tower ocean wave and radar dependence experiment an overview the tower ocean wave and radar dependence experiment toward is a coordinated effort involving both field experimentation and theoretical investigations to address the divergent hypotheses on the mechanisms involved in synthetic aperture radar sar imaging of the ocean surface in the formulation of the experiment it was recognized that three distinct disciplines were to be addressed 1 hydrodynamics 2 radar backscatter and 3 sar image processing the field operations were executed in three 6 week segments during the period october 1984 to january 1986 the naval ocean systems center tower located offshore of mission beach san diego california was used as the focal point for the field operations the primary measurements included in situ capillary and short gravity waves long surface waves and internal waves ambient current and detailed meteorological measurements stereophotography tower based multifrequency radars and an l band sar deployed on board the nasa cv 990 the single most significant result is the determination that none of the available hypotheses on sar imaging of long surface waves could be demonstrated to explain all the sar observations obtained in toward specific results are reported

tsunami generation and propagation from the mjolnir asteroid impact in the late jurassic period about 142 million years ago an asteroid hit the shallow paleo barents sea north of present day norway the geological structure resulting from the impact is today known as the mjlnir crater the present work attempts to model the generation and the propagation of the tsunami from the mjolnir impact a multi material hydrocode sova is used to model the impact and the early stages of tsunami generation while models based on shallow water theories are used to study the subsequent wave propagation in the paleo barents sea we apply several wave models of varying computational complexity this includes both three dimensional and radially symmetric weakly dispersive and nonlinear boussinesq equations as well as equations based on nonlinear ray theory these tsunami models require a reconstruction of the bathymetry of the paleo barents sea the mjolnir tsunami is characteristic of large bolides impacting in shallow sea in this case the asteroid was about 1 6 km in diameter and the water depth was around 400 m contrary to earthquake and slide generated tsunamis this tsunami featured crucial dispersive and nonlinear effects a few minutes after the impact the ocean surface was formed into an undular bore which developed further into a train of solitary waves our simulations indicate wave amplitudes above 200 m and during shoaling the waves break far from the coastlines in rather deep water the tsunami induced strong bottom currents in the range of 30 90 km h which presumably caused a strong reworking of bottom sediments with dramatic consequences for the marine environment

comments on on the focusing issue of synthetic aperture radar imaging of ocean waves by c bruning et al in the above named work see ibid vol 29 p 120 8 1991 c bruning et al present results that show the application of the velocity bunching model to synthetic aperture radar sar images obtained during the tower ocean wave and radar dependence toward experiment the commenters argue that some of the observations presented require classification and discussion an attempt is made in this comment to clarify the issues and to present some new relevant results obtained from the sar x band and ocean nonlinearities chesapeake light tower saxon clt experiment

tsunami in coastal zone due to meteorite impact the impact of a meteorite into the ocean surface is a rare phenomenon however it can be catastrophic especially for the coastal area the aim of the paper is to describe the evolution of the tsunami impulse due to meteorite impact in shallow water including energy dissipation due to bottom friction and wave breaking as the exact nonlinear solutions for tsunami transformation with energy loss due to wave breaking are not known the linearised equations of motion are used and energy loss is parameterised accordingly to describe the evolution of tsunami impulse in shallow water the hilbert transform technique was introduced it facilitates considerably the evaluation of the tsunami impulse transformation its run up and coast inundation range examples are included to illustrate the applicability of the theoretical derivations

impact tsunami eltanin employing classical tsunami theory and elementary assumptions about the initial shape of impact cavities we compute tsunami from the eltanin asteroid collision at 2 15 ma an eltanin impactor 4 km in diameter would have blown an initial cavity as deep as the ocean and 60 km wide into the south pacific and delivered a 200 300 m high tsunami to the antarctic peninsula and the southern tip of south america 1200 1500 km away new zealand 6000 km distant would have met 60 m waves generalizing these results to other size impactors we fit simplified tsunami attenuation laws to maximum tsunami heights extracted from the full wave calculations if eltanin was 1 km in diameter instead of 4 km its waves would have been at least five times smaller an asteroid the size of chicxulub 10 km diameter had it fallen into water deeper than 1000 m would have sent a 100 m tsunami out to 4000 km distance even if shoaling amplifications are neglected r 2002 elsevier science ltd all rights reserved

sedimentary signatures and processes during marine bolide impacts a review abstract studies of submarine impact craters resulting from impacts of comets or asteroids demonstrate that the presence of water and the physical properties of target rocks have a major influence on sedimentary processes associated with meteorite impacts this results in difference in sedimentary signature of bolide impacts in marine environments compared to subaerial impact craters in subaerial impacts the targets are commonly hard rocks frequently of igneous and or metamorphic origin whereas in submarine impacts the targets are mostly unconsolidated or poorly lithified sediments or sedimentary rocks with high volumes of pore water such differences result in variability in crater morphology and in sedimentary processes inside and outside the impact area impacts in shallow water marine neritic environments produced craters with low or absent rims and wide and shallow brims as characterize by both the montagnais on the scotian shelf the mjolnir in the barents sea 45 and 40 km in diameter respectively and the chesapeake bay 90 km in diameter lack of elevated rims is thought to be the result of current reworking and resurge of the water back into the excavated cavity as the water in the crater is vaporized during this process resurge gullies can be cut across the rim while mass and debris flows turbidites and other gravity deposits are produced as results of tsunami and crater wall and central high collapse during and after the crater excavation stage such deposits are found both within and outside the crater structure the only difference between gravity deposits triggered by an impact or other rare events such as earthquakes is the admixture of various melt particles and possible enrichments in iridium in the former impacts near the shelf edge may cause partial collapse of the continental margin as shown by the montagnais and chicxulub impacts some of the gravity and debris flows generated by margin collapse may be channelized with final deposits up to several hundred meters thick extending for hundreds of kilometers from the impact site other impact features such as shatter cones tektites spherules and ni spinels shocked quartz isotropication and partial melts are common to both submarine and subaerial impacts theoretical calculations of the destructive forces of mega tsunami waves triggered by meteorite impact in the ocean greatly exceed those based on geologic evidence a dearth of gigantic tsunami evidence for the chicxulub impact outside of the gulf of mexico where from theoretical modelling the maximum near bottom orbital velocity of water flow crossing the deep north atlantic basin should have been 1 m s could be the result of the mitigating effect of the bathymetry of surrounding area causing wave diffraction and interference calculated maximum horizontal orbital velocity near the seafloor at the shelf for the montagnais impact is 22 m s for a 200 m high wave 5 5 m s for a 50 m high wave at 500 km decreasing to 0 5 m s at 1000 km strong enough to scour the deep ocean bottom and produce distinct erosion surfaces and disconformities in marine sedimentary record however lack of cores across impact horizon prevents confirmation of occurrence of such bottom water flows

calculations of asteroid impacts into deep and shallow water contrary to received opinion ocean impacts of small 500 m asteroids do not produce tsunamis that lead to world wide devastation in fact the most dangerous features of ocean impacts just as for land impacts are the atmospheric effects we present illustrative hydrodynamic calculations of impacts into both deep and shallow seas and draw conclusions from a parameter study in which the size of the impactor and the depth of the sea are varied independently for vertical impacts at 20 km s craters in the seafloor are produced when the water depth is less than about 5 7 times the asteroid diameter both the depth and the diameter of the transient crater scale with the asteroid diameter so the volume of water excavated scales with the asteroid volume about a third of the crater volume is vaporised because the kinetic energy per unit mass of the asteroid is much larger than the latent heat of vaporisation of water the vaporised water carries away a considerable fraction of the impact energy in an explosively expanding blast wave which is responsible for devastating local effects and may affect worldwide climate of the remaining energy a substantial portion is used in the crown splash and the rebound jet that forms as the transient crater collapses the collapse and rebound cycle leads to a propagating wave with a wavelength considerably shorter than classical tsunamis being only about twice the diameter of the transient crater propagation of this wave is hindered somewhat because its amplitude is so large that it breaks in deep water and is strongly affected by the blast wave s perturbation of the atmosphere even if propagation were perfect however the volume of water delivered per metre of shoreline is less than was delivered by the boxing day 2004 tsunami for any impactor smaller than 500 m diameter in an ocean of 5 km depth or less near field effects are dangerous for impactors of diameter 200 m or greater hurricane force winds can extend tens of kilometers from the impact point and fallout from the initial splash can be extremely violent there is some indication that near field effects are more severe if the impact occurs in shallow water

advances in the study of mega tsunamis in the geological record abstract extreme geophysical events such as asteroid impacts and giant landslides can generate mega tsunamis with wave heights considerably higher than those observed for other forms of tsunamis in this paper we review recent advances in the study of mega tsunamis in the geological record focusing on well documented examples that have captured particular attention over the past decade we provide up to date background on the source mechanisms of tsunami generation during asteroid impacts and ocean island landslides which are the largest landslides on earth we also discuss the main sources of uncertainty for modelling such mega tsunamis and for addressing associated hazards

the effect of dust deposition on the soils of the land of israel abstract loess and aeolian dust affected soil formation to different degrees in most parts of the land of israel in the arid desert the loess was re eroded from slopes and sedimented as fluvial loess in along the valleys by flood water in areas with slight precipitation loess remains on slopes sedimentation rates are slower and loessial serosems are formed in the mildly arid areas in the northern negev the loess covers most of the landscape and occurs in thick sequences intercalated with several superimposed strongly developed loessial brown soils sedimentary and weathering processes occurred simultaneously and sediment palaeosols profiles up to 12 m thick were formed in areas further away from the desert aeolian deposition decreased as a result loessial brown soils grade into dark brown grumic soils and grumusols aeolian dust input also affected soils of the sand dunes of the coastal plain and in the terra rossa soils of the mountainous region

focusing simulations of synthetic aperture radar ocean images the sar ocean images obtained in the tower ocean wave and radar dependence experiment toward are carefully analyzed at different focus settings and compared with simulated results based on various theories for imaging surface waves the agreement between the experimental data and all of the sar simulations except one is found to be favorable there is also surprisingly close agreement among the different theoretical models themselves suggesting a closer fundamental similarity among the contending theories than was previously thought it is shown that the width of the focusing curve has an inverse dependence on the sar integration time for the toward conditions it is found that the image modulation due to azimuth traveling surface waves is greater than that due to range traveling waves

the two scale radar wave probe and sar imagery of the ocean a two scale formulation of oceanic backscatter of microwave radiation which has previously been applied to the dual frequency scatterometer is applied here to the two scale radar wave probe and sar imagery of the ocean a two scale radar wave probe is a microwave system which coherently detects signals scattered from a very small patch of the ocean surface it is shown that a sar image may be described as a convolution of the am part of the output of a two scale wave probe with the power spectrum of the fm part of the output thus sar images are not faithful reproductions of cross section variations over the surface distortions occur as a result of variable surface velocities examples of this distortion are derived from two scale wave probe data taken in the gulf of mexico application of a focusing correction does not remove the distortion from the simulated image of a nearly sinusoidal azimuth traveling wave large v r0 ratios minimize the distortion however

the tsunami phenomenon abstract with human activity increasingly concentrating on coasts tsunamis from japanese tsu harbour nami wave are a major natural hazard to today s society stimulated by disastrous tsunami impacts in recent years for instance in south east asia 2004 or in japan 2011 tsunami science has significantly flourished which has brought great advances in hazard assessment and mitigation plans based on tsunami research of the last decades this paper provides a thorough treatise on the tsunami phenomenon from a geoscientific point of view starting with the wave features tsunamis are introduced as long shallow water waves or wave trains crossing entire oceans without major energy loss at the coast tsunamis typically show wave shoaling funnelling and resonance effects as well as a significant run up and backflow tsunami waves are caused by a sudden displacement of the water column due to a number of various trigger mechanisms such are earthquakes as the main trigger submarine and subaerial mass wastings volcanic activity atmospheric disturbances meteotsunamis and cosmic impacts as is demonstrated by giving corresponding examples from the past tsunamis are known to have a significant sedimentary and geomorphological off and onshore response so called tsunamites form allochthonous high energy deposits that are left at the coast during tsunami landfall tsunami deposits show typical sedimentary features as basal erosional unconformities fining upward and landward a high content of marine fossils rip up clasts from underlying units and mud caps all reflecting the hydrodynamic processes during inundation the on and offshore behaviour of tsunamis and related sedimentary processes can be simulated using hydro and morphodynamic numerical models the paper provides an overview of the basic tsunami modelling techniques including discretisation guidelines for appropriate temporal and spatial resolution as well as the nesting method furthermore the boussinesq approximation a simplification of the three dimensional navier stokes equations is presented as a basic theory behind numerical tsunami models which adequately reflects the non linear dispersive wave behaviour of tsunamis the fully non linear boussinesq equations allow the simulation of tsunamis e g in the form of n waves based on the various subtopics presented recommendations for future multidisciplinary tsunami research are made it is especially discussed how the combination of sedimentary and geomorphological tsunami field traces and numerical modelling techniques can contribute to derive locally relevant tsunami sources and to improve the assessment of tsunami hazards considering the individual pre history and physiogeographical setting of a specific region

a pliocene mega tsunami deposit and associated features in the ranquil formation southern chile abstract an exceptionally large tsunami affected the coastline of southern chile during the pliocene its backflow eroded coarse beach and coastal dune sediments and redistributed them over the continental shelf and slope sandstone dykes and sills injected from the base of the resulting hyperconcentrated flow into underlying cohesive muds assisted in plucking up large blocks of the latter and incorporating them into the flow locally the rip up intraclasts were fragmented further by smaller scale injections to form a distinct breccia of angular to rounded mudstone clasts within a medium to coarse sandstone matrix sandstone sills in places mimic normal sedimentary beds complete with structures resembling inverse gradation planar laminae as well as ripple and trough cross lamination these were probably formed by internal sediment flow and shear stress as the semi liquefied sand was forcefully injected into cracks in borehole cores such sills can easily be misinterpreted as normal sedimentary beds which can have important implications for hydrocarbon exploration

estimating ocean coherence time using dual baseline interferometric synthetic aperture radar a new technique for measuring the coherence time of the ocean surface at radar wavelengths has been developed and tested this technique requires an interferometric synthetic aperture radar system with at least two unique baselines along the direction of platform motion the coherence time of the surface may be presented as a high resolution coherence time map this technique was tested using the jpl airsar along track interferometer measurements of the ocean coherence at the l band were made at high spatial resolution under a variety of conditions a new operating technique that results in the required two baselines is described some parametric analysis is performed pertaining to the design of such a system a representative interferometric data set acquired at the strait of messina in 1991 is presented to illustrate the technique the interferometric phase data reveal and measure tidal currents flowing through the strait while the coherence time image shows considerable structure not visible in the backscatter or phase image coherence times in and around the strait were measured to be of the order of 0 1 s at the l band which is in agreement with previous estimates and measurements

focusing of synthetic aperture radar ocean images with long integration times synthetic aperture radar sar images obtained in the sar and x band ocean nonlinearities chesapeake light tower saxon clt experiment are processed with long integration times 6 s and analyzed to study the effects of focusing two images with near azimuth traveling waves were chosen for the study the first image consists of relatively short wavelength wind waves traveling in the same general direction as the aircraft the second image consists of a long atlantic swell traveling in the opposite direction to the aircraft at these long integration times the image spectral intensities are found to be sensitive to the focus setting the spectral intensity at the optimum focus is 400 of that at zero focus for the first image and 167 for the second image the focusing curves for both images agree well with those predicted by a model developed by several groups and referred to here as the consensus model this model predicts an optimum focus setting that is equal to one half of the effective phase speed of the dominant wave in the azimuth direction the velocity bunching model underpredicts the optimum focus setting significantly the study concludes that in long integration time sar processing of surface waves such as the spotlight mode the image contrast is sensitively dependent on the focus setting and that the optimum focus setting is given by one half of the effective phase speed of the dominant surface wave

theory for synthetic aperture radar imaging of the ocean surface with application to the tower ocean wave and radar dependence experiment on focus resolution and wave height spectra a one dimensional model is developed to simulate azimuthal synthetic aperture radar sar imaging of the ocean surface the model developed here is general and can admit both the distributed surface and the velocity bunching approaches computer simulations are performed to test the validity of this model the simulations show that the time dependent modulation patterns due to the radar cross section variation and the velocity bunching effects give optimum focusing around half the phase velocity of the long wave it is shown that the focus dependence is due to an incoherent integration process and not due to motion induced phase errors it is argued that the radar reflectivity is correlated over distances small in comparison with the sar resolution in the simulations the radar reflectivity is assumed to be spatially decorrelated also given are the relative importance of the various effects that degrade the azimuthal resolution it is shown that the limited radar temporal coherence due to the velocity spread of short waves degrades the azimuthal resolution of the sar this coherence time depends on sea state and radar wavelength it is shown that the orbital acceleration effects are small in comparison with the smearing due to the velocity spread it is found that the degraded azimuthal resolution of the radar minimizes the nonlinear effects of velocity bunching the simulations show that in the tower ocean wave and radar dependence experiment toward sar imaging at l band is reasonably linear

salt diapir influenced shallow marine sediment dispersal patterns insights from outcrop analogs unique outcrop exposures of two salt diapirs a secondary salt weld and associated syndiapiric strata in northeast mexico offer an important perspective on salt influenced petroleum reservoirs by allowing recognition and description of salt related sandstone depocenters spectacular progressive unconformities and halokinetic sequences coupled with laterally continuous exposures permit accurate correlation and interpretation of syndiapiric units analysis of the syndiapiric upper cretaceous delgado sandstone member potrerillos formation delineates regional shoreline sediment dispersal locally impacted by diapiric relief and the distribution and internal character of salt diapir proximal sandstone depocenters sequence stratigraphic correlation defines striking relationships between highstand hst and transgressive systems tracts tst stratal thinning trends and salt diapir relief transgressive systems tract and highstand systems tract strata show thinning and lithofacies shoaling trends toward diapirs however the latter is more pronounced in the hst and occurs at a greater distance from salt diapirs within 1 2 km 0 6 1 2 mi sandstone depocenters roughly 0 5 1 0 km 0 3 0 6 mi wide and 0 5 0 2 km 0 3 0 1 mi thick are present in both tst and hst strata and consist of sandier shallower water facies however depocenters are better developed in tst strata as thicker stratigraphic sections on updip diapir margins we propose that sandstone depocenters formed by preferential sediment reworking and shelf ridge development on landward diapir margins during marine transgression elevated diapir relief and higher subsidence rates adjacent to salt diapirs likely enhanced this process additionally depocenters adjacent to el papalote diapir are smaller and contain deeper water facies than the age equivalent depocenters adjacent to el gordo diapir suggesting that it had higher broader sea floor relief

comparison of simulated and measured synthetic aperture radar image spectra with buoy derived ocean wave spectra during the shuttle imaging radar b mission during the sir b mission over the north sea two successful synthetic aperture radar sar data takes with simultaneous buoy measurements of ocean wave spectra have been obtained on october 6 and 8 1984 on october 6 the sar imaging of ocean waves was predicted as strongly nonlinear and on october 8 as almost linear the sir b experiment confirmed the theoretical predictions by applying the sar imaging model based on velocity bunching theory the sar image spectra are calculated from the measured ocean wave spectra these calculated sar image spectra are compared with the sir b derived sar image spectra and it is shown that both agree quite well this is considered as a further experimental confirmation for the velocity bunching model that has been proposed for describing sar imaging of ocean surface waves

reconciliation of theories of synthetic aperture radar imagery of ocean waves several theories of synthetic aperture radar sar imagery of ocean waves especially those dealing with the focusing issue are examined we show that the time dependent theories of lyzenga 1988 and of kasilingam and shemdin 1988 and the velocity bunching theory of bruning alpers and shroter 1991 are identical for short integration times but diverge on the focusing issue for long integration times the reason for the divergence is simply that velocity bunching theory assumes that integration times are short compared with ocean wave periods the inference is that the phase speed of the ocean wave plays a secondary nearly negligible role to that of orbital velocity and acceleration in determining the optimum focus setting for short integration times but becomes dominant as integration times are increased for the case of zero focus adjustment these focus dependent theories are shown to reduce to those of plant and keller 1983 and of hasselmann et al 1985 thus several of the apparently differing theories of sar imagery of the ocean are reconciled and shown to be a single consistent theory

the meteorite impact induced tsunami hazard when a cosmic object strikes the earth it most probably falls into an ocean depending on the impact energy and the depth of the ocean a large amount of water is displaced forming a temporary crater in the water column large tsunami like waves originate from the collapse of the cavity in the water and the ejecta splash because of the far reaching destructive consequences of such waves an oceanic impact has been suggested to be more severe than a similar sized impact on land in other words oceanic impacts may punch over their weight this review paper summarizes the process of impact induced wave generation and subsequent propagation whether the wave characteristic differs from tsunamis generated by other classical mechanisms and what methods have been applied to quantify the consequences of an oceanic impact finally the impact induced tsunami hazard will be evaluated by means of the eltanin impact event

tsunami hazard assessment and risk in aotearoa new zealand a systematic review ad 1868 2012 abstract this paper presents a systematic review of peer reviewed journal articles scientific reports books and research theses covering tsunami hazard assessment and risk in aotearoa new zealand a nz fifteen electronic databases were examined using an array of keyword search strings to comprehensively gather all available sources of information spanning 1868 2012 ad 222 references were identified as directly relevant to tsunami hazard assessment and risk in a nz with a further 51 references identified by scrutinising the original 222 references the amount of information as well as the emphasis of the science contained in these 273 references differs greatly between documents a meta analysis of this collective scholarship shows six principal areas of scientific endeavour i observation and cataloguing of modern and historical tsunami impacts caused by earthquakes and landslides ii modelling and evaluation of near and far field generated tsunamis iii detailed mapping and assessment of offshore seismic and other geological structures responsible for near field tsunami generation iv investigation and cross referencing of holocene palaeo records of tsunami deposits preserved in wetlands dunes and other coastal landforms v survey and reconnaissance of modern and historical tsunami impacts and vi guidance for tsunami hazard mitigation preparedness and land use planning synthesising all of these references it is clear that a nz has been affected by remote regional and locally generated tsunami during the historic pre written and pre human periods further scientific knowledge of tsunami risk and the forces responsible for tsunami generation has greatly improved however in spite of the many scientific advances detailed in this review much more remains to be done to better understand and deal with the diverse tsunami hazard and risk facing a nz

oceanic impacts a growing field of fundamental geoscience the importance of oceanic impacts of collisional events and resulting energy release are briefly described data collection methods from the eltanin a mesosiderite projectile deep water impact are presented

tsunami hazard evaluation of the eastern mediterranean historical analysis and selected modeling seismic sea waves in the eastern mediterranean have been reported since written history first emerged several thousand years ago we collected and investigated these ancient and modern reports to understand and model the typical tsunamigenic sources with the ultimate purpose of characterizing tsunami hazard along the levant coasts surprisingly only 35 of the tsunami reports could be traced back to primary sources with the balance remaining questionable the tsunamis varied in size from barely noticeable to greatly damaging and their effects ranged from local to regional overall we list 21 reliably reported tsunamis that occurred since the mid second century b c along the levant coast along with 57 significant historical earthquakes that originated from the local continental dead sea transform dst system an in depth evaluation shows that 10 tsunamis are clearly associated with on land dst earthquakes and therefore as formerly suggested they probably originated from offshore seismogenically induced slumps eight tsunamis arrived from the remote hellenic and cypriot arcs one from italy and two are left with as yet unrecognized sources a major conclusion from this work is that onshore earthquakes commonly produce tsunamis along the levant coastline and that analogous situations are present elsewhere in the mediterranean as well as along the california coast and in another regions with active faults near the coast we modeled three typical scenarios and in light of the sumatra experience we examined the more likely severe magnitudes this of course leads us toward the upper range of expected run ups the models show that sooner than five minutes after a strong earthquake produces an offshore slump which occurs after close to a third of the large dst earthquakes a 4 to 6 m run up may flood part of the syrian lebanese and israeli coasts tsunamis from remote earthquakes however arrive later and produce only 1 to 3 m run ups but are more regional in extent online material tsunami modeling and reports

theory of synthetic aperture radar ocean imaging a marsen view this paper reviews basic synthetic aperture radar sar theory of ocean wave imaging mechanisms using both known work and recent experimental and theoretical results from the marine remote sensing marsen experiment several viewpoints that have contributed to the field are drawn together in a general analysis of the backscatter statistics of a moving sea surface a common focus for different scattering models is provided by the mean image impulse response function which is shown to be identical to the spatially varying frequency variance spectrum of the local complex reflectivity coefficient from the analysis has emerged a more complete view of the sar imaging phenomenon than has been previously available a new generalized imaging model is proposed

evaluating the impacts of huge waves on rocky shorelines an essay review of the book tsunami the underrated hazard abstract tsunami the underrated hazard draws together and summarizes a wealth of information about the nature impacts and causes of tsunamis written from a natural hazards perspective the book stresses that large tsunamis can affect even protected coasts that have not experienced large tsunamis historically many deposits and erosional features described and discussed as tsunami signatures have yet to be linked specifically with tsunamis cited references in the book do not necessarily support a tsunami origin for these features because accepted scientific citation practices have not been followed although rocky shorelines in southeastern australia the hawaiian islands and elsewhere generate and preserve a variety of boulder and block deposits and erosional features their sediment dynamics and geomorphology are poorly studied and unequivocal criteria for distinguishing between deposits of storms and tsunamis have yet to be developed despite its shortcomings this book should be on the library shelves of all marine geoscientists who study modern and ancient shorelines however it should be used with great circumspection because the process product relationships it assumes are equivocal

a semi spectral modelling of landslide tsunamis summary a new semi spectral technique based on integral equations is introduced for the landslide tsunami problem the technique does not use the shallow water approximation and resolves the dispersive surface wavefield generated by sliding material over a bathymetric profile the wave scattering due to the bathymetric profile on which the slide occurs is calculated solving an integral equation on the free surface the linearized kinematic and dynamic boundary conditions are imposed method of images is adopted to solve for a source sink distribution on the bathymetry to simulate the motion of the landslide and to satisfy the kinematic condition on the sea bottom an asymptotic relation for the far field is also derived the application to a landslide tsunami generation scenario in the sea of marmara reveals that a thickness h submarine mass failure on the southern rim of the c onarcok basin would create a wave peak of around 0 5 h on the 1000 m deep c onarcok basin

geological record and reconstruction of the late pliocene impact of the eltanin asteroid in the southern ocean in 1995 an expedition on board the research vessel fs polarstern explored the impact site of the eltanin asteroid in the southern ocean the only known asteroidimpact into a deep ocean basin analyses of the geological record of the impact region place the event in the late pliocene 2 15 myr and constrain thesize of the asteroid to be 1 km the explosive force inferred for this event places it at the threshold of impacts believed to have global consequences and its studyshould therefore provide a baseline for the reconstruction and modelling of similar events which are common on geological timescales

the eltanin asteroid impact possible south pacific palaeomegatsunami footprint and potential implications for the pliocene pleistocene transition large asteroid impacts are rare and those into the deep ocean are rarer still the eltanin asteroid impact around 2 51 0 07 ma occurred at a time of great climatic and geological change associated with the pliocene pleistocene boundary numerical models of the event indicate that a megatsunami was generated although there is debate concerning its magnitude and the region wide extent of its influence we summarise the existing evidence for possible eltanin megatsunami deposits in antarctica chile and new zealand while also examining other potential sites from several locations mainly around the south pacific region in reviewing these data we note that these events were unfolding at the same time as those associated with the pliocene pleistocene boundary and as such most of the geological evidence from that time has a climatic interpretation the potential climatic and geological ramifications of the eltanin asteroid impact however have failed to be considered by most researchers studying this time period although we are not advocating that all geological activity at that time is connected with the eltanin asteroid impact it raises interesting questions about the role potentially played by such catastrophic events in contributing to or even triggering epochal transitions copyright 2012 john wiley sons ltd

comparisons of simulated and actual synthetic aperture radar gravity wave images the synthetic aperture radar sar images obtained with the jet propulsion laboratory s l band system in the tower ocean wave and radar dependence toward oceanographic experiment are compared with images generated by a simulation program implementing a sar ocean imaging model based on two scale hydrodynamic and electromagnetic scattering approximate models a critically regarded test of a theory of sar ocean imaging is its prediction of the best image focus dependence on surface motion the primary means of comparison here is an estimate of the best focus parameter that uses a subimage cross correlation technique the focus parameter estimates for both the actual and simulated images show 1 a reversal in sign with reversal in dominant longwave direction relative to the sar direction 2 a magnitude increase with an increase in magnitude of the angle between the dominent long wave and sar axes and 3 an independence of the altitude and also the range to velocity ratio all equivalent velocity estimates are of the order of the dominant longwave phase velocity normalized by the sar vehicle velocity and agree well qualitatively though there are some quantitative differences these behaviors are in agreement with a related analytical prediction the visibility of the long waves sar image artifacts for this toward data set increased with increased altitude and also with increased range to velocity ratio for both the actual and simulated images as was predicted by a related analysis agreement of spectral density estimates of the actual and simulated sar images generally required an order of magnitude increase in the strength of the hydrodynamic interaction of the long and short waves this may indicate as have surface measurements in toward and other experiments that the two scale model does not fully describe this nonlinear interaction with this interaction adjustment a comparison of actual and simulated images using an alternative focus criterion showed very close agreement in some cases

the 2011 japanese 9 0 magnitude earthquake test of a kinetic energy wave model using coastal configuration and offshore gradient of earth and beyond abstract based on geological investigations of coastal geometry and stratigraphy offshore gradient variation wave velocity energy and quartz grain microtexture analysis of key sites inundated by tsunamis during the holocene we have developed a postulated model that could be used to assess modern and ancient onshore environmental conditions during tsunami emplacement given that tsunami waves can travel up to 900 km h the kinetic energy of the wave is determined by frictional release on the offshore slope to seabed nearshore sand and sediment supply and coastal geomorphology specifically coast linearity or embayments that constrict wave energy with gentle offshore gradients and relatively linear coastlines the kinetic energy of the tsunami is decreased by friction with the seabed and radiated outward along the coast thus producing reduced flooding of the affected coast and fewer collisions of entrained grains in contrast steep offshore gradients reduce friction to mere milliseconds of wave impact and embayments specifically narrow coastal constrictions increase wave energy both of which increase on land run up heights and importantly to our proposed model grain collision effects damage to quartz grains deposited by tsunamis along coastal extents ranges from slight on linear coasts with gentle offshore gradients to highly resurfaced mineral surfaces on coasts with steep offshore gradients and narrow embayments our model can be further tested through collection analyses and comparison of quartz grains in relatively low and high energy environments of the recently tsunami impacted northeastern coast of japan for example the location of the fukushima nuclear plant along a linear coastline with a less steep offshore gradient may have attenuated the energy of the incoming wave and thus yielding less resurfaced grains when compared to the coastline located to the north of sendai city where coastal embayments of variable size coupled with steep offshore gradients would produce higher energy waves of greater magnitude as attested by greater penetration inland with considerable loss of life and property damage and resulting highly deformed grain surfaces the model could be applicable for assessing modern and ancient coastal environmental conditions on earth and postulated ancient marine conditions on the red planet

pliocene mass failure deposits mistaken as submarine tsunami backwash sediments an example from hornitos northern chile abstract in this study we question the former interpretation of a shallow marine backwash tsunami origin of a conspicuous pliocene coarse clastic unit at hornitos northern chile and instead argue for a debris flow origin for this unit we exclude a relation to a tsunami in general and to the eltanin impact in particular the observed deposit at hornitos was not generated either directly impact triggered tsunami or indirectly submarine mass flow caused by seismic shaking by an impact re calculation of the alleged impact tsunami including consideration of the van dorn effect shows that an impact in the southern ocean did not cause a significant tsunami at hornitos impact related seismic shaking was not able to trigger slides several thousands of kilometers away because the eltanin event was a deep sea impact that did not create a crater additionally the biostratigraphic age of 5 1 2 8 ma of the associated la portada formation is not concurrent with the newly established age of 2 511 0 07 ma for the eltanin impact instead we argue for an origin of the conspicuous unit at hornitos as a debris flow deposit caused by an earthquake in the andean subduction zone in northern chile our re interpretation considers the local synsedimentary tectonic background a comparison to recent submarine tsunami sediments and recent examples of mass wasting deposits along the chilean margin the increased uplift during the pliocene caused oversteepening of the coastal scarp and entailed a contemporaneous higher frequency of seismic events that triggered slope failures and cliff collapses the coarse clastic unit at hornitos represents an extraordinary potentially tsunami generating mass wasting event that is intercalated with mass wasting deposits on a smaller scale

the eltanin impact and its tsunami along the coast of south america insights for potential deposits abstract the eltanin impact occurred 2 15 million years ago in the bellinghausen sea in the southern pacific while a crater was not formed evidence was left behind at the impact site to prove the impact origin previous studies suggest that a large tsunami formed and sedimentary successions along the coast of south america have been attributed to the eltanin impact tsunami they are characterized by large clasts often several meters in diameter our state of the art numerical modeling of the impact process and its coupling with non linear wave simulations allows for quantifying the initial wave characteristic and the propagation of tsunami like waves over large distances we find that the tsunami attenuates quickly with r r 1 2 resulting in maximum wave heights similar to those observed during the 2004 sumatra and 2011 tohoku oki tsunamis we compute a transport competence of the coastal flow and conclude that for the northernmost alleged tsunami deposits especially for those in hornitos chile the transport competence is about two orders of magnitude too small to generate the observed deposits

asteroid impact tsunami of 2880 march 16 summary nasa scientists have given a 1 1 km diameter asteroid 1950 da a 0 0 to 0 3 per cent probability of colliding with the earth in the year 2880 this article examines a scenario where 1950 da strikes the sea 600 km east of the united states coast travelling at 17 8 km s 1 the asteroid would blow a cavity 19 km in diameter and as deep as the ocean 5 km at the impact site tsunami waves hundreds of metres high would follow as the transient impact cavity collapses the tsunami disperses quickly but because the waves are so large initially destructive energy carries basin wide within two hours of the scenario impact 100 m waves make landfall from cape cod to cape hatteras within 12 hours 20 m waves arrive in europe and africa water velocity at the deep ocean floor exceeds 1 m s 1 to 800 km distance strong enough to leave a widespread tsunami signature in the sedimentary record

on the focusing issue of synthetic aperture radar imaging of ocean waves it is widely accepted that the imaging of ocean surface waves by synthetic aperture radar sar can be adequately described by velocity bunching theory in conjunction with the two scale wave model however it has been conjectured that this theory is incapable of explaining why under certain conditions the image contrast of airborne sar imagery of ocean waves can be enhanced by defocusing the sar processor in the present study the velocity bunching theory is defended