determination of mmax from background seismicity and moment conservation we describe a simple method to determine the probability distribution function of the magnitude m max and return period t r of the maximum plausible earthquake on crustal faults the method requires the background seismicity rate estimated from instrumental data and the rate of interseismic moment buildup the method assumes that the moment released by the seismic slip is in balance with the moment deficit accumulated in between earthquakes it also assumes that the seismicity obeys the gutenberg richter gr law up to m max we took into account the aftershocks of large infrequent events that were not represented in the instrumental record so that we could estimate the average seismicity rate over the entire fault history we extrapolated the instrumental record using the gr law to model the frequency of larger events and their aftershocks this increased the frequencies of smaller events on average when these smaller events were newly extrapolated they predicted a higher frequency of larger events we iterated this process until stability was reached and then we assumed moment balance when we found the maximum magnitude we have found this method to be appropriate in applications involving examples of fault with good historical catalogs we then showed examples of applications to faults with no historical catalogs we present results from nine cases for the san andreas fault system we find m max 8 1 0 3 with t r380 950 120 yrs for the north anatolian fault m max 8 0 0 3 with t r275 650 135 yrs for the main himalayan thrust m max 9 0 0 2 with t r1200 2700 550 yrs for the japan trench m max 9 3 0 3 with t r520 1200 220 yrs for the sumatra andaman trench m max 9 0 0 3 with t r200 450 80 yrs for the bocono fault m max 7 3 0 3 with t r160 360 70 yrs for the altyn tagh fault m max 8 0 0 3 with t r900 2000 400 yrs for the dead sea transform m max 7 8 0 3 with t r1000 2400 450 yrs and for the kunlun fault m max 8 0 0 3 with t r1000 2000 450 yrs

the gutenberg richter or characteristic earthquake distribution which is it abstract paleoearthquake and fault slip rate data are combined with the cit usgs catalog for the period 1944 to 1992 to examine the shape of the magnitude frequency distribution along the major strike slip faults of southern california the resulting distributions for the newport inglewood elsinore garlock and san andreas faults are in accord with the characteristic earthquake model of fault behavior the distribution observed along the san jacinto fault satisfies the gutenberg richter relationship if attention is limited to segments of the san jacinto that are marked by the rupture zones of large historical earthquakes or distinct steps in fault trace the observed distribution along each segment is consistent with the characteristic earthquake model the gutenberg richter distribution observed for the entirety of the san jacinto may reflect the sum of seismicity along a number of distinct fault segments each of which displays a characteristic earthquake distribution the limited period of instrumental recording is insufficient to disprove the hypothesis that all faults will display a gutenberg richter distribution when averaged over the course of a complete earthquake cycle but given that 1 the last 5 decades of seismicity are the best indicators of the expected level of small to moderate size earthquakes in the next 50 years and 2 it is generally about this period of time that is of interest in seismic hazard and engineering analysis the answer to the question posed in the title of the article at least when concerned with practical implementation of seismic hazard analysis at sites along these major faults appears to be the characteristic earthquake distribution

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

potential field imaging of palaeozoic orogenic structure in northern and central europe abstract the trans european suture zone tesz is the most fundamental lithospheric boundary in europe separating the ancient crust of the fennoscandian shield east european craton from the younger crust of central europe and extending deep into the mantle geophysical potential field images provide an overview of the entire palaeozoic orogenic system of northern and central europe for the first time the tesz is largely concealed by sedimentary basins of permian cenozoic age geological observations are largely restricted to local basement highs and deep boreholes and the coverage of deep seismic surveys is widely spaced despite experiments recently acquired within the europrobe programme by contrast the potential field data offer a relatively detailed coverage of standardised observations throughout the tesz while some features of the images may be sourced in the near surface particularly in the gravity image much of their content reflects the structure of the underlying palaeozoic basement at the scale presented the images highlight the most fundamental features of the crustal structure of the tesz these include the strong contrast between the highly magnetic crust of the east european craton and the less magnetic palaeozoic accreted terranes of central europe the lateral continuity of terranes and their internal structure particularly where arc magmatic complexes are involved and the location and geometry of the terrane boundaries oceanic sutures and strike slip zones that separate them

cretaceous and cenozoic non marine deposits of the northern south yellow sea basin offshore western korea palynostratigraphy and palaeoenvironments abstract palynological analyses of two wells haema 1 and kachi 1 located in two sub basins of the northern south yellow sea basin have been carried out in order to establish a palynostratigraphic breakdown of the sedimentary succession and to determine environments of deposition seven assemblage zones and two assemblage subzones have been erected on the basis of frequency variations in and occurrences of biostratigraphically significant palynomorphs as follows classopollis ephedripites assemblage zone az barremian albian alisporites aquilapollenites penetetrapites az which is subdivided into an alisporites rugubivesiculites assemblage subzone cenomanian lower maastrichtian and an aquilapollenites penetetrapites assemblage subzone upper maastrichtian momipites coryluspollenites az paleocene caryapollenites inaperturopollenites az lower middle eocene quercoidites pinuspollenites az upper eocene liquidambarpollenites fupingopollenites magnastriatites az lower middle miocene graminidites persicarioipollis az pliocene the depositional environments represented by the well sections are considered to have been generally fluvio lacustrine and the climate to have varied between semi arid and wet and subtropical and warm temperate except during the late eocene and pliocene when a cool temperate climate prevailed six stages in the development of the sub basins are recognised these are 1 initial stage of rift or pull apart basin formation during the late jurassic cretaceous 2 subsidence from the paleocene to middle eocene 3 alternation of uplift and subsidence in the late eocene 4 synrift inversion and erosion through the oligocene 5 uplift during the early miocene and 6 widespread subsidence from the middle miocene onwards apart from during the early pliocene when the region was subjected to uplift once more

interplate coupling in the kanto district central japan and the boso peninsula silent earthquake in may 1996 i studied crustal deformation in the kanto district central japan based on continuous gps data horizontal as well as vertical displacement rate demonstrate significant interaction between the landward kanto block and the philippine sea plate although the subduction effect of the pacific plate is not apparent it is reasonable to consider the entire kanto district is displaced westward due to the interaction with the pacific plate the gps velocity data were inverted to estimate the slip deficit distribution on the sagami trough subduction zone the result delineates a strongly coupled region on the plate interface part of which corresponds to the 1923 kanto earthquake the strongly coupled region is located shallower than 20 km in addition the plate interaction is laterally heterogeneous even in the same depth range implying thermal structure is not the only factor controlling interplate coupling the gps data also detected a silent earthquake event on the interface of the philippine sea slab east of the boso peninsula in the middle of may 1996 the silent rupture propagated over a 50 km 50 km wide area during about a week the maximum slip was approximately 50 mm and the released seismic moment was 4 7 1018nm mw 6 4 there was a small seismicity triggered by this silent event the silent slip was located in the peripheral of the strongly coupled area suggesting that frictional properties and or stress conditions are inhomogeneous on the plate boundary interface

seismicity of california s north coast at least three moment magnitude m 7 earthquakes occurred along california9s north coast in the second half of the nineteenth century the m 7 3 earthquake on 23 november 1873 occurred near the california oregon coast and likely was located on the cascadia subduction zone or within the north american plate the m 7 0 earthquake on 9 may 1878 was located about 75 km offshore near the mendocino fault the surface wave magnitude m s 7 0 earthquake on 16 april 1899 was located about 150 km offshore within the gorda plate there were at least three m 7 north coast earthquakes in the 35 years before 1906 two m 7 earthquakes in the 20 years after 1906 no m 7 earthquakes from 1923 until 1980 and four m 7 earthquakes since 1980 the relative seismic quiescence after 1906 for m 7 earthquakes along california9s north coast mimics the post 1906 seismic quiescence in the san francisco bay area for m 6 earthquakes the post 1906 relative quiescence did not extend to lower magnitudes in either area the 18 april 1906 earthquake apparently influenced the rate of occurrence of m 7 north coast earthquakes as it apparently influenced the rate of m 6 earthquakes in the san francisco bay area the relative seismic quiescence along the california north coast region after 1906 should be taken into account when evaluating seismic hazards in northwest california

visualization of 3d wave propagation from the 2000 tottori ken seibu japan earthquake observation and numerical simulation the dense networks of strong ground motion instruments in japan k net and kik net provide a means of direct visualization of regional wave propa gation during large earthquakes for the 2000 tottori ken seibu earthquake mw 6 6 in western japan snapshots of ground motion derived directly from interpolation of a large number of array observations demonstrate clearly the nature of the source radiation and the character of the seismic wave field propagating to regional dis tances in western japan the wave field from the earthquake is characterized in most parts by the dominance of high frequency 0 2 5 hz lg waves on three component acceleration records and longer period t 10 sec fundamental mode love waves in tangential displacement the presence of strong lateral variations in the crust and upper mantle structures such as the low velocity superficial layer and the high velocity philippine sea plate with shallow subduction into the mantle impose sig nificant modifications on the regional wave field further insight into the nature of the seismic wave field is gained by comparison of the observations with numerical simulation for a 3d model including sedimentary basins by an embedded submesh a multigrid parallel computation using a hybrid pseudospectral finite difference method allows the inclusion of a realistic model of the source process for the 2000 tottori ken seibu earthquake there is good agreement in the dominant features of the regional wave field propagating through the complex structure of western japan however the differences between the observations and the computer simulations indicates the need for further refinement of the source and structural models the inclusion of amplification effects for the population centers in sedimentary basins means that the modeling procedure is already suitable for estimating the main pattern of ground motion for future earthquake scenarios

crustal block kinematics and seismic potential of the northernmost philippine sea plate and izu microplate central japan inferred from gps and leveling data 1 we clarify the contemporary deformation observed by gps and leveling for the greater tokyo kanto eastern tokai and the izu islands region where the izu ogasawara bonin arc is subducting and colliding with the central part of the japan arc from these data we develop a kinematic model of fault sources with variable components of seismic and aseismic slip under the assumption that the contemporary deformation during 1995 2000 is representative of the long term interseismic strain field the geodetic data are inverted to estimate the rotation poles of the crustal blocks the degree of elastic strain accumulation on faults and the volumetric inflation sources beneath volcanoes the present crustal movements are explained by four crustal blocks the izu microplate the central japan block the pacific plate and the philippine sea plate along the suruga and sagami margins of the philippine sea plate lie strongly coupled faults which include sites of the 1854 m 8 4 tokai 1923 m 7 9 kanto and 1703 m 8 2 genroku kanto earthquakes in contrast the philippine sea plate boundary immediately north of the izu peninsula site of m 7 5 collisional earthquakes is only weakly coupled the boundary between the izu microplate and the philippine sea plate experiences left lateral motion with the rate of 30 mm yr most of this boundary is locked and thus has a large potential of future earthquakes the izu microplate is found to rotate rapidly clockwise at 10 myr with a rotation pole relative to the central japan block located just north of its northern boundary the pole and angular velocity of the izu microplate depends however on the assumed location of the boundary with the exception of the site of the 1938 m 7 earthquake swarm which we infer has the current potential to produce a m 8 1 earthquake the pacific megathrust has a very low seismic potential although the geodetic data have little resolving power for much of the pacific plate interface east of tokyo

seismic hazard in western canada from gps strain rates versus earthquake catalog 1 probabilistic seismic hazard analyses psha are commonly based on frequency magnitude statistics from 50 100 yearlong earthquake catalogs assuming that these statistics are representative of the longer term frequency of large earthquakes we test an alternative psha approach in continental western canada including adjacent areas of northwestern u s a using regional strain rates derived from 179 global positioning system gps horizontal velocities gps strain rates are converted to earthquake statistics seismic moment rates and ground shaking probabilities in seismic source zones using a logic tree method for uncertainty propagation median gps based moment rates and shaking estimates agree well with those derived from earthquake catalogs in only two zones puget sound and mid vancouver island in most other zones median gps based moment rates are 6 150 times larger than those derived from earthquake catalogs shaking estimates 2 5 times larger although the gps based and catalog estimates commonly agree within their 67 uncertainties this discrepancy may represent an under sampling of long term moment rates and shaking by earthquake catalogs in some zones however a systematic under sampling is unlikely over our entire study area although not demonstrated with a high confidence level long term regional aseismic deformation may account for a significant part of the gps catalog discrepancy and in some areas represent as much as 90 of the total deformation budget in order to integrate gps strain rates in psha models seismic versus aseismic partitioning of long term deformation needs to be quantified and understood in terms of the underlying mechanical processes

a new tectonic model for the laurentia avalonia baltica sutures in the north sea a case study along mona lisa profile 3 abstract we present a new model for the lithospheric structure of the transitions between laurentia avalonia and baltica in the north sea northwestern europe based on 2 d potential field modelling of mona lisa profile 3 across the central graben with constraints from seismic p wave velocity models and the crustal normal incidence reflection section along the profile the model shows evidence for the presence of upper and lower palaeozoic sedimentary rocks as well as differences in crustal structure between the palaeo continents laurentia avalonia and baltica our new model together with previous results from transformations of the gravity and magnetic fields demonstrates correlation between crustal magnetic domains along the profile and the terrane affinity of the crust this integrated interpretation indicates that a 150 km wide zone characterized by low grade metamorphosis and oblique thrusting of avalonia crust over baltica lower crust is characteristic for the central north sea area the magnetic susceptibility and the density across the coffee soil fault range from almost zero and 2715 kg m3 in avalonia crust to 0 05 si and 2775 kg m3 in baltica crust the model of mona lisa profile 3 indicates that the transition between avalonia and baltica is located beneath the central graben with a ramp flat ramp geometry our results indicate that the initial rifting of the central graben and the viking graben was controlled by the location of the caledonian collisional suture located at the coffee soil fault and that the deep crustal part of baltica extends further to the west than hitherto believed

helicosporous fungi and early eocene pollen eureka sound group axel heiberg island northwest territories two types of helicosporous fungal spores were recovered from a sample from the iceberg bay formation eureka sound group at strand fiord axel heiberg island these spores appear to be identical to those produced by the recent genera helicoon helicodendron and helicosporium the associated pollen flora indicates an early eocene age for the sample and interval from which it was collected the pollen and spores suggest that swamp forest vegetation dominated by trees of taxodiaceae cupressaceae and growing in a temperate climate was present at or close to the site of deposition

strain and rotation rate patterns of mainland greece from continuous gps data and comparison between seismic and geodetic moment release we processed data from 100 continuous gps stations to provide new insights into the crustal motion and deformation of central and western greece we used the derived velocity field to evaluate two dimensional strain and rotation rate tensors and we mapped the dilatation and maximum shear strain rates in central peloponnese and epirus we documented a 90 switch in the extension direction which can be explained on the basis of the plate boundary configuration evidence for an extended deformation pattern in central greece was found additionally we detected two pairs of shear belts one in akarnania nw peloponnese and one in north aegean we delineated two rotational domains that dominate the present day pattern moreover we saw no geodetic evidence for north anatolian fault growth toward central greece we translated the geodetic strain rates into rates of seismic moment release and compared them with earthquake catalog based moment rates in the central ionian sea the geodetic strain is completely released seismically which is indicative of a fully coupled seismogenic zone however for most of the study area the geodesy based moment rates are at least 2 times higher than the earthquake based rates we attribute this mainly to earthquake catalog representativity over the long term situation however for the gulf of corinth it is unrealistic to associate the high ratio of geodetic to seismic moment rates only to incompleteness of the earthquake catalog instead long term aseismic deformation must be an important mechanism accommodating a considerable portion of the strain budget especially at its western part

late paleocene arctic coastal climate inferred from molluscan stable and radiogenic isotope ratios abstract characterizing polar climates during past warm intervals is important for understanding greenhouse climate dynamics because high latitude surface temperatures and precipitation patterns are extremely sensitive to global climatic conditions model data comparisons of high latitude climates during past warm intervals cretaceous eocene pliocene are currently at odds specifically simulations of past warm climates produce polar regions characterized by sub freezing temperatures and significant seasonality whereas limited fossil proxy data indicate higher mean annual temperatures and low seasonality i e an equable climate we have constructed a data set to infer northern hemisphere polar marine temperatures during the late paleocene seasonal and mean annual temperature and the oxygen isotopic composition of precipitation are reconstructed for an arctic coastal setting during the thanetian 57 58 ma using fossil shell stable isotope profiles we estimate that coastal water temperatures varied between 10 and 15 c during the seasons of growth presumably spring summer and fall these findings support paleontological evidence implying northern hemisphere polar climates were seasonally warm during the late paleocene in addition estuarine fossil oxygen isotope profiles show periodic excursions to low values as low as 19 vpdb which indicate seasonal pulses of isotopically depleted freshwater

pre earthquake signals underlying physical processes abstract prior to large earthquakes the earth sends out transient signals sometimes strong more often subtle and fleeting these signals may consist of local magnetic field variations electromagnetic emissions over a wide range of frequencies a variety of atmospheric and ionospheric phenomena great uncertainty exists as to the nature of the processes that could produce such signals both inside the earth s crust and at the surface the absence of a comprehensive physical mechanism has led to a patchwork of explanations which are not internally consistent the recognition that most crustal rocks contain dormant electronic charge carriers in the form of peroxy defects o 3 si oo sio 3 holds the key to a deeper understanding of these pre earthquake signals from a solid state physics perspective when rocks are stressed peroxy links break releasing electronic charge carriers h known as positive holes the positive holes are highly mobile and can flow out of the stressed subvolume the situation is similar to that in a battery the h outflow is possible when the battery circuit closes the h outflow constitutes an electric current which generates magnetic field variations and low frequency em emissions when the positive holes arrive at the earth s surface they lead to ionization of air at the ground air interface under certain conditions corona discharges occur which cause rf emission the upward expansion of ionized air may be the reason for perturbations in the ionosphere recombination of h charge carriers at the surface leads to a spectroscopically distinct non thermal ir emission

history of ancient megathrust earthquakes beneath metropolitan tokyo inferred from coastal lowland deposits abstract metropolitan tokyo is located directly above a subduction zone that has generated two megathrust earthquakes in the past 300 years however the timing of older megathrusts on this margin is poorly understood in this study we aim to constrain the timings of past megathrust earthquakes using coastal stratigraphy paleoecology radiocarbon dating and archaeological records from coastal lowlands an investigation of 13 boreholes in the southern coastal area of metropolitan tokyo found evidence for 4 m of uplift in a 6000 year period however we found that net vertical displacement in the last 1000 years is approximately zero results suggest that preservation of usually ephemeral lagoon sediments occurred on three occasions in the past 1000 years and radiocarbon dating results show that the timings of these preservation episodes are close to that of major historical earthquakes we thus attribute the intermittent preservation of the ephemeral lagoon deposits to coseismic uplift caused by the megathrust earthquakes the candidates of the megathrust earthquakes are events that took place in 1703 ce the 13th century and 878 ce since these events produced no net vertical displacement due to inter seismic subsidence we propose that earthquakes responsible for long term uplift of this region took place prior to the 9th century this research also demonstrates the value of preserved intertidal sediments as paleoseismological archives where net tectonic displacement is neutral

slow earthquakes and great earthquakes along the nankai trough abstract we have reexamined reports indicating that slow deformation occurred before the great japan earthquakes of 1944 tonankai and 1946 nankaido and find that the observations are well founded although no quantitative models have previously been proposed to explain all of the relevant data we show that they are satisfied by a simple model for both earthquakes the model based on known properties of subduction zones has slow slip on the subduction interface in an area deeper than the seismic rupture if this model is correct and a similar physical situation holds for an anticipated tokai earthquake existing instruments will be able to reveal the pre slip in real time while differences among the deformation time series at different sites will provide strong constraints on the slow rupture propagation these differences could result in delaying the recognition of a coherent event

the 2011 m 9 0 tohoku oki earthquake more than doubled the probability of large shocks beneath tokyo 1 the kanto seismic corridor surrounding tokyo has hosted four to five m 7 earthquakes in the past 400 years immediately after the tohoku earthquake the seismicity rate in the corridor jumped 10 fold while the rate of normal focal mechanisms dropped in half the seismicity rate decayed for 6 12 months after which it steadied at three times the pre tohoku rate the seismicity rate jump and decay to a new rate as well as the focal mechanism change can be explained by the static stress imparted by the tohoku rupture and postseismic creep to kanto faults we therefore fit the seismicity observations to a rate state coulomb model which we use to forecast the time dependent probability of large earthquakes in the kanto seismic corridor we estimate a 17 probability of a m 7 0 shock over the 5 year prospective period 11 march 2013 to 10 march 2018 two and a half times the probability had the tohoku earthquake not struck

significance of stress transfer in time dependent earthquake probability calculations 1 a sudden change in stress is seen to modify earthquake rates but should it also revise earthquake probability data used to derive input parameters permit an array of forecasts so how large a static stress change is required to cause a statistically significant earthquake probability change to answer that question effects of parameter and philosophical choices are examined through all phases of sample calculations drawing at random from distributions of recurrence aperiodicity pairs identifies many that recreate long paleoseismic and historic earthquake catalogs probability density functions built from the recurrence aperiodicity pairs give the range of possible earthquake forecasts under a point process renewal model consequences of choices made in stress transfer calculations such as different slip models fault rake dip and friction are tracked for interactions among large faults calculated peak stress changes may be localized with most of the receiving fault area changed less than the mean thus to avoid overstating probability change on segments stress change values should be drawn from a distribution reflecting the spatial pattern rather than using the segment mean disparity resulting from interaction probability methodology is also examined for a fault with a well understood earthquake history a minimum stress change to stressing rate ratio of 10 1 to 20 1 is required to significantly skew probabilities with 80 85 confidence that ratio must be closer to 50 1 to exceed 90 95 confidence levels thus revision to earthquake probability is achievable when a perturbing event is very close to the fault in question or the tectonic stressing rate is low

a new 1649 1884 catalog of destructive earthquakes near tokyo and implications for the long term seismic process 1 in order to assess the long term character of seismicity near tokyo we construct an intensity based catalog of damaging earthquakes that struck the greater tokyo area between 1649 and 1884 models for 15 historical earthquakes are developed using calibrated intensity attenuation relations that quantitatively convey uncertainties in event location and magnitude as well as their covariance the historical catalog is most likely complete for earthquakes m 6 7 the largest earthquake in the catalog is the 1703 m 8 2 genroku event seismicity rates from 80 years of instrumental records which include the 1923 m 7 9 kanto shock as well as interevent times estimated from the past 7000 years of paleoseismic data are combined with the historical catalog to define a frequency magnitude distribution for 4 5 m 8 2 which is well described by a truncated gutenberg richter relation with a b value of 0 96 and a maximum magnitude of 8 4 large uncertainties associated with the intensity based catalog are propagated by a monte carlo simulation to estimations of the scalar moment rate the resulting best estimate of moment rate during 1649 2003 is 1 35 1026 dyn cm yr 1 with considerable uncertainty at the 1 level 0 11 0 20 1026 dyn cm yr 1 comparison with geodetic models of the interseismic deformation indicates that the geodetic moment accumulation and likely moment release rate are roughly balanced over the catalog period this balance suggests that the extended catalog is representative of long term seismic processes near tokyo and so can be used to assess earthquake probabilities the resulting poisson or time averaged 30 year probability for m 7 9 earthquakes is 7 11

cause of m 7 intraslab earthquakes beneath the tokyo metropolitan area japan possible evidence for a vertical tear at the easternmost portion of the philippine sea slab 1 we perform travel time tomography beneath kanto japan to obtain detailed structures of the wedge shaped serpentinized mantle previously observed in the philippine sea slab the results suggest that the western boundary of the serpentinized mantle serpentine boundary is subvertical and p and s wave velocities vary by 15 20 across it over the short distance of 10 km two intraslab earthquakes in 1921 m7 0 and 1987 east off chiba earthquake m6 7 are inferred to have occurred along the serpentine boundary accompanied by right lateral movement based on analyses of focal mechanisms and aftershock distribution a subvertical earthquake cluster penetrating the entire philippine sea slab is observed along the serpentine boundary and four earthquakes in the cluster have strike slip focal mechanisms similar to that of the 1987 earthquake focal mechanisms obtained for past large earthquakes and present day microearthquakes suggest a concentration of right lateral deformation along the mechanically weak serpentine boundary the philippine sea slab may have been torn in two along this boundary with the eastern portion being left behind relative to subduction of the western portion assuming that one of the large aftershocks m7 1 of the 1923 kanto earthquake m7 9 which occurred off the boso peninsula ruptured the same asperity as did the 1987 earthquake the slip deficit accumulated along the serpentine boundary during the 64 year interval is consistent with the fault slip of the 1987 earthquake interaction between the seismic slip along the plate interface and the serpentine boundary can explain the series of m7 class earthquakes before and after the 1923 kanto earthquake

investigation of early eocene water vapor transport and paleoelevation using oxygen isotope data from geographically widespread mammal remains the oxygen isotope composition 18 o of apatite from mammalian tooth enamel can be used to infer the 18 o value of ingested water which is in turn related to that of precipitation stored in surface reservoirs therefore the 18 o value of phosphate from fossil tooth enamel can be used to infer the 18 o value of these reservoirs in the past in this paper tooth enamel from a semiaquatic mammal taxon coryphodon collected from five early eocene localities in north america is used to construct patterns in 18 o values of river water for this time period at all localities the 18 o value of river water 18 o r is estimated to have been higher during the early eocene relative to present day north american rivers although the 18 o vs latitude gradient was shallower during the eocene higher 18 o r values are consistent with warmer eocene air masses being able to hold more water vapor and with an increase in the poleward transport of both moisture and latent heat the regular decrease in 18 o r with latitude indicates that global atmospheric circulation patterns and hydrological transport were not much different from those of the present although the shallower 18 o vs latitude gradient during the eocene may reflect regional differences in precipitation evaporation and river recharge at a more regional scale the 18 o value of river water can provide insight into topographic relief during the early eocene in the case of intermontane basins of wyoming differences in average 18 o r values between basins indicate that laramide mountain relief was on the order of 475 m it is suggested that anomalously low 18 o r values reported previously do not provide unambiguous evidence for permanent snow at higher elevations and may instead reflect brief episodes of cooler winters and or altered atmospheric circulation patterns

a slab fragment wedged under tokyo and its tectonic and seismic implications a three dimensional evaluation of earthquake hypocentres beneath the kanto basin in japan reveals the presence of a distinct 25 km thick and 100 km wide body its fast seismic velocity and the presence of a double seismic zone suggest that it is a fragment of the pacific slab rather than an extension of the philippine sea slab this implies that the penetration of the philippine sea slab is much shallower beneath the kanto basin than was previously thought the philippine sea and pacific plate slabs both subduct beneath tokyo and so their configuration and seismic potential have been subject to intensive study1 2 3 4 5 6 7 8 previous work suggests that the philippine sea slab extends up to 100 km northwest of tokyo and subducts to a depth of 90 km beneath the kanto basin where it is folded against the underlying pacific slab here we evaluate seismic data in three dimensions and delineate a distinct 25 km thick and 100 km wide body beneath the kanto basin that has hitherto been considered to be part of the philippine sea slab we find that several of its characteristics such as its high seismic velocity and the presence of a double seismic zone point instead to an affinity with the pacific slab implying that the philippine sea slab penetrates to depths of only 35 40 km beneath the kanto basin we propose that the body is a fragment of pacific lithosphere that formed by the collision of two intersecting seamount chains with the japan trench 2 3 million years ago we suggest that such slab fragments may not be uncommon especially where seamount subduction deforms trenches and near triple junctions

estimates of regional and local strong motions during the great 1923 kanto japan earthquake ms 8 2 part 2 forward simulation of seismograms using variable slip rupture models and estimation of near fault long period ground motions abstract this article addresses the forward simulation of regional and local strong motions from the 1923 kanto japan earthquake ms 8 2 using two variable slip rupture models the wald and somerville 1995 slip model ws slip model derived from geodetic and teleseismic data and a resampled version of the takeo and kanamori 1992 slip model tk slip model that was obtained from the forward simulation of the ewing seismoscope record at hongo hng epicentral distance r 60 km green9s functions are calculated using flat layered velocity models for specific source receiver paths which were developed in our first article sato et al 1998 for regional stations sendai r 350 km and gifu r 220 km the ws slip model provides a much better match to the waveform data than the tk slip model for local station hng the first 40 sec of the n77 e imamura seismogram is successfully reproduced by both of the slip models although the arrivals are delayed in the tk slip model the large amplitude long duration long period 13 sec later phases in the southwest component ewing seismogram are not reproduced by either of the slip models our results suggest that the ws slip model gives a better representation of the overall rupture process of the 1923 event than the tk slip model does near fault long period ground motions calculated at several stations using the ws slip model suggest that the motions at hng were not the largest in the tokyo metropolitan area during the 1923 event in addition we estimate that the ground motions near the southern margin of the fault plane were significantly larger than the recorded near fault motions of recent magnitude 7 earthquakes such as northridge and kobe for periods longer than several seconds this suggests that design codes based on the experience of these recent events may not adequately describe the long period response expected during a magnitude 8 earthquake

characteristic silent earthquakes in the eastern part of the boso peninsula central japan 1 analysis of global positioning system gps data shows transient crustal deformation in the boso peninsula central japan for about fifty days from october 2002 the southeastward horizontal displacements detected suggest the occurrence of interplate aseismic slip between the philippine sea plate and the north american plate six years after a similar event in 1996 we estimate an area of aseismic slip with moment magnitude mw 6 6 centered off the boso peninsula adjacent to associated seismic activity slip evolution of the 2002 aeismic slip started on october 4 and migrated from north to south for about ten days followed by gradual subsidence and restarting of slip which lasted until december 2 propagating more southward similarities in focal area and slip process between the 1996 and the 2002 events suggest the boso aseismic slips as characteristic silent earthquakes together with the repetitive occurrence of seismic swarm in a similar region every six to seven years a more tightly coupled southern area that did not release enough energy in the 1996 event may have caused the differences in magnitude central slip area and duration between the 1996 and the 2002 events if the hypothesized recurrence interval for strain accumulation is true based on swarm seismicity

two current seismic quiescences within 40 km of tokyo summary two highly significant seismic quiescence anomalies that started in 1993 0 exist currently within about 40 km of tokyo they are located in central saitama province at 35 99 n 139 56 e and in tokyo bay south of funabashi at 35 59 n l39 94 e the radii of the anomalous volumes are approximately 15 km centred at about 25 and 20 km depth respectively the seismicity rate during the quiescence was less than 10 per cent background rate in both cases the significance of these quiescences measured by the standard deviate z test comparing the rate of the last three years to the backgound rate is higher than for any other rate changes present in the catalogue zmax 7 5 and 7 2 respectively however episodes of highly significant quiescences which could have been interpreted as precursors but were not followed by main shocks also exist in the data set a third seismic quiescence was found to be in progress since 1993 3 0 5 in nw saitama province at 36 18 n 139 22 e it has a radius of 14 km and is less significant than the other two anomalies zmax 6 8 in a polygon that covers the areas of all three quiescences defined above the seismicity rate since 1994 is only 30 per cent of the previous background rate i e 100 earthquakes that would normally have occurred did not this analysis is based on the earthquake catalogue of the national institute for earth science and disaster prevention for the years 1980 1996 2 and mmin 1 0 as well as for the years 1986 2 1996 2 with mmin 0 1 the anomalies are equally clear in the clustered and in the full catalogues to avoid contamination by explosions only nighttime data 19 00 to 7 00 hours local time were used the frequency magnitude distributions in the quiescent volumes at central saitama nw saitama and funabashi have b values of 1 3 1 5 and 1 1 respectively based on the hypothesis that crustal volumes with high b values may not be capable of m6 earthquakes these three quiescent volumes may be ruled out as source volumes for main shocks of these magnitudes using lilt seismic quiescence hypothesis alone it is a reasonable interpretation to suggest that m 6 5 0 5 earthquakes are expected to terminate each of the three quiescences within 1 year 1 year from now with a 50 per cent probability each the interpretation that all three quiet volumes could rupture together in a large earthquake seems less likely however based on the information that the quiescences are located in volumes with b values above the average b 0 8 it can be argued that the three current quiescences are false alarms the fact that these two lines of evidence allow opposing interpretations in these cases shows that neither hypothesis is sufficiently tested thus the quiescence hypothesis is not advanced enough for issuing earthquake predictions nevertheless it is important that scientific tests of prediction scenarios are formulated in real time so we can learn how to modify our hypotheses to make them useful for prediction in the future

palynology paleoclimatology and correlation of middle miocene beds from porcupine river locality 90 1 alaska abstract beds in the upper ramparts canyon of the porcupine river alaska 67 20 n 141 20 w yielded a flora rich in pollen of hardwood genera now found in the temperate climates of north america and asia the beds are overlain or enclosed by two basalt flows which were dated to 15 2 0 1 ma by the 40 ar 39 ar method fixing the period of the greatest abundance of warm loving genera to the early part of the middle miocene the assemblage is the most northern middle miocene flora known in alaska organic bed 1 underlies the basalt and is older than 15 2 ma but is of early to middle miocene age the pollen assemblage from organic bed 1 is dominated by conifer pollen from the pine and redwood cypress yew families with rare occurrences of temperate hardwoods organic bed 2 is a forest floor containing redwood trees in life position engulfed by the lowest basalt flow a pine log has growth rings up to 1 cm thick organic beds 3 and 4 comprise lacustrine sediment and peat between the two basalt flows their palynoflora contain conifers and hardwood genera of which about 40 have modern temperate climatic affinities hickory katsura walnut sweet gum wingnut basswood and elm pollen are consistently present and beech and oak alone make up about 20 of the pollen assemblage a warm high latitude climate is indicated for all of the organic beds but organic bed 3 was deposited under a time of peak warmth climate data derived by comparison with modern east asian vegetation suggest that at the time of deposition of organic bed 3 the mean annual temperature mat was ca 9 c the warm month mean temperature wmmt was 20 c and the cold month mean temperature cmmt was ca 2 c in contrast the modern mat for the region is 8 6 c wmmt is 12 6 c and cmmt is 28 c organic beds 3 and 4 correlate to rocks of the middle miocene late seldovian stage of cook inlet and also probably correlate to and more precisely date the lower third of the suntrana formation in the alaska range beds at unalaklect part of the upper mackenzie bay sequence in the beaufort mackenzie basin and the mary sachs gravel of banks island this suggests that forests with significant percentages of temperate deciduous angiosperms existed between latitudes 60 and 72 n during the early middle miocene

a plate tectonic scenario for the iapetus and rheic oceans abstract the tectonics dynamics and biogeographic landscape of the early paleozoic were dominated by the opening and expansion of one large ocean the rheic and the diminution to terminal closure of another iapetus an understanding of the evolution of these oceans is thus central to an understanding of the early paleozoic but their chronicle also presents a rich temporal profile of the wilson cycle illustrating continental scale rifting microcontinent formation ocean basin development arc accretion and continent continent collision nevertheless contemporary paleogeographic models of the iapetus and rheic oceans remain mostly schematic or spatiotemporally disjointed which limits their utility and hinders their testing moreover many of the important kinematic and dynamic aspects of the evolution of these oceans are impossible to unambiguously resolve from a conceptual perspective and the existing models unsurprisingly present a host of contradictory scenarios with the specific aim to resolve some of the uncertainties in the evolution of this early paleozoic domain and a broader aim to instigate the application of quantitative kinematic models to the early paleozoic i present a new plate tectonic model for the iapetus and rheic oceans the model has realistic tectonic plates which include oceanic lithosphere that are defined by explicit and rigorously managed plate boundaries the nature and kinematics of which are derived from geological evidence and plate tectonic principles accompanying the presentation and discussion of the plate model an extensive review of the underlying geological and paleogeographic data is also presented

the 1992 nicaragua earthquake a slow tsunami earthquake associated with subducted sediments the 1992 nicaragua earthquake was a tsunami earthquake that is it generated tsunamis disproportionately large for its surface wave magnitude m s the moment magnitude m w determined from long period 250 s surface waves was 7 6 significantly larger than the 20 s m s of 7 this m s m w disparity is also characteristic of tsunami earthquakes the nicaragua earthquake is the first tsunami earthquake to be captured by modern broadband seismic networks allowing us to present here seismograms of sufficiently high quality to make inferences about the rupture mechanisms we conclude that the nicaragua earthquake was a slow thrust earthquake which occurred on the subduction interface between the cocos and north american plates and because of the absence of sediments on the trench floor offshore of nicaragua the slip propagated up dip all the way to the ocean bottom exciting large tsunamis the occurrence of slip on a plate interface filled with soft subducted sediments caused the rupture process to be slower than in ordinary subduction zone thrust earthquakes our results reinforce the idea that tsunami warning systems using long period 100 s waves are necessary to reduce the hazard from this type of earthquake

a dislocation model of strain accumulation and release at a subduction zone strain accumulation and release at a subduction zone are attributed to stick slip on the main thrust zone and steady aseismic slip on the remainder of the plate interface this process can be described as a superposition of steady state subduction and a repetitive cycle of slip on the main thrust zone consisting of steady normal slip at the plate convergence rate plus occasional thrust events that recover the accumulated normal slip because steady state subduction does not contribute to the deformation at the free surface deformation observed there is completely equivalent to that produced by the slip cycle alone the response to that slip is simply the response of a particular earth model to embedded dislocations for a purely elastic earth model the deformation cycle consists of a coseismic offset followed by a linear in time recovery to the initial value during the interval between earthquakes for an elastic viscoelastic earth model elastic lithosphere over a viscoelastic asthenosphere the postearthquake recovery is not linear in time records of local uplift as a function of time indicate that the long term postseimic recovery is approximately linear suggesting that elastic earth models are adequate to describe the deformation cycle however the deformation predicted for amore simple elastic half space earth does not reproduce the deformation observed along the subduction zones in japna at all well if stick slip is restricted to the main thrust zone as recognized earlier by shimazaki seno and kato the uplift profiles could be explained if stick slips were postulated to extend along the plate interface beyond the main thrust zone to a depth of perhaps 100 km but independent evidence suggests that stick slip at such depths if unlikely less

tohoku earthquake a surprise abstract we consider three questions related to the 2011 tohoku mega earthquake 1 why was the event size so grossly underestimated by japan s national hazard map 2 how should we evaluate the chances of giant earthquakes in subduction zones 3 what is the repeat time for magnitude 9 earthquakes off the tohoku coast the maximum earthquake size is often guessed from the available history of earthquakes a method known for its significant downward bias we show that historical magnitudes systematically underestimate this maximum size of future events but the discrepancy shrinks with time there are two quantitative methods for estimating the corner magnitude in any region a statistical analysis of the available earthquake record and the moment conservation principle however for individual zones the statistical method is usually ineffective in estimating the maximum magnitude only the lower limit can be evaluated the moment conservation technique which we prefer matches the tectonic deformation rate to that predicted by earthquakes with a truncated or tapered magnitude frequency distribution for subduction zones the seismic or historical record is insufficient to constrain either the maximum or corner magnitude however the moment conservation principle yields consistent estimates for all the subduction zones the corner magnitude is of the order 9 0 9 7 moreover moment conservation indicates that variations in estimated corner magnitude among subduction zones are not statistically significant another moment conservation method applied at a point on a major fault or plate boundary also suggests that magnitude 9 events are required to explain observed displacement rates at least for the tohoku area the global rate of magnitude 9 earthquakes in subduction zones predicted from statistical analysis of seismicity as well as from moment conservation is about five per century five actually happened

twenty years of paleoseismology in italy abstract italy has one of the most complete and historically extensive seismic catalogues in the world due to a unique and uninterrupted flow of written sources that have narrated its seismic history since about the end of the iron age seismic hazard studies have therefore always been mainly based upon this huge mass of data nevertheless the italian catalogue probably lacks many m 6 5 events the seismogenetic structures responsible for which are characterized by recurrence times that are longer than the time span covered by our historical sources for these reasons and as in other countries earthquake data that in italy have been derived from paleoseismological studies should finally become a necessary ingredient in seismic risk assessment indeed over the past 20 years some hundred trenches have been excavated supplying reliable and conclusive data on the recent activities of many faults through to many robust datings of surface fault events these studies have provided the ages of several unknown or poorly known m 6 5 earthquakes here we summarize the state of the art of paleoseismology in italy and present a first catalogue of 56 paleoearthquakes pci that occurred mainly in the past 6 kyr the pci integrates the historical instrumental seismic catalogue and extends it beyond the recurrence time of the seismogenetic faults 2000 1000 yr we feel confident that the use of the pci will enhance future probabilistic seismic hazard assessment and thus contribute to more reliable seismic risk mitigation programs

evidence for kilometre scale neogene exhumation driven by compressional deformation in the irish sea basin system simon p holford paul f green jonathan p turner gareth a williams richard r hillis david r tappin ian r duddy

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

tsunami earthquake can occur elsewhere along the japan trench historical and geological evidence for the 1677 earthquake and tsunami since the 11 march 2011 tohoku earthquake the mechanisms of large earthquakes along the japan trench have been intensely investigated however characteristics of tsunami earthquakes which trigger unusually large tsunami remain unknown the earthquake of 4 november 1677 was a tsunami earthquake striking the southern part of the japan trench its source mechanism remains unclear this study elucidates the fault slip and moment magnitude of the 1677 earthquake and tsunami based on integrated analyses of historical documents tsunami deposits and numerical simulation geological survey results the analytical results of thickness and grain size distributions and diatoms revealed that tsunami deposits in a small pond at 11 m elevation were probably formed by the 1677 event this finding and historical descriptions are useful as important constraint conditions to estimate unusually large fault slips and moment magnitude of the 1677 earthquake numerical simulation results reveal that 8 34 8 63 moment magnitude with the large 11 16 m slip area is necessary to satisfy the constraint conditions this fault slip and magnitude are equivalent to those of the 1896 sanriku earthquake a well known tsunami earthquake in the northern part of the japan trench we therefore conclude that a tsunami earthquake of moment magnitude 8 3 8 6 with unusually large slip can occur elsewhere along the japan trench this point should be considered for future tsunami risk assessment along the japan trench and along any trench having similar tectonic settings to those of the japan trench

an earthquake catalog for seismic hazard assessment in ecuador building a unified and homogeneous earthquake catalog is a preliminary step for estimating probabilistic seismic hazard in a country ecuador a territory of 600 km 500 km is characterized by an active seismicity both in the shallow crust and in the subduction zone several international and local earthquake catalogs are available covering different time and spatial windows characterized by different magnitude types and uncertainties after a careful analysis of each catalog in particular for completeness and uncertainty levels we propose a priority scheme for merging the instrumental catalogs moreover several historical earthquakes are analyzed to estimate epicentral location and magnitude completing the solutions obtained in a previous publication once the historical earthquakes are appended to the instrumental catalog the resulting catalog covers five centuries in the cordillera region next homogenization of magnitudes and removal of aftershocks is performed different options are studied and the impact on the recurrence curve is evaluated for the cordillera region within 2 5 and 1 latitude the average occurrence of an earthquake with m w 6 0 is 10 20 years based on the historical catalog

magnitude and location of historical earthquakes in japan and implications for the 1855 ansei edo earthquake 1 japan meteorological agency jma intensity assignments ijma are used to derive intensity attenuation models suitable for estimating the location and an intensity magnitude mjma for historical earthquakes in japan the intensity for shallow crustal earthquakes on honshu is equal to 1 89 1 42mjma 0 00887 h 1 66log h where mjma is the jma magnitude h 2 h2 1 2 and and h are epicentral distance and focal depth km respectively four earthquakes located near the japan trench were used to develop a subducting plate intensity attenuation model where intensity is equal to 8 33 2 19mjma 0 00550 h 1 14 log h the ijma assignments for the mjma7 9 great 1923 kanto earthquake on the philippine sea eurasian plate interface are consistent with the subducting plate model using the subducting plate model and 226 ijma iv vi assignments the location of the intensity center is 25 km north of the epicenter mjma is 7 7 and mjma is 7 3 8 0 at the 1 confidence level intensity assignments and reported aftershock activity for the enigmatic 11 november 1855 ansei edo earthquake are consistent with an mjma 7 2 philippine sea eurasian interplate source or philippine sea intraslab source at about 30 km depth if the 1855 earthquake was a philippine sea eurasian interplate event the intensity center was adjacent to and downdip of the rupture area of the great 1923 kanto earthquake suggesting that the 1855 and 1923 events ruptured adjoining sections of the philippine sea eurasian plate interface

probability of rupture of multiple fault segments fault segments identified from geologic and historic evidence have sometimes been adopted as features limiting the likely extends of earthquake ruptures there is no doubt that individual segments can sometimes join together to produce larger earthquakes this work is a trial of an objective method to determine the probability of multisegment ruptures the frequency of occurrence of events on all conjectured combinations of adjacent segments in northern california is found by fitting to both geologic slip rates and to an assumed distribution of event sizes for the region as a whole uncertainty in the shape of the distribution near the maximum magnitude has a large effect on the solution frequencies of individual events cannot be determined but it is possible to find a set of frequencies to fit a model closely a robust conclusion for the san francisco bay region is that large multisegment events occur on the san andreas and san gregorio faults but single segment events predominate on the extended hayward and calaveras strands of segments

the iapetus suture zone in england scotland and eastern ireland a reconciliation of geological and deep seismic data deep seismic profiles in the irish and north seas have successfully imaged crustal structure across the iapetus suture zone a problem with current interpretations is that the reflectors chosen as the suture project to the top of the basement well to the south of the solway line the palaeontologically defined trace of the suture we present a revised interpretation in which a reflectivity boundary common to all the profiles is identified as the leading edge of imbricated avalonian crust in effect the footwall of the suture zone this projects to the surface close to the solway line obviating the need to invoke northward backthrusting of the suture

the 1923 kanto earthquake reevaluated using a newly augmented geodetic data set 1 this study revisits the mechanism of the 1923 ms 7 9 kanto earthquake in japan we derive a new source model and use it to assess quantitative and qualitative aspects of the accommodation of plate motion in the kanto region we use a new geodetic data set that consists of displacements from leveling and angle changes from triangulation measurements obtained in surveys between 1883 and 1927 two unique aspects of our analysis are the inclusion of a large number of second order triangulation measurements and the application of a correction to remove interseismic deformation the geometry of the fault planes is adopted from a recent seismic reflection study of the kanto region we evaluate the minimum complexity necessary in the model to fit the data optimally our final uniform slip elastic dislocation model consists of two adjacent 20 dipping low angle planes accommodating reverse dextral slip of 6 0 m on the larger eastern plane and 9 5 m on the smaller western plane with azimuths of 163 and 121 respectively the earthquake was located in the sagami trough where the philippine sea plate subducts under honshu compared to the highly oblique angle of plate convergence the coseismic slip on the large fault plane has a more orthogonal orientation to the strike of the plate boundary suggesting that slip partitioning plays a role in accommodation of plate motion what other structure is involved in the partitioning is unclear uplift records of marine coastal terraces in sagami bay document 7500 years of earthquake activity and predict average recurrence intervals of 400 years for events with vertical displacement profiles similar to those of the 1923 earthquake this means that the average slip deficit per recurrence interval is 50 of the relative plate convergence these findings of plate motion partitioning and slip deficit lead us to suggest that instead of a simple recurrence model with characteristic earthquakes additional mechanisms are necessary to describe the accommodation of deformation in the kanto region so far obvious candidates for these alternative mechanisms have not been discovered

early carboniferous extension in east avalonia 350 my record of lithospheric memory abstract despite reactivations during variscan and alpine orogenies and the opening of the northern atlantic avalonia is one of the few regions where the initial mid paleozoic basin structure is still recognisable largely intact and well studied its kinematics and dynamics remain however largely unknown in particular in view of the successive late paleozoic to recent evolution of the basin consequently the importance of the mid palaeozoic tectonic evolution and structural controls are often overlooked and poorly understood in basin studies in this paper we reassess the importance of mid palaeozoic tectonics on subsequent sedimentary basin evolution of north western europe to this end we analyse the dynamics of early variscan extension in avalonia based on the integration and re evaluation of available geophysical and geological data from lithosphere to basin scales based on a revised crustal map of the thor suture zone we present a new paleo tectonic reconstruction and tectonic scenario for the devonian carboniferous rifting these findings are key for a better understanding of long lived tectonic segmentation and post rifting deformation phases our findings indicate that the structural grain of many crustal fault dominated sedimentary basin structures such as the north sea central graben were created in the early carboniferous consequently the main basement structuration of northwest europe was completed before the variscan orogeny and successive post variscan extension and inversion phases reactivated the existing basement structures without creating major new fault groups incorporation of the paleozoic structural grain allows for a consistent tectonic framework for the mesozoic contributing to fundamental understanding of basin evolution from our tectonic framework analysis avalonia therefore stands out as a fine example of long lived lithosphere memory spanning over 350 my of structural control in geodynamic evolution

geometry and relative motion of the philippine sea plate and pacific plate beneath the kanto tokai district japan the recent acquisition of high density and improved seismic data by the kanto tokai k t observational network of the national research institute of earth science and disaster prevention requires the revision of conventional plate configuration models for the k t district we propose a new interpretation of the configuration and relative motion of the philippine sea phs plate pacific pac plate and eurasian eur plate on the basis of the distribution of hypocenters velocity structure and focal mechanisms in the k t district the new model for the configuration of the phs and pac slabs clearly delineates the phs slab subducting northwestward beneath the k t district from the sagami and suruga troughs and the pac slab subducting westward beneath the phs slab from the japan trench the thickness of the descending phs slab is estimated to be 30 5 km the proposed configuration of the phs slab is significantly different from those obtained by other researchers including our own previous study the new model is fully consistent with global plate motion data the new model leads to an interpretation of the tectonic processes taking place beneath the k t district for the sagami trough wing of the phs slab the northeastern portion of the slab is dipping northwestward in direct contact with the upper surface of the pac slab the southwestern portion carrying the izu peninsula has been bent upward because of its buoyancy producing the observed contorted shape for the suruga trough wing the dip direction of the phs slab gradually changes from northwestward at the eastern portion to northward at the western portion the new model also indicates the presence of offset within the phs slab between the sagami and suruga trough wings this area is characterized by a low level of seismic activity the absence of a high velocity structure and the presence of quaternary volcanoes it seems reasonable to speculate that the distribution of quaternary volcanic edifice construction is controlled by the location of the offset within the phs slab in view of this new model the tectonic processes of large earthquakes which occurred recently in the studied area are also reexamined

estimating earthquake location and magnitude from seismic intensity data analysis of modified mercalli intensity mmi observations for a training set of 22 california earthquakes suggests a strategy for bounding the epicentral region and moment magnitude m from mmi observations only we define an intensity magnitude m i that is calibrated to be equal in the mean to m m i mean m i where m i mmi i 3 29 0 0206 i 1 68 and i is the epicentral distance km of observation mmi i the epicentral region is bounded by contours of rms m i rms m i m i rms m i m i where rms is the root mean square rms m i m i is the minimum rms over a grid of assumed epicenters and empirical site corrections and a distance weighting function are used empirical contour values for bounding the epicenter location and empirical bounds for m estimated from m i appropriate for different levels of confidence and different quantities of intensity observations are tabulated the epicentral region bounds and m i obtained for an independent test set of western california earthquakes are consistent with the instrumental epicenters and moment magnitudes of these earthquakes the analysis strategy is particularly appropriate for the evaluation of pre 1900 earthquakes for which the only available data are a sparse set of intensity observations

late paleozoic strike slip faults in maritime canada and their role in the reconfiguration of the northern appalachian orogen major late paleozoic faults many with documented strike slip motion have dissected the ordovician devonian appalachian orogen in the maritime provinces of atlantic canada activity alternated between east west faults minas trend and ne sw faults appalachian trend nw se faults canso trend were probably conjugate to minas trend faults major dextral movement on faults with appalachian trend in total between 200 and 300 km began in the late devonian this movement initiated the maritimes basin in a transtensional environment at a releasing bend formed around a promontory in the laurentian margin and thinned the crust accounting for the major subsidence of the basin appalachian trend strike slip continued in the mississippian but was accompanied by major movement on e w minas trend faults culminating around the mississippian pennsylvanian boundary juxtaposing the meguma and avalon terranes of the appalachians close to their present day configuration however strike slip continued during the pennsylvanian permian interval resulting in transpressional deformation that reactivated and inverted earlier extensional faults a final major episode of transtension mainly sinistral occurred during the mesozoic opening of the atlantic ocean restoration of movements on these faults amounting to several hundred kilometers of slip explains anomalies in the present day distribution of terranes amalgamated during early paleozoic appalachian tectonism in the restored geometry the nashoba and ellsworth terranes of ganderia are adjacent to one another and the meguma terrane lies clearly outboard of avalonia a restored post acadian paleogeography not the present day geometry of the orogen should be used as a basis for reconstructions of its earlier paleozoic history

a summertime rainy season in the arctic forests of the eocene the discovery of exceptionally well preserved fossil wood revealed that extensive forests existed north of the arctic circle during the eocene ca 45 55 ma subsequent paleobotanical studies led researchers to suggest eastern asia as a modern analog based on the distribution of nearest living relatives during the last decade proxy based reconstructions of mean annual paleoprecipitation productivity and relative humidity have led workers to characterize the climate of the arctic forests as similar to today9s temperate forests of the pacific northwest using a new model we reconstructed the seasonal timing of paleoprecipitation from high resolution intra ring carbon isotope measurements of fossil wood we showed that the eocene arctic forests experienced on average 3 1 times more precipitation during summer than winter entirely dissimilar to the pacific northwest where summer precipitation is only one half to one sixth of the winter precipitation this new result shows that although mean annual climate conditions may have been similar to the mean annual conditions the pacific northwest consideration of seasonality implies that the temperate forests of eastern asia represent the best overall modern analog for the eocene arctic forests

comparison of magnitudes estimated by the japan meteorological agency with moment magnitudes for intermediate and deep earthquakes abstract the magnitude m jma estimated by the japan meteorological agency jma is generally referred to in japan for the regional seismicity in the area m jma is determined from maximum displacement amplitudes of the total seismic wave traces for earthquakes shallower than 60 km m jma is determined by tsuboi9s formula and for earthquakes deeper than 60 km by katsumata9s formula these relations were designed to give almost the same magnitude value as that of gutenberg and richter we compared m jma with moment magnitude m w which can be calculated from the centroid moment tensor cmt solutions it was found that the average difference between m jma and m w is not significant for shallow earthquakes in the magnitude range from 5 to 7 but it is significant at a low level for the earthquakes of deeper foci the averaged difference reaches about 0 4 magnitude units for the focal depth of 600 km we derived an attenuation function for the maximum displacement amplitude assuming the validity of the moment magnitude this relation between epicentral distance and amplitude for shallow earthquakes is almost identical to the one calculated from tsuboi9s formula it is suggested that the estimated attenuation function for deep focus earthquakes reflects the specific q and velocity structure that is peculiar to the subduction zone

widespread seismicity excitation throughout central japan following the 2011 m 9 0 tohoku earthquake and its interpretation by coulomb stress transfer 1 we report on a broad and unprecedented increase in seismicity rate following the m 9 0 tohoku mainshock for m 2 earthquakes over inland japan parts of the japan sea and izu islands at distances of up to 425 km from the locus of high 15 m seismic slip on the megathrust such an increase was not seen for the 2004 m 9 1 sumatra or 2010 m 8 8 chile earthquakes but they lacked the seismic networks necessary to detect such small events here we explore the possibility that the rate changes are the product of static coulomb stress transfer to small faults we use the nodal planes of m 3 5 earthquakes as proxies for such small active faults and find that of fifteen regions averaging 80 by 80 km in size 11 show a positive association between calculated stress changes and the observed seismicity rate change 3 show a negative correlation and for one the changes are too small to assess this work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there which is likely quite common