plane in 2004 and suggests that the 1994 earthquake occurred on a ne sw fault perpendicular to the fault which ruptured in 2004 previous tectonic models of the area proposed a bookshelf model of block rotation with nne ssw left lateral faults this model requires modification to accommodate the observation of right lateral slip on a nw se fault plane for the 2004 earthquake and we prefer to interpret the fault orientations as due to a zone of distributed shear with a right lateral fault striking at 115 and conjugate clockwise rotating left lateral faults striking at 25

coseismic deformation of the may 21st 2003 mw 6 8 boumerdes earthquake algeria from gps measurements 1 on may 21st 2003 a mw 6 8 earthquake struck the central part of northern algeria causing extensive damage in the boumerdes area 40 km east of algiers it is among the largest events to occur in the western mediterranean over the past 25 years we present gps measurements of horizontal coseismic displacements that provide new constraints on the rupture geometry modeling the data with a uniform dislocation on a rectangular fault in an elastic half space we find that the rupture occurred on a reverse fault dipping 42 s with its upper edge 6 km offshore and lower edge 4 km inland the amplitude distribution of the coseismic displacements indicates that the rupture did not reach the surface at least in its western part and ended to the west around 3 4 e offshore faults like that of the boumerdes earthquake could account for part of the africa eurasia relative plate motion in the western mediterranean and represent a significant seismic threat for algeria

the beginning of the ice age in europe and its major subdivisions abstract the time range of the quaternary is discussed in terms of the view that this period is essentially the one in the earth s history in which during certain intervals inland ice developed in the northern hemisphere this process first became evident about 2 3 ma bp since then the quaternary thus defined has witnessed many climatic variations although for practical reasons it is not feasible to assign the status of stage to each distinclty warm or cold phase climatic change is nevertheless the most appropriate basis for world wide correlation it seems possible to use both climatic change and other correlation parameters to arrive at a practicable subdivision of the quaternary period into stages before about 1 ma vegetational succession during interglacials in western europe differed from that seen in later times a possible cause for this divergence is discussed in the later part of the quaternary after about 1 ma two distinct types of warm temperate intervals occurred one associated with high sea levels and an oceanic climate the other showing lower sea levels and a cooler and more continental climate the difference between these two types is shown by comparison of the distribution of abies during these time intervals

vertical profiles of longshore currents and related bed shear stress and bottom roughness the vertical structure of the mean wave driven longshore current over a barred beach is examined on three strong current days during the duck94 experiment and it is found that the bottom boundary layer is well described by a logarithmic profile mean correlation coefficient for all 22 profiles 0 98 the logarithmic profile fits better in the trough where turbulent bottom boundary layer processes predominate than over the bar where breaking wave induced turbulence generated at the surface modifies the profile the surface layer in the presence of waves is well described by adjusting the logarithmic profile for the intermittent presence of water and adding the alongshore component of the mass transport velocity slope of the least squares linear regression between model predictions and observations 1 005 and root mean square rms error of 7 bed shear stresses calculated from logarithmic velocity profiles are equated to a quadratic bottom shear stress formulation the associated bed shear stress coefficients vary by more than an order of magnitude across the surf zone 0 0006 0 012 bottom roughness was measured throughout the nearshore using a sonic altimeter mounted on a moving platform the bed shear stress coefficients are positively correlated with bottom roughness linear correlation coefficient 0 6 a higher linear correlation coefficient 0 8 is obtained by subtracting skin friction from the total bed shear stress

faulting parameters of the 1999 mula earthquake southeastern spain abstract the seismicity of southern spain is characterized by low to moderate earthquake activity magnitudes

testing the earthquake early warning parameter correlations in the southern iberian peninsula the south of the iberian peninsula is of especial interest for the application of earthquake early warning system eews technologies due to the past occurrence of damaging earthquakes such as the 1755 lisbon earthquake however there are several critical issues that need to be addressed in order to develop an eews in this area the first is the magnitude scale inhomogeneity of the available catalogues a second is that most of the available broad band seismograms for this area correspond to earthquakes with magnitudes less than 6 0 recorded at distances greater than 100 km and sometimes with a low signal to noise ratio and third the occurrence of large earthquakes in this area means that the standard eews time window normally used needs to be tested in order to check whether it is long enough our paper describes the results of homogenizing the catalogue magnitudes by using empirical relationships to obtain the moment magnitude mw a criterion based on a threshold value for the signal to noise ratio is applied in order to avoid noise contaminated seismogram data an important part of the study is a check of whether the correlations previously obtained for south iberia are valid for other neighbouring areas such as algeria and for larger earthquakes finally since recent studies have shown that the larger the earthquake the longer the time window needed to properly estimate the magnitude the window was increased progressively from 0 to 20 s in order to study the behaviour of the eews parameters for the largest earthquakes in the database

study of the damaging earthquakes of 1911 1999 and 2002 in the murcia southeastern spain region seismotectonic and seismic risk implications a detailed study of four earthquakes that occurred in the murcia region southeastern spain in 1911 1999 and 2002 has been carried out new intensity maps have been plotted for the march and april 1911 shocks these show maximum values of vii viii ems we have found values of vi and v respectively for the 1999 and 2002 earthquakes surface wave magnitudes range from 5 2 for the bullas 2002 event to 5 7 for the march 1911 event focal mechanisms for the mula 1999 and bullas 2002 events indicate reverse and strike slip motions with scalar seismic moments of 5 9 10 16 n m and 8 6 10 15 n m respectively and focal dimensions of 4 0 and 1 5 km both earthquakes were recorded at epicentral distances greater than 21 km showing low values of peak ground acceleration pga 0 020 g these records involve a ground motion less than the ones expected in the region according to different hazard studies the seismic hazard map that we obtained for the murcia region for a return period of 475 years shows higher values than those given in the spanish building code ncse 02 2002 e g 0 24 g for pga in the city of murcia compared with 0 16 g in the code

observed and predicted bed forms and their effect on suspended sand concentrations abstract in this paper we study the effect of bed forms on suspended sand concentrations and we compare three existing bed form predictors to field and laboratory measurements over a wide range of conditions and propose a new predictor that better collapses the measured bed form dimensions we apply the different bed form predictors to estimate the suspended sediment concentration distributions based on the 1d advection diffusion equation and the bed form enhanced shear stress which includes the flow contraction effect according to nielsen coast eng 10 1986 23 predictions of suspended sand concentration improve when including a bed form predictor interestingly it does not make much difference which bed form predictor is implemented but more whether a bed form predictor is implemented however the choice of a particular bed form predictor is more important when the bed form effect in the sand transport model is based a roughness length scale k s and thus on 2 instead of where k s is nikuradse s equivalent roughness length scale is the bed form height and is the bed form length this is the case in the van rijn van rijn l c 2000 general view on sand transport by currents and waves data analysis and engineering modelling for uniform and graded sand transpor 2000 and crosmor 2000 models z2899 20 z2099 30 z 2824 30 wl delft hydraulics delft the netherlands sand transport model for example we discuss the effect of so called long wave ripples on the suspended sand concentrations

tide induced bedload transport pathways in a multiple sand ridge system offshore of hainan island in the beibu gulf northwest south china sea modern sand transport pathways in a multiple sand ridge system are elusive and have rarely been studied in recent years we report herein a field with four en echelon linear sand ridges offshore of hainan island in the beibu gulf and describe the distribution and morphology of these sand ridges in detail for the first time dune crest comparisons and seismic profiles are also interpreted to assess sand transport over the dunes based on a delft 3d model regional tidal currents and tide induced bedload transport in the multiple sand ridge system were simulated to provide insights into the related bedload transport paths the results show that bedload transport and residual flows are mostly directed to the south on the east side of the sand ridges and to the north on the west side and these differences coincide with dune asymmetries and migrations cross ridge transport is weak and mostly converges on the crests of sand ridges from the two flanks the bedload transport is unbalanced on either flank of the sand ridges thus leading to the asymmetry and crest kinks of the sand ridges a distinct correlation is not observed between the net cross ridge sand transport and sand ridge asymmetry in this system cross swale transport is significant between the neighboring sand ridges and helps construct the bedload transport circulation in the swales sand accretion also occurs in the swales and benefits from the southwestward bedload transport from the north end of sand ridge 3 distinct evidence has not been found for closed bedload transport circulation around sand ridges in this multiple sand ridge system although limited clockwise current vortices develop on several sand ridges additional field observations and simulations are required to characterize the suspended load transport in a multiple sand ridge system and the effects of local sand supply conditions on sand transport also need further evaluation copyright c 2018 john wiley sons ltd

residual flow bedforms and sediment transport in a tidal channel modelled with variable bed roughness abstract the frictional influence of the seabed on the tidal flow in shelf seas and estuaries is usually modelled via a prescribed spatially temporally invariant drag coefficient in practice the seabed exhibits considerable variability particularly spatially that should in principle be included in simulations local variations in the seabed roughness k s alter the flow strength and hence local sediment transport rates the effect of using a spatially temporally varying k s is assessed here with reference to a tidal channel menai strait n wales in which the variability of the bedforms has been monitored using multi beam surveying the channel not only exhibits strong tidal flow but also a residual induced flow that is used here as diagnostic to assess various bed roughness formulations tested in a telemac model tidal simulations have been carried out with both constant and temporally spatially variable k s and the predicted residual flow is shown to be sensitive to these representations for a mean spring neap sn cycle with variable k s the average residual flow is calculated to be 525 m 3 s 1 consistent with observations this residual flow can be recovered using imposed constant values of k s in the range 0 15 m to 0 3 m the results suggest that the overall effective roughness of the seabed is less than half of the maximum local roughness due to the dunes in mid channel but more than the spatially averaged k s value in the channel as a whole by about 50 simulations carried out with an m 2 alone tide using variable k s produce a somewhat smaller by 7 residual flow of 491 m 3 s 1 the use of an equivalent m 2 tide of amplitude enhanced by 7 3 reconciles these estimates the main contribution to k s is made by dunes which are modelled using van rijn s 2007 formulation subject to an additional history effect the modelled k s is found to equal approximately the observed height of the dunes along mid channel transects rather than half the height as expected this is attributed to the non equilibrium nature of the bedforms in the reversing tidal flow which exhibited shorter wavelength and more symmetrical profiles than dunes in steady flow

earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records 1 we show that the low pass filtered peak amplitudes of initial p and s wave seismic signals recorded in the vicinity of an occurring earthquake source correlates with the earthquake magnitude and may be used for real time estimation of the event size in seismic early warning applications the earthquake size can be therefore estimated using only a couple of seconds of signal from the p or s wave onsets i e while the rupture itself is still propagating and rupture dimension is far from complete we argue that dynamic stress release and or slip duration on the fault in the very early stage of seismic fracture scales both with the observed peak amplitude and with the elastic energy available for fracture propagation the probability that a fracture grows to a larger size should scale with the energy initially available citation zollo a m lancieri and s nielsen 2006 earthquake magnitude estimation from peak amplitudes of very early seismic signals on strong motion records geophys res lett 33 l23312 doi 10 1029 2006gl027795

early magnitude and potential damage zone estimates for the great mw 9 tohoku oki earthquake the mw 9 0 2011 tohoku oki earthquake has reopened the discussion among the scientific community about the effectiveness of earthquake early warning for large events a well known problem with real time procedures is the parameter saturation which may lead to magnitude underestimation for large earthquakes here we measure the initial peak ground displacement and the predominant period by progressively expanding the time window and distance range to provide consistent magnitude estimates m 8 4 and a rapid prediction of the potential damage area this information would have been available 35 s after the first p wave detection and could have been refined in the successive 20 s using data from more distant stations we show the suitability of the existing regression relationships between early warning parameters and magnitude provided that an appropriate p wave time window is used for parameter estimation we interpret the magnitude under estimation as a combined effect of high pass filtering and frequency dependence of the main radiating source during the rupture process

sediment transport part i bed load transport a method is presented which enables the computation of the bed load transport as the product of the saltation height the particle velocity and the bed load concentration the equations of motions for a solitary particle are solved numerically to determine the saltation height and particle velocity experiments with gravel particles transported as bed load are selected to calibrate the mathematical model using the lift coefficient as a free parameter the model is used to compute the saltation heights and lengths for a range of flow conditions the computational results are used to determine simple relationships for the saltation characteristics measured transport rates of the bed load are used to compute the sediment concentration in the bed load layer a simple expression specifying the bed load concentration as a function of the flow and sediment conditions is proposed a verification analysis using about 600 alternative data shows that about 77 of the predicted bed load transport rates are within 0 5 and 2 times the observed values

unified view of sediment transport by currents and waves i initiation of motion bed roughness and bed load transport attention is given to the properties of sediment beds over the full range of conditions silts to gravel in particular the effect of fine silt on the bed composition and on initiation of motion critical conditions is discussed high quality bed load transport data sets are identified and analyzed showing that the bed load transport in the sand range is related to velocity to power 2 5 the bed load transport is not much affected by particle size the prediction of bed roughness is addressed and the prediction of bed load transport in steady river flow is extended to coastal flow applying an intrawave approach simplified bed load transport formulas are presented which can be used to obtain a quick estimate of bed load transport in river and coastal flows it is shown that the sediment transport of fine silts to coarse sand can be described in a unified model framework using fairly simple expressions the proposed model is fully predictive in the sense that only the basic hydrodynamic parameters dep

impact of typhoon chan hom on the marine environment and sediment dynamics on the inner shelf of the east china sea in situ seafloor observations abstract the suspended sediment transport in the inner shelf of the east china sea ecs varies seasonally and most of the suspended sediments are transported southward in winter however the influence of typhoons which usually take place in summer on the marine environments and sediment transport processes in the mud wedge area of the ecs inner shelf has not been elucidated an in situ monitoring platform moored approximately 440 km south of the yangtze river mouth at a water depth of 40 m was resting on the seabed of the ecs inner shelf when typhoon chan hom passed through the area a 49 day data set of the temperature suspended sediment concentration ssc chlorophyll a chl a concentration and currents was recorded from this platform and analyzed in this study to characterize typhoon chan hom and evaluate the associated sediment transport the analysis of the data obtained shows that during the typhoon passage the temperature decreased by approximately 0 8 c the maximum near bottom current reached 152 0 cm s an average ssc of 919 mg l was observed with peak hourly values exceeding 1785 mg l and the ssc and chl a concentrations reached approximately 50 and 10 times the corresponding values during the pre typhoon period respectively during the typhoon passage most of the suspended particles near the seabed were derived from the resuspension of bottom surface sediments the chl a concentration near the seabed increased greatly because of surface sediment resuspension and the input of additional terrigenous nutrients transported by the typhoon passage the net suspended sediment flux ssf associated with the passage of typhoon chan hom was directed southwestward and landward sediment transport during chan hom accounted for approximately 89 of the total southwestward ssf and 44 of the total landward ssf during the whole observation period analysis of the wavelet power spectra reveals that in the upper water layers the semidiurnal tidal currents prevailed before and after the typhoon passage however this dominant factor disappeared during the typhoon passage compared with winter storms in the ecs summer typhoons such as chan hom mainly transport locally resuspended sediments and sediment flux is landward in the across shelf direction our study highlights the significant role of typhoons in the resuspension and redistribution of sediments and transport of suspended matter from north to south in the mud wedge area of the ecs

identifying dynamic equilibrium of an undeveloped alluvial stream by extremal hypotheses abstract the indeterminate channel problem arises from uncertainty in finding a closure relation for alluvial channels created by self organizing erosional and depositional processes extremal hypotheses have been proposed as one potential approach to closing the system of governing equations for alluvial channels many different extremal hypotheses have been presented but no substantive evidence has been developed to select which hypothesis may be most appropriate for natural alluvial river systems this paper evaluates the ability of ten extremal hypotheses to identify dynamic equilibrium across a geomorphic gradient in the remote and undeveloped mid latitude watershed of rio murta chile this study a introduces extremal hypotheses b describes the field site and geomorphic conditions and c examines which extremal hypotheses are supported by the field data in identifying the evolutionary trend toward dynamic equilibrium the extremal hypotheses that identified dynamic equilibrium within the geomorphic gradient in the field are 1 minimum kinetic energy 2 minimum specific stream power 3 maximum friction factor and 4 maximum total friction factor which collectively support minimizing kinetic energy of the system

observations and modelling of nearshore sediment sorting processes along a barred beach profile abstract the understanding of cross shore sediment sorting is of primary importance for the design of sand nourishments and for assessing the suitability of the seabed to different ecological species in this paper sediment sorting processes were investigated by using a combination of physical and detailed numerical modelling data from large scale wave flume experiments were used to validate a 2dv cross shore delft3d model the model solves coupled short wave averaged equations for flow sediment transport bed composition and bed level change the infra gravity wave motions were explicitly resolved in order to investigate sorting processes eight sediment fractions were used as well as a layered bed stratigraphy the effects of different wave conditions high energetic and more moderate energetic waves on the morphodynamic profile development and sorting processes were investigated the delft3d model reproduced the profile development and bar position very accurately additionally model predictions of sediment sorting across the profile fitted very well with the available observations the numerical model simulations showed the importance of including short wave grouping and infragravity wave effects in order to reproduce the cross shore profile development especially the breaker bar dynamics and sediment sorting processes infragravity waves contribute to larger sediment entrainment and more offshore bar development besides leading to a better prediction of the bed profile infragravity waves also lead to a better prediction of the bed composition model results are in agreement with experimental data showing its capabilities in functioning as a tool to predict sorting processes

stochastic prediction of sediment transport in sand gravel bed rivers classical deterministic bedload transport predictors are applied to sand gravel bed rivers the turbulent bed shear stress is modeled according to a probability distribution to obtain realistic bedload transport rates at incipient motion in extending the predictors to stochastic predictors for nonuniform sediment many parameters that represent near bed turbulence and the particle size distribution must be chosen the parameters that give realistic results are chosen by analyzing the results of a new experimental flume dataset with relatively large water depths choosing other combinations of parameters may give equal total bedload transport rates but at the cost of large errors in fractional transport rates attention is given to the hiding exposure phenomenon and a hindrance effect related to nonuni form sediment validation based on two independent field datasets shows that successful predictions of particle sizes near the threshold for motion are feasible using the stochastic approach while the deterministic approach gives successful predictions well above incipient motion

desert paleoenvironmental data from cave speleothems with examples from the chihuahuan somali chalbi and kalahari deserts abstract pollen bearing lake bog and spring sediments are relatively scarce in many arid and semiarid regions of the world and few are dateable beyond the 14c range we have obtained pollen spectra from speleothems collected from caves in the somali chalbi and kalahari deserts suggesting that these deposits may be an important future source of desert paleovegetation data as cave speleothems can be dated by the 230th 234u method to c 350 000 yr b p and by the tl and esr methods potentially to 1 m y b p and can sometimes give paleotemperature and paleohydrologic data they could provide a first glimpse of desert paleoenvironments during isotope stages 4 9 ages of speleothems from the chihuahuan kalahari and somali chalbi deserts suggest that there was more available moisture in the southwestern u s a and in northwestern bostwana during glacials and interstadials of the last c 300 000 years but that wetter conditions in the horn of africa corresponded with interglacials and perhaps to a lesser extent with interstadials pollen from three northern somalia speleothems indicate more mesic conditions in the horn of africa at 10 000 11 800 and 176 500 yr b p while speleothem pollen spectra from matupi cave in northeastern zaire presently surrounded by tropical rainforest suggest a savanna grassland at this cave c 14 000 yr b p

waveform inversion of small to moderate earthquakes located offshore southwest iberia summary in this paper we apply the kinematic waveform inversion kiwi tools to the study of smallto moderate earthquakes in southwest sw iberia the earthquakes have magnitudes in the range ml 3 5 4 9 with the exception of one earthquake with magnitude ml 6 0 most events are located offshore are recorded with a large azimuthal gap and generate waves that travel throughastronglyheterogeneous crustalstructure weobtainnewestimatesofcentroid depth seismic moment strike dip and rake for 12 of the 29 studied events the earthquakes whose waveforms we cannot successfully model are 1 located too far from the stations 2 have small magnitude hence low signal to noise ratio or 3 are located within the cadiz basin which is a major sedimentary basin that affects wave propagation notably our results indicate that onshore earthquakes occur at shallow depths 15 km whereas offshore earthquakes occur deeper down to 46 km focal mechanisms indicate transpressive faulting

shear stress and sediment transport calculations for swash zone modelling it is shown that the observed difference in sediment transporting efficiency by the swash uprush compared with the downrush could be mainly due to greater bed shear stress for a given velocity in the more abruptly accelerated uprush the bed shear stress generated by an arbitrary free stream velocity time series is modelled in terms of usual wave boundary layer models plus a phase lead phi tau of the bed shear stress compared with the free stream velocity at the peak frequency with this approach the total transport amounts in uprush and downrush can be modelled satisfactorily with the same sediment transport formula without the need for different uprush and downrush coefficients while the adaptation of sediment transport formulae from steady flow can thus lead to the right total amounts of sediment moved by this method the timing of the instantaneous sediment transport rates are probably not accurately modelled due to the highly unsteady nature of the swash and the presence of pre suspended sediment in the uprush nevertheless the proposed method is a useful intermediate step before we have a complete understanding of sediment transport under very rapid accelerations and of the relative contribution of pre suspended sediment to the onshore sediment transport in swash zones c 2002 published by elsevier science b v

seismicity and focal mechanisms in south spain abstract recent improvements in regional seismological networks allow a better definition of the seismicity and the determination of focal mechanisms in south spain this region is part of the lithospheric plate boundary between africa and eurasia and shows a continuous seismic activity of moderate magnitude m h h 650 km earthquakes also occurring in the region eight fault plane solutions have been determined that can be related to the tectonics of the area the solutions for the shallow shocks are compatible with regional stresses with horizontal compressions in nw se direction and tensions in e w direction that produce normal faulting along the n30 to 60 w and n10 to 30 e systems of faults the mechanisms of the intermediate depth shocks can be explained in terms of a subduction zone from africa in a nw direction that is under compression

wave formed sand ripples at duck north carolina a recently developed acoustic multiple transducer array was utilized to measure small scale bed forms in the nearshore and inner shelf regions at duck north carolina two populations of wave formed ripples were observed short wave ripples swr with heights ranging from 3 mm to 2 cm and lengths ranging from 4 to 25 cm and long wave ripples lwr with heights ranging from 3 mm to 6 cm and lengths ranging from 35 to 200 cm the swr were only present sometimes and their presence or absence was determined by a critical value of the near bed mobility number the swr were highly dynamic sometimes flattening during wave groups and reforming over several incident wave periods the lwr in contrast were almost always present they were longer and lower relief than predicted by models or generally observed previously both swr and lwr were often observed to migrate shoreward but were rarely observed to migrate seaward the dimensions of the swr when they were present were predictable by the nielsen 1981 model or the wiberg and harris 1994 model to within approximately a factor of 2

net currents in the wave bottom boundary layer on waveshape streaming and progressive wave streaming the net current streaming in a turbulent bottom boundary layer under waves above a flat bed identified as potentially relevant for sediment transport is mainly determined by two competing mechanisms an onshore streaming resulting from the horizontal non uniformity of the velocity field under progressive free surface waves and an offshore streaming related to the nonlinearity of the waveshape the latter actually contains two contributions oscillatory velocities under nonlinear waves are characterized in terms of velocity skewness and acceleration skewness with pure velocity skewness under stokes waves and acceleration skewness under steep sawtooth waves and both separately induce offshore streaming this paper describes a 1dv reynolds averaged boundary layer model withk eturbulence closure that includes all these streaming processes the model is validated against measured period averaged and time dependent velocities from 4 different well documented laboratory experiments with these processes in isolation and in combination subsequently the model is applied in a numerical study on the waveshape and free surface effects on streaming the results show how the dimensionless parameterskh relative water depth and a kn relative bed roughness influence the dimensionless streaming velocity and shear stress and the balance between the mechanisms for decreasing kh the relative importance of waveshape streaming over progressive wave streaming increases qualitatively consistent with earlier analytical modeling unlike earlier results simulations for increased roughness smaller a kn show a shift of the streaming profile in onshore direction for all kh finally the results are parameterized and the possible implications of the streaming processes on sediment transport are shortly discussed