the mid norwegian margin a discussion of crustal lineaments mafic intrusions and remnants of the caledonian root by 3d density modelling and structural interpretation the high density lower crustal body lcb on the mid norwegian margin is almost universally interpreted to represent magmatically underplated material added to the crust during early tertiary opening of the ne atlantic the thickness of the lcb is uneven and its distribution along the margin is sharply limited by margin perpendicular lineaments three dimensional density modelling constrained by petrophysical and seismic data was performed to investigate the expression of the various lineaments bivrost jan mayen gleipne etc in the crustal architecture with and without the lcb the bivrost lineament separating the voring and lofoten margin segments is clearly expressed and so is arguably a lineament in the sw voring margin notably most of the lineaments can be interpreted as offshore prolongations of major onshore detachments stemming from late caledonian orogenic collapse an alternative interpretation of the lcb is thus that it represents high grade metamorphic rocks remnant from the caledonian root determining the nature of the lcb has profound effects for the volume estimate of magmatic rocks in the north atlantic igneous province and consequently also for the degree of crustal thinning and heat flow

temporal variation in the magnitude frequency distribution during the guy greenbrier earthquake sequence the recent increase in earthquake activity in the central u s has led to concerns about the hazard posed by induced earthquakes understanding earthquake phenomena and monitoring in all settings can be improved by the detection of small events however the catalog of induced earthquakes is incomplete for small events due to the sparse instrumentation this is particularly true in settings of low background seismicity like the central u s we apply single station template matching to detect small earthquakes during the guy greenbrier sequence in central arkansas and find over 100 times more earthquakes than are registered in the advanced national seismic system catalog between july 2010 and october 2011 a complete catalog over nearly 4 units of magnitude enables us to analyze the magnitude frequency distribution of induced earthquakes we find that earthquakes deviated from the gutenberg richter statistics during the operation of nearby injection wells but returned to gutenberg richter statistics after the wells were shut in

new moho map for onshore southern norway a recent seismic refraction study across southern norway has revealed that the up to 2469 m high southern scandes mountains are not isostatically compensated by a thick crust rather the moho depths are close to average for continental crust with elevations of similar to 1 km evidence from new seismic data indicate that beneath the highest topography moho depths are around 38 40 km these measurements are similar to 2 km deeper than early estimates interpolated from coarsely spaced refraction profiles but up to 3 km shallower than receiver function estimates for the area moho depth variation beneath the mountains roughly correlates with changes in surface topography indicating that topography is at least to the first order controlled by crustal thickness however the highest mountains do not overlie the thickest crust and additional support for topography for example from flexural strength in the lithosphere low densities in the upper mantle or mantle dynamics is likely the relationship between topography and moho depth breaks down for the oslo graben and the fennoscandian shield to the east and north high density lower crustal rocks below oslo graben and increasing crust and lithospheric thicknesses below the fennoscandian shield may produce a negative correlation between topography and moho depth

el cuchillo seismic sequence of october 2013 july 2014 in the burgos basin northeastern mexico hydraulic fracturing or reservoir induced seismicity

is there evidence for magmatic underplating beneath the oslo rift we challenge some of the long standing beliefs related to the permian oslo rift structure often referred to as a case example type locality for continental rifting the crustal structure of the oslo rift was long presumed to be thinned proterozoic crust overlying a permian high density layer interpreted as magmatic underplating new data support an alternative view of the crustal structure in the oslo rift region the bouguer gravity high in the region shows a strong asymmetry a steep westward facing gradient to the west of the rift and a much gentler eastern gradient we present a 3d density model based on petrophysical and seismic information which accounts for the bouguer gravity high using an eastward extension of old precambrian structures without invoking a prominent magmatic underplated structure reactivation of old pre rift structures appears to be an important feature affecting the evolution and location of the permo carboniferous oslo rift

experimental analysis of debris motion due the obstruction from fixed obstacles in tsunami like flow conditions abstract experimental research was conducted focusing on debris motion over a horizontal apron featuring vertical obstacles in the path of the debris propagation the apron was designed as a typical representation of a harbor threatened by an inundating tsunami the experimental setup idealized often complex harbor settings the debris was a scaled down 20 foot shipping container modelled at a 1 in 40 froude length scale offand onshore regions were separated by a vertical quay wall which allowed the incoming elongated solitary wave used to represent the first part of a tsunami to steepen break and propagate over the initially dry surface as a tsunami like bore in the path of propagation a varying number of debris were entrained within the inundating bore over the horizontal apron the entrained debris interacted with regularly spaced vertical obstacles representing infrastructure and houses within the propagation path varying debris and obstacle arrangements were tested to evaluate the effects the obstacles would have on the debris maximum longitudinal displacement and the spreading angle the main conclusion is that the spreading angle of the debris is not as significantly altered by the presence of obstacles on the harbor apron whereas the maximum longitudinal displacement of the debris was significantly affected

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

seismic constraints on a large mafic intrusion with implications for the subsidence history of the danish basin 1 seismic refraction data from the estrid 1 profile are used for seismic velocity modeling along the strike of a large mafic intrusion in the norwegian danish basin central denmark the p wave velocity structure identifies a 8 km thick sedimentary succession with velocities between 1 8 and 5 7 km s the top basement is defined by a step to vp 6 2 km s in the middle to lower crust a high velocity body vp 6 7 km s with its top located at about 10 12 km depth is interpreted as a high velocity and high density gabbroic intrusion of permian age this high velocity body explains the large 50 mgal positive gravity anomaly known as silkeborg gravity high the intrusion has a minimum volume of 40 000 km3 which implies that the magma influx and the consequent cooling of the lithosphere from high temperature could have had profound effects on the subsidence of the danish basin in particular because the magma probably intruded during only a few events and other similar structures cover much of the basin an anomalously high velocity gradient from 7 0 km s in the middle crust to 7 7 km s at 30 32 km depth in the central part of the intrusion coincides with an interval without moho reflections indicative of a gradual transition zone between the crust and the mantle this feature may show the location of the feeder dykes of the intrusion

sveconorwegian igneous complexes beneath the norwegian danish basin abstract gravity and magnetic anomalies have previously been interpreted to indicate strongly magnetic permian or even tertiary intrusive bodies beneath the skagerrak waterway such as the skagerrak volcano and beneath silkeborg in denmark our combined modelling of the magnetic and gravity anomalies over these rock bodies indicates that a steep upward magnetisation is required to explain the magnetic anomalies at the surface reminiscent of the magnetic direction in the sveconorwegian rocks of the rogaland igneous province in southern norway the younger rocks of the permian oslo rift region have intermediate and flat magnetisation that is inadequate to explain the observed magnetic field the positive part of the skagerrak aeromagnetic anomaly is continuous with the induced anomalies associated with the eastward extension of the rogaland igneous province this relation also suggests that rocks of the rogaland igneous province and its offshore extension are responsible for the skagerrak anomalies both the negative remanence dominated aeromagnetic anomaly and the positive gravity anomaly can be modelled using constraints from seismic reflection lines and available density data and rock magnetic properties a 7 km thick complex of ultramafic mafic intrusions is located below a southward dipping 1 4 km thick section of mesozoic sediments and 1 2 km of palaeozoic sediments the enormous body of dense ultramafic mafic rocks implied by the modelling could be the residue of the parental magma that produced the voluminous rogaland anorthosites the application of similar petrophysical properties in the forward modelling of the silkeborg source body provides an improved explanation of the observed gravity and magnetic anomalies compared with earlier studies the new model is constrained by magnetic depth estimates from the located euler method ranging between 6 and 8 km forward modelling shows that a model with a reverse magnetic body anorthosite situated above a dense mafic ultramafic body may account for the silkeborg anomalies the anorthosites may have formed by differentiation of the underlying mafic intrusion similar to the intrusive relations in the rogaland igneous province we conclude that there is strong evidence for a sveconorwegian age for both the skagerrak and the silkeborg anomalous rock bodies

recrystallization or cooling ages in situ uv laser 40ar 39ar geochronology of muscovite in mylonitic rocks the intra grain 40 ar 39 ar age distributions of muscovite from greenschist facies mylonite zones are shown to be sensors of metamorphic history textures compositions and in situ uv laser ablation 40 ar 39 ar data from two extensional shear zones demonstrate that cooling ages can be distinguished from neo or recrystallization ages deformed muscovite porphyroclasts and recrystallized shear band muscovite from the pogallo shear zone ivrea zone southern alps reveal variable intra grain 40 ar 39 ar ages with internal age variations of more than 65 ma the wide range of 40 ar 39 ar ages within compositionally homogeneous grains is consistent with diffusion dominated argon loss controlled by observable intra grain microstructures in contrast intra grain 40 ar 39 ar ages of muscovite fish from proterozoic mylonite of the porsgrunn kristiansand shear zone southern norway display only minor age dispersion and age variations are correlated with changes in muscovite composition the sympathetic age composition correlations in different muscovite microstructures directly relate to sequential neo and recrystallization of muscovite and ultimately provide insight into the protracted recrystallization history during extensional deformation along the porsgrunn kristiansand shear zone

implications of the 26 december 2004 sumatra andaman earthquake on tsunami forecast and assessment models for great subduction zone earthquakes results from different tsunami forecasting and hazard assessment mod els are compared with observed tsunami wave heights from the 26 december 2004 indian ocean tsunami forecast models are based on initial earthquake information and are used to estimate tsunami wave heights during propagation an empirical forecast relationship based only on seismic moment provides a close estimate to the observed mean regional and maximum local tsunami runup heights for the 2004 indian ocean tsunami but underestimates mean regional tsunami heights at azimuths in line with the tsunami beaming pattern e g sri lanka thailand standard forecast models developed from subfault discretization of earthquake rupture in which deep ocean sea level observations are used to constrain slip are also tested forecast models of this type use tsunami time series measurements at points in the deep ocean as a proxy for the 2004 indian ocean tsunami a transect of deep ocean tsunami amplitudes recorded by satellite altimetry is used to constrain slip along four subfaults of the m 9 sumatra andaman earthquake this proxy model performs well in comparison to observed tsunami wave heights travel times and inundation patterns at banda aceh hypothetical tsunami hazard assessments models based on end member estimates for average slip and rupture length m w 9 0 9 3 are compared with tsunami observations using average slip low end member and rupture length high end member m w 9 14 consistent with many seismic geodetic and tsunami inversions adequately estimates tsunami runup in most regions except the extreme runup in the western aceh province the high slip that occurred in the southern part of the rupture zone linked to runup in this location is a larger fluctuation than expected from standard stochastic slip models in addition excess moment release 9 deduced from geodetic studies in comparison to seismic moment estimates may gen erate additional tsunami energy if the exponential time constant of slip is less than approximately 1 hr overall there is significant variation in assessed runup heights caused by quantifiable uncertainty in both first order source parameters e g rupture length slip length scaling and spatiotemporal complexity of earthquake rupture

the kapuskasing uplift a geological and geophysical synthesis over the past decade the kapuskasing uplift has been the subject of intense geological and geophysical investigation as lithoprobe s window on the deep crustal structure of the archean superior province enigmatic since its recognition as a positive gravity anomaly in 1950 the structure has been variably interpreted as a suture rift transcurrent shear zone or intracratonic thrust diverse studies including geochronology geothermobarometry and various geophysical probes provide a comprehensive three dimensional image of archean 2 75 2 50 ga crustal evolution and proterozoic 2 5 1 1 ga cooling and uplift the data favour an interpretation of the structure as an intracratonic uplift related to hudsonian collision eastward across the southern kapuskasing uplift erosion levels increase from 10 km in the michipicoten greenstone belt through the wawa gneiss domain 10 20 km into granulites 20 30 km of the kapuskasing structural zone juxtaposed against the low grade swayze greenstone belt al

inclined k ar illite age spectra in brittle fault gouges effects of fault reactivation and wall rock contamination k ar clay fraction ages of brittle faults often vary with grain size decreasing in the finer size fractions producing an inclined age grain size spectrum k ar ages and mineralogical characterization of gouges from two normal faults in the kongsberg silver mines southern norway suggest that inclined spectra derived from brittle fault rocks reflect the mixing of inherited components with authigenic mineral phases the ages of the coarsest and finest fractions constrain faulting at c 260 270 ma and reactivation around 200 210 ma respectively this study demonstrates how wall rock contamination influences the k ar age of the coarsest size fractions and that authigenic illite and k feldspar can crystallize synkinematically under equivalent conditions and thus yield the same k ar ages

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

shoaling on steep continental slopes relating transmission and reflection coefficients to green s law the propagation of long waves onto a continental shelf is of great interest in tsunami modeling and other applications where understanding the amplification of waves during shoaling is important when the linearized shallow water equations are solved with the continental shelf modeled as a sharp discontinuity the ratio of the amplitudes is given by the transmission coefficient on the other hand when the slope is very broad relative to the wavelength of the incoming wave then amplification is governed by green s law which predicts a larger amplification than the transmission coefficient and a much smaller amplitude reflection than given by the reflection coefficient of a sharp interface we explore the relation between these results and elucidate the behavior in the intermediate case of a very steep continental shelf

laboratory scale generation of tsunami and long waves abstract physical modeling of long waves in laboratories is still a valuable and trustworthy option to study long wave propagation run up and near shore dynamics and complex nonlinear interactions of approaching wave and macroroughness elements on the shore yet problems develop if full scale measured time series of real tsunami or numerically derived time series are to be adequately modeled in a timewise meaningful and scaled experiment hence an in depth review of the state of the art long wave generation methods in laboratory wave flumes and basins is conducted the study reveals that improved laboratory techniques could significantly contribute to enhance the accuracy and applicability of experimental tests this would give important information on the interaction between the shoreline and infrastructures on land in order to deduce valuable information on the topic of tsunami inundation processes or wave induced impacts on houses in this light a novel wave generation technique using high capacity pipe pumps under some control and a loop feedback control is meticulously developed and discussed the wave generation facility is successfully tested for single sinusoidal leading depression waves as well as for prolonged solitary and leading depression n waves of varying duration the long wave generation technique is further assessed in terms of its capability to generate long waves abstracted from prototype conditions the influence of controller settings on the resulting waves is discussed

crustal structure and composition of the oslo graben norway abstract although more than 250 my old the oslo graben has retained a distinctive distribution of p wave velocities associated with rifting intrusion and underplating of the thinned crustal section we calculate poisson s ratio values from crustal p and s wave velocities along an 400 km long profile across the southern scandinavian peninsula with a focus on the oslo graben plutonic rocks are now exposed at the surface in the graben due to post rifting erosion and the corresponding low 5 5 km s p wave velocities extend to depths of 3 km the p wave velocity and poisson s ratio between depths of 6 and 34 km are 5 higher inside than outside the rift boundaries which together with thickening of the 7 km s lower crust beneath the rift indicate magmatic intrusions poisson s ratio of 0 27 and high 7 1 7 4 km s velocities indicate a heterogeneous composition lower crust the thickened high velocity lower crust is 1 5 times wider than the surface expression of the rift and extends to both the east and west of the main rift axis depth dependant extension may have occurred within the rift and may account for the significant volumes of volcanic output despite the small surface extension observed the added volume of intrusive material may explain why the moho up warp is small as little as 2 km at the rift based on the new p wave velocities poisson s ratio measurements and the thickness of the magmatic underplate apparent values for the rift are estimated to be 1 5 but when intrusion within the crust is included could be as high at 2 3

swash an operational public domain code for simulating wave fields and rapidly varied flows in coastal waters abstract a computational procedure has been developed for simulating non hydrostatic free surface rotational flows in one and two horizontal dimensions its implementation in the publicly available swash an acronym of simulating waves till shore is intended to be used for predicting transformation of surface waves and rapidly varied shallow water flows in coastal waters this open source code http swash sourceforge net has been developed based on the work of stelling and zijlema 2003 stelling and duinmeijer 2003 zijlema and stelling 2005 zijlema and stelling 2008 the governing equations are the nonlinear shallow water equations including non hydrostatic pressure and provide a general basis for describing complex changes to rapidly varied flows typically found in coastal flooding resulting from e g dike breaks and tsunamis and wave transformation in both surf and swash zones due to nonlinear wave wave interactions interaction of waves with currents and wave breaking as well as runup at the shoreline the present paper provides a complete description of the numerical algorithms currently used in the code the code is benchmarked using some analytical problems moreover the numerical results are validated with various cases of laboratory data with the principal aim to convey the capabilities of the swash code in particular emphasis is put on an analysis of model performance and associated physical implications serial and parallel performance scalings are also presented

formation of undular bores and solitary waves in the strait of malacca caused by the 26 december 2004 indian ocean tsunami 1 deformation of the indian ocean tsunami moving into the shallow strait of malacca and formation of undular bores and solitary waves in the strait are simulated in a model study using the fully nonlinear dispersive method fndm and the korteweg devries kdv equation two different versions of the incoming wave are studied where the waveshape is the same but the amplitude is varied full amplitude and half amplitude while moving across three shallow bottom ridges the back face of the leading depression wave steepens until the wave slope reaches a level of 0 0036 0 0038 when short waves form resembling an undular bore for both full and half amplitude the group of short waves has very small amplitude in the beginning behaving like a linear dispersive wave train the front moving with the shallow water speed and the tail moving with the linear group velocity energy transfer from long to short modes is similar for the two input waves indicating the fundamental role of the bottom topography to the formation of short waves the dominant period becomes about 20 s in both cases the train of short waves emerging earlier for the larger input wave than for the smaller one eventually develops into a sequence of rank ordered solitary waves moving faster than the leading depression wave and resembles a fission of the mother wave the kdv equation has limited capacity in resolving dispersion compared to fndm

fluid injection and seismic activity in the northern montney play british columbia canada with special reference to the 17 august 2015 mw 4 6 induced earthquake in this article we analyzed the recent seismic activity in the northern montney play of british columbia in 2015 and its connection with fluid injection hydraulic fracturing and long term injection of gas and wastewater disposal in the region the earthquake sequence used in this study includes 676 events from 3 october 2014 to 31 december 2015 from the progress energy earthquake catalog with moment magnitude as small as 1 spatial and temporal correlation of seismic activity with the fluid injection in the region revealed that these events are better correlated with hydraulic fracturing correlation coefficient of 0 17 at confidence level close to 99 7 with a lag time between 0 and 2 days than other types of injection using the double difference relocation technique we obtained depth constraints for some of the events for which supplementary industry provided waveforms were available the depths of these events range from 0 5 to 2 5 km and are mostly constrained above the target zone where hydraulic fracturing was taking place the best fit moment tensor solution for the event on 17 august 2015 gives a moment magnitude of 4 6 and a predominantly thrust mechanism in the northwest southeast direction with a shallow focal depth of 4 km this is consistent with that obtained through double difference relocation for this event 1 3 km given the depth uncertainty of the moment tensor inversion electronic supplement 1 tables of injection volumes and seismicity parameters and figure of monthly distribution of seismic events and location of fluid injection sites in the vicinity of the 17 august 2015 m w 4 6 event 1 http www bssaonline org lookup suppl doi 10 1785 0120160175 dc1

numerical simulation of nonlinear long waves in the presence of discontinuous coastal vegetation abstract we presented numerical simulations of long waves interacting with arrays of emergent cylinders inside regularly spaced patches representing tsunamis interacting with discontinuous patchy coastal vegetation we employed the fully nonlinear and weakly dispersive serre green naghdi equations sgn until the breaking process starts while we changed the governing equations to nonlinear shallow water equations nsw at the vicinity of the breaking wave peak and during the run up stage we modeled the cylinders as physical boundaries rather than approximating them as macro roughness friction our results show that the cylinders provide protection for the areas behind them however they might also cause amplification in local water depth in those areas the presented results are extensively validated against the existing numerical and experimental data our results demonstrate the capability and reliability of our model in simulating wave interaction with emergent cylinders

seismology speed and size of the sumatra earthquake we now have a clearer picture of the seismic features of last year s gigantic event our seismological results reveal that indonesia s devastating sumatra andaman earthquake on 26 december 2004 was 2 5 times larger than initial reports suggested second only to the 1960 chilean earthquake in recorded magnitude they indicate that it slowly released its energy by slip along a 1 200 km fault generating a long rupture that contributed to the subsequent tsunami now that the entire rupture zone has slipped the strain accumulated from the subduction of the indian plate beneath the burma microplate has been released and there is no immediate danger of a similar tsunami being generated on this part of the plate boundary although large earthquakes on segments to the south still present a threat

full scale cfd simulation of tsunamis part 1 model validation and run up abstract this paper presents numerical simulations of the propagation shoaling and run up of full scale tsunami waves the simulations are performed with a model solving reynolds averaged navier stokes equations with k turbulence closure and is one of very few studies involving cfd simulations at full tsunami scale involving full resolution of small scale dispersive effects as well as wave breaking it is demonstrated that a combination of previous analytical and empirical expressions for run up heights and inundation speeds match those simulated well this indicates that these are reasonable first approximation even in cases where the underlying assumption of linearity of the incoming tsunami is violated as well as in cases where breaking occurs though they generally slightly underestimate both run up height and inundation speed it is shown that the run up of tsunamis can manifest in different ways depending on the initial wave shape and slope of the coast and three qualitative run up types previously identified in the literature are described in detail it is further shown that the shorter waves of an undular bore which appear during lengthy propagation in shallow water can either maintain their shape the entire distance to shore or break far offshore creating a breaking bore it is demonstrated the front of the breaking bore will not appear as steep for n waves as single waves because these need to re wet the drawn down region before reaching the original shoreline finally the importance of shorter waves riding on the front of the tsunami is discussed it is shown that they have little impact on the run up height and inundation speed but are important in terms of local flow velocities the results presented here are part 1 of a larger study where part 2 involves details of the tsunami induced boundary layer dynamics bed shear stresses and implication for sediment transport

effect of lithosphere thickness heterogeneities in controlling rift localization numerical modeling of the oslo graben 1 we present 2 d thermo mechanical and numerical modeling at lithospheric scale to assess the impact of pre existing lithosphere thickness contrast on rift localization the results of the modeling suggest that thickness heterogeneity was responsible for focussing rifting and passive asthenospheric upwelling in the permo carboniferous oslo graben at the western margin of the fennoscandian shield these findings are consistent with inferences from recent studies showing that both the crust mantle boundary and the base of the lithosphere are and were deeper at the eastern margin of the oslo graben resulting in contrasting crust and lithosphere thickness

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

debris flow generated tsunamis and their dependence on debris flow dynamics abstract debris flow generated tsunamis can be extremely dangerous for lakeside settlements and infrastructure debris flow composition strongly affects debris flow thickness and velocity and therefore also the generated tsunami this interaction is however poorly understood we investigate the effects of debris flow volume composition gravel sand clay water and subaerial outflow slope on wave celerity and amplitude in a small scale physical model consisting of an inclined outflow channel which transits into a three dimensional water reservoir we find that upon debouching a debris flow pushes the water forward until wave celerity exceeds subaqueous debris flow velocity i e froude number wave celerity has the strongest relation with debris flow velocity debris flow velocity increases with increasing water and clay content up to 22 which both lubricate the flow far field leading wave amplitude has the strongest relation with debris flow momentum velocity times effective mass which is mostly a function of debris flow thickness water and clay content we test the applicability of published semi empirical equations for predicting tsunami amplitude generated by dry landslides and show that they are to some extent also applicable to debris flow potential scale effects especially considering the smallest waves and water depths could influence the applicability of these predictors and translation of the results to the field scale our results demonstrate the importance of debris flow composition on tsunami generation and evolution and thus the necessity of including flow composition in predictive simulation models

the swash of solitary waves on a plane beach flow evolution bed shear stress and run up the swash of solitary waves on a plane beach is studied using large scale experiments ten wave cases are examined which range from non breaking waves to plunging breakers the focus of this study is on the influence of breaker type on flow evolution spatiotemporal variations of bed shear stresses and run up measurements are made of the local water depths flow velocities and bed shear stresses using a shear plate sensor at various locations in the swash zone the bed shear stress is significant near the tip of the swash during uprush and in the shallow flow during the later stages of downrush in between the flow evolution is dominated by gravity and follows an explicit solution to the nonlinear shallow water equations i e the flow due to a dam break on a slope the controlling scale of the flow evolution is the initial velocity of the shoreline immediately following waveform collapse which can be predicted by measurements of wave height prior to breaking but also shows an additional dependence on breaker type the maximum onshore directed bed shear stress increases significantly onshore of the stillwater shoreline for non breaking waves and onshore of the waveform collapse point for breaking waves a new normalization for the bed shear stress which uses the initial shoreline velocity is presented under this normalization the variation of the maximum magnitudes of the bed shear stress with distance along the beach which is normalized using the run up follows the same trend for different breaker types for the uprush the maximum dimensionless bed shear stress is approximately 0 01 whereas for the downrush it is approximately 0 002

a review of volcanic island evolution and magma production rate an example from a cenozoic island arc in the caribbean different stages of volcanic island evolution are evident in the cenozoic lesser antilles arc developed near the eastern edge of the caribbean plate the early stage of seamount evolution is represented by the kick em jenny submarine volcano near the southern end of the arc the volcanically active islands known as the volcanic caribbees are composed of a series of composite volcanoes and are examples of an emergent volcanic island stage those islands that were formerly active known as the limestone caribbees provide evidence that an erosional to submergent stage occurred in the northern part of the island arc during the oligocene and miocene epochs growth of the islands and underlying crust is dependent upon the magma production rate along the arc which has for the last 100 ka ranged from less than 1 km 3 to 40 km 3 these differences in magma production and volcanic rock composition along the arc are attributed to the obliquity of plate convergence and the plate convergence rates

on the runup of long waves on a plane beach 1 using the records of free surface fluctuations at several locations during the 2011 japan tohoku tsunami we first show that the leading tsunami waves in both near field and far field regions are small amplitude long waves these leading waves are very different from solitary waves we then focus on investigating the evolution and runup of non breaking long waves on a plane beach which is connected to a constant depth region for this purpose we develop a lagrangian numerical model to solve the nonlinear shallow water equations the lagrangian approach tracks the moving shoreline directly without invoking any additional approximation we also adopt and extend the analytical solutions by synolakis 1987 and madsen and schaffer 2010 for runup and rundown of cnoidal waves and a train of multiple solitary waves the analytical solutions for cnoidal waves compare well with the existing experimental data and the direct numerical results when wave amplitudes are small however large discrepancies appear when the incident amplitudes are finite we also examine the relationship between the maximum runup height and the leading wave form it is concluded that for a single wave the accelerating phase of the incident wave controls the maximum runup height finally using the analytical solutions for the approximated wave forms of the leading tsunamis recorded at iwate south station from the 2011 tohoku japan tsunami we estimate the runup height

the moho depth distribution in fennoscandia and the regional tectonic evolution from archean to permian times abstract from a variety of seismic refraction and reflection profiling results a new detailed moho depth map for the fennoscandian part of the baltic shield has been compiled a complementary crystalline crustal thickness map was compiled for denmark the skagerrak sea offshore western norway and adjacent areas where sedimentary strata reach maximum thicknesses of 10 km and even more these maps are discussed in relation to tectonic evolution and crustal ages of fennoscandia seismic velocities bouguer gravity and seismicity areas deviating from the proposed age thickness relationships are the kola peninsula archean and the oslo rift permian the average crustal thickness in the former area is around 44 km while the latter area is associated with a moho elevation of 3 5 km maximum crustal thicknesses in excess of 50 km have been found in southwestern and central finland and correlate with a crust of proterozoic age the caledonides of western norway do not exhibit as elsewhere a crustal root sub moho p n and s n seismic velocities are relatively small in that area and bouguer gravity values are strongly negative intracrustal p velocity variations do not seem to reflect geological age or specific tectonic features although the seismicity is moderate in fennoscandia most of the earthquake activity and in particular the largest earthquakes are confined to areas where the crustal thinning is most pronounced

wave characteristic and morphologic effects on the onshore hydrodynamic response of tsunamis abstract while the destruction caused by a tsunami can vary significantly owing to near and onshore controls we have only a limited quantitative understanding of how different local parameters influence the onshore response of tsunamis here a numerical model based on the non linear shallow water equations is first shown to agree well with analytical expressions developed for periodic long waves inundating over planar slopes more than 13 000 simulations are then conducted to examine the effects variations in the wave characteristics bed slopes and bottom roughness have on maximum tsunami run up and water velocity at the still water shoreline while deviations from periodic waves and planar slopes affect the onshore dynamics the details of these effects depend on a combination of factors in general the effects differ for breaking and non breaking waves and are related to the relative shift of the waves along the breaking non breaking wave continuum variations that shift waves toward increased breaking such as steeper wave fronts tend to increase the onshore impact of non breaking waves but decrease the impact of already breaking waves the onshore impact of a tsunami composed of multiple waves can be different from that of a single wave tsunami with the largest difference occurring on long shallow onshore topographies these results demonstrate that the onshore response of a tsunami is complex and that using analytical expressions derived from simplified conditions may not always be appropriate

runup of solitary waves on a circular island this is a study of the interactions of solitary waves climbing up a circular island a series of large scale laboratory experiments with waves of different incident height to depth ratios and different crest lengths is described detailed two dimensional run up height measurements and time histories of surface elevations around the island are presented a numerical model based on the two dimensional shallow water wave equations including runup calculations was developed numerical model predictions agreed very well with the laboratory data and the model was used to study wave trapping and the effect of slope under certain conditions enhanced runup and wave trapping on the lee side of the island were observed suggesting a possible explanation for the devastation reported by field surveys in babi island off flores indonesia and in okushiri island japan

hydraulic fracturing and the crooked lake sequences insights gleaned from regional seismic networks within central alberta canada a new sequence of earthquakes has been recognized as of 1 december 2013 in a region of previous seismic quiescence near crooked lake 30 km west of the town of fox creek we utilize a cross correlation detection algorithm to detect more than 160 events to the end of 2014 which is temporally distinguished into five subsequences this observation is corroborated by the uniqueness of waveforms clustered by subsequence the crooked lake sequences have come under scrutiny due to its strong temporal correlation 99 99 to the timing of hydraulic fracturing operations in the duvernay formation we assert that individual subsequences are related to fracturing stimulation and despite adverse initial station geometry double difference techniques allow us to spatially relate each cluster back to a unique horizontal well overall we find that seismicity in the crooked lake sequences is consistent with first order observations of hydraulic fracturing induced seismicity

linking changes in tectonic style with magmatism in northern europe during the late carboniferous to latest permian abstract early carboniferous to permian magmatism associated with rifting within the northern foreland of the variscan orogen was widespread across europe during the long period of magmatic activity the regional tectonic setting changed across the region from early carboniferous extension and basin formation to a rifting wrenching style of deformation in the late carboniferous stephanian to early permian wrenching and faulting were accompanied by widespread voluminous and episodic magmatic extrusion intrusion and underplating this was followed by thermal relaxation and the development of the northern and southern permian basins in later permian times thermal relaxation was punctuated by a permo triassic phase of extension and graben formation 40ar 39ar ar step heating dating for mineral separates and whole rock samples of magmatic rocks from southern scandinavia oslo graben and south sweden and rugen north germany provides further radiometric evidence for three of the proposed periods of magmatic activity in the region latest carboniferous to earliest permian ages c 300 310 ma were obtained for volcanic rocks in the oslo graben and dolerite sills and dykes in south sweden and north germany this phase can be time correlated with magmatic activity that occurred throughout europe during large scale dextral wrenching that followed the variscan orogeny a second phase of alkaline intrusions is confined to the oslo graben and related to caldera collapse around c 275 ma the third permo triassic phase c 250 ma is considered to be related to a new tectonic cycle involving extension that triggered minor melting of enriched fertile mantle

the oslo rift a review the tectonomagmatic history of the oslo rift may be subdivided into 5 main periods stage 1 300 ma development of a shallow depression stage 2 300 295 ma roughly simultaneous onset of widespread basalt volcanism b1 and vertical movement along nnw sse to n s trending faults stage 3 295 275 ma main rifting period accompanied by volcanism dominated by rhomb porphyry lavas latites stage 4 275 240 ma change of magmatic style from basaltic shield volcanism to central volcanoes of mixed compositions many of which went through caldera collapses intrusion of composite batholiths of intermediate to granitic compositions stage 5 240 ma dike intrusions may have continued into triassic time both the crust and total lithosphere under the rift are thinned relative to the precambrian basement on both sides a 12 km thick high density and high velocity body occupies the lower crust along the rift axis and extends under the eastern and western rift shoulder petrological and geochemical data imply that this massive layer represents dense cumulates and gabbroic rocks formed from mantle derived magmas in deep crustal magma chambers two mantle sources one nearly undepleted age corrected nd of about 1 and sr of 10 to 15 the other mildly depleted nd of about 4 sr of 10 contributed melts to the oslo rift magmatism the two sources are interpreted as different parts of a heterogeneous upper mantle which before the rifting event belonged to the subcontinental lithosphere on their way to the surface the mantle derived magmas were retained in deep crustal magma chambers where they underwent extensive fractional crystallization some also suffered moderate contamination anatectic melts and melts formed by mixing between mantle derived and anatectic melts gave rise to syenitic and granitic intrusions

full scale cfd simulation of tsunamis part 2 boundary layers and bed shear stresses abstract this paper presents results from numerical simulations of the propagation and run up of full scale tsunamis using a reynolds averaged navier stokes model with emphasis on the resulting boundary layers and bed shear stresses spatial distributions of the shields and rouse parameters during run up and draw down show that for the tsunamis considered with a sediment grain size corresponding to medium sand considerable sediment transport shields parameter o 10 o 100 can be expected during run up and that the sediment transport can be expected to be dominated by suspended load the results likewise show that the expected sediment transport during draw down will similarly be considerable and dominated by suspension the tsunami induced boundary layers are monitored in time and the observed boundary layer thickness ranges from spanning only a small fraction of the water depth to spanning the entire depth the velocity profiles beneath the tsunamis are shown to have good correspondence with a logarithmic profile within the boundary layer similarly the bed shear stresses beneath the tsunamis are investigated and a new and simple engineering model is developed for predicting the temporal variation of the bed shear stress based only on a free stream velocity signal the new engineering model is shown give better predictions for the bed shear stress than a standard manning approach and is likewise shown in the appendix to produce reasonable predictions for shorter wind scale waves it is finally also shown how the temporal evolution of the boundary layer thickness can be predicted based on the free stream velocity signal alone the results presented here are part 2 of a larger study where part 1 presents the model validation and detailed descriptions of the run up process

an experimental study of the interaction of two successive solitary waves in the swash a strongly interacting case and a weakly interacting case abstract the interaction of successive solitary waves in the swash zone have been studied using large scale experiments with a simple bathymetry of a constant depth region where the water depth was 1 72 m and a plane beach whose slope was 1 12 two wave cases were considered where two successive solitary waves of the same height were generated one after the other so that the wave crests were separated by the effective wavelength associated with a single solitary wave in the weakly interacting case the swash period associated with a single solitary wave is smaller than the time period separating the successive wave crests which leads to similar run ups for the first and second wave whereas in the strongly interacting case the swash period associated with a single solitary wave is larger than the time period separating the successive wave crests which leads to a significant reduction in the run up of the second wave the degree to which there is an interaction between the swash uprush of the second wave and the downrush of the first wave is found to be related to the solitary wave slope parameter which predicts breaker type of the first wave previous data from literature are found to support this claim measurements of bed shear stress bed pressure and the free surface displacement at a location near the stillwater shoreline are used to describe how the dynamics of the boundary layer differ when the downrush of the first wave meets the incoming second wave in both cases

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

tsunami source of the 2004 sumatra andaman earthquake inferred from tide gauge and satellite data tsunami source of the 2004 sumatra andaman earthquake was esti mated from a joint inversion of tsunami waveforms recorded on tide gauges and sea surface heights captured by satellite altimetry measurements the earthquake the largest in the past 40 years caused devastating tsunami damage to countries around the indian ocean but the tsunami source in particular its northern end was not well resolved although aftershocks and crustal deformation extended from off north western sumatra island through the nicobar islands to the andaman islands some seismic wave analyses indicated a shorter source length several hundred kilometers we used tsunami waveforms recorded at 12 tide gauge stations around the source and the sea surface heights measured by three satellites jason1 topex poseidon and envisat we numerically computed tsunami propagation using realistic bathym etry more than 66 000 depth points were digitized from nautical charts and combined with the etopo2 data inversion of satellite data indicates that the tsunami source extended to the andaman islands with a total length of 1 400 km but such a model produces much larger tsunami waveforms than observed at indian tide gauge stations inversion of tide gauge records and the joint inversion indicate that the tsunami source was about 900 km long the largest slip about 13 to 25 m was located off sumatra island and the second largest slip up to 7 m near the nicobar islands the slip distribution is similar for different rupture velocities and rise times with a slow velocity of 1 km sec and a rise time of 3 min yielding the largest variance reduction

skagerrak graben the offshore continuation of the oslo graben abstract new seismic mapping of skagerrak reveals eight structural provinces in particular the skagerrak graben appears to be the continuation of the oslo graben the skagerrak graben is defined by two major late paleozoic faults trending northeast southwest connecting with the faults bounding the oslo graben extensive rotated block faulting is observed within the graben and a thickness of more than 2 s twt of lower paleozoic sediments has been preserved along the boundary faults sediments of probable late paleozoic age have been deposited as erosional products from the fault scarps and a central uplifted area a substantial part of these sediments may have a volcaniclastic origin the skagerrak graben continues to the north as a province of igneous rocks exposed at the sea floor with precambrian basement on either side the skagerrak graben is flanked by small half grabens containing probable early paleozoic sediments indicating that a wider area was involved in the rift process the formation of the skagerrak graben is related to the dextral strike slip movements along the sorgenfrei tornquist zone in late paleozoic time the kimmerian extensional movements along this zone indicate however a decoupling of the skagerrak graben at this time only minor inversion in the southwestern part of the skagerrak graben reflects the major inversion tectonism along the sorgenfrei tornquist zone in late cretaceous early tertiary times

temporal relationship between injection rates and induced seismicity normalized cross correlation of effective functions was originally developed to differentiate induced and natural seismicity we apply this methodology to data sets acquired during hydraulic stimulation of shale gas to study temporal relationship between seismicity and the injection delays of seismicity induced by hydraulic fracturing are compared with delays of seismicity related to changes of the water level in a dam a new observation is made we show that seismicity induced by hydraulic fracturing and measured by the normalized cross correlation can have very positive to even short negative delay after the injection we explain this observation by rapid decline of induced seismicity after decrease of injection on the contrary we show that the seismicity triggered by water impounding in a dam is characterized by longer delays due to much greater distance between lake and the induced seismicity we show how it is possible to measure the delay by the cross correlation methodology despite periodicity of the signals

deep injection and closely monitored induced seismicity at paradox valley colorado the u s bureau of reclamation s paradox valley unit pvu extracts aquifer brine from nine shallow wells along the dolores river paradox valley in southwestern colorado and after treating high pressure injects the brine 4 3 4 8 km below the surface pvu injects at rates between 800 and 1300 l min since 1991 pvu has emplaced over 4 106 m3 of fluid and induced more than 4000 surface recorded seismic events the events are recorded on the local 15 station paradox valley seismic network the induced seismicity at paradox separates into two distinct source zones a principle zone 95 of the events asymmetrically surrounding the injection well to a maximum radial distance of 3 km and a secondary ellipsoidal zone 2 5 km long and centered 8 km northwest of the injection well the expansion of these zones has stabilized since mid 1999 about three years after the onset of continuous injection within the principal zone hypocenters align in distinct linear patterns showing at depth stratigraphy and the local wray mesa fracture and fault system the primary faults of the wray mesa system are aseismic striking subparallel to the inferred maximum principal stress direction with one or more faults probably acting as fluid conduits to the secondary seismic zone individual seismic events in both zones do not discernibly correlate with short term injection parameters however a 0 5 km2 region immediately northwest of the injection well responds to long term large scale changes in injection rate and the surpassing of a threshold injection pressure focal mechanisms of the induced events are consistent with simple double couple strike slip moments and subhorizontal extension to the northeast in addition the fault planes are consistent with principal stress directions determined from borehole breakouts more than 99 9 of the pvu seismicity is below human detection m 2 5 however approximately 15 events have been felt locally with the largest being a magnitude m 4 3 because of the m 4 3 and two earlier felt m 3 5 events and injection economics pvu changed injection strategies three times since 1996 these changes reduced seismicity from 1100 events year to as low as 60 events year

cross shore sediment transport under breaking solitary waves 1 laboratory experiments were performed to examine the cross shore sediment transport processes under breaking solitary waves on a fine sand beach the initial beach slope of 1 12 was exposed to a positive solitary wave eight times the beach was rebuilt and exposed to a negative solitary wave eight times the wave motion and sediment transport were not affected much by the beach profile change from the initial profile the positive solitary wave plunged violently near the shoreline and suspended a considerable volume of sand the plunging wave with no seaward flow impeding its run up caused large run up on the foreshore the strong downrush following the large run up resulted in erosion on the foreshore and deposition seaward of wave run down on the other hand the negative solitary wave collapsed against the seaward flow induced by the free surface slope of the negative wave and caused less sediment suspension the wave run up against the seaward flow was much smaller the weak downrush following the small run up resulted in deposition on the foreshore and erosion near the wave collapsing point these limited laboratory experiments indicate the importance of the initial wave profile for swash sediment dynamics and the capacity of a single wave in causing noticeable beach profile changes

self subduction of the pangaean global plate one of the most striking and rare occurrences in the earth s history is the amalgamation of most of the continental lithosphere into one supercontinent the most recent supercontinent pangaea lasted from 320 to 200 million years ago here we show that after the continental collisions that led to the formation of pangaea plate convergence continued in a large wedge shaped oceanic tract we suggest that plate strain at the periphery of the supercontinent eventually resulted in self subduction of the pangaean global plate when the ocean margin of the continent subducted beneath the continental edge at the other end of the same plate our scenario results in a stress regime within pangaea that explains the development of a large fold structure near the apex of the palaeotethys ocean extensive lower crustal heating and continental magmatism at the core of the continent as well as the development of radially arranged continental rifts in more peripheral regions of the plate

propagation and amplification of tsunamis at coastal boundaries when tsunamis hit a coastal area they often cause substantial damage and loss of life at locations otherwise well protected from normal even severe wind generated waves an example of such a catastrophe took place on 12 december 1992 when an earthquake of magnitude ms 7 5 occurred in the eastern region of flores island indonesia1 2 one of the areas hardest hit by the resulting tsunamis was babi a small coastal island two villages on the island were completely destroyed even though both were located in sheltered areas where wave conditions are normally calm here we describe the results of numerical and laboratory experiments that show how unlike wind generated waves tsunamis are capable of penetrating into sheltered coastal areas without significantly losing their energy for the case of babi island the original tsunami wave was split into two with one wave propagating around each side of the island the two waves met in the sheltered region and the subsequent amplification of wave amplitude resulted in the destructive flow onto the beach

effect of bed roughness on tsunami bore propagation and overtopping abstract the accurate modelling of overtopping of coastal defences by tsunami waves is of vital importance for the formulation of disaster management strategies to improve knowledge of this phenomena the authors conducted experiments on coastal structure overtopping using bores that were generated by a dam break mechanism three types of structures were tested namely a coastal dyke a wall and a wall of infinite height the results highlight the necessity to consider the energy present in a bore to determine if a structure will be overtopped or not as a result of these experiments an empirical formula to determine the height of overtopping given the incident bore height and velocity was validated the study highlights the importance of clearly modelling the velocity and froude number of a tsunami such experiments should be conducted on rough beds for which a suitable manning s n seems to be around 0 06 sm 1 3 the study also contrasted the results obtained to those of the asce7 method and concludes that the manning s n values recommended in asce7 are probably too low

human induced seismicity and large scale hydrocarbon production in the usa and canada we compare current and historic seismicity rates in six states in the usa and three provinces in canada to past and present hydrocarbon production all states provinces are major hydrocarbon producers our analyses span three to five decades depending on data availability total hydrocarbon production has significantly increased in the past few years in these regions increased production in most areas is due to large scale hydraulic fracturing and thus underground fluid injection furthermore increased hydrocarbon production generally leads to increased water production which must be treated recycled or disposed of underground increased fluid injection enhances the likelihood of fault reactivation which may affect current seismicity rates we find that increased seismicity in oklahoma likely due to salt water disposal has an 85 correlation with oil production yet the other areas do not display state province wide correlations between increased seismicity and production despite 8 16 fold increases in production in some states however in various cases seismicity has locally increased multiple factors play an important role in determining the likelihood of anthropogenic activities influencing earthquake rates including i the near surface tectonic background rate ii the existence of critically stressed and favorably oriented faults which must be hydraulically connected to injection wells iii the orientation and magnitudes of the in situ stress field combined with iv the injection volumes and implemented depletion strategies a comparison with the seismic hazard maps for the usa and canada shows that induced seismicity is less likely in areas with a lower hazard the opposite however is not necessarily true

an idealized model for tsunami study 1 an idealized mathematical model of tsunami evolution in deep sea and across the continental shelf is proposed the initial value problem in deep sea is related to the well known cauchy poisson problem and the tsunami propagation across the continental shelf is derived using the linearized shallow water equations when analyzing different cases of tsunamis in deep sea it was found that tsunamis evolve into two basic wave types one resembles a single wave and the other a wave packet the analysis of different cases of tsunamis at the shoreline reveals that the continental shelf due to its geometrical properties serves as a tsunami amplifier producing tsunami amplitudes up to 20 times larger than those at the edge of the continental shelf a comparison with tsunami measurements suggests that the idealized model may be used for a reliable assessment of the principle hydrodynamic properties of the tsunami such as the tsunami amplitude and its half period

numerical simulation of tsunami scale wave boundary layers this paper presents a numerical study of the boundary layer flow and properties induced by tsunami scale waves for this purpose an existing one dimensional vertical 1dv boundary layer model based on the horizontal component of the incompressible reynolds averaged navier stokes rans equations is newly extended to incorporate a transitional variant of the standard two equation k turbulence closure the developed numerical model is successfully validated against recent experimental measurements involving transient solitary wave boundary layers as well as for oscillatory flows collectively demonstrating the ability to reproduce accurate velocity profiles turbulence and bed shear stresses on both smooth and rough beds the validated model is then employed for the study of transient wave boundary layers at full tsunami scales covering a wide and realistic geophysical range in terms of the flow duration bottom roughness and associated reynolds numbers for this purpose three different synthetic idealised tsunami wave descriptions are considered i e invoking 1 single wave solitary like but with independent period and wave height 2 sinusoidal and 3 n wave descriptions the flow boundary layer thickness turbulence and bed shear stresses induced are systematically monitored and parameterised under both hydraulically smooth and rough bed conditions the results generally support a notion that the boundary layers induced by tsunami scale waves are both current like due to their long durations as well as wave like in the sense that the boundary layer will not necessarily span the entirety of the water column the results likewise suggest that there is a continuum connecting wind wave and tsunami wave scales as existing expressions commonly used for characterising boundary layer properties beneath wind waves maintain reasonable accuracy when extrapolated to full tsunami scales boundary layers driven by actual field measured tsunami signals are likewise simulated stemming from both the 2004 indian ocean as well as the 2011 tohoku events these results are reconciled with the various synthetic tsunami signals considered generally confirming their usefulness as idealised tsunami waves

laboratory experiments of tsunami runup on a circular island laboratory experiments of a 7 2 m diameter conical island were conducted to study three dimensional tsunami runup the 62 5 cm tall island had 1 on 4 side slopes and was positioned in the center of a 30 m wide by 25 m long flat bottom basin solitary waves with height to depth ratios ranging from 0 05 to 0 20 and source lengths ranging from 0 30 to 7 14 island diameters were tested in water depths of 32 and 42 cm twenty seven capacitance wave gages were used to measure surface wave elevations at incident and four radial transects on the island slope maximum vertical runup measurements were made at 20 locations around the perimeter of the island using rod and transit a new runup gage was located on the back or lee side of the island to record runup time series

the oslo graben gravity high and taphrogenesis abstract the paleo oslo rift oslo graben system is geophysically characterized by a pronounced gravity high a reinterpretation of gravity data in the region using a flexible inversion scheme indicates that the causative body has a density contrast of 0 06 g cm 3 the inversion results also suggest that this body is most likely located in the upper part of the lower crust and extends eastward well outside the graben area proper estimates of crustal thicknesses before and after the rifting aborted suggest that rifting commenced in the south and then progressed northwards the corresponding pole of rotation was located approximately 240 km nne of the city of oslo the hypocentres of 7 small local earthquakes were found to be located on the periphery of the anomalous body as derived from gravity modeling seismic investigations including 3 d imaging using norsar data have failed to provide conclusive evidence on intrusion of asthenospheric material in the lithosphere as part of the oslo graben taphrogenesis the explanation proposed here is that the geophysical imprints of oslo rift oslo graben evolutionary processes within the upper mantle have been considerably weakened over the associated time span of some 150 200 ma finally it is hypothesized that the asthenospheric injection into the lithosphere took place over a relatively small cross sectional area of the moho the further ascent of the gabbroic magma was partly hindered by the relatively rigid upper crust thus causing extensive lateral flow eastwards outside the oslo graben proper in the 10 20 km depth range

are the norwegian mountains compensated by a mantle thermal anomaly at depth article i nfo article history the norwegian mountains or scandes represent a long mountain range stretching from southern norway to the arctic and is characterised by a rugged topography and peaks up to 2 5 km high the origin of this mountain chain far away from any plate boundary remains a matter of passionate debates inside the geoscientific community hot mantle fingers originating from the iceland plume impacting the base of the scandinavian lithosphere and creating asthenospheric diapirs is one of the most accepted hypotheses for explaining cenozoic uplift in norway in order to test this hypothesis we conducted integrated gravity and thermal modelling we used the dense ngu gravity grid i e one measurement every 3 km and modelled the depth extent and the mass deficit associated to the compensating loads located below the southern scandes assuming that the density deficit below the scandes is purely thermal in origin thermal modelling allowed for testing the magnitude of the potentially associated temperature anomaly and its impact on surface heat flow recently acquired heat flow data were used in order to constrain the results from the thermal modelling the results of our integrated geophysical modelling rule out the possibility that the present day topography of the southern scandes is compensated by a deep seated asthenospheric diapir however our modelling does not exclude that thermal processes in the deep mantle could have initiated or assisted recent uplift of the southern scandes

crustal properties of the northern scandinavian mountains and fennoscandian shield from analysis of teleseismic receiver functions supplementary data are available at gj i online https academic oup com gji article lookup doi 10 1093 gji ggy140 supplementary data figure s1 a teleseismic events mw 5 8 recorded by scanlips2 between july 2007 and september 2009 for p receiver function study b teleseismic events mw 5 8 recorded by scanlips3d between july 2013 and september 2014 for p receiver function study in both cases the blue star corresponds to the centre of the seismic array figure s2 a synthetic p receiver functions for a moho depth of 43 km and vp vs of 1 73 from three crustal models in red a model with two layers upper and lower crust for the crust and step discontinues in green a model with three layers upper lower crust and transitional moho with highvp and step discontinuities in blue a gradual model between upper crust and moho b sensibility of amplitude of direct p arrival and ps conversion for different slowness and for two crustal model on the left a step moho model and on the right a gradual moho model table s1 informations about seismic stations and number of events used in this study for each instruments 70xx scanlips2 13xx scanlips3d table s2 compilation of p rfs analysis and previous works ottemoller midzi 2003 olsson et al 2008 silvennoinen et al 2014

the 26 december 2004 sumatra tsunami analysis of tide gauge data from the world ocean part 1 indian ocean and south africa the m w 9 3 megathrust earthquake of december 26 2004 off the northwest coast of sumatra in the indian ocean generated a catastrophic tsunami that was recorded by a large number of tide gauges throughout the world ocean part 1 of our study of this event examines tide gauge measurements from the indian ocean region at sites located from a few hundred to several thousand kilometers from the source area statistical characteristics of the tsunami waves including wave height duration and arrival time are determined along with spectral properties of the tsunami records

u pb systematics in volcanic and plutonic rocks of the krokskogen area resolving a 40 million years long evolution in the oslo rift abstract the development of the oslo rift started in the latest carboniferous in the northern foreland of the variscan orogen the initial intensive and mainly mafic magmatism at around 300 ma was followed by a period of some 40 m y of mafic and felsic volcanic and plutonic activity the present study applied u pb in zircon on rocks of the krokskogen area northwest of oslo to resolve in greater detail the sequence of events in this evolution a major challenge however has been the absence or paucity of zircon and their low quality for dating in some of the important units especially the alkalic latitic rhomb porphyries the earliest rhomb porphyry flow rp1 yields an age of 299 7 0 4 ma it was thus coeval with the earliest basaltic and alkalic eruptions in the southern part of the oslo graben flows rp6 and rp7 yield overlapping ages of 285 5 0 8 and 284 9 0 5 ma and rp11 is 280 2 0 5 ma the baerum oppkuven and heggelia caldera volcanoes and the slottet kjelsasite pluton developed at 276 7 to 275 9 ma while the oyangen caldera is somewhat younger at 273 272 ma a kjelsasite stock has an age of 265 4 0 6 ma predating the 262 3 0 5 ma blindern rhomb porphyry like dyke which is among the youngest magmatic expressions in the rift the new data stress the importance of the magmatic burst at around 300 ma possibly plume related along the entire oslo rift and sharpens our understanding of the timing of the subsequent protracted sequence of magmatic events reflecting continuous heating and stress in the lithosphere likely broadly controlled by processes accompanying the closing of pangea

the 9 april 1993 earthquake in south central texas was it induced by fluid withdrawal an earthquake that occurred 9 april 1993 about 80 km south of san antonio is the largest earthquake known mblg 4 3 in south central texas in historic times the earthquake was felt over a 4000 km2 area and modified mercalli intensities were as high as vi at a gas production facility near fashing texas similar smaller events have occurred since 1973 at three sites near fashing pleasanton and falls city texas we propose a list of nine yes no questions to assess whether a sequence of earthquakes may have been induced by fluid withdrawal the criteria suggest that at least two sites fashing and pleasanton had earthquakes that were induced by fluid withdrawal related to ongoing oil and gas production an alternative possibility is that these events are the southwesternmost examples in a band of weak natural seismic activity between 135 and 240 km from the coast of the gulf of mexico and extending from this region east to the texas louisiana border in addition some injection occurs at all three sites although the volumes of fluid injected at fashing and pleasanton are low enough as to make injection an unlikely cause

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

a stretching model for the oslo rift abstract data on the tectonic and magmatic activity crustal thickness seismic velocity and gravity have been integrated to constrain a stretching model for the late carboniferous early permian oslo rift the crustal structure and numerical modelling of temperature and melt generation during rifting suggest that the oslo rift in skagerrak developed in response to crustal stretching with a factor between 1 4 and 1 6 however upper crustal extension by faulting accounts for a stretching factor of only 1 1 1 2 thermal expansion of the lithosphere due to an increased asthenospheric potential temperature the intrusion of melted mantle material into the lower crust and probably a lowering of the erosional base by a fall in sea level all contributed to the erosion of 2 4 km of lower palaeozoic pre rift sediments over large areas the lateral extent of the thermal anomaly reached far beyond the oslo and skagerrak grabens

the 23 october 1904 ms 5 4 oslofjord earthquake reanalysis based on macroseismic and instrumental data abstract on 23 october 1904 the area of the oslofjord was struck by an m s 5 4 earthquake that was felt over much of northern europe we collected information available from seismological bulletins of the time and also seismogram copies from a number of seismic stations in europe this allowed for the first time for this earthquake an instrumental epicentral location even if the observation capabilities at that time were poor due to low seismograph amplification and timing problems after a careful selection and weighting of published onset times the reported observations from the seismic stations in uppsala hamburg potsdam gottingen leipzig and tartu could be used for this instrumental location of the event we also performed an inversion of the available macroseismic observations based on the kinematic function kf for the radiation of body waves from a line source because the problem is nonlinear and also bimodal for pure dip slip mechanisms we used a sharing niching genetic algorithm to perform the inversion the new epicenter obtained from the kf intensity inversion is consistent with the new instrumental solution giving a location in the lower crust 25 30 km and close to the eastern coast of the oslofjord near the junction of two major fault zones the kf inversion was moreover able to constrain the fault plane mechanism with an almost vertical rupture plane striking north northeast south southwest 206 212 with a mixed mechanism approximately 64 rake angle the ambiguity of which is resolved by the polarities of the pn onset observed on the horizontal components of the uppsala wiechert seismograph the magnitude of the event has previously been assessed to m s 5 4 based on the size of the felt area observations and a value of m s 5 4 has now been independently confirmed both through the new intensity inversion and through the instrumental data

rifting in heterogeneous lithosphere inferences from numerical modeling of the northern north sea and the oslo graben oslograbenevolvedinthecoldandstableprecambrian lithosphere of fennoscandia whereas the northern northsearifttookbirthinfreshlyreworkedcaledonian lithosphere huge volumes of magmatic rocks characterize the relatively narrow oslo graben in contrast little magmatism is documented for the wide northern north sea rift differences in timing between both rifts are inferred but still debated we present numerical thermomechanical models along a lithospheric e w section that involves both the oslo graben and the northern north sea area because the modeled section crosses the boundary between caledonian and proterozoic provinces thermal and compositional heterogeneities are considered as is suggested by various geophysical data sets we also consider lithospheric thickness heterogeneities in the precambrian lithosphere modeling results suggest that the northern north sea was on top of weak lithosphere very sensitive to far field stresses consequently we suggest that rifting in the northern north sea began as early as regional extension was effective i e late carboniferous early permian and does not postdate the oslo graben as it is commonly assumed rifting in the strong precambrian lithosphere is unexpected modeling results suggest thatapre existinglithosphericthicknesscontrastwithin the fennoscandian lithosphere favored rifting in the oslo graben index terms 8109 tectonophysics continental tectonics extensional 0905 8159 tectonophysics evolution of the earth rheology crust and lithosphere 8020 structural geology mechanics 9335 information related to geographic region europe 9614 information related to geologic time paleozoic keywords numerical modeling rifting rheology lithosphere oslo graben north sea citation pascal c and s a p l cloetingh rifting in heterogeneous lithosphere inferences from numerical modeling

seismic imaging of upper crustal basement faults in the skagerrak sea abstract the continental upper crystalline crust appears almost non reflective on many deep seismic reflection profiling sections typically only the major faults and lithological boundaries are imaged whereas smaller scale faults are usually not identified a deep seismic survey 0 16 s twt covering the skagerrak sea was undertaken in 1987 although the northeastern part of the skagerrak has only thin or no sediment cover the data in the depth range 0 6 s twt were reprocessed to commercial exploration standards close inspection of these high quality sections provides evidence of abundant moderately steep dipping 20 50 faults that can be traced to depths of 10 13 km fault geometry which can be inferred at profile intersections is in accordance with the general tectonic fabric observed on land and beneath the skagerrak sea these areas were deformed during the proterozoic sveconorwegian orogeny and during the formation of the permian oslo rift due to post permian erosion of the skagerrak sea proper the relative age and movements of the basement faults could not be determined this study shows that under favorable conditions faults in the upper crystalline crust are mappable by seismic means such measurements have the potential for resolving variations in block geometry with depth and also recent seismotectonic movements

recovering water wave elevation from pressure measurements the reconstruction of water wave elevation from bottom pressure measurements is an important issue for coastal applications but corresponds to a difficult mathematical problem in this paper we present the derivation of a method which allows the elevation reconstruction of water waves in intermediate and shallow waters from comparisons with numerical euler solutions and wave tank experiments we show that our nonlinear method provides much better results for the surface elevation reconstruction compared to the linear transfer function approach commonly used in coastal applications more specifically our method accurately reproduces the peaked and skewed shape of nonlinear wave fields therefore it is particularly relevant for applications on extreme waves and wave induced sediment transport

dynamic processes controlling evolution of rifted basins abstract the extension of the lithosphere controlling the development of rifted basins is driven by a combination of plate boundary forces frictional forces exerted on the base of the lithosphere by the convecting asthenosphere and deviatoric tensional stresses developing over upwelling branches of the asthenospheric convection system although mantle plumes are not a primary driving force of rifting they play an important secondary role by weakening the lithosphere and by controlling the level of rift related volcanic activity a distinction between active and passive rifting is only conditionally justified the extension of the lithosphere depending on its rate and magnitude and the potential temperature of the asthenosphere can cause by adiabatic decompression partial melting of the lower lithosphere and upper asthenosphere in rift systems the level and timing of volcanic activity is highly variable the lack of volcanic activity implies passive rifting an initial passive rifting stage can be followed by a more active one during which magmatism plays an increasingly important role magmatic destabilization of the moho may account for the frequently observed discrepancy between upper and lower crustal extension factors combined with evidence for thermal thinning of the mantle lithosphere this suggest that the volume of the lithosphere is not necessarily preserved during rifting as advocated by conventional stretching models the structural style of rifts is controlled by the rheological structure of the lithosphere the availability of crustal discontinuities that can be tensionally reactivated the mode orthogonal or oblique and amount of extension and the lithological composition of pre and syn rift sediments simple shear extension prevails in rifts that subparallel the structural grain of the basement pure shear extension is typical for rifts cross cutting the basement grain pre existing crustal and mantle lithospheric discontinuities contribute to the localization of rift systems the duration of the rifting stage of extensional basins is highly variable stress field changes can cause abrupt termination of rifting in major rift systems progressive strain concentration on the zone of future crustal separation entails abandonment of lateral rifts depending on constraints on lateral block movements crustal separation can be achieved after as little as 9 my and as much as 280 my of rifting activity syn rift basin subsidence is controlled by isostatic adjustment of the crust to mechanical stretching of the lithosphere its magmatic inflation and thermal attenuation of the mantle lithosphere post rift basin subsidence is governed by thermal reequilibration of the lithosphere asthenosphere system deep seated thermal anomalies related to syn rift pull up of the asthenosphere lithosphere boundary have decayed after 60 my by about 65 and after 180 my by about 95 the magnitude of post rift subsidence is a function of the rift induced thermal anomaly and crustal density changes the potential temperature of the asthenosphere and initial water depths intraplate stresses can have an overprinting effect on post rift subsidence stretching factors derived from post rift subsidence analyses must be corrected for such effects

left lateral transpressive deformation and its tectonic implications sveconorwegian orogen baltic shield southwestern sweden abstract the mylonite zone mz is a major ductile deformation zone in the sveconorwegian orogen baltic shield of southwestern sweden and southeastern norway which has a strike length of over 400 km and an across strike width which often exceeds 5 km it is an orogen parallel deformation zone which formed under retrogressive metamorphic conditions relative to the higher grade structures in the surrounding crustal units the mz marks a conspicuous metamorphic break in the area south of lake vanern and a distinct lithological break in the area north of this lake regional metamorphic considerations suggest that its surface exposure represents an oblique section through the crust with deeper levels exposed along the southern parts of the zone and shallower levels exposed farther north structural studies in three areas north of lake vanern varmlandsnas kil and torsby charlottenberg suggest that the mz displays coeval left lateral strike slip and reverse dip slip senses of shear characteristic of a transpressive tectonic regime active under upper greenschist facies conditions in the northernmost torsby charlottenberg area at relatively shallow crustal levels the mz splays out to form two left lateral contractional strike slip duplexes which together define a positive flower structure regionally the mz defines the western flank of an east verging thrust system which formed in the eastern part of the sveconorwegian orogen the structures within this thrust system preceded the mz contain a subordinate left lateral strike slip component of movement and were rotated into the sveconorwegian frontal deformation zone sfdz in the frontal part of the orogen the mz is inferred to have formed in an extrusive dispersive tectonic environment which developed in connection with a slightly oblique collision and crustal shortening in a wnw ese direction the initial stages of this collision produced the east verging thrust system and shortening was absorbed at this stage by crustal thickening late possibly out of sequence thrusting with a right lateral strike slip sense of shear along the sfdz marked the waning stages of crustal shortening in the sveconorwegian orogen

an experimental study of wave run up at a steep beach this paper presents experiments on run up of strongly nonlinear waves on a beach of 10 54 inclination velocity fields are obtained by the piv particle image velocimetry technique acceleration measurements are also attempted but it is difficult to obtain useful results in every case in addition free surface profiles are extracted from digital images and wave resistance probes the investigation focuses on the dynamics of the early stages of the run up when steep fronts evolve in the vicinity of the equilibrium shoreline but maximum run up heights are also reported measurements on moderately nonlinear waves are compared to results from long wave theories including a numerical boussinesq model and analytic shallow water results from the literature in particular the applicability of the long wave theories is addressed however most attention is given to run up of high incident solitary waves that are on the brink of breaking at the shoreline in one case a temporarily slightly overturning wave front is found that neither develops into a plunger or displays appreciable spilling this feature is discussed in view of measured velocity and acceleration patterns and with reference to the dam break problem effects of scaling as well as viscous damping are also briefly discussed

the lithosphere asthenosphere system in fennoscandia abstract we present a summary of the available information on rayleigh wave dispersion data for the fennoscandian region the observations have been combined to produce regional dispersion relations which have then been subjected to the hedgehog inversion procedure the results are presented on a map outlining the thickness of the lid and the shear velocities in both the lid and the asthenosphere channel lid thickness up to around 135 km is found in the bothnia north central finland area with if any weak shear velocity contrast to the underlying layer the surrounding areas are characterized by lid thickness up to around 75 km a stronger low velocity zone to lid contrast may be found in the caledonian and baltic sea area 0 25 0 45 km s taking into account moho depth data and the aforementioned results a map of the lithosphere asthenosphere system was derived

structure of the scandes lithosphere from surface to depth abstract in this review we give an overview of geophysical data and models available for the scandinavian mountains and adjacent areas as they are of relevance to the debate about the existence and cause of neogene uplift emphasis is given to potential field and petrophysical data of which the earth science communities of norway and sweden have a long tradition of acquisition and interpretation this is reflected in the wealth and dense coverage of data available the topography of the scandes mountain chain correlates to a large degree with a bouguer gravity low which suggests isostatic compensation but comparison with magnetic and petrophysical data shows that the gravity low is partly influenced by the trans scandinavian igneous belt signals due to the effects of surface geology can be further eliminated by considering the near surface density distribution as provided by petrophysical sampling to illuminate the entire lithospheric structure active and passive seismic and magnetotelluric data can be used recent and ongoing experiments are aimed at improving the existing models of the lithosphere integration of these different geophysical data sets allows the structure of the lithosphere of the scandes and its surroundings to be addressed seismic models show no pronounced crustal root below the scandes which could provide isostatic compensation but instead an increase of crustal thickness towards the central fennoscandian shield from the integrated model isostatic compensation is inferred to be largely controlled by the density distribution of the crust and that a high density lower crust to the east of the scandes is necessary to achieve isostatic equilibrium on a regional scale we demonstrate the typical crustal structure with profiles crossing from the scandes into the shield and a combined onshore offshore basement map

insights into the magmatic architecture of the oslo graben by petrophysically constrained analysis of the gravity and magnetic field 1 a new model of the crustal structure of the oslo graben with a special emphasis on the location of magmatic intrusions is presented based on the interpretation of gravity and magnetic data constrained by petrophysical data seismics and surface geology three dimensional modeling shows that the gravity high above the oslo rift is caused by a combination of crustal thinning and the presence of a high density body in the upper crust related to precambrian gneiss complexes at the western flank of the rift the short wavelength gravity anomalies are correlated with the outcropping low density magmatic rocks of permian age that extend to the depths of 1 5 4 km in addition simultaneous modeling of aeromagnetic data sets collected at two flight altitudes 50 and 3400 m using susceptibility and remanence within a range of reasonable magnetic properties suggests an underlying intrusion with a depth extent up to 15 km magnetization and density of the intrusion are increasing with depth leading to a small density contrast but a large contrast in magnetization with the surrounding rocks therefore only modeling of the magnetic field can resolve the nature of the deep intrusions the three dimensional model provides a new estimate of the volume of magmatic material in the oslo graben system 63 000 km3 this is only two thirds of the values proposed earlier 95 000 km3 as we disregard high volume magmatic underplating correlation with structural data surface geology and deep lithospheric features shows that the distribution of extrusive rocks in the oslo rift can be related to the timing and onset of rifting

flow and sediment transport induced by a plunging solitary wave 1 two parallel experiments involving the evolution and runup of plunging solitary waves on a sloping bed were conducted 1 a rigid bed experiment allowing direct hot film measurements of bed shear stresses and 2 a sediment bed experiment allowing for the measurement of pore water pressures and for observation of the morphological changes the two experimental conditions were kept as similar as possible the experiments showed that the complete sequence of the plunging solitary wave involves the following processes shoaling and wave breaking runup rundown and hydraulic jump and trailing wave the bed shear stress measurements showed that the mean bed shear stress increases tremendously with respect to that in the approaching wave boundary layer by as much as a factor of 8 in the runup and rundown stages and that the rms value of the fluctuating component of the bed shear stress is also affected by as much as a factor of 2 in the runup and hydraulic jump stages the pore water pressure measurements showed that the sediment at or near the surface of the bed experiences upward directed pressure gradient forces during the down rush phase the magnitude of this force can reach values as much as approximately 30 of the submerged weight of the sediment the experiments further showed that the sediment transport occurs in the sheet flow regime for a substantial portion of the beach covering the area where the entire sequence of the wave breaking takes place the bed morphology is explained qualitatively in terms of the measured bed shear stress and the pressure gradient forces