global earthquake forecasts summary we have constructed daily worldwide long and short term earthquake forecasts these forecasts specify the earthquake rate per unit area time and magnitude on a 0 5 degree grid for a global zone region between 75n and 75s latitude 301 by 720 grid cells we use both the global centroid moment tensor gcmt and preliminary determinations of epicenters pde catalogues like our previous forecasts the new forecasts are based largely on smoothed maps of past seismicity and assume spatial and temporal clustering the forecast based on the gcmt catalogue with the magnitude completeness threshold 5 8 includes an estimate of focal mechanisms of future earthquakes and of the mechanism uncertainty the forecasted tensor focal mechanism makes it possible in principle to calculate an ensemble of seismograms for each point of interest on the earth s surface we also introduce a new approach that circumvents the need for focal mechanisms this permits the use of the pde catalogue that reliably documents many smaller quakes with a higher location accuracy the result is a forecast at a higher spatial resolution and down to a magnitude threshold below 5 0 such new forecasts can be prospectively tested within a relatively short time such as a few years because smaller events occur with greater frequency the forecast s efficiency can be measured by its average probability gains per earthquake compared to the spatially or temporally uniform poisson distribution for the short term forecast the gain is about 2 0 for the gcmt catalogue and 3 7 for the pde catalogue relative to a temporally random but spatially localized null hypothesis preliminary tests indicate that for the long term global spatial forecast the gain is of the order 20 25 compared to the uniform event distribution over the earth s surface we can also prospectively test the long term forecast to check whether it can be improved

seismic gaps and earthquakes 1 mccann et al 1979 published a widely cited seismic gap model ascribing earthquake potential categories to 125 zones surrounding the pacific rim nishenko 1991 published an updated and revised version including probability estimates of characteristic earthquakes with specified magnitudes within each zone these forecasts are now more than 20 and 10 years old respectively and sufficient data now exist to test them rather conclusively for the mccann et al forecast we count the number of qualifying earthquakes in the several categories of zones we assume a hypothetical probability consistent with the gap model e g red zones have twice the probability of green zones and test against the null hypothesis that all zones have equal probability the gap hypothesis can be rejected at a high confidence level contrary to the forecast of mccann et al the data suggest that the real seismic potential is lower in the gaps than in other segments and plate boundary zones are not made safer by recent earthquakes for the 1991 nishenko hypothesis we test the number of filled zones the likelihood scores of the observed and simulated catalogs and the likelihood ratio of the gap hypothesis to a poissonian null hypothesis for earthquakes equal to or larger than the characteristic magnitude the new seismic gap hypothesis failed at the 95 confidence level in both the number and ratio tests if we lower the magnitude threshold by 0 5 for qualifying earthquakes the new gap hypothesis passes the number test but fails in both the likelihood and likelihood ratio tests at the 95 confidence level

renewal models of seismic recurrence applied to paleoseismological and historical observations abstract because paleoseismology can extend the record of earthquakes back in time up to several millennia it represents an opportunity to study how earthquakes recur through time and thus to provide innovative contributions to seismic hazard assessment based on a database of recurrence from paleoseismology we collected 19 sequences with 5 up to 14 dated events on a single fault by using the age of the paleoearthquakes with their associated uncertainty and the historical earthquakes we tested the null hypothesis that the observed inter event times come from a uniform random distribution poisson model we used the concept of likelihood for a specific sequence of events under a given occurrence model the difference dlnl of the likelihoods estimated under two hypotheses gives an indication of which between the two hypotheses fits better the observations to take into account the uncertainties we used a monte carlo procedure computing the average and the standard deviation of dlnl for 1000 inter event sets by choosing the occurrence time of each event within the limits of uncertainty and estimating the probability that a value equal to or larger than an observed dlnl comes by chance from a poisson distribution of inter event times these tests were carried out for the log normal gamma weibull double exponential and brownian passage time bpt distributions our results show that a renewal model associated with a time dependent hazard and some kind of predictability of the next large earthquake on a fault is significantly better than a plain time independent poisson model only for four out of the 19 sites examined in this study the lack of regularity in the earthquake occurrence for more than 30 of the examined faults can be explained either by the large uncertainties in the estimate of paleoseismological occurrence times or by physical interaction between neighboring faults

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

regional earthquake likelihood models i first order results abstract the regional earthquake likelihood models relm working group designed a 5 year experiment to forecast the number spatial distribution and magnitude distribution of subsequent target earthquakes defined to be those with magnitude 4 95 m 4 95 in a well defined california testing region included in the experiment specification were the description of the data source the methods for data processing and the proposed evaluation metrics the relm experiment began on 1 january 2006 and involved 17 time invariant forecasts constructed by seismicity modelers by the end of the experiment on 1 january 2011 31 target earthquakes had occurred we analyze the experiment outcome by applying the proposed consistency tests based on likelihood measures and additional comparison tests based on a measure of information gain we find that the smoothed seismicity forecast by helmstetter et al 2007 based on m 2 earthquakes since 1981 is the best forecast regardless of whether aftershocks are included in the analysis the relm experiment has helped to clarify ideas about testing that can be applied to more wide ranging earthquake forecasting experiments conducted by the collaboratory for the study of earthquake predictability csep online material figures and tables showing the relm testing region and collection region definitions numerical results associated with the relm experiment and the uncorrected forecast by ebel et al 2007

transverse tectonics in the sikkim himalaya a magnetotelluric study abstract the tectonics of seismically active sikkim himalaya as inferred by numerous seismological studies is distinct from the conventional thrust tectonics proposed for the himalayan collision belt here focal mechanisms of several moderate magnitude earthquakes and composite fault plane solutions of microearthquakes have revealed strike slip motion along faults transverse to the northward convergence direction of the indian plate in the present study we analyze broadband magnetotelluric data of 12 sites located along an approximately n s profile cutting across major geological sub domains of sikkim to test whether magnetotelluric strikes also support such transverse tectonic nature of the region we have performed strike analysis of the data by two decomposition approaches as well as by phase tensor method the study has revealed local variations in the strike directions within the region consistent with the geological and tectonic setup and the presence of transverse tectonic features in the region of main central thrust zone mctz where major axis of phase ellipses align in nnw sse to nw se direction this trend coincides with the one obtained by microseismic data recorded after the september 18 2011 earthquake mw 6 9 magnetotelluric strike analysis thus supports the presence of nnw to nw trending transverse tectonic zone in mctz

dependence of earthquake recurrence times and independence of magnitudes on seismicity history the fulfillment of a scaling law for earthquake recurrence time distributions is a clear indication of the importance of correlations in the structure of seismicity in order to characterize these correlations we measure conditional recurrence time and magnitude distributions for worldwide seismicity as well as for southern california during stationary periods disregarding the spatial structure we conclude that the relevant correlations in seismicity are those of the recurrence time with previous recurrence times and magnitudes in the latter case the conditional distribution verifies a scaling relation depending on the difference between the magnitudes of the two events defining the recurrence time in contrast with our present resolution magnitude seems to be independent on the history contained in the seismic catalogs except perhaps for southern california for very short time scales less than about 30 min for the magnitude ranges analyzed

segmentation and supercycles a catalog of earthquake rupture patterns from the sumatran sunda megathrust and other well studied faults worldwide abstract after more than 100 years of earthquake research earthquake forecasting which relies on knowledge of past fault rupture patterns has become the foundation for societal defense against seismic natural disasters a concept that has come into focus more recently is that rupture segmentation and cyclicity can be complex and that a characteristic earthquake model is too simple to adequately describe much of fault behavior nevertheless recognizable patterns in earthquake recurrence emerge from long high resolution spatially distributed chronologies researchers now seek to discover the maximum minimum and typical rupture areas the distribution variability and spatial applicability of recurrence intervals and patterns of earthquake clustering in space and time the term supercycle has been used to describe repeating longer periods of elastic strain accumulation and release that involve multiple fault ruptures however this term has become very broadly applied lumping together several distinct phenomena that likely have disparate underlying causes we divide earthquake cycle behavior into four major classes that have different implications for seismic hazard and fault mechanics 1 quasi periodic similar ruptures 2 clustered similar ruptures 3 clustered complementary ruptures rupture cascades and 4 superimposed cycles segmentation is likewise an ambiguous term we identify master segments and asperities as defined by barriers to fault rupture these barriers may be persistent rarely or never traversed frequent occasionally traversed or ephemeral changing location from cycle to cycle we compile a catalog of the historical and paleoseismic evidence that currently exists for each of these types of behavior on major well studied faults worldwide due to the unique level of paleoseismic and paleogeodetic detail provided by the coral microatoll technique the sumatran sunda megathrust provides one of the most complete records over multiple earthquake rupture cycles long historical records of earthquakes along the south american and japanese subduction zones are also vital contributors to our catalog along with additional data compiled from subduction zones in cascadia alaska and middle america as well as the north anatolian and dead sea strike slip faults in the middle east we find that persistent and frequent barriers rupture cascades superimposed cycles and quasi periodic similar ruptures are common features of most major faults clustered similar ruptures do not appear to be common but broad overlap zones between neighboring segments do occur barrier regions accommodate slip through reduced interseismic coupling slow slip events and or smaller more localized ruptures and are frequently associated with structural features such as subducting seafloor relief or fault trace discontinuities this catalog of observations provides a basis for exploring and modeling root causes of rupture segmentation and cycle behavior we expect that researchers will recognize similar behavior styles on other major faults around the world

centroid moment tensor solutions for january march 1992 abstract centroid moment tensor solutions are presented for 160 earthquakes that occurred during the first quarter of 1992 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward

extensional tectonics and mafic plutons in the ketilidian rapakivi granite suite of south greenland abstract the early proterozoic rapakivi suite in the ketilidian mobile belt of south greenland is bimodal with an abundance of mafic plutons which mingled and hybridised with the rapakivi granites basic rocks lacking signs of hybridisation and with mineralogy and bulk compositions apparently unaffected by proximity to the granites are enriched in large ion lithophile element lile relative to high field strength element hfse and have moderate nb depletion these are characteristics common to basic rocks found in back arc basins this tectono magmatic environment supports a model for the late ketilidian of crustal extension probably caused by slab roll back and is in keeping with the low pressure high temperature metamorphic conditions which prevailed when the rapakivi suite was emplaced nd and sr isotopes confirm the juvenile character of the ketilidian crust and rapakivi granites hybrid mafic rocks have low end compared to depleted mantle while apparently unhybridised examples have also undergone some isotopic modification

detrital zircon age constraints on the provenance of sandstones on hatton bank and edoras bank ne atlantic abstract u pb dating of detrital zircons shows that the provenance of cretaceous palaeogene sandstones on hatton and edoras banks sw rockall plateau comprises magmatic rocks dated at c 1800 ma and c 1750 ma respectively their depositional setting first cycle mineralogy and unimodal detrital zircon populations suggest that these sandstones are of local origin the zircon age data are therefore considered to provide constraints on these poorly understood areas of the rockall plateau the u pb dates are directly comparable with u pb zircon crystallization ages from granitoid rocks reported from the ketilidian belt of southern greenland and from the rhinns complex of western britain hf isotopic data from the edoras bank sample are consistent with derivation from a juvenile palaeoproterozoic block in conjunction with previously reported sm nd t dm model ages from the ketilidian belt rockall bank and the rhinns complex these data extend the known distribution of a large juvenile palaeoproterozoic terrane spanning the southern ne atlantic in contrast hf isotopic data from the hatton bank sample imply a large contribution from archaean crust the zircon population from edoras bank also contains sparse mesoproterozoic grains providing evidence for the presence of volumetrically minor grenville age intrusions in the southern part of the rockall plateau

proposal for a terrane based nomenclature for the lewisian gneiss complex of nw scotland the current nomenclature for the lewisian gneiss complex has evolved from lithological and structural correlations made prior to any dating initial flawed geochronological studies gave some names an apparent chronological standing but as work advanced fitting events into a coherent regional framework became increasingly difficult modern dating studies have shown that the lewisian gneiss complex was progressively assembled from disparate blocks of archaean continental crust and juvenile proterozoic arcs which satisfy the definition of terranes each terrane had its own separate accretionary and metamorphic history followed by a common history once juxtaposed against other terranes based on a new compilation of modern geochronology allied to the many detailed structural and metamorphic studies this paper proposes a new systematic terminology for the lewisian gneiss complex that is more applicable to this new tectonic framework

a model of characteristic earthquakes and its implications for regional seismicity regional seismicity i e that averaged over large enough areas over long enough periods of time has a size frequency relationship the gutenberg richter law which differs from that found for some seismic faults the characteristic earthquake relationship but all seismicity comes in the end from active faults so the question arises of how one seismicity pattern could emerge from the other the recently introduced minimalist model of vazquez prada et al of characteristic earthquakes provides a simple representation of the seismicity originating from a single fault here we show that a characteristic earthquake relationship together with a fractal distribution of fault lengths can accurately describe the total seismicity produced in a region the resulting earthquake catalogue accounts for the addition of both all the characteristic and all the non characteristic events triggered in the faults the global accumulated size frequency relationship strongly depends on the fault length fractal exponent and for fractal exponents close to 2 correctly describes a gutenberg richter distribution with a b exponent compatible with real seismicity

comparing foreshock characteristics and foreshock forecasting in observed and simulated earthquake catalogs in this paper we compare the empirical results regarding foreshocks obtained from the japan data with results for synthetic catalogs in order to clarify whether or not the corresponding results are consistent with the description of the seismicity by a superposition of background activity and epidemic type aftershock sequence etas models this question is important because it is still controversially discussed whether the nucleation process of large earthquakes is driven by seismically cascading etas type or by aseismic accelerating processes to explore the foreshock characteristics we first applied the same clustering algorithms to real and synthetic catalogs and analyzed the temporal spatial and magnitude distributions of the selected foreshocks most properties are qualitatively the same in the real data and in synthetic catalogs however we find some quantitative differences particularly in the temporal acceleration spatial convergence and magnitude dependence which also depend on the assumed synthetic catalogs furthermore we calculated forecast scores based on a single link cluster algorithm which could be appropriate for real time applications we find that the japan meteorological agency catalog yields higher scores than all synthetic catalogs and that the etas models having the same magnitude sequence as the original catalog performs better more close to the reality than etas models with randomly picked magnitudes we also find that the etas model that takes account of the triggering effect by small earthquakes below threshold magnitude performs more closely to the reality

anisotropy and phase splits in magnetotellurics abstract several recent papers suggesting that the electrical conductivity of the lower crust and upper mantle are anisotropic have been based upon magnetotelluric mt observations of phase splits the mt analogue of shear wave splitting the emphasis on the phase rather than the amplitude response results from the distorting effect of conductivity variations in the overlying crust these variations distort the amplitude response from deeper levels and make inferences based on the amplitude difficult at the long periods needed to probe the conductivity at upper mantle depths the mt phase response a tensor is negligibly affected by small scale conductivity variations in the overlying crust however the mt phase response of a half space with a uniform but anisotropic conductivity is independent of polarization direction and no phase split occurs using simple anisotropic layered models we demonstrate that a phase split is produced by the conductivity change at the interface between the isotropic and anisotropic layers the maximum phase difference reflecting the conductivity contrast gradient between the principal conductivities of the anisotropic layer and the isotropic layer s conductivity in the general case where none of the principal axes of the anisotropic conductivity layer lie in the plane of the surface the orientation at which the maximum phase difference occurs i e the principal axis of the phase tensor is determined by the horizontal projection of conductivity tensor s ellipsoid in such cases the orientation of the maximum phase split will not be aligned parallel to any of the conductivity tensor s principal axes mt phase splits are a consequence of spatial differences or gradients in conductivity not the intrinsic bulk properties of the conductivity tensor itself and in this respect are fundamentally different from shear wave splitting

double branching model to forecast the next m 5 5 earthquakes in italy abstract the purpose of this work is to set up a new forecasting model named double branching for large earthquakes in italy the model is time dependent since it assumes that each earthquake can generate or is correlated to other earthquakes through different physical mechanisms in a recent paper marzocchi w lombardi a m 2008 a double branching model for earthquake occurrence j geophys res 113 b08317 doi 10 1029 2007jb005472 we have shown that the model applied to two worldwide catalogs in different time magnitude windows shows a good fit to the data and its earthquake forecasting performances are superior to what is obtained by the etas single branching model and by the poisson models remarkably the model can be tested in a forward perspective which is the most straightforward way to evaluate the reliability of any forecasting model here we apply this model to the italian historical seismicity of the last four centuries with magnitude mw 5 5 this application shows that the time dependent features are comparable to what observed in other applications for different time space magnitude window moreover the comparison of the forecasting capability of the double branching model and of a spatially variable stationary poisson process used in italy for seismic hazard assessment shows that the former has significantly better performances finally we provide some probability maps for different temporal windows

the longer it has been since the last earthquake the longer the expected time till the next we adopt a iognormal distribution for earthquake interval times and we use a locally determined rather than a generic coefficient of variation to estimate the probability of occurrence of characteristic earthquakes we extend previous methods in two ways first we account for the aseismic period since the last event the seismic drought in updating the parameter estimates second in calculating the earthquake probability we allow for uncertainties in the mean recurrence time and its variance by averaging over their likelihood both extensions can strongly influence the calculated earthquake probabilities especially for long droughts in regions with few documented earthquakes as time passes the recurrence time and variance estimates increase if no additional events occur leading eventually to an affirmative answer to the question in the title the earthquake risk estimate begins to drop when the drought exceeds the estimated recurrence time for the parkfield area of california the probability of a magnitude 6 event in the next 5 years is about 34 per cent much lower than previous estimates furthermore the estimated 5 year probability will decrease with every uneventful year after 1988 for the coachella valley segment of the san andreas fault the uncertainties are large and we estimate the probability of a large event in the next 30 years to be 9 per cent again much smaller than previous estimates on the mojave pallett creek segment the catalog includes 10 events and the present drought is just approaching the recurrence interval so the estimated risk is revised very little by our methods

the ml 5 3 epagny french alps earthquake of 1996 july 15 a long awaited event on the vuache fault the ml 5 3 epagny earthquake that occurred on 1996 july 15 in the vicinity of annecy french alps was the strongest event to shake southeastern france in the last 34 years moderate to serious damage in the annecy area is consistent with msk intensities of vii viii this earthquake occurred on the vuache fault a geologically well known morphologically clear nw se trending strike slip fault that links the southern jura mountains with the northern subalpine chains the hypocentre was located in mesozoic limestones at shallow depths 1 3 km the focal mechanism indicates left lateral strike slip motion on a n136 e striking plane dipping 70 to the ne abundant field evidence was gathered in the days following the main shock several hundred aftershocks were recorded thanks to the rapid installation of a 16 station seismic network all aftershocks occurred along the southernmost segment of the vuache fault defining a 5 km long 3 5 km deep n130 e striking rupture zone dipping 73 to the ne the fault plane solutions of 60 aftershocks were found to be consistent with left lateral slip on nw se striking planes at the se tip of the aftershock zone we found ground cracks parallel to the fault close to the annecy meythet airport runway at the nw tip near bromines we observed left lateral displacement of concrete walls in a building we also noticed flow changes in two springs close to that locality geodetic levelling across the fault revealed about 1 cm of uplift for the region north of the fault the recording of aftershocks with a six station accelerometric network showed that lacustrine deposits locally amplified the ground motion up to eight times which explains how this moderate magnitude shock could cause such heavy damage historical records draw attention to the central segment of the vuache fault which has been locked for at least 200 years situated nw of the 1996 aftershock zone between the mandallaz and vuache mountains this segment forms a 12 km long potential seismic gap where other m5 events or one single m6 event might occur

evidence for an early proterozoic crustal province in the north atlantic region published sm nd data for the ketilidian belt of greenland the rockall bank in the north atlantic and the islay inishtrahull block of the british isles are used to suggest the existence of a single early proterozoic crustal province in the north atlantic region with a crustal formation age of c 1 96 ga the three sub provinces also have similar metamorphic histories as documented by sr and pb isotope data they probably represent one or more island arcs which were accreted to the laurentian craton 100 ma later in the 1 85 to 1 75 ga ketilidian laxfordian orogeny a line of suture between the archaean craton and early proterozoic accreted terranes is tentatively proposed

earthquake statistics at parkfield 2 probabilistic forecasting and testing construct two probabilistic forecasts h 1 with a spatially varying b value and h 2 with a uniform b value and test these hypotheses against each other both hypotheses use a spatially varying seismicity level a value determined from past seismicity we used a range of sampling parameters magnitude threshold cell size etc to assure robust results we found that in most of the tests hypothesis h 1 showed a higher likelihood than h 2 although both are a poor approximation to the seismicity data the most positive results for h 1 are obtained for testing magnitude ranges down to m 1 5 and with sampling radii as defined in paper 1 as appropriate for parkfield the superior performance of h 1 suggests that spatially varying b values should be considered in earthquake forecasts index terms 7215 seismology earthquake parameters 7223 seismology seismic hazard assessment and prediction 7230 seismology seismicity and seismotectonics keywords earthquake statistics probabilistic forecasting parkfield

seismic activity at the mct in sikkim himalaya abstract a microearthquake survey in the sikkim himalaya raised a question whether the north south segment of the main central thrust mct in this part of the himalaya is seismically active fault plane solution of a cluster of events occurred below this segment of the mct shows right lateral strike slip motion the seismic observations and the geological evidences suggest that a nne ssw trending strike slip fault beneath this segment caused right lateral movement on the mct and is seismically active

noncharacteristic behavior and complex recurrence of large subduction zone earthquakes the last few years have been remarkable with respect to the number of large underthrusting earthquakes in subduction zones that reruptured plate boundary segments that failed in previous great events availability of modern seismic data for two consecutive large earthquakes rupturing the same portion of the plate interface provides the opportunity to compare the spatial distribution of moment release for both events such comparisons have been made for the plate boundary segments that failed in 1 the 1957 mw 8 6 1986 mw 8 0 and 1996 mw 7 9 aleutian islands earthquakes 2 the 1963 mw 8 5 and 1995 mw 7 9 kuril islands earthquakes 3 the 1971 mw 8 0 and 1995 mw 7 7 solomon islands earthquakes and 4 the 1968 mw 8 2 and 1994 mw 7 7 northern honshu earthquakes the spatial distribution of moment release for all four of the initial great earthquakes and two of the repeat events has been determined in previous studies here slip distributions for the three most recent events are determined from inversion of source time functions derived by empirical greens function analysis of long period surface waves and broadband body waves comparisons of the spatial distribution of moment release for sequential earthquake ruptures reveal considerable differences in the pattern of recurrent fault slip the 1994 northern honshu and 1995 solomon islands earthquakes primarily fill in areas of slip deficit left by their preceding events rather than rerupture identical asperities the 1995 kuril islands and the 1996 aleutian islands earthquakes both rerupture portions of an asperity distribution defined by preceding events but with variable amounts of slip this study provides the first direct evidence that recurrence of large circum pacific plate boundary events is more complex than repeat rupture of dominant asperities recurrent fault slip for the four plate boundary segments studied does not support characteristic slip models either where failure on an entire fault segment occurs repeatedly in events with nearly identical rupture lengths locations and slip magnitudes or where failure of individual asperities occurs with identical slip functions through consecutive earthquake cycles these sequential slip patterns are not consistent with physical models of earthquake rupture where slip complexity is exclusively controlled by invariant geometric and or material heterogeneity but suggest that dynamic considerations are also important

seismotectonics of the himalayan collision zone geometry of the underthrusting indian plate beneath the himalaya fault plane solutions and well determined focal depths of medium sized earthquakes topography and landsat imagery in conjunction with seismicity maps cross sections and available geological information are used to investigate the present tectonics of the himalayan continental collision zone most of the accurately located epicenters of events along the himalayan arc 78 e 95 e that occurred between 1961 and 1981 are concentrated in a narrow zone about 50 km wide lying between the northerly dipping main boundary mbt and main central mct thrusts most of these events are located just south of the mct though the epicenters of the events are in general well located their depths as determined by teleseismic travel time data are very unreliable events with accurately determined depths obtained from identification of surface reflected phases define a simple planar zone from about 10 km and 20 km depth with an apparent dip of about 15 this result is all the more remarkable considering that the events used were located along about an 1800 km length of the himalyan arc except for one all available focal mechanisms of events within this zone indicate shallow 30 north dipping thrusts this shallow north dipping zone apparently defines a part of the detachment that separates the underthrusting indian plate from the lesser himalayan crustal block the spatial extent and the geometry of this interplate thrust zone strongly indicate that the mbt and nearby subsidiary surface and blind thrusts rather than the mct are currently the most active structures of the himalayan arc we suggest that the great himalayan earthquakes m 8 occur along the same detachment surface as defined by the thrust type medium sized events events located to the south of the mbt and beneath the ganges foredeep show normal faulting with t axes perpendicular to the himalayan trend the above results suggest that the indian continental plate is underthrusting the himalayan crustal blocks in a relatively coherent and simple geometry and that this geometry is not much different from that observed along oceanic subduction zones the november 19 1980 earthquake that occurred near the mct near 88 5 e shows a predominantly strike slip focal mechanism one of the nodal planes of this mechanism is transverse to the himalayan structural grain and moreover this plane has a trend similar to that of the recently mapped yadong gulu rift in the tethyan himalaya and in southern tibet just northeast of the earthquake we interpret this predominantly left lateral strike slip mechanism to indicate a possible genetic relationship between transverse structural features in the underthrusting indian plate the kishangang basement fault and the upper himalayan blocks and tibet

the structure of the rockall trough from seismic refraction and wide angle reflection measurements there are few detailed descriptions of the deep crustal structure of failed cratonic rifts and passive margins despite their import ance in constraining the variety of structural models invoked to account for their common structural symmetry or gross half graben form1 3 such deep crustal structure profiles also have considerable value in defining the continent ocean boundary con straining plate reconstructions and determining the overall setting of sedimentary basin development the rockall trough in the north atlantic ocean is a sinuous elongate bathymetric depression 200 km wide and more than 2 000 m deep lying between rockall plateau and the british isles and the structure nature and age of its underlying crust are disputed in the absence of deep crustal structure profiles the presence of oceanic crust has been assumed because the trough has to be accommodated in reconstructions of the north atlantic although stretched continental crust is equally plausible the nature of the crust is important for the precise reconstruction of the late jurassic early cretaceous plate history and setting of sedimentary basins of the north atlantic4 8 the nature of the crust beneath the trough as well as the structure thickness and composition of the sedimentary cover is also relevant to oil exploration here we report the first observations of deep crustal structure across the rockall trough and its margins from seismic refraction and wide angle reflection profiles our results show that the northern rockall trough is underlain by highly stretched continental crust and not by oceanic crust as previously postulated

detrital zircon age constraints on basement history on the margins of the northern rockall basin detrital zircon dating has proven to be an effective way to constrain ages of submerged basement terranes on the margins of the northern rockall basin a region where direct evidence of crustal affinities is scarce or absent zircons have been dated from sandstones of palaeocene oligocene age known to have been derived from the east hebridean platform and west rockall and george bligh highs the results show that the hebridean platform is a westward extension of the lewisian complex with archaean and palaeoproterozoic ages that can be directly correlated with events identified in the outer hebrides and northwest scotland the detrital zircons derived from the hebridean platform also provide evidence for a mesoproterozoic thermal event and two phases of intrusions in the palaeozoic the rockall high consists of a palaeoproterozoic terrane dated as c 1760 1800 ma similar to ages previously determined from both basement samples and detrital sediment the data also provide evidence for the subsequent intrusion of alkaline igneous rocks in the palaeocene eocene the george bligh high represents an archaean terrane heavily affected by palaeoproterozoic tectonothermal events and was also the site of intrusion of alkaline igneous rocks in the palaeocene

age and crustal evolution of crystalline basement in western ireland and rockall 1department of geology university college dublin belfield dublin 4 ireland 2 royal ontario museum toronto canada 3 department of mineral resources engineering university of nottingham nottingham ng7 2rd uk 4 british geological survey keyworth nottingham ng12 5gg uk

geochemical and isotopic constraints on the nature and age of basement rocks from rockall bank ne atlantic an isotopic and geochemical reappraisal of samples from rockall bank ne atlantic indicates that the granulites and granites present on the bank have little anity with the lewisian of nw scotland with which they have been previously associated new pb rb sr and sm nd data together with existing k ar data indicate that the rocks formed at about 1625 ma although this is contemporaneous with late laxfordian events in nw scotland the high model p value of 8 03 indicates that the rocks were not derived by metamorphic reworking of ancient lewisian crust but largely represent pristine mantle contributions at this time in this sense the rockall terrane is comparable with the islay terrane which has a model p value of 7 9 but is apparently somewhat older c 1800ma the rockall basement rocks therefore represent a pre viously unrecognized crust formation event in the north atlantic region and reconstructions of proterozoic geology will need to take into account the presence of this crustal block of predominantly juvenile mantle derived material the rockall area may also be considered a likely source for the torridonian sediments of nw scotland our knowledge of the geology of the rockall plateau ne atlantic fig 1 has not advanced significantly since the review published by roberts 1975 subsequent work on the eastern ne atlantic area has largely concentrated on the development of the rockall trough which marks the eastern limit of the plateau as summarized by smythe 1989 and on the development of the volcanic passive margin that marks the

are earthquakes predictable summary the answer to the above question depends on the definition of earthquake prediction we discuss several definitions and possible classifications of earthquake prediction methods we also consider various measures of prediction efficiency review several recent examples of earthquake prediction and describe the methods that can be used to verify prediction schemes we conclude that an empirical search for earthquake precursors that forecast the size of an impending earthquake has been fruitless despite considerable effort in several countries no statistically rigorous validation of proposed precursory phenomena is available therefore reported cases of precursors can be explained by random noise or by chance coincidence we present evidence that earthquakes are non linear chaotic scale invariant phenomena the most probable consequence of earthquake self similarity is a lack of earthquake predictability as popularly defined that is a forecast of a specific individual earthquake many small earthquakes occur throughout any seismic zone demonstrating that the critical conditions for earthquake nucleation are satisfied almost everywhere apparently any small shock can grow into a large event thus it is likely that an earthquake has no preparatory stage this sceptical view of current earthquake prediction efforts should not be interpreted as a statement that any further attempts to mitigate the destructive effects of earthquakes are futile the seismic moment conservation principle when combined with geodetic deformation data offers a new way to evaluate the seismic hazard not only for tectonic plate boundaries but also for areas of low seismicity that is the interiors of continents earthquake clustering with a power law temporal decay omori s law can be used to estimate the rate of future earthquake ocurrence realtime seismology can facilitate relief efforts after large earthquakes and eventually provide an immediate warning of severe shaking a few seconds or tens of seconds before the shaking starts

discussion a unifying model for the torridon group early neoproterozoic nw scotland product of post grenvillian extensional collapse by ge williams and j foden the torridonian succession in nw scotland is a well exposed sequence of sedimentary rocks that record the early neoproterozoic geological evolution of laurentia an excellent review by stewart 2002 summarised the observations on the three main torridonian units the stoer sleat and torridon groups the torridon group deposited between 1000 950 ma was initially interpreted as a rift basin stewart 1982 and williams 2001 but a number of studies rainbird et al 2001 kinnaird et al 2007 and krabbendam et al 2008 have now concluded that it represents a foreland basin positioned in front of the grenville orogen 1200 960 ma in a recent paper in earth science reviews williams and foden 2011 propose instead that the torridon group was deposited in an extensional collapse basin we question this conclusion and take this opportunity to highlight aspects of their new interpretation that we find equivocal

seismic moment distribution revisited ii moment conservation principle summary we compare the tectonic rate with earthquake data using several theoretical distributions to approximate the seismic moment frequency relation we derive formulae to estimate parameters of the seismic moment distributions by comparing the earthquake occurrence rate with tectonic strain we analyse the tectonic moment rate and the earthquake moment distribution for several types of tectonic environments including subduction zones plate bounding transform faults and deforming continental regions in this analysis we use finer subdivisions of tectonic regions to infer whether earthquake size distribution properties established previously for large provinces flinn engdahl seismic regions could be applied to smaller zones extending over a few hundred kilometres although the shortness of the available earthquake catalogues makes our results less reliable several conclusions can be drawn from the analysis the universality of the parameter the slope of the moment frequency relation is reasonably well confirmed for all of these tectonic regions and their subdivisions in each region we estimate the strain rate or relative plate motion from a plate tectonic model active fault data or geodetic data according to the moment frequency relation the ratio of the tectonic moment rate to the earthquake rate depends on the value the corner magnitude mc and the effective seismogenic thickness we find that this ratio does not vary systematically with the relative plate velocity the ratio of parallel to perpendicular plate motion time since the last major earthquake and the length of fault zone segments established by previous earthquake history we obtain similar results for the western united states and southeast asia the corner magnitude is approximately equal to that for the circum pacific rim and there is no systematic dependence of the mc parameter on a geographic region or strain rate assuming the commonly accepted values for seismogenic thickness elastic modulus and 100 per cent seismic coupling the corner magnitude values for plate boundary zones and continental areas are 8 3 8 8 i e similar to those values obtained by statistical analysis

statistical aspects of parkfield earthquake sequence and parkfield prediction experiment abstract this note discusses three interconnected statistical problems concerning the parkfield sequence of moderate earthquakes and the parkfield prediction experiment a is it possible that the quasi periodic parkfield sequence of characteristic earthquakes is no uncommon specific phenomenon the research hypothesis but can be explained by a preferential selection from available earthquake catalogs to this end we formulate the null hypothesis earthquakes occur according to the poisson process in time and their size follows the gutenberg richter relation we test whether the null hypothesis can be rejected as an explanation for the parkfield sequence b if the null hypothesis cannot be refuted what is the probability of magnitude m 6 earthquake occurrence in the parkfield region c the direct goal of the parkfield experiment is the registration of precursory phenomena prior to a m6 earthquake however in the absence of the characteristic earthquake can the experiment resolve which of the two competing hypotheses is true in a reasonable time statistical analysis is hindered by an insufficiently rigorous definition of the research model and inadequate or ambiguous data however we show that the null hypothesis cannot be decisively rejected the quasi periodic pattern of intermediate size earthquakes in the parkfield area is a statistical event likely to occur by chance if it has been preferentially selected from available earthquake catalogs the observed magnitude frequency curves for small and intermediate earthquakes in the parkfield area agree with the theoretical distribution computed on the basis of a modified gutenberg richter law gamma distribution using deformation rates for the san andreas fault we show that the size distribution of the parkfield characteristic earthquakes can also be attributed to selection bias according to the null hypothesis the yearly probability of a m 6 earthquake originating in the parkfield area is less than 1 signifying that several more decades of observation may be needed before the expected event occurs by its design the parkfield experiment cannot be expected to yield statistically significant conclusions on the validity of the research hypothesis for many decades

moment tensor solutions estimated using optimal filter theory global seismicity 1990 moment tensor solutions estimated using optimal filter theory are listed for 114 moderate to large size earthquakes occurring during 1990

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

comparison of characteristic and gutenberg richter models for time dependent m 7 9 earthquake probability in the nankai tokai subduction zone japan summary earthquake forecasts are usually underinformed and can be plagued by uncertainty in terms of the most appropriate model and parameter values used in that model in this paper we explore the application of two different models to the same seismogenic area the first is a renewal model based on the characteristic earthquake hypothesis that uses historical palaeoseismic recurrence times and fixed rupture geometries the hazard rate is modified by the coulomb static stress change caused by nearby earthquakes that occurred since the latest characteristic earthquake the second model is a very simple earthquake simulator based on plate motion or fault slip rates and adoption of a gutenberg richter magnitude frequency distribution this information is commonly available even if historical and palaeoseismic recurrence data are lacking the intention is to develop and assess a simulator that has a very limited parameter set that could be used to calculate earthquake rates in settings that are not as rich with observations of large earthquake recurrence behaviour as the nankai trough we find that the use of convergence rate as a primary constraint allows the simulator to replicate much of the spatial distribution of observed segmented rupture rates along the nankai tonankai and tokai subduction zones although we note rate differences between the two forecast methods in the tokai zone we also see enough similarities between simulations and observations to suggest that very simple earthquake rupture simulations based on empirical data and fundamental earthquake laws could be useful forecast tools in information poor settings

what can physical source models tell us about the recurrence time of earthquakes abstract earthquake prediction no matter what the timescale has been and continues to be a contentious subject and it is indubitably a prominent challenge for modern seismology and earthquake physics indeed few natural events can have the catastrophic consequences of earthquakes earthquakes today account for about 60 of natural fatalities a physical description of an earthquake represents an amenable approach to the prediction but it suffers of some limitations basically due to the notorious ignorance about the initial state of a given fault and about the physical law controlling its traction evolution independent on those intrinsic epistemic limitations the concept of the earthquake recurrence based upon the idea of the cyclic or characteristic earthquake has been often invoked to describe and thus to predict subsequent instability events on a seismogenic structure in this paper by using the simplest analog fault model the one degree of freedom mass spring system we quantitatively show that the concepts of the recurrence time and the earthquake cycle have limitations even making them meaningless we will discuss in a compendious synopsis all the possible physical mechanisms which can dramatically affect the recurrence time our conclusions emphasize again that the competing mechanisms potentially occurring during faulting even in the simplest and idealized condition of an isolated fault can significantly complicate the regular cyclicity of earthquakes predicted by the analog fault system these conclusions can contribute to the debate about the role of the physical modeling of earthquakes in the contest of seismic hazard assessment

assessment of source probabilities for potential tsunamis affecting the u s atlantic coast abstract estimating the likelihood of tsunamis occurring along the u s atlantic coast critically depends on knowledge of tsunami source probability we review available information on both earthquake and landslide probabilities from potential sources that could generate local and transoceanic tsunamis estimating source probability includes defining both size and recurrence distributions for earthquakes and landslides for the former distribution source sizes are often distributed according to a truncated or tapered power law relationship for the latter distribution sources are often assumed to occur in time according to a poisson process simplifying the way tsunami probabilities from individual sources can be aggregated for the u s atlantic coast earthquake tsunami sources primarily occur at transoceanic distances along plate boundary faults probabilities for these sources are constrained from previous statistical studies of global seismicity for similar plate boundary types in contrast there is presently little information constraining landslide probabilities that may generate local tsunamis though there is significant uncertainty in tsunami source probabilities for the atlantic results from this study yield a comparative analysis of tsunami source recurrence rates that can form the basis for future probabilistic analyses

application of a modified pattern informatics method to forecasting the locations of future large earthquakes in the central japan we propose a modification of the pattern informatics pi method that has been developed for forecasting the locations of future large earthquakes this forecast is based on analyzing the space time patterns of past earthquakes to find possible locations where future large earthquakes are expected to occur a characteristic of our modification is that the effect of errors in the locations of past earthquakes on the output forecast is reduced we apply the modified and original methods to seismicity in the central part of japan and compared the forecast performances we also invoke the relative intensity ri of seismic activity and randomized catalogs to constitute null hypotheses we do statistical tests using the molchan and relative operating characteristic roc diagrams and the log likelihoods and show that the forecast for using the modified pi method is generally better than the competing original pi forecast and the forecasts from the null hypotheses using the bootstrap technique with monte carlo simulations we further confirm that earthquake sequences simulated based on the modified pi forecast can be statistically the same as the real earthquake sequence so that the forecast is acceptable the main and innovative science in this paper is the modification of the pi method and the demonstration of its applicability showing a considerable promise as an intermediate term earthquake forecasting tool

unusually large tsunamis frequent a currently creeping part of the aleutian megathrust current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust here we report geological evidence for large tsunamis occurring on average every 300 340 years near the source areas of the 1946 and 1957 aleutian tsunamis these areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate that the megathrust is currently creeping at sedanka island evidence for large tsunamis includes six sand sheets that blanket a lowland facing the pacific ocean rise to 15 m above mean sea level contain marine diatoms cap terraces adjoin evidence for scour and date from the past 1700 years the youngest sheet and modern drift logs found as far as 800 m inland and 18 m elevation likely record the 1957 tsunami previously unrecognized tsunami sources coexist with a presently creeping megathrust along this part of the aleutian subduction zone

the structure and subsidence of rockall trough from two ship seismic experiments coincident multichannel seismic reflection and refraction profiles acquired northwest of britain during a two ship seismic experiment in the southern rockall trough provide evidence for a thin 6 km syn rift crust below rockall trough the variation of seismic velocity with depth is consistent with either oceanic crust similar to that found in other parts of the north atlantic or with thinned continental crust heavily intruded by syn rift igneous rocks the syn rift crust beneath rockall trough is now buried by nearly 5 km of sediments that are intruded by tertiary volcanics varying in extent from isolated sills to a large sill complex extending 100 km laterally the basement imaged on seismic profiles exhibits a band of subhorizontal reflectors that extend laterally over distances of up to 40 km which they interpret as sediments intercalated with submarine lava flow generated during the opening of the trough estimates of stretching from crustal thinning and from subsidence indicate that rockall trough has undergone extensive rifting beta 6 upwelling asthenosphere beneath the thinned lithosphere generated at least 1 3 km thickness of melt as it decompressed the molten rock rose upward from the mantle until it was in part extruded as lava flows and in partmore intruded into the crust less

currently active regions of decelerating accelerating seismic strain in central asia 1 accelerating preshock seismic strain in a broad critical region and decelerating preshock seismic strain in a narrower seismogenic region constitute a model for intermediate term prediction of strong main shocks an effort is made in the present work for a forward test of the decelerating accelerating seismic strain d as model by identifying such patterns and estimating the corresponding probably ensuing strong main shocks m 7 0 in central asia 20 n 45 n 42 e 105 e five such patterns have been identified and the origin time magnitude and epicentral geographic coordinates of each of the corresponding main shocks have been estimated predicted model uncertainties of the estimated time magnitude and space parameters of these probably ensuing main shocks as well as appropriate statistical tests against a standard gutenberg richter seismicity distribution are also presented to allow a future objective evaluation of the model s efficiency for intermediate term earthquake prediction

why earthquake hazard maps often fail and what to do about it abstract the 2011 tohoku earthquake is another striking example after the 2008 wenchuan and 2010 haiti earthquakes of highly destructive earthquakes that occurred in areas predicted by earthquake hazard maps to be relatively safe here we examine what went wrong for tohoku and how this failure illustrates limitations of earthquake hazard mapping we use examples from several seismic regions to show that earthquake occurrence is typically more complicated than the models on which hazard maps are based and that the available history of seismicity is almost always too short to reliably establish the spatiotemporal pattern of large earthquake occurrence as a result key aspects of hazard maps often depend on poorly constrained parameters whose values are chosen based on the mapmakers preconceptions when these are incorrect maps do poorly this situation will improve at best slowly owing to our limited understanding of earthquake processes however because hazard mapping has become widely accepted and used to make major decisions we suggest two changes to improve current practices first the uncertainties in hazard map predictions should be assessed and clearly communicated to potential users recognizing the uncertainties would enable users to decide how much credence to place in the maps and make them more useful in formulating cost effective hazard mitigation policies second hazard maps should undergo rigorous and objective testing to compare their predictions to those of null hypotheses including ones based on uniform regional seismicity or hazard such testing which is common and useful in similar fields will show how well maps actually work and hopefully help produce measurable improvements there are likely however limits on how well hazard maps can ever be made because of the intrinsic variability of earthquake processes

earthquake recurrence in nw and central himalaya abstract in this study we compare himalayan seismic moment release estimates derived from strain rate observations with those derived from large historical earthquakes and to this end we use a reassessed catalogue of historical earthquakes from western and central himalaya since the beginning of the 16th century we have computed seismic moment rates within six contiguous segments along the himalayan arc and compared these using kostrov s formula with moment rates computed from recent global strain rate estimates and regional studies while the ratios between strain based moment rate estimates and those inferred from observed seismicity vary significantly between the segments we find on the average consistently larger strain based values by about a factor of two based on seismicity from the last 515 years the moment rate ratio is however significantly reduced when shorter catalogues are used to 1 28 for the last 215 years and to 1 05 for the last 115 years which is an almost perfect match the possible inclusion of afterslip in the model would further improve the 515 year match this is indicating that a significant part of the difference possibly most of it is likely to be caused by incompleteness of the longer earthquake catalogue possibly combined with underestimated magnitudes the difference between geodetic and seismic estimates for the more complete part of the catalogue is smaller than previously reported along the western himalayan frontal thrust in fact the only region where a significant moment rate difference is found in our study is in se himachal pradesh in terms of seismic hazard it is found that the moment rate reduction of about a factor of two when going from 115 to 515 years leads to a reduction in the 475 year pga of about 26 it is also found that using 50 years of usgs seismicity data between 1963 and 2012 leads to a 40 lower hazard as compared to using moment release for the last 115 years

large trench parallel gravity variations predict seismogenic behavior in subduction zones we demonstrate that great earthquakes occur predominantly in regions with a strongly negative trench parallel gravity anomaly tpga whereas regions with strongly positive tpga are relatively aseismic these observations suggest that over time scales up to at least 1 million years spatial variations of seismogenic behavior within a given subduction zone are stationary and linked to the geological structure of the fore arc the correlations we observe are consistent with a model in which spatial variations in frictional properties on the plate interface control trench parellel variations in fore arc topography gravity and seismogenic behavior

the 2004 parkfield earthquake the 1985 prediction and characteristic earthquakes lessons for the future the 1985 prediction of a characteristic magnitude 6 parkfield earth quake was unsuccessful since no significant event occurred in the 95 time window 1985 1993 anywhere near parkfield the magnitude 6 earthquake near parkfield in 2004 failed to satisfy the prediction not just because it was late it also differed in character from the 1985 prediction and was expectable according to a simple null hypothesis furthermore the prediction was too vague in several important respects to meet the accepted definition of an earthquake prediction an event occurring by chance and meeting the general description of the predicted one was reasonably probable the original characteristic earthquake model has failed in comprehensive tests yet it is still widely used modified versions employed in recent official seismic hazard calculations allow for interactions between segments and uncertainties in the parameters with more adjustable parameters the modified versions are harder to falsify the characteristic model as applied at parkfield and elsewhere rests largely on selected data that may be biased because they were taken out of context we discuss implications of the 2004 event for earthquake prediction the characteristic earthquake hypothesis and earthquake occurrence in general

how can one test the seismic gap hypothesis the case of repeated ruptures in the aleutians the test that kagan and jackson 1991 1995 applied to the seismic gap hypothesis did not bring us closer to understanding the generation of large earthquakes on the contrary it led some to the conclusion that the rebound theory of earthquake generation should be rejected we disagree with this point of view and argue that a global test of the simplified gap hypothesis cannot be done because it cannot account for differences in the slip history of fault segments and tectonic differences between separate plate boundaries kagan and jackson did show however that the original gap hypothesis was oversimplified and should be refined we propose that consideration of all the facts including slip history and seismicity patterns in the andreanof islands show that the concept of seismic gaps and the elastic rebound theory are correct for that segment of the plate boundary the coseismic slip in the m w 8 7 earthquake that broke this plate boundary segment in 1957 was only 2 m as published before the repeat earthquake of 1986 m w 8 and thus using a plate convergence rate of 7 3 cm year the return time in this cycle was expected to be less than 30 years unless substantial aseismic creep occurs this supports the time predictable model of mainshock recurrence in addition kisslinger et al 1985 and kisslinger 1986 noticed a seismic quiescence in the subsequent source volume before the 1986 earthquake and attempted to predict it the specific parameters he estimated were not entirely correct although his interpretation of the observed quiescence as a precursor was we conclude that the 1986 m w 8 andreanof earthquake was not an example that disproves the seismic gap hypothesis on the contrary it shows that the hypothesis that plate motions reload plate boundaries after most of the elastic energy is released in great ruptures was correct in this case this suggests that great earthquakes occur preferably in mature gaps we believe the testing of the seismic gap hypothesis by algorithm on a global scale is an example that illustrates that overly simplified tests can lead to erroneous conclusions to make progress in the actual understanding of the physics of the process of great earthquake ruptures one must consider all the facts known for case histories

crustal structure at the se greenland margin from wide angle and normal incidence seismic data abstract results from a seismic refraction and reflection line along the southeast coast of greenland give information on both the precambrian structures on the greenland continent and on the effects of the tertiary breakup of the north atlantic three seismic stations on the greenland coast recorded the airgun shots from a 279 km reflection seismic line approximately 20 km offshore the maximum offset recorded was 313 km the wide angle data show crustal thickness variation from 39 km in the south to 49 km in the north with an 8 to 17 km thick high velocity 7 5 km s layer at the base of the crust interpreted as underplating related to the opening of the north atlantic in the tertiary the boundary between the early proterozoic ketilidian orogen in the south and the archaean block to the north show little variation in seismic velocities and the reflection pattern suggests that the archaean underlies the ketilidian at depth we see no evidence that the julianehab batholith at the boundary between rocks of the ketilidian orogen and the north atlantic block is a deep structure

deformation characteristics of co seismic surface ruptures produced by the 1850 m 7 5 xichang earthquake on the eastern margin of the tibetan plateau the eastern margin of the tibetan plateau is bounded by a n s trending active fault zone including the zemuhe fault which is an important tectonic boundary in studies of continental dynamics and deformation modes here we present the kinematic mechanism and deformation features of co seismic surface ruptures caused by a large historic earthquake that occurred upon the zemuhe fault field investigations and interpretations of aerial photographs reveal a nnw sse trending surface rupture zone less than 100 m wide defined by en echelon fractures mole tracks and fault scarps over a length of 60 km trench excavations and radiocarbon age data confirm that the surface rupture zone was produced by the 1850 m 7 5 xichang earthquake gullies preserved on the youngest alluvial fans and the lowest terrace risers in the area record systematic left lateral offsets of 1 4 6 0 m and vertical offsets of 0 2 0 65 m resulting from the 1850 earthquake topographic and geologic evidence reveals that the spatial distribution of the 1850 co seismic surface rupture was controlled by pre existing geological structures of the zemuhe fault the present results confirm that the zemuhe fault plays an important role as a major strike slip fault in the southeastward motion of the southeastern tibetan plateau and that the southern segment of the zemuhe fault has high seismic potential

the blackstones bank igneous complex geochemistry and crustal context of a submerged tertiary igneous centre in the scottish hebrides the blackstones bank located about 60 km wsw of the isle of mull in western scotland is a submarine plutonic complex in the british tertiary igneous province geochemical and isotopic analysis of gabbros microgabbros and basic dykes shows that the magmas interacted strongly with crustal rocks during their emplacement the isotopic signature of the contaminated tertiary intrusions shows no evidence of any interaction with archaean basement despite the location of the blackstones complex to the west of the great glen fault instead the blackstones rocks have crustal signatures resembling the proterozoic basement and cover rocks of western islay it is therefore inferred that early proterozoic crust extends to the west of the great glen fault at this point on the scottish continental shelf in addition the occurrence of similar isotopic signatures in tertiary igneous rocks east of the loch gruinard fault confirms that early proterozoic basement extends under the grampian block of mainland scotland when combined with published evidence from the rockall bank the new data constrain the location of an archaean proterozoic crustal suture with a wnw trajectory which cuts across the continental shelf of northwest britain

geological implications from geochemical and isotopic studies of upper cretaceous and lower tertiary igneous rocks around the northern rockall trough major trace rare earth element geochemistry and isotopic data have been obtained for offshore igneous rocks from around the northern rockall trough ne atlantic ocean most comprise basalts derived from the sub rockall hebridean asthenospheric mantle but subcontinental lithospheric mantle generated the phono tephrites of rosemary bank and melting of upper crust was responsible for the peraluminous dacites of well 163 6 1a crustal contamination of the lavas around the rockall trough suggests that the lewisian islay rockall bank basement terrane boundary crosses the trough and passes between george bligh and rockall banks basalts representing uncontaminated mantle derived material are scarce but the available data indicate that the cretaceous basalts of rosemary bank and anton dohrn have higher 206 pb 204 pb ratios than the younger palaeocene lavas of rockall bank the hebrides shelf and well 163 6 1a implying significant geographic and or temporal changes in mantle composition

correlating seismicity parameters and subsidence in the tokai region central japan 1 we demonstrate that transients in subsidence rate in the tokai area of central japan correlate with changes in the rate and size distribution of earthquakes three largely independent seismic catalogs cover this region national research institute for earth science and disaster prevention nied japanese meteorological agency jma and japan university network catalog junec comparing seismicity patterns between these three data sets offers a unique opportunity to verify seismicity anomalies based on independent sources a study of data quality magnitude reporting consistency and consistency across the three data sources reveals that the nied data for the period 1981 2002 are best suited for seismicity analysis we spatially and temporally map seismicity rates finding that a significant decrease in the earthquake rate of m 2 0 events coincides with an accelerated subsidence period however this anomaly disappears when including smaller magnitudes in the analysis this relative quiescence of larger events can readily be explained when interpreting the transient in seismicity in the framework of a change in the earthquake size distribution or b value the background b value of about 0 8 increased in the period 1987 5 1989 5 to a value of b 1 2 a highly significant change that can be confirmed in all three data sets the correlation between subsidence and b value change is significant stress tensor inversions of focal mechanism data for the anomalous period show an increase in thrusting type earthquakes while a unique interpretation of the relationship between subsidence and b value is not possible we propose that an increase in the locking stress a slow stick event is consistent with all observations

seismicity based earthquake forecasting techniques ten years of progress abstract earthquake fault systems interact over a broad spectrum of spatial and temporal scales and in recent years studies of the regional seismicity in a variety of regions have produced a number of new techniques for seismicity based earthquake forecasting while a wide variety of physical assumptions and statistical approaches are incorporated into the various methodologies they all endeavor to accurately replicate the statistics and properties of both the historic and instrumental seismic records as a result the last ten years have seen significant progress in the field of intermediate and short term seismicity based earthquake forecasting these include general agreement on the need for prospective testing and successful attempts to standardize both evaluation methods and the appropriate null hypotheses here we differentiate the predominant approaches into models based upon techniques for identifying particular physical processes and those that filter or smooth the seismicity comparison of the methods suggests that while smoothed seismicity models provide improved forecast capability over longer time periods higher probability gain over shorter time periods is achieved with methods that integrate statistical techniques with our knowledge of the physical process such as the epidemic type aftershock sequence etas model or those related to changes in the b value for example in general while both classes of seismicity based forecasts are limited by the relatively short time period available for the instrumental catalog significant advances have been made in our understanding of both the limitations and potential of seismicity based earthquake forecasting there is general agreement that both short term forecasting on the order of days to weeks and longer term forecasting over five to ten year periods is within reach this recent progress serves to illuminate both the critical nature of the different temporal scales intrinsic to the earthquake process and the importance of high quality seismic data for the accurate quantification of time dependent earthquake hazard

predominance of high th u magmatic zircon in brazilian shield sandstones the strong predominance of magmatic th u 0 2 zircon grains in quartz sandstones from 10 locations in the brazilian shield as measured by sensitive high resolution ion microprobe shrimp introduces a strong bias in the tectonic interpretation of source terrains because the metamorphic sources remain undetected in the detrital population zircon grains from many mature and some immature sedimentary terrains show th u ratios 0 2 ratios commonly considered magmatic complemented by the near absence of metamorphic th u ratios 0 1 metamorphic rims on magmatic zircon grains from the brazilian shield are nearly absent from quartz sandstones only being present in shielded young cores of a few crystals high u metamorphic portions of zircon grains are more defective and liable to undergo comminution by abrasion during weathering and transport and they do not remain in the sand fraction ages obtained from detrital zircon in mature sandstones reflect magmatic sources not the full spectrum of orogenic events only less mature sedimentary rocks preserve a full record of orogenic rocks in the source mostly magmatic events were characterized in previous zircon provenance studies brazilian shield detrital zircon may be a proxy for equivalent investigations in other provinces of the world

earthquake potential in and around china estimated from past earthquakes 1 we present an earthquake potential estimate for magnitude 5 4 or larger earthquakes for china the potential is expressed as the rate density or the probability per unit area magnitude and time and it is based on smoothed seismicity we constructed a special earthquake catalog which combines previous catalogs covering different times after deriving regression relationships we estimated moment magnitudes for some events then we used the special catalog for constructing our smoothed seismicity model and testing it retrospectively using maximum likelihood we estimated the completeness threshold the b value and the corner magnitude we adopted a kind of gutenberg richter distribution with modifications at higher magnitude and assumed a uniform b value and upper magnitude limit derived from the special catalog from smoothed seismicity we estimated local a values we have begun a prospective test finding that earthquakes since the beginning of 2000 are quite compatible with the model

the effect of regional borders when using the gutenberg richter model case study western anatolia a probabilistic seismic hazard analysis psha for western anatolia is presented using the gutenberg richter g r frequency magnitude relation since the modeling is sensitive to the location of seismotectonics boundaries to use the information content of the observed earthquake data as a general rule the borders of the affected area are extended in this study the effect of the region s definition on the g r model is debated on the western anatolian region which is one of the most seismically active and rapidly deforming regions of the world throughout the ages calculations are carried out for two subregions and one combined region as a whole using the seismic catalog from 1900 to 2005 the data sets are determined by the region s borders with the parameters computed according to these data sets by the least squares and maximum likelihood methods and then future predictions are estimated via these parameters comparing the results with historical earthquake records most appropriate regional borders for western anatolia are defined and for this new region g r model parameters are obtained

new seismic gap hypothesis five years after we use earthquake data from 1989 1994 to test a forecast by nishenko based on the seismic gap theory we refer to this forecast as the new seismic gap hypothesis because it is the first global forecast based on the seismic gap hypothesis that considers the recurrence time and characteristic earthquake magnitude specific to each plate boundary segment nishenko s forecasts gave probabilities that each of about 100 zones would be filled by characteristic earthquakes during periods of 5 10 and 20 years beginning on the first day of 1989 only the first of these can be tested now we used three tests based on 1 the total number of zones filled by characteristic earthquakes 2 the likelihood that the observed list of filled zones would result from a process with the probabilities specified in nishenko s hypothesis and 3 the likelihood ratio to that of a poissonian null hypothesis the null hypothesis uses a smoothed version of seismicity since 1977 and assumes a gutenberg richter magnitude distribution we used both the harvard centroid moment tensor and the national oceanic and atmospheric administration preliminary determination of epicenters catalogs in our test we also used several different magnitude cutoffs in our tests because nishenko s forecast did not specify a clear relationship between the characteristic earthquake magnitude and the threshold magnitude for a successful prediction using a strict interpretation that only earthquakes equal to or larger than the characteristic magnitude should be counted both catalogs show only two qualifying earthquakes in the entire area covered by the forecast the predicted number is 9 2 and the discrepancy is too large to result from chance at the 99 confidence level the new seismic gap hypothesis predicts too many characteristic earthquakes for three reasons first forecasts were made for some zones specifically because they had two or more earthquakes in the previous centuries biasing the estimated earthquake rate second open intervals before the first event and after the last event are excluded in calculation of recurrence rate third the forecast assumes that all slip in each zone is released in characteristic earthquakes of the same size while in fact considerable slip is released by both smaller and larger earthquakes the observed size distribution of earthquakes is inconsistent with the characteristic hypothesis instead of a deficit of earthquakes above the characteristic limit earthquake numbers are distributed according to the standard gutenberg richter relation by lowering the magnitude threshold for qualifying earthquakes it is possible to reduce the discrepancy between the observed and predicted number of earthquakes to an acceptable level however for every magnitude threshold we tried the new seismic gap model failed the test on the number of filled zones or the likelihood ratio test or both at least at the 95 confidence level

triassic sand supply to the slyne basin offshore western ireland new insights from a multi proxy provenance approach to assess provenance data and derive basin infill models with a higher level of certainty it is vital to understand how minerals used in sedimentary provenance behave in the sedimentary system a multi proxy approach helps ensure rigour in how provenance data are interpreted u pb geochronology of refractory zircon and relatively less stable apatite and pb isotopic analysis of labile k feldspar are employed in this study to reassess the provenance of triassic sandstones in the slyne basin offshore western ireland this approach aims at reducing the potential bias in each method producing a complementary dataset u pb zircon and apatite geochronology yields archean paleoproterozoic ages caledonian ages and previously unrecognized permo triassic ages pb isotopic analysis of k feldspar does not identify the permo triassic as a source the detection of permo triassic aged detritus may suggest that volcanism was more widespread than previously recognized these results support the hypothesis of a triassic drainage divide between the basins offshore western ireland and those onshore britain and in the irish sea sand supply was dominantly from the north with significant input from the flanks of the basin and previously unrecorded sources such as permian aged rocks playing an important role the provenance signal is consistent and homogenized throughout the sampled sequence indicating that the drainage system was long lived supplementary material details of laboratory and sample preparation data tables and summary pie charts for each sample are available at https doi org 10 6084 m9 figshare c 4571096

long term probabilistic forecasting of earthquakes we estimate long term worldwide earthquake probabilities by extrapolating catalogs of seismic moment solutions we base the forecast on correlations of seismic moment tensor solutions the forecast is expressed as a map showing predicted rate densities for earthquake occurrence and for focal mechanism orientation focal mechanisms are used first to smooth seismicity maps to obtain expected hazard maps and then to forecast mechanisms for future earthquakes several types of smoothing kernels are used in space domain we use the 1 distance kernel for the distribution of seismicity around any epicenter the kernel is parameterized using two adjustable parameters maximum distance and directivity distribution of seismicity around an epicenter with regard to the focal mechanism of an earthquake for temporal prediction we use the poisson hypothesis of earthquake temporal behavior we test these forecasts we use the first half of a catalog to smooth seismicity level and the second half of the catalog is used to validate and optimize the prediction to illustrate the technique we use available data in the harvard catalog of seismic moment solutions to evaluate seismicity maps for several seismic regions the method can be used with similar catalogs the technique is completely formal and does not require human operator intervention hence the prediction results can be objectively tested moreover the maps can be used as the poisson null hypothesis for testing by the likelihood method against any other prediction model which shares the same sample space the same zones time window and acceptance criteria

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

non poissonian earthquake occurrence in coupled stress release models and its effect on seismic hazard summary most seismic hazard estimations are based on the assumption of a poisson process for earthquake occurrence even though both observations and models indicate a departure of real seismic sequences from this simplistic assumption instrumental earthquake catalogues show earthquake clustering on regional scales while the elastic rebound theory predicts a periodic recurrence of characteristic earthquakes on longer timescales for individual events recent implementations of time dependent hazard calculations in california and japan are based on quasi periodic recurrences of fault ruptures according to renewal models such as the brownian passage time model however these renewal models neglect earthquake interactions and the dependence on the stressing history which might destroy any regularity of earthquake recurrences in reality to explore this we investigate the coupled stress release model a stochastic version of the elastic rebound hypothesis in particular we are interested in the time variability of the occurrence of large earthquakes and its sensitivity to the occurrence of gutenberg richter type earthquake activity and fault interactions our results show that in general large earthquakes occur quasi periodically in the model the occurrence probability of large earthquakes is strongly decreased shortly after a strong event and becomes constant on longer timescales although possible stress interaction between adjacent fault zones does not affect the recurrence time distributions in each zone significantly it leads to a temporal clustering of events on larger regional scales the non random characteristics especially the quasi periodic behaviour of large earthquakes are even more pronounced if stress changes due to small earthquakes are less important the recurrence time distribution for the largest events is characterized by a coefficient of variation from 0 6 to 0 84 depending on the relative importance of small earthquakes

worldwide doublets of large shallow earthquakes abstract we investigated all the pairs of mw 7 5 shallow earthquakes in the harvard catalog that occurred at a centroid distance of less than 100 km we showed that most of these pairs have similar focal mechanisms because these earthquakes generally should have focal regions in excess of 100 km diameter their rupture zones apparently intersect for all these pairs the time interval is significantly less than the time span needed for plate motion to accumulate the strain released by the first event these observations conflict strongly with quasi periodic recurrence models on which the seismic gap hypothesis is based power law recurrence fits these earthquake ob servations much better introduction many models used to forecast long term seismic hazard are based on the quasi periodic or seismic cycle hypothesis of large earthquake occurrence this hypothesis assumes that the probability of a large earthquake is low after signifi cant release of seismic energy and that danger increases only when tectonic plate motion accumulates strain sufficient for a new strong event several models have been formulated to apply this idea to long term earthquake prediction mccann

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

a comparison of historical and paleoseismicity in a newly formed fault zone and a mature fault zone north canterbury new zealand the timing of large holocene prehistoric earthquakes is determined by dated surface ruptures and landslides at the edge of the australia pacific plate boundary zone in north canterbury new zealand collectively these data indicate two large m 7 earthquakes during the last circa 2500 years within a newly formed zone of hybrid strike slip and thrust faulting herein described as the porter s pass to amberley fault zone ppafz two earlier events during the holocene are also recognized but the data prior to 2500 years are presumed to be incomplete a return period of 1300 2000 years between large earthquakes in the ppafz is consistent with a late holocene slip rate of 3 4 mm yr if each displacement is in the range 4 8 m historical seismicity in the ppafz is characterized by frequent small and moderate magnitude earthquakes and a seismicity rate that is identical to a region surrounding the structurally mature hope fault of the marlborough fault system farther north this is despite an order of magnitude difference in slip rate between the respective fault zones and considerable differences in the recurrence rate of large earthquakes the magnitude frequency distribution in the hope fault region is in accord with the characteristic earthquake model whereas the rate of large earthquakes in the ppafz is approximated but over predicted by the gutenberg richter model the comparison of these two fault zones demonstrates the importance of the structural maturity of the fault zone in relation to seismicity rates inferred from recent historical and paleoseismic data

a mutually consistent seismic hazard source model for southern california abstract a previous attempt to integrate geological geodetic and observed seismicity data into a probabilistic hazard source model predicted a rate of magnitude 6 to 7 earthquakes significantly greater than that observed historically one explanation was that the discrepancy or apparent earthquake deficit is an artifact of the upper magnitude limit built into the model this was controversial however because removing the discrepancy required earthquakes larger than are seen in the geological record and larger than implied from empirical relationships between fault dimension and magnitude although several articles have addressed this issue an alternative integrated source model without an apparent deficit has not yet appeared we present a simple geologically based approach for constructing such a model that agrees well with the historical record and does not invoke any unsubstantiated phenomena the following factors are found to be influential the b value and minimum magnitude applied to gutenberg richter seismicity the percentage of moment released in characteristic earthquakes a round off error in the moment magnitude definition bias due to historical catalog incompleteness careful adherence to the conservation of seismic moment rate uncertainty in magnitude estimates obtained from empirical regressions allowing multi segment ruptures cascades and the time dependence of recurrence rates the previous apparent deficit is shown to have resulted from a combination of these factors none alone caused the problem nor solves it the model presented here is relatively robust with respect to these factors

frequency moment distribution of earthquakes in the aleutian arc a test of the characteristic earthquake model the frequency moment distribution of earthquakes is derived for discrete regions of the entire aleutian arc both for segments which have ruptured in historic times and those regions which have been identified as seismic gaps this distribution is then compared to the moment of the largest event in the respective region or for gaps the largest event which is likely to occur based on a plate kinematic model of accumulated moment data for this study are based upon three data sources instrumental data are utilized for the 18 yr subsequent to the establishment of the world wide standardized seismograph network wwssn data for events of magnitude 7 and greater have been carefully collected and are presumed to be complete for the time period 1899 to present the last data set is comprised of the largest event in each region either an actual earthquake or the moment estimate based on current plate slip rates data were normalized to the recurrence time of the largest event in the respective zone in all cases the data seriously underestimate the largest moment event indicating that a characteristic earthquake model is appropriate for individual fault zones however if the data are combined for the entire arc the largest event is closely predicted this indicates that a b value model may be utilized only for regions in which there is a distribution in the size of earthquake producing faults

testing earthquake forecast hypotheses abstract this paper outlines methodological aspects of the statistical evaluation of earthquake forecast hypotheses the recent debates concerning predictability of earthquakes clearly show how this problem is centred on the difficulty of systematically testing the numerous methodologies that in the years have been proposed and sustained by the supporters of prediction this difficulty starts sometimes from the lack of a quantitative and rigorous definition of the concerned precursor and other times from the lack of continuous observations upon which statistical analyses could be based the application of rigorous statistical methods with the aim of verifying any prediction method requires a univocal definition of the hypothesis or the model characterising the concerned anomaly or precursor so as it can be recognised objectively in any circumstance and by any observer a simple definition of an earthquake forecasting hypothesis could consist of the identification of particular sub volumes of the total time space volume usually named alarm volumes within which the probability of occurrence of strong earthquakes is higher than the average the test of a similar model needs the observation of a sufficient number of past cases upon which to carry out a statistical analysis aimed to determine the rate at which the precursor has been followed success rate or not followed false alarm rate by the target seismic event or the rate at which a target event has been preceded alarm rate or not preceded failure rate by the precursor a valid forecast hypothesis is expected to maximise success and minimise false alarms with regard also to the maximisation of the probability gain some geophysicists prefer a statistical approach such as the bayes criterion based on the computation of the likelihood of an observed realisation of seismic events and on the comparison of the likelihood obtained under different hypotheses this method can be extended as it has recently been the case for models of earthquake clustering to algorithms that allow the computation of the density distribution of the conditional probability of earthquake occurrence in space time and magnitude another approach to assess the validity of an earthquake forecast hypothesis could be that of estimating the total cost that the community has to pay in relation to earthquakes and choosing the model that minimise such cost whatever method is chosen for building up a new hypothesis the final assessment of its validity should be carried out by a test on a new and independent set of observations the implementation of this test could however be problematic for seismicity characterised by long term recurrence

the geology of the uk hatton rockall margin abstract seismic potential field sea bed sample and shallow drilling data have been used to investigate the geology of the uk part of the rockall plateau most of the rockall plateau is underlain by early proterozoic rockall bank islay terrane metamorphic basement although george bligh bank and the north eastern end of hatton bank may be underlain at depth by lewisian rocks the basement crops out on rockall bank but occurs at a much deeper level beneath hatton bank and hatton basin the widespread palaeogene lavas of rockall plateau have been sourced from large central igneous complexes rockall swithin sandastre mammal lyonesse and sandarro local volcanoes and fissures some of the lavas may also have been derived from the incipient rift axis west of hatton bank at the time of continental break up differences in seismic facies allow the extent of the lavas from the large centres to be mapped where the lavas are absent beneath parts of hatton bank either due to non emplacement or subsequent erosion during the cenozoic seismic data image the underlying mesozoic and older rocks here bgs boreholes 99 1 and 99 2a have proved mid cretaceous albian shales and sandstones respectively beneath a thin cenozoic cover the mesozoic and older rocks appear to be quite extensive and are folded and faulted mesozoic strata are not observed on rockall bank in uk waters the post lava cenozoic succession of rockall plateau can be sub divided into three megasequences separated by two unconformities which by analogy with rockall basin have been designated c30 intra late eocene and c10 intra early pliocene the ages can be corroborated by dsdp odp boreholes in the hatton basin the cenozoic succession contains eocene prograding fan sequences contourite deposits on the flanks of the banks and shallow faulting some of which affects the present day sea bed structurally rockall high appears mainly as a large basement block whereas hatton high is more complex exhibiting half grabens inversion structures and reverse fault geometries due to cenozoic tectonism the northern end of hatton high is a large anticline with its axis aligned ene wsw the structural differences between the highs may be due to their locations with rockall high exhibiting fewer tectonic effects due to its more landward intraplate setting further away from plate margin deformation

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

comparison of early aftershock forecasting for the 2008 wenchuan m s 8 0 earthquake the ms8 0 earthquake that occurred in wenchuan sichuan in 2008 provides an important case for the study of operational earthquake forecasting and short term aftershock forecasting of major disaster inducing earthquakes in china this paper focuses on the comparative study of the applicability of the epidemic type aftershock sequence etas model the reasenberg jones r j model and the omi r j model which are widely adopted internationally for short term aftershock forecasting and seismic hazard mitigation strategy research we compare the stability of model parameters and aftershock occurrence rate forecasting and evaluate the effectiveness of forecasting using the n test and t test with multiple time windows the results show that the sequence parameters of the etas model the r j model and the omi r j model tend to stabilize after 15 50 15 50 and 6 00 days following the earthquake respectively and the attenuation of the wenchuan ms8 0 earthquake is rather normal compared to the etas model and the r j model the omi r j model obtain steadier model parameters in a shorter time with significantly smaller parameters porj corj borj and standard deviations among the three models the overall aftershock occurrence rate forecasted by the r j model is the highest followed by the omi r j model while that of the etas model is the lowest n test results show overall forecasting effectiveness of 93 8 80 7 and 97 7 for the etas r j and omi r j models respectively with the etas and omi r j models superior to the r j model and the omi r j model slightly better than the etas model the overall information gain per earthquake calculation results show that the etas model is superior to the omi r j and r j models while the omi r j model is better than the r j model thus the combined use of the etas and omi r j models by focusing on their respective strengths might ensure optimal performance these maneuverable forecasting approaches to short term aftershock model forecasting will play a vital role in efficient post disaster relief emergency management decision making and post disaster reconstruction

why is probabilistic seismic hazard analysis psha still used abstract even though it has never been validated by objective testing probabilistic seismic hazard analysis psha has been widely used for almost 50 years by governments and industry in applications with lives and property hanging in the balance such as deciding safety criteria for nuclear power plants making official national hazard maps developing building code requirements and determining earthquake insurance rates psha rests on assumptions now known to conflict with earthquake physics many damaging earthquakes including the 1988 spitak armenia event and the 2011 tohoku japan event have occurred in regions relatively rated low risk by psha hazard maps no extant method including psha produces reliable estimates of seismic hazard earthquake hazard mitigation should be recognized to be inherently political involving a tradeoff between uncertain costs and uncertain risks earthquake scientists engineers and risk managers can make important contributions to the hard problem of allocating limited resources wisely but government officials and stakeholders must take responsibility for the risks of accidents due to natural events that exceed the adopted safety criteria

a statistical investigation of the earthquake predictions using lurr in terms of the spatial scanning of lurr load unload response ratio we have been predicting the seismic tendency within the next year for the mainland of china from 1995 to 2003 in order to make the quantitative retrospective assessment of lurr method we compare the results with poisson null hypothesis the results show that the prediction by lurr method is much better than poisson hypothesis

evaluation of geodynamic activity of the dead sea transform fault by radon gas concentrations twelve radon lines of dosimeters detectors were placed across the jordan valley active fault which is a segment of the active dead sea transform fault system each line of the dosimeters shows one or more peaks of radon anomaly concentrations some of these peaks prove the intersection of the fault trace with these lines in areas where the fault plane is inferred in other lines the peaks correspond to the arrangement of faults in areas of pull apart basins sag ponds or pressure ridges formed due to the left or right step of the fault sag ponds usually show low radon emanations because they are the place for the accumulation of very fine sediments which decreases their porosity and hence the upward migration of the radon gas the northern part of the jordan valley relatively shows high radon emanation which could be attributed to the presence of a seismic gap in the upper jordan valley

a precise u pb zircon age for the inishtrahull syenitic gneiss county donegal ireland smd zircon fractions from the deformed alkaline igneous complex on inishtrahd county donegal ireland yield near concordant u pb ages of 1779 3 ma interpreted as dating the igneous crystallization of the gneiss9s precursor sm nd depleted mantle model ages range from 1912 ma to 1978 ms the similarity of the model ages and the crystallization age indicates that the protoliths were derived from a depleted mantle source essentially uncontaminated by older crust the isotopic data confirm previous tentative correlations of the inishtrahull rocks with those of islay in southwestern scotland archaean crust is apparently absent from this region consistent with recent models placing a southern limit on the archaean along the line of the great glen fault zone pre caledonian orthogneisses in scotland and ireland south of the great glen fault zone have generally been correlated with the late archaean lewisian complex of northwestern scotland e g wilkinson 1907 mccallien 1930 bowes hopgood 1975 dixon et al 1990 although aftalion max 1987 concluded that the lewisian was absent from the annagh division gneisses of north mayo ireland there are now several lines of evidence to suggest that archaean crust may be absent southeast of the great glen fault zone e g fitches et al 1990 daly 1990 halliday et al 1985 a large area of pre caledonian basement here termed the rhinns complex is thought to be present within the fault bounded colonsay west islay block fig 1 bentley et al 1988 fitches et al 1990 marcantonio et al 1988 which extends from colonsay in

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

the parkfield california earthquake prediction experiment five moderate magnitude 6 earthquakes with similar features have occurred on the parkfield section of the san andreas fault in central california since 1857 the next moderate parkfield earthquake is expected to occur before 1993 the parkfield prediction experiment is designed to monitor the details of the final stages of the earthquake preparation process observations and reports of seismicity and aseismic slip associated with the last moderate parkfield earthquake in 1966 constitute much of the basis of the design of the experiment

emplacement of rapakivi granite and syenite by floor depression and roof uplift in the palaeoproterozoic ketilidian orogen south greenland in the palaeoproterozoic ketilidian orogen of south greenland tabular intrusions of the rapakivi granite suite exposed at graah fjelde lindenow fjord and qernertoq and a mesoproterozoic syenite of the gardar province exposed at paatusoq were emplaced by a combination of roof uplift and floor depression the strain associated with the emplacement of the intrusions mainly involved redistribution of mass vertically within the lithosphere space for the emplacement of the rapakivi plutons was not created during regional extension on low angle ductile shear zones as claimed by some previous workers and there is no evidence that emplacement of the intrusions coincided with extensional collapse of the orogen following crustal thickening the rapakivi granites post date peak metamorphism in the orogen by 35 46 ma and their contacts cross cut and clearly post date intense flat lying d1 d2 fabrics that formed by partitioning of deformation into arc normal and arc parallel components during oblique convergence

an overview on the seismic zonation and microzonation studies in india abstract the present study presents a review on the progressive development of the seismic zonation map of india both from official agencies and also from independent individual studies the zonation map have been modified and updated regularly with the occurrence of major destructive earthquakes over the years in the indian subcontinent with the addition of new data this study discusses the criteria chosen for the progressive zonation and the major earthquakes that were responsible for retrospection of the earlier published maps the seismic zonation maps of india have also been prepared by various independent workers by adopting different approaches to achieve the purpose of the zonation despite the endeavors from various sources to provide a solution for the problem of earthquake hazards in india there were many limitations on the zonation map as it gives the picture at a regional scale mostly on the bedrock level without addressing the local site conditions but nevertheless the seismic zonation map gives basic guidelines for any region to know the hazard scenario and if any city or urban population is under threat from seismic point of view further site specific seismic microzonation may be carried out in the international scenario the global seismic hazard assessment program gshap in 1999 prepared a hazard map for world in terms of peak ground acceleration pga with a 10 probability of exceedance in 50 years but it turned out to be an underestimation of the hazard parameter when compared with the observed pga to tackle the problem of seismic hazards there was a need to have a detail study on the local site conditions in terms of its geological geophysical and geotechnical properties with the advent of better instrumentation and knowledge on the mechanics of earthquakes it was possible to identify zones of hazards at a local level and this gives rise to the study of seismic microzonation seismic microzonation work has been carried out in india in some of the strategic important mega cities and industrial build up that has the potential of being damaged from future earthquakes as has been shown in the past though the microzonation map is not the final output map as it can still be updated at later stage with more input data it does provide a more realistic picture on the site specific seismic hazard