random variability explains apparent global clustering of large earthquakes 1 the occurrence of 5 mw 8 5 earthquakes since 2004 has created a debate over whether or not we are in a global cluster of large earthquakes temporarily raising risks above long term levels i use three classes of statistical tests to determine if the record of m 7 earthquakes since 1900 can reject a null hypothesis of independent random events with a constant rate plus localized aftershock sequences the data cannot reject this null hypothesis thus the temporal distribution of large global earthquakes is well described by a random process plus localized aftershocks and apparent clustering is due to random variability therefore the risk of future events has not increased except within ongoing aftershock sequences and should be estimated from the longest possible record of events

impressive abrasion rates of marked pebbles on a coarse clastic beach within a 13 month timespan abstract in this paper the abrasion rate on a coarse clastic beach was evaluated by calculating the volume loss recorded on indigenous pebbles within a 13 month timespan the experiment was carried out at marina di pisa italy on an artificial beach that was built to counteract the erosion processes affecting this sector of the coast a total of 240 marble pebbles 120 rounded and 120 angular were marked using the rfid technology and injected on the beach the volume loss measured after consecutive recovery campaigns was progressively increasing reaching the maximum value after 13 months 61 overall the average volume loss is consistent between rounded and angular pebbles at any time 59 3 and 64 2 after 13 months respectively meaning that the roundness is not a primary control factor on abrasion rate the pebbles that did not reach such abrasion rates after 8 and 10 months volume loss less than 20 were found at heights equal or greater than 2 m above mean sea level on the crest of the storm berm that formed during the strongest storms this implies that the highest wearing is achieved in the lower portion of the backshore which is also the area that underwent major topographic modifications here sea water action might also exert chemical influence on the pebbles adding to the mechanical abrasion the main result of this research indicating an impressive volume loss on beach pebbles in a short timespan could be of key importance for coastal managers the optimization of coarse sediment beach nourishments is also relevant taking into right consideration that the volume loss due to sediment abrasion might exceed 50 of the original fill volume just after 1 year in the most dynamic portion of the beach

particle path characteristics at the large gravel bed river danube results from a tracer study and numerical modelling a tracer study performed on a 3 km long reach of the danube river in austria is presented forty artificial stones of three different sizes intermediate b axis 25 mm 40 mm 70 mm were produced and a coded radio acoustic transmitter was implanted the measurement system had to be improved to be applicable to large rivers with water depths up to 12 m the positions of the stones were observed approximately once a week depending on hydrology over a period of at least one year by radio tracking from a boat including a 15 year flood event transport paths and velocities as well as the incipient motion of bedload transport could be monitored for the first time on a large gravel bed river the particle paths were found to be mostly bankline parallel even though the stones passed a 30 river bend the median of the transverse particle displacement was found to be 4 of the longitudinal displacement calculations considering both transverse slope and transverse flow velocities showed transverse transport to be 6 6 of the longitudinal transport indicating that marginal lateral transport is mainly influenced by morphology a three dimensional 3d numerical model using a stochastic particle tracing approach was validated with the data indicating that the observed positions are well reproduced by the model within the observation period 74 of all stones passed the reach with more than 1000 detections particle transport could be characterized by a mean travel velocity of about 10 m per day variable for the different grain sizes single tracer stones were transported up to 1000 m during a single flood event size selective behaviour could be shown and the incipient motion of the large 70 mm gravel was detected at lower discharges than predicted by commonly used uniform bedload transport formulae copyright 2012 john wiley sons ltd

nearshore hydrodynamics beachface cobble transport and morphodynamics on a pacific atoll motu abstract measurements of wave transformation beachface cobble transport and shoreline morphology change were undertaken over a 14 month period at fatato island a cobble and sand motu on the southeast rim of funafuti atoll tuvalu results document significant cobble transport and beach profile change on fatato during a year in the absence of any significant high energy wave events changes in beachface volume were measured on 11 across shore beach profiles and show marked variations of 7 1 and 7 01 m3 between profiles and between survey periods net volumetric beachface change over the 14 month experiment was approximately zero indicating a balance between erosion and deposition and net conservation of sediment volume on the ocean shoreline cobble movement was measured using passive integrated transponder pit tags inserted in 300 randomly selected clasts mean b axis 75 mm on the mid beachface tagged particles were re surveyed after 6 and 14 months achieving 76 recovery and identify large excursions of clasts on the beachface and dominant southwest alongshore transport with an average net movement of 68 m after 14 months a simple agent based probabilistic model was developed to simulate cobble movement and explore the coupling between hydrodynamic and shoreline processes model simulations reveal predominant south westerly cobble transport is driven by mean wave conditions associated with easterly trade winds and long period swell events that approach the reef from the south drive episodic north easterly transport reversals and significant onshore transport that can strand particles on the upper beach results present the first observations of morphodynamic behaviour of an atoll motu and highlight the highly dynamic nature of motu shorelines under mean energy conditions such results challenge conventional perspectives that motu are storm adjusted landforms that require extreme events to stimulate geomorphic change and inform future projections of island change

earthquake patterns in diverse tectonic zones of the globe we extend existing branching models for earthquake occurrences by incorporating potentially important estimates of tectonic deformation and by allowing the parameters in the models to vary across different tectonic regimes we partition the earth s surface into five regimes trenches including subduction zones and oceanic convergent boundaries and earthquakes in outer rise or overriding plate fast spreading ridges and oceanic transforms slow spreading ridges and transforms active continental zones and plate interiors everything not included in the previous categories our purpose is to specialize the models to give them the greatest possible predictive power for use in earthquake forecasts we expected the parameters of the branching models to be significantly different in the various tectonic regimes because earlier studies bird and kagan in bull seismol soc am 94 6 2380 2399 2004 found that the magnitude limits and other parameters differed between similar categories we compiled subsets of the cmt and pde earthquake catalogs corresponding to each tectonic regime and optimized the parameters for each and for the whole earth using a maximum likelihood procedure we also analyzed branching models for california and nevada using regional catalogs our estimates of parameters that can be compared to those of other models were consistent with published results examples include the proportion of triggered earthquakes and the exponent describing the temporal decay of triggered earthquakes we also estimated epicentral location uncertainty and rupture zone size and our results are consistent with independent estimates contrary to our expectation we found no dramatic differences in the branching parameters for the various tectonic regimes we did find some modest differences between regimes that were robust under changes in earthquake catalog and lower magnitude threshold subduction zones have the highest earthquake rates the largest upper magnitude limit and the highest proportion of triggered events fast spreading ridges have the smallest upper magnitude limit and the lowest proportion of triggered events the statistical significance of these variations cannot be assessed until methods are developed for estimating confidence limits reliably some results apparently depend on arbitrary decisions adopted in the analysis for example the proportion of triggered events decreases as the lower magnitude limit is increased possibly because our procedure for assigning independence probability favors larger earthquakes in some tests we censored earthquakes occurring near and just after a previous event to account for the fact that most such earthquakes will be missing from the catalog fortunately the branching model parameters were hardly affected suggesting that the inability to measure immediate aftershocks does not cause a serious estimation bias we compare our branching model with the etas model and discuss the differences in the models parametrization and the results of earthquake catalogs analysis

transport of gravel and cobble on a mixed sediment inner bank shoreline of a large inlet grays harbor washington gravel and cobble transport measurements were obtained by particle tracing experiments from a mixed sand gravel and cobble beach at the head of a crenulate shaped shoreline half moon bay in grays harbor washington the direct measurements and results provide insight regarding the differential transport of gravel and cobble sized material on mixed sediment beaches the results are of relevance to the development of both predictive formulae for coarse grained sediment transport and guidance for practical gravel and cobble beach design net alongshore transport of gravel and cobble is generally several times greater than the net cross shore transport at half moon bay larger and smaller particles both move preferentially alongshore however smaller particles tend to move across shore more than larger particles particle transport distance during a tidal cycle increases with particle size or mass up to a point beyond which the particle transport rate begins to decrease with increasing size the direct relationship between transport rate and particle size may reflect the selective entrainment and the rejection or overpassing of larger particles which are more exposed to fluid forces on the beach surface than smaller particles which are sheltered within the matrix of larger particles as well as the higher susceptibility to burial of smaller particles the decrease in transport rate for the largest sizes may reflect the limited competency of the fluid forces to transport larger and heavier particles under the observed conditions the direct transport measurements are consistent with the overall particle size and shape distributions observed on this crenulate shaped inner bank beach whereby the larger and flatter particles have tended to outrun the smaller and more spherical particles in the downdrift direction

a field based classification scheme for gravel beaches a tripartite classification of gravel beaches based upon morphodynamic properties is proposed and demonstrated for 42 new zealand beaches the main advantage of this scheme is that it is based on simple visual classification that can be applied globally in the field and is underpinned by morphodynamic differences between the beach types the three types identified from the results are 1 pure gravel beach 2 mixed sand and gravel beach 3 composite gravel beach pure gravel beaches have steep slopes tan 0 08 0 24 and gravels extending from the storm berm to below mean low water spring tide level mixed sand and gravel beaches have moderate slopes tan 0 04 0 13 with sand and gravel entirely mixed both cross shore and at depth composite gravel beaches have a steep gravel berm fronted by a low angle intertidal terrace with overall beach slopes of tan 0 05 0 14 on composite beaches there is distinct hydrodynamic cross shore sorting of the sand and gravel component these broad types are tested using discriminant analysis and the three classes are shown to be highly significant f 16 24 df 8 p 0 00005 the key discriminating variables are iribarren number beach width average grain size and storm berm height

boulders as a signature of storms on rock coasts this paper is the first review of coastal boulder studies it serves as a peer reviewed introduction to a special issue on the topic of boulders as a signature of storms on rock coasts since 2004 and the indian ocean tsunami most coastal boulder research has been focused on using boulders as sedimentary signatures of palaeo tsunami events and the most commonly used transport equations typically suggest that large boulder deposits are products of tsunami rather than storms there is growing empirical evidence demonstrating on inter annual to century timescales that storm waves are capable of transporting and depositing boulders of significant size at elevations well above sea level current process studies of how boulders are eroded transported and deposited have not received wide attention by rock coast geomorphologists or palaeoenvironmental reconstruction scientists this special issue is framed around the goal of highlighting our current understanding of the role of storm waves as a driving mechanism for boulder erosion transport and deposition here we review the current state of knowledge about boulder dynamics boulder responses to storms and boulders as sedimentary signatures of storm events we identify gaps in our conceptual and quantitative understanding lastly we propose means of addressing research gaps improving consistency between researchers and collecting multi purpose data this review and the papers contained within the special issue provide an improved understanding of coastal dynamics particularly the role storms can play in influencing erosion rates and depositional patterns of coarse material i e boulders or larger which has hitherto been under represented in the literature

on the profile evolution of three artificial pebble beaches at marina di pisa italy abstract in this paper the profiles of three artificial coarse grained beaches located at marina di pisa tuscany italy were monitored from april 2008 to may 2009 in order to define the response of the beaches to major storms that occurred during the study two beaches are similar the third differs in length and in the level of protection being less than half the length of the others and devoid of an offshore submerged breakwater the work was achieved by means of accurate topographic surveys intended to reconstruct the beach profile from the backshore up to the foreshore upper shoreface transition step the surveys were performed with an rtk gps instrument which provided extremely precise recording of the beach the most significant features of the beaches were tracked during each survey in particular the landward foot of the storm berm the crest of the storm berm the coastline and the step crest were monitored five cross shore transects were traced on each beach along these transects any meaningful slope change was recorded to obtain accurate sections of the beach the field datasets were processed with autocad software to compare the beach profile evolution during the year long research the results showed a comparable evolution of the twin beaches the resulting storm berm retreat of about 15 to 19 m is a remarkable feature considering the coarse grain size and the offshore protection due to the absence of the breakwater the third beach was characterized by even higher values of recession over 20 m and showed hints of wave reflection related processes after the huge steep storm berm had been formed and grown after the high energy events these processes were not as evident on the twin beaches these results underline the different response of three similar protection schemes and the importance that frequent monitoring of the beach morphology holds when it comes to coastal management issues

probabilistic forecasting of earthquakes we present long term and short term forecasts for magnitude 5 8 and larger earthquakes we discuss a method for optimizing both procedures and testing their forecasting effectiveness using the likelihood function our forecasts are expressed as the rate density that is the probability per unit area and time anywhere on the earth our forecasts are for scientific testing only they are not to be construed as earthquake predictions or warnings and they carry no official endorsement for our long term forecast we assume that the rate density is proportional to a smoothed version of past seismicity using the harvard cmt catalogue this is in some ways antithetical to the seismic gap model which assumes that recent earthquakes deter future ones the estimated rate density depends linearly on the magnitude of past earthquakes and approximately on a negative power of the epicentral distance out to a few hundred kilometres we assume no explicit time dependence although the estimated rate density will vary slightly from day to day as earthquakes enter the catalogue the forecast applies to the ensemble of earthquakes during the test period it is not meant to predict any single earthquake and no single earthquake or lack of one is adequate to evaluate such a hypothesis we assume that 1 per cent of all earthquakes are surprises assumed uniformly likely to occur in those areas with no earthquakes since 1977 we have made specific forecasts for the calendar year 1999 for the northwest pacific and southwest pacific regions and we plan to expand the forecast to the whole earth we test the forecast against the earthquake catalogue using a likelihood test and present the results our short term forecast updated daily makes explicit use of statistical models describing earthquake clustering like the long term forecast the short term version is expressed as a rate density in location magnitude and time however the short term forecasts will change significantly from day to day in response to recent earthquakes the forecast applies to main shocks aftershocks aftershocks of aftershocks and main shocks preceded by foreshocks however there is no need to label each event and the method is completely automatic according to the model nearly 10 per cent of moderately sized earthquakes will be followed by larger ones within a few weeks

logic tree approach for probabilistic tsunami hazard analysis and its applications to the japanese coasts for probabilistic tsunami hazard analysis ptha we propose a logic tree approach to construct tsunami hazard curves relationship between tsunami height and probability of exceedance and present some examples for japan for the purpose of quantitative assessments of tsunami risk for important coastal facilities a hazard curve is obtained by integration over the aleatory uncertainties and numerous hazard curves are obtained for different branches of logic tree representing epistemic uncertainty a ptha consists of a tsunami source model and coastal tsunami height estimation we developed the logic tree models for local tsunami sources around japan and for distant tsunami sources along the south american subduction zones logic trees were made for tsunami source zones size and frequency of tsunamigenic earthquakes fault models and standard error of estimated tsunami heights numerical simulation rather than empirical relation was used for estimating the median tsunami heights weights of discrete branches that represent alternative hypotheses and interpretations were determined by the questionnaire survey for tsunami and earthquake experts whereas those representing the error of estimated value were determined on the basis of historical data examples of tsunami hazard curves were illustrated for the coastal sites and uncertainty in the tsunami hazard was displayed by 5 16 50 84 and 95 percentile and mean hazard curves

a numerical model for shore normal sediment size variation on a macrotidal beach this paper describes a computer simulation model which is designed to predict the selective shore normal sorting of grain sizes in the nearshore environment the model simulates wave shoaling wave height attenuation due to frictional losses and breaking using linear theory up to the break point and a breaker decay model in the surf zone peak horizontal orbital velocities at the bed are calculated from stokes second order wave theory the peak onshore and offshore velocities are used with the threshold expression of komar and miller 1975 to generate a spatial pattern of size variation of threshold grain diameter along a profile normal to the shore from deep water to the swash zone the predicted grain size is used in an hydraulic interpretation of grain size distribution on the intertidal profile based on the hydrodynamic variations over a tidal cycle on a macrotidal beach the model is successful in predicting the broad pattern of increasing grain size in the onshore direction which has been observed in nature comparisons between measured and predicted grain size distributions indicate that the predictions of the model are better than those of previous models but the model is more successful at predicting sediment size distributions than at predicting mean sizes on a beach profile

longshore transport of cobbles on a mixed sand and gravel beach southern hawke bay new zealand abstract few large scale field measurements of longshore sediment transport have been undertaken on beaches composed of coarse sediments in part owing to difficulties associated with measurement in energetic swash zones in which large clasts are moving here we present results from a field experiment in which passive integrated transponder tags were used to investigate patterns of cobble transport over 8 months on a mixed sand and gravel beach on the east coast of new zealand the study objectives were to document rates of alongshore transport and measure rates of cobble abrasion under field conditions cobble recovery rates were highly variable over the study period with 30 60 recovery at site 1 compared to much lower 0 20 recovery rates at sites 2 and 3 consistent uni directional patterns of net alongshore sediment transport were observed the median cobble transport rate was approximately 500 m over 207 days indicating long term net northward transport rates on the order of 2 2 5 m day results highlight a number of factors in addition to longshore energy flux that are important for understanding the observed patterns in particular across shore sediment transport during storms may have been smaller at site 1 than the other sites owing to lesser wave exposure this is partly responsible for higher cobble recovery rates at this site and also an increased amount of time during which cobbles were able to be transported alongshore on the lower beachface unique to this study results demonstrate the use of pit tags to provide direct measurement of cobble abrasion under natural processes repeat weight measurement on individually tracked cobbles show that after 207 days the median loss was 11 3 g or 1 8 of total weight there was a general trend of abrasion increasing with net transport distance but longshore cobble movement was highly variable ranging from 130 to 2500 m

ultralong period seismic study of the december 2004 indian ocean earthquake and implications for regional tectonics and the subduction process analysis of the earth s longest period normal modes shows that the december 2004 sumatra andaman earthquake was much larger mw 9 3 than ini tially inferred from surface wave data and involved slip on a much longer fault than initially inferred from body wave data the seismic moment and relative excitation of the normal modes indicate that the entire aftershock zone ruptured consistent with the large tsunami amplitudes in thailand sri lanka and india an apparent increase in seismic moment with period results from interference between parts of the fault the earthquake resulted from subduction of the indian plate beneath the burma microplate a sliver plate between the indian and sunda plates hence the rate and direction of convergence depends on the motion of the burma plate which is not well known convergence would be highly oblique if the rate of motion between burma and sunda is that inferred from spreading in the andaman sea and less if a slower rate is inferred from the sagaing fault the december earthquake was much larger than expected from a previously proposed relation based on the idea of seismic coupling in which such earthquakes occur only when young lithosphere subducts rapidly moreover a global reanalysis finds little support for this correlation hence we suspect that much of the apparent differences between subduction zones such as some trench segments but not others being prone to m w 8 5 events and hence oceanwide tsunamis may reflect the short earthquake history sampled this possi bility is supported by the variability in rupture mode at individual trench segments

nonintrusive spatiotemporal smart debris tracking in turbulent flows with application to debris laden tsunami inundation abstractflood disasters such as dam breaks and surges from extreme hurricanes or tsunamis entrain and transport substantial amounts of submerged or floating debris understanding of motion and spatiotemporal distribution of debris entrained by a flood is thus of great importance to hydraulic coastal and structural engineers the displacement of debris to a location where it may eventually impact critical infrastructure requires scientific attention at the laboratory scale first in this context the design and application of a novel smart debris system utilizing off the shelf components is presented and discussed the system tracks the spatial location and orientation of a multitude of debris specimens and it proposes an accurate tool to assess their individual trajectory velocity and momentum in a laboratory environment contrary to the traditional camera based approach of video tracking which often fails once objects are submerged the proposed smart debris system delivers six degree of freedom 6d

slip length scaling in large earthquakes the role of deep penetrating slip below the seismogenic layer coseismic slip is observed to increase with earthquake rupture length for lengths far beyond the length scale set by the seismogenic layer the observation when interpreted within the realm of static dislocation theory and the imposed limit that slip be confined to the seismogenic layer implies that earthquake stress drop increases as a function of rupture length for large earthquakes and hence that large earthquakes differ from small earthquakes here a three dimensional elastodynamic model is applied to show that the observed increase in coseismic slip with rupture length may be satisfied while maintaining a constant stress drop across the entire spectrum of earthquake sizes when slip is allowed to penetrate below the seismogenic layer into an underlying zone characterized by velocity strengthening behavior is this deep coseismic slip happening during large earthquakes we point to a number of additional associated features of the model behavior that are potentially observable in the earth these include the predictions that a substantial fraction on the order of one third of the total coseismic moment is due to slip below the seismogenic layer and that slip below the seismogenic layer should be characterized by long rise times and a dearth of high frequency motion

the 2011 tohoku oki earthquake tsunami similarities and differences to the 869 jogan tsunami on the sendai plain a post tsunami field survey following the 2011 tohoku oki earthquake tsunami was carried out to asses inundated area in sendai plain northeast japan the type of inundation was classified into two categories major and minor according to the amount of accumulated debris garbage and sediment major and minor inundations were identified up to 4 and 5 km from the coastline respectively many artificial geomorphological features such as roadway embankments and canals were believed to have affected the run up process of the tsunami the inundation area of the 2011 tsunami on the sendai plain is compared with that of the 869 jogan tsunami which was reconstructed using numerical modeling based on available historical and geological records the inundation area of the 2011 tohoku oki tsunami is comparable to that of the 869 jogan tsunami although a direct comparison is difficult due to differences in geomorphological contexts between the paleo period and the present

the role of morphology on the displacement of particles in a step pool river system abstract although studies of sediment transport in steep and coarse grained channels have been more numerous in recent years the dynamics of sediment transport in step pool river systems remain poorly understood this paper investigates displacements of individual clasts through spruce creek quebec canada a classic step pool channel and the effects of the channel morphology on the path length of the clasts passive integrated transponder tags pit were used to track the displacement of 196 individual particles over a range of discharges including the bankfull stage clasts were tracked after five sequences of flood events the results showed that the distance distributions match a two parameter gamma model equal mobility transport occurs for the particle size investigated during each sequence of flood events mean travel distance of the clasts can be estimated from excess stream power and the mobility of the clasts is more than an order of magnitude less than the model reported in riffle pool channels the dominant morphological length scale of the bed also controls the path length of the clasts these results confirm some preliminary observations on sediment transport in step pool channels

application of the parabolic bay shape equation to sand and gravel beaches on mediterranean coasts reply to the comments of d e reeve abstract the authors wish to focus on certain aspects which had not been discussed previously in schiaffino et al 2012 these aspects cover the methodology adopted to obtain the coefficients proposed for the parabolic bay shape equation and the approach adopted for the evaluation of their applicability and reliability for sand and gravel beaches in particular results concerning shoreline variability as regards control point and wave direction are submitted

measuring pebble abrasion on a mixed sand and gravel beach using abrasion baskets abstract the abrasion of sediments on mixed sand and gravel beaches has important consequences for local sediment budgets as abrasion often accounts for the major loss of beach volume here we report an innovative method using abrasion baskets to measure abrasion in the swash zone of mixed sand and gravel beaches this method offers significant advantages over laboratory based tumbler experiments traditionally used to determine abrasion rates the very high recovery rate from our method is also a significant advantage over previous field methods using radio frequency identification technology to measure abrasion where tagged particles are often lost either three or five abrasion baskets were placed across the swash zone on a mixed sand and gravel beach at timaru south island new zealand to measure the abrasion occurring on labeled sediments placed in the baskets over two experiments results showed measurable abrasion across the swash zone with higher abrasion rates occurring in the middle of the swash zone and lower rates towards the swash limit and at the breaker zone results also illustrate the role of changing wave energy on abrasion loss a relationship between particle size and abrasion rate was also found similar to previous laboratory results reported in the literature our preliminary experiments lead us to define an abrasion zone and this idea may help shape future research on abrasion processes on mixed sand and gravel beaches

global frequency of magnitude 9 earthquakes for decades seismologists have sought causal relationships between maximum earthquake sizes and other properties of subduction zones with the underlying notion that some subduction zones may never produce a magnitude 9 or larger event the 2004 andaman m w 9 2 earthquake called into question such ideas given multicentury return times of the greatest earthquakes ignorance of those return times and our very limited observation span i suggest that we cannot yet make such determinations present evidence cannot rule out that any subduction zone may produce a magnitude 9 or larger earthquake based on theoretical recurrence times i estimate that one to three m9 earthquakes should occur globally per century and the past half century with five m9 events reflects temporal clustering and not the long term average

measurements of beach pebble attrition in palliser bay southern north island new zealand the beaches of palliser bay exposed to oceanic waves from the south are composed of mixed sand and gravel derived from mountain ranges of greywacke and argillite that rise above both sides of the bay beach gravel tracer experiments each using up to 75 tonnes of limestone pebbles were conducted at three sites increase in the roundness of these tracer pebbles at each site during the year of observation was compared with the increase in roundness and rate of weight loss of limestone and greywacke pebbles in a laboratory tumbler the comparison enabled estimation of the rate of attrition of the natural beach pebbles a weight loss of 41 per year was found for pebbles at the most exposed site and 15 and 7 at the other two sites

evidence for self similar triangular slip distributions on earthquakes implications for earthquake and fault mechanics we characterize average slip distributions on earthquakes beyond their individual heterogeneity for that we analyze a large number of seismic slip distributions both measured at the surface after earthquakes 44 profiles and derived from slip inversion models 76 models investigating the overall shape of these slip profiles we find that they are roughly triangular both along strike and dip and most of them 70 80 are asymmetric long linear slopes and high slip gradients therefore are the key ingredients to describe earthquake slip profiles the scaling relations between maximum displacement and length or width suggest furthermore that the triangular slip profiles are self similar such slip patterns make earthquakes dominated by one major zone of maximum slip hence one major asperity analyzing the position of hypocenters with respect to these asperities we find that earthquakes nucleate at a distance from them that averages 20 30 of their total length compiling observations on 56 earthquakes we show that this distance i e the asperity size is structurally defined we then compare the earthquake slip profiles to cumulative slip profiles measured on long term faults of various ages and sizes and find that all profiles have a similar shape triangular and asymmetric hence combining data for a large number of earthquakes leads to point out average generic characteristics of the coseismic slip that are similar to those that emerge from the accumulation of events with time on a single fault this suggests that these characteristics result from robust physical properties

application of the parabolic bay shape equation to sand and gravel beaches on mediterranean coasts abstract the equation most commonly used to describe the bay planform was proposed by hsu and evans 1989 and it was obtained through empirical analysis of sand beach planforms in the last decade interest in gravel sediments increased owing to their greater stability on beaches compared with sand sediments due to the differences between the morphodynamics of sand and gravel beaches which is strictly influenced by their different hydraulic characteristics it was necessary to create a predictive instrument for this beach type as well therefore in this study the standard hsu and evans equation 1989 was modified in order to make it applicable not only to sand beaches but also to gravel beaches the shoreline was computed according to a parabolic model in polar coordinates whose coefficients are considered linearly dependent on the wave direction and related to the beach type the estimation of the free parameters of the model was performed according to a statistical analysis of a shorelines data set of mediterranean sand and gravel embayed beaches

observations of surface cobbles at two southern california beaches abstract southern california beaches are often sandy but with largely undocumented cobble patches and berms we describe the first multi year spatially extensive observations of surface cobbles at southern california beaches the variation spatial and temporal of surface cobble distribution and backshore e g upper foreshore cobble morphology slope vertical extent and elevation are characterized using 11 years 2008 2018 of observations spanning 4 8 km of shoreline at cardiff and torrey pines state beaches quarterly global positioning system surveys of beach elevation and visually identified sediment type either sand or cobble are used to create 1076 cross shore profiles cobbles were not exposed continuously at either of these predominantly sandy beaches the 202 cross shore profiles with backshore cobbles and sandy foreshores are used for morphology analysis consistent with previous studies cobble and sandy morphologies varied seasonally and cobbles were most exposed during winter when wave energy increased extensive vertical extent 2 m backshore cobbles were usually fronted by low elevation low slope sandy foreshores at torrey pines cobble patches were occasionally exposed mid profile on primarily sandy summer beaches persistent 2008 2015 backshore cobbles at cardiff were apparently buried in 2016 by effects of a 2012 sand nourishment formation of year round cobble piles on these seasonally sandy beaches may result from chronically reduced sand input owing to anthropogenic controls on river flooding and coastal cliff erosion e g dams and seawalls

small earthquakes tectonic forces earthquake scaling and frequency of occurrence relations require that small earthquakes be just as important as larger ones in redistributing the forces that drive relative displacements across active faults of any dimension including plate boundaries

geomorphological control on boulder transport and coastal erosion before during and after an extreme extra tropical cyclone extreme wave events in coastal zones are principal drivers of geomorphic change evidence of boulder entrainment and erosional impact during storms is increasing however there is currently poor time coupling between pre and post storm measurements of coastal boulder deposits importantly there are no data reporting shore platform erosion boulder entrainment and or boulder transport during storm events rock coast dynamics during storm events are currently unexplored here we use high resolution daily field data to measure and characterize coastal boulder transport before during and after the extreme northeast atlantic extra tropical cyclone johanna in march 2008 forty eight limestone fine medium boulders n 46 and coarse cobbles n 2 were tracked daily over a 0 1 km2 intertidal area during this multi day storm boulders were repeatedly entrained transported and deposited and in some cases broken down n 1 or quarried n 3 during the most intense days of the storm eighty one percent n 39 of boulders were located at both the start and end of the storm of these 92 were entrained where entrainment patterns were closely aligned to wave parameters these data firmly demonstrate rock coasts are dynamic and vulnerable under storm conditions no statistically significant relationship was found between boulder size mass and net transport distance graphical analyses suggest that boulder size limits the maximum longshore transport distance but that for the majority of boulders lying under this threshold other factors influence transport distance paired analysis of 20 similar sized and shaped boulders in different morphogenic zones demonstrates that geomorphological control affects entrainment and transport distance where net transport distances were up to 39 times less where geomorphological control was greatest these results have important implications for understanding and for accurately measuring and modelling boulder entrainment and transport coastal managers require these data for assessing erosion risk 2016 the authors earth surface processes and landforms published by john wiley sons ltd

using passive integrated transponder pit tags to investigate sediment transport in gravel bed rivers abstract in gravel bed rivers measuring the displacement of individual grains by fluid flow is essential in order to understand sediment transport processes and to investigate changes in channel morphology we present preliminary results of a new technique that traces pebble movements by inserting 23 mm passive integrated transponders pit into individual clasts because each pit has its own signal identification this technique is ideal for tracking the individual movements of episodically transported particles in gravel bed rivers two hundred and four tagged particles were inserted into a 130 m long reach of a gravel bed river with a 2 slope and a bed material with a d50 of 70 mm the b axis size of the tagged particles ranged from 40 mm to 250 mm recovery percentages after two competent floods were 96 and 87 clearly demonstrating the effectiveness of this new technique buried particles can be recovered at a depth of 0 25 m pit tags are also suited for long term studies over several years

earthquake slip distribution a statistical model 1 the purpose of this paper is to interpret slip statistics in a framework of extended earthquake sources we first discuss deformation pattern of the earth s surface from earthquakes and suggest that continuum versus block motion controversy can be reconciled by a model of the fractal distribution of seismic sources we consider earthquake slip statistical distributions as they can be inferred from seismic moment frequency relations and geometrical scaling for earthquakes using various assumptions on temporal earthquake occurrence these distributions are synthesized to evaluate the accuracy of geologic fault slip determinations and to estimate uncertainties in long term earthquake patterns based on paleoseismic data because the seismic moment distribution is a power law pareto a major part of the total seismic moment is released by major earthquakes m 10 19 5 n m moment magnitude m 7 for these large earthquakes the rupture is confined to the upper brittle crust layer we review the various moment frequency and earthquake scaling relationships and apply them to infer the slip distribution at area and site specific regions simulating the seismic moment and strain accumulation process demonstrates that some synthetics can be interpreted as examples of a quasiperiodic sequence we demonstrate the application of the derived slip statistical relations by analyzing the slip distribution and history of the san andreas fault at wrightwood california

seismic gap hypothesis ten years after the seismic gap hypothesis states that earthquake hazard increases with time since the last large earthquake on certain faults or plate boundaries one of the earliest and clearest applications of the seismic gap theory to earthquake forecasting was by mccann et al 1979 who postulated zones of high medium and low seismic potential around the pacific rim in the 10 years since there have been over 40 large m 7 0 earthquakes enough to test statistically the earlier forecast we also analyze another forecast of long term earthquake risk that by kelleher et al 1973 the hypothesis of increased earthquake potential after a long quiet period can be rejected with a large confidence the data suggest that contrary to these forecasts places of recent earthquake activity have larger than usual seismic hazard whereas the segments of the circum pacific belt with no large earthquakes in recent decades have remained relatively quiet the clustering of earthquake times does not contradict the plate tectonic model which constrains only the long term average slip rate not the regularity of earthquakes

a field experiment on the development of sedimentary structures in a gravel bed river in gravel bed rivers bed sedimentary structures exert a significant influence on the stability of the bed particle motion and stream dynamics a detailed description of the development of sedimentary structures is essential to define the overall activity of sediment transport this paper aims to improve our understanding of the dynamics of sedimentary structures at the reach scale using a field approach the objectives of the study are 1 to describe the processes of sedimentary structures development from a manipulated bed surface and 2 to show the effect of keystones on the development of the sedimentary structures by monitoring the displacement of individual tagged particles we investigated the dynamics of sedimentary structures in three 15 m long reaches of a small gravel bed river characterized by moderate slope and high relative roughness the bed material is composed of a range of gravel sizes with sparse boulders that remain immobile during most flows we have disrupted the bed surface material of the first reach to create a disorganized bed surface two reaches where the bed material remained undisturbed were used as control sections detailed topographic maps and passive transponders were used to describe the formation processes of sedimentary structures the initial manipulations of the bed led to a more fragmented surface in the experimental section however sedimentary structures developed very quickly with an equilibrium bed surface developing after only two sediment transport events of low magnitude discharge this rapid adjustment of the bed is associated with the development of key sedimentary structures anchored by the large boulders at the reach scale these structures increased the probability of congested areas in the displacement of bed material in both control sections sedimentary structures were maintained during the experiment copyright 2007 john wiley sons ltd

aftershock zone scaling we investigate the distribution of aftershock zones for large earthquakes scalar seismic moment m 10 19 5 n m moment magnitude m 7 mainshocks are selected from the harvard centroid moment tensor catalog and aftershocks are selected from the preliminary determination of epicenters neic catalog the aftershock epicenter maps are approximated by a two dimensional gaussian distribution the major ellipse axis is taken as a quantitative measure of the mainshock focal zone size the dependence of zone length l on earthquake size is studied for three representative focal mechanisms thrust normal and strike slip although the numbers of mainshocks available for analysis are limited maximum a few tens of events in each case all earthquakes show the same scaling m l 3 no observable scaling break or saturation occurs for the largest earthquakes m 10 21 n m m 8 therefore it seems that earthquake geometrical focal zone parameters are self similar

from fine sand to boulders examining the relationship between beach face slope and sediment size abstract it is a long standing maxim that coarser sediment sizes are associated with steeper beach face slopes but because most work has focused on sandy beaches few data are available for the pebble cobble or boulder size ranges little is known therefore about how beach morphology and grain size relate at the coarser size grades we compiled data from the literature 2144 measurements of beach face slope with associated grain sizes covering the range from very fine sand to boulders this meta analysis shows that beach faces do tend to steepen as average grain size increases at least up to the cobble size range but the trend is not simple although previous studies suggested a simple power law relationship between grain size and beach face slope in fact the data distribution is best fit by a curve that is steep at the finer grain sizes but is much more gentle as grain size coarsens and may trend downward for boulders fine and medium sands have the greatest range of reported slopes and the data support the importance of effective weight modification and boundary layer dynamics as primary controls on beach face steepness at these fine size grades around the very coarse sand size grade a plateau marks a shift in beach dynamics as hydraulic conductivity increases beaches switch to being infiltration dominated the trend toward steeper slopes continues but at a lower and steady rate from granules through cobbles there appears to be a falloff in slope for the coarsest boulder deposits but we note that this is based on very few locations so should be considered preliminary the overall data distribution is described by a power law function tan a d 50 0 125 b c the broadness of each transition zone also shows that a range of factors other than grain size governs where that tipping point occurs in the cobble and boulder size ranges there are two deposit categories boulder beaches and supratidal boulder ridges although not commonly thought of as beaches boulder ridges record long term storm deposition and reworking on the highest energy coasts supratidal ridges and boulder beaches seem to show different slope grain size relationships with the steepest slopes occurring in boulder ridges and with boulder beaches showing more gentle gradients than other coarse clastic beaches but our data set reveals how little quantitative information exists about the coarsest end of the beach spectrum and invites further work to investigate the sedimentology of cobble and boulder dominated systems

transport trajectories of smart pebbles on an artificial coarse grained beach at marina di pisa italy implications for beach morphodynamics abstract in this paper transport pathways for coarse sediments were studied on an artificial pebble beach located at marina di pisa tuscany italy radio frequency identification rfid technology was used to trace the pebbles the rfid technique is an inexpensive and reliable methodology that is used to address sediment displacement along the coastline the use of low frequency radio signals 125 khz enabled the detection of the marked pebbles within a range of 40 cm on the underwater and subaerial portions of the beach about one hundred pebbles were sampled on the beach and paired with passive transponders the tracers were released along a series of cross shore transects march 2009 the pebbles were injected on the fair weather berm on the swash zone and on the step crest along each transect the recovery campaign was carried out in may 2009 fifty three pebbles were detected this number is rather high given the intensity of the three storms that hit the coast during the period of the experiment and the significant reworking that this beach is subjected to even under fair weather conditions the analysis of the tracer pathways highlighted twofold convergent longshore movement on the beach the trajectories indicated that the longshore movement dominated the cross shore movement but there was no prevailing transport direction to explore the morphology of the sea bottom fronting the beach a topographic survey was carried out using an echo sounder the survey showed the presence of two distinct shoals 20 m off the coastline that are responsible for the resulting coarse sediment transport these results confirm that even mild sea bottom irregularities may significantly affect sediment transport dynamics along a beach suggesting that accurate planning for defense schemes such as artificial coarse replenishment must begin with an in depth knowledge of the morphology of the sea floor such information may increase the durability and or the efficiency of the intervention

seasonal patterns of coarse sediment transport on a mixed sand and gravel beach due to vessel wakes wind waves and tidal currents direct measurements of coarse sediment gravel transport are presented and analyzed from a mixed sand and gravel beach on bainbridge island puget sound wa that is exposed to wind waves vessel wakes and tidal currents in order to quantify the relative role of different forcing mechanisms and the corresponding time scales of morphological response radio frequency identification rfid passive integrated transponder pit technology is implemented in two coincident yearlong tracking studies of sediment particles and complemented with beach profile surveys and meteorological and hydrodynamic measurements the sampling of the gravel tracers provides sufficient resolution to reveal the dominant seasonal transport patterns which include a range of wave climates during winter storms the predominant transport is due to wind waves in an alongshore uni directional process whereas tides and wakes play a relatively minor role in non storm intervals transport is brought about by the combination of vessel wakes and tidal currents although tidal currents are not sufficient to initiate sediment movement alone the combination of tidal currents and vessel wakes generate significant transport and provide a mechanism for post storm recovery re distributing sediment onshore morphologic response occurs as a seasonal fluctuation of the upper beach profile from steep to flat and in sediment composition from gravel to coarse sand between non storm and storm conditions respectively these results which are unique in their duration suggest that mixed sand and gravel beaches experience different modes of behavior over the range of forcing conditions observed during a typical year they point to the need for including grain composition in modeling mixed sand and gravel beach response and the need for long term observations of both forcing and response

coastal upwelling in the california current system abstract coastal upwelling in the california current system has been the subject of large scale studies off california and baja california and of small scale studies off oregon recent studies of the winds along the entire coast from 25 n to 50 n indicate that there are significant along shore variations in the strength of coastal upwelling which are reflected in the observed temperature distribution active upwelling appears to be restricted to a narrow coastal band about 10 25 km wide along the entire coast but the region influenced by coastal upwelling may be much wider intensive observations of the upwelling zone during summer off oregon show the presence of a southward coastal jet at the surface a mean vertical shear a poleward undercurrent along the bottom and persistently sloping isopycnals over the continental shelf most of the upwelling there occurs during relatively short periods several days long of upwelling favorable winds during the upwelling season off oregon the offshore ekman transport is carried by the surface ekman layer and the onshore return flow occurs through a quasi geostrophic interior it is not known whether the structure and dynamics observed off oregon are typical of the upwelling zone along the entire coast though some of the same features have been observed off baja california current and future research will eventually show whether the oregon results are also applicable in the region of persistently strong upwelling favorable winds off northern california and in the region of complex bathymetry off central and southern california

a new 1649 1884 catalog of destructive earthquakes near tokyo and implications for the long term seismic process 1 in order to assess the long term character of seismicity near tokyo we construct an intensity based catalog of damaging earthquakes that struck the greater tokyo area between 1649 and 1884 models for 15 historical earthquakes are developed using calibrated intensity attenuation relations that quantitatively convey uncertainties in event location and magnitude as well as their covariance the historical catalog is most likely complete for earthquakes m 6 7 the largest earthquake in the catalog is the 1703 m 8 2 genroku event seismicity rates from 80 years of instrumental records which include the 1923 m 7 9 kanto shock as well as interevent times estimated from the past 7000 years of paleoseismic data are combined with the historical catalog to define a frequency magnitude distribution for 4 5 m 8 2 which is well described by a truncated gutenberg richter relation with a b value of 0 96 and a maximum magnitude of 8 4 large uncertainties associated with the intensity based catalog are propagated by a monte carlo simulation to estimations of the scalar moment rate the resulting best estimate of moment rate during 1649 2003 is 1 35 1026 dyn cm yr 1 with considerable uncertainty at the 1 level 0 11 0 20 1026 dyn cm yr 1 comparison with geodetic models of the interseismic deformation indicates that the geodetic moment accumulation and likely moment release rate are roughly balanced over the catalog period this balance suggests that the extended catalog is representative of long term seismic processes near tokyo and so can be used to assess earthquake probabilities the resulting poisson or time averaged 30 year probability for m 7 9 earthquakes is 7 11

particle size and shape in pebble beach sedimentation an in depth investigation was made of beach gravel fabrics at two beach sites located on the glamorgan heritage coast wales u k granulometric data from 31 080 pebbles were obtained and analysis confirmed the existence of a basic shape differentiation structure when the b axis was used at gileston beach a low energy location and nash beach a high energy location the use of the b axis in size and shape analysis seems to have led some workers to incorrect rejection of size as a factor in determining the transportational and depositional potential of a particle an inferred energy model can be constructed where the influence of particle size on sorting is predominant when energy conditions are high and particle shape factors predominate when energy conditions are low the c axis standard deviation value was the most effective discriminator of variation in shore parallel sedimentation structures at both beaches for shore normal structural discrimination the c axis mean and standard deviation values were the most effective

pebble and cobble transport on a steep mega tidal mixed sand and gravel beach abstract natural tracer pebbles and cobbles were deployed on a steep slope 0 1 mixed sand and gravel mega tidal beach located at the head of the bay of fundy two experiments were carried out to investigate the response of natural pebble and cobble sized material both to energetic wave conditions during individual storm events and to tidal only forcing conditions between storms net displacement of different tracer sizes was the focus of the first experiment while the effect of different shapes was tested in the second the pebbles and cobbles were painted in fluorescent colors labeled and their positions measured at low tide over periods of 10 12 days the tracers were emplaced at mid tide level on the beach face at low water and later recovered and re deployed on successive low tides net travel distance and direction were measured upon recovery hydrodynamic forcing conditions and local morphology at mid tide level on the beach face were monitored continuously during the experiments in the first experiment recovery rates were 100 during calm and moderate wave conditions hs 0 5 m but decreased significantly in more energetic wave forcing hs up to 1 m recovery rates were lower for smaller tracers during a three day wind wave event net displacements of up to 48 m were measured comparable net displacements were observed for all tracers maximum displacements were 39 m onshore 42 m offshore and 46 m alongshore in calm conditions maximum displacements were less than 1 m indicating that the bottom stresses due to tidal currents alone are too low to cause significant tracer displacement on time scales of weeks despite the high tidal range in the second experiment recovery rates were lower due to more energetic wave forcing significant wave heights reached hs 0 5 m on 80 of the particle tracking days and hs 1 m on 30 of the days flat pebbles and cobbles reached the longest transport distances with a maximum net displacement of 98 m the flat tracers were observed to be flipped by the shore break and to ride the swash bore and were in this manner transported long distances shoreward up to 66 m in both experiments the directions of alongshore displacements were consistent with deviations of the angle of wave incidence from the shorenormal tracer burial and re exposure was observed via rotary imaging sonar with the evolution and migration of m wavelength ripples the study allowed a direct correlation of pebble and cobble tracer displacements to hydrodynamic forcing during individual storm events with consideration of tracer particle size and shape

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

observations of coarse sediment movements on the mixed beach of the elwha delta washington abstract mixed beaches with poorly sorted grains of multiple sizes are a common and globally distributed shoreline type despite this rates and mechanisms of sediment transport on mixed beaches are poorly understood a series of tracer deployments using native clasts implanted with radio frequency identifier rfid tags was used to develop a better understanding of sediment transport directions and magnitudes on the mixed grain size beach of the elwha river delta using tracer samples selected to match the distribution of the coarse fraction on the beach we find that all grain sizes up to large cobbles 128 256 mm were mobile under most measured wave conditions and move in relationship to the direction of the alongshore component of wave energy as estimated by incident breaking wave angles in locations where the breaking wave is normal to the shoreline we find that tracers move in both alongshore directions with approximately equal frequency in locations where breaking waves are oblique to the shoreline we find that alongshore transport is more unidirectional and tracers can approach average velocities of 100 m day under winter wave conditions we use the tracer cloud to estimate the beach active width the mobile layer depth and sediment velocity our results suggest that while sediment velocity increases under increased incident wave angles the active layer depth and width decrease reducing sediment flux at the site with the more oblique breaking waves this result is contrary to what is suggested by traditional wave energy transport models of alongshore sediment transport

geochemistry and petrogenesis of sikait leucogranite egypt an example of s type granite in a metapelitic sequence the sikait leucogranite slg is a body of porphyritic garnet granite intruded a metapelitic sequence and interlayered orthogneisses multiple deformation and low to medium grade metamorphism of the sequence was closely associated with pluton emplacement textural features of the slg indicate that subsolidus plastic deformation was induced during the extensive thrusting the granite is strongly peraluminous alkali rich and hfs high field strength elements depleted with low contents of ree all facts that substantiate the geochemical characteristics of s type granites

tohoku earthquake a surprise abstract we consider three questions related to the 2011 tohoku mega earthquake 1 why was the event size so grossly underestimated by japan s national hazard map 2 how should we evaluate the chances of giant earthquakes in subduction zones 3 what is the repeat time for magnitude 9 earthquakes off the tohoku coast the maximum earthquake size is often guessed from the available history of earthquakes a method known for its significant downward bias we show that historical magnitudes systematically underestimate this maximum size of future events but the discrepancy shrinks with time there are two quantitative methods for estimating the corner magnitude in any region a statistical analysis of the available earthquake record and the moment conservation principle however for individual zones the statistical method is usually ineffective in estimating the maximum magnitude only the lower limit can be evaluated the moment conservation technique which we prefer matches the tectonic deformation rate to that predicted by earthquakes with a truncated or tapered magnitude frequency distribution for subduction zones the seismic or historical record is insufficient to constrain either the maximum or corner magnitude however the moment conservation principle yields consistent estimates for all the subduction zones the corner magnitude is of the order 9 0 9 7 moreover moment conservation indicates that variations in estimated corner magnitude among subduction zones are not statistically significant another moment conservation method applied at a point on a major fault or plate boundary also suggests that magnitude 9 events are required to explain observed displacement rates at least for the tohoku area the global rate of magnitude 9 earthquakes in subduction zones predicted from statistical analysis of seismicity as well as from moment conservation is about five per century five actually happened

circum pacific seismic potential 1989 1999 the seismic potential for 96 segments of simple plate boundaries around the circum pacific region is presented in terms of the conditional probability for the occurrence of either large or great interplate earthquakes during the next 5 10 and 20 years i e 1989 1994 1989 1999 and 1989 2009 this study represents the first probabilistic summary of seismic potential on this scale and involves the comparison of plate boundary segments that exhibit varying recurrence times magnitudes and tectonic regimes presenting these data in a probabilistic framework provides a basis for the uniform comparison of seismic hazard between these differing fault segments as well as accounting for individual variations in recurrence time along a specific fault segment and uncertainties in the determination of the average recurrence time

radio frequency identification rfid technology applied to the definition of underwater and subaerial coarse sediment movement abstract in this paper radio frequency identification technology has been applied to track both underwater and subaerial displacement of pebbles along an artificial coarse beach at marina di pisa italy several preliminary laboratory tests have been performed to adapt the rfid technique for underwater use which has been the primary impediment to this promising approach to the study of coarse sediment transport and movement tests showed the reliability of low frequencies for this kind of work since they enable good signal transmission and reception through water passive abs plastic transponders were inserted into about 100 pebbles and released onto the beach in march 2009 a core 125 reader was chosen as the operating antenna to continuously transmit low frequency 125 khz signals an acoustic signal toned whenever a pebble was detected while the unambiguous identification code of the pebble is shown immediately on the screen of a laptop connected to the reader the positions of the pebbles were recorded with a total station after two months may 2009 74 marked pebbles were retrieved 77 of the total the positions of the retrieved pebbles were also recorded with the total station thus allowing calculation of the coarse sediment transport tendency about 60 of the recovered pebbles 44 out of 74 were found on the upper shoreface the analysis of the marked pebble trajectories revealed a divergent transport movement in the northernmost sector of the beach this movement was probably triggered by an irregularity of the submerged breakwater fronting the shoreline the southern sector is characterised by chaotic pathways related to the formation and evolution of beach cusps this outcome highlights and confirms the importance of a complete definition of the beach system with no separation between the underwater and the subaerial portion of the shore when it comes to sediment transport and movement this successful application of rfid technology to the underwater environment provides a chance to broaden understanding of a topic in need of further study

measuring sediment transport and bed disturbance with tracers on a mixed beach abstract a new tracer deployment method is applied to the problem of resolving rates and patterns of littoral sediment transport on mixed beaches we applied the method at the morphologically complex meso tidal beach fringing the elwha river delta washington clasts were transformed into tracers using radio frequency identifier rfid tags these tracers were deployed in and on the bed along a cross shore oriented beach transect along and cross shore variations in tracer velocity were used to estimate sediment transport patterns including the depth and cross sectional area of the disturbed bed and bulk alongshore transport rates we found that the peak bed disturbance averaged 22 of the tidal maximum significant wave height and that tracer velocity declined approximately logarithmically with depth in the bed across all deployments the maximum alongshore tracer velocity occurred between 1 0 and 2 0 m above mean lower low water mllw corresponding to elevations 0 3 m below and 0 7 m above mean sea level msl at this location alongshore bulk sediment transport rates estimated from the advection of tracers ranged from 1 1 to 173 1 m3 d under significant wave heights of 0 1 to 2 1 m and these transport rates related linearly to measured wave energy transport both the volumetric sediment transport rates and a cerc type k coefficient derived from the results agreed well with results from other published studies

multi day anchor ice cycles and bedload transport in a gravel bed stream summary river dynamics in cold regions and the physical processes involving ice formation and release remain relatively understudied topics current research suggests that anchor ice forms in diurnal cycles and has the potential to move sediments when released from the bed given the importance of river ice dynamics studies are needed to describe the physical processes of anchor ice and its impact on sediment transport the study presented in this paper investigated in situ anchor ice formation on the stoke river in quebec canada in the fall of 2012 we observed multi day anchor ice formation cycles and release which usually ended with a small runoff event during a cycle there was little or no release of anchor ice thus allowing its gradual growth as the air temperature remained cold surface and anchor ice layers also often merged leading to the formation of thick ice masses sediment transport was monitored using bed particles individually tagged with passive integrated transponders pit tags movement of the experimental particles measured after each multi day cycle event ranged from 0 5 to 4 m possible transport mechanisms include 1 anchor ice rafting 2 ice jam breakup creating a jave with high erosive capacity 3 flow corridors through anchor ice masses with high erosive capacity 4 mechanical pushing of particles by drifting ice blocks during ice breakup and 5 entrainment by flow or drifting ice blocks of anchored ice with strong ice pebble bonds given the coincidental occurrence of anchor ice release and runoff events it is uncertain which specific mechanism caused the particles to move this study is a step forward in understanding the behavior of anchor ice processes and ice related sediment transport

probabilistic seismic hazard assessment for japan a probabilistic seismic hazard assessment was performed for the japanese islands and surrounding areas seismic hazard parameters characteristic of the seismic history of the regions were obtained the probability of occurrence of a large m 7 earthquake within a 10 and 50 year period was also calculated regions of very high levels of hazard occur where the pacific phillipine and eurasian plates meet high probabilities of occurrence of a large m 7 earthquake within a 10 and 50 year period occur within the region where the pacific plate subducts with the eurasian plate

short term displacements of marked pebbles in the swash zone focus on particle shape and size abstract in this paper two short term experiments with tracers on a mixed beach are presented the aim was to understand how the size and shape of pebbles can affect their transport under low energy conditions sediment transport was studied by means of rfid technology to univocally monitor every single marked pebble a size subdivision of injected pebbles was conducted based on three classes big from 5 5 to 6 5 phi medium from 5 to 5 5 phi and small from 4 5 to 5 phi two recoveries were realised 6 and 24 h after the injection during a single day the wave motion was very low in the first experiment and low to moderate in the second never exceeding 0 4 m the results showed that discs are less dynamic than spheres but can cover greater distances regarding the sediment size big pebbles are less dynamic if compared to finer classes and they move preferentially down the swash zone towards the step or do not move up slope if already at the step very low and steady energy conditions facilitate cross shore and offshore movement of pebbles rather than a slight raise in wave height producing predominant longshore transport even with non marginal displacements low to moderate energy conditions can also produce some trend displacement based on the pebble shape even though t tests showed that shape was not statistically significant for pebble displacement the displacements of medium and small sized pebbles show a statistical dissimilarity compared to the big ones to refine the velocity estimation necessary to initiate pebble movement the threshold velocity formulas known up to now should involve the shape parameter especially for the short term better knowledge of the relationship between the sediment s characteristics and dynamics is critical to forecast the durability of replenishment material and to establish the suitability of fill material relative to native beach material hence a better understanding of the role of particle characteristics is necessary

the use of passive integrated transponder pit tags to trace cobble transport in a mixed sand and gravel beach on the high energy oregon coast usa abstract cobble transport is investigated on a mixed sand and gravel beach on the high energy oregon coast using radio frequency identification technology rfid to detect passive integrated transponder pit tags inserted in the gravels pit tags are glass encapsulated transponders that are activated when an antenna passes near them with each tag characterized by its own unique identification number the tags are sealed within the cobbles minimizing any effect on the hydrodynamic character of the particles the tags draw power from the antenna itself and have a potential lifespan of up to 50 years pit tags are simple to use and inexpensive permitting the release and tracking of large numbers of gravel particles as a result pit tags have tremendous potential for examining the complexities of particle movement and the parameters that control their distribution on the beach our experiments have been conducted at cape lookout state park on the northern oregon coast on a composite beach where a seasonally variable sand beach fronts a mixed sand and gravel beach with the latter impacted by waves only during the winter when the sand beach is cut back a total of 400 cobble tracers have been released at five different locations subsequent monitoring of the gravel tracers revealed that they can be detected up to 1 m below the surface of the beach using a 1 0 m diameter antenna and up to 0 5 m below the surface using a smaller 0 3 m diameter antenna while their positions were determined using a trimble 5700 5800 rtk dgps survey system gravel tracer recovery rates were found to vary significantly between the different release points from as high as 90 recovery after 8 months to a low of 18 after 17 months the lowest recovery rates are thought to be due to the extent of aggradation of the sandy beach during the summer partially covering the gravel berm and burying the tracer particles to depths where they could not be detected by the antennas used with our rfid system relocation of the gravel tracers has revealed a predominant northward migration of the cobbles and locally demonstrate a strong cross shore transport both upslope and downslope movements initial attempts to examine the relationship between the transport distances and particle sizes and shapes have thus far revealed that the larger gravels are tending to outrun the smaller particles this is despite the fact that both small and large particles were found to be capable of being transported both short and long distances in contrast our results revealed no relationships between particle shape and distance moved in time it is expected that the pit tag tracers may begin to yield more definitive patterns of sorting the results did highlight that the gravel movement occurs predominantly near the sand gravel beach junction on the profiles a region dominated by a higher incidence of wave breaking and strong swash activity finally our analyses revealed the potential for using pit tags to provide field assessments of the abrasion rates of gravel particles having already found measurable degrees of weight loss to abrasion in our experiments

dimensionless critical shear stress in gravel bed rivers this paper first compiles critical shear stress values from 26 studies of gravel bed rivers gbrs worldwide the most frequently proposed value of the shields criterion c is 0 045 but three major groups with c values ranging from 0 100 were identified second dimensionless critical shear stresses the shields criterion were evaluated for 14 gbrs 18 sites with watershed areas ranging from 12 to 3000 km2 different approaches were used to identify the initial movement of the bed material painted and pit tag pebbles sediment traps and bedload samplers the shields criterion c was estimated using the total shear stress and the grain shear stress several shear stresses were also estimated using shear velocities for bedload transport we obtained an average shields criterion c of 0 040 the values were higher in small rivers 0 050 than larger rivers 0 030 because of more significant bedform shear stresses the shields criterion c was lower when the grain shear stress was used and only reached 0 019 different values are also proposed in relation to the type of mobilization the c value for partial transport was 0 025 and exceeded 0 040 for full transport usually reached in association with discharges with a 10 year return period the values based on the results of sediment traps and a bedload sampler were greater than those obtained using tracers but these differences are smaller than those usually reported in the literature

measuring gravel transport and dispersion in a mountain river using passive radio tracers random walk models of fluvial sediment transport recognize that grains move intermittently with short duration steps separated by rests that are comparatively long these models are built upon the probability distributions of the step length and the resting time motivated by these models tracer experiments have attempted to measure directly the steps and rests of sediment grains in natural streams this paper describes results from a large tracer experiment designed to test stochastic transport models we used passive integrated transponder pit tags to label 893 coarse gravel clasts and placed them in halfmoon creek a small alpine stream near leadville colorado usa the pit tags allow us to locate and identify tracers without picking them up or digging them out of the streambed they also enable us to find a very high percentage of our rocks 98 after three years and 96 after the fourth year we use the annual tracer displacement to test two stochastic transport models the einstein hubbell sayre ehs model and the yang sayre gamma exponential model gem we find that the gem is a better fit to the observations particularly for slower moving tracers and suggest that the strength of the gem is that the gamma distribution of step lengths approximates a compound poisson distribution published in 2012 this article is a us government work and is in the public domain in the usa

new gripping and binding device greatly improves preparation of natural clasts for rfid tracking abstractradio frequency identification technology rfid has allowed for tracking of individual clasts implanted with passive integrated transponder pit tags through sedimentary systems providing recovery rates much higher than older sediment tagging methods such as painted or magnetic clasts however preparation of natural clasts for pit tag implantation has been time consuming and dangerous with rates of catastrophic failure of clasts of 66 or more moreover failure rates increase as clast size decreases the authors present an improved methodology that provides nearly 100 success rates and allows for drilling of clasts down to 23 mm along the intermediate diameter the gripping and binding device gabi prevents clasts from rotating and is effective when used in conjunction with the rhythmically applied pressure drilling technique gabi is simple and inexpensive to build and can be used in a field setting the improved safety and effectiveness of the method will allow for greater application of

tsunami hazard probability in japan abstract an analysis of future tsunami hazard on the coast of the japanese islands is made in terms of probability for a coastal site being hit by a tsunami of which the wave height exceeds a certain level during a period from 2000 to 2010 tsunami wave height at a site on the pacific coast is estimated mostly based on numerical experiment in which a typical fault model of the tsunami generating earthquake is assumed meanwhile probability of the tsunami generating earthquake occurring during 2000 to 2010 is evaluated either from historical data of earthquake occurrence or from near shore crustal strain accumulation combining the wave height estimate with the probability evaluation of tsunami occurrence probabilities of a site being hit by a tsunami of which the wave height exceeds certain levels are evaluated on the pacific coast it seems that the probability for a violent tsunami of which the wave height exceeds 5 m is highest along the pacific coast in central japan reaching a value of 41 per cent on the other hand a probability value as high as 69 per cent is found for a moderately large tsunami having a wave height of 1 m or so along the shikoku and kyushu coasts a crude probability evaluation is also made for tsunamis on the japan sea coast where tsunami activity is substantially lower than that of the pacific coast the probability for a violent tsunami seems to amount to only 1 per cent or so for a 10 yr period similar probabilities for tsunamis excited by a distant source off peru chile kamchatka and aleutian alaska are also evaluated in this case probabilities of tsunami wave height exceeding 1 and 3 m are respectively evaluated as 19 and 15 per cent on the pacific coast such probabilities being not quite negligible