earthquake scaling laws for creeping and non creeping faults the dependence of the summed moment release on the fault dimension differs between non creeping faults and creeping faults or volcanic regions this can be attributed to different earthquake scaling laws the number n of events with fault length l scales for non creeping faults as n l l 2 and for creeping faults as n l l 3 this difference offers a means for mapping the distribution of creep in the seismogenic crust

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

rapid localized glacio isostatic uplift at glen roy scotland many studies involving measurement of the altitudes of fossil marine and lacustrine shorelines have demonstrated glacioisostatic tilting particularly in north america fennoscandia and the british isles such studies are normally illustrated by height distance diagrams in which fossil shorelines are portrayed as straight lines in some studies the shoreline relation diagram is used to analyse and illustrate the altitudinal data1 3 before constructing such a diagram it is assumed that a simple pattern of glacioisostatic uplift has prevailed warping of shorelines as opposed to uniform tilting has been inferred in north america4 6 on the other hand harme7 envisaged block movements in fennoscandia sauramo8 also proposed dislocations but his interpretation was rejected by hyyppa9 more recently the concept of the scandinavian shield as a stable area has been dismissed10 11 here we provide evidence from scotland for shoreline dislocation by differential movement of blocks of the earth s crust

statistical physics seismogenesis and seismic hazard the scaling properties of earthquake populations show remarkable similarities to those observed at or near the critical point of other composite systems in statistical physics this has led to the development of a variety of different physical models of seismogenesis as a critical phenomenon involving locally nonlinear dynamics with simplified rheologies exhibiting instability or avalanche type behavior in a material composed of a large number of discrete elements in particular it has been suggested that earthquakes are an example of a self organized critical phenomenon analogous to a sandpile that spontaneously evolves to a critical angle of repose in response to the steady supply of new grains at the summit in this stationary state of marginal stability the distribution of avalanche energies is a power law equivalent to the gutenberg richter frequency magnitude law and the behavior is relatively insensitive to the details of the dynamics here we review the results of some of the composite physical models that have been developed to simulate seismogenesis on different scales during 1 dynamic slip on a preexisting fault 2 fault growth and 3 fault nucleation the individual physical models share some generic features such as a dynamic energy flux applied by tectonic loading at a constant strain rate strong local interactions and fluctuations generated either dynamically or by fixed material heterogeneity but they differ significantly in the details of the assumed dynamics and in the methods of numerical solution however all exhibit critical or near critical behavior with behavior quantitatively consistent with many of the observed fractal or multifractal scaling laws of brittle faulting and earthquakes including the gutenberg richter law some of the results are sensitive to the details of the dynamics and hence are not strict examples of self organized criticality nevertheless the results of these different physical models share some generic statistical properties similar to the universal behavior seen in a wide variety of critical phenomena with significant implications for practical problems in probabilistic seismic hazard evaluation in particular the notion of self organized criticality or near criticality gives a scientific rationale for the a priori assumption of stationarity used as a first step in the prediction of the future level of hazard the gutenberg richter law a power law in energy or seismic moment is found to apply only within a finite scale range both in model and natural seismicity accordingly the frequency magnitude distribution can be generalized to a gamma distribution in energy or seismic moment a power law with an exponential tail this allows extrapolations of the frequency magnitude distribution and the maximum credible magnitude to be constrained by observed seismic or tectonic moment release rates the answers to other questions raised are less clear for example the effect of the a priori assumption of a poisson process in a system with strong local interactions and the impact of zoning a potentially multifractal distribution of epicentres with smooth polygons the results of some models show premonitory patterns of seismicity which could in principle be used as mainshock precursors however there remains no consensus on both theoretical and practical grounds on the possibility or otherwise of reliable intermediate term earthquake prediction

seismic moment distribution summary we review possible errors in determining the size of earthquakes we propose that the size distribution can be effectively defined only for earthquake sequences not for individual earthquakes as a result of the error analysis we question the validity of many reported correlations between the 6 value and spatio temporal characteristics of tectonics and seismicity the study of the distribution of earthquake seismic moment largely avoids the influence of these errors and biases and is therefore superior to the standard analysis of the magnitude frequency law the gamma distribution is applied to describe the distribution of seismic moments of earthquake sequences this distribution which generalizes the well known gutenberg richter g r relation is characterized by two parameters we use the maximum likelihood method to determine the parameters of the gamma distribution for worldwide earthquakes in different depth ranges the empirical distribution is derived from the moment tensor catalogue compiled by the harvard group the p value for scalar seismic moment of earthquake sequences an analogue of the 6 value in the g r magnitude frequency law is close to 1 2 for all earthquakes the value predicted by a critical branching model of seismicity this result which will be improved as more seismic moment data become available provides input for modelling of seismicity based on percolation or on self organized criticality models if 3 equals 1 2 then using the critical branching model we find that most small earthquakes in available catalogues are dependent shocks i e aftershocks even among earthquakes of intermediate magnitudes the number of dependent events may exceed that of independent events

episodic river flooding events revealed by palynological assemblages in jurassic deposits of the brent group north sea spore and pollen sporomorph assemblages from middle jurassic marine deposits of the brent group in the northern north sea are investigated to assess temporal and spatial variations in vegetation and depositional processes four wells were sampled for palynology from the penguins cluster and the don north east fields through the rannoch formation shoreface succession hyperpycnite deposits occur throughout but are concentrated within the lower part of the section these are expressed by sand prone beds displaying waxing and waning current motifs normally graded muddy beds and structureless mudstones hyperpycnal hypopycnal deposits resulting from episodic river flooding represent important sedimentary features as they may be preserved below fair weather wave base in more offshore settings and potentially be the only record of the former presence of a nearby river mouth the hyperpycnites typically contain abundant botryoccocus spp amorphous organic matter aom and hinterland sporomorph taxa with relatively few marine components compared to associated marine shoreface facies variations in palynofacies assemblages and botryococcus spp abundances indicate frequent river mouth avulsion ordination of samples using non metric multidimensional scaling nmds indicates that shoreface samples of the sampled wells are relatively distinct but hyperpycnite samples are highly similar regardless of their sampled well this suggests that depositional processes and spore pollen sources i e catchment zones were similar among hyperpycnite events across different wells abundant bisaccate pollen botryococcus spp and aom within interpreted hyperpycnites suggest sediment mixing along the fluvial drainage path during flooding events the terrestrial signature of hyperpycnite sporomorph assemblages demonstrates that underflows remained coherent as they descended the shoreface profile with little turbulent mixing with ambient marine waters sporomorph assemblages display few large changes through time suggesting vegetation on the adjacent coastal plain was relatively static through the studied interval

holocene crustal movements and sea level changes in great britain crustal downwarping has occurred throughout southern and south eastern england and most of wales for at least the last 4000 years but the type of movement in some areas of southern and eastern england is more complicated than simple linear subsidence highest estimated rates of subsidence since 4000 bp are for the thames estuary and norfolk up to 2 mm yr glacio isostatic processes have resulted in uplift in northern england and mainland scotland the rates of uplift have decreased throughout the holocene estimates for the present range from zero in south lancashire and the tees estuary to over 1 mm yr though less than 2 mm yr in central scotland over 400 sea level index points from the databank of 904 cases collected for igcp project 200 are grouped into 15 main areas and used to investigate the nature of crustal movements in great britain since 8800 bp but there are significant deficiencies in available data which constrain the analysis

a seismological model for earthquakes induced by fluid extraction from a subsurface reservoir a seismological model is developed for earthquakes induced by subsurface reservoir volume changes the approach is based on the work of kostrov 1974 and mcgarr 1976 linking total strain to the summed seismic moment in an earthquake catalog we refer to the fraction of the total strain expressed as seismic moment as the strain partitioning function a probability distribution for total seismic moment as a function of time is derived from an evolving earthquake catalog the moment distribution is taken to be a pareto sum distribution with confidence bounds estimated using approximations given by zaliapin et al 2005 in this way available seismic moment is expressed in terms of reservoir volume change and hence compaction in the case of a depleting reservoir the pareto sum distribution for moment and the pareto distribution underpinning the gutenberg richter law are sampled using monte carlo methods to simulate synthetic earthquake catalogs for subsequent estimation of seismic ground motion hazard we demonstrate the method by applying it to the groningen gas field a compaction model for the field calibrated using various geodetic data allows reservoir strain due to gas extraction to be expressed as a function of both spatial position and time since the start of production fitting with a generalized logistic function gives an empirical expression for the dependence of on reservoir compaction probability density maps for earthquake event locations can then be calculated from the compaction maps predicted seismic moment is shown to be strongly dependent on planned gas production

seismotectonics and the earthquake frequency magnitude distribution in the aegean area summary a study of aegean seismotectonics and the resulting frequency magnitude distribution on a broad scale is undertaken using the tectonic model of le pichon angelier this implies a tectonic moment release rate due to the spreading of the aegean of 17 8 times 1018 n m 1 yr 1 over the past 13 ma if stretching is due mainly to a series of normal faults dipping at about 45 in a seismogenic crust 10 20 km deep the moment magnitude relation from an instrumental magnitude catalogue is log m0 a bm with a 10 970 0 294 b 1 206 in si units this is established from 50 events of magnitude ms 5 3 whose scalar seismic moments m0 have been evaluated in a homogeneous manner for the region by spectral analysis of surface waves at 30 60 s period by contrast published body wave analyses from waveform modelling at 20 s period and moment tensor analyses seem to produce seismic moments which are lower by a factor of two or so on average this moment magnitude relation implies a seismogenic moment release rate due to stretching in the aegean of 14 times 1018 n m 1 yr 1 during the time period 1918 81 and 17 times 1018 n m 1 yr 1 for the period 1964 81 within a factor of two or so uncertainty this implies that the energy release in the brittle crust due to aegean spreading is substantially seismic within the stated accuracy and is also relatively stationary even when compared with the tectonic moment release rates a similar comparison using the same tectonic model shows that the subducting slab is sinking beneath the hellenic arc almost completely aseismically and that processes such as near vertical slab pull and confined thermal expansion could explain most of the observed seismic energy release by internal deformation of the slab the frequency magnitude statistics for the area of active extension has a characteristic earthquake of magnitude 7ms corresponding approximately to fault depths of 10 14 km for an aspect ratio of 2 and a strain drop of 10 4 this is close to the observed seismogenic depth 10 20 km for well determined earthquakes in the aegean area

flexural rigidity of fennoscandia inferred from the postglacial uplift the earth s response to glacial loading unloading offers exceptional promise for the study of the physical properties of the lithosphere in particular tilting of paleoshorelines is very sensitive to the lithosphere rigidity to determine the flexural rigidity the isostatic response to deglaciation in fennoscandia is modeled using an earth model with a layered mantle viscosity overlain by an elastic lithosphere the flexural rigidity and asthenosphere viscosity is allowed to vary to get a match between theoretical and observed present rate of uplift and tilting of paleoshorelines five different ice thickness models are used for a relatively thin ice 2500 m in central areas the resulting flexural rigidity is more or less uniform over fennoscandia with a value of 1023 n m elastic thickness te 20 km this is regarded as minimum for the flexural rigidity of central fennoscandia the pattern of the present rate of uplift and the tilts of the paleoshorelines of the area also sets an upper bound of the flexural rigidity 2 5 1025 n m te 110 km in more central areas of fennoscandia the flexural rigidity at the western coast of norway does not seem to exceed 1023 n m te 50 km the most likely glacier model gives a flexural rigidity of 1023 n m te 20 km at the norwegian coast increasing to above 1024 n m te 50 km in central parts of fennoscandia

biogenic chaos cryptobioturbation and the work of sedimentologically friendly organisms abstract biogenic chaos from an ichnological point of view can be defined as total bioturbation of sediment by infaunal organisms such that the original sedimentary fabric and associated sedimentary structures are entirely destroyed the truth however is that not all forms of thorough bioturbation are purely destructive as improbable as it initially sounds sediment can be pervasively potentially 100 bioturbated and yet have suffered remarkably little distortion of the original bedding in nature there exist many different levels of organism communities historically the study of any natural system begins with the most obvious attention grabbing elements only later do the more innocuous aspects come to be discovered and appreciated ichnology shows a similar historical pattern the most obvious aspects of the science the discrete burrow or track forms have been well studied for many years only recently have more subtle biogenic disturbances such as micro borings bacterial trails meiofaunal burrows infaunal tiering etc gained attention likewise another level of bioturbation cryptobioturbation exists and is becoming more evident in the rock record owing to its diminutive and obscure nature cryptobioturbation has not received widespread attention as the name implies cryptobioturbation is characteristically small in scale and exceedingly subtle in expression what sets it apart from other forms of bioturbation however is its tendency to preserve rather than to destroy the sediment s primary physical structure the fabric that results from cryptobioturbation can have significant influence on resulting permeability and porosity trends in some systems where both cryptically bioturbated sandstone and generally unburrowed sandstone are present mini permeameter measurements show that numerous heterogeneities are retained in the unburrowed sandstone resulting in a wide range of permeabilities in contrast cryptically bioturbated sandstone intervals show that these heterogeneities are less pronounced and the resulting permeability curve is more uniform the effect of cryptobioturbation does not result in enhanced permeabilities but rather diminishes internal heterogeneities leading to a more uniform permeability distribution

fractals in geology and geophysics the definition of a fractal distribution is that the number of objectsn with a characteristic size greater thanr scales with the relationn r d the frequency size distributions for islands earthquakes fragments ore deposits and oil fields often satisfy this relation fractals were originally introduced by mandelbrot to relate the length of a coastline to the length of the measuring stick this application illustrates a fundamental aspect of fractal distributions scale invariance the requirement of an object to define a scale in photographs of many geological features is one indication of the wide applicability of scale invariance to geological problems scale invariance can lead to fractal clustering geophysical spectra can also be related to fractals these are self affine fractals rather than self similar fractals examples include the earth s topography and geoid

highland boundary fault zone tectonic implications of the aberfoyle earthquake sequence of 2003 the highland boundary fault zone hbfz is one of the major faulted tectonic boundaries in great britain historically seismicity has occurred in this zone around the town of comrie but an earthquake sequence that occurred in 2003 near the village of aberfoyle ml 1 3 3 2 was the first significant activity to be recorded in the hbfz since the installation of modern seismograph networks in the 1970s this study describes detailed analysis of these data the waveform signals of the events were almost identical and by applying a cross correlation technique combined with multiple event location the alignment of the events was found to be wsw ene this alignment matches one of the nodal planes determined by joint focal mechanism analysis the fault plane dips to the northwest and shows oblique sinistral strike slip with normal movement the orientation of the event alignment matches the direction and orientation of observed features in the hbfz hence it is concluded that the wsw ene striking nodal plane was the causative fault that is associated with the hbfz the orientation of maximum compressional stress is rotated from the regional average expected due to the mid atlantic ridge push force this rotation is possibly explained by stresses due to postglacial rebound smaller events in the sequence were used as empirical green s functions and deconvolved from the larger events to determine source time functions the corresponding corner frequencies matched results from spectral fitting showing that the events were of relatively low stress drop

temporal changes in the cumulative piecewise gradient of a variant of the gutenberg richter relationship and the imminence of extreme events abstract it is generally found that the relative frequencies of occurrence of earthquakes of different magnitudes in seismogenic zones have a power law distribution for a long term dataset the overall slope of this logarithmically transformed distribution is usually indicated by a best fit straight line and expressed as a b value this slope is stable and normally lies between 0 8 and 1 2 the actual value depending on the region examined and the threshold selected for data completeness the linearity of the distribution can be used to make statistical inferences about the potential for larger events over the long run and with appropriate reservations may even be extrapolated to magnitudes that are beyond recent experience we suggest the same information can also be viewed over shorter intervals in terms of an empirical piecewise distribution with relative frequencies of occurrence at adjacent magnitude steps controlling the local slope of the distribution an emergence through time of an excess number of lower magnitude earthquakes causes temporal changes to appear in the low end piecewise gradients of this distribution a marked excursion away from an overall uniform trend for the particular zone may be indicative of an imminent larger event on two separate occasions in 1982 and 1997 such temporal variations were seen in the magnitude distributions of sequences of events near tobago west indies and used to anticipate subsequent damaging mainshocks the recognition of temporal departures from overall linearity of the magnitude frequency relation in a suitable dataset may thus provide an evidential element that can contribute to earthquake forecasting this phenomenological approach was used in the analysis of the neic global dataset of earthquakes of magnitude 6 1 and bigger for the period 1973 2003 to explore its wider applicability trends in the piecewise gradients of the global data were interpreted as pointing to an imminent great earthquake perhaps exceeding magnitude 8 5 such an event did occur shortly afterwards in the form of the great sumatran earthquake of 2004 12 26 following that event global magnitude production continued to exhibit sharp imbalances in the lower magnitude bins indicating that another similar event was likely the second sumatran earthquake on 2005 03 28 satisfied that projection since that time a magnitude production imbalance persists in the global dataset suggesting the system could be poised to output an earthquake or earthquakes in the magnitude range 8 6 9 0 or even greater this contribution describes the piecewise gradient approach and examines its application to global earthquake data

experiments on bed configurations in fine sands under bidirectional purely oscillatory flow and the origin of hummocky cross stratification abstract we made experiments on bed configurations in bidirectional purely oscillatory flows at a wide range of oscillation periods t and maximum orbital velocities um in two closed flow ducts 0 1 m and 0 4 m wide the motivation was that understanding of bed configurations in oscillatory flows with long periods and high velocities during storm induced deposition in the shallow ocean is needed for interpreting the stratification in such deposits the ripples produced were classified geometrically as two dimensional 2d or three dimensional 3d in plan view geometry and dynamically as oscillatory current ripples dependent upon the patterns of flow and sediment transport specific to the existence of the oscillation itself and reversing current ripples dependent on he existence of the current in one direction or the other during the oscillation runs in the small duct with effectively 0 19 mm and 0 30 mm sand showed the familiar small 2d oscillatory current ripples at short t and low um passing into much larger ripples with spacing up to 2 m at periods of 6 20 s and velocities up to 1 m s with no apparent limit on size with increasing t and um even in such a narrow duct there was some evidence of 3d geometry of the large ripples runs in the large duct with effectively 0 11 mm sand at a single period of about 9 5 s showed a progression from small 2d oscillatory current ripples through small 3d reversing current ripples to large round crested 3d oscillatory current ripples with prominent superimposed 3d to 2d reversing current ripples the large 3d ripples which increased in spacing to 1 3 m at the h ghest attainable um of 1 m s shifted in position and changed in size with time seemingly at random causing substantial local and temporary erosion and deposition at a given point on the bed there was no net aggradation during the runs but a deposit was synthesized by taking a time series of sidewall bed profiles during a run in which large 3d ripples developed from an initially plane bed and changed irregularly in size and position as they grew toward equilibrium and then plotting the profiles one above the previous with a constant upward increment the resulting stratification is strikingly similar to much hummocky cross stratification in ancient sandstones this suggests that some hummocky cross stratification is generated during sediment fallout from strong purely oscillatory flows at moderate to long oscillation periods as large 3d oscillatory current bed forms develop from a planar bed during strong but waning flow

palaeoecology of syn rift topography a late jurassic footwall island on the josephine ridge central graben north sea abstract understanding rift topography is essential for determining source areas sediment pathways and the type of sediment delivered to a rift basin factors essential for interpreting petroleum systems in ancient rifts here we investigate upper jurassic sediments from the josephine ridge region of the central graben north sea by integrating geophysical palynological petrophysical and sedimentological datasets to analyse the palaeoenvironments of the jade and judy horsts the tops of which are not preserved interpretation of geophysical and petrophysical data together with core descriptions shows study wells to step progressively away from the josephine ridge into adjacent grabens one hundred and five palynological samples from six wells range from the oxfordian to the lower tithonian spanning the syn rift period of the central graben samples from the adjacent grabens and the jade horst are rich in dinoflagellate cysts and possess

earthquakes as self organized critical phenomena a cellular automation model with threshold elements previously proposed by bak et al 1988 which generates 1 f noise and self organizes into a critical state is studied as a model for earthquake occurrence the model explains some of fractal features of earthquakes such as the power law distribution of the size of the earthquake the model is modified so that every earthquake may trigger aftershocks the modified trigger model explains other fractal features of earthquakes such as the power law decay of aftershock frequency and the power law decay of aftershock frequency and the power law correlation of the hypocenter distribution

constraints on the frequency magnitude relation and maximum magnitudes in the uk from observed seismicity and glacio isostatic recovery rates summary earthquake populations have recently been shown to have many similarities with critical point phenomena with fractal scaling of source sizes energy or seismic moment corresponding to the observed gutenberg richter g r frequency magnitude law holding at low magnitudes at high magnitudes the form of the distribution depends on the seismic moment release rate mand the maximum magnitude m max the g r law requires a sharp truncation at an absolute maximum magnitude for finite m i n contrast the gamma distribution has an exponential tail which allows a soft or credible maximum to be determined by negligible contribution to the total seismic moment release here we apply both distributions to seismic hazard in the mainland uk and its immediate continental shelf constrained by a mixture of instrumental historical and neotectonic data tectonic moment release rates for the seismogenic part of the lithosphere are calculated from a flexural plate model for glacio isostatic recovery constrained by vertical deformation rates from tide gauge and geomorphological data earthquake focal mechanisms in the uk show near vertical strike slip faulting with implied directions of maximum compressive stress approximately in the nnw sse direction consistent with the tectonic model maximum magnitudes are found to be in the range 6 3 7 5 for the g r law or 7 0 8 2 m l for the gamma distribution which compare with a maximum observed in the time period of interest of 6 1 m l the upper bounds are conservative estimates based on 100 per cent seismic release of the observed vertical neotectonic deformation glacio isostatic recovery is predominantly an elastic rather than a seismic process so the true value of m max is likely to be nearer the lower end of the quoted range

subglacial bedforms reveal an exponential size frequency distribution subglacial bedforms preserved in deglaciated landscapes record characteristics of past ice sediment flow regimes providing insight into subglacial processes and ice sheet dynamics individual forms vary considerably but they can often be grouped into coherent fields typically called flow sets that reflect discrete episodes of ice flow within these bedform size frequency distributions predominantly height width and length are currently described by several statistics e g mean median and standard deviation that arguably do not best capture the defining characteristics of these populations this paper seeks to create a better description based upon semi log plots which reveal that the frequency distributions of bedform dimensions drumlin mega scale glacial lineation and ribbed moraine plot as straight lines above the mode this indicates by definition an exponential distribution for which a simple and easily calculated yet statistically rigorous description is designed three descriptive parameters are proposed gradient the exponent characterising bedforms likely least affected by non glacial factors area normalised y intercept 0 quantifying spatial density and the mode below small features are less prevalent due to i measurement data sampling and mapping fidelity ii possible post glacial degradation or iii genesis not being created sub glacially this new description has the benefit of being insensitive to the impact of potentially unmapped or degraded smaller features and better captures properties relating to ice flow importantly using flow sets can now be more usefully compared with each other across all deglaciated regions and with the output of numerical ice sheet models applications may also exist for analogous fluvial and aeolian bedforms identifying the characteristic exponential and that it is typical of emergent subglacial bedforms is a new and potentially powerful constraint on their genesis perhaps indicating that ice sediment interaction is fundamentally stochastic in nature

the exceptional earthquakes in kaliningrad district russia on september 21 2004 abstract the earthquakes of magnitudes m w 5 0 and 5 2 in the kaliningrad enclave of russia on september 21 2004 were unexpected in a low seismicity area the earthquakes caused moderate damage in the kaliningrad enclave and smaller damage in northern poland and in southern and western lithuania the largest earthquake was the strongest ever recorded instrumentally in the region and it was felt at distances up to 800 km in directions towards the west and south the perceptibility area is abruptly cut off by the tornquist teisseyre zone the south west margin of the east european craton the earthquakes are instrumentally located at depths 16 20 km under the central northern part of the sambia peninsula in the kaliningrad enclave for these events it is noted that the macroseismic calculations of 10 19 km depths are in reasonable agreement the source mechanism of the largest earthquake was determined to be a right lateral strike slip on a wnw ese near vertical fault of orientation almost parallel to the tornquist teisseyre zone and to the north coast of the sambia peninsula based on available stress information it is interpreted that the underlying cause of the earthquakes is the absolute plate motion historical information is scanty it is searched in an attempt to evaluate past seismic activity in the region and to evaluate vulnerable weakness zones in the geological structures

a sedimentological approach to refining reservoir architecture in a mature hydrocarbon province the brent province uk north sea improved reservoir characterisation in the mature brent province of the north sea aimed at maximising both in field and near field hydrocarbon potential requires a clearer understanding of sub seismic stratigraphy and facies distributions in this context we present a regional high resolution sequence stratigraphic framework for the brent group uk north sea based on extensive sedimentological re interpretation of core and wireline log data combined with palynostratigraphy and published literature this framework is used to place individual reservoirs in an appropriate regional context thus resulting in the identification of subtle sedimentological and tectono stratigraphic features of reservoir architecture that have been previously overlooked we emphasise the following insights gained from our regional high resolution sequence stratigraphic synthesis 1 improved definition of temporal and spatial trends in deposition both within and between individual reservoirs 2 development of regionally consistent predictive sedimentological models for two enigmatic reservoir intervals the broom and tarbert formations and 3 recognition of subtle local tectono stratigraphic controls on reservoir architecture and their links to the regional middle jurassic structural evolution of the northern north sea we discuss the potential applications of these insights to the identification of additional exploration potential and to improved ultimate recovery

dating of late holocene beach shoreline positions by regional correlation of coseismic retreat events in the columbia river littoral cell usa abstract beaches and barrier spits of the columbia river littoral cell crlc 160 km in length experienced substantial progradation 0 5 2 5 km in width during the late holocene the accreted beach plains and barriers preserved evidence of episodic catastrophic retreat that was forced by coseismic subsidence the abrupt subsidence events 0 5 1 5 m submergence are associated with slip on the underlying cascadia megathrust with a mean recurrence interval of 500 yr ground penetrating radar gpr profiles taken across the barriers and beach plains show high angle beach retreat scarps 3 15 m vertical relief and foredune ridge slump scarps 5 15 m vertical relief the upper shoreface retreat features are correlated throughout the littoral cell by radiocarbon age position relative to abandoned foredune ridges and distinct sequences of large and small scarps particularly large retreat scarps 10 15 m in height are associated with the first oldest and fourth oldest prehistoric scarps a and d respectively a maximum of 10 retreat scarps in the long beach subcell date from 216 211 calrcybp to 4756 114 calrcybp the youngest seven scarps a g are correlated between all four subcells showing a regional response to the coseismic strain cycles backshore disturbance features 1 3 m vertical relief are observed in the gpr profiles but they are not identified here due to their discontinuities between adjacent profiles at 5 km longshore spacing the seven regional scarps a g are directly correlated to seven coseismic subsidence events reported to date between 0 3 and 3 2 ka the correlation of scarps to earthquake events provides high resolution proxy ages for shoreline positions in late holocene time the proxy shoreline positions are dated at 0 3 1 1 1 3 1 7 2 5 2 8 and 3 2 ka based on buried wetland sequences from adjacent tidal basins the paleoshoreline dating demonstrates that the onset of net shoreface progradation between 4 7 and 0 3 ka was delayed with increasing distance 0 100 km from the columbia river sand source the history of beach progradation reflects the sequential filling of bay and shoreface accommodation spaces located down drift of the columbia river mouth these late holocene shoreline changes portend future redistributions of existing sand within the littoral system as the limited sand reserves continue to migrate away from the columbia river mouth source

seismogenesis and state of stress in the uk abstract in this paper i present a compilation of focal mechanisms for earthquakes with magnitudes greater than 3 0 ml in the british isles that can be used to help constrain our understanding of seismicity and it s driving forces in the british isles the fault plane solutions consist of both previously published mechanisms for significant british earthquakes and new solutions calculated from regional and local data for more recent and smaller earth quakes that were previously unpublished focal mechanisms for earthquakes in the uk are dominantly strike slip with northwest southeast compression and northeast southwest tension or reverse with northwest southeast com pression in many cases there is also an oblique component to the slip p and t axes from individual solutions are relatively well constrained in azimuth though less so in dip with p axes orientation for most events clustering between north and north west indicating sub horizontal compression however some spatial variation in p and t axes orientation is also apparent with near north northeast compression and east west extension in north west scotland changing to northwest southeast compression in england and wales i estimate a best fitting stress tensor under the assumption of uniform stress using two different inversion methods for both the entire focal mechanism data set and two different subsets of the data the results from the two different datasets suggest that there is a significant difference in the stress state between northwest scotland and england and wales calculated 1 directions for england and wales are northwest southeast consistent both with existing stress data and expected stresses from first order plate motions by contrast the inversion results for northwest scotland show near east west extension with possible 1 and 2 directions lying in a north south band and that the magnitudes of 1 and 2 are similar the relative magnitude of the principal stresses r determined for england and wales suggests that the intermediate stress 2 is close to the average value of 1 and 3 the clear difference in the stress inversion results between northwest scotland and england and wales suggests that the principal stress directions expected from first order plate motions have been modified in scotland by local stress conditions due to glacio isostatic adjustment

plate motions and crustal deformation over the past 30 years the plate tectonic paradigm has revolutionized the earth sciences through its powerful yet elegant quantitative treatment of large scale crustal deformation and through its conceptually integrative role within the earth sciences this review summarizes several important developments in plate tectonic research for the period 1991 to early 1994 with emphasis placed on publications that have either significantly improved our understanding of plate motions and their relation to crustal deformation or have raised significant new questions revisions to the geomagnetic reversal time scale cenozoic plate motions microplate kinematics oblique convergence and deformation of forearcs and kinematic information derived from detailed bathymetric and side scan sonar studies are featured

probabilistic models for earthquakes with large return periods in himalaya region determination of the frequency of large earthquakes is of paramount importance for seismic risk assessment as large events contribute to significant fraction of the total deformation and these long return period events with low probability of occurrence are not easily captured by classical distributions generally with a small catalogue these larger events follow different distribution function from the smaller and intermediate events it is thus of special importance to use statistical methods that analyse as closely as possible the range of its extreme values or the tail of the distributions in addition to the main distributions the generalised pareto distribution family is widely used for modelling the events which are crossing a specified threshold value the pareto truncated pareto and tapered pareto are the special cases of the generalised pareto family in this work the probability of earthquake occurrence has been estimated using the pareto truncated pareto and tapered pareto distributions as a case study the himalayas whose orogeny lies in generation of large earthquakes and which is one of the most active zones of the world has been considered the whole himalayan region has been divided into five seismic source zones according to seismotectonic and clustering of events estimated probabilities of occurrence of earthquakes have also been compared with the modified gutenberg richter distribution and the characteristics recurrence distribution the statistical analysis reveals that the tapered pareto distribution better describes seismicity for the seismic source zones in comparison to other distributions considered in the present study

statistical relations among earthquake magnitude surface rupture length and surface fault displacement abstract in order to refine correlations of surface wave magnitude fault rupture length at the ground surface and fault displacement at the surface by including the uncertainties in these variables the existing data were critically reviewed and a new data base was compiled earthquake magnitudes were redetermined as necessary to make them as consistent as possible with the gutenberg methods and results which make up much of the data base measurement errors were estimated for the three variables for 58 moderate to large shallow focus earthquakes regression analyses were then made utilizing the estimated measurement errors the regression analysis demonstrates that the relations among the variables magnitude length and displacement are stochastic in nature the stochastic variance introduced in part by incomplete surface expression of seismogenic faulting variation in shear modulus and regional factors dominates the estimated measurement errors thus it is appropriate to use ordinary least squares for the regression models rather than regression models based upon an underlying deterministic relation in which the variance results primarily from measurement errors significant differences exist in correlations of certain combinations of length displacement and magnitude when events are grouped by fault type or by region including attenuation regions delineated by evernden and others estimates of the magnitude and the standard deviation of the magnitude of a prehistoric or future earthquake associated with a fault can be made by correlating m s with the logarithms of rupture length fault displacement or the product of length and displacement fault rupture area could be reliably estimated for about 20 of the events in the data set regression of m s on rupture area did not result in a marked improvement over regressions that did not involve rupture area because no subduction zone earthquakes are included in this study the reported results do not apply to such zones

recent fault movement and palaeoseismicity in western scotland abstract field study at two locations in western scotland is described and gives evidence for fault movement and seismic activity during the late and post glacial epochs the evidence comprises levelling survey of raised marine shorelines remote sensing study of lineaments radiocarbon dating of quaternary sediment and detailed field examination of faults and fault gouge material vertical fault displacements of up to 3 m are observed on a c 10 500 year old raised marine shoreline on the isle of mull and repeated predominantly lateral movement is observed on a prominent 14 km long fault lineament active since ice retreat and as recently as c 2000 yrs b p the fault movements are located close to the edge of the area formerly covered by the loch lomond readvance ice cap 11 000 10 000 yrs b p they are considered to have been caused by rapid rates of isostatic rebound soon after deglaciation

fennoscandian earthquakes whole crustal rupturing related to postglacial rebound local and regional earthquake locations provide seismic evidence that large shield earthquakes have occurred in northern fennoscandia these paleoearthquakes with fault lengths of up to 160 kilometers and average displacements of up to 15 meters were triggered by nonisostatic compressive stresses caused by the removal of the ice at the end of the last deglaciation the fennoscandian faults were probably formed by single events that ruptured through most of the crust the largest event moment magnitude mw 8 2 was larger than other known stable continent earthquakes outside failed rifts or extended crust

a wave in the earth as the great ice sheets of the last ice age melted and retreated their weight was lifted from the underlying earth this unloading and resulting crustal stress may have induced postglacial faulting and earthquakes in his perspective johnston discusses results reported in the same issue by arvidsson p 744 which indicate evidence of very large postglacial earthquakes along the parvie fault of northern sweden

new method of estimating regional stress orientations application to focal mechanism data of recent british earthquakes summary it is demonstrated how a recently devised graphical method for estimating palaeostresses from exposed striated fault planes can be adapted for use with earthquake focal mechanism data provided the data set includes one or more earthquakes for which the fault plane can be identified the principal stress directions can be determined more precisely than by using the alternative right dihedra method using the new so called right trihedra method stress directions are found which are compatible with recent british earthquakes the method can also be used in the case of some focal mechanisms to resolve the ambiguity regarding which focal plane corresponds to the fault plane

high resolution seismic imaging of a younger dryas and holocene mass movement complex in glacial lake windermere uk the stratigraphy and sedimentological processes operating over the last 15 000 years within glacial lake windermere uk at the mouth of cunsey beck were imaged by a decimetre resolution seismic reflection survey a complex of fifteen mass movement deposits was identified as contemporaneous with the younger dryas and two within the overlying holocene drape the high vertical resolution and dense grid of profiles allowed pseudo three dimensional mapping of individual events along with the determination of their relative temporal relationships the size of the mass wasting deposits has been estimated to range between 2100 and 100 000 m3 the geometry structure and relationship to the existing stratigraphy suggest a rapid emplacement of the younger dryas mass movement deposits facilitated by climatic changes making subaqueous slopes unstable with possible triggering by seismic activity morphometric parameters such as volume and planar surface area indicate a greater mobility of the younger dryas mass movement deposits compared to the holocene events the sediments of all imaged mass movement deposits are believed to originate from the slope deposits of the lake the age of two holocene mass movement deposits triggered by flooding or terrestrial debris flows is estimated to be 2400 and 4400 years bp

the dudley earthquake of 2002 a moderate sized earthquake in the uk the 4 7 ml dudley earthquake on 22 september 2002 at 23 53 utc was widely felt throughout england and wales and was the largest earthquake to occur onshore in the united kingdom uk since the magnitude 5 1 ml bishop s castle earthquake in 1990 the earthquake hypocentre determined from inversion of observed p and s wave travel time data suggests a source depth of 14 km and this depth estimate is supported by forward modelling of observed waveforms focal mechanisms obtained from both first motion polarities of local observations and moment tensor inversion of regional observations show left lateral strike slip faulting along a near vertical near north south striking fault plane whose orientation is in good agreement with the surface expression of the observed faults in the region two aftershocks were recorded within the location error ellipsoid of the mainshock comparison of the waveform signals revealed that the mainshock and aftershocks were nearly co located and possibly had the same source mechanism the observed peak ground acceleration is found to be less than that predicted using empirical relations which have been considered applicable in the uk seismic moment m0 and stress drop were measured from on scale records where lg arrivals were clear and then used to give better estimates of the peak ground accelerations using a stochastic approach

localization and fault growth in layered brittle ductile systems implications for deformations of the continental lithosphere we present experiments and numerical simulations dealing with the growth of faults in thin brittle ductile systems to understand deformation modes in the continental lithosphere experiments were uniaxial shortening of layers of dry sand and silicone putties of various viscous resistances for large strength ratios between the brittle and ductile layers r 5 10 the deformation localizes into two shear bands the fault pattern is created before reaching 10 shortening and has fractal dimensions varying between 1 6 and 1 8 for small strength ratios r 5 10 deformation never localizes the fault pattern is homogeneous with a trivial dimension of 2 and grows continuously during deformation the transition between localized and homogeneous deformation occurs when the mechanical resistance of brittle layers is 5 10 times larger than the resistance of ductile layers this transition was also investigated by means of electrical analog simulations a fuse network which represents an elasto brittle layer is coupled with a capacitor layer which models strain rate dependent fluids an ac potential is applied and the fuses progressively burned out until they form a connected network the ac potential frequency is a tuning parameter similar to the applied strain rate in experiments a critical frequency is obtained marking a transition between a localization mode where the density of burned fuses decreases as the system size increases and a delocalization mode where the density of burned fuses remains constant with increasing system size the scaling dependency of the fracture process as well as the critical frequency are consistent with experimental results available information on the rheology of the continental lithosphere shows that this mechanical transition is bracketed by the possible range of brittle to ductile strength ratios

a stochastic earthquake ground motion prediction model for the united kingdom low seismicity regions such as the united kingdom uk pose a challenge for seismic hazard analysis in view of the limited amount of locally recorded data available in particular ground motion prediction is faced with the problem that most of the instrumental observations available have been recorded at large distances from small earthquakes direct extrapolation of the results of regression on these data to the range of magnitudes and distances relevant for the seismic hazard analysis of engineered structures generally leads to unsatisfactory predictions the present study presents a new ground motion prediction equation gmpe for the uk in terms of peak ground acceleration pga peak ground velocity pgv and 5 damped pseudospectral acceleration psa based on the results of numerical simulations using a stochastic point source model calibrated with parameters derived from local weak motion data the predictions from this model are compared with those of previous gmpes based on uk data other gmpes derived for stable continental regions scrs as well as recent gmpes developed for the wider european area

ground motion difference between two moderate size intraplate earthquakes in the united kingdom two moderate size earthquakes occurred in the united kingdom the first near folkestone in 2007 with m w 4 0 and the second near market rasen in 2008 with m w 4 5 both were strongly felt and caused some nonstructural damage the earthquakes occurred at significantly different depths the folkestone earthquake at 5 km and the market rasen earthquake at 20 km we determined the seismic moment and the stress drop of the two mainshocks and two smaller earthquakes in the same locations by modeling the source displacement spectra we found stress drops of 30 34 bar and 344 136 bar for the folkestone and market rasen mainshocks respectively this is a significant difference considering the earthquakes are only 275 km apart and both are of intraplate origin we applied the stochastic ground motion modeling technique and used the stress drop and seismic moment to compute vertical component peak ground acceleration the modeled ground motions are consistent with the observations we also computed vertical peak ground acceleration for a hypothetical m w 6 0 high stress drop 200 bar earthquake and found that it would be 4 6 m sec2 at 20 km hypocentral distance

paleoenvironmental reconstruction based on palynofacies analysis of the aptian albian succession of the sergipe basin northeastern brazil abstract palynofacies analyses were carried out on 272 core samples from two wells gtp 17 se and gtp 24 se in the sergipe basin with the aim of reconstructing the paleoenvironments of the upper aptian middle albian for the palynofacies analysis the kerogen categories were counted and subjected to cluster analyses for detailed environmental analysis kerogen distribution trends and parameters were applied based on percentages of kerogen categories total organic carbon analysis was also used the stratigraphic distribution of palynofacies associations that defined eight palynofacies units in well gtp 17 se and ten in well gtp 24 se reflects a continuous terrestrial influx throughout the succession amorphous organic matter aom and palynomorph groups show moderate to high percentages especially in well gtp 24 se the increase in relative abundance of these groups suggests that a long term a transgression and or a decreasing terrestrial influx occurred in the area from the bottom to top six depositional environments were identified in wells gtp 17 se and gtp 24 respectively and they reflect the progressive increase in marine influence as the basin evolved brackish lagoon conditions changed to more open marine conditions as sea level changed during the separation of south america from africa

statistics of characteristic earthquakes statistical methods are used to test the characteristic earthquake hypothesis several distributions of earthquake size seismic moment frequency relations are described based on the results of other researchers as well as my own tests evidence of the characteristic earthquake hypothesis can be explained either by statistical bias or statistical artifact since other distributions of earthquake size provide a simpler explanation for available information the hypothesis cannot be regarded as proven

an estimate of the stress tensor in sweden using earthquake focal mechanisms abstract an estimate of the state of stress in sweden is made by inversion of the fault plane solutions of naturally occurring earthquakes it is shown that the stress state in southern sweden is significantly different from that in northern sweden in southern sweden the principal compression is in a roughly nw se direction similar to that prevailing in northwest europe as a whole this stress direction is is consistent with the stresses expected on the basis of motions of the major tectonic plates in northern sweden however there is no strongly dominant stress direction this latter observation is consistent with a situation in which processes other than first order plate motions are important the most likely explanation in this case is the effect of the deglaciation of fennoscandia which is producing rates of rebound as high as 9 mm year in northern sweden

wave enhanced sediment gravity flows and mud dispersal across continental shelves reappraising sediment transport processes operating in ancient mudstone successions recent studies of marine shelf sediment dispersal show that wave enhanced sediment gravity flows are widespread phenomena and can transport large volumes of fluid mud rapidly across low gradient shelves flow evolution is controlled by sediment supply seabed gradient and spatial distribution of wave energy at the seabed using existing flow models we predict that such flows in mud dominated sediments will develop a three part microstratigraphy produced by changing flow conditions beginning with wave induced turbulent resuspension then development of a wave enhanced sediment gravity flow prior to lutocline collapse and suspension settling petrographic examination of modern flow deposits collected from the eel shelf reveals that resultant beds possess a microstratigraphy consistent with our hypothesis a silt rich basal subunit with curved ripple laminae abruptly overlain by a subunit composed of continuous intercalated silt clay laminae and an upper clay rich drape analyses of beds from ancient mud rich outer shelf and basinal successions cleveland ironstone jurassic uk and mowry shale cretaceous united states show that they too contain beds with this three part organization suggesting that such flows were active in these ancient settings too recognition of these microstructures in these ancient mud dominated successions demonstrates that sediment in these settings was commonly reworked and transported advectively downslope by high energy events contrasting with previous interpretations of these units that deposition was dominated by quiescent suspension settling identification of these recognition criteria now allows the products of this newly recognized sediment dispersal mechanism to be identified in other shale dominated successions

palynofacies analysis and organic walled dinoflagellate cysts as indicators of palaeo hydrographic changes an example from holocene sediments in skalafjord faroe islands abstract this study documents holocene variations in organic matter deposition from ca 6350 cal yr bc to ad 1430 in skalafjord faroe islands and uses this information to assess palaeo hydrographic conditions the chronology of the interval studied is based on five ams 14 c ages based on the total sedimentary organic content the sediments dating to ca 6350 cal yr bc to ad 160 have been deposited under dysoxic bottom water conditions suggesting good ventilation in the water column the sediments dating to ca ad 160 1090 have been deposited under decreasing oxygen availability from ad 1090 to 1430 suboxic bottom water conditions characterised the fjord high terrestrial influx characterised most sediments in the study interval however moderate terrestrial influx was recorded in sediments dating to ca 6350 5670 cal yr bc based on the dinoflagellate cyst assemblages changes in the nutrient availability were inferred in the waters of the fjord over the study period the nutrients were minimal at ca 6350 5670 cal yr bc they increased in the interval ca 5670 685 cal yr bc and became very abundant at ca 685 cal yr bc to ad 1260 a decreasing trend in nutrient availability was inferred in sediments of age ca ad 1260 1430 a qualitative approach was used for the reconstruction of holocene sea surface temperature conditions based on dinoflagellate cyst and acritarch assemblages the estimated sea surface parameters highlighted the mid holocene final stage of the climatic optimum ca 6350 5300 cal yr bc the neo glaciation period ca 5300 cal yr bc to ad 260 a general climatic amelioration during the period ca ad 260 1090 and a cooling at ca ad 1090 1260

wave modified turbidites combined flow shoreline and shelf deposits cambrian antarctica sandstone tempestite beds in the starshot formation cen tral transantarctic mountains were deposited in a range of shoreline to shelf environments detailed sedimentological analysis indicates that these beds were largely deposited by wave modified turbidity currents these currents are types of combined flows in which storm generated waves overprint flows driven by excess weight forces the interpreta tion of the tempestites of the starshot formation as wave dominated turbidites rests on multiple criteria first the beds are generally well graded and contain bouma like sequences like many turbidites the soles display abundant well developed flutes they also contain thick divisions of climbing ripple lamination the lamination however is dominated by convex up and sigmoidal foresets which are geometries identical to those produced experimentally in current dominated com bined flows in clear water finally paleocurrent data support a tur bidity current component of flow asymmetric folds in abundant con volute bedding reflect liquefaction and gravity driven movement and hence their orientations indicate the downslope direction at the time of deposition the vergence direction of these folds parallels paleocur rent readings of flute marks combined flow ripples and a number of other current generated features in the starshot event beds indicating that the flows were driven down slope by gravity the wave component of flow in these beds is indicated by the presence of small to large scale hummocky cross stratification and rare small two dimensional ripples wave modified turbidity currents differ from deep sea turbidity cur rents in that they may not be autosuspending and some proportion of the turbulence that maintains these flows comes from storm waves such currents are formed in modern shoreline environments by a com bination of storm waves and downwelling sediment laden currents they may also be formed as a result of oceanic floods events in which intense sediment laden fluvial discharge creates a hyperpycnal flow event beds in the starshot formation may have formed from such a mechanism oceanic floods are formed in rivers of small to medium size in areas of high relief commonly on active margins the starshot formation and the coeval douglas conglomerate are clastic units that formed in response to uplift associated with active tectonism sedi mentological and stratigraphic data suggest that coarse alluvial fans formed directly adjacent to a marine basin the geomorphic conditions were therefore likely conducive to rapid fluvial discharge events asso ciated with storms the abundance of current dominated combined flow ripples at the tops of many starshot beds indicates that excess weight forces were dominant throughout deposition of many of these beds

jurassic early cretaceous paleogeography and paleoenvironments of the north eastern margin of gondwana insights from the carpentaria basin australia abstract although jurassic early cretaceous sedimentary systems were extensively developed on northeastern gondwana deciphering their paleogeography has been complicated by poor exposure and the lack of a robust chronostratigraphic framework the southeastern margin of the carpentaria basin northeastern australia is one of the few regions where these sedimentary systems are extensively exposed employing a combination of facies analysis and new data from paleontology and detrital zircon geochronology we present a temporally and environmentally refined paleogeographic framework for this region a late jurassic southeasterly directed marine incursion invaded northeastern gondwana extending inland across the carpentaria basin as demonstrated by a thin 30 m marine influenced fluvio estuarine stratigraphic succession capped by a sequence bounding 30 myr paraconformity the depositional hiatus marked the late jurassic early cretaceous uplift of the euroka arch with loss of sedimentary and fluvial connectivity between the carpentaria basin and adjoining eromanga basin subsequent deposition by low accommodation fluvial systems resulted in a thin fluviatile depositional package developing during the early cretaceous paleocurrent and provenance data indicate that the middle to late jurassic c 170 160 ma fluvial systems predating the paraconformity extended from the eromanga basin to the south across the southeastern carpentaria basin transporting sediment from distal sources in the lachlan orogen of southeastern australia fluvial systems of the southeastern carpentaria basin post dating the paraconformity and euroka arch uplift show a provenance shift to easterly sources in the mossman orogen and kennedy igneous association previously unrecognised jurassic early cretaceous igneous activity provided a persistent source of sediment to the southeastern carpentaria basin succession due to reworking of air fall tuff from an active magmatic arc located on the continental margin of northeastern gondwana

determination of magnitudes of ancient earthquakes from dimensions of observed seismodislocations abstract equations to estimate the magnitude of ancient earthquakes where seismotectonic crustal deformations normal faults strike slip faults etc have been preserved in the epicentral region are presented the equations are based on the results of over one hundred earthquakes including 96 recent continental earthquakes in the magnitude range 5 2 8 7

bayesian analysis of extreme earthquake occurrences part ii application to the san jacinto fault zone of southern california abstract the bayesian extreme value distribution of earthquake occurrences developed in the first part of this study is tested and applied to the estimation of seismic hazards for the san jacinto fault zone of southern california prior estimates of seismicity are developed from seismotectonic data based on standard seismological relationships among seismic moment slip rate earthquake recurrence rate and magnitude these estimates are then updated using bayes9 theorem and historical estimates of seismicity associated with the san jacinto fault zone bayesian extreme value distributions available from the literature are found either to overestimate exceedance probabilities of earthquake occurrences or require more complex computations as compared to the distribution proposed in this study on the other hand the conventional extremevalue distribution of earthquake occurrences first proposed by epstein and lomnitz 1966 was found to give results consistent with the bayesian distribution of this study if updated estimates of the seismicity parameters are used and the standard deviations of these parameters are restricted to be less than about 25 per cent of their mean values the bayesian analysis of extreme earthquake occurrences for the 300 km long san jacinto fault zone indicated a rather large sensitivity to the uncertainty associated with the prior seismotectonic estimate of seismicity using moderate estimates of this uncertainty magnitudes of 6 2 6 9 7 1 7 4 and 7 5 are found to be associated with return periods at 10 50 100 500 and 1000 yr for an upper bound magnitude of 7 5 m s on the fault zone these estimates lie approximately midway between those based on historical and seismotectonic estimates of seismicity estimated magnitudes are reduced significantly for return periods of 50 to 1000 yr if upper bound magnitude is restricted to a value of 7 0 m s closer to the largest historical earthquake observed on the zone in this case for example the 100 and 1000 yr earthquakes have magnitudes of 6 8 and 7 0 respectively

seismic moment frequency relation for shallow earthquakes regional comparison we determine the parameter values for the seismic moment frequency relation using flinn engdahl s regionalization of global seismicity and the harvard centroid moment tensor data the earthquake size distribution is approximated by the gamma law a version of the gutenberg richter distribution with an exponential taper at the maximum moment there is no statistically significant variation of the fj value the analog of the b value for all seismic regions except for the midocean ridge systems for the latter regions fj 0 93 whereas for all other zones fj 0 63 the maximum moment mxg can be statistically evaluated only for subduction zones treated as a whole mxg 10 21 2 x 10 22 newton m which corresponds to the worldwide mxg value for other regions as well as for single subduction zones mxg is determined by comparing the number of events in each zone with the seismic moment rate calculated on the basis of the nuvel 1 model of plate motion for subduction zones we obtain the estimate of mxg which agrees with the statistical value giving evidence that most tectonic deformation is released by earthquakes we test the hypothesis that no statistically significant variation in mxg occurs in subduction and continent collision zones the hypothesis cannot be rejected with available data for the midocean ridges the mxg estimate cannot be unambiguously determined it is quite possible that the estimate is significantly biased because only a small part of tectonic deformation at the ridges is released by earthquakes these results have importance in evaluating seismic risk and may also lead to developing a physical theory for earthquake generation

maximum earthquake magnitudes in the aegean area constrained by tectonic moment release rates summary seismic moment release is usually dominated by the largest but rarest events making the estimation of seismic hazard inherently uncertain this uncertainty can be reduced by combining long term tectonic deformation rates with short term recurrence rates here we adopt this strategy to estimate recurrence rates and maximum magnitudes for tectonic zones in the aegean area we first form a merged catalogue for historical and instrumentally recorded earthquakes in the aegean based on a recently published catalogue for greece and surrounding areas covering the time period 550 bc 2000 ad at varying degrees of completeness the historical data are recalibrated to allow for changes in damping in seismic instruments around 1911 we divide the area up into zones that correspond to recent determinations of deformation rate from satellite data in all zones we find that the gutenberg richter gr law holds at low magnitudes we use akaike s information criterion to determine the best fitting distribution at high magnitudes and classify the resulting frequency magnitude distributions of the zones as critical gr law subcritical gamma density distribution or supercritical characteristic earthquake model where appropriate we determine the ratio of seismic to tectonic moment release rate low values of 1 0 the seismic and tectonic moment release rates are then combined to constrain recurrence rates and maximum credible magnitudes in the range 6 7 7 6 m w where the results are well constrained based on extrapolating the short term seismic data with current earthquake data many of the tectonic zones show a characteristic distribution that leads to an elevated probability of magnitudes around 7 but a reduced probability of larger magnitudes above this value when compared with the gr trend a modification of the generalized gamma distribution is suggested to account for this based on a finite statistical second moment for the seismic moment distribution