a kinematic model for recrystallization and texture development in olivine polycrystals the interpretation of seismic anisotropy in the mantle requires a knowledge of the relationship between the lattice preferred orientation lpo of crystals and the convective flow field in order better to understand this link we present a model for the evolution of lpo in olivine aggregates that deform by both intracrystalline slip and dynamic recrystallization dynamic recrystallization depends on the dislocation density of the grains which is a function of the applied local stress grains with a large density of dislocations lower their bulk strain energy by nucleating strain free sub grains at a rate proportional to a dimensionless nucleation parameter grains with high energy are then invaded by grains with low energy by grain boundary migration at a rate proportional to a dimensionless grain boundary mobility m the value of is constrained by observed lpo patterns in experimentally deformed olivine aggregates and m is constrained by the temporal evolution of the strength of the lpo for m 125 75 and 3 the model predictions agree well with the experimental results numerical calculations of lpo using our model are significantly faster than those based on viscoplastic self consistent or equilibrium based theories making the model especially suitable for applications for complex convective flows

the 2006 2007 kuril islands great earthquake sequence the southwestern half of a 500 km long seismic gap in the central kuril island arc subduction zone experienced two great earthquakes with extensive preshock and aftershock sequences in late 2006 to early 2007 the nature of seismic coupling in the gap had been uncertain due to the limited historical record of prior large events and the presence of distinctive upper plate trench and outer rise structures relative to adjacent regions along the arc that have experienced repeated great interplate earthquakes in the last few centuries the intraplate region seaward of the seismic gap had several shallow compressional events during the preceding decades notably an m s 7 2 event on 16 march 1963 leading to speculation that the interplate fault was seismically coupled this issue was partly resolved by failure of the shallow portion of the interplate megathrust in an m w 8 3 thrust event on 15 november 2006 this event ruptured 250 km along the seismic gap just northeast of the great 1963 kuril island m w 8 5 earthquake rupture zone within minutes of the thrust event intense earthquake activity commenced beneath the outer wall of the trench seaward of the interplate rupture with the larger events having normal faulting mechanisms an unusual double band of interplate and intraplate aftershocks developed on 13 january 2007 an m w 8 1 extensional earthquake ruptured within the pacific plate beneath the seaward edge of the kuril trench this event is the third largest normal faulting earthquake seaward of a subduction zone on record and its rupture zone extended to at least 33 km depth and paralleled most of the length of the 2006 rupture the 13 january 2007 event produced stronger shaking in japan than the larger thrust event as a consequence of higher short period energy radiation from the source the great event aftershock sequences were dominated by the expected faulting geometries thrust faulting for the 2006 rupture zone and normal faulting for the 2007 rupture zone a large intraplate compressional event occurred on 15 january 2009 m w 7 4 near 45 km depth below the rupture zone of the 2007 event and in the vicinity of the 16 march 1963 compressional event the fault geometry rupture process and slip distributions of the two great events are estimated using very broadband teleseismic body and surface wave observations the occurrence of the thrust event in the shallowest portion of the interplate fault in a region with a paucity of large thrust events at greater depths suggests that the event removed most of the slip deficit on this portion of the interplate fault this great earthquake doublet demonstrates the heightened seismic hazard posed by induced intraplate faulting following large interplate thrust events future seismic failure of the remainder of the seismic gap appears viable with the northeastern region that has also experienced compressional activity seaward of the megathrust warranting particular attention

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

seismic evidence for sharp lithosphere asthenosphere boundaries of oceanic plates the mobility of the lithosphere over a weaker asthenosphere constitutes the essential element of plate tectonics and thus the understanding of the processes at the lithosphere asthenosphere boundary lab is fundamental to understand how our planet works it is especially so for oceanic plates because their relatively simple creation and evolution should enable easy elucidation of the lab data from borehole broadband ocean bottom seismometers show that the lab beneath the pacific and philippine sea plates is sharp and age dependent the observed large shear wave velocity reduction at the lab requires a partially molten asthenosphere consisting of horizontal melt rich layers embedded in meltless mantle which accounts for the large viscosity contrast at the lab that facilitates horizontal plate motions

the 2010 2014 3 global earthquake rate increase in light of a heightened global earthquake rate during the first quarter of 2014 and recent studies concluding that large earthquakes affect global seismicity for extended periods we revisit the question whether the temporal distribution of global earthquakes shows clustering beyond that expected from a time independent poisson process we examine a broad window from 1979 to 2014 3 for m 7 0 shocks and a narrow window for m 5 0 seismicity since 2010 that has higher than average rates we test whether a poisson process can be falsified at 95 confidence to assess the degree of dependent clustering in the catalogs if aftershocks within at least one rupture length from main shocks foreshocks are filtered then we find no evidence of global scale m 5 2 5 6 depending on parameters clustering since 2010 that demands a physical explanation there is evidence for interdependence below this threshold that could be a consequence of catalog completeness or a physical process

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

alluvial charcoal in the sigatoka valley viti levu island fiji abstract charcoal concentrations in alluvial sediments throughout the sigatoka and adjacent catchments western viti levu island fiji were located sampled and where possible dated the earliest date 5579 5052 cal year bp almost certainly predates human arrival and represents a natural fire perhaps associated with drought conditions during an el nino event the next three dates are clustered around the time just after initial human arrival in fiji 2900 2700 cal year bp and could mean that humans transited the area 40 km inland within this time the next date 1520 1260 cal year bp is not associated with any other the final five dates are likewise clustered around the time of the ad 1300 event and are believed to mark the time when permanent inland upland settlement was established in this part of viti levu

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

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

role of a low viscosity zone in stabilizing plate tectonics implications for comparative terrestrial planetology 1 earth s near surface layer its lithosphere is broken into quasi rigid plates that form the upper thermal boundary layer for mantle convection since the discovery of plate tectonics it has been widely conjectured but only recently demonstrated that this peculiar style of convection may be facilitated by an upper mantle low viscosity zone lvz over which the plates glide easily the lvz or asthenosphere concept dates from 19th century investigations of isostatic support of mountain belts and is supported by modern evidence for a seismic low velocity zone and by studies of postglacial rebound and dynamic compensation of the earth s gravity field here we show in both two dimensional 2 d cartesian and 3 d spherical earth models that combining a pronounced lvz and a plastic yield stress to allow localized weakening of the cold thermal boundary layer results in a distinctly plate tectonic style of convection with 30 toroidal surface motion for the 3 d case recycling of water into the upper mantle at subduction zones is a plausible cause of earth s lvz whereas venus is dry and lacks both an lvz and plate tectonics

space time etas models and an improved extension for sensitive detection of anomalous seismicity such as quiescence and activation in a given region we need a suitable statistical reference model that represents a normal seismic activity in the region the regional occurrence rate of the earthquakes is modeled as a function of previous activity the specific form of which is based on empirical laws in time and space such as the modified omori formula and the utsu seki scaling law of aftershock area against magnitude respectively this manuscript summarizes the development of the epidemic type aftershock sequence etas model and proposes an extended version of the best fitted space time model that was suggested in ogata ogata y 1998 space time point process models for earthquake occurrences ann inst statist math 50 379 402 this model indicates significantly better fit to seismicity in various regions in and around japan d 2005 elsevier b v all rights reserved

influence of asperities along subduction interfaces on the stressing and seismicity of adjacent areas abstract dmowska r and lovison l c 1992 influence of asperities along subduction interfaces on the stressing and seismicity of adjacent areas in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 23 43 we have investigated the influence of large scale fault inhomogeneities in large subduction earthquakes on the style of deformation and seismic behavior of the incoming oceanic plate and slab at intermediate depths during the earthquake cycle the zones of the large subduction events of rat islands 1965 alaska 1964 and valparaiso 1985 have been searched for earthquakes with m b 5 0 if available and for time periods as long as possible it has been found that in general the seismicity in the incoming oceanic plate clusters in front of asperities areas of highest seismic moment release and strongest locking and is positioned relative to them in the direction of plate motion it is usually lacking in areas adjacent to non asperities that is to zones that slip during the main event but with appreciably smaller seismic moment release and possibly slip seismically aseismically during the whole cycle similar behavior occurs in the downgoing slab at intermediate depths where seismicity during the cycle clusters but less strongly than in the oceanic crust next to asperities and down dip from them we infer that the locking of asperities causes higher stresses associated with the earthquake cycle itself to occur in areas adjacent to asperities both up dip and down dip from them along the direction of plate motion and that such stressing is much less pronounced in the areas adjacent to non asperities this opens the possibility of identifying the areas of highest seismic moment release in future subduction earthquakes and carries implications for where the highest deformation and possibly precursory phenomena and or nucleation of a future event might occur

are spontaneous earthquakes stationary in california 1 aftershocks and some main shocks are triggered with timing controlled by preceding events the remaining spontaneous earthquakes presumably respond to tectonic stresses we consider whether triggered events can be reliably identified whether the rest are stationary and whether external phenomena control them to all three questions some studies of earthquake physics and hazard assume answers many suggest that stress changes from large distant earthquakes can alter the local spontaneous earthquake rate we demonstrate significant differences in the apparent earthquake rate after declustering by different methods and we present criteria for assessing the influence of such distant events the estimated spontaneous earthquake rate depends on the lower magnitude threshold of included events whether spontaneity is treated in binary or probabilistic form as well as assumptions about catalog completeness different statistical tests give different answers to the question of stationarity we examine a reported rate change in southern california and the suggestion that it might have resulted from the 1960 chile and 1964 alaska earthquakes the rate change itself is questionable if it has occurred it was probably not caused by those distant events because the rate change is not present in northern california or in all parts of southern california

origin of azimuthal seismic anisotropy in oceanic plates and mantle abstract seismic anisotropy is ubiquitous in the earth s mantle but strongest in its thermo mechanical boundary layers azimuthal anisotropy in the oceanic lithosphere and asthenosphere can be imaged by surface waves and should be particularly straightforward to relate to well understood plate kinematics and large scale mantle flow however previous studies have come to mixed conclusions as to the depth extent of the applicability of paleo spreading and mantle flow models of anisotropy and no simple globally valid relationships exist here we show that lattice preferred orientation lpo inferred from mantle flow computations produces a plausible global background model for asthenospheric anisotropy underneath oceanic lithosphere the same is not true for absolute plate motion apm models a 200 km thick layer where the flow model lpo matches observations from tomography lies just below the 1200 c isotherm of a half space cooling model indicating strong temperature dependence of the processes that control the development of azimuthal anisotropy we infer that the depth extent of shear and hence the thickness of a relatively strong oceanic lithosphere can be mapped this way these findings for the background model and ocean basin specific deviations from the half space cooling pattern are found in all of the three recent and independent tomographic models considered further exploration of deviations from the background model may be useful for general studies of oceanic plate formation and dynamics as well as regional scale tectonic analyses

a late quaternary record of environmental change and human impact from new caledonia a late quaternary vegetation record is presented from a lowland site on the leeward southwest coast of new caledonia plum swamp is a backswamp on the plum river at around 10 m a s l just within the ultramafic terrain that dominates the southern third of new caledonia pollen analysis charcoal analysis radiocarbon dating and stratigraphic analysis are employed to reconstruct the vegetation and sedimentary history of the valley the vegetation record commences at around 20 000 yr bp and shows that from this time up until the late holocene the valley was forested the greater representation of taxa more prevalent at higher altitudes during the late glacial suggests a response to cooling and an enrichment of the lowland forest with more montane elements the late glacial transition between 14 000 and 9000 yr bp is a period of instability within the valley when vegetation is disturbed by fire forest recovers after this and there is increasing stability until the arrival of people in the late holocene at around 3000 yr bp the initial colonisers of new caledonia had a profound effect upon the vegetation of the valley converting the lowland forest to a stunted and species poor maquis on the ultramafic sediments and melaleuca woodland on the non ultramafic substrates however sedimentary processes are relatively unchanged during this time dramatic geomorphic change does occur in the catchment though during the latter part of the 20th century as a consequence of mining q 2001 elsevier science b v all rights reserved

a comparison of late quaternary forest changes in new caledonia and northeastern australia a pollen record from lake xere wapo southeast new caledonia is the longest continuous terrestrial record to be recovered from the tropical southwest pacific and reveals a series of millennial scale changes in vegetation over the last 130 000 yr a comparison of the lake xere wapo record with the key northeast australian record of lynch s crater reveals regional patterns of change from 120 000 to 50 000 yr ago the vegetation around lake xere wapo alternated between rainforest and maquis with fire an important disturbance factor in the last 50 000 yr fire is almost absent from the record and the vegetation assumes a character unprecedented in the preceding 100 000 yr dominated by dacrydium and podocarpus pollen the most compelling aspect of the comparison with lynch s crater is that the much discussed araucaria decline at around 45 000 yr ago in northern queensland is matched by a similar decline in the lake xere wapo record d 2005 university of washington all rights reserved

reconstruction of far field tsunami amplitude distributions from earthquake sources the probability distribution of far field tsunami amplitudes is explained in relation to the distribution of seismic moment at subduction zones tsunami amplitude distributions at tide gauge stations follow a similar functional form well described by a tapered pareto distribution that is parameterized by a power law exponent and a corner amplitude distribution parameters are first established for eight tide gauge stations in the pacific using maximum likelihood estimation a procedure is then developed to reconstruct the tsunami amplitude distribution that consists of four steps 1 define the distribution of seismic moment at subduction zones 2 establish a source station scaling relation from regression analysis 3 transform the seismic moment distribution to a tsunami amplitude distribution for each subduction zone and 4 mix the transformed distribution for all subduction zones to an aggregate tsunami amplitude distribution specific to the tide gauge station the tsunami amplitude distribution is adequately reconstructed for four tide gauge stations using globally constant seismic moment distribution parameters established in previous studies in comparisons to empirical tsunami amplitude distributions from maximum likelihood estimation the reconstructed distributions consistently exhibit higher corner amplitude values implying that in most cases the empirical catalogs are too short to include the largest amplitudes because the reconstructed distribution is based on a catalog of earthquakes that is much larger than the tsunami catalog it is less susceptible to the effects of record breaking events and more indicative of the actual distribution of tsunami amplitudes

on the deformation cycle of a strongly coupled plate interface the triple earthquakes of 16 march 1963 15 november 2006 and 13 january 2007 along the kurile subduction zone 1 the great plate interface kurile earthquake of 15 november 2006 mw 8 3 was immediately followed by normal aftershocks in the outer rise of the central kurile subduction zone two months later at a distance 50 km from this event the 13 january 2007 mw 8 1 earthquake with a pure normal mechanism occurred in the outer rise of the central kurile the 15 november 2006 earthquake ruptured an area of 280 150 km2 with maximum slip of almost 7 m while the 13 january 2007 earthquake ruptured an area of 240 40 km2 with a maximum slip of almost 14 m these two significant events were preceded by a major reverse earthquake on 16 march 1963 mw 7 7 that took place close to the location of the 13 january 2007 earthquake these very different earthquakes demonstrate the different stages of the deformation cycle along strongly coupled plates at the central kurile arc and present a rare case of stress regime reversal over a short time span in order to understand the details of these three earthquakes we inverted for the source rupture processes of the earthquakes and delineated the location and dimension of asperities the role of gravity and topography anomalies and their correlation to the asperity distribution as well as the long term seismicity is studied in detail using trench parallel bouguer anomaly we have identified the differences in the asperities and the location of larger normal outer rise aftershocks as well as the location of 13 january 2007 earthquake we also show that the long term seismicity of the central kurile arc is confined to the intraslab and not the plate interface the static stress transfer for these earthquakes showed that the stress on optimally oriented thrust faults is increased in the northeastern part of the rupture area of the 15 november 2006 earthquake absence of major and great earthquakes to the northeastern immediate vicinity of the rupture area of the 15 november 2006 earthquake supports the hypothesis that this area is mature for the next strong earthquake along the kurile arc

long term tsunami data archive supports tsunami forecast warning research and mitigation in response to the 2004 indian ocean tsunami the united states began a careful review and strengthening of its programs aimed at reducing the consequences of tsunamis several reports and calls to action were drafted including the tsunami warning and education act public law 109 424 signed into law by the president in december 2006 noaa s national geophysical data center ngdc and co located world data center for geophysics and marine geology wdc gmg maintain a national and international tsunami data archive that fulfills part of the p l 109 424 the ngdc wdc gmg long term tsunami data archive has expanded from the original global historical event databases and damage photo collection to include tsunami deposits coastal water level data dart buoy data and high resolution coastal dems these data are used to validate models provide guidance to warning centers develop tsunami hazard assessments and educate the public about the risks from tsunamis in this paper we discuss current steps and future actions to be taken by ngdc wdc gmg to support tsunami hazard mitigation research to ultimately help save lives and improve the resiliency of coastal communities

kuril islands tsunami of november 2006 1 impact at crescent city by distant scattering 1 a numerical model for the global tsunami computation constructed by kowalik et al 2005 2007a is applied to the tsunami of november 15 2006 in the northern pacific with spatial resolution of one minute numerical results are compared to sea level data collected by pacific dart buoys the tide gauge at crescent city cc recorded an initial tsunami wave of about 20 cm amplitude and a second larger energy packet arriving 2 hours later the first energy input into the cc harbor was the primary direct wave traveling over the deep waters of the north pacific interactions with submarine ridges and numerous seamounts located in the tsunami path were a larger source of tsunami energy than the direct wave travel time for these amplified energy fluxes is longer than for the direct wave prime sources for the larger fluxes at cc are interactions with koko guyot and hess rise tsunami waves travel next over the mendocino escarpment where the tsunami energy flux is concentrated owing to refraction and directed toward cc local tsunami amplification over the shelf break and shelf are important as well in many locations along the north pacific coast the first arriving signal or forerunner has lower amplitude than the main signal which often is delayed understanding this temporal distribution is important for an application to tsunami warning and prediction as a tsunami hazard mitigation tool we propose that along with the sea level records which are often quite noisy an energy flux for prediction of the delayed tsunami signals be used

evolution of olivine lattice preferred orientation during simple shear in the mantle article i nfo understanding the variation of olivine lattice preferred orientation lpo as a function of shear strain is important for models that relate seismic anisotropy to the kinematics of deformation we present results on the evolution of olivine orientation as a function of shear strain in samples from a shear zone in the josephine peridotite southwest oregon we find that the lpo in harzburgites re orients from a pre existing lpo outside the shear zone to a new lpo with the olivine 100 maximum aligned sub parallel to the shear direction between 168 and 258 shear strain the strain at which 100 aligns with the shear plane is slightly higher than that observed in experimental samples which do not have an initial lpo while our observations broadly agree with the experimental observations our results suggest that a pre existing lpo influences the strain necessary for lpo alignment with the shear direction in addition olivine re alignment appears to be dominated by slip on both 010 100 and 001 100 due to the orientation of the pre existing lpo fabric strengths quantified using both the j and m indices do not increase with increasing shear strain unlike experimental observations our natural samples do not have a secondary lpo peak the lack of a secondary peak suggests that subgrain rotation recrystallization dominates over grain boundary migration during fabric re alignment harzburgites exhibit girdle patterns among 010 and 001 axes while a dunite has point maxima combined with the observation that harzburgites are finer grained than dunites we speculate that additional phases i e pyroxenes limit olivine grain growth and promote grain boundary sliding grain boundary sliding may relax the requirement for slip on the hardest olivine system enhancing activation of the two easiest olivine slip systems resulting in the 010 and 001 girdle patterns overall our results provide an improved framework for calibration of lpo evolution models

the 2009 samoa tonga great earthquake triggered doublet great earthquakes having seismic magnitudes of at least 8 usually involve abrupt sliding of rock masses at a boundary between tectonic plates such interplate ruptures produce dynamic and static stress changes that can activate nearby intraplate aftershocks as is commonly observed in the trench slope region seaward of a great subduction zone thrust event1 the earthquake sequence addressed here involves a rare instance in which a great trench slope intraplate earthquake triggered extensive interplate faulting reversing the typical pattern and broadly expanding the seismic and tsunami hazard on 29 september 2009 within two minutes of the initiation of a normal faulting event with moment magnitude 8 1 in the outer trench slope at the northern end of the tonga subduction zone two major interplate underthrusting subevents both with moment magnitude 7 8 with total moment equal to a second great earthquake of moment magnitude 8 0 ruptured the nearby subduction zone megathrust the collective faulting produced tsunami waves with localized regions of about 12 metres run up that claimed 192 lives in samoa american samoa and tonga overlap of the seismic signals obscured the fact that distinct faults separated by more than 50 km had ruptured with different geometries with the triggered thrust faulting only being revealed by detailed seismic wave analyses extensive interplate and intraplate aftershock activity was activated over a large region of the northern tonga subduction zone

field survey and geological effects of the 15 november 2006 kuril tsunami in the middle kuril islands the near field expression of the tsunami produced by the 15 november 2006 kuril earthquake mw 8 1 8 4 in the middle kuril islands russia including runup of up to 20 m remained unknown until we conducted a post tsunami survey in the summer of 2007 because the earthquake occurred between summer field expeditions in 2006 and 2007 we have observations topographic profiles and photographs from three months before and nine months after the tsunami we thoroughly surveyed portions of the islands of simushir and matua and also did surveys on parts of ketoi yankicha ryponkicha and rasshua tsunami runup in the near field of the middle kuril islands over a distance of about 200 km averaged 10 m over 130 locations surveyed and was typically between 5 and 15 m local topography strongly affected inundation and somewhat affected runup higher runup generally occurred along steep protruding headlands whereas longer inundation distances occurred on lower flatter coastal plains sediment transport was ubiquitous where sediment was available deposit grain size was typically sand but ranged from mud to large boulders wherever there were sandy beaches a more or less continuous sand sheet was present on the coastal plain erosion was extensive often more extensive than deposition in both space and volume especially in areas with runup of more than 10 m the tsunami eroded the beach landward stripped vegetation created scours and trim lines cut through ridges and plucked rocks out of the coastal plain

minimum magnitude of completeness in earthquake catalogs examples from alaska the western united states and japan we mapped the minimum magnitude of complete reporting m c for alaska the western united states and for the junec earthquake catalog of japan mc was estimated based on its departure from the linear frequency magnitude relation of the 250 closest earthquakes to grid nodes spaced 10 km apart in all catalogs studied mc was strongly heterogeneous in offshore areas the mc was typically one unit of magnitude higher than onshore on land also mc can vary by one order of magnitude over distance less than 50 km we recommend that seismicity studies that depend on complete sets of small earthquakes should be limited to areas with similar mc or the minimum magnitude for the analysis has to be raised to the highest com mon value of mc we believe that the data quality as reflected by the mc level should be used to define the spatial extent of seismicity studies where mc plays a role the method we use calculates the goodness of fit between a power law fit to the data and the observed frequency magnitude distribution as a function of a lower cutoff of the magnitude data mc is defined as the magnitude at which 90 of the data can be modeled by a power law fit mc in the 1990s is approximately 1 2 0 4 in most parts of california 1 8 0 4 in most of alaska aleutians and panhandle excluded and at a higher level in the junec catalog for japan various sources such as ex plosions and earthquake families beneath volcanoes can lead to distributions that cannot be fit well by power laws for the hokkaido region we demonstrate how neglecting the spatial variability of m c can lead to erroneous assumptions about deviations from self similarity of earthquake scaling

stress triggering in thrust and subduction earthquakes and stress interaction between the southern san andreas and nearby thrust and strike slip faults 1 we argue that key features of thrust earthquake triggering inhibition and clustering can be explained by coulomb stress changes which we illustrate by a suite of representative models and by detailed examples whereas slip on surface cutting thrust faults drops the stress in most of the adjacent crust slip on blind thrust faults increases the stress on some nearby zones particularly above the source fault blind thrusts can thus trigger slip on secondary faults at shallow depth and typically produce broadly distributed aftershocks short thrust ruptures are particularly efficient at triggering earthquakes of similar size on adjacent thrust faults we calculate that during a progressive thrust sequence in central california the 1983 mw 6 7 coalinga earthquake brought the subsequent 1983 mw 6 0 nunez and 1985 mw 6 0 kettleman hills ruptures 10 bars and 1 bar closer to coulomb failure the idealized stress change calculations also reconcile the distribution of seismicity accompanying large subduction events in agreement with findings of prior investigations subduction zone ruptures are calculated to promote normal faulting events in the outer rise and to promote thrust faulting events on the periphery of the seismic rupture and its downdip extension these features are evident in aftershocks of the 1957 mw 9 1 aleutian and other large subduction earthquakes we further examine stress changes on the rupture surface imparted by the 1960 mw 9 5 and 1995 mw 8 1 chile earthquakes for which detailed slip models are available calculated coulomb stress increases of 2 20 bars correspond closely to sites of aftershocks and postseismic slip whereas aftershocks are absent where the stress drops by more than 10 bars we also argue that slip on major strike slip systems modulates the stress acting on nearby thrust and strike slip faults we calculate that the 1857 mw 7 9 fort tejon earthquake on the san andreas fault and subsequent interseismic slip brought the coalinga fault 1 bar closer to failure but inhibited failure elsewhere on the coast ranges thrust faults the 1857 earthquake also promoted failure on the white wolf reverse fault by 8 bars which ruptured in the 1952 mw 7 3 kern county shock but inhibited slip on the left lateral garlock fault which has not ruptured since 1857 we thus contend that stress transfer exerts a control on the seismicity of thrust faults across a broad spectrum of spatial and temporal scales

tsunami sources of the november 2006 and january 2007 great kuril earthquakes abstract along the northern kuril trench a great interplate earthquake occurred in november 2006 followed by an outer rise normal fault event in january 2007 surface wave magnitudes m s 7 8 and 8 2 indicate that the 2007 event was larger while the global cmt solutions m w 8 3 and 8 1 indicate that the 2006 event was larger tsunamis from both events were recorded at tide gauge stations in japan russia and the united states as well as deep ocean assessment and reporting of tsunamis dart systems and cabled tsunami sensors installed on deep ocean bottom inversion of 52 tsunami waveforms indicates that the 2006 tsunami source was about 200 km long extending from the epicenter to northeast the largest slips of 4 7 m are estimated on the northeastern subfaults for the 2007 event inversion of 32 waveforms shows that the tsunami source was about 120 km long with the largest slip of 3 5 m on the northeastern subfault the agreements between the observed and synthetic tsunami waveforms are generally good for both events not only within the inversion time windows but also for the later phases which were not used in inversions the slip distributions yield the seismic moment of m w 8 1 for the 2006 event and m w 7 9 for the 2007 event the seismic moment of the 2006 event was larger than the 2007 event from comparison of tsunami data regardless of fault model

a late holocene record of human impact from the southwest coast of new caledonia a late holocene vegetation record is presented from the southwest coast of new caledonia lac saint louis is a freshwater swamp at 3 m a s l adjacent to the river coulee delta pollen analysis charcoal analysis radiocarbon dating and stratigraphic analyses have been used to reconstruct the vegetation and sedimentary history of the swamp the sediment record commences at 6000 bp and reflects rapid flood plain development associated with postglacial sea level rise this rapid accumulation of sediment ceased around 5500 bp and the site became a freshwater swamp from 5500 to 3000 bp the pollen record reflects several aspects of this coastal landscape coastal forest the swamp surface and the adjacent mangrove zone at 3000 bp charcoal levels increase significantly in conjunction with abrupt changes in the pollen record mangrove pollen declines and pollen indicative of coastal forest is replaced by pollen indicative of coastal savanna these changes coincide with the commencement of the archaeological record in new caledonia and mirror similar changes in other late holocene records elsewhere on the island and are interpreted as representing human impact yam terraces surrounding lac saint louis may have been built around 2000 bp based on mineral magnetic measurements and charcoal accumulation the decline in mangrove vegetation adjacent to site may be the result of a late holocene fall in sea level increased sedi ment accumulation along the coastal foreshore as a result of forest clearance in the river coulee s catch ment however is also considered

distribution of tsunami interevent times 1 the distribution of tsunami interevent times is analyzed using global and site specific hilo hawaii tsunami catalogs an empirical probability density distribution is determined by binning the observed interevent times during a period in which the observation rate is approximately constant the empirical distributions for both catalogs exhibit non poissonian behavior in which there is an abundance of short interevent times compared to an exponential distribution two types of statistical distributions are used to model this clustering behavior 1 long term clustering described by a universal scaling law and 2 omori law decay of aftershocks and triggered sources the empirical and theoretical distributions all imply an increased hazard rate after a tsunami followed by a gradual decrease with time approaching a constant hazard rate examination of tsunami sources suggests that many of the short interevent times are caused by triggered earthquakes though the triggered events are not necessarily on the same fault

bridging great earthquake doublets through silent slip on and off fault aftershocks of the 2006 kuril island subduction earthquake toggled by a slow slip on the outer rise normal fault of the 2007 great earthquake 1 the november 2006 great thrust earthquake of moment magnitude m w 8 3 on the plate boundary in the kuril chishima islands triggered as many vigorous normal faulting aftershocks in the outer rise region seaward of the trench as on fault aftershocks here we show that the aftershocks for a 40 day period preceding the january 2007 m w 8 1 event in the outer rise were less frequently observed than the rate expected by both the omori utsu formula and the epidemic type aftershock sequence etas model while at the same time were more frequent along the plate boundary we discuss whether such simultaneous quiescence and activation in the pervasive 2006 aftershocks might have been initiated by the onset of aseismic slip on the 2007 rupture plane the stable fault sliding in an elastic half space demonstrates progressive stress shadowing in the outer rise and stress loading along the plate boundary furthermore the rate and state dependent friction of dieterich quantitatively simulates temporal changes in seismic behavior the same trends of the anomalous activities last in both zones after the 2007 rupture which suggests that the slips continuously take place in the similar region on the fault throughout the period before and after the rupture the kuril case implies that temporal seismic quiescence in an aftershock sequence is useful in evaluating the possibility of the subsequent triggered event thus suggesting itself as a potential earthquake forecasting model together with pervasive earthquake clustering models

methods for measuring seismicity rate changes a review and a study of how the m w 7 3 landers earthquake affected the aftershock sequence of the m w 6 1 joshua tree earthquake the development of fault interaction models has triggered the need for an accurate estimation of seismicity rate changes following the occurrence of an earthquake several statistical methods have been developed in the past to serve this purpose each relying on different assumptions e g stationarity gaussianity pertaining to the seismicity process

thermal structure radial anisotropy and dynamics of oceanic boundary layers defining the oceanic lithosphere as a thermal boundary layer allows to explain to first order age dependent bathymetry and isotropic wave speeds in contrast ss precursors and receiver functions suggest a subhorizontal interface within this layer on top of a radially anisotropic zone comparing a suite of geodynamic scenarios against surface wave dispersion data and seismic discontinuities we find that only weak age dependency of the radially anisotropic zone is compatible with observations we show that this zone is confined from below by a second weaker seismic interface while observed azimuthal anisotropy is consistent with lattice preferred orientation of olivine due to asthenospheric flow underneath the lithosphere radial anisotropy requires additional contributions perhaps from petrological fabrics or melt ponding this implies that seismic reflectors previously associated with the base of the lithosphere are instead associated with preserved structures embedded in it they carry information about plate formation but have little control on plate deformation

sea surface temperature estimates for the tropical western pacific during the last glaciation and their implications for the pacific warm pool twenty deep sea sediment cores from the western pacific between 30 n and 30 s provide evidence of sea surface temperature sst changes throughout the tropics and subtropics glacial ssts were estimated using the modern analog technique mat applied to planktonic foraminifers and planktonic foraminiferal 18o changes we used 18o to identify the last glacial maximum the mat method differs from the traditional transfer function approach in that it utilizes a global coretop database and estimates paleotemperature by finding analogs from the modern coretop samples in addition the mat approach appears to be less susceptible than the transfer function technique to biases introduced by carbonate dissolution our results indicate that tropical ssts differed by less than 2 c from present away from the tropics 30 n and 30 s ssts were at least 3 c cooler our results differ from those of previous studies in the western pacific by using a set of well preserved high sedimentation rate cores from shallow regions the results of this study clearly indicate that a western pacific warm pool existed during the last glacial maximum lgm providing a heat and moisture source for a walker circulation cell similar to that of today we propose that a steeper lapse rate existed during the last glacial maximum and that this can explain at least part of the discrepancy between marine and terrestrial temperature estimates adjacent to new guinea for the lgm

explanation of temporal clustering of tsunami sources using the epidemic type aftershock sequence model temporal clustering of tsunami sources is examined in terms of a branching process model it previously was observed that there are more short interevent times between consecutive tsunami sources than expected from a stationary poisson process the epidemic type aftershock sequence etas branching process model is fitted to tsunami catalog events using the earthquake magnitude of the causative event from the centennial and global centroid moment tensor cmt catalogs and tsunami sizes above a completeness level as a mark to indicate that a tsunami was generated the etas parameters are estimated using the maximum likelihood method the interevent distribution associated with the etas model provides a better fit to the data than the poisson model or other temporal clustering models when tsunamigenic conditions magnitude threshold submarine location dip slip mechanism are applied to the global cmt catalog etas parameters are obtained that are consistent with those estimated from the tsunami catalog in particular the dip slip condition appears to result in a near zero magnitude effect for triggered tsunami sources the overall consistency between results from the tsunami catalog and that from the earthquake catalog under tsunamigenic conditions indicates that etas models based on seismicity can provide the structure for understanding patterns of tsunami source occurrence the fractional rate of triggered tsunami sources on a global basis is approximately 14 online material figures of residual analysis for tsunami and earthquake catalogs

environmental change in the late pleistocene and later holocene at wanda site soroako south sulawesi indonesia abstract this paper reports the pollen analysis of an 8 m core from a mire at 445 m altitude and 2 s latitude on ultramafic soils near the western shore of lake matano south sulawesi the area is almost undisturbed by humans and the record is believed to cover about 50 75 000 yr b p with some breaks in the record a section from 17 000 to around 5500 yr b p and the last 1000 years of the record may be missing or disturbed the results show that montane forest grew around the site continuously through the late pleistocene with a maximum increase in higher altitude taxa from 35 000 to after 17 000 yr b p the time of glacial maxima elsewhere also in this period increases in grass and casuarina indicate possible drier conditions the holocene sections record lower altitude forest with increased taxonomic diversity including secondary species the results show that vegetation in the region has been sensitive to climatic change the pleistocene ecology being consistent with a temperature change of about 2 5 3 5 c with a phase up to 50 drier than present the site climate was possibly affected by shelf exposure in the gulf of bone due to lower sea levels however the tropical forest demonstrates overall long term stability in which changes in dominance may reflect minor shifts in disturbance and tree longevity a distinctive record of fine charcoal occurs throughout the deposit this shows that the forest has never been continuously fire free for a very long time the cause of the fires may be natural as no evidence for human occupation was discerned

a great earthquake doublet and seismic stress transfer cycle in the central kuril islands temporal variations of the frictional resistance on subduction zone plate boundary faults associated with the stick slip cycle of large interplate earthquakes are thought to modulate the stress regime and earthquake activity within the subducting oceanic plate here we report on two great earthquakes that occurred near the kuril islands which shed light on this process and demonstrate the enhanced seismic hazard accompanying triggered faulting on 15 november 2006 an event of moment magnitude 8 3 ruptured the shallow dipping plate boundary along which the pacific plate descends beneath the central kuril arc the thrust ruptured a seismic gap that previously had uncertain seismogenic potential although the earlier occurrence of outer rise compressional events had suggested the presence of frictional resistance within minutes of this large underthrusting event intraplate extensional earthquakes commenced in the outer rise region seaward of the kuril trench and on 13 january 2007 an event of moment magnitude 8 1 ruptured a normal fault extending through the upper portion of the pacific plate producing one of the largest recorded shallow extensional earthquakes this energetic earthquake sequence demonstrates the stress transfer process within the subducting lithosphere and the distinct rupture characteristics of these great earthquakes illuminate differences in seismogenic properties and seismic hazard of such interplate and intraplate faults

a long vegetation history from lowland irian jaya indonesia abstract this paper reports the pollen analysis of a 10 m core from a mire at 780 m altitude and 2 s latitude on ultrabasic soils on a northern coastal range of new guinea the area is almost undisturbed by humans and the record is believed to cover about 60 000 yr b p the results show that montane forest grew around the site continously through the late pleistocene with a distinct increases in higher altitude taxa from 25 000 to 10 500 yr b p the time of glacial maxima elsewhere the invasion of the site by lower altitude forest which commenced at 10 500 yr b p was reversed after a few hundred years and was not finally completed until about 7000 yr b p the results show that vegetation in the region has been sensitive to climatic change the pleistocene ecology being consistent with a temperature change of about 3 4 c times of change agree with other tropical areas even though the site climate was probably affected by changing sea levels however the tropical forest demonstrates overall long term stability in which changes in dominance may reflect minor shifts in disturbance and tree longevity a distinctive record of fine charcoal occurs after 10 900 yr b p but not at any level prior to that time this shows that the forest was continously fire free for a very long time the charcoal is probably an indication of anthropogenic disturbance which may correlate with the spread of agricultural innovation in lowland new guinea an increase in secondary species after 7000 yr b p may be a result of minor anthropogenic activity or the result of warmer conditions and shorter tree life in the lower altitude forests

probabilistic tsunami hazard assessment at seaside oregon for near and far field seismic sources 1 the first probabilistic tsunami flooding maps have been developed the methodology called probabilistic tsunami hazard assessment ptha integrates tsunami inundation modeling with methods of probabilistic seismic hazard assessment psha application of the methodology to seaside oregon has yielded estimates of the spatial distribution of 100 and 500 year maximum tsunami amplitudes i e amplitudes with 1 and 0 2 annual probability of exceedance the 100 year tsunami is generated most frequently by far field sources in the alaska aleutian subduction zone and is characterized by maximum amplitudes that do not exceed 4 m with an inland extent of less than 500 m in contrast the 500 year tsunami is dominated by local sources in the cascadia subduction zone and is characterized by maximum amplitudes in excess of 10 m and an inland extent of more than 1 km the primary sources of uncertainty in these results include those associated with interevent time estimates modeling of background sea level and accounting for temporal changes in bathymetry and topography nonetheless ptha represents an important contribution to tsunami hazard assessment techniques viewed in the broader context of risk analysis ptha provides a method for quantifying estimates of the likelihood and severity of the tsunami hazard which can then be combined with vulnerability and exposure to yield estimates of tsunami risk

stress transfer and seismic phenomena in coupled subduction zones during the earthquake cycle an elementary mechanical model of a coupled subduction zone is presented it is used to study the transfer of extensional stresses along the underthrusting plate and shear stress interactions between the plate itself and its thrust contact zone with the overriding plate during the earthquake cycle the model assumes an elastic plate which deforms one dimensionally has shear drag interactions treated approximately by the elsasser procedure with a maxwellian viscoelastic mantle and is subject to steady gravitational sinking forces great thrust earthquakes are simulated as sudden stress relieving displacements at the contact zone between the slab and overriding plate the model allows analysis of the space and time variable stresses in the main thrust zone the adjacent oceanic plate and the subducting slab over each earthquake cycle stress variations leading to outer rise events are discussed as well as stress changes responsible for intraplate seismicity downdip from the main thrust zone based on simulations of periodic great earthquakes the results of simulated slow progression of deformation slip from below into the thrust contact zone are also presented such preslip occurring over a time scale that is small in comparison with the whole seismic cycle e g of the order of a tenth or so is shown to transiently slow the rate of buildup of or even relieve extensional stresses in the slab in the absence of preslip those stresses build up steadily in time during the latter part of the cycle the results have implications for induction of sesimic quiescence as well as for explaining patterns of seismicity in relation to spatial position along the underthrusting plate and to time throughout the cycle correlations are reported between the model simulations and seismicity observations from coupled subduction zones around the world the observations include tensional outer rise events after large subduction earthquakes and compressional ones in the latter parts of the cycle normal tensional intraplate earthquakes preceding the main thrust events and positioned downdip from the thrust zones and interlaced periods of seismic activity in the lower part of the main thrust zone and in the descending slab

absence of remotely triggered large earthquakes beyond the mainshock region earthquakes trigger damaging aftershocks in nearby regions but whether they also trigger large earthquakes over significant distances has been unclear analysis of seismic data since 1979 suggests that earthquakes triggered more large shocks only over distances of about 1 000 km and did not increase the seismic hazard risk on a global scale

plate tectonic analysis of shallow seismicity apparent boundary width beta corner magnitude coupled lithosphere thickness and coupling in seven tectonic settings a new plate model is used to analyze the mean seismicities of seven types of plate boundary crb continental rift boundary ctf continental transform fault ccb continental convergent boundary osr oceanic spreading ridge otf oceanic transform fault ocb oceanic convergent boundary sub subduction zone we compare the platelike nonorogen regions of model pb2002 bird 2003 with the centroid moment tensor cmt catalog to select apparent boundary half widths and then assign 95 of shallow earthquakes to one of these settings a tapered gutenberg richter model of the frequency moment relation is fit to the subcatalog for each setting by maximum likelihood best fitting values range from 0 53 to 0 92 but all 95 confidence ranges are consistent with a common value of 0 61 0 66 to better determine some corner magnitudes we expand the subcatalogs by 1 inclusion of orogens and 2 inclusion of years 1900 1975 from the catalog of pacheco and sykes 1992 combining both earthquake statistics and the plate tectonic constraint on moment rate corner magnitudes include the following crb graphic 1 ctf graphic 2 ccb graphic 3 ocb graphic 4 and sub graphic 5 coupled lithosphere thicknesses are found to be the following crb graphic 6 ctf graphic 7 ccb graphic 8 osr graphic 9 for normal faulting and graphic 10 for strike slip otf graphic 11 and graphic 12 at low medium and high velocities ocb graphic 13 and sub graphic 14 in general high coupling of subduction and continental plate boundaries suggests that here all seismic gaps are dangerous unless proven to be creeping in general low coupling within oceanic lithosphere suggests a different model of isolated seismic fault patches surrounded by large seismic gaps that may be permanent online material global seismic subcatalogs of shallow earthquakes 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif 3 embed inline graphic 3 gif 4 embed inline graphic 4 gif 5 embed inline graphic 5 gif 6 embed inline graphic 6 gif 7 embed inline graphic 7 gif 8 embed inline graphic 8 gif 9 embed inline graphic 9 gif 10 embed inline graphic 10 gif 11 embed inline graphic 11 gif 12 embed inline graphic 12 gif 13 embed inline graphic 13 gif 14 embed inline graphic 14 gif

pleistocene vegetation of the humid tropics of northeastern queensland australia abstract the humid tropics area of northeastern queensland has provided a substantial and detailed history of rainforest and rainforest savanna interactions from the pollen analysis of a number of sites on the volcanic atherton tableland through the latter part of the quaternary period a recent extension of the record to close to the base of the quaternary from examination of an offshore core provides a broad regional and temporal context for evaluation of the true significance of late quaternary changes it is apparent that the major sustained change in the vegetation of the region occurred relatively recently probably within the last 140 000 yr and that this change was time transgressive it involved the replacement of extensive moist rainforest by open eucalypt woodland and is considered to have been most likely caused by the burning activities of aboriginal people some aspects of the record from this region can contribute to the history of rainforest on a global scale but other features of it re inforce the unique nature of the development of australian vegetation patterns

seismic coupling and outer rise earthquakes variation of interplate seismic coupling at subduction zones is a major factor controlling the size of the largest underthrusting events this variation also has a profound effect on the regional intraplate stresses in the vicinity of the subduction zone outer rise seismicity is strongly correlated with variations in interplate coupling reflecting the stress state of the interplate coupled zone over 200 outer rise earthquakes with known focal mechanisms are used to investigate the relationship between stresses in the outer rise and interplate seismic coupling these events occur within the downgoing i e oceanic plate near the bathymetric trench axes and generally fall into the categories of tensional normal or compressional thrust with their tensional or compressional stress axes oriented approximately horizontal and perpendicular to the trench in uncoupled subduction zones only tensional outer rise earthquakes occur which indicates that the outer rise is dominated by tensional stresses associated with plate bending and or slab pull forces in strongly coupled subduction zones both tensional and compressional outer rise events are found these events are related both spatially and temporally to the distribution of large underthrusting earthquakes and are thus an integral part of the earthquake cycle in the strongly coupled regions tensional outer rise events follow large underthrusting events as the outer rise is temporarily in tension due to the underthrusting motion compressional outer rise events take place as compressional stress slowly accumulates oceanward of locked sections of the interplate zone in four instances compressional outer rise earthquakes have been followed by large underthrusting events which have occurred 2 4 7 and 19 years after the associated outer rise event the remaining compressional outer rise events are located in regions that are either known seismic gaps or in regions where the seismic potential is unknown the occurrence of compressional outer rise earthquakes suggests that compressional stress is accumulating in the adjacent interplate region and that there is the potential for a future large underthrusting event in the region thirty compressional outer rise events have been located in trench segments of middle and south america the kurile islands the tonga and kermadec islands the new hebrides arc and the solomon islands regions in both the southern kamchatka and northern new hebrides regions the outer rise seismicity indicates that the stress regimes in the outer rise have changed with time from tensional following a previous large underthrusting event to compressional at present thus three stages of the cycle from underthrusting to tensional outer rise regime to compressional outer rise regime are present requiring only the occurrence of the next underthrusting event to complete the cycle the occurrence of compressional outer rise events is useful for assessing the seismic potential of a region on an intermediate time scale

trans pacific upper mantle shear velocity structure 1 we use 50 tonga fiji events recorded at the broadband trinet array southern california to develop a pure path upper mantle shear velocity model across the pacific at the epicentral distances of 70 95 multibounce s waves up to s5 are observed including their triplicated branches which become particularly clear after stacking since these s wave multiples turn at various depths simultaneously modeling their differential traveltimes and waveforms provides strong constraints on the radial velocity structure we parameterize the velocity model according to a priori information from the previous oceanic models so that we can take a grid search approach to fully investigate possible interdependencies among the model parameters we construct synthetics with a reflectivity code and study both the sh and sv components by modeling the whole recordings from events at different depths with different mechanisms we are able to separate shallow low velocity zone lvz features from deeper structure our preferred model pac06 contains a fast lid vsh 4 78 km s 1 vsv 4 58 km s 1 with a thickness of 60 km the underlying lvz is prominent with the lowest velocities vsh 4 34 km s 1 and vsv 4 22 km s 1 occurring at a depth of 160 km these velocities are below the estimates of solid state lvz suggesting the presence of partial melt the anisotropy vsv vsh of pac06 extends to 300 km depth which is constrained by s5 turning at this depth besides the 406 km and 651 km discontinuities pac06 also has a small 1 velocity jump at 516 km we consider these main features of pac06 to be well determined since pac06 explains a large data set from various events therefore it is ideally suited for comparing with mineralogical models

southern hemisphere westerly wind changes during the last glacial maximum paleo data synthesis changes in the strength and position of southern hemisphere westerly winds during the last glacial cycle have been invoked to explain both millennial and glacial interglacial climate fluctuations however neither paleo models nor paleodata agree on the magnitude or even the sign of the change in wind strength and latitude during the most studied glacial period the last glacial maximum lgm compared to the recent past this paper synthesizes paleo environmental data that have been used to infer changes in lgm winds data compilations are provided for changes in terrestrial moisture dust deposition sea surface temperatures and ocean fronts and ocean productivity and existing data on southern hemisphere ocean circulation changes during the lgm are summarized we find that any hypothesis of lgm wind and climate change needs to provide a plausible explanation for increased moisture on the west coast of continents cooler temperatures and higher productivity in the subantarctic zone and reductions in agulhas leakage around southern africa our comparison suggests that an overall strengthening an equatorward displacement or no change at all in winds could all be interpreted as consistent with observations if a single cause related to the southern westerlies is sought for all the evidence presented then an equatorward displacement or strengthening of the winds would be consistent with the largest proportion of the observations however other processes such as weakening or poleward shifts in winds a weakened hydrological cycle extended sea ice cover and changed buoyancy fluxes cannot be ruled out as potential explanations of observed changes in moisture surface temperature and productivity we contend that resolving the position and strength of westerly winds during the lgm remains elusive based on data reconstructions alone however we believe that these data reconstructions of environmental conditions can be used in conjunction with model simulations to identify which processes best represent westerly wind conditions during the lgm

assessing historical rate changes in global tsunami occurrence summary the global catalogue of tsunami events is examined to determine if transient variations in tsunami rates are consistent with a poisson process commonly assumed for tsunami hazard assessments the primary data analyzed are tsunamis with maximum sizes 1m the record of these tsunamis appears to be complete since approximately 1890 a secondary data set of tsunamis 0 1m is also analyzed that appears to be complete since approximately 1960 various kernel density estimates used to determine the rate distribution with time indicate a prominent rate change in global tsunamis during the mid 1990s less prominent rate changes occur in the early and mid 20th century to determine whether these rate fluctuations are anomalous the distribution of annual event numbers for the tsunami catalogue is compared to poisson and negative binomial distributions the latter of which includes the effects of temporal clustering compared to a poisson distribution the negative binomial distribution model provides a consistent fit to tsunami event numbers for the 1m data set but the poisson null hypothesis cannot be falsified for the shorter duration 0 1m data set temporal clustering of tsunami sources is also indicated by the distribution of interevent times for both data sets tsunami event clusters consist only of two to four events in contrast to protracted sequences of earthquakes that make up foreshock main shock aftershock sequences from past studies of seismicity it is likely that there is a physical triggering mechanism responsible for events within the tsunami source mini clusters in conclusion prominent transient rate increases in the occurrence of global tsunamis appear to be caused by temporal grouping of geographically distinct mini clusters in addition to the random preferential location of global m 7 earthquakes along offshore fault zones

global omori law decay of triggered earthquakes large aftershocks outside the classical aftershock zone 1 triggered earthquakes can be large damaging and lethal as evidenced by the1999 shocks in turkey and the 2001 earthquakes in el salvador in this study earthquakes with ms 7 0 from the harvard centroid moment tensor cmt catalog are modeled as dislocations to calculate shear stress changes on subsequent earthquake rupture planes near enough to be affected about 61 of earthquakes that occurred near defined as having shear stress change 0 01 mpa the ms 7 0 shocks are associated with calculated shear stress increases while 39 are associated with shear stress decreases if earthquakes associated with calculated shear stress increases are interpreted as triggered then such events make up at least 8 of the cmt catalog globally these triggered earthquakes obey an omori law rate decay that lasts between 7 11 years after the main shock earthquakes associated with calculated shear stress increases occur at higher rates than background up to 240 km away from the main shock centroid omori s law is one of the few time predictable patterns evident in the global occurrence of earthquakes if large triggered earthquakes habitually obey omori s law then their hazard can be more readily assessed the characteristic rate change with time and spatial distribution can be used to rapidly assess the likelihood of triggered earthquakes following events of ms 7 0 i show an example application to the m 7 7 13 january 2001 el salvador earthquake where use of global statistics appears to provide a better rapid hazard estimate than coulomb stress change calculations

kuril islands tsunami of november 2006 2 impact at crescent city by local enhancement 1 crescent city cc is particularly susceptible to tsunami attack the combination of tsunami signal enhancement by both distant bathymetric features and local nearshore resonance seems to be responsible for this behavior application of global tsunami propagation models to the kuril islands tsunami of november 2006 in the companion paper kowalik et al 2008 delineated the importance of distant bathymetric features for both tsunami wave amplification and for increased duration of the tsunami arriving at cc these distant features were responsible for delivering the late high energy signal which was delayed by 2 hours from the predicted arrival time additional local amplification and increased duration are caused by the shelf bathymetry adjacent to cc as the initial tsunami arrives at cc the shelf trapping mechanism tends to excite the gravest of the natural modes this oscillation is slowly shifted toward the natural mode closest to the period of the incident tsunami wave packet short duration wave trains tend to influence the tsunami response at cc harbor in such a way that 1 hour after the first wave arrival a much stronger wave will be generated owing to the tendency of the shelf to initially ring at the frequency of the gravest mode practical implications of distant and local amplification relate to the potential hazard near cc highlighting the need for awareness of the tsunami signal duration in this respect two timescales are important for this event the 2 hour time delay due to distant bathymetric features and the 1 hour delay due to local offshore bathymetry

tropical vegetational change in the late pleistocene of new caledonia the south eastern plateau of new caledonia 22 s preserves remnants of a deep regolith of ultramafic soils which is extensively gullied or eroded to form large alluvial fans dated sediments from four closed basins on the plaine des lacs ca 220 m altitude show that organic muds were accumulating prior to 30 000 yr b p over the next 5000 14 000 years limonitic clays infilled two basins as a result of slope instability in their catchment resistant laterite and bog iron surfaces became exposed during the period 30 000 15 000 yr b p by erosional events that seem to have been of greater magnitude than any in the earlier pleistocene two sites lake emeric and lake suprin were chosen for pollen analysis during the phases of organic deposition of these lakes nothofagus forests collapsed several times and were replaced by gymnostoma maquis apparently as a result of fires these pleistocene fires were associated with some inorganic deposition presumably due to the substantial loss of primary forest cover regeneration of forest usually followed after an estimated gap of several centuries thus fire was able to cause forest retreats of the same order of magnitude as that caused by massive fires today the low nutritional status of the soils or lateritic crusts means that as now forest had difficulty reclaiming sites human activity is unknown prior to 3000 years ago so the major erosion is presumed to have had natural causes thus many of the wide ranging changes are the result of natural instability in the sub tropics and some may be much older than hitherto thought climate change towards periods of dry fire prone conditions may have been an underlying cause in the holocene some climatic factor possibly cyclonic storms seems to prevent organic sedimentation switching from cyclone free to cyclone prone at the end of the pleistocene may reflect temperature change in sea surfaces in the region

olivine anisotropy suggests gutenberg discontinuity is not the base of the lithosphere tectonic plates are a key feature of earth s structure and their behavior and dynamics are fundamental drivers in a wide range of large scale processes the operation of plate tectonics in general depends intimately on the manner in which lithospheric plates couple to the convecting interior current debate centers on whether the transition from rigid lithosphere to flowing asthenosphere relates to increases in temperature or to changes in composition such as the presence of a small amount of melt or an increase in water content below a specified depth thus the manner in which the rigid lithosphere couples to the flowing asthenosphere is currently unclear here we present results from laboratory based torsion experiments on olivine aggregates with and without melt yielding an improved database describing the crystallographic alignment of olivine grains we combine this database with a flow model for oceanic upper mantle to predict the structure of the seismic anisotropy beneath ocean basins agreement between our model and seismological observations supports the view that the base of the lithosphere is thermally controlled this model additionally supports the idea that discontinuities in velocity and anisotropy often assumed to be the base of the lithosphere are instead intralithospheric features reflecting a compositional boundary established at midocean ridges not a rheological boundary

an evaluation of tsunami hazard using bayesian approach in the indian ocean abstract the present study deals with the estimation of tsunami hazard parameters maximum regional tsunami intensity imax slope value where b log10 e of tsunami intensity frequency relationship and tsunami activity rate in the whole indian ocean as well as andaman sumatra java asj region using bayesian statistics technique for this purpose a reliable homogeneous and complete tsunami catalog during the period 1797 to 2006 with tsunami intensities soloviev imamura intensity scale i 2 0 having average wave heights h 2 83 m is utilized the slope b value of linear tsunami intensity frequency relationship log10 n a b i of g r type for observed tsunami data with intensities i 2 0 is calculated as 0 41 the applied method of bayesian statistics follow three assumptions viz poissonian character of tsunami events existence of the frequency intensity relation of g r type with a cut off maximum value of tsunami intensities and catalog contains rather sizable events in this study the maximum regional tsunami intensity imax has been estimated as 5 39 0 30 and 5 41 0 31 for the whole indian ocean and asj regions respectively which is reasonably comparable to the maximum observed tsunami intensity of 5 0 for august 27 1883 indonesia tsunami the slope value of tsunami intensity frequency relationship is calculated as 0 81 for both the indian ocean and asj regions by bayesian statistics theory we have also estimated quantiles of true and apparent tsunami intensities for future time intervals of 20 30 40 and 50 years with confidence limits for probability levels of 50 60 70 80 90 and 95 in the indian ocean along with asj region it is observed that the differences between true and apparent quantiles of tsunami intensities are negligible revealing that a good quality of tsunami data is used in the study the results estimated in the present study have potential useful implications in the probabilistic tsunami hazard assessment in the indian ocean region