seismic evidence for reactivation of a buried hydrated fault in the pacific slab by the 2011 m9 0 tohoku earthquake 1 we employ seismic tomography to estimate detailed 3d seismic velocity structures in the focal area of an intraslab earthquake m7 1 which occurred on april 7 1 month after the 2011 tohoku earthquake m9 0 near its source area the results show a low velocity zone around the focal area of the m7 1 event and that the aftershock activity is limited to the upper 15 km of the oceanic mantle the lateral extent of the low velocity zone is comparable to the distribution of aftershocks suggesting a concentration of fluids in the aftershock area the angle between the aftershock alignment and the dip of the slab surface is estimated to be 60 which is consistent with the dip of an oceanward dipping normal fault observed at the outer trench slope these observations suggest that the m7 1 intraslab event occurred as a result of reactivation of a buried hydrated fault that formed prior to subduction the upper 15 km of the oceanic mantle may be locally hydrated by bending related tensional faulting at the outer trench slope

inversion of complex body waves we have developed a method that inverts seismic body waves to determine the mechanism and rupture pattern of earthquakes the rupture pattern is represented as a sequence of subevents distributed on the fault plane this method is an extension of our earlier method in which the subevent mechanisms were fixed in the new method the subevent mechanisms are determined from the data and are allowed to vary during the sequence when subevent mechanisms are allowed to vary however the inversion often becomes unstable because of the complex trade offs between the mechanism the timing and the location of the subevents many different subevent sequences can explain the same data equally well and it is important to determine the range of allowable solutions some constraints must be imposed on the solution to stabilize the inversion we have developed a procedure to explore the range of allowable solutions and appropriate constraints in this procedure a network of grid points is constructed on the i plane where and i are respectively the onset time and the distance from the epicenter of a subevent the best fit subevent is determined at all grid points then the correlation is computed between the synthetic waveform for each subevent and the observed waveform the correlation as a function of and i and the best fit mechanisms computed at each i grid point depict the character of allowable solutions and facilitate a decision on the appropriate constraints to be imposed on the solution the method is illustrated using the data for the 1976 guatemala earthquake

source parameters of some large earthquakes in northern aegean determined by body waveform inversion average source parameters for three large north aegean events are obtained from body wave inversion for the moment tensor the parameters for the events are as follows

normal faulting earthquakes beneath the outer slope of the japan trench after the 2011 tohoku earthquake implications for the stress regime in the incoming pacific plate 1 after the 2011 mw 9 1 tohoku earthquake numerous intraplate earthquakes occurred beneath the outer slope of the japan trench based on ocean bottom seismograph observations these earthquakes occurred in the oceanic crust and uppermost mantle of the pacific plate at depths shallower than about 40 km and had normal faulting focal mechanisms at all depths before the 2011 earthquake normal faulting earthquakes beneath the outer trench slope occurred only at depths shallower than 20 km whereas those at depths of around 40 km had reverse faulting mechanisms these observations suggest that the stress regime in the pacific plate was changed by the 2011 earthquake the tensional stresses that now extend to depths of about 40 km may play an important role not only in the occurrence of large normal faulting earthquakes but also in hydration of the uppermost mantle of the incoming pacific plate prior to the subduction

order of magnitude increase in subducted h2o due to hydrated normal faults within the wadati benioff zone it is widely proposed that the oceanic mantle is hydrated by outer rise normal faults and carries large amounts of water to the deep mantle however the extent of oceanic mantle hydration is poorly constrained by existing observations and is a major source of uncertainty in determining the total water delivered to the mantle full waveform modeling of dispersed p wave arrivals from events deep within the wadati benioff zone of northern japan shows that hydrated fault zone structures are present at intermediate depths analysis of the p wave coda associated with events 5 35 km below the top of the slab gives an overall indication of the bulk hydration of the subducting oceanic mantle and can be explained by a 40 km thick layer that is 17 31 serpentinized this suggests that the top of the oceanic mantle is 2 0 3 5 wt hydrated subducting 170 318 tg m y of water per meter of arc beneath northern japan this order of magnitude increase in the estimated h 2 o fl ux in this arc implies that over the age of the earth the equivalent of as many as 3 5 present day oceans of water could be subducted along the kuril and izu bonin arcs alone these results offer the fi rst direct measure of the lower lithosphere hydration at intermediate depths and suggest that regassing of the mantle is more vigorous than has previously been proposed

source parameter inversion of a reservoir induced seismic sequence lake kariba africa 1963 september summary the depth and seismic source parameters of the three largest reservoir induced earthquakes associated with the impoundment of lake kariba africa were determined using a moment tensor formalism of the generalized inverse technique the events characterized by mb 5 5 consisted of the foreshock and main event 0640 and 0901 gmt 1963 september 23 and the principal aftershock 0703 gmt 1963 september 25 from the analysis of analogue rift valley source crustal models a three layer over a half space model were selected for the analysis of the lake kariba events the epicentral proximity and the comparable source parameters of the three large events suggest a common source fault with an approximate strike of s 9 w 4 dip of 62 10 and rake of 266 4 the body wave modelling indicates that the lake kariba events occurred at depths of less than 10 km the inferred source parameters complemented by the structural maps derived from the photo interpretation of landsat imagery of the region indicate a normal fault that uniquely transects the reservoir s deep sanyati basin in a north south heading the active fault seems to correlate with the location of the umi river s submerged river channel the confirmation of shallow depths and the determination of source parameters establishes a basis for addressing the actual triggering mechanisms of these earthquakes

moment tensor inversions and dipping slabs moment tensor inversions were performed on synthetic teleseismic p and sh body wave data for two plausible orientations of intermediate depth earthquakes located in a slab a ray method was used to generate the synthetic p and sh data for dipping slab models plane layered green s functions were assumed in the inversions even though the synthetic data contained the effect of slab dip this was done to simulate the typical situation where horizontal plane layers are assumed in mechanism studies the inversion of data from an oblique slip source for dipping slabs up to 45 gave the assumed double couple source when the initial mechanism was a near vertical dip slip type results from the inversion showed significant departures from the assumed mechanism a surprising result was that even though the presence of a dipping slab can occasionally distort the radiation pattern enough to yield fictitious source orientations amplitudes and polarities were satisfactorily explained within typical variations seen in real data thus the non double couple terms in the moment tensor can compensate for the perturbing effects of slab dip

depth determination for shallow teleseismic earthquakes methods and results the depths of moderate sized shallow earthquakes can be routinely determined to an accuracy of several kilometers using teleseismic data alone making it possible to determine the vertical positions of earthquakes within the lithosphere this capability provides a valuable tool for plate tectonic studies since earthquake depths can be used to constrain lithospheric thermal and mechanical structure at plate boundaries and in intraplate regions two basic techniques are used for depth analyses surface wave spectra can be used to determine focal depths as mode excitation reflects the behavior of the eigenfunctions with depth the primary limitation on such studies stems from lateral heterogeneity of velocity structure the waveforms of body waves are also diagnostic of focal depth which controls the time separation between the direct arrival and near source surface reflections these studies can be limited by a partial trade off between depth and source time function duration the reliability of the body wave modeling approach now in general use is shown by excellent agreement between depths determined by different investigators using different algorithms the depth determination is robust to typical uncertainties in focal mechanism and near source structure the trade off with source time function duration generally does not produce major difficulties for small events ms 6 5 for larger events the trade off can be resolved using a approach in which for a given depth the time function yielding the best fit to a suite of seismograms is found by deconvolution deconvolution at a series of depths yields a misfit function whose minimum indicates the focal depth tests with synthetic data show that the deconvolution process yields reliable depth estimates even given uncertainties in focal mechanism and near source structure it successfully handles multiple sources moderate sized finite sources and horizontally propagating ruptures good results are obtained for vertically propagating ruptures until the fault area becomes so large that waveforms differ significantly from the point source approximation a number of important tectonic results have emerged from studies using these depth determination methods the maximum depth of oceanic intraplate seismicity increases with lithospheric age and is approximately bounded by the 750 c isotherm this depth roughly equals the flexural thickness of the lithosphere but is much less than the depth to the low velocity zone indicated by surface wave dispersion the maximum depth of continental intraplate seismicity is also temperature limited but by a lower temperature these observations are consistent with the rapid weakening of the appropriate rocks with depth predicted by standard temperature dependent rheologies the maximum depth of oceanic transform seismicity corresponds to an isotherm of about 400 c this temperature is lower than would be predicted from the intraplate results and may indicate that transforms are either hotter or weaker than expected the depths of ridge crest earthquakes large enough for teleseismic analysis are extremely shallow 0 8 km the depth distribution of seismicity in continental normal faulting regions provides constraints on the nature of the extension process at subduction zones precise depth determinations can resolve the upper and lower flexural regions in the bending downgoing plate precisely locate the plate interface and map the vertical extent and position of faulting in large earthquakes

systematic changes in the incoming plate structure at the kuril trench 1 recent seismic structural studies in trench outer rise regions have shown that vp within the incoming oceanic plate systematically decreases toward the trench probably owing to bending and fracturing of the plate to understand the mechanisms acting to reduce vp vs is critical because the vp vs ratio is a sensitive indicator of lithology porosity and the presence of fluid in the outer rise region of the kuril trench we conducted an extensive seismic refraction and reflection survey that revealed systematic changes in vp vs and vp vs our results suggest that water content within the incoming oceanic plate increases toward the trench accompanied by the development of bending related fractures at the top of the oceanic crust consistent with the seawater percolation our results support the idea that plate bending and fracturing during the bending in the outer rise of the trench play an important role in the water cycle of subduction zones

bending of the subducting oceanic plate and its implication for rupture propagation of large interplate earthquakes off miyagi japan in the japan trench subduction zone 1 we present the results of an onshore offshore wide angle refraction and reflection experiment off miyagi in the central japan trench forearc region there are two rupture zones of large interplate earthquakes here the landward rupture zone and the trenchward rupture zone to examine the influence of plate boundary geometry on the distributions of the rupture zones we determined reflector geometries from reflections the subducting oceanic plate increases its dip from about 5 to 13 around 143 2 e this bending point in the oceanic plate corresponds to the eastern edge of the trenchward rupture zone moreover another bending point may be present at approximately 142 3 e which corresponds to the eastern edge of the landward rupture zone the coincidence between bending points in the oceanic plate and the edges of rupture zones suggests that changes in the plate boundary geometry may affect rupture propagation of interplate earthquakes in the direction of plate convergence

seismic evidence of tectonic control on the depth of water influx into incoming oceanic plates at subduction trenches water transported by slabs into the mantle at subduction zones plays key roles in tectonics magmatism fluid and volatiles fluxes and most likely in the chemical evolution of the earth s oceans and mantle yet incorporation of water into oceanic plates before subduction is a poorly understood process several studies suggest that plates may acquire most water at subduction trenches because the ocean crust and uppermost mantle there are intensely faulted caused by bending and or slab pull and display anomalously low seismic velocities the low velocities are interpreted to arise from a combination of fluid filled fractures associated to normal faulting and mineral transformation by hydration mantle hydration by transformation of nominally dry peridotite to water rich serpentinite could potentially create the largest fluid reservoir in slabs and is therefore the most relevant for the transport of water in the deep mantle the depth of fracturing by normal fault earthquakes is usually not well constrained but could potentially create deep percolation paths for water that might hydrate up to tens of kilometers into the mantle restrained only by serpentine stability yet interpretation of deep intraplate mineral alteration remains speculative because active source seismic experiments have sampled only the uppermost few kilometers of mantle leaving the depth extent of anomalous velocities and their relation to faulting unconstrained here we use a joint inversion of active source seismic data and both local and regional earthquakes to map the three dimensional distribution of anomalous velocities under a seismic network deployed at the trench seafloor we found that anomalous velocities are restrained to the depth of normal fault micro earthquake activity recorded in the network and are considerably shallower than either the rupture depth of teleseismic normal fault earthquakes or the limit of serpentine stability extensional micro earthquakes indicate that each fault in the region slips every 2 3 months which may facilitate regular water percolation deeper teleseismic earthquakes are comparatively infrequent and possibly do not cause significant fracturing that remains open long enough to promote alteration detectable with our seismic study our results show that the stability field of serpentine does not constrain the depth of potential mantle hydration

palaeoecological studies of holocene lake sediments from west greenland abstract colonisation by plants and animals and subsequent biotic development in west greenland was studied by analyses of macrofossils in four holocene lake sequences one of the lake basins located near the outer coast was deglaciated shortly after the transition from the last glacial stage to the holocene and a basal date of 12 100 11 300 cal years bp was obtained two of the lake basins located near the margin of the greenland ice sheet were deglaciated several millennia later the oldest sediments contain low diversity floras and faunas some of the first immigrants were chironomidae and daphnia pulex soon followed by other insects crustaceans and other invertebrates water mosses ranunculus confervoides hippuris vulgaris and potamogeton filiformis were among the first plants that colonised the lakes the earliest holocene terrestrial flora in west greenland was probably entirely herbaceous with salix herbacea and empetrum nigrum being some of the first woody plants to arrive a number of invertebrates are new to the fossil fauna of greenland and the ostracod ilyocypris bradyi that was found in one sequence from 7000 to 6500 cal years bp has not been recorded from greenland before

incoming plate faulting in the northern and western pacific and implications for subduction zone water budgets abstract the greatest uncertainty in the amount of water input into the earth at subduction zones results from poor constraints on the degree of mantle serpentinization in the incoming plate recent studies suggest that the depth of serpentinization within the incoming plate mantle is likely controlled by the depth of extensional faulting caused by lithospheric bending at the outer rise and trench we explore the maximum depth of extension within the incoming plate at northwestern pacific subduction zones in order to estimate the depth limit of serpentinization and to identify any significant variation between subduction zone segments we relocate trench earthquakes to identify which events occurred within the incoming plate and determine accurate depths for 63 incoming plate earthquakes occurring during 1988 2011 by inverting teleseismic broadband p and sh waveforms we observe that the top 10 15 km of the incoming plate mantle experiences extensional faulting at all of the subduction zones with a reasonable sample of earthquakes 60 of the total number of extensional earthquakes occur at crustal depths or within the top 5 km of the incoming plate mantle 80 occur above 10 km within the mantle and 95 occur above 15 km there is evidence for variation throughout the different regions of study for example extensional earthquakes occur down to 20 km below the crust in the western aleutians and izu bonin we propose that the incoming plate mantle is most strongly hydrated in the upper 5 km and that partial serpentinization exists regionally within the incoming plate mantle to 15 km making reasonable assumptions about the degree of serpentinization and incorporating previous estimates of crustal water we calculate that the total water carried into the northern and western pacific subduction zones is generally higher than previous estimates and is approximately 4 6 10 8 tg myr or 45 70 10 3 tg myr per kilometer of subduction zone

implications for the dating of wisconsinan weichselian late glacial events of systematic radiocarbon age differences between terrestrial plant macrofossils from a site in sw ireland abstract ams radiocarbon dates were obtained from salix herbacea leaves carex seeds and bulk organic detritus from a lake sediment profile of wisconsinan weichselian lateglacial age in sw ireland there is a systematic age difference between the dated series from the two types of macrofossils with ages obtained from salix herbacea leaves being 900 to 1500 14 c years younger than those obtained from carex seeds the latter tend to be more in accord with dates from the total organic detritus in the lake sediment although the bulk organic fraction invariably registered the older ages intact survival of the fragile salix leaves indicates that they are unlikely to have been physically transferred within the sediment matrix and or otherwise reworked from the surrounding catchment hence these macrofossils are the more likely to be contemporaneous with the time of deposition however there is no significant correlation between measured 14 c age and depth in the salix values which scatter over a range of 700 14 c years in contrast the age depth relationship for carex shows a significant reversal possibly reflecting the redeposition of these macrofossils and therefore giving radiocarbon ages that are anomalously old the data have important implications for the dating of lake sediment sequences by ams radiocarbon measurement of terrestrial plant macrofossils

body wave analysis for shallow intraplate earthquakes in the korean peninsula and yellow sea abstract four medium size shallow intraplate earthquakes from the korean peninsula and yellow sea have been studied in order to find their source mechanisms focal depths source time functions and seismic moments focal depths obtained by matching short period synthetic seismograms to the observations are found to be very shallow between 6 and 9 km to determine the source mechanisms source time functions and seismic moments we inverted teleseismic long period p and sh waves from gdsn data although the inversions are performed on only a few teleseismic body waves the radiation patterns of the moment tensors are consistent with most of the p wave first motion polarities observed at regional and teleseismic distances the overall agreement in relative amplitudes and waveforms between observations and synthetics indicates that the earthquake source parameters are reasonably well determined for two earthquakes from the yellow sea and one from the north korean peninsula the mechanisms are predominantly of strike slip style while the earthquake in the central korean peninsula shows a dip slip faulting consistent ene wsw trending compression p axis and nnw sse tension t axis are found for all studied earthquakes

impact of bending related faulting on the seismic properties of the incoming oceanic plate offshore of nicaragua impact of bending related faulting on the seismic properties of the incoming oceanic plate offshore of nicaragua

geophysical evidence for hydration of the crust and mantle of the nazca plate during bending at the north chile trench water transported in subducting oceanic plates plays a key role in a number of phenomena including intraslab seismicity and arc magmatism however the locus of plate hydration and water distribution in crust and mantle of plates entering subduction zones is debated we present evidence for anomalously low seismic velocities and densities of the crust and upper mantle of the nazca plate at the north chile trench crustal seismic velocities at the trench are lower than velocities of mature fast spreading crust and even lower than velocities of highly extended slow spreading crust in addition the nazca plate at the north chile trench may contain an 20 km thick upper mantle layer with 17 serpentine which implies 2 5 wt water these results document pervasive rock alteration by water percolation linked to bending related extensional faulting

point source inversion techniques abstract a variety of approaches for obtaining source parameters from waveform data using moment tensor or dislocation point source models have been investigated and applied to long period body and surface waves from several earthquakes generalized inversion techniques have been applied to data for long period teleseismic body waves to obtain the orientation time function and depth of the 1978 thessaloniki greece event of the 1971 san fernando event and of several events associated with the 1963 induced seismicity sequence at kariba africa the generalized inversion technique and a systematic grid testing technique have also been used to place meaningful constraints on mechanisms determined from very sparse data sets a single station with high quality three component waveform data is often sufficient to discriminate faulting type e g strike slip etc sparse data sets for several recent california earthquakes for a small regional event associated with the koyna india reservoir and for several events at the kariba reservoir have been investigated in this way although linearized inversion techniques using the moment tensor model are often robust even for sparse data sets there are instances where the simplifying assumption of a single point source is inadequate to model the data successfully numerical experiments utilizing synthetic data and actual data for the 1971 san fernando earthquake graphically demonstrate that severe problems may be encountered if source finiteness effects are ignored these techniques are generally applicable to on line processing of high quality digital data but source complexity and inadequacy of the assumed green s functions are major problems which are yet to be fully addressed

a procedure for modelling shallow dislocation sources summary expressions for displacements on the surface of a layered half space due to an arbitrary oriented shear dislocation are given in terms of generalized ray expansions useful approximations of these expressions for shallow events as recorded at teleseismic distances for realistic earth models are presented the results of this procedure are used to generate synthetic p sv and sh waveforms for various assumptions of stress drop

the meckering earthquake of 14 october 1968 a possible downward propagating rupture average source parameters of the 1968 meckering australia earthquake are obtained by the inversion of body waves the objectives of the inversion are the elements of the moment tensor and the source time history an optimum source depth of 3 km is determined but because of source complexity the point source assumption fails and the moment tensor obtained at that depth has a large nondouble couple term compensated linear vector dipole 34 per cent the source parameters of the major double couple are strike 341 dip 37 rake 61 and seismic moment 8 2 1025 dyne cm the source time function is of approximately 4 sec duration with a long rise time and a sharp fall off the fault length is constrained on the surface by the observed surface break and results from vertical displacement modeling suggest a width of approximately 10 km in the middle assuming a dip of 37 that restricts the entire faulted area to lie above 6 km depth two finite fault models for the earthquake are presented with rupture initiating at a point 1 near the top of the fault and 2 at the bottom of the fault both models produce similar long period synthetics but based on the short period waveforms model 1 is favored it is argued that such a rupture process is the most reasonable in this cold shield region

aftershocks near the updip end of the 2011 tohoku oki earthquake abstract the march 2011 m w 9 0 tohoku oki earthquake activated shallow aftershocks with normal faulting focal mechanisms near the trench axis to investigate stress state in the shallow subduction zone near the trench axis we used ocean bottom seismographs obss to record earthquakes from august to october 2011 we estimated hypocenter locations and focal mechanisms of the recorded earthquakes by using a grid search method in a 2 d velocity model based on an active seismic survey the results show that most of the earthquakes occurred within both the overriding and subducting plates with very few on the plate interface and none in the most seaward 45 km of the overriding plate aseismic wedge the low seismicity along the plate interface is consistent with the nearly complete stress drop on the megathrust fault in the m w 9 0 earthquake focal mechanisms indicate that trench normal tension is pre dominant in both plates and extends to a depth of about 30 km at least on the other hand several trench normal compressional earthquakes were located at the landward end of the aseismic wedge these earthquakes suggest horizontal compression of the overriding prism that may be caused by a strengthening of the shallowest part of the megathrust

a very broadband study of the 1994 deep bolivia earthquake sequence we have examined the source process of the june 9 1994 bolivia earthquake in the period range of body waves to free oscillations a series of moment tensor inversions were performed on various teleseismic wave types and frequency bands to infer the source parameters and to map the temporal character of the source process time independent moment tensor inversion of the body waves p and sh yields a source time function of 46 seconds duration with four major pulses of moment release with moment release dominated by the third pulse the focal mechanism is dominantly dip slip on the sub horizontal nodal plane strike 287 dip 8 and slip 74 the best bodywave fit requires a non double couple component of approximately 7 although this could be due to an isotropic component of the source it is at the margin of resolution time dependent moment tensor inversion of the body waves which yields independent time histories for each moment tensor element shows that the source orientations fault plane and slip direction change very little throughout the rupture duration analysis at several frequencies shows that the seismic moment is very stable 3 0 1021 nm 6 at periods greater than 150 seconds and that the isotropic moment is negligible given the resolution we also modeled the p waves for the january 10 1994 event the strong aftershock of june 9 1994 and the august 8 1994 earthquake rotation of the p axes for events after the mainshock may suggest a possible stress adjustment

double difference tomography the method and its application to the hayward fault california we have developed a double difference dd seismic tomography method that makes use of both absolute and relative arrival times by reducing systematic errors using the more accurate relative arrival times the method produces an improved velocity model simultaneously it yields event locations of a quality equivalent to those of the dd location method while avoiding simplifying assumptions of that method we test this method on a synthetic dataset and find that it produces a more accurate velocity model and event locations than standard tomography we also test this method on a hayward fault california earthquake dataset spanning 1984 1998 the earthquakes relocated by this method collapse to a thin line along the fault trace consistent with previous results the dd velocity model has sharper velocity contrasts near the source region than the standard tomography model

modeling the seismic source and tsunami generation of the december 12 1992 flores island indonesia earthquake on december 12 1992 a large earthquake m s 7 5 occurred just north of flores island indonesia which along with the tsunami it generated killed more than 2 000 people in this study teleseismicp andsh waves as well aspp waves from distances up to 123 are inverted for the orientations and time histories of multiple point sources by repeating the inversion for reasonable values of depth time separation and spatial separation a 2 fault model is developed next the vertical deformation of the seafloor is estimated from this fault model using a detailed bathymetric model linear and nonlinear tsunami propagation models are tested the data consist of a single tide gauge record at palopo 650 km to the north as well as tsunami runup height measurements from flores island and nearby islands assuming a tsunami runup amplification factor of two the two fault model explains the tide gauge record and the tsunami runup heights on most of flores island it cannot however explain the large tsunami runup heights observed near leworahang on hading bay and riangkroko on the northeast peninsula massive coastal slumping was observed at both of these locations a final model which in addition to the two faults includes point sources of large vertical displacement at these two locations explains the observations quite well

tectonic features of the japan trench convergent margin off sanriku northeastern japan revealed by multichannel seismic reflection data near the japan trench convergent plate margin the seaward edge of the continental plate is deformed by subduction of the oceanic plate we report the results of a multichannel seismic survey in the northern japan trench in which this deformed zone is demarcated from the rigid continental framework by a pronounced landward dipping reflector the oceanic plate also undergoes deformation as the two plates interact in the subduction processes resulting in a progressive deformation or destruction of a horst structure along the top of the subducting oceanic crust this may eventually lead to the formation of a smooth plate boundary at the greater depth more than 45 km landward from the trench axis a smooth reflector suggesting a stable slip plane is visible along and above the oceanic crust our data indicate that the deformed zone pinches out landward 60 km from the axis at 13 km depth and the slip plane becomes less obvious there seismicity of interplate earthquakes rapidly increases landward from this location leading us to speculate that this is where coupling at the plate boundary becomes strong enough for earthquakes to occur we conclude that the updip limit of the seismogenic zone of interplate earthquakes in the study area is characterized by the tectonic feature of a pinchout of the deformed sediments which overlie the subducting oceanic crust

effect of trench outer rise bending related faulting on seismic poisson s ratio and mantle anisotropy a case study offshore of southern central chile summary several trench outer rise settings in subduction zones worldwide are characterized by a high degree of alteration fracturing and hydration these processes are induced by bending related faulting in the upper part of the oceanic plate prior to its subduction mapping of p and s wave velocity structures in this complex tectonic setting provides crucial information for understanding the evolution of the incoming oceanic lithosphere and serves as a baseline for comparison with seismic measurements elsewhere active source seismic investigations at the outer rise off southern central chile 43 s were carried out in order to study the seismic structure of the oceanic nazca plate seismic wide angle data were used to derive 2 d velocity models of two seismic profiles located seaward of the trench axis on 14 5 ma old crust p01a approximately parallel to the direction of spreading and p03 approximately parallel to the spreading ridge and trench axes we determined p and s velocity models using 2 d traveltime tomography we found that the poisson s ratio in the upper crust layer 2 ranges between 0 33 at the top of the crust to 0 28 at the layer 2 3 interface while in the lowermost crust and uppermost mantle it reaches values of 0 26 and 0 29 respectively these features can be explained by an oceanic crust significantly weathered altered and fractured relative high poisson s ratios in the uppermost mantle may be likely related to partially hydrated mantle and hence serpentinization thus the seismic structure of the oceanic lithosphere at the southern central chile outer rise exhibits notable differences from the classic ophiolite seismic model normal oceanic crust these differences are primarily attributed to fracturing and hydration of the entire ocean crust which are direct consequences of strong bending related faulting at the outer rise on the other hand the comparison of the uppermost mantle p wave velocities at the crossing point between the perpendicular profiles 90 km oceanward from the trench axis reveals a low degree of pn anisotropy 2 per cent

strong motion seismology although this is the first review on this topic to appear in a quadrennial report the roots of strong motion seismology extend back to at least 1932 when far sighted engineers in the seismological field survey of the u s coast and geodetic survey installed rugged fieldworthy instruments designed to make on scale recordings of large earthquakes carder 1964 these instruments are called accelerographs for their output closely mimics ground acceleration hudson 1979 the original instruments and their offspring have provided a wealth of information about ground motions of direct use to engineers due in large part to the continued devotion of the seismological field survey now part of the branch of engineering seismology and geology at the u s geological survey the number of recordings has increased substantially particularly in the last two decades and multiple recordings of a few california earthquakes have provided the data necessary to begin to unravel the complexities of the ground motions and to predict these motions on an empirical basis although seismologists used accelerograph records in studies of earthquake energy and ground motion attenuation as long ago as 1942 gutenberg and richter 1942 1956 widespread seismological use of the records began with aki s 1968 analysis of the 1966 parkfield earthquake

electromagnetic detection of plate hydration due to bending faults at the middle america trench water plays an important role in the processes occurring at subduction zones since the release of water from the downgoing slab impacts seismicity and enhances arc volcanism geochemical indicators suggest that the nicaraguan slab is anomalously wet yet the mechanism of slab hydration remains poorly constrained extensional bending faults on the incoming oceanic plate of the middle america trench offshore nicaragua have been observed to penetrate to mantle depths suggesting a permeable pathway for hydration of the crust and serpentinization of the upper mantle low seismic velocities observed in the uppermost mantle of the incoming plate have been explained as serpentinization due to deep fluid penetration but could also be explained by intrinsic anisotropy and fractures in the absence of fluid circulation here we use controlled source electromagnetic imaging to map the electrical resistivity of the crust and uppermost mantle along a 220 km profile crossing the trench offshore nicaragua along the incoming plate our data reveal that crustal resistivity decreases by up to a factor of five directly with the onset of the bending faults furthermore a strong azimuthal anisotropy compatible with conductive vertical fault planes is observed only on the faulted trench seafloor the observed resistivity decrease and anisotropy can be explained by a porosity increase along vertical fault planes which we interpret as evidence that the lithospheric bending faults provide the necessary permeable fluid pathways required for serpentinization of the uppermost mantle this implies that most serpentinisation happens at the trench with the width of the faulting region and the density of fractures controlling the extent of upper mantle alteration this observation explains why the heavily faulted trench offshore nicaragua is associated with an anomalously wet slab whereas other sections of the middle america trench containing fewer bending faults have less fluid flux from the subducting slab

the last interglacial climate during the last 10 000 years the holocene has been relatively mild and stable in contrast the climate during the last interglacial is often portrayed as more variable but as kukla discusses in this perspective evidence for a more stable last interglacial is emerging furthermore the transition to the next glacial proceeded in stages and was not uniform across europe

water input into the mariana subduction zone estimated from ocean bottom seismic data the water cycle at subduction zones remains poorly understood although subduction is the only mechanism for water transport deep into earth previous estimates of water flux1 3 exhibit large variations in the amount of water that is subducted deeper than 100 kilometres the main source of uncertainty in these calculations is the initial water content of the subducting uppermost mantle previous active source seismic studies suggest that the subducting slab may be pervasively hydrated in the plate bending region near the oceanic trench4 7 however these studies do not constrain the depth extent of hydration and most investigate young incoming plates leaving subduction zone water budgets for old subducting plates uncertain here we present seismic images of the crust and uppermost mantle around the central mariana trench derived from rayleigh wave analysis of broadband ocean bottom seismic data these images show that the low mantle velocities that result from mantle hydration extend roughly 24 kilometres beneath the moho discontinuity combined with estimates of subducting crustal water these results indicate that at least 4 3 times more water subducts than previously calculated for this region3 if other old cold subducting slabs contain correspondingly thick layers of hydrous mantle as suggested by the similarity of incoming plate faulting across old cold subducting slabs then estimates of the global water flux into the mantle at depths greater than 100 kilometres must be increased by a factor of about three compared to previous estimates3 because a long term net influx of water to the deep interior of earth is inconsistent with the geological record8 estimates of water expelled at volcanic arcs and backarc basins probably also need to be revised upwards9 seismic images of earth s crust and uppermost mantle around the mariana trench show widespread serpentinization suggesting that much more water is subducted than previously thought

climatic reconstruction of the weichselian pleniglacial in northwestern and central europe a multiproxy approach is applied to reconstructing accurately the weichselian pleniglacial climate 72 13 ka in northwestern and central europe standardised translations are used to transform proxy data into climate parameter values for six characteristic time windows quantitative reconstructions of the temperature regime are derived from periglacial coleoptera and botanical evidence while aeolian and fluvial evidence provide qualitative information on wind activity and precipitation respectively the early pleniglacial 74 59 ka the cold period between 41 38 ka and the late pleniglacial 27 13 ka are characterised by a strong north to south climatic gradient over northwestern europe during the last glacial maximum discontinuous permafrost was established in northern france whereas the continuous permafrost zone extended from the uk belgium the netherlands germany and poland to the nordic ice sheets prominent wind activity and a relatively low precipitation typify these periods in contrast an indistinct west to east climate gradient was present in the relatively more temperate intervals e g 50 41 ka seasonally frozen ground conditions prevailed in northwestern europe whereas discontinuous permafrost may be suggested for central germany it appears that the climate conditions in northwest and central europe were controlled by three major factors the scandinavian ice sheet the north atlantic surface water circulation and the russian continent 1998 john wiley sons ltd

complex source process of the 17 august 1999 izmit turkey earthquake broadband teleseismic p wave data at epicentral distances of 30 90 are inverted to retrieve the complex source process of the 17 august 1999 izmit earthquake a comparison of the waveforms of the mainshock with those of the aftershocks suggests a spatially complex rupture process having a duration of more than 45 sec inversion and modeling of broadband p waveforms are performed in this time window incorporating a priori field observations of coseismic displacements both single point and multiple point source representations are determined we found that the rupture process can be divided into at least three steps in the first step rupture initiated from the hypocenter and extended bilaterally along the e w striking fault with an almost pure right lateral strike slip motion the eastern portion of the rupture front passed through the sapanca lake and stopped around akyazi whereas the western portion stopped near hersek this step lasted for 22 23 sec releasing a total moment of 1 43 1020 n m the dislocation was concentrated briefly at two areas one near golcuk and the other between the sapanca lake and akyazi slip in these two areas was concentrated in the upper 10 km of the crust after 1 2 sec a second source started possibly initiating on an underwater fault west of hersek although its rupture lasted for almost 20 sec its moment release was very low just 0 17 1020 n m another 8 9 sec later the easternmost fault segment between akyazi and the area west of duzce was triggered with a rupture lasting for more than 15 sec producing little energy in the short period band with slip concentrated in a zone extending vertically 25 km to the surface and with a moment of 0 61 1020 n m manuscript received 22 september 2000

source inversion of seismic waveforms the koyna india earthquakes of 13 september 1967 abstract the treatment of the seismic source inverse problem when diverse forms of waveform data are available is simple and elegant using a moment tensor formalism if earth structure is known and its effects predictable in terms of vertically inhomogeneous elastic layered models then all types of wave phenomena e g surface waves body waves leaky modes etc for a purely deviatoric moment tensor point source may be represented by at most a sum of three green9s functions for an arbitrary symmetric moment tensor point source one additional green9s function is needed for the p sv system however elegant this formalism may be for posing the linear inverse problem the major difficulties lie in earth structure unknowns and resultant nonlinearities in the green9s functions which can cause significant trade offs with source parameters a hybrid inversion procedure is set up to gain insight into the probable unknowns in particular problems by incorporating both a linearized least squares gradient method for the moment tensor or double couple and smoothed time function parameters and a nonlinear systematic trial and error search for moment tensor or double couple parameters for several assumptions of green9s function the inversion technique is applied to near regional waveform data from a small earthquake associated with the koyna reservoir which occurred 13 september 1967 as the second in a group of three events with very similar waveshapes but differing amplitudes the magnitudes of the second and third events are smaller by 0 2 and 0 8 units respectively compared to the first the absolute magnitude for the first event is poorly constrained but is estimated to be 4 0 to 4 5 rather than the previously published value of 5 5 to 6 0 from the similarity of waveshapes all three events are inferred to have the same mechanism and occurred within about 2 km of the same hypocenter the results from moment tensor and double couple inversions for event 2 data indicate that source depth was 5 km and that left lateral faulting occurred on a plane with a strike of n20 e 5 dip of 90 15 and a rake of 0 35 the inferred far field time function is approximately 3 sec in duration unusually long for the seismic moment of 9 10 22 dyne cm yielding a possible stress drop of about 0 05 bars a fault map was constructed from landsat image interpretation and shows a predominance of nnw to nne striking faults in the koyna area which is used to infer the appropriate nodal plane in the inversion results these faults tend to define a broad en echelon zone which parallels the western ghats in this area

transportation of h2o beneath the japan arcs and its implications for global water circulation abstract in order to understand the transportation and circulation of h2o in subduction zones geological and seismological observations and the corresponding quantitative modeling are reviewed and consolidated with a special emphasis on the japan arcs the japan arcs are ideal for such a study in that 1 they are very active magmatically and seismically with abundant high quality observations and 2 subduction parameters change significantly along the japan arcs allowing one to investigate how the variations of input parameters affect the resultant structures and processes first numerical models for the transportation of h2o and melting are introduced the generation and migration of aqueous fluid its interaction with the convecting solid and melting are considered based on the realistic phase relationships of the peridotitic and basaltic systems application of the models to the japan arcs and comparison between the model results and the observations distribution of volcanoes and seismic structures along the japan arcs are then discussed the three cases from the ne central and sw japan arcs clarify the following points first an aqueous fluid released from the subducting oceanic crust forms a serpentinite layer in the mantle wedge just above the subducting slab maintaining a condition close to equilibrium in terms of hydration dehydration reactions during aqueous fluid migration second most of the h2o is subducted to a depth where serpentine and chlorite in the serpentinite layer break down this depth depends on the thermal structure of the slab and is greater for the older plate beneath the japan arcs as a consequence aqueous fluid and melt are in general not supplied straight upward to the volcanic front this result is rather different from the conventional view finally based on the understanding obtained from the japan arcs the global budget and circulation of h2o are discussed even after the completion of dehydration of major hydrous mineral phases in the subducting materials especially at the base of the mantle wedge just above the subducting slab nominally anhydrous phases of the upper mantle assemblage i e olivine pyroxenes garnet can carry a significant amount of h2o 1 1 1011 to 7 8 1011 kg yr 1 into the deep mantle the minimum estimate is comparable to the outflow of h2o from the mantle at mid ocean ridges and hotspots while the maximum estimate greatly exceeds it the large estimated range is mainly due to the uncertainty of the maximum h2o contents in the nominally anhydrous minerals of the upper mantle which controls the net influx of h2o into the deep mantle through subduction zones water subduction magmatism global circulation

on the extent of mantle hydration caused by plate bending when bent at subduction zones oceanic plates are damaged by normal faulting and this bending related faulting is widely believed to cause deep mantle hydration down to 20 30 km deep the buoyancy of water or equivalently confining pressure however makes it difficult to bring water down even if faulting is deep extension associated with plate bending generates negative dynamic pressure but the magnitude of such dynamic pressure is shown to be insufficient to overcome confining pressure seismic velocity anomalies that have been used to infer the extent of mantle hydration are reviewed and it is suggested that small crack like porosities which can be produced by thermal cracking and further enhanced by bending related faulting is sufficient to explain such velocity anomalies the presence of such porosities however does not necessarily lead to the substantial hydration of oceanic plates because of confining pressure whereas the depth extent of bending generated porosities is uncertain the theory of thermal cracking can be used to place a lower bound on the amount of water contained in the slab mantle 0 03 0 07 wt h2o and this lower bound is suggested to be more than sufficient to explain the lower plane earthquakes of the double seismic zone by dehydration embrittlement

frequency dependent seismic attenuation in the inner core 1 a viscoelastic interpretation 1 using reference source time functions broadband velocity waveforms of pkikp in the distance range 150 180 are inverted for a viscoelastic model of inner core attenuation a mean q at 1 hz of 307 90 is determined from 345 available pkikp ray paths both global and regional results find a depth dependent attenuation in the deep inner core with anisotropic attenuation resolved in regional results attenuation is much stronger in the upper 300 km of the inner core the preferred model of viscoelastic attenuation is frequency dependent with very weak velocity dispersion our data do not resolve any hemispherical differences of attenuation in the deep inner core

moment tensor inversion of complex earthquakes summary moment tensor inversion methods can be applied with success in the determination of source properties of simple earthquakes however these methods utilize the assumption of a point source which is inadequate for modelling many complicated shallow earthquakes for complex earthquakes an inversion using finite faulting models is desirable but the number of parameters involved requires that a good starting model be found or that independent constraints be placed on some of the parameters a method is presented for low pass filtering both the data and green s functions passing only signals with wavelengths greater than the dimension of the entire fault the filter tends to smooth complications in the waveforms and allows application of the point source moment tensor inversion this method is applied to body waves from the 1978 thessaloniki greece earthquake the 1971 san fernando earthquake and to a multiple point source synthetic model of the san fernando event for the thessaloniki event although a multiple source mechanism has been suggested inversion results before and after filtering were essentially identical indicating that a point source mechanism is sufficient in modelling the long period teleseismic body waves in the case of the san fernando earthquake the point source green s functions were incapable of simultaneously modelling the p and sh waves inversion of p waves alone resulted in extreme parameter resolution problems but allowed constraint in one axis of the moment tensor and suggested an overall source time function inversion of a synthetic san fernando data set yielded similar results but allowed an investigation of the shortcomings of the method under controlled circumstances although the results may require substantial interpretation the method presented represents a simple first step in the analysis of complex earthquakes

toward a homogeneous moment magnitude determination for earthquakes in greece and the surrounding area a strategy is presented in order to produce a statistically homogeneous catalog of historical and present century earthquakes of the aegean area by expressing the size of all these earthquakes in the moment magnitude scale records of the mainka and wiechert intermediate period t 4 sec seismographs in athens have been used to calculate the magnitudes of earthquakes that occurred in greece and its surrounding area albania s yugoslavia s bulgaria and w turkey during the whole instrumental period since 1911 this magnitude m has also been used to derive empirical relations with macroseismic data it is shown here that m is equivalent to moment magnitude mw for a wide range of earthquake sizes 5 0 m 8 0 and to the surface wave magnitude ms for large earthquake sizes 6 m 8 0 it is also shown that the local magnitude ml for earthquakes in greece is half a unit smaller than the moment magnitude in the low magnitude range 4 5 ml 6 0 this could be attributed to a magnification smaller than the nominal for the wood anderson seismographs in greece v 1000 relations are also proposed to calculate moment magnitude when other magnitudes m ml ms and mb are known for earthquakes in greece

rupture process of the 2011 tohoku oki earthquake and absolute elastic strain release 1 on 11 march 2011 the tohoku oki earthquake in eastern japan and the devastating tsunami that followed it caused severe damage and numerous deaths to clarify the rupture process of the earthquake we inverted teleseismic p wave data applying a novel formulation that takes into account the uncertainty of green s function which has been a major error source in waveform inversion the estimated seismic moment is 5 7 1022 nm mw 9 1 associated with a fault rupture 440 km long and 180 km wide along the plate interface the source process is characterized by asymmetric bilateral rupture propagation but we also found continuous slips up dip from the hypocenter which led to a large maximum slip 50 m long slip duration 90 s and a large stress drop 20 mpa the long slip duration large stress drop extensional normal faulting aftershocks in a previously compressional stress regime and low angle normal slips at approximately the depth of the plate interface suggest that the earthquake released roughly all of the accumulated elastic strain on the plate interface owing to exceptional weakening of the fault the stress accumulated on the plate interface was about 20 mpa near the trench and 0 10 mpa in the down dip source region

pore fluid effects on elastic wave velocities of serpentinite and implications for estimates of serpentinization in oceanic lithosphere abstract recent seismic refraction surveys at various outer rise regions have identified low seismic velocities in the uppermost mantle which is indicative of mantle hydration serpentinization related to water infiltration along bending related faults prior to subduction serpentinization could lead to the development of pore spaces during hydration reaction which influences seismic velocity here we measured the elastic wave velocity of low temperature serpentinites with various porosities and reevaluated the degree of serpentinization of the oceanic mantle in outer rise regions accounting for pore fluid effects experimental results show that the elastic wave velocity of serpentinite decreases with increasing porosity this relationship indicates that the estimated degree of serpentinization decreases with increasing serpentinite porosity we then applied these experimental data to the geophysical observations of the outer rise regions to reevaluate the amount and the type of water carried into earth s interior at subduction systems

estimation of earthquake source parameters of the may 4 1972 event of the hellenic arc by the inversion of waveform data abstract average source parameters of the may 4 1972 m s 6 5 earthquake southwest of crete are obtained by the inversion of body waves a source depth of 40 km is determined which places the source in the mantle the source parameters of the major double couple are strike 309 dip 18 rake 89 and seismic moment m 0 2 62 10 25 dyn cm the source time function is of 5 s duration with a long rise time the mechanism obtained corresponds to a pure thrust with the p axis almost perpendicular to the hellenic arc although a point source is assumed the resulting synthetics match satisfactorily the observed waveforms

rupture distribution of the 1977 western argentina earthquake abstract teleseismic p and sh body waves are used in a finite fault waveform inversion for the rupture history of the 23 november 1977 western argentina earthquake this double event consists of a smaller foreshock mo 5 3 1026 dyn cm followed about 20 s later by a larger main shock mo 1 5 1027 dyn cm our analysis indicates that these two events occurred on different fault segments with the foreshock having a strike dip and average rake of 345 45 e and 50 and the main shock 10 45 e and 80 respectively the foreshock initiated at a depth of 17 km and propagated updip and to the north the main shock initiated at the southern end of the foreshock zone at a depth of 25 to 30 km and propagated updip and unilaterally to the south the north south separation of the centroids of the moment release for the foreshock and main shock is about 60 km the apparent triggering of the main shock by the foreshock is similar to other earthquakes that have involved the failure of multiple fault segments such as the 1992 landers california earthquake such occurrences argue against the use of individual mapped surface fault or fault segment lengths in the determination of the size and frequency of future earthquakes

are the lower planes of double seismic zones caused by serpentine dehydration in subducting oceanic mantle in a number of subduction zones earthquakes at 50 200 km depth define two dipping planes separated by 20 40 km that appear to merge downdip upper plane earthquakes are inferred to occur within the subducting oceanic crust whereas lower plane earthquakes occur in the subducting oceanic mantle beneath northeast japan the results of a new finite element heat transfer model suggest that the lower seismic plane cuts across isotherms at a shallow angle lower plane earthquakes occur at 550 800 c at 100 km depth and at 350 600 c at 160 km depth these conditions coincide with the dehydration reaction antigorite serpentine forsterite enstatite h 2 o which suggests that lower plane earthquakes may be triggered by dehydration embrittlement which in turn suggests that the subducting oceanic mantle is partially hydrated serpentinization may occur in the trench outer rise region where faulting may promote infiltration of seawater several tens of kilometers into the oceanic lithosphere if this hypothesis is correct current subduction zone h 2 o budgets may significantly underestimate the amount of bound h 2 o entering the subduction factory

facies and allostratigraphy of high latitude glacially influenced marine strata of the early permian southern sydney basin australia the sydney basin of new south wales australia is a foreland basin containing a thick up to 10 km permo triassic succession the southern margin of the basin exposes strata deposited during late palaeozoic glaciation of south eastern gondwana the early permian wasp head pebbley beach snapper point formations and wandrawandian siltstone were deposited between 277 and 258 ma on a polar glacially influenced continental margin adjacent to ice sheets located over east antarctica and eastern australia sedimentary facies together with related ichnofacies and fauna can be grouped into six facies associations that record marine sub environments ranging from high energy storm dominated inner shelf to turbidite dominated upper slope settings cold marine conditions with near freezing bottom water temperatures are recorded by glendonites ice rafted debris most likely deposited by icebergs occurs in almost all facies associations an allostratigraphic approach emphasizing the recognition of bounding discontinuities i e erosion surfaces and marine flooding surfaces is used to subdivide the early permian stratigraphy into facies successions three types of succession can be identified and record changes in the relative influence of allocyclic controls such as basin tectonics sediment supply and glacio eustatic sea level variation together sedimentological and allostratigraphic data allow reconstruction of the depositional history of the south western margin of the sydney basin initial marine sedimentation characterized by sediment gravity flows and storm deposited sandstones of the lower wasp head formation occurred adjacent to a faulted basin margin overlying successions within the upper wasp head pebbley beach and snapper point formations record aggradation in inner to outer shelf settings along a storm and glacially influenced continental margin tectonic subsidence and basin flooding is recorded by deeper water turbidites of the wandrawandian siltstone

the effect of assumed source structure on inversion of earthquake source parameters the eastern hispaniola earthquake of 14 september 1981 abstract teleseismic body waves from the 14 september 1981 eastern hispaniola earthquake were inverted using different source structure models comparison of the inversion results showed that the non double couple clvd component of the moment tensor may be interpreted as a measure of deficiencies in the inversion procedure increasing the complexity of the source structure model to improve the fit of the green9s functions to the observed seismograms improving the data set9s azimuthal coverage and leaving the time function free to compensate partially for the deficiencies of the green9s functions all can decrease the size of the clvd component for an earthquake in which the direct arrival is clearly separated from the crustal phases an inversion of the direct p and sh waves only assuming a half space source structure model is adequate to determine the source double couple orientation and time function the moment tensor for the hispaniola earthquake indicates thrust faulting on an east west striking fault plane dipping 30 to 35 to the south the pressure axis is oriented north south the intermediate axis east west and the tension axis is nearly vertical the source time function is a simple 3 sec long triangular pulse the slip vector is consistent with the slip vectors for nearby earthquakes as determined in other studies and indicates that the slab is moving down dip to the south

earthquake distribution in the subduction zone off eastern hokkaido japan deduced from ocean bottom seismographic and land observations summary in 1986 observations of microearthquakes were conducted with the use of five ocean bottom seismometers obss on the continental slope east of the kushiro submarine canyon ksc off hokkaido island japan the observation area is located about 50 100 km landward of the southern kuril trench beneath which the pacific plate is subducted toward hokkaido island the obs data were analysed together with land data on hokkaido island to determine the precise earthquake distribution and the geometry of the subducted plate the obs data revealed for the first time the seaward seismicity east of ksc high and shallow seismicity is concentrated in an area between the coast line of hokkaido island and the 2000 m isobath a region between the 2000 and 4000 m isobaths corresponds to the source area of an interplate earthquake occurring in 1973 the nemuro hanto oki earthquake m 7 4 the obs array detected more than 10 events in this region most of them however are classified as earthquakes occurring within the subducted plate and the remarkable aftershock activity of the 1973 event is not recognized the seismic activity is extremely low between the 4000 and 6000 m isobaths as is commonly seen in subduction zones the seismicity is also very low beneath the trench in contrast with the adjacent trench areas in a vertical section taken perpendicular to the trench axis most of the located events form a seismic plane dipping landward the dip angle of the plane is 20d 25d beneath the continental slope while 35d 40d under hokkaido island the change in dip angle occurs 150 km landward of the trench axis this seismic plane is located 30 40 km below the plate boundary defined from the aftershock distribution of the nemuro hanto oki event the seismicity on the plate boundary is correlated with the geometry of the subducted plate the high activity occurs in a restricted region where the subducted plate shows a remarkable bend the seismic activity obtained is different from those in the adjacent regions along the southern kuril trench in particular the regional difference in seismicity is remarkable between the western and eastern sides of ksc our result suggests that the subduction zone along the kuril trench is divided into several tectonic blocks and ksc is one of their boundaries

the seismology of greece abstract a review and a bibliography are given of the seismological literature for the area of greece in the period from 1950 up to the present time the aim is to incorporate all aspects of seismology starting with instrumental installations passing on to earthquake catalogues statistics and effects and ending up with structural properties and seismotectonics the purpose is to provide a service to every geophysicist who has an interest in this tectonically complex area and particularly to the numerous researchers engaged in geophysical expeditions to greece

seismicity focal mechanisms and tectonics in the last four years there has been a tremendous increase in the detail of tectonic processes reported in the typical seismotectonic study new data from many local and regional networks of seismographs established during the previous four year period plus the now routine application of improved hypocentral location procedures long period body wave modelling and moment tensor inversion using digitally recorded data have increased resolution of both the hypocentral location and the nature of the faulting process consequently research emphasis has been on local tectonics or those aspects of regional and global tectonics requiring high resolution i briefly describe below some of the highlights of these studies

the strangest 0 05 of the geological history abstract the historical geological perspective is the main cause that much more is known about young rocks than about older ones most is therefore obviously known about quaternary rocks but this does not imply that the quaternary is understood much better than the older periods on the contrary facies distributions particularly in glacigenic successions seem often so much more chaotic than in successions from other periods that the quaternary could be considered as the strangest 0 05 in the geological history it is most unlikely however that the quaternary differs so much from other periods it must therefore be concluded that many of the apparent discrepancies between quaternary and older rocks either are due to different approaches followed during investigations or reflect a geologically still immature situation because destructive agents have had insufficient time to remove material or to obscure specific characteristics in spite of these probably fundamental differences between quaternary and older sediments that will disappear with time it is likely that the application of quaternary investigation methods to older rocks and that of hard rock research methods to quaternary successions may contribute substantially to a better understanding of both the remote geological past and the nearby geological history

moment tensor inversion of the 1983 january 17 kefallinia event of ionian islands greece summary the source parameters of the recent 1983 january 17 ionian island event are obtained by the inversion of body waves an optimum source depth of 8 km is determined and the source parameters of the major double couple are strike 60 dip 47 rake 174 and seismic moment m0 7 3 1025 dyne cm this mechanism implies a strike slip dextral fault with a small thrust component this solution ascertains the existence of a transform fault connecting the northwestern edge of the hellenic are with the compressional zone which is produced by the collision of the apulian plate with the eurasian plate along the adriatic north ionian coast this right lateral strike slip fault probably terminates the hellenic subduction zone

insight into complex rupturing of the immature bending normal fault in the outer slope of the japan trench from aftershocks of the 2005 sanriku earthquake mw 7 0 located by ocean bottom seismometry 1 the distribution of aftershocks of a large mw 7 0 normal faulting earthquake beneath the outer slope of the japan trench in 2005 measured in 2007 using ocean bottom seismographs indicates that the earthquake was involved with a set of conjugate normal faults although the faults reach to the upper mantle the estimated vp and vp vs show no remarkable changes that can be related to extensive hydration in the crust or uppermost mantle the absence of horst graben topographic structure in the rupture area suggests that immaturity of the bending fault system is responsible for the relatively unhydrated lithosphere several earthquakes below the aftershock zone may belong to the lower plane seismicity of the shallow double seismic zone because no earthquakes were recorded in the area for more than 80 years before the 2005 event shallow extensional and deep compressive earthquakes may be activated concurrently in the focal area of this earthquake

regional pn body wave magnitude scale mb pn for earthquakes along the northern mid atlantic ridge we obtained a robust regional body wave magnitude scale mb pn for earthquakes along the northern mid atlantic ridge by using pn wave recorded at continental stations the new magnitude scale is mb pn log10 a nm 1 86 log10 100 km c 1 62 where a is the zero to peak amplitude of pn wave on the simulated vertical wood anderson seismogram in nanometers is the epicentral distance in kilometers 1 86 represents amplitude attenuation c is the station correction and 1 62 anchors the mb pn to the moment magnitude mw plus amplitude loss in the two crustal legs by using moment magnitude as reference we obtained the event magnitude adjustments ema which represent the difference between the known long period mw and the short period mb pn emas correlate with the source property where ridge events show strong long period waves but poor high frequency signals which lead to mb pn mw and negative adjustment of 0 20 0 24 m u almost all normal faulting events are along spreading ridges whereas strike slip events are along the fracture zones and transform faults hence we developed source specific magnitude adjustments ssma which range from 0 27 m u for earthquakes along the ridges to 0 26 m u for earthquakes along the transform faults using ssma we obtained a regional pn magnitude that is consistent with mw and mb p the regression relationship is mw 0 91 mb pn ssma 0 46 with a standard deviation of 0 15 m u

lithostratigraphical correlation of micromammal sites and biostratigraphy of the upper pliocene to lower pleistocene in the northeast guadix baza basin southern spain the plio pleistocene non marine sequence in the northeast guadix baza basin southern spain comprises alluvial and lacustrine deposits baza formation the results of a revised lithostratigraphical correlation between sections from the middle and upper members of the baza formation in the northeast part of the basin supported by detailed mapping is presented the position of micromammal sites in the lithostratigraphical scheme together with the results of intensive palaeontological sampling for small mammal remains has allowed us to develop a high resolution biostratigraphical framework for the area this provides an opportunity to refine the biozonation for the plio pleistocene micromammal faunas and to define faunal events from the late villanyian late pliocene to the early pleistocene on the basis of the lithostratigraphical and biostratigraphical approaches we obtain the following sequence of biozones for the late pliocene to early pleistocene kislangia gusii mimomys cf reidi m oswaldoreigi allophaiomys pliocaenicus and a burgondiae copyright 2000 john wiley sons ltd

an event stratigraphy for the last termination in the north atlantic region based on the greenland ice core record a proposal by the intimate group it is suggested that the grip greenland ice core should constitute the stratotype for the last termination based on the oxygen isotope signal in that core a new event stratigraphy spanning the time interval from ca 22 0 to 11 5 k grip yr bp ca 19 0 10 0 k 14 c yr bp is proposed for the north atlantic region this covers the period from the last glacial maximum through termination 1 of the deep ocean record to the pleistocene holocene boundary and encompasses the last glacial late glacial of the traditional northwest european stratigraphy the isotopic record for this period is divided into two stadial episodes greenland stadials 1 gs 1 and 2 gs 2 and two interstadial events greenland interstadials 1 gi 1 and 2 gi 2 in addition gi 1 and gs 2 are further subdivided into shorter episodes the event stratigraphy is equally applicable to ice core marine and terrestrial records and is considered to be a more appropriate classificatory scheme than the terrestrially based radiocarbon dated chronostratigraphy that has been used hitherto 1998 john wiley sons ltd

modelling short period crustal phases at regional distances for the seismic source parameter inversion abstract waveforms of short period crustal phases observed at regional distances are modelled in an attempt to retrieve the source parameters of small earthquakes for a simple shield type crustal structure the synthetic seismograms calculated for elementary source mechanisms show that the waveforms of crustal phases are quite distinct for different source mechanisms and suggest that these features can be used to constrain the source mechanisms waveforms of the crustal phases are also strongly affected even by small variations in the crustal thickness as well as in the focal depth a generalized linearized waveform inversion technique is used to invert the regional crustal phases for a deviatoric moment tensor source the inversion technique is applied to regional short period records from a small earthquake in central sweden for determining its source parameters the waveform inversion which mainly used lg waves produced a satisfactory fit between the observed and synthetic records suggesting that the source mechanism and focal depth estimates were reasonable the focal depth of 40 km obtained for the event studied suggests the occurrence of a deep crustal earthquake and demonstrates the usefulness of crustal phases in studying small intraplate earthquakes

inversion of teleseismic body waves for the moment tensor of the 1978 thessaloniki greece earthquake seismograms from wwssn and canadian network stations were modeled to determine the source parameters of the 20 june 1978 thessaloniki greece earthquake m s 6 4 the depth of the initial rupture was constrained to 11 1 km by comparison of the arrival times of surface reflections with synthetic short period seismograms a focal sphere plot of first motion polarities provided little constraint on other focal parameters except to indicate that predominantly normal faulting was involved a generalized inverse technique utilizing the moment tensor formalism was applied to teleseismic p and sh waves for six increments of depth the moment tensor obtained indicated a nearly horizontal n trending tension axis and a nearly vertical compression axis and yielded the following double couple source parameters strike 280 7 dip 55 3 rake 65 5 seismic moment 5 7 1025 dyne cm and a skewed triangular source time function with a rise time of about 1 sec and duration of 6 to 8 sec due to indications of multiple or finite source effects for this event and the assumption in the moment tensor formalism of a point source a low pass filter was applied to the data and the inversions were repeated the results were nearly identical with those of the original inversion suggesting that any individual sources had similar mechanisms or that the point source model is sufficient for this earthquake

mantle wedge water contents estimated from seismic velocities in partially serpentinized peridotites 1 water carried into subduction zones with the down going plate and subsequently released by dehydration reactions at depth affects the composition of the mantle wedge triggers partial melting and affects subduction zone seismicity partially serpentinized peridotite may be a significant reservoir for water in the subducted plate the mantle wedge and the overriding plate here we develop a model that relates the degree of serpentinization and water content of partially serpentinized peridotites to their seismic p wave velocities in partially serpentinized ultramafic rocks a 1 decrease in p wave velocity corresponds to a 2 4 increase in serpentine content and a 0 3 0 18 moles m3 increase in h2o content up to a maximum of 13 where there is evidence of serpentinization mantle serpentine content is typically 15 corresponding to 4 5 wt h2o 6 10 moles m3

frost and soils implications for paleosols paleoclimates and stratigraphy abstract frost is a pedogenetic agent this paper describes the use of frost features in soil for paleoclimatic and stratigraphic interpretation it is possible to differentiate periods of frost activity from those of temperate pedogenesis by macroscopic and microscopic criteria and to distinguish between soils with pre syn and epigenetic frost effects an experimental approach is necessary to determine initial frost effects because they are usually difficult to observe at natural active sites work with ecologists also clarifies the evolution of frost affected soils under climatic and vegetational constraints vegetation has important effects on the thermal and hydraulic regimes of soils and on erosion susceptibility the recognition of fossil cryosoils often allows the reconstruction of sequences of paleoclimatic events in periods or environments with little or no micropaleontological evidence the interrelations between frost and other pedogenetic processes allow a better understanding of climatic evolution and deterioration throughout the neogene and especially during the quaternary and the holocene most of the inherited frost features in european soils are younger than 480 ka bp the differentiation between frost and tectonic perturbations is very important for calculation of soil erosional budgets