onset of scour below pipelines and self burial abstract this paper summarizes the results of an experimental study on the onset of scour below and self burial of pipelines in currents waves pressure was measured on the surface of a slightly buried pipe at two points one at the upstream side and the other at the downstream side of the pipe both in the sand bed the latter enabled the pressure gradient which drives a seepage flow underneath the pipe to be calculated the results indicated that the excessive seepage flow and the resulting piping are the major factor to cause the onset of scour below the pipeline the onset of scour occurred always locally but not along the length of the pipeline as a two dimensional process the critical condition corresponding to the onset of scour was determined both in the case of currents and in the case of waves once the scour breaks out it will propagate along the length of the pipeline scour holes being interrupted with stretches of soil span shoulders supporting the pipeline as the span shoulder gets shorter and shorter more and more weight of the pipeline is exerted on the soil in this process a critical point is reached where the bearing capacity of the soil is exceeded general shear failure at this point the pipe begins to sink at the span shoulder self burial it was found that the self burial depth is governed mainly by the keulegan carpenter number the time scale of the self burial process on the other hand is governed by the keulegan carpenter number and the shields parameter diagrams are given for the self burial depth and the time scale of the self burial process

a tectonic boundary for the southern colorado plateau abstract a tectonic boundary should be defined by changes in tectonic elements tectonic elements would include such parameters as structural style stress orientations volcanism heat flow seismicity and changes in crustal thickness examination of these tectonic elements for the southern colorado plateau suggests that the southwestern part of the physiographic plateau appears to be tectonically part of the basin and range province i therefore propose a boundary at 112 w longitude the locus of seismicity and recent volcanism and also the site of crustal thickening and a change of structural style the tectonic boundary of the southern colorado plateau is suggested to form part of the eastern boundary of the southern basin and range seismotectonic region this seismotectonic region is bounded on the north by the las vegas shear zone nevada seismic zone and has a different stress orientation than the northern basin and range from which it began to evolve separately 13 m y ago the present principal stress orientation of the southern basin and range of arizona appears to be the result of compound movements of the san andreas transform and garlock las vegas shear zone resulting in a shear couple affecting the crust in arizona and an associated ne sw least principal stress orientation

the impact of scour processes on a smothered reef system in the irish sea the irish sea like many marine areas is threatened by anthropogenic activities in particular the pisces reef system a series of smothered rocky reefs are subject to fishing pressures as a result of their position within a nephrops norvegicus fishery in an area of sediment deposition and retention the reefs modify the environment by increasing the energy of near bottom currents which results in localised scouring this is the first study to attempt to characterise and investigate the ecological functioning of the pisces reef system a multidisciplinary approach was essential for accurate investigation of the area to facilitate more effective management of the benthic habitats of the reef system this study integrates acoustic seismic grab sampling and video ground truthing methods for benthic habitat discrimination orientation of the scour hollows also suggest that seabed features could be used to infer dominant flow regimes such as the irish sea gyre the data revealed significant geology benthos relationships a unique biotope was described for the reef habitat and it was demonstrated that scouring may influence community composition through disturbance mechanisms this study provides preliminary information required for management of a unique habitat within a uniform region

analysis of the 4 february 1976 chino valley arizona earthquake abstract this m b 4 9 earthquake was located about 20 km north of prescott in the transition zone between the basin and range and colorado plateau provinces several lines of approach were used to determine the focal mechanism p wave first motions surface wave amplitude and phase spectra and synthetic seismograms the preferred focal mechanism displays northwest trending nodal planes with predominantly normal movement the inferred fault plane strikes 120 dips 40 sw with a slip of 100 and a depth of 10 to 15 km the seismic moment is 1 0 10 23 dyne cm the azimuth of least horizontal stress is inferred to be 37 lithostatic stress generated by variations in elevation and density between the crusts of the southern basin and range and colorado plateau may contribute to the inferred stress orientations uplift and resultant extension in this zone of thin lithosphere and relatively high heat flow may also be important microearthquake studies in the chino valley during the summers of 1978 and 1979 indicate a microseismicity rate of 0 3 events per day this is an order of magnitude less than that observed in the intermountain seismic belt

singular points at berm breakwaters scale effects rear round head and longshore transport abstract design aspects other than the profile development of the seaward side have been investigated in this paper aspects such as scale effects rear stability round head design and longshore transport have been treated here based on extensive test series on two different berm breakwater designs a first conclusion is that scale effects were not present in a 1 35 scale model compared with a 1 7 large scale model with wave heights up to 1 7 m a first design rule was assessed on the relationship between damage at the rear of a berm breakwater and the crest height wave height wave steepness and rock size tests on a berm breakwater head showed that enlarging the berm height at the crest and therefore the amount of rock in the berm was effective with regard to stability finally the onset of longshore transport due to oblique wave attack was studied and compared with literature formulae were derived for this onset of transport and also for the range of more serious transport up to longshore transport of coarse gravel

a heuristic evaluation of long term global sea level acceleration in view of the scientific and social implications the global mean sea level rise gmslr and its possible causes and future trend have been a challenge for so long for the twentieth century reconstructions generally indicate a rate of gmslr in the range of 1 5 to 2 0 mm yr 1 however the existence of nonlinear trends is still debated and current estimates of the secular acceleration are subject to ample uncertainties here we use various gmslr estimates published on scholarly journals since the 1940s for a heuristic assessment of global sea level acceleration the approach alternative to sea level reconstructions is based on simple statistical methods and exploits the principles of meta analysis our results point to a global sea level acceleration of 0 54 0 27 mm yr century 1 between 1898 and 1975 this supports independent estimates and suggests that a sea level acceleration since the early 1900s is more likely than currently believed

preliminary analysis of acceleration of sea level rise through the twentieth century using extended tide gauge data sets august 2014 this work explores the potential for extending tide gauge time series from the permanent service for mean sea level psmsl using historical documents psmsl ancillary data and by developing additional composite time series using near neighbor tide gauges the aim was to increase the number completeness and geographical extent of records covering most or all of the twentieth century the number of at least 75 complete century scale time series have been approximately doubled over the original psmsl data set in total over 4800 station years have been added with 294 of these added to 10 long southern hemisphere records individual century scale acceleration values derived from this new extended data set tend to converge on a value of 0 01 0 008 mm yr2 this result agrees closely with recent work and is statistically significant at the 1 sigma level possible causes of acceleration and errors are briefly discussed results confirm the importance of current data archeology projects involving digitization of the remaining archives of hard copy tide gauge data for sea level and climate studies

global and regional sea level change during the 20th century sea level variations prior to the launch of satellite altimeters are estimated by analyzing historic tide gauge records recently a number of groups have reconstructed sea level by applying eof techniques to fill missing observations we complement this study with alternative methods in a first step gaps in 178 records of sea level change are filled using the pattern recognition capabilities of artificial neural networks afterward satellite altimetry is used to extrapolate local sea level change to global fields patterns of sea level change are compared to prior studies global mean sea level change since 1900 is found to be 1 77 0 38 mm yr 1 on average local trends are essentially positive with the highest values found in the western tropical pacific and in the indian ocean east of madagascar where it reaches about 6 mm yr 1 regions with negative trends are spotty with a minimum value of about 2 mm yr 1 south of the aleutian islands although the acceleration found for the global mean 0 0042 0 0092 mm yr 2 is not significant local values range from 0 1 mm yr 2 in the central indian ocean to 0 1 mm yr 2 in the western tropical pacific and east of japan these extrema are associated with patterns of sea level change that differ significantly from the first half of the analyzed period i e 1900 1950 to the second half 1950 2000 we take this as an indication of long period oceanic processes that are superimposed to the general sea level rise

the hiding exposure effect revisited a method to calculate the mobility of bimodal sediment mixtures abstract predicting seabed mobility is hampered by the limited accuracy of sediment transport models when the bed is composed of mixed sediments the hiding exposure he effect modifies the threshold of motion of individual grain classes in sediment mixtures and its strength is dependent on the grain size distribution however an appropriate method of predicting this effect for bimodal sediment mixtures remains to be developed the prototypical example of a bimodal mixture is that consisting of a well sorted sand and gravel for the fine and coarse fractions respectively through a comprehensive series of laboratory experiments the he effect has been quantified for a full range of sand gravel mixtures from pure sand to pure gravel the choice of which has been underpinned by an integrated study of offshore geophysical and sedimentological data found in coastal and shelf seas in the sand gravel mixtures used in the present study the critical shear stress needed to mobilise the sand and gravel fractions increased by up to 75 and decreased by up to 64 respectively compared to that needed to mobilise well sorted sediment of similar size the he effect was found to be dependent on the percentage of gravel coarse mode present in the bimodal mixture whereby the effect for the mixture is the weighted sum of the he effect for the fine and coarse modes

experimental observations of tsunami induced scour at onshore structures tsunami inundation of the coastal environment can induce scour at structure foundations leading to failure a series of experiments are made using a unique pneumatic long wave generator to generate tsunami wave periods of 25 147 s equating to 3 17 3 min at 1 50 froude scale the waves propagate over a sloping bathymetry and impinge upon a square structure founded onshore in a flat sediment bed flow velocity height and scour depth are recorded as a function of time during tsunami inundation the rate of scour is observed to be time dependent equilibrium which is not attained is argued to be an inappropriate measure for time dependent transient flows such as tsunami in which the flow velocity depth and direction are variable the maximum scour depth is recorded and critically is observed not to be equal to the final depth due to significant sediment slumping when flow velocities reduce in the latter stages of inundation current and wave scour predictor equations over predict the scour while the asce 7 16 method under predicts comparisons with available data in the literature show longer inundation durations increase the amount of scour

numerical study on the interaction among a nonlinear wave composite breakwater and sandy seabed most previous investigations related to composite breakwaters have focused on the wave forces acting on the structure itself from a hydrodynamic aspect the foundational aspects of a composite breakwater under wave induced cyclic loading are also important in studying the stability of a composite breakwater in this study numerical simulations were performed to investigate the wave induced pore water pressure and flow changes inside the rubble mound of the composite breakwater and seabed foundation the validity and applicability of the numerical model were demonstrated by comparing numerical results with existing experimental data moreover the present model clearly has shown that the instantaneous directions of pore water flow motion inside the seabed induced by surface waves are in good agreement with the general wave induced pore water flow inside the seabed the model is further used to discuss the stability of a composite breakwater i e the interaction among nonlinear waves composite breakwater and seabed numerical results suggest that the stability of a composite breakwater is affected by not only downward shear flow generating on the seaward slope face of the rubble mound but also a high and dense pore water pressure gradient inside the rubble mound and seabed foundation

numerical modeling of breaking wave induced seawall scour abstract scour is recognised as one of the major causes of seawall failure this paper presents numerical modelling of seawall scour due to wave impact on a vertical seawall the modelling of waves hydrodynamics is based on the solution of the reynolds averaged navier stokes equations with the k model fifth order stokes waves are generated in a numerical wave tank nwt using the relaxation method the free surface under the breaking wave is captured with the level set method the wave field is coupled with a sediment transport algorithm to simulate seawall scour the model is validated for an accurate wave field and the seawall scour due to the wave impact the accuracy of the simulations is assured by comparing the numerical results with the theory and the experimental observations the numerical results give insight into the seawall scour process through different stages the results show that the seawall scour is governed by the breaking wave impact on the seawall the development of the standing wave due to the reflected wave energy from the seawall leads to further sediment transport seawards finally the model is used to simulate seawall scour for different scenarios of seawall locations incident wave height and seabed slope the study examines the wave impact on the seawall toe and resulting scour the maximum seawall scour is observed when the seawall is located at the intersection point of the still water depth and the bed slope a displacement of the seawall from the intersection point leads to a decrease in the wave impact the surf similarity parameter 0 is recognised as an important factor affecting the seawall scour

sediment erosion by gortler vortices the scour hole problem reference lhe article 2004 010view record in web of science record created on 2007 09 04 modified on 2016 08 08

scour at the head of a vertical wall breakwater abstract this paper presents the results of an experimental investigation on the near bed flow patterns the bed shear stress amplification and scour around the head of a vertical wall breakwater using regular waves the keulegan carpenter number kc based on the diameter of the breakwater head is found to be the major parameter that governs the flow and the equilibrium scour depth basic flow structures are identified as function of kc the scour depth is found to increase with increasing the keulegan carpenter number the necessary extent of the conventional stone protection is studied an empirical formula is worked out for the width of the protection layer as function of kc also the effects of head shape the angle of attack and the presence of a co directional current are investigated the results indicate that the scour depth is increased considerably in the presence of a current likewise the scour depth is increased when the head shape is changed from a round shape to a sharp edged one it is found that the angle of attack is also an influencing factor as regards the scour depth

flow under standing waves part 2 scour and deposition in front of breakwaters abstract a 3 d general purpose navier stokes solver was used to calculate the 2 d flow in front of the breakwater the k sst shear stress transport model was selected as the turbulence model the morphologic model of the present code couples the flow solution with a sediment transport description and routines for updating the computational mesh based on the mass balance of sediment laboratory experiments of scour also were conducted in a wave flume to obtain data for model verification both in the numerical simulations and in the laboratory experiment two kinds of breakwaters were used a vertical wall breakwater and a sloping wall breakwater slope 1 1 5 numerically obtained scour deposition profiles were compared with the experiments the numerical results show that the equilibrium scour depth normalized by the wave height decreases with increasing water depth to wave length ratio although the numerical results obtained for vertical wall breakwaters are consistent with the existing experimental data including the present experiment the numerical results for the sloping wall case appear to be not very satisfactory

three dimensional calculation of scour around cylinders the flow of water around a cylinder was calculated by a numerical model the model used a finite volume method to solve the nontransient navier stokes equations for three dimensions on a general nonorthogonal grid the k e turbulence model was used to solve the reynolds stress term the flow field gave the shear stress on the boundaries which was used to calculate sediment concentration for the bed elements the diffusion convection equation for the sediment concentration was solved and continuity for the sediment concentration gave changes in the bed elevation using the modified bed a new flow field was calculated and also a new sediment concentration this sequence was repeated until the depth of the calculated scour hole was identical to the depth of the scour hole from a physical model study the rest of the geometry of the resulting scour hole compared well with the measured scour hole from the experimental study also other flow characteristics given by the numerical model were found to be in ag

longitudinal current induced by oblique waves along coastal structures the time and depth averaged equations in a porous medium are used to analyse how dissipation inside an infinitely long vertical breakwater generates an alongbreakwater ab current inside the structure this mean current is transferred seawards and leewards by turbulent diffusion based on a theoretical eddy viscosity law an analytical solution is obtained the mean current velocity profile depends on characteristics such as water depth wave height wave period and angle of incidence and on porous medium properties including porosity and friction in the neighbourhood of the structure the simultaneous action of waves and the ab current are taken into account to study the potential sediment transport patterns seawards of the structure the obtained results may help to explain the formation of bars almost parallel to the breakwater under certain circumstances the presence of the breakwater enhances the sediment transport in the zone closest to the seaward face which may induce scouring at the toe of the structure

mechanics of the scouring and sinking of submerged structures in a mobile bed a physical model study abstract wave induced flow velocity and turbulence may cause scouring in the seabed around coastal structures depending on the wave climate and tidal water depth a 3 d physical modelling study was conducted to investigate the possible causes of the sinking of two submerged coastal structures on the santa maria del mar smm beach spain the experimental investigation was conducted by employing a froude similarity law with a geometric scale of 1 20 and the submerged modular structure was subjected to different wave climates and tidal water levels the combinations of the significant wave height and peak period were chosen from in situ real wave conditions that were monitored during the sinking of the prototype structures linking and unlinking conditions for the modules in the structure were investigated in this study the results show that the modules sank to approximately 48 of their height at the end of the tests with storm waves and semi linking conditions of low water depth most of the experimental results were compatible with the prototype monitoring results tests with proper linking among the modules and tests with an appropriate gravel foundation resulted in a sustainable solution because they presented much less or almost no scouring and sinking

analysis of the 2009 earthquake swarm near sunset crater volcano arizona abstract a swarm of microearthquakes occurred on october 31 2009 within 5 km of the sunset crater arizona volcano a detailed study of the swarm was warranted because of its location near a young volcanic construct and its proximity to the population center of flagstaff arizona the question posed in this study was whether the swarm was the result of tectonic stress release during fault slip or due to stresses driven by magmatic processes this question was addressed by analyzing and comparing the physical and seismic characteristics of the swarm to the regional tectonic environment and to the characteristics of tectonic swarms in arizona and magmatic volcanic swarms elsewhere this analysis included swarm duration frequency of events b value focal depths and epicentral pattern of the swarm the comparison of the salient features of the 2009 sunset crater swarm to both magmatic and tectonic swarms indicates that the sunset crater swarm has features similar to magmatic swarms and is a potential magmatic swarm candidate

twentieth century global mean sea level rise is the whole greater than the sum of the parts confidence in projections of global mean sea level rise gmslr depends on an ability to account for gmslr during the twentieth century there are contributions from ocean thermal expansion mass loss from glaciers and ice sheets groundwater extraction and reservoir impoundment progress has been made toward solving the enigma of twentieth century gmslr which is that the observed gmslr has previously been found to exceed the sum of estimated contributions especially for the earlier decades the authors propose the following thermal expansion simulated by climate models may previously have been underestimated because of their not including volcanic forcing in their control state the rate of glacier mass loss was larger than previously estimated and was not smaller in the first half than in the second half of the century the greenland ice sheet could have made a positive contribution throughout the century and groundwater depletion and reservoir impoundment which are of opposite sign may have been approximately equal in magnitude it is possible to reconstruct the time series of gmslr from the quantified contributions apart from a constant residual term which is small enough to be explained as a long term contribution from the antarctic ice sheet the reconstructions account for the observation that the rate of gmslr was not much larger during the last 50 years than during the twentieth century as a whole despite the increasing anthropogenic forcing semiempirical methods for projecting gmslr depend on the existence of a relationship between global climate change and the rate of gmslr but the implication of the authors closure of the budget is that such a relationship is weak or absent during the twentieth century

the role of scour in shipwreck site formation processes and the preservation of wreck associated scour signatures in the sedimentary record evidence from seabed and sub surface data fully submerged shipwreck sites act as open systems with the exchange of material sediment water organic and inorganic objects and energy wave tidal storm across system boundaries formation processes at wreck sites are driven by some combination of chemical biological and physical processes with physical processes dominant in initial phases of site formation scouring and associated depositional patterns that form in response to hydrodynamic forcing are commonly the dominant physical processes acting at shipwreck sites scour is initiated by the introduction of a shipwreck to the seafloor leading to increases in flow velocity and turbulent intensity around the structure near field and far field scour pits form at wreck sites due to the interaction of horseshoe and lee wake vortices with the mobile substrate the morphology of resultant scour signatures are controlled by the orientation of the wreck structure in relation to the prevailing hydrodynamic regime the morphology and size of the wreck and individual site components the hydrodynamic regime currents waves or combined waves and currents bathymetry and the geology of the site seafloor and sub surface conditions individual objects or artefacts may act as nuclei to promote scour at a local scale under high energy conditions groups of artefacts and or disarticulated structural components emanating from a wreck may compound natural scour processes by rolling or sliding under suitable environmental conditions wreck associated scour features can be preserved in the sedimentary record

experimental study of 2d scour and its protection at a rubble mound breakwater abstract this study deals with the 2d scour at the trunk section of a rubble mound breakwater two breakwater models with slopes of 1 1 2 and 1 1 75 are employed for the experimental study of the scour in a wave flume 2d scour at a vertical wall breakwater was also included as a reference case tests were conducted with both regular waves and irregular waves it was found that the scour deposition pattern in front of the rubble mound breakwater emerges in the form of alternating scour and deposition areas lying parallel to the breakwater similar to the case of the vertical wall breakwater the maximum scour depth however was found to be smaller in the present case than that of the vertical wall breakwater case in the case of the irregular waves the scour depth at the breakwater decreases with respect to that experienced in the case of the regular waves countermeasures for toe protection were also investigated for the following cases 1 the protection apron with one layer of stones and 2 that with several layers of stones the mechanism of slumping down of stones of the protection apron was also considered the results of the toe protection study are given in the form of diagrams

wave scour around piles this paper reports the results of an experimental study on the scour around a vertical pile and in groups of piles submitted to wave forcing in particular the influence of the wave non linearity on local scour around single piles has been studied in fact as the characteristics of non linear waves evolves in the domain the scour processes shall depend on the position of the piles i e on the local characteristics of the waves the scour processes around vertical piles located in the surf zone are also discussed in this paper

seismicity and tectonics of the blue ridge area of the mogollon plateau arizona abstract the seismicity of the blue ridge area of the mogollon plateau exists within a framework of tertiary volcanics and normal faulting the seismicity includes earthquake sequences in 1989 and 2005 with principal events as large as richter local magnitude m l 4 6 national earthquake information center neic analysis of this seismicity indicates that it is characterized by normal faulting on northwest trending planes the normal faults form part of the cataract creek fault system that has historically generated earthquakes as large as surface wave magnitude m s 6 2 brumbaugh 1991 bausch and brumbaugh 1997 regionally these northwest trending fracture systems faults of the southern colorado plateau appear to pose the greatest seismic hazard to the grand canyon national park with almost five million visitors per year and the rapidly growing flagstaff area

experiments in reconstructing twentieth century sea levels abstract one approach to reconstructing historical sea level from the relatively sparse tide gauge network is to employ empirical orthogonal functions eofs as interpolatory spatial basis functions the eofs are determined from independent global data generally sea surface heights from either satellite altimetry or a numerical ocean model the problem is revisited here for sea level since 1900 a new approach to handling the tide gauge datum problem by direct solution offers possible advantages over the method of integrating sea level differences with the potential of eventually adjusting datums into the global terrestrial reference frame the resulting time series of global mean sea levels appears fairly insensitive to the adopted set of eofs in contrast charts of regional sea level anomalies and trends are very sensitive to the adopted set of eofs especially for the sparser network of gauges in the early 20th century the reconstructions appear especially suspect before 1950 in the tropical pacific while this limits some applications of the sea level reconstructions the sensitivity does appear adequately captured by formal uncertainties all our solutions show regional trends over the past five decades to be fairly uniform throughout the global ocean in contrast to trends observed over the shorter altimeter era consistent with several previous estimates the global sea level rise since 1900 is 1 70 0 26 mm yr 1 the global trend since 1995 exceeds 3 mm yr 1 which is consistent with altimeter measurements but this large trend was possibly also reached between 1935 and 1950

bed scouring downstream of hydraulic structures under steady flow conditions experimental analysis of space and time scales and implications for mathematical modeling abstract sediment transport and bed deformation in alluvial rivers are space and time dependent the knowledge of the space and time scales can be helpful for the definition of predictive procedures of an alluvial reach response to changing boundary conditions in this work attention is paid to scouring process occurring downstream of the rigid basement of a hydraulic structure the analysis is focused on transient bed profiles which are determined under steady flow conditions by a decrease of the upstream sediment transport rate in particular the paper is aimed at improving understanding of the space and time scales required by the alluvial system to reach the equilibrium conditions for this purpose movable bed runs are carried out in a straight laboratory channel for two values of the water discharge during each run the longitudinal bed profiles are measured at different times based on experimental data spatial scale factors of the bed scouring and of the bed load transport to reach the equilibrium conditions are defined particularly it is found that the scour length varies especially during the first evolution phase and then it oscillates around of a mean value that is about 40 of the channel reach interested by the phenomenon under consideration an expression is found for the adaptation coefficient which allows the estimation of the spatial delay of the bed load transport rate using both the collected data and literature data an expression defining the time scale of scouring is deducted according to this expression the non dimensional time scale is related to shields parameter through an exponential law then by the help of a 1 d numerical model previously developed by the writer the implications for choosing the spatial and temporal resolutions on which numerical results depend significantly are shortly discussed the results show that the time and space scales which represent physical constraints of the spatial and temporal resolutions need to be properly defined in order to simulate the scouring process evolution

active faulting and seismicity in a prefractured terrane grand canyon arizona structural and seismic data for the eastern grand canyon were analyzed to determine the relationship between basement fractures surface faulting and seismicity published structural data were compared with the results of focal mechanism analysis of tremors occurring in the eastern canyon region during the period 1989 2004 previous studies of the geology of this area indicate that the fault and joint trends exposed in the surface rocks and through the entire sedimentary section were first established with predominant northeast and northwest trends in precambrian time the northwest trends of this prefractured terrane correlate with a dominant northwest trend of nodal planes in the seismic data suggesting that the present stress system in the region is favoring the reactivation of the preferentially oriented pre existing northwest trending fractures

experimental investigation into 3d scour processes around a gravity based oscillating water column wave energy converter abstract experimental investigations measuring both bed elevation changes and near structure flow velocities were undertaken to investigate wave scour processes around a model oscillating water column owc wave energy converter wec for a range of incident wave conditions at approximately 1 20 scale the experiment design was informed by a proposed 200 kw owc wec deployment site at king island australia the measurements provide the first experimental data on scour around an owc wec structure and one of the most comprehensive experimental studies of wave scour around a large rectangular cross section structure high resolution scour erosion and deposition patterns were measured using an above water laser based system for normally incident waves scour holes were observed to develop on all four corners and the size of the scour holes at the four corners increased with the keulegan carpenter kc number an additional scour hole trench also formed along the upstream face of the owc wec due to the flow in out of the owc wec internal chamber changing the incident wave propagation angle by 20 has a significant effect on the observed scour patterns with reduced scour on the front and back corners but significant scour holes remaining on the other two corners it is found that if the model is not sufficiently embedded into the sediment bed scour can undermine a significant area under the structure with quadrant shaped scour holes underneath the back corners extending to approximately 25 of the total base area suggesting a risk of differential settlement in field conditions

microplate capture rotation of the western transverse ranges and initiation of the san andreas transform as a low angle fault system tectonic rotation of the western transverse ranges block is explained by capture of the partially subducted monterey microplate by the pacific plate at about anomaly 6 time ca 20 ma as pacific monterey spreading slowed and eventually ceased the slip vector along the gently northeast dipping subduction interface beneath the california margin changed from slightly oblique subduction to transtensional dextral transform motion this change in slip vector and a shift of pacific plate motion eastward along the already subducted monterey plate interface imply that the san andreas transform began as a system of low angle faults that locally subjected the overriding continental margin to distributed basal shear and crustal extension this basal shear produced the rotated western transverse ranges this model helps explain the timing of initial rotation and basin formation the sudden appearance of widely distributed transform motion well inland of the margin in early miocene time why the western transverse ranges uniquely rotated as a large coherent crustal block and several fundamental structural characteristics of central and southern california the model also provides major constraints on the amount of pacific north america strike slip motion the position through time of offshore oceanic plates relative to onshore geology and a general explanation for what may happen as a spreading ridge approaches a trench and the subduction zone evolves into a transform system

is there a 60 year oscillation in global mean sea level 1 we examine long tide gauge records in every ocean basin to examine whether a quasi 60 year oscillation observed in global mean sea level gmsl reconstructions reflects a true global oscillation or an artifact associated with a small number of gauges we find that there is a significant oscillation with a period around 60 years in the majority of the tide gauges examined during the 20th century and that it appears in every ocean basin averaging of tide gauges over regions shows that the phase and amplitude of the fluctuations are similar in the north atlantic western north pacific and indian oceans while the signal is shifted by 10 years in the western south pacific the only sampled region with no apparent 60 year fluctuation is the central eastern north pacific the phase of the 60 year oscillation found in the tide gauge records is such that sea level in the north atlantic western north pacific indian ocean and western south pacific has been increasing since 1985 1990 although the tide gauge data are still too limited both in time and space to determine conclusively that there is a 60 year oscillation in gmsl the possibility should be considered when attempting to interpret the acceleration in the rate of global and regional mean sea level rise

seismicity and active faulting of the kanab fredonia area of the southern colorado plateau 1 detailed study of the historic seismicity of the kanab fredonia area adds information to the location of the colorado plateau tectonic boundary in this area and to the nature of contemporary seismicity and faulting on this part of the colorado plateau historic seismicity over 45 years 1959 2004 defines a band of activity which extends through fredonia arizona and into southern utah around kanab the area is dominated by north trending high angle normal faults the spatial distribution of epicenters consists of clusters associated with the west kaibab big springs and toroweap sevier faults indicating that these faults may be active four focal mechanism solutions show basin range style high angle normal faulting on north to north northwest trending surfaces that are parallel to subparallel in most cases to mapped quaternary faults this suggests a present east west extension occurring on the southern colorado plateau for the kanab fredonia area and an expansion of the adjacent basin range province eastward into the plateau as far as the west kaibab big springs faults the west kaibab big springs faults are proposed to be the tectonic boundary of the southern colorado plateau in this area since they mark the limit of significant seismic activity that is combined with basin range type faulting

global sea level trend in the past century data derived from tide gauge stations throughout the world indicate that the mean sea level rose by about 12 centimeters in the past century the sea level change has a high correlation with the trend of global surface air temperature a large part of the sea level rise can be accounted for in terms of the thermal expansion of the upper layers of the ocean the results also represent weak indirect evidence for a net melting of the continental ice sheets

recent global sea level acceleration started over 200 years ago 1 we present a reconstruction of global sea level gsl since 1700 calculated from tide gauge records and analyse the evolution of global sea level acceleration during the past 300 years we provide observational evidence that sea level acceleration up to the present has been about 0 01 mm yr2 and appears to have started at the end of the 18th century sea level rose by 6 cm during the 19th century and 19 cm in the 20th century superimposed on the long term acceleration are quasi periodic fluctuations with a period of about 60 years if the conditions that established the acceleration continue then sea level will rise 34 cm over the 21st century long time constants in oceanic heat content and increased ice sheet melting imply that the latest intergovernmental panel on climate change ipcc estimates of sea level are probably too low

scour at the round head of a rubble mound breakwater abstract this study complements the investigation on scour around the head of a breakwater reported in the companion paper where the case of vertical wall breakwater was considered the present study deals with the case of rubble mound breakwater two key mechanisms with regard to the scour processes around the round head of the breakwater are identified one is the steady streaming occurring around the head in plan view this generates a scour hole in front of the breakwater the second one is the plunging breaker which occurs locally at the breakwater head this generates a scour hole at the lee side of the breakwater the keulegan carpenter number based on the base diameter of the breakwater head appears to be the main governing parameter regarding the streaming induced scour while a parameter namely t p gh s h involving the peak wave period tp the significant wave height hs the water depth h and the acceleration due to gravity g appears to be the main governing parameter regarding the breaker induced scour the scour depth increases with increasing values of these parameters the conventional stone protection is investigated in the study an empirical formula is developed for the extent of the protection layer

a 20th century acceleration in global sea level rise 1 multi century sea level records and climate models indicate an acceleration of sea level rise but no 20th century acceleration has previously been detected a reconstruction of global sea level using tide gauge data from 1950 to 2000 indicates a larger rate of rise after 1993 and other periods of rapid sea level rise but no significant acceleration over this period here we extend the reconstruction of global mean sea level back to 1870 and find a sea level rise from january 1870 to december 2004 of 195 mm a 20th century rate of sea level rise of 1 7 0 3 mm yr 1 and a significant acceleration of sea level rise of 0 013 0 006 mm yr 2 this acceleration is an important confirmation of climate change simulations which show an acceleration not previously observed if this acceleration remained constant then the 1990 to 2100 rise would range from 280 to 340 mm consistent with projections in the ipcc tar

onshore scour characteristics around submerged vertical and semicircular breakwaters abstract a laboratory study is presented herein investigating the two dimensional onshore scour along the base of submerged vertical and semicircular breakwaters experiments were conducted with normally incident monochromatic waves breaking at the breakwater on both sloping and horizontal sandy bottoms a principle conclusion of this investigation is that the characteristics of onshore breakwater scour are independent of submerged breakwater shape type it is also concluded that the onshore scour patterns can be divided into two distinct regimes that solely rely on the keulegan carpenter number kc h i w bw wbw breakwater crest width hi incident wave height for kc values larger than the scour forms detached from the breakwater while for kc values smaller than or equal to the scour occurs attached to the onshore breakwater face three important scour characteristics are investigated maximum scour depth smax scour length ls and the distance of smax location from the onshore breakwater face ds smax value is observed to be regime independent and rely on both kc and the mobility number h i t sinh k h 2 g d g reduced gravitational acceleration d median diameter of the sediment k wave number h still water depth t wave period while ls and ds are observed to be regime dependent and rely only on kc semi empirical parameterizations to predict smax ls and ds values for onshore breakwater scour are proposed

a partial cell technique for modeling the morphological change and scour abstract a novel partial cell technique applied on structured grids is developed to track the deformation of water soil interface associated with beach morphological change and toe scour in front of coastal structures it allows the use of the same orthogonal structured grids for morphological sediment transport and hydrodynamic models therefore has the advantage of consuming less cpu and without the need to adapt grids to the evolving beach morphology an improved sand slide model with better mass conservation is introduced to resolve the avalanche behaviour of the sediment motion the rans vof hydrodynamic model has been extended to cope with complex bathymetry the newly developed numerical model suite coupling the rans vof model a bedload sediment transport model and a morphological model using the partial cell technique are validated against the analytical solutions and laboratory measurements for different incoming wave conditions local water depths and bottom slopes this study reveals the key processes that govern the behaviour of beach morphology change in front of a vertical coastal structure during storms the model data comparisons demonstrate the robustness of partial cell technique to capture the movement of the water soil interface

suction removal of sediment from between armor blocks this paper presents the results of an experimental investigation on suction removal of sediment from between armor blocks stones placed on a loose bed the process of suction has been investigated it was found that the vortices that form in the holes between the armor blocks are key to the process the sediment swept into these vortices is entrained into the main body of the flow by these same vortices the suction removal of sediment from between the armor blocks the critical condition for the onset of suction was determined it was found that the onset of suction is governed by two parameters 1 the shields parameter based on the sediment size and 2 the ratio of sediment size to stone size d d the variation of the critical shields parameter for suction as a function of d d was determined for a broad range of the parameter d d namely 0 001 d d 1 the timescale of the suction process and the downward displacement of stones the general lowering of the armor layer have also been investigated

a simplified method to downscale wave dynamics on vertical breakwaters abstract a coastal structure is usually designed with the final objective to guarantee its functionality and stability throughout its life cycle regarding stability the three main failure modes are sliding overturning and failure of the foundations to accomplish the design objectives a design sea state is usually used when calculating the loads and scour around the structure this design sea state corresponds to a certain sea state with specific return period values of a significant wave height however the combination of different simultaneous sea state parameters can produce other critical situations compromising the stability of the structure which then require the calculation of long time series of wave forces corresponding to long term historical wave situations moreover a design force associated to a certain return period can be defined from the time series of the stability parameters the most accurate techniques which can be used to estimate structure stability are based on numerical and physical models but these are very time consuming and the calculation of long time series is therefore unfeasible here we propose a hybrid methodology to transform wave conditions into wave forces acting upon vertical structures and scour around it the methodology consists of a selection of a subset of sea states representative of wave climate at the structure location using a maximum dissimilarity algorithm the wave forces acting upon the structure and scour around it for the wave situations selected are then estimated as is the reconstruction of the calculated parameters corresponding to historical sea states using an interpolation technique based on radial basis function the validation of the results through a direct comparison between reconstructed series and analytically semi empirical formulations calculated ones confirms the ability of the developed methodology to reconstruct time series of stability parameters on vertical breakwaters this methodology allows its application to numerical and physical models

the role of computational fluid dynamics in understanding shipwreck site formation processes studies indicate that physical processes commonly dominate the initial stages of wreck site formation detailed knowledge and understanding of hydro and sediment dynamics are therefore imperative for studies dealing with site formation and in situ preservation in this investigation the results of computational fluid dynamic modelling over a shipwreck site are presented using a high resolution surface derived from multi beam echo sounder data and boundary conditions constrained by field measurements sediment samples and flow measurements simulation of the 3 dimensional flow velocity field around the wreck site and secondary products derived from the computational model confirm that flow velocity and turbulence are both amplified by the presence of the wreck causing changes in the morphology of the flow regime flow contraction the formation of lee wake vortices behind the structure accompanied by vortex shedding and increased turbulence are all observed shear stress and tke amplification three to four times greater than ambient values are recorded downstream of the wreck structure benefits of this approach for studies of site formation and in situ conservation include the inexpensive open source and desk based nature of the investigation

bottom pressure distribution due to wave scattering near a submerged obstacle the dynamic pressure distribution on the bottom of a wave flume due to the interaction of water waves with a submerged structure is investigated experimentally and analytically for both first and second order gravity waves of finite amplitude the dynamic pressure excess is found to be very important even for incoming waves propagating in deep water conditions in this depth condition a high pressure zone thirty times larger than the dynamic pressure excess expected in the absence of the obstacle is found in its vicinity on the other hand a low pressure zone is observed in the vicinity of the submerged obstacle for incoming waves propagating in smaller depth conditions in any case pressure gradients remain important the second order disturbance is found to be larger than first order in deep water conditions for some specific conditions and locations this result is interpreted in terms of nonlinear coupling of first order components including local modes

hydrodynamic and morphodynamic response of isolated and multiple low crested structures experiments and simulations abstract low crested structures for beach defence purposes are frequently configured in the form of cells this paper investigates the hydrodynamic and morphological response of such defence schemes by means of laboratory experiments and numerical simulations experiments were carried out at the large mobile bed basin of the laboratorio di idraulica costiera of the politecnico di bari it tests peculiarity is the simultaneous simulation of three different types of lateral confinement a channel representative of an indefinitely long structure and two areas with narrow and wide gaps representative of a common scheme and of an almost isolated structure respectively submerged zero freeboard and emerged conditions were tested a typical storm of the northern adriatic sea was reproduced by 6 wave attacks water level and currents were measured in front and behind the structures at gaps and roundheads results focusing on rip current intensities and piling up are presented and discussed an extensive plan view of wave intensities and flow patterns inside the basin is provided through numerical simulations with mike 21 numerical suite the sand bed was surveyed along 30 profiles covering the narrow gap area and the isolated structure roundheads for the submerged conditions tests 15 of these profiles and the shoreline position were monitored after each step of the simulated storm average and maximum values of local erosion at the structure toe are presented time evolution of erosion at gaps is related to the main hydrodynamic variables through bijker sediment transport formula evaluation of volume changes in the protected area shows that sand is in average trapped behind the barriers being transported offshore from gaps and returning inshore over the crest the observed and reconstructed transport mechanism is a combination of bed load and suspended transport the latter being slightly more important bed level changes are well predicted by morphodynamic simulations performed with mike 21 cams

numerical and experimental investigation of flow and scour around a circular pile the flow around a vertical circular pile exposed to a steady current is studied numerically and experimentally the numerical model is a three dimensional model the model validation was achieved against new experimental data which include two component laser doppler anemometry lda flow measurements and the hot film bed shear stress measurements and reported in the present paper and the data of others and a k w turbulence model was used for closure the model does not have a free surface facility and therefore is applicable only to cases where the froude number is small fr 0 0 2 the flow model was used to study the horseshoe vortex and lee wake vortex flow processes around the pile the influence on the horseshoe vortex of three parameters namely the boundary layer thickness the reynolds number and the bed roughness was investigated in the latter investigation the steady solution of the model was chosen a study of the influence of the unsteady solution on the previously mentioned flow processes was also carried out the ranges of the parameters covered in the numerical simulations are the boundary layer thickness to pile diameter ratio is varied from 2 x 10 2 to 10 2 the pile reynolds number from 10 2 to 2 10 6 and the pile diameter to roughness ratio from 2 to about 10 3 the amplification of the bed shear stress around the pile including the areas under the horseshoe vortex and the lee wake region was obtained for various values of the previously mentioned parameters the steady state flow model was coupled with a morphologic model to calculate scour around a vertical circular pile exposed to a steady current in the case of non cohesive sediment the morphologic model includes i a two dimensional bed load sediment transport description and ii a description of surface layer sand slides for bed slopes exceeding the angle of repose the results show that the present numerical simulation captures all the main features of the scour process the equilibrium scour depth obtained from the simulation agrees well with the experiments for the upstream scour hole some discrepancy up to 30 was observed however for the downstream scour hole the calculations show that the amplification of the bed shear stress around the pile in the equilibrium state of the scour process is reduced considerably with respect to that experienced at the initial stage where the bed is plane

new estimates of secular sea level rise from tide gauge data and gia modelling summary during the last three decades at least 30 independent estimates of the secular global mean sea level rise gmslr have been published based on sufficiently long tide gauge tg records despite its apparent simplicity the problem of gmslr is fraught with a number of difficulties which make it one of the most challenging questions of climate change science not surprisingly published estimates show considerable scatter with rates ranging between 1 and 2 mm yr 1 for observations on the century timescale in previous work the importance of glacial isostatic adjustment gia upon the assessment of the gmslr has been clearly demonstrated in particular starting from the 1980s gia models have been routinely employed to decontaminate tg observations from the effects of melting of the late pleistocene ice sheets to fully highlight the sea level variations driven by climate change however uncertainties associated with the earth s rheological profile and the time history of the past continental ice sheets can propagate into the gia corrections after revisiting previous work and estimates we suggest a significant modification of the criteria for the selection of the tgs which are most suitable for the robust assessment of the secular gmslr in particular we seek a set of tgs for which gia corrections are essentially independent of the parametrization of the rheological profile of the earth s mantle and of the detailed time chronology of surface loading this insensitivity is established by considering predictions based upon three gia models widely employed in the recent literature namely ice 3g ice 5g and the one developed at the research school of earth sciences of the national australian university applying this approach and selection criteria previously proposed in the literature we identify a set of 22 sufficiently evenly distributed tgs by simple statistical methods these records yield a preferred gia independent gmslr estimate since 1880 namely 1 5 0 1 mm yr 1 rms 0 4 mm yr 1 wrms 0 3 mm yr 1 this value is consistent with various previous estimates based on secular tg observations and with that proposed for the 20th century by the intergovernmental panel on climate change ipcc fourth assessment report 1 7 0 5 mm yr 1

sinking floatation of pipelines and other objects in liquefied soil under waves abstract this paper presents the results of an experimental study where the sinking and floatation of a pipeline and other objects namely a sphere and a cube in a silt bed was investigated the bed was exposed to progressive waves two kinds of experiments were made the undisturbed flow experiments and the experiments with the structure model a pipeline a sphere and a cube in the former experiments the pore water pressure was measured across the soil depth the pore water pressure built up as the waves progressed the soil was liquefied for wave heights larger than a critical value regarding the experiments with the structure model the displacement of the structure sinking or floatation was measured simultaneously with the pore water pressure the influence of various parameters such as the initial position of the object the specific gravity the soil layer thickness and the wave height was investigated it was found that while the pipe sank in the soil to a depth of 2 3 times the pipe diameter the sphere sank to even larger depths the pipe with a relatively small specific gravity initially buried floated to the surface of the soil the drag coefficients for the objects sinking in the liquefied soil were obtained

on berm breakwaters stability scour overtopping abstract experimental studies on the stability of multilayer berm breakwaters have been carried out two stone mass densities have been used the results have been compared with the results of homogenous berm breakwaters and with other results of multilayer berm breakwaters an equation for the berm recession for homogenous berms has been derived including the effect of stone gradation and water depth erosion at and erosion protection of berm breakwaters have been investigated as well as wave overtopping discharges

chalk shore platform erosion in the vicinity of sea defence structures and the impact of construction methods erosion of the intertidal chalk platform in the vicinity of groynes and seawalls is evident to the naked eye along many stretches of the engineered coastline of southeast england leading to undermining and eventually failure of these structures however quantification of the magnitude and spatial extent of the erosion has been difficult to date because of a lack of data about the past elevation of the platform the application of softcopy photogrammetry makes it possible to recreate past platform elevations from historic air photographs and to compare these with elevations from modern air photographs coastal sea defence structures have been installed along the chalk coast east of brighton at various dates over the past 70 years during this period the construction methods have changed from predominantly manual labour to a reliance on heavy machines the analysis of erosion patterns around structures built since the 1970s using heavy machinery show that surface lowering is 4 to 25 times greater in the vicinity of these structures than across the platform as a whole in contrast there is no similar pattern of increased erosion around structures built using predominantly manual labour in the 1930s a four fold increase in average surface lowering is found also along a vehicle trackway that crosses the mid platform depressions developed by enhanced lowering in the front of seawalls generate their own dynamic of increased erosion by trapping pebbles and cobbles that enhance the abrasion of the chalk through bedload transport under standing waves in front of the walls

on postglacial sea level summary an exact method is presented for calculating the changes in sea level that occur when ice and water masses are rearranged on the surface of elastic and viscoelastic non rotating earth models the method is used to calculate the instantaneous elastic and delayed vi scoelastic sea level changes following the partial melting of late quaternary ice sheets we find that there can be large errors in the usual assumption that changes in sea level are uniform over the ocean basins if a quantity of ice equivalent to a uniform 100 m rise in sea level melts from the laurentide and fennoscandian ice sheets then in the south pacific the instantaneous rise in sea level can be as large as 120m in the north atlantic the instantaneous rise is always less than 100 m there is a zone in the north atlantic with almost no sea level change and near greenland and norway the sea level falls rather than rises by over 100 m one thousand years after the melting a forebulge migrating towards the ice loads causes water to flow from the south pacific into the north pacific suggesting that raised beaches should occur in the south pacific the gravitational attraction of an ice mass upon a nearby ocean tends to hold sea level high in the vicinity of the ice this extra load near the ice may have a significant influence on postglacial isostatic adjustment

scour around coastal structures a summary of recent research abstract this paper summarizes the results of the european union marine science and technology eu mast iii project scour around coastal structures scarcost the summary is presented under three headings 1 introduction 2 flow and scour processes with the subheadings flow and scour processes around vertical cylinders flow and scour processes at detached breakwaters flow and scour processes at submerged breakwaters and the effect of turbulence on sediment transport and 3 sediment behaviour close to the structure with the subheadings field measurement and analysis of wave induced pore pressures and effective stresses around a bottom seated cylinder non linear soil modelling with respect to wave induced pore pressures and gradients wave induced pressures on the bottom for non linear coastal waves including also wave kinematics development of a numerical model linear soil modelling to calculate wave induced pore pressures the effect of liquefaction on sediment transport penetration of blocks in non consolidated fine soil and cyclic stiffness of loose sand the paper also includes a discussion of the role of scale effects in laboratory testing and the applicability of the results obtained in supporting engineering design

present day motion and deformation of the colorado plateau 1 we analyze data from continuous gps stations in the southwestern united states and present the first observations of a systematic motion of the colorado plateau region relative to a north america fixed reference frame westward velocities increase rapidly across the wasatch fault system which comprises the plateau s northwestern margin but increase more gradually between the great plains and the mojave desert province we detect no significant extension across most of the rio grande rift but extension could be as high as 0 5 mm yr 1 along its southernmost portion we suggest that the motion between the plateau and stable continent may partly be accommodated instead across the jemez lineament only when we consider gps velocities within the plateau s center do the data support a rigid body rotation of 0 103 ma 1 around a pole in the northern rocky mountains we conclude that active extension has encroached into the plateau from both the east and west

contemporary seismicity faulting and the state of stress in the colorado plateau the contemporary seismicity of the colorado plateau based on seismic monitoring in the past 30 yr can be characterized as being of small to moderate magnitude and contrary to earlier views of a low to moderate rate of occurrence with earthquakes widely distributed concentrations of earthquakes have been observed in a few areas of the plateau the most seismically active area of the colorado plateau is the eastern wasatch plateau book cliffs where abundant small magnitude seismicity is induced by coal mining the largest earthquakes observed to date of estimated richter magnitude m l 5 6 have generally occurred in northern arizona although very few earthquakes can be associated with known geologic structures or tectonic features in the colorado plateau seismicity appears to be the result of the reactivation of pre existing faults lacking surficial expression but favorably oriented to the tectonic stress field the small to moderate size of the earthquakes and their widespread distribution are consistent with a highly faulted precambrian basement and upper crust and a moderate level of differential tectonic stress earthquakes in the plateau generally occur in the upper crust from the near surface to a depth of 15 20 km although events have been observed in both the lower crust and uppermost mantle in areas of low to normal heat flow the latter suggests that temperatures are sufficiently low at these depths that brittle failure and hence earthquakes are still possible the predominant mode of tectonic deformation within the plateau appears to be normal faulting on northwest to north northwest striking faults with some localized occurrences of strike slip faulting on north west or northeast striking planes at shallow depths the contemporary state of stress within the plateau is characterized by approximate northeast trending extension in contrast to the previous belief that the plateau was being subjected to east west tectonic compression one area of the plateau the eastern wasatch plateau and book cliffs may still be characterized by compressive stresses however the nature of these stresses is not well understood

local scour at roundhead and along the trunk of low crested structures abstract this paper summarizes the results of an experimental study on scour around submerged breakwaters the objective of the study is to make a systematic study of scour around low crested structures submerged breakwaters both the trunk scour and the roundhead scour have been investigated the breakwater models have a side slope of 1 1 5 to substantiate scour measurements velocity measurements also were made the latter data were used to obtain steady streaming in front of the breakwater regarding the trunk scour study the experiments indicated that substantial scour may occur at the toe of the structure this is irrespective of whether the breakwater is impermeable or porous the scour data although very limited indicated that the scour depth is in the same order of magnitude as in the case of emerged breakwaters the trunk experiment further showed that scour deposition bathymetry does not exhibit the pattern experienced in the case of emerged breakwaters where the scour and deposition areas are correlated with the nodal and antinodal points of the standing wave in front of the structure furthermore it was found that scour occurs not only at the offshore side of the breakwater but also at the onshore side as for the roundhead scour study it was found that severe scour can be experienced at the roundhead the scour can occur both at the offshore side of the roundhead and at the back the one at the offshore side is caused by the combined effect of severe waves and the steady streaming and that at the back is caused by wave breaking wave overtopping it was found that the streaming induced scour is governed by the free board to wave height ratio f h and the keulegan carpenter number kc while the plunging breaker induced scour is governed by the free board to water depth ratio f h and the plunger parameter t w g h h tw being the wave period the maximum scour depth at the toe of the structure and the plan view extent of the scour hole are given in terms of the governing parameters the results from the present laboratory tests for the roundhead scour are compared with prototype observations undertaken in the present study recommendations are made for toe protection for both the trunk scour and the roundhead scour

modelling the effect of wave overtopping on nearshore hydrodynamics and morphodynamics around shore parallel breakwaters wave overtopping nearshore coastal structures such as shore parallel breakwaters can significantly alter the current circulation and sediment transport patterns around the structures which in turn affects the formation of tombolos and salients in the nearshore area this paper describes the implementation of a wave overtopping module into an existing depth averaged coastal morphological mode coast2d and model applications to investigate the effect of wave overtopping on the hydrodynamics and morphodynamics around a group of shore parallel breakwaters the hydrodynamic aspects of the model were validated against a series of laboratory conditions the model was then applied to a study site at sea palling norfolk uk where 9 shore parallel segmented breakwaters including 4 surface piercing and 5 low crested breakwaters are present for the storm conditions in nov 2006 the model results were compared with laboratory data and field measurements showing a good agreement on both hydrodynamics and morphological changes further analysis of wave overtopping effect on the nearshore hydrodynamics and morphodynamics reveals that wave overtopping has significant impacts on the nearshore circulation sediment transport and the resulting morphological changes within such a complex breakwater scheme under the storm and macro tide conditions the results indicate the importance of including the wave overtopping in modelling nearshore morphodynamics with the presence of coastal structures

current induced scour at monopile foundations subjected to lateral vibrations abstract monopile foundations are the most common foundation type of offshore wind turbines in the ocean environment in addition to threats related to scour of the foundation offshore monopiles of wind turbines also are subjected to lateral vibrations induced by waves and winds over the past decades the scour process induced by flow and pile soil interactions has been independently investigated by researchers from the fields of hydraulic coastal engineering and soil mechanics respectively very few studies can be found in the published literature on lateral vibration effects on scour at monopile foundations the objective of this experimental study is to improve understanding of the mechanics of current induced scour at monopiles subjected to lateral vibrations with a non cohesive bed when compared to a non vibrating monopile the results show that scouring around its vibrating counterpart is comparatively faster during the first few hours of the test this is primarily due to soil densification and the subsidence process induced by monopile seabed interactions increasing both the frequency and amplitude of the monopile vibration would decrease the equilibrium scour depths and scour hole slopes the reduction of equilibrium scour depth likely is due to the effect of sediment ratcheting motions on the surface of the scour hole an empirical dimensionless equation is proposed to estimate equilibrium scour depth at monopiles subjected to lateral vibrations

seismic and tectonic analysis of the 2014 2015 flagstaff arizona earthquake sequence abstract the 1 december 2014 moment magnitude m w 4 7 arizona earthquake occurred 13 km southwest of the city of flagstaff arizona flagstaff is located within the northern arizona seismic belt and the san francisco volcanic field the flagstaff area is subject to infrequent moderate magnitude earthquakes such as the 1993 cataract creek m w 5 3 and the 1912 surface wave magnitude m s 6 2 events the epicenter of the m w 4 7 earthquake lies 2 km to the east of the oak creek normal fault this is the most proximal event to the fault in the last 40 years since the seismographic networks were first deployed the earthquake was recorded throughout northern arizona by stations of the arizona integrated seismic network data were also acquired by the network from two foreshocks of duration magnitude m d 3 2 and 2 8 and 27 aftershocks m d 1 4 3 0 locations were obtained using hypoinverse 2000 and epicenters were accurate in most cases to within 3 0 km or less fault plane solutions were obtained from the mainshock and from seven of the other events of the sequence analysis of the data indicates that release of the stress was controlled by the presence of pre existing structures including the oak creek fault and prominent fractures in the hanging wall block of the fault this is the first well documented fault slip sequence in northern arizona that has shown 1 active northeast ne trending fracture and 2 a pattern of alternation of stress release on ne and northwest nw trending fractures the alternation of stress release accommodates southeast se directed slip on both ne and nw trends the reactivation of the oak creek fault in northern arizona appears to be the result of the westward motion of the colorado plateau producing a strain rate field that implies nw se extension

inferring stress from faulting from early concepts to inverse methods abstract we review the evolution of concepts on and methods of estimating the state of stress from fault movements theories of failure in isotropic materials suggested a simple geometrical construction of optimal principal stress directions from a fault plane and its associated slip these optimal directions align shear stress and slip directions and maximize the difference between shear stress and frictional resistance on the fault plane optimal stress directions for calcite twinning are obtained by a similar construction with the difference that they maximize shear stress force representation of seismic sources independently introduced pressure p and tension t axes at positions that also maximize shear stress on both nodal planes frictional slip theory and the constraint that slip and shear stress directions be parallel allowed to address reactivation of pre existing faults this suggested that stress could also be inverted from reactivated fault and slip data or earthquake focal mechanisms early methods relied on geometrical constructions as a substitute for calculations whereas later methods relied on software as these calculations became tractable with the help of computers similar methods were developed for the inversion of stress from crystal twin gliding with non optimal geometry with a different criterion that relies on a threshold of the component of shear stress along the gliding line even though these methods seek a common stress tensor compatible with fault and slip data their main use is to separate polyphase data into homogeneous subsets and help deciphering complex tectonic histories fault and slip data can also be analyzed to constrain the strain rather than the stress tensor in most cases this involves a summation and yields an average strain for the considered rock volume stress inversion thus appears better suited for differentiating heterogeneous data whereas strain analysis appears better suited for homogenizing them

reconstruction of regional mean sea level anomalies from tide gauges using neural networks 1 the 20th century regional and global sea level variations are estimated based on long term tide gauge records for this the neural network technique is utilized that connects the coastal sea level with the regional and global mean via a nonlinear empirical relationship two major difficulties are overcome this way the vertical movement of tide gauges over time and the problem of what weighting function to choose for each individual tide gauge record neural networks are also used to fill data gaps in the tide gauge records which is a prerequisite for our analysis technique a suite of different gap filling strategies is tested which provides information about stability and variance of the results the global mean sea level for the period january 1900 to december 2006 is estimated to rise at a rate of 1 56 0 25 mm yr which is reasonably consistent with earlier estimates but we do not find significant acceleration the regional mean sea level of the single ocean basins show mixed long term behavior while most of the basins show a sea level rise of varying strength there is an indication for a mean sea level fall in the southern indian ocean also for the the tropical indian and the south atlantic no significant trend can be detected nevertheless the south atlantic as well as the tropical atlantic are the only basins that show significant acceleration on shorter timescales but longer than the annual cycle the basins sea level are dominated by oscillations with periods of about 50 75 years and of about 25 years consequently we find high lagged correlations between the single basins

scour development around a jacket structure in combined waves and current conditions compared to monopile foundations abstract this paper presents the results of an experimental study on the scour development of a hydraulic transparent offshore foundation exposed to combined waves and current irregular waves propagating perpendicular to a current were simulated in a wave current basin the physical model tests were conducted in a length scale of 1 30 while measurements of the scour development over time were achieved by echo sounding devices placed at several locations at the upstream and downstream side of the jacket structure insights were gained on the scour development and time scale of the scouring process around a complex jacket structure for different wave current conditions the results were presented with respect to the keulegan carpenter kc number and the relative wave current velocity wave conditions were adjusted so that kc numbers between 6 7 and 23 4 could be tested in a systematic wave current test program with tests reaching from wave dominated conditions up to current dominated conditions measured scour depths were critically assessed by an extrapolation to expected equilibrium scour depths with respect to the current flow direction the experiments showed generally larger scour depths at the upstream side and lower scour depths on the downstream side for each pile of the jacket structure the development of global scour around the structure intensified with increasing relative wave current velocity as a result a practical formulation is proposed for the reliable prediction of local scour depths around a jacket foundation in combined wave current conditions finally dimensionless time scales and observed as well as predicted scour depths are compared to values for the scour development around monopiles

probabilistic surface reconstruction of coastal sea level rise during the twentieth century we present a new surface reconstruction procedure based on the bayesian inference method for coastal relative sea level variation during the twentieth century average rates are computed from tide gauge records models based on a voronoi tessellation adapt to the level of information which proves well suited to the strong heterogeneity of data each point of the reconstructed surface is defined through a probability density function a format particularly well adapted to this climate related datum the resolution of reconstructed surfaces strongly varies among the six large regions considered and within a given region anomalous sea level variations recorded locally are shown to reflect either anthropogenic effects or well identified fast tectonics for a poor data coverage these can cause a problematic distortion of the reconstructed surface europe north america australia and africa present a single trend with a decreasing precision of the reconstructed surface as a function of resolution of the tide gauge record the most prominent feature in europe is the pronounced uplift of fennoscandia coasts of united states have the best resolution in north america and present stronger rates of sea level rise on the atlantic than their european counterparts australia especially in the north and africa are poorly resolved asia and south america depart clearly from this trend a relatively uniform rise is obtained for asia in spite of a good tide gauge record conversely the reconstructed surface for south america presents an exceptional degree of roughness at odds with a relatively poor record overall this method not only offers a new assessment of sea level change validating earlier results but also quantifies the reliability of estimates

rapid source mechanism analysis of the april 29 1993 cataract creek mw 5 3 northern arizona earthquake abstract the source mechanism of two moderate size normal faulting earthquakes located slightly south of the grand canyon in arizona are studied using several near real time seismic wave analysis procedures the events are found to have source depths near 10 to 15 km and the smaller of the two events m b 4 8 is used to provide empirical green9s functions to analyze the rupture directivity of the larger m w 5 3 mainshock these events indicate complexity in the crustal stress environment on the western margin of the colorado plateau