the present day stress field of australia abstract the unusual present day crustal stress pattern of the australian continent has been the subject of scientific debate for over 25 years the orientation of maximum horizontal present day stress s hmax in continental australia is unlike all other major tectonic plates in that the stress pattern shows regional variability and it is not oriented sub parallel to the direction of absolute plate motion previous studies on the stress pattern of australia revealed that the complex stress pattern of the continent is controlled at a first order by the superposition of plate tectonic forces exerted at the plate boundaries however prior analysis of the contemporary australian crustal stress pattern have been unable to model or explain the stress pattern observed in most of eastern australia and has not extensively addressed the numerous smaller scale variations in stress orientation the recent development of unconventional reservoirs in australia has resulted in a greatly increased amount of new data for stress analysis in previously unstudied or poorly constrained areas in eastern australia in addition stress analysis in conventional hydrocarbon mineral and geothermal exploration in all other parts of the continent provides the opportunity to review and update the australian stress map asm this study presents the new release of the asm with a total of 2150 stress data records in australia increased from 594 data records in 2003 the 2016 asm contains 1359 data records determined from the interpretation of drilling related stress indicators 650 from earthquake focal mechanism solutions 139 from shallow engineering measurements and two from geological indicators the results reveal four distinct regional trends for the s hmax orientation in australia including a nne ssw s hmax trend in northern and northwestern australia which rotates to a prevailing e w orientation in most western and south australia the orientation of s hmax in eastern australia is primarily ene wsw and swings to nw se in southeastern australia a comparison between the new asm database and neotectonic features further confirms the role of contemporary stress in recent deformation of the australian crust the 2016 asm reveals significant discrepancies between newly observed s hmax orientations and predictions by published geomechanical numerical models for the australian continent forces generated at the boundary of indo australian plate remain the major control on the regional crustal stress pattern in continental australia however the increased data density particularly in eastern australia reveals numerous local perturbations of the stress field that were not previously clearly captured hence the key findings of the new release are that local intra plate stress sources are more significant than previously recognized particularly in eastern australian basins and cause substantial local scale rotations of the present day crustal stress pattern that have not been factored into existing australian stress models

models for midcontinent tectonism an update during the past decade significant progress has been made in defining the nature of midcontinent tectonism as a result of an improved geophysical geologic data base which permits an integration of seismicity data crustal structures and current stress directions critically placed microseismic networks have shown that many earthquakes with common focal mechanisms occur in specific spatial patterns the direction of the maximum horizontal compressive stress is generally directed east northeast which supports an origin associated with ridge push forces related to movement of the north american plate crustal structures have been mapped locally by seismic studies and regionally by extensive gravity and magnetic anomaly data these data have been used to relate current seismicity and associated tectonism to one of two models increasing evidence from across the midcontinent supports reactivation of preexisting zones of crustal weakness appropriately oriented with respect to the prevailing stress field the zone of weakness model as the dominant control on contemporary tectonism and the local basement inhomogeneity model as a mechanism for minor low energy release earthquake activity

atoll reef island formation and response to sea level change west island cocos keeling islands abstract reef islands around the margin of coral atolls generally comprise unconsolidated holocene sands and gravels overlying a reef flat or cemented conglomerate platform such islands have accreted within the last 3000 4000 years since sea level has reached a level close to present and the reef flat and conglomerate platform have formed island morphology consists of an oceanward ridge a less distinct lagoonward ridge and low lying central depression several alternative models of how such reef islands might have developed are examined in relation to chronology and sediment provenance particularly in the context of the cocos keeling islands where this issue has been debated since darwin visited the atoll which of these models appears most appropriate for an elongate reef island on the atoll margin is assessed using conventional radiocarbon dating of coral shingle and accelerator mass spectrometry ams radiocarbon dating of individual sand grains from pits across west island the dating results suggest that both coral clasts and individual grains of various components are generally reliable and replicable indicators of the chronology of island accumulation implying rapid transport of skeletal material after death of the contributing organisms across the reef flat zone and relatively little reworking the central part of west island appears to have formed first with oceanward accretion up until about 2000 years bp gradual oceanward accretion with lesser lagoonward extension has continued beyond 2000 years bp at the northern and southern ends of the island and a sequence of lagoonward recurving spits has formed adjacent to the inter island passage at the southern end of the island radiocarbon dating of fossil microatolls indicates a gradual fall of sea level over this period which appears to have had little effect on the pattern of island accretion

teleseismic delay times in a 3 d earth and a new look at the s discrepancy summary when the earliest measurements of the earth s normal modes became available it was soon noticed that v models satisfying this new data set were generally slower than models based on s traveltimes this s discrepancy has since then been attributed to the influence of dispersion that accompanies attenuation but it ignores a competing process that may have the same effect in a heterogeneous earth seismic rays will bend to take advantage of local high velocity anomalies this effect is difficult to quantify because of the computational problems associated with the determination of minimum traveltime paths in heterogeneous earth models in three dimensions we have developed a new method to find absolute minimum traveltimes even in very complicated earth models and applied this to a large number of rays generated in different random earth models the s discrepancy is a function of correlation length and amplitude of v heterogeneity a standard deviation u of 0 15 km sc with a correlation length of 200 km in the whole mantle would give a discrepancy even larger than observed at a 60 and must be discarded a u of 0 15 km s in the upper mantle and 0 05 km s elsewhere explains a discrepancy of 1 2 s depending on the correlation length since the total discrepancy is estimated to be about 4 s this still allows for effects of attenuation we conclude that the s wave discrepancy can be used to set limits to the heterogeneity in the lower mantle at short correlation lengths with our present day knowledge of the magnitude of the discrepancy a heterogeneity larger than 1 per cent with correlation length 200 km is unlikely

reactivation of ancient antarctic rift zones by intraplate seismicity buried deep beneath the antarctic polar ice sheet the geological structure and tectonic activity of east antarctica have long remained unknown the apparent lack of tectonic seismicity was thought to be anomalous relative to other continental interiors and has been attributed to a lack of intraplate stress due to the surrounding spreading ridges and low absolute plate velocity or to the weight of ice sheets increasing the normal stress here we report 27 intraplate tectonic earthquakes detected by the agap gamseis seismic array during 2009 in the interior of east antarctica which represents locally recorded seismicity in the region the earthquakes are primarily extensional and located at shallow to mid crustal depths beneath sedimentary basins aligned linearly adjacent to the gamburtsev subglacial mountains the basins may be part of an ancient continental rift system which provides a zone of pre existing tectonic weakness that focuses the seismicity these events when combined with events in published catalogues of antarctic seismicity indicate levels of seismicity in east antarctica of the same order of magnitude as that of other stable cratons such as the canadian shield

long term behaviour of australian stable continental region scr faults abstract australia boasts arguably the richest late neogene to quaternary faulting record in stable continental region scr crust anywhere in the world variation in fault scarp length vertical displacement proximity to other faults and relationship to topography permits division of the continent according to fault character six onshore neotectonic domains are recognised with an additional offshore domain proposed by analogy with the eastern united states each domain relates to a distinct underlying crustal type and architecture broadly considered to represent cratonic non cratonic and extended environments in general greater topographic expression associated with faults occurring in extended crust relative to non extended crust suggests a higher rate of seismic activity in the former setting consistent with observations worldwide using the same reasoning non cratonic crust might be expected to have a higher rate of seismic activity than cratonic crust this distinction together with the variation in fault character between domains should be recognised in attempts to identify analogous systems worldwide a common characteristic of morphogenic earthquake occurrence in australia appears to be temporal clustering periods of earthquake activity comprising a finite number of large events are separated by much longer periods of seismic quiescence at the scale of a single fault and of proximal faults in several instances there is evidence for deformation at scales of several hundred kilometres switching on and off over the last several million years what is not clear from the limited palaeoseismological data available is whether successive active periods are comparable in terms of slip number of events magnitude of events etc regardless this apparent bimodal recurrence behaviour poses challenges for probabilistic seismic hazard assessment psha these rely on the simplifying assumption that large earthquake recurrence for long return periods is not random i e poissonian presently our ability to incorporate such time dependent models is limited by available data

holocene fringing reefs and sea level change in mangaia island southern cook islands abstract holocene relative sea levels in oceanic islands that are situated sufficiently far from glaciated regions provide basic information for the study of the melting histories of the continental ice sheets and of the rheological structure of the earth we have studied mangaia island south cooks as one such oceanic island located in the middle pacific ocean in addition to the usual geological and geomorphological observations of geomorphic features associated with former shorelines we have used a portable drilling sampler for shallow borings of coral reefs geological and geomorphological studies of the coast of mangaia island have revealed that there was a higher sea level than the present in the mid holocene the heights and ages of emerged microatolls on the emerged bench indicate that the sea reached a maximum level of 1 7 m around 4000 3400 yr b p and then emergence is considered to have occurred between 3400 and 2900 yr b p at the same time the reef crest formed in the period from 5000 to 3400 yr b p emerged above the sea and suffered erosion as a result of this change in sea level upward reef growth from the fore reef slope began to form a new reef crest by 2000 yr b p to seaward of the old reef crest the reef margin of mangaia grew outward intermittently with seaward jump of the reef front in accordance with a fall of sea level in the late holocene the presence of fossil reef crests or eroded algal ridges on modern reef flats is a rather common feature in the south pacific the geomorphic development of such features on reef flats can be explained by the effect of the late holocene fall in sea level

tomographic images of a mantle circulation model sampling convection in the earth s mantle by seismic tomography is difficult as evidenced by the uneven distribution of seismic stations and events with some regions being well imaged compared to others here we quantitatively explore tomographic filtering on earth structure by tracing isc p body wave data through a computer simulation of mantle circulation which accounts for internal heating of the mantle by radioactive decay heatflux from the core a depthwise increase in viscosity and plate motion history of the past 120 million years the travel time residuals are inverted by solving jointly for structure and hypocentral parameters with explicit damping and smoothing we recover the farallon and tethys slabs as well as some low velocity anomalies associated with hot upwelling flow suggesting that tomographic filtering is probably minor in areas of high ray density

control of tectonic inheritance on continental intraplate strain rate and seismicity abstract present day deformation and seismicity of continental lithosphere are characterized by a first order dichotomy between plate boundary zones pbz and stable continental regions scr whereas the former are associated with high strain and seismicity rates the latter tend to remain un deformed except in localized regions of higher strain and seismicity commonly related to fossilized paleo pbz acting as locally weaker domains because of their low amplitudes these intraplate strain and seismicity rates are particularly difficult to measure and characterize in this study we propose a simple model to explain and quantify first order continental strain rate variations focusing on intraplate regions assuming near failure equilibrium on 1d lithosphere profiles we derive steady state strain rates driven by tectonic forces as a function of rheological models that include new strain weakening rheologies in order to simulate tectonic inheritance within this framework inherited strain weakening plays a fundamental role in allowing for and explaining strain and seismicity concentration in intraplate weak zones our model predicts strain rates in intraplate weak zones up to two to three orders of magnitude higher compared to stable cratons due to the effect of tectonic inheritance on rheology weakening these model predictions are in agreement with empirical estimations in intraplate regions and can provide a conceptual framework for characterization of scr strain and seismicity rates

seismically fast geodynamic mantle models we show that biased sampling of earth structure by body waves provides an additional explanation for the fact that short period body wave seismic velocity models are faster than long period free oscillation models apparent dispersion we do this by tracing a set of body waves used in global tomography studies through synthetic seismic models derived from mantle circulation models the histograms of the arrival time residuals have a negative mean for all the models investigated we interpret that this results from a predominance of rays sampling the fast structures of subduction zones due to the concentration of sources there the interpretation successfully passes two tests the first showed that the signal is tectonically controlled while the second involved breaking the correlation between ray paths and structures when no bias is found the negative mean implies that earth as sampled by body waves is fast compared to an average reference earth e g as measured from free oscillations this effect and others will need to be quantified before attenuation can be extracted from the apparent dispersion

vegetation change in the coastal lowland rainforest at avai o vuna swamp vava u kingdom of tonga avai o vuna swamp a small coastal wetland in vava u kingdom of tonga produced a 4500 year pollen and sediment record results are 1 a mid holocene sea level highstand is confirmed for tonga between about 4500 and 2600 14 c yr b p marine clay contains pollen from mangroves rhizophora mangle coastal forest trees barringtonia asiatica and cocos nucifera and rainforest trees alphitonia rhus hedycarya and calophyllum 2 microscopic charcoal first appeared at 2600 14 c yr b p coincident with the arrival of polynesians 3 cocos pandanus excoecaria macaranga and elaeocarpaceae pollen reflects the establishment of a mixed coastal lowland rainforest in the last 2500 years 4 the loss of hedycarya elaeocarpus calophyllum and guettarda and the reduction of terminalia and taxa in the papilionaceae family by about 1000 years ago may be due to habitat destruction and the loss of dispersal capabilities of some species through the extinction of the two largest pigeons in tonga d 2005 university of washington all rights reserved

tomographic pn velocity and anisotropy structure in the central and eastern united states abstract a total of 19 166 pn phase readings from the international seismological centre isc and the national earthquake information center neic catalogs as well as hand picked arrivals from the incorporated research institutions for seismology iris data management center were inverted to map the velocity and anisotropy structure of the lithospheric mantle in the central and eastern united states ceus our pn tomographic model shows a broad region of very fast velocity under the north american craton the northern ceus and significant lateral variations within the rest of the ceus the surface locations of the major intraplate seismic zones are near the edges of high velocity anomalies which is consistent with the notion that stress accumulation and hence focused deformation are likely to occur at the rheological boundaries around the rigid lithospheric root however the ancient rifts show no clear correlation to the low velocity anomalies in the lithospheric mantle our pn anisotropic model shows a complex pattern of fast directions with an overall north south trend in the ceus that may reflect the preserved fabrics of the cratonic lithosphere nonetheless high pn anisotropy seems to wrap around the high velocity blocks which may indicate local deformation around the rigid blocks

haskell 1935 revisited the haskell 1935 value of 1021 pa s for mantle viscosity is a classic and enduring constraint on the rheology of the earth s interior we revisit this inference using spherically symmetric self gravitating maxwell viscoelastic earth models our inference is based on both forward and inverse analyses of decay times associated with uplift at two sites considered by haskell angerman river sweden and oslo norway rather than the raw relative sea level rsl data at these sites we demonstrate that predictions of the decay time associated with the angerman river data are insensitive to variations in both the late pleistocene ice load history and the lithospheric thickness of the earth model the predictions at oslo are sensitive to both these inputs and hence decay times at this site provide a remarkably robust constraint on mantle viscosity we derive a constraint on the average viscosity of the mantle of 0 65 1 10 1021 pa s where the average resolved by the data encompasses a region which extends from the base of the lithosphere to a depth of near 1400 km this indicates that many previous analyses which have invoked the haskell value of 1021 pa s as a constraint on the average upper mantle i e above 670 km depth viscosity alone have misinterpreted the resolving power of the inference furthermore our analysis indicates that a number of apparently contradictory inferences of viscosity based on fennoscandian data satisfy the new rigorous interpretation of the haskell constraint finally we demonstrate how the ambiguity in the upper mantle lower mantle viscosity contrast associated with the haskell average may be reduced by invoking decay time constraints estimated from rsl curves in hudson bay a preliminary inversion of decay times at angerman river and richmond gulf in hudson bay suggests a contrast of approximately an order of magnitude between the average viscosities of the upper mantle and the top 1000 km of the lower mantle however a conclusive analysis in this regard must await the determination of consistent decay time estimates for the hudson bay region

mapping spherical seismic into physical structure biases from 3 d phase transition and thermal boundary layer heterogeneity summary earth s mantle is to a very good first approximation spherically symmetric with lateral deviations in seismic velocities and density of only a few per cent this observation has led to the common assumption that average radial seismic models reflect the mantle s average physical structure we test this assumption by using a set of dynamically generated mantle structures and comparing seismic velocities for the average radial physical state with laterally averaged seismic velocities the thermal and thermochemical dynamic circulation models are earth like in terms of convective vigour thermal structure and geographical pattern of heterogeneity we find that in general averaged seismic structure is not distinguishable from the seismic structure of the physical average within the uncertainty bounds of seismic reference models an exception is near phase boundaries where phase boundary topography broadens the averaged seismic jump relative to the discontinuity at physical reference conditions in an inversion for 1 d seismic structure where narrow discontinuities are imposed these biases may map into a lower jump and substantially stronger velocity gradients above and below the interface than are actually present other small biases in averaged structure occur in thermal boundary layers including those that form above chemical piles these biases are caused by large lateral variations in temperature not compositional variability

postglacial rebound and the focal mechanisms of eastern canadian earthquakes a detailed numerical model of postglacial rebound for the eastern canadian arctic is described with special attention being paid to baffin island this numerical model is able to account for the observed uplift patterns as recorded by the relative sea level histories of discrete sites distributed throughout the study area these uplift patterns show regional trends so the same model can be used to interpolate between data sites and to estimate the uplift history at any arbitrary site within the study area by treating the lithosphere as a thin elastic plate spatial variations in the uplift pattern can be translated into estimates of lithospheric stress the model predicts the variations in uplift as a function of both space and time since deglaciation and can therefore be used to estimate the temporal evolution of lithospheric stress following deglaciation the stress so calculated is treated as a perturbation to an ambient stress field having its origin in other processes postglacial rebound is shown to

the sao vicente earthquake of 2008 april and seismicity in the continental shelf off se brazil further evidence for flexural stresses summary the continental margin and shelf of most stable intraplate regions tend to be relatively more seismically active than the continental interior in the southeast continental margin of brazil a seismiczoneextendsfromriograndedosultoespeismicactivityoccurring mainly along the continental slope and suggesting a close relationship with flexural stresses caused by the weight of the sediments in this region earthquakes with magnitudes larger than 5m b occurevery20 25yr onaverage thefocalmechanismsolutionsofpreviousearthquakes in this zone indicated reverse faulting on planes dipping approximately 45 with horizontal p axes the recent 5 2m b earthquake of 2008 april 23 occurred 125 km south of s ao vicente and was well recorded by many stations in se brazil as well as at teleseismic distances in north america and africa its focal depth was 17 km locating the hypocentre in the lower crust a well determined focal mechanism solution shows one vertical nodal plane and one subhorizontal nodal plane thep a ndt axes exhibit large dips which were confirmed by ar egional moment tensor inversion this unusual orientation of the fault mechanism can be attributed to a rotation of the principal stress directions in the lower crust caused by flexural effects due to the load of recent sedimentation

upper crustal earthquake swarms in sao caetano reactivation of the pernambuco shear zone and trending branches in intraplate brazil abstract seismogenic fault reactivation of continental scale structures has been observed in a few intraplate areas but its cause is still a matter of debate the objective of the present study is to analyze two seismic swarms that occurred along the ew trending pernambuco ductile shear zone and in a ne trending branch in 2007 and 2010 in sao caetano county northeastern brazil we studied both epicentral areas using a nine and a seven station network during 180 and 54 days respectively the results indicate that the 2007 swarm correspond to a right lateral strike slip fault with a normal component of slip strike 74 dip 60 and rake 145 and the 2010 swarm corresponds to a normal fault strike 265 dip 79 and rake 91 the former reactivated a ne trending branch whereas the latter reactivated the main e w trending mylonitic belt of the pernambuco shear zone these results are consistent with seismogenic reactivation of this major structure generated by the present day ew trending compression and ns trending extension as observed by previous studies this shear zone was reactivated as rift faults in the cretaceous during the south america africa breakup however our study confirms that the basement fabric such as continental scale ductile shear zones show evidence of crustal weakness outside areas of previous rifting and it reveals the potential for large earthquakes along dormant rift segments associated with major basement shear belts

magnitudes and locations of the 1811 1812 new madrid missouri and the 1886 charleston south carolina earthquakes we estimate locations and moment magnitudes m and their uncertainties for the three largest events in the 1811 1812 sequence near new madrid missouri and for the 1 september 1886 event near charleston south carolina the intensity magnitude m i our preferred estimate of m is 7 6 for the 16 december 1811 event that occurred in the new madrid seismic zone nmsz on the bootheel lineament or on the blytheville seismic zone m i is 7 5 for the 23 january 1812 event for a location on the new madrid north zone of the nmsz and 7 8 for the 7 february 1812 event that occurred on the reelfoot blind thrust of the nmsz our preferred locations for these events are located on those nmsz segments preferred by johnston and schweig 1996 our estimates of m are 0 1 0 4 m units less than those of johnston 1996b and 0 3 0 5 m units greater than those of hough et al 2000 m i is 6 9 for the 1 september 1886 event for a location at the summerville middleton place cluster of recent small earthquakes located about 30 km northwest of charleston

paleoseismology of the mount narryer fault zone western australia a multistrand intraplate fault system our paleoseismological study of faults and fault related folds comprising the mount narryer fault zone reveals a mid to late quaternary history of repeated morphogenic earthquakes that have influenced the planform and course of the murchison roderick and sanford rivers western australia the dominant style of deformation involves folding of near surface sediments overlying discrete basement faults carbon 14 optically stimulated luminescence and in situ produced 10 be constrain the timing of the events and late quaternary slip rates associated with fault propagation folds in tectonically uplifted and deformed alluvial channel deposits a flight of five inset fluvial terraces is preserved where the murchison river flows across the roderick river fault these terraces which we infer to be coseismic are consistent with at least four late quaternary seismic events on the order of moment magnitude m w 7 1 within the last 240 k y secondary shears expressed on the folds indicate a component of dextral strike slip displacement quaternary slip rates on the underlying faults range from 0 01 to 0 07 mm yr 1 with a total slip rate for the zone between 0 04 and 0 11 mm yr 1 these rates are intermediate to those in the adjacent mesozoic basin 0 1 mm yr 1 and precambrian craton 1 and so provide insight into how tectonic strain is partitioned and transferred across a craton margin

mantle circulation models with sequential data assimilation inferring present day mantle structure from plate motion histories data assimilation is an approach to studying geodynamic models consistent simultaneously with observables and the governing equations of mantle flow such an approach is essential in mantle circulation models where we seek to constrain an unknown initial condition some time in the past and thus cannot hope to use first principles convection calculations to infer the flow history of the mantle one of the most important observables for mantle flow history comes from models of mesozoic and cenozoic plate motion that provide constraints not only on the surface velocity of the mantle but also on the evolution of internal mantle buoyancy forces due to subducted oceanic slabs here we present five mantle circulation models with an assimilated plate motion history spanning the past 120 myr a time period for which reliable plate motion reconstructions are available all models agree well with upper and mid mantle heterogeneity imaged by seismic tomography a simple standard model of whole mantle convection including a factor 40 viscosity increase from the upper to the lower mantle and predominantly internal heat generation reveals downwellings related to farallon and tethys subduction adding 35 bottom heating from the core has the predictable effect of producing prominent high temperature anomalies and a strong thermal boundary layer at the base of the mantle significantly delaying mantle flow through the transition zone either by modelling the dynamic effects of an endothermic phase reaction or by including a steep factor 100 viscosity rise from the upper to the lower mantle results in substantial transition zone heterogeneity enhanced by the effects of trench migration implicit in the assimilated plate motion history an expected result is the failure to account for heterogeneity structure in the deepest mantle below 1500 km which is influenced by jurassic plate motions and thus cannot be modelled from sequential assimilation of plate motion histories limited in age to the cretaceous this result implies that sequential assimilation of past plate motion models is ineffective in studying the temporal evolution of core mantle boundary heterogeneity and that a method for extrapolating present day information backwards in time is required for short time periods of the order of perhaps a few tens of myr such a method exists in the form of crude backward convection calculations for longer time periods of the order of a mantle overturn a rigorous approach to extrapolating information back in time exists in the form of iterative nonlinear optimization methods that carry assimilated information into the past through the use of an adjoint mantle convection model

spatiotemporal complexity of continental intraplate seismicity insights from geodynamic modeling and implications for seismic hazard estimation continental intraplate seismicity seems often episodic clustered and mi grating the observed seismicity shows both spatial clustering in seismic zones and scattering across large plate interiors temporal clustering followed by long periods of quiescence and migration of seismicity from one seismic zone to another here we explore the complex spatiotemporal patterns of intraplate seismicity using a 3d visco elasto plastic finite element model the model simulates tectonic loading crustal failure in earthquakes and coseismic and postseismic stress evolution for a later ally homogeneous lithosphere with randomly prespecified perturbations of crustal strength the model predicts various spatiotemporal patterns of seismicity at different timescales spatial clustering in narrow belts and scattering across large regions over hundreds of years connected seismic belts over thousands of years and widely scat tered seismicity over tens of thousands of years the orientation of seismic belts coincides with the optimal failure directions associated with the assumed tectonic loading stress triggering and migration cause spatiotemporal clustering of earth quakes when weak zones are included in the model the predicted seismicity initiates within the weak zones but then extends far beyond them if a fault zone is weakened following a large earthquake repeated large earthquakes can occur on the same fault zone even in the absence of strong tectonic loading these complex spatiotemporal patterns of intraplate seismicity predicted in this simple model suggest that assessment of earthquake hazard based on the limited historic record may be biased toward over estimating the hazard in regions of recent large earthquakes and underestimating the hazard where seismicity has been low during the historic record

evidence for smoothly falling sea level relative to north queensland australia during the past 6 000 yr post glacial sea level curves are expected to differ between different parts of the world as a result of global isostatic changes1 or perhaps other forms of geoidal changes2 i report here results from the inner part of the northern great barrier reef which seem to show a pattern of smoothly falling sea level during the past 6 000 yr the results are consistent with stratigraphical results from prograded mangrove coasts on the nearby north queensland mainland the region is remote from the tectonically active margin of the south west pacific ocean and the results contribute to the global data set relevant to isostatic changes being assembled by the international sea level project igcp project no 61 they also provide a baseline relevant to holocene coral reef growth in the inner great barrier reef

have we seen the largest earthquakes in eastern north america abstract the assumed magnitude of the largest future earthquakes mmax is crucial in assessing seismic hazard especially for critical facilities like nuclear power plants estimates are made using various methods and often prove too low as for the 2011 tohoku japan earthquake estimating mmax is particularly challenging within tectonic plates where large earthquakes are infrequent vary in location and time and often occur on previously unrecognized faults for example it is unclear whether the short historical record includes the largest possible earthquakes along the eastern continental margin of north america we explore this issue by generating synthetic earthquake histories and sampling them over a few hundred years due to the short histories the maximum magnitudes appearing most often in a sub catalog m max a are often smaller than the maximum magnitude in the parent catalog m max p that can occur future earthquakes along the continental margin may thus be significantly larger than those observed to date more generally these simulations demonstrate that the largest earthquake in a catalog likely reflects a combination of catalog length a region s earthquake productivity and relative proportion of small to large events for regions with low seismicity small variations in b value the ratio of large to small events due to sampling has a significant impact on the expected recurrence times of large magnitude earthquakes although the precise likelihood of observing m max p depends on the distribution of recurrence times a catalog shorter than an earthquake s mean recurrence time will likely not contain an event of that size as a result mmax cannot always be reliably estimated from earthquake catalogs

potentialities uncertainties and complexities in the response of coral reefs to future sea level rise coral islands formed of largely unconsolidated sands only a few metres above sea level are thought to be particularly vulnerable to sea level rise consequent upon global warming however scenarios which predict catastrophic flooding and loss of island area need reassessment particularly in the light of the continued downwards revision of projected rates of future sea level rise revised questions concern the interactions between reef growth and sea level change biophysical constraints on coral growth and the importance to reef systems of potential changes in the magnitude frequency and location of tropical cyclones and hurricanes it is clear that most reefs have the growth potential to meet even the highest of future sea level rise scenarios but too little is known about physiological and physical constraints to reef growth to adequately evaluate the importance of these two factors in constraining this potential at the present time future sea level rise in the tropical oceans and coral reef responses will take place against a backdrop of inter regional differences in holocene sea levels resulting from the varying interaction of eustatic and hydro isostatic processes these differences have generated varying constraints on the development of modern reefs and varying inherited topographies upon which future sea level changes will be superimposed these controls are particularly important in assessing differences in vulnerability to future sea level rise for reef islands in the pacific ocean and the caribbean sea

causes of intraplate seismicity in central brazil from travel time seismic tomography abstract new results of travel time seismic tomography in central brazil provide evidence that the relatively high seismicity in this region is related to the thinner lithosphere at the limit between the amazonian and sao francisco paleocontinents the transition between these paleocontinents is marked by low velocity anomalies spatially well correlated with the high seismicity region which are interpreted as related to the lithospheric thinning and consequent rise of the asthenosphere which have increased the temperature in this region the low velocity anomalies suggest a weakness region favorable to the build up of stress the effective elastic thickness and the strain stress regime for the study area are in agreement with tomographic results a high velocity trend is observed beneath the parnaiba basin where low seismicity is observed indicating the presence of a cratonic core our results support the idea that the intraplate seismicity in central brazil is related to the thin lithosphere underlying parts of the tocantins province between the neighboring large cratonic blocks

mid continental earthquakes spatiotemporal occurrences causes and hazards abstract large earthquakes in north china australia northwestern europe central and eastern united states and other mid continents show complex spatiotemporal patterns that do not fit existing earthquake models individual faults or fault zones tend to fall into long term thousands of years or longer dormancy after a cluster of ruptures whereas large earthquakes seem to roam between widespread faults these behaviors are characteristic of complex dynamic systems of interacting faults in such systems widespread faults collectively accommodate slow tectonic loading and a major fault rupture both transfers stress to the neighboring faults and perturbs loading conditions on distant faults because of the slow tectonic loading local stress variations from fault interaction or nontectonic processes or changes of fault strength could trigger mid continental earthquakes the precise spatiotemporal occurrence of large mid continental earthquakes may be unknowable an intrinsic limitation of complex dynamic systems but their qualitative system behavior may be understood by a system approach this approach would render some commonly used concepts such as seismic cycles recurrence intervals characteristic earthquakes and seismic gaps inadequate or irrelevant in mid continents and calls for rethinking of the probability estimates based on these concepts it requires a better understanding of fault interactions on multiple spatial and temporal scales rather than focusing solely on the balance of tectonic loading and yield strength of individual faults or fault segments it also indicates the need for paleoseismic and geodetic studies extending beyond areas where recent large earthquakes occurred and for hazard assessments to reduce the biasing influence of the most recent large earthquakes that tend to dominate the short and incomplete earthquake records

lithospheric response to volcanic loading in the southern cook islands abstract the response of the ocean lithosphere to volcanic island loading has been investigated for the southern cook islands of rarotonga mangaia and the aitutaki mauke group using 1 estimates of the change with distance from the load of uplift of islands located on the flexure created arch 2 geoid height perturbations as observed with the geos 3 and seasat radar altimeters and 3 bathymetric evidence for the moat and arch about the island loads the effective flexural rigidity for rarotonga is found to be higher than for the older and nearby islands of mangaia and aitutaki this together with an earlier result for tahiti 1 suggests that stress relaxation of the lithosphere has occurred and that this layer behaves as a viscoelastic material with an effective viscosity of about 5 10 10 25 poise the observations for the flexural rigidity do not indicate any dependence on the age of the lithosphere at the time the loading occurred this suggests that there are no significant differences in lithospheric properties for plates in the age range of 6 7 10 7 years altimeter passes to the east of mauke indicate that there may be an uncharted submarine extension of the aitutaki mauke chain

episodic activity of a dormant fault in tectonically stable europe the rauw fault ne belgium abstract our knowledge about large earthquakes in stable continental regions comes from studies of faults that generated historical surface rupturing earthquakes or were identified by their recent imprint in the morphology here we evaluate the co seismic character and movement history of the rauw fault in belgium which lacks geomorphological expression and historical present seismicity this 55 km long normal fault with known neogene and possibly early pleistocene activity is the largest offset fault west of the active roer valley graben its trace was identified in the shallow subsurface based on high resolution geophysics all the layers within the late pliocene mol formation 3 6 to 2 59 ma are displaced 7 m vertically without growth faulting but deeper deposits show increasing offset a paleoseismic trench study revealed cryoturbated but unfaulted late glacial coversands overlying faulted layers of mol formation in between those deposits the fault tip was eroded along with evidence for individual displacement events fragmented clay gouge observed in a micromorphology sample of the main fault evidences co seismic faulting as opposed to fault creep based on optical and electron spin resonance dating and trench stratigraphy the 7 m combined displacement is bracketed to have occurred between 2 59 ma and 45 ka the regional presence of the sterksel formation alluvial terrace deposits limited to the hanging wall of the rauw fault indicates a deflection of the meuse rhine confluence 1 0 to 0 5 ma by the fault s activity suggesting that most of the offset occurred prior to at this time interval in the trench sterksel formation is eroded but reworked gravel testifies for its former presence hence the rauw fault appears as typical of plate interior context with an episodic seismic activity concentrated between 1 0 and 0 5 ma or at least between 2 59 ma to 45 ka possibly related to activity variations in the adjacent continuously active roer valley graben

intraplate seismicity in mid plate south america correlations with geophysical lithospheric parameters mid plate south america remains one of the least studied regions of intraplate seismicity little is known about the origin and controlling factors that make this area the least seismically active intraplate region in the world we analysed the distribution of intraplate seismicity and its correlation with several geophysical lithospheric parameters in an attempt to establish which factors might promote or inhibit the occurrence of intraplate earthquakes we found that above average seismicity occurs mostly in neoproterozoic fold belts associated with areas having a positive gravity anomaly lower elastic thickness higher heat flow thinned crust and a negative s wave anomaly at 100 km depth associated with non cratonic crust cratonic areas with a higher elastic thickness and lower heat flow are associated with low rates of seismicity our study suggests that the most important controlling factors are elastic thickness and heat flow we propose that earthquake prone areas with these favourable conditions correspond to regions of weakened lithosphere where most of the regional lithospheric stresses are supported by the overlying brittle upper crust these areas act as local concentrators of the regional compressional stress field with the stress build up then leading to the occurrence of intraplate seismicity

maximum magnitude mmax in the central and eastern united states for the 2014 u s geological survey hazard model probabilistic seismic hazard assessment psha requires an estimate of m max the moment magnitude m of the largest earthquake that could occur within a specified area sparse seismicity hinders m max estimation in the central and eastern united states ceus and tectonically similar regions worldwide stable continental regions scrs a new global catalog of moderate to large scr earthquakes is analyzed with minimal assumptions about enigmatic geologic controls on scr m max an earlier observation that scr earthquakes of m 7 0 and larger occur in young 250 23 ma passive continental margins and associated rifts but not in cratons is not strongly supported by the new catalog scr earthquakes of m 7 5 and larger are slightly more numerous and reach slightly higher m in young passive margins and rifts than in cratons however overall histograms of m from young margins and rifts and from cratons are statistically indistinguishable this conclusion is robust under uncertainties in m the locations of scr boundaries and which of two available global scr catalogs is used the conclusion stems largely from recent findings that 1 large southeast asian earthquakes once thought to be scr were in actively deforming crust and 2 long escarpments in cratonic australia were formed by prehistoric faulting the 2014 seismic hazard model of the u s geological survey represents ceus m max as four point probability distributions the distributions have weighted averages of m 7 0 in cratons and m 7 4 in passive margins and rifts these weighted averages are consistent with m max estimates of other scr pshas of the ceus southeastern canada australia and india

warmer or cooler late holocene marine palaeoenvironments interpreting southeast australian and brazilian sea level changes using fixed biological indicators and their δ18o composition abstract relic inter tidal assemblages of sessile organisms which are referred to as fixed biological indicators fbis are shown to be useful proxies for late holocene climatic and environmental changes as well as direct indicators of short term fluctuations in sea level a detailed comparison of change in the inter tidal assemblages of two southern hemisphere sites at comparable latitudes port hacking new south wales south east australia and the laguna imbituba region of southern brazil indicates periods of marked similarities in the timing and nature of changes at 5200 3800 cal years bp and differences after 2400 cal years bp there is sufficient concurrence of cooling phases and falling sea levels to strongly suggest that in some cases global rather than regional forcing factors are at work the value of inter tidal organisms as indicators of changed environments is developed by identifying the past and present distributions of the common marker species tubeworms barnacles and mussels the 18 o content of these extant specimens at port hacking confirmed changes in ocean water temperature and associated sea level behaviour corresponding to invasion or extinction of temperature sensitive species a similar pattern is repeated although in a less marked fashion in the laguna imbituba region of southern brazil

stability in the south pacific surface marine 14c reservoir over the last 750 years evidence from american samoa the southern cook islands and the marquesas abstract although minor climatic and sea level changes have been documented for the south pacific during the late holocene our understanding of the consequent impact of these changes on the marine 14 c reservoir and therefore the 14 c content of shellfish is limited ultimately this has implications for documenting the chronology of human movement and adaptation in this region in this paper we compare marine reservoir r data obtained from tightly controlled archaeological proveniences with known age pre ad 1950 shells from the southern cook islands american samoa and marquesas islands results indicate that there has been no significant change in the near shore marine reservoir in these three locations over the last ca 750 years furthermore known age pre ad 1950 shell samples provide more precise r values for use in sample calibration than archaeological paired shell charcoal samples this is attributed in part to the limitations of assigning provenance and age to material from archaeological sites on the basis of these results we conclude that the known age pre ad 1950 shell derived r values can be used to calibrate shell 14 c results from deposits of late holocene age

a three dimensional p wave velocity model for the charlevoix seismic zone quebec canada 1 a three dimensional p wave velocity model has been developed for the charlevoix seismic zone csz the csz is located along the st lawrence river 100 km northeast of quebec city canada and is one of the most active seismic zones in eastern north america five earthquakes with magnitudes equal to or exceeding 6 0 have occurred in the csz in historic time and around 200 earthquakes occur annually hypocenters are located in precambrian basement rocks basement rocks have been affected by numerous tectonic events including grenvillian collision iapetan rifting and meteor impact we performed a sequential tomographic inversion for p wave velocity structure based upon 3093 p wave arrivals from 489 earthquakes recorded by 12 stations high velocity is associated with the center of the impact crater the region of high velocity is surrounded by low velocities interpreted to be highly disrupted rocks an elongated high velocity region is present at midcrustal depths that trends parallel to the st lawrence river earthquakes avoid the high velocity body and separate into two bands one on either side of the feature larger earthquakes magnitude 4 have occurred along the northern edges of the high velocity region

the plate tectonic approximation plate nonrigidity diffuse plate boundaries and global plate reconstructions the central assumption of plate tectonics that plate interiors are rigid remains a useful but uncertain approximation strain rates of stable plate interiors are bounded between 10 i12 10 i11 year i1 and 4 10 i10 year i1 the narrowness of all plate boundaries the other main assumption of plate tectonics as originally conceived is contradicted by many observations both in the continents and in the oceans some diffuse plate boundaries in both continents and oceans exceed dimensions of 1000 km on a side diffuse plate boundaries cover 15 of earth s surface the maximum speed of relative plate motion across any one diffuse plate boundary ranges from 2t o 15 mm year which is faster than some upper bounds on intraplate motion across stable plate interiors 2m m year i1 strain rates in diffuse plate boundaries can be as high as 10 i8 year i1 25 times higher than the upper bound on strain rates of stable plate interiors but 600 times lower than the lowest strain rates across typical narrow plate boundaries the poles of rotation of the plates flanking a diffuse oceanic plate boundary tend to be located in the diffuse boundary which is a consequence of the strong coupling across the boundary

large intraplate earthquakes and static stress changes in the south china coastal region abstract a number of moderate earthquakes occurred in the south china continental edge or coastal area several large earthquakes are sparsely distributed along the seismic belt with the northeast direction between the south china and the continental shelf of the south china sea coulomb stress changes of the 1969 yangjiang main shock ms 6 4 with the following events of the 1986 ml 5 4 the 1987 ml 5 4 and the 2004 ml 5 2 in the yangbian bay area are studied the complex stress patterns of the main shock caused by the dextral pinggang strike slip fault imported on the planes of the normal fault strike slip fault and thrust fault of three events indicate that the distribution of aftershocks mainly located in the areas of positive stress changes and part of aftershocks fall into the stress shadow area due to the reactivity of the local faults the 1969 yangjiang event occurred between the intraplate and the broad plate boundary zone setting when we apply on the empirical relationship between the aftershock durations and the fault loading rate the intersection fault model is proposed and could explain the stress changes of the yangjiang earthquake sequences in south china coastal area the future hazard assessment requires to take account of the stress increase area along the tip of the main shock source fault and off fault stress increase area

global scale models of the mantle flow field predicted by synthetic tomography models using a multi disciplinary technique incorporating the heterogeneous resolution of seismic tomography geodynamical models of mantle convection and relationships derived from mineral physics we investigate the method of using seismic observations to derive global scale 3d models of the mantle flow field we investigate the influence that both the resolution of the seismic model and the relationship used to interpret wavespeed anomalies in terms of density perturbations have on the calculated flow field we create a synthetic seismic tomography model from a 3d spherical whole mantle geodynamic convection model and compare present day global mantle flow fields from the original convection model and from a geodynamical model which uses the buoyancy field of the synthetic tomography model as an initial condition we find that to first order the global velocity field predicted by the synthetic seismic model correlates well with the flow field from the original convection model throughout most of the mantle however in regions where the resolving power of the seismic model is low agreement between the models is reduced we also note that the flow field from the synthetic seismic model is relatively independent of the density velocity scaling ratio used 2010 elsevier b v all rights reserved

on the modified mercalli intensities and magnitudes of the 1811 1812 new madrid earthquakes we reexamine original felt reports from the 1811 1812 new madrid earthquakes and determine revised isoseismal maps for the three principal mainshocks in many cases we interpret lower values than those assigned by earlier studies in some cases the revisions result from an interpretation of original felt reports with an appreciation for site response issues additionally earlier studies had assigned modified mercalli intensity mmi values of v vii to a substantial number of reports that we conclude do not describe damage commensurate with intensities this high we investigate several approaches to contouring the mmi values using both analytical and subjective methods for the first mainshock on 02 15 lt december 16 1811 our preferred contouring yields m 7 2 7 3 using the area moment regressions of johnston 1996 for the 08 00 lt on january 23 1812 and 03 45 lt on february 7 1812 mainshocks we obtain m 7 0 and m 7 4 7 5 respectively our magnitude for the february mainshock is consistent with the established geometry of the reelfoot fault which all evidence suggests to have been the causative structure for this event we note that the inference of lower magnitudes for the new madrid events implies that site response plays a significant role in controlling seismic hazard at alluvial sites in the central and eastern united states we also note that our results suggest that thrusting may have been the dominant mechanism of faulting associated with the 1811 1812 sequence

late holocene sea level changes in the northwest tuamotu islands french polynesia abstract field surveys of several sea level indicators exposed in situ reef framework conglomerates coral colonies and tridacna shells in a growth position sea corrosion notches carried out on six atolls from the nw tuamotus mataiva rangiroa arutua kaukura apataki and takapoto and data from four subsurface boreholes drilled through mataiva show that during the late holocene mean sea level msl reached a maximum elevation at approximately 0 9 m it remained above the present msl from between 6000 and 5500 yr b p until at least 1200 yr b p human settlements on the atolls were extremely unlikely and probably impossible throughout this time the area investigated seems to have been tectonically quite stable during the late holocene a local curve of msl variations may be representative of the regional eustatic pattern

fringing reef growth and morphology a review abstract fringing reefs are generally not simple veneers of coral growth along tropical shorelines extensive research over the past few decades based on radiocarbon dating of holocene reef deposits has indicated that they can develop in a complex variety of ways even though the surface morphology may appear relatively simple the principal factor that appears to determine the growth and morphology of fringing reefs is the available accommodation space sea level fluctuations are important primarily because the sea surface determines the absolute accommodation space for a given reef this means that a reef established during a period of sea level rise will be able to accrete vertically as space is created above it if however the reef establishes at or grows to the sea surface thereby occupying all the available accommodation space it can no longer accrete vertically and begins to build laterally the morphology and chronostratigraphy of a range of holocene fringing reefs are described on the basis of which six fringing reef growth models are identified in model a the fringing reef is established at depth and primarily accretes vertically towards the sea surface reef growth in model b initiates at sea level and due to the lack of vertical accommodation space grows laterally model c has a similar morphology to model b however the reef progrades over a non reefal sediment wedge episodic lateral and vertical growth occurs in model d with a stepwise progradation of the reef front the remaining models are characterised by seaward reef framework behind which unconsolidated sediments accumulate in model e reef crest growth forms a barrier leading to the development of a backreef lagoon model f has a similar morphology to model e except that the reef crest is formed by hurricane rubble accumulation rather than framework accretion and is periodically reworked

a compilation of igneous rock volumes at volcanic passive continental margins from interpreted seismic profiles abstract the rifting and breakup of continents and subsequent seafloor spreading give rise to passive continental margins many of which are underlain by enormous volumes of igneous rocks and termed volcanic passive margins the relationships between the igneous rocks rifting and mantle plumes remain unresolved despite extensive studies and proposed alternative models to support such studies we use published previously interpreted seismic reflection and refraction data to compile a dataset of igneous rock volumes and geometries at volcanic passive continental margins the volmir volcanic passive margin igneous rocks dataset is based on margin crossing profiles on which the volumes and geometries of both shallow seaward dipping reflector sdr and deeper high velocity lower crustal hvlc units can be measured it includes information about the ages of continental breakup and profile distances from the associated euler pole and from hotspots that may have played roles in the breakup process despite local variations the dataset shows general patterns the average ratio of sdr to hvlc volumes 0 3 0 4 is relatively consistent between profiles implying that formation of these units is related during continental breakup the volumes of igneous rocks display a moderate positive correlation with distances from the euler pole but only a weak negative correlation with distances from the nearest hotspot at the time of margin formation suggesting that in continental breakup lithospheric processes passive rifting have greater effects than hotspots active rifting these results suggest that this dataset will be useful for exploring aspects of the rifting process relationships between volcanic rifted margins and potential explanations for their similarities and differences

low deformation rate in the koyna warna region a reservoir triggered earthquake site in west central stable india abstract we analyse nine years of gps measurements of crustal deformation from the koyna warna region within the stable india plate the koyna warna region experienced a strong earthquake on 10 december 1967 m 6 3 that is considered to have been induced by the impoundment of the koyna reservoir and the continuing earthquake activity in the region is considered to be associated with the koyna and warna reservoirs the earthquakes occur in a very small region of 30 10 km2 in two well defined seismic zones the nne ssw trending koyna seismic zone and the nnw sse trending warna seismic zone these zones are characterised by predominantly left lateral strike slip motion and normal motion respectively in 2003 we initiated campaign mode gps measurements in the region analysis of the gps data collected over nine years indicate low to moderate deformation rate

crustal structure across the three gorges area of the yangtze platform central china from seismic refraction wide angle reflection data abstract we present active source seismic data recorded along a 300 km long profile across the three gorges area of the western yangtze platform central china from west to east the profile crosses the zigui basin huangling dome and jianghan basin the derived crustal p wave velocity structure changes significantly across the tongchenghe fault that lies at the transition from the huangling dome to the jianghan basin west of the tongchenghe fault beneath the zigui basin and the huangling dome we observe a 42 km thick crust of relatively low average velocity 6 3 6 4 km s in contrast east of the tongchenghe fault beneath the jianghan basin the crust is only 30 km thick and has a high average velocity 6 6 6 7 km s a west east variation in crustal composition along the tongchenghe fault is also inferred west of the fault p wave velocities suggest a felsic composition with an intermediate layer at the base of the crust whilst east of the fault felsic intermediate and mafic crustal layers are apparent our results suggest that the crust beneath the jianghan basin has been thinned by rifting accompanied by intrusion of the lower crust by mafic dikes and sills the west to east division of the crust in the three gorges area coincides with first order geophysical contrasts in gravity topography crustal and lithospheric thickness

steady plumes produced by downwellings in earth like vigor spherical whole mantle convection models if mantle thermal upwellings plumes are the cause of volcanic hot spots then observations suggest that plumes are relatively fixed with nonuniform distribution and limited lifetimes to date fixity of upwellings has only been shown in models of convection at either low vigor or with layering though studies where the lower mantle has high viscosity do frequently show upwellings with much lower drift velocities than the surface velocity since more vigorous convection traditionally shows more time dependence fixity of upwellings has not been expected for nonlayered convection at earth like vigor rather we might expect slow but increasing drift velocities i have undertaken numerical models of whole mantle convection in three dimensional spherical geometry at approaching earth like vigor surprisingly these simulations show prominent steady virtually fixed plumes arising from self organization controlled by the smaller but numerous cold downwellings if downwelling subduction dominates earth s interior dynamics then this work suggests that plume fixity need not require layering the regular spacing and permanence of model upwellings contrast with observations of hot spots though in these models which do not simulate plates the fixity and regular spacing result from the freedom of downwellings to occur everywhere except where plumes reach the surface i suggest that on earth this feedback is weakened by the presence of plates but that whole mantle thermal convection can still produce relatively fixed plumes though we might expect them to be weaker more mobile and transient

230th dating of coral abraders from stratified deposits at tangatatau rockshelter mangaia cook islands implications for building precise chronologies in polynesia abstract polynesian archaeology has relied primarily on 14c dating to establish the timing and tempo of human colonization of the eastern pacific ensuing cultural development and human environmental interactions despite advancements in 14c dating including accelerator mass spectrometry selection of short lived plant remains to avoid in built age and the use of bayesian models to refine 14c based chronologies large uncertainties introduced during calibration to calendar ages can severely limit the resolution of 14c dates in this context 230th dating of coral abraders a common artifact in many polynesian archaeological sequences can potentially provide much more precise dates we report 25 230th dates for acropora and porites coral abraders from a well studied stratified archaeological sequence at tangatatau rockshelter mangaia site man 44 cook islands develop screening criteria to identify reliable 230th dates from buried contexts and compare the results with a recent bayesian 14c chronology for the site visual characteristics gray color microcrystalline sugary texture can aid identifying altered corals before analysis but are non diagnostic of the suitability of samples for dating some corals that were fully remineralized to calcite preserved suitable u and th isotopic compositions and produced ages in agreement with 14c and pristine aragonitic coral 230th dates suggesting that unlike subaerially exposed corals buried corals may be susceptible to mineral alteration without perturbing the u series isotopic systematics possibly due to burial under reducing conditions in general corals with reliable 230th dates preserve initial 234u 238u ratios in equilibrium with seawater and have 230th 232th ratios 10 reliable dates at man 44 cluster within layers preserve stratigraphic order and agree with the previous 14c chronology precise 230th dates median 7 4 yr all errors 2 from coral abraders support early polynesian arrival on mangaia by 1011 6 5 8 ce and the arrival of the sweet potato ipomoea batatas no later than 1361 1466 ce indicating that trans pacific voyaging had introduced this south american native plant to the cook islands by the mid 15th century with suitable samples 230th dating of corals from stratified sequences has great potential for developing refined chronologies for polynesian and other pacific archaeological sites

glacial rebound and relative sea level variations a new appraisal summary late pleistocene and holocene changes in sea level at technically stable shorelines contain information on the melting history of the ice sheets and on the response of the earth to changes in surface loads on time scales of 104yr some separation of parameters defining the ice loads and the earth s response can be achieved by examining sea level change at different sites around the world and at different epochs this paper examines the mathematical requirements for obtaining satisfactory solutions for the sea level equation rather than emphasizing results for the earth s response to the surface loads an examination of the equation expressing the sea level variation on a viscoelastic earth indicates that careful consideration needs to be given to both the definition of the ice load and the geometry of the redistributed water load if geophysically significant earth response parameters are to be deduced from observations of relative sea level the spectrum of the 5 x 5 area mean description of the ice load widely used in glacial rebound studies contains significant power at high degrees n 30 and can result in substantial spatial variations in sea level unless a thick lithosphere is introduced in the earth s response function a smoothed 1 1 description of the ice model avoids these high degree oscillations in relative sea level and produces satisfactory sea level results without requiring a thick lithosphere at far field sites the holocene sea levels are sensitive to the earth s response to the meltwater loading in the vicinity of the site and a high degree spatial resolution of coastline geometry is required to model the mantle flow driven by the differential loading about the site at some sites convergence of the solution to the sea level equation is not obtained even when the solution is expanded to degree 180 convergent solutions at lower degrees can be achieved by introducing earth models with a moderately thick lithosphere if high resolution ice and meltwater load models are not used then the tendency will be to overestimate the effective elastic thickness of the lithosphere estimates of mantle viscosity are also of questionable value if these high resolution models are not used a preliminary examination of sea levels at sites in both the near and far field places an upper limit of about 50 80 km on the effective lithospheric thickness these sea level observations are also consistent with an upper mantle viscosity of about 1021 pas with a lower mantle viscosity in the range of 1021 1023pa s

some seismological and geometric features of intraplate earthquakes to understand the nature and cause of intraplate earthquakes we carried out a systematic search for common features associated with them various geological geophysical and seismic data were analyzed and geometric and seismic parameters were compared for 29 intraplate events m 4 5 occurring worldwide the results suggest that intraplate earthquakes occur by the reactivation of pre existing zones of weakness in a compressional stress regime which is generally oriented parallel to the absolute direction of plate motion two styles of faulting were observed for type a earthquakes observed in the eastern united states eastern china western europe and west africa deformation occurs by strike slip motion on steeply dipping faults type b events are usually associated with thrust or normal faulting and were observed in eastern canada fennoscandia australia and peninsular india focal depths did not explain the differences between type a and type b earthquakes rather the differences are due to the perturbation of a regional stress field by a local stress field the regional stress field for type a events is primarily due to ridge push forces the method of stress perturbation varied from region to region the earthquakes in the type b category were further divided into three subcategories type b1 occurring in eastern canada and fennoscandia type b2 occurring in australia peninsular india and central brazil and type b3 occurring in the gulf coast of the u s the inferred causes of the perturbing stresses are deglaciation intracontinental resistive forces resulting from the collision of plates and the deposition of a large thickness of sediments respectively type a events were found to be associated with intersecting faults and generally supported the intersection model of talwani 1988 and had analogs in plate boundary events

the intracratonic caraibas itacarambi earthquake of december 09 2007 4 9 mb minas gerais state brazil abstract on december 9 2007 a 4 9 mb earthquake occurred in the middle of the sao francisco craton in a region with no known previous activity larger than 4 mb this event reached intensity vii mm modified mercalli causing the first fatal victim in brazil the activity had started in may 25 2007 with a 3 5 magnitude event and continued for several months motivating the deployment of a local 6 station network a three week seismic quiescence was observed before the mainshock initial absolute hypocenters were calculated with best fitting velocity models and then relative locations were determined with hypodd the aftershock distribution indicates a 3 km long rupture for the mainshock the fault plane solution based on p wave polarities and hypocentral trend indicates a reverse faulting mechanism on a n30 e striking plane dipping about 40 to the se the rupture depth extends from about 0 3 to 1 2 km only despite the shallow depth of the mainshock no surface feature could be correlated with the fault plane aeromagnetic data in the epicentral area show short wavelength lineaments trending nne ssw to ne sw which we interpret as faults and fractures in the craton basement beneath the surface limestone layer we propose that the caraibas itacarambi seismicity is probably associated with reactivation of these basement fractures and faults under the present e w compressional stress field in this region of the south american plate

a global earthquake discrimination scheme to optimize ground motion prediction equation selection we present a new automatic earthquake discrimination procedure to determine in near real time the tectonic regime and seismotectonic domain of an earth quake its most likely source type and the corresponding ground motion prediction equation gmpe class to be used in the u s geological survey usgs global shakemap system this method makes use of the flinn engdahl regionalization scheme seismotectonic information plate boundaries global geology seismicity cat alogs and regional and local studies and the source parameters available from the usgs national earthquake information center in the minutes following an earthquake to give the best estimation of the setting and mechanism of the event depending on the tectonic setting additional criteria based on hypocentral depth style of faulting and regional seismicity may be applied for subduction zones these criteria include the use of focal mechanism information and detailed interface models to discriminate among outer rise upper plate interface and intraslab seismicity the scheme is validated against a large database of recent historical earthquakes though developed to assess gmpe selection in global shakemap operations we anticipate a variety of uses for this strategy from real time processing systems to any analysis involving tectonic classification of sources from seismic catalogs

great earthquakes in low strain rate continental interiors an example from se kazakhstan the lepsy fault of the northern tien shan se kazakhstan extends e w 120 km from the high mountains of the dzhungarian ala tau a subrange of the northern tien shan into the low lying kazakh platform it is an example of an active structure that connects a more rapidly deforming mountain region with an apparently stable continental region and follows a known palaeozoic structure field based and satellite observations reveal an 10 m vertical offset exceptionally preserved along the entire length of the fault geomorphic analysis and age control from radiocarbon and optically stimulated luminescence dating methods indicate that the scarp formed in the holocene and was generated by at least two substantial earthquakes the most recent event dated to sometime after 400 years b p is likely to have ruptured the entire 120 km fault length in a m w 7 5 8 2 earthquake the lepsy fault kinematics were characterized using digital elevation models and high resolution satellite imagery which indicate that the predominant sense of motion is reverse right lateral with a fault strike dip and slip vector azimuth of 110 50 s and 317 343 respectively which is consistent with predominant n s shortening related to the india eurasia collision in light of these observations and because the activity of the lepsy fault would have been hard to ascertain if it had not ruptured in the recent past we note that the absence of known active faults within low relief and low strain rate continental interiors does not always imply an absence of seismic hazard

active faulting in apparently stable peninsular india rift inversion and a holocene age great earthquake on the tapti fault we present observations of active faulting within peninsular india far from the surrounding plate boundaries offset alluvial fan surfaces indicate one or more magnitude 7 6 8 4 thrust faulting earthquakes on the tapti fault maharashtra western india during the holocene the high ratio of fault displacement to length on the alluvial fan offsets implies high stress drop faulting as has been observed elsewhere in the peninsula the along strike extent of the fan offsets is similar to the thickness of the seismogenic layer suggesting a roughly equidimensional fault rupture the subsiding footwall of the fault is likely to have been responsible for altering the continental scale drainage pattern in central india and creating the large west flowing catchment of the tapti river a preexisting sedimentary basin in the uplifting hanging wall implies that the tapti fault was active as a normal fault during the mesozoic and has been reactivated as a thrust highlighting the role of preexisting structures in determining the rheology and deformation of the lithosphere the slip sense of faults and earthquakes in india suggests that deformation south of the ganges foreland basin is driven by the compressive force transmitted between india and the tibetan plateau the along strike continuation of faulting to the east of the holocene ruptures we have studied represents a significant seismic hazard in central india

t waves from the great 1994 bolivian deep earthquake in relation to channeling of s wave energy up the slab we report the observation of t phases recorded at a number of pacific island sites following the great bolivian deep earthquake of june 9 1994 by studying their arrival times at the various stations we unravel the process of conversion from seismic to acoustic energy at the south american coastline we find that the maxima of amplitude of the phase are incompatible with propagation along the great circle from source to receiver but rather require the generation of the acoustic wave at a common point at the arica bight for all stations in the south pacific and even farther south for stations in hawaii and the bonin islands the timing of these conversions corresponds to the arrival of regional s waves at the conversion points the high frequency nature of the t phase requires the channeling of the s wave from the seismic source to conversion point through low attenuation material which in turns adds supportive evidence for the mechanical continuity of the downgoing slab under that section of south america despite the observed gap in seismicity between 300 and 600 km

stress channelling and partitioning of seismicity in the charlevoix seismic zone quebec canada summary the charlevoix seismic zone csz in the st lawrence valley of quebec is historically the most active in eastern canada the structurally complex region comprises rift faults formed during the opening of the iapetus ocean superimposed by a 350 ma meteorite impact structure resulting in a circular highly fractured zone although seismicity is localized along two steeply dipping planar rift parallel zones previous work indicates that most of the large scale rift faults bound the low magnitude background seismicity rather than generate earthquakes themselves in order to gain insight into the mechanics of the partitioning of this seismicity a 2 d model of the csz was built using the stress analysis code flac the rift faults are represented by frictional discontinuities the heavily fractured impact structure is represented by an elastic continuum of reduced modulus boundary displacements are used to generate a regional stress field with the major horizontal component in the direction of tectonic loading given a high strength the rift faults have little effect on the stress patterns stress trajectories naturally flow around the crater of reduced elastic modulus leaving the fractured area with lower stresses than the background level however when the rift faults have low strength they are unable to support stress trajectories inclined to them due to the resolved shear stress exceeding their strength this prevents trajectories from flowing out of the rift effectively channelling higher magnitude stresses into the region of the impact structure between the faults low strength bounding faults can thus explain the localization of seismicity into linear bands rather than distributed seismicity throughout the impact structure it also explains how the rift faults act as boundaries to regions of low magnitude seismicity these results indicate that the interplay between faults of varying strength and zones of differing elastic modulus can give rise to complicated stress patterns and can explain many of the seismicity patterns observed in the csz this has implications for other intraplate seismic zones as it shows an example of how regional weak faults can modify stress conditions around local structures and drive seismicity the results are particularly relevant for other regions located within rifted crust such as the new madrid seismic zone which possibly display evidence of stress channelling

traveltime dispersion in an isotropic elastic mantle strong lower mantle signal in differential frequency residuals we study wavefield effects of direct p and s waves in elastic and isotropic 3 d seismic structures derived from the temperature field of a high resolution mantle circulation model more specifically we quantify the dispersion of traveltime residuals caused by diffraction in structures with dynamically constrained length scales and magnitudes of the lateral variations in seismic velocities and density 3 d global wave propagation is simulated using a spectral element method intrinsic attenuation i e dissipation of seismic energy is deliberately neglected so that any variation of traveltimes with frequency can be attributed to structural effects traveltime residuals are measured at 15 22 5 34 and 51 s dominant periods by cross correlation of 3 d and 1 d synthetic waveforms additional simulations are performed for a model in which 3 d structure is removed in the upper 800 km to isolate the dispersion signal of the lower mantle we find that the structural length scales inherent to a vigorously convecting mantle give rise to significant diffraction induced body wave traveltime dispersion for both p and s waves the difference between long period and short period residuals for a given source receiver pair can reach up to several seconds for the period bands considered here in general these differential frequency residuals tend to increase in magnitude with increasing short period delay furthermore the long period signal typically is smaller in magnitude than the short period one that is wave front healing is efficient independent of the sign of the residuals unlike the single frequency residuals the differential frequency residuals are sur prisingly similar between the lower mantle and the whole mantle model for corresponding source receiver pairs the similarity is more pronounced in case of s waves and varies between different combinations of period bands the traveltime delay acquired in the upper mantle seems to cancel in these differential signals depending on the associated wavelengths and the length scales of structure at shallow depth differential frequency residuals may thus prove useful to precondition tomographic inversions for the lower mantle structure such as to reduce the influence of the upper mantle for certain length scales overall standard deviations of the diffraction induced traveltime dispersion between the longest 51 s and the shortest 15 s period considered here are 0 6 and 1 0 s for p and s waves respectively for comparison the corresponding standard deviations of the 15 s residuals are 1 0 s and 2 8 s in the lower mantle model standard deviations are 0 3 and 0 6 s respectively which gives an average lower mantle contribution to the total dispersion of 50 per cent for p waves and 60 per cent for s waves

coseismic surface deformation caused by the 23 march 2012 mw 5 4 ernabella pukatja earthquake central australia implications for fault scaling relations in cratonic settings abstract on 23 march 2012 at 09 25 utc an m w 5 4 earthquake occurred in the eastern musgrave ranges of north central south australia near the community of ernabella pukatja several small communities in this remote part of central australia reported the tremor but there were no reports of injury or significant damage this was the largest earthquake recorded on mainland australia in the past 15 years and resulted in the formation of a 1 6 km long surface deformation zone that included reverse fault scarps with a maximum vertical displacement of more than 0 5 m extensive ground cracking and numerous rock falls the earthquake occurred in nonextended stable continental region scr cratonic crust more than 1900 km from the nearest plate boundary surface deformation from the ernabella earthquake provides additional constraint on relations of surface rupture length to earthquake magnitude such relations aid in interpreting australia s rich record of prehistoric seismicity and contribute to improved estimates of scr seismic hazard worldwide based upon an analysis of new and reinterpretation of existing surface rupture length data faults in nonextended stable cratonic australia appear to produce longer surface ruptures for earthquakes larger than m w 6 5 than rupture lengths estimated using existing moment to rupture length scaling relations the implication is that the estimated maximum or characteristic magnitude of paleoearthquakes in such settings may be overestimated where the estimate is based only on the length of the prehistoric fault scarp

self consistent earthquake fault scaling relations update and extension to stable continental strike slip faults using seismic moment m length l data for stable continental region scr faults augmented by data not included in previous studies this article reassesses and confirms the bilinear scaling relation for the dip slip faults of leonard 2010 furthermore using the new data i propose a separate bilinear relation for estimating magnitude from surface rupture length there are now a small number of scr strike slip earthquakes for which the fault dimensions have been estimated i use these to constrain a trilinear scaling relation for this class of fault for the four fault types interplate dip slip interplate strike slip scr intraplate dip slip and scr intraplate strike slip the scaling relations for the 10 permutations of m d l w and a are given

an updated global earthquake catalogue for stable continental regions reassessing the correlation with ancient rifts summary we present an updated global earthquake catalogue for stable continental regions scrs i e intraplate earthquakes that is available on the internet our database contains information on location magnitude seismic moment and focal mechanisms for over 1300 m moment magnitude 4 5 historic and instrumentally recorded crustal events using this updated earthquake database in combination with a recently published global catalogue of rifts we assess the correlation of intraplate seismicity with ancient rifts on a global scale each tectonic event is put into one of five categories based on location i interior rifts taphrogens ii rifted continental margins iii non rifted crust iv possible interior rifts and v possible rifted margins we find that approximately 27 per cent of all events are classified as interior rifts i 25 per cent are rifted continental margins ii 36 per cent are within non rifted crust iii and 12 per cent iv and v remain uncertain thus over half 52 per cent of all events are associated with rifted crust although within the continental interiors i e away from continental margins non rifted crust has experienced more earthquakes than interior rifts no major change in distribution is found if only large m 6 0 earthquakes are considered the largest events m 7 0 however have occurred predominantly within rifts 50 per cent and continental margins 43 per cent intraplate seismicity is not distributed evenly instead several zones of concentrated seismicity seem to exist this is especially true for interior rifts taphrogens where a total of only 12 regions are responsible for 74 per cent of all events and as much as 98 per cent of all seismic moment released in that category of the four rifts taphrogens that have experienced the largest earthquakes seismicity within the kutch rift india and the east china rift system may be controlled by diffuse plate boundary deformation more than by the presence of the ancient rifts themselves the st lawrence depression canada besides being an ancient rift is also the site of a major collisional suture thus only at the reelfoot rift new madrid seismic zone nmsz usa is the presence of features associated with rifting itself the sole candidate for causing seismicity our results suggest that on a global scale the correlation of seismicity within scrs and ancient rifts has been overestimated in the past because the majority of models used to explain intraplate seismicity have focused on seismicity within rifts we conclude that a shift in attention more towards non rifted as well as rifted crust is in order

state of the art of national landslide databases in europe and their potential for assessing landslide susceptibility hazard and risk abstract a landslide inventory is the most important information source for quantitative zoning of landslide susceptibility hazard and risk it should give insight into the location date type size activity and causal factors of landslides as well as resultant damage in europe many countries have created or are creating national and or regional landslide databases ldbs yet little is known on their contents completeness format structure language use and accessibility and hence on their ability to perform national or transnational landslide zoning therefore this study presents a detailed analysis of existing national ldbs in the eu member states eu official candidate and potential candidate countries and efta countries and their possible use for landslide zoning these national ldbs were compared with a subset of 22 regional databases twenty two out of 37 contacted european countries currently have national ldbs and six other countries have only regional ldbs in total the national ldbs contain 633 696 landslides of which 485 004 are located in italy while austria the czech republic france norway poland slovakia and the uk also have 10 000 landslides in their ldbs national ldbs are generally created in the official language of each country and 58 of them contain other natural hazards e g floods and sinkholes about 68 of the ldbs contain less than 50 of all landslides in each country but a positive observation is that 60 of the ldbs are updated at least once a year or after a major event most landslide locations are collected with traditional methods such as field surveys aerial photo interpretation and analysis of historical records currently integration of landslide information from different national ldbs is hampered because of differences in language and classification systems for landslide type and activity other problems are that currently only half of the national ldbs have a direct link between spatial and alphanumeric information and that public access is generally restricted or limited a minimum set of features to be included in national ldbs is suggested and a flow chart is presented that classifies european countries by ability to perform national scale landslide susceptibility hazard and risk analyses

mineral virginia earthquake illustrates seismicity of a passive aggressive margin 1 the august 2011 m 5 8 mineral virginia earthquake that shook much of the northeastern u s dramatically demonstrated that passive continental margins sometimes have large earthquakes we illustrate some general aspects of such earthquakes and outline some of the many unresolved questions about them they occur both offshore and onshore reaching magnitude 7 and are thought to reflect reactivation of favorably oriented generally margin parallel faults created during one or more wilson cycles by the modern stress field they pose both tsunami and shaking hazards however their specific geologic setting and causes are unclear because large magnitude events occur infrequently microseismicity is not well recorded and there is little if any surface expression of repeated ruptures thus presently active seismic zones may be areas associated with higher seismicity over the long term the present loci of activity that migrates or aftershock zones of large prehistoric earthquakes the stresses causing the earthquakes may result from platewide driving forces glacial isostatic adjustment localized margin stresses and or dynamic topography the resulting uncertainties make developing cost effective mitigation strategies a major challenge progress on these issues requires integrating seismic geodetic and geological techniques

paleoshoreline record of relative holocene sea levels on pacific islands abstract understanding the history of relative holocene sea levels on pacific islands is important for constraining fundamental geodynamic theories interpreting the environments of early human occupation sites and forecasting future environmental conditions on the islands an observational paleoshoreline record is provided by emergent paleoshoreline indicators formed at higher relative sea levels hence standing at higher elevations than modern counterparts emergent paleoshoreline notches in limestone seacliffs record paleo high tide levels and emergent paleoreef flats record paleo low tide levels whereas emergent paleobeachrock locally records paleo intertidal levels both paleonotches and paleoreefs occur along the coasts of high standing islands exposing volcanic bedrock and uplifted reef complexes but low lying coralline atolls lack sufficient relief to preserve paleonotches controls on relative holocene sea level include global eustatic and regional hydro isostatic changes in ambient sea level relative to island landmasses and shifts in the elevations of islands relative to sea level caused by thermal subsidence of the oceanic lithosphere or thermally rejuvenated loci of hotspot volcanism by flexure of the lithosphere under the load of growing volcanic edifices hawaii samoa society islands by arching of the lithosphere over trench forebulges loyalty islands niue bellona rennell and by tectonism within forearc belts between active volcanic chains and trenches mariana islands tonga vanuatu the dominant pattern of relative sea level change where not overprinted by local tectonism or lithospheric flexure was a uniform early holocene rise in eustatic sea level followed by a regionally variable late holocene hydro isostatic drawdown in sea level the resultant was a mid holocene highstand in relative sea level that affected the development of shoreline morphology throughout the tropical pacific ocean the earliest human migrations into intra oceanic island groups of both the northwestern and southwestern pacific ocean followed close on the heels of the mid holocene sea level highstand and took advantage of newly attractive coastal environments engendered by sea level drawdown the effects of the mid holocene highstand were modified to varying degrees in different island groups by geodynamic uplift or subsidence

stress perturbation associated with the amazonas and other ancient continental rifts the state of stress in the vicinity of old continental rifts is examined to investigate the possibility that crustal structure associated with ancient rifts specifically a dense rift pillow in the lower crust may modify substantially the regional stress field both shallow 2 0 2 6 km depth breakout data and deep 20 45 km depth crustal earthquake focal mechanisms indicate a n to nne maximum horizontal compression in the vicinity of the paleozoic amazonas rift in central brazil this compressive stress direction is nearly perpendicular to the rift structure and represents a 75 rotation relative to a regional e w compressive stress direction in the south american plate elastic two dimensional finite element models of the density structure associated with the amazonas rift as inferred from independent gravity modeling indicate that elastic support of this dense feature would generate horizontal rift normal compressional stresses between 60 and 120 mpa with values of 80 100 mpa probably most representative of the overall structure the observed 75 stress rotation constrains the ratio of the regional horizontal stress difference to the rift normal compressive stress to be between 0 25 and 1 0 suggesting that this rift normal stress may be from 1 to 4 times larger than the regional horizontal stress difference a general expression for the modification of the normalized local horizontal shear stress relative to the regional horizontal shear stress shows that the same ratio of the rift normal compression relative to the regional horizontal stress difference which controls the amount of stress rotation also determines whether the superposed stress increases or decreases the local maximum horizontal shear stress the potential for fault reactivation of ancient continental rifts in general is analyzed considering both the local stress rotation and modification of horizontal shear stress for both thrust and strike slip stress regimes in the amazonas rift case because the observed stress rotation only weakly constrains the ratio of the regional horizontal stress difference to the rift normal compression to be between 0 25 and 1 0 our analysis is inconclusive because the resultant normalized horizontal shear stress may be reduced for ratios 0 5 or enhanced for ratios 0 5 additional information is needed on all three stress magnitudes to predict how a change in horizontal shear stress directly influences the likelihood of faulting in the thrust faulting stress regime in the vicinity of the amazonas rift a rift normal stress associated with the seismically active new madrid ancient rift may be sufficient to rotate the horizontal stress field consistent with strike slip faults parallel to the axis of the rift although this results in a 20 40 reduction in the local horizontal shear stress within the seismic zone sparse stress data in the vicinity of the seismically quiescent midcontinent rift of the central united states suggest a stress state similar to that of new madrid with the local horizontal shear stress potentially reduced by as much as 60 thus the markedly different levels of seismic activity associated with these two subparallel ancient rifts is probably due to other factors than stress perturbations due to dense rift pillows the modeling and analysis here demonstrate that rift normal compressive stresses are a significant source of stress acting on the lithosphere and that in some cases may be a contributing factor to the association of intraplate seismicity with old zones of continental extension

smooth or oscillating late holocene sea level curve evidence from the palaeo zoology of fixed biological indicators in east australia and beyond abstract the nature of late holocene sea level change has important palaeo environmental implications for the understanding of past and present coastal oceanic and climatic systems this study develops a fixed biological indicator fbi method based on tubeworm barnacle assemblages in order to construct a late holocene sea level curve for south east australia it also compares changes within and between mid latitude regions of the southern hemisphere using the palaeo biology of inter tidal sub fossils that have provided time elevation data covering the past 5000 years five sites from around the mouth of the port hacking estuary 29 km south of sydney are described in detail the results suggest that rather than relative sea level describing a stable or smoothly falling pattern from a maximum of 1 0 m above present over the last 5000 years on the southeast australian coast there have been complex movements from a maximum of over 1 5 m with at least one marked fall between 3500 and 3400 yr bp and the possibility of a small positive oscillation around 1900 yr bp furthermore changes in the inter tidal species at our sites suggest that there was a period between 4300 and 2800 years where ocean temperatures were warmer than present our port hacking findings are compared with other studies from the east coast of australia as well as the pacific islands and brazil evidence from each location suggests a broad similarity in the timing of environmental events and marine fluctuations across an expanse of the southern hemisphere are such similarities coincidental or part of mechanisms common to mid latitude southern hemisphere regions

seismic moment assessment of earthquakes in stable continental regions ii historical seismicity summary this part i study in conjunction with part 11 develops a method to determine within specified uncertainty bounds the seismic moment and thus moment magnitude of all earthquakes of stable continental regions scr for which instrumental or intensity data exist its basis is polynomial regression analysis using a database of scr earthquakes with direct seismic moment determination the independent variables include modern teleseismic magnitudes and regional magnitudes part i and isoseismal areas or number of recording stations part 11 part i11 is an application of the methodology of parts i and i1 to several major historical earthquakes all data used in the regressions are assigned individual uncertainties estimated from the literature or from experience formal confidence limits 68 per cent or 95 per cent on both the regression formulas and the predicted seismic moment values are then possible via error propagation analysis the most complete development is for the teleseismic magnitudes m and mb for both the final regression for log m is a quadratic formula that closely emulates the relationship between amplitude magnitudes and log m expected from dislocation theory and source scaling arguments regressions are also derived for the regional magnitudes mlg and m because there are many scr events mainly pre 1964 that have no teleseismic magnitudes prediction uncertainties from teleseismic magnitudes in moment magnitude units are in the ao 18 0 28 range and from regional magnitudes in the ko 23 0 38 range over a wide magnitude band finally the methodology developed here is generic even though the database is specific application to plate boundary oceanic intraplate or active continental intraplate regions should be straightforward

holocene sea levels in oceanic islands implications for the rheological structure of the earth s mantle abstract relative sea levels in oceanic islands that are situated sufficiently far from glaciated regions were studied in relation to the rheological structure of the earth s mantle the local hydro isostatic adjustment associated with the mantle flow from the oceanic side to an inland side depends on the size of the island the effective upper mantle viscosity and the elastic plate thickness the relative sea level has a significant dependence on the upper mantle rheology for islands with a radius larger than 10 km but it is almost independent of the upper mantle rheology for islands with a radius less than 10 km in other words the observed sea level changes in such small islands follow the global isostatic adjustment which depends strongly on the lower mantle viscosity in fact the relative sea levels in small oceanic islands impose important constraints on the lower mantle viscosity on the other hand the effective upper mantle viscosity and the elastic plate thickness are determined by analyzing the relative sea levels for islands greater than 10 km the observed sea level curves in japan and new zealand are consistent with the effective viscosity of the upper mantle equal to 2 to 6 10 21 poises the effective elastic plate thickness for japan and new zealand is estimated to be less than 50 km and greater than 100 km respectively the thickness of the lithosphere obtained by sea level curves in japan and new zealand is compatible with the results obtained by seismological studies

fault geometry and earthquakes in continental interiors abstract although large earthquakes in continental interiors are much less frequent than those along plate boundaries they have been responsible for a disproportionate amount of destruction i present a testable model for strain accumulation and seismicity in the upper crust of continental interiors intersecting faults provide a focus for strain build up resulting in local pockets of high strain accumulation rigid plates typically deform at strain rates 10 10 to 10 9 strain yr 1 but at intersecting fault zones strain accumulates at anomalously high rates of 10 8 to 10 7 strain yr 1 i e the strain rates are comparable with those at plate boundaries the resulting large earthquakes are associated with relatively short return times hundreds of years typically one of the intersecting faults appears to split and to offset the other main fault defined as a fault on which the larger offset occurs forming two parallel strands separated by a jog i also observe a rotation of one leg of the main fault with respect to the other the region of intersection is usually associated with intense fracturing increased microseismicity and uplift

intraplate deformation of the indian subcontinent 1 while deformation at the earth s surface primarily occurs along tectonic plate boundaries major earthquakes have shaken regions deep within continental interiors three of the largest m 7 5 historic intraplate earthquakes occurred within the indian subcontinent suggesting the possibility of significant intraplate deformation we consider surface velocities determined from new gps data collected at 29 continuous gps stations and 41 survey mode gps stations in india between 1995 and 2007 to find a north south shortening rate of 0 3 0 05 nanostrain yr 1 which may be accommodated by 2 1 mm yr of more localized convergence across central india southward motions at 4 7 mm yr of sites on the shillong plateau in northeast india reflect rapid shortening and high earthquake hazard associated with active thrust faults bounding the plateau the width and magnitude of the elastic strain accumulation field across the himalaya varies little from 76 90 longitude but the strain is more broadly distributed and convergence rates are higher along the eastern 200 km of the range

localization of intraplate deformation through fluid assisted faulting in the lower crust the flinders ranges south australia abstract in this paper we present a hypothesis for localized intraplate deformation in the continental crust of south central australia that involves fluid assisted reactivation of faults in the mid to lower crust using data from a temporary seismometer deployment in the flinders ranges we show that earthquakes relocated in a 3d velocity model cluster in elongated low vp vs anomalies that extend to depths exceeding 20 km and are aligned with the axis of the flinders ranges in the northern flinders ranges these low vp vs anomalies can be interpreted as fractured neoproterozoic to cambrian sediments that separate two cratonic blocks the gawler craton to the west and the curnamona province in the east previous studies of helium isotopes in springs to the north of the area provide evidence of mantle derived fluids that may influence faulting at depth our focal mechanism and stress inversion results show a regionally compressive stress field that provides no evidence for stress concentration we also argue that mechanisms for localized faulting such as thermal weakening and isostatic rebound also fail to account for the occurrence of earthquakes at mid to lower crustal depth in this area of high heat flow and that the focused seismicity can only be explained by high pore fluid pressure in the lower crust

quantitative impact of structural inheritance on present day deformation and seismicity concentration in intraplate deformation zones abstract structural inheritance i e paleo tectonic areas acting as weakened domains appear to be a key element localizing the seismicity in intraplate deformation zones however the impact of structural inheritance on the observed present day seismicity and strain rate concentration remains to be quantified in this study we quantify through 2d numerical modeling the localization and amplification factor of upper crustal strain rates induced by structural inheritance our 2d models are constrained by intraplate velocity boundary conditions and include rheology laws that accounts for inherited strain weakening in both the brittle and ductile layers of the lithosphere the role of structural inheritance is investigated for different localization of the weakened domain in the lithosphere for an average intraplate geotherm moho temperature ca 500 c brittle weakening i e inherited faults alone induces a limited amplification factor of upper crustal strain rates of ca 4 ductile weakening can increase the amplification factor to ca 7 when localized in the lower crust but has no effect when localized in the lithospheric mantle overall the amplification factors of upper crustal strain rates vary between 1 and 27 depending on the location of the weakened area in the lithosphere and on the different possible net driving forces crustal strengths amounts of weakening and geotherms these model amplification factors are in reasonable agreement with those derived from gps and seismicity data over large spatial scale several hundreds of kilometers in north america

intraplate earthquake swarm in belo jardim ne brazil reactivation of a major neoproterozoic shear zone pernambuco lineament summary intraplate earthquakes in stable continental areas have been explained basically by reactivation of pre existing zones of weakness stress concentration or both zones of weakness are usually identified as sites of the last major orogeny provinces of recent alkaline intrusions or stretched crust in ancient rifts however it is difficult to identify specific zones of weakness and intraplate fault zones are not always easily correlated with known geological features although northeastern brazil is one of the most seismically active areas in the country magnitudes 5 roughly every 5 yr with hypocentral depths shallower than 10 km and seismic zones as long as 30 40 km no clear relationship with the known surface geology can be usually established with confidence and a clear identification of zones of weakness has not yet been possible here we present the first clear case of seismic activity occurring as reactivation of an old structure in brazil the pernambuco lineament a major neoproterozoic shear zone the 2004 earthquake swarm of belo jardim magnitudes up to 3 1 and the recurrent activities in the nearby towns of sao caetano and caruaru magnitudes up to 4 0 and 3 8 show that the pernambuco lineament is a weak zone a local seismic network showed that the belo jardim swarm of 2004 november occurred by normal faulting on a north dipping e w oriented fault plane in close agreement with the e w trending structures within the pernambuco lineament the belo jardim activity was concentrated in a 1 5 km e w by 2 km downdip fault area and average depth of 4 5 km the nearby caruaru activity occurs as both strike slip and normal faulting also consistent with local structures of the pernambuco lineament the focal mechanisms of belo jardim caruaru and s caetano indicate e w compressional and n s extensional principal stresses the ns extension of this stress field is larger than that predicted by numerical models such as those of coblentz richardson and we propose that additional factors such as flexural stresses from the nearby sergipe alagoas marginal basin could also affect the current stress field in the pernambuco lineament

the intraplate porto dos gauchos seismic zone in the amazon craton brazil abstract the largest earthquake observed in the stable continental interior of the south american plate occurred in serra do tombador mato grosso state brazil on january 31 1955 with a magnitude of 6 2 mb since then no other earthquake has been located near the 1955 epicentre however in porto dos gauchos 100 km northeast of serra do tombador a recurrent seismicity has been observed since 1959 both serra do tombador and porto dos gauchos are located in the phanerozoic parecis basin two magnitude 5 earthquakes occurred in porto dos gauchos in 1998 and 2005 with intensities up to vi and v respectively these two main shocks were followed by aftershock sequences lasting more than three years each local seismic stations have been deployed by the seismological observatory of the university of brasilia since 1998 to study the porto dos gauchos seismic zone pgsz a local seismic refraction survey was carried out with two explosions to help define the seismic velocity model both the 1998 and 2005 earthquake sequences occurred in the same wsw ene oriented fault zone with right lateral strike slip mechanisms the epicentral zone is in the parecis basin near its northern border where there are buried grabens generally trending wnw ese such as the deep mesoproterozoic caiabis graben which lies partly beneath the parecis basin however the epicentral distribution indicates that the 1998 and 2005 sequences are related to a n60 e fault which probably crosses the entire caiabis graben the 1955 earthquake despite the uncertainty in its epicentre does not seem to be directly related to any buried graben either the seismicity in the porto dos gauchos seismic zone therefore is not directly related to rifted crust the probable direction of the maximum horizontal stress near porto dos gauchos is roughly e w consistent with other focal mechanisms further south in the pantanal basin and paraguay but seems to be different from the nw se direction observed further north in the amazon basin the recurrent seismicity observed in porto dos gauchos and the large 1955 earthquake nearby make this area of the parecis basin one of the most important seismic zones of brazil

reef coralgal assemblages as recorders of paleobathymetry and sea level changes in the indo pacific province the coralgal framework within the outer reef margin of many indo pacific reefs exhibits three main shallow water communities the environmental significance of which can be inferred by comparison with their modern counterparts a community dominated by tabular acropora gr hyacinthus cytherea with branching pocillopora damicornis p eydouxi montipora digitata occasional domal faviids and mm thick crusts of the coralline algae lithophyllum and mesophyllum mainly typical of the 6 15 m paleodepth range a community including robust branching acropora gr danai robusta a humilis a digitifera and subordinate favia stelligera echinopora gemmacea associated to vermetid gastropods and thick coralline crusts of hydrolithon cf onkodes and neogoniolithon cf fosliei flourishing in depths less than 6 m in medium to high water energy settings a community composed of domal porites cf lutea and p cf lobata with occasional acropora gr danai robusta and cm thick crusts of coralline algae in sheltered habitats in depths less than 10 m these biological assemblages allow us to determine relationships between reef growth and paleobathymetry and consequently to reconstruct regional relative sea level curves high water energy reefal assemblages provide stronger evidence for reconstructing sea level curves than low energy buildups because they have generally been controlled by a keep up growth mode subsiding reef sites seem to be more reliable indicators of sea level variations because they usually present expanded reef sequences

differences in attenuation among the stable continental regions 1 there are systematic differences in the attenuation of damaging earthquake ground motions between different stable continental regions scrs seismic intensity and weak motion data show that the attenuation in seismic waves for eastern north america ena is less than for india africa australia and northwest europe if ena ground motion attenuation relations are used in seismic hazard models for other scrs as is commonly done then the estimated ground motions and resulting hazard may be too large if an attenuation model that averages observations from ena and the other scrs is used to estimate the magnitudes of large historical earthquakes in ena as is the case for recent estimates of m for the 1811 1812 new madrid missouri and the 1886 charleston south carolina events then the magnitude estimates for these events will be too large as will be the resulting hazard

variations of the lithospheric strength and elastic thickness in north america we evaluate the effect of temperature variations on strength and effective elastic thickness te of the lithosphere of the north american na continent to this purpose we use two thermal models that are corrected for compositional variations and anelasticity effects in the upper mantle these thermal models are obtained from a joint inversion of gravity data and two recent seismic tomography models na07 and sl2013sv the crustal rheology was defined using nacr14 the most recent na crustal model this model specifies seismic velocities and thickness for a three layer model of the crystalline crust strength in the lithosphere and in the crust has similar distributions indicating that local geotherms play a dominant role in determining strength rather than crustal composition a pronounced contrast is present in strength between cratonic and off cratonic regions lithospheric strength in the off cratonic regions is prevalently localized within the crust and te shows low values 150 km in contrast to previous results our models indicate that phanerozoic regions located close to the edge of the cratons as the appalachians are characterized by low strength we also find that locally weak zones exist within the cratons e g beneath the intracratonic illinois basin and midcontinent rift seismic tomography models na07 and sl2013sv differ mainly in some peripheral parts of the cratons as the proterozoic canadian platform the grenville and the western part of the yavapai mazatzal province where the integrated strength for the model na07 is 10 times larger than in model sl2013sv due to a temperature difference 200 c in the uppermost mantle the differences in te between the two models are less pronounced in both models proterozoic regions reactivated by meso cenozoic tectonics e g rocky mountains and the mississippi embayment are characterized by a weak lithosphere due to the absence of the mechanically strong part of the mantle lithospheric layer intraplate earthquakes are distributed along the edges of the cratons demonstrating that tectonic stress accumulates there while the cores of the cratons remain undeformed in both models intraplate earthquakes occur in weak lithosphere 0 5 1013 pa s te 15 km or near the edges of strong cratonic blocks characterized by pronounced contrasts of strength and te

role of large scale tectonic forces in intraplate earthquakes of central and eastern north america central and eastern united states ceus have experienced large intraplate earthquakes yet at present there is no comprehensive model to explain stresses strain and seismicity in this intraplate setting models to explain the intraplate stresses in ceus include glacio isostatic adjustment ridge push effects local stresses along preexisting fracture zones and large scale convection in this paper we present a self consistent model of the dynamics of ceus that explains the stress field responsible for these intraplate earthquakes the earthquakes represent slow ongoing deformation associated with forces arising from a combination of lithosphere topography and structure together with the effects of density driven mantle flow using gps data we calculate strain rates that are likely to arise from tectonic effects and conclude that intraplate strain rates associated with tectonic effects are unlikely to exceed 1 x 10 9 year 1 we test several models of lateral viscosity variations by comparing model stress orientation output with earthquake moment tensors shmax directions from stress inversion and p axes of earthquakes a model that satisfies stress and earthquake constraints and also strain rate magnitude constraints requires high viscosity 1025 pa s craton and old oceanic lithosphere of the western atlantic block and weaker 5 x 1024 pa s accreted appalachian terrane other strength contrasts within the lithosphere are likely present incorporation of these into future models using constraints from seismology along with refined geodetic measurements and improved estimates of crust and upper mantle densities is needed to further refine long term dynamic models and better evaluate the hazards associated with this very slow ongoing permanent deformation within the eastern and central united states

estimation of the seismic moment rate from an incomplete seismicity catalog in the context of the insight mission to mars we evaluate methods to estimate the global seismic moment rate of a planet from the k 1 largest events observed during a limited and possibly short time span as can be expected for example for lander missions to mars the feasibility of the approach is demonstrated with a temporary broadband seismometer that was recording in the mojave desert california for 86 days in 2014 and by application to the global centroid moment tensor cmt catalog subsets thereof and a catalog of stable continental regions seismicity from the largest event observed at goldstone alone m w approximate to 7 9 we estimate the earth s global moment rate to be 1 03 x 10 22 n m yr whereas an estimation based on the 10 strongest events yields a rate of 5 79 x 10 21 n m yr summation of 42 yr of global cmt solutions results in an average of 7 61 x 10 21 n m yr in general a 2 yr interval of global cmt solutions is sufficient to estimate the earth s annual moment rate to within a factor of 5 or better a series of numerical experiments with more than 560 million synthetic catalogs based on the tapered gutenberg richter distribution shows that the estimation is rather insensitive against an unknown slope of the distribution and that bias and variance of the estimator depend on the ratio between moment rate and corner moment of the size frequency distribution moment rates of published mars models differ by a factor of 1000 or more tests with simulated catalogs show that it will be possible to reject some of these models with data returned by nasa s insight mission after two years of nominal mission life time