the evolution of regional seismicity between large earthquakes 1 we describe a simple model that links static stress coulomb modeling to the regional seismicity around a major fault unlike conventional coulomb stress techniques which calculate stress changes we model the evolution of the stress field relative to the failure stress background seismicity is attributed to inhomogeneities in the stress field which are created by adding a random field that creates local regions above the failure stress the inhomogeneous field is chosen such that when these patches fail the resulting earthquake size distribution follows a gutenburg richter law immediately following a large event the model produces regions of increased seismicity aftershocks where the overall stress field has been elevated and regions of reduced seismicity where the stress field has been reduced stress shadows the high stress levels in the aftershock regions decrease due to loading following the main event combined with the stress shadow from the main event this results in a broad seismically quiet region of lowered stress around the epicenter pre event seismicity appears as the original stress shadows finally fill as a result of loading the increase in seismicity initially occurs several fault lengths away from the main fault and moves inward as the event approaches as a result of this effect the seismic moment release in the region around the future epicenter increases as the event approaches synthetic catalogues generated by this model are virtually indistinguishable from real earthquake sequences in california and washington

correlation of fluctuations in cladoceran planktonic littoral ratio between three cores from a small lake in southern finland holocene water level changes the main aim of the study was to test the cladoceran planktonic littoral p l method in holocene lake level studies with three cores from a small lake iso lehmalampi 60 21 n 24 36 e in south

unusual earthquakes in the gulf of alaska and fragmentation of the pacific plate two recent ms 7 6 strike slip earthquakes in the northern gulf of alaska ruptured a composite 250 km long north striking zone in the pacific plate these shocks are attributed to a combination of enhanced tensional stress in the pacific plate seaward of and following the great mw 9 2 alaska earthquake of 1964 and compressional stress resulting from collision of the yakutat terrane with north america the occurrence of these shocks reflects fragmentation of the northeast corner of the pacific plate possibly the initial step in establishing a new plate boundary seaward of the current boundary

seismic rupture and arc segmentation within the shumagin islands seismic gap alaska the locations of teleseismically well recorded earthquakes suggest that up to 80 of the shumagin gap has ruptured seismically during the last 90 years an earthquake in 1917 ms 7 9 nucleated near the gap s eastern edge and appears to have ruptured as much as a 200 km long section of the gap and an event in 1948 ms 7 5 appears to have ruptured the deepest portion of the main thrust zone 30 km in the central section of the gap the rupture extents of these earthquakes suggest that the gap can be divided into two or three smaller arc segments these observations do not preclude the possibility of failure of the entire region in a single great earthquake mw 8 5 in the near future the two historically documented recurrence intervals for the eastern portion of the gap are 59 and 70 years if the average recurrence interval for large earthquakes near the shumagin islands is 65 years the conditional probability of a large earthquake rupturing this portion of the arc in the next 20 years is between 62 and 96

shumagin seismic gap alaska peninsula history of great earthquakes tectonic setting and evidence for high seismic potential the shumagin seismic gap a segment of the plate boundary along the eastern aleutian arc has not ruptured during a great earthquake since at least 1899 1903 because at least 77 years have elapsed since the shumagin gap last ruptured in a great earthquake and repeat times for the 1938 rupture zone and part of the shumagin gap are estimated to be 50 to 90 years a high probability exists for a great earthquake to occur within the shumagin gap during the next one to two decades reconsideration of the rupture zones of the aleutian earthquakes of 1938 1946 and 1948 suggests that those events did not break the interplate boundary beneath the shumagin islands thus the shumagin seismic gap extends from the western end of the 1938 rupture zone to the eastern end of that of 1946 these boundaries also coincide with transverse structural features at least the eastern half of the shumagin gap broke in great earthquakes in 1788 and 1847 and possibly in 1898 1903 the shumagin gap is probably not the result of aseismic slip rather plate motion is accommodated there seismically and episodically and can be expected to produce large earthquakes in the future although there is no definitive evidence of long term precursors of a possible future earthquake several observations suggest that the shumagin gap is in an advanced stage of the earthquake cycle both teleseismic and local network data indicate a near absence of seismic activity m 2 above a depth of 30 km along the main thrust zone within the gap this is in strong contrast to adjacent portions of the arc where seismic activity is scattered across most of the main thrust zone two earthquakes with high stress drops 600 900 bars which occurred at the base of the main thrust zone may indicate the accumulation of a considerable amount of strain energy within the gap a possible seismic gap at the eastern end of the aftershock zone of the aleutian earthquake of 1957 has been identified near unalaska island an earthquake that nucleates in the shumagin gap could also rupture the possible unalaska gap to the west the 1938 aftershock zone to the east or both with resultant magnitude up to mw 9 0 alternatively the shumagin gap alone or in one of the above combinations could rupture in a series of very large earthquakes instead of a single great shock past alaska aleutian earthquakes including those of 1788 1938 1946 1957 1964 and 1965 have generated very large tsunamis future large earthquakes in the shumagin islands region could generate wave heights of several tens of meters along shorelines near the rupture areas the shumagin gap is one of two major gaps along the united states portion of the alaska aleutian plate boundary and is one of the few areas in the united states where processes leading to a great earthquake are likely to be observed within a reasonable span of time

accelerating moment release revisited examples of application to italian seismic sequences abstract from simple considerations we propose a revision of the accelerating moment release amr methodology for improving our knowledge of seismic sequences and then hopefully in a close future to reach the capability of predicting the main shock location and occurrence with sufficient accuracy the proposed revision is based on the introduction of a reduced benioff strain for the earthquakes of the seismic sequence where for the same magnitude and after a certain distance from the main shock epicentre the closer the events the more they are weighted in addition we retain the usual expressions proposed by the ordinary amr method for the estimation of the corresponding main shock magnitude although this parameter is the weakest of the analysis then we apply the revised method to four case studies in italy three of which are the most recent seismic sequences of the last 9 years culminating with a shallow main shock and one is instead a 1995 1996 swarm with no significant main shock the application of the r amr methodology provides the best results in detecting the precursory seismic acceleration when compared with those found by ordinary amr technique we verify also the stability of the results in space applying the analysis to real data with moving circles in a large area around each main shock epicentre and the efficiency of the revised technique in time comparing the results with those obtained when applying the same analysis to simulated seismic sequences

accelerated preshock deformation of broad regions in the aegean area twenty four regions where accelerating deformation has been observed for a few decades before corresponding strong m 6 0 7 5 mainshocks are identified in the broader aegean area to a first approximation these preshock regions have elliptical shapes and the radius r in km of a circle with an area equal to the corresponding ellipse is related to the moment magnitude m of the mainshock by the equation log r 0 42 m 0 68 the dimension of each preshock region is about seven to ten times larger than the rupture zone fault length of the corresponding mainshock the time variation of the cumulative benioff strain was satisfactorily fitted by a power law relation which is predicted by statistical physics if the mainshock to which accelerating strain rates leads is considered as a critical point the duration t in years of the accelerating benioff strain release period is given by the relation log t 5 94 0 75 log s r where s r is the mean benioff strain rate release per year for 104 km2 in the preshock region calculated by the complete available data m 5 2 for the entire instrumental period 1911 1998 the importance of identifying and investigating such regions for better understanding the dynamics of the active part of the lithosphere as well as for earthquake prediction and time dependent seismic hazard assessment is discussed

retrospective on the accelerating seismic release asr hypothesis controversy and new horizons abstract the hypothesis that large earthquakes may be preceded by a period of accelerating seismicity or accelerating seismic release asr was proposed about twenty years ago a compilation of almost one hundred peer reviewed publications on this topic since the late 1980s to the present day shows that the rate of asr studies increased gradually until 2004 but decreased afterwards this negative trend is amplified by a recent increase in the number of negative results and criticisms of the asr hypothesis the author suggests that much of the recent negativity regarding this topic is due to the formulation of this hypothesis as a power law fit to cumulative seismicity series this approach is intrinsically linked to the consensus for criticality evident from an overview of the asr literature to explain the emergence of power laws in earthquake populations the holistic view of the earth s crust as a complex system restricts seismicity pattern analyses to the study of main features such as power laws while a reductionist view would allow for more refined ones such a paradigm shift or sea change might be under way in the asr literature where in 2007 a new approach was proposed to explain the asr power law from combined concepts of elastic rebound and geometry reductionism versus holism is a fundamental problem that not only applies to the study of asr but also to the broader field of earthquake physics and earthquake predictability science

intermediate term earthquake prediction using the modified time to failure method in southern california abstract based on retrospective modeling of earthquakes from the southern california earthquake catalog along with previously published evaluations from the new madrid seismic zone the modified time to failure method may be used as an intermediate term earthquake prediction technique for locating and predicting the size and time of a future mainshock modeling previous mainshocks for hypothesis development indicates that the method predicts the actual magnitude of the mainshock to within approximately 0 5 magnitude units the error associated with the time of failure is approximately 1 1 years assuming the last precursory event is known when the last event in the precursory sequence is not known the predicted magnitude remains similar but the predicted time will require refinement as additional events are added with time to the sequence the mainshock location can also be identified within a circular region with a radius on the order of tens of kilometers criteria are provided for defining acceleration sequences and mainshock locations the criteria reduce the number of false predictions but also eliminate some mainshocks from our evaluation mainshocks as small as magnitude 5 5 occurring between 1980 and 1995 were evaluated from the southern california earthquake catalog scc the results were used in association with previous studies to develop a method that can be used for practical future prediction applications the modified time to failure method was used to search the scc for future mainshocks occurring after 17 august 1998 one region satisfied all the criteria and may be modeled by the modified time to failure method the region likely to have a mainshock is a 65 km radius area centered at 31 43 n 115 47 w northern baja california mexico the predicted magnitude is 6 36 0 55 and the predicted time of failure is 1998 565 7 25 98 1 127 years the addition of future precursory events will allow refinement of the predicted values

relationship between magnetic components and diagenetic features in reddened triassic alluvium st bees sandstone cumbria uk summary the st bees sandstone is a reddened lower triassic sandy alluvial sequence which has suffered a complex history of iron oxide diagenesis detrital clay oxides have been post depositionally reddened and particulate grain coatings of haematite precipitated syntaxial overgrowths of haematite and titaniferous haematite have been precipitated on coarse detrital oxides specularites in situ alteration of specularite principally the martitization of detrital titanomagnetite and titanomaghaemite has taken place also ferromagnesian phyllosilicates principally biotite have suffered partial to complete pseudomorphism by tine grained haematite these diagenetic changes took place during contemporary geomagnetic field variations and each diagenetic phase carried a magnetic component recording the direction and hence date of its formation in general magnetizations can be described as pigment dominant specularite dominant or mixed pigment specularite using a combination of chemical and thermal demagnetization the individual magnetic components can be isolated using zijderveld vector diagrams four examples are illustrated a a specularite dominant magnetization in which a reversed component carried by coarse detrital grains had a superimposed normal component carried by authigenic overgrowths of haematite both components are considered to be triassic in age b a pigment dominant magnetization carried primarily by clay oxide pellicles formed during intrastratal alteration the main isolated component has an anomalous direction and its precise time of formation cannot be determined c a mixed specularite pigment magnetization in which a normal specularite component has a superimposed normal pigment component these normal components are considered to be of different triassic ages d a mixed specularite pigment magnetization in which a near horizontal specularite component possibly due to inclination error has a superimposed

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

seismic activity on neighbouring faults as a long term precursor to large earthquakes in the san francisco bay area activity in moderate size earthquakes accelerated in the several decades before the large california earthquakes of 1989 1906 and 1868 this type of precursor seems to require the presence of several major faults in close enough proximity to one another that moderate size shocks are selectively triggered on surrounding faults during the latter stages of the cycle of strain buildup to large earthquakes it may be possible to use quantitative aspects of similar seismic precursors to make predictions of large earthquakes on timescales of a few years to one decade

accelerating seismic crustal deformation in the southern aegean area a region of intense accelerating seismic crustal deformation has been identified in the southwestern part of the hellenic arc broader area of cythera island the identification is performed using a detailed parametric grid search of the broader southern aegean area for accelerating energy release behavior the identified region has similar properties with past preshock critical regions which have been identified for strong mainshocks in the aegean area based on such observations which suggest that this region is at a critical state that can lead to a critical point that is to the generation of a mainshock an estimation is made of the possible epicenter coordinates magnitude and origin time of this oncoming large m 7 0 earthquake the estimation procedure is validated on the basis of retrospective analysis of strong events in the aegean area as well as by appropriate application on synthetic random catalogs these results the existence of similar observations of accelerating seismic deformation in eastern part of southern aegean and independent information on the time distribution of large earthquakes m 6 8 for the whole southern aegean indicate that the generation of strong earthquakes in this area in the next few years must be considered as very probable

an observational test of the origin of accelerating moment release before large earthquakes 1 a progressive increase of seismic activity distributed over a wide region around a future earthquake epicenter is termed accelerating moment release amr this phenomenon has been observed in several studies over the last 15 years although there is no consensus about the physical origin of the effect in a recent hypothesis known as the stress accumulation sa model the amr is thought to result from the last stage of loading in the earthquake cycle in this view the increasing seismicity is due to minor stress release as the whole region becomes sufficiently stressed for the major event to occur the stress accumulation model makes specific predictions about the distribution of events in an amr sequence because the amr is predicted to be a result of loading on the main fault the precursory activity should be concentrated in the positive lobes of the far field stresses calculated by a backslip dislocation model of the main shock to test this model amr is first found in optimal circular regions around the epicenters of each of the m w 6 5 earthquakes in central and southern california since 1950 a backslip dislocation model is then used to determine which of the precursory events occur in the regions predicted by stress accumulation amr is shown to occur preferentially in the lobes of the backslip stress field predicted by the stress accumulation model

late quaternary sea level change in southern beringia postglacial emergence of the western alaska peninsula abstract postglacial sea level trends have varied dramatically across the bering platform because of differences in coastal and shelf geologic settings emergent shorelines and basal peats along the western alaska peninsula indicate that relative sea level has fallen since regional deglaciation occurred ca 13 000 cal yr bp age elevation determinations on four shorelines 25 m 10 ka 16 m 9 6 6 ka 6 m 2 1 ka and 2 3 m 1 8 0 6 ka in the vicinity of cold and morzhovoi bays provide an estimate of the pace and timing of of sea level change since the last glacial maximum lgm 22 17 ka isostatic recovery and shoreline regression following the disintegration of continental and alpine ice has been interrupted by transgressive conditions at least twice since deglaciation changes in the balance between eustatic sea level rise and isostatic uplift resulted in the reactivation of marine scarps during the early to middle holocene but terrace cutting and a gap in the archaeological record about 2 1 ka suggest that sudden tectonic displacements also influence the record reconstructions of coastal paleogeography constrain the timing and distribution of regional archaeological settlement periods of shoreline erosion during stillstands or transgressions and the episodic reorganization of intertidal environments that accompanies tectonic displacements have conditioned site preservation potential and long term adaptive strategies

accelerating seismic moment release and outer rise compression possible precursors to the next great earthquake in the alaska peninsula region the moment release rate in the kodiak island ki segment increased prior to the great 1964 prince william sound earthquake mw 9 2 starting in 1983 the moment release rate in the shumagin island si segment shows a similar increase in july 1990 an outer rise reverse earthquake showed arc normal compression at a depth of 42 km seaward of the alaska peninsula ap segment because accelerating moment release and arc normal compression have both been proposed as precursors to large and great earthquakes we suggest this is evidence that the si ap region is nearing the end of the seismic cycle between large thrust earthquakes

the response of flood plain ecosystems to the late glacial and early holocene hydrological changes a case study from a small central european river valley abstract we use a range of environmental variables to explore the possible drivers influencing the biota especially the composition of aquatic invertebrates during the younger dryas yd and early holocene eh in different river valley sites a well developed meandering river and the confluence zone of headwater streams using pollen macrofossil cladoceran and chironomid as well as geochemical and lithological data as proxies for environmental factors i e water depth and temperature we attempt to show that these different sites display similar hydroclimatic signals especially floods the geochemical records in the studied valley are correlated with environmental factors such as the evolution of the vegetation the intensification phase of slope processes and fluvial activities cladocerans and chironomids potentially play important roles in the recognition of flood episodes in the study sites and any shift in their diversity and especially the co occurrence of planktonic sediment associated cladocerans with rheophilic chironomids could be valuable indicators of floods and flow episodes the variable changes in water levels at the sites reconstructed by the cladoceran based water depth model were positively associated with changes in lithophilic elements k na al mg and ti sio2 biog ter and fe mn and our estimates of the paleohydraulic parameters for the study sites are generally consistent with changes in the composition of aquatic invertebrates the recorded yd floods appear to be synchronous regardless of the size and the different geological and geomorphological settings of each part of the river catchment our investigation demonstrates that flood magnitude increases in the downstream direction along the valley the common increases in the water level at all study sites from the grabia river valley are significant from 12 400 to 12 200 and from 11 900 to 11 800 cal bp and are comparable with those from elsewhere in poland and europe

can damage mechanics explain temporal scaling laws in brittle fracture and seismicity time delays associated with processes leading to a failure or stress relaxation in materials and earthquakes are studied in terms of continuum damage mechanics damage mechanics is a quasi empirical approach that describes inelastic irreversible phenomena in the deformation of solids when a rock sample is loaded there is generally a time delay before the rock fails this period is characterized by the occurrence and coalescence of microcracks which radiate acoustic signals of broad amplitudes these acoustic emission events have been shown to exhibit power law scaling as they increase in intensity prior to a rupture in case of seismogenic processes in the earth s brittle crust all earthquakes are followed by an aftershock sequence a universal feature of aftershocks is that their rate decays in time according to the modified omori s law a power law decay in this paper a model of continuum damage mechanics in which damage microcracking starts to develop when the applied stress exceeds a prescribed yield stress a material parameter is introduced to explain both laboratory experiments and systematic temporal variations in seismicity

evolving towards a critical point a review of accelerating seismic moment energy release prior to large and great earthquakes there is growing evidence that some proportion of large and great earthquakes are preceded by a period of accelerating seismic activity of moderate sized earthquakes these moderate earthquakes occur during the years to decades prior to the occurrence of the large or great event and over a region larger than its rupture zone the size of the region in which these moderate earthquakes occur scales with the size of the ensuing mainshock at least in continental regions a number of numerical simulation studies of faults and fault systems also exhibit similar behavior the combined observational and simulation evidence suggests that the period of increased moment release in moderate earthquakes signals the establishment of long wavelength correlations in the regional stress field the central hypothesis in the critical point model for regional seismicity is that it is only during these time periods that a region of the earth s crust is truly in or near a self organized critical soc state such that small earthquakes are capable of cascading into much larger events the occurrence of a large or great earthquake appears to dissipate a sufficient proportion of the accumulated regional strain to destroy these long wavelength stress correlations and bring the region out of a soc state continued tectonic strain accumulation and stress transfer during smaller earthquakes eventually re establishes the long wavelength stress correlations that allow for the occurrence of larger events these increases in activity occur over longer periods and larger regions than quiescence which is usually observed within the rupture zone of a coming large event the two phenomena appear to have different physical bases and are not incompatible with one another

sediment isotope tracers from lake saarikko finland and implications for holocene hydroclimatology abstract multi component isotopic analyses on a sediment core from lake saarikko finland give insight into holocene climate changes in northern europe oxygen isotopic records from aquatic cellulose and authigenic carbonate reflect consistent similar trends in hydrological balance and are employed jointly to infer relative changes in lake water temperature other geochemical and isotopic tracers shed light on fluctuations in lake level and nutrient cycling facilitating the interpretation of the oxygen isotopic archives in the early holocene 10 000 9000 cal yr bp the lake level was low and dry conditions prevailed despite low temperatures higher lake levels and depleted oxygen isotopic values 9000 7500 cal yr bp were probably caused by several factors higher effective humidity an isotopically depleted precipitation source a cold event around 8300 cal yr bp and increased spring snowmelt in contrast higher summer temperatures lower effective humidity lower lake levels and enriched oxygen isotopic values were experienced during the mid holocene 7500 3300 cal yr bp the occurrence of the warmest inferred lake water and the most enriched cellulose oxygen isotope values 6000 5000 cal yr bp is consistent with a summer temperature maximum inferred from other proxy sources from the region the late holocene was characterized by higher effective humidity and higher lake levels increase in spring snowmelt and colder temperatures most likely related to the little ice age induced a drastic change in the lake hydrology and probably caused the formation of its present outlet 800 cal yr bp changes in the lake hydrological balance and climate variables inferred from oxygen isotopic records can be related to atmospheric circulation most clearly to changes in the dominance and strength of westerly air flow as well as summertime anticyclonic circulation

modeling earthquake cycles in the shumagin subduction segment alaska with seismic and geodetic constraints deformation associated with the earthquake cycle in the shumagin islands segment of the alaska aleutian subduction zone is analyzed with the use of a two dimensional finite element model the model consists of an oceanic plate dipping under an upper plate both of which respond elastically to stress fluctuations in the earthquake cycle and these are underlain by asthenospheric mantle and mantle wedge regions which respond viscoelastically it is tailored to the geometry of the shumagin islands region by using seismicity to define the position of the interplate interface and partially coupled region along it the model is preconditioned by forcing this interface to undergo periodically repeated slips up to and including the time of the may 31 1917 event ms 7 4 in that region with each chosen to be consistent with the moment and estimated rupture area of that event we investigated the dependence of model results for geodetic signals on the strength of seismic coupling between the plates and viscoelastic relaxation of deviatoric stresses in the mantle including in the mantle wedge close to the plate junction and along the aseismic downdip continuation of the thrust interface in models with significant relaxation in the wedge or downdip thrust zone results show that as the intraseismic stage matures there is a region of diminished compressional strain rates and even of locally extensional rates on the earth s surface above the downdip end of the seismically coupled zone based on the seismic estimates of the location of the coupled zone this region is in the area of the shumagin islands we find that if approximately 20 of the convergence takes place seismically compatible with the previous seismic history and if an extensive region of relaxed deviatoric stress is assumed to be present in the wedge and or along the downdip interface then deformations predicted by the model can be made consistent with the measured strain data from the shumagin islands geodetic network lisowski et al 1988 larson and lisowski 1994 as well as uplift and tilt data savage and plafker 1991 beavan 1992 our model simulations here suggest that the shumagin segment is capable of large earthquakes the hypothesis of totally aseismic subduction is not similarly consistent with all geodetic constraints

an observational test of the stress accumulation model based on seismicity preceding the 1992 landers ca earthquake abstract we test the bowman and king bowman d d king g c p 2001a accelerating seismicity and stress accumulation before large earthquakes geophys res lett 28 21 4039 4042 bowman d d king g c p 2001b stress transfer and seismicity changes before large earthquakes c r acad sci paris 333 591 599 stress accumulation model by examining the evolution of seismicity rates prior to the 1992 landers california earthquake the stress accumulation sa model was developed to explain observations of accelerating seismicity preceding large earthquakes the model proposes that accelerating seismicity sequences result from the tectonic loading of large fault structures through aseismic slip in the elasto plastic lower crust this loading progressively increases the stress on smaller faults within a critical region around the main structure thereby causing the observed acceleration of precursory activity a secondary prediction of the sa model is that the precursory seismicity rates should increase first at the edges of the critical region with the rates gradually rising over time at closer distances to the main fault we test this prediction by examining year long seismicity rates between 1960 and 2004 as a function of distance from the landers rupture to quantify the significance of trends in the seismicity rates we auto correlate the data using a range of spatial and temporal lags we find weak evidence for increased seismicity rates propagating towards the landers rupture but cannot conclusively distinguish these results from those obtained for a random earthquake catalog however we find a strong indication of periodicity in the rate fluctuations as well as high correlation between activity 130 170 km from landers and seismicity rates within 50 km of the landers rupture temporally offset 1 5 2 years the implications of this spatio temporal correlation will be addressed in future studies

the palaeoecological development of the late medieval moat multiproxy research at rozprza central poland abstract the rozprza stronghold functioned as a seat of a noble family since at least the early14th century ad in the form of the motte and bailey residence the remains of the residence are situated in the central part of mid luci za river valley on the river terrace remnant adjoining a strongly expanding floodplain the situation and state of preservation give a unique opportunity to conduct research that explain the construction process detailed history of the medieval moat and palaeoenvironmental reconstruction of the valley floor radiocarbon and dendrochronological dating and analysis of artefacts confirmed 14th century age of the moat organic deposits gyttja peat and organic mud of moat fill allowed for a set of multiproxy analyses based on sediment cores the research results indicate shallow water with brief episodes of in wash in the first stage 13th 14th c ad followed by a transformation into telmatic habitat in the second phase of the moat development from 16th 17th c ad the deposition of overbank alluvium took place within the moat ditch system as late as the 18th and or 19th c ad we studied the development of this moat environment in the context of valley floor changes

parallel 3 d simulation of a fault gouge using the lattice solid model despite the insight gained from 2 d particle models and given that the dynamics of crustal faults occur in 3 d space the question remains how do the 3 d fault gouge dynamics differ from those in 2 d traditionally 2 d modeling has been preferred over 3 d simulations because of the computational cost of solving 3 d problems however modern high performance computing architectures combined with a parallel implementation of the lattice solid model lsm provide the opportunity to explore 3 d fault micro mechanics and to advance understanding of effective constitutive relations of fault gouge layers in this paper macroscopic friction values from 2 d and 3 d lsm simulations performed on an sgi altix 3700 super cluster are compared two rectangular elastic blocks of bonded particles with a rough fault plane and separated by a region of randomly sized non bonded gouge particles are sheared in opposite directions by normally loaded driving plates the results demonstrate that the gouge particles in the 3 d models undergo significant out of plane motion during shear the 3 d models also exhibit a higher mean macroscopic friction than the 2 d models for varying values of interparticle friction 2 d lsm gouge models have previously been shown to exhibit accelerating energy release in simulated earthquake cycles supporting the critical point hypothesis the 3 d models are shown to also display accelerating energy release and good fits of power law time to failure functions to the cumulative energy release are obtained

viscosity of oceanic asthenosphere inferred from remote triggering of earthquakes a sequence of large interplate earthquakes from 1952 to 1965 along the aleutian arc and kurile kamchatka trench released accumulated stresses along nearly the entire northern portion of the pacific plate boundary the postseismic stress evolution across the northern pacific and arctic basins calculated from a viscoelastic coupling model with an asthenospheric viscosity of 5 x 10 17 pascal seconds is consistent with triggering of oceanic intraplate earthquakes temporal patterns in seismicity at remote plate boundaries and space based geodetic measurements of anomalous velocity over an area 7000 by 7000 kilometers square during the 30 year period after the sequence

hydroclimatic variations over the last millennium in eastern finland disentangled by fossil cladocera abstract future climate warming is expected to alter atmospheric moisture balance and therefore paleoclimatic archives of past moisture and hydrological patterns may provide understanding of the magnitude speed and ecosystem responses to the regionally altered climatic regimes the present study aimed at disentangling millennial variation in hydroclimatic parameters including summer effective moisture lake levels and ice free season by using sedimentary cladoceran fossils we used a site specific cladoceran based inference model to reconstruct lake level fluctuations in a 1500 yr sediment record from lake pieni kauro eastern finland in the context of previously established paleoclimatic data of summer temperature and precipitation in addition we applied cladoceran planktonic littoral ratio mean body size and abundance of fossil ephippia as supplementary proxies for paleoclimatic interpretations the results showed that lake level was lower during the pre and early medieval climate anomaly mca around 500 1000 ad than at present and started to rise toward the culmination during the little ice age lia around 1600 1700 ad when the lake level was higher than at present pelagic cladoceran body size was larger and abundance of ephippia increased during the lia suggesting significant reduction in the length of the ice free season and lower water temperatures comparison of the lake level reconstruction with the previous paleoclimatic data suggested that effective moisture has had a long term negative relationship with temperature and positive relationship with summer precipitation in eastern finland the results indicated that the pre and early mca was warm and dry long ice free season low summer effective moisture and the culmination of the lia was cool and moist reduced ice free season increased summer effective moisture unraveling the seasonality of the multicentury hydroclimatic patterns in eastern finland may offer important insights in linking the large scale atmospheric circulation patterns to seasonal climate events

acoustic emission experiments of rock failure under load simulating the hypocenter condition a series of acoustic emission ae experiments of rock failure have been conducted under cyclic load in tri axial stress tests to simulate the hypocenter condition the specimens are loaded by the combined action of a constant stress intended to simulate the tectonic loading and a small sinusoidal disturbance stress analogous to the earth tide induced by the sun and the moon each acoustic emission signal can indicate the occurrence time location and relative magnitude of the damage micro crack in the specimen the experimental results verified some precursors such as lurr load unload response ratio and aer accelerating energy release before macro fracture of the samples a new parameter the correlation between the ae and the load has been proposed to describe the loading history on the eve of some strong earthquakes the correlation between the benioff strain and the coulomb failure stress cfs decreases similar to the variation of lurr prior to strong earthquakes

electro magnetic earthquake bursts and critical rupture of peroxy bond networks in rocks abstract we propose a mechanism for the low frequency electromagnetic emissions and other electromagnetic and electric phenomena which have been associated with earthquakes the mechanism combines the critical earthquake concept and the concept of crust acting as a charging electric battery under increasing stress the electric charges are released by activation of dormant charge carriers in the oxygen anion sublattice called peroxy bonds or positive hole pairs php where a php represents an o 3 x oo yo 3 with x y si 4 al 3 i e o in a matrix of o 2 of silicates we propose that php are activated by plastic deformations during the slow cooperative build up of stress and the increasingly correlated damage culminating in a large critical earthquake recent laboratory experiments indeed show that stressed rocks form electric batteries which can release their charge when a conducting path closes the equivalent electric circuit we conjecture that the intermittent and erratic occurrences of em signals are a consequence of the progressive build up of the battery charges in the earth crust and of their release when crack networks percolate through the stressed rock volumes providing a conductive pathway for the battery currents to discharge em signals are thus expected close to the rupture either slightly before or after that is when percolation is most favored the proposed mechanism should be relevant for the broader understanding of fractoemissions

recent ecological change in a remote scottish mountain loch an evaluation of a cladocera based temperature transfer function recent ecological changes in a small scottish mountain loch loch coire fionnaraich lcfr were inferred using cladocera analysis and an application of a cladocera based temperature transfer function approach modern assemblages of cladocera from 68 mountain lakes in scotland and norway were used to derive the transfer function among 21 measured environmental variables mean summer lake surface water temperature lswt accounted for the highest 8 variation in a redundancy analysis of the modern data a quantitative inference model r2 0 72 rmsep 1 81 c for summer lswt was developed using linear partial least squares regression and calibration the resulting reconstructed summer lswt at lcfr was compared with local instrumental air temperature records over the last 20 yr and the central england temperature cet series over the last 110 yr the reconstruction showed a broadly similar pattern to the local instrumental temperature records however the relationship between the longer cet series and reconstructed summer lswt was poor suggesting that the site was relatively insensitive to temperature changes prior to the recent warming of the last few decades clear changes in cladoceran species diversity and relative abundance of littoral taxa coincident with the most recent period of climate warming recorded both locally and in the cet suggest that cladocera do respond to climate change however their response to temperature is complex and indirect the underlying mechanism leading to change in cladocera assemblages may involve changes in trophic status and habitat availability of the system it is concluded that understanding other factors such as atmospheric pollution controls of community dynamics of cladocera and the overall ecological complexity of mountain lakes is required before any reliance can be placed on a cladocera temperature transfer function for reconstructing climatic change crown copyright 2008

fault parameters and tsunami excitation of the may 13 1993 shumagin islands earthquake the shumagin islands earthquake of may 13 1993 occurred in a previously identified seismic gap where a large subduction earthquake is expected we analyzed long period surface waves and p waves recorded on the iris stations to estimate the fault parameters the centroid moment tensor solution shows that the focal mechanism is a thrust type with the strike parallel to the aleutian trench the seismic moment is 2 0 1019 nm and the corresponding moment magnitude is 6 8 the moment tensor rate function inversion from p waves also yields a similar focal mechanism and seismic moment in addition this computation provides estimates of 10 s for the duration of the source time function and 35 km for the best point source depth these seismological analyses indicate that the fault mechanism of the 1993 earthquake was as expected but that the magnitude was too small to fill the gap this earthquake did not generate a tsunami large enough to be observed at the sand point alaska tide gauge or at an ocean bottom pressure gauge at distances of 100 and 300 km respectively numerical tsunami simulations result in amplitudes at both stations that are within the background noise level additional numerical experiments also suggest that the small tsunami amplitudes are due to the location of the source area in the shallow shelf region

precursory seismic activation and critical point phenomena in this paper we relate the behavior of seismicity prior to a characteristic earthquake to the excitation in proximity to a spinodal instability we illustrate the spinodal instability as the upper limit of superheated water prior to a steam explosion we draw an analogy between the steam explosion and a characteristic earthquake and show that the power law activation associated with the spinodal instability is essentially identical to the power law increase in benioff strain observed prior to characteristic earthquakes we find that theory and actual data give very similar results

the shumagin islands alaska earthquake of 31 may 1917 abstract although macroseismic reports indicate that great earthquakes have occurred in the vicinity of the shumagin gap of the eastern aleutian arc the largest well documented event within the gap has been an m s 7 5 event that occurred in 1948 this earthquake apparently ruptured only a 75 km long segment of the 200 km long gap and as such is not considered a gap filling event relocations of turn of the century seismicity by boyd and lerner lam 1988 suggest however that another more poorly documented event nucleated near the shumagin islands on 31 may 1917 an m s of 7 9 determined from a single station bulletin has been assigned to this event although consistent with its apparent aftershock distribution macroseismic reports appear to be too small for such a large event we use surface waves to estimate the moment and rupture bounds and body waves to constrain the focal mechanism and depth of the 1917 event the average m s at 13 azimuthally well distributed stations is 7 4 0 3 much smaller than the previous estimate of 7 9 the spatial variation in individual magnitude estimates is azimuthally dependent 7 9 to the west and 6 8 to the east implying source directivity assuming a thrust fault mechanism body wave inversion yields a source depth of 29 km and m w of 7 4 in addition assuming rupture velocity and rupture propagation along arc to the west consistent with the aftershock distribution a rupture length of 75 km and m w of 7 5 are required to match long period surface waves recorded at uppsala sweden and gottingen germany these results suggest that the average slip of the 1917 event was only about 75 to 150 cm and was restricted to the easternmost portion of the gap these results when combined with rupture zones and recurrence intervals of other eastern aleutian events imply a temporally heterogeneous rupture style where the rupture bounds and consequently the sizes of earthquakes vary from cycle to cycle estimating the magnitudes or rupture extents of the next series of events based on the previous series appears to be unjustified

late weichselian and holocene record of the paleoenvironmental changes in a small river valley in central poland abstract the developmental history from the oldest dryas to the late holocene of a paleolake and mire located in a river valley in central poland was studied using high resolution records of pollen macrofossils cladocera sedimentology and geochemistry from a 14 c dated sediment core we inferred temperature and water level dynamics using cladocerans and palynological and geochemical methods were employed to investigate natural fluvial activity particularly for these elements that are difficult to find through sedimentological methods our research demonstrates how climate fluctuation in the late glacial and holocene periods influenced the development of a paleolake and mire in a small river valley and shows the importance of long term research to establish hydroclimatic conditions in biogenic sediments we propose that water level fluctuations were important in modifying biotic assemblages the results of our multiproxy analysis clearly suggest that the main driver of changes in aquatic and terrestrial ecosystems as well as in geomorphological processes in the valley was climate reconstructed temperatures generally follow the known trends showing an increase at the beginning of the bolling allerod and holocene and a decrease at the beginning of the oldest and younger dryas similarly periods of water level increase are synchronous with climatic changes however the local environmental forces were a significant factors affecting biotic diversity in the studied time span fish predation macrophyte structure ph and calcium content partly influence the results of the cladoceran based water depth reconstruction in particular interestingly the cladoceran inferred summer temperature reconstruction for pawlowa appear realistic although the temperature trends can be considered reliable our results indicate the important role of local factors which control the species composition of the subfossil assemblages

estimates of long term probabilities for future great earthquakes in the aleutians we compute probabilities for future great earthquakes in the aleutian arc probability distributions are fitted to recurrence periods of great aleutian evens m sub w or 7 8 since 1788 given a probability distribution and data of the last grat earthquake in each arc segment time dependent conditional probabilities are determined for future periods of interest we obtain for the next two decades high probabilities 99 to 30 for great earthquakes in the shumagin yakataga unalaska and kommandorski seismic gaps these probabilities are higher than for any other assessed region of the u s believed to be capable of great earthquakes low probabilities 17 to 9 are found for segments that ruptured most recently in 1965 1964 and 1957 recurrence periods for great earthquakes measure on average about 80 years but vary substantially whether recurrence periods for great aleutian earthquakes follow a normal log normal or any other probability distribution is not resolved because in most arc segments the known seismic record embraces at best one or two recurrences the resulting uncertainty affects the magnitude of estimated probabilities especially in seismic gaps that have not ruptured for a long time in some instances a normal distribution yields a three times higher probability than the correspondingmore log normal distribution less

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

accelerated seismic release and related aspects of seismicity patterns on earthquake faults observational studies indicate that large earthquakes are sometimes preceded by phases of accelerated seismic release asr characterized by cumulative benioff strain following a power law timeto failure relation with a term tf t m where tr is the failure time of the large event and observed values of m are close to 0 3 we discuss properties of asr and related aspects of seismicity patterns associated with several theoretical frameworks the subcritical crack growth approach developed to describe deformation on a crack prior to the occurrence of dynamic rupture predicts great variability and low asymptotic values of the exponent m that are not compatible with observed asr phases statistical physics studies assuming that system size failures in a deforming region correspond to critical phase transitions predict establishment of long range correlations of dynamic variables and power law statistics before large events using stress and earthquake histories simulated by the model of ben zion 1996 for a discrete fault with quenched heterogeneities in a 3 d elastic half space we show that large model earthquakes are associated with nonrepeating cyclical establishment and destruction of long range stress correlations accompanied by nonstationary cumulative benioff strain release we then analyze results associated with a regional lithospheric model consisting of a seismogenic upper crust governed by the damage rheology of lyakhovsky et al 39 over a viscoelastic substrate we demonstrate analytically for a simplified 1 d case that the employed damage rheology leads to a singular power law equation for strain proportional to t f t 1 3 and a nonsingular power law relation for cumulative benioff strain proportional to t f t 1 3 a simple approximate generalization of the latter for regional cumulative benioff strain is obtained by adding to the result a linear function of time representing a stationary background release to go beyond the analytical expectations we examine results generated by various realizations of the regional lithospheric model producing seismicity following the characteristic frequency size statistics gutenberg richter power law distribution and mode switching activity we find that phases of asr exist only when the seismicity preceding a given large event has broad frequency size statistics in such cases the simulated asr phases can be fitted well by the singular analytical relation with m 1 3 the nonsingular equation with m 0 2 and the generalized version of the latter including a linear term with m 1 3 the obtained good fits with all three relations highlight the difficulty of deriving reliable information on functional forms and parameter values from such data sets the activation process in the simulated asr phases is found to be accommodated both by increasing rates of moderate events and increasing average event size with the former starting a few years earlier than the latter the lack of asr in portions of the seismicity not having broad frequency size statistics may explain why some large earthquakes are preceded by asr and other are not the results suggest that observations of moderate and large events contain two complementary end member predictive signals on the time of future large earthquakes in portions of seismicity following the characteristic earthquake distribution such information exists directly in the associated quasi periodic temporal distribution of large events in portions of seismicity having broad frequency size statistics withrandom or clustered temporal distribution of large events the asr phases have predictive information the extent to which natural seismicity may be understood in terms of these end member cases remains to be clarified continuing studies of evolving stress and other dynamic variables in model calculations combined with advanced analyses of simulated and observed seismicity patterns may lead to improvements in existing forecasting strategies

july mean temperature and annual precipitation trends during the holocene in the fennoscandian tree line area pollen based climate reconstructions july mean temperature and annual precipipation during the last 9900 cal yr bp were recon structed from pollen assemblages preserved in a sediment core from northern finland quantitative recon structions were performed using a modern pollen climate calibration model based on weighted averaging partial least squares regression the predictive ability of the model was evaluated against modern meteoro logical data using leave one out cross validation the prediction error for july mean temperature is c 1 0 c and for annual precipitation 340 mm the july mean temperatures during the earliest holocene were low c 1 1 0 c and annual precipitation was high c 600 800 mm between 8200 and 6700 cal yr bp july mean temperatures reached their maxima 12 5 13 0 c which are c 1 4 1 7 c higher than at present at the same time precipitation decreased during the late holocene july mean temperatures declined and the last 2000 years have been the coolest since the early holocene precipitation has slightly increased the spatial coherence between our results and of several other climate reconstructions from northern europe indicates that the holocene climate was strongly influenced by north atlantic oceanic and atmospheric circulation patterns we propose that the distinctly oceanic climate of the early holocene was due to enhanced westerly latitudinal airflow which was replaced at c 8200 cal yr bp by a more meridional flow pattern and by the development of predominantly anticyclonic summer conditions

precursory accelerating seismic moment release amr in a synthetic seismicity catalog a preliminary study 1 a power law like acceleration of seismic moment release amr has been proposed as a precursor to large earthquakes because of problems with real world data we have used a synthetic seismicity model of 256 interacting faults embedded in a 3 d elastic half space to search for periods of amr preceding the largest events mw 7 1 in only 5 of 18 cases does the amr model fit the data significantly better than a linear moment release and then only weakly so this proportion or higher occurs in 8 of 1000 randomized catalogs we conclude that either amr is unlikely to be a common precursor or that factors contributing to the amr pattern in the real world are missing from the synthetic model

statistical physics approach to understanding the multiscale dynamics of earthquake fault systems 1 earthquakes and the faults upon which they occur interact over a wide range of spatial and temporal scales in addition many aspects of regional seismicity appear to be stochastic both in space and time however within this complexity there is considerable self organization we argue that the occurrence of earthquakes is a problem that can be attacked using the fundamentals of statistical physics concepts of statistical physics associated with phase changes and critical points have been successfully applied to a variety of cellular automata models examples include sandpile models forest fire models and particularly slider block models these models exhibit avalanche behavior very similar to observed seismicity a fundamental question is whether variations in seismicity can be used to successfully forecast the occurrence of earthquakes several attempts have been made to utilize precursory seismic activation and quiescence to make earthquake forecasts some of which show promise

sedimentary cladocera as indicators of past water level changes in shallow northern lakes the usability of subfossil cladocera assemblages in reconstructing long term changes in lake level was examined by testing the relationship between cladocera based planktonic littoral p l ratio and water level inference model in a surface sediment dataset and in a 2000 yr sediment record in finland the relationships between measured and inferred water levels and p l ratios were significant in the dataset implying that littoral taxa are primarily deposited in shallow littoral areas while planktonic cladocerans accumulate abundantly mainly in deepwater locations the 2000 yr water level reconstructions based on the water level inference model and p l ratio corresponded closely with each other and with a previously available midge inferred water level reconstruction from the same core showing a period of lower water level around ad 300 1000 and suggesting that the methods are valid for paleolimnological and climatological use

how cold was the little ice age a proxy based reconstruction from finland applying modern analogues of fossil midge assemblages climate dynamics during the past ca 700 years in southern finland were reconstructed using fossil midge diptera nematocera assemblages aiming to estimate quantitatively the temperature change that has occurred from the little ice age to the present midge stratigraphies of two sediment cores from eastern and southern finland were chosen to be examined for temperature inferences utilizing the modern analogue technique the new midge based temperature inference model had a coefficient of determination of 0 901 and a prediction error of 0 498 c showing improvement over the previous finnish models the combined curve of the inferred temperatures derived from both of the cores showed a decrease towards ca 1700 ad when temperatures were approximately 1 c cooler than the past 700 years average and almost 2 c colder than present the temperatures began to increase in southern finland from 1800 ad and in eastern finland from 1900 ad onwards the highest temperatures were reached at the top of the core representing the present climate warming although there was slight overestimation in the recent inferred values the reconstructed trends were in close correspondence with the previous proxy based historical and measured data that suggests that the reconstruction was realistic and reliable

new observational information on the precursory accelerating and decelerating strain energy release recent reliable data are used to study the behavior of seismic activity before 46 strong shallow earthquakes m 6 0 which correspond to five complete samples of mainshocks these samples include 6 mainshocks m 6 0 7 1 that occurred in western mediterranean since 1980 17 mainshocks m 6 0 7 2 which occurred in the aegean greece and surrounding area since 1980 5 mainshocks m 6 4 7 5 that occurred in anatolia since 1980 12 mainshocks m 6 0 7 3 that occurred in california since 1980 and 6 mainshocks m 7 0 8 3 that occurred in japan since 1990 in all 46 cases a similar precursory seismicity pattern is observed specifically it is observed that accelerating benioff strain square root of seismic energy release caused by preshocks occurs in a broad circular region critical region with a radius about eight times larger than the fault length of the mainshock in agreement with results obtained by various research groups during the last two decades however in a much smaller circular region seismogenic region with a radius about four times the fault length the corresponding preshock strain decelerates with the time to the mainshock the time variation of the strain follows in both cases a power law but the exponent power is smaller than unit m 0 3 in the case of the accelerating preshock strain and larger than unit m 3 0 in the case of the decelerating preshock strain predictive properties of this decelerating in accelerating out strain model are expressed by empirical relations the possibility of using this model for intermediate term earthquake prediction is discussed and the relative model uncertainties are estimated

reconstruction of the holocene palaeoenvironmental conditions accordingly to the multiproxy sedimentary records from lake pilvelis latvia abstract reconstruction of the holocene palaeoenvironment conditions in southeastern latvia is based on multiproxy records from lake pilvelis pollen plant macrofossil and microfossil analysis loss on ignition loi measurements 14 c dating humic substances content humification index and elemental composition of gyttja organic mass the data complex obtained in the result of multiproxy studies of sediments in lake pilvelis indicates significant changes in the depositional environment during the lake development data from lake pilvelis show that the start of organic rich sediments formation before approximately 9750 cal bp when birch pine forest dominated in the surrounding landscape diagrams and data sets show six remarkable comparatively short cooling periods during the holocene which are related to changes in temperature and water level and influenced values and variability of remains the investigation recognized the 8 4 ka bp and 4 6 ka bp cold events while other cooling events can be recognised conditionally during the events of 4 0 ka bp the water level decreased extremely and the climate was probably drier indicated by the comparison of records from lake pilvelis mazais svetinu bog and lake razna a comparison of pollen data from lake pilvelis with lake kurjanovas mazais svetinu bog and lake razna shows some similarities revealing features of cooler climatic conditions approximately at the time characterised by an increase of betula and herb pollen

multicentennial megadrought in northern europe coincided with a global el nino southern oscillation drought pattern during the medieval climate anomaly the el nino southern oscillation enso is a pacemaker of global climate and the accu rate prediction of future climate change requires an understanding of the enso variability recently much debated aspects of the enso have included its long term past and future changes and its associations with the north atlantic and european sectors potentially in inter action with the north atlantic oscillation and the atlantic multidecadal oscillation here we present the fi rst european dendroclimatic precipitation reconstruction that extends through the alternating climate phases of the medieval climate anomaly and the little ice age we show that northern europe underwent a severe precipitation defi cit during the medieval climate anomaly which was synchronous with droughts in various enso sensitive regions worldwide while the subsequent centuries during the little ice age were markedly wetter we attribute this drought primarily to an interaction between the enso and the north atlantic oscillation and to a lesser or negligible degree to an interaction between the enso and the atlantic multidecadal oscillation

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

temperature and effective moisture variability in southern finland during the holocene quantified with midge based calibration models effective moisture and temperature dynamics during the late glacial and holocene were reconstructed from fossil midge diptera nematocera assemblages in lake hirvijarvi southern finland quantitative inferences were performed using midge based transfer functions for water depth and mean july air temperature the aim was to identify major trends in holocene climate development the results were generally consistent with patterns found in previous investigations from nearby regions and indicated some distinct differences in palaeoclimate between southern and northern finland the results indicate that the region was characterised by a very cold late pleistocene cool and moist but drying early holocene warm and moist mid holocene and cool and moist late holocene a progressive trend of increasing lake levels from the early holocene towards the present was evident the results of this study provide implications for regional differences in effective moisture between southern and northern finland during the holocene copyright 2010 john wiley sons ltd

palaeoecological record of natural changes and human impact in a small river valley in central poland abstract the developmental history of a mire located in the grabia river valley central poland spanning the last 9000 years was investigated using high resolution records of pollen cladocera and geochemistry from a 14c dated core the study demonstrates the value of cladocera palynological and geochemical methods in research into human impact and natural fluvial activity particularly for those elements that are difficult to find through sedimentological methods our research shows the importance of long term reconstructions in establishing palaeohydroclimatic conditions and determining the human impact on the mire we propose that water level fluctuations were important in modifying biota assemblages periods with higher water levels are synchronous with climatic changes but in the subatlantic they also correspond to phases of human activity in the valley the probable phases of increased fluvial activity of the grabia river coincide in general with periods of wet climate deforestation and soil erosion the main phases that show increases in the water level in the lower part of grabia river valley are estimated at ca 5800 5500 bc 4500 4300 bc 4200 3800 bc and 400 ad the water level changes of 1300 ad 1500 ad and 1650 ad as well as those of the last century were most strongly influenced by a combination of natural and anthropogenic factors anthropogenic events were particularly significant during the middle ages and in the last century

seismicity trends and potential for large earthquakes in the alaska aleutian region the high likelihood of a gap filling thrust earthquake in the alaska subduction zone within this decade is indicated by two independent methods analysis of historic earthquake recurrence data and time to failure analysis applied to recent decades of instrumental data recent may 1993 earthquake activity in the shumagin islands gap is consistent with previous projections of increases in seismic release indicating that this segment along with the alaska peninsula segment is approaching failure based on this pattern of accelerating seismic release we project the occurrence of one or morem 7 3 earthquakes in the shumagin alaska peninsula region during 1994 1996 different segments of the alaska aleutian seismic zone behave differently in the decade or two preceding great earthquakes some showing acceleration of seismic release type a zones while others show deceleration type d zones the largest alaska aleutian earthquakes in 1957 1964 and 1965 originated in zones that exhibit type d behavior type a zones currently showing accelerating release are the shumagin alaska peninsula delarof and kommandorski segments time to failure analysis suggests that the large earthquakes could occur in these latter zones within the next few years

spatial distribution of turn of the century seismicity along the alaska aleutian arc abstract epicenters determined for instrumentally observed earthquakes occurring around the turn of the century have figured prominently in estimates of seismic hazard along the alaska aleutian arc unfortunately because of poor timing control and a sparse station distribution the locations quoted in the older catalogs can be very unreliable more reliable epicenter estimates and quantitative assessments of the errors associated with these estimates are needed to address issues related to seismic hazard seventeen earthquakes with surface wave magnitudes above 6 8 that were recorded between 1898 and 1917 are relocated using a modified least squares criterion epicentral estimates are determined using p s and s p arrival times with the a priori constraint that the final location must be near the geographically defined arc although epicenters determined using a standard least squares criterion can be located up to 800 km from the arc the arc proximity constraint provides tectonically more meaningful locations which to a high degree of confidence fit the travel time observations as well as the unconstrained locations epicentral shifts of up to 1 200 km are observed between the relocations and those reported in the earlier catalogs seventy five per cent confidence bounds on the along arc location of each event vary from 30 to 400 km several large events m s 6 9 occurred within or near the rupture zone of the 1965 rat islands earthquake and may indicate that this zone failed in a sequence of events around the turn of the century of the four events previously suggested as being possible candidates for rupturing either the shumagin or unalaska seismic gaps none relocate near these arc segments the relocation of a large m s 7 9 earthquake which occurred in 1917 within the shumagin islands region however provides the first strong evidence of largescale seismic moment release within this intensely studied seismic gap

seismic potential of the queen charlotte alaska aleutian seismic zone the 5000 km long queen charlotte alaska aleutian seismic zone is subdivided into 17 unequally sized segments their boundaries are delineated based on the prior distribution of large and great earthquakes the 17 segments are chosen to represent areas likely to be ruptured by characteristic earthquakes this term usually implies repeated breakage of a plate boundary segment by either a large or great earthquake whose source dimensions remain consistent from cycle to cycle this definition does not exclude the possibility that occasionally adjacent characteristic earthquake segments may break together in a single giant event that is larger than the characteristic size outlined conversely a segment can also sometimes break in a series of smaller ruptures formal computations of the conditional probabilities for future large and great earthquakes in the 17 segments of the queen charlotte alaska aleutian seismic zone are based on the following data sets and findings 1 recurrence intervals from historic and geologic data 2 direct recurrence time estimates based on rates of relative plate motion and the size or displacement of the most recent characteristic event in each segment and 3 the application of a lognormal distribution of recurrence times for large and great earthquakes results of these computations indicate seven areas that have high i e 60 conditional probabilities for the recurrence of either large or great earthquakes within the next 20 years 1988 2008 these areas include cape st james yakataga the shumagin islands unimak island and the fox delarof and near islands segments of the aleutian arc when a shorter time interval is considered 1988 1998 those segments more likely to rupture in large ms 7 7 7 rather than great earthquakes have a high conditional probability these areas include the unimak fox and delarof islands segments the largest uncertainties in these forecasts stem from the short historic record providing a single recurrence time estimate for some segments or widely varying estimates for others from the unknown importance of aseismic slip and from a vague definition of characteristic earthquake size in fact characteristic earthquake size may not be a time invariant quantity

intermediate term earthquake prediction using precursory events in the new madrid seismic zone abstract earthquake prediction may be possible for some mainshock events the time to failure method described by varnes 1989 and bufe and varnes 1990 uses precursory events foreshocks to define an accelerated energy release curve by fitting an equation to the data a predicted time of failure and magnitude can be calculated until recently this method has been used in only a few studies in tectonically active areas and for moderate to large magnitude mainshock events using the microearthquake network data set from the new madrid seismic zone nmsz which is reasonably complete for earthquakes of magnitude 1 5 in the area of interest the method has yielded predicted values of past events as small as m b 3 5 the network data set used in this evaluation covers the time interval from 29 june 1974 to 20 july 1995 for the nmsz there have been 36 earthquakes of magnitude 3 5 over the 21 yr period in which the network has been operating because precursory events are required for the application of the time to failure method mainshocks that occurred before 1980 do not have enough data to adequately define the accelerated energy release curve therefore we utilized the 26 earthquakes that occurred after 1980 and that had a magnitude 3 5 sixteen of the 26 mainshock events were modeled in most cases the precursory sequences yielded predicted times of failure and magnitudes that were reasonably close to the actual mainshock values the remaining mainshocks including those occurring before 1980 could not be modeled due to either 1 not enough events to adequately define the precursory sequence or 2 interfering events that disrupt the accelerated energy release curve in addition two events were modeled from the nuttli catalog nuttli 1979 along with one that used a combination of both catalogs nineteen earthquakes with magnitudes 3 5 were evaluated using the time to failure method the first calculation using the time to failure method gave predicted results with large error bounds essentially no upper bound on the predicted magnitude an empirical relationship between parameters has helped to constrain the range of the predicted magnitude and to a lesser extent the estimated time of failure this relationship modifies the time to failure equation and yields predicted values for magnitudes that have an upper limit another empirical relationship suggests that the logarithm of the moment of the mainshock increases linearly with the logarithm of the size of the precursory event search diameter the relative seismicity of the region also influences the optimum search diameter used to find precursory events in addition to the evaluation of the acceleration sequences associated with the mainshocks an analysis of the occurrence of false positive acceleration sequences acceleration sequences that do not end in a mainshock was conducted the preliminary false positive analysis was conducted by randomly selecting potential mainshock locations the results yielded a false positive acceleration sequence occurrence rate of 2 with the incorporation of the empirical relationships into the time to failure method the potential for future intermediate term earthquake predictions for the nmsz is encouraging

predictive modeling of the seismic cycle of the greater san francisco bay region the seismic cycle for the san francisco bay region is synthesized by a model combining the pre and post 1906 seismic histories the long term acceleration of seismic release seismic moment benioff strain release or event count in the seismic cycle and the shorter term accelerations preceding the larger earthquakes within that cycle are modeled using an empirical predictive technique called time to failure analysis in which rate of seismic release is proportional to an inverse power of the remaining time to failure the exponent of time to failure in the accelerating sequences appears to be scale invariant and the length of the full cycle is estimated at 269 50 years the 1989 loma prieta earthquake which is the culmination of the first subcycle in the present long term seismic cycle should have been predictable with an uncertainty of 2 years in time and 0 5 in magnitude although the specific location at loma prieta was not predictable by this technique if our model is correct and if the loma prieta earthquake is the culmination of a subcycle the san francisco bay region should be entering a relatively long 20 50 years period of seismic quiescence above magnitude 6 a great earthquake such as the 1906 san francisco event would appear to be more than a century in the future

stress transfer to the denali and other regional faults from the m 9 2 alaska earthquake of 1964 stress transfer from the great 1964 prince william sound earthquake is modeled on the denali fault including the denali totschunda fault segments that ruptured in 2002 and on other regional fault systems where m 7 5 and larger earth quakes have occurred since 1900 the results indicate that analysis of coulomb stress transfer from the dominant earthquake in a region is a potentially powerful tool in assessing time varying earthquake hazard modeled coulomb stress increases on the northern denali and totschunda faults from the great 1964 earthquake coincide with zones that ruptured in the 2002 denali fault earthquake although stress on the susitna glacier thrust plane where the 2002 event initiated was decreased a southeasterly trending coulomb stress transect along the right lateral totschunda fairweather queen charlotte trend shows stress transfer from the 1964 event advancing slip on the totschunda fairweather and queen charlotte segments including the southern fairweather segment that ruptured in 1972 stress transfer retarding right lateral strike slip was observed from the southern part of the totschunda fault to the northern end of the fairweather fault 1958 rupture this region encompasses a gap with shallow thrust faulting but with little evidence of strike slip faulting connecting the segments to the northwest and southeast stress transfer toward failure was computed on the north south trending right lateral strike slip faults in the gulf of alaska that ruptured in 1987 and 1988 with inhibitory stress changes at the northern end of the northernmost 1987 rupture the northern denali and totschunda faults including the zones that ruptured in the 2002 earthquakes follow very closely within 3 for about 90 an arc of a circle of radius 375 km the center of this circle is within a few kilometers of the intersection at depth of the patton bay fault with the alaskan megathrust this inferred asperity edge may be the pole of counterclockwise rotation of the block south of the denali fault these observations suggest that the asperity and its recurrent rupture in great earthquakes as in 1964 may have influenced the tectonics of the region during the later stages of evolution of the denali strike slip fault system

a multiproxy study of younger dryas and early holocene climatic conditions from the grabia river paleo oxbow lake central poland abstract a multi proxy reconstruction of water depth temperature and precipitation inferred from cladocera chironomidae and pollen assemblages has been obtained from wierczyna paleo oxbow central poland during the younger dryas yd and early holocene results suggest that the yd was relatively cold and comprised two main phases the first ca 12 500 12 000 cal yrs bp is characterized by a continental climatic regime and a decrease in winter temperatures and precipitation but an increase in spring summer precipitation the second phase ca 12 000 11 500 cal yrs bp was more mild with a variable continental climate an increase in summer and winter temperature a lengthening of the growing season and increased annual precipitation the reconstructed water level generally follows changes in spring and summer precipitation and length of growing season the frequency and timing of hydroclimatic oscillations at wierczyna show strong similarities to records from other sites in europe this confirms that oxbows and valley mire ecosystems respond to rapid climate change during the yd and early holocene this study therefore brings new insights into the effects of climate changes on river environments especially during the yd we also discuss the limitations of water depth temperature and precipitation reconstructions inferred from the studied biotic assemblages

configurational entropy of critical earthquake populations we present an approach to describe the evolution of distributed seismicity by configurational entropy we demonstrate the detection of phase transitions in the sense of a critical point phenomenon in a 2d site percolation model and in temporal and spatial vicinity to the 1992 m7 3 landers earthquake in southern california our findings support the assumption of intermittent criticality in the earth s crust we also address the potential usefulness of the method for earthquake catalogue declustering

decelerating precursory seismicity in vrancea abstract preshock seismic excitation followed by seismic quiescence has been observed in the seismogenic region of strong shallow mainshocks the strain released by such preshocks is decelerating with the time to the mainshock and is fitted by a power law with a power value larger than unit this model is tested in the present work for the intermediate depth earthquakes of the vrancea region generated in an isolated seismogenic zone proper for such testing a backward application of this decelerating preshock strain model for the case of 4 3 1977 m 7 5 earthquake for which reliable data are available shows a good fit of the power law pattern to the seismic activity preceding the main shock the occurrence rate of recent intermediate depth shocks in vrancea indicates that this region is currently in a state of decelerating seismic deformation which may lead to the generation of a strong intermediate depth mainshock there at about the beginning of the third decade of the present century the respective uncertainties are unknown due to lack of previous relative studies