three dimensional splay fault geometry and implications for tsunami generation megasplay faults very long thrust faults that rise from the subduction plate boundary megathrust and intersect the sea floor at the landward edge of the accretionary prism are thought to play a role in tsunami genesis we imaged a megasplay thrust system along the nankai trough in three dimensions which allowed us to map the splay fault geometry and its lateral continuity the megasplay is continuous from the main plate interface fault upwards to the sea floor where it cuts older thrust slices of the frontal accretionary prism the thrust geometry and evidence of large scale slumping of surficial sediments show that the fault is active and that the activity has evolved toward the landward direction with time contrary to the usual seaward progression of accretionary thrusts the megasplay fault has progressively steepened substantially increasing the potential for vertical uplift of the sea floor with slip we conclude that slip on the megasplay fault most likely contributed to generating devastating historic tsunamis such as the 1944 moment magnitude 8 1 tonankai event and it is this geometry that makes this margin and others like it particularly prone to tsunami genesis

the development of the central european continental crust since the early archaean based on conventional and ion microprobe dating of up to 3 84 b y old detrital zircons abstract archaean components up to 3 84 b y old have been detected by ion microprobe dating of zircon from various sediments and metasediments of the european hercynides moldanubian of northeastern bavaria and the massif central the early archaean age of 3 84 b y was obtained within the euhedral core of a detrital grain from a moldanubian paragneiss the same detrital zircon grain reveals at least three metamorphic overprints at 2 59 b y b p 1 94 b y b p and 460 m y b p and at least two cycles of mechanical abrasion during surface recycling in the early proterozoic and after the pan african cycle it is thus the crystal with the most complex geological history ever detected further archaean ages for the crystallization of primary magmatic zircons probably in the course of continental crust formation in the first cycle provenances of the two studied areas were found at 3 15 2 9 2 76 and 2 65 b y b p and in a few cases between 2 6 and 2 5 b y b p early proterozoic crust forming events between about 1 75 and 2 15 b y b p play an important role especially for the sediments and metasediments of the montagne noire at the southern rim of the massif central middle and late proterozoic ages cluster around 1 0 b y b p and 600 m y b p for all analysed samples therefore the deposition of the metasedimentary precursors took place after the pan african cycle which is in line with the rb sr whole rock systematics of central european metasediments the ages of metamorphism in the different source areas could be inferred in some cases by lower intercept ages obtained on single detrital grains the following sequence coinciding with times of magmatic events has been so far established 2 59 1 94 and 1 0 b y b p and 600 m y b p thus ion probe dating is also capable of defining secondary effects in the respective provenances which are typical for orogenic cycles the ubiquitous presence of pan african detrital zircons in european metasediments is a strong indication that the detrital material was derived from gondwana however from the presence of metamorphic units including eclogitefacies rocks which probably formed at different continental margins and at various times between about 500 m y and 330 m y ago it is probable that various gondwana derived microcontinental plates contributed to the different basin fillings the gondwana derived detritus is also supported by the observation of two periods of relative quiescence or non activity around 2 3 b y ago and especially around 1 5 b y ago which is a typical feature observed in gondwana cahen et al 1984 but not in laurasia the other possible source of the detritus the lack of zircons crystallized between 3 84 and 3 15 b y ago might have different causes thus the continental crust of the european hercynides probably developed since the early archaean and grew via many crustal accretion events to its present state

igneous and tectonic evolution of the batchawana greenstone belt superior province a u pb zircon and titanite study u pb isotopic dating of zircon and titanite from all the major litho tectonic units of the batchawana belt an archean greenstone belt of the abitibi subprovince of the superior province in canada shows that the belt evolved during a period of about 60 ma between about 2730 and 2670 ma ago the earliest date of 2729 3 2 ma was found in a predominantly tholeiitic metavolcanic sequence the base of which is intruded by a tonalite dated at 2716 2 ma younger ages of 2720 10 ma 2709 2ma 2711 2ma 2701 2ma and 2698 2 ma date rocks at increasingly higher stratigraphic levels of a mixed tholeiitic calc alkalic metavolcanic sequence which is itself overlain by a thick succession of clastic metasedimentary rocks subsequent deformation of the supracrustal sequences produced isoclinal folding and culminated in metamorphism ranging from lower greenschist to amphibolite facies and anatexis related to the intrusion of syn to late tectonic plutons four phases of which have ages of 2678 4 2ma 2677

pre alpine variscan inheritance a key for the location of the future valaisan basin western alps the boundary between the helvetic and the penninic brianconnais zones has long been recognized as a major fault penninic front in the western alps a narrow oceanic domain has been postulated at least along part of this boundary the valaisan ocean however the information provided by the pre triassic basement has not been fully exploited and will be discussed here in detail the igneous and metamorphic history of the pre triassic basement shows significant differences between the external massifs from the helvetic zone with abundant late carboniferous granites and the basement of the brianconnais zone including the internal massifs dora maira gran paradiso monte rosa devoid of carboniferous granites a major coal bearing basin the zone houillere opened along this boundary this limnic intramontane basin has never been properly investigated the zone houillere is not comparable with the external paralic flexural basins on both sides of the variscan belt but shows similarities with the saar saale basin like the latter we interpret the zone houillere as a transtensional basin opened along a major crustal scale fault zone namely the east variscan shear zone the permian magmatism and sedimentation displays contrasting distributions being absent or very localized in the helvetic zone and widespread in the penninic zone the above data indicate that the structural inheritance from the variscan belt plays a major role in defining the future location of the valaisan basin i e the boundary between the european palaeomargin and the brianconnais microcontinent

how is strain localized in a meta granitoid mid crustal basement section spatial distribution of deformation in the central aar massif switzerland abstract this study investigates strain distribution in granitoid rocks formerly in the middle crust in the central aar massif switzerland and places the deformation behavior in the tectonic framework of the alpine orogeny strain is heterogeneously distributed in terms of strain partitioning forming several hundreds of closely spaced shear zones sz 80 sz km with sz thicknesses the majority of the steep shear zones preferentially accommodated upward motion by the southern block leading to an increase in peak metamorphic conditions from 250 c in the north to 450 c in the south of the aar massif the shear zones initiated at about 18 20 km depths during a stage of crustal thickening handegg phase subsequent deformation reactivated some shear zones with a gradual transition from reverse dip slip over oblique slip to strike slip shear zones under local transpressional conditions oberaar phase

an energy duration procedure for rapid determination of earthquake magnitude and tsunamigenic potential summary we introduce a rapid and robust energy duration procedure based on the haskell extended source model to obtain an earthquake moment and a moment magnitude med using seismograms at teleseismic distances 30 90 this procedure combines radiated seismic energy measures on the p to s interval of broadband signals and source duration measures on high frequency p wave signals the med energy duration magnitude is scaled to correspond to the global centroid moment tensor cmt moment magnitude mcmtw and can be calculated within about 20 min or less after origin time ot the measured energy and duration values also provide the energy to moment ratio used for identification of tsunami earthquakes the med magnitudes for a set of recent large earthquakes match closely mcmtw even for the largest great earthquakes these results imply that the med measure is accurate and does not saturate after the 2004 december 26 sumatra andaman mega thrust earthquake magnitude estimates available within 1 hr of ot ranged from m 8 0 to 8 5 the cmt magnitude available about 3 hr after ot was mcmtw 9 0 and several months after the event mw 9 1 9 3 was obtained from analysis of the earth normal modes the energy duration magnitude for this event is med 9 2 a measure that is potentially available within 20 min after ot after the 2006 july 17 java earthquake the magnitude was evaluated at m 7 2 at 17 min after ot the cmt magnitude available about 1 hr after ot was mcmtw 7 7 the energy duration results for this event give med 7 8 with a very long source duration of about 160 s and a very low value indicating a possible tsunami earthquake

the brabant massif as part of armorica gondwana upb isotopic evidence from detrital zircons u pb isotopic ratios of zircons are used as time dependent geochemical tracers for the formation of the zircons and for the sum of processes and their intensities effective for the disturbance of the u pb systems during the history of the zircons by comparison detrital zircons can thus serve as indicators for the provenance of clastic sediments the u pb systematics of 57 carefully selected fractions of detrital zircons from four cambrian sandstones of the ardennes and the brabant massif have been investigated according to the u pb data features of color and shape of these zircons are suited for distinguishing to major groups 1 1 colourless mainly rounded subordinately subhedral or euhedral zircons which are characterized by u contents below 300 ppm and by apparent 207pb 235u ages between 0 53 ga and 1 65 ga 2 2 reddish generally subrounded to very well rounded zircons with u contents from 240 ppm to more than 800 ppm and apparent 207pb 235u ages between 1 75 ga and 2 4 ga from the group of colourless zircons only one fraction yields concordant u pb data and documents a cadomian panafrican crystal growth at 545 ma u pb data of the other colourless zircons arrange in a fan shaped area in the concordia diagram below concordia and from 530 ma to 600 ma zircons with such u pb characteristics are well known from central and southern europe they suggest a strong cadomian pan african influence the reddish zircons are dominantly derived from archean to early proterozoic crystalline rocks based on these results and on comparison with u pb data of other detrital zircons the ardennes and the brabant massif must be regarded to be coherent to the gondwana continental plate before the caledonian orogeny

i type granitoids as indicators of a late paleozoic convergent ocean continent margin along the southern flank of the central european variscan orogen a belt of carboniferous to permian i type granitoid bodies is in the basement thrust sheets of the alps which correspond to the southern flank of the central european variscan orogen these predominantly granodioritic plutons contrast with a contemporaneous belt of s type granites which extends to the north of the alps in the moldanubian section of the variscan orogen the observed regional duality of variscan plutonism resembles the plutons along active circum pacific continental margins in that there are outer i type plutons and inner s type granitoid belts therefore central europe could have undergone a cordilleran type orogenic event in late paleozoic time involving northwestward subdcution of the paleo tethys ocean

geodynamic model for the palaeozoic crustal consolidation of western and central europe abstract the crystalline basement of western and central europe consists of a mosaic of crustal elements which were consolidated during pre grenvillian the grenvillian dalslandian morarian cadomian caledonian and hercynian orogenic cycles contemporaneous with the caledonian suturing of the precambrian laurentia greenland and fennosarmatian shields a number of gondwana derived cadomian micro cratons were accreted to the southern margin of laurasia following the late caledonian paroxysm the devonian and early carboniferous evolution of europe was dominated by continued northward subduction of the proto tethys plate at an arc trench system parallelling the southern margin of laurasia the accretion of additional gondwana derived continental fragments back arc rifting and a sinistral translation of major proportions between the laurentia greenland and the fennosarmatian sub plates the acadian and bretonian orogenies were of the pacific type the visean collision of gondwana with laurasia marked the onset of the himalayan type variscan orogeny during which collision related compressive stresses overpowered the devonian early carboniferous back arc rift systems and caused the development reactivation of a subduction zones the central armorican and saxothuringian successor basins became folded and destroyed during the latest visean whilst the variscan foredeep became scooped out in part by nappes involving the basement during the late westphalian major crustal shortening during the variscan diastrophism was accompanied by the anatectic remobilisation of subducted crustal and upper mantle material and a widespread syn and late orogenic magmatism the latest carboniferous early permian reorientation of the convergence direction between gondwana and laurasia induced the development of a complex wrench fault system transecting the variscan fold belt and an extensive post orogenic volcanism the hypotheses summarised here require confirmation by further palaeomagnetic and radiometric data and faunal analyses

hydrological connectivity in river deltas the first order importance of channel island exchange deltaic systems are composed of distributary channels and interdistributary islands while previous work has focused either on the channels or on the islands here we study the hydrological exchange between channels and islands and point at its important role in delta morphology and ecology we focus our analysis on wax lake delta in coastal louisiana usa and characterize the surface water component of hydrological connectivity through measurements of water discharge and hydraulic tracer propagation we find that deltaic islands are zones of significant water flux as 23 54 of the incoming distributary channel flux enters the islands a calculation of the travel times through a channel island complex shows travel times through the islands to be at least 3 times their channel counterparts a dye release experiment also indicates that travel times in islands are much longer that those within channels as dye remained in the island for the 3 8 day duration of the experiment additionally islands are more sensitive than channels to environmental forces such as tides which cause flow reversal and thus can increase travel times through the islands our work defines the hydrological network of a river delta to include not only the distributary channel network but also the interdistributary islands quantifies the implications of channel island hydrological connectivity to travel times through the system and discusses the relevance of our findings to channel mouth dynamics at the delta front and the potential for denitrification in coastal systems

tsunami early warning within five minutes tsunamis are most destructive at near to regional distances arriving within 20 30 min after a causative earthquake effective early warning at these distances requires notification within 15 min or less the size and impact of a tsunami also depend on sea floor displacement which is related to the length l width w mean slip d and depth z of the earthquake rupture currently the primary seismic discriminant for tsunami potential is the centroid moment tensor magnitude m w cmt representing the product lwd and estimated via an indirect inversion procedure however the obtained m w cmt and the implied lwd value vary with rupture depth earth model and other factors and are only available 20 30 min or more after an earthquake the use of more direct discriminants for tsunami potential could avoid these problems and aid in effective early warning especially for near to regional distances previously we presented a direct procedure for rapid assessment of earthquake tsunami potential using two simple measurements on p wave seismograms the predominant period on velocity records t d and the likelihood t 50 ex that the high frequency apparent rupture duration t 0 exceeds 50 55 s we have shown that t d and t 0 are related to the critical rupture parameters l w d and z and that either of the period duration products t d t 0 or t d t 50 ex gives more information on tsunami impact and size than m w cmt m wp and other currently used discriminants these results imply that tsunami potential is not directly related to the product lwd from the seismic faulting model as is assumed with the use of the m w cmt discriminant instead information on rupture length l and depth z as provided by t d t 0 or t d t 50 ex can constrain well the tsunami potential of an earthquake we introduce here special treatment of the signal around the s arrival at close stations a modified real time m wpd rt magnitude and other procedures to enable early estimation of event parameters and tsunami discriminants we show that with real time data currently available in most regions of tsunami hazard event locations m b and m wp magnitudes and the direct period duration discriminant t d t 50 ex can be determined within 5 min after an earthquake occurs and t 0 t d t 0 and m wpd rt within approximately 10 min this processing is implemented and running continuously in real time within the early est earthquake monitor at ingv rome http early est rm ingv it we also show that the difference m b log10 t d t 0 forms a rapid discriminant for slow tsunami earthquakes the rapid availability of these measurements can aid in faster and more reliable tsunami early warning for near to regional distances

secular variation in the isotopic composition of nd in tethys seawater abstract this preliminary nd isotopic study of authigenic glauconites that are mineralogically chemically isotopically rb sr k ar and stratigraphically well characterized suggests that these minerals can be used to determine the nd isotopic evolution of ancient ocean water generally glauconites indicate the same evolutionary history of nd in tethys seawater as published data for marine phosphates e g fish remains mn ores and fossil debris the initial nd values define a smooth curve with lowest values of 9 to 10 for the cretaceous and lower tertiary highest nd values have been found for 150 200 ma tethys seawater that was influenced by both a nonradiogenic continental component and a greater input of young mantle derived material

introduction to historical and recent catastrophic tsunamis in the world volume ii tsunamis from 1755 to 2010 eighteen papers on past and recent destructive tsunamis are included in volume ii of the pageoph topical issue historical and recent catastrophic tsunamis in the world three papers discuss deep sea dart and coastal tsunami observations warning systems and risk management in the pacific ocean four papers examine the 1755 lisbon 1964 alaska 2003 algeria and 2011 haiti tsunamis four more papers as well as some papers in volume i report on various aspects of the 2010 chile tsunami two papers present some results of field survey and modelling investigation of the 2010 mentawai indonesia tsunami three papers report on modelling efforts of tsunami generation by earthquake and landslide and of tsunami propagation finally two papers discuss hazard assessment using a probabilistic approach

drowning of the mississippi delta due to insufficient sediment supply and global sea level rise global sea level rise reduced sediment supply and subsidence threaten the stability of the mississippi delta calculations of riverine sediment load and storage indicate that 10 000 13 500 km2 of the delta could be submerged by ad 2100

the delta connectome a network based framework for studying connectivity in river deltas abstract many deltas including the mississippi river delta have been losing land at fast rates compromising the safety and sustainability of their ecosystems knowledge of delta vulnerability has raised global concern and stimulated active interdisciplinary research as deltas are densely populated landscapes rich in agriculture fisheries oil and gas and important means for navigation there are many ways of looking at this problem which all contribute to a deeper understanding of the functioning of coastal systems one aspect that has been overlooked thus far yet fundamental for advancing delta science is connectivity both physical how different portions of the system interact with each other as well as conceptual pathways of process coupling in this paper i propose a framework called delta connectome for studying connectivity in river deltas based on different representations of a delta as a network after analyzing the classic network representation as a set of nodes e g bifurcations and junctions or regions with distinct physical or statistical behavior and links e g channels i show that from connectivity considerations the delta emerges as a leaky network that continuously exchanges fluxes of matter energy and information with its surroundings and evolves over time i explore each network representation and show through several examples how quantifying connectivity can bring to light aspects of deltaic systems so far unexplored and yet fundamental to understanding system functioning and informing coastal management and restoration this paper serves both as an introduction to the delta connectome framework as well as a review of recent applications of the concepts of network and connectivity to deltaic systems within the connectome framework

archean protoliths within early proterozoic granulitic crust of the west european hercynian belt possible relics of the west african craton granulites from the bay of biscay area have been studied by using u pb and sm nd methods results on four granulites suggest two major events of crustal growth and high grade metamorphism the first is archean 2 7 ga and the second is early proterozoic 1 9 ga in the hercynian belt the oldest basement remnants known so far are about 2 0 ga and are located in the northern armorican massif the 2 7 ga orthogneiss protolith age from the bay of biscay is the first direct evidence of archean crust involved in the hercynian belt major events at 2 7 1 8 and 0 6 ga in the hercynian belt suggest that european precambrian microplate s were part of the west african craton where the same sequence of events is observed

the mantle magnitude mm and the slowness parameter θ five years of real time use in the context of tsunami warning we study a database of more than 119 000 measurements of the mantle magnitude mm introduced by okal and talandier 1989 obtained since 1999 as part of the operational procedures at the pacific tsunami warning center the perfor mance of this method is significantly affected by the seismic instrumentation at the recording station with the very broadband sts 1 and ks54000 systems offering the lowest residuals between measured values of mm and those predicted from the har vard centroid moment tensor cmt catalog and also by the period at which spec tral amplitudes are measured with the best results between 70 and 250 sec with such mild restrictions estimates of seismic moments can be obtained in real time by retaining either the maximum value of mm measured on each record or its average over the various mantle frequencies with the resulting residuals on the order of 0 1 0 2 moment magnitude units mm deficiencies in the case of the two large earthquakes of peru 2001 and hokkaido 2003 are attributed to azimuthal bias from an excess of stations principally in north america in directions nodal for the focal mechanism and directivity patterns we further study a group of more than 3000 measurements of the energy to moment ratio h introduced by newman and okal 1998 which allows the real time identification of teleseismic sources violating scaling laws and in particular of so called tsunami earthquakes the use of a sliding window of analysis in the computation of h allows the separation of late earthquakes characterized by a delayed but fast moment release from truly slow earthquakes many such events are recognized notably on major oceanic and con tinental strike slip faults introduction and background we present detailed analyses of a large dataset resulting from implementation as part of the operational procedures of the pacific tsunami warning center ptwc of the real time calculation of the mantle magnitude mm and of the slowness parameter h as defined and introduced by okal and talandier 1989 and newman and okal 1998 re spectively during the past five years more than 119 000 individual measurements of mm and 3000 values of h have been computed through automated algorithms these values contribute to the estimation of the source characteristic of distant earthquakes in the framework of the real time as sessment of their tsunamigenic potential this study offers a progress report on the performance of the algorithms and in particular discusses the influence of instrumentation at the various reporting stations as the final revision of this article was being prepared the occurrence of the great sumatra earthquake on 26 de cember 2004 provided an opportunity to extend the concepts of mm and h to a range of magnitudes unexplored for the

first measurement of ice bedrock interface of alpine glaciers by cosmic muon radiography the shape of the bedrock underneath alpine glaciers bears vital information on the erosional mechanism related to the flow of ice so far several geophysical exploration methods have been proposed to map the bedrock topography though with limited accuracy here we illustrate the first results from a technology called cosmic ray muon radiography newly applied in glacial geology to investigate the bedrock geometry beneath the aletsch glacier situated in the central swiss alps for this purpose we installed new cosmic muon detectors made of emulsion films at three sites along the jungfrau railway tunnel and measured the shape of the bedrock under the uppermost part of aletsch glacier jungfraufirn our results constrain the continuation of the bedrock ice interface up to a depth of 50 m below the surface where the bedrock underneath the glacier strikes ne sw and dips at 45 5 this documents the first successful application of this technology to a glaciated environment

teleseismic estimates of radiated seismic energy the e m 0 discriminant for tsunami earthquakes we adapt the formalism of boatwright and choy for the computation of radiated seismic energy from broadband records at teleseismic distances to the real time situation when neither the depth nor the focal geometry of the source is known accurately the analysis of a large data set of more than 500 records from 52 large recent earthquakes shows that this procedure yields values of the estimated energy ee in good agreement with values computed from available source parameters for example as published by the national earthquake information center neic the average logarithmic residual being only 0 26 units we analyze the energy to moment ratio by defining log10 ee m0 for regular earthquakes this parameter agrees well with values expected from theoretical models and from the worldwide neic catalogue there is a one to one correspondence between values of that are deficient by one full unit or more and the so called tsunami earthquakes previously identified in the literature as having exceedingly slow sources and believed due to the presence of sedimentary structures in the fault zone our formalism can be applied to single station measurements and its coupling to automated real time measurements of the seismic moment using the mantle magnitude mm should significantly improve real time tsunami warning

the evolution of the polymetamorphic basement in the central alps unravelled by precise u pb zircon dating the u pb age determinations of zircon and rutile from the aar massif reveal a complex evolution of the central alpine basement the oldest components are found in zircons of metasediments which bear cores of archean age the u pb age of discordant prismatic zircons of the same rocks ranges between 580 and 680 ma an age that is typical for pan african metamorphism the zircons are interpreted as pan african detritus with archean inheritance the provenance region of the pan african zircons is assumed to be a terrane of gondwana affinity i e the w african craton or the pentevrian microplate the caledonian metamorphism left a pervasive structural imprint in amphibolite facies on the rocks of the aar massif it is dated at 456 2 and 445 ma by zircons of a layered migmatitic gneiss and a migmatitic leucosome respectively both occurring in the northernmost zones of the massif hercynian metamorphism never exceeded greenschist facies conditions and is recorded by zircon in a garnet amphibolite and by rutile in a meta psammite that yield an age of 330 ma both zircon and rutile are considered to be products of retrograde mineral reactions and therefore do not date the peak conditions of hercynian metamorphism the gastern granite at the western end of the aar massif is a contaminated granite that intruded at 303 4 ma contemporaneously with the wide spread late hercynian post collisional i type magmatism the study demonstrates the potential of isotope dilution u pb dating of single grains and microfractions in deciphering complex evolutionary histories of polymetamorphic terrains

threshold for particle entrainment into suspension laboratory observations regarding the limit conditions for particle entrainment into suspension are presented a high speed video system was used to investigate conditions for the entrainment of sediment particles and glass beads lying over a smooth boundary as well as over a rough bed the results extend experimental conditions of previous studies towards finer particle sizes a criterion for the limit of entrainment into suspension is proposed which is a function of the ratio between the flow shear velocity and particle settling velocity observations indicate that particles totally immersed within the viscous sublayer can be entrained into suspension by the flow which contradicts the conclusions of previous researchers a theoretical analysis of the entrainment process within the viscous sublayer based on force balance considerations is used to show that this phenomenon is related to turbulent flow events of high instantaneous values of the reynolds stress in agreement with previous observations in the case of experiments with a rough bed a hiding effect was observed which tends to preclude the entrainment of particles finer than the roughness elements this implies that as the ratio between particle and roughness element sizes becomes smaller progressively higher bed shear stresses are required to entrain particles into suspension on the other hand an overexposure effect was also observed which indicates that a particle moving on a smooth bed is more prone to be entrained than the same particle moving on a bed formed by identical particles

balancing aggradation and progradation on a vegetated delta the importance of fluctuating discharge in depositional systems vegetation is an important component of constructional landscapes as plants enhance deposition and provide organic sediment that can increase aggradation rates to combat land loss we conducted two sets of laboratory experiments using alfalfa medicago sativa to determine the effects of plants on channel organization and large scale delta dynamics in the first set we found that rapid vegetation colonization enhanced deposition but inhibited channelization via increased form drag that reduced the shear stress available for sediment entrainment and transport a second set of experiments used discharge fluctuations between flood and base flow or interflood interfloods were critical for reworking the topset via channel incision and lateral migration to create channel relief and prevent rapid plant colonization these low flow periods also greatly reduced the topset slope in the absence of vegetation by removing topset sediment and delivering it to the shoreline floods decreased relief by filling channels with sediment resulting in periods of rapid progradation and enhanced aggradation over the topset surface which was amplified by vegetation the combination of discharge fluctuations and vegetation thus provided a balance of vertical aggradation and lateral progradation we conclude that plants can inhibit channelization in depositional systems and that discharge fluctuations encourage channel network organization to naturally balance against aggradation thus variations in discharge are an important aspect of understanding the ecomorphodynamics of aggrading surfaces and modeling vegetated deltaic systems and the combined influences of plants and discharge variations can act to balance vertical and lateral delta growth

tsunami early warning using earthquake rupture duration and p wave dominant period the importance of length and depth of faulting summary after an earthquake rapid real time assessment of hazards such as ground shaking and tsunami potential is important for early warning and emergency response tsunami potential depends on seafloor displacement which is related to the length l width w mean slip d and depth z of earthquake rupture currently the primary discriminant for tsunami potential is the centroid moment tensor magnitude mcmtw representing the seismic potency lwd and estimated through an indirect inversion procedure the obtained mcmtw and the implied lwd value vary with the depth of faulting assumed earth model and other factors and is only available 30 min or more after an earthquake the use of more direct procedures for hazard assessment when available could avoid these problems and aid in effective early warning here we present a direct procedure for rapid assessment of earthquake tsunami potential using two simple measures on p wave seismograms the dominant period on the velocity records td and the likelihood that the high frequency apparent rupture duration t0 exceeds 50 55 s t0 can be related to the critical parameters l and z while td may be related to w d or z for a set of recent large earthquakes we show that the period duration product tdt0 gives more information on tsunami impact and size than mcmtw and other currently used discriminants all discriminants have difficulty in assessing the tsunami potential for oceanic strike slip and backarc or upper plate intraplate earthquake types our analysis and results suggest that tsunami potential is not directly related to the potency lwd from the seismic faulting model as is assumed with the use of the mcmtw discriminant instead knowledge of rupture length l and depth z alone can constrain well the tsunami potential of an earthquake with explicit determination of fault width w and slip d being of secondary importance with available real time seismogram data rapid calculation of the direct period duration discriminant can be completed within 6 10 min after an earthquake occurs and thus can aid in effective and reliable tsunami early warning

a simple universal equation for grain settling velocity abstract a new equation is presented for sediment fall velocity as a function of grain diameter for given values of fluid viscosity and fluid and solid density sediment fall velocity is a fundamental parameter in the modeling and interpretation of fluviatile and coastal deposition the equation applies to the entire range of viscous to turbulent conditions and its simple explicit form makes it easy to use in computer models and other applications in sedimentology geomorphology and engineering the equation is derived from dimensional analysis and converges on stokes law for small grains and a constant drag coefficient for large grains its two physically interpretable parameters are easily adjusted for shape effects or for the use of sieve diameter rather than nominal grain diameter it gives a close fit to published and new experimental data for both quartz sand and low density materials with no more error than previous equations of more complicated form

fast determination of earthquake magnitude and fault extent from real time p wave recordings s u m m a r y this work is aimed at the automatic and fast characterization of the extended earthquake source through the progressive measurement of the p wave displacement amplitude along the recorded seismograms we propose a straightforward methodology to quickly characterize the earthquake magnitude and the expected length of the rupture and to provide an approximate estimate of the average stress drop to be used for earthquake earlywarning and rapid response purposes we test the methodology over a wide distance and magnitude range using a massive japan earthquake accelerogram data set our estimates of moment magnitude source duration length and stress drop are consistent with the ones obtained by using other techniques and analysing the whole seismic waveform in particular the retrieved source parameters follow a self similar constant stress drop scaling median value of stress drop 0 71 mpa for the m 9 0 2011 tohoku oki event both magnitude and length are underestimated due to limited available p wave time window ptws and to the low frequency cut off of analysed data we show that in a simulated real time mode about 1 2 seconds would be required for the source parameter determination of m 4 5 events 3 10 seconds for m 6 7 and 30 40 s for m 8 8 5 the proposed method can also provide a rapid evaluation of the average slip on the fault plane which can be used as an additional discriminant for tsunami potential associated to large magnitude earthquakes occurring offshore

global seismicity of 2003 centroid moment tensor solutions for 1087 earthquakes abstract centroid moment tensor cmt solutions are presented for 1087 earthquakes that occurred during 2003 the solutions are obtained using the method of dziewonski et al dziewonski a m chou t a woodward j h 1981 determination of earthquake source parameters from waveform data for studies of global and regional seismicity j geophys res 86 2825 2852 and applying corrections for aspherical earth structure as represented by the whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward dziewonski a m woodward r l 1992 acoustic imaging at the planetary scale in emert h harjes h p eds acoustical imaging vol 19 plenum press new york pp 785 797 the model of inelastic attenuation of durek and ekstrom durek j j ekstrom g 1996 a radial model of inelasticity consistent with long period surface wave attenuation bull seism soc am 86 144 158 is used to predict the decay of the waveforms the focal mechanisms of the largest or otherwise significant earthquakes of 2003 are reviewed

turbulent characteristics of a shallow wall bounded plane jet experimental implications for river mouth hydrodynamics jets arising from rivers streams and tidal flows entering still waters differ from most experimental studies of jets both in aspect ratio and in the presence of a solid bottom boundary and an upper free surface despite these differences the applicability of experimental jet studies to these systems remains largely untested by either field or realistically scaled experimental studies here we present experimental results for a wall bounded plane jet scaled to jets created by flow discharging into floodplain lakes a characteristic feature of both our prototype and experimental jets is the presence of large scale meandering turbulent structures that span the width of the jets in our experimental jets we observe self similarity in the distribution of mean streamwise velocities by a distance of six channel widths downstream of the jet outlet after a distance of nine channel widths the velocity decay and the spreading rates largely agree with prior experimental results for plane jets the magnitudes and distributions of the cross stream velocity and lateral shear stresses approach self preserving conditions in the upper half of the flow but decrease in magnitude and deviate from self preserving distributions with proximity to the bed the presence of the meandering structure has little influence on the mean structure of the jet but dominates the jet turbulence a comparison of turbulence analysed at time scales both greater than and less than the period of the meandering structure indicates that these structures increase turbulence intensities by 3 5 times and produce lateral shear stresses and momentum diffusivities that are one and two orders of magnitude greater respectively than turbulence generated by bed friction alone

tsunami early warning using earthquake rupture duration 1 effective tsunami early warning for coastlines near a tsunamigenic earthquake requires notification within 5 15 minutes we have shown recently that tsunamigenic earthquakes have an apparent rupture duration t0 greater than about 50 s here we show that t0 gives more information on tsunami importance than moment magnitude mw and we introduce a procedure using seismograms recorded near an earthquake to rapidly determine if t0 is likely to exceed t 50 or 100 s we show that this duration exceedance procedure can be completed within 3 10 min after the earthquake occurs depending on station density and that it correctly identifies most recent earthquakes which produced large or devastating tsunamis this identification forms a complement to initial estimates of the location depth and magnitude of an earthquake to improve the reliability of tsunami early warning and in some cases may make possible such warning

the 25 october 2010 mentawai tsunami earthquake from real time discriminants finite fault rupture and tsunami excitation 1 the moment magnitude 7 8 earthquake that struck offshore the mentawai islands in western indonesia on 25 october 2010 created a locally large tsunami that caused more than 400 human causalities we identify this earthquake as a rare slow source tsunami earthquake based on 1 disproportionately large tsunami waves 2 excessive rupture duration near 125 s 3 predominantly shallow near trench slip determined through finite fault modeling and 4 deficiencies in energy to moment and energy to duration cubed ratios the latter in near real time we detail the real time solutions that identified the slow nature of this event and evaluate how regional reductions in crustal rigidity along the shallow trench as determined by reduced rupture velocity contributed to increased slip causing the 5 9 m local tsunami runup and observed transoceanic wave heights observed 1600 km to the southeast

hf isotope systematics in granitoids from the central and southern alps first initial hf isotopic compositions for samples from the alpine domain are presented and discussed the results are mainly based on zircons and a few whole rocks with ages between 30 and 450 ma of those so far analyzed the present day hf isotopic compositions of zircons from non metamorphic and metamorphic granitoid rocks vary between 0 2824 and 0 2829 zircon populations with concordant u pb ages have much higher initial 176hf 177hf than inversely discordant populations which have been contaminated with older zircons containing less radiogenic hf correlated nd hf crustal residence ages have been found involving model parameters of ehf end f lu hf f sm nd 1 6 for the depleted mantle and f lu hf f sm nd 1 2 for elemental fractionations in the crust the model implies 176lu 177hf of 0 017 for the bulk crust it is suggested that the granitoid rocks are the result of mixing of subcontinental mantle derived magmas with 1 7 ga old recycled and partially molten crustal material the continental mantle component mass ratio values for the granitoids range between 0 3 and 2

precambrian tholeiitic dacitic rock suites and cambrian ultramafic rocks in the pennine nappe system of the alps evidence from sm nd isotopes and rare earth elements major element trace element and sm nd isotope analyses were made of polymetamorphic hornblendefelses plagioclase amphibolites and banded amphibolites from the berisal complex in the simplon area italy switzerland to determine their age origin and genetic relationships in light of major and rare earth element data the hornblendefelses are inferred to have originally been pyroxene rich cumulates the plagioclase amphibolites and the dark layers of the banded amphibolites to have been tholeiitic basalts and the light layers dacites the sm nd isotope data yield isochron ages of 475 81 ma for the hornblendefelses 1 018 59 ma for the plagioclase amphibolites and 1 071 43 ma for the banded amphibolites the 1 ga magmatic event is the oldest one ever found in the crystalline basement of the pennine nappes the sm nd isotope data support the consanguinity of the tholeiitic dark layers and the dacitic light layers of the banded amphibolites with the tholeiitic plagioclase amphibolites and the ultramafic hornblendefelses

the volcano sedimentary evolution of a post variscan intramontane basin in the swiss alps glarus verrucano as revealed by zircon u pb age dating and hf isotope geochemistry the late palaeozoic glarus verrucano basin gvb glarus alps eastern switzerland formed as an intramontane graben in the aftermath of the variscan orogeny its fill the glarus verrucano consists of immature alluvial fan and playa lake deposits with intercalated bimodal volcanics basalts and rhyolites despite its importance for local and regional geology no modern sedimentologic or stratigraphic studies on the gvb exist by means of sedimentologic and geochronologic studies we reconstruct the volcano sedimentary evolution of the gvb it developed at the carboniferous permian boundary and experienced a first bimodal volcanic phase around 285 ma for the same time indications for temporarily humid climate in the otherwise rather arid early permian are demonstrated e g pyrite bearing sandstones during the middle and early late permian increasing aridity is indicated by playa deposits fanglomerates and subaerial ignimbrites which mark a second silicic volcanic phase at 268 ma the detrital zircon age spectra are dominated by late variscan ages and thus demonstrate that older sedimentary and metamorphic rocks once forming the variscan nappe edifice were already mostly eroded at that time finally some larger scale speculations are given which could indicate a causal connection between the widespread tectono magmatic mid permian episode and the local development of the glarus verrucano basin

mid ordovician u pb ages of porphyroids in the peloritan mountains ne sicily palaeogeographical implications for the evolution of the alboran microplate petrographic geochemical and geochronological work on a metavolcanic suite interbedded in a metapelitic sequence of the palaeozoic basement in the peloritan mountains sicily is used to contribute to a better understanding of the pre variscan geodynamic evolution of the former alboran microplate major and trace element data show that the volcanic suite consists of two main groups an intermediate unit of andesites and dacites with volcanic arc affinity and a felsic porphyroid unit of rhyolites with peraluminous composition isotope dilution thermal ionization mass spectrometry u pb analyses for single and multigrain zircon fractions from four samples of the felsic porphyroids yield results that are tightly clustered on or near concordia giving caradoc ages in the range of 456 452 ma the consistent morphological characteristics and oscillatory zoning of the zircons indicate single stage magmatic crystallization xenocrystic zircon grains with ages of 1150 and 2015 ma indicate that these rocks were developed upon a cratonic basement with grenvillian and transamazonian components hence supporting a peri gondwanan origin from the combined evidence we conclude that this portion of the alboran microplate formed as a mid ordovician volcanic arc in a sector of the peri gondwanan terranes that was affected by a tectonothermal caradoc event

morphology versus upb systematics in zircon a high resolution isotopic study of a zircon population from a variscan dike in the central alps upb isotopic measurements on individual zircon crystals combined with morphological analyses permit the identification of three distinct components within the zircon population of the saedelhorn diorite a variscan dike from the western gotthard central alps switzerland i 94 of the grains in the zircon population are elongate crystals with pronounced skeletal morphology indicative of rapid growth from a supercooled melt ii 5 of the population consist of turbid mostly subhedral zircons frequently showing d type morphology classification according to pupin and turco 1 and elevated uranium contents compared to the skeletal variety single crystal and multi grain upb isotopic data of group i and ii zircons define an intrusion age of 293 5 4 m y for the dike iii rare transparent zircon crystals 1 of the zircon population yield apparent upb ages in the range of 370 490 m y and display morphological and isotopic characteristics closely resembling those of a caledonian orthogneiss intruded by the dike this implies presence of assimilated wall rock components in the macroscopically homogeneous dike sample a comparison of the data obtained by conventional analysis of multi grain zircon fractions and those obtained by grain by grain analysis demonstrates that age resolution is considerably improved by single crystal upb dating furthermore quantitative identification of zircon components assimilated by the ascending magma along its path to the present level of exposure is feasible by the latter technique since it is likely that such zircon grains are common to a broad variety of magma types valuable information on age and composition of crustal layers not accessible to direct observation may readily become available by application of precise micro analytical techniques low initial143nd 144nd end 2 7 at the time of intrusion of the saedelhorn dike requires the magma to be derived partially or totally from a crustal source for this crustal precursor a model age of 1050 m y tdm is obtained indicating that proterozoic crust was involved in the petrogenesis of the variscan intrusives of the gotthard area

isotope systematics in minerals biotite rejuvenation and exchange during alpine metamorphism abstract the hercynian schists and granites of the helvetic basement aar massif in the central swiss alps are overprinted by low grade alpine metamorphism and associated deformation rb sr and k ar ages of biotites are systematically reset by the later greenschist facies event this rejuvenation is apparently controlled by temperature mineral chemistry and grain size and independent of deformation and exsolution thermally activated volume diffusion best explains this behaviour with ar and sr having similar activation energies and diffusion rates for sr showing a greater dependence on biotite composition feldspars and apatite also show increasing equilibration to the alpine event and together with alpine equilibria in the micas reveal important changes in the isotopic compositions of exchanging reservoirs these spatial and temporal variations must be assessed before true mineral ages can be calculated generally the higher grade equilibria show less radiogenic exchange reflecting increased dilution by external fluids of radiogenic components released at the main front of isotopic resetting rb sr ages of alpine muscovites in the granites suggest a maximum possible age of metamorphism of 25 ma in this low grade area this implies significant diachroneity in the timing of peak metamorphism in the central alps with the relatively delayed metamorphism in this area a reflection of the later initial thickening and delayed uplift of the helvetic basement

application of mwp to deep and teleseismic earthquakes the broadband moment magnitude m wp tsuboi et al 1995 allows for the effective determination of earthquake magnitude by using broadband p waveforms it was developed to determine moment magnitude of shallow earthquakes around the japanese islands for early tsunami warnings tsuboi et al 1995 demonstrated that m wp shows good agreement with the m w from harvard centroid moment tensor cmt solutions in the present study we show that m wp is also applicable to deep earthquakes and earthquakes recorded at teleseismic distances the m wp proves to be useful for quick accurate size estimates of earthquakes recorded at both regional and teleseismic distances occurring at any depth

the mississippi delta region past present and future the mississippi delta region of south louisiana houses a wealth of resources within a dynamic subsiding landscape foundations for the delta region reflect neogene evolution of the depocenter whereas details of the modern landscape reflect late pleistocene to holocene evolution of the alluvial deltaic plain the holocene delta plain was constructed by cyclical growth of deltaic headlands followed by avulsion and relocation of the fluvial sediment source abandoned headlands were then submerged and reworked while a new headland was created at the site of active fluvial sediment input historic period levees have decoupled the delta plain from its fluvial sediment source at the same time global sea level rise was accelerating which has accelerated delta plain submergence diversions of mississippi river water and sediment are necessary to achieve delta plain sustainability but upstream dams trap 50 of the total sediment load and there is not enough supply to keep pace with subsidence and accelerated

alluvial fans formed by channelized fluvial and sheet flow i theory alluvial fans and fan deltas are of three basic types those built up primarily by the action of constantly avulsing river and stream channels those constructed by sheet flows and those resulting from the successive deposition of debris flows the present analysis is directed toward the first two types a mechanistic formulation of flow and sediment transport through river channels is combined with a simple quantification of the overall effect of frequent avulsion to derive relations describing the temporal and spatial evolution of mean i e averaged over many avulsions bed slope and elevation in an axially symmetric fan an example of a fan formed predominantly by the deposition of sand is compared to a similar one formed predominantly by the deposition of gravel in each example the case of channelized flow is compared to the case of sheet flow the model is applied to the tailings basin of a mine in the companion paper

mechanism of the 1992 nicaragua tsunami earthquake the 1992 nicaragua earthquake generated larger tsunamis than expected from its surface wave magnitude ms 7 2 and is known as a tsunami earthquake seismological studies showed that the duration was very long for its size about 100 s other studies have shown that the seismic moment estimated from tsunamis is an order of magnitude larger than that from seismic waves even after the long duration is accounted for numerical computations of tsunamis from various fault models are made to reconcile this discrepancy comparison of calculated waveforms with tide gauge records shows that the fault width is 40 km much narrower than the aftershock area and extends only into the upper 10 km of the ocean bottom slip amount on the fault is estimated to be 3 m from amplitude comparisons the fault length is estimated to be 250 km slightly longer than the aftershock area from comparison of the tsunami height distribution the rigidity around the shallow fault may be smaller than that of a standard underthrust fault and the seismic moment is estimated as 3 1020 nm consistent with the seismic observations a slow rupture on the shallow fault presumably in the subducted sediments is responsible to the unusually large tsunami excitation

dynamic single thread channels maintained by the interaction of flow and vegetation most rivers on earth today flow as a single channel in some cases with occasional islands and follow a more or less sinuous course however single thread channels have proven difficult to reproduce and study experimentally experimental self formed channels tend to widen and subdivide leading to a braided pattern cohesive sediment has been the main mechanism studied for stabilizing banks and producing a single thread channel we show how laboratory experiments using vegetation to stabilize banks can organize the flow and convert the planform morphology from braided to single thread our experimental strategy a repeated cycle of short periods of high water discharge alternating with longer periods of low discharge accompanied by plant seeding and growth leads to the evolution of a dynamic self maintaining single thread channel with well defined banks and floodplain by eliminating weak flow paths the vegetation corrals the water into a single dominant channel until the reduction in total wetted width leads to a new self organized state in which the flow removes vegetated area as fast as it is produced the new channel is deeper and has a broader distribution of depths than the braided one with channel size adjusted to carry almost all the flood flow the resulting system maintains a dynamic steady state via similar mechanisms to those that operate in meandering channels in the field specifically erosion at the outside of bends bend growth and bar development our methodology provides a basis for experimental development of self sustaining high amplitude meanders and has applications for river management and basic research purposes

deformation at the frictional viscous transition evidence for cycles of fluid assisted embrittlement and ductile deformation in the granitoid crust abstract mid crustal deformation is classically characterized by the transition from ductile to brittle deformation defining the frictional to viscous transition fvt here we investigate an exhumed continental mid crustal basement section in order to envisage the relationship between ductile and brittle deformation at the fvt our detailed study from km to micro scale shows that under greenschist metamorphic conditions deformation is accommodated by a dense network of highly localized ductile shear zones in the investigated case it is not quartz which defines the overall ductile deformation behavior but the viscous granular deformation in shear zones with an ultrafine grained polymineralic matrix consisting of quartz feldspar sheet silicates and epidote during viscous granular flow mass transfer processes under the presence of fluids promote a chemo mechanical mixing resulting in grain size reduction and reaction softening coeval with this ductile deformation fluid assisted embrittlement occurs as indicated by biotite coated fractures cataclasites and injection of non cohesive polymineralic gouge material into secondary fractures inside the host rock the embrittlement during predominant ductile deformation occurs in cycles i e prolonged periods of slow viscous granular flow are interrupted by rapid brittle deformation we interpret this fluid assisted cyclic embrittlement evidenced by injection of the fluidized material into off fault fractures as an alternative equivalent to pseudotachylites and as a microstructural indicator for paleo seismic activity with exhumation and associated cooling localized deformation persists in the ultrafine grained polymineralic shear zones but progressively transitions to cataclastic flow and finally to pressure dependent frictional flow always showing cycles of slow interseismic flow and fast seismic injection events overall in the granitic crust of the aar massif brittle and ductile deformation coexist up to deformation temperatures of minimum 450 c indicating that the fvt has to be placed in a rather wide range from 8 km up to 18 20 km in the granitoid crust